| 摘要 |
<p>A high-tensile, cold-rolled steel plate with excellent formability, suitable as material for bodies of lightweight automobiles or the like, and which comprises 0.002 to 0.015% of C; not more than 1.2% of Si; 0.04 to 0.8% of Mn; 0.03 to 0.10% of P; 0.02 to 0.10% (not less than N% x 4) of Al; C% x 3 to (C% x 8 + 0.020%) of Nb; and the balance of Fe. This plate is produced by hot-rolling steel slab of the above-described formulation while adjusting the total draft to not less than 90% and the rolling speed of finish roll to not less than 40 m/min., winding the rolled product at a temperature not lower than 600 C, cold-rolling the resulting hot-rolled coil to obtain cold-rolled steel band of the final thickness, continuously annealing it at 700 to 800 C for 10 sec to 5 min, and then cooling it to 500 C at a cooling speed of not less than 60 C/min. Steel of the above-described formulation wherein Si content is 0.5% or less is suited for continuous galvanizing. </p> |
