| 摘要 |
PURPOSE:To provide the title steel plate comparable to one produced by use of box-type annealing by a method wherein steel ingot contng. specific amount of C, Si, and Mn, with specific amount of specific element such as P is hot- and cold-rolled to produce steel plate, which is heated to a specified temperature, then is continuously annealed, into which a specific strain is introduced, and thereafter is processed by aging. CONSTITUTION:A steel ingot used consists of in %: C: 0.03-0.2, Si<=3, Mn: 0.2-2, one or more selected from the group consisting of P: 0.03-0.2, Mo: 0.1-0.6, Nb: 0.01-0.1, V: 0.01- 0.1, Ti: 0.02-0.2, Zr: 0.01-0.2, W: 0.01-0.2, and Ni: 0.1-0.5, and further Al: 0.15 or less, the rest: Fe. The ingot is hot rolled at wonding temperature of 600 deg.C or more, and is cold rolled under reduction ratio of 30% or more to produce a steel plates. The steel plates are uniformly heated at a temperature higher than recrystallization and less than 850 deg.C to effect continuous annealing. Then, strain of 0.3-3% is introduced into the steel plates, which undergo overaging treatment at 250-350 deg.C. The process thus provides the title steel plates wherein defects to occur in the conventional continuous annealing are improved. |
