激光诱导电弧耦合热源的构建及绿色焊接技术应用

通过对激光脉冲作用期间和之后的等离子体行为以及激光"匙孔"行为进行研究,提出了激光诱导电弧耦合热源的放电机制。结果表明,激光"匙孔"和"匙孔"等离子体的形成是实现激光诱导电弧的重要条件,激光"匙孔"和电弧等离子体在激光脉冲作用消失之后均经历了一段时间才逐渐恢复至激光作用之前的状态,二者的延迟恢复相互促进,共同提高了激光诱导电弧的作用效果。在理论分析的指导下实现了镁合金的激光诱导电弧耦合热源高速高效优质焊接。     

工艺参数对304不锈钢脉冲Nd∶YAG激光/TIG电弧复合焊焊缝成形的影响

研究了304不锈钢脉冲Nd:YAG激光TIG电弧复合热源焊接工艺参数对焊缝成形的影响.结果表明,脉冲Nd:YAG激光/TIG电弧复合焊焊缝横截面面积大于单一激光焊焊缝横截面面积与单一TIG焊焊缝横截面面积之和,具有协同效应;激光功率增大时,复合焊焊缝熔深和熔宽均增大,复合焊焊缝横截面面积增大,复合热源热效率也增大;离焦...     

激光与电弧相互作用时的电弧形态及焊缝特征

激光与电弧的复合热源在焊接过程中，由于激光的压缩与引导作用，可以在焊接速度增加时，电弧仍然较稳定。在去掉激光同轴保护气流而只采用TIG的保护气体进行保护时，由于激光同轴气体的冲击、压缩和冷却作用的消失，等离子气体将会随着电流、激光功率的增加而增大，因而引起焊缝横截面的变化。通过调整激光与电弧的规范参数，并用CCD摄取各参数下的电弧图像以分析等离子体的长大情况，然后将得到的焊缝沿横截面剖开。通过对各种参数下等离子体图像和焊缝横截面之间的相互的关系进行分析，得到与常规情况下相比熔宽较宽而熔深较浅的焊缝的焊接参数。这种产生涂敷型焊缝的参数可用于高速表层涂覆。     

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%.     

钛合金T形结构激光-电弧复合焊接成形工艺

采用低功率激光诱导电弧复合热源对TC4钛合金进行T形结构件穿透焊接工艺试验。分析激光与电弧复合热源间距(D_(la))、冷填丝条件、热输入对T形件焊缝成形的影响规律,测试分析T形结构穿透焊接接头横截面形貌、微观组织、力学性能及断口形貌。结果表明,激光-电弧复合焊接方法可以实现钛合金T形结构正面及背面焊缝成形的精确控制。当D_(la)=2时使激光与电弧获得最佳的耦合效果,增强了复合热源的穿透能力,改善了焊缝背面成形;冷填丝的加入能够有效改善焊缝正面的咬边及烧穿问题;激光与电弧热输入的协调是实现焊缝正面熔宽控制的主要因素之一。     

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...     

热源间距对激光-电弧复合焊焊缝成形和组织的影响

采用CO2激光与MAG电弧进行旁轴复合焊接,研究了不同热源间距对焊缝形貌、熔宽及熔深的影响,分析了焊接顺序对不同热源间距时的焊缝形貌、深宽及微观组织的作用机理.研究表明:对于中碳高强钢,采用激光后置的复合焊接形式较好,电弧对焊接金属起到预热和微熔作用,提高了材料对激光的吸收率,增加熔深,热源间距为2mm时,熔深最大;而热源间距为4 mm和6 mm时,焊缝表面形貌较好,但激光前置时两热源的耦合效果较差;激光后置时的焊接接头显微组织均匀,微观缺陷少.     

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.     

激光/等离子电弧复合热源能量参数对钛合金焊缝成形的影响

在对钛合金激光/等离子电弧复合焊与单一激光焊的焊缝成形进行比较的基础上,研究了激光在复合等离子电弧后主要焊接工艺参数对焊缝成形的影响.结果表明,随激光功率增大和焊接速度降低,复合焊与单一激光焊焊缝的横截面形貌均由钉形向近X形转变.与单一激光焊相比,复合焊焊缝的余高和咬边较大.激光/等离子电弧"协同效应"随激光功率和焊接速度变化而不同,从而影响复合焊焊缝的熔宽和熔宽比.随焊接电流从零增大到60 A,焊缝熔宽略有增大,而焊缝熔宽比基本保持不变.     

背反射增效激光焊接熔池匙孔相变及流场分析

建立了背反射增效激光焊焊接熔池流动中气相区、液相区和固相区的统一模型，在模型中考虑了等离子体/蒸气云和小孔吸收机制，综合了表面张力、热浮力和重力的作用. 基于数值计算得到了熔池的三相匙孔相变以及流场，重点分析了表面张力对熔池流动和传热的影响. 此外，通过钛合金薄板的背反射增效激光焊接试验对模型进行了验证. 结果表明，匙孔引发等离子体/蒸气云与背面垫板诱发羽辉的耦合作用，是X形焊缝熔池形貌形成的主要原因；同时，表面张力是形成背反射增效激光焊接熔池内“椭圆回流环”的主要驱动力.     

