Generally, the shape of the castings processed by aluminum casting is more complicated, the thickness is uneven, the grains are coarse, and the segregation is severe. Therefore, proper heat treatment is required before normal use. The usual heat treatment processes include annealing, quenching aging and stabilization tempering. The purpose of the heat treatment of cast aluminum alloy is to eliminate the internal stress of the casting; eliminate the casting segregation and change the shape of the needle-like composition in the alloy arrangement; improve the mechanical function of the aluminum alloy; stabilize the size, arrangement and function of the parts at high temperatures; improve the casting Machinability.

① Annealing is carried out in a special aluminum alloy annealing furnace, and the room temperature is increased to 280～300℃. According to the thickness of the casting, the size of the furnace and the placement method, the holding time is reasonably confirmed, generally 2～3h, and it can be completed. During the annealing process, after the power is turned off, the furnace door is opened and the castings are scattered on the cooling table to cool in the air. Stacking is strictly prohibited.

②Quenching and aging Considering that cast aluminum alloy contains more impurities, uneven arrangement and eutectic arrangement with low melting point, the heating temperature of quenching is lower than the temperature of maximum solubility. The quenching heating temperature is generally 500-535℃, and the furnace should be installed below 350℃. It should be heated slowly, and the holding time should be 2-20h. Considering the prevention of deformation and cracking of complex parts, the cast aluminum alloy should be cooled in 80-100℃ water. When selecting the quenching temperature, the influence of the above factors should be considered to avoid overheating or overburning. The intent and effect of the aging effect have been introduced by the editor of Aite Trading. It is divided into two types: full aging and incomplete aging, which should be selected according to the specific requirements of the parts, so I won’t repeat them here.

③After quenching, the stabilized tempering parts can be stabilized and tempered in a special electric furnace to replace the aging treatment. Usually, the tempering temperature is higher than the artificial aging temperature and close to the working temperature of the casting. After the heat preservation is completed, it is air-cooled.