Coated sand casting process is a casting process widely used in automobile, aviation, machinery, electric power, metallurgy and other industries. Its core lies in the coating technology, the formation of a layer of resin film on the surface of the sand particles, so as to improve the quality and performance of castings. Coated sand casting process mainly includes the following steps:
Preparation of raw materials: the main raw materials for coated sand include raw sand (such as silica sand or zircon sand), resin (such as phenolic resin, furan resin) and hardener. These raw materials are mixed according to a certain proportion, through the mixer stirred thoroughly to ensure that the resin is evenly distributed on the surface of the sand grains.
Sand mixing: Mix the prepared raw materials, control the sand temperature to avoid too high or too low to affect the coating effect. During the sand mixing process, the resin, hardener and other additives are evenly distributed on the surface of sand grains.
Laminating: The mixed sand is put into the laminating machine, after high temperature heating and pressure treatment, the resin melts and penetrates between the sand grains to form a film. Temperature and pressure should be controlled during the laminating process to ensure the integrity and thickness of the film.
Sand injection: The sand coated with the film is loaded into the sand injection machine, and the sand is injected into the mold under a certain pressure to form the prototype of the casting. The pressure should be kept stable during the sand shooting process to prevent the sand from leaking or underfilling.
Shelling: After the casting cools down, remove it from the mold, remove the excess sand on the surface, and reveal the complete surface of the casting. Avoid damaging the casting surface during the shelling process.
Cleaning and processing: the casting surface cleaning and processing, remove burrs, flying edges and other defects, so that it meets the requirements of the final product. Clean and process the process to choose the appropriate tools and process parameters, to avoid damage to the castings.
Quality Inspection: Quality inspection of the castings, including size, appearance, internal structure and other aspects of the test. After passing the quality test, they can be packed and put into storage.
Characteristics of coated sand include suitable strength properties, good fluidity, clear contour of the produced sand, dense organization, good surface quality, high dimensional accuracy, good collapsibility, etc. It can be used in a wide range of applications. Its scope of application is wide, can be used for both casting and sand core, can be used in conjunction with each other as well as with other sand types. The production process of coated sand mainly has three kinds of cold method, warm method and hot method, at present most of the production adopts hot method coated process.