| 摘要 |
PURPOSE:To produce a zinc-plated thin steel sheet having thermal hardenability by subjecting rimmed steel contg. limited compsns. of C, Mn, P, S, N, etc. to hot and cold rolling and to annealing for controlling the contents of C and N then to zinc plating. CONSTITUTION:The rimmed steel consisting of <=0.09% C, 0.15-0.45% Mn, <= 0.03% P, <= 0.03% S, <=0.006% N and the balance Fe and unavoidable impurities is subjected to ordinary hot rolling and is coiled at <=600 deg.C. After pickling, the hot-rolled steel plate is cold-rolled at >=40% draft and is then annealed by heating the same to a 580-740 deg.C temp. region in a gaseous atmosphere contg. H2 and N2 and holding the same at these temps. to control C to <=0.004% and N to 5-15ppm. In succession, the cold-rolled steel plate is heated to 450-800 deg.C and is applied with continuous zinc plating and an alloying treatment; thereafter the plated steel plate is subjected to skin pass rolling, whereby the zinc-plated thin steel sheet which has good deep drawability and formability and hardens during baking of painting is obtained. |
