柴油机缸体铸件去应力退火工艺实验

Experiment of Stress Annealing Process for Diesel Engine Cylinder Block Castings

采用正交实验法与钻孔法研究了不同退火工艺参数对某柴油机缸体残余应力的影响,分析了退火工艺中各个参数对残余应力影响的主次关系,获得了各参数的优水平,并通过补充实验进一步分析了保温温度与保温时间对残余应力的影响,确定了最优工艺参数。实验结果表明:去应力退火不仅能够降低缸体残余应力幅值而且能使残余应力均匀化;退火工艺中保温温度对残余应力的影响最大,其次为保温时间,然后为升温速度,最后为降温速度;残余应力值幅值随保温温度的提高而降低,但保温温度达到630℃以后继续升高温度残余应力变化不再明显;保温时间的延长有助于残余应力的释放,试验中缸体残余应力释放的时间约为6.5 h;此缸体的最佳退火工艺为以80℃/h的速度将温度上升至630℃,保温6.5 h,然后以35℃/h的降温速度随炉冷却至200℃空冷。

The effects of stress annealing process parameters on residual stress of diesel engine cylinder block castings were studied by orthogonal experimental method and drilling method, and the primary and secondary relations of annealing process parameters affecting residual stress were determined. The influences of heat preservation temperature and holding time on the reduction of residual stress were analyzed in detail, and the optimum process parameters were obtained. The experiment results show that, stress annealing not only can reduce residual stress, but can make the residual stress homogeneous. Heat preservation temperature has the most important influence on the reduction of residual stress, the second is heat preservation time, the third is heating speed, and the final is cooling speed. With the increasing of heat preservation temperature, the residual stress value was reduced, but residual stress changes are not obvious when the heat preservation temperature reached 630 ℃ Extending holding time contributed to the release of residual stress, and residual stress did not decrease with the increasing of holding time when the holding time more than 6.5 hours. The optimal annealing process parameters of the cylinder body castings are that heating rate, heating temperature, holding time and cooling speed are 80 ℃/h, 630 ℃, 6.5 h, 35 ℃/h furnace cooling to 200 ℃ and air cooling.