For its good plasticity, corrosion resistance and lightweight of aluminum alloys, this type of metal material is widely used in automotive, aerospace, shipbuilding and other fields. With the development of China’s manufacturing industry, the demand for the aluminum alloys and aluminum alloy castings is increasing, which will push forward aluminum casting industry.The main methods of aluminum castings are divided into pressure die casting and gravity casting. Here we will analysize the difference between two kinds of casting processes.
Die Casting for Aluminum Components
Die casting or pressure die casting refers to the casting process that liquid metal is injected into mold under ther external forces (excluding gravity). Die Casting is divided into High Pressure Die Casting and Low Pressure Die Casting.
High pressure die casting is usually called die casting, which the liquid aluminum is poured into the interior, and quickly filled the mold cavity through its high pressure on high speed, then the liquid aluminum will get solidificated under pressure to form aluminum castings.
Features of Aluminum Die Castings:
- Good surface finish, general reach Ra6.3 even Ra1.6.
- Can not be heat treated.
- High gas tightness, high strength and surface hardness, but low elongation.
- The mold cost is higher, but long serving life.
- High production efficiency.
- Can produce thin wall parts, little machining allowance.
Gravity Casting for Aluminum Components
Aluminum gravity die casting refers to the injection mold process of liquid aluminum under the earth’s gravity. Gravity casting is divided into: Sand mold casting, metal mold casting, etc.
Now most used gravity casting method is a metal mould casting process, which mould is made of heat-resisting alloy steel. The strength, size and appearance of aluminum castings are higher than other methods.
Liquid aluminum in gravity casting generally was poured into the gate by manual. The final product will be achieved by its own weight of liquid metal, and full fills of mould cavity, exhaust, cooling and demould. The general process is: liquid aluminum smelting, casting material filling and exhaust, cooling, demould, heat treatment, shot blasting and machining.machining.
Features of Aluminum Gravity Castings:
- The surface finish of product is not high, prone to pit after shot blasting.
- Less inner porosity, and heat treatment can be performed.
- Low product density, slightly worse strength, but high elongation rate.
- Low mould cost is low and long mould serving life.
- low production efficiency, thus increasing the production cost.
- Unsuitable for the production of thin wall parts.
When considering the casting method of aluminum components, you choose mainly by the wall thickness of a product. When the wall thickness of a aluminum component is larger than 8 mm, die casting can cause a lot of gas holes inside. Therefore, we can complete thicker aluminum products using gravity casting process.