激光-电弧复合焊接过程中等离子体的耦合行为

激光-电弧复合热源可以形成3种焊缝横截面的形貌,根据焊接参数对焊缝横截面形貌的影响建立了激光和电弧等离子体相互作用的物理机制.通过考察复合焊接过程中电弧等离子体中原子分布状态、电弧辐射光谱信息以及激光"匙孔"的行为对机制进行了验证.结果表明,激光对电弧等离子体的作用是通过激光形成的"匙孔"及其内部等离子体实现的,在适当参数下,电弧等离子体弧柱会进入激光"匙孔"内部,并与"匙孔"等离子体发生耦合放电,最终形成复合等离子体.电弧等离子体和"匙孔"等离子体的耦合作用有利于提高热源的能量密度.     

激光与电弧间距对激光复合焊熔滴过渡的影响

采用高速摄影设备研究了在两种焊接电流工艺参数下激光与电弧的间距变化对CO2激光-MIG电弧复合焊接熔滴过渡过程的影响.试验发现,在高速MIG焊接时熔滴过渡不稳定,在激光-MIG复合焊接时,由于激光光致等离子体对熔滴的热辐射作用和对电弧的吸引作用而改变了电弧的形态及相应的熔滴的受力状态,使得熔滴的过渡过程发生了改变,对于不同的焊接电流工艺参数,存在不同的最佳激光与电弧间距.结果表明,在最佳间距下,即两个等离子体的耦合作用良好时,熔滴过渡形式为单一的稳定射流过渡,电流电压恒定,焊缝成形良好.     

钽薄板TIG焊接电弧形态的研究

通过高速摄像方法研究了钽薄板TIG焊接过程中，保护气体及工艺参数不同时电弧形态的变化规律及其对焊接质量的影响。结果表明：保护气体不同时，电弧形态明显不同。采用TIG焊焊接钽板时使用氦弧能得到更好的焊接质量；当弧长不变，增加焊接电流时，电弧有效作用范围变犬，电弧温度及能量密度高。熔池增大速度较快；当焊接电流不变，弧长增加时，电弧有效加热半径变大，但由于弧长增加而引起电孤热能分散。熔池增长速度较慢，热影响区范围增大。焊接工艺参数的变化时电弧形态的影响规律，对制定钽薄板TIG焊接过程中较为合理的工艺参数具有重要意义。     

电弧气体中CO_2含量对大功率激光复合焊等离子体及熔深影响的研究

文中采用大功率CO_2激光-熔化极电弧复合焊,以12 min厚船用E级钢板为试样进行堆焊,通过在电弧气体Ar中加入不同体积分数的CO_2,研究CO_2含量对激光电弧复合焊等离子体及焊缝熔深的影响。试验结果表明,电弧气体CO_2体积分数为15%与25%时,焊接过程等离子体比5%CO_2时有所减小;与此同时焊缝熔深有所增加。15%CO_2,25%CO_2时,焊缝熔深与5%CO_2相比分别增加3%,5.1%;25%CO_2时,焊缝熔深与15%CO_2相比增加2%。     

铝合金激光-电弧双面焊接头特征分析

采用激光-电弧双面焊工艺进行铝合金焊接试验，发现该工艺不仅可以获得稳定可靠的焊接过程与美观的焊缝成形，还可以有效地增加接头熔深和降低焊接成本。主要研究了焊接参数对双面焊接头特征的影响。结果表明，激光功率增加时，双面焊两侧的熔宽都以同样的趋势增大；焊接电流增大时，电弧侧熔宽的增加趋势明显大于激光侧；增加激光功率或提高焊接电流都会引起焊缝最小熔宽的增大，且焊缝最小熔宽的深度也发生一定的变化。随焊接速度的提高，激光侧的深宽比增加，而电弧侧的深宽比减小。     

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...     

氮氩气体保护TIG焊接电弧数值分析

以TIG焊接电弧为对象,依据磁流体动力学理论构建电弧的数学模型,运用ANSYS有限元分析软件对二维稳态下轴对称的、氩氮混合气体保护的TIG焊接电弧进行了数值分析,得到了50%N2 Ar混合气体保护下焊接电弧的温度场、速度场的形态分布特征.并通过与纯氩气保护的TIG焊接电弧温度、压力以及等离子体速度等分布的比较,得出了加入氮气作为保护气体时,TIG焊接电弧能量及形态的分布变化.对比结果表明,加入氮气作为保护气体提高了TIG焊接电弧的电弧温度、等离子体速度和电弧压力,能得到更高能量密度的焊接电弧.     

低功率YAG激光-TIG电弧复合焊接镁合金薄板工艺

以2 mm厚AZ31B变形镁合金薄板为研究对象开展低功率脉冲YAG激光-TIG电弧复合热源焊工艺研究,分析了激光与电弧的能量匹配对焊缝成形的影响规律.结果表明,镁合金薄板低功率YAG激光-TIG电弧复合热源焊接过程中,激光能量与电弧能量之间的相互匹配将直接影响焊缝的表面成形,获得理想焊接接头的工艺参数区间相对较狭小.为使焊缝成形均匀连续,焊接过程中需要对焊缝背面采用氩气进行保护,当保护气体流量为5～10 L/min时获得了具有最佳性能的焊接接头,其拉伸载荷达到镁合金母材的95%以上.     

