激光+双丝脉冲MAG复合焊的焊接稳定性

研究激光和Ar+He混合气体中He气体体积分数对激光+双丝脉冲MAG复合焊焊接稳定性的影响。搭建激光+双丝脉冲熔化极活性气体保护(Metal active-gas, MAG)复合焊焊接系统,利用LabVIEW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和熔滴过渡过程,实时监测焊接过程。观察后丝短路和前丝断弧情况并对前丝电弧电压进行单因素方差分析,研究Ar+He混合气体中He气体体积分数对焊接稳定性影响;比较焊接过程中激光的有无对熔滴过渡的影响,分析激光对焊接稳定性影响。结果发现随着He气体体积分数增大,后丝对应短路次数增多,当He气体体积分数为50%时,前丝出现断弧现象,大于50%,断弧时间随之增加,焊接稳定性变差;激光+双丝脉冲MAG复合焊和双丝脉冲MAG复合焊相比,加入激光可稳定电弧,为熔滴提供一附加力,该力促进熔滴过渡,使熔滴过渡尺寸减小,加大过渡频率,改善熔滴过渡,提高焊接稳定性。     

工程应用中的钛型CO_2气体保护药芯焊丝熔滴过渡

分析了GMAW熔滴过渡形态,重点探讨了钛型渣系CO2气体保护药芯焊丝的电弧、熔滴过渡特性,并以工程应用实例论证该类焊丝熔滴主流过渡形态。结果表明,GMAW用焊丝的工艺质量很大程度取决于熔滴过渡形态和电弧行为。熔化极气体保护电弧焊主要熔滴过渡形态是滴状过渡、短路过渡和喷射过渡。钛型渣系CO2气体保护药芯焊丝的电弧形态应属于活动、连续型,在大电流、强规范(含高的电弧电压)条件下施焊时,该焊丝熔滴主流过渡形态是非轴向滴状过渡。     

纵向磁场对MAG焊电弧及熔滴过渡的控制作用

将纵向磁场应用于98%Ar+2%O2和80%Ar+20%CO2保护的射流过渡MAG焊,借助高速摄像手段研究外加纵向磁场对MAG焊电弧形态及运动特征的影响规律,揭示纵向磁场对MAG焊电弧的作用本质在于压缩电弧.通过分析液流束末端的液态金属的受力情况,确立纵向磁场作用下MAG焊的熔滴过渡机制.试验结果表明,外加纵向磁场使得相对"静态"的锥形MAG焊电弧转变为高速旋转的螺旋状电弧,并且随着励磁电流的增大,电弧旋转角速度加快、可见弧长缩短、电弧电场强度提高.同时外加纵向磁场的引入还能够降低焊接电流、提高熔滴过渡频率和焊丝熔化系数.外加纵向磁场对射流过渡MAG焊接过程稳定性的影响特点与所采用的保护气体的物理性质相关.     

细丝大电流MAG焊接机理

借助高速摄像机研究不同保护气氛下(98%Ar+2%O2、T.I.M.E.气体、80%Ar+20%CO2)细丝大电流MAG焊的电弧形态及熔滴过渡特征,并在此基础上通过分析液锥和焊接电弧的受力情况,建立液锥的运动模型,同时指出液锥与焊接电弧的空间位置关系以及这两者的运动相关性.研究结果表明,细丝大电流MAG焊的液锥运动属于自磁旋转,即液锥在电极磁场力和电弧力的作用下偏离焊丝轴线一定角度并绕焊丝轴线高速旋转.液锥偏角的相对大小由电弧烁亮区包覆液锥的面积决定,当电弧烁亮区包覆液锥的面积增大时,液锥偏角反而变小,焊接过程的稳定性增强.驱动电弧高速旋转的力是由液锥磁场提供的,电弧偏角及其旋转角速度分别与液锥偏角和液锥旋转角速度密切相关.     

激光功率对CO2激光-MAG电弧复合焊电弧与熔滴行为的影响

采用高速摄像系统观测熔滴过渡模式和等离子体形态的变化,并采集焊接过程中的电弧和熔滴图像,利用电弧分析仪记录电弧信号,通过试验深入研究激光功率对CO2激光-熔化极活性气体保护焊(Metal active gas,MAG)电弧复合焊接的电弧形态、焊接稳定性、熔滴过渡频率的影响。研究表明,焊接电流的增加减小了实际热源间距,并且实际热源间距在2 mm附近效果最佳;带电粒子在主辅导电通道内的运动产生扰动或漂移、焊接模式的跳变和过渡模式的改变是电流、电压波形出现紊乱和尖角波形的主要原因;激光的加入降低了熔滴过渡频率和过渡稳定性;焊接电流为160A、180 A时,激光-电弧复合焊接的熔滴过渡频率均随着激光功率的增加而先减小后增大,但其过渡频率介于160 A和180 A电弧焊接时熔滴过渡频率之间。     

