Si-containing high-strength cold rolled steel sheet, method of producing the same, and automotive members (as amended)
AssigneeJfe Steel Corporation
InventorsHiroyuki Masuoka, Reiko Sugihara, Takashi Kawano
Life of this patent
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Abstract
A Si-containing high-strength cold rolled steel sheet has a chemical composition comprising C: 0.0˜20.3 mass %, Si: 0.8˜2.0 mass %, Mn: 1.0˜5.0 mass % and the remainder being Fe and inevitable impurities with a ratio of Si content to Mn content (Si/Mn) exceeding 0.4, and has a tensile strength TS of not less than 780 MPa, wherein a metallic structure of the steel sheet surface contains polygonal ferrite and/or bainitic ferrite having a Si concentration of not more than 3.0 mass % and a grain size of not more than 10 μm and does not have a Si-containing oxide layer on the steel sheet surface.
Claims11
1-6. (canceled)
A Si-containing high-strength cold rolled steel sheet having a chemical composition comprising C:
- 0.02˜0.3 mass %, Si:
- 0.8˜2.0 mass %, Mn:
- 1.0˜5.0 mass % and the remainder being Fe and inevitable impurities with a ratio of Si content to Mn content (Si/Mn) exceeding 0.4 and having a tensile strength TS of not less than 780 MPa, wherein a metallic structure of the steel sheet surface contains polygonal ferrite and/or bainitic ferrite having a Si concentration of not more than 3.0 mass % and a grain size of not more than 10 μm and does not have a Si-containing oxide layer on the steel sheet surface.
Dependencies are inferred from the claim text.