The dimensional precision of the investment casting is higher, generally can reach ct4-6 (sand casting is ct10~13, die-casting is ct5~7), of course, because of the complex process of the investment casting, the factors that influence the casting dimension precision are more, such as the shrinkage of the mould material, the deformation of the melt mode, the line quantity change in the heating and cooling process,
The shrinkage rate of the alloy and the deformation of castings during solidification, so the size accuracy of ordinary investment castings is higher, but the consistency still needs to be improved (using medium and high temperature wax casting size uniformity to improve a lot). When the mold is pressed, the surface finish of the mold cavity is high, so the surface finish of the mold is also relatively high. In addition, the shell is made from a refractory coating made of a special binder and refractory material that is resistant to high temperatures, with a high surface finish in the cavity in direct contact with the molten metal.
Therefore, the surface finish of the investment casting is higher than the general casting part, and can reach ra.1.6~3.2μm. The biggest advantage of investment casting is that the investment casting has a high dimensional accuracy and surface finish, so it can reduce the machining work, but the parts require a higher part to leave a little processing allowance, and even some castings only leave grinding, polishing allowance, without mechanical processing can be used.
Thus, the use of investment casting method can save a lot of machine tool equipment and processing time, greatly saving metal raw materials. Another advantage of the investment casting method is that it can be used to cast complex castings of various alloys, especially for casting high temperature alloy castings. such as the blade of a jet engine, its streamlined outer profile and cooling of the inner cavity, with the machining process can hardly be formed.
The production of investment casting process can not only achieve mass production, ensure the consistency of castings, but also avoid the stress concentration of residual knife pattern after machining.