C21D
Modifying the physical structure of ferrous metals
Official title: 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)
C21D (Modifying the physical structure of ferrous metals) appears on 14,647 US grants and 15,422 published applications in this corpus.
Search patents in C21D- Granted patents
- 14,647
- Published applications
- 15,422
- Assignees
- 4,175
- Inventors
- 27,174
- Latest grant
- 6 Oct 2026
Filings by year
| Year | Granted patents | Published applications |
|---|---|---|
| 1976 | 178 | 0 |
| 1977 | 150 | 0 |
| 1978 | 156 | 0 |
| 1979 | 115 | 0 |
| 1980 | 158 | 0 |
| 1981 | 131 | 0 |
| 1982 | 129 | 0 |
| 1983 | 171 | 0 |
| 1984 | 169 | 0 |
| 1985 | 166 | 0 |
| 1986 | 190 | 0 |
| 1987 | 144 | 0 |
| 1988 | 175 | 0 |
| 1989 | 193 | 0 |
| 1990 | 172 | 0 |
| 1991 | 178 | 0 |
| 1992 | 165 | 0 |
| 1993 | 176 | 0 |
| 1994 | 182 | 0 |
| 1995 | 171 | 0 |
| 1996 | 176 | 0 |
| 1997 | 182 | 0 |
| 1998 | 227 | 0 |
| 1999 | 228 | 0 |
| 2000 | 245 | 0 |
| 2001 | 291 | 68 |
| 2002 | 274 | 266 |
| 2003 | 290 | 319 |
| 2004 | 239 | 341 |
| 2005 | 165 | 250 |
| 2006 | 135 | 289 |
| 2007 | 124 | 282 |
| 2008 | 119 | 331 |
| 2009 | 157 | 455 |
| 2010 | 219 | 499 |
| 2011 | 237 | 454 |
| 2012 | 277 | 512 |
| 2013 | 304 | 617 |
| 2014 | 342 | 683 |
| 2015 | 369 | 833 |
| 2016 | 437 | 880 |
| 2017 | 572 | 862 |
| 2018 | 584 | 872 |
| 2019 | 732 | 917 |
| 2020 | 690 | 882 |
| 2021 | 649 | 810 |
| 2022 | 730 | 954 |
| 2023 | 603 | 878 |
| 2024 | 619 | 846 |
| 2025 | 691 | 688 |
| 2026 | 471 | 634 |
By publication year. Applications have been published since 2001. 2026 runs to 8 Oct.
Main groups
Granted patents with any code in the group
- C21D 9/00Heat treatment8,598
- C21D 1/00General methods or devices for heat treatment6,542
- C21D 8/00Modifying the physical properties of ferrous metals or ferrous alloys by deformation6,355
- C21D 2211/00Microstructure comprising significant phasesIndexing code3,808
- C21D 6/00Heat treatment of ferrous alloys3,515
- C21D 7/00Modifying the physical properties of iron or steel by deformation1,499
- C21D 2201/00Treatment for obtaining particular effectsIndexing code738
- C21D 2221/00Treating localised areas of an articleIndexing code699
All 16 main groupsShow fewer
- C21D 11/00Process control or regulation for heat treatments525
- C21D 10/00Modifying the physical properties by methods other than heat treatment or deformation449
- C21D 3/00Diffusion processes for extraction of non-metals313
- C21D 2261/00Machining or cutting being involvedIndexing code221
- C21D 2251/00Treating composite or clad materialIndexing code217
- C21D 5/00Heat treatments of cast-iron190
- C21D 2241/00Treatments in a special environmentIndexing code80
- C21D 2281/00Making use of special physico-chemical meansIndexing code44
Recent patents
- Housing of an induction hardening tool6 Oct 2026US 12,752,288 B2Aktiebolaget Skf
- Forged steel roll for cold rolling6 Oct 2026US 12,752,325 B2Nippon Steel Corporation
- Workpiece holding device6 Oct 2026US 12,753,453 B2Aktiebolaget Skf
- High strength steel sheet and method of producing same6 Oct 2026US 12,753,454 B2Jfe Steel Corporation
- Ultra-high strength cold rolled steel sheet having excellent bendability, and method of manufacturing same6 Oct 2026US 12,753,455 B2Posco
- Blank, production method for structural member and structural member8 Oct 2026US 2026/0307133 A1Nippon Steel Corporation
- A cold rolled martensitic steel and a method of martensitic steel thereof8 Oct 2026US 2026/0308706 A1
- Non-oriented electrical steel plate with high magnetic induction and manufacturing method thereof8 Oct 2026US 2026/0308707 A1Baoshan Iron & Steel Co., Ltd.
- Steel plate and method for manufacturing same8 Oct 2026US 2026/0308708 A1Posco
- Martensitic stainless steel strip8 Oct 2026US 2026/0308709 A1Proterial, Ltd.
Most cited
By later US patents
- Method for annealing stapler anvils1,469US 5,173,133 AUnited States Surgical Corporation · 1992
- Surface hardening of cams of motor-vehicle camshafts1,402US 4,312,685 AAudi NSU Auto Union Aktiengesellschaft · 1982
- Systems for percutaneous bone and spinal stabilization, fixation and repair1,069US 6,127,597 ADiscoTech N.V. · 2000
- Method of making iron golf clubs with flexible impact surface459US 4,398,965 APepsiCo, Inc. · 1983
- Hydrogen annealing process and apparatus therefor428US 6,527,884 B1Hitachi Kokusai Electric Inc. · 2003