| Tungsten inert gas (TIG) arc welding method is widely used for the key componentmanufacturing in the realms of aviation, spaceflight and nuclear power station etc due to itsadvantages of stable welding process, regular weld seam and high quality metallurgic property.But the disadvantages of low welding efficiency, high heat input and biggish deformation ofTIG welding method doesn’t completely meet the demand of high quality and high efficiencywelding manufacture of key component. Based on the secular investigation of laser-arc hybridwelding technology, Harbin Welding Institute (HWI) has presented a new laser-cold mateltransfer (CMT) arc hybrid welding technology under argon atmosphere, and verified theapplied feasibility of laser-CMT hybrid welding method for the manufacture of keycomponents in the realms of aviation, spaceflight and nuclear power station etc. With argon asshielding gas, the stainless steel laser-CMT hybrid welding results of HWI indicated that, theCMT arc was attracted to the the laser-heated spot, and the stability of hybrid arc in hybridwelding process was prominent; Comparing with nomal CMT welding method, continuousweld seam was obtained in laser-CMT hybrid welding process under high welding velocity;The welding quality of laser-CMT hybrid weld joint was as good as nomal TIG weldingmethod. But the results of HWI also indicated that, the defects of irregular formation and lackof fusion at the bilateral edges of weld seam were found in stainless steel laser-CMT hybridwelding process under argon atmosphere. In this paper, the stainless steel scan laser-CMT archybrid welding technology under argon atmosphere is investigated to solve the above defectsof irregular formation and lack of fusion at the bilateral edges of weld seam produced bynomal laser-CMT hybrid welding method without scanning.In the paper, directed toward304stainless steel scan laser-CMT arc hybrid weldingtechnology with argon as shielding gas, the effects of hybrid welding parameters on the weldseam formation are researched; The characteristics of hybrid welding stability and moltenpool are investigated; And the spreading mechanism at the bilateral edges of hybrid weldseam is analysed. And based on the above investigations, comparing with the20mm thick304stainless steel TIG welding with filler wire method, the formation of weld joint, mechanicalproperty of weld joint and welding efficiency of scan laser-CMT arc hybrid weldingtechnology under argon atmosphere are discussed. The investigate results indicated that:The scan laser-CMT arc hybrid welding technology is an effectual method to solve thedefects of irregular formation and lack of fusion at the bilateral edges of weld seam, and iseasy to obtain regular and continuous formation of hybrid weld seam. The scanning motion of laser before CMT arc is helpful to elongate the solidified time of molten metal at the edge ofmolten pool, and to make the molten metal at the center of molten pool to spread to the weldseam edge, therefore obtaining the regular and continuous hybrid weld seam.The effects of scan laser-CMT arc hybrid welding parameters (including distancebetween laser and arc, welding velocity and welding current) on the weld seam formations(weld penetration, weld width and weld reinforcement) are the same as nomal laser-CMThybrid welding method without scanning. To obtain regular and continuous hybrid weld seamedge, there is a certain matching relationship between the weld pool widths producedindividually by scan laser welding and CMT welding. When the welding velocity v=0.6m/minand welding current I=132A, it is able to obtain regular and continuous formation of hybridweld seam edge while the the weld pool width ratio between scan laser welding and CMTwelding is reach to1.2. The optimizational parameters of scan laser-CMT arc hybrid weldingunder argon atmosphere are scan laser power P=2kW, laser scanning width W=9mm andlaser scanning frequency f≥52Hz while the welding velocity v=0.6m/min and weldingcurrent I=132A.Comparing with nomal CMT arc welding, in scan laser-CMT hybrid welding processunder argon atmosphere, the hybrid welding process stability is improved, the hybrid arc islighter, the metal transfer frequency is increase, the distributing of short-circuit time andshort-circuit cycle are centralized. Comparing with the deep penetration mode of laser andlaser-CMT welding without scanning, the welding mode of scan laser weding and scanlaser-CMT hybrid welding is turn to thermal conductivity welding mode, which is propitiousto eliminate welding porosity and to decrease the peak temperature of heat-affected zone.The mechanical properties (includeing impact toughness, tensile property, side bandproperty and hardness), microstructure and weld seam formation of20mm thick304stainlesssteel scan laser-CMT arc hybrid weld joint are as good as that of nomal TIG welding withfiller wire. And the welding efficiency of scan laser-CMT hybrid welding method is5times asthe TIG welding with filler wire. |
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