November 01, 2022 4 min read
Collectors like trivia. The things they collect, be they figurines or sneakers or (ahem) an unreasonable number of knives, effect a magical fetish attraction that compels the collector to learn more and more about them. It doesn't even need to be learning, per se; absorbing questionable opinions and idle discussions can scratch that itch just as well. For collectors (and curious practical users) of knives, a major realm of trivia is steel chemistry. Once you dig beyond the simple distinctions like carbon vs stainless and high-alloy vs low-allow, it can be easy to feel overwhelmed by the hundreds (thousands?) of knife steels on the market, enmeshed in a confusing mix of national and proprietary naming conventions and subdivided into various grades and modifications.
If you would like to clear some of this confusion and get a handle on the more esoteric points of steel chemistry, I have good news and bad news for you. The good news is that a lot of the variety and complexity of steels is illusory, and can be collapsed into a much smaller collection of analogous and equivalent recipes. The bad news is that some of the variety and complexity is very real, and reflects the sometimes mind-boggling mix of interacting factors that influence a steel's performance. Of course, if you like nothing better than finding new puzzles to solve, then that is also good news.
Let's start with most arbitrary differences: naming conventions. There are several regional sets of conventions for naming steels, including: AISI/SAE (American), DIN (German), W-Nr (also German), and JIS (Japanese). The same recipe will have a different name under each of these systems, despite being the same substance, chemically speaking. The format of these naming conventions is not completely arbitray, and gives some information about the steels. Under AISI, for instance, W2, O2 and A2 are steels quenched in Water, Oil and Air, respectively. Under W-Nr, which uses a 1.#### format, 1.2##, 1.3## and 1.4## indicate low-alloy non-stainless steels, high-speed tool steels, and stainless steels respectively. DIN is the most straightforward format, where a name like X50CrMoV15 indicates that a steel has 0.50% Carbon, with additions of Chromium, Molybdenum and Vanadium, and that the largest alloying addition (listed first, in this case Chromium) amounts to 15%. I can't decipher the Japanese system yet. It's nice to have mysteries left to solve.
For beginners, just deciphering the differences between white carbon, blue carbon, and the different grades of each can be a lot to wrap your head around!
Another completely arbitrary difference is proprietary product names. Even under the same national/regional naming system, company A and company B will have different names for the same recipe. Things get even more complicated by knife companies (rather than steel companies) using proprietary names for the steels they use, usually (always?) to appear as if they are offering something unique to the consumer. So, in a scenario where there are two geographic areas, each with two different steel makers, each of which sells to two different knifemakers, consumers could find the same steel under eight different names. The more common the recipe (for example, X50CrMoV15, a.k.a. 1.4116, used in most European kitchen knives), the more names it will tend to have, since it is produced and used by many companies across the globe, and many of those companies want to distinguish their products.
I would guess (don't hold me to this) that another source of mostly-arbitrary difference is "lawyer-designed" steels. Say company A patents a steel recipe with specified ranges (e.g. 1-1.15% carbon, 1.7-1.9% tungsten). Depending on how the patent is worded, company B could market a steel with a recipe just outside the specs of company A's patent, and avoid legal infringment. Practically speaking, normal variation can result in some of company A's batches being closer to company B's recipe and visa-versa.
These differences aren't always completely arbitrary, or without practical importance. Some regional standards will have a wider range of variability than others, and some companies will regularly produce steel at the higher or lower end of an acceptable range. This can be the result of targeting a certain part of a recipe's range for certain qualities, or of having the technical means to ensure more uniform batches. Major consumers of steel, like the Henckels and Victorinoxes of the world, often ask steel makers to supply them with slightly modified versions of common steels, to ensure high quality and/or to optimally suit their production processes. These user-specific modifications are't necessarily superior in any absolute sense, but they can allow knife companies to acheive better and more uniform final results with a streamlined production process.
Miyabi, owned by Zwilling, uses Japanese knife steels such as VG10 and ZDP189 under different titles, which can add to the confusion.
Another real difference is how the steel is actually produced. Ingot steels are produced by melting the ingredients together, mixing them and pouring the steel into a block to solidify. Powdered metallurgy (PM) steels are molten and mixed, then sprayed out in fine droplets which solidify into a powder, which is then heated and pressed just enough to solidify into a block. High-alloy steels will tend to have finer and more evenly distributed carbides when produced by powdered metallurgy, and some very high carbide steels cannot practically be made without it. Two examples of powder metallurgy steels that will be familiar to Japanese knife users are ZDP-189 and SG2/SuperGold. ZDP-189 needs powder metallurgy to keep its ludicrous amount of chromium carbides small and spread out, while SG2 needs it to keep its vanadium-enriched chromium carbides similarly under control. Different companies have different methods for powder metallurgy, and advertise their steels with phrases like "3rd generation micro-clean particle technology". While the technical differences between companies' PM methods aren't always trivial, they are not as unique as their proprietary names suggest. The difference between any two PM methods is much smaller than the difference between any ingot method and any PM method (provided that the steel is complex enough to benefit from the PM process).
Hopefully, this has been helpful in clarifying some of the apparent differences can be ignored in your pursuit of nerdy steel knowledge. In the next installment, I'll try to group together the differences that can't be ignored, along the lines of what actually matters to knife makers and users.
This article was a guest post by our customer Mike O'Brien, a Montreal-based writer and knife nerd.
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