Advanced equipment is undoubtedly an essential factor in ensuring product quality, aluminum alloy castings, but the role of molds in casting is also very important. Especially for aluminum alloy automotive parts production enterprises, the accuracy and durability of molds have a significant impact on product quality.
In black metal casting, the mold is mainly used to form a mold cavity. Generally, the mold itself does not directly contact the metal liquid, especially for non-metallic mold castings with complex shapes. The material in contact with the hot metal liquid is the molding material, mainly the molding sand, which makes the molding material the main factor affecting the quality of the casting. Aluminum alloy gravity casting, on the other hand, is different. Due to its low melting point and good casting performance, the shape of castings is generally formed directly by molds during mass production, such as the aluminum alloy cylinder block and cylinder head of engines. This not only helps to improve labor productivity, but more importantly, by adjusting the temperature distribution in different parts of the mold, the microstructure and grain size of castings can be controlled to improve casting quality. At the same time, it avoids environmental pollution caused by the extensive use of molding materials and improves working conditions in the workshop.
As the complexity of the casting shape varies, aluminum alloy gravity casting molds also vary. Even for the same part, different casting processes often result in different mold forms, but regardless, aluminum alloy gravity casting molds still have their commonalities.
Firstly, it is necessary to choose a suitable casting process, as the quality of the casting process directly affects the quality of the castings and the yield of the process. Some domestic mold manufacturers have started using solidification simulation to assist in casting process design. Through computer simulation of the filling and solidification process, they have identified and overcome hot spots that are prone to casting defects. This is very important and effective in improving the reliability of casting process design and effectively preventing unnecessary rework of molds during debugging.
Secondly, the mold should have good heat capacity. A thick and sturdy mold frame and module that meet the requirements not only effectively guarantees the lifespan of the mold, but also plays a very important role in regulating the temperature field during the continuous working process of the mold. Some mold factories, in order to reduce costs and save materials, blindly reduce the effective thickness of the molds to achieve the goal of reducing weight, but little do they know that this not only greatly reduces the service life of the molds, but also makes the castings easy to deform, affecting the dimensional accuracy of the castings. In severe cases, it will lead to batch scrapping of castings, causing losses to the foundry, and more seriously, damaging the reputation of the mold factory itself.
Third, the mold should have a more reliable cooling system and air extraction system. By cooling, not only can labor productivity be effectively improved, but also the temperature field of castings can be adjusted, the cooling speed of castings can be controlled, thereby affecting the internal structure and grain size of castings, and achieving the goal of effectively controlling the mechanical properties of castings. As the name suggests, gas extraction is the process of artificially expelling gas from the inside of the mold cavity to the outside of the mold cavity in order to reduce the possibility of porosity defects in the casting. At the same time, the installation of exhaust plugs can also adjust the mold temperature in local small areas, which plays an important role in preventing and overcoming aluminum alloy cracking and shrinkage.
Fourthly, there must be a mold positioning device that matches the casting machine and a convenient mold installation system. The positioning device is not only the key to ensuring the size of the casting, reducing burrs and seams, but also the key to ensuring the normal operation of the casting machine. It can be said that without a good positioning device in the mold, there will be no good qualified castings. The mold must be easy to install and disassemble because aluminum alloy gravity casting requires the mold to be removed and repainted and repaired at regular intervals. If disassembly is inconvenient, it will inevitably increase the labor intensity of workers, occupy more labor time, and reduce production and efficiency.