| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength galvanized steel sheet which has excellent deep drawability, secondary working brittleness resistance and plating characteristics, and has tensile strength of about >=400 MPa. SOLUTION: In the production of the galvanized steel sheet, as stock components, particularly, Nb is contained in 0.001 to 0.2 mass%, also, Ti is contained in 0.002 to 0.05 mass% so as to satisfy 0.3×(C/12)<=Nb/93<=3.0×(C/12) Ti, further, Ti/48<= 1.5×(N/14+S/32) and N-(14/48)Ti<=0 are satisfied, and Mo is contained in the range of 0.05 to 2.0 mass%. A steel slab is heated and soaked at 950 to 1,300 deg.C, and is thereafter hot-rolled. The steel sheet is coiled at 400 to 850 deg.C, and is thereafter picked. The steel sheet is subjected to cold rolling of 50 to 95% and recrystallization annealing at 700 to 950 deg.C. The steel sheet is thereafter subjected to skinpass rolling, and again, galvanizing treatment including pickling and annealing is performed thereto.
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