基于高速CCD摄像的短路过渡焊接熔滴检测与分析

建立了基于高速CCD摄像的熔滴图像检测和焊接电流、电弧电压同步采集系统,在给出短路过渡模式下的熔滴尺寸定义并简述基于MATLAB平台的熔滴尺寸与电弧信号分析系统的基础上,对平特性电源短路过渡CO2焊接熔滴尺寸变化特征及其与工艺性能间的关系进行了试验研究.结果表明,熔滴尺寸呈分散性较大的正态分布(1～2倍焊丝直径),过大或过小的熔滴尺寸均不利于短路过渡焊接过程的稳定性.根据熔滴的形成和过渡过程,初步分析了影响熔滴尺寸的主要因素及控制熔滴尺寸的途径,即短路过程结束后焊丝端部的残余液态金属量和燃弧能量的随机性导致了熔滴尺寸的不确定性,对其进行有效控制将提高熔滴尺寸和短路过渡过程的一致性,进而改善短路过渡CO2焊接的工艺性能和焊接质量.     

Metal transfer and arc behaviour of novel consumable and non-consumable electrode indirect arc droplet welding

Abstract

The consumable and non-consumable electrode indirect arc droplet welding is a novel method that applies an indirect arc generated between a consumable electrode and a non-consumable electrode to welding. It was successfully used to overlap join the thin zinc coated steel plate. In the point to point (consumable electrode and non-consumable electrode) configuration, the stable metal transfer was obtained. The globular, projected spray and streaming spray transfer modes were promoted. With the increase in welding power, the metal transfer became faster and more stable. At the same time, the indirect arc became brighter, smaller and more stable. The arc self-regulation guaranteed the stable burning of the indirect arc. The desire stability was observed from the fluctuation of the welding current and the arc voltage waveforms. The side concentrated melting on the root of the droplet produced high pinch effect, which facilitated the detachment of the droplet.     

短路过渡CO2焊接熔滴尺寸控制

分析了短路过渡CO2焊接的熔滴形成过程及焊接电流波形对熔滴形状及短路过渡历程的影响规律,对采集获得的焊接过程中的焊接电流信号进行数学处理,采用最小二乘法建立了波形控制短路过渡焊接的焊丝熔化模型.在此基础上,通过控制燃弧初期脉冲电流的宽度调整燃弧能量的大小,对熔滴尺寸控制进行了试验研究.结果表明,随着燃弧脉冲电流宽度的增加,熔滴尺寸单调增加,这说明改变燃弧初期脉冲电流的宽度可以有效地控制燃弧能量和熔滴尺寸的大小.     

基于FLUENT的高压断路器弧触头喷溅侵蚀流动特性分析

高压断路器动作时,触头间会形成电弧,并伴随蒸发和喷溅现象,造成触头材料侵蚀和接触系统的失效.为研究高压断路器烧蚀故障的喷溅机理特征,建立了弧触头熔池的流动与传热模型,并运用FLUENT软件分析了触头在不同弧根下的熔池温度场、流场和压力分布.计算结果表明:在两种弧根条件下,均形成了半圆形的熔池,弧根较小的情形下不利于能量的散发和电弧的运动,导致流速较大,增大电极的侵蚀.熔池的流体流速随电流的增大而增大,且电流越大,弧根区内流体流速由最小值上升到最大值的速度越快,熔池深度方向的熔化速度也加快.     

变极性等离子电弧稳定性及其控制

以变极性等离子电弧稳定性机理及其控制方法为研究对象,自行研制了80C196KC单片机为控制核心,主电路为双逆变型电路拓扑结构的VPPA1型变极性等离子焊接电源.重点分析小电流过零再引燃机理及其在大规范焊接条件下变极性等离子弧焊接系统及其电弧的稳定性.分别提出了在小电流焊接时通过程序设定方法将变极性等离子电弧由正极性变反极性之前提高过零电流,而大规范焊接条件下则控制过零电流的新观点,对科学认识变极性等离子电弧特性及其焊接过程控制有重要的指导意义.     

Metal transfer characteristics of GMAW with strip electrode

Abstract

The metal transfer process of gas metal arc welding with strip electrode is observed by a high speed digital camera system. Because the rectangular strip electrode has a large width/thickness ratio, the pendant droplet is elliptical in shape, and multicurrent channels are generated. The Lorentz force induced between the multicurrent channels drives the droplet and welding arc to move along the strip electrode end, but the droplet always lags behind the welding arc. The movement results in uncertain droplet’s detaching location and transition trajectory. The projected transfer mode is promoted, and the streaming and rotating transfer modes are restrained. With the increase in welding power, the droplet motion is faster but more stable. The stability can be reflected from the fluctuation of the welding current and arc voltage waveforms.     

