Low pressure casting means that the mold is usually placed above the sealed crucible, and compressed air is introduced into the crucible to generate low pressure on the surface of the molten metal (0.06~0.15MPa), so that the molten metal rises from the furnace. The riser tube fills the mold and controls the solidification casting method. This casting method has good feeding and compact structure, easy to cast large thin-walled composite castings, no risers, and metal recovery rate of 95%. No pollution, easy to realize automation. However, the equipment cost is high and the production efficiency is low. Therefore, low pressure casting is usually used for casting non-ferrous alloys.

When performing low-pressure casting, compressed air needs to be added to the furnace, and the molten metal will flow from the riser into the cavity. After the molten metal solidifies, the compressed air in the furnace is released, and the unsolidified metal flows back into the furnace from the riser.

The aluminum hub and blades in the hydraulic torque converter core adopt low-pressure casting technology, and the resulting castings have dense structure and good mechanical properties; high process output and high production efficiency. The production efficiency of the die-casting process of the same product is three times that of gravity casting; smooth and clean, which can reduce the machining allowance.

During the operation of low-pressure casting, the paint should be cleaned before using the mold. After the production cycle, the paint fails or the surface is uneven, and a grinding wheel is needed to polish the paint. Then clean the aluminum shavings of the eject lever and clean the exhaust plug. Baking mold, the working temperature is (360±10)℃, so the mold should be baked to the working temperature before work.

When the mold is heatedSpray paint at 300°C, and the paint must be uniform and free from sagging. Set up the core and set the process parameters. The process parameters of low pressure casting are mainly the temperature of aluminum water, the pressure speed and pressure setting of the equipment. These three factors will affect the quality of the casting, and if it is not set well, it will lead to defects such as sand sticking, insufficient casting and suffocation. Therefore, parameter setting is very important for casting.

Compared with traditional gravity casting, low-pressure casting can greatly increase the output of castings and have high working efficiency. Due to the crystallization under pressure, the structure of the casting is dense and the tensile strength can reachMore than 200MPa. However, low-pressure casting has higher requirements for equipment, molds and processes, and a little carelessness will lead to batch waste. Temperature, exhaust and filling parameters need to be controlled.