万瓦级激光-电弧复合穿透焊接成形缺陷研究

为了研究万瓦级光纤激光-电弧复合穿透焊接时的焊缝成形规律与缺陷产生的过程,以20 mm厚Q235低碳钢为研究对象,采用平焊方法,对不同激光功率、焊接速度、焊接电流条件下的焊缝正背面成形特征进行研究,并利用高速摄像对焊接过程中背面熔池的流动变化、焊瘤及飞溅的产生过程进行了观察分析。结果表明,采用万瓦级激光-电弧复合焊进行穿透焊接时,单一通过改变激光功率、焊接速度或焊接电流难以获得良好的焊缝成形,焊缝易出现正面凹陷、背面焊瘤以及飞溅等缺陷。背面焊瘤及大量飞溅的产生是导致焊缝正面凹陷的重要原因,而不稳定的激光穿透导致熔融金属液体受到的金属蒸气反冲力波动较大,是导致背面形成焊瘤及飞溅的重要原因之一。     

粗丝高速MAG焊驼峰焊道形成机理分析

对粗丝((Φ)3.2)高速MAG焊驼峰焊道缺陷的形成机理进行了研究.采用高速摄像采集系统对焊接过程中的电弧形态和熔池流动状况进行了高速摄像,通过对试验所得图像的认真分析,重点研究了粗丝((Φ)3.2)高速MAG焊驼峰焊道缺陷的形成机理,提出了动态平衡点的观点,认为动态平衡点远离电弧是焊缝产生驼峰焊道缺陷的根本原因.任何促使动态平衡点移向电弧的因素都有利于抑制焊缝产生驼峰焊道缺陷;任何促使动态平衡点远离电弧的因素都有利于驼峰焊道缺陷的形成.同时利用上坡焊和下坡焊试验对驼峰焊道形成机理进行了焊接试验验证.     

高速TIG-MIG复合焊焊缝驼峰及咬边消除机理

搭建了TIG-MIG复合焊试验平台及电参数-高速图像同步采集系统,进行了一系列低碳钢高速TIG-MIG复合焊工艺试验,研究了高速TIG-MIG复合焊的电弧形态、熔滴过渡及熔池行为对焊缝成形的影响,并确定了合适的匹配参数.结果表明,MIG焊电流在240~300 A,且TIG焊电流与MIG焊电流相当时,TIG-MIG复合焊焊接过程稳定,即使在焊接速度高达2.5 m/min时,焊缝仍无驼峰、咬边等缺陷,与传统MIG焊相比,熔深增加,熔宽减小.TIG-MIG复合焊由于电弧间的相互作用,两电弧指向发生偏转,电弧压力减小,焊接过程不产生弧坑,且熔宽变窄,这是避免驼峰和咬边缺陷的主要原因.     

激光深熔TIG复合焊电弧特性及熔池行为的研究

对10 mm的Q345B板进行光纤激光与深熔TIG旁轴复合焊接实验,探究激光与电弧的最佳复合方式,利用高速摄像系统观测电弧形态和熔池行为的变化,并分析激光对电弧和熔池的影响机制。实验结果表明:焊枪垂直,激光倾斜30°的复合方式所得到的焊缝熔深最大。复合焊接利用激光增强熔池金属流动的特性弥补了深熔TIG高速焊接焊缝无法成型的缺陷。     

激光-电弧复合热源焊接钛合金薄板T形结构件

采用低功率激光-电弧复合热源工艺进行钛合金薄板T形结构件的焊接,焊后采用光学显微镜、X射线衍射仪等设备对接头进行分析.结果表明,激光-电弧复合热源焊接过程中激光可以诱导增强电弧、提高电弧穿透能力,采用激光-电弧复合热源易于进行T形结构件的连接;焊缝形成均匀细密鱼鳞纹,接头背面熔透均匀、过渡平缓,焊缝宽度小;焊缝主要由α＇相和β相组成,焊接时脉冲激光和TIG脉冲电流对熔池的搅拌作用及金属蒸气和等离子体喷射对熔池的搅拌作用使得细小α＇针疏松散乱;Al元素和Mn元素含量稳定,没有发生成分偏析.     

