Aluminum alloy is widely used in automobile manufacturing, aerospace, shipbuilding and other fields because of its good plasticity, corrosion resistance, and light weight. With the development of China's manufacturing industry, the demand for aluminum alloy and aluminum alloy castings is increasing, which will also promote the development of aluminum alloy casting industry. At present, aluminum alloy casting methods are divided into pressure casting and gravity casting. This article will analyze the differences and characteristics of the two casting processes in detail.
Aluminum alloy casting processes are roughly divided into two types: gravity casting and pressure casting.
Aluminum alloy pressure casting refers to the process of injecting molten metal into the mold under the action of other external forces (excluding gravity). Pressure casting is divided into high pressure casting and low pressure casting.
High-pressure casting is what we usually call die-casting. The molten aluminum is poured into the press chamber, and the mold cavity is filled at high speed through its pressure, and the molten aluminum is solidified under pressure to form aluminum castings.
The characteristics of aluminum alloy die castings are:
1. The surface finish of the product is good, generally reaching Ra6.3 or even Ra1.6.
2. No heat treatment is allowed.
3. The product has high air tightness, high casting strength and surface hardness, but low elongation.
4. The mold cost is high and the service life is short.
5. High production efficiency.
6. Thin-walled parts can be produced with small machining allowance.
Gravity casting of aluminum alloy refers to the process of injecting molten aluminum into the mold under the action of the earth's gravity. Gravity casting is divided into: sand casting, metal (steel mold) casting, lost foam casting, etc.
Now the most widely used is metal mold (steel mold) casting. The mold is made of heat-resistant alloy steel. The strength, size, and appearance of cast aluminum castings are higher than those of other casting processes.
The molten aluminum of gravity casting is generally poured into the gate manually, and the cavity is filled with the weight of the molten metal, exhausted, cooled, and the mold is opened until the sample is obtained. The process flow is generally: molten aluminum smelting, casting filling, exhausting , Cooling, mold opening, cleaning, heat treatment, processing.
The characteristics of aluminum alloy gravity casting are:
1. The surface finish of the product is not high, and it is easy to produce pits after shot blasting.
2. There are few pores inside the aluminum casting, which can be heat treated.
3. The product has low compactness and weaker strength, but high elongation.
4. The mold cost is low and the mold has a long service life.
5. The production efficiency is low, which increases the production cost.
6. The process is relatively simple and not suitable for the production of thin-walled parts.
When choosing which process to produce the product, the choice is mainly based on the wall thickness of the workpiece. When the wall thickness of the product is greater than 8mm, die casting will cause a lot of pores in the wall, so thicker products can be completed by gravity casting. .