空心钨极同轴填丝焊空间热场分布特征

利用理论建模与试验相结合的方法,系统研究了空心钨极同轴送丝焊接过程中焊丝熔化热量的来源. 结果表明,基于磁流体力学的理论模型分析结果和实际情况高度吻合;在高温电弧热辐射及钨极热传导共同作用下,钨极内孔形成的梯度式高温区会对焊丝起到一定的预热作用;环状空心钨极电弧中轴线上近几何中心区域的温度最高,焊接电流400 A时温度高达13 700 K;熔滴与液态熔池接触后电势相等,在最小电压原理作用下,部分高温电弧的阳极作用区会由液态熔池转变至焊丝表面,同时部分焊接电流会从焊丝流过,形成的电阻热也是高效熔丝的主要原因之一;熔滴过渡分析结果表明空心钨极同轴填丝焊接具有较高的工艺稳定性,是一种极具发展前景的焊接新方法.     

空心钨极同轴填丝焊接丝弧交互作用机制

空心钨极同轴填丝焊接焊丝与电弧(丝-弧)交互过程是决定焊接质量的关键.首先利用高速摄像观察分析了空心钨极电弧与实心钨极电弧形态,及其对焊缝成形特征的影响规律,然后构建了熔丝过程受力模型,系统分析了同轴填丝焊接过程中熔滴形成及过渡过程动力学特征.结果表明,空心钨极电弧表面辐照区域大于实心钨极,在大电流工艺条件下焊缝成形稳定;熔滴形成阶段,焊丝末端熔滴处于静力平衡状态,在较大表面张力作用下,无法自发从焊丝末端直接过渡进入熔池;熔滴过渡阶段,部分电流从焊丝流过,产生电磁收缩力,引起焊丝与熔池之间的熔滴摆动.     

激光功率对激光-双丝脉冲MIG复合焊接电弧形态及熔滴过渡的影响

通过搭建激光-双丝脉冲MIG复合焊接系统,利用高速摄像与电信号采集系统对激光-双丝脉冲MIG复合焊接在不同激光功率下的电压电流信号及高速摄像信号进行同步采集,研究激光功率对焊接过程的电弧形态、熔滴过渡过程的影响.结果发现,由于激光等离子体与电弧等离子体的相互作用,电弧形态和熔滴受力状态发生改变.随着激光功率的增大,激光对电弧的吸引能力增强,促进熔滴过渡的等离子流力竖直向下的分力减小,熔滴过渡频率降低.     

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.     

基于冷金属过渡的电弧增材制造钛合金螺旋桨成形机理及组织性能

通过对基于冷金属过渡(CMT)的电弧增材制造成形过程中电弧形态、电流电压同步信号和熔池形貌的同步检测分析,研究了电弧不同阶段的熔滴过渡形式和熔池金属的受力状态,探明了悬垂结构成形过程中的熔池金属的受力机制,实现了钛合金螺旋桨的成形,并分析成形后的组织性能。研究结果表明,通过对CMT电弧热输入和电弧力的精细控制,能够在无支撑条件下实现螺旋桨叶片的快速成形,同时获得良好的力学性能。在本研究条件下,钛合金CMT增材制造过程中熔滴过渡主要以短路过渡的形式进行,降低基值和短路阶段的焊接电流能够增加悬垂结构倾角,且当I基值/I峰值小于0.3时,钛合金螺旋桨最大倾角达到53.26°。基于优化后的工艺成形船用Ti6321合金,内部组织致密且无贯穿式的粗大柱状晶,力学性能达到同级别锻件标准,水平方向和竖直方向的各向异性不明显。     

外加纵向磁场GTAW焊接机理：Ⅰ电弧特性

针对外加纵向磁场GTAW（gas tungsten-arc welding)焊接过程,采用红外热像伪着色法测定了外加纵向磁场GTAW焊接电弧的温度场,并建立了外加纵向磁场GTAW焊接电弧热流密度径向分布模型,对焊接电反外形的变化,焊接电弧电流,电压与外加纵向磁场强度变化的关系进行了研究。     

脉冲TOPTIG焊熔滴过渡特性分析

TOPTIG焊是一种新型的机器人TIG填丝焊接工艺,具有不同于普通TIG填丝焊的熔滴过渡特性,文中通过搭建TOPTIG焊接试验平台,利用高速摄像和电信号采集系统,对在不同条件下的焊接过程进行高速摄像和电信号的同步采集,从而对TOPTIG焊的熔滴过渡特性进行了研究.结果表明,熔滴与熔池相接触时,由于电磁力的作用使得电弧发生偏转.熔滴过渡只能通过接触熔池的方式来实现,在过渡过程中,熔滴的重力和其与熔池之间的表面张力是促进过渡的主要作用力.电弧峰值电流和送丝速度存在一个合理的匹配区间,并且随着峰值电流的增大,匹配区间缩窄.     

