Simulation Analysis Of The Magnesium Alloy Cylinder Head Casting Processes

The competition in the automotive industry, to some extent, is the process of continuously getting rid of the stale and bringing forth the fresh, which is necessary condition for a car company to keep an invincible position in the market competition. Where in new materials and techniques continuously used is the highlight for the automobile development. Especially the application of magnesium alloys, which is as a representative light and energy saving material, has received much more concern. Compared with other metal structural materials, magnesium alloy has low density, high specific strength and stiffness, excellent vibration damping and noise reduction capability. However, the fatal weakness the magnesium existed is the low strength and poor heat resistance, which limits its application, to some extent, in automobile parts. In the casting process, at the same time, the fast solidification speed and wide solidification region, as well as high filling speed requirement, have included many defects for the magnesium alloy casting parts. It seems that it is necessary to simulate the solidification process of magnesium alloy to predict the where the defects is formed and how the casting technique is designed.A heat resistant Mg-Sn-Si-Sr alloy was used and the casting processes were simulated in this paper. Firstly, three-dimensional software was used to build the solid model of cylinder head. Secondly, based on the permanent gravity casting and low pressure casting methods, the filling and solidification processes were simulated by using ProCAST software. Furthermore, the casting defects were predicted for each condition. The results were summarized as follows.(1) The three-dimensional solid model, the temperature and fluid field during filling process were constructed.(2) The technique parameters and the casting processes were designed according to the characteristics of the permanent gravity casting and low pressure casting methods.(3) Under the condition of permanent gravity casting method, when the pouring temperature was set at 680℃, the gating and filling systems designed can achieve directional solidification and realize the feeding requirements by contribution of riser and the runner. However, there are some flaws close to the runner side. Which can be reduced by setting the side risers and increasing the pouring temperature to 700℃.(4) In the low pressure casting condition, when the pressure accelerating speed and holding pressure were set at 0.026MPa/s and 0.85MPa respectively, a smooth pouching process was observed. Compared with permanent gravity casting method, the shrinkage defect in volume fraction was significantly reduced.