Failure Analysis And Prediction Of Boiler Welded Joints

The welding process occupies a large proportion in the manufacture of boilers.Most of the boiler components are connected by welding methods.At the same time,because the welded joints are mostly in a discontinuous structure and the operating environment of the boiler is harsh,the pressure exerted on the welded joints is much higher than other parts,and failure events are more likely to be caused.The welding process is affected by various factors,such as welding parameters,the nature of the base metal,welding design,as well as the environment and operators,resulting in welding defects.The welding defects cause the stress concentration of the welded joints,and it is also the starting point for the initiation of welding cracks,which causes great hidden troubles in the welding joint quality.The welding process is also accompanied by an intrinsic phenomenon,namely residual stress.Excessive residual stress will reduce the bearing capacity of the welded joints,and will also cause the welded joints to deform,affecting subsequent processing.Therefore,it is of great significance to study the influence of various factors in the welding process on the welded joints,to ensure the welding quality and to reduce the occurrence of welding joint failure events.Based on the background of the welding production of Kunming Boiler Co.,Ltd.,based on the welding process and various influencing factors,this article makes the following researches on the failure of the welding process:1.Use FMECA analysis method to determine the scope of failure analysis of welded joints,identify the failure modes of welded joints,identify the causes and consequences of failure of welded joints,and use RPN method to rank the failure modes of welded joints.2.Combine the fuzzy analytic hierarchy process to optimize the entire welding failure analysis process.By obscuring RPN results and analyzing the probability,consequence,and detectability of welding failure events by introducing weights,and performing fuzzy CA analysis,the ranking of the impact degree of various failure modes on welding failures is obtained,and the most influential failure modes are identified.,make countermeasures.3.According to the results obtained by the above two methods,the Bow-tie model of welded joint failure is established.The failure process of the welded joint isused to understand the failure process of the welded joint,and the preventive and control measures are introduced at the same time.The welding failure prevention measures and the welding failure control are adopted.Measures to reduce the probability of welding failure,reduce the degree of the consequences of welding failure,and constantly improve the prevention and control methods,and ultimately make the welding failure at an acceptable level.4.The welding finite element model was established by using Simufact.welding software.The influence of welding process parameters on welding residual stress and deformation was analyzed,and the actual welding process basis was optimized.5.A fatigue life prediction method based on energy method and grey GM(1,1)model is proposed.The fatigue life prediction of welded joints can be easily obtained and the fatigue life of welded joints can be obtained.The results are more accurate and can be solved.The fatigue test takes time and effort.