What are the characteristics of investment castings

Update:29 Mar 2019
Summary:

The biggest advantage of investment casting is that bec […]

The biggest advantage of investment casting is that because of the high dimensional accuracy and surface finish of the investment casting, it can reduce the machining work, but only a small amount of machining allowance is required on the parts, and even some castings only Leave the grinding and polishing allowance and use it without machining. It can be seen that the investment casting method can save a lot of machine tool equipment and processing man-hours, and greatly save metal raw materials.

Another advantage of the investment casting method is that it can cast messy castings of various alloys, especially for casting high temperature alloy castings. For example, the blade of a jet engine, the streamlined profile and the cooling cavity, cannot be formed by machining. The production by the investment casting process not only enables mass production, ensures the consistency of the castings, and avoids the stress concentration of the residual knives after machining.

Investment castings have high dimensional accuracy, generally up to CT4-6 (sand casting is CT10~13, die casting is CT5~7). Of course, because the process of investment casting is messy, there are many factors affecting the dimensional accuracy of castings, such as mold. The shrinkage of the material, the deformation of the investment mold, the change in the amount of the shell during the heating and cooling process, the shrinkage of the alloy, and the deformation of the casting during the coagulation process, etc., so the dimensional accuracy of the general investment casting is high, but Consistency still needs to be improved (the consistency of castings for medium and high temperature waxes is much improved).

When the investment is limited, the profile with a high surface finish of the cavity is selected, and thus the surface finish of the investment mold is relatively high. In addition, the shell is made of a high-temperature resistant special binder and a refractory material, and the refractory paint is coated on the investment mold, and the inner surface of the cavity directly touched by the molten metal has a high surface finish. Therefore, the surface finish of the investment casting is higher than that of the general casting, and generally reaches Ra.1.6~3.2pm.