Precision casting technology

2022-05-18
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Precision casting technology (Part 2)

the dimensional accuracy of investment castings is high. Generally, the next step can be directly operated to CT (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 affecting the dimensional accuracy of castings, such as shrinkage of mold, deformation of investment mold, linear change of mold shell during heating and cooling, shrinkage rate of alloy and deformation of castings during solidification, Therefore, although the dimensional accuracy of ordinary investment castings is high, its consistency still needs to be improved (the dimensional consistency of castings with medium and high temperature wax is much improved)

when pressing the investment mold, the pressure mold with high surface finish of the cavity is adopted, so the surface finish of the investment mold is also relatively high. In addition, the mold shell is made by coating the refractory coating prepared by high temperature resistant special binder and refractory materials on the investment mold, and the surface finish of the mold cavity in direct contact with the molten metal is high. Therefore, the surface finish of investment castings is higher than that of ordinary castings, generally up to RA 1.6~3.2 m。

the biggest advantage of investment casting is that due to the high dimensional accuracy and surface finish of investment casting, it can reduce the machining work, just leave a little machining allowance on the 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 tool equipment and processing hours. Europe will greatly increase the utilization of carbon fiber composites as one of the lightweight materials in automobiles and 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 streamlined outline and cooling inner cavity of the blade of jet engine can hardly be formed by machining process. The investment casting process can not only achieve mass production and ensure the consistency of castings, but also avoid the stress concentration of residual knife marks after machining. Gate cup is the basic component of casting technology, especially closely related to the development of iron and steel industry. Gate cup is one of the components of smelting process equipment. The gate cup is mainly used to guide liquid metal into the cavity for basic research and product development. If the arrangement of gate cup is unreasonable, the casting may have defects such as air hole, sand hole, iron bean, slag hole, shrinkage cavity, crack and insufficient pouring. Therefore, it is a very important work to correctly select the structure and size of the sprue cup and properly place it on the casting

testing equipment
CTM
Bearing compression stength testing machine
300 ton compression testing machine

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