High strength steel sheet and method for manufacturing the same
US9200343B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 28, 2011 |
| Grant date | Dec 1, 2015 |
| Priority date | — |
| Expiry date | Feb 28, 2031 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D2211/008
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A high strength steel sheet has tensile strength of at least 1470 MPa and (tensile strength ×total elongation) of at least 29000 MPa·% with a composition including, by mass %, C.: 0.30% to 0.73%, Si: 3.0% or less, Al: 3.0% or less, Si+Al: at least 0.7%, Cr: 0.2% to 8.0%, Mn: 10.0% or less, Cr+Mn: at least 1.0%, P: 0.1% or less, S: 0.07% or less, N: 0.010% or less, and remainder as Fe and incidental impurities; and processing the steel sheet such that microstructure satisfies area ratio of martensite with respect to the microstructure of 15% to 90%; content of retained austenite of 10% to 50%; at least 50% of the martensite is constituted of tempered martensite and area ratio of the tempered martensite with respect to the microstructure is at least 10%; and area ratio of polygonal ferrite with respect to the microstructure is 10% or less.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.