Shortages of Silica Sand
Silica sand has rich sources, high refractoriness, and is not wetted with metal melt. Today, it still accounts for more than 90% of the original casting sand. With the continuous improvement of casting quality, comprehensive cost control, environmental protection and other requirements, the shortcomings of silica sand itself are becoming more and more prominent:
① poor thermal stability, phase transformation, easy to form vein defects;
② At high temperature, it is easy to react with iron oxide to form iron olivine, resulting in sand sticking;
③ The refractoriness is relatively low, and it is easy to react with manganese oxide to form slag, which is difficult to adapt to the casting of medium and high alloy steel and high manganese steel;
④ It is easy to break, and the resulting SiO2 and dust may cause workers to suffer from silicosis after breathing. Therefore, casting production needs more and more raw sand with better performance. Since then, foundry workers have developed, developed and popularized dozens of special foundry sands.
Special sand and Fused Ceramic Sand
Special sand generally has the characteristics of high fire resistance, good thermal conductivity, small thermal expansion, strong resistance to slag erosion, etc. the widely used are staggered sand, chromite ore, olivine sand, magnesia, etc. in casting, it is mainly used for the casting of alloy steel or carbon steel that is easy to stick to sand, and is often used for coated sand, mold surface sand, coating, special core, etc. due to the unsatisfactory particle shape, it is difficult to regenerate. Due to difficulties in recycling and other reasons, the overall effect is poor, and the whole production line is rarely used. These special sands are generally formed by mineral processing, crushing, screening, and calcination. There is no change in composition and structure. They are generally called natural special sands. At present, facing the gradual shortage of resources, mining restrictions, and so on, the price is becoming more and more expensive.
Since the end of the 20th century, some enterprises and research institutions in Japan, China, Germany and other countries have used kaolin and bauxite as raw materials to produce ceramic spherical sand with different compositions and phases through granulation, sintering, melting, air crushing and other processes. In addition to the above advantages of natural special sand, it also has the advantages of less binder consumption, good fluidity, good permeability, high strength. With the characteristics of breaking resistance and adapting to various molding and core making processes, it has been rapidly popularized and applied in the past decade.
Among them, fused ceramic sand has the best comprehensive performance and the most extensive application.
Ceramic Sand Major Parameters：
1.Shape: Sphere
2.Angle Factor: ≤1.1, very spherical
3.Bulk Density: 1.95-2.05 (g/cm3)
4.Refractoriness: ≥1790℃
5.Thermal expansion: 0.13％ (10 minutes at 1000℃)