GMAW电弧对Nd∶YAG激光传输的影响

针对脉冲过渡熔化极气体保护焊(gas metal arc welding,GMAW)电弧和短路过渡GMAW电弧,通过保持GMAW电弧正常态,Nd:YAG激光水平逐层、逐点扫描穿过脉冲电弧区域的试验方式,获得了Nd∶YAG激光穿过GMAW电弧后的激光折射和散射结果.试验发现,波长为1.064μm的Nd∶YAG激光穿过脉冲GMAW电弧激光光斑会略微变小,并且不同电弧区域对激光的影响能力基本相同;激光穿过短路GMAW电弧后激光光斑也会略微变小,不同电弧区域对激光的影响也基本相同.结果表明,GMAW电弧可以近似看作各项同性的激光传输介质,还可以近似认为GMAW电弧对波长1.064μm的Nd:YAG激光是透明的.     

GMAW脉冲电弧对Nd:YAG激光能量的吸收

揭示了激光-电弧复合热源焊接过程中GMAW电弧对Nd∶YAG激光的吸收作用,对深入分析激光和电弧的耦合机制具有重要意义.通过保持脉冲GMAW电弧正常态,Nd∶YAG激光水平逐层、逐点扫描穿过脉冲电弧区域的试验方式,获得了Nd∶YAG激光穿过脉冲GMAW电弧后的能量损失情况.结果表明,波长为1.064μm的Nd∶YAG激光穿过保护气成分为Ar/CO2=80/20的脉冲GMAW电弧的任何区域都几乎不损失能量,波长为1.064μm的Nd∶YAG激光穿过不同电流强度的脉冲GMAW电弧也几乎不损失能量.     

GMAW电弧对激光传输影响的综合分析

针对Nd:YAG激光穿过GMAW电弧后,激光光斑会变小的现象,分别从GMAW电弧对Nd:YAG激光的吸收和折射两个角度进行了分析.结果表明,假设Nd:YAG激光状态改变全部由于GMAW电弧吸收现象造成时,脉冲GMAW电弧的吸收率为0.7%,短路GMAW电弧的吸收率为2.0%;假设Nd:YAG激光状态改变全部由于GMAW...     

Numerical analysis of temperature profile and weld dimensions in laser ＋ GMAW hybrid welding of aluminum alloy T-joint

The temperature fields in the transient state and weld dimensions in laser ＋ gas metal arc welding （GMAW） hybrid welding of aluminum alloy T-joint for different welding conditions were calculated using the developed heat source model, and the effect of welding speed on them was analyzed. The results show that the temperature field for the first weld pass only shows the feature of GMAW and the one for the second weld pass has the characteristics of both laser welding and GMAW. Welding speed can affect greatly weld dimensions and temperature distribution. When welding speed reaches 3.5 m/min, the fusion zones of two weld passes are separated and the maximum peak temperature of thermal cycle on the workpiece surface decreases largely.     

Effects of welding voltage on process stability in hyperbaric gas metal arc welding

Based on hyperbaric gas metal arc welding （GMAW） experiments at ambient pressure of 0. 8 MPa, the process stability of different welding voltages was studied. The experiments were carried out with a high speed camera system including infrared laser backlight and electric signal acquisition system. Keeping wire feed speed at 8 m/min, arc length increases linearly with the increase of welding voltage in O. 8 MPa argon environment. Under this condition, all the metal transfer modes are droplet repelled transfer and the transfer frequency increases with increasing welding voltage. The number of deviating spatter is less with relatively high welding voltage. The results of electric signal waveforms show that the probabilities of short circuit and arc interruption decrease firstly and then increase with increasing welding voltage. When the welding voltage is 37 V, the hyperbaric welding process is the most stable with no probability of short circuit and arc interruption.     

Effect of laser characteristics on the weld shape and properties of penetration laser weld of BT20 titanium alloy

The laser beam welding of BT20 titanium alloy was conducted to investigate the weld shape, microstructures and properties. The full penetration weld characteristics produced by CO2 laser and by YAG laser were compared. The results show that the full penetration weld of YAG laser welding closes to “X” shape, and weld of CO2 laser welding is “nail-head” shape.Those result from special heating mode of laser deep penetration welding. The tension strength of CO2 laser and YAG laser joints equal to that of the base metal, but the former has better ductility. All welds consist mainly of the acicular a phase and a few β phase in microstructure. The dendritic crystal of CO2 laser weld is a littlefiner than YAG laser weld. According theresearch CO2 laser is better than YAG laser for welding of BT20 titanium alloy.     

