Casting Porosity — Root Cause Analysis & 8D Correcti...

What Is Casting Porosity? Casting porosity is internal void formation in a casting, produced either by dissolved gas (gas porosity) or by shrinkage during solidification (shrinkage porosity). Machined surfaces reveal the voids as round pores or irregular sponge-like cavities, and pressure-tight castings such as engine blocks, pump bodies and valve housings fail leak tests because of them. Porosity is a process problem: melt quality, gating and risering design, and solidification control. It is investigated in D4 with process data, simulation and metallurgical evidence. Symptoms Visible holes on machined surfaces: round for gas porosity, irregular for shrinkage Leak test failures on pressure-tight castings (blocks, pump bodies, valve bodies) Tensile test bars breaking at pore locations, reducing mechanical strength X-ray or CT showing internal void clusters Porosity exposed at different depths after machining, causing surface finish defects Affected Components Aluminium castings (gravity, low-pressure and high-pressure die casting) Iron castings (sand casting and shell moulding) Automotive: engine blocks, cylinder heads, transmission housings, brake calipers Industrial: pump bodies, compressor housings, hydraulic valve bodies Aerospace: structural brackets and landing-gear components Detection Methods X-ray / DR: 2D projection detects internal porosity above about 2% of section thickness CT scan (3D): quantifies pore volume fraction, location and...