Blowhole defect in a cast iron part.
Learn more about sand casting defects at Wikipedia.org.
Technical Process
For sand casting, molten alloy is poured into a sand mold at room temperature. Any moisture in the mold produces gases/vapors resulting in casting defects that can undermine the life of the component. Numerous
types of defects can occur during sand casting including mold erosion, metal penetration, sand fusing to the casting, drops, run outs, scabs, swells, and burn-ons.
The investment casting process pours molten alloy into a hot, dry ceramic shell, hence no gases are created. Hot-shell pouring ensures greater fluidity of the molten alloy. Investment castings cool more uniformly through the cross section. As a result, there is less residual stress and fewer cracks are created as the molten alloy cools.