Heat treatment of ferrous alloys

Introduced: July 1974

CPC subdivides this area 4x more granularly than IPC with 6 additional codes.

6 codes are CPC-only extensions.

1 shared codes have differing titles between IPC and CPC.

IPC defines codes here since 1974.

Child Classifications

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C21D 6/001 CPC only CPC only
C21D 6/002 CPC only CPC only
C21D 6/004 CPC only CPC only
C21D 6/005 CPC only CPC only
C21D 6/007 CPC only CPC only
C21D 6/008 CPC only CPC only
C21D 6/02 Hardening by precipitation since 1974 IPC+CPC Available in IPC and CPC
C21D 6/04 Hardening by cooling below 0 degrees Celsius since 1974 IPC+CPC Available in IPC and CPC

Class C21,2013–2023, worldwide · Source: EPO PATSTAT

Class C21,2013–2023, worldwide · Source: EPO PATSTAT