Analysis of Mold Flow in the Low Pressure Die Casting of Aluminum Alloy Wheels

摘要

Low pressure die casting has been used as a major method of producing automobile aluminum alloy wheels. Due to opacity of the molds and the geometric complexity of the wheels, setting up the manufacturing parameters is quite a laborious work. It requires many working experiences and try-and-error efforts to avoid the wheel defects. As a result, a lot of time and costs need to be paid for correcting the molds before beginning the wheel production. The purpose of this study is to reduce the waste of time and costs by introducing the computer-aided- engineering (CAE) to help set up the process parameters. This work discusses the influences of the pressure slops and cooling means on the filling and solidification of a real mold. Results show that the wheel defects resulting from the entrained air and shrinkage pores could be reduced by adjusting the pressure rising speed, the cooling time and locations, as well as the thickness of the mold release agents and geometry of the molds. Results from the simulation reveal that aluminum liquid hits the mold cavity, producing a lot of entrained air. Such entrained air could be eliminated by reducing the pressure speed. When only natural convection is applied to the mold cooling, shrinkages occur in the areas with great thickness change, such as in the interface between the spokes and rim and in the decorated pores. For the sake of defect elimination, adding force convection at certain locations of the molds and modifying the thickness of the mold release agents are helpful to achieve the directional solidification by adjusting the local heat flux.