How to Conduct Leakage Testing for Aluminum Squeeze Castings

Imagine that a critical part of a vehicle’s braking system fails due to a tiny, undetected leak in its aluminum casting component.

Such a failure could cause serious safety issues.

That’s why leakage testing in aluminum squeeze castings is not only a process but also a necessity to ensure safety and efficiency in many high-demand applications.

Leakage testing for aluminum squeeze castings is carried out with strict inspection procedures to guarantee the integrity and impermeability of the castings. The water immersion testing and helium leakage testing are the main methods used. By these means, we can find out the tiniest defects in the castings, which are critical to making sure that the products can perform reliably under various pressures and conditions, especially in applications such as aerospace and automotive industries.

Understanding the importance of leakage testing will help manufacturers to realize the value of strict quality assurance measures.

It’s not only about meeting industry standards but also ensuring the highest safety and functionality of the final products.

The Critical Importance of Leakage Testing

Leakage testing is particularly critical for aluminum squeeze castings due to the specific applications and properties of these components.

Here are several reasons to explain the importance of conducting leakage tests on aluminum squeeze castings:

Ensuring High-Stress Applications

Aluminum squeeze castings are widely applied in high-stress applications such as automotive components, aerospace parts, and industrial machinery.

In these applications, castings should be free from porosity and other defects, which could cause structural failures under pressure.

Leakage testing is to ensure that these castings can bear the operational stresses without failure.

Maintaining Pressure Tightness

Many aluminum squeeze castings are designed to hold or resist high pressure. 

For example, components like hydraulic cylinders, pump bodies, and fluid transportation systems must keep the pressure without leakage to work properly. 

Leakage testing is to confirm that these components can reliably contain fluids and gases under certain pressures, which is very important for their applications.

Enhancing Durability

To find out and deal with the leakage in aluminum squeeze castings during manufacturing is to ensure the overall durability of the final products. 

The components that pass strict leakage tests are less likely to fail prematurely, which is very important to cut down the maintenance cost and extend the service life of the machinery.

Preventing Corrosion and Material Degradation

Leaks may cause unwanted substances to enter into components, which could result in corrosion or other forms of material degradation. 

This is particularly critical for the castings exposed to corrosive agents or extreme conditions. 

Leakage testing is to guarantee that these components can keep their integrity and functionality in the long run.

Our Advanced Leakage Testing Methods

At CEX Casting, we adopt various advanced methods and state-of-the-art instruments to carry out leakage tests meticulously.

Water Immersion Testing

Overview

Water immersion testing, also called “bubble test”, is a simple but effective method to detect leakage in cast aluminum components.

It’s performed by immersing the part in water and observing if there are air bubbles coming out.

The picture below shows the water immersion testing we conducted for the squeeze casting auto parts.
Water Immersion Testing
Step-by-Step Process

Preparation: the casting is cleaned and visually inspected to make sure that there is no surface contamination or residual particles, which may affect the test.

If necessary, the component is sealed properly to close off the parts that are not to be tested or should not let water in.

Submersion: the prepared casting is fully immersed into a container filled with water. 

The water temperature and pressure can be adjusted according to the specific requirements of the test, to simulate the operational conditions.

Air Pressure Application: while the component is immersed, the air pressure is carefully applied inside. 

The pressure level is predetermined according to the operational specifications of the casting and its use.

Observation: the component is observed closely to see if there are any air bubbles emerging. 

The bubbles indicate that there are leaks. Each bubble stream can help locate the exact position of a leak, which is helpful for further analysis and corrective actions.

Documentation and Analysis: the results of the test are documented, which records the positions and the severity of the leaks. 

Post-Test Handling: after the test, the component is taken out of the water, dried, and re-inspected to see if any further actions are needed according to the test results.

This may include repairs, further tests, or changes to the manufacturing process.

Instrument

Submersion Tank with Transparent Walls: the core instrument in water immersion testing is the submersion tank. 

This tank is typically constructed with transparent walls to allow for clear visibility during the testing process. 

The size of the tank depends on the size of the castings being tested; it must be large enough to fully submerge multiple or large castings at once if necessary.

Water Circulation and Filtration: in order to keep the view clear and make sure the test is carried out accurately, the tank is equipped with a water filtration and circulation system, which can keep the water clean and free from impurities that may block the view of emerging bubbles from leaks.

Pressure Systems: the tank is also set up with connections for air compressors, which can pressurize the casting internally and force air through any leaks, making them visible as streams of bubbles in the water.

Temperature Control System: the tank includes a temperature control system to adjust the water temperature. 

This feature is useful when testing needs to simulate specific environmental conditions or when the physical properties of the testing medium may affect the results.

Submersion Tank

Helium Leakage Testing

Overview

Helium leakage testing is one of the most sensitive leak detection methods.

It is particularly effective because helium atoms are small and can easily escape through tiny imperfections where other molecules might not.

There are several helium leakage testing methods, in CEX, we use the sniffer gun method.

Helium Leakage Testing
Step-by-Step Process

Preparation: the casting is first sealed, except for any test ports, which are used to introduce helium into the component.

All surfaces should be clean and free of contaminants to ensure accurate results.

Helium Introduction: fill the sealed chamber with helium at a certain pressure inside the tested casting.

