To learn what is die casting porosity, first let us learn the basics – what is porosity? According to Dictionary.com, the definition porosity, is the state or condition of being porous – or full a tiny openings “pores”. These pores (miniature air pockets) might be visible to the surface and even hidden within the material walls. With that in mind, die casting porosity occurs with numerous variable factors that include:
- Material climate and Tooling / Mold Die
- Metal Purity
- Design of the mold
- Design of the cast parts
- Pressure of the casting machines
- The machine shot speeds
- Tooling injection speed, release speed and spray speed
- Material “wall” thickness can experience shrinkage
Reference the picture above to see extreme cases of trapped air porosity in die castings.
During the casting cycle, molten material (aluminum or zinc) is loaded within a die shot chamber. Next, this molten material is plunged or injected through a tremendous force caused by the injector piston arm. This pressure must be steady and precise, to rapidly flush this die casting metal into the cast die.
During this injection phase, air inside the chamber is pushed with the material into the tooling or mold. This is an efficient and tempestuous operation. Then, a second source of air is flushed into the tooling – while the existing molten metal gets ejected and overflows from the mold vents.
Next, the molten aluminum or zinc receives a cooling down process. This allows the metal to reach handling temperature and solidify within the tooling. What’s the end result? A fully die cast product!
Ningbo Xusheng Die Castings USA use aluminum and zinc materials since they are non ferrous metals. This means that our non ferrous metals or die casting alloys do not include Iron properties, since Iron is arguably the most critical element for corrosion and oxidation. Other common types of non ferrous metals used in the metalworking and casting industries include copper, tin, lead and magnesium.
What to avoid in your parts?
Porosity in die casting will degrade the product quality and integrity. Especially if the porous areas in the die casting are large enough to affect overall shell strength. Pay close attention to this dangerous porosity in close pressure castings. Contact the Engineering Staff and Quality Control departments at Ningbo Xusheng Die Castings USA, they are thoroughly educated in the prevention and avoidance of die casting porosity.