Research Of Large Thick Plate Narrow Gap Twin-wire Submerged Arc Welding Process

In the face of the increasingly complex marine environment and the acceleration of clean energy to achieve carbon neutrality,the production quality and efficiency of wind power tower equipment for wind power generation in marine engineering also need to be further improved,with the increase of wind tower wall thickness and diameter,for large thick plate welding,ordinary submerged arc welding has been unable to meet the actual production efficiency and quality requirements of enterprises.Therefore,based on the welded steel of wind power towers,this thesis studies the welding process of narrow double filament submerged arc welding with a new welding technology for large and thick plates with a thickness of 60 mm and above,improves the welding efficiency and welding quality,and establishes an effective finite element model of large-thick plate narrow-gap twin-wire submerged arc welding by means of numerical simulation,further explores the variation law of temperature field and welding residual stress distribution during the welding process of large-thick plate narrow-gap twin-wire submerged arc welding,optimizes the test process,improves the test efficiency,and reduces unnecessary repetitive tests.The main research contents of this thesis are as follows:Through the field visit and online investigation of many submerged arc welding manufacturing enterprises such as CCCC Third Airlines,Daming Heavy Industry and Erchong Group,from the equipment stability,maintenance cost and work efficiency of multifilament submerged arc welding,the scheme of foreign welding power supply plus other domestic welding auxiliary equipment was selected,and a test platform with high stability and economy was built,based on this platform,the welding process of ordinary monofilament submerged arc welding and narrow gap double-wire submerged arc welding was studied and compared,and different welding process parameters(such as welding current and welding voltage were obtained,welding speed,etc.)on the influence of weld forming and welding quality,summarized the reasonable welding process parameter range of large thick plate narrow gap twin-wire submerged arc welding,and calculated that the welding efficiency of narrow gap twin-wire submerged arc welding is increased by 51%compared with ordinary monofilament submerged arc welding.In order to further improve the welding efficiency of narrow gap twin-wire submerged arc welding,a new narrow gap U-shaped small groove size was designed based on 75 mm thick DH36 steel,and the new process of small groove narrow gap twin-wire submerged arc welding was explored by adopting anti-deformation measures and single-layer single pass welding.It is found that when the new single-layer single-pass welding method is adopted for small-groove narrow gap double-wire submerged arc welding,the sidewall fusion is good and there is no slag inclusion when the deviation between the straight gun and the oblique gun is less than 3 mm,and when the deviation of the two guns is greater than 3 mm,it is easy to produce slag inclusion and poor sidewall fusion.Through the SWSWELD finite element simulation software,the submerged arc welding model of large thick plate narrow gap twin-wire is established,the actual weld section size is compared with the simulation results,and the accurate heat source parameters are obtained through heat source checking,and the error rate of the simulated melt pool width and high is controlled within 5%.The thermocouple device is used to measure the thermal cycle curve of the heat-affected zone and the temperature change trend of the simulated thermal cycle curve,which has the characteristics of fast heating and slow cooling,which verifies the effectiveness of the model.At the same time,according to the thermoelastic-plastic finite element theory,the residual stress distribution state of large thick plate narrow gap double-wire submerged arc welding was obtained by simulation,and the stress was mainly concentrated in the middle and both ends of the weld,showing a dumbbell-like distribution.It also provides theoretical guidance for the subsequent use of the model to explore the influence of different welding parameters on the temperature field,residual stress and welding deformation of large or extra thick plates,which reduces the cost of manpower and material resources.