Metal transfer and arc behaviour of novel consumable and non-consumable electrode indirect arc droplet welding

Abstract

The consumable and non-consumable electrode indirect arc droplet welding is a novel method that applies an indirect arc generated between a consumable electrode and a non-consumable electrode to welding. It was successfully used to overlap join the thin zinc coated steel plate. In the point to point (consumable electrode and non-consumable electrode) configuration, the stable metal transfer was obtained. The globular, projected spray and streaming spray transfer modes were promoted. With the increase in welding power, the metal transfer became faster and more stable. At the same time, the indirect arc became brighter, smaller and more stable. The arc self-regulation guaranteed the stable burning of the indirect arc. The desire stability was observed from the fluctuation of the welding current and the arc voltage waveforms. The side concentrated melting on the root of the droplet produced high pinch effect, which facilitated the detachment of the droplet.     

Voltage change in the GMAW process due to the influence of a droplet travelling in the arc

Abstract

Experimental measurements have been made to investigate the meaning of the fluctuation or noise of electrical signals for the gas metal arc welding process through globular to spray transfer mode, with particular attention being paid to the so-called 'drop spray' transition mode. The results reveal that the welding arc voltage is significantly affected by the molten droplet travelling in the arc. A sharp drop in arc voltage appears just after the detachment of the droplet, reaching its minimum quickly and then recovering, according to the location of the droplet in the arc. Although the full explanation of the feature requires further study, we believe that an important influence is the geometrical effect. The existence of the droplet in the arc path significantly affects the geometrical shape of the arc and arc attachment at the anode, and hence the overall voltage of the arc.     

激光功率对激光-双丝脉冲MIG复合焊接电弧形态及熔滴过渡的影响

通过搭建激光-双丝脉冲MIG复合焊接系统,利用高速摄像与电信号采集系统对激光-双丝脉冲MIG复合焊接在不同激光功率下的电压电流信号及高速摄像信号进行同步采集,研究激光功率对焊接过程的电弧形态、熔滴过渡过程的影响.结果发现,由于激光等离子体与电弧等离子体的相互作用,电弧形态和熔滴受力状态发生改变.随着激光功率的增大,激光对电弧的吸引能力增强,促进熔滴过渡的等离子流力竖直向下的分力减小,熔滴过渡频率降低.     

Investigation on arc sound and metal transfer modes for on-line monitoring in pulsed gas metal arc welding

The arc sound was found to be strongly related to both process parameters and weld quality, like voltage and current signals, in gas metal arc welding. In this investigation, the acquired welding arc sound signal along with current and voltage signals were analyzed in time domain as well as frequency domain to correlate them with the various process parameters and metal transfer modes. The arc sound of continuous as well as pulsed gas metal arc welding at various process parameters was also compared. A major variation of auxiliary arc sound frequency peaks was observed due to change of pulse shape as evidenced by frequency domain analysis. The arc sound was also used to detect welding defects.     

交流脉冲MIG弧焊电源及弧长控制

AC PMIG的控制模式是一周一脉一滴，脉冲电流设计在电弧EP极性时间里，其余时间均为基值电流。弧焊电源一次逆变控制电流快速动态过程，二次逆变控制电弧极性。控制系统采用双闭环结构，内环模拟控制电弧电流，外环80C196KC单片机控制电弧电压及电弧极性。根据电弧电压偏差信号及电弧状态，设计了四个控制规则及其控制参数的计算方法。正常焊接状态时变频控制交流脉冲频率。采用这种控制方案，获得了稳定性高、熔滴过渡均匀的焊接过程。     

Arc behavior in two wire tandem submerged arc welding

The behavior of leading and trailing arc root dimensions and arc interaction in the two-wire tandem submerged arc welding process was studied using real-time recorded current and voltage waveforms, and CCD arc images for a wide range of experimental conditions. Physical and regression equations were developed to predict the arc interaction and dimensions as a function of the welding condition. The influence of the arc interaction on the molten droplet transfer direction was studied. The arc center displacements (arc interaction) under different welding conditions were fairly well predicted by the corresponding physical models. The arc root dimensions were unsymmetrical and increased with an increase in the welding current and voltage while the same decreased with the increase in the arc center displacements. This variation was reasonably envisaged by the developed regression models. The detached molten electrode droplet followed the arc axis at the time of detachment and deposited into the weld pool.     

双丝间接电弧氩弧焊的熔滴过渡

采用氙灯背光高速摄像系统及示波器对双丝间接电弧氩气保护焊的熔滴过渡及其对应的电压、电流波形进行了研究.结果表明,双丝间接电弧氩弧焊焊接电流与电弧电压的不同匹配选择,熔滴具有短路过渡、大滴过渡、混合过渡、射滴过渡、射流过渡等不同过渡形式.随着焊接电流的增大熔滴尺寸减小,熔滴细化,随电弧电压的增大,熔滴尺寸减小.熔滴过渡形式与电压、电流的波形之间有很好的对应关系.     

