Advantages of coated ceramic sand relative to silica sand coated sand

The coated sand process is a very important molding and core making process in the casting industry. For a long time, the silica sand coated sand has always occupied a large market share. In the 21 st century, many special sands are rapidly applied in the coated sand industry, among which the ceramic sand has good comprehensive performance and is widely used. Compared with silica sand coated sand, coated ceramic sand has the following advantages :

1. High refractoriness - the refractoriness of ceramic sand is ≥ 1800 °C, while the refractoriness of silica sand is generally between1550 °C -1690 °C. Coated ceramic sand can be used to pour casting alloys with high pouring temperature ( cast carbon steel, alloy steel, stainless steel, etc. ). Silica sand coated sand is generally used in the casting of cast iron and non-ferrous alloys. 

2. Higher strength and toughness-Because the ceramic sand grain shape is nearly round and the specific surface area is small, the strength and toughness are higher when the same amount of resin is added, which is more suitable for making cores with complex shape and small cross-sectional area.

3.Low thermal expansion rate-According to relevant data, the thermal expansion coefficient of gem sand is 6 × 10-6 / °C ( 20-1000 °C ), and the thermal expansion coefficient of silica sand is 23 × 10-6 / °C ( 20-1000 °C ). The use of coated gem sand can eliminate or reduce the common expansion defects when using silica sand coated sand. 

4.High regeneration rate-Because the ceramic sand has higher particle hardness and strength than the silica sand, the breakage rate is lower, and the breakage rate is lower in the molding, pouring, cleaning, especially in the regeneration process. It can obtain a higher regeneration rate, reduce waste sand emissions, reduce costs, and reduce environmental pollution. 

5.Good fluidity-ceramic sand grain shape is round, the angular factor is less than 1.1, the silica sand is polygonal, the better silica sand angular factor is about 1.3, and the flow of coated ceramic sand is better during core making. In addition, the density of ceramic sand is larger, the sand shooting momentum is higher, and it is easy to obtain a denser complex core, so as to obtain a casting with a smooth surface.

6.Low resin content-Compared with silica sand coated sand, the resin content of coated ceramic sand can be reduced by 30-40 % under the same strength requirements. In most cases, the gas evolution of the coated ceramic sand can be controlled below 13ml / g, and it is also relatively reduced by 30-40 %, which not only reduces the material cost, but also reduces the probability of casting porosity. 

7.The casting surface quality is good, the size precision is high-as artificial sand, ceramic sand particle size distribution is wide, especially in the smaller particle size, grain shape is more round, making the use of fine sand, still has high permeability, is conducive to reduce the casting surface roughness, improve the surface quality of the casting, the use of shell mold process usually does not use paint, can partially replace the precision casting process. 

8.The main chemical composition of neutral-ceramic sand with stable chemical properties is required Al2O3, and the main mineral phases are mullite and corundum. The thermochemical properties are stable, neutral, and not easy to be eroded by acid-base oxides. It is suitable for the casting of various casting alloys ( including manganese steel ).