Generally, the shape of aluminum alloy casting castings is more complex, the thickness is uneven, the structure is coarse, and the segregation is serious. Therefore, it can be used normally after proper heat treatment. Typical heat treatment processes include annealing, quench aging and stable tempering. The purpose of aluminum alloy casting heat treatment is to eliminate the internal stress of the casting. Eliminate casting segregation and change the shape of needle-like components in the alloy structure; improve the mechanical properties of aluminum alloys; stabilize the size, structure and performance of parts at high temperatures; improve the workability of castings. The following is a brief introduction to the process flow of aluminum alloy casting heat treatment.

① Annealing

In a special aluminum alloy annealing furnace, the room temperature is raised280-300°C. According to the thickness of the casting, the size of the furnace and the form of placement, the holding time is reasonably determined, generally 2 to 3 hours, and the annealing process can be completed. Then cut off the power supply, open the furnace door, and spread the castings on the cooling table for air cooling. It is strictly forbidden to stack them.

② Quenching and aging

Considering that aluminum alloy casting contains more impurities, uneven structure and low melting point eutectic structure, the heating temperature of quenching is lower than the solubility temperature. The quenching heating temperature is generally500-535 ℃, the furnace temperature should be lower than 350 ℃. It should be heated slowly and the holding time should be 2-20h. Considering the prevention of deformation and cracking of complex parts, aluminum alloy casting products should be cooled in water at 80-100°C. When selecting the quenching temperature, the influence of the above factors should be considered to avoid overheating or excessive combustion. The aging of aluminum alloy casting products is divided into two types: complete aging and incomplete aging, which should be reasonably selected according to the specific requirements of the parts.

③ Stable tempering

After the aluminum alloy casting parts are quenched, they can be stabilized and tempered in a special electric furnace instead of aging treatment. Typically, the tempering temperature is above the artificial aging temperature and close to the working temperature of the casting. After the heat preservation is completed, the temperature can be air-cooled.