| 摘要 |
PROBLEM TO BE SOLVED: To prevent the deterioration of surface properties caused by a striped pattern notably appearing in a galvannealed steel sheet for automotive panel use in which a Ti-containing extra-low-carbon steel sheet with high formability is used as a basis material. SOLUTION: The steel sheet has a chemical composition containing, by mass,≤0.0038% C,≤0.20% Si, 0.03 to 0.2% Mn,≤0.03% P,≤0.03% S, 0.010 to 0.23% Al,≤0.0040% N,≥0.003% Ti and 0.021 to 0.05% Nb and further containing≤0.0020% B if necessary. Further, with respect to the Ti content in this chemical composition, Mn/äS-(32/48)×Ti*}≥14 is satisfied and also any of the following conditions (1) to (3) are satisfied: (1) Ti≤0.014% is satisfied; (2) S-(32/48)×Ti*≤0 is satisfied (where Ti* satisfies Ti*=Ti-(48/14)×N and also satisfies Ti*=0 when Ti*≤0); and (3) Ti≤(48/14)×N+(48/32)×S is satisfied. COPYRIGHT: (C)2008,JPO&INPIT
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