脉冲MIG焊熔滴过渡控制的新进展

介绍脉冲MIG焊（熔化极惰性气体保护焊）熔滴过渡控制的发展现状,分析了现有控制法存在的局限性,阐述一种最新的控制法—熔滴过渡光谱控制法的原理、优越性及其进展。指出这方面的发展趋势。电弧光谱信号在反映脉冲MIG焊熔滴过渡方面有很大的优越性,其信号品质和灵敏度远胜过以往的信号。相应的光谱控制法已在实验室成功地实现了脉冲MIG焊1峰0基的精确控制,并可能推广用于2峰0基、3峰0基的控制,甚至推广用于连续电流焊条件下熔滴过渡的控制中,工艺适应性宽,前景广阔。     

脉冲MIG焊建模仿真分析及弧长控制

针对脉冲MIG焊过程中的电弧稳定性问题,建立基于尖端不稳定熔滴过渡理论的焊丝熔化动态电弧模型,并对焊接过程中的电弧电压、电弧长度及熔滴过渡尺寸进行仿真,得到与实际焊接相似的电弧电压波形,分析脉冲电流下熔滴过渡频率及影响电弧稳定性的因素,且进行弧长稳定控制的仿真研究,在此基础上运用快速原型技术建立铝合金脉冲MIG焊控制系统,采用电弧电压反馈对铝合金脉冲MIG焊过程进行送丝调节的弧长控制试验。研究表明:所建立的铝合金脉冲MIG焊焊丝熔化动态电弧模型很好反映了实际焊接过程,揭示出脉冲MIG焊焊接过程中熔滴过渡时间间隔具有一定的不确定性和电弧长度的不稳定性,通过电弧电压反馈控制可显著改善铝合金脉冲MIG焊过程电弧系统的稳定性。     

熔滴过渡光谱传感与控制的研究

焊接电弧光谱是一个丰富的信息源,电弧的各种物理过程都能在电弧光谱中体现,利用电弧光谱信息能很好地检测和控制脉冲焊熔滴过渡。对电弧光谱辐射情况和对光辐射和接收系统进行了深入的研究和分析,抛弃了一般特征光谱检测设备所必需采用的光谱仪和复杂的光路系统,选用干涉滤光片,选择光谱窗口,设计并制作小型光谱传感器。对喷射过渡过程进行了熔滴过渡检测,利用光谱信息实现了脉冲焊熔滴过渡精确控制为焊接过程精确控制提供了一种新的方法和手段。     

双旁路耦合电弧MIG焊熔滴过渡受力分析

针对双旁路耦合电弧熔化极惰性气体保护(Metal inert gas,MIG)焊过程,使用高速摄像采集不同旁路电流下的熔滴过渡图像,通过图像处理提取熔滴过渡数据信息,并对熔滴所受的主要作用力进行定量计算。根据计算结果对比分析不同参数下熔滴受力的动态变化情况,研究旁路电弧对熔滴过渡的促进机理。结果表明,在焊接总电流较大的情况下电磁力对双旁路耦合电弧MIG焊熔滴过渡的影响最显著,旁路电弧可以促进熔滴上弧根面积的扩展和熔滴缩颈的形成,通过增加向下的电磁力来促进熔滴过渡,且旁路电流越大旁路电弧对熔滴过渡的促进作用越明显;在焊接总电流不变的情况下,随着旁路电流的增加熔滴过渡频率随之增加,熔滴尺寸随之减小,熔滴过渡形式逐渐由大滴过渡转变为喷射过渡。     

