Spraying Requirements and Casting Conditions of Aluminum Die Castings

Ⅰ. The casting situation of the aluminum die casting

To produce high-quality aluminum die casting, many processes and steps must be passed. In each process great attention must be paid to the details and it is not allowed to make any mistakes. Among them, the coating method of the aluminum die casting will also affect the quality of the surface of the die casting.

During the operation of aluminum die casting, the phenomena of insufficient casting often occurs. The main reason is that the metal mold conducts heat too fast, and the melting point of aluminum is low, which causes the aluminum liquid to cool down before filling the cavity during the flow. In order to avoid insufficient casting of aluminum die casting, the following problems should be noticed:

1. Increase the casting temperature;

2. Perform necessary heating and heat preservation on aluminum die casting molds, or spray heat-preserving paint inside the aluminum die casting molds;

3. Improve the pouring system to make the pouring more smooth and shorten the filling time;

4. The metal model has certain requirements for the thickness of the cavity wall. If the cavity wall is too thin, then other processes should be considered.

Ⅱ. How to spray aluminum die castings

Preparation of aluminum die casting before spraying: The surface quality of the metal cavity wall is very important for the adhesion of the coating. The new metal mold must be thoroughly cleaned, deoiled and rust removed, and the parts with the pattern drift angle must be polished by crocus cloth and assorted files (because the tapered hole processed by the CNC milling machine is microscopically in the ladder pattern, and is not a flat inclined surface, so it is difficult to demold). Besides, the original coating must also be thoroughly removed from the used aluminum die casting mold.

The thermal insulation of the coating of aluminum die castings depends not only on the thickness of the coating, but also on the porosity of the coating itself. The porosity of the coating is largely affected by the used spraying conditions and methods. Because the degree of formation of pores in the coating basically depends on the evaporation rate of the water contacting the carrier on the surface of the mold cavity. The most commonly used aluminum casting coating method is spraying, but sometimes brushing is used, such as in the pouring system and the riser area. Spraying at the temperature of about 170°to 200°can generally obtain the best coating effect, but the spraying equipment and paint viscosity have an impact on the quality of the coating deposited layer. Therefore, depending on the spraying equipment and the viscosity of the paint, the temperature should be slightly improved so as to achieve the best effect.