Casting mainly includes back pressure casting and low pressure casting. The pressure of low-pressure casting is relatively low, so it is called “low-pressure casting”. Low pressure casting mainly uses the pressure of gas, adds liquid metal into the mold, and condenses and forms under the action of pressure. Backpressure casting is relatively advanced, and the metal is sucked into the mold through vacuum, which can ensure that all impurities are discharged under the condition of constant temperature. There are no pores in the low-pressure casting, with uniform density and high strength. The principle of low-pressure casting is: in the sealed container, using compressed air, the liquid metal can rise to the mold cavity along the liquid pipe under the action of gas pressure, and under the condition of gas pressure, the solidification of aluminum alloy wheel hub casting can be ensured, and then the gas pressure can be removed to send the non condensed liquid metal into the container.
By controlling the speed of gas pressure pressurization in the container, the speed of liquid metal rising and punching can be managed. Therefore, the low-pressure die casting technology is relatively stable and easy to control. Under a certain pressure, the aluminum alloy wheel hub casting can crystallize and solidify, so as to ensure that the aluminum alloy wheel hub casting has a good feeding effect and promote the organization to be closer. In low-pressure casting, risers are usually not placed, and the pouring system is relatively small, but the reuse rate of metal is relatively high. The low-pressureof aluminum wheel hub is continuously improved and optimized. Based on the runner, the riser is used to not only cancel the heater, but also increase the feeding effect of the gate to prevent blockage. In the process of applying the filter screen, it can ensure that the aluminum liquid is more stable in the stamping process and prevent the quality problems of aluminum alloy wheel hub castings. In the process of controlling the temperature of the mold, the temperature of the mold is detected through the “thermocouple”, and finally the temperature is fed back to the control system to automatically turn on and off the water cooling and air cooling in the mold, so as to ensure that the temperature in the mold can reach the thermal balance. In the aspect of controlling pressurization, the pressurization parameters can be accurately calculated and controlled by using computer and PLC.
The process of low-pressure casting was relatively mature. At that time, the cost was higher than that of gravity casting, but affected by the process itself, it could not meet the treatment requirements of wheels larger than 18 feet, especially polishing, electroplating and other coating processes. In low-pressure casting and gravity casting, the shape and size of aluminum alloy hub castings are formed through molds. 40% of the casting wastes are directly related to molds. High quality mold should not only ensure the size and shape of aluminum alloy wheel hub casting, but also ensure the quality of aluminum alloy wheel hub casting, including internal quality and surface quality, so as to prolong the service life of the mold.