So I like to plot the two properties against each other to get an idea of the performance category where a steel sits. All things pocket knives. You can read more about the decrease in vanadium carbide with chromium content in this article about carbides. This results in fewer imperfections and weaknesses in the steel's grain structure. Small vanadium carbides are the key to high values in the crossed-cylinder test. Enter your email address to subscribe to this blog and receive notifications of new posts by email. So it seems that the M390 Steel Will has been selling isn't M390. In particular, S90V has similar toughness to many other PM stainless steels while also having significantly better edge retention. Stress relief: All metals have residual stress that is created when it solidifies from its liquid phase into a solid phase. Increased amounts of vanadium in powder metallurgy were being used in steels like CPM-10V which achieved better combinations of toughness and wear resistance so this makes sense as the route for designing early powder metallurgy stainless steels. It wasn’t until S30V a few years later than an intentional addition of 0.2% nitrogen was used in a commercial product. weapons platforms and guidance systems), Automotive (e.g. Awesome blog. Any reasonably sized production knife company that cares about their name should be able to afford a Rockwell test and a steel test a random sampling of the products, especially at the prices some of these items go for. M390 / CPM 20CV is a PM stainless steel that offers good wear resistance with excellent corrosion resistance through the use of high chromium and vanadium content. So it seems that the M390 Steel Will has been selling isn't M390. Especially when you put mustard on it... Wtf? The 14.5% V version I have called S145V has never been commercially produced as far as I know. You can see these against the superior properties of the non-stainless vanadium-alloyed PM steels in the following chart: S90V and S125V get their superior toughness-edge retention balance through vanadium carbide. Reviews on Amazon greatly help the book show up in searches and let people know what to expect, so if you have one please go write a review. Toughness and Heat Treating Response For a while I had a toughness chart which showed a relatively high value of about 8-9 ft-lbs for M390 at ~62 Rc in our toughness testing which … [3] Modern Plastics, vol. This is perhaps expected as the most common martensitic stainless steel for high wear applications was 440C with ~17% chromium. Increasing one tends to decrease the other. BÖHLER M340 BÖHLER M390 BÖHLER M340 BÖHLER M390 Heat treatment: without subzero treatment Hardening temperature: 1.2083 at 1020 °C (1870 °F); M340 ISOPLAST at 1000 °C (1830 °F); M390 … A married couple who had previously tested Phil’s knives reported processing 75 large salmon before the knife required resharpening. In other words, for an upgrade in toughness over S110V it would be better to switch to S35VN or CPM-154 rather than to S90V. It is, however, very effective in enhancing heat-treated martensitic steels, such as high carbon and high chromium steels, as well as tool steels. I think it was also affected by the release of S30V in 2001 which was promoted as being designed specifically for knives and easier to work with. I am always skeptical of knife companies who don't own grinding wheels. Vanadium carbides are very hard and contribute greatly to wear resistance but are detrimental to toughness in conventionally-produced steels. BÖHLER M390 MICROCLEAN is a martensitic chromium steel produced with powder metallurgy. The final version also had even higher carbon than either version that was shown in the patent (3.3 vs 2.95% carbon). Microstructure. Now I bought a batch of steel M390 and want to work on it. They compared vanadium content vs wear resistance for a range of steels at different chromium levels and found that a 14% Cr content led to greatly increased performance. High vanadium steels like 10V had very high results in the crossed-cylinder wear test so Crucible metallurgists were also trying to get higher values in their stainless steels. You can read more about corrosion testing and predicting corrosion resistance based on composition in this article. The average nitrogen content in the commercial S125V is not public information. Reduced Cr (14%) relative to earlier PM stainless steels (16%+) led to better wear resistance without sacrificing toughness or corrosion resistance. Without going through this process, the metal can be prone to strains and fatigue. I personally prefer steels with finer structures and better toughness but I cover everything. He reported that the knife went through a whole week without getting dull. There's no shortage of knife companies out there. Hello again Larrin. Cryogenic treatments were first commercialized in the mid-to-late 1960s. “Stellar Steels.” Blade Magazine. Since powdered steel relies on the proper distribution of fine grains, Vanadium is a must. Cryogenic treatment of certain metals is known to provide three beneficial effects: The process of cryogenically treating a metal part involves very slowly cooling the metal using gaseous liquid nitrogen. Kajinic also patented S110V a few years later. All of these previously released PM stainless steels had high chromium (16-24%) for corrosion resistance in combination with some amount of vanadium for wear resistance. It is sometimes said that the type of steel is the body, but that the heat treatment determines the soul of the steel. So the benefits are not lost as a result of further processing, such as grinding. Later he got a new furnace and began heat treating the knives to higher hardness. I have one knife made out of S90V. Tomes, and Phil Wilson all agreed that grinding and finishing S90V was very difficult, which we would expect based on its high wear resistance. There are namely different recipes to harden the same type of steel. Crucible then patented a steel with very high wear resistance called MPL-1, the patent for which was submitted in 1986 [2]. The non-stainless 10V without chromium carbides has a finer overall carbide structure with less clumping of carbides. Final Edit: Decided to amend the OP since more info came out. “Corrosion resistant, high vanadium, powder metallurgy tool steel articles with improved metal to metal wear resistance and a method for producing the same.” U.S. Patent 5,936,169, issued August 10, 1999. My new book Knife Engineering now has over 100 ratings on Amazon, which is very exciting. And under 100. The composition was recently announced so I analyzed the composition. S90V has a finer microstructure than M390 or ZDP-189, the average carbide size appears to be smaller than S60V though S90V has more “clumping” of carbides. GET THE PITCHFORKS! It has both higher edge retention and toughness than M390, ZDP-189, and S110V, for example. Improved wear resistance: Cryogenic hardening increases the precipitation of eta-carbides. Terence Bell wrote about commodities investing for The Balance, and has over 10 years experience in the rare earth and minor metal industries. In other words, 5 vs 2.5 ft-lbs is roughly as significant as 10 vs 5 ft-lbs. So I’m not sure why they didn’t further pursue a nitrogen-modified version since the stated improvement in the patent was in the area of crossed-cylinder wear. After more investigation from the community, the consensus does lean more toward the M390 being legit and the blades in question have a very bad heat treat. Where to set the cutoff between “high” wear resistance stainless steels and “medium” I’m not sure, but I also have articles about ZDP-189, S60V, M390, and S30V.

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