CPM S30V steel controversy
- In 2002 CRK announced that they were switching to the new steel for Sebenzas. CPM S30V is a stainless steel, somewhat similar to CPM-3V steel. Initially it[S30V] was said to be stainless CPM 3V, but later that didn't really turned out to be the case. Chemical composition is quite different, S30V has almost twice the Carbon, Chromium and Vanadium in it. For the curious minds - CPM S30V vs. CPM 3V steel composition comparison. As it turned out eventually, S30V still doesn't beat CPM 3V neither in toughness nor in edge holding, my Phil Wilson CPM 3V utility scalpel knife which is at 62HRC does perform better than S30V at 60HRC. Theoretically, S30V steel is a better cutlery steel than the BG-42 steel. It offers greater toughness and wear resistance and slightly better corrosion resistance. As Crucible states, CPM S30V was developed with the knife industry in mind. That was true. Crucible did work closely with several famous US knifemakers and asking their opinion about the future steel. Although, I have to note, despite some claims(mainly overzealous CRK fans) CRK didn't invent S30V steel, nor was the only maker participating in S30V development and research. Rob Simonich, Phil Wilson, Jerry Hossom were amongst the makers approached by Crucible to help with S30V development.Back in 2002, it is a subject of the heated debate on the CRK forum at BladeForums. That went on for a while. Today, almost a decade later, every once in a while there's still a debate about that steel :) The thing is, despite of the attempts to make the S30V steel easier to heat treat for the makers, it turned out pretty uneasy. In the beginning, very few makers could treat it properly, so you can imagine, factory knives were far from perfect. Either overhardened and suffering from the chipping issues, or underhardened and not having nearly as good edge holding as it should've been. That turned a lot of people away from S30V, or made them very skeptical about it. I was one of those too. Even today I try to stay away from that steel. I have just one blade in S30V Trace Rinaldi TTKK.
The specific problem with CPM S30V and CRK was the hardness they choose for Sebenzas. The short story would be that, practically every known knifemaker who worked with S30V agreed that 60-61 Rockwell hardness would be the optimal value for this steel. That is, to get the best wear resistance without compromising toughness. However CRK choose to use 57-58 HRC then, and later bumped up a point 58-59HRC. The explanation from CRK is that this is suffice for most cutting needs, makes sharpening easier and keeps the blade tough enough to withstand some abuse. Since S30V is a better steel, tougher and more wear resistant the end user would have an improved knife.
Some of the knife nuts(myself included) started asking questions. Obviously, The major concern was the lower HRC. While HRC alone doesn't define knife edge holding ability, it is one of the key factors. Lower HRC means lower wear resistance and lower edge strength which is far worse. If S30V is slight improvement over BG-42 then it is questionable what will happen to the overall edgeholding ability when the HRC is dropped by 3-4 points, 60-61 with BG-42 and 57-58 or even 58-50HRC with S30V. For experienced knife users the ease of sharpening is not the most important factor anyway. And with 3-4 point lower hardness the advantages of S30V may disappear completely. So, the question being asked was if S30V at 57-58 is an improvement or not? One of the logical explanations for the lower HRC is reduction of the manufacturing costs, i.e. softer metal is easier to work with, the furnace doesn't need to be heated to as high temperatures as it'd be required for 61HRC, hence the production costs are less. The "ease of field sharpening" argument doesn't hold any water for me, I have hard time imaging how 400$ folder gets sharpened on some rock found in the field because the owner couldn't afford a decent sharpener? Most of those Sebenzas are really pampered and don't see much cutting action to begin with.
