At present, several commonly used precision casting methods in factories can meet practical production needs, but the performance indicators of mold materials are directly related to the quality of precision castings, which directly affects the dimensional accuracy and quality of precision castings. Therefore, higher requirements need to be put forward for the size and quality control of mold castings, and the performance requirements that mold materials need to meet are as follows:
1. It is necessary to have a smaller linear shrinkage rate and the smallest expansion coefficient within the softening temperature to achieve the dimensional accuracy that the mold material should have.
2. Small heat capacity, moderate melting point, convenient for making wax shells and removing wax from the shells.
3. The mold material should have sufficient hardness and strength at room temperature, and also have high thermal stability slightly above room temperature. To avoid various fractures, damages, or surface scratches in actual production and daily life.
4. When in the molten state, the viscosity is low, which gives it good flow and forming performance. For castings with thin walls and complex shapes, this requirement is very important, that is, they can fill the mold cavity well during injection and the mold material can flow out smoothly during demolding.
5. The mold material should have a fine grain structure, resulting in a surface finish and good covering model.
6. The residual ash content should be low, which means that after sufficient calcination, the inner wall of the hollow mold shell has almost no other substances left, in order to prevent affecting the surface quality of the casting and affecting other properties.
7. Low temperature volatile matter content ensures the reusability of the mold material and facilitates recycling and treatment.
8. The mold material should also have high chemical stability and good coating performance. During the preparation process, no volatile harmful gas should be produced, the harm to the environment should be as small as possible, and there should be no chemical reaction with the coating surface. The component source of the mold material is sufficient and cheap.