Squeeze casting represents a sophisticated manufacturing process that melds the strengths of casting and forging to create top-notch metal components. This innovative technique is also referred to as thixoforming and liquid metal forging.
Non-ferrous alloys like magnesium, copper, and aluminum are used to produce high-quality metals through it. The parts manufactured through squeeze casting have enhanced mechanical properties with near-net-shape.
Direct vs. Indirect Squeeze casting?
Let’s clarify the meanings and distinctions between direct and indirect squeeze casting.
Direct Squeeze casting
As the name suggests, it refers to the manufacturing process in which molten metal is directly injected into the die cavity. This process is done during the time when squeezing or pressurizing force is applied.
The force not only helps in compacting the metal but it also assures less porosity within its parts. Thus, the key characteristic of direct squeeze casting is a simultaneous injection of the molten metal while applying pressure to make high-quality components.
Indirect Squeeze casting
In this process, the molten metal is injected not directly into the die but rather into a pre-chamber or sleeve. Only after that, metal is transferred from the pre-chamber or sleeve into the die cavity. It is also ensured that squeeze or pressurized force is applied during this process.
Differentiation
- Injection Point: In direct squeeze die casting, the injection point of molten metal is directed towards the cavity while in indirect casting, molten metal is injected into sleeve or pre-chamber.
- Pressure Application: Through direct squeeze casting, pressure is applied over the molten metal as it enters the die cavity whereas pressure is applied in an indirect method when metal is in pre-chamber or sleeve.
- Mold Complexity: Direct squeeze casting is simpler as it requires no additional components like pre-chamber or sleeve is required in indirect squeeze casting.
- Applications: Components with straightforward geometrics are favored for direct squeeze casting while large or intricate components are best developed through indirect squeeze casting.
Manufacturing Process of Squeeze Casting
There are different processing steps performed to manufacture components through squeeze casting as this is a specialized and precision-oriented method. Following is the overview of all the necessary manufacturing process steps of squeeze casting.
- Melting:
A high-temperature furnace is used to melt the selected metal or alloy. The metal is heated until it converts into liquid form.
- Die Preparation:
Usually, a two-part mold is developed in which one part remains stationary while the other part becomes movable. The desired shape of the final output is engraved into the mold.
- Injection:
The molten metal is either injected directly into the die cavity as the case in direct squeeze casting or transferred to a pre-chamber or sleeve as the case in indirect squeeze casting.
- Squeeze or Pressure Application:
During the injection phase, a constant extrude or pressure is applied over the metal to ensure its compactness as well as reduce the porosity.
- Cooling and Solidification:
The mold is cold after it is successfully injected into the cavity so that it can easily solidify. In order to create a fine and uniform microstructure, controlled cooling is really important.
- Ejection:
Once the component has been cooled appropriately, the ejection phase comes in. A moveable part of the mold is often used to retract the component from the cavity.
- Post Processing and Quality Control:
Finishing such as trimming, machining, surface finishing, or tolerance is applied during this phase. Moreover, the finished goods are inspected for adherence to quality standards and identifying defects, dimensions, and mechanical faultlines.
Features
Since it is an advanced manufacturing process that has a lot of benefits and limitations, it comes with distinctive features. However, the key features of squeeze casting are as follows.
- Combination of Casting and Forging:
It combines the processes of casting and forging making it easier to manufacture complex shapes along with reduced porosity.
- Near-Net-Shape Components:
The parts or components produced through squeeze casting require very little processing or machining which in turn reduces material waste and production costs.
- Improved Mechanical Properties:
Applying pressure during the solidification process in squeeze casting provides it with superior mechanical properties. Higher strength, dependable fatigue resistance, and enhanced ductility are some of its improved mechanical characteristics.
- Complex Geometrics:
It enables the production of complex and intricate design geometrics. Thus, it makes the components easier to be used in a wide range of industries.
- Thixotropic Materials:
It is completely compatible with thixotropic materials. These materials exhibit properties of both solid and liquid. Moreover, this is a major difference when compared to squeeze casting vs. die casting. Aluminum squeeze casting and other types of materials can also be used.
- Cost-Effective:
It is a very cost-effective method when it comes to high-precision requirements as it requires very little post-processing.
Squeeze Casting vs. Liquid Forging
Squeeze casting and liquid forging have a lot of similarities as well as differences. Following are some of the key differences in process steps and material considerations between them.
Process Steps:
- Injection and Pressure Application:
The injection and pressure application of squeeze casting and liquid forging is quite the same. In squeeze die casting, molten metal is directly injected into the die cavity whereas, in liquid forging, a preform is prepared and then transferred into the die cavity.
- Cooling and Solidification:
After all the injection and forging operations are completed, the next phase consists of cooling and facilitation of solidification while controlling pressure. This step also contains numerous similarities.
- Ejection:
Ejection is also a common process step in both – squeeze casting as well as in liquid forging.
- Material Considerations:
Material consideration is a different step when it comes to comparing squeeze die casting and liquid forging. Squeeze casting is suitable for a variety of non-ferrous alloys such as aluminum, copper, and magnesium. It is most suitable for alloys that do not exhibit the properties of thixotropic behavior.
On the other hand, liquid forging is best suitable for thixotropic materials. It could be said as more specialized in forming alloys like some aluminum alloys as well.
- Precision:
It is well known for its high precision as well as reliable and tight tolerances. With excellent dimensional accuracy, it becomes easier to produce near-net-shape components. On the other hand, liquid forging does not provide much precision than squeeze casting. However, it requires some additional steps to reach the desired precision level.
- Applications:
Since it has high-level precision, its applications include aerospace, automotive, and numerous electronics manufacturing. Whereas, the applications of liquid forging include areas where thixotropic materials are beneficial such as some automotive components like steering knuckles and in other manufacturing processes.
Conclusion
In conclusion, squeeze casting proves to be a remarkable method that provides precision, strength, and versatility. It has the ability to fit with every design specification through its near-net-shape capability. With its affordability and flexibility, it becomes feasible for almost every type of application.