Method for producing a high strength steel sheet having high ductility, formability and weldability, and obtained steel sheet
US11713502B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | May 7, 2018 |
| Grant date | Aug 1, 2023 |
| Priority date | — |
| Expiry date | Nov 22, 2039 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC22C38/14
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A method for producing a high-strength steel sheet having high ductility, formability and weldability includes providing a cold-rolled sheet, with a composition containing: 0.15% ≤C≤0.23%, 1.4% ≤Mn≤2.6%, 0.6% ≤Si≤1.3%, with C+Si/10≤0.30%, 0.4% ≤Al≤1.0%, with Al≥6(C+Mn/10)−2.5%, 0.010% ≤Nb≤0.035%, 0.1% ≤Mo≤0.5%, annealing the sheet at 860° C.-900° C. to obtain a structure consisting of at least 90% austenite and at least 2% intercritical ferrite, quenching to a temperature between Ms-10° C. and Ms-60° C. at a rate Vc higher than 30° C./s, heating to a temperature PT between 410° C. and 470° C. for 60 s to 130 s, hot-dip coating the sheet, and cooling to room temperature. The microstructure includes 45% to 68% of martensite, consisting of 85% to 95% partitioned martensite having a C content of at most 0.45%, and fresh martensite; 10% to 15% retained austenite; 2% to 10% intercritical ferrite; 20% to 30% lower bainite.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.