Development And Process Characteristics Of Flux Strips For Ultra-narrow Gap Welding

Flux strips constrained arc ultra-narrow gap welding is a welding method in which the arc is confined by the flux strips,and the arc is concentrated on the sidewall and root of the groove.It has the advantages of low heat input,high welding efficiency,and good welding joint performance.The laboratory has developed several flux strips,but all of them require manual placement of the flux strips at the bottom of the groove,which severely hinders the industrial application of flux strips constrained arc ultra-narrow gap welding.For this reason,this paper proposes a successive feeding flux strips ultra-narrow gap welding method,designs a new type of flux strips structure,and develops a set of flux strips preparation equipment.The flux strips is matched with the ultra-narrow gap special welding gun to carry out the process test to study the influence of welding parameters on the welding formation.The U-shaped flux strips structure is designed,which is formed by bonding small flux sheets.Small ridges are evenly spaced inside the flux strips to control the distance between the welding wire and the small flux sheets.The flux composition is marble,fluorite,ferro-titanium,ferromanganese,ferrosilicon,and quartz sand.The best flux composition ratio is 58:29:5:2:1:5.The flux strips should have good rigidity,and use high temperature resistant thermal conductive silicone rubber as the best adhesive.Due to the high hydrogen content in the adhesive,the method of adding iron oxide powder to the adhesive is used to reduce the number of hydrogen holes in the weld.When the mass ratio of iron oxide powder to adhesive is 4:5,eliminate the hydrogen holes in the weld.At the same time,a set of flux strips preparation device was also developed.This device is composed of a mold barrel and an automatic gluing device,which improves the preparation efficiency of the flux strips.The prepared flux strips is combined with a special ultra-narrow gap welding torch to conduct a process test,and the relative position of the welding wire and the flux strips,the matching relationship between the thickness of the flux sheet and the flux strips feeding speed,and the influence of the welding voltage on the welding appearance are studied.The results show that when the distance between the welding wire and the adhesive is 1?1.3mm,the flux sheet can burn evenly,which effectively solves the problem of the flux strip deflection caused by the unmelted flux sheet near the adhesive being inserted into the molten pool;when the welding voltage range is between 20V and 22V,the flux sheet with a thickness of 0.8mm can be matched with flux strips feeding speed range of 3.3mm/s to 4.2mm/s;a flux sheet with a thickness of 0.9mm can be matched with flux strips feeding speed range of 2.7mm/s?3.0mm/s;For the flux sheet with a thickness of 0.7mm,increasing the flux strips feeding speed can never get a good welding appearance.Analysis believes that increasing the thickness of the flux sheet can enhance the restraint effect on the arc,and the thicker flux sheet can match the slower flux strips feeding speed.The arc characteristics and droplet transition form under different flux sheet thicknesses and welding voltages are studied.By analyzing the current and voltage waveforms,it is found that during the process of reducing the thickness of the flux sheet from 0.9mm to 0.6mm and increasing the welding voltage from 19V to 24V,the arc gradually transfers from the bottom of the groove to the sidewall of the groove and burns,and the forms of droplet transfer are all transitions from short-circuit transition to short-circuit transition and coexistence of slag wall transition.