Steel sheet
AssigneeNippon Steel Corporation
InventorsKatsuya Nakano, Kunio Hayashi, Yuri Toda, Eisaku Sakurada, Akihiro Uenishi
Life of this patent
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Abstract
A steel sheet includes a predetermined chemical composition and a metal structure represented by, in area fraction, ferrite: 30% to 50%, granular bainite: 5% to 20%, martensite: 30% to 55%, bainite: less than 35%, and retained austenite and pearlite: 10% or less in total. Preferably, of the steel sheet, a tensile strength is 1180 MPa or more, elongation is 10% or more, and a hole expansion value is 20% or more. Further preferably, a VDA bending angle in the case where a thickness is set to t (mm) is “7.69t2−38.4t+109” or more.
Claims12
A cold-rolled steel sheet comprising:
- a chemical composition represented by, in mass %,
- C:
- 0.09% to 0.15%,
- Si:
- 0.2% to 2.5%,
- Al:
- 0.01% to 1.00%,
- Mn:
- 1.0% to 3.0%,
- P:
- 0.02% or less,
- S:
- 0.01% or less,
- N:
- 0.007% or less,
- O:
- 0.006% or less,
- Cr:
- 0.00% to 1.00%,
- Mo:
- 0.00% to 1.00%,
- B:
- 0.0000% to 0.010%,
- Nb:
- 0.000% to 0.30%,
- Ti:
- 0.000% to 0.30%,
- Ni:
- 0.00% to 1.00%,
- Cu:
- 0.00% to 1.00%,
- V:
- 0.000% to 0.50%,
- Mg:
- 0.0000% to 0.04%,
- REM:
- 0.0000% to 0.04%, and
- the balance:
- Fe and impurities;
- and
- a metal structure represented by, in area fraction,
- ferrite:
- 30% to 50%,
- granular bainite:
- 5% to 20%,
- martensite:
- 30% to 55%,
- bainite:
- less than 35%, and
- retained austenite and pearlite:
- 10% or less in total,
- wherein
- a tensile strength is 1180 MPa or more.
Dependencies are inferred from the claim text.