Influence of Properties of Molding Materials on Casting Quality

The performance of the mold manufacturing raw materials not only ensures the accuracy of the specifications of the stainless steel silica sol investment castings but also ensures the investment molds have a high surface smoothness, good compressive strength, and are light weight. It should also have good casting to its advantage. The mold material is generally prepared with wax, chrome green, and plastic (anti-corrosion coating). All mold materials mainly prepared with wax materials are called wax-based mold materials, and their melting point is low, which is 60–700 °C; all mold materials mainly prepared with chrome green are called epoxy-based mold materials, and their melting point is slightly higher, about 70–1200 °C.

1. Preparation is to mix a variety of raw materials that make up the mold material into a uniformly distributed body and to make the condition of the mold material meet the requirements of pressing investment molds. During the preparation, the method of heating is mainly used to melt and mix various raw materials into one, and then, under the cooling state, the silica sol mold material is vigorously stirred to make the mold material into a paste state for pressing. Sometimes it is also possible to melt the mold material into a liquid state and pour the investment mold directly.

2. Recycling of molding materials Due to the high quality standard of investment mold products, most of the investment molds for stainless steel castings are pressed with new materials. The recycled mold material after the mold is released is used to make the investment mold of the gate system after remelting and filtering. When wax-based molding materials are used, the molding materials obtained after the mold is released can be recycled and used to produce new investment patterns. However, in the application of the circulation system, the performance of the mold material will be affected: the ductility will increase, the ash content will increase, the fluidity will decrease, the shrinkage rate will increase, and the color tone will change from white to brown. This key is related to the qualitative change of the polyether in the mold material. Therefore, in order to restore the original performance of the old mold material to the greatest extent, high-quality shaft sleeve castings need to remove soap salt from the old mold material. Common methods include sulfuric acid (hydrochloric acid) solution, activated clay treatment, and electrolysis.