Squeeze casting refers to a state-of-the-art metal forming technique which is a combination of the casting and forging approaches. Squeeze casting involves the injection of molten metal into a mold and applying pressure during the process of solidification. This pressure ensures a reduction in the number of defects within the casting, increased density and enhanced mechanical properties.
Squeeze casting is different from the other traditional casting processes in the sense that the resultant products have fewer pores, more strength and better quality. It is commonly used to manufacture parts in the automotive, aerospace and industrial industries.
Given Raidymold’s thorough knowledge of pressure forming techniques such as the pressure assisted feeding in the squeeze casting technique, Raidymold incorporates modern mold filling and solidification concepts in its mold design. In order to mitigate against the problems of shrinkage defects, Raidymold has focused on areas where there are irregular wall thicknesses and hot spots by optimizing the gating systems, overflow systems and cooling systems. This results in the compensation of shrinkage by the molten aluminum.
What Is Squeeze Casting and How Does the Process Work?
Squeeze casting, also known as liquid metal forging, is a manufacturing process in which molten aluminum is introduced into a mold cavity at low velocity and then solidified under high applied pressure. Unlike high-pressure die casting, which relies on high-speed injection to fill thin-walled cavities, squeeze casting emphasizes controlled, laminar flow and sustained pressure during solidification to eliminate porosity and refine the microstructure.
The Basic Steps of the Squeeze Casting Process
Mold Preheating
The mold (which usually consists of high-quality tool steel) is heated up to the set temperature to facilitate metal filling.
Low-Velocity Filling
The molten aluminum is injected into the mold cavity slowly (below 2 m/s, mostly below 0.5 m/s) to prevent turbulence, air entrapment, and oxides.
High Pressure Application
Almost immediately after filling, a high-pressure ram or punch is applied on the molten material. The pressure remains high until solidification is achieved.
Solidification Under Pressure
During solidification, the metal remains under pressure, preventing porosity and shrinkage cavity formation and producing a dense and fine-grained structure.
Part Ejection
After the process of solidification is completed, the formed part is removed from the mold. Thanks to the near-net shape of the produced parts, there is usually little machining or finishing needed.
Direct vs Indirect Squeeze Casting
There are two main types of squeeze casting as follows:
Direct Squeeze Casting: In this type, pressure is directly applied to the metal melt in the die cavity using a punch. It is easier in nature and more suitable for simple and thick-walled parts.
Indirect Squeeze Casting: In this type, pressure is indirectly applied to the metal melt using a gating system or runner. It is more flexible in nature and involves a more complicated mold design.
The objective in both cases is the same, that is, to obtain high density and low porosity parts.
Key Advantages of the Squeeze Casting Process
Squeeze casting offers several compelling benefits, particularly for applications demanding high structural integrity and mechanical performance.
Superior Mechanical Properties
Parts produced by squeeze casting exhibit mechanical properties that approach those of forged components. The combination of low-velocity filling and high-pressure solidification results in:
- Higher tensile and yield strength
- Improved ductility and elongation
- Enhanced fatigue resistance
- Better impact toughness
These properties make squeeze-cast aluminum ideal for safety-critical automotive and aerospace components.
Very Low Porosity and High Density
The sustained pressure during solidification effectively eliminates gas porosity and shrinkage defects. This results in parts with near-zero internal porosity, which is critical for:
- Pressure-tight applications (e.g., hydraulic components, brake systems)
- Components requiring high reliability under cyclic loading
- Parts that must pass stringent X-ray or leak-testing standards
T6 Heat Treatment Compatibility
Unlike many HPDC parts, which can develop surface blisters during T6 heat treatment due to trapped gas, squeeze-cast aluminum can be safely heat-treated without this risk. This allows for further enhancement of mechanical properties through precipitation hardening.
Reduced Machining and Post-Processing
The high dimensional accuracy and excellent surface finish achieved through squeeze casting often eliminate the need for extensive secondary operations. This reduces overall manufacturing costs and lead times, especially for high-value components.
Good Dimensional Accuracy and Surface Finish
The controlled solidification and high pressure result in parts with tight tolerances and smooth surfaces, reducing the need for additional finishing processes.
Main Disadvantages and Limitations
Despite its advantages, squeeze casting is not suitable for every application. Understanding its limitations is crucial for selecting the right process.
