脉冲MAG-TIG双电弧打底单面焊双面成形机制分析

基于中厚板打底焊接存在着自动化程度及效率低的问题,采用脉冲熔化极气体保护焊-钨极氩弧焊(MAG-TIG)双电弧热源焊接对板厚为24 mm的Q235-B进行打底焊接单面焊双面成形工艺研究及机制分析. 结果表明,脉冲MAG-TIG双电弧热源打底焊接时,利用TIG电弧与MAG电弧间的电磁力来调节MAG电弧在熔池前端的加热位置,使得一部分电弧热量直接作用于钝边上;结合焊接电弧放电行为与熔池流动分析发现,打底成形稳定性最佳时,利用TIG电弧与熔池的剪切力使得液态金属向后方流动,熔池前端底部液态金属减少,易于平衡稳定,可获得熔透均匀、连续、稳定的打底焊缝背面成形.     

高强铝合金双脉冲VPPA焊缝成形机理

建立双脉冲VPPA(variable polarity plasma arc)焊接系统,进行7A52高强铝合金双脉冲VPPA焊接工艺试验,研究低频脉冲调制叠加高频脉冲对VPPA焊接过程中焊缝成形和焊缝力学性能的影响. 结果表明,低频脉冲周期性振荡液态熔池,可获得表面饱满的鱼鳞纹焊缝;高频脉冲使电弧更为集中,有效地提高了电弧能量密度,穿透力加强;双脉冲耦合振荡加强了对熔池的搅动作用细化了铝合金焊缝晶粒. 焊接接头抗拉强度达到384.13 MPa,相比VPPA焊接接头强度提高了10.21%左右;焊接接头断面收缩率和断后伸长率均有一定程度的提高. 铝合金双脉冲VPPA焊接工艺提高了焊接接头力学性能.     

大厚板双面双TIG电弧打底焊熔池成形特性

采用视觉图像监测法对新开发的双面双TIG电弧错位同步打底焊熔池成形特性进行了研究.结果表明,根部预留间隙是保证打底焊根部熔合的有效措施,可以实现大厚板不清根焊接.脉冲TIG焊是大厚板打底焊的优选方法,峰值期间电弧熔化能力强,坡口根部两侧边缘熔化良好.基值期间熔池迅速凝固,防止了下淌.双TIG电弧错位同步打底焊时,后电弧的加入导致两弧之间工件高温区增加,前电弧熔池拉长.焊缝宏观金相显示母材充分熔化,没有侧壁未熔合,焊缝正表面成形圆滑过渡,没有气孔、裂纹、夹渣、咬边等成形缺陷.     

Effects of torch configuration and welding current on weld bead formation in high speed tandem pulsed gas metal arc welding of steel sheets

Abstract

Undercut and humping bead are the common defects that limit the maximum welding speed of tandem pulsed gas metal arc (GMA) welding. In order to increase the maximum welding speed, effects of the inclination angle, interwire distance and welding current ratio between the leading wire and trailing wire on bead formation in high speed welding are investigated. The undercut and humping bead is attributed to the irregular flow of molten metal towards the rear part of the weld pool. This irregular flow can be prevented by the trailing wire with a push angle from 5° to 13° , which provides an appropriate component of arc force in the welding direction. The irregular flow is also related to the distance between the leading wire and the trailing wire, and the flow becomes regular when the distance is in the range 9–12 mm. Moreover, the stabilisation of the bulge of the weld pool between the two wires, the presence of enough molten metal below the trailing arc, and the reduced velocity of molten metal flow towards the rear part of the weld pool, are essential to increase the maximum welding speed. These conditions can be obtained by adjusting the ratio of the leading arc current to the trailing arc current. A maximum welding speed as high as 4–4·5 m min^?1 is achieved by setting the current ratio to a value ranging from 0·31 to 0·5.     

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.     

双丝串列电弧焊焊缝成形的试验分析

将旋转电弧传感器和双丝串列电弧焊结合起来,开发了旋转电弧引导的、两个电弧在同一个熔池上燃烧的双丝串列电弧焊方法,对其焊缝成形工艺进行了研究.分析了焊接电流、焊接电压、双丝间距、电弧旋转等参数对焊缝成形的影响.结果表明,随着焊接电流的增大,熔敷速度增加,焊缝成形系数呈现先增大后减少的变化规律.而焊接电压的增大则会使焊缝成形系数略有减小.对双丝间距的研究发现,当间距为15 mm时,焊接质量较好.与普通双丝串列焊相比,前置电弧旋转时熔池底部变得平坦,最大熔深有所减小,平均熔深有所增加,这将有助于减少焊缝的应力集中.与单丝旋转电弧焊相比,焊接熔敷速度显著增大,有效避免了高速焊接时的咬边现象.     

