Optimal Design On Structure And Die Casting Process For Magnesium Alloy Cover Of Engine

High pressure casting is a process of nearly-molding, which is featured with less pollution high efficiency and high rate of metal- recycling. So far it is the most common molding method of the magnesium alloy components. The distribution of the temperature field of mould in die casting process (of magnesium alloy) has great influence on the die casting component quality, the service life of the mould and productivity etc. On the one hand, the temperature field of the mould will influence the process of mold-filling and cooling conditions of the die casting components and further more, will affect its molding quality and the quality of the internal organization. On the other hand, mould have been functioned constantly by fast chilling and heating in the die casting process and the temperature field of the mould have determined its heat stress bearing capacity as well as the tendency for deformation and cracks. That is to say, it will influence the service life. In order to improve the die-casting component quality and the service lifes for the mould, many researchers have conducted numerical simulation of the temperature field in die casting process of aluminum alloy so that they can analyze the influences of the process conditions on the temperature field of the mould in die casting process. However, there is relatively less study on the numerical stimulation on the rules of change on the temperature field for the mould in die casting process of magnesium alloy. If a comparison has been made between magnesium alloy and aluminum alloy, there is less heat content in the metal liquid with the same volume and less release of latent heat. Therefore, the characteristics of mold-filling and cooling for magnesium alloy in the die casting process are different from those of aluminum alloys.The characteristic of the temperature field distribution of the cover of engine in die casting and mold-filling process of magnesium alloy has been calculated and analyzed and in addition, the characteristic of the temperature field distribution of the covers as well as the mould in die casting and recycling process of magnesium alloy in the present paper on the basis of the cover of engine of die casting components of magnesium alloys employed by Shenyang -China Bus and by using Z-Cast numerical simulation software jointly developed by Korean Cubictek Co. Ltd, Korean Research Institute of Production and Technology and Shenyang Research Instituteof Foundry. It is shown that in the casting process of magnesium alloy cover, the temperature inside the mould increase and decrease periodically with the continuity of the cycles of die casting. After the metal liquid has been injected, the temperature of the mould will go up to the maximum value in the shortest time and then will go down quickly and next the speed of change is constant. With the increase of the distance to the die casting components, the ranges and speed of the change on the temperature of the mould are gradually reduced.On the basis of the results of the simulation, the selection of the best die casting processing parameters for the magnesium alloys were an injection temperature of 670X^, a plunger head speed of 6m/s and a mould temperature of 240°C, which have been tested on the Model No. EVOLUTION 53D die casting machine made by Swiss BULHER Corp. and it has been proved that the result for simulation is correct and reliable.The simulation on the temperature field of the mould has provided certain evidences for the optimization of the processing parameters and expanding service life of the mould It has also laid a foundation for the field of the stress along with the calculation of the deformation of the mould.