The Research On Constrained Arc By Flux Strips Of Ultra-narrow Gap Welding Applied To Medium Plate

Constricting arc with flux strips of ultra-narrow gap welding method of welding medium plate has a certain application prospect because of its high production efficiency and low heat input,can reduce the residual stress and residual deformation after welding.However,the production efficiency of the flux strips is low and easy to be damaged,which seriously hinders the popularization and application of the ultra-narrow gap welding method in industry?the flux sheet chain has been developed by our group,which is formed by the bonding of the glass fiber net and the flux sheet to replace the flux strip and can stably bind the welding arc in the groove ?The shortcomings of the ultra-narrow gap welding torch are further improved.Two special welding torches were designed in order to solve the problem of insufficient rigidity and complicated structure of the previous narrow gap welding torch.The first welding torch which is composed of a copper c onductive plate and a steel supporting plate to improve the integral rigidity of the welding torch,The clamping force between the conductive nozzle and ceramic pressing block can make the solder wire and conductive nozzle closely contact when the wire pas s through the middle position of the conductive nozzle and the ceramic pressing block.However,it is found that the conductive nozzle is not easy to change because of the rising of arc during the experiment.For this reason,another welding torch was designed which was employed brass as the raw materials.The overall structure of the welding torch is composed of three parts which are the screw nut,wire nut,gun respectively.The welding torch and welding machine were fixed by the screw nut,The screw nut can ensure the excellent conductivity of the welding torch,The wire is always in contact with the conductive nozzle in the conveying process.The results show that the welding torch can solve the defects of the first welding torch,and can meet the requirements of the ultra-narrow gap welding.In order to solve the problem of the flux strips,two kinds of flux sheet structure and the glass fiber net are designed.The first flux sheet structure is rectangular,and the second structure is a circular small notch rectangle.It is found that the first flux sheet and the glass fiber net is not suitable for the welding seam of the groove and is not conducive to filling,cover welding.however,another flux sheet chain can be well adapted.The glass fiber net is a net which is formed by the cross winding of the four warp threads of a glass fiber rope.And the glass fiber wetting agent is coated at the intersection of the warp and weft,and the glass fiber net has a certain stiffness.The glass fiber net and the flux sheet are bonded into a flux sheet to be folded into the groove,and the contact force can be tightly contacted with the side wall of the groove by the elastic force in order to confine the arc.Experimental study on double-sided Molding of single-side welding of Ultra-narrow Gap Root Welding Process was carried out on Q235 A medium Plate by using the weld flux sheet chain restraint arc.The welding voltage mainly determines the fusion of the side wall of the groove,and the welding current determines the shape of the back of the root weld.It can realize the single side welding and double side forming of root weld under the matching process parameters.It has some advantages in constrainting the arc welding of X70 pipeline steel with the flux sheet chain compared with conventional welding method.The heat input of welding joint is small,and the width of heat affected zone is narrow.The microstructure of the weld zone is mainly acicular ferrite and the heat affected zone are polygonal ferrite and bainite.The coarse grain zone does not soften and the hardness is higher than the base metal.It impact toughness of heat affected zone and weld zone is well.