EH36钢厚板双面双弧打底焊焊缝组织及性能

EH36钢厚板广泛应用于造船行业,文中采用多层多道双面双弧机器人MAG自动化立焊工艺焊接EH36钢,具有显著的优点和广阔的应用前景.打底焊是多层多道焊接中最重要的工艺过程,对接头性能有着重要影响.文中对打底焊接头组织和性能进行了研究.结果表明,厚板双面双弧立焊打底接头组织主要为针状铁素体和先共析铁素体.在经历随后的多层...     

Characterization of welding arc and weld pool formation in vacuum gas hollow tungsten arc welding

An experimental method is suggested to obtain the effective arc radii for various welding conditions in vacuum gas hollow tungsten arc welding. The irradiance distribution of welding arc next above the anode workpiece is obtained by applying Abel inversion algorithm to the CCD arc image, and then used to determine the distribution of arc heat flux, arc pressure and current density from the physical relations of arc irradiance, temperature and current density in gas tungsten arc welding. The resultant arc models are then adopted to simulate the gas hollow tungsten arc welding process for various gas flow rates.     

690 MPa级双丝埋弧焊接头的组织与性能

采用自主开发的抗拉强度690 MPa级埋弧焊丝对16.3 mm厚同等强度级别钢板进行了双面双丝埋弧焊接试验,研究了焊接接头的组织和性能。焊缝组织性能测试结果表明,先焊面焊缝由针状铁素体、粒状贝氏体、上贝氏体及少量M-A组元和晶界铁素体组成,而后焊面焊缝则由针状铁素体、多边形铁素体、上贝氏体及少量M-A组元组成;先焊面硬度值（247 HV5）高于后焊面（232 HV5）与先焊面存在的粒状贝氏体组织有关;先焊面和后焊面的-20 ℃小试样冲击吸收能量分别为106 J和119 J,先焊面较低的冲击吸收能量与其较低含量的针状铁素体及粒状贝氏体的存在有关。全焊缝力学性能测试结果表明,焊缝的抗拉强度768 MPa,-20 ℃韧性≥ 165 J,断后伸长率为20 %。热影响区组织性能测试结果表明：先焊面和后焊面的热影响区组织特征相似,其中粗晶区和临界再热粗晶区均由上贝氏体和粒状贝氏体组成,细晶区和临界区分别由多边形铁素体和M-A组元,以及上贝氏体、粒状贝氏体、多边形铁素体和M-A组元构成;上述各区域（粗晶区、临界再热粗晶区、细晶区和临界区）的硬度值分别为236、232、229和234 HV5,其中粗晶区硬度值最高、其-20 ℃冲击吸收能量≥ 169 J。上述焊缝区和热影响区的组织和性能测试表明：焊接接头具有较好的强度与低温冲击韧性匹配。     

细丝双弧共熔池脉冲MAG高速焊脉冲参数匹配研究

利用研制的双丝脉冲MAG焊装备及数字化协同控制系统,在协同控制模式主机和从机不同外特性组合方式下,进行了双丝高速脉冲MAG焊工艺试验研究,根据实验结果分析总结出两路脉冲参数最佳配合方式以及相互影响规律.实验表明,通过对双丝脉冲MAG焊工艺实验来掌握主从脉冲参数规律,为最大程度减少主从电弧之间的影响,保证双丝高速脉冲焊接过程稳定,为提高焊缝质量提供了技术指导,具有针对性和实际意义.     

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.     

Analysis of weld pool vibration characteristics in pulsed gas metal arc welding

Using highspeed camera image measuring and processing, the contour of the weld pool was extracted accurately in pulsed metal inert gas (P-MIG) welding. Based on this extraction method, time and frequency domain characteristics at different points along the contour of the weld pool were analyzed for one pulse one droplet and one pulse two droplets, respectively. The results show that, because of the wave super position that was created by the pulsed arc and droplet impacting the weld pool, the oscillation amplitude along the weld pool fluctuated and decreased with an increase in distance from the point to the arc center. The oscillation near the arc center was complex and intense for one pulse two droplets, and the amplitude were relatively small because the oscillation caused by the pulsed arc could be offset by the molten droplet impact. The weld pool oscillation that was caused by the pulsed arc was stronger than that caused by the droplet.     

