C21C PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
Introduced: September 1968
Classification Context
- Section:
- CHEMISTRY; METALLURGY
- Class:
- METALLURGY OF IRON
- Subclass:
- PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
Description
C21C covers the refining of pig iron and the production of wrought iron and steel through various metallurgical processes, including treatment of ferrous alloys in their molten state. This subclass encompasses converters, furnaces, and processing methods designed to remove impurities and adjust chemical composition to achieve desired steel grades and properties. Technologies include basic oxygen processes, electric arc furnace operations, ladle metallurgy, and related thermal and chemical treatments. The scope extends to ferroalloy processing and molten metal handling techniques essential to modern steelmaking, but excludes mining, ore preparation, and the initial production of pig iron in blast furnaces (covered under C21B).
Additional Content
Glossary
Pig-iron intermediate product of smelting iron ore with a high-carbon fuel, e.g. coke, charcoal Wrought-iron iron alloy with low carbon content and fibrous inclusions Tuyères tubes, nozzles or pipes through which air is blown into a furnace
Limiting references
Treating molten metals during moulding , Making liquid steel by direct processes
Related Keywords
4 direct subcodes
Child Classifications
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Top Applicants
Top 10 applicants by patent filingsfor class C21, 2013–2023, worldwide · Source: EPO PATSTAT
- JFE STEEL JP 7,470
- POSCO (POHANG IRON AND STEEL COMPANY) KR 4,615
- JFE STEEL 4,538
- NIPPON STEEL CORPORATION JP 4,536
- ARCELORMITTAL LU 2,597
- NSSMC (NIPPON STEEL & SUMITOMO METAL) JP 2,241
- ANGANG STEEL COMPANY 2,126
- NSSMC (NIPPON STEEL & SUMITOMO METAL) 1,783
- BAOSHAN IRON & STEEL COMPANY 1,620
- HYUNDAI STEEL COMPANY KR 1,545