不同波长激光对激光—MAG电弧复合焊接熔滴行为的影响

通过计算分析了金属对Nd：YAG激光和CO2激光的吸收率;以8.0mm厚高强钢板为试验材料,采用高速摄像系统观测熔滴过渡模式和等离子体形态的变化.建立脉冲MAG焊接熔滴力学模型,从熔滴受力角度分析了不同波长两种激光YAG激光和C02激光在激光—MAG焊接中对熔滴过渡形式和熔滴过渡频率的影响.结果表明,Nd：YAG激光和CO2激光输出特性存在差异,金属表面对YAG激光的吸收率约为CO2激光的3倍多;在焊接电流180A、焊接电压26V、光丝间距3mm的相同条件下,YAG激光—MAG电弧复合焊接熔滴过渡频率高于CO2激光—MAG电弧复合焊接的熔滴过渡频率,且熔滴过渡频率均随着激光功率的增加而降低,但是增加等量的激光功率,YAG激光—MAG电弧复合焊接熔滴过渡频率下降幅度更大;CO2激光—MAG电弧复合焊接过程中,熔滴的过渡形式由射滴过渡转变为颗粒过渡,在YAG激光—MAG电弧复合焊接过程中,熔滴过渡形式主要为射滴过渡.     

CO_2气体保护焊技术问答?

1.二氧化碳气体保护焊(以下简称 CO_2焊接)时,“熔滴过渡”是怎么回事?共有几种过渡形式?采用短路过渡的短弧焊为什么适于薄板和空间全位置焊接?[答]:CO_2焊接是一种熔化极气体保护焊,在进行 CO_2焊接时,在电弧的热作用下,焊丝不断地被熔化,液体金属不断地离开焊丝未端进入熔池.这个过程称为“熔滴过渡”。熔滴过渡是 CO_2焊接中的一个重要环节,     

保护气体对高氮钢焊接熔滴过渡模式和气孔缺陷的影响研究

采用激光-电弧复合热源对8 mm厚的高氮钢板进行焊接试验,研究不同保护气体组成对焊缝形貌、熔滴过渡特征和气孔缺陷的影响。结果表明,采用纯氩做保护气体时,熔滴过渡模式以射流过渡为主,并伴有少量排斥过渡;保护气体成分为Ar+N₂混合气体时,熔滴过渡模式为短路过渡;保护气体成分为Ar+N₂+O₂混合气体时,熔滴过渡模式为射流过渡。保护气体的组成对焊缝气孔缺陷也存在一定的影响,保护气体为纯氩时,焊缝气孔率最大,其值为2.52%;保护气体为90% Ar+10% N₂时,气孔率最低,仅为0.16%;Ar+N₂中添加1%的O₂后,气孔率略有升高,但与纯氩时相比,气孔率仍下降明显。采用Ar+N₂+O₂三元混合气作为保护气体时,能够有效抑制焊缝内气孔数量,同时可以改善熔滴过渡模式,提高焊接过程稳定性。     

钛型渣系气保护药芯焊丝熔滴过渡及其控制

从熔滴过渡形态及分类、过渡形态与工艺性关系、熔滴过渡机理、熔滴过渡影响因素及控制等方面．探讨了钛型渣系气保护药芯焊丝熔滴过渡及其控制原理。结果表明．该焊丝熔滴过渡的基本形态是非轴向滴状过渡．在电弧电压较纸瞬时，亦会发生短路过渡行为这类焊丝熔滴过渡形态对工艺性的影响，取决于焊接规范参数的变化．主要是焊接电流．并通过影响熔滴过渡指数．进而使工艺性指标发生之，依据该焊丝熔滴形成过程特点，建立了药芯焊丝熔滴过渡受力模型，焊接电流变化时．不同的作用力对熔滴过渡起主要作用。通过调整药芯组成物，选择焊丝截面形状，改变焊丝直径和钢带厚度．优化焊接工艺参数．改变作用于熔滴上相关力的大小或方向．最终实现对熔滴过渡的控制。     

