Effects of pulse parameters on arc characteristics and weld penetration in hybrid pulse VP-GTAW of aluminum alloy

A novel ultrafast-convert hybrid pulse variable polarity gas tungsten arc welding process(HPVP-GTAW)is developed.High frequency pulse square-wave current which has a frequency of more than 20 kHz is exactly integrated in the positive polarity current duration.The effects of pulse current parameters on arc characteristics and weld penetration have been studied during the HPVP-GTAW process using Al-5.8 Mg alloy plates.The arc characteristics studied by arc voltage and its profile,weld penetration noted by the ratio of weld depth to width have been found to be influenced significantly by the pulse current.The experimental results show that the HPVP-GTAW process can improve the arc profile predominantly and obtain the higher weld penetration with lower heat input.The observation may help in understanding the weld characteristics with respect to variation in the pulse current parameters which may be beneficial in using the novel HPVP-GTAW process to produce the better weld quality of aluminum alloy plates.     

Arc characteristics and behaviour of metal transfer in pulsed current GMA welding of stainless steel

The variation in arc characteristics, stability in shielding of arc environment and behaviour of metal transfer with a change in pulse parameters have been studied by high speed video-photography during pulsed current gas metal arc (P-GMA) weld deposition using austenitic stainless steel filler wire. A comparative study of similar nature has also been carried out during gas metal arc (GMA) weld deposition in globular and spray transfer modes. The effect of pulse parameters has been studied by considering their hypothetically proposed summarized influence defined by a dimensionless factor ? = [(I_b/I_p) ft_b], mean current and arc voltage and correlation between welding parameters and arc characteristics have been established. The arc characteristics studied by its root diameter, projected diameter, length and stiffness measured in terms of arc pressure and the behaviour of metal transfer noted by the droplet diameter and velocity of droplet at the time of detachment have been found to vary significantly with the variation in ?. At a given ? the experimentally measured values of the behaviour of metal transfer are found well in agreement to their corresponding theoretical values estimated through mathematical expressions reported earlier. The increase of ? and the ratio of (I_b/I_p) have been found to adversely affect the stability of shielding jacket and arc profile especially at high arc voltage.     

铝合金P-MIG焊接电流对电弧形态的影响

通过对铝镁合金进行脉冲氩弧焊(P-MIG),在相同平均电流和平均电压工作条件下,调节不同峰值电流和基值电流,获得了不同的电弧形态.峰值电流对电弧形态有着重要的影响,而基值电流基本没有影响.基值电流是维持电弧燃烧的参数,在基值时间阶段,必须给定一个足够大的基值电流才能维持电弧的稳定燃烧.文中定义了电弧形态的表征值,针对电流对电弧形态表征值的影响进行了分析.峰值电流是决定电弧温度和脉冲能量的重要参数,铝合金电弧充分燃烧时电弧长度、电弧宽度和电弧纵向截面面积随着峰值电流增加而增加.

Abstract：

Under the same average welding current and welding voltage, by regulating the different based current and peak current, the Al-Mg alloy was welded with Al-Mg filler wire. The photos of welding arc were obtained by using high-speed video photography.Peak current has great influence on the shape and characteristics of the arc. With increasing the peak cunent value, rotated arc appears and pulsed rotated metal transfer behavior occurs. Based current has little influence on the arc shape. Base current is the important parameter for keeping arc burning. At pulse off time, it must be given base current value which is large enough to keep the arc burning stably. In this study, the arc shape is defined by arc length, arc width and arc portrait cross-section area, which will be influenced by the weld current. Peak current is important parameter of arc temperature and pulse energy. The study shows that when the arc is burning at pulse on time, the arc length, arc width and arc pomait cross-section area increase with raising peak current.     

双丝脉冲MAG焊的熔滴过渡及工艺特征

搭建了并列式双丝脉冲MAG焊工艺试验系统,通过双丝脉冲协调控制器连接试验所用的两台电焊机,在试验过程中采集了焊接电流、电弧电压信号,并用高速摄像机对焊接过程的电弧行为与熔滴过渡过程进行了同步拍摄．应用上述试验系统,在实现稳定焊接过程的基础上,分别研究了脉冲峰值电压与脉冲基值电压、两个焊丝在垂直于焊道方向上的距离、焊枪倾角这三个因素对电弧行为、熔滴过渡过程及焊缝表面成形与焊缝几何尺寸的影响．确定了最理想的脉冲峰值一基值电压,并且发现在文中所述试验参数下,焊丝间距11mm为两电弧形成共熔池、同焊道的上临界距离．结果表明,随着焊枪倾角的增加,焊缝熔深增加,熔宽减小,在焊接速度和送丝速度不变的前提下余高增加．     

双电弧共熔池脉冲GMAW电源的复合外特性

利用自行研制的双电弧软开关脉冲GMAW装备,从弧长控制、熔滴过渡以及焊缝成形等角度对双电弧脉冲GMAW三种复合外特性进行了试验研究.结果表明,主机I-I,从机I-I复合外特性的熔滴过渡均匀,可控性好,但电弧自调节作用较差,适合薄板高速焊接;主机U-I,从机U-I复合外特性的熔滴过渡可控性欠佳,但电弧自调节作用较强,较适合大参数厚板焊接;主机I-I,从机U-I复合外特性中主机的熔滴过渡可控性好,电弧自调节能力有限,从机的电弧自调节作用较强,但熔滴过渡可控性欠佳.     

