Research on the Application of Coercivity in Residual Stress Evaluation of Blades
The martensitic stainless steel turbine blades required post welding heat treatment(PWHT)to reduce residual stresses during welding,but there was a lack of a fast and non-destructive(NDT)way to evaluate the stress relief heat treatment process.The distribution of residual stresses in welded blades was analyzed by using magnetic coercivity and drilling residual stress detection methods through prefabricating comparative specimens.The results showed that in the comparison specimens,the maximum principal stress in the heat affected zone(HAZ)of the weld seam measured by the drilling method decreased by 55％after heat treatment,which was lower than the material yield strength of 550 MPa,and the coercive force detection value decreased by 20％.After heat treatment,the coercivity in the HAZ of the evaluated specimen decreased by 4 6％,and the coercivity decreased to the same level as that of the base metal,indicatimg that the residual stress at the weld position of the specimen was effectively controlled.The feasibility of NDT assessment of PWHT process and stress distribution in welded joints of martensitic stainless steel based on coercivity was verified.
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维普
