The material used to make the investment is called mold material. In order to obtain high-quality molds, foundries must choose suitable mold materials. Due to the many steps in precision casting, the performance requirements for mold materials are also different. In terms of the following characteristics, the molding materials used in the foundry for precision casting should meet certain requirements.

1. Weldability

The weldability of the mold material indicates the bonding properties between the mold materials. When a foundry combines a single melt module into a module, the mold material is required to have good welding performance and high welding strength, which is beneficial to the combination of the investment mold and avoids the module from breaking at the welding point during transportation and shell making.

2. Coatable

The wetting affinity of the mold material for the refractory coating is called coatability. When the foundry is manufacturing the shell, it is required that the surface of the investment mold be sufficiently wetted by the refractory coating and uniformly coated. The coating quality of the mold material directly affects the integrity of the cavity shape and surface finish.

3. Melting Point

The melting point of the mold material suitable for precision casting production should not be too high or too low, generally in60 ℃ ~ 100 ℃ range. Because according to the general performance of the mold material, when the melting point is moderate, the molten mold has a certain strength and thermal stability; at the same time, it facilitates the preparation of the mold material, the preparation and melting of the molten mold, and adapts to the requirements of production mechanization and automation. Shorten the production cycle.

4. Shrinkage

The shrinkage of the mold material is expressed as when cooled within a certain temperature range.Percent change in diameter of "round sample. FoundryusedThe requirement for the shrinkage of the mold material is usually less1.2%, so there are no defects such as shrinkage on the investment mold, and its value is stable. The shrinkage rate of the mold material is small, which can make the size of the investment mold closer to the size of the cavity, and can reduce the deformation during cooling, thereby ensuring the accuracy of the investment mold.

5. Thermal stability

When the standard test is heated, the deformation deflection reachesThe temperature of 2mm is the softening point of the mold material, that is, the thermal stability. FoundryusedThe softening point of the mold material should normally be no less35°C to 40°C, otherwise it will be difficult to ensure the strength and accuracy of the investment in summer. According to practical experience, the softening point of the mold material should be 10 ℃ ~ 15 ℃ higher than the temperature at the molding and shell making work site.