CO2气体保护焊电弧现象中对焊丝添加稀土金属的影响研究

一、概述 CO2气体保护焊（以下简称CO2焊）开发于20世纪50年代,由于焊接电源和焊接材料的改进,近年来这种焊接方法已发展成为主流焊接法,但是CO2焊会在熔滴自由过渡时产生较多的飞溅,因此,目前已把降低飞溅作为一个专门的研究课题。本文针对CO2焊电弧现象和焊丝成分的影响进行研究。关于CO2焊有资料报道：焊丝中碳含量降低,而钛含量增加,可以有效地抑制短路过渡的飞溅,但是效果不明显。     

Mathematical modeling of flux consumption during twin-wire welding

Mathematical models for flux consumption during twin-wire welding with direct current electrode positive and direct current electrode negative have been presented. The models illustrate the flux consumption in the form of a function relation between different process parameters. The present work is the result of a large number of experimental observations, modelling, and subsequent validation. The accuracy and predictability along with the use of shop-floor controllable parameters as model inputs make the proposed models useful for industrial application. The effects of process parameters have been further analyzed. The analysis revels that current, voltage, wire diameters and polarity are the major factors influencing the flux consumption during the twin wire welding, while welding speed and contact-tube-to-work-piece-distance are found to be significant with electrode negative. One of the important observations during the present investigation is regarding influence of dissimilar wire diameters at the lead and trail wires on the flux consumption. Mathematical analysis of magnetic field generated in the vicinity of the arc, particularly with dissimilar diameter, affects the arc deflection and affects the flux consumption.     

Weld deviation detection based on wide dynamic range vision sensor in MAG welding process

Weld deviation detection is a precondition for welding automation. Capturing high-quality welding images and extracting deviation information using image processing methods are two steps for weld deviation detection. In this paper, based on the analysis of the imaging characteristics during metal active gas (MAG) welding process, real-time welding images are acquired clearly and steadily using a wide dynamic range vision sensor. According to the connection relationship between the top of the arc and the end of the wire during MAG welding process, a method for determining the wire centreline is proposed. After extracting the precise arc region, the region of interest (ROI) is segmented along the welding direction. To detect the two edges of the V-groove, an improved Canny algorithm is developed. Furthermore, both the Hough Transform and a screening method based on prior knowledge are used to connect V-groove edges. The V-groove centreline is then determined. As a result, the weld deviation between the wire centreline and the V-groove centreline is calculated. Further experiments showed that the precision range of deviation detection can be controlled within ±0.25 mm, which can meet the requirement of real-time welding. This deviation can be used as the input variable for a welding robot, thus laying the foundation for MAG welding automation.     

带状电极窄间隙MAG焊

为解决窄间隙焊接中普遍存在的侧壁和焊缝根部熔合不良的问题,基于减小间隙宽度让电弧直接加热间隙侧壁的思路,提出采用矩形截面的带状电极代替常规的圆形焊丝作为熔化极伸入到间隙中进行焊接,利用特殊形状的带状电极在间隙中自动形成的摆动电弧来改善对间隙侧壁和根部的加热,实现窄间隙焊接。研制专用的焊枪,研究间隙宽度、电弧电压和送带速度对间隙中带极端部电弧行为的影响。试验发现,电弧在间隙中的摆动受间隙宽度、电弧电压和送带速度的影响程度依次降低。间隙宽度对电弧的摆动具有决定性作用,间隙太宽电弧不能摆动;电弧电压过高导致电弧沿侧壁攀升得不到抑制,而送带速度主要与电弧电压搭配,保证焊接过程的稳定性,二者对间隙中电弧的摆动行为影响较小。结果表明,合理匹配间隙宽度、电弧电压和送带速度可以实现稳定的摆动电弧,获得侧壁和焊缝根部熔合良好的窄间隙焊缝。     

不同极性下的三丝间接电弧中厚板焊接研究

三丝间接电弧焊是一种新型电弧焊技术,电弧放电通道形成于三个电极之间,电极极性的连接方式会对焊接过程产生重要影响。为揭示不同极性连接方式的三丝气体间接电弧中厚板焊接过程工艺特点,采用主丝接正和主丝接负的连接方式分别对8mm Q345低碳钢板进行了对接焊试验。结果表明,在两种极性连接方式的三丝间接电弧中厚板焊接过程中,由于电弧形态以及熔滴过渡路径的差异,主丝接正时的稳定性不受电弧所处阶段的影响;而主丝接负时,熔滴在焊接阶段容易发生短路爆炸造成焊接稳定性下降,这是焊缝表面气孔以及接头局部未熔合缺陷产生的主要原因;随着焊接电流的增大,两种极性下的电弧弧柱区宽度均增大,且主丝接正时的弧柱区的电子温度均大于主丝接负时的。     

