Silica Sand undergoes an alpha-beta phase transformation at approx 350oC – 650oC. This corresponds to the temperature zone that the mould experiences during cooling. This can lead to expansion defects such as veining or cracking in castings where silica sand moulds are used
Chromite has a much lower expansion over the same temperature range. In addition, the Chromite expansion does not have the same stepped expansion; therefore the likelihood of these expansion type defects is significantly reduced.
Lower thermal expansion generally results in improved dimensional stability in finished castings.