Preparation of qualified castings for rapid investment casting

From the actual casting results of trial casting, it can be found that the upper part of the diffuser blade has some defects, and the side blade also has different degrees of defects at the bottom. Considering that in the actual casting process, the upper blade is the first to be poured, and the blade is thin, the top of the blade can not be filled by alloy because the internal air can not be discharged. Therefore, it is necessary to optimize and upgrade the gating system of the diffuser. Considering the use of riser, it is the most effective and popular process measure in controlling solidification and compensating shrinkage. The main function of riser is feeding to prevent shrinkage of components, and it also has the function of exhaust and slag collection. Therefore, the specific scheme of optimizing the gating system is as follows: one dark riser is added to each of the upper eight blades to facilitate the exhaust; one open riser is added to each of the side blades, which not only has the exhaust effect, but also has a certain feeding effect on the blade. The actual optimized gating system is shown in Figure 1.

The optimized gating system went through the casting process of shell preparation, shell preheating, alloy pouring, casting solidification, shelling cleaning and riser cutting again, and the castings were sandblasted. The final diffuser casting is shown in Fig. 2, which verifies the feasibility of the gating system design and pouring process scheme (shell preheating temperature 1115 ℃, pouring temperature 1600 ℃, pouring speed 3kg / s), and provides certain technical support for subsequent rapid investment casting. After inspection, the casting has complete appearance, no defects such as insufficient pouring, smooth surface and clear outline. The results show that it meets the technical requirements of this kind of casting.

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