Detection: the spectrometer is used to detect and measure the rate of helium leakage.

It can pick up extremely low concentrations of helium, making it possible to detect very small leaks.

Identification of Leak Points: when a leak is detected, the exact location can often be pinpointed, allowing for targeted corrective actions. 

A sniffing gun connected to the spectrometer is used to manually scan the component surface to find precisely where helium is escaping.

Documentation and Analysis: results from the helium test are recorded, noting the severity and exact locations of any leaks. 

This data is crucial for quality control, further improvements in the casting process, and ensuring the component meets the required specifications.

Post-Test Procedures: after testing, the helium is safely removed from the component, and the part is either repaired or retested as necessary based on the findings.

Instrument

Spectrometer: the heart of the detector, the mass spectrometer, is designed to identify the presence of helium. 

It works by ionizing helium atoms and then using magnetic and electric fields to measure their mass-to-charge ratio, which distinguishes helium from other gases present.

Vacuum System: includes a vacuum pump to evacuate air from the testing chamber and the component being tested, creating a vacuum necessary for accurate testing.

This system can also be used to create a pressure differential that drives helium into leak points.

Helium Sensor: detects and quantifies the amount of helium, providing precise measurements of leak rates. 

This is essential for ensuring the component meets the stringent leak-tightness specifications.

Display and Interface: the helium leak detectors come with digital displays and user interfaces that allow operators to set parameters, monitor testing in real-time, and analyze results. 

These interfaces can often connect to computers for data logging and more detailed analysis.

Sniffer Gun: this hand-held device is connected to the spectrometer and is used to manually locate leaks by detecting helium concentrations around the surface of the casting.

The picture below shows the helium leakage testing we conducted for the squeeze casting auto parts.

Helium Leakage Testing Instrument

Testing Procedures

Our testing procedures are tailored to meet the rigorous standards demanded by our customers:

Determine Testing Requirements: each project begins with a detailed analysis of the customer’s requirements and specifications to ensure the testing parameters are appropriately set. 

Below are some common leakage testing requirements from our customers.

leakage testing requirements from customers

Fixture Preparation: custom fixtures are designed and built for each part to ensure it is securely held and accurately tested without introducing variables that could affect the outcome.

At CEX, we have the in-house capability to design and manufacture fixtures for leakage testings according to different requirements.

fixture for leakage testing
Conducting Tests: the parts undergo tests using the above methods. Each part is tested under controlled conditions to ensure consistent and reliable results.

Analysis of Results: the results are carefully analyzed to determine if the part meets all the required specifications. Any failure leads to a review and adjustment of the production process to eliminate the issue.

Castings We Developed that Passed Leakage Testing

We have numerous success stories where castings have passed stringent leakage testing.

Here are some castings we developed that are used in high-standard industries, including automotive and fluid control.

castings passed leakage testing

Why Squeeze Castings Pass Leakage Testing

Aluminum squeeze castings are distinguished by their excellent leakage resistance, which is mainly attributed to the following intrinsic properties of the squeeze casting process:

High Density and Low Porosity: the squeeze casting process applies a specially designed feeding system and high pressure to the molten aluminum during solidification, which significantly reduces the formation of porosity.

The resulting high-density castings have few air voids or gaps where leaks may occur.

This makes squeeze castings ideal for stringent leakage testing.

Enhanced Material Integrity: the high pressure during squeeze casting not only minimizes porosity but also promotes a finer and more uniform microstructure.

Such uniformity contributes to the overall strength and integrity of the cast part.

Stronger and more coherent material properties ensure that the casting can withstand internal pressures without cracking or leaking, which is essential for passing leakage tests.

Improved Surface Finish: squeeze casting generally yields a better surface finish compared to traditional sand casting or even some die-casting methods.

A smoother surface reduces the likelihood of surface-related defects or imperfections that may cause leaks.

This superior finish contributes to better sealing when components are assembled, further enhancing the leak-tightness of the final product.

Controlled Solidification: the controlled application of pressure during the solidification phase of squeeze casting helps to achieve directional solidification.

This control minimizes the occurrence of shrinkage defects.

By directing how and where the material solidifies, we can ensure that critical areas of the casting are solid and free from defects that could compromise the casting’s ability to contain fluids or gases.

Customization and Precision: squeeze casting allows for precise control over casting parameters, including pressure, temperature, and cooling rates.

This level of control enables us to tailor the process to the specific requirements of the part being produced, optimizing material properties for leak-tightness based on anticipated service conditions.

Use of High-Quality Moulds: the moulds used in squeeze casting are typically made from high-quality steel and are designed with a special exhaust system.

These customized moulds can withstand the huge pressure at the moment of forming further expel the gas and leave minimal room for leak paths.

Conclusion

Leakage testing is a key part of our quality control procedures at CEX Casting.

It guarantees that every aluminum squeeze casting we produce meets the highest quality and safety standards.

Through strict testing, advanced techniques, and constant improvement, we are committed to providing products that meet and exceed our customers’ expectations.

This commitment to quality helps us maintain our position in the aluminum squeeze casting industry, especially in markets requiring the highest precision and reliability.

Contact us for more information about our squeeze casting process and case study.

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