My brother in law is a machinist and he sharpens large circ. saw blades (18-24" & 1/8" thick) for mills in the area. the ones that cant be sharpend any more he throws them away or brings them to me. I have no idea what they'r made of but when i cut out a knife blank i can put it in a vice and it is all I can do to just barely bend it by hand & the steel will hold a beautiful edge. Once the steel is buffed (i dont like a polish blade) I coat it with teflon car wax and wipe it off. do that after every hunting season and never had any problems. ive made dozens of them and give them to family and friends with no complaints