Casting defects
We would like present some defects of castings and its development. Casting are very sensitive parts because a metal change from liquid state to solid state. It makes problem with homogenity of part sometimes. The understanding of process of development defects lead to eliminate those defects and improve the quality of part.

Blowhole

Shape of the defect is round

Size of blowhole is different from less than 1 mm to several 1mm.

The defect is mostly by gravity casting into sand or mold include sand cores.

Cause of defect:

-shape of casting (critical area for venting) difficult to apply boss

-area of join two or more metal streams in mold

Solution proposal:

-change speed of filling mold by metal

-change position of boss

-slant mould

Oxid in Al casting "Hot crack"

An Amorphous structure can created during solidification od casting.

The structure can lead to surface defects.

After cutting is visible uncrystalic section.

This defect is created in process of solidification. The cosidering about modification of casting process to stabilize thermal condition is efective or change of metal flow in mould.