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Hot core box coated sand for high smoothness. Low-cost green sand (recommended Nanjing red sand), resin sand with high dimensional accuracy (divided into water-washed sand and scrubbed sand)
Coated sand. The surface of the sand particles is covered with a layer of solid resin film molding sand or core sand before molding. There are two coating processes: cold method and hot method: the cold method uses ethanol to dissolve the resin, and urotropine is added during the sand mixing process, so that the two are coated on the surface of the sand grains, and the ethanol volatilizes to obtain the coated sand; Method: Preheat the sand to a certain temperature, add resin to melt, stir to coat the surface of the sand, add urotropine aqueous solution and lubricant, cool, crush and sieving to obtain coated sand.
The hot core box coated sand process is to inject the sand material mixed with foundry sand, thermosetting resin and catalyst into a core box with a heating device, and heat it to 180-250°C to heat the sand material close to the surface of the core box. Under the action of temperature, the binder can be polycondensed and hardened in a short time to form a core without entering the oven for drying.
Using coated sand hot core box core shooting machine, the dimensional accuracy of coated sand castings is CT7~CT8, and the surface roughness Ra value is in the range of 6.3 to 12.5m. The forming quality of the coated sand process can reach the level of the water glass investment casting process, which is an ideal process method.
Green sand is also called green sand. In the foundry production, the sand mixture is made of bentonite as a binder and then mixed with water and other additives, which can be used for molding cores. The sand mold (core) can be poured directly without drying. This kind of sand is called green sand in the foundry industry. At present, green sand is one of the most important casting production processes.
Resin sand Crystrip plastic pellets are pellets made of thermoplastic acrylic or polymerized thermosetting amines. The angular pellet design provides an effective treatment method for most dry strip surface coatings. Crystrip plastic is chemically inert. Through proper use and recycling, this dry strip method can reduce the generation of hazardous waste and reduce environmental pollution.
The raw resin sand is divided into ordinary resin sand, water-washed resin sand, scrub resin sand, etc. Since the mud content in scrub sand is already small, it can greatly reduce the waste of resin sand and should be selected first. Secondly, choose water-washed resin sand, but never use untreated raw sand. The price of scrubbing sand itself is not high, generally ranging from 50 yuan/t to 70 yuan/t, but the freight is relatively high.