Porosity in High Pressure Die Casting

Porosity in high-pressure die casting (HPDC) refers to the presence of air or gas pockets within the casting material, which can affect the structural integrity and quality of the final product. Here are some key points about porosity in HPDC:

1. Causes of Porosity:

   • Gas Entrapment: During the injection of molten metal into the die cavity, air or gas can get trapped within the metal, especially at high injection speeds.
   • Shrinkage: As the molten metal solidifies, it can shrink and create voids if the material doesn’t flow properly to fill the cavity completely.
   • Die Filling and Solidification Issues: Improper gating or venting designs, as well as inadequate cooling rates, can contribute to porosity.

2. Impact on Properties:

   • Porosity can weaken the mechanical properties of the casting, such as tensile strength, fatigue resistance, and ductility.
   • It can also affect the casting's appearance and surface finish.

 

Squeeze Pin for Porosity Remedy

In high-pressure die casting (HPDC), a squeeze pin is a crucial component used to control the porosity and improve the quality of the castings. Here’s a detailed explanation of what a squeeze pin is and its role in the HPDC process:

What is a Squeeze Pin?

A squeeze pin is a mechanical device integrated into the die casting tooling, specifically designed to minimize porosity by exerting additional pressure on the molten metal during solidification. It consists of a pin or a rod that can be pneumatically or hydraulically actuated to apply pressure to the casting as it solidifies.

Role of Squeeze Pin in HPDC:

1. Reducing Porosity:

   • One of the primary functions of a squeeze pin is to reduce or eliminate gas porosity in the castings. During the high-pressure injection phase of HPDC, air or gases can become trapped in the molten metal. The squeeze pin, when activated, applies pressure to the casting just before or during solidification, compressing the metal and forcing any trapped gases to escape.

2. Improving Mechanical Properties:

   • By reducing porosity, the squeeze pin helps improve the mechanical properties of the casting. It enhances the density and integrity of the metal structure, leading to increased tensile strength, better fatigue resistance, and improved ductility.

3. Enhancing Surface Finish:

   • Minimizing porosity also results in a smoother surface finish of the casting. This is particularly important for applications where aesthetics or minimal post-processing are critical.

4. Process Control:

   • Squeeze pins are controlled through the die-casting machine’s programming and can be adjusted based on the specific requirements of the part being cast. This allows for precise control over the pressure applied and the timing of the squeeze pin operation during the casting cycle.

 

Squeeze Pin in Inspire Cast

Use the component tab in Inspire Cast to create squeeze pin on the location where Porosity exists. But before that measure the size of shrinkage to identify the parameter for creating Squeeze pin as given in below images.

       

Correct value value for Squeeze pin generation can be analyzed from shrinkage volume and the time for actuation. Check the time taken during solidification to understand when the hot spot will be created as shown in below images.

       

Once the simulation with squeeze pin actuation is finished, we can check the improved porosity behavior. 

Conclusion:

In summary, a squeeze pin plays a significant role in enhancing the quality and reliability of high-pressure die castings by reducing porosity and improving mechanical properties. It is a vital tool in the die casting industry for producing high-quality, defect-free components that meet stringent performance and aesthetic requirements.