Porosity is found in many cast metal components, but is particularly prevalent in aluminium and magnesium die castings. There are three main types of porosity:
FLOW POROSITY: Resulting in surface or internal defects caused by poor pressure or metal flow conditions in the process.
GAS POROSITY: Usually internal, caused by trapped gases of various kinds in the die. Gas porosity comes from three main sources in die-casting: trapped air, steam and burned lubricant.
SHRINK POROSITY: The most common and most difficult to control, caused by the change in volume as the metal changes state from liquid to solid.
Casting porosity impacts everyone in the manufacturing supply chain, as it is present to varying degrees in all castings. It appears as a collection of voids in the structure and takes three basic forms:
- Engine blocks
- Gearbox housing
- Cylinder heads
- Pumps/pump components
- Engine Covers
- Filter housings
- Compressor components
- Thermostat housings