Carbon vs Stainless

[Cliff Stamp]

There are some odd arguments made about stainless steels being inferior to carbon steels inherently with no real argument given as to why/how. Often what tends to happen are comparisons which are not about stainless vs not but something else. For example ATS-34 is much more brittle than S7, but is this because ATS-34 is stainless or is it because ATS-34 has a much higher carbon content and a much higher carbide volume? Verhoeven was one of the first to publish had data showing that stainless steels could not only compete with carbon steels, they could easily out perform them, even forged carbon and even damascus steels : http://docs.lib.purdue.edu/cgi/viewcont ... ntext=icec" target="_blank . Roman also has argued, and has data showing that there is an argument (assuming you can harden it) that AEB-L and similar are better steels than 1095 and similar on the basis of edge stability, edge holding and of course corrosion resistance.

However direct materials data is often hard to come by as these are in general so very different types of materials that people often don't compare them. What ends up then is comparisons at best which look at properties of one compared to some other reference and then using that reference to another and then based on how A and B compared to C you try to make some inference about A vs B. But often the materials test are not identical and thus this inference is weak at best. It is easy to see how this logic can be wrong if you do a little MMA-math for example and you can show how just about any fighter is better than another by being able to find someone that they beat that beat the other guy.

However such materials data is possible to find, though it might be called something you don't expect because how such steels are described in industry is a little different. For example "Properties of High Strength Steels by B. Johansson, et. al." refers to the following :

-1095
-420
-UHB SS 716 (420HC)
-ASI 301 (non-heat treatable steel, usually used cold rolled)
-17-7 PH (this is a very low carbon, precipitation hardening stainless)

It might seem odd to think of 420 as a high-strength steel when it has 0.18% carbon, but you have to keep in mind that there are a LOT of steels. These steels also have tool overlap as they are all used for valves for example. Now what are the properties, some of which might be surprising, to start this is the hardness that they were compared at (converted from HV) :

-1095 : 53
-420 : 51
-716 : 54
-301 : 43
-17-7 PH : 46

Now there are some interesting points such as UHB SS 716 has by far the smallest number of inclusions, followed by 1095 and then there is a big jump to the rest. This is an indication of the quality of the steel and is set not by the type specifically but by the tolerances on it by the maker/manufacturer

A few more interesting things :

-the tensile strength is very similar between 1095, 420 and SS 716, the other two are much weaker

-at a given tensile strength, the two martensite steels are tougher than 1095

-the other austenitic steels are tougher again, but can not reach the same level of strength

-420J2 is significantly tougher than UHB SS 716 (again similar to 420HC)

The reason for this is "...due to the larger amounts of chromium carbides in the UHB SS 716. When the material deforms plastically, voids are initiated in the carbide-matrix interface giving rise to a more favorable path for crack propagation."

Of course they also look at wear resistance (abrasive, the steels are exposed to aluminum oxide and SiC3) and the ranking (from least to best) :

-17-7 PH
-AISI 301
-1095
-420
-SS 716

The differences get smaller as you move down the list. The paper also looks at things like fatigue, creep and other properties of the steels such as blankability.

In short, it might not be the obvious choice that for example for a rough use type of knife that making it from 1095 and under hardening it makes a superior choice to a 420 or 420HC type steel. It certainly isn't true that in general that 1095 would have superior material properties.

Full papers :


-Verhoeven et. al. : http://www.bestexcompany.com/parks/kniv ... ournal.pdf" target="_blank

-B. Johansson, et. al. : http://docs.lib.purdue.edu/cgi/viewcont ... ntext=icec" target="_blank