| 摘要 |
PROBLEM TO BE SOLVED: To produce a galvanized steel sheet which is a base material for a surface treated steel sheet used as an automotive exterior material free from the generation of pinholes after coating, and to provide a method for producing the same. SOLUTION: At the time of subjecting a low carbon or extra-low carbon Al killed steel slab contg., by weight, <=0.08% C, <=0.2% Si, 0.1 to 1.5% Mn and <=0.08% P to hot rolling, coiling is executed under the cooling conditions shown by [TC-500×(1+4×P[wt.%])]/Cr<1000/√P[wt.%]+5×-104×C[wt.%]; TC: the coiling temp. ( deg.C); CR: the average cooling rate ( deg.C/sec) to 500×(1+4×P[wt.%]) deg.C after the coiling, and P segregation in the grain boundaries is made small as much as possible. The obtd. hot rolled steel sheet is subjected to cold rolling and annealing, and then galvanized.
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