I reacted to a video by Alec Steele where they designed a new knife steel at a fancy facility.
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Video
There is also a video that presents the same information:
Knife Steel Tests and Ratings
I have tested many knife steels over the past several years and reported the results in many articles. I also have an article where I created ratings for each steel based on those past experiments. In that article I spent quite a bit of space on what is behind the properties of each steel. For example, I showed an equation I developed that predicts the CATRA edge retention of different steels based on carbide types, carbide volume, steel hardness, and the edge angle of the blade. I wanted to try to demystify the ratings a bit to show that steel results are somewhat predictable based on certain factors. Of course there are always many counter-examples where we test a steel and are surprised by a result, usually in the negative direction. With enough investigation it is possible to find out why a result was different than the expectation, though of course we don’t always have the resources to do that.
So in an ideal world we would have experimental data for each steel and don’t have to speculate on how good the steel might be. Before I started doing my testing there was very little 3rd party data available for comparing steels between companies. So Crucible or Uddeholm, etc. might compare the general properties between their own steels but generally not between their steels and the competitors’. And the companies rarely have data for everything about a steel, many data sheets are missing wear resistance or toughness experimental results, etc. But can the average knife enthusiast look at a steel composition and make a reasonable estimate of its properties? Can it be done just by looking at one or two elements and then checking with a chart? (As opposed to complicated equations). I decided to see if such a thing could be possible. I will also point out some of the cases where the estimates break down and why.
This might be my worst idea ever, as now my comments will be filled with people asking about every possible outlier in the predictions. At least you will be better at predicting steel properties than AI.
Compositions
So for these predictions, I am trying to find the best correlations I can using only the published elemental composition of each steel. These are available in many places, such as the steel manufacturer websites, in articles on my website, in Knife Engineering 2nd edition, or Zknives.com has a huge database of them. For the high alloy steels, it also lists whether it is “ingot” (conventional steelmaking) or PM (powder metallurgy), which will be relevant for the toughness predictions.
Carbon Steels
Low Alloy Steels
High Alloy Steels
High Speed Steels
Stainless Steels
Edge Retention
Edge retention seems to be the favorite property of knife enthusiasts so we will start there. I have a big article on CATRA edge retention here that discusses a lot of the individual grades and why they land where they do.
One thing I showed was a chart comparing some different stainless and non-stainless steels to each other and the overall amount of carbide to show that more carbide leads to higher wear resistance and edge retention:
Those different color dots correspond to different amounts of chromium and vanadium because those are important factors for edge retention:
You can see micrographs of the steels to get an idea of the increase in carbide volume:
CPM-3V
CPM-4V
CPM-10V
CPM-15V
The steels with low chromium (5-7.5%) and vanadium additions form a very hard vanadium carbide, and because of the high hardness of those carbides they have a stronger effect on edge retention for a given carbide volume. Chromium carbides are significantly softer and so you need a lot more carbide to achieve the same level of wear resistance. Increasing amounts of chromium in the steel reduces the amount of vanadium carbide formed for a given amount of vanadium, and replaces it with the softer chromium carbides. However, because the total carbide volume is generally higher for those grades, the edge retention is actually pretty consistent for a given amount of vanadium:
However, this is not perfect of course. Most of the steels I “normalized” to a hardness of 61 HRC so we are comparing the steels and not the steel and hardness at the same time. The effect of hardness on CATRA edge retention is relatively predictable if you look at the angled grey dashed lines on the CATRA chart. Z-Max, Maxamet, and Rex 121 are above the line for the other steels because they have a lot of tungsten/molybdenum carbide in them and also because they were tested at very high hardness levels and aren’t really designed to be used at lower hardness. So I didn’t normalize them to 61 HRC. Also when you look at the 0% vanadium region it ranges all the way from 300 to 750 mm or so. This is because there are steels with little or no vanadium that can have a lot of chromium carbide and still have relatively high wear resistance. Those steels still need high carbon to form all of those carbides, however, which also includes those extreme high speed steels like Rex 121. So I found that carbon was actually the simplest predictor of edge retention:
There are still some steels that are relatively low compared to others, such as the cluster of steels in the 300 mm range at 1-1.5% carbon. Those are low alloy steels with very soft iron carbides called cementite. So I broke out the steels into different categories and the predictions get even better:
So to get an estimate of edge retention based on composition you follow this process:
Nothing is perfect of course but that can give you an idea of where the properties might land. Note that it is not separated by stainless vs carbon steel, all of the stainless steels are within the “high alloy” category in this case. Could also probably break out steels designed to be used at over 66 HRC but this is close enough for our purposes I think. This does not factor in nitrogen since there are very few steels with which to build an estimate. Nitrogen could probably be added to the carbon, or perhaps use 6/7 multiplied by nitrogen because of the atomic weight difference.
Toughness
Toughness is also greatly controlled by steel hardness and carbide volume. However, the carbide hardness matters a lot less for toughness, and instead it is the carbide size that is very important in this case, which we didn’t discuss at all for edge retention. One of the big differentiators here is the technology used to make the steel. The most expensive knife steels are made with powder metallurgy, which leads to a smaller carbide size. So you can get higher toughness for a given amount of carbide. One example would be D2 steel made with conventional steelmaking, powder metallurgy, or an in-between technology called sprayform. You can see the difference in carbide size and toughness below:
CPM-D2 (powder metallurgy)
PSF27 (sprayform D2)
D2 (conventional steelmaking)
The amount of carbide matters just as much as the size as the carbides, however. More carbide reduces toughness because they are very hard particles, and are the sites where cracks will initiate and grow. Here is a chart showing powder metallurgy steels and the strong correlation with toughness and carbide volume:
However, we do not know what the carbide volume is just based on the composition, so we need some other factor for estimating. The closest we have is again looking at the carbon content, since you need more carbon to form more carbide:
So that gives us a reasonably good estimate of toughness though not perfect of course. While you can see that toughness drops relatively rapidly up to 1.5% carbon this can be somewhat misleading. In terms of expected performance, toughness behaves more on a log scale. Plotting it that way shows the following:
As an example of how even a relatively low carbon steel can end up with poor toughness look at 1.4116, which is a stainless steel with 0.5% C,15% Cr, and a small amount of Mo and V. With the low carbon content we would predict a relatively high toughness value. However, it only tested about 8 ft-lbs even though it was only 57 HRC. When analyzing the microstructure I found there were some very large carbides. These large carbides will of course limit the toughness. It is likely possible with better processing to reduce or eliminate these large carbides, but poor processing can turn a good steel into a bad steel.
A large carbide I found in 1.4116 stainless steel
I tried to break it down further so the spread for each carbon content is smaller though it does start to get messy:
The conventional steels, whether high or low alloy are relatively close to powder metallurgy below about 1% carbon but rapidly drop. The high alloy steels see this steep drop because the carbide size becomes more and more difficult to control as the carbide volume increases. Low alloy steels have significantly less carbide for a given amount of carbon but they have more issues with “plate martensite” above about 0.85% carbon. You can read more in this article about forging knife steels. The biggest counterexample is 52100 which is the blue dot at 1% carbon and ~30 ft-lbs. The 1.5% Cr makes it less prone to having plate martensite.
The highest points on the chart are the yellow ones which are the powder metallurgy non-stainless steels. Both PM high speed (light blue) and PM stainless steels (orange) are significantly below. The reason is that the stainless steels have a significant amount of chromium carbide, and in powder metallurgy steels the chromium carbides are significantly larger than the vanadium carbides. The amount of carbide for a given carbon content is also generally higher, probably because the high chromium leads to more overall carbide. The high speed steels instead have significantly amounts of tungsten/molybdenum carbides which are also larger than vanadium carbides. Counterexamples for the above are MagnaCut, MagnaMax, and CPM-M4. MagnaCut and MagnaMax were designed to not have chromium carbides, so they behave more similarly to the non-stainless steels. CPM-M4 has less tungsten/molybdenum carbide than most other high speed steels, and is overall more balanced than other high speed steels.
Corrosion Resistance
I have a previous article about corrosion resistance testing and the factors that lead to high corrosion resistance. I also wrote about corrosion resistance and tested a bunch of steels for the MagnaCut article. Of course one of the most basic aspects of a stainless steel is having at least 10.5% Cr. However, the chromium content alone does not tell you the corrosion resistance because not all of that chromium will go towards the corrosion resistance but instead will end up as chromium carbides (which are detrimental to corrosion resistance). But the correlation is still pretty good with bulk chromium:
MagnaCut has high corrosion resistance for a given chromium content for two reasons: 1) all of the chromium is in solution rather than being locked up in a carbide, and 2) it has no chromium carbides in the heat treated condition and those carbides are bad for corrosion resistance. D2 and ZDP-189 have low corrosion resistance for their level of chromium. These steels have very high carbon and thus form a lot of chromium carbide, reducing the amount of chromium in solution available for creating the chromium oxide protective film at the surface. So I tried to plot Cr divided by carbon and see if that gave a better correlation, since D2 and ZDP-189 have a low Cr/C ratio:
The trend now does not show those outliers that are too low but has a bunch of values that are above the trendline. Also Vanax and LC200N have a significant amount of carbon replaced by nitrogen so it is hard to plot them with the others. One reason there are many values that are above the trend line is because they have significant amounts of vanadium and thus much of that carbon is going toward the formation of vanadium carbides rather than chromium carbides. So I broke them out by whether the steels had sizeable vanadium additions:
Definitely not getting perfect predictions but not terrible. You should be able to get a decent idea of the corrosion resistance by looking at the ratio of Cr over C from the bulk composition. Anything over a “7” or so would be stainless. One check of this chart would be an old steel called K190 which is a powder metallurgy version of an even older steel called D7, which is a non-stainless with 12.5% Cr and 4% V, which puts it into the high vanadium group. However, its Cr/C is still only 5.4 which would still predict it to be non-stainless. MagnaCut would be a 9.3 despite its relatively low Cr content so that still predicts it to be stainless, though that predicts it to be roughly an 8 out of 10 rather than its true 9.5. MagnaMax prediction is significantly worse even though its corrosion resistance is roughly the same, because it has much more carbon than MagnaCut, though with more V and Nb it still does not form chromium carbides. So as with all of the above estimates there are going to be outliers that do not work with the predictions.
Toughness-Edge Retention Balance
Of course you can see that our best correlations for both edge retention and toughness were with carbon. In other words, increasing carbon leads to an increase in edge retention but a reduction in toughness. And of course increasing one property leads to a reduction in the other. However, some things can improve the edge retention-toughness balance such as using vanadium alloying and powder metallurgy production.
Summary and Conclusions
So surprisingly you can get a decent estimate of knife steel properties including edge retention, toughness, and corrosion resistance just by looking at the carbon, chromium, and vanadium content. It was a fun exercise though I’m still not completely sure how much utility it has. Of course this isn’t perfect and there are so many hundreds of caveats to this estimate that you can’t take any estimate like this as gospel. But hopefully it will lead to fewer people believing that “steel X has crazy high edge retention!!!” because they can check the carbon content and know right away that their claim is questionable.
The post How to Estimate Knife Steel Properties appeared first on Knife Steel Nerds.
Upcoming Blade Show Atlanta
I will be at Blade Show in just a few days (June 5-7). I will be teaching two classes: “Factors that Affect Edge Retention” and “What is Coming Next for Knife Steel?” You can buy tickets by clicking here.
Video
Here is the video version of the following article:
Custom vs Industry Heat Treating
In a previous article I wrote about the wide series of tests we performed to dial in the heat treatment of MagnaMax using small furnaces and plate quenching. But many knife companies and knifemakers will “send out” to a larger heat treater and the process is different in several ways. There are also a handful of knife companies that have their own large-scale heat treating facilities. Big tool steel heat treaters most commonly use large vacuum furnaces that utilize a pressurized gas quench. I previously wrote about how this affects the heat treating and final properties in this article, which will have many more details than I will provide here. One of the major differences is that the pressurized gas quench is slower than a plate quench. That is a generalization, of course, if a piece of steel is very large it is certainly possible for a plate quench to be slower than a small, thin piece with a gas quench. And gas quenches can have a range of speed based on the pressure (measured in “bars”) and how loaded up with steel the furnace is. The slower quench can lead to reduced hardness and toughness, because undesirable carbides can form at grain boundaries during the slow cooling speed. The 2% molybdenum in MagnaMax helps with this because it is a very effective element for “hardenability,” which is how slow you can cool and still achieve full hardness. For example, Uddeholm compared their improved Vanadis 8 to their earlier Vanadis 10 [1], which increased Mo from 1.5 to 3.6% and showed experimentally the difference in hardness with cooling rate:
You can see that if the quench is sufficiently fast that the hardness does not further increase with even faster quenches. This is also true for toughness, though there can be cases where toughness is reduced from a slower cooling rate without that also showing up as reduced hardness. In the previous article I showed data that MagnaCut had slightly reduced toughness when heat treated with a gas quench vs a faster plate quench:
MagnaMax Experiments
Hardness
I worked with Peters’ Heat Treating to test the large scale heat treating of MagnaMax. Fortunately we had the previous data already from the plate quench heat treatments which narrows down the range of things we needed to test. Typically the “optimal” temperatures do not change with the slower cooling rate, just the resulting hardness and toughness. We used 1 x 3 inch coupons for each heat treatment to measure the hardness. 2050°F was used with and without cryo, and 2100°F and 2150°F austenitizing temperatures were used with cryo only. For each of those austenitizing temperatures they were tempered at 300, 350, 400, 500, 700, 900, and 950°F. They were quenched with a “2 bar” pressurized gas quench, which means roughly twice the pressure of the atmosphere. I measured the hardness for each of these which generated the following chart:
I also measured the hardness of the charpy coupon specimens which used 2050-350°F (with and without cryo) and 2150-350°F. These came up a bit higher in hardness then the hardness coupons, perhaps because they were smaller (0.4 x 2.17 inches). With the plate quench heat treatments the situation was reversed where the charpy coupons tested a bit lower than the hardness coupons. The hardness coupons for plate quenching were 1 x 1.5 inches and the charpy coupons were heat treated in groups of three so the overall dimensions were 1.5 x 2.17 inches. So I plotted the hardness for all of those conditions to compare the plate quench to the gas quench:
So you can see that the gas quench generally led to somewhat lower hardness than the plate quench, as expected from the slower cooling rate. This is one of the reasons why knife companies can have a harder time reaching the same hardness values of a custom knifemaker. There are other factors as well, such as the knife company heat treating many more knives, which means that there can be more variation in temperature within the large furnaces, and variation in steel composition by using steel from multiple batches over multiple years. So this explains why knife companies typically advertise hardness with a range, such as 61-63 HRC, from the factors I just mentioned plus also statistical variability in the hardness testing itself.
Toughness
The 2050-350°F coupons tested relatively similarly with and without cryo, despite the two conditions being about 1 HRC different with the hardness coupons. The non-cryo condition measured 61.3 HRC and the cryo condition measured 61.6 HRC. The 2150-350°F coupon measured 63.8 HRC. The toughness decreased linearly with higher hardness. When comparing to the plate quench, the toughness is slightly lower as expected:
New Data Sheet and Recommended Heat Treatments
So using all of the data generated so far I made a new data sheet to summarize the heat treatment and properties of the grade for knifemakers, knife manufacturers, and heat treating companies. You can read the datasheet here.
My general recommendations for heat treating do not change based on the difference in furnace type and quench rate, I still recommend 2150°F and 350°F with a cryo treatment. Of course it is possible to customize that further for higher hardness at the cost of some toughness or vice versa. I definitely encourage knife companies to contact me if they want to test the hardness-toughness balance of their heat treatments and to dial in things to where they want them to be.
[1] Tidesten, Magnus, Anna Medvedeva, Fredrik Carlsson, and Annica Engström-Svensson. “A new cold work PM-grade combining high wear resistance with high ductility.” BHM Berg-und Hüttenmännische Monatshefte 162, no. 3 (2017): 117-121.
The post MagnaMax Industry vs Custom Heat Treatment appeared first on Knife Steel Nerds.
Wide Release Date for MagnaMax for Small Knifemakers
MagnaMax will be on sale May 1st, 2026 at 9am on Niagara Specialty Metals’ online store: https://nsm-ny.com/shop/
You can create an account beforehand so that you are ready to buy once the steel goes live. We made the following commercial to get pumped for the release:
Intro
I wrote an article (and created a video) about MagnaMax properties a few months ago. So I won’t be rehashing all of the properties here. Basically, MagnaMax is designed to have enhanced wear resistance and edge retention vs MagnaCut with similar corrosion resistance and hardness potential.
You will also see in the chart above that MagnaMax offers superior toughness and edge retention to the popular M390 and 20CV. It is very difficult to improve both of these properties at the same time, so this is a big improvement. It also maintains similar toughness to grades CPM-154, S35VN, and Vanax, which were formerly the toughest PM stainless steels prior to MagnaCut. So it offers a significant edge retention improvement to those grades, which have had a reputation for good properties in the past.
That property summary article did not have specific heat treatment recommendations because I was waiting on the final material. The initial heat of steel had carbon on the low end of the specification, so it wasn’t as representative of the average material as I wanted. No change was made to the target composition or the specification, it just landed at the lower end for carbon. So now that I have received and tested material closer to the midpoint of the specification I performed a more comprehensive set of tests. Knifemaker Matthew Gregory helped to make the majority of the toughness coupons.
High Level Heat Treatment Summary
Before we get into all of the details I can give a simple summary so you don’t get lost.
With Cryo:
Austenitize 2100-2250°F (1150-1230°C). The baseline temperature for good properties is 2150°F (1175°C).
Plate quench for faster cooling and slightly higher hardness.
After cooling to approximately room temperature, place immediately in liquid nitrogen. The amount of time it sits in the liquid nitrogen doesn’t matter that much, it just needs to reach the temperature. An hour is fine. What does matter is not wasting time before putting it in the liquid nitrogen. You don’t need to check the hardness beforehand.
Temper 300-450°F (150-230°C) twice for two hours each time. 350°F (175°C) is a baseline temperature for good properties.
Without Cryo:
Use your household freezer. It is a myth that it doesn’t have any effect. There is no reason to do no cold treatment. Everybody has or can get a freezer. Dry ice is even better, but despite being about 100°F colder than a freezer often behaves closer to a freezer than to liquid nitrogen.
Austenitize 2050-2100°F (1120-1150°C). 2100°F (1150°C) is a good temperature. It might be possible to go somewhat higher but I worry about excess retained austenite.
Plate quench for faster cooling and slightly higher hardness.
After cooling to approximately room temperature, place immediately in the freezer or dry ice. The amount of time it sits in the freezer doesn’t matter that much, it just needs to reach the temperature. An hour is fine. What does matter is not wasting time before putting it in the freezer. You don’t need to check the hardness beforehand.
Temper 300-450°F (150-230°C) twice for two hours each time. 350°F (175°C) is a baseline temperature for good properties.
Austenitizing hold times:
The required hold time changes with temperature. This is the soak time required after the piece reaches the temperature. It rarely hurts to add extra minutes, it is more common to have an issue with undersoaking.
2050°F (1120°C): 20 minutes
2100°F (1150°C): 15 minutes
2150°F (1175°C): 10 minutes
2200°F (1205°C): 5 minutes
2250°F (1230°C): 5 minutes
Hardness and Cryo
I first made a series of coupons to test the hardening response, including with the addition of a freezer or liquid nitrogen treatment after quenching. I used the soak times in the section above.
You can see that with no cold treatment the peak hardness was 2050°F (1120°C) after tempering at 300°F (150°C). Hardness drops with higher temperatures from excess retained austenite. Hardness rose when using liquid nitrogen all the way to 2250°F (1230°C). It would be unlikely to keep rising much beyond this temperature and the possibility of melting grain boundaries starts to become more of a danger. The freezer also rose all the way up to 2250°F but to a lesser extent. Because the increase was small beyond 2100°F (1150°C) this is why I limited my recommendation for the freezer to that temperature. That makes me think both the retained austenite and hardness of the martensite were increasing beyond that temperature, leading to relatively flat behavior. Excess retained austenite can lead to worse sharpening behavior when deburring. Overall this hardening response is not radically different than MagnaCut.
Nothing too crazy showed up in the tempering. You can see that a cold treatment leads to less hardness loss in tempering. Compare 2050°F with and without a cold treatment, or 2100°F with liquid nitrogen vs the freezer. Note that I have a single curve for both freezer or liquid nitrogen from 2050°F, and this was because the two were sufficiently similar to have a single line. Plus don’t want to make the chart too busy.
You will also notice that the hardness reaches an initial minimum at 600°F (315°C) and then rose to a secondary peak around 900°F (480°C). This is known as “secondary hardening.” I don’t recommend tempering in that range, especially with stainless steels, because it reduces corrosion resistance. For example see two Vanax coupons below, both sprayed with 1% saltwater. The one of the left was tempered at 400°F (200°C) and the one on the right was tempered at 1000°F (540°C).
