EXPERIMENTAL INVESTIGATION ON FORMING PROCESS OF HUMPING BEAD IN HIGH SPEEDMAG ARC WELDING

开展了高速活性气体保护( MAG)电弧焊接工艺实验, 确定出了不同焊接电流条件下形成驼峰焊道时的临界焊接速度、相邻驼峰之间的距离以及同一驼峰焊道“波峰”和“谷底”的断面形貌. 基于高速MAG电弧焊熔池的视觉检测图像, 分析了驼峰焊道的产生机理, 并利用上坡焊和下坡焊实验进行了验证. 同时, 也分析了保护气体成分对高速MAG电弧焊焊缝成形的影响.     

高速MAG电弧焊驼峰焊道产生过程的实验研究

开展了高速活性气体保护（MAG）电弧焊接工艺实验,确定出了不同焊接电流条件下形成驼峰焊道时的临界焊接速度、相邻驼峰之间的距离以及同一驼峰焊道“波峰”和“谷底”的断面形貌．基于高速MAG电弧焊熔池的视觉检测图像,分析了驼峰焊道的产生机理,并利用上坡焊和下坡焊实验进行了验证．同时,也分析了保护气体成分对高速MAG电弧焊焊缝成形的影响．     

高气压环境脉冲MAG焊气体混合比对焊接稳定性的影响

分析了压力环境下气体混合比对脉冲MAG焊飞溅率及焊缝熔池形状的影响. 结果表明,压力环境下相同比例的保护气体在流速不变的情况下,起活性作用的气体组分相对较多,电弧弧柱紊乱加剧,飞溅剧烈,焊接过程极不稳定. 为获得高气压环境下稳定的焊接过程,减小飞溅率,通过提高混合气体配比中氩气体积分数来降低活性气体造成的能量损失,从而减少飞溅. 防止缺陷的产生. 综合考虑飞溅率、熔滴过渡稳定性及焊缝熔池形状等因素,在0.3 MPa环境压力下使用90%Ar+10%CO₂混合气进行焊接可获得最佳的焊接效果. 气体配比的有效调节对于提高高气压环境下脉冲MAG焊焊接过程稳定性和焊接质量具有显著作用.     

High speed TIG–MAG hybrid arc welding of mild steel plate

A TIG–MAG hybrid arc welding process was proposed to achieve high speed welding. The influences of hybrid arc welding parameters on welding speed and weld appearance were studied through orthogonal experiment and the microstructures and mechanical properties of weld were tested and compared with that of the conventional MAG weld. The TIG–MAG hybrid arc welding speed could reach up to 3.5 m/min for bead-on-plate welding of 2.5 mm thick mild steel plate under the condition of high quality of weld appearance and 4.5 m/min for butt welding of 2 mm thick mild steel plate, respectively. The mechanical properties of hybrid arc weld were not lower than that of the conventional MAG weld. The assistant TIG arc could effectively stabilize the MAG welding current and MAG arc voltage in high speed TIG–MAG hybrid arc welding process. The stable hybridization obtained by balance between TIG and MAG welding current and proper wire-electrode distance was a key factor to stabilize the welding process.     

U型钢机器人快速MAG焊接工艺研究

采用机器人对U型钢试件进行快速MAG焊接工艺试验,通过对立缝焊接过程电流、电压、速度等工艺参数及摆动幅度、摆动频率、两侧壁停留时间等机器人运动参数对焊接过程及焊后结果的影响进行分析,结合立角焊接过程熔池受力特性对焊接过程的影响,配合平角及立向弯角焊接,形成一套连贯有效的U型钢快速MAG焊接工艺并能用应用于实际产品。结果表明,在保证焊接稳定性的前提下,焊接电流、电弧电压适当减小,焊接速度适当增加,摆动参数适当减小,有利于焊后焊缝良好成形及效率提高;最终工艺应用在产品上,降本增效,满足生产质效需求。     

基于视觉的焊接缺陷熔池图像特征探讨

针对MAG焊电弧光谱特点,采用被动式视觉传感方法,利用CCD摄像机配合近红外复合滤光系统消除弧光干扰,获取MAG焊熔池图像.从MAG焊焊接缺陷产生的机理及熔池流态出发,采用同步对比试验,研究了熔池图像特征与焊接缺陷的映射关系,提取出表面气孔、焊塌、焊穿等焊接缺陷所对应的熔池图像特征.结果表明,一种焊接缺陷往往有多种视觉图像特征,通过熔池图像特征判断表面气孔、焊塌、焊穿等焊接缺陷具有良好可行性,为基于视觉的焊接缺陷自动在线预测提供了技术依据.     

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.     

