METHOD FOR PRODUCING COLD ROLLED STEEL SHEET FOR SOFT-ORGANIC COATING HAVING EXCELLENT MOLDING PROPERTY

摘要

PURPOSE: A cold rolled steel sheet for soft-organic coating is provided to secure a certain level of annealing-hardening property and to have an excellent molding property. CONSTITUTION: An aluminium killed steel slab contains 0.0020 to 0.0030wt% of C, less than 0.02wt% of Si, 0.07 to 0.40wt % of Mn, 0.008 to 0.04wt% of P, 0.008 to 0.015wt% of S, 0.05 to 0.08wt% of soluble Al, less than 0.0020wt% of N and 0.006 to 0.01wt% of Nb. The slab is satisfied with an equal to or more than 25 weight rate of Al/N and a 0.33 to 0.5 range of an atom rate of Nb/C. Herein, the slab is homogenization-heat treated at more than 1200°C and is hot-rolled at 900 to 950°C. The slab is wound up at 700 to 750°C and is cold-rolled at the 70 to 80% of depression rate. The slab is continuously annealed at 770 to 830°C and roughly rolled by 1.5 to 2.0%.