Steel sheet and manufacturing method therefor
US11377710B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 30, 2018 |
| Grant date | Jul 5, 2022 |
| Priority date | — |
| Expiry date | May 3, 2038 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/26
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A steel sheet has a chemical composition with a steel structure containing, by volume fraction, soft ferrite: 0-30%, retained austenite: 3-40%, fresh martensite: 0-30%, pearlite and cementite: 0-10%, and a remainder including hard ferrite. In the steel sheet, a number proportion of retained austenite having an aspect ratio of 2.0 or more in the total retained austenite is 50% or more, and a soft layer having a thickness of 1-100 μm is present. In the soft layer, a volume fraction of ferrite grains having an aspect ratio of less than 3.0 is 50% or more, and a volume fraction of retained austenite is 50% or more of the volume fraction of the retained austenite of the inside of the steel sheet. A peak of an emission intensity at a wavelength indicating Si appears in a range of more than 0.2 μm to 5 μm or less from the surface.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.