| 摘要 |
PURPOSE:To improve the baking hardenability and powdering resistance of a cold rolled steel sheet contg. C, Si, Mn, P, Al, S, N and Ti limited to a prescribed range by subjecting such steel sheet to galvanizing and alloying treatment under prescribed conditions. CONSTITUTION:The steel contg., by weight %, 0.0005-0.007% C, <=0.5% Si, <=1% Mn, <=0.1% P, 0.005-0.1% Al and in addition, <=0.005% S+N and further Ti of the effective content of 3-20 times [C%] is melted. The effective content of Ti mentioned above is expressed by (Ti%)-48/14(N%)-48/32(S%). The cold rolled sheet of the steel produced in the above-mentioned manner is heated to 400-550 deg.C and is galvanized. The galvanized sheet is subjected to the alloying treatment at 700-850 deg.C. The concn. of Fe in the alloyed galvanizing layer on the surface is adjusted to 15-35% and the rate of baking hardening to >=3kgf/mm<2>.
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