The dimensional accuracy of investment casting is relatively high, generally up to ct4-6 (ct10-13 for sand casting and ct5-7 for die casting). Of course, due to the complex process of investment casting, there are many factors that affect the dimensional accuracy of the casting, such as the shrinkage of the mold material, the deformation of the investment mold, the linear change of the shell during the heating and cooling process, the shrinkage rate of the alloy and the deformation of the casting during the solidification process, etc., so Although the dimensional accuracy of common investment casting is high, its consistency still needs to be improved.
When pressing the melting die, the pressing die with high surface finish of the cavity is used, so the surface finish of the melting die is also relatively high. In addition, the shell is made by coating the refractory coating made of special high temperature resistant binder and refractory on the investment mold, and the surface finish of the cavity directly contacting with the molten metal is high. Therefore, the surface finish of investment casting is higher than that of general casting, generally ra.1.6 ~ 3.2 μ M.
The biggest advantage of investment casting is that due to its high dimensional accuracy and surface finish, it can reduce the machining work. Only a little machining allowance can be left for the parts with high requirements, and even some castings only have grinding and polishing allowance, which can be used without machining. It can be seen that the investment casting method can save a lot of machine equipment and working hours, and greatly save metal raw materials.
Another advantage of investment casting is that it can cast complex castings of various alloys, especially superalloy castings. For example, the streamlined profile and cooling inner cavity of the blade of jet engine can hardly be formed by machining technology. Using investment casting technology to produce can not only achieve batch production, ensure the consistency of castings, but also avoid the stress concentration of residual knife marks after machining.