Experimental study on welding characteristics of CO2 laser TIG hybrid welding process

Abstract

The experiments of CO₂ laser TIG paraxial hybrid welding with 4 mm thick AISI 321 stainless steel sheet have been performed. The arc images and welding characteristics have been investigated with different energy ratios between laser and arc. The experimental results indicate that the hybrid welding is similar to laser welding and has also two welding mechanisms: deep penetration welding and heat conduction welding. Because of the effect of keyhole induced by laser, the arc root can be stabilised and compressed, and the current density and the penetration depth are all increased significantly, which show the characteristics of deep penetration welding. However, when the current is increased to a critical value, the laser induced keyhole disappears and the arc expands obviously, which decreases the penetration depth, so that the welding mechanism has been changed from deep penetration welding to heat conduction welding. Furthermore, the effects of distance between laser beam and electrode, pulsed laser and hybrid manners on hybrid welding characteristics have also been studied.     

CO_2激光焊接的同轴检测与熔透控制I.熔透状态特性及其同轴检测

对激光深熔焊的熔透状态进行了分类 ,指出了“仅熔池透”和“适度熔透”的形成条件和焊缝成形特征。建立了一套CO2 激光深熔焊熔透状态的同轴检测系统 ,研究了焊接工艺参数和熔透状态发生变化时等离子体同轴光信号的变化规律。发现在板厚不变的条件下 ,随热输入的变化 ,焊接过程由“仅熔池透”达到“适度熔透”时 ,同轴等离子体光信号强度的增量绝对值最大。     

电场提高激光-TIG复合焊熔深的机制

通过对比电场对单激光和单TIG焊接电弧在镁合金板材上堆焊熔深的影响,分析了外加电场对激光-TIG复合焊熔深的影响机制.同时通过研究在不同激光功率、不同TIG电流强度下电场的作用效果,对该机制进行了验证.结果表明,外加电场对激光-TIG复合焊熔深的作用是通过对激光小孔内等离子中带电粒子运动的控制来实现的.外加电场使小孔内电子向小孔底部运动时,可以增加焊接熔深;激光功率越大,外加电场增加熔深效果越明显;增大TIG焊接电流,削弱外加电场对熔深的增加作用.     

Microstructure and mechanical properties of wrought magnesium alloy AZ31B welded by laser-TIG hybrid

The laser-TIG hybrid welding was mainly used to weld the wrought magnesium alloy AZ31B. The tech-nical characteristics of laser-TIG hybrid welding process was investigated and the interactional mechanism between laser and arc was discussed, at the same time the microstructure and mechanical properties of the wrought magnesi-um alloy AZ31B using laser-TIG hybrid welding were analyzed by optical microscope, EPMA, SEM, tensile ma-chine, hardness machine. The experimental results show that the presence of laser beam boosts up the stability of the arc during high speed welding and augments the penetration of weld； the crystal grains of magnesium alloy weld are fine without porosity and cracks in the best welding criterion and the microstructure of HAZ does not become coarse obviously. The elements profile analysis reveals that Mg content in the weld is lower than that of the base metal, but Al content is higher slightly. Under this experimental condition, the wrought magnesium alloy AZ31B joint can be achieved using laser-TIG hybrid process and the tensile strength of the joint is equivalent to that of the base metal.     

CO_2激光与TIG复合焊接铝合金

以铝合金2A12为主要研究对象,研究CO2激光与TIG复合热源焊接铝合金的工艺特点,设计制造了双焦点激光-电弧复合焊接头,讨论了影响复合焊接的各工艺参数。结果表明:影响复合焊接过程的主要工艺参数有激光功率、焊接速度、焊接电流、激光焦点位置以及两热源之间的距离等,并且在比较宽的参数范围内CO2激光与TIG复合焊接铝合金焊缝成形美观、无气孔等缺陷,焊速显著提高,是一种理想的焊接工艺。     

Correlation between laser-wire distance and Nd：YAG laser ＋ P-GMA hybrid welding heat input parameters

