Techniques for preventing porosity in die casting

You can measure the level of porosity using X-rays, CT scan, or cutting a section of the casting and examining it under a microscope. CT scans are the most preferred technology due to their ease of use, reliability, and robustness. However, porosity in your casting can affect the die casting cost and material quality. Instead of combating try the tips below to prevent it.

Ensure High-Quality Material

Choose a dry and clean material that will not generate water vapor or any form of gas during the die casting process. Also, choose high-quality refining agents and coatings that don't emit volatile gases as they can lead to porosity.

Designate Specifications and Tolerances for Some Areas

During the design stage, specify the specifications and tolerance for an allowable defect to allow for porosity in some less critical areas while preventing it in others.

Porosity accounts for about 5% of a die casting volume. It is impossible to eliminate them completely. Instead, it is better to contain them in a non-critical part of the casting where it doesn't affect the die casting’s assembly, physical, and functional properties.

Improve Mold Design

Improving the mold design can help prevent both gas and shrinkage porosity. The most common way of reducing the formation of pores is by maintaining the die casting wall thickness. Other ways to improve the mold design include:

Change the thickness of the gate

Change the direction of the gate

Set the overflow and discharge groove for easy discharge of gases

Ensure the overflow chute is less than 60% of the inner gate’s total cross-sectional area to improve the slag discharge effect.

Reduce sharp corners and pockets because they don’t let air escape

Add more vents to allow air to escape.

Control Cooling Time and Temperature As the Alloy Solidifies

Controlling the cooling time and temperature is important because the metal part will shrink during solidification. One way of preventing this is to improve the mold’s cool-down rates. For example, in aluminum die-casting, you should supercool the thick part to have the same temperature as the thin part and avoid unequal cooling.

Proper Pressure and Shot Speed of Die Casting Machine

Using the right pressure and shot speed can ensure consistent pouring speed. Consistent pouring speed will reduce tumbling during the injection process, reducing the formation of air pocket that leads to porosity. Regulating the pressure is an important way of combating gas porosity.

Make Sure the Right Temperature During the Die Casting Process

The temperature of the alloy plays an important role in the shrinking rate of the alloy. Therefore, you should use the right temperature as specified by the manufacturers. For example, for aluminum die casting, reduce the temperature to reduce volume shrinkage, shrinkage holes, and ultimately shrinkage porosity.

Make Metal Parts with Machining and Die Casting

Machining and die casting are applicable in different contexts for product manufacturing. However, both processes can be combined in metal parts fabrication to make a high-quality product cost-effectively.

Pengfeng Precision offers die casting services and CNC machining services so you can create parts of the highest quality in a short period.Our company has successfully passed the ISO 9001-2018 quality management system certification. At the same time, the company also strives to fulfill its social responsibilities and has obtained ISO 14001 certificates.