| 摘要 |
PURPOSE:To improve tube making property and to prevent the occurrence of defects after tube making by specifying steel components, their percentages, hot rolling and cold rolling conditions, and annealing conditions, respectively. CONSTITUTION:A steel has a composition consisting of, by weight, 0.02-0.10% C, <=0.5% Si, 0.1-00.5% Mn, 0.002-0.04% P, <=0.04% S, <=0.08% Al, and the balance Fe with inevitable impurities. This steel is hot-rolled at a finishing temp. not lower than the Ar3 point at <=650 deg.C coiling temp., cold-rolled at >=50% draft, and successively box annealed at a temp. between the recrystallization temp. and 680 deg.C, or, the above steel is cold-rolled and then continuously annealed at <=750 deg.C. By this method, the cold rolled steel sheet excellent in tube making property can be obtained. Further, shape after tube making, the condition of bead machined part, etc., can be improved into superior state. |
