利用模拟指导大型复杂结构零件的工艺优化能节约大量的人力和物力。采用模拟的方法研究了浇注工艺（浇注时间和温度）对重力铸造铝硅合金机体组织（二次枝晶间距）的影响。结果表明：材料级阶梯样件和重力铸造铝硅合金机体的模拟结果和试验结果具有较好的对应关系，模拟结果的偏差较小。浇注时间一定时，随着浇注温度升高，二次枝晶间距先减小后增大，最佳浇注温度为695 ℃；浇注温度一定时，随着浇注时间增加，二次枝晶间距先减小后增大，最佳浇注时间为60 s；浇注时间一定时，随着浇注温度升高，凝固时间先减少后增加；浇注温度一定时，随着浇注时间增加，凝固时间先减少后增加。

Using simulation to guide the process optimization of large and complex structural parts can save a lot of manpower and material resources. Based on the simulation method, the effect of pouring process including pouring time and temperature on the secondary dendrite arm spacing microstructure of gravity cast aluminum silicon alloy body was studied. The results indicate that there is a good correspondence between the simulation and experimental results for the material level step sample and the gravity cast aluminum silicon alloy body, and the deviation of simulation is relatively small. The secondary dendrite arm spacing first decreases and then increases as the pouring temperature increases when the pouring time is constant or as the pouring time increases when the pouring temperature is constant, and the optimal pouring temperature and time are 695 ℃ and 60 s respectively. In addition, the solidification time first decreases and then increases with the increase of pouring temperature when the pouring time is constant or with the increase of pouring time when the pouring temperature is constant.