(2) Mold wall thickness for Casting Flow Formed Aluminum Alloy Wheels. The mold cavity is closed by the bottom mold, the top mold and the side mold. The mold wall thickness refers to the thickness of the three parts.
In the initial stage of the filling process, the heat dissipation of the casting is mainly heat conduction, that is, the heat is absorbed by the mold itself, and the amount of heat absorbed depends on the quality of the mold (the heat absorption and mass quality are achieved under the premise that the temperature rise of the mold is fixed). In proportion, the mold heats up and absorbs heat, and the aluminum liquid cools down. When the two reach the heat balance, the heat dissipation method based on conduction heat dissipation basically stops. At this stage, because the heat conduction heats up quickly, and there is a large temperature difference between the mold and the aluminum liquid, the aluminum liquid has a chilling effect when solidified. At this time, the solidified structure of the outer surface of the casting is dense and the mechanical properties are good. Inferred from this situation, increasing the wall thickness of the mold for Flow Formed Aluminum Alloy Wheels can obtain a relatively long chilling effect, thereby obtaining a high-quality tissue layer of a large thickness.
The top and side dies form the rim of the wheel. Since the thickness of the rim itself is small, the wall thickness of the mold is too thick, which may cause uneven heat and cold everywhere in the rim, resulting in casting defects. Therefore, the thickness of the top and side molds is mainly to ensure the strength of the mold, and at the same time take into account the forming factors of the rim. According to the general experience, it is better to take the wall thickness of 25-30mm for the upper mold and 30mm for the side mold.