Compared with traditional die-casting, semi-solid rheological die-casting technology has characteristics of low forming temperature, long mold life, smoother mold filling, denser structure, good product quality, and can improve production conditions. It is currently widely used in automobiles, communications, electrical appliances, aerospace and medical fields. Semi-solid slurry preparation is a key link in development of rheological die-casting technology. Currently, semi-solid slurry preparation technologies such as stirring method, heat enthalpy method, serpentine runner method, and shear low-temperature casting method have been developed at home and abroad. However, although semi-solid forming technology has been applied so far, it needs further improvement and development both theoretically and technically.
With development of computer technology, numerical simulation technology has been widely used in study of semi-solid die-casting filling and solidification processes. Through numerical simulation of die-casting production process, defects that may occur during solidification process can be more accurately predicted. Through application of computer numerical simulation technology in casting production, quality of castings has been improved, product development cycle has been shortened, and material costs have been saved.
For aluminum alloy 5G wireless router box lid castings, Zhizhu Chaoyun CAE cloud platform was used to numerically simulate die-casting filling process of aluminum alloy box lid castings. Process was optimized through simulation, and mold was designed based on process optimization results. and manufacturing. And using Al-8Si aluminum alloy as raw material, self-developed uniformly accelerated barrel incubation semi-solid rheological die-casting process was used to conduct production tests of router box lid castings.

Figure 1 shows box cover of a certain type of 5G wireless router, which is made of Al-8Si aluminum alloy. Maximum outer dimension of casting is 126mm*126mm*21mm. Wall thickness is uneven, with thin wall part being about 2mm and thick wall part being about 7mm. Aluminum alloy density is 2.5g/cm3, critical solid phase ratio is 67.5%, liquidus temperature is 615℃, and solidus temperature is 555℃. It is produced using a die-casting process. Router box cover is a shell-like aluminum alloy die-casting. There are holes that need to be cast on three sides, that is, a three-sided core-pulling mechanism is required. Therefore, inner gate can only be set on the side without core-pulling, as shown in the circle in Figure 1. A Toyo BD-250V5 die-casting machine is used. Projected area of die-casting part is 158cm2. Two cavities are selected, and two process plans are designed, as shown in Figure 2.

 

Figure 1 Three-dimensional view of router box cover

 

Figure 2 Die-casting process plan for box lid castings

 

Figure 3 Simulation results of die-casting filling process of Scheme 1

 

Figure 4 Simulation results of die-casting filling process of Scheme 2
Plan 2 was used to design and manufacture mold, self-developed uniformly accelerated barrel incubation semi-solid rheological die-casting process was used to conduct actual production tests of router box lid castings. Exit temperature of aluminum alloy liquid is 640℃. Injection punch adopts uniform acceleration injection during low-speed injection stage. Injection acceleration is about 0.86m/s2, maximum low-speed speed is about 0.64m/s, and high-speed speed is 2.0m/ s, mold preheating temperature is about 200℃. Figure 5 shows microstructure and physical picture of semi-solid die-casting part of router box cover. It can be seen that primary α-Al phase in structure at all positions is mostly nearly spherical, with fine grains and even distribution, and has obvious semi-solid structure characteristics.

 

Figure 5 Microstructure and physical picture of semi-solid die-casting part of router box cover

 

Figure 6 X-ray flaw detection diagram of router box cover casting

Zhizhu Chaoyun CAE cloud platform was used to conduct simulation analysis and optimization of die-casting process plan for router box cover. Based on simulation optimization results, a suitable process plan was determined and actual mold design, manufacturing and actual trial production were carried out. Semi-solid rheological die-casting process was incubated by self-developed uniformly accelerated barrel for actual production. Produced die-casting parts were inspected by X-ray transmission and no defects such as shrinkage cavities, shrinkage porosity, pores and inclusions were found, and their thermal conductivity reached 165.3W/ (m·K), quality meets technical requirements.