立向高速GMAW驼峰焊缝形成机理及抑制措施

文中运用自主研发的爬壁机器人焊接试验平台对立向高速熔化极气体保护焊(GMAW)驼峰焊缝进行试验研究。研究发现，立向上焊时，当焊接电流保持不变，焊接速度增加到某一临界值时，立向GMAW会产生驼峰焊缝缺陷。通过高速摄像可知，熔池中由电弧压力、熔滴冲击力和重力作用下产生动量很大的后向液体流是立向高速GMAW形成驼峰焊缝的主要原因；立向下焊时，因焊接方向和焊枪倾斜位置发生改变，熔池中由电弧压力和熔滴冲击力作用下产生的后向液体流流向与自身重力方向相反，使后向液体流的动量减小，可有效抑制驼峰焊缝的形成。试验表明，采用立向下焊工艺时，当焊接电流为200 A、焊接速度为2.4 m/min时，GMAW仍无驼峰焊缝产生，焊接效率大大提高。     

TIG-MIG复合焊电弧分析及计算模拟

采用高速摄像系统对TIG-MIG复合焊系统的起弧和稳弧过程进行观察。用帕邢定律分析在有MIG焊电弧提供的导电通道情况下TIG焊电弧击穿的路径,确定了双电弧复合焊时的起弧过程,并用Fluent软件对双电弧系统不同起弧路径下的工件温度场进行模拟。研究发现,当电极间距小于8.5 mm时,TIG焊在MIG焊引弧后,2个熔池可形成一共同熔池;而间距为10 mm时引弧后2个熔池形成"8"字形;间距为12 mm时,2个电弧中间有一低温区,呈分离态。根据模拟结果制备的焊接接头最大抗拉强度为518 MPa。     

中厚板对接MAG-TIG双电弧打底焊研究

研究了MAG-TIG双电弧复合热源中厚钢板自由成形打底焊接工艺,采用高速摄像机采集焊接过程中的电弧形态和熔池流动行为,焊后采用光学显微镜、万能力学性能测试仪等设备对接头进行测试分析。结果表明:与单独脉冲MAG焊相比,MAG-TIG双电弧复合热源打底焊接工艺熔透均匀,且正、反面自由成形连续、稳定;TIG电弧的存在对MAG电弧产生电磁排斥力,使MAG电弧稳定作用于熔池前端;拉伸测试获得的平均拉伸强度为466 MPa,断裂均发生在远离焊缝和热影响区的母材;通过调整TIG电弧的作用位置和电流大小,可以控制MAG电弧加热位置,以及焊接熔池上方热输入的分配,实现了MAG-TIG复合焊接熔池流动行为的调控。     

耦合电弧钨极GPCA-TIG焊工艺

将耦合电弧钨极和GPCA焊方法结合,形成了耦合电弧钨极GPCA-TIG焊方法,该方法可实现深熔深高速度焊接.对比分析了在较高焊接速度时常规TIG焊、耦合电弧钨极TIG焊和耦合电弧钨极GPCA-TIG焊的焊缝表面成形和截面形貌,发现耦合电弧钨极GPCA-TIG焊可避免咬边和驼峰焊道的产生,并且焊缝熔深有所增加.耦合电弧钨极GPCA-TIG焊工艺试验表明,焊缝熔深和熔宽随焊接速度的减小和外喷嘴位置的升高而增大,随着弧长和外层氧气流量的增加先增加后略有减小;随着焊接速度的减小,弧长和外层氧气流量的增大,焊缝咬边减轻,外喷嘴相对高度变化时焊缝均未出现咬边.     

超高功率激光-电弧复合焊接特性分析

为了对超高功率激光-电弧复合焊接过程特性有深入的理解. 借助高速摄像,以焊接过程中羽辉和飞溅为主要研究对象,对比分析了激光功率从5 kW增加到30 kW时,激光热源与不同电弧热源复合,以及是否填丝对焊接特性的影响规律. 结果表明,激光功率增加,羽辉和飞溅面积的均值都呈增加趋势,两者的波动程度也呈上升趋势;冷丝的添加在降低焊缝熔深的同时使激光-MAG复合焊接过程中的稳定性变差;激光-TIG复合填丝焊接过程的稳定性明显优于另外两种焊接形式;高功率激光复合焊接时,高温羽辉对激光的散射和吸收作用会使熔深增加趋势放缓.     

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.     

焊丝熔化方式对激光焊接过程的影响

研究了两种焊丝熔化方法(电弧预熔丝激光焊、激光填丝焊)激光焊接过程对匙孔稳定性以及焊缝成形的影响，进一步研究了焊丝熔化方法对焊接接头质量的影响，并对比分析了两种焊丝熔化方式对焊接速度的适应性. 结果表明，电弧预熔丝激光焊过程中，熔池表面匙孔开口尺寸变化不大，匙孔较为稳定；激光填丝焊方法由于熔化的液态金属距离匙孔边缘很近，焊接过程中熔池表面匙孔开口尺寸变化较大,而且容易出现熔池表面匙孔的闭合. 与激光填丝焊相比，电弧预熔丝激光焊熔化的焊丝端部可以沿熔池边缘流入，与匙孔边缘的距离较远，匙孔稳定性较好，焊缝气孔数量较少. 当焊接速度为8 m/min时，电弧预熔丝激光焊的焊缝成形良好；而激光填丝焊焊缝背面成形不连续，并且出现了未焊透的缺陷.     

