Method for manufacturing a high-formable, high-strength cold-rolled steel sheet excellent in resistance to secondary working embrittlement
US5542994A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 23, 1994 |
| Grant date | Aug 6, 1996 |
| Priority date | — |
| Expiry date | Dec 23, 2014 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D2211/005
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A method of producing a high-formable, high-strength cold-rolled steel sheet from a steel slab comprising a steel with very low carbon content, one or both of Ti and Nb as a composition for forming a carbide or a nitride, and B in the range satisfying the following expression: EQU 0.001 A.ltoreq.B (wt %).ltoreq.0.003 A wherein A is a parameter determined approximately by the following expression with reference to the relation: A=P (wt %)+0.2 Mn (wt %)+0.8 Si (wt %)-0.2, subjecting the steel to a hot rolling so as to finish at a temperature between about Ar.sub.3 transformation temperature and about Ar.sub.3 transformation temperature +100 C.degree.. Thereafter, the steel is successively subjected to coiling, cold-rolling and, then, continuous annealing at temperatures between Ac.sub.1 transformation temperature +5 C.degree. and Ac.sub.1 transformation temperature +50 C.degree., and not lower than 860 C.degree.. Thus, a volume percentage of a low temperature transformation phase is controlled within the range of about 5 to about 50%, thereby obtaining a high strength cold-rolled steel sheet having a tensile strength of 38 kgf/mm.sup.2 or more, plus excellent formability and resistan…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.