Lightweighting automobiles is one of the best ways to achieve high speed, safety, energy saving, environmental protection, and comfort. Therefore, some light alloys, such as aluminum and magnesium, are widely used due to their low density, high specific strength, and high specific stiffness. They are also Ideal material for automotive lightweighting. In die-casting process of aluminum and magnesium alloys, liquid or semi-liquid high-temperature metal is filled at high speed and high pressure, and solidifies rapidly at high temperature, which makes fluidity and feeding effect of alloy worse, it is easy to produce defects such as flow marks, cold shuts, insufficient pouring, shrinkage cavities, and shrinkage porosity, which affects quality of castings. At the same time, high temperature and high pressure can easily cause cracks in mold and reduce service life of mold.
Oil pump body is made of Al-9Si-3Cu, with a density of 2.75g/cm3, a specific heat capacity of 0.880kJ/(kg·℃), a thermal conductivity of 120W/(K·m), a melting point of 593℃, and a freezing point of 521℃, and a latent heat of fusion of 662kJ/dm3. Selection of die-casting machine, simulation of gating system and optimization of process parameters were discussed, and optimal solution suitable for production was found.
Rough three-dimensional diagram of oil pump body is shown in Figure 1. This product is a pressure-bearing part and requires high air tightness in pump chamber, requiring no leakage under 400kPa pressure. Moreover, structure of this part is complex, with multiple bosses and grooves. Average wall thickness is 4mm. Three core pulls need to be installed at the three long holes. Therefore, when choosing a die-casting machine, choose a die-casting machine with a tonnage larger than theoretical value to facilitate subsequent parameter adjustment and ensure quality of castings.

 

Figure 1 Three-dimensional diagram of mold bace

 

Figure 2 3D model of blank with gating system

 

Figure 3 Particle tracking

 

Figure 4 Solidification temperature field (filling rate 95.27%)

 

Figure 5 Improved particle tracking

 

Figure 6 Solidification temperature field (filling rate 95.21%)

 

Figure 7 Cutaway section of casting
In mold design process, advantages of Magma software are fully utilized to realize simulation of filling process, solidification process, velocity field, and particle tracking, so as to effectively predict structure and size defects of die-casting mold before casting production, predict types and locations of possible defects. Then design reasonable castings, mold structures, gating systems, determine reasonable process parameters to shorten design and development cycle, improve quality and life of die-casting mold, and improve production efficiency. By optimizing gating system, adjusting process parameters, and adding cooling methods to overheated parts, optimal process plan was determined and mold design and development cycle was shortened.