低电流TIG电弧辅助MIG高速焊咬边缺陷抑制机理及措施的研究

基于温度场、流场、熔滴过渡以及电弧形态检测,开展低电流钨极氩弧焊(Tungsten inert gas welding,TIG)辅助熔化极惰性气体保护(Metal inert gas welding,MIG)高速焊工艺试验。从传热、传质以及受力等角度分析低电流TIG辅助电弧对高速MIG咬边缺陷的抑制机理,并分析各工艺参数对最终焊缝成形的影响。相比常规MIG高速焊,低电流TIG辅助电弧能有效降低MIG高速焊前部熔池边缘的温度梯度,延长熔池存在时间,促进液态金属向焊缝边缘填充。电弧力和熔滴冲击力是影响高速焊咬边缺陷的主要作用力,低电流TIG辅助电弧对MIG熔滴冲击力改变较小,但两电弧耦合后,电弧静、动压力明显降低,可有效地抑制MIG高速焊中咬边缺陷的产生。此外,正交工艺试验显示,丝-极间距和焊枪倾角是影响复合焊工艺的重要参数,而钨极距工件距离和TIG焊接电流则对咬边缺陷的影响较小,通过对丝-极间距和焊枪倾角的调节能快速实现该复合焊工艺参数的优化,抑制咬边缺陷。     

双旁路耦合电弧铝合金MIG焊熔滴过渡形态研究

提出双旁路耦合电弧熔化极惰性气体保护(Dual bypass metal inert-gas,DB-MIG)电弧焊方法并建立试验系统.该方法以传统熔化极惰性气体保护焊接电弧为主弧,引入两路对称的电流可控的非熔化极旁路电弧并与主弧形成耦合电弧进行焊接.由于旁路电弧的分流作用,在保持较高焊丝熔化电流的同时可有效降低母材输入电流,并且旁路电弧力的作用对熔滴过渡也有显著的影响.设计专用的窄带滤光系统,实现无激光背光的焊接熔滴过渡行为的高速摄像,获得不同旁路电流参数条件下的铝合金DB-MIG焊熔滴过渡的高速摄影图像并进行分析.试验结果表明总电流恒定的情况下,熔滴过渡形态随旁路电弧电流参数改变而改变.对DB-MIG焊条件下作用于熔滴上的电弧力的分布进行理论分析,解释试验现象,理论分析和研究表明双旁路耦合电弧可以促进熔滴过渡并可显著降低喷射过渡的临界电流.     

直流脉冲氩弧焊在容器封底焊中的应用

常见的焊接方式焊接电流大都是连续恒定的,调节方式比较单一。而脉冲电流是周期脉冲式的,调节参数众多。它由维持电弧燃烧的基值电流和用于加热并熔化工件焊丝、并使熔滴从焊丝脱落和向熔池过渡的峰值电流组成。它的特点决定了它在封底焊中保证根部熔透和防止背面焊瘤中有着独特的应用。     

《机械工程学报》英文版2004年第17卷第3期目次摘要预告

焊接熔滴过渡光谱信息的获取与模式识别韩国明 何雨 云绍辉 李俊岳(天津大学材料科学与工程学院 天津 300072)为了对各种熔滴过渡形式进行识别,利用熔滴过渡光谱信息模式识别系统,采集了熔化极气体保护焊(MIG、MAG、CO2)五种熔滴过渡形式的光谱信号作为样本。通过计算机进行预处理,创造性地提取了多个熔滴过渡光谱信号波形关键性的特征,建立了判别法则和最小距离分类器。结果表明,此方法可成功地对各种熔滴过渡形式进行模式识别,     

脉冲DE-GMAW过程熔滴受力分析及电流波形设计研究

针对为了实现铝-钢高效高质量的连接,提出一种高效低热输入的脉冲旁路耦合电弧熔化极惰性气体保护焊(Double-electrode gas metal arc welding,DE-GMAW)方法。为了使其焊接过程熔滴平稳过渡,分析旁路电弧对熔滴过渡时电流密度的影响,确定脉冲DE-GMAW熔滴过渡时电磁力的作用机制,在主路为脉冲电流情况下,分别设计旁路波形与主路组合形式即为恒定电流、交替脉冲电流和同步脉冲电流三种形式的研究,并使用高速摄像拍摄熔滴过渡图像,进行对比分析试验验证。结果表明,焊接电流波形及组合形式不同会导致作用于焊接熔滴的受力发生改变,从而使得焊接过程的稳定性与焊接质量也发生变化,对比分析得出采用同步脉冲电流时的脉冲旁路耦合电弧熔化极惰性气体保护焊焊接过程稳定、熔滴过渡均匀一致且焊缝成形平整美观。     

