The fracture reason of high-pressure outer cylinder bolt

Abstract

Abstract The power plant experienced a cylinder bolt fracture accident during the power generation process of the unit. This study conducted fracture research and analysis on fractured bolts through a series of macroscopic and microscopic detection methods. The analysis results indicated that the cause of the bolt fracture accident of the high-pressure outer cylinder of the 5th steam turbine this time was the improper heat treatment process during the bolt material processing stage, which resulted in coarse grain size and severe insufficient impact toughness of the bolt material. Finally, the crack occurred at the position with the largest load and gradually expanded in a brittle manner until the overall fracture failure.