High-strength steel sheet and production method for same, and production method for high-strength galvanized steel sheet
US10662496B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 5, 2015 |
| Grant date | May 26, 2020 |
| Priority date | — |
| Expiry date | Aug 13, 2036 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D2211/005
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
Disclosed is a high-strength steel sheet having a tensile strength (TS) of 780 MPa or more and excellent in ductility, fatigue properties, balance between high strength and ductility, surface characteristics, and sheet passage ability that can be obtained by providing a predetermined chemical composition and a steel microstructure that contains, by area, 20-50% of ferrite, 5-25% of bainitic ferrite, and 5-20% of martensite, and that contains, by volume, 10% or more of retained austenite, in which the retained austenite has a mean grain size of 2 μm or less, a mean Mn content in the retained austenite in mass % is at least 1.2 times the Mn content in the steel sheet in mass %, and the retained austenite has a mean free path of 1.2 μm or less.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.