基于数值模拟的压铸过程低速工艺优化

低速压射过程中冲头的运动分为封闭浇料口、匀加速和匀速低速三个阶段,各个阶段的工艺参数对压室内金属液的流动形态都有重要作用,进而影响铸件中气孔缺陷的产生。采用数值模拟技术来研究不同工艺参数下压室内金属液的流动形态,对低速工艺进行优化。针对压射过程冲头的运动特征,引入了移动速度、压力边界条件,开发了压室压射过程三维数值模拟程序。结合慢压射临界速度理论,模拟了不同料口封闭速度、加速度和慢压射速度下压室内金属液波形的发展。模拟结果表明采用优化的工艺参数可以降低压室内的卷气。

Optimization of Slow Shot Parameters in a Die Casting Process by Numerical Simulation Technique

In the slow shot phase of a die casting process, three stages of the plunger movement are involved, which are sealing off the pouring hole, acceleration to the constant speed and constant speed motion. The operation conditions in these stages have influence on the flow patterns of molten metal and the air entrapment in the shot sleeve. Numerical simulation is used to analyze the flow of molten metal and optimize the values of the operation conditions. According to the plunger motion characteristics, the moving boundary condition of velocity and pressure in the injection process was considered and a three-dimensional numerical model was developed. Based on the critical plunger speed concept, the influence of the plunger speed before sealing the pouring hole, the plunger acceleration and the slow shot velocity on the evolution of the wave surface profile were investigated. The results of the numerical simulation show optimum operation conditions can avoid or minimize air entrapment during the slow shot phase.