Realization Of Ultra-narrow Gap Welding With Ultra-fine Granular Flux Consticting Arc

UNGW(Ultra-narrow gap welding) which is an efficient, low-cost welding technology is widely used in some important structural components, such as pressure vessels, boilers, construction, bridges, ships, heavy machinery and high-pressure pipe welding and so on because of its low energy, low residual stress after welding, small deformation of the work piece, narrow heat-effected zone, etc. However, NGW there exists the problem of unlock-welding of sidewall fusion, in order to get good-welding of side wall fusion in the case of not swinging the arc, the distance between both sides of the wall can be reduced to solve this problem. But the arc of UNGW there exists the problem of moving upwards easily.This paper is based on the principle of constraining arc to prevent the arc moving upwards and the principle of effection on the arc when submerged arc welding flux slag particles formed by melting wall binding. The method of UNGW with Ultra-fine Granular Flux Consticting Arc is adopted in the experiments, and a welding torch and welding fixtures which are applicable for the UNGW are designed. Series of the experimental are taken.The follow conclusions is drawn:The method of UNGW with Ultra-fine Granular Flux Consticting Arc can effectively prevent the arc bound to rise, the welding process can be stable, reliable, and a good weld can be formed. The designed of welding torch and welding fixture structure could meet the demands of the UFGF-UNGW well. Under the condition that other parameters are fixed, the larger the number of the mesh particle flux, the longer the constraints form, which makes the tendency of the "convex" welding seam increase. The adoption of the "V"-shaped particles of metal mesh liner flux during the process of the UNGW process ca significantly enhance the arc's heating effect to the root of the side wall, which is helpful to increase the penetration depth of the lateral roots, thus ensuring the quality of the fusion of UNGW. the matching relationship between voltage and current is ascertained by experiments. The matching relationship indicates that voltage range being fit for UFGF-UNGW is about 22-31V under the current range of 200-320A; Under any certain current within the matching range of voltage and current, the formation of the UFGF-UNGW has the law of "Lack of fusion on sidewalls", "Good weld" and "Undercut" in turn with the increasing of voltage. The action relationships among arc, molten slag wall and sidewalls can be improved by properly adjusting the voltage and the current of arc, which makes cathode spot distribute properly in ultra-narrow gap, thus realizes the effective control over weld formation of UFGF-UNGW.