| 摘要 |
PURPOSE:To obtain tough composite roll having inner layer of large tensile strength, by composing core material of special cast steel having a specified compsn. and specifying heat treating condition after diffusion heat treatment. CONSTITUTION:High Cr material contg. by weight 10-20% Cr is centrifugally cast to hollow-shaped outer layer. After the solidification, special cast steel composed of 0.5-1.0% C, 0.3-0.8% Si, 0.4-0.9% Mn, <=2% Ni, <=0.5% Cr, <=0.4% Mo and the balance Fe is cast as inner layer to roll shape. Roll-shaped body after casting the inner and outer layers is subjected to diffusion heat treatment in which it is heated to 900-1,000 deg.C then cooled to <=600 deg.C. Thereafter, the body is stepwisely held at temps. higher and lower than transformation point i.e. 750-780 deg.C and 680-710 deg.C, next, subjected to granulation heat treatment in which it is cooled to <=600 deg.C then quenched and annealed. In this way, composite roll having inner layer of >=60kg/mm<2> tensile strength is obtd. |
