| 摘要 |
PURPOSE:To obtain the titled cold rolled plate by adding a specified small amount of Ti to steel having a specified high Mn content, controlling the C content to a specified low level at the time of blowing out after refining in a converter, and restricting the ratio between P% and S% of the steel to a specified value. CONSTITUTION:Steel is refined in a converter and discharged so as to adjust the C content to 0.03-0.08wt% at the time of blowing out. This steel contg., by wt., 0.03-0.09% C, 0.02-0.12% Ti, 1.8-2.5% Mn, 0.005-0.2% Al, 0.001-0.02% N, 0.01-0.025% P, <0.01% S (P%/S%>=1.3), <0.5% Si and <0.02% O as principal components is hot rolled at >1,200 deg.C slab heating temp., >870 deg.C hot rolling finish temp. and <650 deg.C hot coiling temp. and cold rolled at 30-80% reduction ratio. Recrystallization annealing is then carried out at 830-900 deg.C annealing temp. to obtain a steel plate having 10-70ppm acid-insoluble N content, 0.01-0.09% acidinsoluble Ti content, 50-90kg/mm<2> tensile strength and >0.7 yield ratio. |
