Manufacturing method for large thin-walled impeller

Abstract

The invention discloses a manufacturing method for a large thin-walled impeller. An upper mold body of a mold is internally provided with annular grooves and exhaust plugs so that exhausting can be improved, a cooling cone is arranged on the upper mold body and cooling rings are arranged on the upper surface of the upper mold body so that the cooling speed of castings can be increased, and meanwhile a sand mold is used at the bottom of a gypsum core so that heat preservation of molten aluminum at the bottom and feeding of the castings can be facilitated. The program allowing integral casting of the thin-walled and large-size impeller to be achieved by improving exhausting and cooling is adopted for the mold, the forming quality is good, and precision is high; a first concave part is arranged to position the first circular face of the end portion of the impeller, the impeller is locked to a bottom plate through first pressing pieces, welding is not needed, and fixation is convenient and rapid; and after the first round of machining is conducted on the impeller, a second concave part is arranged to position the second circular face of the impeller, fastening is conducted through second pressing pieces, machining is conducted on the impeller in order, the situation that some faces are not machined due to clamps or other reasons is avoided, and the surface precision of the impeller is improved.

Description

technical field [0001] The invention relates to the field of impeller manufacturing, in particular to a method for manufacturing a large thin-walled impeller. Background technique [0002] The impeller is an important part of products such as water turbines, steam turbines, aero engines, rocket engines, expanders, pumps, fans, compressors, etc. Its function is to pressurize or convert the gas or liquid passing through it. The impeller is usually composed of discs, blades, connectors and other parts, and is divided into open, semi-closed and closed impellers according to their structure. [0003] Most closed integral impellers have thin walls, twisted blades, complex structures, high requirements for dimensional accuracy and surface roughness, and cannot be manufactured by machining. In order to obtain impellers with high precision and high surface roughness, precision casting processes are required. Due to precision casting production The process is complex and technically ...

AI Technical Summary

Problems solved by technology

[0004] 1) When low-pressure casting large thin-walled impellers, the pressure control of the entire casting process cannot be controlled in the same way as ordinary impeller low-pressure casting. Large-scale thin-walled impellers require more precise pressure control during the casting process, and the process of pressure control is also difficult. It should be more in line with the characteristics of large thin-walled impellers;

[0005] 2) When using existing casting molds for casting of large thin-walled impellers, often due to the unreasonable mold structure, the cooling sequence of the upper and lower molds is not from top to bottom, and the impeller castings are cooled from the outside to the inside , the internal blade structure of the impeller cannot get an effective cooling effect, the cooling speed of the impeller casting is not uniform throughout the cooling process, the cooling degree is not uniform, and the final formed impeller casting has defects such as shrinkage and porosity;

[0006] 3) Due to the large diameter of the large thin-walled impeller, the existing casting mold has poor air permeability when casting a large impeller, resulting in poor exhaust during the casting process, and resistance will be generated when the casting solution is filled into the mold, resulting in Insufficient pouring of impeller castings, or the gas in the mold cannot be discharged, and molten metal gas entrainment occurs, which causes defects such as pores and sand holes in the impeller castings, and the structure and performance are low, which affects the performance of the impeller castings;

[0007] 4) Since the impeller wall is relatively thin, especially for large thin-walled closed impellers, the thinnest part is less than 1.2mm, direct clamping is easy to cause deformation and rupture, causing damage to the impeller, which will not only further bring troubles for subsequent lathe processing Difficulty, and in most cases, after the impeller is damaged, the impeller will be scrapped, which greatly increases the production cost;

[0008] 5) Due to the complexity of the clamping tools, many surfaces on the impeller have not been machined, which greatly reduces the precision of turning; the impeller is directly set on the bottom plate for impeller support, and there is no effective positioning of the impeller, so During the turning process, it is easy to cause cracks on the surface of the impeller due to vibration, and at the same time, there are great safety hazards, which further reduce the machining accuracy;

[0009] 6) During heat treatment, if Figure 7 and Figure 8 As shown, the upper and lower blades of the impeller are very thin, and when they reach the solid solution temperature, they have almost no mechanical properties, and are easily damaged by the flowing cooling medium, causing deformation or rupture

The cooling medium enters from the gap between adjacent blades, that is, the radial direction of the impeller, which will cause collisions between the upper blade and the lower blade, resulting in deformation of the blade and even cracks, such as Figure 8 As shown in , the upper blade and the lower blade deform upward and downward respectively, which deviate from the theoretically correct position, which is not conducive to the precision manufacturing of the impeller

[0010] 7) For some impellers, the central axis of the impeller is shorter than the height of the impeller, and during the heat treatment of the impeller, when the impeller is placed on the bottom plate, there is no support for the central axis hole, so the central axis hole is also prone to deformation due to gravity , or the support of the central shaft hole cannot be applied to various impellers of different sizes, resulting in that the central shaft of the impeller is prone to deformation due to no support during heat treatment

[0011] Therefore, it is necessary to further research and analyze the manufacturing method of the impeller; in addition, the existing technology not only has no perfect means to manufacture large thin-walled impellers, but also casts and manufactures other large thin-walled complex aluminum parts, such as large thin-walled bearings. , pressure vessels, and large thin-walled castings used in aerospace, national defense, and automotive industries also have many defects. Therefore, further in-depth research on related issues is required

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