Formation of hardened layers on aluminium alloy surfaces by the plasma transferred arc process

A new criterion for stability analysis of the gas metal arc welding (GMAW) process is proposed and presented in this work, based on acoustic emission generated by the arc during short-circuiting metal transfer. For the experimental development an AWS ER70S-6 wire with a diameter of 0.8 mm and a DEP 401 rectifier were used. The weld bead was carried out on a 4-mm-thick AISI 1020 steel plate. Several welding conditions were studied with variation of the process parameters during the deposition of the beads. The acoustic emission signals were acquired using a measurement system composed of a MV-201 microphone, with a sensitivity of 10 ± 3 mV Pa^? 1 and frequency bandwidth of 20 Hz to 170 dB to 100 kHz, and a data acquisition card coupled to a PC. A stability index was proposed. Eventually, a statistical analysis for validation of the obtained experimental results was carried out. The outputs allowed obtained a relationship between the acoustic signals and the arc voltage signals. The feasibility of the proposed index, and the effectiveness of the method as a novel means of analysing the stability of arc welding, was demonstrated based on acoustic emission for analyses of GMAW process stability.     

旁路耦合微束等离子弧热特性及焊缝成形特点

针对传统微束等离子弧焊中焊丝熔敷率与焊接电流不能解耦的局限,提出旁路耦合微束等离子弧焊方法.通过给外填焊丝添加一电流,使焊丝与焊枪钨极间产生一个旁路电弧,实现熔化母材热量与熔化焊丝热量的解耦,确保熔化母材电流稳定的同时提高填充焊丝的熔化速度.对旁路耦合微束等离子弧焊的熔敷率、母材热输入及焊缝成形质量进行试验研究.结果表明,该方法既保持了传统微束等离子弧焊的优点,又在提高焊丝熔敷率的同时降低母材的热输入;并在其它焊接参数保持不变时,随旁路电流的增加,焊缝的熔宽、熔深和稀释率减小,余高和成形系数增大.     

高频脉冲变极性焊接工艺性能研究

分析了高频脉冲电流对变极性焊接电弧特性、焊接工艺及焊缝性能的影响,试验结果表明,高频电流脉冲能够较大程度地压缩电弧等离子体、提高电弧轴向压力及电弧挺度,在相同焊接电流有效值的情况下,频率在5kHz以上的电流脉冲能将电弧力提高到普通变极性焊接的260%左右.同时高频脉冲电流能够提高变极性焊接的焊缝熔深,减小焊缝正面余高以及改善焊接效率.对于2219-T6时效强化铝合金而言,采用叠加10 kHz高频脉冲变极性焊接工艺,焊缝抗拉强度在未经任何焊后热处理的情况下能够达到300 MPa左右,相当于母材强度的67%.     

低气压对自保护药芯焊丝焊缝成形的影响

对低气压地区自保护药芯焊丝电弧焊接的焊缝成形及其影响因素进行了研究.结果表明,在相同焊接工艺参数设定下,气压愈低,焊缝的熔深愈浅、熔宽愈宽、余高愈小;气压降低导致电弧的冷却作用减弱,弧柱区的直径与正常气压相比将增大,电弧的稳定性和挺度下降.电弧行为的改变影响了焊缝成形质量,气压越低,焊缝成形的对称性越差;焊炬高度的增加对焊缝成形及电弧稳定性同样有不利影响,适当增加送丝速度和降低电弧电压有助于焊缝成形质量的改善.研究结果为低气压地区的自保护药芯焊丝焊接工艺参数制定和优化提供了科学依据.     

铜钢异种材料等离子弧焊接头性能

采用LHM-200等离子弧焊机对1 mm紫铜与低碳钢异种材料进行了熔透型等离子弧焊试验,得到了内部无缺陷、外观成形良好的接头.观察了接头的显微组织,并分析了工艺参数对接头力学性能的影响.结果表明,焊缝区中心显微组织呈细胞群状,界面两侧的组织特征呈现显著的不同,焊缝与铜侧界面没有明显的熔合线,局部呈漩涡状,钢侧与焊缝连接处出现了明显的分界线;最佳工艺为焊接电流为65 A,焊接速度为0.4 cm/s,离子气流量为0.7 L/min,此时接头抗拉强度可达176 MPa,试样断裂于铜母材热影响区.     