In laser+P-GMA hybrid welding,laser-wire distance is an important parameter to describe the distance from laser spot to the center of the pulsed gas metal arc.The experiments results show that the optimal laser-wire distance with the deepest weld penetration increases with welding current and laser power being increased and decreases with welding speed being increased.Welding current,laser power and welding speed determine the hybrid welding heat input in laser+arc hybrid welding process,so there is a correlation between the optimal laser-wire distance and the hybrid heat input welding parameters for the deepest weld penetration: the optimal laser-wire distance increases with the heat input being increased.The positive correlation between the optimal laser-wire distance and the hybrid welding heat input is induced by the characteristics of the limited influence of P-GMA welding process on laser transmission and the dependence of weld penetration of hybrid welding on laser power.     

铝合金交流脉冲双面弧焊工艺试验及特点分析

通过工艺试验,详细分析了LYl2CZ铝合金板交流脉冲等离子弧（PA）-钨极氩弧（GTA）双面弧焊（DSAW）的工艺特点。通过与常规钨极氩弧焊和等离子弧焊工艺比较,发现该工艺可以显著增加熔深,减小焊后热变形,提高焊接生产效率。分别采用多孔喷嘴和单孔喷嘴进行了对比试验,其中采用多孔喷嘴能够有效防止双弧的产生,采用单孔喷嘴能够获得较大熔深。当采用小孔型交流脉冲双面弧焊工艺焊接铝合金时,由于小孔的存在,焊接过程中阴极雾化效果降低,影响焊缝成形及质量。     

铝合金激光-小功率脉冲MIG电弧复合热源焊接特性分析

针对5A06铝合金,通过一系列对比数据综合分析了MIG焊和激光MIG复合热源焊接技术在焊缝熔深、焊缝成形、焊接速度、焊接热输入等方面的优缺点.结果表明,在MIG平均电流小于200 A的小功率脉冲MIG电弧区域内,等热输入且等焊接速度条件下,激光-MIG复合热源焊接技术与MIG相比可以提高焊缝深宽比1～2倍,增加焊缝熔深0.43～2.5倍;等热输入且等平均焊接电流条件下,与MIG相比,激光MIG复合热源焊接技术可以提高焊接速度0.6～1.5倍,增加焊缝熔深0.5～5.9倍;激光MIG复合热源焊接技术可以用高于MIG焊0.6～6.5倍的焊接速度和更小的焊接热输入获得与MIG同样的焊缝熔深;与MIG焊相比,激光MIG复合热源焊缝的铺展性更好,更适合于高速焊接;MIG复合2 kW的激光能量后会增加平均电弧电压、减小平均电流.     

铝合金激光-MIG复合填丝焊稳定性分析

通过与铝合金激光-MIG复合焊方法相对比,主要研究了铝合金激光-MIG复合填丝焊的焊缝成形、熔深稳定性、余高稳定性、焊缝气孔率、激光匙孔特征、等离子体特征. 试验结果表明,在合适的工艺参数条件下,铝合金激光-MIG复合填丝焊焊接过程稳定,焊缝成形良好,额外填入的焊丝可以连续稳定地过渡到熔池中,激光匙孔具有明显的形成、长大、湮灭周期性变化特征;相同工艺参数条件下,铝合金激光-MIG复合填丝焊的焊缝熔深稳定性、余高稳定性与激光-MIG复合焊相当,激光匙孔开口面积约增加15.34%,等离子体+电弧总面积约增加1.95%.     

CO2激光焊接的同轴检测与熔透控制I.熔透状态特性及其同轴检测

对激光深熔焊的熔透状态进行了分类,指出了“仅熔池透”和“适度熔透”的形成条件和焊缝成形特征。建立了一套CO2激光深熔焊熔透状态的同轴检测系统,研究了焊接工艺参数和熔透状态发生变化时等离子体同轴光信号的变化规律。发现在板厚不变的条件下,随热输入的变化,焊接过程由“仅熔池透”达到“适度熔透”时,同轴等离子体光信号强度的增量绝对值最大。     

铝合金激光-多股绞合焊丝MIG复合焊特性分析

选用多股绞合焊丝替代传统焊丝,将激光热源与多股绞合焊丝MIG焊热源相匹配.借助高速摄像系统,提取焊接过程中熔池和匙孔特征量,开展5A06铝合金激光-多股绞合焊丝MIG复合焊工艺特性研究,探讨了不同工艺参数下焊缝成形与熔池行为相关性及焊接气孔规律性研究.结果表明,主要焊接工艺参数对焊缝成形的影响规律与常规焊丝激光-电弧复...     

