Process for manufacturing cold-rolled and annealed steel sheet with a very high strength, and sheet thus produced
US11414722B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 3, 2019 |
| Grant date | Aug 16, 2022 |
| Priority date | — |
| Expiry date | Dec 31, 2039 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC23G1/08
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A process for manufacturing a cold-rolled steel sheet with a strength of at least 1200 MPa and an elongation at break greater than 10%. A steel is provided having a microstructure comprising 65 to 90% bainite. A semifinished product is cast from the steel and heated to a temperature greater than 1150° C. The semifinished product is hot rolled to obtain a hot-rolled sheet; the coiled and pickled. Cold-rolling occurs with a reduction ratio of between 30 and 80% so as to obtain a cold-rolled sheet; and then reheating occurs at a rate Vc between 5 and 15° C./s up to a temperature T1 between Ac3 and Ac3+20° C. and held at said temperature T1 for a time t1 between 50 and 150 s. The sheet is cooled at a rate VR1 greater than 40° C./s but below 100° C./s down to a temperature T2 between (Ms−30° C. and Ms+30° C.). The sheet is maintained at temperature T2 for a time t2 between 150 and 350 s, and then cooled at a rate VR2 of less than 30° C./s down to an ambient temperature.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.