| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a high-strength galvannealed steel sheet extremely high in tensile strength and excellent in bending properties and stretch-flanging properties, and a method for manufacturing the same. <P>SOLUTION: The steel plate has a chemical composition including, by mass, C: >0.07% and≤0.15%, Si: >0.001% and≤0.80%, Mn: >2.1% and≤3.5%, P:≤0.02%, S:≤0.01%, sol. Al:≥0.001% and≤0.40%, Ti:≥0.030% and≤0.25%, B: >0.0015% and≤0.010%, and N:≤0.01%, and has a steel structure including, by area%, ferrite:≥20% and≤60% and residual austenite:≥0.5% and≤3.0%, non-recrystallized ferrite being <0.5%. The galvannealed steel sheet has a mechanical characteristic in which tensile strength (TS) is 980 MPa or more. <P>COPYRIGHT: (C)2012,JPO&INPIT</p> |