Back then I wasn't very sure what was the case, considering CRK excellent reputation and customer service. CRK stated clearly that their choice of HRC had nothing to do with the ease of grinding or manufacturing costs, and was dictated purely by performance issues. I was very enthusiastic about S30V when it was announced, but once I've heard about 58 HRC I've decided to wait for more results. To be fair those few reports with new S30V blades were positive, though nobody has compared BG-42 Sebenza with S30V directly. Well, later on Chris Reeve(actually direct source of the quote is not stated, but from the wording it's quite clear), the owner and founder of CRK said following: At RC 58-59, the blade will hold a good edge and will be easy enough to sharpen. One of our tests resulted in S30V cutting 14,000 linear inches of e-flute cardboard before notable edge wear against 12,000 for BG42. I have been completely satisfied with the performance of S30V. This quote is often used by CRK's S30V proponents to prove its benefits over BG-42 steel, however, CRK never stated hardness neither of S30V, nor of the BG-42 blade used in the test. It's hard to believe 61HRC BG-42 blade could be outdone by 58-59HRC steel, even in a machine test. The cardboard test in a CATRA style machine mainly tests steel wear resistance, and CPM S30V being high on Vanadium is definitely more wear resistant than BG-42 steel. However, wear resistance is just one of the many factors involved in knife edge holding and in most of the cases it's not even the most important. What is more important, the actual use of the knives though. Machines, unlike us humans, don't get affected by fatigue, stress and other factors. They hold perfectly consistent angle constantly, and that does make huge difference in edge holding. Humans do get tired, make mistakes etc. For the edge those mistakes translate into lateral loads on the edge, which as the thinnest part of the blade is the most vulnerable to damage, i.e. resistance to rolling and dentin is critical. In other words steel hardness is very important, if not critical. Doesn't matter what steel is at 58HRC, and which one is at 61HRC, it takes less force to deform 58HRC steel, that's the measurement. And most of the time, the blade dulling is due to the deformation, not because of the metal wear.
One of the key advantages of the CPM S30V steel is the fact that if S30V is tougher than BG-42, even at 61 HRC it would've been tougher and more wear resistant than BG-42 used in Sebenzas until 2002. I myself never had troubles with edge chipping on my small Sebenza, and haven't heard many complaints regarding chipping Sebenzas in general, therefore personally I, would be fine with S30V hardened at 61 HRC. After all Sebenza is a small pocket knife and has a reputation of an exceptional cutter, thus you don't really chop trees with it. And I already stated my opinion about ease of sharpening.
For the reference, Crucible representative stated that: if you are not sure what jobs you will ask of the knife (cutting, prying, picking, chopping, you get the picture) then we recommend HRC 58+/-. If you are sure you only need edge retention (i.e. you know you will only be slicing or carving) then HRC 60+/- is OK. So we think unless you know you are in the latter category, HRC 58 is the best choice.. It's more than obvious to which category Sebenza folder belongs, isn't it ;)
Later, there was this update on the topic - Phil Wilson's article in July 2002 issue of Blade magazine. This thread on the bladeforums provides more details, but the key points would be:
- Edge holding will be proportional to hardness to a large degree;.
- Edge holding on a level with or better than 154CM/ATS-34 or D2 steel at the same hardness;
- Bending strength and impact toughness that are improvements over ATS-34/154CM and D2, hopefully approaching A2 steel;
As of today, well I am convinced that CRK's use of S30V at 58-59HRC is dictated by reducing manufacturing costs and possibly to protect them from abusive(or stupid) user's complaints too, but not by steel limitations. Ok, may be ease of sharpening, but that's pretty much a side effect of having easy to manufacture/grind and hard to break knife. Based on my experience with S30V blades at 61HRC and 59HRC, I can definitely say that there is nothing too hard about sharpening that steel even at 61HRC. Takes good polish, grinding is fairly easy. As long the user knows how to sharpen it's just fine. Obviously, S30V at 57HRC is even easier to sharpen, but the sacrifice in strength and edge holding is far to great to accept it, especially in an folder that costs 400$ or even more. Still, there's a lot of knife nuts out there swearing by their 58-59HRC S30V Sebenzas :) I don't say it is a bad knife BTW, but 61HRC is what that steel should be for the folder and in some even bigger blades, and I don't feel 400$ price tag for underhardened Sebenza is a justified price.
- Specifications:
- Model: Millennium Classic Small Sebenza;
- Blade: Latrobe BG-42 steel, 60-61 HRC;
- Length: 73mm (2.875");
- Width: 23mm (0.925");
- Thickness: 3.2mm(0.125");
- Open: 175mm (6.875");
- Weight: 3 oz.(85g);
- Handle: 3.2mm(0.125") thick 6AL4V titanium;
- Lock Mechanism: Frame Lock;
- Warranty: Limited Lifetime;
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Last updated - 05/19/19