【作者】 王小朋；

【导师】 王旭友；

【作者基本信息】 机械科学研究总院 ， 材料加工工程， 2012， 硕士

【摘要】 TIG焊接过程稳定、焊缝成形美观、焊接接头冶金性能高，是目前我国核电、航空、航天等领域关键部件焊接制造的常用方法之一。但是，TIG焊接效率低、焊接热输入大、容易导致较大的焊接变形。因此，随着我国核电、航空、航天等领域的快速发展，TIG焊接方法仍难以完全满足我国各领域对其关键部件优质、高效焊接制造的需求。哈尔滨焊接研究所在激光-电弧复合焊接研究的基础上，充分利用CMT弧焊特点，提出了纯Ar保护激光-CMT电弧复合焊接新方法，并研究了该方法在我国核电、航空、航天等领域关键部件优质、高效焊接制造的应用可行性。在不锈钢纯Ar保护激光-CMT复合焊接研究中发现，激光对电弧具有吸引作用，有利于增强焊接电弧挺度，提高焊接过程稳定性；与CMT弧焊相比，在高速焊接条件下，复合焊接可以获得连续成形的焊缝；与TIG焊接相比，复合焊接质量与TIG焊接相当。但前期研究发现，纯Ar保护不锈钢激光-CMT复合焊接焊缝边沿仍存在成形不规则及部分未熔合等现象。本论文在充分考虑激光扫描焊接特点的基础上，提出采用激光扫描-CMT电弧复合焊接方法以解决该问题。本论文针对304不锈钢，在纯Ar保护条件下，分析了激光扫描-CMT电弧复合焊接参数对焊缝成形的影响规律，研究了复合焊接电弧、熔池特点，探讨了复合焊接焊缝边沿铺展机理。在此基础上，与不锈钢厚板TIG填丝焊对比，从接头成形、综合力学性能及焊接效率等方面探讨了纯Ar保护激光扫描-CMT复合热源焊接取代TIG填丝焊的可行性。研究结果表明：采用激光扫描-CMT复合焊接技术可有效解决纯Ar保护不锈钢焊缝边沿成形不规则、部分未熔合等问题。激光在电弧前扫描，延长了熔池边沿液态金属的凝固时间，有利于熔池金属向焊缝边沿铺展，最终获得成形规则、稳定的焊缝。激光扫描-CMT复合焊接时，光丝间距、焊接速度、焊接电流对焊缝成形（熔深、熔宽、余高）的影响规律与非激光扫描焊接时基本一致；仅当激光扫描焊接熔池宽度与CMT焊接熔池宽度良好匹配时，才可获得成形良好的焊缝；当焊接速度v=0.6m/min，焊接电流I=132A时，满足良好焊缝成形的激光扫描焊接熔池宽度与CMT焊接熔池宽度的比值为1.2左右；当焊接速度v=0.6m/min，焊接电流I=132A时，复合焊接焊缝边沿连续成形的最优工艺参数为：激光扫描功率达到2KW，激光扫描宽度W=9mm，激光扫描频率f≥52Hz。与CMT电弧焊接相比，激光扫描-CMT复合焊接过程稳定性提高，其复合焊接电弧亮度增强、熔滴过渡频率提高、短路时间和短路周期分布更集中；与激光不扫描深熔焊接对比，激光扫描-CMT复合焊接的焊接模式已转变为热导焊，有利于消除焊接气孔、降低热影响区的峰值温度。激光扫描-CMT复合焊接接头力学性能（包括冲击韧性、拉伸、弯曲、硬度）与TIG填丝焊相当，组织与TIG填丝焊相差不大；效率是TIG填丝焊的5倍以上。更多还原

【Abstract】 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.更多还原