Numerical analysis of weld pool geometry in pulsed current plasma arc welding

Numerical analysis of weld pool shape and size is of great significance for selection and optimization of the process parameters in pulsed current plasma arc welding (PAW). In this paper, a mathematical model and relevant algorithm are developed to determine the temperature profiles and weld pool geometry in pulsed current PAW through employing an adaptive heat source model. The volumetric heat source consists of semi-ellipsoid at upper part and a conic body at lower part along the workpiece thickness direction. The dynamic variation features of weld pool shape during a pulse cycle are numerically simulated. The calculated weld cross-section is consistent with the measure one.     

HPVP-GTAW电弧力及焊接质量分析

分别以3种不同材质铝合金平板材料为试验对象,研究分析了复合超高频脉冲方波变极性钨极氩弧焊接(HPVP-GTAW)过程中电弧力的变化及其对焊缝成形特征和接头力学性能的影响.结果表明,与常规变极性氩弧焊工艺相比,脉冲方波电流的加入使得HPVP-GTAW电弧力显著增加,同时焊缝熔透率大幅提高,接头力学性能得到明显改善和提高;保持脉冲电流幅值和占空比基本不变,在10～80 kHz范围内,脉冲电流频率对焊接过程产生了重要影响,频率为40 kHz时,HPVP-GTAW电弧力和焊缝熔透率均达到最大,分别约为常规变极性焊接电弧的1.9倍和1.7倍.     

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.     

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.     

Effects of shielding gas composition on arc characteristics and droplet transfer in tandem narrow gap GMA welding

The effects of shielding gas composition in tandem narrow gap gas metal arc welding were studied. The shielding gas included argon, carbon dioxide and helium. The arc characteristics and droplet transfer process were analysed. The results show that in the same welding parameters, the trail wire welding current is higher than the lead wire welding current. With the increase of carbon dioxide content, the welding currents of two wires decrease, and the trail wire droplet transfer mode transforms from spray transfer to projected transfer. With the increase of helium content, the welding currents increase and the lead wire droplet transfer mode transforms from projected transfer to spray transfer. The weld width is the largest when the shielding gas mixture is 80%Ar10%CO₂10%He.     

磁场对双丝间接电弧焊熔滴过渡的影响

对磁场作用下的双丝间接电弧气体保护焊熔滴过渡变化规律进行了研究,通过励磁线圈对间接电弧施加外部横向及纵向磁场,磁感应强度值由特斯拉计侧出,熔滴过渡过程借助于高速摄像系统拍摄,并由示波器同步记录下电流和电压值的变化.研究表明,随正向横向磁场强度增加,熔滴颗粒变细,过渡频率增加,随负向横向磁场强度增加,熔滴颗粒变大,过渡频...     

Analytical studies on thermal behaviour and geometry of weld pool in pulsed current gas metal arc welding

In view of the criticality of pulsed current gas metal arc welding (P-GMAW) due to simultaneous influence of the pulse parameters on thermal and metal transfer behaviour of the process an analytical model has been developed for predicting the temperature and geometry of the weld pool by appropriately considering two types of heat sources of different nature. The model considers the impact of heat in droplets of filler metal depositing in the weld pool in addition to initial arc heating. The model assumes the primary heat transfer to weld pool is the initial arc heating considered as continuous heat source (arc heat source) of double ellipsoidal nature followed by deposition of superheated filler metal considered as point heat source of interrupted nature superimposed on the first one. The dissimilar nature of the two heat sources is treated by different analytical techniques to estimate their temperature distribution in weld pool and HAZ at its vicinity. The geometry of the weld pool has been estimated by evaluation of the weld isotherms causing melting of the base metal under the influence of two heat sources acting on the weld pool. The impact of impinging droplets on weld pool has been considered to determine the depth at which the droplets transfer their heat in it. The predicted temperature and geometry of the weld pool as well as the temperature of HAZ are found well in agreement to the experimental values with a deviation of the order of ±10% in case of the weld deposition of Al–Mg alloy and commercial aluminium especially at high mean current of the order of 180 A and beyond the transition current of the filler wire. However, prediction of weld pool temperature and weld geometry is relatively different at comparatively lower mean current of 150 A below the transient current of the filler wires is not up to the mark.     

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.     

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.     

铝合金交流脉冲双面弧焊工艺试验及特点分析

通过工艺试验,详细分析了LYl2CZ铝合金板交流脉冲等离子弧（PA）-钨极氩弧（GTA）双面弧焊（DSAW）的工艺特点。通过与常规钨极氩弧焊和等离子弧焊工艺比较,发现该工艺可以显著增加熔深,减小焊后热变形,提高焊接生产效率。分别采用多孔喷嘴和单孔喷嘴进行了对比试验,其中采用多孔喷嘴能够有效防止双弧的产生,采用单孔喷嘴能够获得较大熔深。当采用小孔型交流脉冲双面弧焊工艺焊接铝合金时,由于小孔的存在,焊接过程中阴极雾化效果降低,影响焊缝成形及质量。