| 摘要 |
PURPOSE:To enhance the cold and heat hardenability by annealing a rimmed steel contg. specified amounts of C, Mn, P, S and N after hot and cold rolling in an atmosphere with a specified N content while blowing gaseous NH3 is an amount satisfying a specified equation. CONSTITUTION:A rimmed steel consisting of, by weight, 0.02-0.1% C, 0.15- 0.8% Mn, 0.03-0.1% P, <0.02% S, <0.005% N and the balance Fe with inevitable impurities is hot rolled by an ordinary method and cold rolled. The rolled steel is then annealed at 600-800 deg.C in an atmosphere with 30-200ppm N content and 4-75% gaseous H2 content while blowing gaseous NH3 in an amount satisfying the equiation, wherein PH2 is the partial pressure of hydrogen, PNH3 is the partial pressure of ammonia, and N is the soluble N content in the steel. |
