| 摘要 |
PURPOSE:To form the steel structure into a middle and fine grain structure having excellent characteristics in low heat energy consumption, in preparing structural steel of a forging machine, by utilizing coarse crystal grain growth inhibiting effect due to nitride of Ti, Zr and Hf to reduce a number of heat treating processes. CONSTITUTION:In preparing structural steel of a forging machine, a continuous cast steel segment is prepared from steel having a composition containing 0.12- 0.8% C, 0.1-1.0% Si, 0.3-2.5% Mn, 0.01-0.05% Al, one or more of Ti, Zr, Hf in an amount of 0.0075-0.035% calculated from formula Ti%+0.53XZr%+ 0.27X Hf%, (0.29XTi%+0.15XZr%+0.08XHf%)-0.015% N or one or more of 2% or less Cr, 3% or less Ni, 0.5% or less Mo and heated to 1,120-1,300 deg.C to be rolled and forged. Without necessitating heat treatment such as tempering, annealing or the like, the structure thereof can be formed into a middle and fine grain structure. |