脉冲激光-电弧复合焊接镁合金过程中熔池行为与气孔产生的关系研究

激光-电弧复合焊接镁合金过程中气孔是一种重要缺陷。本文针对复合热源焊接过程中熔池行为和激光匙孔引起的气孔之间的关系进行了实验研究。研究中重点考查了激光脉冲对熔池的冲击作用，匙孔的动态行为以及气孔的形成规律。研究结果表明激光脉冲的参数决定其对液态熔池的冲击作用，较强的激光脉冲作用可以有效抑制气孔的形成；液态金属的行为主要有匙孔行为主导；匙孔的尺寸和开-闭状态直接影响焊后气孔的形成；过高的激光脉冲功率会导致焊后气孔的形成；匙孔开口维持时间越长，焊后气孔数量越少。     

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.     

10kW光纤激光焊接缺陷的形成

研究了未熔透光纤激光焊接过程中工艺参数对小孔型气孔、热裂纹和飞溅的影响,并讨论焊接缺陷形成机理. 结果表明,随着光纤激光焊接速度的增加,焊缝气孔和热裂纹倾向降低. 当焦点位置在工件表面时,气孔倾向最大;而当焦点位置由入焦向离焦偏移时,热裂纹敏感性增加. 光纤激光焊接气孔是由小孔不稳定引起的,而小孔不稳定性同时引起了熔池后部凝固前沿形状的变化,提高了焊缝热裂纹的敏感性. 较慢速光纤激光焊接飞溅的形成主要在于小孔开口处前沿熔池的凸起,其程度可能与小孔的稳定性有关.     

Detecting and tracking of welding line in visual plasma robotic welding

The formation of stable back beads in joining of the thick materials is important in order to achieve high-quality welded metal joints. Plasma welding uses the high welding current density, which is suitable for thick materials. The keyhole in the plasma welding depends on the pilot gas and the welding current. The voltage behaviour depends on the keyhole situation. If the torch is moved away from the welding line in conventional GMA welding, the welding voltage and the welding current are changed due to variations of the arc length. But the welding voltage does not change with the arc length in plasma welding, because the welding voltage depends on the situation of the keyhole. The authors tried to observe the weld pool on the top side by using a CCD camera. The timing of the shutter in the CCD camera is investigated to take clear images of the weld pool. As a result, the clear images of the weld pool were taken when the welding current was reduced to 30 A and an interference filter of 950 nm was attached to the CCD camera. The weld pool shape was changed with the torch position in the groove. The image-processing method was developed to detect the top of the weld pool. The torch position was estimated by processing the weld pool images. The digital control was designed to trace the welding line. The performance of the controller was verified by carrying out tracking experiments.     

低功率YAG激光-MAG电弧复合焊接不锈钢

以0Cr18Ni9Ti不锈钢钢板为试验材料,研究了低功率脉冲YAG激光-脉冲MAG电弧复合热源和单脉冲MAG焊接不锈钢.结果表明,低功率脉冲YAG激光-脉冲MAG电弧复合热源同样具有大功率激光-电弧复合焊接才有的增加熔深、提高焊接速度、稳定焊接过程等优点;低功率脉冲YAG激光的加入改变了电弧形态,电弧根部被吸引和压缩现象显著,提高了能量利用率;与单脉冲MAG堆焊相比,在相同焊接速度下复合焊最大能增加熔深1.3倍,在相同熔深下复合焊的焊接速度可以提高50%;复合焊焊缝的晶粒较单MAG焊缝中的晶粒细小,其焊缝抗拉强度比单MAG的好,断裂属于延性断裂.     

CO2 laser-micro plasma arc hybrid welding for galvanized steel sheets

A laser lap welding process for zinc-coated steel has a well-known unsolved problem-porosity formation. The boiling temperature of coated zinc is lower than the melting temperature of the base metal, which is steel. In the autogenous laser welding, the zinc vapor generates from the lapped surfaces expels the molten pool and the expulsion causes numerous weld defects, such as spatters and blow holes on the weld surface and porosity inside the welds. The laser-arc hybrid welding was suggested as an alternative method for the laser lap welding because the arc can preheat or post-heat the weldment according to the arrangement of the laser beam and the arc. CO₂ laser-micro plasma hybrid welding was applied to the lap welding of zinc-coated steel with zero-gap. The relationships among the weld quality and process parameters of the laser-arc arrangement, and the laser-arc interspacing distance and arc current were investigated using a full-factorial experimental design. The effect of laser-arc arrangement is dominant because the leading plasma arc partially melts the upper steel sheets and vaporizes or oxidizes the coated zinc on the lapped surfaces. Compared with the result from the laser-TIG hybrid welding, the heat input from arc can be reduced by 40%.