Toughness
We also tested a series of charpy toughness coupons for this heat of MagnaMax. I used my standard coupon which is quarter size (2.5 x 10 mm) and unnotched. Three coupons were tested for each condition. We used liquid nitrogen in the heat treatment of all of these coupons directly after the quench. We used austenitizing temperatures of 2000-2250°F (1095-1230°C) and tempering temperatures of 300, 350, and 450°F (150, 175, 230°C).
The hardness was slightly lower than the small hardness coupons I showed results from before:
Looking at the resulting toughness, it rose from 2000 to 2050°F (1095 to 1120°C), was relatively flat up to 2200°F (1205°C), and then dropped somewhat up to 2250°F (1230°C). This is why I recommended a baseline austenitizing temperature of 2150°F (1175°C) as this appears to be roughly the peak hardness-toughness, though an argument could also be made for 2200°F (1205°C), in part due to a couple of the 2150°F results being on the low end and a couple of the 2200°F being on the high end. This is likely due to statistical variability of testing.
You can also see that toughness increases with tempering temperature as we would expect, which also corresponds to a hardness decrease. Lower hardness generally correlates with higher toughness.
There was a greater increase in toughness between 300 and 350°F (150-175°C) than between 350 and 450°F (175-230°C), which is why I recommended 350°F (175°C) as the baseline tempering temperature.
Hardness-Toughness Balance
But what we would like to maximize is the highest toughness for a given hardness. So I plotted hardness vs toughness below.
You will notice that the maximum hardness-toughness combinations were generally 2150-2200°F (1175-1230°C) and tempering at 350-450°F (175-230°C). The exceptions include: 1) 2100°F (1150°C) with 450°F (230°C) because that combination gave the best properties for lower hardness. And 2) For maximum hardness you need 2150-2250°F (1175-1230°C) in combination with the minimum tempering temperature of 300°F (150°C). I next overlaid those best heat treatment conditions on top of the similar non-stainless steels K390, Vanadis 8, and CPM-10V:
Erasteel MM#1 is the first heat that was shown in the prior article about MagnaMax properties, and Erasteel MM#2 is the final tested material above. You can see that both have a similar hardness-toughness balance, though the new one is skewed to somewhat higher hardness, as expected from more carbon. You will also see that the toughness is very similar to K390 and Vanadis 8, an excellent result given that MagnaMax is a stainless steel with similar wear resistance. So we greatly improved corrosion resistance over those steels while maintaining their other properties. I next plotted those hardness-toughness values vs other stainless powder metallurgy steels:
You can see that MagnaMax has superior hardness-toughness than virtually all of the powder metallurgy stainless steels apart from MagnaCut. This includes steels with a good reputation for toughness including Vanax, XHP, S35VN, and CPM-154. And below I have the more complete graph of stainless steels which is a bit busy:
Corrosion Resistance
I compared the final higher carbon version of corrosion resistance to the earlier and both passed the 1% saltwater corrosion test. Showing a picture of two clean samples isn’t very interesting, so here is the earlier image of MagnaMax vs other steels:
Each of those was austenitized from 2150°F (1175°C). MagnaMax (and MagnaCut) were designed for all of the chromium carbides to be dissolved around 2050°F (1120°C). After the chromium carbides are dissolved the corrosion resistance doesn’t appreciably change with even higher temperatures. This is different than most other stainless steels which have chromium carbides all the way up to the melting temperature. But using even higher than 2050°F does provide some factor of safety, better ensuring the chromium carbides are fully dissolved.
The other main factors for corrosion resistance are quench rate and tempering temperature. I mentioned in the tempering section that tempering above about 750°F (400°C) leads to a reduction in corrosion resistance and I showed a test with Vanax to illustrate that. Quenching isn’t an issue unless it is very slow, which leads to carbides precipitating on the grain boundaries which can reduce corrosion resistance.
Edge Retention
The primary factors for edge wear resistance are carbide volume, carbide hardness (controlled by type), and steel hardness. While the carbides are very important when comparing different steels, there is less of an impact within a given steel. It is true that austenitizing higher dissolves a bit more carbide but this effect is generally drowned out by the increase in hardness. So in general, achieving a higher hardness results in greater edge retention, and there isn’t much point in worrying about the exact austenitizing and tempering temperatures that were used to get there. I have the graph below of CATRA results I tested previously to show where MagnaMax lands and the effect of hardness on the results:
Summary and Conclusions
So I have shown the majority of the heat treatment data that I generated and my reasoning for the different recommendations. I am overall happy with how the heat treatment response ended up. If you want to see the simplified heat treatment recommendations, scroll back near the top where it said “High Level Heat Treatment Summary.” Hopefully that is simple enough for everyone. If not then ask questions in the comments. MagnaMax will be on sale May 1st, 2026 at 9am on Niagara Specialty Metals’ online store: https://nsm-ny.com/shop/
The post How to Heat Treat MagnaMax Steel appeared first on Knife Steel Nerds.
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I have two classes for “Blade University” at Blade Show Atlanta coming up the beginning of June. They are titled “Factors that Affect Edge Retention” and “What is Coming Next for Knife Steel?” Read more and buy tickets here: https://bladeshow.com/show-info/classes/
YouTube Video
Bark River Closing Down
American company Bark River Knives is shutting down. There is a pretty good write-up of the situation in this Outdoor Life article. One thing the article doesn’t discuss is the large number of people coming out now who say that Bark River or Mike Stewart owes them money for past services or products. Since the company is going away, I thought this was a good opportunity to discuss the mistakes it made in design and manufacturing that others can learn from. This includes other knife manufacturers and custom knifemakers. And for knife buyers, you can look for signs that indicate issues with a knife before purchasing it.
Mislabeling of Steel
One of the biggest controversies of the Bark River situation is the owner, Mike Stewart, admitting that they were purchasing China-produced blanks, reworking them, and stamping CPM-154 and “Made in USA” on them. He also defended this practice saying in their testing the steel was almost as good as CPM-154 and that since they performed “5 operations” on each knife that counted as Made in USA. Testing a steel and saying it is “almost the same” does not mean you can mislabel it. I think that much is basic. You can’t buy a car manufactured in China and decide it works just as well as a Dodge Charger and slap the logo on it. This would be illegal for infringing a trademark, both for the Dodge Charger and for the CPM-154. Also, Mike Stewart seems to have a very poor understanding of what “Made in USA” entails. Even if he had started with raw barstock from China and manufactured the knife from start to finish it would still not be legal to mark it as “Made in USA.” He would have to have a qualified label like “Made in USA from imported materials” or something along those lines. But even that label would of course not qualify when starting with a finished knife blank from China. But as a steel metallurgist, the most upsetting part to me is the misrepresentation of what the steel is. It’s obvious they just don’t care what the steel is as long as they can justify putting a label on it they think would sell better.
Broken Bark River Scout Knife
In 2022 there was a video from Dutch Bushcraft Knives (DBK) where they tested a knife in MagnaCut from Bark River Scout and it broke at the jimping while they were batoning (autocorrect does not like either of those words).
They talked to Bark River and were told the fault was with the steel and they pointed out some discoloration in the fracture surface, claiming this indicated an inclusion in the steel. An inclusion is a non-metallic compound in steel like an oxide or sulfide. Inclusions are present in every piece of steel, the question is about how many and how big. Inclusions that are so large you can see them with the naked eye are rare, and the discoloration they pointed out in the video does not look consistent with an inclusion.
Another Broken Bark River Scout
Bark River broke a knife of the same model in MagnaCut during manufacturing and sent it to Niagara Specialty Metals requesting an investigation into the steel. Bob Shabala of Niagara sent the blade to an independent third-party metallurgist named Gary Maddock. He evaluated the broken blade and sent a report to Niagara and Bark River.
Stress Concentrations
So this is a completely different knife of the same model that broke in the same exact place. And not even from using the knife but just while manufacturing it. So we must start discussing what a “stress concentration” is (also called a “stress riser”). I wrote a whole article about stress concentrations back in 2019. As the name implies, a stress concentration is any region of a part where the stress is concentrated. One simple way of concentrating stress is by having a reduced area in a portion of a part. As a metallurgist we often perform “tensile tests” where the standard is to have a reduced cross-section in the region to be tested. This ensures (almost 100%) that the fracture will occur in that reduced area:
Stress is just load divided by area, so if the width in that region is half of the rest of the flat piece, the stress would be twice as much in that region. However, stress concentrations can be much more extreme than this. The most common example of a bad stress riser is a sharp corner. This leads to very high stress in a small region of a part, such as is shown in this simulation:
The red region shows a much higher stress than the rest of the part being pulled apart. So we can predict with some high level of certainty that this part would break right at those sharp corners. This is all relevant, of course, because the jimping on that knife led to a stress concentration when the knife is being flexed.
So how could Bark River have avoided the stress concentration of the jimping? One method is to remove the jimping altogether, of course. There has been debate in the knife community for decades as to whether jimping is beneficial. Another way would be to round out the design of the jimping to reduce the stress concentration. Making it shallower and more rounded would be beneficial. An example would be this FreeReign knife from Demko:
Surface Roughness
Another important factor in this knife breaking is that the method used to cut the blank led to a very rough surface, and that surface was not cleaned up within the jimping.
So Gary Maddock noted that the rough surface in that jimping may have accentuated the stress riser. The rough surface has many discontinuities in it; basically areas that already look like a crack. It makes crack initiation easier because a crack is already half formed. The other thing he noted is that there was “No evidence of thermal damage” and “Microstructure appears normal under the surface.” He noted this because laser cutting can lead to a “heat affect zone” (HAZ) where the microstructure can be different than the rest of the steel. Laser cutting essentially means the steel is being locally melted, so when steel has been melted and resolidified this leads to a cast structure which is likely to be more brittle than the rest. Even away from the melted region the steel can be rehardened and thus be harder and more brittle than the bulk steel. So for both the possibility of HAZ with laser cutting and for high surface roughness with laser or waterjet it is best to refinish the perimeter of blades after they are cut out.
Bark River MagnaCut Corrosion Resistance
Some Bark River Knives were reported to easily stain or rust in MagnaCut. Mike Stewart claimed that was because MagnaCut is not a stainless steel. He claimed “i would never have listed this as a True Stainless – Crucible does but I disagree with them.”
It is silly that he was claiming to have knowledge of what classifies a steel as stainless better than the steel manufacturer itself. The most basic definition of what a stainless steel is is that it has at least 10.5% Cr, which MagnaCut has. However, this definition is overly simplistic, as there are some steels like D2 tool steel which are famously not stainless despite having enough chromium to meet that definition. The high carbon (and lack of most other elements) in D2 means that about half of its chromium is tied up in carbides and thus cannot contribute to corrosion resistance. The stain resistance from chromium comes from the element forming a chromium oxide layer at the surface. If the chromium has already formed a compound with the carbon it is not able to form a compound with oxygen. This available chromium is known as chromium “in solution” in the iron. As I have covered in the article about MagnaCut development, it was designed to not have any chromium carbide in the microstructure after heat treatment. As another side note, while the bulk chromium of MagnaCut is 10.7%, because the steel is about 8% vanadium/niobium carbide (leaving 92% steel matrix), the chromium in solution is actually higher than 10.7%, closer to 11%. This is because very little chromium is present in the vanadium and niobium carbides. In other words, if there was no chromium in those carbides the chromium in solution would be 10.7 divided by the volume of the steel matrix, 0.92 = 11.63%. And the true test of corrosion resistance is in actual corrosion testing, where MagnaCut does very well compared with other stainless knife steels.
Heat Treatment
I talked to people with some knowledge of Bark River heat treating and I did not uncover any practices that would lead to poor corrosion resistance on that side. As far as I know Bark River only sends knives to outside heat treating companies, and what information I could obtain indicated they did not request any modifications to the heat treatment.
Belt Contamination?
Another theory I have seen commonly is that Bark River is using the same belts on MagnaCut that they used on non-stainless steels, leading to easily rustable particles on the steel. Bark River vehemently denies this, claiming that they do not mix the belts. This could be true but particles left of the steel could still pose an issue. For example, they might not be thinking of certain polishing steps they are performing where it is unlikely they are swapping anything out – such as buffing wheels. However, one thing to note is that particles left on steel, even stainless steel particles left on itself, can still promote corrosion. These particles are very small and very high surface area, and they act as sites for corrosion to initiate. There is a standard industry practice called acid passivation where stainless steel is treated with a weak acid, typically nitric or citric acid, which is for the purpose of removing free iron from the surface. These practices are not that common in the knife industry as far as I have seen but it is still a good example of how the condition of the surface is very important for future corrosion resistance. There are many other factors that a corrosion expert would want to discuss such as surface finish (finer is better), whether the steel is in contact with any other metals such as pins or bolts, etc.
Do We Know Why?
I cannot say definitively why Bark River knives have had reports of poor corrosion resistance with MagnaCut. The above is only laying out some of the possibilities.
Did Bark River Actually Use MagnaCut?
There is a video from Gravy Train Outdoors where he claims to have XRF tests that show Bark River MagnaCut knives were not actually made with MagnaCut. XRF testing is common for confirming the composition of steel when someone is concerned it has been mixed up. These testers are often called “Positive Metal Identification” (PMI) testers. However, I reviewed this video and found many problems with this testing:
The report from Gary Maddock did not include a composition measurement but the microstructure does look like MagnaCut. Niagara Specialty Metals reported that they checked it with XRF before sending it to Maddock but did not formally record the result.
KnivesShipFree has had some independent XRF testing performed and not found any knives to be mislabeled in their inventory apart from the Chinese mislabeled CPM-154.
DLT has shipped knives to Niagara Specialty Metals to check their knives with XRF.
While I can’t rule out the possibility of there being mislabeled MagnaCut knives from Bark River, I have not seen any evidence to suggest that there are.
Conclusions
Stress concentrations are quite common in knives, both production and custom. It seems to be an element that is rarely considered by designers and makers. If you want a high-performing knife that won’t break, they need to be considered in the design process and when purchasing a knife. For knife manufacturers and knifemakers it also helps to test a knife in ways that are at the extremes of their intended use case. This type of testing would have quickly shown Bark River that their knife was not ready to handle any task with small flexing forces.
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Video
There is also a video version of the following article:
Metallurgists and Knifemakers
Back in 2022, I did a YouTube video called “Do Knifemakers Know How to Heat Treat?” I found video clips where knifemakers explained how to heat treat and how it works, and then I pointed out the misconceptions and misunderstandings they had about metallurgy and heat treating. It worked well because responding to how the knifemakers explained things let me address commonly repeated, untrue claims. Because when I cover my own material, I’m typically just teaching, rather than correcting misunderstandings. However, a handful of comments on the video said I was being unfair or unkind to the knifemakers.
I was a bit surprised by those comments because I thought, “Of course I know more about how steel works because I am a professional PhD metallurgist, so no one should be offended about teaching my discipline.” However, we can always debate the proper tone for such things. But I also think some people misinterpreted my mindset in the video as criticizing, or even parodying, the knifemakers’ understanding of metallurgy. There are also some knife buyers (and even fellow knifemakers) who will lionize the heat-treating prowess of certain knifemakers and believe that they know more than they do. The level of metallurgical understanding of knifemakers varies widely, from knowing almost nothing to having a professional level of knowledge. Many knifemakers are curious about metallurgy because they want to make the best possible products.
Blade Cutlery Hall of Fame Dad and Me
This is largely why I became a metallurgist. My dad, in his knifemaking and Damascus-making, loved learning about metallurgy, and I wanted to learn about it as well. (You can watch an interview with him here). Growing up, my father and I were always excited about the prospect of speaking with metallurgists, such as employees at Crucible Steel or Professors like John Verhoeven. Hoping to gain some secret knowledge from these professionals who had dedicated decades to studying steel. Even now that I am a metallurgist, there is still much to learn. I often learn new things from blacksmiths, bladesmiths, and knifemakers. They may have practical experience that contributes to my understanding of steel. So this article is dedicated to the times when craftsmen taught metallurgists things.
“Damned Good Stuff” and Impact Testing
Harry Brearley invented stainless steel in the early 20th century (1912-1914ish), and he developed the common 420 stainless steel, which remains widely used in knives. I wrote a whole chapter in my book, The Story of Knife Steel, about him and what led to the discovery of stainless steel. I pulled a lot of quotes from him because I thought he was funny and interesting.
Brearley credited cutlery manager Ernest Stuart of Mosley Cutlery Company with the success of stainless steel [1]: “It is due to him to say that, from the very first trials, he had confidence in the possibilities of the steel. He made unremitting efforts to adapt the process of knife-making to the unusual qualities of the steel and, so far as the initial use of stainless steel for cutlery is concerned, the credit is due to him and his firm.” Stuart was also the one who named it “stainless” steel, giving it the name it still has today.
The reason I bring up Brearley is because of things he wrote about working with practical craftsmen (such as Ernest Stuart) and their contributions to the understanding of metallurgy. His father was a steelworker and had no scientific training. Brearley said that he was “in appreciation of men, typified by my father, who have exerted a greater favourable influence on the practice of steel-making than they are given credit for.”[1] “The value of scientific control, with its measurings and weighings, is undeniable, but it is sadly blemished by a strutting vanity and snobbish intellectual pride which smothers with confusions aspects of a subject it does not understand.”[1]
Brearley also said that his brother was a more hands-on person than he was [1]: “He is a better workman, a better observer and more resourceful experimentalist than I am; but he has stuck to the furnaces, mills and forges and done things whilst I have read about them, and looked at things other people were doing, and taken some trouble to describe them in the language learned from books.”
Caption from Brearley: “My brother (sees) more with the naked eye than most people see in them using laboratory equipment. On the other hand, I spent about 20 years in a laboratory, mainly occupied in measuring things. The picture is intended to be symbolic: My brother on the right-hand side is looking at a fractured surface of a piece of an ingot, and I on the left-hand side am pretending to be doing something with a pair of calipers.”
To illustrate the fact that ordinary workers often have methods that are superior to the scientist, Brearley described the history of toughness testing [1]:
For a century or two the blacksmith has been in the habit of ending a bar of iron or steel after first nicking it with a slate. When the bar is broken, as intended, through the nick, the effort required to break it, appreciated by the smith’s muscles, is registered in his mind – his extremes of judgement are “rotten” and “damned good stuff.” There is not the slightest doubt in the smith’s mind that the material he intends to make something from is all the worse for being “rotten” and all the better for being “D.G.S.” Many years ago, thirty maybe, a young man in Rugby, named Izod, was called upon to explain why of two pieces of steel one failed hopelessly and the other did its job very well. Both chemical analysis and every conventional form of mechanical testing showed that the two pieces were identical; but this young man knew they were not. Bethinking himself of the blacksmith, he notched both pieces, and found the one was “rotten” and the other “D.G.S.” In order to state the difference, which was the only difference he could find, quantitatively, he made a pendulum hammer very much like the existing Izod testing machine, and then went to South Africa, blissfully unconscious that his Rugby adventure was the lead to a new kind of official testing.
This is a good example of a time when blacksmiths had a simple test for telling whether a piece of steel was processed correctly, and the methods used by the metallurgists would not reveal these most basic properties. The common test used back then by metallurgists, which continues to this day, is the tensile test. The tensile test involves pulling a piece of steel (tension/tensile) until it breaks. The load capacity of the steel is measured during this test along with how much the steel has elongated while it is tested. This generates a “tensile curve” that shows the yield strength, ultimate strength, and ductility (amount of elongation) of the steel. So there is a lot of information that is gained in one simple test.
You’ll see the different regions of a tensile test above. The “elastic deformation” region is where if you remove the load the piece of steel returns to its original dimensions. This is like bending a paper clip and letting go, it returns to the original shape. You will notice that the “curve” is in fact a straight line in the elastic region; as you load the steel it gets longer, and if you let go it returns to its original length. However, if the “yield point” is exceeded, the steel will remain permanently elongated. Just like if you bend a paper clip too far it will remain bent. The “ultimate strength” is the maximum stress the steel can take (stress is load divided by cross-section). The stress actually drops after that until the steel breaks while the steel “necks,” the steel reduces its cross-section before fracture.
In Edwin Izod’s recounting of his learning about impact testing he said [2]:
For some considerable time, however, owing probably to the greater facilities now available, tensile tests … seem to have displaced almost every other test, and in many present-day specifications for steel no other test is prescribed. In special cases, however … it is usual to include a falling-weight test. … [O]bviously a steel that possesses inability to withstand shock would be immediately detected by this method, and it is highly probable that many cases of peculiar breakage would have been avoided had a standard brittleness test been specified, as well as a tensile test; in fact, fractures have occurred in steel which are inexplicable by known chemical or standard physical tests; and some experiments … show that a ductile steel, as evidenced by the usual tensile tests, may be exceedingly brittle.
