Low pressure casting is to place the mold on the closed holding furnace, and the mold cavity is connected with the molten metal in the furnace through the liquid riser. When working, add pressurized air into the furnace, and the liquid metal will flow into the mold cavity from the liquid riser. After the liquid metal solidifies, the compressed air in the furnace is released, and the non solidified metal flows back to the furnace from the liquid riser.
Low pressure casting technology for aluminum wheel and blade in the torque converter core shows many advantages, such as compact casting structure and good mechanical properties; The technological yield is high, and the technological yield of gravity casting of the same kind of products is 70% ~ 80%; High production efficiency, the production efficiency of the same kind of product die casting process is three times that of gravity casting; The surface is bright and clean, which can reduce the machining allowance.
Before the low-pressure casting, the mold shall be checked first. The coating shall be cleaned before the mold is used. The coating has become invalid or the surface is uneven after a production cycle. The coating shall be polished off with a grinding wheel. Then clean the aluminum chips of the ejector rod and clean the vent plug; Its ideal working temperature is (360 ± 10) ℃, so the mold should be baked to the working temperature before work.
When the mold is heated to 300 ℃, the coating must be uniform without sagging; Lower core; Set process parameters. The technological parameters of low pressure casting are mainly the temperature of molten aluminum, the pressurization rate and pressure setting of equipment. These three factors will affect the quality of castings, resulting in sand sticking, insufficient pouring, choking and other defects, so the parameter setting is very important for castings. Then pouring.
Compared with traditional gravity casting, low pressure casting can greatly improve the yield of castings, and has high work efficiency. As it crystallizes under pressure, the structure of the casting is dense, and the tensile strength can reach more than 200MPa. However, low-pressure casting has high requirements for equipment, molds and processes, and a little carelessness will lead to batch scrap.
