To produce a good quality aluminum alloy die-casting, a lot of steps and processes are required, and no error can occur in every process. The brushing method of aluminum alloy die-casting painting and coating is also an important part of the die-casting surface quality.
1) The surface quality of the metal cavity wall before coating is very important for the adhesion of the paint. The new metal type must be thoroughly cleaned, de-oiled and rusted. The part with the draft angle must be polished with the use of assorted files and fine emery cloth ( Because the taper hole of the CNC milling machine is microscopically stepped, it is not a smooth slope, and it is difficult to demold. The already used mold must also completely remove the original coating. The traditional removal method is to manually remove with a wire brush or an emery cloth, which has low efficiency and serious mold wear. Sand blasting is used to blow quartz sand to the surface of the cavity with compressed air. This method is not only efficient, but also improves the adhesion of the paint. Recently, some merchants often introduce dry ice shot-blast cleaning methods. It is said that the effect is good, but it has not yet been promoted.
2) The thermal insulation of the coating 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 influenced by the application methods and conditions used, since the degree of formation of voids in the coating is essentially dependent on the evaporation rate of the contact surface of the mold cavity with the carrier water, the most commonly used mold coating. The application method is spraying, but sometimes it is applied by brush, such as in the pouring system and riser area. Spraying at around 170°-200° often results in the best coating results, but coating viscosity and spray equipment have an effect on the quality of the deposited layer of the coating. Therefore, depending on the viscosity of the coating and the spraying equipment, sometimes it is necessary to slightly A little higher is the best spraying temperature. When the mold temperature is higher, the paint will be strongly reflected between the carrier water and the high temperature. Generally, a large coating porosity will be obtained, and the thermal insulation performance of the coating will be better, but due to excessive mold temperature, it will cause strong “Rebound” makes it difficult for the coating to adhere to the surface of the cavity, so that the adhesion and life of the coating to the mold will be reduced. On the contrary, when spraying at a lower temperature, although the life of the coating is higher, the coating is denser and the insulation is deteriorated, and an excessively low spraying temperature causes the coating to be uneven and forms a patch. When the mold is heated to the operating temperature, coating cracking and peeling defects occur, and the moisture absorbed in the coating evaporates at high temperatures, also causing the adhesive film to crack.