What is Ceramic Sand for foundry?
Ceramic sand for foundry is a kind of spherical casting sand different from traditional casting sand. It is also be called ceramsite sand. Since its invention in the 1990s, ceramic sand has become the mainstream product of recyclable casting sand. In the past, the molding sand used for casting was mainly silica sand, chromite sand, and zircon sand. They are mostly natural materials. Ceramic sand is a kind of artificial casting sand produced by industrial mass production.
The production process of Ceramic sand for foundry:
The raw material of ceramic sand is natural bauxite. Firstly, bauxite is calcined, which can improve the purity of alumina. The second step is to melt bauxite at high temperatures by fusing process. The third step is to blow the molten bauxite material into high alumina ceramic beads of different sizes with high-pressure gas. The fourth step is getting ceramic beads cool and sieve the sand to different grades according to the diameter. Then store them separately. The fifth step is to mix ceramic sand according to the particle size required by customers.
Inspection process of ceramic sand for foundry:
The quality control process of ceramic sand gets three parts:
- Raw material inspection. It mainly detects the grade of bauxite.
- Inspection of semi-finished products produced. It mainly tests the chemical composition and physical and thermodynamic properties of ceramic sand.
- Finished product inspection. It mainly detects the chemical composition and particle size distribution(AFS fineness) of ceramic sand after mixing.
Performance characteristics of ceramic sand for foundry:
- The refractoriness of ceramic sand is higher than that of silica sand.
The refractoriness of ceramic sand is more than 1790 ℃, which is significantly higher than that of quartz sand. It can overcome the high temperature of molten steel during pouring.
2. Low coefficient of thermal expansion. The thermal expansion rate of ceramic sand is half of that of chromite sand. And, it’s 25% of that of silica sand. A low expansion rate can reduce the deformation and casting defects caused by the thermal expansion of molding sand.
The thermal expansion coefficients of ceramic sand and other casting sand are compared as follows:
|Sand Type||Thermal expansion Rate|
3. Spherical particle shape.
The appearance of ceramic sand is smooth spherical and quasi-spherical beads. Its angle coefficient is 1.06. The molding sand with small-angle coefficient can improve the filling rate of casting molding. Thus, there will be gaps in the middle of spherical particles to improve the air permeability of molding sand. The ball-shaped ceramic sand has good fluidity and can reduce the porosity defects of castings.
4. When ceramic sand is used as resin-coated sand, the amount of binder can be greatly reduced. So as to reduce the comprehensive casting cost. At the same time, the mechanical properties of RCS, such as tensile strength and flexural strength, will be greatly improved. In addition, the gas output of RCS is also reduced by about 50%. It can effectively improve the deformation and reduce the unqualified rate of castings.
5. Ceramic sand has high strength. The hardness of ceramic sand and the particle size change rate of coated sand during recycling are shown in the table below:
|Origin sand of RCS||Mohs hardness||Particle size reduction|
It can be seen that the particle size reduction of the original sand with ceramic sand as the coated sand is very low during secondary use, which improves the recovery and utilization rate of the coated sand.
6. Ceramic sand has low SiO2 content and produces less dust, which can improve the production environment of foundry enterprises.
Application of ceramic sand for foundry:
- Lost foam foundry raw sand and V-method casting. It is mainly used in lost foam casting to produce iron castings, steel castings, high manganese steel.
- No-bake sand casting raw sand. For example, the casting with furan resin, alkali phenolic resin, water glass and other binders.
- Shell molding casting molding sand. It is mostly used for precision casting and core sand of cold core box and hot core box in precision parts, especially for engine parts.
- Coated sand. Shell molding sand and core sand in investment casting.
- Casting coating and refractory coating.
- Raw materials of ladle drainage sand.
- Materials for 3D printing.