Mr. Zowada,

I'm new to knife collecting. I have noticed that both custom and factory knife makers seem to have a favorite steel. Some go as far as to say that no one can make a knife as good as theirs if they don't have their special steel. The most notable are Cold Steel with their Carbon V and Busse Combat with their INFI. What do you know about these steels and their relative merits?

George Urbaczka

George,

Thank you for your question. I need to start out by saying that due to confidentiality concerns there is a lot that I can't say. One thing I won't say is which is one better. I'll leave that one for the companies to fight out. Both are excellent steels made specially for the individual companies and both make great knives. When buying a factory made knife the real issue usually comes down to quality control and heat treating, not the steel that the knife is made from.

Cold Steel's Carbon V is a high carbon tool steel. I had the privilege of using some of it several years ago. It forges well, heat treats easily and is an all around wonderful steel for forging. It seems to take the best properties of my favorite forging steels (O1, W2, and L6) and combines them into one.

Because it is so forgiving in the heat treat it is especially suited for large production runs, or a guy with just a forge and a torch. When you heat treat it with more advanced equipment, it makes some of the best knives I have ever seen. It will tarnish with use, but so will Purdy shotguns. Just keep it clean. My only regret is that I can't buy it. I would use it for most of my carbon steel forging.

Busse Combat's INFI is a steel that is beginning to unravel all my theories about high chromium steels. Jerry Busse sent me some recently to test its' suitability for forging by custom makers. At this point I have only done preliminary testing, but the results are very intriguing.

While this isn't truly a stainless steel INFI does resist staining about like ATS-34.  It is stronger than any stainless steel I have ever seen. I think it will rival O1 in tensile strength and L6 in impact strength. After shaving a lot of cardboard it will easily keep up with, and probably surpass most carbon steels on edge holding. Finally, there is a rust resistant steel that really cuts and cuts and cuts�

One of the weird things I noticed was how the hardness test marks looked under the microscope. In many carbon steels the dent crater will have cracks around the edge. This is especially true if the steel is not martempered. Even at a hardness of 62HRC INFI just seems to mush out of the way like putty.

INFI is an air hardening steel. It is also difficult to forge. You really have to hit it to get it to move. For heat treating, kilns and liquid nitrogen are required. But, if you have access to the equipment this could be one of the best all around knife steels ever. Hopefully, Jerry will make it available to custom makers.



Photos:

INFI test blade used for preliminary tests.
Hardness tester dent at 150X. O2 tool steel at 65HRC, not tempered. Note the cracks on the edge of the crater.