Evaluation Method for Welding Defects of Steam Turbine Rotor

Abstract

The invention belongs to the field of steam turbine rotor welding manufacturing and discloses a welding defect evaluation method of a steam turbine rotor. The welding defect evaluation method comprises the following steps: the first step, adopting ultrasound accelerated fatigue tests on rotors of different batches with different welding processes to respectively obtain the maximum defect size of the structures of the rotors of different batches to be used as the initial defect size; the second step, respectively measuring a fatigue threshold value and estimating material intrinsic threshold value of the rotor of each batch under conditions of a plurality of stress ratios; the third step, obtaining a computational formula of the fatigue threshold value of the rotor of each batch; the fourth step, expanding two batches of welding initial defect sizes to certain specific sizes and determining merits of the welding process by virtue of comparison of the fatigue threshold value. By utilizing the welding defect evaluation method, welding defect type and distributed information are obtained by adopting very high cycle fatigue tests, defects are treated as cracks, and the welding defect is evaluated and the welding process is optimized by applying the relationship of short crack closure, fatigue threshold value and crack length.

Description

technical field [0001] The invention belongs to the field of welding manufacturing of steam turbine rotors, and relates to a method for evaluating welding defects of steam turbine rotors based on ultra-high cycle fatigue. Background technique [0002] The welding and manufacturing of steam turbine rotor can meet the advantages of large unit capacity, good compactness, and easy quality assurance, and is widely used in thermal power and nuclear power fields. The manufacturing process of the welded rotor is complicated, and the reliability of the welding process and its selection are highly required. The Chinese patent "Single-Cylinder Steam Turbine Welding Rotor and Its Welding Method" (Application No.: 201010585886.2) provides a welding method for a steam turbine, and does not involve the evaluation of the welding process. In order to assess the performance and reliability of the welded rotor, the existing technology often passes strength tests under simulated service condit...

AI Technical Summary

Problems solved by technology

The manufacturing process of the welded rotor is complicated, and the reliability of the welding process and its selection are high.

The Chinese patent "Single Cylinder Steam Turbine Welding Rotor and Its Welding Method" (Application No.: 201010585886.2) provides the welding method of the steam turbine and does not involve the evaluation of the welding process

The monitoring of welding quality is mainly based on non-destructive testing, and its defect detection ability is limited by the level and ability of detection. Non-destructive testing methods still have certain difficulties in accurately obtaining the size and location of welding defects.

In addition, the safety evaluation theory and life prediction technology after defects are detected are not perfect. The existing domestic standard GB / T19624-2004 "Safety Evaluation of Pressure Vessels Containing Defects in Use" only involves static failure modes such as plastic limit, and cannot be used for evaluation of welding The advantages and disadvantages of the process provide reference

The selection of process conditions for steam turbine rotor welding manufacturing lacks mature technical support, and it is necessary to propose a new welding defect assessment method

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