双丝间距对激光-双电弧复合焊接过程稳定性的影响

采用多信息融合技术对激光-双电弧脉冲复合焊在不同双丝间距下的电流信号、电压信号、高速摄像信号进行同步采集,研究双丝间距对焊接过程的电弧行为、熔滴过渡过程及焊缝表面成形的影响,并依据混沌理论和算法,从非线性角度对激光-双丝脉冲MIG焊接过程的电流信号进行了最大Lyapunov指数(LE)计算.结果表明,激光-双丝脉冲MIG焊接过程是一个混沌过程,由于激光光致等离子体和电弧等离子体的相互作用改变电弧的形态和熔滴受力状态,进而影响焊缝成形,在一定的焊接工艺参数下存在最佳双丝间距,在最佳双丝间距下,电弧稳定,焊缝成形良好,且此时最大LE值及其标准方差最小.     

TIG-MIG复合焊电弧特性机理分析

采用TIG-MIG复合焊电弧改善传统单一TIG及MIG焊的不足.基于PID闭环控制,实现恒流恒压外特性输出,从而实现TIG-MIG电弧复合.研究了复合电弧的电弧特性、熔滴过渡形式及不同极性接法对焊缝的影响.结果表明,TIG焊电弧对MIG焊电弧具有良好的维弧作用.TIG-MIG焊电弧复合熔滴过渡过程,TIG焊电弧稳定燃烧,为了保持最小的能量消耗而作用于熔滴上,对熔滴具有加热作用.直流反接具有良好的阴极雾化清理作用.TIG-MIG焊电弧复合能够有效降低焊接飞溅,促进焊缝铺展及成形,实现高效化、优质化的焊接.     

短路过渡CO2焊接熔滴尺寸控制

分析了短路过渡CO2焊接的熔滴形成过程及焊接电流波形对熔滴形状及短路过渡历程的影响规律,对采集获得的焊接过程中的焊接电流信号进行数学处理,采用最小二乘法建立了波形控制短路过渡焊接的焊丝熔化模型.在此基础上,通过控制燃弧初期脉冲电流的宽度调整燃弧能量的大小,对熔滴尺寸控制进行了试验研究.结果表明,随着燃弧脉冲电流宽度的增加,熔滴尺寸单调增加,这说明改变燃弧初期脉冲电流的宽度可以有效地控制燃弧能量和熔滴尺寸的大小.     

基于高速CCD摄像的短路过渡焊接熔滴检测与分析

建立了基于高速CCD摄像的熔滴图像检测和焊接电流、电弧电压同步采集系统,在给出短路过渡模式下的熔滴尺寸定义并简述基于MATLAB平台的熔滴尺寸与电弧信号分析系统的基础上,对平特性电源短路过渡CO2焊接熔滴尺寸变化特征及其与工艺性能间的关系进行了试验研究.结果表明,熔滴尺寸呈分散性较大的正态分布(1～2倍焊丝直径),过大或过小的熔滴尺寸均不利于短路过渡焊接过程的稳定性.根据熔滴的形成和过渡过程,初步分析了影响熔滴尺寸的主要因素及控制熔滴尺寸的途径,即短路过程结束后焊丝端部的残余液态金属量和燃弧能量的随机性导致了熔滴尺寸的不确定性,对其进行有效控制将提高熔滴尺寸和短路过渡过程的一致性,进而改善短路过渡CO2焊接的工艺性能和焊接质量.     

一种基于DSP的脉冲MIG焊波形控制方法的研究

在基于DSP的弧焊逆变电源的数字控制系统上,针对脉冲MIG焊熔滴过渡过程的控制,提出了中值波形控制方法,采用前中值波形控制方法对钢进行焊接试验,研究了中值电流和中值时间对焊接过程的影响规律,得出了新工艺方法及与之相匹配的工艺参数.结果表明:当中值时间固定,中值电流较小时,焊接过程不稳定,易产生短路或断孤现象;中值电流较大时,中值阶段的作用与峰值阶段的作用相同,收不到预设的效果;当中值电流为一理想值时,焊接效果较好.当中值电流固定,中值时间较短时,不足以过渡熔滴;中值时间过长,易产生短路过渡;当中值时间为一理想值时,焊接效果较好.     

GMAW熔滴过渡过程稳定性自相关分析

检测了熔化极气体保护焊(GMAW)中焊接电流和电弧电压大小等参数特征,利用数字信号分析与处理中的时域自相关特性原理,分析GMAW熔滴过渡过程的稳定性与参数关系,判断焊接电流和电压是否具有周期性.阐述焊接电弧系统中,电流自身、电压自身及电流和电压相互的变化存在相互关联,并对焊接电流和电压信号进行自相关分析,获得信号时域的周期和方差等特征信息,直观地反映出弧焊过程与熔滴过渡过程的稳定性.     

