2. Vacuum low pressure casting
The vacuum low-pressure casting method vacuums the mold during the pressurization filling process. After the filling is completed, the casting is allowed to crystallize and solidify under a constant pressure, and the casting is fully filled, so that the casting structure is dense and the mechanical properties are improved. This method is mostly used for precision casting of Al and Mg alloy castings. The advantages are as follows:
(1) The presence of vacuum negative pressure can make the mold sand tight and increase the strength of the mold.
(2) Moderately increase the degree of vacuum, so that the filling time becomes shorter, not only the filling speed is accelerated but also stable.
(3) Vacuum low-pressure casting can accelerate the fluidity of aluminum alloy at low temperature, avoid the phenomenon of aluminum alloy suction by high-temperature casting, and increase the pinhole defects of castings.
(4) The castings have good formability, which is favorable for forming castings with clear outlines and smooth surfaces and large thin-walled castings.
(5) The castings are densely organized and have high mechanical properties.
(6) Under normal circumstances, no riser is required, so that the yield of molten metal is greatly improved, usually up to 90%.
(7) The working environment is good and the equipment is simple, which contributes to mechanization and automation.