基于被动光的MAG管道打底焊焊缝边缘提取方法

焊缝跟踪是实现焊接自动化的前提条件.间隙的变化会影响基于熔化极气体保护焊（metal active gas,MAG）的管道自动打底焊的焊接质量,为此设计了基于电荷耦合器件（charge-coupled device,CCD）视觉传感的MAG打底焊焊接过程监控系统.但从CCD获取的焊接过程的图像通常具有很大噪声,亟需设计...     

工件倾角对脉冲MAG焊接熔池形态和焊缝尺寸的影响

在相同MAG焊接参数条件下,采用单因素试验方法对不同倾角的工件进行了上坡焊和下坡焊工艺试验. 通过高速摄像技术以及图像处理技术提取了熔池边缘及尺寸等特征参数信息,并对熔池面积、后拖角等相关参数进行了修正. 分析了工件倾角对熔池宽度、长度、面积、后部面积、后拖角等特征参数以及焊缝成形的影响. 结果表明,当工件倾角超过30°时,工件倾角对熔池形态特征参数和焊缝尺寸有比较明显的影响,且该影响在上坡焊和下坡焊中的表现不同. 研究结果对减少非水平位置焊接产生的焊接缺陷和改善焊接工艺具有重要的指导意义.     

基于视觉的不锈钢Nd：YAG激光焊焊接熔池和小孔的图像处理

在激光焊接过程中存在众多干扰因素,为保证焊接质量,需要对激光焊进行质量控制。实现焊接质量控制的关键是表征焊接质量信息的获取,而焊接熔池和小孔包含丰富的焊接质量信息。针对不锈钢Nd：YAG激光焊,构建了同轴视觉检测系统,获得了熔池和小孔图像。根据熔池和小孔图像的特点,设计了图像处理算法,并分别针对熔池和小孔确定了搜索起始点和搜索准则。     

Seam tracking based on estimation of weld position using Kalman filtering

Abstract

A seam tracking method is presented based on the estimation of weld position during the gas tungsten arc welding process. Kalman filtering of the weld pool images from a visual sensor is applied to compute recursively the solution to the weld position equations which are established based on an estimation of the centroid position of the weld pool images. This centroid, the position of which corresponds with the weld position, is extracted as the measurement eigenvector. The evolution of the weld position data from the weld pool images can be described through an appropriate process model, so that the weld position can be detected by applying a Kalman filter. This allows adjustment of the welding torch position in real time, which may significantly reduce processing time and promote seam tracking accuracy. Simulations and actual welding experiments have demonstrated the effectiveness of the proposed algorithm in the presence of weld pool image noise and have demonstrated the robustness of weld position detection for seam tracking.     

焊接现场脉冲GTAW熔池图像动态检测

通过熔池的动态观测可以获得焊接过程的稳定性和连续性等信息.熔池的动态观测目前基本上停留在试验室阶段,焊接现场对熔池进行观测在改进工艺和指导生产等方面更具意义.针对焊接现场焊接电源不能修改,非计算机可控,电流电压波形未知等问题,在焊接现场建立了一套焊接熔池图像动态检测系统.根据焊接现场脉冲GTAW的特点,采用"外同步取像"方式确定了焊接现场取像的关键制约因素--取像时刻;并利用电弧光谱分析建立了减小弧光干扰的复合滤光系统;在适合的取像时刻,CCD摄像系统配合复合滤光系统,在焊接现场检测到了清晰的熔池图像.     

光纤激光焊接熔池和小孔的高速摄像与分析

采用主动光源和光学窄带滤光片等辅助器件,利用高速摄像技术对光纤激光焊接过程中的熔池和小孔进行了拍摄,获得了较为清晰的熔池和小孔图像,以及不同激光功率下光纤激光焊接熔池和小孔的实际尺寸,可以为光纤激光焊接熔池和小孔的模拟提供可靠的参考依据。对高速摄像图片和焊缝熔深波动以及焊缝形貌进行了分析。结果表明:小孔前沿附近是光纤激光焊接过程中飞溅产生的主要区域;利用高速摄像可以监测焊缝的熔深变化;熔池温度最低的区域为熔池后部的中轴线两侧,而非熔池边界处。     

基于视觉的MAG焊接熔池的标定

焊接熔池几何尺寸能够在一定程度上反映熔透信息,准确可靠的检测出熔池几何尺寸,对于实现熔透控制具有重要的意义.在MAC(metal active gas)焊中,由于熔敷金属在试件表面堆积,使熔池表面与试件上表面形成一定的倾角,导致基于视觉传感器检测到的熔池长度尺寸出现了误差.文中分析了产生误差的原因,给出了修正误差的方法,并从熔池侧面测量了熔池表面的倾角.根据测量得到的数据,对从熔池正前方检测到的熔池长度尺寸进行了修正,得到了较准确的熔池长度.     

