【作者】 瞿怀宇；

【导师】 黄勇；

【作者基本信息】 兰州理工大学 ， 材料加工工程， 2012， 硕士

【摘要】 近些年，A-TIG焊由于普遍存在涂敷工序复杂、活性剂配方开发时间过长以及活性剂的引入量不易精确控制等缺点限制了它的广泛应用。电弧辅助活性TIG焊，即AA-TIG焊（Arc assisted Activating TIG Welding）是根据活性TIG焊提出的一种新型的活性焊接方法。为了进一步提高焊接生产效率，本课题组在AA-TIG焊的基础上提出了耦合电弧AA-TIG焊，并进行了初步试验研究。在焊接方向上，辅助电弧在前，通入一定配比的惰性气体（如Ar、He等）与活性气体（如CO₂，O₂等）的混合气体作为保护气，采用较小的焊接电流。主电弧在后，通入惰性气体（如Ar、He等）作为保护气体，采用较大的焊接电流。焊接过程中两个电弧同时引燃施焊，该方法焊接过程稳定而且容易实现自动化焊接，进一步提高焊接生产率。电弧特性的研究对耦合电弧AA-TIG焊缝成形机理的研究以及对该焊接方法的改进具有重要意义。本文在上述试验的基础上研究了耦合电弧AA-TIG焊的电弧特性，并对该方法的优越性作了简单分析，结合电弧特性初步探讨了其焊缝成形的机理。试验包括三部分：首先是搭建耦合电弧AA-TIG焊电弧特性测量分析平台，主要包括耦合电弧形态的采集系统、电弧压力测量系统、阳极电流密度测量系统、阳极温度场测量系统、电弧电压采集系统以及焊接工艺试验平台。其次是进行了耦合电弧AA-TIG焊电弧特性的测量与分析，主要包括5部分内容：（1）采集耦合电弧AA-TIG焊电弧形态，结果表明：2mm钨极间距条件下，焊接电流、弧长对耦合电弧的形态影响较小，耦合电弧AA-TIG电弧形态跟传统单弧形态相近，均呈现钟罩型；而在4mm钨极间距条件下，由于受到主弧与辅弧非对称因素的影响，随着弧长与电流的变化，耦合电弧形态发生偏转，电弧形态均向主弧一侧偏转；与传统单弧TIG比，耦合电弧轴向横截面积变化梯度较小。（2）测量耦合电弧AA-TIG焊电弧压力，结果表明：与传统单弧相比，耦合电弧AA-TIG焊的电弧压力要显著降低，并且在2mm钨极间距条件下，随着焊接电流的减小、弧长的增大以及辅助电弧中氧含量的减小其电弧压力峰值减小；随着钨极间距的增大，耦合电弧AA-TIG电弧压力分布由高斯分布向双峰分布过渡。（3）对耦合电弧AA-TIG焊的阳极电流密度进行测量，结果表明：在2mm钨极间距条件下，耦合电弧AA-TIG焊阳极电流密度的分布均服从高斯分布，且随着焊接电流的增大，电流密度峰值显著增大，随着弧长的增大电流密度峰值降低，氧气流量对电流密度峰值的影响较小；而随着钨极间距的增大，电流密度的分布由高斯分布向双峰分布过渡，且主电弧处的电流密度峰值大于辅弧处的电流密度峰值。（4）测量耦合电弧AA-TIG焊阳极温度的分布，结果表明：在相同的焊接规范下，工件上的同一个测量点，传统单弧TIG焊的温度高于耦合电弧A A-T I G焊，随着钨极间距的增大耦合电弧中心处温度降低，边缘处温度升高，即钨极间距较小时温度更为集中。（5）对耦合电弧AA-TIG的电弧电压进行采集，结果表明：耦合电弧AA-TIG焊的主弧电弧电压大于辅弧电压且均小于相同电流条件下的传统单弧TIG的电弧电压；随着弧长的增大，耦合电弧AA-TIG焊的主弧电压与辅弧电压变化规律相同。其三是进行了焊接工艺试验验证，通过工艺试验表明：相比传统单弧TIG焊，耦合电弧AA-TIG焊的焊接效率提高、应用范围更广，其能够一次焊透8mm厚的304不锈钢板，焊缝熔深为传统TIG焊的2-3倍；在500mm/min的焊接速度下，其焊缝表面成形良好且焊缝熔深有所提高；在1200mm/min的焊接速度下焊接2mm厚的不锈钢板单面焊双面成形。本文最后结合电弧特性对耦合电弧AA-TIG焊焊缝成形机理进行了简要的分析认为：耦合电弧AA-TIG焊焊缝熔深增加的机理主要是氧元素的引入改变了不锈钢熔池表面张力温度梯度系数，使Marangoni对流方式发生改变，液态金属更容易向焊缝底部流动，从而显著的增大了焊缝熔深；而耦合电弧AA-TIG高速焊接时焊缝成形良好是电弧特性和氧元素共同影响的结果，氧的引入降低了熔池金属的粘度，电弧压力显著降低使得熔池金属后排作用力减小，从而熔池金属更容易回流填满弧坑，改善焊缝成形。由此说明，耦合电弧AA-TIG焊接法在保证焊接质量的前提下，提高焊接生产效率，节约生产成本，是一种具有潜在开发价值的焊接方法。更多还原

