Technology Research On Filaments And Swing Submerged Arc Welding For Cryogenic Vessels Made Of Austenitic Stainless Steel

Welding is one of the key processes in the manufacture of cryogenic vessels，thequality of welding is directly related to the safety and reliability of the cryogenic vessel.With the development of cryogenic technology, manufacture of high-parameter, large scalecryogenic container requires increasingly higher technology of welding. In this paper,according to the welding problems of stainless steel liner with wall thickness4~10mm, awelding technology called “thin wire submerged arc＋swing” was proposed, a newfilaments and swing submerged arc welding equipment was developed and the technologyof filaments and swing submerged arc welding was studied. This technology applied to thepractical work of the welding of stainless steel liner cryogenic container. The welding heatinput reduced by54%, which can effectively solve the problem of overburn and largedeformation of stainless steel during welding by means of ordinary submerged arc welding.The welding equipment is composed of welding head, control box, welding powersource and feeding wire unit. The welding head achieves the oscillation of welding gun withthe adjustable swinging scope of3-10mm and frequency of0-2.5Hz by the rotation andsliding of eccentric wheel; the effective track of the girth weld roundness error wasachieved by the rotation mechanism and triax-oriented floating mechanism. Throughexperimental study, the parameters of filaments and swing submerged arc welding weredetermined as follows: the welding current is220～230A, the welding voltage is28～32V,the welding speed is450～500mm/min, the wire extension is12～15mm, the weavingamplitude is5～7mm and the swing frequency is1.5～2Hz. The study found that the weldwidth of swing welding increased by30%on average, when other conditions keep constant.When swing frequency changes from0Hz to1.5Hz, weld microstructure changes from thecoarse strong directional dendrites to weak directional thin dendrites and grains will berefined. When the swing frequency increases to1.5Hz, the microstructure in fusion zonewill be fined to small equiaxed grains. The coarse strong austenitic crystal cellular branchno longer exists, a tiny branches crystal crisscross distribution state, part of the weld areaappears small isometric. Based on the Gauss distribution, the model of strip heat source simulating the electricarc weaving was derived, and by which the temperature field of filaments and swingsubmerged arc welding of0Cr18Ni9was simulated using ANSYS software. The resultsshow that the width and length of the weldpool increase quickly at the beginning, thenslower, when the weldpool reaches quasi steady state, the width and length of the weldpoolalso don’t change. The temperature of the nodes near the welding seam can exceed1100°Cwhile the heat source is close to these nodes, and the temperature of these nodes will be lessthan200°Cwhile the heat source is away from them. In the node away from the center ofthe weld6mm, if the temperature of the node is less than250°C, the node’stemperature-rising speed is smaller, and if the temperature exceeds250°C, the node’stemperature-rising speed is greater. The simulation results show good agreement with theexperimental results which were obtained AUTOTEST-8C temperature collection system.