How to solve the problems of casting process defects-swelling sand and casting fin?
Swelling sand and casting fin are the common defects in casting.The drape seam often occurs in the parting surface of the casting, which is a sheet metal protrusion with uneven thickness perpendicular to the surface of the casting.Swelling sand is the irregular lump metal protrusion formed on the inner and outer surfaces of castings.Swelling sand is also a manifestation of local pits in molding sand, so that castings show roughness and imprecision.
The reasons for this phenomenon are: the compactness of molding sand is not enough, strength is not enough; It may also be that the water is too high; Or because when casting, the pressure is not uniform, it is too large; Or cast too fast.
The scheme of prevention is to improve the compactness and uniformity of the casting mould, and not to have too loose local compactness; Adjust the sand mixing process, try to use ceramic foundry sand; Control the moisture and improve the strength; In addition, the casting speed is slowed down and the pressure is reduced.
Ceramic foundry sand is spherical particles with good fluidity, strong permeability, and good permeability, which is conducive to the production of high-precision castings.With low coefficient of thermal expansion, the properties of ceramic foundry sand are comparable to zircon sand; Casting expansion defects do not occur when molding sand is prepared with ceramic foundry sand.The ceramic foundry sand has a smooth surface and a compact structure, so that that adhesive can evenly cover.Ceramic foundry sand is a neutral material, acid, alkali adhesive can be used. It has good recycling performance and high cost performance. As an innovation of traditional molding material, the ceramic foundry sand is more and more recognized in the casting industry, and more and more enterprises are using it in practice.