coated sand. The surface of the sand is covered with a solid resin film before molding or core sand.

Main features 1, vibration sand cleaning, high strength, low gas generation, low expansion;

2, good dispersion, high surface finish of the casting;

3, shell type no layer, good thermal stability, good thermal conductivity, good fluidity, casting surface flat;

4, high strength, high temperature resistance, low expansion, good mold release, good sand resistance;

5. The shell layer is uniform without peeling, and the curing speed is fast;

The main varieties of commercial coated sand in China are as follows:

(1) ordinary coated sand is composed of quartz sand, thermoplastic phenolic resin, ulotropine and calcium stearate, without related additives. Suitable for the production of general cast iron.

(2) High strength and low gas generation film sand is the replacement of ordinary film sand, by adding relevant additives and adopting a new process to prepare, its strength is more than 30% higher than ordinary film sand, gas generation is also significantly reduced, suitable for the production of complex precision cast iron.

(3) high-temperature coated sand has the characteristics of high strength and long heat resistance at high temperature, which is suitable for the production of complex thin-wall cast iron parts such as automobile engine cylinder block, cylinder head and container corner.

(4) collapsible coated sand has good strength and excellent low temperature collapsibility, which is suitable for the production of non-ferrous metal castings.

(5) Other special requirements Coated sand In order to meet the needs of different products, a series of special coated sand has been developed, such as: centrifugal casting coated sand, cold coated sand, wet coated sand, anti-sticky sand, anti-veining, anti-orange peel coated sand and so on.

There are two coating processes: cold method and hot method: the resin is dissolved with ethanol, and ulotropine is added in the sand mixing process, so that the two are coated on the surface of the sand, the ethanol volatilizes, and the coated sand is obtained; The sand is preheated to a certain temperature by heat method, the resin is added to melt it, the resin is coated on the surface of the sand by stirring, and the water solution and lubricant are added to cool, break and sift the coated sand. Used for steel casting, cast iron.