Defects in Casting

The different types of defects in a casting may be due to pattern and moulding box equipment, moulding sand, cores, gating system or molten metal. Some of the defects are as follows:

1. Mould shift

It results in a mismatching of the top and bottom parts of a casting, usually at the parting line.

2. Swell

It is an enlargement of the mould cavity by molten metal pressure resulting in localized or general enlargement of the casting.

3. Fins and flash

These are thin projections of metal not intended as a part of casting. These usually occur at the parting line of the mould.

4. Sand wash

It usually occurs near the ingates as rough lumps on the surface of a casting.

5. Shrinkage in casting

It is a crack in the casting or dishing on the surface of a casting which results from unequal contraction of the metal during solidification.

6. Hot tear

It is an internal or external ragged discontinuity in the metal casting resulting from hindered contraction occurring just after the metal has solidified.

7. Sand blow or blow hole in casting

It is an excessively smooth depression on the outer surface of a casting.

8. Honeycombing or slag holes in casting

These are smooth depressions on the upper surface of the casting. They usually occur near the ingates.

9. Scabs

These are patches of sand on the upper surface of the casting.

10. Cold shuts and misruns

These occur when the mould cavity is not completely filled and an incomplete casting results.

11. Pour short

This defect in casting occurs when the mould cavity is not completely filled because of insufficient metal.

12. Run-outs and bust-outs

These permit drainage of the metal from the cavity and result in incomplete castings.