CPC Main Group C21D 6/00 Heat treatment of ferrous alloys 8 direct subcodes Child Classifications Navigate with arrow keys, Enter to open C21D 6/001 C21D 6/002 C21D 6/004 C21D 6/005 C21D 6/007 C21D 6/008 C21D 6/02 Hardening by precipitation C21D 6/04 Hardening by cooling below 0 degrees Celsius