The so-called investment casting process is simply to use fusible materials (such as wax or plastic) to make a fusible model (referred to as the investment model or model), coated with several layers of special refractory coating on it, after drying and hardening After forming an integral mold shell, use steam or hot water to melt the model from the mold shell, and then put the mold shell in the sand box, fill it with dry sand molding, and finally put the mold into the roaster. Roasting (if high-strength shell is used, the mold shell after demolding can be directly roasted without molding), after the mold or shell is roasted, molten metal is poured into it to obtain a casting.
Stainless steel castings have high dimensional accuracy, generally up to CT4-6 (sand casting is CT10~13, die casting is CT5~7). Of course, due to the complicated process of investment casting, there are many factors that affect the dimensional accuracy of castings, such as mold The shrinkage of the material, the deformation of the investment mold, the linear change of the mold shell during heating and cooling, the shrinkage rate of the alloy, and the deformation of the casting during the solidification process, so although the dimensional accuracy of the general investment casting is high, but its Consistency still needs to be improved (consistency of castings using medium and high temperature wax materials is much improved). When pressing the investment mold, a mold with a high surface finish of the cavity is used. Therefore, the surface finish of the investment mold is also relatively high. In addition, the mold shell is made of a high-temperature special adhesive and a refractory paint made of refractory material, which is coated on the investment mold. The surface of the mold cavity that is in direct contact with the molten metal has high smoothness. Therefore, the surface finish of investment castings is higher than that of general castings, generally up to Ra.1.6~3.2μm.