Slower Cycle Time and Lower Production Rate
Squeeze casting typically has longer cycle times (2–5 minutes per part) compared to HPDC (30–120 seconds). This makes it less suitable for high-volume production runs where speed is a primary concern.
Higher Equipment and Tooling Investment
The process requires specialized equipment capable of applying and maintaining high pressure during solidification. Additionally, molds must be designed to withstand significant mechanical and thermal loads, leading to higher initial tooling costs.
Limited Suitability for Very Thin Walls and Extremely Complex Shapes
While squeeze casting can produce complex geometries, it is generally less capable than HPDC when it comes to extremely thin walls or highly intricate features. The low-velocity filling limits the ability to fill very fine details without defects.
Strict Process Control Requirements
Achieving consistent quality in squeeze casting demands precise control over multiple parameters, including:
- Melt temperature
- Mold temperature
- Injection speed
- Applied pressure and hold time
Any deviation can lead to defects such as cold shuts, incomplete filling, or residual porosity.
Size Limitations Due to Press Capacity and Pressure Requirements
The maximum size of squeeze-cast parts is constrained by the capacity of the press and the ability to maintain uniform pressure across the entire casting. Very large components may require prohibitively large and expensive equipment.
Squeeze Casting vs High Pressure Die Casting for Aluminum
Understanding the differences between squeeze casting and HPDC is essential for selecting the right process for your application.
| Feature | Squeeze Casting | High-Pressure Die Casting (HPDC) |
|---|---|---|
| Fill Velocity | Low (< 2 m/s, often < 0.5 m/s) | High (30–60 m/s) |
| Pressure Application | During solidification | During injection |
| Porosity Level | Very low (near-zero) | Moderate to high (depending on process control) |
| Mechanical Properties | Near-forged quality | Good, but typically lower than squeeze casting |
| T6 Heat Treatment | Fully compatible | Risk of blistering |
| Typical Wall Thickness | Moderate to thick | Very thin to moderate |
| Cycle Time | 2–5 minutes | 30–120 seconds |
| Production Rate | Lower | Higher |
| Cost per Part (High Volume) | Higher | Lower |
| Best For | Structural, safety-critical, high-integrity parts | High-volume, thin-walled, complex housings |
Choose Squeeze Casting When:
- High strength is required
- Low porosity is important
- Mechanical performance is the priority
- Structural aluminum components are needed
Choose High Pressure Die Casting When:
- Large production volume is required
- Complex geometries are needed
- Thin-wall designs are important
- Cost efficiency is a major factor
At Raidy Mold, we will develop a die-casting mold solution tailored to your specific needs, proceeding based on a combination of your preferences and our professional recommendations.
Key Process Parameters in Squeeze Casting and Their Effects
Achieving optimal results in squeeze casting requires careful control of several critical parameters.
Pressure Magnitude and Hold Time
- Typical Range: 50–150 MPa
- Impact: Higher pressure and longer hold times reduce porosity and refine grain structure, but excessive pressure can lead to mold damage or part distortion.
Melt Temperature
- Typical Range: 650–720°C (depending on alloy)
- Impact: Too high a temperature can cause excessive shrinkage and coarse grains; too low can lead to incomplete filling or cold shuts.
Mold Temperature
- Typical Range: 200–300°C
- Impact: Proper mold temperature ensures smooth metal flow and controlled solidification. Incorrect temperatures can cause thermal shock, cracking, or poor surface finish.
Injection Speed
- Typical Range: < 2 m/s (often < 0.5 m/s)
- Impact: Low speed minimizes turbulence and air entrapment, but too slow can result in premature solidification before the cavity is filled.
Common Defects in Squeeze Casting and Prevention Strategies
While squeeze casting produces high-quality parts, certain defects can still occur if the process is not properly controlled.
Gas Porosity and Shrinkage Cavities
- Cause: Insufficient pressure or premature release of pressure during solidification.
- Prevention: Ensure adequate pressure is maintained throughout the entire solidification phase.
Cold Shuts and Incomplete Filling
- Cause: Low melt or mold temperature, or excessively slow injection speed.
- Prevention: Optimize temperature profiles and injection parameters to ensure complete cavity filling before solidification begins.
Cracking and Hot Tearing
- Cause: Excessive thermal stress or improper ejection timing.