Welding characteristics in different laser-TIG hybrid manners

An experiment for determining the laser-TIG hybrid welding characteristics was carried oat in three kinds of hybrid methods: CO2 laser-TIG coaxial hybrid, CO2 laser-TIG paraxial hybrid and Nd: YAG laser-TIG paraxial hybrid. The experimental results indicate that hybrid welding has two welding mechanisms in CO2 laser-TIG hybrid welding: deep penetration welding and heat conduction welding. As the effect of the laser-induced keyhole, the arc root is condensed, the current density and penetration depth increase significantly, the welding characteristic is apt to deep penetration welding.When current increases to some degree, the keyhole induced by laser disappears, which produces a shallow penetration and wide bead. The weld exhibits heat conduction welding characteristics. Furthermore, the arc images and weld bead crosssections of three kinds of hybrid manners were also compared and analyzed at different welding currents, which established the foundation for understanding the welding characteristics of laser-TIG hybrid welding comprehensively.     

Metal transfer characteristics of tandem narrow gap GMAW for flat welding position

A series of experiments of tandem narrow gap GMAW for flat welding position were carried out. The arc behavior and metal transfer process were observed by a high-speed photography system. The effects of the welding parameters on the metal transfer were investigated. The results show that the arc behavior and metal transfer process of tandem narrow gap GMAW are different from these of bead-on-plate tandem GMAW. The arc behavior and metal transfer process are influenced by the distance between the two wires, the peak voltage, the pulse frequency and the peak time. With the increase of the distance between the two wires, the metal transfer mode gradually transforms from one pulse-multi droplets into one pulse-one droplet, and the average welding current increases. With the increase of the peak voltage, pulse frequency or peak time, the metal transfer mode transforms from one pulse-one droplet into one pulse-multi droplets, and the arc tends to occur between the wire and the sidewall.     

Determining the boundaries of globular-to-spray transfer in robotic GMAW

Robotic gas metal arc welding （GMAW） experiments were conducted using an ERTOS-1 electrode with Ar ＋ 10% CO2 shielding gas, and the welding current and arc voltage signals were collected by a data acquisition system. The boundaries between globular transfer and spray transfer in terms of the welding current and arc voltage were determined according to the waveform of electric signals and the Fourier transform results of arc voltage. The optimum welding parameters for the two transfer modes were obtained, which laid a foundation for the numerical simulation and control of GMAW process.     

Hybrid Laser-GMAW Welding of High Strength Quenched-Tempered Steels

High-strength quenched and tempered (HSQT) steels have been widely used in structural applications where light weight is of primary design interest.Gas metal arc welding is a common way to join QT steels.When GMAW is used to join the HSQT steel,multi-pass is usually required to achieve full penetration.In addition,weld crack is often observed because of HSQT steel’s high susceptibility to hydrogen embrittlement.In addition,due to the large amount of heat input from the arc,the heat affected zone is often softened.This reduces the ductility and strength of welds and makes the weld weaker than the base metal.In this study,a hybrid laser/GMAW process is proposed to produce butt joint for 6.5mm thick HSQT A514 steel plate.Hydrogen diffusion mechanism is first discusses for GMAW and hybrid laser-GMAW welding processes.Metal transfer mode during the hybrid laser/GMAW welding process is also analyzed.A high speed CCD camera with 4000 frame/second is used to monitor the welding process in real time.Welds obtained by GMAW and hybrid laser/GMAW techniques are compared and tested by static lap shear and dynamic impact.Effects of gap between two metal plates and laser beam/GMAW torch spacing on weld property are studied.By appropriately choosing these two parameters,crack-free butt joints with full penetration can be successfully obtained by the hybrid laser/GMAW welding process for HSQT A514 steel plate.     

Nd:YAG激光+脉冲GMAW复合热源焊接参数对焊缝熔宽的影响

通过试验研究了Nd:YAG激光 脉冲GMAW复合热源焊接过程中焊接工艺参数对焊缝熔宽的影响.结果表明,复合热源焊缝熔宽随电弧功率和激光功率的增大而增大,随焊接速度的提高而减小,而光丝间距和离焦量对复合热源焊缝熔宽影响相对较小.复合热源焊缝熔宽远大于激光焊缝熔宽而仅稍大于脉冲GMAW焊缝熔宽,说明在复合热源焊接过程中脉冲GMAW决定焊缝熔宽,这主要是由于激光束加热区域远小于电弧加热区域造成的.试验结果的分析比较还表明,在激光 电弧复合热源焊接过程中激光功率的增大还极大地提高了焊接速度.     

