Porosity

In practice

In powder metal, porosity is often intentional: it holds oil in self-lubricating bushings and can be filled by infiltration where strength or sealing matters.

Where it comes up

• Zinc and aluminum die castingMolten zinc or aluminum injected into steel dies at high pressure. Thin walls and net shape at 2,500+ parts a year.
• Powdered metalNet-shape gears, bushings, and structural parts pressed from metal powder and sintered, with little or no machining.

Related terms

Cold shut

A cold shut is a casting defect where two streams of molten metal meet but fail to fuse, leaving a visible seam or weak line. It comes from low metal temperature, slow fill, or poor gating. In die casting, cold shuts often appear far from the gate on thin sections.

Infiltration

Infiltration is a powder metal process where molten copper is drawn into the pores of a sintered steel part by capillary action. It raises density, strength, and impact toughness and can seal parts for pressure tightness. Copper-infiltrated steels carry the MPIF FX material designation.

Shot size

Shot size is the volume or weight of material injected into a mold in one cycle, including parts and runners. Molders typically want a shot to use about 20–80% of a press's barrel capacity to avoid degraded resin or inconsistent fill. In die casting, shot size drives machine and shot sleeve selection.