Nowadays the Role of Silica Sand still Can't Be Ignored
At present, natural silica sand has an absolute advantage in the raw sand used for casting. The most desirable feature is abundant reserves and low price, cheap and easy to get, which can not be compared with other raw sand. In addition, it also has high enough refractoriness to withstand the effect of pouring temperature on most casting alloys.
The particles are hard and can withstand the pounding pressure during molding and the impact during old sand regeneration impact and friction. It still has the strength to maintain its shape when it is close to its melting point, which can adapt to the basic working conditions of casting features, but its disadvantages are also quite obvious, mainly including:
·The thermal stability is poor, and the phase transformation occurs at about 570 ℃, accompanied by large volume expansion, which is the reason for the expansion defect of the casting
·poor chemical stability at high temperature, easy to react with FeO to form fusible iron olivine, resulting in casting sand sticking on the surface
·The dust generated during crushing will cause workers to suffer from Silicosis
·There are many wastes. With the increasing requirements of environmental protection, the cost of waste treatment is increasing.
The Opportunity for the Emergence of Fused ceramic sand
Nowadays, with the increasing requirements for casting quality and the increasingly stringent requirements for environmental protection and cleaner production, it has become a consensus that silica sand is not an ideal raw sand, and the search for an alternative material for silica sand has become an important research topic. Zircon sand, olivine sand and chromite sand are the main non siliceous sands widely used in the foundry industry.
Zircon sand has a variety of characteristics suitable for casting raw sand and is an ideal molding material. However, zircon sand is only widely used in investment casting due to its small reserves and high price. The reserves of olivine sand and chromite are large, and the price is low.
It is also cheaper than zircon sand, but both are made of crushed ore, with poor grain shape and much more expensive than silica sand. At present, they are only used for some steel castings.
Another way to seek substitute for silica sand is to develop manufactured granular materials.
It has a history of more than 30 or 40 years. In the past 10-20 years, it has gradually entered the practical application stage, and has been paid attention to by the foundry industry. At present, the artificial casting sand mainly includes carbon sand, enstatite sand and fused ceramic sand, of which fused ceramic sand is a more mature one.
Fused Ceramic Sand Appears for the First Time
Fused ceramic sand was developed by carb ceramics in the United States in the 1980s. The original name of the product was "Ceramcore", which is a manually fired ceramic spherical particle, which was initially used as oil support in the oil and gas industry agents. In the early 1990s, the United States and Japan successively applied fused ceramic sand to the foundry industry as a substitute for silica sand. The grain diameter of fused ceramic sand is 0.053 ~ 3.36mm.