Sand Casting defects

Casting Defects and Common Problem :

1.     Defects due to sand - 

The moulding and core sand mixture should be strong as well as collapsible at the same time. Hence, it cannot have rock-hardness to withstand the heavy temperature and flow of metal with density is around 7.5. This compromise leads to sand fall, breakage of mould or core, sand wash. The sand is detached from the mould or core is expected to passout through the flow off but it is not possible practically hundred percent. Hence, some sand is entrapped in the liquid material and subsequently in the solidified casting.

The binders in the mould and sand core mix evolves fumes, gases and vapours which also cannot pass out totally. That’s why, final casting carries such defects like gas holes, blow holes, gas porosity.

If any defects or broken part in mould or core it will be disturbs the geometrical shape and parameter of the casting.

     2.     Defects due to flow of liquid metal –

If the flow of the liquid material in the cavity is slow, it leads to solidification of the leading prior to reaching its destination. Such kind of defect is called ‘cold shut’ or ‘lap’.

      3.    Defects due to improper solidification –

Some intricate shape of casting or in general casting having some certain zones where the liquid metal solidified too fast or too slow rate of solidification.

Its lead defects like cracks or hot tears at the component (casting) section. On the other side some other components zones are subject to localised shrinkage.

     4.  Some other defects like mould swelling, mould mismatches, dirt inclusion, warping, drop, rat tails, veins and buckle, misrun, fusion, pinholes, flash, fin and burrs.

To read more...  Casting Design Guidelines