What properties should metal stamping sand have?

The quality of molding sand and core sand directly affects the quality of castings. Poor quality of molding sand will cause defects such as pores, sand holes, sand sticking, and sand inclusions in castings. Good molding sand should have the following properties: 1) After the gas-permeable high-temperature molten metal is poured into the mold, the mold is filled with a large amount of gas. These gases must be smoothly discharged from the mold. The performance of the sand that allows gas to pass through is called For breathability. Otherwise, the casting will have defects such as porosity and insufficient pouring. The air permeability of the mold is affected by factors such as the particle size of the sand, the clay content, the moisture content and the compactness of the sand mold. The finer the sand size, the higher the clay and moisture content, the higher the compactness of the sand mold, and the worse the air permeability. 2) Strength The ability of sand to resist external force damage is called strength. The molding sand must have high enough strength to not cause collapse in the process of modeling, handling, and closing, and it will not damage the surface of the mold during pouring. The strength of the molding sand should not be too high, otherwise it will cause defects in the casting due to the decrease of air permeability and concession. 3) Fire resistance High temperature molten metal will have a strong heat effect on the mold after being poured, so the molding sand must have the ability to resist high temperature heat effect, that is, fire resistance. If the molding material has poor fire resistance, the casting is prone to sand sticking. The more SiO2 content in the molding sand, the larger the molding sand particles, and the better the fire resistance. 4) Plasticity refers to the ability of molding sand to deform under the action of external force, and to maintain the existing shape completely after the external force is removed. The plasticity of the modeling material is good, the modeling operation is convenient, and the formed sand mold has an accurate shape and a clear outline. 5) The volume of concessionable castings shrinks when condensing, and the molding sand should have a certain ability to be compressed, which is called concessionability. The retreat of molding sand is not good, and the casting is prone to internal stress or cracking. The tighter the molding sand, the worse the concession. Adding wood chips and other things to the molding sand can improve the concession. Previous post: Advantages of stainless steel electrical stamping parts