【Abstract】 In recent years, because of the faults of A-TIG welding which include complexityof coating process, too long time for development of surfactant formula, controllingintroduction quantity of surfactant hard and inaccuracy and so on. Those limits A-TIGwelding widely used. Arc assisted activating TIG welding, namely AA-TIG welding isproposed a new type of activating welding method.In order to further improve the welding production efficiency, on the previousbasis, this research group had been done experiment research for double welding torchcoupling arc AA-TIG. Its welding speed is higher than ordinary TIG welding. Itassembles two tilted welding torch, which generates the coupling arc through the twotungsten pole of inclining plank. In welding direction, the assisted arc which isshielded by mixed gases which include the inert gas （such as Ar, He） and active gas（such as CO₂, O₂） is in the front with smaller welding current. In primarily TIGwelding arc which is shielded by the inert gas （such as Ar, He） is in the behind with thelarger current. In the welding process, two welding torches weld at the same time. Thiswelding process is very stable and the productivity is further improved than theordinary TIG welding.Arc characteristic is great significance to study the mechanism of coupling arcAA-TIG weld shape and the improvement of the welding method. This paper hadstudied the arc characteristics of the coupling arc AA-TIG welding basis on these trialsand made a simple analysis about the advantages of the method. The mechanism of itsweld forming is discussed combined with the arc characteristic. Test consists of threeparts:Firstly, the measurement and analysis platform for coupling arc AA-TIG weldingarc characteristics is built, main including coupling arc shape acquisition system, thearc pressure measurement system, the anode current density measurement system, theanode temperature field measurement system, the arc voltage acquisition system andthe welding process test platform.The second is the measurement and analysis of the coupling arc AA-TIG weldingarc characteristic which includes five parts:（1） Collection of coupling arc AA-TIGwelding arc shape, the results show that: Under2mm tungsten spacing conditions, thecoupling arc AA-TIG arc shape is similar with the traditional single-arc which showed a bell-type and it is little impacted by welding current and the arc length. But under4mm tungsten spacing conditions, due to the factors of the main arc and assisted arcasymmetric, with the arc length and current changes the coupling arc shape deflectedand the arc shape towards to the main arc side. Compared to the traditional single-arcTIG, the coupling arc axial cross-sectional area gradient is smaller.（2） The coupled arcAA-TIG welding arc pressure measurement, the results show that: Compared with thetraditional single-arc, the coupling arc AA-TIG welding arc pressure was significantlylower. At2mm tungsten spacing conditions, with the welding current decreases, thearc length increases and the oxygen content of assisted arc reduce the arc pressure peakdecreases. With the tungsten electrode spacing increases, the coupling arc AA-TIG arcpressure distribution transition from Gaussian distribution to a bimodal distribution.（3）Coupling arc AA-TIG welding current density of the anode measurements, the resultsshow that: At2mm tungsten spacing conditions, the distribution of the anode currentdensity of the coupling arc AA-TIG welding is belong to Gaussian distribution. Withthe welding current increased, the peak value of the current density was significantlyincreased. With the arc length increased the peak of the current density reduced. Theinfluence of oxygen flow rate on peak current density is small. With the tungstenelectrode spacing increases, the current density distribution transition from theGaussian distribution to the bimodal distribution. And the peak value of the currentdensity of the main arc is bigger than the peak value of the current density of theassisted arc.（4） Measurement of the anode temperature distribution of the coupling arcAA-TIG welding, the results show that: Under the same welding procees, thetemperature of the traditional single-arc TIG welding is higher than the coupling arcAA-TIG welding at the central point on the workpiece. With tungsten electrodespacing increases the center temperature of the coupling arc decreases, the edgetemperature elevated. The smaller of the tungsten electrode spacing the temperature ismore focused.（5） Acquisition of the coupling arc AA-TIG arc voltage, the results showthat: The coupling arc AA-TIG welding arc voltage of the main arc is greater than theassisted arc voltage and both of them are less than the traditional single-arc TIG arcvoltage under the same current conditions. With the arc length increases, the variationvoltage of the main arc and the assisted arc is the same of the coupling arc AA-TIGwelding.The third is the welding process test validation. The process test results show that:compared to traditional single-arc TIG welding, the welding efficiency of the coupling arc AA-TIG welding is improved and the applications range is wider. Its penetration is2-3times of the conventional TIG welding and the penetration depth of coupling arcAA-TIG welding can reach8mm at one welding on the304stainless steel. At500mm/min welding speed, weld surface forming is good and weld penetration increased.At1200mm/min welding speed, it is one-side welding of2mm stainless steel platewith two-side forming.Finally a brief analysis of the forming mechanism of the coupling arc AA-TIGweld combined with arc characteristics show that: the mechanism of coupling arcAA-TIG weld penetration increased is the introduction of oxygen change the surfacetension-temperature gradient coefficient of the stainless steel pool. The Marangoniconvection changes and the liquid metal flows to the bottom of weld, whichsignificantly increases the weld penetration. The weld forming is good of coupling arcAA-TIG welding at high speed because of the arc characteristics and oxygen elements.Oxygen reduces the viscosity of the molten metal and arc pressure significantlyreduced the pool metal rear force. Thus the molten metal is easier to reflux to fill thepool to improve weld forming. These show that the coupling arc AA-TIG weldingprocess can ensure welding quality and improve welding productivity, reduceproduction costs. It is a potential development value of the welding method.更多还原