The reasons for the cracking of the neutral surface of the TP347H steel elbow of a boiler panel reheater in a power station are analyzed by means of macroscopic morphology observation,chemical composition analysis,mechanical performance test,microstructure observation,stress state analysis and other test methods.The results show that a large number of Cr-containing carbides precipitated at the grain boundary after long-term high-temperature operation of the elbow,leading to weakening of chromium depletion at the grain boundary,intergranular oxidation,and initial crack initiation.Numerical analysis of the stress of the elbow shows that the inner wall of the neutral surface of the elbow bears tensile stress,and the mechanical damage of the outer wall of the neutral surface aggravates the stress concentration.After the micro cracks in the oxidation notch position of the inner wall are initiated,they continue to move from the inside to the outside under the action of tensile stress.The crystal expands until it penetrates the pipe wall,causing leakage.
reheater tubeTP347H steelneutral plane of elbowintergranular oxidationstress cracking
维普
万方数据
