Failure Analysis Of Cr5Mo Atmospheric And Vacuum Distillation Unit Industrial Pipeline Welded Joints

The cracks found in the welding joints of a Cr5Mo atmospheric and vacuum distillation unit industrial pipe during the overhaul,this will seriously affect the safety of the pipeline.For this reason,failure analysis was performed on the Cr5Mo atmospheric and vacuum distillation unit industrial pipeline.The reasons for the failure of welded joints were derived through macro crack analysis,crack microscopic analysis,fusion line area analysis and physical and chemical properties analysis,and recommendations and follow-up monitoring methods were proposed.The main research contents are as follows:1.Through the study of domestic and foreign pipeline failure analysis cases and failure analysis techniques,object summed up the failure reasons and analysis methods of pipe welding joints,and summarized the general industrial pipe welding joint failure analysis process.2.This subject develops and refines the failure analysis process for Cr5Mo industrial pipe welded joints of atmospheric and vacuum devices,and explains each analysis step in the analysis process.3.This topic selects two typical failed industrial pipes of Cr5Mo for a large-scale refinery company's atmospheric and vacuum equipment.According to the industrial pipe failure analysis process,the macro crack analysis,crack micro analysis,fusion line area analysis and physical and chemical performance analysis of welded joints are carried out.The object determined the cause of failure and proposed the next steps for improvement.Through the analysis process of the failure analysis of Cr5Mo atmospheric and vacuum distillation unit industrial pipelines welded joints,the following conclusions are drawn:The crack in is hot crack,which is caused by poor weld formation,stress concentration,short high-temperature residence time and rapid cooling speed.The heat affected zone has low impact properties and there are many lack of fused defects that causes the hot crack to expand from the heat affected zone.Compared with the failure analysis process of general industrial pipe welding joints,the failure analysis process proposed in this paper is more feasible for the analysis of crack failure.