| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a high tensile hot dip galvannealed steel sheet excellent in shape fixability, plating adhesion and ductility, and its manufacturing method. <P>SOLUTION: The galvannealed steel sheet contains, by mass%, 0.10-0.30% C,≤0.2% Si, 1.0-3.0% Mn, and 0.5-2.0% Al, and satisfies the following formula 1, and contains, by volume%, 3-50% martensite. Moreover, the galvannealed steel sheet may contain at least one of Ni, Co and Cu, and/or at least one of Ti, Nb and V, and/or at least one of Mo, Cr and B. The above formula 1 is expressed as 2≤Si (%) + Al (%) + Mn (%)≤4. This steel sheet can be manufactured by controlling a temperature and a time of a low temperature holding after annealing, cooling rate after galvannealing of the steel sheet of the composition. <P>COPYRIGHT: (C)2004,JPO</p> |
