A brief evaluation of one of the newest blade steels that is starting to be used by custom makers.

Stainless steels, in one form or another, are almost as common as normal carbon steels that I have previously discussed, but again, few(many knife makers and enthusiasts excluded) know what makes a steel "stainless".

Actually the word stainless must have been a marketing tool originally used to sell the first tools and knives made from them ( other than industrial applications) because many steels which are  technically stainless will still rust in salt water. However, most stainless steels do a good job in water other than salt water.
So, what makes a regular carbon steel which is 98+% Iron(Fe) and highly prone to rust, stainless.

In a few words it is the addition of an element called Chromium(Cr). I have never seen pure chromium, but I was once told by an electroplater that the chrome plating we all have on our vehicles is actually an electroplate coating of copper(Cu), followed by a shiny silvery metal called
nickel (Ni), covered by another electroplate coating of chrome. According to him, chrome is a clear coat, put on as a top coating because of its tremendous hardness and see thru colorless aspect. It's like a clearcoat paint coating on many automobiles.
You might ask how much chrome do we have to put in the mix to get a stainless steel. The accepted percentage is 13%, minimum. This amount was no doubt arrived at by much experimentation and testing, and we will learn that all the other elements that go into steel today to make all the various specialty steels were also arrived at by just plain hard work on the part of metallurgists.
It is also important to note that the Chromium doesn't just make the steel rust resistant, it also acts as a hardening agent by forming carbides with some of the carbon present in the steel matrix. These hardening agents are what give blade steels their edge holding ability..Other elements also form these carbides, and they all help to make the steel superior in edge holding and other aspects.

Some tool steels, like D2, come close to being stainless. In D2's case, it has about 12% Cr, and that 1% difference between 12 and 13% sure makes a difference. D2 will rust! You might well say, "why not just add some more Chromium and cover your bases". The answer to that question is probably best answered by a metallurgist, but I can take a stab at it and say that a small change in % of any of the alloying elements can make a big difference in properties and performance, and adding more in this case may degrade the purpose of the steel.

Someday I will try to publish a composite table of all the steels I can find along with all the alloying elements present, and their percentages. These tables are available now from several sources, and my job would be to combine them into one complete table. I bring this up because, when you see this table, you will marvel at the strange percentages (some well less than 1%) of some of the alloying elements, and the sheer number of them that are in some steels. It's actually more complicated than that, because some alloying elements actually enhance others that are already present!
We have come a long way from the first stainless steels which were noted for their "mushiness, poor workability, and poor edge holding ability. There are many stainless steels now with series names like 300 or 400 and others, all with specific formulations to perform well at specific tasks..

One of the most popular stainless steels for knife building in the past, and still used, is 440C. It has an astounding 18% chromium along with a few other alloy elements. It is a "high" carbon steel in its own right, and has more than enough chrome to make the stainless classification. It holds an edge well and can be used in salt water if rinsed off at the end of the day. I notice that some manufacturers still make these knives for us as boat or dive knives.

I will close by saying that the quest for the perfect knife steel is still going on, but has come much closer to reality these past few years, and that will be the topic for another discussion.

Dr. K.

After a month or two traveling this summer I am doing something I have had on the back burner for several months, namely publish a comprehensive table on knife steels, including comments on the blade steels themselves, and some short notes on each of the alloy elements and their basic purposes.

I have not included some steels like 420HC and 01760-1, but I will do so later, since in my opinion, 420HC is not really a custom knife steel that I would want to buy as my blade steel, and 01760-1 and others of this type are used mostly by forgers for high end custom knives. I owe them both a separate description and evaluation.

Anyone who buys or collects knives these days knows there has been an explosion of superb alloy steels being brought to the market, first by custom makers, and then by major knife companies. We are all the beneficiaries of this, but it would seem to me that you should know what to expect from your blade steel before you buy any knife.

Several great knife companies, like Spyderco and Benchmade, have published some good tables and descriptions of blade steels. I have gone beyond their tables by utilizing data sheets from two of the major, special purpose, alloy steel makers. Both Crucible and Timken/Latrobe have done an outstanding job of developing and documenting these new "super" steels. I have not accessed any of the Japanese companies yet, but probably will, as time permits.

This table is as accurate as I can make it, but may have errors. I have drawn on all my knowledge and reading, in addition to the sources I have mentioned, to provide what I hope is a complete working document for a blade buyer.

Click Here to see the Table