MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)

Introduced: September 1968

Description

C21D encompasses heat treatment processes and equipment that alter the physical and mechanical properties of ferrous metals and alloys through controlled thermal cycles, including annealing, tempering, hardening, normalizing, and stress relief. The class also covers general-purpose heat treatment apparatus applicable to both ferrous and non-ferrous metals, as well as specific processes for improving workability such as decarburization and softening treatments. This classification excludes specialized surface treatment methods (covered under C21C) and specific alloy composition modifications, focusing instead on structural transformation achieved via temperature control and cooling regimens.

Title

Titles differ between systems:

IPC: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING

CPC: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)

Full Title

Full titles differ between systems:

IPC:

MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING

CPC:

MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)

Of 16 combined children, 9 exist in both systems.

7 codes are CPC-only extensions.

Note: 7 CPC extensions are marked as secondary classification only.

4 shared codes have differing titles between IPC and CPC.

Child Classifications

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C21D 1/00 General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering IPC+CPC Available in IPC and CPC
C21D 10/00 Modifying the physical properties by methods other than heat treatment or deformation since 1980 +1 CPC IPC+CPC Available in IPC and CPC
C21D 11/00 Process control or regulation for heat treatments since 1974 +1 CPC IPC+CPC Available in IPC and CPC
C21D 2201/00 Treatment for obtaining particular effects 2nd only +5 CPC CPC only CPC only
C21D 2211/00 Microstructure comprising significant phases 2nd only +9 CPC CPC only CPC only
C21D 2221/00 Treating localised areas of an article 2nd only +3 CPC CPC only CPC only
C21D 2241/00 Treatments in a special environment 2nd only +2 CPC CPC only CPC only
C21D 2251/00 Treating composite or clad material 2nd only +2 CPC CPC only CPC only
C21D 2261/00 Machining or cutting being involved 2nd only CPC only CPC only
C21D 2281/00 Making use of special physico-chemical means 2nd only +2 CPC CPC only CPC only
C21D 3/00 Diffusion processes for extraction of non-metals; Furnaces therefor (local protective coatings C21D1/72) IPC+CPC Available in IPC and CPC
C21D 5/00 Heat treatments of cast-iron IPC+CPC Available in IPC and CPC
C21D 6/00 Heat treatment of ferrous alloys since 1974 +6 CPC IPC+CPC Available in IPC and CPC
C21D 7/00 Modifying the physical properties of iron or steel by deformation (apparatus for mechanical working of metal B21, B23, B24) IPC+CPC Available in IPC and CPC
C21D 8/00 Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) since 1980 IPC+CPC Available in IPC and CPC
C21D 9/00 Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor +12 CPC IPC+CPC Available in IPC and CPC