PRODUCTION OF HIGH STRENGTH COLD ROLLED STEEL PLATE FOR DEEP DRAWING HAVING NON-AGING CHARACTERISTIC AND EXCELLENT HARDENABILITY BY BAKING OF PAINTING BY CONTINUOUS ANNEALING

摘要

PURPOSE:To obtain a titled cold-rolled steel plate which is virtually free from yield point elongation as annealed by hot and cold rolling low carbon Al-killed steel then soaking the steel plate by continuous annealing in a prescribed temp., range followed by cooling above the specific average cooling rate from said temp. CONSTITUTION:The low carbon Al-killed steel contg. 0.001-0.010% C, =1.5% Mn, =1.0% Si, 0.04-0.12% P, 0.005-0.20% Al, =0.007% N, B and N in 0.5- 2.5 B/N (by weight %) is treated as follows: Said Al-killed steel is hot-rolled at above Ar3 finishing temp. and is then coiled at =650 deg.C. The coiled steel plate is cold-rolled at =75% cold rolling draft. In succession the steel plate obtained by the cold rolling is soaked in a 730 deg.-Ar3 point temp. range by continuous annealing and is then cooled quickly at =60 deg.C/sec average cooling rate from the soaking temp. -450 deg.C. As a result, the intended cold-rolled steel plate is obtained.