Testing Erasteel MagnaCut (vs Crucible Original)

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.