Squeeze Casting Process – Advantages and Disadvantages
Squeeze Casting Process
Squeeze casting, also known as liquid metal forging, is a combination of casting and forging process.
The molten metal is poured into the bottom half of the pre-heated die. As the metal starts solidifying, the upper half closes the die and applies pressure during the solidification process. The amount of pressure thus applied is significantly less than used in forging, and parts of great detail can be produced. Coring can be used with this process to form holes and recesses. The porosity is low and the mechanical properties are improved.
Both ferrous and non-ferrous materials can be produced using this method.
Squeeze casting is a method of forming metal into shapes by using two dies that are squeezed together. Most casting techniques use two dies that are squeezed together before the metal is added but, in squeeze casting, the two are pushed together after the metal is added. This is done with liquid metal, and the upper die is only removed when the metal has cooled. By using this technique, the metal will typically come out stronger, with a better grain and less metallic shrinking. This commonly is done with magnesium, aluminum and their alloys, but many other metals can be used.
Most casting techniques involve the use of two dies, but squeeze casting uses the dies in a different way. The two casts normally are placed together and liquid metal is poured into the case. With a squeeze cast, a pool of liquid metal is placed in the bottom die and an upper die comes in and squeezes the metal into a shape. Pressure is being applied via the upper die, so this is not strictly casting, as it adds forging to create a hybrid technique.
Only liquid metal can be used in this application. While materials such as plastic can melt at high temperatures, this technique will not be suitable to cast plastic. After the upper die is set, workers wait until the metal is completely cool. Once cool, the upper die will be released and the required shape will have been cast into the now-solid metal.
Non ferrous alloys like aluminum, magnesium, and copper alloy components are readily manufactured using this process . The squeeze casting process, combining the advantages of the casting and forging processes, has been widely used to produce quality castings . Because of the high pressure applied during solidification, porosities caused by both gas and shrinkage can be prevented or eliminated . The cooling rate of the casting can be increased by applying high pressure during solidification, since that contact between the casting and the die is improved by pressurization, which results in the foundation of fine-grained structures
- Casting temperatures depend on the alloy and the part geometry. The starting point is normally 6 to 55°C above the liquidus temperature.
- Tooling temperatures ranging from 190 to 315°C are normally used
- Pressure levels of 50 to 140 MPa are normally used
- Lubrication For aluminum, magnesium, and copper alloys, a good grade of colloidal graphite spray lubricant has proved satisfactory when sprayed on the warm dies prior to casting
Advantages Of Squeeze Casting process :
- Offers a broader range of shapes and components than other manufacturing methods
- Little or no machining required post casting process
- Low levels of porosity
- Good surface texture
- Fine micro-structures with higher strength components
- No waste material, 100% utilization
Disadvantages Of Squeeze Casting process :
- Costs are very high due to complex tooling
- No flexibility as tooling is dedicated to specific components
- Process needs to be accurately controlled which slows the cycle time down and increases process costs.
- High costs mean high production volumes are necessary to justify equipment investment
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