Aluminum alloys are widely used in production of automotive parts due to their light weight, high strength, and corrosion resistance. Aluminum alloy gearbox shells, shells, and side covers work in harsh environments, requiring alloy to have properties such as light weight and good heat dissipation. Quality of material can be controlled by purification, refining, refinement, and metamorphism to stabilize quality of casting. Since gearbox side cover works in a special environment, it has special requirements for wear resistance, heat resistance, deformation resistance, and air tightness, and its die-casting process development has certain difficulties.
Graphic Results
Die-casting of automobile transmission side cover developed in this project is shown in Figure 1. Casting has an outline size of 425 mm*355 mm*71 mm, a weight of 3.3 kg, an average wall thickness of 2.3 mm, and a projected area of 112280 mm2. Casting is made of Al-11Si-2Cu, with multiple thick-walled hot spots, which are prone to shrinkage defects; product blank flatness requirement is 0.6 mm, and there is no obvious indentation on appearance; after product processing, one shrinkage hole on sealing surface is allowed for Φ0.5~1.0 mm, and two are allowed for less than Φ0.5 mm. After bearing hole is machined, no shrinkage hole is allowed to be exposed; inner cavity leak test pressure is 0.05 MPa, and leakage is ≤8 mL/min; oil channel leak test pressure is 0.3 MPa, and leakage is ≤8 mL/min; hardness (HB) is ≥58. Casting is produced on a 13500 kN die-casting machine.

 

Picture 1 Transmission side cover die casting

 

Picture 2 Casting scheme 1

 

Picture 3 Casting scheme 2

 

Picture 4 Vernier hole is pouring direction

 

Picture 5 Drain bolt is pouring direction
Weight of die casting is 3.3kg, weight of slag bag and overflow channel is 0.52kg, effective length of injection is 70cm, and punch radius is 5cm, so distance from starting point of inner gate fast injection is about 50cm.

Table 1 Die casting process parameter selection

 

Figure 6 No pores in oil channel and bearing hole

 

Figure 7 Defects in different positions of product

 

Figure 8 Shrinkage hole at feed port

 

Figure 9 Mold temperature arrangement

 

Figure 10 Product cold shut

 

Figure 11 Core needle buckle at feed port

 

Table 2 Comparison of hardness of die castings during water cooling and normal cooling

 

Table 3 Measurement results of flatness of die castings

 

Figure 12 Die casting flatness measurement points
Reasonable inlet design is not only an important guarantee for good internal quality of castings, but also an important basis for good surface forming of castings; high-pressure cooling of core pins solves shrinkage defects at hot spots of die castings; reasonable exhaust structure design is an important method to reduce cold shut defects on casting surfaces; reasonable demoulding slope of core pins can greatly reduce mold failures and improve production efficiency; appropriate Cu content is an important means to ensure hardness requirements of castings; reasonable distribution of dynamic and fixed mold clamping force can improve flatness of die castings.