Optimization And Analysis Of Welding Process Of Nuclear Power Main Pipeline Of 316NG

Welding is a process in which two or more kinds of materials are permanently bonded by means of diffusion and penetration between molecules(atoms).Ring welding is one of the most common connection modes for nuclear power pipelines.Therefore,it is very important to know the accurate temperature and stress distribution in the heat influence area of the pipeline ring during the process of welding for the safe of operation and maintenance of pipelines.In this paper,the nuclear power pipeline of 316 NG was studied to analyze the distribution of welding temperature field and stress field and the optimal welding parameters of 316 NG nuclear power main pipeline by using finite element numerical simulation method.The main contents of this paper are as follows:(1)The simplified model of nuclear power welded joints—plate butt welded joints was studied.We implemented a design of experiment of the plate butt welded joints model with the method of Latin Square to find the optimized parameters of welding process.The expriments were numeric simulation to explore the optimzal parameters of current,volt,speed and cooling time of welding process.(2)The range method was used to analyze the results of simulation of welding residual stress of 316 NG to evaluate the influence of the parameters in welding process,and find the optimal welding process parameter combination.The equation to express the relationship between welding residual stress and welding process parameters were also obtained.(3)In order to understand the internal and external surface residual stress distribution of 316 NG pipelines in detail,the distribution of residual stress of the model after welding process was simulated based on the optimal welding process parameters,and the results of welding specimens were compared and verified by physical experiments.(4)Crack propagation models were constructed at the position of the maximum tensile stress after welding,and the crack propagations were calculated by stress intensity factor and J integration to evaluate the crack pattern which will provide useful information for the guarantee of welding quality and the maintenance of pipeline welded joints.In this paper,the finite element numerical simulation method was used to simulate the welding residual stress of nuclear power main pipeline of 316 NG by thermal-structural indirect coupling method.The Latin Square method was used in the design of experiment of the welding process to find the optimal welding process parameters.The optimized process parameters were applied to the main pipe for welding,and the crack propagation analysis was carried out on the potential cracks places which provide a guarantee for the welding quality and the reliability of the equipment.