Nowadays Foundry- Steel Castings
For a long time, the production of steel castings in China mostly adopts the sodium silicate sand process, but the sodium silicate sand has poor collapsibility, and the sand block formed after pouring is difficult to break, which causes great difficulties in the reclamation of sand and the cleaning of castings. With the continuous rapid development of the foundry industry, people's requirements for production technology, casting quality, labor environment and etc. continue to improve. In the technical transformation of the foundry workshop, more and more enterprises choose resin sand process.
The Demand for Fused Ceramic Sand meets the Needs of Modern Foundry
In order to reduce and prevent sand sticking caused by penetration of molten steel into sand mold (core), since the application of resin bonded sand in the 1980s, chromite sand has been used as surface sand at the wall thickness and hot joints of steel castings in production to prevent metal penetration and sand sticking. Therefore, from the aspects of environmental protection, resource conservation and humanistic care, a new type of foundry sand is needed to replace the above common sand and make up for the deficiencies and defects in all aspects. A new type of artificial sand - fused ceramic sand came into being.
Fused Ceramic Sand Manufacturing Process
Fused ceramic sand is also known as electric melting ceramsite. Aluminum oxide 65%~80% bauxite raw materials are put into the electric arc furnace. The bauxite raw materials are melted into liquid by using the high temperature generated by the electric arc discharge. When the liquid flows out of the furnace, 70~85m/s air pressure is applied to it so as to be crushed and cooled by the strong wind, the smooth sand particles with spherical shape or close to spherical shape are obtained.
Due to the physical and chemical properties of fused ceramic sand, it has the following characteristics:
(1) Fused ceramic sand has small thermal expansion coefficient, good mold stability, no cracking, and reduces casting defects such as veins caused by sand expansion.
(2) The particle size of fused ceramic sand is close to spherical, the surface is smooth, and the structure is compact, so that the binder can be evenly covered and the fluidity is good.
(3) Fused ceramic sand has high hardness, is not easy to break, does not produce ash powder, can reduce the amount of resin added, can reduce the gas generation of mold / core sand, and reduce the risk of pore formation.
(4) The mullite phase of fused ceramic sand is much higher than that of sintered products. It has high fire resistance and exceeds the pouring temperature of molten steel. It is suitable for the molding of large steel castings and alloy steel. It can completely replace chrome ore sand and is convenient for molding without sand sticking.
(5) It has good recycling performance, high durability and recycling recovery rate, and the recycling rate is as high as 98 compared with chromite sand and zircon sand, its price is only 30-50% of zircon sand. At the same time, because the sand particle is spherical and its surface area is small, the amount of resin added can be reduced by 30-50, and the amount of sodium silicate added ≤ 4; The casting defects caused by binder are reduced and the yield of castings is improved.
The emergence of fused ceramic sand is favored by the majority of enterprise customers, and the use of it in steel castings is also increasing.