回火出炉空冷时温度对40Cr钢调质大锻件表面残余应力的影响

Effect of Tempering Air Cooling Temperature on Surface Residial Stress of 40Cr Steel Quenched and Tempered Heavy Forging

为了解40Cr钢大锻件高温回火后表面残余应力的情况,应用X射线应力分析方法研究了该钢50 mm及170 mm两种试样在高温回火后的表面残余应力与出炉冷却温度的关系,并计算了800 mm调质大锻件在400℃下出炉空冷时的最大热应力。结果表明:调质大锻件在高温回火冷却到心部达400℃以上出炉空冷时,对其残余应力有显著影响;而在低于400℃出炉时,对其残余应力无明显影响,此时800 mm以下大锻件的最大热应力对锻件不构成开裂危险。

In order to investigate the surface residual stress of 40Cr steel quenched and tempered heavy forging after high temperature tempering, relationship between surface residual stress and tempering cooling temperature of mm and mm 40Cr steel specimens was studied by using X-ray stress measurement. The maximal instantaneous thermal stress in the mm quenched and tempered heavy forging cooling below 400℃ was caculated. The results show that effect on the residual stress was serious as the quenched and tempered heavy forging cooling in air and its center temperature was above 400℃, and the effect was slight as the temperature was lower than 400 ℃. The maximal instantaneous thermal stress of the quenched and tempered heavy forging which size was smaller than mm could not cause the cracking.