304L不锈钢激光-脉冲MAG复合焊电弧特性及焊缝成形分析

针对SUS304L不锈钢激光-脉冲MAG复合焊接过程激光与脉冲MAG电弧的过程参数匹配及优化控制问题,系统研究了过程参数对电弧特性及焊缝成形尺寸的影响,获得了复合焊接过程的电弧特性及成形控制策略.结果表明,激光的介入会使复合焊接过程稳定性加强,当脉冲MAG电弧处在电流基值时,较大的激光功率会吸引MAG电弧而造成基值电压的波动,并且大功率激光会对脉冲MAG电弧具备一定的压缩作用,但在峰值阶段影响幅度较小.焊缝形貌的几何尺寸与过程参数的耦合效应有着直接的关系,过程参数的匹配优化能够有效控制焊缝成形尺寸.     

旋转电弧传感器的结构优化及散热分析

通过现用同轴旋转电弧传感器的长期试验,针对实际焊接中其存在的不足,对其结构进行了优化。摒弃了实际工作环境下不安全的水冷冷却方式,采用轴流式风扇与散热孔结合的方式散热;为避免试验中因焊接电流泄漏而击穿电机的现象,选用陶瓷材质的调心球轴承;为提高焊接保护气体的实时性,增加焊接的安全性,将保护气体的进气口下移,并设计了导气罩;最后,选用小体积电机,减小了旋转电弧传感器的体积及质量。水平直角焊接试验显示,新型旋转电弧传感器能够满足焊缝成形要求,在焊接自动化领域有很大的实用价值。     

镁合金AZ31B的激光-TIG复合热源缝焊工艺

以AZ31B变形镁合金为主要对象,研究了其激光-TIG复合热源缝焊工艺特点,探讨了缝焊表面成形、缝焊熔深的影响因素以及缝焊缝的抗剪强度变化规律。结果表明,激光-TIG复合缝焊的焊缝为明显的“图钉型”形貌,上部分为TIG电弧焊接成形,下部分为典型的激光焊接成形。镁合金复合热源缝焊具有焊接速度高、焊缝成形美观、焊接参数范围较宽等特点,接头抗剪强度较高,是一种优良的焊接方式。     

TIG arc characteristics in different atmospheres (part 1)

Summary

The physical properties of gases such as density, thermal and electrical conductivity, as well as ionisation potential, determine to a great extent the operational characteristics of welding arcs. These properties may vary widely for different gases. As a result, arc voltage, heat output, mean radius, thermal profile, performance and other parameters which influence bead geometry (shape, width and penetration) depend on the chemical composition of the shielding gas. Rather complex physical models have been proposed to explain and quantify the effects of shielding gas chemical composition on welding arc performance. The influence of arc atmosphere may also be easily predicted by empirical methods. However, only changes in arc operational parameters and weld bead geometry due to variations in gas composition appear in the literature. This article presents an optical study of the TIG welding arc, based on a digital system of image capture and welding parameter recording, during arc operation. Variations in arc aspect, dimensions and electrical parameters were observed, and the results related to the physical properties of gases and mixtures used, as well as forecasts by theoretical models.     

Comparative evaluation of tungsten inert gas and laser welding of AZ31 magnesium alloy

Abstract

Welding of AZ31 Mg alloy was conducted using various welding techniques, namely, tungsten inert gas (TIG) welding with Ar shielding gas, TIG welding with He shielding gas, CO₂ laser welding, and YAG laser welding. The results were comparatively evaluated in terms of weld bead formation and microstructural characterisation. It was found that TIG welding with both Ar and He gas shielding produced good welds without major defects. The penetration capacity can be improved using He gas shielding. Owing to their high energy density, CO₂ and YAG lasers can produce weld beads having high aspect ratio. Among the four techniques used, the YAG laser produced the finest weld microstructure, whereas TIG with Ar gas shielding produced the coarsest microstructure. Shielding is a key factor controlling the O contents in the welds. The more effective the shielding provided the lower the O content in the weld. Hardness reduction in the weld metals and heat affected zones was observed for all the techniques owing to the elimination of strengthening effects by the welding operation. In summary, the present study demonstrated advantages and limitations of the various welding techniques and provided an in depth understanding of the weldability of AZ31 Mg alloy.     