电弧弧长对激光-电弧复合焊飞溅和底部驼峰的影响

由于热源形式的特殊性,激光-电弧复合焊接过程中激光和电弧间易发生相互干扰,产生飞溅和底部驼峰等缺陷。以590 MPa级船用高强钢为研究对象,研究了电弧弧长对激光-电弧复合焊飞溅和焊缝底部驼峰的影响。为了深入研究激光-电弧复合焊飞溅和底部驼峰的产生机理,利用高速摄像设备对熔滴过渡行为和焊缝底部熔池进行了观察。结果表明,适当缩短电弧弧长可以降低激光和电弧间的相互干扰,提高复合焊接过程的稳定性,进而降低飞溅产生的倾向。底部驼峰是小孔熔透性差和底部熔池流动不连续所引起的。缩短电弧弧长可以对底部驼峰的产生起到抑制作用,这是因为缩短电弧弧长可以降低等离子体对激光的吸收,提高激光的能量利用率,增加小孔熔透性和稳定性。 创新点： 研究了电弧弧长对激光-电弧复合焊飞溅和底部驼峰的影响,采用高速摄像方法对底部熔池流动进行了观察,进一步明确了激光-电弧复合焊接焊缝底部驼峰的产生原因。     

Novel hybrid method： pulse CO2 laser-TIG hybrid welding by coordinated control

0IntroductionRecently,laser-arc hybrid welding,as a rising spe-cial manufacture technology,has attracted more and moreinterest and attentions of some researchers and weldingcompanies.But,concerning laser-TIG hybrid welding,most of the research in this area mainly focused on contin-uous wave laser-TIG arc hybrid welding[1-3].In previousworks,because of the absorption and defocusing of laserenergy by hybrid arc plasma,the energy loss of laser wasvery serious when laser traversed arc in continu…     

铝合金双光束/单光束激光-TIG复合焊

针对4mm厚5A06铝合金,分析了双光束光纤激光-TIG复合焊的焊缝成形特点、气孔率、匙孔动态特征及接头力学性能,并与单光束光纤激光-TIG复合焊对比。结果表明,在获得相同焊缝背面熔宽条件下,与单光束激光-TIG复合焊相比,双光束激光-TIG复合焊的焊缝背面成型连续性、均匀性更优且熔宽波动较小,焊缝气孔率降低50%以上,激光匙孔开口面积平均值更大,波动变异系数更小;双光束激光-TIG复合焊接头抗拉强度、断后伸长率、显微硬度、组织与单光束激光-TIG复合焊结果差别不大。     

高强铝合金VPPA-MIG复合焊接焊缝成形机理

VPPA-MIG复合焊集VPPA穿透力强和MIG焊熔敷效率高的优点,弥补了单VPPA焊工艺区间窄且需立焊和MIG焊熔深浅的不足. 使用Red Lake Y4高速摄像获取6 mm厚2A12铝合金VPPA-MIG复合焊接熔池图像,建立了熔池受力模型. 对比分析了复合热源不同能量配比对焊缝成形和熔池形貌的影响及VPPA-MIG与单MIG焊缝成形特点. 结果表明,VPPA-MIG复合热源相比单VPPA热源易保持焊缝成形稳定性. VPPA电流接近穿孔阈值时,配合较低功率MIG热源可以获得6 mm厚2A12铝合金良好焊缝成形;VPPA能量比例过低时,小孔较浅,熔化效率较低,不能起到增加熔深的作用;VPPA能量比例过大,易使熔池失稳,焊缝成形不良. 热源输入功率相同时,VPPA-MIG复合焊比MIG焊显著增加焊缝熔深和深宽比,提高生产效率.     

