High-strength galvannealed steel sheet having excellent formability and fatigue resistance and method for manufacturing the same
US9580785B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 3, 2014 |
| Grant date | Feb 28, 2017 |
| Priority date | — |
| Expiry date | Dec 2, 2034 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC23C2/29
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
The present invention provides a method for manufacturing a high-strength galvannealed steel sheet. The method includes hot-rolling a slab to produce a hot-rolled sheet having a microstructure in which a total area ratio of bainite and martensite is 80% or more, cold-rolling the hot-rolled sheet to produce a cold-rolled steel sheet, continuously annealing the cold-rolled steel sheet by heating to 750° C. to 900° C. at an average heating rate of 8° C./s or more from 500° C. to an A1 transformation point, holding the steel sheet for 10 seconds or more, and then cooling the steel sheet to a temperature region of 300° C. to 530° C. at an average cooling rate of 3° C./s or more from 750° C. to 530° C., galvanizing the steel sheet, and further coating-alloying the steel sheet in a temperature region of 540° C. to 600° C. for 5 to 60 seconds.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.