Forming Of Horizontal Welding Seam With Ultra-narrow Gap Of Flux Strips Constraining Arc

Using horizontal welding process instead of manual arc welding to butt pipe fittings,not only ensures the welding quality,but also improves the welding efficiency.However,the down-flow of molten pool and undercut restrict the development of horizontal welding technology.The ultra-narrow gap of flux strips constraining arc has low heat and can successfully solve this problem.This paper firstly presents that ultra-narrow gap of flux strips constraining arc applied to the horizontal welding process of pipe jointing.Firstly,a set of horizontal welding equipment for ultra narrow gap was developed;Secondly,the formation process of weld pool in ultra narrow gap horizontal welding is studied,The formation rule of weld pool under different welding parameters is analyzed,The process specification of ultra narrow horizontal welding process is defined;Finally The welding experiment of cast steel was carried out according to the welding process specification of ultra narrow gap,the micro-structure and mechanical properties of the weld were analyzed.Now,the results of the experiment are summarized as follows:(1)A set of experimental equipment is designed for ultra narrow gap horizontal welding,Firstly,the structure of plate welding gun is designed,It has successfully solved the problems of poor conductivity and wire sticking in the welding process by improving the structure,Using the conductive nozzle of CO₂gas shielded welding as the consumables of ultra narrow gap welding,It not only convenient the replacement of consumables,but also saves the cost of welding.Secondly,In the structural design of the welding device,the height adjustment device of the welding gun and the traveling mechanism are designed as a whole.It not only reduces the size of the whole device,but also facilitates the assembly of welding equipment,The position of welding gun can be ensured directly by the relative position relationship between traveling mechanism and groove,greatly shorten the assembly time and improve the welding efficiency.Finally,design the flux sheet for pipe welding of ultra narrow gap,reduces the thickness of fiberglass mesh,realize the horizontal welding of ultra narrow gap.(2)The effects of welding voltage,welding current and welding speed on the formation of weld pool in ultra narrow gap horizontal welding were studied,the influence of weld morphology on the formation of weld pool is defined.The results show that,With the increase of welding voltage,the downward flow of molten pool decreases.When the voltage is 21-22V,the weld is well formed.When the welding voltage is higher than 22V,weld with a raised center is formed.With the increase of welding current,the mount of molten pool flowing down decrease before increase.When the welding current is 175-195A,the weld is well formed.With the increase of welding speed,the mount of downward flow decrease before increase.When the welding speed is 8-10 mm/s,the weld is well formed.(3)Through the analysis of the stress on the horizontal weld pool with super narrow gap,the formation of molten pool is mastered.The results show that,during ultra narrow gap horizontal welding,the formation process of molten pool is mainly affected by gravity and surface tension of up sidewall on molten pool,and when they are similar,the quality of weld is good.The gravity of molten pool is mainly controlled by welding current and welding speed,surface tension is controlled by welding voltage.therefore,during ultra narrow gap horizontal welding,only the reasonable cooperation among welding voltage,welding current and welding speed can ensure the good weld formation.(4)According to the welding specification,the butt joint experiment of steel casting is carried out,and the weld cross section morphology and the formation process of molten pool are analyzed,which provides theoretical basis for the application of ultra narrow gap horizontal welding method in butt joint of steel casting.