Research On All Position Narrow Gap Laser Welding Technology For Stainless Steel Pipeline

Austenitic stainless steel pipeline is used in high quality performance installations because of its good anti-corrosion properties,high tensile strength,easily work-hardened and non magnetism in the solid solvency condition.However,Austenitic stainless steel has a higher coefficient of structural expansion,and the stress generated in the welding process is easy to lead to weld deformation,and its thermal conductivity is low,resulting in poor liquidity of the molten pool,and defects such as pores and inclusions are easy to occur in the welding process.Compared with other welding methods,the heat source of narrow gap laser welding is highenergy density laser beam,which can quickly heat and cool,reduce the heat affected area,and reduce welding deformation.At the same time,the design of narrow gap groove can make the molten pool more stable and improve the welding quality.Therefore,taking the narrow gap laser all position welding of Austenitic stainless steel pipeline as the research object,through digital simulation and experimentation,exploring stainless steel pipeline all-position narrow gap welding related technologies and processes.of all position narrow gap welding of stainless steel pipeline,and provide basic data for all position welding of stainless steel pipeline.The main research content is as follows:(1)Numerical simulation of laser welding with the help of Fluent simulation software,the study of different laser power and welding speed in the case of the welded joint heat profile and welding seam shape features.As the laser power increases,the high-temperature area and maximum temperature of the welded joint increase,and the maximum width of the weld slightly increases,while the depth increases significantly;As the welding speed increases,the temperature field of the welded joint and the variation trend of the weld shape characteristics are exactly opposite.These simulation results provide theoretical guidance for subsequent welding experiments.(2)Firstly,taking the flat welding position as the research object,the influence of welding parameters such as laser power,welding speed,and defocusing amount on weld formation was studied through welding experiments.The experiment shows that as the defocusing amount decreases,the weld reinforcement decreases,and using negative defocusing is more conducive to obtaining a higher penetration depth;The influence of laser power and welding speed on weld formation corresponds to the conclusions of numerical simulation.The parameters of narrow gap laser welding were optimized,and the obtained weld seam has good double-sided formation and no obvious defects in the macroscopic morphology of the cross-section.At the same time,it provides reference data for welding experiments in other spatial positions.(3)On the basis of the flat welding position experiment,other typical spatial position laser welding experiments were carried out,and the influence of laser head posture on weld formation was mainly studied.This provides a reference for adjusting the posture of the laser head when moving along the circumferential area of the pipeline during full position welding.(4)Based on the various typical narrow gap laser welding experiments in spatial positions mentioned above,an adjustment plan for laser power,defocusing amount,welding speed,and laser head posture was designed.The full position welding experiment of stainless steel pipeline was carried out using a variable parameter method,and the pipeline welded joints for microscopic tissue observation,mechanical performance,the findings suggest that the weld is uniformly organised,with a small heat-affected area of,and the weld zone is mainly composed of austenite and ferrite.The mechanical properties and corrosion properties of the welded joint are excellent,and all parameters and indexes meet the requirements of the standard.