Analysis of energy utilisation efficiency in laser–GTA hybrid welding process

The effect of welding parameters on energy utilisation efficiency in laser–gas tungsten arc (GTA) hybrid welding process is investigated. Then, optimum butt joints are made by laser welding, GTA welding and laser–GTA hybrid welding, and the energy consumption in each process is calculated and compared. Both plasma and keyhole behaviours are studied. Results indicate that the parameter Dla greatly affects the energy utilisation efficiency in hybrid welding. The reason is that Dla determines keyhole behaviour and laser induced plasma, and these determine the coupling discharge of laser induced and GTA plasmas. Compared with laser and GTA welding, hybrid welding is more energy efficient.     

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。     

电弧对激光吸收与散焦的定量测量

复合热源焊接过程中，激光与电弧之间相互作用的物理机制一直是复合热源焊接技术研究中的难点。激光形成的锁孔对电弧有吸引、压缩作用，由于激光穿过电弧时能量被电弧吸收和散焦，对锁孔的稳定形成有直接影响，因此研究激光穿过复合电弧时的吸收与传输特性对分析复合热源焊接机理、合理选择工艺参数有重要意义。文中设计一种新型试验方法，采用激光烧蚀有机玻璃的方法定量测量CO2激光穿过电弧时，电弧对激光的吸收与散焦特性，通过有机玻璃的烧蚀深度和烧蚀宽度反映激光能量的损耗，获得了不同焊接电流与电弧位置对激光能量的影响规律。     

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.     

Effect of laser parameters on arc behavior of laser-TIG double-side welding for aluminum alloy

The influence of laser parameters on arc behavior of laser-TIG double-side welding was investigated by utilizing CCD sensor and image processing methods. It was found that arc images had an obvious transformation from laser preheating to laser plasma ejected from the keyhole bottom, resulting in the phenomena of arc column convergence and arc root constriction. The attraction phenomenon of the laser and the arc is also found in laser-TIG double-side welding. More noteworthy is that the behavior of arc attraction or constriction became much obvious at a lower current or laser plasma ejected from the keyhole bottom. The decrease in arc voltage had a certain relation with the improvement of arc stability.     

Process and joint characterizations of laser-MIG hybrid welding of AZ31 magnesium alloy

High power laser-metal inert gas (MIG) hybrid welding of AZ31 Mg alloys was studied. Microstructure and fracture surface of welded joints were observed by optical microscope and scanning electron microscope. The mechanical properties of welded joints were evaluated by tensile test. Under the optimal welding parameters, the stable process and sound joints were obtained. The tensile strength efficiency of welded joints recovered 84-98% of the substrate. It was found that the arc was compressed and stabilized by the laser beam during the hybrid welding. The compressed extent of arc column increased with laser power, and the process stability could be improved by increasing laser power and arc current or slowing welding speed. The arc stabilized mechanism in laser-MIG hybrid welding of Mg alloys was summarized in two factors. First, the laser keyhole fixes the arc root and improves the igniting ability of the arc. Second, the electromagnetic force is downward and increased by the laser-arc interaction, which prevents the overheating of the droplet and smoothes droplet transfer from the wire to the weld pool.     

Characteristic of laser-MIG hybrid welding with filling additional cold wire for aluminum alloy

The weld appearance,deposition rate,welding efficiency,stability of arc,laser keyhole characteristic,and weld property were studied by using a novel laser-MIG hybrid welding process with filling wire of aluminum alloy. The results were also compared with those by conventional laser-MIG hybrid welding process. It was found that with the suitable process parameters this novel welding process for aluminum alloy was stable and final weld bead had fine appearance. Compared to conventional laser-MIG hybrid welding process,during this novel welding process the stability of arc,the laser keyhole characteristic and the weld property were similar,while the keyhole cycle frequency and keyhole opening area had differences of 1. 23% and 15. 34%,respectively,and the welding efficiency increased by about 31% without increasing heat input.     

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...     

铝合金变极性等离子弧穿孔焊过程控制

分析了铝合金变极性等离子弧穿孔立焊工艺特点,提出了通过对焊接参数的精确控制,实现变断面铝合金变极性等离子弧穿孔立焊工艺的方法,并将焊接电流、离子气流量和焊接速度确定为变断面铝合金变极性等离子弧穿孔立焊过程的被调节参数.保持穿孔熔池上"热"和"力"的动态平衡是调节焊接参数的根本依据,是实现变断面试件自动焊接的关键所在.采用单片机为核心的控制器对焊接参数进行实时调节,动态保持穿孔熔池上热和力平衡,实现了变断面铝合金变极性等离子弧穿孔立焊工艺.