Filter equipment has high power consumption, high integration, and high requirements for heat dissipation, requiring sufficient heat dissipation from the filter heat dissipation shell. Therefore, it is required that the heat dissipation shell of the filter has a high thermal conductivity, and the heat dissipation fins on the surface of the shell should be as thin as possible. On the premise of meeting the product strength, it should be designed as lightweight as possible for easy installation and maintenance. The manufacturing of this type of product often uses die casting technology, but the heat dissipation shell of the die cast filter has defects such as air holes and oxide inclusions. The wall thickness of the heat dissipation fins is relatively large, and the minimum wall thickness that can be achieved is 1.5mm. This makes the heat dissipation shell heavier and has poor heat dissipation performance, reducing the usability of the product.
The semi-solid die casting technology uses a semi-solid metal slurry that is in the temperature range of liquid and solid phases. During the die-casting process, due to the high solid fraction, viscosity, and round grain size of the metal slurry, under appropriate injection parameters, the metal slurry will flow in a near laminar manner to fill the mold cavity. The filling process is smooth and uniform, and near net forming can be achieved. Early semi-solid die casting technology was mainly used to solve the problems of porosity and oxide inclusions in thick and large die castings, and there is relatively little research on semi-solid die casting for ultra-thin wall aluminum alloy precision structural parts. The mass production of ultra-thin wall aluminum alloy precision structural filter heat dissipation shells (with a wall thickness of 0.8~1.0mm) was achieved by using the RSF (Rapid Slurry Forming) semi-solid slurry technology imported from Sweden, combined with die casting process. The basic principle of RSF semi-solid slurry technology is to use Entropy Exchange Material (EEM) as a coolant to absorb heat and provide external nucleation particles, thereby promoting the non-uniform nucleation of metal liquid. The metal semi-solid slurry is quickly prepared by controlling the enthalpy entropy of the melt.
Through previous research on RSF semi-solid die casting, it was found that the injection low speed value and high low speed transition position have a significant impact on the filling state of the semi-solid slurry during semi-solid die casting. If the speed conversion time is early, the semi-solid slurry will produce problems such as splashing and curling. Therefore, based on the RSF semi-solid rapid pulping technology, this project aimed to meet the development needs of precision structural components for filter heat dissipation shells. MAGMA software was used to simulate the filling state of semi-solid slurry for filter heat dissipation shells at different injection low speed values and high/low speed switching positions. The optimal semi-solid die-casting parameters obtained from the simulation were verified in actual production.
Graphic and textual results
Figure 1 shows the heat dissipation shell of the filter. The part has a regular shape and is composed of several rectangular heat sinks arranged horizontally on the same plane. The heat sink requires a uniform wall thickness and a wall thickness of 0.8~1.0mm, with a demolding slope of about 1 ° and no shrinkage or porosity on the surface.
The simulation results of the above three schemes indicate that the injection low speed value and the high-low speed switching position have a significant impact on the semi-solid filling process. Comparing Scheme 1 and Scheme 2, it can be seen that when the injection speed is switched earlier, the semi-solid slurry with higher viscosity will still be filled in a jet like manner under the action of high-speed injection, resulting in sharp blade like splashes at the front end of the filling process. Delaying the position of switching between high and low speeds can allow a large amount of semi-solid slurry to flow smoothly into the mold cavity and spread out evenly. When low-speed injection is converted to high-speed injection, the flat slurry will evenly distribute the force generated by high-speed injection in various parts of the slurry, without concentrating the filling force in a certain area, thus significantly improving the splashing jet situation.
The actual production of the filter heat dissipation shell was carried out using a low injection speed of 0.1m/s and a high low speed switching position of 720mm, and qualified die castings were obtained. The surface of the die-casting part has no defects such as shrinkage, porosity, etc. The wall thickness of its heat sink is uniform and roughly maintained within the range of 0.8~1.0mm, which is roughly consistent with the simulation results, thus verifying the reliability of the simulation results.
Author of this article:
Zhang Yu, Wang Liandeng, Xu Pengpeng
School of Mechanical Engineering and Automation, Fuzhou University
Wang Qinfeng
College of Mechanical and Energy Engineering, Jimei University
Wang Liandeng, Cao Haichun, Zheng Jiangshui, Luo Zhenhua
Fujian Ruiaomaite Light Metal Co., Ltd
This article comes from: "Special Casting and Nonferrous Alloys" magazine, "Die Casting Weekly" strategic partner
