What are the advantages and limitations of fused Ceramic sand compared with silica sand and several main special types of 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.
However, 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.
·Thermal stability is poor, phase transition occurs, and veining defects are easy to form.
·At high temperature, it is easy to react with iron oxide to form iron olivine, resulting in sand sticking.
·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.
· It is easy to break, and the SiO2 dust generated after breathing may cause workers to suffer from silicosis. Therefore, casting production needs more and more raw sand with better performance.
Development of special sand
Since the 1840s, foundry workers have developed, developed and popularized dozens of special foundry sands. Special sand generally has the characteristics of high fire resistance, good thermal conductivity, small thermal expansion and strong resistance to slag erosion. Zircon sand, chromite sand, olivine sand, magnesia and so on are commonly used. In casting, it is mainly used for casting alloy steel or carbon steel that is easy to stick to sand, and it is often used for coated sand, mold surface sand, coating, special core and so on. Due to the particle shape is not ideal, regeneration. 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 last 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 is widely used.