So he found that a rapid impact test behaved differently a tensile test. This became known as the Izod impact test, which is similar to the Charpy impact test. The difference between an impact test and a tensile test is in the “strain rate” of the test. Tensile tests are done with a relatively slow increase in load being applied. If you take a knife edge and flex it, or take a whole knife and bend it, you are performing an operation relatively similar to a tensile test (or a bend test), where the load/stress is applied fairly slowly. However, if the steel is rapidly impacted the behavior is somewhat different. This is like chopping something hard with a knife, or dropping a knife tip-first into the ground. The knife may have been fine with cutting hard materials, but when dropped the tip broke off. The rapid rate of an impact test can induce brittle behavior in otherwise ductile materials. Blacksmiths had already known this from their experience with breaking pieces of steel, but it took metallurgists longer to figure that out.
Schematic diagram of Charpy impact test
Tensile tests also reveal brittle materials (see below), which shows up with a low ductility result. In fact the majority of knife steels are very high in hardness and contain brittle carbides, so most of them do not have much ductility in a tensile test. Bending tests tend to do better with tool steels because the tested volume is smaller. However, there are certain types of embrittlement that do not show up in a tensile or bending test and are better revealed through impact testing because of the strain rate difference.
Example tensile curves from here
Frank J. Richtig
I previously wrote about Richtig in an article about his knives. I also covered his history in The Story of Knife Steel book. Richtig began as a blacksmith apprentice at 19 years old in 1906. In 1908 he and a friend set up their own blacksmithing shop until 1923, when he sold his share. In about 1916, he began experimenting with a heat treating process for knives. In July 1925, he leased a shop and began producing knives. Despite his previous experience as a blacksmith, his knives were made by stock removal. His typical knives had a cast aluminum handle though some rare knives had leather washer handles. He primarily produced kitchen and butcher knives though also produced some fighting knives for soldiers.
A Richtig butcher knife that I own
In the early 1930s, Richtig and his wife began traveling to the state fair to demonstrate the superiority of his knives. They would take old pieces of steel like railroad spikes, axles, or horseshoes, and he would hammer the knife through the steel and then slice through newspaper afterward. In 1936 his knives were featured in Ripley’s Believe It or Not!, which was published in newspapers across the country. Richtig advertised that his knives could pass these tests due to superior heat treating [3] : “We have discovered and developed a special new process in tempering knives. This method of tempering assures you of a better and more lasting quality of cutlery.”
Richtig in Ripley’s Believe it or Not
Richtig did, however, say that hammering his knives through iron or steel would void the warranty, and that the knives were ground somewhat thicker for the demonstrations [4]:
If knife proves to be defective in any way within six months after purchase, return same to us and we will gladly replace it. However, if the knife blade back shows it has been hammered upon or shows abuse in anyway, the guarantee is void and the knife will not be replaced… These knives are made of high-grade steel and are suitable for all ordinary uses in the home or place of business. They will do all we claim for them. In reference to the cutting of cold chisels, axles and many other steel articles, I wish to say that in my steel and iron-cutting demonstrations, I use the same steel and temper you will find in my regular stock knives. The size and thickness of the blade is the same, the only difference you will find is in the grinding of the cutting edge. I do not sell my knives for the purpose of cutting steel and iron. The purpose of my steel-cutting demonstrations is to show the toughness and temper in my knives. Many thousands of people have seen my steel-cutting demonstration and were greatly amused by them. Striking a knife with a heavy hammer in cutting steel requires special skill and experience, both of which I have learned and mastered during the thirty years I have been making and improving these knives. My knives are made for general all-around use where good, substantial knives are required.
Richtig’s impressive feats have led many to try to find his heat treatment process. Measurements of Richtig’s knives revealed that the steel composition was nothing special, a simple high-carbon steel like 1095 or W1 [5] . Richtig used steel from the Ryerson Steel Company in Chicago, branded as Ryolite [6] .
When Glen Lambert asked him about his heat treating process, Richtig answered [7], “A man is entitled to some secrets, and that’s mine.” He told Lambert [7] “he had found no one worthy of being told or taught his knifemaking, and until he did, nobody was going to get his ‘secret.’ During his declining years no one came forward, and when he passed away … so did the tempering process.” Of course, this didn’t stop people from trying to recreate his heat treatment. His legend only grew in recent decades as two research papers were published in 2000 [5] and 2015 [8]. The 2000 paper proposed that Richtig had been using an “austempering” process for a bainite microstructure, a type of heat treatment that wasn’t discovered until after Richtig was already famous for his knives’ superior heat treatment. Read about austempering and bainite in this article. In the research reported in 2015, they heat treated 1095 steel using an austempering process and could not match the superior properties reported in the 2000 research paper!
However, there are problems with this conclusion. One is that the hardness of Richtig’s knives varied widely; the knife the researchers attempted to mimic was only 39 Rc, while another knife they tested averaged 50 Rc. The butcher knife I purchased measures 57 Rc. Harlan “Sid” Suedmeier has also tested several Richtig knives and found them to vary in hardness. While Richtig owned a Paragon electric furnace for heat treating, Suedmeier is not sure when he obtained it, which could explain some of the variability. Paragon furnaces did not start until 1948, though perhaps he had another furnace before then.
The two knives analyzed in the 2000 paper
The very low-hardness knife from the research paper is thicker than many of his other blades, and the microstructure shows evidence that the knife wasn’t fully hardened. This “intermediate” microstructure is challenging to mimic with a typical oil quench and temper, or even austempering treatment. The soft phases are very ductile and give the overall steel greater ductility. So the blade that was used for the tensile testing was likely softer than the majority of Richtig knives and was not representative of the typical properties.
The large knife was only 39 Rc and was not fully hardened as can be seen by the remaining pearlite and ferrite
The small knife was fully hardened
Another issue in the 2015 paper where they tried to mimic the 39 Rc knife was that they used a test specimen size that was much larger than what was used when generating the strength-ductility values in the original 2000 paper. The use of a larger test specimen leads to the same strength value but a significantly lower ductility value. One of the researchers from the 2015 paper, Dr. Jared Teague, has since commented that he believes the specimen size is likely the cause of the lower ductility values in that study.
Comparison of tensile curves from a small tensile specimen (red) and a standard tensile specimen (blue). The small tensile specimen had the same strength but measured much greater ductility.
When comparing the tensile properties of the soft Richtig knife to quenched and tempered 52100 in the 2000 paper, they found that the soft steel had better ductility (strain) for a given level of strength (blue dots). Another evidence of the underhardened nature of the soft Richtig knife is comparing the yield strength (red dots) where you can see that the Richtig knife yielded at a much lower stress.
And while the researchers from the two papers were impressed by the properties of the underhardened steel from Richtig’s large knife, in their testing they even found that 52100 austempered at 300°C (570°F) had superior strength (blue dots) and ductility (green dots). However, the 400°C austempered condition was similar to the Richtig knife for strength and ductility. However, the yield strength was higher for the researchers 400°C austempered condition. This shows that it is unlikely that Richtig was using austempering for bainite.
So how did Richtig accomplish his steel-cutting feats? He gave us the clues in the information he had previously provided: he left the edge thicker, and he had 30 years of experience cutting iron and steel with them. Sid Suedmeier, an expert on Richtig knives, shared similar thoughts. I asked him what Richtig’s secret was, and he gave me a one-word answer: “Practice” [9]. The steel and heat treating that Richtig used were not necessarily extraordinary, but he made good knives and was not afraid to test them. His showmanship in demonstrating his knives gave the buying public an irresistible hook, and he became famous for it. But I think Richtig’s most impressive feat might be bamboozling metallurgists several decades later into believing he was using a super heat treatment.
Questek Ferrium M60S Steel
M60S was a brand new steel designed specifically for knives and cutlery that was announced back in 2003. I have written about this steel previously in this article, where I more thoroughly described its history and the design behind it. Here is the first page of the datasheet which advertises what was supposed to make it better:
Questek is a company that designs new materials using “Integrated Computational Materials Engineering” (ICME). In other words, they use computer simulations to design new materials. This sounded especially forward-thinking and advanced in 2003. A new knife steel designed by computer-aided metallurgists? Wow! However, this steel never came to market. I contacted the inventors of this steel about why it didn’t come to market and Professor Greg Olson told me by email: “I recall denting of cutting edges due to early yielding from retained austenite.” I had remembered this result. Knifemaker Jerry Hossom reported edges that deformed easily from a sample of the grade he had been provided, heat treated to 60 HRC [10]. Hossom also reported that a knife in S30V had very little damage [11].
Jerry Hossom test of chopping an 8d nail. 61 HRC 154CM (top) and 60 HRC M60S (bottom).
What led to the easy deformation? It wasn’t hardness, 60 HRC was roughly the same as the 61 HRC of the 154CM blade. The difference was in the yield strength of the material. Typically yield strength and hardness are highly correlated, but there are some cases where they deviate. If you look at the M60S datasheet you will see that it says at 60 HRC the yield strength was 250 ksi and the ultimate strength was 350 ksi. This is a relatively low “yield ratio,” or the ratio of yield strength to ultimate strength, YS/UTS. This means that in terms of yielding behavior, the stress required to deform this steel would be lower than other steels heat treated to 60 HRC. I have seen some people speculate that this lower yield strength comes from the strength of this steel being achieved with carbide precipitation rather than strictly higher carbon martensite. However, when comparing the yield strength of Ferrium-series steels [12] to AerMet-series steels [13-16], a non-stainless precipitation strengthened steel, the Ferrium yield strength is significantly lower (M60S is the orange dot):
You can see that as the ultimate strength increases, the yield strength of the two sets of materials diverges more and more. This is somewhat clearer if we plot vs yield ratio instead:
You can see that for the AerMet grades the yield ratio was flat with increasing ultimate strength (and hardness), but for the Ferrium grades like M60S the yield ratio decreased. So while a lower hardness/strength Ferrium grade has been commercialized as Ferrium S53, the yield strength issue became more relevant after pushing the hardness up to 60+ HRC for knives. As Professor Olson noted, this was due to excessive retained austenite in the higher strength Ferrium grade M60S. When steel is quenched from high temperature it transforms from the austenite phase to the hard martensite phase. With certain compositions and temperatures, the austenite does not fully convert, leading to “retained” austenite. Retained austenite can lead to reduced yield strength even while at the same hardness:
Caldie data from [17]
Data from [18]
The Ferrium grades may be more prone to having excess retained austenite than AerMet due to the high chromium content required for being a stainless. It might be possible to modify the alloy design to overcome this limitation but it probably wasn’t worth the time and expense required for doing so. But this is yet another case where a practical test by a craftsman revealed an issue that metallurgists did not predict beforehand. In Professor Olson’s email to me he had also noted that Al Pendray had made a knife in the steel, which I have included a picture of below.
Al Pendray knife in Ferrium M60S
Metallurgists and Knifemakers Working Together
Of course for many of the examples above, the knifemakers/craftsmen and metallurgists were not antagonistic towards each other. Some of the best breakthroughs happen when they work together on a common goal. One of my favorite examples is bladesmith Al Pendray and metallurgist John Verhoeven.
Al Pendray was a bladesmith trying to develop a consistent process for making Wootz. Verhoeven is an emeritus metallurgy professor. Both men reported that they needed the other to solve the question of how Wootz Damascus was made. I won’t recount the entire history here. Verhoeven has a book about the history which I reviewed here. And I also have a chapter about it in The Story of Knife Steel. There are also a couple of videos on YouTube (Video 1 and Video 2). But I will include a couple of my favorite quotes about what the two thought of each other.
Pendray Wootz knife
Verhoeven said about Pendray [19]: “He could have gone to college and gotten a Ph.D. just like that. I never worked with anybody that could learn faster. And he is extremely patient. I think Al is an amazing man. It’s been a pleasure for me to know him.” Verhoeven also reported that Pendray said that it was another famous metallurgist who encouraged him to pursue the mysteries of Wootz [20]: “Al often spoke in a sort of reverent tone of ‘Dr. Cyril Stanley’ and how Dr. Smith had taken him aside at the meeting, encouraged him in his work, saying that it was his opinion that the mystery of how to make these blades would probably be solved by a working smith.”
My Own Experiences
I did a really big study on pattern-welded Damascus a few years ago. My father was a major supporting person in this study as he produced quite a bit of the Damascus for the study. One of the combinations he wanted to look at was 1095 and nickel. The nickel is very soft while the 1095 was heat treated to high hardness like normal for a knife. He felt this might be a good combination to determine if the “Damascus cutting effect” could happen, an old claim that a combination of hard and soft metals could lead to a saw-tooth or serration effect leading to higher slicing edge retention. I told him we shouldn’t waste our time because it wouldn’t work but he insisted. When we tested it we found – it out-cut plain 1095 by a significant margin, out-cutting every other low alloy steel combination, even ApexUltra/L6. In other words, we proved the Damascus cutting effect. And while we didn’t find that effect for several other combinations, it took my knifemaker father to convince me to look at it in the first place.
I hope you enjoyed being tricked into learning about tensile tests in these stories of metallurgists and craftsmen.
[1] Brearley, Harry. Steel-Makers and Knotted String. Maney Pub, 1995.
[2] https://archive.org/details/sim_engineering_july-december-1903_76/page/431/mode/1up
[3] https://history.nebraska.gov/blog/stronger-steel
[4] Suedmeier, Harlan. “More About Richtig Knives.” Knives ’88. 1987.
[5] Wadsworth, Jeffrey, and Donald R. Lesuer. “The knives of Frank J. Richtig as featured in Ripley’s Believe It or Not!®.” Materials characterization 45, no. 4-5, 2000: 315-326.
[6] Suedmeier, Harlan. Phone conversation, 2022.
[7] Lambert, Glen. “F.J. Richtig: Believe It or Not Cutler.” Knives ’84. 1983.
[8] Teague, J., R. LeMaster, J. Rinksc, A. Winkelmannd, and L. Bartlett. “Attempted Replication of Frank Richtig’s Forgotten Steel Heat Treatments.”
[9] Suedmeier, Harlan. Phone Interview, 2019.
[10] https://www.bladeforums.com/threads/3v-why-arent-more-companies-using-it.407739/post-3800523
[11] https://www.bladeforums.com/threads/s30v.485714/page-2#post-4754204
[12] Kuehmann, Charles J., Gregory B. Olson, and Herng-Jeng Jou. “Nanocarbide precipitation strengthened ultrahigh-strength, corrosion resistant, structural steels.” U.S. Patent 7,967,927, issued June 28, 2011.
13] https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/AerMet%20340.pdf
[14] https://www.carpentertechnology.com/hubfs/Data%20Sheets/AerMet100.pdf
[15] https://www.carpentertechnology.com/hubfs/Data%20Sheets/AerMet_360_Datasheet.pdf
[16] https://www.carpentertechnology.com/hubfs/Data%20Sheets/AerMet%20310.pdf
[17] Rehan, Muhammad Arbab, Anna Medvedeva, Berne Högman, Lars‐Erik Svensson, and Leif Karlsson. “Effect of Austenitization and Tempering on the Microstructure and Mechanical Properties of a 5 wt% Cr Cold Work Tool Steel.” steel research international 87, no. 12 (2016): 1609-1618.
[18] Park, W., M. R. Hilton, A. R. Leveille, and P. C. Ward. “Microstructure, fatigue life and load capacity of PM tool steel REX20 for bearing applications.” Tribology & Lubrication Technology 55, no. 6 (1999): 20.
[19] Oppenhemier, Todd. Alfred Pendray, Wootz Hunter – An Homage to a Remarkable Craftsman. YouTube video, 2018.
[20] Verhoeven, J.D. Damascus Steel Swords: Solving the Mystery of How to Make Them. 2018.
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Video
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Can You Even Tell the Difference?
I have seen a common comment on knife forums and on my YouTube videos. It seems to be one of those statements that different people unintentionally copy from someone else. Everyone seems to think they thought of it on their own. It has a lot of variations but boils down to one statement: “People can’t tell the difference between knife steels anyway.”
The reason why the variations matter is because people are making different points when saying it. I believe that these kinds of statements started out as a criticism of certain knife buyers: “You never use your knives so you wouldn’t know what knife steel was even used.”
Another variation is to say that “premium” knife steels are all good and the differences between them are so small that nitpicking about which one is used is unimportant.
But I have seen people take this statement to the extreme and claim that there actually is no real difference between steels at all.
Edge Retention
This discussion can go a lot of different ways so let’s start with one of knife enthusiasts favorite topics – edge retention. If we look at the CATRA chart for different steels, for example:
Those tests were all done with identical edge geometry. You can also see the approximate effect of hardness by looking at the dashed diagonal lines (some steels were also tested at multiple hardness levels). You will notice that there are steels that tested under 300 mm of cardstock cut, all the way up to 1150 mm. That is a huge range. If we compared 8670 and Rex 121 in virtually any side by side slicing test with identical edge geometry I find it hard to believe that someone wouldn’t see the difference.
The Car Analogy – Commuter vs Soccer Parent
But most knife users are not doing side by side tests to compare steels. And that’s fine. When we cut random things, a random amount per day (or week, or month) it is very difficult to know how much cutting one knife did vs another. It’s like if I was comparing the gas mileage of two cars. If I was a commuter making the same drive to and from work five days a week and not driving my car at any other time, the comparison would be obvious. I may not even need to run any numbers to know if one car had only 20% better gas mileage, much less 100% better. However, if it is a family car, being driven around for different kids activities, sometimes going to the store, sometimes sitting for two days, etc. it would be very difficult to be able to tell if one car had 20% better gas mileage than another. The usage would be too variable. That doesn’t mean that I’m not actually getting better gas mileage out of one of the cars. It just means that I would have to look at some numbers to find out. (Where this analogy partially falls down is that our cars do show us the average MPG where the knife does not have a record of how much it cuts in between resharpening).
The point I am making is that just because someone couldn’t tell that there was a difference doesn’t mean that there wasn’t a difference. A knife can be cutting longer even if you didn’t notice. That also doesn’t mean that you have to buy a new knife any time there is a new knife steel. Just like you don’t need to buy a new Honda Accord just because they redesigned it for 2026. Engineers make improvements to products, and progress will continue.
Differences within Category
However, I can also agree that there is a level of nitpicking that can be unproductive among knife enthusiasts. This is especially true when people are arguing about minute differences between steels within the same “category.” For example, comparing the edge retention of S30V and M390. The differences are going to be small. There would be little difference to select one knife over another if the main goal was to achieve a small percentage increase in edge retention by selecting M390. That is partially ignoring other tradeoffs between them, of course. But they are both powder metallurgy stainless steels with 4% vanadium with similar edge retention. They are in the same “category.” Sometimes there are improvements with new steels within a given category, or at least a different set of tradeoffs that could be more desirable for different applications. But usually we are not talking about massive differences.
If, however, we are talking about 8670 vs S125V, yes, these steels are massively different. Simple low alloy steels used by forging bladesmiths vs a high wear resistance stainless steel by a stock removal maker would not be the same. These are totally different categories and will behave very differently in many ways. Calling these differences indecipherable would be nonsensical.
Edge Geometry
Steel is only one part of the equation. Every knife buyer knows that different knives can perform very differently even in the same steel. Even if they had identical heat treatments. Because edge geometry is the most important factor for knife performance.
When pure cutting performance is desired, thin, acute edges are king. It makes an even bigger difference than the steel or heat treatment. You can see that the “cheap” AUS-6 with low wear resistance can cut just as long as the high wear resistance S110V. That is if the AUS-6 is at 12.5 dps (25 total degrees) and the S110V is over 20 dps.
So this is another case where knife buyers may be confused about what the real effect of steel is. They might have one knife in a “super” steel that doesn’t cut very well and doesn’t cut very long all because the knife has a thick edge. Then another knife in a common steel that cuts great and keeps cutting. They conclude that the steel type must be nothing but hype.
Toughness
Big chopping knives and axes generally require thicker, more obtuse edges to handle abuse. Below I have images of AEB-L knives that I tested with controlled impacts at 15 dps vs 25 dps. With the 15 dps edge it only took 0.31 ft-lbs to generate a good size chip, and 1.36 ft-lbs to completely blow out the edge. With 25 dps with the same 1.36 ft-lbs there was just a minor ripple.
So just like with edge retention, the edge geometry is going to be most important, before steel type or heat treatment. However, there are real differences in toughness between different steels. Some are more prone to chipping and breaking than others:
I have definitely seen more broken Spyderco knives in high hardness Maxamet and Rex 121 than I have in higher toughness steels. That is the tradeoff. Engineering is all about tradeoffs. If you want the ultimate in wear resistance you will no longer have the ultimate in toughness. Some steels will have a higher wear resistance for a given level of toughness, but there will never be a magic steel that is perfect in every category. This is another of the many reasons why you can’t just say that there is no difference between steels. The right steel should be chosen for the right knife and the right buyer/user.
Toughness is one of those properties where you have enough of it until you didn’t. Either the toughness was sufficient for the task and there was no chipping or breaking, or the knife failed. So there can always be a debate as to whether how much toughness is enough. Because that will change based on the edge geometry and how the knife is being used.