单电源三丝MIG焊的交替燃弧特性

三丝焊作为一种高效的焊接方法受到重视,而电弧形态及燃弧特性是反映焊接过程稳定性,决定焊缝成形及质量的重要因素。试验中搭建三丝熔化极惰性气体保护(Metal inert-gas,MIG)焊系统,利用Mult Daq电信号采集系统采集焊接电流和电弧电压波形,借助高速摄像系统同步拍摄电弧形态及熔滴过渡过程,实时监测焊接过程。观察不同电弧电压下的焊丝燃弧情况及熔滴过渡方式,研究短路过渡和大滴过渡形式下的交替燃弧机理,以及电弧电压对单电源三丝MIG焊交替燃弧过程的影响。结果表明,当焊接电源供给能量较小时,并联的三根焊丝上的电流分配呈现"此消彼长"的规律而导致电弧在焊丝间交替燃烧,且焊丝在电弧空间中的位置决定了焊丝上的电流分配。随着电弧电压的增加,交替燃弧频率减小。当电弧电压达到34 V时,三根焊丝同时燃弧,无交替燃弧现象,交替燃弧频率变为0 Hz。     

CHARACTERISTICS OF DROPLET TRANSFER IN CO2 LASER-MIG HYBRID WELDING WITH SHORT-CIRCUITING MODE

LF6 aluminum alloy plates with 4.5 mm thickness are welded in this experiment.Welding is carried out by using the CO2 laser-MIG paraxial hybrid welding in flat position. The experimental results indicate that the inherent droplet transfer cycle time of conventional MIG arc is changed due to the interaction between CO2 laser beam and MIG arc in the short-circuiting mode of laser-MIG hybrid welding. Because of the preheating action of CO2 laser to electrode and base material, the droplet transfer frequency of MIG arc is increased in the hybrid welding process. When laser power is increased to a certain degree, the droplet transfer frequency is decreased due to the effect of laser-induced keyhole. Furthermore, through analyzing the MIG welding current and arc voltage waveforms and the characteristics of droplet transfer in the hybrid welding process, the effect of laser energy and the action point between laser beam and arc on the frequency of droplet transfer and weld appearance is investigated in details.     

以电弧光谱信号传感MIG/MAG焊熔滴过渡的工艺适应性

熔滴过渡控制的实现，取决于获得宽工艺适应性的熔滴过渡传感信号。通过试验，获取了熔化极气体保护焊电弧，在不同熔滴过渡形式下的光谱分布、谱线信号的时域波形和频域特征。对试验结果的分析表明，电弧光谱信号在上述诸方面均表现出对不同熔滴过渡形式的适应性，是一种有潜力的高品质熔滴过渡信号源。     

BASIC THEORY AND APPLICATIONS OF WELDING ARC SPECTRAL INFORMATION

Welding arc spectral information is a rising welding information source.In some occa- sion,it can reflect many physical phenomena of welding process and solve many problems that cannot be done with arc electric information,acoustic information and other arc information.It is of important significance in developing automatic control technique of welding process and other similar process.Many years study work on welding are spectral information of thc anthor are dis- cussed from three aspects of theory,method and application.Basic theory,view and testing methods of welding arc spectral information has been put forward.In application aspects,many applied ex- amples,for example,monitoring of harmful gases in arc(such as hydrogen and nitrogen)with the method of welding arc spectral information;welding arc spectral imaging of the welding pool which is used in automatic seam tracking;controlling of welding droplet transfer with welding arc spectral information and so on,are introduced.Especially,the successful application in real time controlling of welding droplet transfer in pulsed GMAW is introduced too.These application examples show that the welding arc spectral information has great applied significance and development potentiali- ties.These content will play an important role in applying and spreading welding arc spectral infor- mation technology.     

