| 摘要 |
PURPOSE:To manufacture steel with high toughness at low cost by treating steel, which contains C, Si, Mn, and Al at a specific ratio, by reheating, rolling, forcible cooling, and quenching under specific conditions. CONSTITUTION:Steel which consists of 0.01-0.20% C, <=1% Si, 0.5-3% Mn, 0.01-0.1% Al, the balance Fe with inevitable impurities is reheated above a point Ac3. Then, rolling is carried out at <=900 deg.C under >=30% cumulative pressure within the range of an Ar3 transformation point. Successively, forcible cooling is performed from temperature above the Ar3 point down to <=300 deg.C at a 2-100 deg.C/sec cooling speed. Further, a quenching treatment is performed at some temperature between 500 deg.C and an Ac1 transformation point. For higher strength and toughness, <=10% Ni, 0.01-0.1% Nb, <=1.5% Cr, 0.01-0.1% V, <=1.0% Mo, 0.005-0.03% Ti, <=1.0% Cu, Ca, 0.5-2.0 XS REM, and <=0.003% S are added. |
