镁合金薄壁空心型材挤压壁厚减薄问题的有限元分析及解决方案

FE analysis and solution of wall thickness attenuation during extrusion to produce a complex hollow magnesium profile

对镁合金薄壁空心型材在实际生产过程中出现壁厚减薄的缺陷,采用数值模拟方法进行研究,分析了挤压过程中金属流速和压力分布情况,模拟结果表明,焊合室内压力不均及出模口处沿挤压方向金属流动速度差异,是导致型材壁厚减薄的主要原因,且模拟得到的壁厚值与实际测量值基本吻合。提出了控制型材壁厚的改进方案,对型材挤压模具结构进行改进,即增加焊合室高度和修改分流孔尺寸。其中修改分流孔尺寸的方案能得到壁厚较均匀的型材,是可行的方案。研究结果表明,有限元方法对复杂型材挤压生产中挤压模具和挤压工艺的优化有直接的指导意义。

Present study addressed a practical problem of wall thickness attenuation during extrusion to produce a complex thinwalled hollow magnesium profile. The causes for the wall thickness attenuation were analyzed through FE method. The results showed that imbalance of the pressures inside the welding charhber and velocity near the die exit caused the wall thickness attenuation. The predicted wall thickness agreed with the measured wall thickness very well. Two corrections to optimize the design of porthole die were proposed as increasing the height of the welding chamber and adjusting the shape of porthole. Both could de- crease the extent of the wall thickness attenuation. Adjusting the shape of porthole could balance the metal flow and press well, thus can increase the wall thickness. So it is a viable solution to the problem. The simulation results demonstrated the feasibility of using FEM simulation as a useful tool to solve industrial problems encountered in the production of complex profiles.