& nbsp; Low pressure casting can achieve high mechanization and automation, which not only improves productivity (10-15 types/h), but also reduces many human factors that are not conducive to the production process, improves the yield, and greatly reduces the labor intensity of workers. However, the quality of low-pressure casting parts is influenced by factors such as process plans, process parameters, mold structure, and manual operation, as well as their mutual influence. Any unreasonable design or improper operation of any link may lead to defects in low-pressure casting parts. Among them, the generation of cracks in aluminum alloy wheels is an important factor affecting the production cost and efficiency of enterprises. Therefore, it is particularly important to explore the causes of cracks in low-pressure cast aluminum alloy wheels.1. Reasons for crack formation1.1 Definition of Low Pressure Casting  Inject dry compressed air into a sealed container containing liquid metal, which acts on the metal surface at a certain temperature, causing the liquid metal to enter the mold cavity from bottom to top along the riser. After the metal liquid fills the mold cavity, increase the air pressure, and the metal liquid in the mold cavity solidifies under a certain pressure. Then, release the gas pressure on the liquid surface, allowing the non solidified metal liquid in the riser to fall back into the crucible, Open the mold again and take out the parts.  Cracks in low-pressure cast aluminum alloy wheels mainly occur in areas with concentrated stress, or due to uneven stress distribution during wheel demolding, or liquid solidification at the lifting pipe. Cracks are generally divided into two types: cold cracking and hot cracking.  Cold cracks refer to cracks formed in an alloy below its solidus temperature. Simply put, cold cracking occurs when the casting cools to a low temperature, and the casting stress acting on the casting exceeds the allowable strength or plasticity of the casting itself. Cold cracking often occurs on the surface of castings, with slight oxidation on the surface of the crack; Hot cracking is usually considered to occur during the solidification process of the alloy, and due to the heat transfer effect of the mold wall, the casting always solidifies from the surface. When a large number of dendrites appear on the surface of the casting and overlap into a complete skeleton, the casting will experience solid shrinkage (often represented by linear shrinkage). But at this point, there is still a layer of liquid metal film (liquid film) between the dendrites that has not yet solidified. If the shrinkage of the casting is not hindered in any way, the dendrite layer is not affected by force and can freely contract, thus avoiding stress. When the contraction of the dendrite layer is hindered, it cannot contract freely or is subjected to tensile force, resulting in tensile stress. At this time, the liquid film between the dendrites will be deformed by the tensile force. When the tensile stress exceeds the strength limit of the liquid film, the dendrites will be pulled apart. However, there are still some liquid metals around the torn part. If the liquid film is pulled apart slowly and there is enough liquid around it to flow into the torn part in a timely manner, the torn part will be filled and; Healing”, The casting will not exhibit thermal cracking. If the crack cannot be re formed; Healing”, Castings will experience thermal cracking. The surface of the hot cracking fracture is strongly oxidized, presenting a dark or black color without metallic luster.2  The main factors affecting crack generation  For the same alloy, whether the wheel hub produces cracks often depends on factors such as wheel hub structure, process parameters, and mold temperature.2.1 Impact of Improper Hub Structure Design on Hub Cracks2.1.1 Improper size of the inner fillet is the most common cause of thermal cracking in the wheel hub, as the sharp corners of the wheel hub generate significant stress during cooling. In areas with small inner rounded corners, even if the filling is good and there is no shrinkage cracking, thermal cracking will still occur.2.1.2 Sudden changes in the cross-section of the wheel hub can result in varying cooling rates, and even if the shrinkage is good, it can generate significant stress, causing cracks or cracks to appear after the wheel hub solidifies.2.2 The impact of unreasonable process parameters on wheel hub cracks  In low-pressure casting, due to the long holding time or the long lifting pipe, the liquid inside the lifting pipe solidifies, and bears a certain tensile force when the hub casting is ejected, resulting in cold cracking of the hub. Therefore, designing a reasonable pressure holding time and lifting system is of great significance in reducing the cracking caused by the wheel hub during ejection.2.3  The Effect of Mold Temperature on Wheel Hub Cracks  The mold temperature of low-pressure casting determines the solidification mode of the alloy liquid and directly affects the internal and surface conditions of the casting. It is one of the main reasons for many defects such as dimensional deviation and deformation in the casting, and also has a significant impact on productivity. The mold temperature changes with changes in casting quality, die-casting cycle, die-casting temperature, and mold cooling method.  From the perspective of heat transfer, increasing the mold temperature can reduce the heat transfer intensity between the metal and the mold, and prolong the flow time. Some studies have also shown that increasing the mold temperature can slightly reduce the interfacial tension between the molten metal and the mold. As the mold temperature increases, the filling time slightly decreases, meaning that the filling capacity increases with the increase of mold temperature. Therefore, an appropriate increase in mold temperature is beneficial for reducing stress. If the mold temperature is too low, the casting cools too quickly in the metal mold, and the solidification speed between different parts of the casting is different, it will cause uneven cooling of the casting in the mold, resulting in thermal stress and deformation. As a result, hot cracks and large residual stress and deformation will occur on the finished product of the casting. A higher mold temperature is not conducive to obtaining fine crystalline microstructure, Liquid metal is prone to suction and contraction, increasing the chances of defects such as porosity, shrinkage, and shrinkage in castings. To unify this contradiction, the mold temperature can be appropriately increased without casting defects. Generally, the area where cracks appear in the wheel hub is the spoke or inner wall of the wheel hub. The hub is shown in Figure 1.  & nbsp; & nbsp;& nbsp;3  Improvement measures3.1 Reasonably design the lifting system. Due to the long holding time or the long lifting pipe, the liquid inside the lifting pipe solidifies, causing the hub casting to bear a certain tensile force during ejection, resulting in cold cracking of the hub. Therefore, designing a reasonable lifting system is of great significance in reducing the tendency to crack. The lifting system refers to the channel through which liquid metal enters the mold cavity from the crucible during pouring, including the lifting pipe, insulation sleeve, and casting pouring system. The dimensions of these parts directly affect the distance between the liquid level in the crucible and the inner gate of the casting. The longer this distance, the faster the liquid metal cools down during pouring, which can easily cause early solidification in the riser channel. Therefore, attention should be paid to: ① shortening the distance between the liquid level in the crucible and the inner gate of the casting. This distance involves several aspects such as equipment, technology, molds, etc., so comprehensive consideration should be given to shortening this distance; ② Improve insulation sleeves. Increase the inner diameter of the insulation sleeve appropriately to expand the thickness of the insulation layer, and use materials with good insulation performance as insulation sleeves, such as aluminum silicate fiber felt; ③ Increase the diameter of the lifting pipe appropriately. To prevent early solidification of the riser, the diameter of the riser should be appropriately increased.3.2 Design a reasonable wheel hub structure. When designing the wheel hub structure, sudden changes in the sharp corner structure and cross-section should be avoided, and a structure with rounded corners or uniform thickness should be used.3.3 In the absence of casting defects, increase the mold temperature appropriately.