| 摘要 |
PURPOSE:To make the production of a cold-rolled steel plate having excellent workability possible by subjecting a cold-rolled steel plate of Al killed steel to a continuous annealing treatment under specific conditions. CONSTITUTION:A continuously cast slab of the Al killed steel contg. 0.01-0.08% C, 0.05-0.35% Mn, 0.004-0.100% acid sol. Al, <0.01% N which is <=1/2 the content of Al is hot-rolled and is coiled at <=630 deg.C. After the hot-rolled steel plate is descaled by pickling, the plate is cold-rolled at >=50% draft to a cold- rolled steel plate. In the stage of continuous annealing of such cold-rolled steel plate, the plate is held for 5-240sec at a 650 deg.C-A1 transformation point temp. region or is held for 5-240sec at A1 transformation point -800 deg.C and is cooled down to temp. below the A1 transformation point at <=8 deg.C/sec cooling rate. In succession, the plate is quickly cooled to 550-500 deg.C at 30-100 deg.C/sec cooling rate and after the plate is held for >=15sec at said temp., the same is overaged for 20-300sec at 550-300 deg.C. |