Hardness
Hardness is less a reflection of steel type than it is of heat treatment, but there are still ranges. Some steels can’t go any higher than 60 Rc or even lower. Some steels like the “super” high speed steels can go all the way up to 70 Rc. Hardness is another of the places where I see people misinterpret steel properties, especially when it comes to relatively soft steel. Knives with soft steel will almost always deform rather than chip. This is sometimes misinterpreted as the steel having high “toughness.” If a knife edge deformed it failed due to insufficient strength, not because it was high in toughness. For example, knifemaker Shawn Houston compared an ESEE in relatively soft 1095 and compared it with a MagnaCut knife with similar edge geometry but higher hardness. In the nail chop test the 1095 failed due to deformation while the MagnaCut did not. This was due to hardness, not toughness.
Corrosion Resistance
Stain resistance is one of the more obvious categories, I think, and is less debated. Stainless steels rust less than non-stainless steels. And there are some stainless steels that are better than others. For some buyers it is acceptable to keep their knives oiled and the environment and use isn’t a problem for corrosion. But in either case I think we can all agree that some steels (when heat treated properly) show better resistance to corrosion.
Sharpening
Another area where people generally tend to notice steel difference is in sharpening. However, even in this case it isn’t as simple as some people perceive. Edge geometry is also important for sharpening. Thin edges require very little material to be removed, so even high wear resistance steels aren’t much more work to sharpen. It also matters what abrasives are being used. I used very hard CBN abrasive in my CATRA knives when resharpening and there wasn’t much difference between 8670 and Rex 121 in terms of how much strokes were required to raise a burr. The mechanical removal of material was more the limiting factor. It also matters to what level of polish you are taking it to. Those CATRA knives were only being sharpened to 400 grit. Polishing to high grit levels, especially with softer abrasives, can take much longer with high wear resistance steels with hard vanadium carbides. Heat treatment is also a factor. I found that deburring and getting a crisp edge was challenging with steels that had high retained austenite. I don’t have the space to write about what retained austenite is here, but you can have high retained austenite in virtually any steel if it is heat treated improperly.
Summary
So there was my little rant about whether steels are all the same and no one can tell the difference. They are different. And even if you didn’t notice that doesn’t mean they weren’t different. There are a lot of factors that can control whether someone notices when one knife is outperforming another, with steel being only one of them. And the bigger factor might just be commenters trying to win points with their spicy opinions about steel choices.
The post Knife Steel – Can You Tell the Difference? appeared first on Knife Steel Nerds.
Background
MagnaMax has been in development for a long time. When I first proposed the idea for MagnaCut to Crucible and Niagara in June 2019 I also proposed a high wear resistance version I was calling “stainless 10V.” This version was intended to match the combination of toughness and wear resistance in the non-stainless grades K390, Vanadis 8, and CPM-10V. K390 has developed some popularity in recent years from Spyderco using it in many knives. This steel hits a real sweet spot for having good toughness with very high wear resistance. That high wear resistance gives it excellent edge retention. MagnaMax achieves that same level of toughness and edge retention but with the same excellent corrosion resistance of MagnaCut. MagnaMax achieves these properties by using the same general approach to composition as MagnaCut while increasing carbon, niobium, and vanadium for wear resistance. We are still waiting for the ok from our patent lawyer before releasing the composition, but that will hopefully come soon. The first commercial “heat” of MagnaMax has been delivered to a few knife companies, so it is time to talk about the steel, even if we can’t reveal every detail yet.
With MagnaCut I tried to preach the benefits of “balance” for properties. Not going too extreme for any one property. I promoted the benefits of thinner edges using its excellent toughness, while still having very good wear resistance and edge retention. However, I knew that for some knives they would still benefit from higher edge retention, and that many knife enthusiasts would want a higher edge retention version of MagnaCut. So here it is. I tried to increase the edge retention by a large margin while still maintaining the goal of good balance, and I think the new steel is very successful at achieving that.
Video
There is a video version of the following information:
Edge Retention
The biggest change from MagnaCut is of course the increase in edge retention. MagnaMax matches the edge retention of K390 and Vanadis 8, as was intended:
This also puts it in the same range as steels like CPM-10V and CPM-S110V. It puts it above several notable steels like M390, ZDP-189, S60V, S30V, and CPM-M4. This is a sizeable increase in edge retention over MagnaCut.
Toughness
My stainless toughness chart has gotten pretty busy. MagnaMax is just above Vanax, S35VN, CPM-154, and XHP. These four steels were the toughest powder metallurgy stainless steels available prior to MagnaCut. So MagnaMax matching or exceeding the toughness of these grades is exciting. You will notice that MagnaCut is on the chart twice, once as “MagnaCut” and once as “Erasteel MagnaCut.” You can read about the switch to Erasteel for MagnaCut in this article.
Comparing against its benchmark grades, MagnaMax is the same as Vanadis 8 and K390, a small step above CPM-10V. So even though it is a stainless it still matched the toughness of the non-stainless powder metallurgy steels. So those that have been happy with the toughness of their K390 knives will also be happy with MagnaMax.
Edge Retention-Toughness Balance
Comparing the edge retention and toughness at the same time, MagnaMax also looks excellent on the chart:
With similar edge retention to S110V but substantially higher toughness, the property balance is much better than previous stainless PM steels. This datapoint is for 62 Rc, it could be a bit higher for edge retention at the cost of some toughness at higher hardness. You will notice that in the past, if you wanted higher edge retention than MagnaCut or S35VN, there was a steep drop off in toughness, and the toughness was relatively flat with higher levels of edge retention from there. MagnaMax has similar toughness to S35VN but with much greater edge retention, also highlighting its well-balanced properties. Comparing with the popular M390, MagnaMax is a significant improvement in both toughness and edge retention. Previously this combination of toughness and edge retention was only available in non-stainless powder metallurgy steels.
Microstructure
MagnaMax gets those excellent properties by achieving a very fine carbide structure made up of hard vanadium and niobium carbides. It has a similar amount of carbide to K390, with a somewhat finer carbide size:
MagnaMax
K390
MagnaMax has about 16% carbide volume, which is roughly double MagnaCut. This is why MagnaMax has so much greater wear resistance and slicing edge retention:
MagnaCut
MagnaMax has so much greater toughness than previous high edge retention stainless PM steels because its carbide volume is much lower and the carbides are much smaller. Chromium carbides are relatively large in powder metallurgy steels, so eliminating them from the microstructure gives much better toughness. Notice how big the carbides are in M390:
M390
S90V
S110V
Corrosion Resistance
One of the things that made MagnaCut popular was that its corrosion resistance was surprisingly excellent, better than most other stainless knife steels. I compared its corrosion resistance to other high edge retention stainless steels with my standard 1% saltwater test:
M390 and S110V actually have pretty good corrosion resistance, I had previously given both a “9” in my knife steel ratings. So it isn’t surprising that both of those grades had only a few small rust spots in this test. S90V has worse corrosion resistance and had significant rusting. MagnaMax, however, showed no rust spots in this test.
The Long, Long Development
MagnaMax has been a long time coming. As I said in the intro section, I first proposed it in 2019. We made the first heat with Crucible Steel in 2023. Crucible made a second heat right before their bankruptcy. The first heat was used by a few knifemakers and knife companies but did not have a name yet. So the companies called it different things like MagnaX, ProjectX, etc. That second heat did not provide as much information for dialing in the composition as I had hoped as they overshot the carbon target but a sizeable margin. This heat was primarily sold to Spyderco for their mule series of knives. These knives are a good representation of the steel’s properties, though the high carbon means that the corrosion resistance is lower for that prototype steel than the final versions. It’s still very good corrosion resistance, but not as good as it could have been. Once we have more representations of the final material for testing I will be doing further work like developing final datasheets and ensuring that all of the element targets yield consistent properties even when they are on the lower end or upper end of their allowable ranges. There are a lot more heat treatment combinations I need to test to optimize recommendations so that the material has its best possible combinations of hardness, edge retention, toughness, and corrosion resistance.
Wide Release Date
As I explained above, it is a bit difficult to say what the release date of MagnaMax is/was. In some ways it has already been released. However, the steel has not been given a final, wide release when it can be regularly purchased. There are many pounds of MagnaMax ingots being delivered over the next few months, from our dual powder steel suppliers of Erasteel and Carpenter. The official release date will be some time in Q2 of this year (2026).
Summary
MagnaMax maintains the excellent corrosion resistance and hardness of MagnaCut, while significantly improving its wear resistance and edge retention. This means it took a small cut in toughness, of course. MagnaMax matches the toughness-edge retention balance of K390, which has been popular in Spyderco folders recently. I think this is a sweet spot for performance for a wide range of knives that benefit from high edge retention. I’m excited to see what kinds of knives MagnaMax ends up in.
The post MagnaMax Is Here: The Next Evolution in Knife Steel appeared first on Knife Steel Nerds.
Crucible, Niagara, Erasteel, and MagnaCut
In case you haven’t been following steel news, Crucible Steel went through a bankruptcy and no longer exists. I interviewed Bob Shabala of Niagara Specialty Metals about this transition several months ago. Niagara is the company that purchased ingots from Crucible and would hot roll, anneal, and distribute them to knife companies and steel suppliers. They have also recently started a new online store to better sell directly to individual knifemakers. Niagara has managed to keep production going for a wide range of Crucible (and other) knife steels, including:
MagnaCut, CPM154, S30V, S35VN, S45VN, S90V, 3V, 4V, CruWear (NSM Wear), 154CM, 20CV, M4, CPM D2, D2, 440C ESR, 416SS, 6-4 Titanium. MagnaMax should be available in early 2026.
Erasteel purchased the rights to Crucible Steel trademarks. Erasteel is headquartered in France, but its powder metallurgy production is in Sweden. Niagara worked with Erasteel to retain the exclusive rights to purchase MagnaCut ingots and sell the steel to knifemakers and knife companies. Erasteel produces very high-quality powder metallurgy steel. Bob Skibitski was the head of the powder metallurgy steel production at Crucible Steel for 20 years and was hired by Erasteel. He reports that Erasteel production yields higher-quality, “cleaner” steel. You can read his thoughts in an article on Niagara’s website.
Video
There is a video version of this article:
Previous Testing of European Powder Metallurgy Steels
I have published two studies before comparing manufacturing from different powder metallurgy companies. One compared M390, 20CV, and 204P (with the somewhat different Elmax thrown in). The other compared Z-Wear (same as CPM-CruWear) between Crucible and European production. With the M390/20CV/204P study I found the biggest difference between manufacturers was the oxygen content. Oxygen is an impurity and it leads to oxide inclusions that are detrimental to properties. This is something advertised by companies like Bohler-Uddeholm, that their process is “cleaner” and leads to fewer oxides. However, the toughness of the grades was identical, perhaps in part because the carbide content is quite high and carbide size of M390/20CV/204P are basically the same. Even though Bohler advertises a finer powder size, the carbide size is mostly a result of carbide “coarsening” during high-temperature processing after the powder is made, rather than differences in powder size.
M390
20CV
So the carbide volume, carbide size, and resulting toughness are primarily controlled by the composition and method of manufacture (powder metallurgy) rather than the quality of the production. If the oxides are smaller and in a lower volume than the carbides, then the limiting factor for toughness is the carbide, and so oxide inclusion content doesn’t much come into play.
In the Z-Wear study I thought there might be more of an effect of oxide inclusions than the M390 because it has significantly lower amount of carbide. However, the two steels tested relatively similarly in terms of toughness:
In this case the European-produced version of Z-Wear had slightly higher toughness but it was also at a lower hardness, giving it a slightly worse hardness-toughness balance. In general I called them equivalent in the article. I actually suspect that Zapp had accidentally mixed up the labels of the steels because the oxygen content was lower in the steel that was labeled as “USA” once it was delivered to me. That would mean the European steel had a slightly better hardness-toughness balance, rather than the USA Crucible version.
USA vs European Z-Wear that might have been mislabeled before they were sent to me
Dialing in the Composition for Erasteel MagnaCut
With switching over to Erasteel for MagnaCut production we had several things we needed to figure out. One that might be surprising to people is that steel composition testing is highly dependent on calibration of the instrument and which technique is used. For example, there were significant differences in composition measured between grades in the M390/20CV/204P study and the Z-Wear study. This is not always clear because there is some distribution of composition in manufacturing. If the target is 10% chromium, there is some acceptable range by the manufacturer like 9.5-10.5% Cr. So you can’t measure just one example from different manufacturers and know what the offsets are. So we took pieces of MagnaCut from multiple Crucible “heats” and sent them to Erasteel so that they could have appropriate offsets to match the Crucible material. We will continue to monitor the performance of the new MagnaCut material because of the distributions. If heats on the low end or high end of certain elements are not performing well in one performance category or another we could shift the target or tighten the acceptable ranges. This is the side of development and quality control that is often not seen by the end customer and is probably not very exciting.
Erasteel vs Crucible MagnaCut
One very important part of MagnaCut is its high corrosion resistance. So I tested with my standard 1% saltwater spray test. Most stainless knife steels will see some rust spots with this test. In this case neither the Crucible or Erasteel material showed any rust spots:
I also tested the hardening response. For a given heat treatment the hardness was very similar, perhaps the Erasteel material was slightly higher:
Surprisingly (based on the Z-Wear and M390 results), the toughness of Erasteel MagnaCut was significantly higher:
You can see that the Erasteel MagnaCut was significantly higher, matching AEB-L at ~62 Rc, and exceeding it at ~64 Rc. I wouldn’t necessarily extrapolate that up to AEB-L levels at 60-61 Rc but in that hardness range it was very good. Comparing with non-stainless steels this also makes Erasteel MagnaCut look more competitive:
While Crucible MagnaCut was a bit below the best results of CPM-CruWear and Z-Wear, the Erasteel version matches or exceeds it. In my knife steel ratings I had given MagnaCut a “7” for toughness and CPM-CruWear an “8,” so this is exciting. MagnaCut has a similar carbide volume to CPM-CruWear but has even smaller carbides so it was always a bit disappointing that the measured toughness wasn’t matching it. Perhaps this was a case where oxide inclusions were reducing toughness slightly in the Crucible version. Erasteel MagnaCut even roughly matched the new Bohler K888 steel, advertised for its high toughness, and tested better than steels like Vanadis 4 Extra. One thing to note is that toughness differences are basically on a “log scale,” meaning that differences at small values are bigger than those at large values. So the difference between 5 and 10 ft-lbs is about the same as between 10 and 20 ft-lbs.
One difference I noted in toughness testing is that using an austenitizing temperature of 2150°F (1175°C) and then tempering to desired hardness led to better toughness than lower austenitizing temperatures. With Crucible MagnaCut the optimum property balance was with 2050°F (1120°C).
You can see that for a constant toughness of ~20 ft-lbs that the hardness can be higher for that same toughness with a higher austenitizing temperature, about a 2.5 Rc increase.
Summary and Conclusions
The MagnaCut now being produced by Erasteel matches or exceeds the properties of the previous Crucible version. Specifically the toughness showed an improvement. We will continue to monitor the properties of the new material to ensure the performance meets expectations with the new manufacturing partner.
The post Testing Erasteel MagnaCut (vs Crucible Original) appeared first on Knife Steel Nerds.
Bill Moran and Bob Loveless are the most influential knifemakers in the modern era. They were two key figures in the rise of custom knifemaking, which began in 1970 with the formation of the Knifemakers Guild. Both predated the Guild and had fully formed philosophies on knifemaking before its formation. There are an impressive number of dichotomies between Loveless and Moran. For two men who were influential in a similar time period for making the same product – knives – they had surprisingly different philosophies. Both men served as president of the Knifemakers Guild in the early years: Moran from 1972-1973, and Loveless from 1971-1972 and again from 1973-1974. B.R. Hughes wrote about the two knifemakers in 1986 [1]:
Future knife historians should be aware that Loveless and Moran had little in common. Loveless was an advocate of the stock removal method of making knives using stain-resistant steels, while Moran was a champion of the traditional forged blade. There were other, deeper differences. Loveless felt that quality should not be a condition of membership and that requirements should be as loose as possible to encourage new members. Moran was of the opinion that the Guild should have moderately strict guidelines and that members should be responsible to the Guild for unethical behavior… Be that as it may, the two, not friends by any means, ‘buried the hatchet,’ at least publicly, for the welfare of the Guild.
But looking at Moran and Loveless and how they viewed knifemaking is not only of historical interest. The arguments they were making decades ago are similar to those you can still find between some forging bladesmiths and stock removal knifemakers. And while they weren’t the only knifemakers making those arguments back then, they were two of the most influential voices. So it is valuable to examine the origins of these arguments to understand why some knifemakers still can’t agree.
Moran and Studying the Ancients
Moran was splitting time between a dairy farm and knifemaking from the 1940s. Moran found the book Bowie Knife, published by Raymond Thorp in 1948. Moran recalled [2]: “I must have read that book at least fifty times, and it certainly had a tremendous impact on me. It was during this same period that I began to attend gun shows in the Baltimore area. I was the only knifemaker who exhibited at these shows… People would stop at my table at a gun show back in the 50s and they would like my work, but when they discovered that I wanted $15 or so for a knife, they’d almost run away!” He sold the farm in 1960 and built a new shop, going full time as a knifemaker. Moran emphasized in his 1960 catalog how the study of ancient blades was key to his methods [2]:
I am the only maker of classical ancient blades… I do not make any wild claims that these knives can be used for cutting bolts or metal as a test of the knife’s quality. Moran Knives have long been acclaimed by many leading authorities as being the finest made today. They are probably the most expensive knives made because of the painstaking craftsmanship that goes into them. However, this results in a superior quality that one is unable to obtain in any other way. These knives will be collector items of future years… To my knowledge these knives are the only ones made today that are completely hand forged, hand tempered, and handmade in every respect… An immense amount of research and study of blades and forging techniques from ancient times until today has been required… The tempering process alone can only be learned by many years’ experience. This technique is the same as that used by the blade smiths of the seventeenth century. It was this tempering that enabled those blades to withstand such severe strain in combat.
Moran believed that ancient blades were better than modern knives, which is why he attempted to learn from them, as he said in his 1975 catalog [2]:
We must remember that the finest blades which have ever been made were developed at a time when one’s life depended on his blade. Anyone who does not believe this is true should make a study of ancient blades. It soon would be apparent to them that these were the finest ever made. I have tried to follow the methods and techniques used by the ancient smiths. These methods have worked out quite well for me. In all the years I have been making knives I have never had one returned with a broken blade.
Early Moran Knives. Weyer photo.
Moran Steel Choices
When it came to steel choices, Moran also believed that simpler was better, as he said in 1975 [2]:
Today, we hear a great deal about new and super steels. In over 30 years that I have been engaged in knife making, I have of course tried most all of the steels available in search of a superior steel. It is true that the corrosion resistant steels of today are far superior to the old stainless steels, but, what most people do not realize is that these steels were designed to hold their hardness at a high degree of heat. This of course, is unnecessary in a knife. Most of the high alloy steels have 12 to 18 percent chrome. This is a very definite drawback to good edge-holding qualities. It is true that this steel does have some advantages, such as being corrosion resistant, and this can be important to some people who do not have the time to wipe and oil their blade… Any steel manufacturer will tell you not to use the complex high alloy steels unless you need tools that allow you to cut under high heat, etc. For most tools and especially knife blades, one should stick to the high grade carbon steels. I myself, have found after 30 years of experimentation that the steel with the best all around qualities for a blade is in the straight carbon range. The high alloy steels have far more drawbacks than they have advantages.
Moran’s Differential Heat Treatments
Moran would heat treat his blades to have a hard edge but a “spring” tempered spine and soft tang. In 1960 he said [2] that this gave the blades “a combination of strength and edge holding quality that is unattainable from production made blades.” Again he made an appeal to ancient techniques [3]: “Of course this was a method used hundreds of years ago – especially in Europe – to make a better blade.”
Moran and Forging
Of course Bill Moran was famous for promoting forged blades. He believed that this was an important part of the ancient process, and claimed that it led to improved performance. In 1950 he said [2]: “The bar of steel is heated in a specially designed field stone forge … and forged by hand on the anvil. Every blade is heated and reheated, then forged dozens of times before the forging operation is finished. This hand forging greatly improves the quality of the blade.”
Moran believed that the performance improvement was due in part to the (now discredited) technique of “packing” as he said in 1975 [2]: “I use a technique known as hammer hardening or packing. This is an important step that unfortunately is understood by only a few smith’s. After the blade is forged almost to the finished shape, the blade is then hammered at a rather low heat with rapid, light blows. This causes the grain to be better aligned and the steel to be far more compact. This should only be attempted by a smith with a great deal of experience.” While “packing of molecules” is rarely claimed by bladesmiths anymore (iron atoms cannot be forced closer together), there are some that still perform cold or warm forging techniques for other purposes, so this could just be a case where Moran did not understand the metallurgy though there can be small benefits to the technique anyway.
Moran bowie. Weyer photo.