电弧能量匹配对前后列置双TIG高速焊接焊缝组织与性能的影响

对厚度为1.2 mm的304奥氏体不锈钢板进行前后列置双TIG电弧高速焊接工艺试验,通过对焊缝宏观形貌、组织和拉伸性能进行分析,评定前置电弧能量和后置电弧能量大小匹配对焊缝组织与性能的影响.结果表明,前置电弧能量较高的焊缝中心晶粒平均直径相比母材降低约33.9%,相比后置电弧能量较高的焊缝中心晶粒平均直径降低约26.1%,热影响区晶粒平均直径降低约18.1%.前置电弧能量较高焊缝相比后置电弧能量较高的焊接标准试样抗拉强度提高约7.9%,断后伸长率提高约33.3%,说明前置电弧能量较高有助于获得较高性能的焊缝.     

Simulation analysis of double arc in plasma arc welding

Aimed at plasma arc welding, a mathematic model was established according to the theory of magnetic fluid dynamics. The model was numerically analyzed by ANSYS software. The temperature, current density and plasma velocity distributions of normal arc had been simulated and compared with those of double arc. The results show that the appearance of double arc has made the temperature of the nozzle rise up to 5 000 K. The appearance of side arc could make the current density of the main arc decrease, and also make the maximal temperature of the arc reduce.     

浅谈电站推广手工钨极氩弧焊打底焊接技术

电站中承压部件及管道焊接质量的优劣是影响发电设备安全运行的关键之一。介绍了电站焊接技术的发展现状，阐述了采用手工钨极氩弧焊打底技术的优点、金属极氩弧焊的器具及焊接工艺，在工程的应用中收到满意效果，钨极氩弧焊打底焊接技术在电站安装及检修中值得应用、推广。     

脉冲埋弧焊接头力学性能分析

为了改善埋弧焊时焊接热输入较大,焊接接头力学性能存在的问题,研究了一种新型的采用直流脉冲电流的埋弧焊工艺--脉冲埋弧焊.以16MnR钢板为试验母材,研究了陡降外特性焊接电源匹配变速送丝系统的脉冲埋弧焊工艺对焊接接头力学性能的影响.结果表明,脉冲电弧力对熔池进行有规律的搅拌、振荡,震碎细化了晶粒,有效减小熔敷金属的成分偏析.脉冲埋弧焊可有效改善焊接接头的组织,细化晶粒,提高焊接接头的力学性能.     

脉冲熔化极气体保护焊熔池图像的检测与处理

利用CCD摄像机和复合滤光技术建立了一套熔池图像实时采集系统。利用光谱分析,提出了适合于脉冲熔化极气体保护焊(P-GMAW)熔池成像的滤光光谱窗口,并对中心波长分别为665nm和1064nm滤光系统的成像质量进行了分析。分析了P-GMAW单个脉冲内的不同时刻的熔池图像,研究表明脉冲基值结束期间为最佳的取像时刻。使用中心波长为665nm的滤光系统,从熔池正后方取像,获取了清晰的熔池图像。针对所获取的典型的P-GMAW熔池图像,详细研究了其成像机理。开发了一套熔池图像处理程序,利用该程序提取了完整的熔池轮廓。     

双脉冲TIG焊熔池数值分析

建立了双脉冲电流下TIG焊熔池的三维非稳态数学模型,通过选择合适的边界条件和热物性参数,强烈耦合控制方程组对双脉冲TIG焊熔池进行数值分析,得到了周期性变化的焊接熔池温度场、流场等分布情况,熔宽、熔深的尺寸大小在周期内的变化规律.结果表明,在双脉冲电流作用下的熔池尺寸大于在平均电流作用下的尺寸,有效的增大了焊接熔池尺寸;熔池尺寸随电流的变化具有一定的滞后性,且在高能脉冲作用时的滞后性较强;在双脉冲电流作用下的熔池内部具有更大的流速,其搅拌作用更强.     

Arc behaviour and weld formation in gas focusing plasma arc welding

ABSTRACT

Improving penetrability is a key issue in plasma arc welding (PAW). Increasing plasma energy is one way to improve arc penetrability. Gas focusing plasma arc welding (GF-PAW) platform is self-designed and developed. Role and action mechanism of focusing gas is initially studied. Focusing gas makes no obvious effects on arc pressure distribution and value. Focusing gas changes arc temperature distribution outer orifice, while focusing gas does not affect arc temperature distribution inner orifice. Focusing gas can constrict arc and arc energy increases 210?W with an increase in arc voltage of 1.4?V. GF-PAW can fully penetrate the whole work-piece while PAW can only partially penetrate the work-piece under welding current 150?A. GF-PAW can improve penetrability, and may increase welding speed, and has a potential application in manufacturing.