Views: 5 Author: Site Editor Publish Time: 2020-03-06 Origin: Site
The investment casting process is to use a fusible material to make a fusible model, apply several layers of special refractory coatings on it, dry and harden to form an integral shell, and then use steam or hot water to melt from the shell. Drop the model, then place the mold case in a sand box, fill it with dry sand, and finally place the mold in a baking furnace for high-temperature baking. (For example, when using a high-strength mold case, you can remove the mold without molding. The shell is directly fired). After the mold or shell is roasted, molten metal is poured into it to obtain a casting.
Investment castings have high dimensional accuracy, generally up to CT4-6 (CT10 ~ 13 for sand casting and CT5 ~ 7 for die casting). Of course, due to the complicated process of investment casting, 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 linear change of the mold shell during heating and cooling, the shrinkage of the alloy, and the deformation of the casting during solidification, etc. Although the dimensional accuracy of ordinary investment castings is high, Consistency still needs to be improved (size consistency of castings using medium and high temperature wax materials is much improved).
When pressing the investment mold, a profile 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 shell is made of a refractory paint made of a special high-temperature-resistant adhesive and a refractory material, which is hung on the investment mold, and the inner surface of the cavity directly contacting the molten metal has a high smoothness. Therefore, the surface finish of investment castings is higher than that of general castings, and generally can reach Ra.1.6 ~ 3.2μm.
The biggest advantage of investment casting is that because the investment casting has high dimensional accuracy and surface finish, it can reduce the machining work. It is only necessary to leave a little machining allowance on the parts with higher requirements, even some castings only have Leave the grinding and polishing allowances without using machining. It can be seen that the use of investment casting method can save a lot of machine tool equipment and processing time, and greatly save metal raw materials. Another advantage of the investment casting method is that it can cast complex castings of various alloys, especially high temperature alloy castings. Such as the blades of jet engines, the streamlined profile and cooling cavity can hardly be formed by machining processes. Production by investment casting technology can not only achieve mass production, ensure the consistency of castings, but also avoid the stress concentration of residual knife marks after machining.