Moran and the Reintroduction of Pattern-Welded Damascus
Moran popularized pattern-welded Damascus in the early 1970s. This was due to his studies of ancient blades [4]: “Ever since I can remember, I, like all who love fine blades, have been fascinated with the beautiful Damascus blade. Many legends abound throughout history pertaining to the wonderful quality of these remarkable blades. After years of study and research, I felt I would like to try making them.” Moran would claim that Damascus blades had better properties [5]:
No one was more surprised than I, when I found this steel did have most unusual qualities. I found these blades could be left as-quenched and still have good flexibility, they also would hold a very good edge. Indeed I am now convinced that many of the old legends concerning these blades are true. These blades were far superior to any other blade because of the hundreds of alternating layers of iron and steel. The principle is the same as plywood or the laminated bow. I am now convinced that Damascus blades stopped being made so long ago for the same reason the wonderful composite bows of the Turks died out; that reason being they were so terribly difficult to make and after the fall of the Saracen empire, man went back to the self-bow which was made from a single piece of wood. The same being true for the Damascus blade; it was so much easier to make a blade from a single piece of steel.
Moran presented his first Damascus blades at the 1973 Knifemakers’ Guild Show in Kansas City. Knifemakers and collectors alike were very impressed. Butch Winter wrote [6]: “In those days the Guild Show crowds weren’t that big. There were a few people looking at Moran’s knives but they more or less were agog and didn’t understand what he’d done. The other makers were saying, ‘I wish I could do that,’ or ‘How’d he do that?'” Moran said that pattern-welded Damascus was key to bringing back forging and making his business sustainable [7]:
[T]he first year I showed my Damascus blades in Kansas City, I took in the most money I had ever made at any one show. For the first time, it occurred to me that it just might be possible to earn a decent living making knives. However, making Damascus cut my production by about two-thirds, and as I get older, it seems that I can’t make knives as quickly as I once did, and I was never a very fast bladesmith.”
Early 1970s Moran Damascus dagger. Weyer photo.
Loveless and Knife Design
Bob Loveless first attempted making knives after reading an article about Randall knives in 1953. He tried to buy one from Abercrombie & Fitch (then a sporting goods store) but the salesperson was rude and said it would be many months to be able to purchase one. Loveless made his own knife and returned to Abercrombie to show the rude sales clerk. He found instead that the clerk had been fired, but the floor manager was impressed with his knife and began ordering dozens of them.
Loveless is perhaps best known for his unique design sense. However, early on his knives looked a lot like Randall’s [8]:
[My first knives] looked a lot like knives that Bo Randall produced. The knives all had narrow tangs, single guards, leather washer handles with finger grooves and an aluminum pommel. Looking back, there is really no comparison between what we produce now and those early knives. They might have been good, solid edged tools, but they were lacking in aesthetics. Thankfully, over the years I’ve been able to break out of that early mold and create knives that not only are functional, but also look good.
Early Loveless knives. Weyer photos.
Loveless felt that first the knife must look good, and then when the customer picks it up it has to feel good [9]:
Eye appeal is the very first thing – it has a bearing on whether or not the knife will be accepted… If it is not appealing to the eye, then the prospect won‘t pick it up. If he doesn’t pick it up – you’re lost. But for the intelligent outdoorsman, you have got to get him to pick up the knife.
A knife must feel good in a man’s hand. Whether we realize it or not, our sense of touch is very critical to us. We get a lot of our input from our fingertips … it has to feel good … since we are directing our effort to the user’s hand primarily … it’s important to the knifemaker to understand the function of the hand… The knife designer, if he’s good, realizes that the human hand defines everything from the guard on back, in his work.
Loveless believed that having real experience was important to designing his knives [10]:
Unless you’ve had field experience, you can’t make hunting knives. I see knives with cutting edges that are too thick. With blades that are too long… With awkward and ill-shaped handles. Too many knife makers don’t understand their own hand. Their knives are not user friendly. You can’t teach a guy to make a good hunting knife if he’s never been in the woods, shot a deer, and been up to his elbows in deer guts. It’s like giving a typewriter to a man who is illiterate.
Loveless’s more developed style. Weyer photo.
Loveless and Steel
Loveless saw his process as iterating and improving to develop a knife that was better than any before it [10]:
Knife making can be thought of as an endless chase after perfection in design and execution – an ongoing pursuit of better steels and materials, and, of course, of working hard enough and being lucky enough to realize the measure of success that will give us a decent living. Some of us keep at it, often working long hours into the night after the demands of a regular day job. Sometimes, it becomes too much and we drop out. Yet it keeps calling us back – perhaps later when we can afford a better shop – to try again.
Loveless did not believe in forging of blades, and performed stock removal instead [8]:
I had no idea that flat stock in the steel of my choice (Jessop 139B) was available. When I ran out of steel, I contacted the manufacturer. The woman who answered the telephone suggested that I try their flat stock. I realized right then and there that I’d forged my last knife. Her suggestion was what you might call “a light bulb moment.” When that light came on in my head, I realized that there was no point in beating a piece of round steel stock flat, when you can buy it flat already. No matter what the forging community believes, you can’t improve a piece of steel by heating and beating on it.
While Moran used very simple steels, Loveless was looking for a modern alloy that would enhance performance. Loveless had started with a high nickel steel, Jessop 139B, relatively similar to 15N20 with 2.5% nickel. He liked the steel for its high toughness and found the nickel to improve the corrosion resistance. Next he tried the high silicon shock resisting steel S5 because it had a very high toughness rating according to the steel information he managed to find. The S5 made good knives with excellent toughness and good edge holding but he had issues with sudden fractures in the knives because of the fast brine quenching specified by the datasheet [11]:
S5 has almost 2% Si and 1% Mn, and when everything went just right, we got some very fine working knives out of it. Very high toughness of course, but also very good edge holding. But it was a Brine-quenching steel, and with S5 two problems were never licked: sudden, brittle fracture during testing, and rusting that seemed to pop out of the blade before my eyes. The brittle fracture just shouldn’t have happened, and two out of three times it didn’t. But the third time, I would put knife after knife in the vise for a simple bending test, and watch the damned things bust with very small bends. I hollered at metallurgists, kicked the dog, my kids wouldn’t bring me their report cards, my internist was pulling his hair, and my Old Lady was making me eat out in the shop.
Loveless even managed to request a “special modified melt of slightly different Silico-Manganese Shock steel” [11]. But he still had issues with the knives fracturing because of the severe brine quenching [6]:
I’d end up mumbling to myself, watching the moon go down and the sun come up trying to figure out what was going wrong. Never did, either. So I have a bad taste in my mouth over this kind of steel, which has been recognized for years as the best stuff to make chisels out of…the properties of the Shock steels intrigued me, and still do. But there was the rusting, and I got tired of having to hone my knife everytime I started out hunting, so I began wondering about things like that.
Loveless made a wish list of his ideal steel and eventually found it in 154CM stainless steel, as he wrote in his 1972 catalog:
So all during those years I was building in my mind a picture of what the perfect Loveless Knife steel would be, and what it would offer: working hardness exceeding Rc 62, working ductility and toughness at that hardness, and finally rust-resistance equal to the usual Knifemaker’s 440C, which I had tried but rejected due to poor edge-holding. During the summer of 1971, I learned of a steel made by a leading Tool Steel producer in the East (Crucible). They had developed it for service in the high-temperature regions of the fan-jet engines on the 747 aircraft, and it was alloyed to hold strength at 700 deg. F. My examination of the alloying, and a study of the heat-treating procedures suggested by the maker, led me to think it might be a candidate for fine hunting knives.
I ordered a quantity of 500-lbs, which was delivered in August. Test knives were made immediately, and placed in the hands of friends here in the West and in Canada, and I began hearing from these men, all critical knife users, within two weeks, with their comments. Previously knife buyers had to make a choice when they ordered a knife. The knifemakers, this one included, could offer edge-holding, or rust-resistance, but not both qualities, in the same knife. Typically, those of us who valued field performance preferred to make our knives from one of the better medium or high-carbon Tool Steels, in the judgment that edge-holding was the main reason for the existence of the benchmade knife. But two things were immediately apparent, in the letters commenting on the new knives. First, they did hold their edge, better than did my previous alloy. And second, they didn’t rust, in normal service, even if not cleaned up right away. We had to unlearn some things, and learn some new things, in the way of Shop practice, in making these new knives. But it was soon quite apparent that we had found a new kind of steel, and that this new steel was yielding the results I had been looking for. Knives made from Grade 154CM are indeed fine working knives… Exposure to blood acids in big game stains the blade slightly, if anything, but badly-pitted blades just don’t happen, and even the staining is rare. And the cutting edge holds up better than did the older Silico-Manganese Alloy knives. Blades are put in service at a working hardness of Rc 62-64, and are quite ductile and tough at that hardness… All Loveless Knives made since September of 1971 are of this fine new steel. We have almost 300 knives in the field now, and the results have exceeded my early hopes. The 154CM Alloy has brought new and better quality to Loveless Knives, and it’s the kind of steel I had hoped to find for years.
Weyer photo.
154CM and the Japanese version ATS-34 would become a standard for stock removal makers for decades (and is still used by companies like Emerson). Knifemakers also continue to use CPM-154 and RWL-34 (The RWL stands for Robert W. Loveless). Loveless enjoyed learning about steel and metallurgy. He wrote [11] that his copy of Tool Steels by Roberts, Hamaker, and Johnson was “well-thumbed and beloved.” Loveless wrote an article about metallurgy in 1975 which wasn’t too bad (according to this PhD metallurgist) [11]:
Eight thousand words or so ago, I set out to tell you something about steel, and knifemaking. Whether I succeeded or not is up to you, and how hard you want to work at knowing the world of fine knives. You won’t learn it all from an article, and may never learn it all in one lifetime for all I can see. But that’s what makes it interesting, even challenging, and yes … fun. There’s a little more to it than you thought there was. Right?
Loveless did not believe in “secret” heat treatments, in his article about heat treating he described his process and said sarcastically [11]: “[I]f you’ve ever wondered what goes on behind closed doors at the dark of the moon get ready!” He used modern heat treating methods rather than a forge or torch. He laid out his heat treatment steps for 154CM including a furnace, a cold treatment, and multiple tempers. He summarized the process afterward [11]: “If there’s any ‘secret’ to making knives like this, I’ve given it above, and I encourage you to try for the same results.”
Tradition vs Modernism Continues to This Day
Loveless and Moran seemed to disagree in almost every possible way. However, their fundamental philosophical differences seem to come down to tradition vs modernism. Moran found inspiration in ancient blades and thought that the secrets to superior blades was in the study of those blades. Loveless felt that through iterative design improvements and the use of new steels developed by modern science that superior performance could be obtained. Of course, this is somewhat simplistic. Moran developed new techniques and designs himself, and Loveless said that his tapered tangs could be found on blades from the 1800s.
Moran would take his love for the forged blade and found the American Bladesmith Society in 1976 along with Don Hastings, Bill Bagwell, and B.R. Hughes. This organization continues to this day and has continued to have a strong influence on those that forge blades. It remains relatively uncommon for bladesmiths to forge stainless and high alloy tool steels. While it is true that those steels are more difficult to forge, this is not the only reason why they remain uncommon. After all, it is also more difficult to use these steels with stock removal techniques but they are used much more frequently by those makers. The ABS founders did not believe that new steels were better, as Bill Bagwell said [12]:
Frequently, I note in some bit of literature that so-and-so is using a fantastic jet-age steel for his blades. Frankly, just because a given steel is great when used for the turbines of jet aircraft engines doesn’t necessarily mean that it is the ultimate cutlery steel. A blade that is forged, however, is made from steel that the smith has in effect manufactured expressly for a knife, and this makes possible the toughest, strongest, most effective cutting edge possible, but at the same time this blade will be relatively easy to sharpen once it gets dull.
The ABS bylaws specified (and continue to specify) that a JS or MS stamp cannot be used on a stainless blade, even if forged [13]. They justified this rule by claiming that stainless steels are inferior [13]:
[T]he Society discourages the continuous use of stainless steel for forging blades unless and until forged stainless steel blades have been proven, to the satisfaction of the Board, capable of being forged into quality blades that will consistently pass the standard ABS cutting and bending tests.
The ABS cutting and bending tests are much easier to pass with simple carbon steels since they require a differential heat treatment, which is difficult to perform with a stainless steel because of its high “hardenability” (air cooling leads to full hardness). It isn’t even possible to pass the Journeyman Smith cutting tests with a stainless steel, as the JS cutting test says that “Only forged blades of homogenous carbon steel are allowed.” I think that san-mai and other laminated type construction are ideal for the ABS bending tests, which would work very well with stainless steels. This would also demonstrate forging skill rather than only heat treating skill. The differential heat treatment can be performed with low alloy steels that have not been forged, so they are not an indicator of forged blade performance but only heat treatment. Stainless san-mai has become much more common over the past 10-15 years (though more commonly it is stainless “sides” with a carbon steel core).
The ABS board also claimed that stainless steels do not benefit from forging like carbon steels do. I have continued to hear this claim from many bladesmiths. B.R. Hughes wrote in 1977 [14]:
440C, D2, and 154CM are all … stain resistant steels, and all three will take and retain an edge for long periods of time even under heavy usage. It was not, incidentally, feasible to attempt to forge such sophisticated steels as those mentioned in the last two paragraphs, and the [common] view that many modern cutlers take of forging may in large measure be due to the fact that a few misguided souls even tried to forge 440C and even D2 by guess and by gosh, and the results were mostly awful.
Of course there have been a few brave bladesmiths who have used stainless steel despite the heavy social pressure of the ABS to avoid it, but they have remained a small number. For those who are brave, I have an article on how to effectively heat treat stainless steels that have been forged.
Nick Rossi knives in forged AEB-L
Another big difference between now and then is that the most common stock removal steels were 440C, D2, and 154CM, as Hughes mentioned. Those steels were very different than simple carbon steels. They have much higher carbide volume and thus higher wear resistance, but toughness is limited from those carbide structures. The chromium carbides were also relatively large which also limited toughness. So these steel choices led to very different properties, on the one end were low wear resistance simple steels with good toughness and ease in sharpening, used primarily by forging bladesmiths. On the other end were steels with high wear resistance and relatively low toughness (and some complained about sharpenability), used primarily by stock removal makers. Things have changed since then, such as the rise in popularity of AEB-L. Ironically, that steel dates back to the late 1960s, before the formation of the Knifemakers Guild, but did not become common in USA custom knives until the 2010s. AEB-L was designed for razors, and it has a much finer microstructure and much higher toughness than grades like 440C, D2, and 154CM. It has a much more similar performance profile to a low alloy steel favored by forging bladesmiths. And of course there are now a wide array of powder metallurgy high alloy and stainless steels available with a wide range of properties at different levels of wear resistance, toughness, and corrosion resistance.
I do think that claims from bladesmiths about the superiority of forged blades have slowed down. It was still relatively common in the 1990s and early 2000s but I don’t see it as much anymore. From my perspective the divide between forging bladesmiths and stock removal makers is smaller than ever. I do not see as much arguing about superiority as happened decades ago. It is most common for knifemakers to choose the method that is most appealing to them without making judgments about superiority (or inferiority) of the other method. So I think that improvement should be celebrated.
More History of Knives and Steel
Did you enjoy learning some history of knifemakers and the steels that they used? Then you will love my book The Story of Knife Steel. It is full of stories direct from the mouths of knifemakers, knife company owners, and metallurgists. Learn the development of steels, how they were introduced to knives, and the development of Damascus patterns and techniques. It is available in PDF, paperback, or hardcover. It is also available as a PDF bundle along with Knife Engineering 2nd edition.
[1] Hughes, B.R. “The Knifemakers Guild: Beginnings.” Blade Magazine. August 1986.
[2] Hughes, B.R. and C. Houston Price. Master of the Forge, William F. Moran, Jr. and His Classic Blades. 1996.
[3] McEvoy, Harry K. “A living legend in modern cutlery William F. Moran, Jr.” Knife World. February 1979.
[4] Material handed out at the 1973 Knifemakers Guild Show written by Bill Moran.
[5] Moran Knives brochure 1973.
[6] Hughes, B.R. “Happy 25th, Damascus!” Blade Magazine. November 1998.
[7] Hughes, B.R. “William F. Moran Knifemaker Profile.” American Blade Magazine. April 1979.
[8] Hollis, Durwood. Knifemaking with Bob Loveless. 2010.
[9] Spangenberger, Phil. “R.W. Loveless: Leader in the Field.” Guns & Ammo Guidebook to Knives & Edged Weapons. 1974.
[10] Williams, Al and Jim Weyer. Living on the Edge: Logos of the Loveless Legend. 1992.
[11] Loveless, R.W. “Steel and Knives: A Bladesmith’s Bible.” Knife Digest. 1975.
[12] Hughes, B.R. “Interview: Bill Bagwell.” Knife World. February 1978.
[13] https://www.americanbladesmith.org/wp-content/uploads/2021/03/ABS-ByLaws-2-7-2013-Signed.pdf
[14] Hughes, B.R. “Steel.” Knife World. December 1977.
The post Moran vs Loveless – Knife Steel Edition appeared first on Knife Steel Nerds.
Video
There is a video version of the following information:
What is Buderus?
Buderus is a steel mill in Germany. They have several of their own knife steel products, including Nitro-V, Nitro-B, and Nitro-X7. They have also produced a wide range of standard grades, including 1095, 80CrV2, 15N20, and W2.
Buderus was purchased by Bohler-Uddeholm in 2005, which was then purchased by voestalpine in 2007, meaning Buderus was then owned by voestalpine (voestalpine is not supposed to be capitalized) [1]. Buderus was sold by voestlpine at the end of 2024 [2], and that process was completed in February 2025 by Mutares SE &Co. [2]. The previous owner, voestalpine, stated that they were selling Buderus because they were “concentrating its product portfolio on the technologically demanding high performance materials segment, while simultaneously reducing its share of standardized tool steel and high-grade engineering steel production, the price of which is coming under increasing pressure due to greater competition from outside Europe” [3].
At the time of the sale, Buderus had 1,100 employees and units capable of making steel from beginning to end, including melting, casting, forging, hot rolling, and cold rolling [4]. Mutares is a soulless private equity company, so of course, they did not hold on to Buderus for long. They began the process of selling the hot rolling mill and heat treat facility to GMH Gruppe in August 2025 [5]. Mutares also sold the drop forging unit to a subsidiary of itself, FerrAl United Group (no, corporate business doesn’t make sense). Mutares said this would secure 670 jobs for Buderus, and GMH Gruppe said their two units would account for 300 of those 670 employees [6].
What happened to the other ~450 employees? Those were let go because the steelworks was shut down by Mutares [7], meaning no more melting and casting of steel for Buderus. Electric steelmaking was apparently difficult to make profitable in Germany due to high energy costs [8]. We were also told that the cold rolling mill would shut down. Cold rolling allows steel to be rolled down even thinner than a hot rolling mill, and also gives a better surface finish and tolerances.
GMH Gruppe is also a steel company, so they announced [6] that the acquisition of the Buderus hot mill “closes an existing production gap … expanding product range to dimensions of up to 300 mm square. This enables access to new markets – including those beyond the traditional passenger-car combustion-engine segment.” With the steelworks shut down Buderus can continue to make steel but they will be sourcing ingots from other facilities within GMH Gruppe – these include Georgsmarienhütte GmbH, Stahlwerk Bous, Schmiedewerke Gröditz, and Pleissner Guss [6].
Will Buderus Cease Production of Knife Steel?
I contacted Buderus and asked if they would continue to offer knife steel with these changes. Christian Simon, the head of sales responded, confirming that they would continue to source ingots from the sources within GHM Gruppe listed above, also mentioning Energietechnik Essen GmbH, the company that makes Cronidur 30 (sold as LC200N by Zapp). He then added information specifically about knife steels:
“Based on our billet and strip rolling mills, we can now offer you hot strip from Wetzlar in an even broader range of materials. You can, of course, continue to obtain our popular NITRO grades from us as hot strip. And whether ingot casting, continuous casting, or ESU grades – our modern electric arc furnaces are already producing Green Steel for a sustainable future.
For the time being, Buderus Edelstahl operates under the name GMH Precision Machining GmbH. We will soon provide further information about the new Buderus Edelstahl brand within the GMH Group.”
Sven Kunzer, Managing Director, added in a separate email:
“[N]ow the things are getting clearer. We are offering our knife grades like Nitro-V, Nitro-X7 and Nitro-B as hot rolled strip.”
In other words, no longer available as cold rolled strip, but hot rolled steel will be available. Buderus metallurgist Clemens Trinks sent me a document about their new production route which confirmed that they will be offering steel as thin as 2 mm (0.079″) which is likely thin enough for the majority of applications. Though Clemens also mentioned potential limits for width depending on the grade and that is likely even more so for the very thinnest sizes. The annealing available has also changed due the restructuring, and they have now moved to open air annealing box furnaces. To remove scale they are using shot blasting.
How Are People in the Knife Industry Responding?
