In the January 2003 Tactical Knives, Butch Winter had an article in his "Steel Bin" column on 8670. Butch says it was originally a Sharon Steel known as 0186-5, now being made in Germany. Composition;
Carbon: .70-.75%
Chromium: .4%
Nickel: .85%
Silicon: .25%
Manganese: .5%
Sulfur: .025%
Phosphorus: .025%
Butch also says it is used mainly in circular saws used to cut other steels. It is tough and can be hardened to HRC 58-59.