| 摘要 |
PURPOSE:To obtain the titled cold rolled steel plate by forming a steel contg. specified amounts of C, Mn, Si, P, S and sol. Al into a slab, subjecting the slab to hot finish rolling at a temp. above the A3 point, coiling the rolled plate, cold rolling it, and water-hardening the cold rolled steel plate with sprayed water from a temp. not lower than the temp. obtd. in accordance with the Mn content. CONSTITUTION:A steel consisting of, by wt%, 0.04-0.15% C, 0.5-1.5% Mn, 0.02-1% Si, 0.01-0.1% P, <0.02% S, 0.01-0.1% sol.Al and the balance Fe with inevitable impurities is formed into a slab, and the slab is subjected to hot finish rolling at a temp. below the A3 point, coiled at <=750 deg.C, and cold rolled. The cold rolled steel plate is annealed by heating and soaking at 730-900 deg.C and cooling at 5-30 deg.C/sec cooling rate, and it is hardened with sprayed water from a temp. not lower than the temp. obtd. in accordance with the Mn content within the range of 700-450 deg.C. Heat treatment is then carried out again at <=300 deg.C. Thus, a high tensile cold rolled steel plate with <=65% low yield ratio and >=5kg/mm.<3> high burning hardenability is obtd. |