There is confusion in the knife industry about what exactly is happening with Buderus. New Jersey Steel Baron has been selling Buderus steel to knifemakers for many years now. Their official communication [9] about Buderus said only that Buderus is permanently closing and says that these steels will not be returning. I believe that New Jersey Steel Baron did not know that Buderus is continuing and will continue to offer knife steel. Or perhaps they were ready to move on from Buderus. NJSB is correct that Buderus has been an important supplier of knife steel in recent years. Several difficult to obtain steels like W2 were regularly available in good sizes and prices due to Buderus. Other knife steel suppliers should pick up the slack from NJSB if they decide to no longer purchase these grades from Buderus.
There is also a recent Blade Magazine article [10] that interviewed a few people in the knife industry. They seem to all be under the impression that Buderus is closing for good. So we should get the word out that Buderus is still making knife steel.
Summary and Conclusions
There were some troubling reports about Buderus going away but those were premature. The recent statements I got from Buderus employees about continuing to produce knife steels in hot rolled strip are very positive. They should be able to continue making it through the new group’s steelworks to provide ingots and slabs for hot rolling. I don’t think it should be understated just how many different knife steel grades have been produced by Buderus in recent years, and hopefully for many years in the future.
[1] https://www.voestalpine.com/specialtymetals/en/about-us/history/
[2] https://mutares.com/en/mutares-has-completed-the-acquisition-of-the-business-of-buderus-edelstahl-gmbh-from-the-voestalpine-ag/
[3] https://www.voestalpine.com/group/en/media/press-releases/2024-10-23-voestalpine-sells-buderus-edelstahl-to-mutares/
[4] https://www.buderus-steel.com/en/company/about-us/
[5] https://mutares.com/en/mutares-portfolio-company-buderus-edelstahl-has-signed-an-agreement-to-sell-two-business-units-to-gmh-gruppe/
[6] https://www.gmh-gruppe.de/en/news/acquisition-of-buderus-edelstahl-gmbh-business-units-legally-completed/
[7] https://www.marketscreener.com/news/buderus-edelstahl-to-be-broken-up-after-mutares-takeover-hundreds-of-jobs-affected-ce7c50dedd8af725
[8] https://www.ffh.de/nachrichten/hessen/mittelhessen/442556-buderus-edelstahl-in-wetzlar-das-wars.html
[9] https://newjerseysteelbaron.com/steel-signals-1-on-the-closures-of-crucible-and-buderus/
[10] https://blademag.com/knife-news/buderus-mill-closure-threatens-10xx-carbon-steel-supply-for-knifemakers
The post Buderus Steel Mill Closing? Yes, But Also No appeared first on Knife Steel Nerds.
Patreon
Research like this is made possible by Patreon supporters. That allowed me to purchase the carbide straightening hammers and perform the experiments below. Join at Patreon.com/KnifeSteelNerds if you would like to support further research.
Video
There is also a video version of the following information:
Knife Engineering 2nd Edition
The following study was included in my new book Knife Engineering 2nd Edition. Those that bought the book have already seen some of this information. There are several other studies in the book that have not been published on my website. Go buy the book to see them!
Peening
Using a carbide hammer on a piece of steel is a type of “peening.” Peening is a general term for working the surface of a material, usually by cold work. I have an older article about cold work such as cold rolling and cold forging. And a somewhat newer article where we tested the properties of 52100 after cold working. Cold work strengthens/hardens a metal or material. If you cold work an entire piece such as through cold rolling you get an increase in hardness depending on the percentage of cold work, such as we measured with 52100:
Of course if you cold work too much eventually you will introduce cracks, just like if you continue forging a piece of steel when it has gotten too cold. Peening is a form of cold work that is only applied to the surface. Perhaps the most common and best known form of peening is “shot peening” where steel shot is sprayed against the metal to cold work the surface. This is sometimes done to give a matte finish to metals but generally it is performed to enhance performance of certain parts. The cold work applied to the surface creates an “residual compressive stress.”
Image from [1]
Image from [2]
When knifemakers hear “residual stresses” they sometimes worry but these compressive stresses are not a bad thing. Residual stresses are those stresses that remain when the original force is removed, the stress remains, i.e.. “residual.” Shot peening creates a “compressive” residual stress, as opposed to tensile stress. When the surface is in compression that creates an environment where crack growth is suppressed. You can think of the compressive stress as “pushing” cracks back together rather than pulling the cracks open. So shot peening is often performed on parts that fail to “high cycle fatigue,” or cyclic loading. These are parts like crankshafts, gears, etc. that see millions of cycles and fail due to slow crack growth. Shot peened parts last through many more cycles than those that are not peened. Knives do not generally fail due to high cycle fatigue so this wouldn’t necessarily lead to improvements in knife performance. But we would not expect it to negatively affect performance either.
Image from [2]
However, there can be dangers to peening. Just as a metal can be cold worked so much that it cracks, a part can also be “overpeened” leading to surface cracks, as seen below in 1045 steel:
Image from [1]
Peen Straightening
Straightening pieces by peening has been around for over 100 years. For example, here is one illustration of how to do it from 1910:
Image from [3]
The peening is performed on the opposite side from typical forging. The peening “stretches” the worked surface which returns the piece flat. This can be done with most peening methods including shot peening. However, hammer peening has become common for knifemakers over the past decade or two. This can be performed with a carbide ball or with a chisel.
Image of carbide ball hammer and chisel from Kyle Daily
The chisel and carbide ball lead to somewhat different behavior when it comes to stretching the material. The chisel leads to more “vertical” stretching while the ball leads to even stretching around each impact:
Schematic illustration of the movement of material around a carbide ball impact on the knife. Image from Kyle Daily.
Schematic illustration of the movement of material around a chisel impact on the knife. Image from Kyle Daily.
The chisel is preferential in some ways because generally for straightening you only want material moving in the direction of the curve you are trying to straighten. However, the stress from a chisel can be more dangerous because of how concentrated it is, potentially leading to overpeening. Kyle Daily recommends using a carbide ball hammer (which he makes and sells) and he uses a method where he makes vertical lines of the carbide ball impacts to create the directionality instead.
Image of straightening a knife from Kyle Daily.
Kyle has a YouTube video where he shows his method:
Tests with Peening
I have gotten many questions from knifemakers the past few years asking if straightening by peening is leading to microcracks that are embrittling the steel. As described above, peening, does not mean cracks are forming. It is a cold work process, and as long as the steel is not overly cold-worked there are no negative effects on properties. To test this, I used a carbide ball straightening hammer on some toughness coupons of heat treated MagnaCut. For one condition, I hit the pieces in many places before grinding and finishing both sides (the peened surface was removed). On the other coupon I ground and finished the coupons first and then I hit it many times with the straightening hammer after. With these three different conditions (with three samples of each condition) I measured the impact toughness. This test measures the energy required for breaking the steel. So if there were any pre-existing cracks we would expect to see a reduction in the measured impact toughness. The results in comparison with samples that saw no carbide hammer blows are shown below:
All of the specimens performed very similarly to each other. The one that was straightened after finishing did have slightly higher toughness. I am not sure if this is due to improvement from the peening or if it is just from statistical variability from testing. It isn’t impossible that the surface peening did help a little bit but the improvement was small in either case.
Dangers of Peen Straightening
While my tests showed no negative effect of hammer peening, there are still dangers to the practice. A knifemaker previously sent me a knife that had a crack in the handle. When the handle scales were removed it was found that the crack had initiated within the peening dimples:
It is a bit hard to tell in the pictures but these were relatively deep peening marks. It appears that this steel was “over peened” and thus cracks were formed in the surface of the steel and grew from there.
Summary
Peening is a surface cold working process to create a residual compressive stress in the surface. A compressive residual stress can be beneficial, especially in parts that fail to high cycle fatigue (knives do not generally fail in this way). Peening is an effective way to straighten thin curved pieces of metal, such as warped steel knives. Peening does not negatively affect steel when done properly. However, cracks can be formed if the steel is “over peened.”
[1] Maleki, Erfan, Okan Unal, and Auezhan Amanov. “Novel experimental methods for the determination of the boundaries between conventional, severe and over shot peening processes.” Surfaces and Interfaces 13 (2018): 233-254.
[2] https://www.amtechinternational.com/shot-peening-benefits-gears/
[3] Smith, Robert Henry. Text-book of advanced machine work: prepared for students in technical, manual training, and trade schools, and for the apprentice and the machinist in the shop. Industrial education book Company, 1910.
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New video with Q&A! If you want to ask questions for Q&A videos come join us at Patreon.com/KnifeSteelNerds
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11/18/2025: I added that the book is now available in South Africa from SD Knives & Supplies.
Links to buy are at the bottom of the article!
Video
Knife Engineering
In recent years, I have been mostly known as the “MagnaCut man,” but before MagnaCut, my biggest success was probably with Knife Engineering. When I started my website, Knife Steel Nerds, I hadn’t thought about writing a book because I thought I was doing a website instead. But I soon realized that a website works better for individual articles than it does for introducing an entire subject. So that led me to writing the book Knife Engineering: Steel, Heat Treating, and Geometry. That allowed people to learn the subject in order with all of the appropriate introductory material. The book has been a big success with many copies sold and many rave reviews from knifemakers and knife buyers alike. I tried very hard to make the subject as easy to understand as possible, and so it has been gratifying to hear people say that the book was exactly that.
The Second Edition
So why a second edition? There are a lot of reasons:
1. Since the first edition, I have tried to do as many experiments as possible in areas that I only had prior scientific journal articles to reference for those subjects. These included studies I performed on thermal cycling of both carbon and stainless steels, comparing different types of quench oils, and the performance of Damascus steels. There is an extra chapter in the second edition from one of these studies, all about forge heat treating. I always learn new things by conducting experiments for myself, and of course, I can test knife steels that are currently popular among knifemakers and knife companies. This significantly improved those sections of the book as the data was more directly applicable, and I could compare different types of heat treatments to give better recommendations.
2. One thing that surprised me a bit was that many knifemakers bought Knife Engineering just to see the heat treatment recommendations in the book. So I improved that section by including recommended forging, normalizing, and annealing temperatures for each. Before, those temperatures were only found for select steels in other parts of the book. I also updated each recommendation with whatever new testing I had done since the first edition. The new recommendations section also has its own table of contents with all of the steels listed.
3. New formats and wider availability – since the first edition was published I now have the option of printing the book in hardcover. I have seen some very tattered looking paperbacks of Knife Engineering! I also am publishing a PDF digital copy to Payhip. So the book will be available in paperback, hardcover, and PDF. The PDF edition also means that the book is available anywhere in the world. Before if you were in a country where print on demand was not available the book could be costly to import.
4. There are also many miscellaneous figures and experiments sprinkled throughout the book that make it significantly better when it comes to supporting information. It would be a bit tedious to list them all, but several of them haven’t even appeared on my website. In the first edition I restricted my own heat treating experiments primarily to a later chapter called “Practical Aspects of Heat Treating.” I moved most of those into the relevant chapters including many new experiments – annealing, austenitizing, tempering, etc. That way the new stuff is incorporated into the book and also the reader can learn about it within the chapter rather than a disconnected place later in the book. Overall the text is about 15% longer in terms of word count.
5. An index – the most requested missing thing from the first edition was an index. This was surprisingly painful to make. I had to double-check each page number, and it took forever. I think this is like smoking a pack of cigarettes, where each one removes 28 minutes off the end of your life. That definitely happened when I double-checked the index.
6. Improved formatting – I learned a lot about formatting books while working on my other book, The Story of Knife Steel: Innovators Behind Modern Damascus and Super Steels. There is a lot of extra white space in the first edition, and I wanted to make it look more professional. There are a bunch of charts and figures that look washed out, and so I redid them all to give them more contrast.
7. References – the first edition has the references I used at the end, but I did not include reference numbers within the text. This was a decision I made to improve the flow of the book and so as to not scare away general readers. But I regretted it almost immediately. Readers wouldn’t know which references are backing up which points, so figuring out which to read would be very difficult. I also knew that adding them back in would be way more work than including them in the first place. The references are small “superscript” numbers and I don’t think they have affected the flow of the book at all.
How to Buy
I spent 18 months working on the second edition. I thought it would take me a few weeks and get it knocked out. But it turns out making a new edition of a book is nearly as much work as writing a whole new one. Sometimes it felt like more! So I am excited for people to read it and hear what they think about the new and improved book.
Here are links to buy:
Worldwide
PDF: https://payhip.com/b/98jgz
There is also an available PDF bundle for $10 off if you get both Knife Engineering and The Story of Knife Steel: https://payhip.com/b/XFyLU
I have not put any DRM or anything on the PDF. There is a tiny watermark at the top of the page that gives an order and name so that if the PDF is distributed we know who did it. Please don’t steal the book.
United States
Paperback: https://www.amazon.com/dp/B0FYWBPFWF
Hardcover: https://www.amazon.com/dp/B0FYW8DRGX/
If you don’t see your country below I recommend the PDF.
South Africa: Paperback
United Kingdom: Paperback, Hardcover
Netherlands: Paperback, Hardcover
Japan: Paperback
Australia: Paperback
Comparisons
The hardcover is definitely my favorite version. I’m glad that is an option now. The PDF is great if you have an iPad or can’t get the book in your country.
If you never got a copy of The Story of Knife Steel make sure you get one of those as well!
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We traveled to Nevada to visit my dad, Devin Thomas, and make some Damascus with Pop’s ProCut. Along the way we saw some sites around my hometown and my wife tries to prove that her town is better.
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Patreon
Thank you Patreon supporters! Through Patreon support I was able to pay for metallography and for the consumables for making coupons and running the CATRA experiment. If you want to support more knife steel research please join us at Patreon.com/KnifeSteelNerds
Video
Here is the video version of the following information:
What is Tamahagane?
Tamahagane is the name used in Japan for steel made with their centuries-old process. There are several videos available online to see the process such as this one. It starts with “iron sand” which is a naturally occurring form of iron mostly composed of magnetite, Fe3O4, though can also contain some hematite (Fe2O3) and other constituents like quartz and titanium dioxide [1]. One nice thing about magnetite (as the name suggests) is that it is magnetic, so it can be relatively easily separated from other minerals with magnets. The iron sand is then “smelted,” which is the process of reducing the oxide ore to the base metal, in this case, iron. The smelting is performed in a traditional furnace called a tatara. A clay tub is used which is layered with charcoal and the iron sand [2]. The charcoal acts as a reducing agent to turn the magnetite into iron, and also is a carbon source to turn the iron into steel (steel is iron plus carbon). The charcoal reduces the steel because carbon monoxide and carbon dioxide forms when it burns in air. The carbon monoxide (CO) reduces the magnetite to iron [3]. At the end the clay vessel is broken and the tamahagane is removed, which is in the form of rough and porous sponge-like pieces that also contains slag (large undesirable inclusions). The swordsmith separates pieces by “grade” which corresponds to the approximate content [4]. The grade is determined by color and also the fracture appearance [4]. The swordsmith then forges the pieces gently, and then folds and forge-welds them multiple times to eliminate porosity, remove some slag, even out the carbon content, and break up inclusions and impurities.
The “sponge-like” pieces of tamahagane after smelting. Picture from Wikipedia.
Soo all of that describes the manufacturing process. Ultimately tamahagane is a simple carbon steel. It is even simpler than a typical carbon steel like 1095 or White #1, because it is lacking intentional additions to those steels of manganese and silicon. So the steel has carbon of some content (described next) and then only trace amounts of other elements.
While there are a few individual swordsmiths that make their own tamahagane, most of the tamahagane produced in Japan comes from Nittoho tatara in Shiname Prefecture, the last of its kind. All tamahagane production had ceased by World War II. But this facility was restarted in 1977 and continues to produce the traditional steel for Japanese swordsmiths.
Published Tests of Tamahagane
Carbon Content and Composition
The cutting edge of Japanese swords has typically been found to be around 0.5-0.8% carbon [2, 5-9]. However, there are different types of construction used in Japanese swords, such as the “kobuse” method that uses a low carbon core and a higher carbon sides and cutting edge. Thus, the low-carbon pieces of tamahagane can be used in these low-carbon portions, giving the blades greater ductility and reducing the chance of catastrophic breakage. Measurements of the core carbon content have returned values between 0.01% [7-8] and 0.2% [2]. Sometimes steel with a carbon content in between these two extremes is used on the sides [2,7-8].
Schematic of “kobuse” construction from [3]
However, the carbon content is not always perfectly distributed throughout. Analysis of a modern kogatana knife (utility knife) produced by Sadanao Mikami had a range of carbon from 0.6% on one end to 2.0% on the other [5-6]. The uneven carbon content can come from distributions within the original pieces, mixing of low carbon and high carbon pieces (often done intentionally), and performing an insufficient number of forge-folding operations to even out the carbon. They reported that the average carbon content was 1.03% for the entire knife [5]. There were also small amounts of other elements:
Composition of modern kogatana by Sadanao Mikami [5]
Microstructure and Hardness
Japanese swords are produced to have a “hamon,” a visible line that distinguishes between a soft spine and the hard cutting edge. Thick clay is applied to the blades at the spine to slow the quench rate so that it does not harden. The hard phase at the edge is martensite, and the soft phase is pearlite. At the hamon transition, there is a combination of martensite and pearlite. The low carbon core contains large amounts of soft ferrite. The pearlite content of the core is determined by the carbon content, more carbon means more pearlite.
Images of microstructure from a “modern” sword (1945) and an “old” sword (~600 years old) at different locations [9]
Micrographs of a ~600 year old sword [7]
Studies on the hardness of Japanese swords correspond to these differences in microstructure and carbon content. Typically, the hardness at the edge is between 600-900 HV [2,3, 5,7, 9] and the spine is between 100-300 HV [2, 3, 7, 9]. This corresponds to about 55-67 Rc at the edge and 0-30 Rc at the spine (Note: Rockwell C hardness only reliably goes down to 20).
Microhardness values of ~600 year old sword [7]
Microhardness of a “Koto” style Japanese blade (before 1596 AD) [3]
Microhardness from the 1945 and 600 year old swords [9].
Impurities, Inclusions, Forge Welding, and Folding
A study was performed along with swordsmith Sadanao Mikami on the effect of forging and folding on impurities and inclusions in tamahagane [10]. The process is shown in the figure below:
The forge welding and folding process used in Ref. [10]
The swordsmith started by hammering chunks of tamahagane into sheets, then cutting those sheets into chips. The chips are sorted by carbon content by hitting them with a hammer. High carbon chips break and low carbon chips don’t. The low carbon chips were stacked together and forged together into a bar, then cut and restacked six times (A1-A6); this was repeated with the high carbon chips (B1-B6). Then the low and high carbon bars were stacked together and forge welded together, followed by cutting, restacking, and forge welding six more times (C1-C6). The microstructure became more evenly distributed through the forge welding process as the carbon content became more equalized, as shown in the following images:
Microstructure evolution of tamahagane after forge-folding operations [10]
One common claim of folding and forge welding is the elimination of inclusions, oxides and slag that are present in the original tamahagane pieces. The researchers found that while bands of FeO were present in A1 and B1 from oxides present in the original pieces, they were not found in A6 or B6. In other words, the FeO bands were eliminated by further forging and forge welding. They were originally present in bands from forge welding flat pieces together. They also found silica (SiO2) and Fayalite (Fe2SiO4) inclusions in the steel. The silica particles were less than 1 micron and the Fayalite inclusions were 16-20 microns in length in the A1 and B1 samples. The thickness of the Fayalite bands was significantly smaller than the FeO, about two microns.
Iron oxide bands forge welded into tamahagane during initial forge welding
The Fayalite was reduced from 16-20 microns long in the A1/B1 specimens to 14-15 microns in the A6/B6 specimens. These were further reduced to 13.1 microns in the C1 specimens and down to only 8.2 microns in the C6 specimens. So while forge welding and folding did not significantly reduce the volume fraction of Fayalite inclusions, they were reduced in size, more isotropic (round), and more evenly distributed after that process.
Inclusions in tamahagane steel in the C1 condition (one forge weld of low and high carbon steel), left, and after six folding and forge welding operations, right [10]
In a study on a kogatana knife produced by Sadanao Mikami had relatively homogenous oxide inclusions in the size range of 5-10 microns [5]. They reported a volume of 4-7% inclusions.
Oxide inclusions in modern tamahagane knife [5]
Analysis of a ~600 year old sword [7] found an inclusion content of 0.8-1.9%, which they found to be much higher than the content in a modern production steel (labeled “ordinary steel”).
Volume percent of inclusions in ancient sword vs modern steel [7]
Micrographs of inclusions in ancient sword [7]
Analysis of another ancient sword found an inclusion volume of 1.1% [3]. The authors claimed that this inclusion content is low enough to avoid a “significant reduction in its toughness.”
Inclusions in pre-1596 AD sword (cross-hair scratch added intentionally) [3]
Strength and Toughness
Tensile tests of a sword by swordsmith T. Takaichi were performed and compared with a conventional carbon steel with similar carbon content of 0.55% C [2]. They found that in testing of the steel before heat treating that the conventional steel (S55C) had greater utility than the tamahagane sword steel (S1). When observing the fracture surfaces, they found oxides in the tamahagane and they speculated that it was these oxides that led to the lower ductility.
