What is Fused Ceramic Sand?
Fused ceramic sand is an artificial sand for foundry application, manufactured by spraying the melted calcined bauxite and making it crystallize into spherical sand. The manufacturing process can be roughly divided into four steps: calcination, electrofusion, granulation, and screening.
Thermal expansion properties of Fused ceramic sand and common foundry sand
During the casting process, the core sand will produce obvious thermal expansion after being heated, resulting in changes in the size of the sand mold and damage to the surface, casting defects such as insufficient dimensional accuracy, sand inclusion, scarring, rat tail, etc.
The thermal expansion performance of casting sand mainly depends on its chemical composition, mineral composition and temperature. Moreover, with the change of temperature, the change of linear expansion rate of each kind of casting sand is also different, and many casting sands also have phase transformation during heating. Generally speaking, the lower the thermal expansion coefficient and thermal expansion rate, the better. The thermal expansion rate of Fused ceramic sand is not only as low as 0.13%, but also its mineral composition is relatively stable after melt injection molding, so it is one of the solutions to the thermal expansion defects of sand mold.
The following table summarizes the thermal expansion performance parameters of common foundry sand in our company:
Thermal expansion parameters of common foundry sand
Fused ceramic sand
Coefficient of thermal expansion
(20-1000 ℃) · (x10-6 / ℃)
Thermal expansion rate (%) (1000 ℃)
Influence of main technical indexes of Fused ceramic sand on casting quality
The mud content of Fused ceramic sand also plays an important role in the quality of castings. If the mud content exceeds the standard, the fire resistance and burning point of Fused ceramic sand will be reduced, and the permeability of mold (core) sand will be reduced. Especially for resin sand, the high mud content will greatly reduce the strength of molding sand and core sand, increase the amount of resin binder, and also increase the gas generation of resin sand. The strength, air permeability and gas evolution have seriously affected the quality of castings, but also greatly increased the cost of castings. According to the industry standard of fused ceramic sand for casting (Fused ceramic sand), the mud content of Fused ceramic sand of any brand should not be greater than 0.2%. Therefore, it is suggested that friends in the foundry industry who want to maintain their casting quality and cost should choose to cooperate with Fused ceramic sand manufacturers with good reputation and stable product quality.
Effect of aluminum content in Fused ceramic sand on casting quality
Fused ceramic sand contains more than 65% Al2O3. The higher the aluminum content, the higher the fire resistance and sintering point of Fused ceramic sand. Therefore, the aluminum content of Fused ceramic sand used in the production of castings with different materials is also different. For example, if the pouring temperature of steel castings is generally above 1550 ℃, Fused ceramic sand with aluminum content greater than 73% is recommended; On the contrary, due to low refractoriness and sand melting, the casting will stick to sand. The pouring temperature of iron castings is about 1400 ℃, and the aluminum content of about 70% can be selected to ensure high quality while combining economic benefits.
In addition, the aluminum content also affects the crushing rate and durability of Fused ceramic sand. With high aluminum content, Fused ceramic sand has good mineral phase, low impurity content and high mullite phase, so the crushing rate and durability will be good. Therefore, Fused ceramic sand with higher aluminum content should be selected for occasions requiring multiple strong regeneration.
The rapid popularization and application of Fused ceramic sand benefits from the following casting process advantages:
1. Nearly spherical particles, smooth surface - low binder consumption, low gas generation, good fluidity, good filling, and good collapsibility after pouring.
2. Low thermal expansion rate - the thermal expansion rate of Fused ceramic sand is comparable to that of zircon sand, which is 1/5 of silica sand and 1/2 of chromite sand. The castings produced have high dimensional accuracy, few defects and high yield; Using Fused ceramic sand to prepare mold and core sand can basically eliminate the expansion defects such as casting veins.
3. Good crushing resistance - Fused ceramic sand has compact material, strong crushing resistance, and low crushing rate when reused, which greatly improves the recycling rate of core sand, reduces the discharge of waste sand, and is conducive to cost reduction and environmental protection.
4. High fire resistance - reduce sand sticking, reduce cleaning workload, and improve the surface quality of castings. At the same time, it is especially suitable for the production of sand cores and steel castings with complex shape and small cross-sectional area.
5. The bulk density is relatively small - the bulk density of Fused ceramic sand is about 2 g / cm3, which is less than 2.5-2.9 g / cm3 of chromite sand. The sand core produced is lighter, easy to handle, and can reduce the use of core sand.
6. Good process applicability for binder and casting alloy - the main component of Fused ceramic sand is Al2O3, which is a neutral material. Acid and alkali binder systems can be used, and it is suitable for all kinds of casting alloys.
7. Fused ceramic sand has a wide range of grain size - it can be mixed according to any combination according to requirements to meet different needs of customers.
8. High cost performance - the price of Fused ceramic sand is about 1/3 of that of zirconium sand. Although the unit price of raw sand is higher than that of silica sand, comprehensive evaluation shows that under certain conditions, the use of Fused ceramic sand not only has certain economic benefits, but also has significant environmental benefits and high cost performance.