Reasons for surface nitriding of serpentine spring coupling

The function of the internal and external tooth nitriding surface spotted pump shaft of the toothed coupling is mainly to transmit power and support the impeller to maintain normal operation in the working position.When the pump shaft and the motor shaft adopt a separate structure, they can pass throughSerpentine spring couplingconnection.The outer sleeve with internal teeth and the inner sleeve with external teeth form a serpentine spring coupling, which uses the meshing of internal and external teeth to transmit torque.This type of connection can transmit a large torque and allow a relatively large axial offset, and the accuracy of the installation is relatively low.

The performance of the coupling is related to the efficiency of the entire nuclear main pump, as well as the stable operation, the material and processing of the coupling.Strict quality requirements. During the installation of the pump shaft of the nuclear main pump, it was found that the surface of the nitriding inner and outer teeth of the inner and outer sleeve of the serpentine spring coupling appeared size3.10. The surface spot defects of XNUMXmm color which is slightly darker than normal area and the metallic luster is dim. Such surface spot defects not only affect the apparent quality of the main nuclear pump shaft, but also may have potential hazards to stable service.The material of the serpentine spring coupling is42CrM structural steel.In view of the spot defects appearing on the nitriding surface of the inner and outer teeth, the reasons are mainly analyzed from three aspects. The raw material composition is not uniform; it is caused by the mechanical processing process; and the nitriding process occurs. 

After testing the composition of the processed blank, no abnormal alloy composition was found, and the reason for the uneven raw material was ruled out.The machining processes that affect the apparent quality of the tooth surface are the CNC milling of internal and external teeth and the integrated light-decorated coupling, the processing path of the milling machine tool and the light-decorated grinding block, and the processing mode of action with the inner and outer sleeve of the gear coupling. Spot defects on the surface also exclude the cause of mechanical processing.According to the fact that the hardness of surface spot defects is lower than that of other areas, the possible cause comes from the nitriding process.In addition to the inner and outer tooth surfaces of the toothed coupling, anti-seepage agent should be applied for anti-seepage protection.

Tooth surface anti-seepage agent residues or surface oil stains that have not been completely removed, and foreign matter coverage such as coolants in the machining process may affect the nitriding effect.The effect of the surface residue of the anti-seepage agent on the nitriding process is simulated through experiments, and the scanning electron microscope, electron probe,The x-ray diffractometer and the Vickers hardness tester respectively observe and detect the spot defects of the nitriding layer, and give the cause of the spot defects on the nitriding surface and the elimination measures.The working environment of the serpentine spring coupling is harsh, and the quality control of every processing procedure including nitriding must be strict. The cause of the defects should be carefully analyzed and corresponding countermeasures will be adopted to reduce or even avoid the occurrence of defects and ensure that the snake The processing quality of the spring coupling.

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