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DIFF Main Group
C21D 1/00

General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering

Introduced: September 1968

IPC and CPC are identically structured here. All 15 subcodes exist in both systems.

4 shared codes have differing titles between IPC and CPC.

Child Classifications

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  • C21D 1/02 Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation IPC+CPC Available in IPC and CPC
  • C21D 1/04 with simultaneous application of supersonic waves, magnetic or electric fields IPC+CPC Available in IPC and CPC
  • C21D 1/54 Determining when the hardening temperature has been reached by measurement of magnetic or electrical properties IPC+CPC Available in IPC and CPC
  • C21D 1/55 Hardenability tests, e.g. end-quench tests since 1980 IPC+CPC Available in IPC and CPC
  • C21D 1/82 Descaling by thermal stresses (mechanically B21, B23; chemically C23; electrolytically C25F1/00) IPC+CPC Available in IPC and CPC
  • C21D 1/84 Controlled slow cooling (cooling-beds for metal rolling B21B43/00) since 1980 IPC+CPC Available in IPC and CPC

Top Applicants

Top Applicants (IPC)

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

  1. JFE STEEL JP 7,470
  2. POSCO (POHANG IRON AND STEEL COMPANY) KR 4,615
  3. JFE STEEL 4,538
  4. NIPPON STEEL CORPORATION JP 4,536
  5. ARCELORMITTAL LU 2,597
  6. NSSMC (NIPPON STEEL & SUMITOMO METAL) JP 2,241
  7. ANGANG STEEL COMPANY 2,126
  8. NSSMC (NIPPON STEEL & SUMITOMO METAL) 1,783
  9. BAOSHAN IRON & STEEL COMPANY 1,620
  10. HYUNDAI STEEL COMPANY KR 1,545

Top Applicants (CPC)

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

  1. JFE STEEL JP 8,270
  2. NIPPON STEEL CORPORATION JP 5,222
  3. POSCO (POHANG IRON AND STEEL COMPANY) KR 4,824
  4. JFE STEEL 3,311
  5. ARCELORMITTAL LU 3,239
  6. NSSMC (NIPPON STEEL & SUMITOMO METAL) JP 2,659
  7. HYUNDAI STEEL COMPANY KR 1,492
  8. ANGANG STEEL COMPANY 1,318
  9. BAOSHAN IRON & STEEL COMPANY 1,233
  10. KOBE STEEL JP 1,228