With the continuous development of Industrial Science and technology, the mechanical manufacturing industry and engineering circles have higher and higher requirements on the quality of marine castings, especially the surface quality of castings. Casting coating is a kind of coating applied on the surface of the mold cavity or core to improve its surface fire resistance, chemical stability, metal erosion resistance, sand adhesion resistance and other properties.

With the continuous development of Industrial Science and technology, the mechanical manufacturing industry and engineering circles have higher and higher requirements on the quality of castings, especially the surface quality of castings. Casting coating is a kind of coating applied on the surface of the mold cavity or core to improve its surface fire resistance, chemical stability, metal erosion resistance, sand adhesion resistance and other properties.

It is reported that the coating has the properties of suspension stability, brushing and permeability. According to the theory, whether the casting is bonded or not depends on whether there is a critical thickness of iron oxide layer between the casting and the coating layer, the thickness of which is about 100 μ m。 In order to prevent chemical sand sticking, the oxide thickness shall be increased. When it exceeds the critical thickness, the coating or sintering layer of molding sand and metal oxide is easy to peel off from the casting.

The castings commonly used in injection molding include steel castings, iron castings, and aluminum castings. The quality requirements for castings mainly include the following aspects.

(1) The shape and size of the casting shall meet the requirements of the casting drawing, and its chemical composition and mechanical properties shall meet the specified requirements.

(2) The surface of the casting shall be subject to sand cleaning, and scabs, flash and burrs shall be removed. The residual height shall not be greater than 3mm.

(3) The inside of the casting, especially near the working face, shall be free of defects such as pores, sand holes and cracks, and the non working face shall be free of serious porosity and large shrinkage holes.

(4) The castings shall be subject to heat treatment in time, the steel castings shall be completely annealed, and the iron castings shall be aged to eliminate the internal stress and improve the processing performance.