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Advantages of investment casting


Posted: 2021-10-21 00:00

The so-called investment casting process is simply to use fusible materials to make a fusible model, and apply several layers of special refractory coatings on it. After drying and hardening to form an integral shell, steam or heat is used. The water melts the model from the shell, then puts the shell in the sand box, and fills the mold with dry sand around it. Finally, puts the mold into the roasting furnace and roasts at high temperature (if a high-strength shell is used, it is not necessary The mold shell after demolding is directly fired for modeling). After the mold or mold shell is fired, molten metal is poured into it to obtain a casting.

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 complex process of investment casting, there are many factors that affect the dimensional accuracy of castings, such as molds. The shrinkage of the material, the deformation of the investment mold, the linear change of the shell in the heating and cooling process, the shrinkage of the alloy and the deformation of the casting during the solidification process, etc., so the dimensional accuracy of ordinary investment castings is high, but its Consistency still needs to be improved (the size consistency of castings with medium and high temperature waxes should be improved a lot).

When pressing the investment mold, the pressure type with high surface smoothness of the cavity is used, so the surface smoothness of the investment mold is also relatively high. In addition, the shell is made of a refractory coating made of a special high-temperature adhesive and refractory materials." target="_blank">The coating is hung on the investment mold, and the inner surface of the cavity that is in direct contact with the molten metal has a high smoothness. . Therefore, the surface finish of investment castings is higher than that of general castings, generally reaching Ra.1.6~3.2μm.

The biggest advantage of investment casting is that because investment castings have high dimensional accuracy and surface finish, machining work can be reduced, but only a small amount of machining allowance can be left on the parts with higher requirements, and even some castings only have Leave a grinding and polishing allowance, and it can be used without mechanical processing. It can be seen that the use of 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 complex castings of various alloys, especially high-temperature alloy castings. For example, the blade of a jet engine, its streamlined profile and cooling cavity, can hardly be formed by machining technology. Production by investment casting process can not only achieve mass production, ensure the consistency of castings, but also avoid the stress concentration of residual knife marks after machining