Study on weld formation in a novel rotating arc horizontal GMAW

A novel rotating arc horizontal welding process was developed for solving the sagging of the molten pool which bottlenecks the application and the development of the horizontal welding. The principle of the effect of the rotating arc on the molten pool is that the rotating arc process not only can reduce the welding heat input by prolonging the welding path in the same welding distance caused by the arc rotation, but also disperse the arc force to affect the sidewall periodically to support the molten metal near the upper sidewall. The effects of the rotating speed and arc voltage on the weld formation were studied.The results indicate that there is an appropriate range of the rotating speed and the arc voltage to obtain the defect free horizontal welding.     

钛-铝双丝超音速电弧喷涂过程中熔滴粒子几何特性研究

为了研究工艺参数对钛-铝双丝超音速电弧喷涂熔滴粒子尺寸的影响规律,通过对喷枪出口处气流速度、气体质量流率和金属熔滴质量流率的分析测定,以Nukiyama-Tanasawa模型为基础,建立了喷涂粒子的平均直径与喷涂电压和电流间的解析关系,并对喷涂电压和电流对熔滴粒子平均直径的影响进行了计算机模拟仿真.结果表明:在喷枪结构和雾化气体压力一定时,雾化粒子的平均直径随喷涂电流的增大而增大,随喷涂电压的升高而减小,但总的变化幅度却较小.利用激光粒度分析仪对一定喷涂工艺条件下所得的粒子平均直径进行实验分析,结果与计算值之间的相对误差为9.52%,扫描电镜观察表明粒子形态以球形颗粒为主.     

高气压环境下脉冲电流控制对熔滴过渡的影响

高压环境对焊接电弧和熔滴过渡有很大的负面作用,试验以脉冲MIG焊电流电压波形、U-I相图和熔滴过渡图为主要评价手段,分析了压力环境对脉冲MIG焊的影响规律,总结了脉冲峰值电流和脉冲基值电流的优化对焊接电弧和熔滴过渡稳定性的改善作用. 结果表明,压力环境使电弧燃烧激烈,熔滴过渡不稳定. 脉冲峰值电流的优化能有效提高高气压环境下焊接电弧和熔滴过渡的稳定性. 相比之下,脉冲基值电流的优化虽然对电弧燃烧的稳定性有积极作用,但是效果相对较小. 高压环境下脉冲电流的优化为焊接的稳定性提供有效的技术手段.     

Process and joint characterizations of laser-MIG hybrid welding of AZ31 magnesium alloy

High power laser-metal inert gas (MIG) hybrid welding of AZ31 Mg alloys was studied. Microstructure and fracture surface of welded joints were observed by optical microscope and scanning electron microscope. The mechanical properties of welded joints were evaluated by tensile test. Under the optimal welding parameters, the stable process and sound joints were obtained. The tensile strength efficiency of welded joints recovered 84-98% of the substrate. It was found that the arc was compressed and stabilized by the laser beam during the hybrid welding. The compressed extent of arc column increased with laser power, and the process stability could be improved by increasing laser power and arc current or slowing welding speed. The arc stabilized mechanism in laser-MIG hybrid welding of Mg alloys was summarized in two factors. First, the laser keyhole fixes the arc root and improves the igniting ability of the arc. Second, the electromagnetic force is downward and increased by the laser-arc interaction, which prevents the overheating of the droplet and smoothes droplet transfer from the wire to the weld pool.     

超窄间隙焊接中送进焊剂片与电弧相互作用机制分析

送进式焊剂片约束电弧超窄间隙焊接中，连续送进的焊剂片与电弧相互作用的关系影响着焊接过程的稳定性.采用一种快速中断电弧的方法，得到了熄弧位置处焊缝熔池形态和焊剂片瞬时熔化形貌，分析了焊剂片对电弧的作用长度与电弧受约束程度的关系.结果表明，增加焊剂片送进速度或减小电弧电压，可使焊剂片对电弧的作用长度增加，当增至一定程度时，电弧被有效约束在坡口底部对侧壁根部进行均匀加热，获得根部熔合良好的平焊缝.当焊剂片对电弧的作用长度过小时，电弧的受约束程度减弱，电弧加热区域集中在两侧壁上，很难在坡口根部形成有效熔池，最终形成孔洞焊缝.     

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.     

金属粉末再压缩等离子弧焊接工艺

提高电弧穿透能力是等离子弧焊接领域的重要课题.自主设计并搭建了金属粉末再压缩等离子弧焊接新工艺试验平台,采集焊接过程电信号、视觉信号、弧光光谱信号等,并从焊缝成形、电弧电压、熔融金属过渡、弧光光谱等方面对金属粉末再压缩等离子弧焊接过程进行了初步的研究.在相同焊接电流195 A条件下,与常规等离子弧焊接工艺相比,金属粉末再压缩等离子弧焊接焊缝熔深增加1.29 mm、熔宽减少1.65 mm、电弧电压升高0.63 V.在波长为230 ~ 270 nm范围内,与常规等离子弧焊接相比,金属粉末再压缩等离子弧焊接中Fe和Cr元素的特征谱线明显增多. 结果表明,在相同电流条件下,与常规等离子弧焊接相比,金属粉末再压缩等离子弧焊接电弧穿透能力增强.