Low-pressure casting method, cooling control process and exhaust system of large impeller

Abstract

The invention discloses a low-pressure casting method, a cooling control process and an exhaust system of a large impeller. The low-pressure casting method comprises the steps that a manufactured forming element and a manufactured mold core are dried, and a low-pressure casting mold of the impeller is preheated; a casting material is put in a casting device, heating and smelting are carried out to form a casting solution, and slag removal is carried out on the casting solution when the casting solution reaches the set temperature; the casting mold of the impeller is assembled, and the casting mold of the impeller and the casting device are connected to form an impeller casting system; the low-pressure casting device is subjected to low-pressure mold filling along a set pressure curve; after mold filling is finished, the low-pressure casting mold of the impeller is cooled; and after the temperature of the low-pressure casting mold of the impeller is reduced to the set temperature, the impeller is taken out to be cleaned. In the casting process, the pressure and the speed are adjusted, and therefore short run can be reduced; aluminum liquid oxidization can be controlled by adjusting the aluminum liquid temperature; and shrinkage porosity can be reduced by adjusting the cooling process.

Description

technical field [0001] The invention belongs to the technical field of precision casting, and in particular relates to a low-pressure casting method for a large impeller, a cooling control process and an exhaust system. Background technique [0002] Centrifugal compressors or centrifugal pumps are used to provide pressurization for various fluid flows. This type of compressor or centrifugal pump contains an impeller. When the impeller rotates, the fluid enters in the axial direction, and then accelerates into the circumferential and radial directions. The high-velocity fluid enters the diffuser, and the high-pressure fluid is output after the speed is converted. For this type For compressors or centrifugal pumps, the impellers used are generally large thin-walled alloy precision casting impellers. [0003] Low-pressure casting is a special precision casting method. Low-pressure casting applies low pressure to the molten metal, presses the molten metal into the mold, and mak...

AI Technical Summary

Problems solved by technology

[0004] The diameter of the large thin-walled impeller is relatively large, and the wall of the impeller is relatively thin, the thinnest part of the blade is less than 1.2mm, while the thickness of the blade structure of the entire impeller is small, the shape of the blade is three-dimensional twisted, and the structure is complicated. When the wall impeller is cast, due to these characteristics of the impeller, the impeller castings will have defects such as scale, shrinkage, sand holes, pores, etc., so that the formed impeller castings cannot meet the use requirements

[0005] At present, in the process of low-pressure casting of large thin-walled impellers, due to the large size of large thin-walled impellers, low-pressure casting is performed under a set lower pressure for filling and casting. The main difficulty is that due to the large impeller It belongs to thin-walled parts, and during the filling process of aluminum liquid, it is easy to have nest gas and turbulent flow; in addition, the cooling speed of aluminum liquid is fast and the fluidity decreases rapidly, and the aluminum liquid is easy to stop flowing during the flow process, and it is easy to leak out. Insufficient cast-in-place, large thin-walled impellers that cannot be successfully integrally cast;

[0006] When low-pressure casting large thin-walled impellers, compared with ordinary impellers, the castings are larger and more complex in structure. From core making to casting molding, the same control method as ordinary impeller low-pressure casting cannot be adopted in all aspects;

[0007] When the existing low-pressure casting method casts large thin-walled impellers, the cooling speed and cooling time of the large thin-walled impellers are not well controlled. Often, the outer and upper parts of the mold are cooled faster, and other positions are cooled slowly, resulting in the formation of impeller castings. The cooling effect does not meet the requirements, resulting in defects such as shrinkage and porosity, which will affect the performance of the impeller casting

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