Advantages of Investment Casting

The so-called investment casting process is simply to use fusible materials to make a fusible model, Several layers of special fire-resistant coating “paint” are coated on it. After drying and hardening to form a whole mold shell, the mold is melted off from the mold shell with steam or hot water, then the mold shell is placed in the sand box, and the dry sand molding is filled around it. Finally, the mold is put into the baking furnace and baked at high temperature (if high-strength mold shell is used, the demoulded mold shell can be directly baked without molding) The casting is obtained by pouring molten metal into the casting mold or shell after baking.

The dimensional accuracy of investment castings is relatively high, generally up to CT4-6 (CT10~13 for sand casting and CT5~7 for die casting). Of course, due to the complexity of the investment casting process, there are many factors that affect the dimensional accuracy of castings, such as the shrinkage of the mold material, the deformation of the investment mold, the linear change of the mold shell during heating and cooling, the shrinkage of the alloy, and the deformation of the castings during solidification, the dimensional accuracy of ordinary investment castings is relatively high, However, its consistency still needs to be improved (the dimensional consistency of castings using medium and high temperature wax should be improved a lot).

When pressing the investment mold, the mold with high surface finish of the cavity is used, so the surface finish of the investment mold is also high. In addition, the mold shell is made by coating the refractory coating prepared by the special high-temperature resistant binder and refractory materials on the investment mold, and the surface of the mold cavity in direct contact with the molten metal is smooth. Therefore, the surface finish of investment castings is higher than that of ordinary castings, generally reaching Ra.1.6~3.2 μ m。

The biggest advantage of investment casting is that because investment casting has high dimensional accuracy and surface finish, it can reduce machining work, just leave a little machining allowance on parts with high requirements, and even some castings only leave grinding and polishing allowance, which can be used without machining. It can be seen that the investment casting method can greatly save machine tools, equipment and processing time, and greatly save metal raw materials.

Another advantage of investment casting method is that it can cast complex castings of various alloys, especially superalloy castings. For example, the blade of a jet engine, with its streamlined profile and cooling cavity, can hardly be formed by machining. The investment casting process can not only achieve batch production, ensure the consistency of castings, but also avoid the stress concentration of residual knife lines after machining.