Effect of laser on the welding process of short-circuiting transfer MIG welding of aluminum alloys

In this paper, the effect of laser on the welding process in metal inert gas (MIG) welding of aluminum alloys was studied exploiting high-speed imaging and welding electrical signals collecting. Bead-on-plate welding experiments were conducted using conventional short-circuiting transfer MIG welding and laser-short-circuiting transfer MIG hybrid welding. The obtained results point out that it took less time to strike the arc in laser-MIG hybrid welding, and the stability of arc striking was increased. When the laser was introduced into the arc atmosphere, the arc was compressed, and the welding energy was more concentrated. The arc cathode spot was fixed to the laser beam impinging spot, so the arc could burn stably. In laser-MIG hybrid welding, the droplet short-circuiting transfer stability and the weld appearance were improved significantly. Moreover, an analysis method of judging droplet transfer stability which bases on statistical techniques was proposed. By this method, it can be concluded that the short-circuiting transfer process became more stable in laser-MIG hybrid welding.     

基于周期平均值外特性的脉冲MIG焊弧长稳定性研究

通过对脉冲熔化极惰性气体保护(Metal inert gas,MIG)焊脉冲平均电流电压变化率的计算,提出脉冲周期平均值外特性曲线,并对弧焊电源脉冲周期平均值外特性曲线和电弧静态性曲线的动态稳定工作点进行详细分析,得出利用脉冲平均值外特性控制脉冲MIG焊的控制策略。同时运用双闭环控制实现了基于弧压反馈的I/I模式控制数字化弧焊电源,此电源能在送丝速度稳定情况下自适应弧长扰动变化,实现脉冲弧焊过程一脉一滴熔滴过渡。通过弧长阶跃试验表明,脉冲弧焊过程中焊丝熔化速度快速跟踪弧长变化,具有良好的弧长动态调节性能,保持弧长动态稳定,即焊接过程稳定,焊缝成形良好,同时验证了分析过程正确性和设计过程的可行性。     

一种熔滴过渡特征信息提取和分析的新方法

利用同步采集系统采集了脉冲熔化极氩弧焊(P-MGAW)熔滴过渡过程的电信息和光谱信息。在反映熔滴过渡特征方面,光谱信息变化最为显著,信号强度变化占总强度的47.5％。电弧光谱信息中具有焊丝端头熔化、熔滴长大、缩颈和分离等过程的明显特征。采用Daubechies和Symlets离散小波分别分析了P-MGAW熔滴过渡过程的电信息和光谱信息后发现:电信息和光谱信息在高频细节分量中包含完全对应的熔滴分离特征信息,同时还含有熔滴过渡过程的其他细节特征。     

ACQUIRING AND PATTERN RECOGNITION OF SPECTRUM INFORMATION OF WELDING METAL TRANSFER

In order to recognize various metal transfer modes, by the creation of a pattern recognition system for metal transfer mode, five kinds of spectrum signal in gas metal arc welding (MIG, MAG and CO2) are collected and taken as training samples. These samples are pretreated by computer. Several key characteristic parameters of the spectrum signal are creatively extracted, and a corresponding recognition function and a minimum-distance-classifier are constructed. The results show that using this method, the pattern recognition of several kinds of metal transfer mode for the metal gas arc welding can be done successfully. It has good accuracy and recognition precision, basis for controlling the metal gas arc welding metal transfer automatically, and relative important parameters in welding process, such as the frequency of droplet transfer and the approximate diameter of each droplet, can also be obtained.     

基于电弧光谱的钢熔化极惰性气体保护焊质量判识

通过对熔化极惰性气体保护电弧焊(MIG焊)电弧光谱分布进行采集,研究其光谱分布的基本特征,并基于光谱分布的分析,通过预设干扰因素,对不同特征谱段光谱信号随焊接过程的变化进行采集,寻求MIG焊接质量在线光谱测控的理论依据和工程实现.研究结果表明,MIG焊电弧光谱在不同谱段存在金属谱线和Ar谱线聚集区.在不同弧长下的不同熔滴过渡形态,其光谱信号在特征谱段得到明显反映,电流变化引起的焊道变宽也有很好的特征信号;不同干扰因素引起的焊接缺陷,在焊接电弧光谱信号不同谱段的分布和变化规律不同,通过对特征谱段信息的采集,可以获得关于焊接过程信息的特征信号,从而实现对MIG焊接质量的分类判识.