Advanced gas metal arc welding processes

There is an increased requirement in the automotive, food and medical equipment industries to weld heat-sensitive materials, such as thin sheets, coated thin plates, stainless steel, aluminium and mixed joints. Nevertheless, relevant innovations in arc welding are not widely known and seldom used to their maximum potential. In the area of gas metal arc welding welding processes, digitalisation has allowed integration of software into the power source, wire feeder and gas regulation. This paper reviews developments in the arc welding process, particularly the effect of the set-up of the welding process parameters on waveform deposition. It is found that good weldability, good mechanical joint properties and acceptable process efficiency can be obtained for thin sheets through advanced power source regulation, especially over short circuiting, controlled polarity and electrode wire motion. The findings presented in this paper are valuable for waveform and deposition prediction. The need is furthermore noted for an algorithm that integrates gas flow parameters and wire motion control, as well as a variable sensor on the tip of the electrode, permitting flexibility of control of the current and the voltage waveform.     

Effect of forces on dynamic metal transfer behavior of cable-type welding wire gas metal arc welding

A cable-type welding wire (CWW) gas metal arc welding (GMAW) method was proposed as a novel approach, using CWW for the consumable electrode. Droplet transfer influences the welding process, and the forces on the droplet were analyzed to elucidate the metal transfer phenomenon observed during the welding process. The effects of the arc pressure, rotating force, and welding parameters were analyzed to understand the metal transfer. The special structure of the CWW affected the arc characteristics and forces during metal transfer as part of the welding process. The droplet formed by droplets from each thin wire, the arc, and electromagnetic forces on droplet formation and the coupling process were analyzed. The arc pressure and rotating forces are beneficial to metal transfer and increase the droplet transfer frequency. The droplet size decreases with increasing welding parameters.     

Electromagnetic Characteristic of Twin-wire Indirect Arc Welding

Traditional welding methods are limited in low heat input to workpiece and high welding wire melting rate. Twin-wire indirect arc(TWIA) welding is a new welding method characterized by high melting rate and low heat input. This method uses two wires: one connected to the negative electrode and another to the positive electrode of a direct-current(DC) power source. The workpiece is an independent, non-connected unit. A three dimensional finite element model of TWIA is devised. Electric and magnetic fields are calculated and their influence upon TWIA behavior and the welding process is discussed. The results show that with a 100 A welding current, the maximum temperature reached is 17 758 K, arc voltage is 14.646 V while maximum current density was 61 A/mm2 with a maximum Lorene force of 84.5 uN. The above mentioned arc parameters near the cathode and anode regions are far higher than those in the arc column region. The Lorene force is the key reason for plasma velocity direction deviated and charged particles flowed in the channel formed by the cathode, anode and upper part of arc column regions. This led to most of the energy being supplied to the polar and upper part of arc column regions. The interaction between electric and magnetic fields is a major determinant in shaping TWIA as well as heat input on the workpiece. This is a first study of electromagnetic characteristics and their influences in the TWIA welding process, and it is significant in both a theoretical and practical sense.     

Nd:YAG激光+脉冲MAG电弧复合热源焊接参数对焊缝熔深的影响

试验研究Nd:YAG激光 脉冲MAG电弧复合热源焊接过程中焊接参数对焊缝熔深的影响.研究结果表明,复合热源焊缝熔深随电弧功率和激光功率的增大而增大,随焊接速度的增大而减小,并且在相同参数下,复合热源焊缝熔深稍大于激光焊缝熔深而显著大于脉冲MAG焊缝熔深.对于不同焊接电流,光丝间距在0～3 mm内复合热源焊缝取得最大熔深,且取得最大熔深的光丝间距与焊接电流大小有关;复合热源焊缝熔深在离焦量为2 mm时取得最大值.试验结果分析表明,在激光 电弧复合热源焊接过程中激光功率不仅决定复合热源焊缝熔深,而且可以极大地提高焊接速度:MAG电弧也可提高Nd:YAG激光焊的热效率.     

Wire melting rate of alternating current gas metal arc welding

The wire melting phenomenon in alternating current gas metal arc welding (AC-GMAW) process should be carefully observed and analyzed since it is one of the most important representative characteristics of GMAW process. In this study, a new form of wire melting rate equation for AC-GMAW process is proposed based on energy conservation theory and arc physics. Using experimental data, the wire melting rate coefficients of AC-GMAW are obtained through nonlinear regression analysis. The wire melting rate is influenced not only by the current waveform, electrode polarity, and droplet size but also by the shape of the wire tip. That is, if the wire tip becomes more slender, arc heating has more influence on the wire melting. Using the wire melting rate proposed in this research, the uncertainty of calculating wire melting rate coefficients of AC-GMAW can be excluded comparing to existing method.