High-strength steel sheet and high-strength zinc-coated steel sheet which have excellent ductility and stretch-flangeability and manufacturing method thereof
US9139885B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 16, 2011 |
| Grant date | Sep 22, 2015 |
| Priority date | — |
| Expiry date | Sep 16, 2031 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC25D3/565
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
This high-strength steel sheet includes by mass percentage: 0.05 to 0.4% of C; 0.1 to 2.5% of Si; 1.0 to 3.5% of Mn; 0.001 to 0.03% of P; 0.0001 to 0.01% of S; 0.001 to 2.5% of Al; 0.0001 to 0.01% of N; 0.0001 to 0.008% of O; and a remainder composed of iron and inevitable impurities, wherein a steel sheet structure contains by volume fraction 10 to 50% of a ferrite phase, 10 to 50% of a tempered martensite phase, and a remaining hard phase, wherein a 98% hardness is 1.5 or more times as high as a 2% hardness in a range from ⅛ to ⅜ of a thickness of the steel sheet, wherein a kurtosis K* of the hardness distribution between the 2% hardness and the 98% hardness is −1.2 to −0.4, and wherein an average crystal grain size in the steel sheet structure is 10 μm or less.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.