Many factors such as the shape, wall thickness, material characteristics and size of the mold and the casting have an impact on the product quality of the pressure shell of the turbocharger. Considering that the phenomenon of “hot spot” is frequent in the casting process, it is analyzed that the specific reason is the poor local heat dissipation effect of the mold. The generation of hot spot makes the overall cooling balance and heat balance of the mold unbalanced, destroys the solidification tendency of the casting, and damages the stability and durability of the mold. Therefore, it is necessary to study the Countermeasures of regional mold protection and cooling, so as to ensure the orderly solidification sequence of castings and the heating stability of mold cavity. In the process of casting production, the following main methods are used to solve the problem of “hot spot” formed locally. contain:
① Water cooling: a cooling water channel is constructed inside the mold to achieve the purpose of cooling, so that the mold cavity can be cooled quickly. It is often used when the mold needs rapid heat dissipation. However, a cooling water channel is added and the amount of water required for cooling is set, resulting in more complex internal structure of the cavity, increased manufacturing difficulty and cost, and increased labor intensity of workers;
② Air cooling method: the compressed air method is used to cool the places in the mold that are inconvenient to be cooled with water. The disadvantage is that the cooling efficiency is low, but this measure is easy to implement, so this measure has been widely used;
③ Indirect cooling method: place objects with good heat transfer, such as cold iron, in the area where the “hot spot” of the casting is generated for heat dissipation and cooling. At the same time, heat dissipation devices can be equipped at the end of the cold iron to achieve better cooling;
④ Improving the mold cavity: on the premise of ensuring the machining allowance, improving the cavity shape of the mold can reduce the “hot spot” problem caused by the poor mold cavity;
⑤ Warm coating: for the special position of the casting, especially for the pouring and riser system, similar thermal insulation materials such as heating covering agent are usually used to slow down the solidification time and achieve the best feeding purpose;
⑥ The cooling is realized through the heat pipe technology. In a small temperature gradient, this technology is usually used to transfer the heat from one heat transfer element to the next. The heat loss is small, and the phase change heat transfer principle is adopted;
⑦ Equipped with mold cavity temperature industrial control equipment, so that the mold cavity temperature can be reasonably and effectively controlled or set regionally.