高速旋转电弧窄间隙MAG焊焊缝成形的分析

采用平特性电源,研究了高速旋转电弧窄间隙MAG焊接工艺对焊缝成形的影响规律。结果表明,旋转电弧是通过热量的合理分配来改善焊缝成形,旋转频率对熔化速度的影响很小。提高旋转频率和降低保护气中CO2的含量有利于增加侧壁熔深,改善焊缝成形;但同时也容易造成电弧与侧壁短路,恶化焊缝成形,严重的将出现未熔合。所以在间隙小于10min时旋转频率应小于50Hz。焊接速度的变化不会影响过渡形式,但较低的焊接速度可以得到更大的表面下凹。     

基于光谱诊断的氩氮TIG焊电弧物理特性分析

混合气体保护焊能够提高焊接质量及生产效率，由于混合气体保护焊电弧成分复杂多变，对其物理性能等的研究具有一定的难度. 文中以氩氮混合气体钨极惰性气体保护焊（TIG焊）电弧为研究对象，采用双电荷耦合元件（CCD）电弧光谱图像采集试验系统，获取氩氮混合气体TIG焊电弧Ar I及N I的特征谱图像的动态分布；结合双元素双组分标准温度法对不同浓度（50%Ar + 50%N₂，80%Ar + 20%N₂及100%Ar）的氩氮电弧进行光谱诊断. 结果表明，电弧半径最高收缩50%左右，温度最高升高12%. 通过对氩氮电弧物理性能的定量分析为研究混合气体保护焊焊缝成形的本质奠定了理论基础.     

Weld shape variation and electrode protection under Ar–(Ar–O2) double shielded GTA welding

Abstract

Double shielded gas tungsten arc welding (GTA welding or TIG welding) of an SUS304 stainless steel with pure inert argon as the inner layer shielding and the Ar–O₂ active gas as the outer layer shielding is proposed in this study in order to investigate its effect on the tungsten electrode protection and the weld shape variation. The experimental results show that the inner inert argon gas can successfully prevent the outer layer active gas from contacting and oxidising the tungsten electrode during the welding process. The active gas, oxygen, in the outer layer shielding is decomposed in the arc and dissolves in the liquid pool, which effectively adjusts the active element, oxygen, content in the weld metal. When the weld metal oxygen content is over 70 ppm, the surface tension induced Marangoni convection changes from outward into inward, and the weld shape varies from a wide shallow one to a narrow deep one. The effect of the inner layer gas flowrate on the weld bead morphology and the weld shape is investigated systematically. The results showed that when the flowrate of the inner argon shielding gas is too low, the weld bead is easily oxidised and the weld shape is wide and shallow. A heavy continuous oxide layer on the liquid pool is a barrier to the liquid pool movement.     

不锈钢电弧辅助活性TIG焊

针对不锈钢,提出了一种新型活性YIG焊方法--电弧辅助活性TIG焊,即AA-TIG焊(arc assisted activating TIG welding).该焊接方法通过在正常TIG焊前以活性混合气体作为保护气体,采用小电流钨极电弧预熔待焊焊道表面,可使熔深显著增加,焊接效率大大提高,而且具有可全自动化焊接和工艺可重复性好等优点.分别采用O2+Ar,CO2+Ar,空气作为小电流钨极电弧的保护气体进行了单弧AA-TIG焊.与传统TIG焊比较,发现O2+Ar,CO2+Ar和空气都可显著增加熔深,减小熔宽,焊缝表面成形良好.采用CO2+Ar作为活性混合保护气体进行双弧AA-TIG焊,焊缝成形良好,熔深显著增加.熔深随着焊枪间距减小而增大.     

Application of grey relational analysis to determine welding parameters for Nd:YAG laser GMA hybrid welding of aluminium alloy

Abstract

Grey relational analysis is carried out to develop a new approach for optimization of Nd:YAG laser and gas metal arc hybrid welding parameters. The qualities of a welded material depend on various welding parameters. The parameters chosen for the current study include wire type, shielding gas, laser power, laser focus, travelling speed and wire feedrate. The welding experiments are performed on 6K21-T4 Al alloy sheet which are mostly used in automotive industries. The ultimate tensile stress, the bead width, and the penetration are chosen as the criterion for optimising the welding parameters. The method based on an orthogonal array following Taguchi's recommendation is adopted in the present study. Based on the results of grey relational analysis, a set of optimal welding parameters are obtained. The results show that the optimal welding parameters determined by the grey relational analysis are much improved compared to those from the preliminary set of experimental parameters.     

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.     

低功率激光-双电弧焊接钛合金中厚板工艺及机理

采用单钨极惰性气体保护焊(single tungsten inert gas welding,STIG焊)、双钨极惰性气体保护焊(double tungsten inert gas welding,DTIG焊)、激光-STIG电弧(L-STIG)复合焊和激光-DTIG电弧(L-DTIG)复合焊4种方式对6 mm 厚TA2钛合金进行对接焊试验,实现单面焊双面成形. 结果表明,L-DTIG复合焊的电弧能量更为集中,焊接速度可达680 mm/min. L-DTIG复合焊的热输入为605.5 J/mm,仅是DTIG焊的35.5%和L-STIG复合焊的59.0%. L-DTIG复合焊接头的焊缝区晶粒细小,显微硬度可达229.5 HV. 拉伸试样在母材处断裂,接头抗拉强度优于母材. 加入激光后,L-DTIG复合焊的电弧等离子体中心导电区在xOz和yOz平面电弧分别收缩51.0%,45.5%,电弧根部收缩75.0%. 测得L-DTIG复合焊热源在工件上的电弧压力为3 465 Pa,分别是DTIG焊和L-STIG复合焊的4.17和2.25倍. 较高的电弧收缩比和电弧压力可显著提高焊接效率,降低焊接热输入.