Sand casting is a metal casting process in which specific types of sand are used as a mold material to make replicas of existing metal prototypes. Also known as sand molded casting, this process has been used in manufacturing copies of an original product in bulk for centuries. In the earlier days, companies had their own production plants where this mass production was carried out. However, with the rise in the popularity of outsourcing, now many companies outsource production to foundries, also known as sand casting companies.
Different foundries use different types of base sands for the metal casting process. Each one of the base sands using in metal casting has its own characteristics and benefits. Here are some of the best casting sands used by foundries:
- Silica can be easily found at the beach or river beds and is, therefore, one of the most affordable casting sands used by foundries. The purity levels of silica needed for steel is 98% while that for non-ferrous metals is 94% or higher. Silica is frequently used in bronze sand casting by foundries all over the world.
- Chamotte is made by calcining fireclay and is the second most affordable casting sands. It has coarse grains and can be only used for dry sand casting method. Chamotte has a high fusion point and low thermal expansion and is relatively safer to use than silica.
- Free from silica, olivine sand is a mixture of magnesium and iron orthosilicates from dunite (mineral). It has a high fusion point and low thermal expansion making it one of the most popular casting sands especially in Europe.
- Chromite sand is a solid solution of spinel, a group of minerals that has a high fusion point and thermal conductivity. It can be easily used for stainless steel casting. It has a low percentage of silica and is one of the expensive casting sands.
- With a high fusion point and thermal conductivity along with a low thermal expansion, zircon sand is one of the most expensive casting sands used in foundries. It is two-third zircon oxide and one-third silica and is not easy to find.