| 摘要 |
PROBLEM TO BE SOLVED: To prevent the generation of the defect of nonplating by heating a rolled steel sheet contg. a specified amt. of P to a specified temp., executing cooling, thereafter removing a concentrated layer of the components in the steel on the surface of the steel sheet by pickling, executing reduction by heating in a reducing atmosphere under specified conditions and subsequently applying plating thereon. SOLUTION: A rolled steel sheet contg., by weight, <=0.10% P is heated to the temp. T1 of 750 to 950 deg.C. Reduction by heating after the removal of a concentrated layer of the components in the steel on the surface of the steel sheet by pickling is executed in such a manner that the heating temp. T2 is controlled to 650 to 900 deg.C, and also, both of T2<=T1+K and T2>=-T1+L are satisfied, where K=50 log (H2O/H2)+220, L=1000 P+1440, T1: the heating temp. ( deg.C) before cooling, T2: the heating temp. ( deg.C) at the time of the reduction by heating, H2O: the concn. (vol.%) of H2O in the atmospheric gas at the time of the reduction by heating, H2: the concn. (vol.%) of H2 in the atmospheric gas at the time of the reduction by heating, and P: the content (weight %) of P in the steel.
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