| 摘要 |
PURPOSE:To manufacture easily a high-strength cold-rolled steel plate with supperior press formability by properly selecting conditions during the hot rolling of a steel, a draft during the cold rolling and conditions during the continuous annealing as well as the composition of the steel. CONSTITUTION:A steel contg. 0.02-0.06% C, 0.01-1.0% Si, 0.05-0.30% Mn, 0.01-0.15% P, <0.020% S, 0.020-0.07% sol.Al and <0.0030% N is hot rolled to a plate at a finishing temp. above the Ar3 point and coiled at >650 deg.C. The plate is cold rolled at >=70% draft and held at 750-900 deg.C for 30sec-5min in a continuous annealing furnace. The cold rolled steel plate is cooled from the A1 point to 800 deg.C at 5-30 deg.C/sec cooling rate, hardened in a jet of water, and tempered at 200-500 deg.C for 30sec-5min. A steel plate with 40-60kg/mm.<2> tensile strength and deep drawability is obtd. The plate has a composite structure consisting of ferrite and martensite. |