一种基于亚射流的PMIG焊电弧电压控制方法

针对熔化极脉冲氩弧焊(PMIG焊)主要采用恒流控制和等速送丝的焊接方式,提出了一种基于亚射流的PMIG焊电弧电压控制方法;其控制原理是对每个脉冲周期的平均电弧电压进行检测,当平均电弧电压在亚射流区域内,则完全依靠其在亚射流区域内固有的自身调节能力进行调节,当平均电弧电压超出亚射流区域后,在其它焊接参数不变的条件下,通过改变基值时间来改变脉冲周期内的平均电流值,从而改变焊丝熔化速度,提高电弧调节能力和抗扰动能力.结果表明,采用该控制方法可以显著改善焊接电弧的动态响应特性,有效抑制电弧电压的扰动,焊缝成形均匀一致.     

面向工程应用的BA-GMAW熔滴过渡形态

综述了涉及工程应用的潜弧熔化极气体保护焊(Buried arc gas metal arc welding,BA-GMAW)熔滴过渡形态特征.结果表明,在大电流和相应的焊接参数下,BA-GMAW工艺的熔滴过渡形态有3种,即呈滴状过渡、摆动过渡和旋转过渡.BA-GMAW电弧空腔中电弧形态属于连续、敞开、非活动型;电弧空腔...     

激光-MIG电弧的复合作用及对熔滴过渡的影响

试验研究激光与MIG电弧的相互影响与相互作用,以及激光的加入对MIG电弧形态与熔滴过渡形式的影响.搭建了YAG激光-脉冲MIG电弧复合焊接试验系统,进行了焊接试验并同步采集了焊接过程中的电信号和高速摄像图片信号.通过分析电信号和高速摄像图片可以发现,对于一脉一滴的焊接过程,加入激光后熔滴过渡形式由一脉一滴变为两脉一滴过...     

双丝间接电弧氩气保护焊的熔滴过渡与电弧形态

用高速摄像系统及示波器对双丝间接电弧氩弧焊的熔滴过渡及电弧形态和电弧电压之间的关系进行了深入分析.结果表明,熔滴过渡和电弧电压、电弧形态的规律性变化存在密切的对应关系.熔滴形成、长大、脱离焊丝端部的规律性变化使极性斑点间距及弧柱电阻发生变化导致了电弧电压的波动,从而使电弧形态发生由暗到明、由小到大的规律性变化.随着焊接电流的增大熔滴的过渡形式发生变化,熔滴尺寸减小.不同的熔滴过渡形式其电弧电压的波动也有所不同,射流过渡电压波动较小,而短路过渡电弧电压的波动最大.     

电弧声与铝合金脉冲MIG焊熔滴过渡的相关性

对铝合金脉冲MIG焊过程中电弧声信号与熔滴过渡之间的相关性进行了研究.建立了焊接电弧声信号的计算机采集系统,在此基础上分别利用小波去噪、功率谱密度分析和ARMA(auto regressive and moving average,自相关滑动平均模型)双谱估计等信号处理方法对不同熔滴过渡方式下的电弧声信号进行了分析.三种方法的分析结果均表明熔滴过渡为短路过渡、大滴过渡、射滴过渡、和射流过渡时焊接电弧声具有不同的特征,证明利用电弧声能够对铝合金脉冲MIG焊过程中出现的不同熔滴过渡进行有效地区分.为铝合金脉冲MIG焊熔滴过渡稳定性实时控制和检测提供了一种有效的手段.     

摆动电弧窄间隙GMAW熔滴过渡规律

研究摆动电弧窄间隙焊接中的熔滴过渡规律是深入理解该焊接方法的重要基础,由于受到电弧摆动、窄间隙坡口的影响,摆动电弧窄间隙焊接熔滴过渡比常规焊接更加复杂.采用高速摄像系统及焊接电信号采集系统成功地对摆动电弧窄间隙GMAW的熔滴过渡过程进行观测研究,揭示了摆动电弧窄间隙GMAW的熔滴过渡特性,分析了摆动参数、焊接参数对熔滴过渡的影响.结果表明,由于焊丝在坡口之间的摆动改变了焊丝与侧壁之间的距离,引起了焊接电弧长度的变化,促使焊接电流发生了波动,从而导致了摆动电弧窄间隙焊接熔滴过渡的规律性变化.     

Metal transfer instability in gas metal arc welding

Abstract

This work presents a simplified model of metal transfer in gas metal arc welding. The model incorporates key features of metal transfer including the change in droplet diameters as welding moves from the globular into the spray metal transfer region, and the increase in welding voltage that is observed to occur as the pendant droplet grows. The model predicts that an instability arises in the globular metal transfer region, which leads to deterministic chaos and complex limit cycles with many droplet sizes. The instability also causes deterministic chaos with a characteristic gap in droplet diameters at the transition to spray mode metal transfer. The model explains observed features of metal transfer in some detail, including the existence and location of preferred bands of droplet sizes. Whether the instability is present or not defines the boundary between chaotic globular metal transfer and the stable drop spray transfer mode. The identification of deterministic chaos in gas metal arc welding metal transfer opens the way for new approaches to welding control.