窄坡口等离子-MAG复合焊工艺参数优化

针对转向架构架焊接变形及根部焊道背部成形问题,研究坡口角度为30°的V形窄坡口旁轴式等离子-MAG复合热源焊接工艺.文中以SMA490BW耐候钢平板对接为研究对象,基于响应面法建立了主要影响熔深的等离子电流、MAG电流、焊接速度、等离子气体流量与焊缝根部焊道的熔深、背部余高之间的数学关系模型,并依此模型分析了等离子-MAG复合焊接工艺参数对焊缝熔深能力的影响,获得了合适的复合焊接工艺参数.与普通MAG焊相比,窄坡口等离子-MAG复合焊接工艺既可保证焊缝根部完全熔透又能有效地减小接头的焊接变形.     

Highly efficient TIG welding of Cr13Ni5Mo martensitic stainless steel

A double-shielded TIG welding process using pure He gas as the inner shielding layer and He and CO₂ mixed gas as the outer shielding layer was proposed for the welding of Cr13Ni5Mo martensitic stainless steels. This proposed welding process can successfully address the problem of electrode oxidation with mixed-gas TIG welding and the issue of low weld depth and welding efficiency of traditional TIG welding. A change in the direction of the surface tension convection mode was the primary mechanism that affected the fusion zone profile. When the oxygen content in the weld pool was in the range of 80–120 ppm, the surface tension convection direction changed from outward to inward, resulting in both a larger weld depth and a larger weld depth/width ratio. This process not only allows for a high welding efficiency comparing with traditional TIG welding but also produces better weld impact properties than those of MAG welding (metal active gas welding).     

Supervised descent method for weld pool boundary extraction during fiber laser welding process

In order to obtain a high-quality weld during the laser welding process, extracting the characteristic parameters of weld pool is an important issue for automated welding. In this paper, the type 304 austenitic stainless steel is welded by a 5kW high-power fiber laser and a high-speed camera is employed to capture the topside images of weld pools. Then we propose a robust visual-detection approach for the molten pool based on the supervised descent method. It provides an elegant framework for representing the outline of a weld pool and is especially efficient for weld pool detection in the presence of strong uncertainties and disturbances. Finally, welding experimental results verified that the proposed approach can extract the weld pool boundary accurately, which will lay a solid foundation for controlling the weld quality of fiber laser welding process.     

The role of hydrogen in weld cracking processes – a new look at the problem

The new welding method known as F-MAG, which has been developed based on the CO₂ gas-shielded arc welding method (MAG), increases deposition rate of weld metal. The F-MAG welding method is combined with hot-wire, as has been used in TIG arc- and laser-welding methods. F-MAG is performed using hot-wire which is inserted into the rear part of the weld pool made with the leading electrode. Hot-wire melts by both electrical heating of itself and heat of the weld pool. Multi-layered weld metals were prepared using F-MAG and MAG. Microstructures and mechanical properties of both as-weld and reheated zones in the uppermost layer of the multi-layered weld metals formed with F-MAG and MAG were examined and the effects of hot-wire on microstructures and mechanical properties were analysed. Both the as-weld and reheated zones of the weld metal formed with F-MAG consisted of acicular ferrite (AF), equiaxed ferrite and so on. Both strength and elongation in as-weld and reheated zones formed with F-MAG were superior compared with those formed with MAG. It could be suggested that strength increased by refinement of AF due to increase in the concentration of alloying elements being contained in the hot-wire. Larger elongation of the weld metal in F-MAG compared with that in MAG could be analysed in terms of the Aggregate of AF Laths with nearly Parallel Slip systems between neighboring AF laths (ALPS). The number of AFs contained in an ALPS formed with FMAG is larger than that with MAG, in spite of the sizes of ALPSs formed with MAG and F-MAG being almost same. Deformation occurs over a lot of AFs in the case of finer AF formed with F-MAG through the rotation of the tensile test piece during deformation, resulting in the larger elongation.     

摩托车油箱焊接工艺设计

摩托车油箱焊接采用MAG、MIG熔化焊工艺和电阻焊工艺。上体左、右半壳直焊缝视产品结构不同，分别采用对接熔化焊和搭接缝焊工艺。     

MAG焊熔池图像特征及可用信息分析

针对MAG焊焊接过程的特点,采用被动式视觉传感的方式,利用近红外CCD摄像机,配合1064nm窄带滤光片和0.1%中性减光片组成的复合滤光系统,很好地排除了弧光的干扰,采集到大量高清晰的MAG焊短路过渡、射滴过渡、射流过渡熔池图像.利用数字图像处理技术对熔池图像进行图像处理,并提取出反映焊接质量的图像特征信息.对于单幅熔池图像进行了灰度分析,并提取了三条熔池图像等值轮廓线;对于连续多帧熔池图像,提出了利用熔池图像差影检测和熔池图像平均灰度来研究MAG焊焊接过程的新思路,为熔化极气体保护焊焊接过程质量控制奠定了基础.