Nd:YAG激光+CMT电弧复合热源横焊工艺参数对焊缝形貌的影响

以304不锈钢为对象,借助横焊焊缝横断面图像来分析Nd:YAG激光+CMT电弧复合热源横焊焊缝横断面的成形特征,研究了Nd:YAG激光+CMT电弧复合热源横焊过程中焊接工艺参数对焊缝横断面形貌的影响.结果表明,在Nd:YAG激光+CMT电弧复合热源横焊中,焊接工艺参数对横焊焊缝横断面形貌的影响显著;Nd:YAG激光加入CMT电弧焊中明显提高了复合焊缝以及复合焊中CMT焊缝的熔深;采取适当的焊接工艺参数(小的光丝间距、大的激光功率、小的焊接速度、适合的离焦量以及小的或大的CMT功率)可以避免熔池机械式叠加和焊缝横断面错位现象,使得焊缝成形良好.     

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.     

Nd:YAG激光+脉冲MAG电弧复合热源规范参数对平板堆焊焊缝表面成形的影响

利用余高-熔宽比表示焊缝表面铺展性并与焊缝余高一起作为参数来评价复合热源平板堆焊焊缝的表面成形,通过试验研究了Nd：YAG激光＋脉冲MAG复合热源堆焊过程中焊接规范参数对复合热源平板堆焊焊缝表面成形的影响并分析了激光对复合热源堆焊焊缝表面成形的影响.研究结果表明,在电弧功率变化过程中,随着激光功率的增大,其对平板堆焊焊缝表面成形的影响也逐渐增大;焊接速度变化过程中,激光束能量的加入不仅改善堆焊焊缝表面成形还极大地提高了焊接速度;而在光丝间距和离焦量变化过程中,激光束对复合热源平板堆焊焊缝表面成形的影响很小.     

激光能量对Nd:YAG激光-短路MAG复合热源焊接过程的影响

针对低碳钢材料,通过改变加入的激光功率来研究激光能量因素对激光-短路MAG复合热源焊接过程稳定性和焊缝成形的综合影响.结果表明,对于特定条件下的激光-短路MAG复合热源焊接过程稳定性,存在最佳的激光功率范围,并不是加入的激光功率越大,焊接过程越稳定;从激光-短路MAG复合热源焊缝成形和焊接过程稳定性角度,按照加入的激光能量大小,可以把激光-短路MAG复合热源分为小功率激光能量稳定电弧阶段、过渡阶段和大功率激光能量增加熔深阶段.并针对各个阶段,从熔滴受力角度分析了激光能量因素对焊接过程的影响机制.     

激光-短路MAG复合热源焊接过程稳定性的影响因素

以低碳钢为研究对象,通过焊接电弧分析仪,对比研究了激光-短路MAG电弧复合热源焊接过程中焊接速度、激光与电弧的相对位置对焊接过程稳定性的影响规律.结果表明,随着焊接速度增加,MAG和激光-短路MAG复合热源焊接过程稳定性都会降低,但由于激光的引入,复合热源在高速焊接过程更稳定.与MAG相比,复合热源可以提高极限焊接速度1倍以上;复合热源焊接过程中,与激光在前引导焊接相比,电弧在前引导焊接过程稳定性更高.     

Nd:YAG激光+CMT复合热源电弧形态和熔池形貌

以304不锈钢为研究对象,借助高速摄像记录了YAG激光+CMT复合热源焊接的电弧形态和熔池形貌,研究了不同激光功率和光丝间距下的YAG激光+CMT复合热源焊接的电弧形态和熔池彤貌,并与CMT焊接进行了比较,分析了YAG激光+CMT复合热源焊接的电弧形态和熔池形貌发生变化的机理.结果表明,在Nd:YAG激光+CMT复合热...     

Nd：YAG激光-脉冲MAG复合热源焊熔滴过渡分析

采用高速摄像技术拍摄熔滴形成、长大及脱落的过程,观测并分析激光加入对电弧焊熔滴过渡的影响.结果表明,发现激光改变了熔滴的空间飞行轨迹、过渡稳定性、熔滴过渡模式.并从熔滴受力角度建立了脉冲MAG焊接熔滴力学模型,分析了激光加入后熔滴受力状态的改变情况.分析发现复合激光后,脉冲MAG熔滴还受到额外两个力的作用,即激光小孔产...     

YAG激光与脉冲MIG复合焊接

研究了YAG(掺钕钇铝石榴石 ,Nd 3:Y3Al5O1 2 )激光与脉冲MIG电弧复合焊接铝合金的新工艺 ,设计制造了复合焊接机头 ,探讨了各种规范参数对焊缝成形的影响规律及激光与电弧的复合作用。结果表明 ,在比较宽的参数范围内YAG激光 -脉冲MIG复合焊接铝合金焊缝成形美观 ,无气孔等缺陷 ,熔深与激光单独焊比增加 4倍 ,与脉冲MIG焊接比增加 1倍以上 ,焊速显著提高 ,是一种理想的焊接工艺。