August, 8 , 2014
Sand mold casting material is called plastic material, it is also called molding sand. Modeling materials that making sand core is known as core sand. Quality of molding sand and core sand affect the quality of castings directly. Bad molding sand will make the casting produce pores, trachoma, sticky sand, clip sand. Good molding sand usually has good permeability, high strength, fire resistance, good plasticity and concession.
The mold is filled with a large amount of gas after liquid metal with high temperature poured into. These gas must draining out successfully through the mold. Otherwise it will produce many disadvantages of pores, trachoma, sticky sand, clip sand. Sand particle size,clay content,water content and sand compaction degree all have an effect on permeability of mold. Mold who with more finer sand particle, higher clay and moisture content, higher sand compaction is in worse permeability.
It will generate heat on the mold after puring into liquid metal with high temperature. So sand should have the ability to resist high temperature. Certainly sand must be in high strength to avoid collapse when modeling, handling and closing. While it does not destroy the mold surface when pouring. The strength of sand could not be too high. Because it produce defects with decline of permeability and collapsibility.