Manufacturing method of batch annealing type cold-rolled high tensile steel excellent in moldability and thermosetting property

摘要

High tension cold rolled steel is manufactured by (i) hot finish rolling at more than 880 deg.C, (ii) coiling at 550-600 deg.C, (iii) cold rolling with 75% reduction rate, (iv) batch annealing at 650-700 deg.C for 1-5 hours and (v) cooling at a rate of ln[R(C/hr) =- 18.708C(%)-0.87Mn(%)+2.4P(%)-6.977 sol.Al(%)+ 5.36. The steel comprises 0.01-0.02 wt.% C, 0.2-0.5 wt.% Mn, 0.05-0.1 wt.% P, 0.04- 0.2 wt.% sol.Al, a small amount of impurities, and balance Fe. The steel has good workability and heathardenability.