Actually it is more of a type of construction of the knife then a "type" of steel. It is laminated or layered. Carbon steel in the middle and their standard stainless wrapped around it. The cutting part of the blade is no different than their other knives. It's the lamination of the carbon steel in the middle that makes the difference in strength. I have lots of cold steel knives (including their original Tanto bought in 1985) that are not San Mai and they are all top of the line.Welcome to the forum!
There are around 100 threads dealing with Cold Steel, did you perchance look in the archives or do a search?
San Mai is not a propriety steel to CS as a few makers use it for their blades as well but it is a superior steel to what CS normally uses on their knives...
Carbon V is a trademarked term by Cold Steel, and as such is not necessarily one particular kind of steel; rather, it describes whatever steel Cold Steel happens to be using, and there is an indication they do change steels from time to time. Carbon V performs roughly between 1095-ish and O1-ish, in my opinion, and rusts like O1 as well. I've heard rumors that Carbon V is O1 (which I think is unlikely) or 1095. Numerous industry insiders insist it is 0170-6. Some spark tests done by a rec.knives reader seem to point the finger at 50100-B. Since 50100-B and 0170-6 are the same steel (see below), this is likely the current Carbon V.
AUS-6- AUS-8- AUS-10(aka 6A 8A 10A)
Japanese stainless steels, roughly comparable in carbon content to 440A (AUS-6, .65% carbon) and 440B (AUS-8, .75% carbon) and 440C (AUS-10, 1.1% carbon). AUS-6 is used by Al Mar, and is a competitor to low-end steels like 420J2. Cold Steel's use of AUS-8 has made it pretty popular, as heat treated by CS it won't hold an edge like ATS-34, but is a bit softer (and therefore weaker) and tougher. 8A is a competitor of middle-tier steels like ATS-55 and Gin-1
400 Series Stainless
Before Cold Steel switched to AUS-8, many of their stainless products were marketed as being of "400 Series Stainless". Other knife companies are beginning to use the same term. What exactly *is* 400 Series Stainless? I always imagined it was 440-A, but there's nothing to keep a company from using any 4xx steel, like 420 or 425M, and calling it 400 Series Stainless