The main minerals are kaolin and bauxite. In the casting industry, bauxites are mainly used to produce synthetic mullite for the foundry market. The bauxite resources in China are mainly distributed in such areas as Shanxi, Henan, and Guizhou. The kaolin used as casting material is classified in China as hard kaolin, which possesses plasticity after grinding. Since these kaolins are associated with coal beds, we call them coal series kaolin or coal gangue. China has numerous coal mines and more than 3,000m. tonnes of coal gangue has accumulated. However, not all coal gangue can be used for casting materials. Coal gangue used for the manufacture of casting materials must have an Al:Si ratio >0.8, kaolin content >40 percent, Fe_2O_3 <1.5 percent.
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