1) Reasonable design of liquid lifting system
Because the holding time is too long, or the liquid in the lifting pipe is too long, the liquid in the lifting pipe solidifies, which makes the casting bear a certain tension when it is ejected, thus causing cold crack in the wheel. Therefore, it is very important to design a reasonable lifting system to reduce the crack tendency. Liquid lifting system refers to the channel through which liquid metal enters the mold cavity from the increasing pot during pouring, including liquid lifting pipe, heat preservation sleeve and casting pouring system. The dimensions of these parts directly affect the distance between the liquid level in the increasing pot and the inner gate of the casting. The longer the distance is, the faster the liquid metal will cool down when pouring through the distance, which is easy to cause early solidification of the riser channel. Therefore, it should be noted that:
① Shorten the distance between the liquid level in the increasing pot and the inner gate of the casting. This distance involves several aspects such as equipment, process, mould, etc., so it should be considered comprehensively to shorten this distance;
② Improve the insulation sleeve. Properly increase the inner diameter of the insulation sleeve to expand the thickness of the insulation layer, and use materials with good insulation performance as the insulation sleeve, such as aluminum silicate fiber felt;
③ The diameter of the riser should be increased appropriately. In order to prevent the early solidification of the riser, the diameter of the riser should be increased properly.
2） Reasonable wheel structure design
In the design of hub structure, the sharp corner structure and section should be avoided to change suddenly, and the structure with round corner or uniform thickness should be adopted.
3) Increase mold temperature properly without casting defects
Through the analysis of the causes of the defects of low pressure casting wheel, the quality of low pressure casting wheel is improved.