Advantages and Applications of Low Pressure Die Casting
Ⅰ. Understand low pressure die casting
Low-pressure die casting is a die casting method in which the cavity is filled with liquid metal under low pressure. In low-pressure die casting, in addition to gravity, low-pressure or semi solid metal casting is used to fill the mold with light metals, especially aluminum alloys. During this process, tools or molds are designed and fabricated into the desired shape of the part to be fabricated. It is then mounted on a holding furnace and connected to the molten metal by feed pipes or rods. The furnace is pressurized by introducing air above the surface of the molten metal, causing it to rise steadily in the straw and fill the mold quietly. Air in the mold cavity is vented through appropriately positioned vents in the mold, and when the cavity is filled, curing begins.
Molten metal is pushed into the mold under low pressure. Once cured, the pressure is released and any residual liquid in the tube or cavity is returned to the holding furnace for recovery. After cooling, the casting is removed from the mold, and this process can be repeated multiple times to obtain the quantity ordered by the customer.
Ⅱ. The advantages of low pressure die casting
Low-pressure die-casting can use a sand mold, metal mold, graphite mold, etc. The filling process is not only different from gravity die casting and sand casting like sodium silicate sand casting, but also different from high-pressure die casting. It has the following advantages:
1. The casting mold is filled with pure metal liquid, which improves the purity of the casting. The slag generally floats on the surface of the liquid metal, while the low-pressure die casting is filled by the liquid metal at the bottom of the crucible through the riser, which completely avoids the possibility of the slag entering the mold cavity.
2. The liquid metal filling is stable, reducing or avoiding the phenomenon of stirring, impacting and splashing during liquid metal filling, thereby reducing the formation of oxide slag.
3. Pressurized filling of liquid metal can improve the fluidity of liquid metal, which is conducive to casting castings with clear outline and smooth surface, and is more conducive to casting large thin-walled castings.
4. The castings of low pressure die casting crystallize and solidify under pressure, which can be fully fed and the structure of the castings is dense.
5. Generally, no riser is needed, and the unsolidified metal in the riser can be returned to the crucible for reuse, which greatly improves the recovery rate of molten metal, and the recovery rate can reach 90%.
6. The production operation is convenient, the production efficiency is high, and it is easy to realize mechanization and automation.
Ⅲ. Application of low pressure die casting
Unlike nuclear castings, low-pressure die casting is the earliest anti-gravity casting technology, which has been used in industrial production since the 1940s. Today, low-pressure die casting is mainly used to produce aluminum castings and magnesium castings, such as automobile wheel hubs, cylinder blocks, cylinder heads, pistons, missile casings, impellers, wind wheels, and other complex-shaped castings. In addition, low-pressure die casting can also be used to produce small copper alloys castings, such as pipe fittings and bathroom faucets.