Hybrid laser-arc welding of advanced high-strength steel

This study investigated the synergetic effect between laser beam and electrical arc during hybrid welding by using a spectral diagnostic technique. The synergetic effect increased the energy density in the keyhole and deepened the weld penetration, resulting in a lower plasma electron temperature. The metal transfer mode was a globular one at a small offset distance while a spray mode was achieved with an increase in the offset distance. The decrease in the arc voltage and arc current due to the synergetic effect caused this transition from spray to globular modes. Globular transfer mode destabilized the molten pool and keyhole with the large droplet impingement, leading to the formation of porosity in the corresponding weld bead. The presence of porosity was on-line detected by identifying serious fluctuations in the Fe I electron temperature signals based on the fact that the instability of the molten pool and keyhole is strongly related to the signals coming from the plasma.     

Effect of relative location of laser beam and TIG arc in different hybrid welding modes

Abstract

The laser leading hybrid welding mode [laser tungsten inert gas (laser-TIG)] and TIG leading hybrid welding mode (TIG-laser) were utilised in the magnesium alloy welding process. The effects of TIG arc current and the distance between laser beam and TIG electrode (Dla) on penetration depth and melting efficiency in different hybrid welding modes were investigated. Results reveal that there is a decided difference in variation trend of penetration depth with Dla in different welding modes. The penetration depth increases first and then decreases with the Dla increasing from 1 to 7 mm in TIG-laser hybrid welding mode while the penetration depth decreases monotonously with Dla in laser-TIG hybrid welding mode. The increase percentage of melting efficiency remains at ～20% in laser-TIG hybrid welding mode while the increase percentage fluctuates acutely and achieves the maximal value (～53·14%) at the arc current of 120 A in TIG-laser hybrid welding mode.     

钛合金激光-TIG复合焊接保护状态对焊缝成形及性能影响

用激光-TIG复合热源对2.5 mm厚TA15钛合金进行对接焊试验.利用万能力学拉伸机、红外热成像仪、电子探针（EPMA）、扫描电镜（SEM）等分析手段对焊接接头进行测试分析,并与单TIG焊进行对比.分析焊接工艺参数和接头保护时间对焊接接头形貌和性能的影响.结果表明,实现2.5 mm厚钛合金全熔透焊接时,激光-TIG复合焊比单TIG焊速度更快、热输入更低,焊缝和热影响区更窄,晶粒更细;相同保护条件下,激光-TIG复合焊接头比单TIG焊接头具有更高的强度、塑性和更好的疲劳性能;激光-TIG复合焊缝冷却速率高于单TIG焊,获得良好的保护状态时所需保护时间更短.     

Keyhole formation and its characteristics in laser welding mode transition

Keyhole is the most important characteristic for laser deep penetration welding, and its formation indicates the beginning of laser deep penetration welding mode. The keyhole developing process was analyzed and the keyhole formation time was calculated according to welding speed and the length of weld bead formed in the keyhole formation process. The results showed that the keyhole forms in 40-70 ms at different rate of change of laser power. In laser deep penetration welding process, the variation of light intensity radiated by laser induced plasma can identify the keyhole formation, but it can not be used to estimate the keyhole formation time because of delay effect.     

Nd:YAG激光+CMT电弧复合热源横焊工艺参数对焊缝成形的影响

以304不锈钢为对象,借助焊缝成形参数来评价YAG激光+CMT电弧复合热源横焊焊缝的成形特征,研究了Nd:YAG激光+CMT复合热源横焊过程中焊接工艺参数对焊缝成形的影响.结果表明,在CMT电弧焊接中加入激光可以改善横焊焊缝成形;在激光能量和焊接电流一定时,光丝间距存在一个最佳匹配,使得Nd:YAG激光+CMT复合热源横焊焊缝成形良好;与其它复合热源焊接相对比激光功率对熔深影响较大,对横焊焊缝成形的影响程度与焊接电流有关;焊接速度对横焊焊缝成形影响显著;离焦量对横焊焊缝成形影响较小;电弧功率对横焊焊缝的偏离度影响显著.