Time to read: 6 min
Porosity in die casting is a critical issue that affects the structural integrity and performance of cast parts. This guide offers an in-depth analysis of porosity types, their causes, and effective prevention techniques to ensure the production of high-quality die castings.
Understanding Porosity in Die Casting
Porosity refers to the formation of pores, holes, or air pockets in die-cast parts, which can compromise their strength and lead to corrosion or leakage. While porosity may be acceptable in non-critical areas, it is unacceptable for parts with high-strength requirements.
Major Forms of Porosity in Die Casting
Porosity in die casting takes three primary forms:
Blind Porosity
Blind pores are internal and do not pass through the part, potentially leading to corrosion but not affecting structural integrity unless exposed by post-machining processes.
Through Porosity
These pores penetrate the entire part, creating a leak path and significantly impacting structural integrity and the ability to hold pressure.
Fully Enclosed Porosity
Internal pores that do not affect the part's surface or structural integrity unless exposed by post-machining processes.
Causes of Porosity in Die Casting
Porosity arises from two main causes:
Gas Porosity
Trapped gases during the casting process can lead to surface blisters and internal pores. This can occur due to material emissions, trapped air, or improper venting and gating.
Shrinkage Porosity
Formed when the casting material shrinks unevenly during solidification, often due to incorrect mold design, material wall thickness, or low metal temperatures.
Preventing Porosity with Vacuum Impregnation
Vacuum impregnation is a cost-effective method to permanently seal pores in castings. The process involves:
- Removing trapped air from micropores using a vacuum.
- Impregnating the pores with a sealant using positive air pressure.
- Curing the sealant, typically with heat.
This method preserves the part's assembly, functional, and physical characteristics after sealing.
Tips to Prevent Die Casting Porosity
To prevent porosity, consider the following tips:
- Use high-quality materials that do not generate gas during the casting process.
- Designate allowable defect specifications for less critical areas.
- Improve mold design by maintaining consistent wall thickness and adding vents for gas escape.
- Control cooling time and temperature to manage metal shrinkage.
- Apply proper pressure and shot speed during die casting.
- Ensure the correct alloy temperature to minimize volume shrinkage.
Conclusion
Porosity is a significant concern in die casting that can affect part quality. By understanding the types of porosity and implementing effective prevention strategies, manufacturers can ensure the production of structurally sound and reliable die castings.
For expert die casting services that prioritize quality control, consider partnering with experienced providers like Unofactory. Our commitment to advanced technology and ISO 9001:2015 certification guarantees the delivery of high-quality parts that meet your specifications.