To determine the root cause of through-hole cracking in a flange, detailed methods, including macroscopic and microscopic inspection, microstructural investigations, chemical analysis, hardness measurement, simulation experimentation, and analytic calculations were carried out, in this study. The results show that the cracking was due to overload which was caused by impact. The crack formed in the time period before chromic acid anodization and machining, and the impact stress originated from conveying and revolving transportations. The microstructure, hardness, and chemical compositions of intermediate casing flange all coincide with technical requirements.
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