Advantages And Disadvantages of Squeeze Casting

Squeeze Casting is an advanced process in which molten metal is injected into a mold and then immediately subjected to continuous high pressure to solidify and take shape. It combines the advantages of casting (capable of forming complex shapes) and forging (dense structure). The following is a detailed analysis of its advantages and disadvantages:

The core advantages of Squeeze Casting:

The essence of squeeze casting is: a certain amount of molten aluminum is injected into the mold cavity, and then a huge pressure is directly applied to the liquid or semi-solid metal, causing it to cool and solidify under high pressure to take shape. Its advantages are mainly reflected in the "quality" aspect:

1. Unparalleled mechanical properties - core advantage

This is the most prominent advantage of squeeze casting. Because metals solidify under extremely high pressure (typically 50-100 mpa, or even higher), their internal structure undergoes fundamental changes:

• Eliminating defects: High-pressure forced feeding has completely eliminated traditional casting defects such as shrinkage cavities and porosity.

• Grain refinement: Solidified under high pressure, the grains are significantly refined and the structure is extremely dense.

• Excellent performance: The tensile strength, yield strength, elongation (toughness) and fatigue strength of its products are all very high, approaching or even reaching the level of the same aluminum alloy forgings, far superior to traditional die-castings and gravity castings.

2. It can be strengthened by heat treatment and also welded

Due to the presence of a large number of high-pressure bubbles inside traditional aluminum die-castings, thermal expansion during heat treatment can cause surface bubbling and deformation. Therefore, solution heat treatment (T6 treatment) is usually not suitable for them.

Squeeze castings have a dense structure and no internal pores, so they can undergo complete heat treatments such as solution treatment (T4) and aging treatment (T5/T6) like forgings to further enhance their performance. They also have good weldability. So as to maximize the potential of the material and further enhance its strength and hardness.

3. It features a high surface finish and good dimensional accuracy

High pressure makes the molten aluminum closely adhere to the surface of the mold cavity, resulting in a smooth product surface with clear contours and sharp text and patterns. Solidified under high pressure, it has a small and stable shrinkage, high dimensional accuracy and good consistency of the product.

4. High material utilization rate and near net forming

Compared with traditional forging (which requires large billets and large machining allowances), squeeze casting can form complex-shaped parts in one go, reduce subsequent processing volume, have a high material utilization rate and save costs.

5. Wide range of applications

It is not only applicable to common aluminum alloys, but also highly suitable for the production of high-strength aluminum alloys, aluminum matrix composites and other difficult-to-machine materials, which can fully leverage the high-performance potential of these materials.

The main disadvantages of Squeeze Casting:

Just as its advantages are very prominent, its disadvantages are equally obvious, and to a large extent, these disadvantages limit its application fields.

1. High equipment and mold costs (the main limitation)

• Huge investment in equipment:

The squeeze casting machine not only requires a huge clamping force to prevent the mold from expanding, but also needs an additional high-pressure squeeze system (main cylinder) to apply extremely high pressure. This makes the equipment structure complex, difficult to manufacture and extremely expensive, far exceeding that of traditional die-casting machines and gravity casting machines.

• High mold cost and complex design and manufacturing:

(1) Extremely high strength requirements: Molds (especially cores and sliders) need to withstand continuous high pressure of up to 100 mpa or more, as well as intense thermal cycling. Therefore, top-grade hot work die steel must be used, which is costly.

(2) Complex design: The mold needs to integrate the squeeze punch, a complex cooling system and an exhaust system, which makes the design difficult and the development cycle long.

(3) Service life challenge: Under the repeated impact of extremely high pressure and high-temperature molten aluminum, the mold is prone to thermal fatigue (resulting in cracking), punch wear and deformation, and the maintenance and replacement costs of the mold are very high.

2. Production efficiency is relatively low

The cycle time is relatively long: Unlike the "second punch" high-speed filling of traditional high-pressure die casting, the core process of squeeze casting is "slow pouring and long-term pressure holding under high pressure". To ensure that the part can solidify under pressure throughout the entire cross-section, a relatively long holding time is required. This results in the production cycle of its individual parts being much longer than that of traditional die-casting, and the production efficiency is relatively low.

3. The control requirements for process parameters are extremely strict

High parameter sensitivity: Parameters such as the pouring temperature of the molten aluminum, the mold temperature, the timing of starting to apply pressure, the pressure magnitude, and the holding time need to be precisely matched. Even the slightest deviation of any parameter may lead to the scrapping of the product.

For example, if the pressure is applied too early, the molten aluminum may splash. If the pressurization is too late, the molten aluminum has formed a hard shell and lost its pressurization effect. This requires enterprises to possess profound technological knowledge and experience, as well as precise automated control of the production process.

4. The complexity of the part shape is limited

It is difficult to produce extremely complex parts: Although it can form more complex shapes than forging, compared with traditional die casting, it is very difficult to produce parts with deep cavities, small bone positions, complex thin walls or requiring multiple core-pulling.

Extremely high pressure poses a severe test to the strength of the mold core and core-pulling mechanism. Fine cores are prone to breakage under high pressure. Meanwhile, although molten metal has good fluidity under high pressure, overly complex thin-walled structures may not be fully filled due to rapid solidification.

5. The initial investment risk is high and the application field is specialized

Due to its high cost and slow pace, the squeeze casting process is not suitable for ordinary shell parts with large production volumes but low requirements for mechanical properties (such as electrical appliance casings, toys, etc.).

Application specificity: It is mainly used in key structural components with extreme performance requirements, such as automotive safety parts (control arms, steering knuckles), aerospace components, etc. This means that its target market is relatively niche. Before investing in this technology, enterprises need clear and stable orders for high-end products; otherwise, the investment risk is very high.

The greatest advantage of squeeze casting is that "it can produce aluminum parts with the properties of forgings in a forming method close to that of casting." It sacrificed some production efficiency and increased the initial cost, but brought about a qualitative leap in the strength, toughness and reliability of the product. It is an ideal process choice for manufacturing high-end and high-performance aluminum structural components.