Stress-strain curves and fracture appearance of tamahagane sword steel (S1) and conventional steel (S55C) [2]
In tests of a ~600 year old sword and a 1945 sword, they measured the strength and ductility of the swords with a 4-point bending test [8-9].
4-point bend test of tamahagane swords [9]
They found the ancient sword to form a crack at around 0.88 ton-force, but the blade did not fully break and continued bending until final fracture. The 1945 sword broke at 2.62 ton-force and did not have the load drop from cracking that the ancient sword had. They calculated the bending strength of the swords as 2552 MPa for the ancient sword and 4645 MPa for the 1945 sword. They claimed that these results are “in a range of performance tool steel” [8]. The hardness of the cutting edges were similar in the two swords. Instead, they said the difference in measured strength was because the 1945 sword had a 5 mm hardened area while the ancient sword had only 1 mm of hardened area (see earlier microhardness charts).
I didn’t find much other toughness testing of tamahagane so comparisons between this traditional steel and modern carbon steels are in short supply. I found one study of miniature charpy specimens taken from a Japanese sword [11], but they did not compare with similar tool steels. Furthermore, the values at the edge of the knife where we would probably be more interested were essentially zero:
Image taken from [11]
Effect of Carbon Content on Final Properties
While there seems to be a consensus that the cutting edges of tamahagane Japanese swords are in the range of 0.5-0.8% carbon or so, I am not sure if the carbon content was and is that consistent. There was the one study on the tamahagane knife where they found carbon values as high as 2% within the same knife that read 0.6% in other locations [6]. I also found a study on different iron sand use at the Nittoho tatara (the last major facility remaining), and found that they had moved to a different source of sand that resulted in higher carbon and lower impurities [4]. So I think there is reason to believe that carbon content of tamahagane has gone up in recent decades.
The carbon content is very important to steel properties. One of the best known is the effect of carbon on the resulting as-quenched hardness. The higher the carbon content, the higher the hardness, though it levels out around 0.6% carbon:
Image from [12]
Carbon has an equally strong effect on impact toughness, even when tested at the same hardness for different low alloy tool steels:
Higher carbon also gives steel more iron carbide (cementite) which gives it greater wear resistance. This can give knives greater edge retention because edge wear is slowed. However, for a sword this wear resistance is not really beneficial, and toughness is a much more important property. So the 0.5-0.7% range of carbon would be about optimal for a sword, given the high combination of hardness/strength and toughness that you get from this microstructure. But for smaller knives, kitchen knives, etc made with tamahagane higher carbon could be beneficial for wear resistance.
1.25%C steel with significant carbide content (white particles)
0.6%C steel with almost no visible carbide
My Tamahagane for Testing
I recently went to Japan and took a class from Yuya Nakanishi, also called Masahiro. You can watch a video of our trip to Japan and making the “kogatana” (a utility knife). We took home our two knives that we made with him. However, I also wanted to test the steel for toughness which would be difficult with just the knife, as the standard toughness test uses rectangles. So I asked him if I could have a piece for toughness testing and he let me have one. This piece had already been through the forge welding and folding process. I also asked him what temperatures to use for heat treating and he told me 780°C for austenitizing and 180°C for tempering. I normalized and annealed the piece first, and followed his recommendations by austenitizing for 10 minutes, quenching in water, and tempering twice for one hour at each time.
Image from https://morinokyoto.jp/masahiro_en/
Carbon Content
I measured the broken toughness specimen with LECO combustion for carbon and sulfur content and got 1.06% carbon and 0.001% sulfur. This carbon content puts it into a range similar to White #2 (1.05-1.15%C). This is a good range for a utility knife, though as explained above would be on the high side for a sword. I am not sure if this is because Masahiro intentionally used higher carbon tamahagane for these smaller knives, or if it is due to carbon fluctuations, or higher carbon tamahagane being made at the Nittoho tatara. If I hear back from Masahiro I will update the article. This is very close to the carbon content in the kogatana by Mikami of 1.03% [5], which perhaps provides evidence that the carbon content of tamahagane has increased from older blades. I wasn’t able to measure other elements because of the size of the steel that I had.
Micrographs
The carbide structure looks consistent with the measured carbon content of 1.05%. It has a significant amount of small and evenly distributed carbides, but a smaller volume than the higher carbon 26C3. It looks closer to O1 and 52100, though the carbides are even finer in the tamahagane.
Micrograph of the heat treated tamahagane
O1 steel
52100 steel
Looking at a lower magnification micrograph, the carbide structure appears relatively consistent throughout. There are no visible layers from the forge-folding process. There is a “bright spot” in the upper left portion of the image. Higher magnification reveals that this is not carbide clusters but either an etching artifact or retained austenite.
Lower magnification of tamahagane
Impurities and Inclusions
The inclusion content of the tamahagane provided to me is very low, lower than reported inclusion contents in the journal articles that I cited. Using threshold measurements I estimate the inclusion content to be around 0.1%. I am not sure why this steel is so much “cleaner” than those analyzed in the other studies.
Polished (unetched) surface of tamahagane. Black particles are inclusions.
There is a small amount of orange, square/rectangular particles in the steel. These are likely titanium nitride (TiN) as these particles are typically yellow/orange and angular [13]. Iron sand typically has TiO2 in it [1], and the Mikami blade had 0.03% Ti in it [5], so the presence of TiN is not entirely unexpected. Titanium and nitrogen have a strong affinity for each other, and these particles are often found in steels with small titanium additions.
Titanium nitride particles (TiN)
Hardness
The hardness of my toughness coupon was 64.6 Rc. This is relatively high in hardness, maybe even a bit high for a utility knife. However, it is within a reasonable range, and would provide very good cutting and edge retention. This lines up closely with tempering of other simple high carbon steels, such as 1.25% carbon steel 26C3, shown below. The 26C3 is somewhat lower in hardness, though this steel was tempered in another oven. My furnace is very good at maintaining a consistent temperature during tempering, so “overshooting” is less common.
I am not able to measure the hardness of the edge of the knife that I made at Masahiro Tantojo, as it is only hardened at the edge. It would require cutting it apart and using microhardness measurements to see. Since the knife was tempered by eye by the swordsmith it could be significantly different in hardness. The tempering was performed for a very short period, until it reached a temperature where water would sizzle when he touched the blade. My guess is that it is higher in hardness, somewhere between 65-67 Rc. However, if the carbon content is significantly lower in the blade it is possible that it would also be lower in hardness.
Toughness
Given the relatively high hardness of 64.6 Rc, the toughness was not chart topping. I measured 5.8 ft-lbs. However, this is a relatively high value for that level of hardness, as you can see when compared against other low alloy steels here:
As you can see the toughness falls right on the same line as 26C3 (green line in the upper image). So the tamahagane appears to be behaving similarly to conventionally produced low alloy high carbon steels. Overall I think this is a good result considering that some studies I cited before showed a potential reduction in toughness from oxides.
Edge Retention
Comparing the edge retention is a bit tricky since the kogatana design is different than the standard test knife that I use for CATRA testing. This knife is thinner behind the edge, about 0.010″ (0.25 mm) after sharpening, while our test knives are around 0.015″. This gives the thinner knife an advantage for a given edge angle, as shown in this earlier study on 154CM steel:
There is also the complication that I do not know the hardness of the kogatana knife, my guess is it is in the range of 65-67 Rc. When I tested it with CATRA I got 370 mm, which would also lend credence to the hypothesis that it is on the upper end of hardness.
There aren’t many low-alloy steels I have tested that would be in that hardness range. The light grey dotted lines show the approximate relationship between hardness and edge retention. So you will notice that the tamahagane is on the same line as most of the other low alloy steels, especially after accounting for the knife being thinner behind the edge. This is not too surprising given that most of the low alloy and carbon steels have tested in a similar range after accounting for hardness.
Tim Zowada Information
Tim is a bladesmith who makes his own bloomery steel using iron sand from Lake Superior. He was an author on one of the cited papers above along with Dr. John Verhoeven. He had the following comments after reading my report:
Here are a couple things that might be helpful. In general:
1. The final carbon content is determined by the average initial carbon content and the number of folds. More folds decrease the carbon content. The outside of the billet will decarburize during forging. That decarb layer is folded in with each weld, decreasing the average carbon content. Plus, the oxidation of the billet (scale) will decrease the overall size of the billet during all the folding and welding. For high quality steel, the typical number of of folds will be between 10 and 15. It ends up being a balancing act based on experience. Yoshindo Yoshihara prefers about 0.7% carbon for his swords. His brother prefers 0.6%. Maybe I have that backwards. The Art of the Japanese Sword (Yoshihara) is an excellent book that you should own. I’m not sure why the carbon content varied so much in your blade. My best guess is a low number of folds. A quick nital or ferric chloride etch would tell. You would be able to see lighter and darker bands of varying carbon content. Typically, the carbon content is pretty much homogeneous through the bar by about eight folds.
2. High hardness and low abrasion resistance is an advantage for my straight razor work. At 65 HRC, the blades hold up very well against whiskers. But, with the low abrasion resistance, a clean leather strop will remove enough metal to keep them sharp. They don’t need to go to the stones very often.
3. Like many things, the final carbon content and quality of the steel will vary from smith to smith, and batch to batch. I think what you got was a good representation of high carbon (1.0%) tamahagane.
Summary and Conclusions
Reviewing the prior studies on tamahagane, researchers of this material have been pretty realistic about its properties. At its best, tamahagane performs like other simple carbon steels. The potential for higher oxide inclusion content potentially limits its toughness, though in my own experiments it was roughly in line with the toughness you would expect for a steel made with modern methods. It is very interesting to learn about traditional methods for making steel and how they compare to the more advanced methods that we have developed since.
[1] Tanii, Hiroshi, Tadahiro Inazumi, and Keiichi Terashima. “Mineralogical study of iron sand with different metallurgical characteristic to smelting with use of Japanese classic iron-making furnace “Tatara”.” ISIJ international 54, no. 5 (2014): 1044-1050.
[2] Okayasu, Mitsuhiro, H. Sakai, and T. Tanaka. “Mechanical Properties of Samurai Swords (Carbon Steel) Made Using a Traditional Steelmaking Technology (tatara).” Journal of Material Sciences & Engineering 4, no. 2 (2015): 1-6.
[3] Verhoeven, J. D., and Tim Zowada. “Comparison of Two Swords of Antiquity: The Japanese Sword and the Muslim Crucible Damascus Sword.” Metallography, Microstructure, and Analysis 12, no. 6 (2023): 934-943.
[4] SUZUKI, Takuo, and Kazuhiro NAGATA. “Effect of the charge of” Komori” iron sand on the properties of” Tamahagane” steel produced by” Tatara” operation.” Tetsu-to-hagané 85, no. 12 (1999): 911-916.
[5] Das, Ananda Kumar, Takuya Ohba, Shigekazu Morito, and Muneo Yaso. “Evidence of Lath Martensite in High-C Japanese Sword Produced from Tamahagane Steel by Tatara Process.” In Materials Science Forum, vol. 654, pp. 138-141. Trans Tech Publications Ltd, 2010.
[6] Matsumoto, Chihiro, Ananda Kumar Das, Takuya Ohba, Shigekazu Morito, Taisuke Hayashi, and Go Takami. “Characteristics of Japanese sword produced from tatara steel.” Journal of Alloys and Compounds 577 (2013): S673-S677.
[7] Yaso, Muneo, Toshifumi Takaiwa, Yoshihiro Minagi, Kunichika Kubota, Shigekazu Morito, Takuya Ohba, and A. K. Das. “Study of microstructures on cross section of JAPANESE SWORD.” In European Symposium on Martensitic Transformations, p. 07018. EDP Sciences, 2009.
[8] Yaso, Muneo, Yoshihiro Minagi, Toshifumi Takaiwa, Kunichika Kubota, Tsuyoshi Kanaizumi, Takuya Ohba, Shigekazu Morito, and Taisuke Hayashi. “Study of Metallurgy and Mechanical Property on Japanese Sword.” In Materials Science Forum, vol. 738, pp. 222-227. Trans Tech Publications Ltd, 2013.
[9] Yaso, Muneo, Toshifumi Takaiwa, Yoshihiro Minagi, Tsuyoshi Kanaizumi, Kunichika Kubota, Taisuke Hayashi, Shigekazu Morito, and Takuya Ohba. “Study of Japanese sword from a viewpoint of steel strength.” Journal of Alloys and Compounds 577 (2013): S690-S694.
[10] Takami, Go, Takuya Ohba, Shigekazu Morito, and Ananda Kumar Das. “Microstructural observation on materials of the japanese sword under fold-forging process.” In Materials Science Forum, vol. 654, pp. 134-137. Trans Tech Publications Ltd, 2010.
[11] Misawa, Toshihei, and Shin-Ichi Komazaki. “Ductile-brittel transition evaluation of Japanese sword and weld metals using miniaturized impact specimens.” In European Structural Integrity Society, vol. 30, pp. 119-125. Elsevier, 2002.
[12] Krauss, George. “Martensitic transformation, structure and properties in hardenable steels.” Metallurgical Society AIME,(1978): 229-248.
[13] Descotes, Vincent, Thibault Quatravaux, Jean-Pierre Bellot, Sylvain Witzke, and Alain Jardy. “Titanium nitride (TiN) germination and growth during vacuum arc remelting of a maraging steel.” Metals 10, no. 4 (2020): 541.
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Video
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Misunderstandings about Hardness and Corrosion Resistance of MagnaCut
I have been seeing a disturbing number of comments around the internet saying something like the following: “Larrin says that 60 Rc MagnaCut has better corrosion resistance than 64 Rc MagnaCut, so there are different hardness levels for different applications.” I have never said such a thing. It is true that there are different levels of hardness for various applications, but hardness does not dictate corrosion resistance; therefore, it is not one of the parameters by which they would make this decision. I have a video where I have talked about the pros and cons of higher and lower hardness. How you heat treat a given steel can affect its corrosion resistance but a whole range of hardness values can be achieved with both good or bad heat treatments. I will give a variety of examples for this. A separate but related topic is about how hard different steels can be heat treated to when related to their corrosion resistance. For example, the very corrosion resistant Vanax and LC200N top out around 59-61 Rc. I will explain why they don’t get any harder and why this is partially due to those steels having very high corrosion resistance.
Chromium and Corrosion Resistance
When iron is in a corrosive environment it forms rust – an iron oxide. If you add chromium to iron, the corrosion resistance is increased the more chromium you add. The chromium forms with oxygen to make a passive film at the surface which prevents rust from forming:
The following chart shows an old classic study [1] of corrosion rate of steel in high humidity environments. You will see that the corrosion rate went down with increasing chromium until about 12% Cr. Sometimes the cutoff for a steel being “stainless” is given as 10.5, 11, or 12% chromium. There isn’t any real agreement as far as I can tell. But corrosion resistance will increase with even greater amounts of chromium; it isn’t an on/off after some arbitrary cutoff.
Data adapted from [1]
Heat Treating and Corrosion Resistance
In the annealed (soft) state stainless steel is not yet stainless. When a knifemaker or manufacturer receives steel it is in this annealed condition so it is easy to drill, grind, machine, etc. Most of the chromium is in the form of carbides in the steel. When the chromium is tied up with carbon as a carbide it cannot form the chromium oxide layer at the surface.
There are three major steps to heat treating: austenitizing, quenching, and tempering.
Austenitizing
During austenitizing the steel is heated up to a high temperature and then held, allowing the chromium carbides to be dissolved (or partially dissolved) to put more chromium in solution so that the chromium oxide passive layer can be formed. Below shows the increase in chromium vs austenitizing temperature for Elmax and Vanax:
So one of the key variables for corrosion resistance is the austenitizing temperature because heating it hotter means more chromium in solution. However, the amount of chromium in solution is also controlled in part by the composition. The chromium in solution for Elmax at a very high temperature of 2200°F (the datasheet recommends no higher than 2010°F) is still below Vanax when it is austenitized at 1800°F (well below what the datasheet recommends). Austenitizing at a higher temperature also leads to increased hardness, so in that way higher hardness can sometimes mean improved corrosion resistance.
Quenching
During quenching the steel is rapidly cooled to form the hard phase of steel, martensite. Martensite formation is controlled by temperature rather than time. There is a “martensite start” temperature and a “martensite finish” temperature. In some cases martensite finish can be below room temperature and in that case the steel does not fully transform, meaning some austenite remains in the steel. This is called “retained” austenite. If there is too much retained austenite the hardness is reduced in the steel, and also the edge performance is bad and the knife would be very difficult to sharpen. One of the major factors for martensite start (Ms) and martensite finish (Mf) temperatures is the carbon content, as shown in the chart below.
With higher austenitizing temperatures and more carbide being dissolved, this does not only put more chromium in solution but also more carbon, as seen in this chart of Vanax and Elmax. Or in the case of Vanax, I included the carbon and nitrogen, since nitrogen also contributes to hardness in a similar fashion to carbon.
All of the above happens as long as the quench is sufficiently fast to avoid other competing transformations that will occur with slow cooling. Carbides can precipitate during slow cooling which would also reduce corrosion resistance. This can happen with the relatively common gas quenches that are used in large vacuum furnaces by many knife manufacturers. I covered this in a previous article/video about custom vs production heat treating.
Cryo and Cold Processing
You will notice that the Vanax hardness dropped at 2025°F while the Elmax hardness increased all the way up to 2150°F. These heat treatments included a cryo step in liquid nitrogen after the quench. If cryo had not been used the Vanax would have seen a drop below 2025°F and the maximum hardness would not have been as high. The Elmax likely also would have seen a hardness drop in this tested range. As an example, the following chart shows AEB-L steel when quenched to room temperature vs placed in a freezer or in liquid nitrogen:
AEB-L steel vs austenitizing temperature
The AEB-L achieved its peak hardness around 1975-2000°F just like the Vanax and then dropped in hardness with further increases in austenitizing temperature. It reached a max hardness of around 64 Rc, though when no cold treatment was used it maxed out around 62 Rc. The reason for the drop in hardness above a certain temperature is because of retained austenite. In other words, the martensite finish temperature was below room temperature. Using liquid nitrogen after the quench means cooling the steel to a lower temperature getting closer to martensite finish. However, some retained austenite will stabilize and not be transformed even with the very low temperatures of liquid nitrogen, which is why the hardness still drops with an austenitizing temperature that is too high.
So the use of cryo can allow both higher hardness and corrosion resistance if the austenitizing temperature is increased. For a fixed austenitizing temperature, typically there is a 1-2 Rc increase but the corrosion resistance would not be affected.
Tempering
After quenching, steel is tempered to improve its toughness. The tradeoff is that hardness is also reduced through tempering. Below shows a tempering chart for MagnaCut with different austenitizing temperatures.
Different austenitizing-tempering combinations can be used to achieve the same level of hardness. For example, to achieve ~60 Rc, you could use 1950°F and 300°F, 2000°F and 400°F, or 2100°F and 500°F. Because the higher austenitizing temperature potentially means more chromium in solution we would expect the 2100°F and 500°F combination to achieve the best corrosion resistance for that hardness. A unique aspect of MagnaCut is that all of its chromium carbide is dissolved around 2050°F, as shown in the chart below. So if instead we were heat treating to ~63 Rc, 2050°F and 300°F, 2150°F and 400°F, and 2200°F and 450°F would all have approximately equal corrosion resistance. So austenitizing above 2050°F still leads to an increase in hardness for a fixed tempering temperature but the corrosion resistance would be unaffected.
There is an important aspect to tempering and corrosion when it comes to a different regime of tempering, however. Stainless steels and other high alloy steels see a bump in hardness by tempering above about 750°F, as shown in the following chart for Elmax:
You can see that the hardness sees a peak with tempering around 500°C (930°F). This increase in hardness comes from precipitation of small chromium, molybdenum, tungsten, and vanadium carbides. Because chromium is coming out of solution as a chromium carbide this “secondary hardening” also leads to a decrease in corrosion resistance. Below shows Vanax steel that I tested with a 1% saltwater spray test for 24 hours where one was tempered at 400°F and the other was tempered at 1000°F. The 400°F temper Vanax showed no corrosion while the 1000°F temper led to significant rusting.
Vanax tempered at 400°F (left) or 1000°F (right) before a 1% saltwater spray test
It is relatively common for knifemakers and knife manufacturers to temper at 950-1000°F. They do this for several reasons, though the main one is that the higher tempering temperature means the steel is less sensitive to overheating. This allows them to apply certain coatings to steel (that require higher temperatures to apply than a typical “low” temper of 400°F). It also means they don’t have to be as careful with grinding because the steel can be heated up much higher before approaching the tempering temperature (where the steel would soften).
The high tempering temperature can be used with many stainless steels to achieve similar levels of hardness as the low tempering temperature. In other words, you can have two knives at 60 Rc, 62 Rc, etc. with very different corrosion resistance depending on whether they tempered in the low range or the high range.
