High-strength cold-rolled steel sheet having high r value and process for manufacturing the same
US4961793A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 18, 1988 |
| Grant date | Oct 9, 1990 |
| Priority date | — |
| Expiry date | Nov 18, 2008 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC22C38/16
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A heat-treatment-hardenable cold-rolled steel sheet having a high r value, comprising 0.010% or less of carbon, 0.05 to 0.5% of manganese, 1.0% or less of silicon, 0.001 to 0.030% of sulfur, 0.03% or less of phosphorus, 0.0050% or less of nitrogen, 0.005 to 0.10% of sol. aluminum, and 0.8 to 2.2% of copper with the balance being iron and unavoidable elements and, optionally incorporated therein, either or both of titanium and niobium and further nickel and optionally boron. The steel sheet can be manufactured by subjecting a cold-rolled steel sheet having this composition to recrystallization annealing at a temperature of 750.degree. C. or above and then heat-treating the steel sheet at a temperature ranging from 450.degree. to 700.degree. C. for 1 minute or longer. Alternatively, after the recrystallization annealing, the sheet can be cooled to a temperature of 450.degree. C. or below within 1 minute, followed by work deformation and heat-treating the work-deformed product at a temperature of 450.degree. C. or above to increase the strength of the steel sheet.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.