- Prevention: Use proper mold preheating, controlled cooling, and optimized ejection sequences.
Oxide Inclusions
- Cause: Turbulent filling or exposure of molten metal to air.
- Prevention: Maintain low injection speeds and use protective atmospheres or fluxes where applicable.
Mold Design Requirements for Squeeze Casting Aluminum
Raidy Mold Manufacturer understands that specific design considerations for squeeze casting are crucial for delivering high-quality molds.
Gating and Runner Systems
- Larger Gates: Unlike HPDC, squeeze casting often requires larger gates to facilitate pressure transmission and feeding during solidification.
- Simplified Flow Paths: Low-velocity filling allows for simpler runner designs, but proper sizing is critical to avoid pressure drops.
Venting
- Reduced Air Entrapment: The laminar flow in squeeze casting minimizes air entrapment, but strategic venting is still necessary to allow air escape and prevent back pressure.
Cooling Systems
- Uniform Temperature Distribution: Extended solidification under pressure requires precise cooling control to avoid hot spots and ensure consistent part quality.
- Enhanced Heat Extraction: Efficient cooling channels help reduce cycle times and improve mold life.
Mold Materials and Surface Treatments
- High-Grade Tool Steels: Molds must withstand high mechanical loads and thermal cycling. Common materials include H13 and premium hot-work steels.
- Surface Coatings: Nitriding, PVD, or other surface treatments can improve wear resistance and reduce sticking.
Ejection and Lubrication
- Robust Ejection Systems: High pressure can cause parts to stick, requiring well-designed ejector pins and plates.
- Low-Gas Release Lubricants: Release agents must provide good separation without introducing gases that could cause porosity.
Typical Applications of Squeeze Casting in Automotive and Aerospace
Squeeze casting finds extensive application in industries where the dependability and efficiency of parts are of utmost importance.
** Applications in Automotive Industry
Structural Parts: Suspension arms, steering knuckles, and chassis parts can gain from the high strength and fatigue properties of squeeze cast aluminum.
Brake Parts: Brake calipers and master cylinders need to be pressure-tight and have high integrity.
Powertrain Components: Engine mounts, transmission casings, etc.
** Aerospace and Defense Industry
High-Performance Parts: High-performance parts that need to withstand extreme stresses and strains and cyclic loading such as landing gear parts and structural brackets.
Light Weighting Program: Squeeze casting makes it possible to replace heavy steel parts by lighter aluminum components without affecting performance.
** Others
Hydraulic and Pneumatic Systems: Pressure-tight housing and manifold assemblies.
Machinery: High-strength and high-wear resistant parts for heavy-duty machinery.
FAQ
What is the difference between squeeze casting and die casting?
Both squeeze casting and die casting are based on pressure technology, but the process itself differs. Squeeze casting technology implies applying pressure on metal during its solidification to decrease porosity and enhance mechanical properties of material. In die casting technology, filling of mold cavity with molten metal takes place under conditions of high speeds.
What is the principle of squeeze casting?
Squeeze casting technology implies application of pressure on liquid metal during its solidification within mold. Such pressure leads to the reduction of defects associated with shrinkage and porosity, thus increasing density of the resulting component.
What is the difference between HPDC and squeeze casting?
The difference between squeeze casting and HPDC lies in that in HPDC mold cavity is filled with liquid metal with high speed, which makes this technology perfect for manufacturing of complex components in large quantities.
Cost and Cycle Time of Squeeze Casting: When Is It Economical?
Squeeze casting is an advanced manufacturing process that combines the efficiency of casting with the performance characteristics of forging, offering advantages such as low porosity, high density, high strength, and excellent dimensional stability. However, factors such as higher mold costs, longer production cycles, and design limitations must also be considered when selecting this process.
The choice between squeeze casting and high-pressure die casting should be based on a comprehensive assessment of part geometry, production volume, and performance requirements. High-pressure die casting remains the widely adopted solution for the efficient mass production of complex aluminum alloy parts.
Raidymold specializes in the design and manufacture of high-pressure die casting molds. By leveraging advanced mold engineering, optimized cooling systems, and precision machining technologies, we provide our customers with high-quality, highly reliable die casting mold solutions. Contact us to explore professional mold solutions tailored to your aluminum alloy casting projects.