Hardness vs Corrosion Resistance for Different Steels
So after all of that we can return to our discussion of what makes one steel more corrosion resistant than another. Below shows Vanax and Elmax after a 1% saltwater spray test for 72 hours:
The Elmax rusted while the Vanax did not. Both were austenitized at 1975°F which is the recommended temperature for both steels according to their datasheets, and both were given a temper in the low range (400°F). As shown in the earlier chart, the difference in corrosion behavior is primarily due to higher chromium in solution for Vanax, which would roughly be 11.5% for Elmax and 14.5% for Vanax. As seen in the hardness chart, Vanax would actually be a bit harder than Elmax for this identical heat treatment. However, Elmax can be austenitized at higher temperature and achieve significantly higher hardness than Vanax which reaches its maximum around 61 Rc. The reason is because chromium also reduces martensite start and finish temperatures. Vanax has more chromium in solution for a given carbon/nitrogen in solution:
This means that for a given austenitizing temperature, Ms and Mf are lower in Vanax than in Elmax. So as seen below with an austenitizing temperature of 2025°F, the Ms was about 150°C. The Mf is sufficiently low that even with liquid nitrogen not all of the austenite is transforming to martensite, and thus hardness was lower with 2025 than 2000°F. Elmax, however, still has a predicted Ms above 150°C all the way to 2200°F, which is why its hardness increased all the way to 2150°F (the highest temperature I tried).
Thus an approximate relationship is created when comparing different steels to each other for their maximum hardness vs their corrosion resistance:
This trendline is usually correlated with chromium in solution. For example, Vanax and LC200N have >14% chromium in solution, which gives them a very high corrosion rating but also limits their potential hardness. On the other end of the spectrum is ZDP-189, which achieves very high hardness and is advertised as a stainless steel, but I discovered a few years ago that it is not, in fact, stainless. I measured only 8.6% chromium in solution with ZDP-189, which is quite low. D2, for example, I measured at 7.7% with a relatively conventional heat treatment, which is famously called a “semi-stainless” steel.
There are other complicating parts to this trendline, however. It does not always perfectly correlate with chromium in solution. Molybdenum, for example, is an element known to improve pitting resistance and to strengthen the chromium oxide passive film. In tests I did with 1% saltwater there was an improvement in corrosion resistance for a given chromium in solution if the Mo was increased:
CPM-154 with its high molybdenum content (4%) had acceptable corrosion resistance even with only 9.5% chromium in solution. (Note: the “corrosion ratings” in this chart are a rating of how much the samples rusted and not the same as the “corrosion rating” in the hardness trend plot which are from my knife steel ratings).
You may have also noticed that S90V, S125V, M390, and S110V are all above the hardness-corrosion resistance trendline. In other words, they have unexpectedly high maximum hardness for their corrosion rating. These steels all have a very high volume of carbide (>20%). Carbides are very hard particles and when the volume of them is reaching these high levels it can affect the bulk hardness that is measured. You can see that for the following two charts comparing non-stainless tool steels with different amounts of carbide (Vanadis 4 Extra, 10V, and 15V):
So while M390 and 14C28N both have similar Cr in solution (depending on austenitizing temperature), the M390 reaches higher hardness because it has so much more carbide:
M390 has a lot of carbide
14C28N not much carbide
The other steel above the trendline for hardness-corrosion resistance is MagnaCut. It does not have particularly high carbide volume, about the same as Vanadis 4 Extra:
MagnaCut also does not have particularly high chromium in solution, around 11%. Instead, MagnaCut has superior corrosion resistance to those other steels because all of its chromium carbides are dissolved in heat treatment. With typical stainless steels they have many chromium carbides, and the chromium in solution is lower around each carbide:
Thus the chromium carbides act as corrosion initiation sites. This is somewhat similar to the phenomena called “sensitization” in low carbon stainless steels that are cooled too slowly.
Image from [2]
Instead, all of the carbides in MagnaCut are vanadium or niobium carbides (after heat treating). Therefore those corrosion initiation sites are missing and so it has superior corrosion resistance for a given level of chromium in solution.
Comparing Steels vs Comparing Heat Treatments
Perhaps it is the above discussion that confuses some people, and they mix the low potential hardness of Vanax and LC200N with heat treating of other steels and assume that lower hardness means better corrosion resistance. However, as I have discussed, hardness and corrosion resistance don’t really correlate for an individual steel. If anything, higher hardness sometimes correlates with higher corrosion resistance. If you use higher austenitizing temperatures in combination with a fast quench and cryo, and temper at a low temperature, you get maximum corrosion resistance. That is also a recipe for high hardness (as long as the austenitizing temperature isn’t too high). However, tempering can be increased without detriment to corrosion resistance to heat treat to lower hardness levels (as long as the >750°F range is avoided).
Summary and Conclusions
Austenitizing temperature, quench rate, and tempering can all affect corrosion resistance. Austenitizing higher leads to both higher hardness and better corrosion resistance. Beyond a certain temperature cryo is necessary to get higher hardness, and even then there is a temperature beyond which hardness decreases. Quenching too slowly, as happens often in industry, can lead to a reduction in corrosion resistance. Tempering in the high temperature range (>750°F), also relatively common, significantly reduces corrosion resistance. Combinations of heat treating variables can be used to achieve a range of hardness values while maintaining high corrosion resistance. In other words, hardness does not correlate with corrosion resistance for a given steel. However, when comparing different steels to each other, there is a trend where more corrosion resistant steels typically have a lower maximum hardness. Molybdenum alloying, avoiding chromium carbides (such as in MagnaCut), and having a high volume of carbide all lead to higher potential hardness for a given level of corrosion resistance when comparing different steels to each other.
[1] Binder, W. O., and C. M. Brown. “Atmospheric Corrosion Tests on High-Chromium Steels.” In Proceedings of ASTM, vol. 46, pp. 593-606. 1946.
[2] https://newzelindustries.com/what-is-sensitization-in-austenitic-stainless-steel/
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Video
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Development
In March 2024 Joey Berry of Pop’s Knife Supply called me and said he wanted to develop a new steel. He said that their most popular steel was 80CrV2 and so he wanted to make “80CrV3.” “You mean 80CrV2 but with a little more vanadium?” He said no but some kind of “sequel” to 80CrV2 that would be more exciting. I told him that doesn’t give me much to go off of but I would think about whether I had any good ideas along those lines. I thought about gaps in the market in the area of low alloy knife steels (“Carbon steel”) that would also be usable by the knifemaker that is buying 80CrV2. It occurred to me that our selection of high nickel steels is very limited; 15N20, L6, and 8670 are pretty much it. These steels are high in toughness and offer good hardness to go with it, but have no real wear resistance to speak of. 80CrV2 is in a similar position just without the nickel. I thought if we added some tungsten and vanadium to a high nickel steel we could make the steel more balanced; give it some wear resistance along with the high toughness. Those carbide pinning elements would mean that the steels are more beginner friendly for forge heat treating. 15N20, for example, already sees grain growth around 1500°F (815°C) and so its toughness drops very rapidly even when only slightly overheated. If the tungsten and vanadium were kept in check the forgeability, grindability, and polishability would remain high. This would also offer an alternative to other tungsten/vanadium steels like Blue #1, V-Toku2, Wolfram Special, 1.2519, and others. Those steels don’t have much toughness to speak of, so we could combine the best of the nickel steels with the best of the tungsten/vanadium steels. Another exciting element with the high nickel is the possibility to use the steel in pattern-welded Damascus as a “bright” layer. This gives an option for a higher wear resistance steel with better edge retention for that component of the Damascus. I told Joey about my idea and we decided to move forward with it.
We took the composition I came up with to a steel mill in Europe and they agreed to make it. I spent a bunch of time working on optimal annealing for the somewhat similar 15N20 based on the limitations of their production annealing process. Based on that we generated an annealing procedure to make the steel respond well to forge heat treating.
Composition and Tungsten/Vanadium Carbides
Here is the composition of Pop’s ProCut compared with other grades in its category. The far right column says “MC (%)” which is a calculation of how much total vanadium and tungsten carbide each steel contains after heat treating. One thing you will notice is that since tungsten is a heavy element it does not contribute as much to the MC as you might expect. For example, CruForgeV with 0.75% vanadium has more MC than Wolfram Special which has ~2.25% tungsten. ProCut uses a combination of vanadium and tungsten in a similar fashion to O7 and 1.2519 steels. So it has similar MC to steels like Blue #1, 1.2519/O7, and Wolfram Special, and more MC than Blue #2 and O1. The other nickel nickel steels (15N20, L6, and 8670) of course do not have any MC. These very hard carbides give the steel wear resistance.
Austenitizing, Tempering, and Hardness
A major goal for this grade was to be “easy” to heat treat with a forge. This requires a wide range of austenitizing temperature where full hardness is achieved while avoiding a toughness drop with higher temperatures. 80CrV2 steel varies a lot with starting microstructure, and two of the mills that make the steel lead to very different heat treating response:
So we wanted to avoid this issue that 80CrV2 sees. We did this by keeping the chromium low and also working with the manufacturer to dial in the annealing procedure so that carbides aren’t too coarse (making them difficult to dissolve). I also compared the austenitizing response with my recommended anneal (described later):
You can see that the hardness reaches its maximum around 1475°F and then does not change above that temperature. If using the anneal I recommend the microstructure is a bit finer and so this can be dropped even further to 1375°F. Thus for heat treating in a forge you can heat the steel to “a shade brighter” after reaching nonmagnetic and the steel will fully harden. If you forge and follow the recommending normalizing and annealing procedure you can even quench from nonmagnetic if you wish.
If the steel is austenitized in that range (1475°F or higher) the tempering is roughly the same regardless of the austenitizing temperature. Here are datapoints for both 1550°F and 1625°F:
You can see that the hardness is relatively high, still 64 Rc after tempering at 300°F, which is generally as low as I recommend for tempering most any steel. With a 450°F temper the steel is still above 60 Rc.
Toughness
Austenitizing
In our heat treating and toughness experiments we found three different regions of toughness behavior:
Below 1500°F, the steel shows an increase in toughness with increasing temperature. From 1500-1575°F the toughness is roughly flat. 1625°F and above shows a big jump in toughness where it is flat again up to at least 1675°F. The reason for this behavior we figured out by looking at the microstructure. These images were taken by knifemaker Shawn Houston of Triple B Knives:
1425°F, 400°F temper
1475°F, 400°F temper
1600°F, 400°F temper
You can see that the carbide content is significantly reduced by austenitizing at 1475°F as opposed to 1425°F. This significant change in cementite (iron carbide) raised toughness. Then when the temperature is further increased to 1600°F and above, virtually all of the cementite is gone and all that remains is the small volume of hard vanadium and tungsten carbides. The presence of these small carbides is what prevents grain growth even at high temperatures. The carbides “pin” the grain boundaries.
15N20 and L6, in contrast, show a drop in toughness at much lower temperatures because they do not have those carbides to pin grains. The steel 1.2519 does have the W/V carbides but it sees a drop in toughness above 1500°F because it gets excess carbon in solution, leading to plate martensite. The carbon content in ProCut is controlled so that the matrix carbon does not reach excessive levels even at high temperature. This gives ProCut a very wide austenitizing range.
Tempering and Toughness
Like many other knife steels, ProCut sees a peak in toughness with a tempering temperature of around 450°F (230°C). Above that the toughness drops due to a phenomena called “tempered martensite embrittlement” which happens in all steels. There is lower toughness with tempering at lower temperatures as well, of course, corresponding with the higher hardness. The behavior of toughness with tempering temperature is roughly similar whether using the higher or lower austenitizing temperature range.
Hardness vs Toughness
This creates two different heat treating ranges, where the steel can be austenitized high (1625-1675°F) to max out toughness with some cost to wear resistance and edge retention, or austenitizing lower (1475-1575°F) to retain more carbide for wear resistance. The steel still maintains a toughness advantage vs previous tungsten/vanadium steels due to the nickel addition and controlled carbon content with the lower austenitizing range. However, with the high austenitizing range it achieves levels of toughness similar to 8670, 15N20, and L6 but with enhanced wear resistance due to the small tungsten and vanadium carbides.
To compare with other steels you can look at the following chart:
Grinding and Polishing
I don’t have a quantitative test for grindability. Reports from knifemakers so far say that grinding and polishing is very easy with the steel. Some low alloy steels developed for higher wear resistance like CruForgeV are more difficult to polish due to relatively large vanadium carbides that are found relatively frequently. This steel we controlled the W/V content to try to avoid large carbides. Because of the limitations of standard steelmaking (as opposed to powder metallurgy) there are still very occasional larger carbides but they are much rarer than a steel like CruForgeV. So far those few carbides don’t appear to be affecting polishing and finishing.
A lower magnification image of ProCut showing that large carbides aren’t observed most of the time
One of the rare large carbides in ProCut
A micrograph of CruForgeV showing large carbides. Notice there is a magnfication difference vs the ProCut images.
Quenching, Oil Selection, and Hamon
The “hardenability” of ProCut is relatively high, which I also found in testing of 15N20. The high nickel content gives it this hardenability. Air cooling from 1600°F with 1/8″ steel resulted in 60.7 Rc, though from lower temperatures like 1350°F the hardenability is lower (I measured 35.3 Rc). This means that ProCut can be quenched in virtually any quenching oil, even canola, and with relatively thick cross-sections.
This high hardenability means that ProCut is not well suited for developing a hamon. The best choices for a hamon are low hardenability steels like 1095, W2, and 26C3. I won’t say it is impossible to develop a hamon but there are better choices. It is likely still fine for other differential methods like an edge quench.
Forging, Thermal Cycling
Maximum forging temperatures are most greatly affected by the carbon content. High carbon steels are easier to overheat, leading to crumbling while forging. The carbon content of ProCut is limited to ~0.87% so this is not a huge factor with ProCut. For safety I put in the datasheet to limit forging to 2200°F (1200°C). Some knifemakers, especially Damascus makers, push the boundaries of forging temperatures and this can be dangerous. Like with other steels, if you continue to forge when the steel gets too cold this is also a danger in terms of cracking. I haven’t heard a lot of feedback in this area so let me know how the steel behaves for you. The high hardenability means that the steel can sometimes harden in air while cooling from the forging temperature. This can lead to cracking if there are stress risers in the blade.
The “thermal cycling” procedure for ProCut is relatively simple. Like with other steels I prefer to do a single normalize and anneal, so only two steps. I have written about this procedure in past articles. The normalizing step is for dissolving any undesirable carbides and other structures. For this steel it would be in the range of 1600-1650°F where the cementite is dissolved. With a furnace you can hold at this temperature for 10-15 minutes before air cooling. With a forge by eye you just need to heat somewhere into that range or a bit higher.
The annealing procedure is then done by heating to nonmagnetic and slow cooling. I recommend faster cooling rates than is typical for datasheets and this type of anneal is called a “Fast DET” anneal. For simple heat treatments you can slow cool either in a furnace or in an insulating media like vermiculite (available in the garden section of home improvement stores). I tried a range of cooling rates in my furnace. I held the steel for 30 minutes at 1350°F and slow cooled at different rates to measure the annealed hardness. At 50°F/hr cooling the resulting hardness was 23.9 Rc. After 500°F/hr the hardness was 24.5 Rc. I also tried setting the furnace to 1000°F/hr but it only maintained that cooling rate until about 1250°F and slowed from there, the average rate of cooling was about 680°F/hr. That resulted in 26.2 Rc, which is plenty soft enough. Shawn Houston did an anneal with 250°F/hr and he measured 21.2 Rc. Here is the microstructure after normalizing and annealing at 1350°F for 30 minutes, and cooling at 250°F/hr:
Normalized and “Fast DET” annealed microstructure of ProCut (21.2 Rc)
“As-received” annealed microstructure of ProCut (12 Rc)
You can see that the faster annealing procedure results in a finer microstructure which is why the austenitizing response was different (see the prior as-quenched hardness chart). The toughness was still relatively similar despite the very different starting microstructure (see the toughness vs austenitizing temperature chart). Those datapoints were generated using a 100°F/hr anneal which is what I recommended in the datasheet. Somewhat faster and slower cooling rates would have a similar result.
Use in Damascus
The high nickel content means that ProCut is a good replacement for 15N20 or L6 as a bright layer in pattern-welded Damascus. This gives an option for providing higher edge retention whereas 15N20 and L6 have almost no wear resistance apart from their hardness. An initial forging experiment with 1084 and ProCut resulted in excellent contrast:
Edge Retention
Pop’s ProCut did surprisingly well in the CATRA test. The heat treatments performed were 1650°F with a 450°F temper (61.2 Rc), and 1500°F with a 300°F temper (64 Rc). As I have written about before, CATRA is not the best for low alloy steels because the sand particles in the test media are harder than cementite (iron carbides). Even with different media they wouldn’t be at the top of the chart but they would be a bit better. It could be that the relatively low amount of cementite in ProCut helped for the CATRA test. But even if that were the case if we compare with another steel with low cementite content like 8670 or 1095, there was a significant boost to edge retention through the tungsten and vanadium additions. Perhaps with the lower carbon compared with other W/V steels meant that there was less of tungsten and vanadium found in the cementite, allowing them to form more of the hard WC and VC carbides.
Toughness-Edge Retention Balance
With the high toughness plus the unexpectedly good CATRA numbers the ProCut looks very good compared with other low alloy steel options:
Corrosion Resistance
This is a non-stainless steel and should not be expected to be stainless. People say that the 2% nickel in 15N20 gives it somewhat better corrosion resistance than carbon steels but I have not developed a test for comparing corrosion resistance of low alloy steels.
Cryo
There is a certain lore out there with knifemakers claiming that some steels “need” cryo and other steels “don’t benefit” from cryo. Part of this lore is that low alloy and carbon steels are in the “don’t benefit” category. Simple carbon steels and low alloy steels still see an increase in hardness with cryo, typically 0.5-2 Rc depending on the steel and the heat treatment. There is a small cost to toughness because of the increase in hardness. ProCut is the same. As an example of another low alloy steel we experimented with see 52100. I did experiments from 1500°F and 1650°F and found, as expected, that hardness increased. The higher temperature led to a bigger bump from cyro which is also typical. None of the edge retention or toughness tests I showed in the article so far used cryo in any of the heat treatments. But if you want even higher hardness for edge retention and strength you can add a cryo step after quenching.
Comparisons to Other Steels
1084 and 15N20
These steels are relatively “easy” to heat treat in that you can heat them up and quench them and get full hardness. However, they are very easy to overheat leading to grain growth and a drop in toughness. They also have almost no carbide thus having very little wear resistance.
80CrV2
This steel is also lacking in wear resistance though overheating is not much of an issue because of the vanadium addition. It also varies a lot between manufacturers and needs more temperature prior to quenching making it more difficult to perform a forge heat treatment.
52100
In the lower austenitizing range (for higher wear resistance), ProCut compares favorably with 52100 in terms of properties. 52100 has a very good combination of toughness and wear resistance. ProCut is easier to heat treat for an amateur knifemaker and also has the option of the high toughness heat treatment.
O1 and 1095
These are old standard steels. O1 has the benefit of being “oil hardening” so it is easier to quench. I have found both to be very sensitive to overheating because of excess carbon in solution. See my article on O1.
5160, 8670, and L6
These steels have significant chromium additions so they are more difficult to heat treat in a forge. They also don’t have any carbide left over after heat treating and thus their wear resistance is very low.
Blue #2, Wolfram Special, 1.2519
These steels have similar wear resistance for edge retention but significantly lower toughness and do not have the benefits of being beginner friendly.
ApexUltra
This is another low alloy steel I helped develop. It has significantly higher wear resistance and attainable hardness than ProCut, which also means lower toughness. I would recommend ApexUltra for those looking for maximum performance in the “carbon steel” category. Though I wouldn’t call it a difficult steel, it is best for makers that have a bit of experience first.
Heat Treatment Recommendations
In a Forge
Heat to “one shade brighter” after reaching nonmagnetic, quench in oil (most types are fine), and temper twice for one hour each time at 300-450°F (150-230°C) to desired hardness.
In a Furnace
Maximum toughness: 1650°F (900°C) for 10-15 minutes.
Higher edge retention: 1500°F (815°C) for 10-15 minutes
Quench in oil (most types are fine), and temper twice for one hour each time at 300-450°F (150-230°C) to desired hardness.
Thermal Cycling after Forging
1625-1675°F for 10-15 minutes, air cool. Without a controlled furnace, heat into that rough range and establish an even temperature distribution prior to cooling.
1350°F for 30 minutes, cool at 100°F/hr to 1100°F. After that it can be cooled more rapidly. Without a controlled furnace, heat to nonmagnetic and slow cool such as in vermiculite.
Summary and Conclusions
I am happy with how Pop’s ProCut turned out. It offers good balanced performance when compared with other low alloy non-stainless steels. Better edge retention than 1095, O1, 80CrV2, L6, 15N20, etc. And depending on the heat treatment its toughness approaches 8670, 15N20, and 5160. And on top of this it is beginner friendly, being easy to heat treat, grind, and finish.
The post Pop’s ProCut – A New Carbon Steel for Knives appeared first on Knife Steel Nerds.
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