The Thermal Conductivity of chromite sand is higher than the other commercially available foundry moulding sands. This results in a mild chilling of the surface and a thicker solidified skin. This thicker skin improves the casting surface and reduces the likelihood of casting defects. Generally, foundries use Chromite Sand for one of the following reasons:

• to promote directional solidification (particularly in smaller/thinner-walled castings) when positioned in specific areas,
• to position around steel chills to significantly reduce the likelihood of cracking around the chills, or
• in the manufacturing of larger castings, to use chromite sand as the moulding material to promote a thicker solidifying skin as the molten metal rises up the mould face. This reduces the risk of it being washed away which allows faster filling times. This high heat abstraction rate also aids in inhibiting penetration and burn on defects.

Solidification Time of a 150mm Sphere with various mould materials.