汽车发动机前支架球化浇注工艺的优化设计

实际生产条件下，对球铁生产工艺进行正交设计优化，对其试样进行金相组织观察和力学性能测试。试验结果表明，铁液在相同的出炉温度条件下，球化处理时间延长，石墨球长大且数量减少；在相同的球化处理时间条件下，铁液出炉温度的提高，也使石墨球变大数量减少；在相同的浇注条件下，铁液出炉温度高，球化处理时间长，同样使石墨球长大且数量减少；石墨球的长大且数量减少，对强度和硬度的变化不明显，而冲击韧性、断面收缩率和延伸率有所下降；确定最佳的工艺参数为铁液出炉温度为1525℃，球化处理时间为2min，浇注温度为1400℃。

Optimal Design of the Pouring Process of the Front Bracket of Ductile Iron Automotive Engine

Orthogonal design of ductile iron production technology has been optimized with sample metallographie examination and mechanics property testing under actual production conditions. The test results showd that under the same condition of tapping temperature, extended spberoidization treatment time of molten iron made graphite spheres volume increased and their quantity decreased. In the same spheroidization treatment time and rising molten iron＇s tapping temperature made the graphite spheres volume increased and their quantity decreased. Under the same pouring condition, rising tapping temperature and extended spheroidization treatment time of molten iron made the graphite spheres volume increased and their quantity decreased. Increased graphite spheres volume and decreased quantity did not affect the ductile iron＇s strength and hardness obviously, but did decrease its impact toughness, section shrinkage and elongation. It has been decided that the best process parameters are as follows： the tapping temperature of molten iron 1525℃, the spheroidization treatment time 2min and the pouring temperature 1400℃.