A power factor correction circuit for a single-phase arc welding power source using digital soft switching technology is proposed. The overall hardware structure of the system, the topology principle of the selected soft switch boost circuit, and the software design approach are discussed. The power factor correction results of the soft switch are verified under two conditions: electronic load and TIG arc welding. By using the electrical signals of the resonating capacitor and switching tube, it is confirmed that the circuit successfully achieved zero current conduction and zero voltage turn off. Through testing the power factor and efficiency of electronic loads at different powers, it was confirmed that the power factor can reach 0.985 or above, and the overall efficiency has been improved. Through TIG arc welding experiments under different welding currents, the corrected electrical signals are analyzed to verify the effectiveness of power factor correction for single-phase arc welding power.

A zero-voltage switching (ZVS) push–pull self-oscillating arc ignition circuit was proposed, marking the first application of ZVS technology in welding arc ignition systems. The circuit’s working principle was analyzed, and time-domain waveforms of the switching transistors verified the realization of soft switching. A conducted interference test platform was established in order to assess the circuit’s electromagnetic compatibility under no-load and arc ignition transient conditions. In comparison with conventional domestic arc ignition circuits, the proposed ZVS circuit demonstrated substantially diminished quasi-peak interference levels, with a reduction exceeding 9.5 dB in both instances. Additionally, under no-load conditions, the ZVS circuit demonstrated interference levels comparable to those of a commercial Fronius system, while during arc ignition transients, it exhibited an over 5 dB reduction. The findings of this study demonstrate that the incorporation of soft-switching techniques into arc ignition circuits can effectively mitigate conducted interference, thus providing a promising and practical approach for industrial welding equipment.

An experimental platform was built for simultaneous acquisition of the input and output electrical signals as well as droplet transfer images during the welding process. By analyzing the rectifier circuit of the welder, the calculation method of the instantaneous input power, the instantaneous input power envelope, and the input pulsating energy (EP) were given. The input pulsating energy was found to better characterize the dynamical change process at the output terminal upon comparison. Then, the short circuiting transfer, free transfer and mixed transfer patterns were obtained by varying the wire feeding speed and the given voltage. Based on the standard variance (SD) and coefficient of variation of the input pulsating energy (v(Ep)), the parameter variations in different transition patterns and the stability of the transition process were compared and analyzed. The results reveal that the v(Ep) was greater than 18% for short circuiting transfer and less than 9% for free transfer.

In this study, a platform for a welding experiment, used to collect input and output electrical signals, was constructed, and the algorithm for the input pulsating energy interpolation line (IPEI) was given. Experiments with MAG surface straight line welding were conducted at various voltages. Analysis of the IPEI in relation to the welding current was performed while combining real-world welding occurrences with high-speed camera images of droplet transfer. It was established that the IPEI can be employed as a characteristic parameter to assess the stability of the short-circuiting transfer process in MAG welding. The three criteria for assessing the stability were the spectrum, approximation entropy, and coefficient of variation. A comparative analysis was conducted on each of these approaches. It was determined that the most effective technique is approximation entropy. The approximation entropy of the welding current and IPEI are also highly consistent, with a correlation coefficient as high as 0.9889.

基于高速摄像机触发模式的特点,提出了一种基于电信号监测的可控自触发电弧图像采集系统.介绍了系统硬件平台组成和软件总体框架,论述了以电信号有效值为监测条件的相关控制触发算法,叙述了电信号和电弧图像同步采集的具体实现方法,并以表面涂有油污的试样进行了电弧图像采集系统的试验验证.结果表明,该系统能够有效基于电信号可靠自动触发高速摄像机拍摄,抓捕涂有油污表面的过渡过程信息.相比于正常焊接过程,试样表面存在油污时,过渡周期明显增加,电弧形态呈现出较大的发散性.

The shape of welding arc is closely related to the quality of welding. For micro plasma arc welding (MPAW), however, the change of arc shape is not obvious enough to evaluate the quality of welding, due to the small size of welding arc. Thus, it needs to extract the specific features of arc shape through image processing algorithm to judge its change quantitatively. Furthermore, for workpiece with bright surface, it is difficult to extract the arc shape directly from the arc images because of the strong arc reflection on the workpiece surface. In this paper, a new method based on vertical Sobel operator was proposed to overcome the above-mentioned challenges, and to extract the clear arc shapes from the arc images of pulse micro plasma arc welding (P-MPAW). The arc length, arc width and the height difference between two sides of arc were extracted as characteristic parameters to reveal the influence of different welding defects on the arc shape. The changes of arc characteristic parameters have been studied in depth, when there are different defects such as burn through, misalignment, undercut, concave deformation, excessive gap and overlap. The results show that, excessive welding gap and misalignment, caused by the assembly and machining accuracy, have obvious characteristics in the instantaneous arc shape. The defects caused by welding thermal process like burn through, concave deformation, overlap and undercut have their own distinctive characteristics in the changing process of the arc shape.

A method was proposed to identify the boundary between droplet and welding wire by processing the image from high-speed photography in the process of Variable Polarity Cold Metal Transfer (VP CMT). The droplet volume and its variation trend in electrode positive (EP) phase and electrode negative (EN) phase of aluminum wire with different parameters were obtained. The results indicated that the melting volume of aluminum wire exhibited a positive linear relationship with the input work of plasma phase, and the droplet increasing volume of aluminum wire in EN phase was approximately 2.2 times that of EP phase under same input work. The droplet transfer process was divided into droplet rapid growth and slow growth stage according to the droplet growth rate. The welding parameters and droplet growth property in the first cycle after the polarity switching (EN to EP, EP to EN) were different from that in the following cycle.

基于CMT Advanced+P焊接方法,以ER5356铝合金焊丝对7075铝合金和TC4钛合金组成的搭接接头进行熔钎焊试验,并对接头进行微观组织及力学性能分析.结果表明,焊接接头主要由焊缝区、铝合金侧热影响区和钎焊界面区组成;焊缝区主要是等轴晶;铝合金侧热影响区的晶粒表现出轧制特性,并在晶界附近析出大量金属间化合物;钎焊界面区存在由钛侧向焊缝区进行生长的锯齿状金属间化合物层,该化合物层厚度1～2.5μm,主要由Al-Ti金属间化合物组成;接头拉伸后断裂位置位于铝合金侧热影响区附近,断裂类型属于混合断裂,最高抗剪强度达到293.1 MPa.

结合弧焊焊接的内在特性,给出了机器人焊枪自转角的定义.基于三相功率分析仪,搭建了机器人功率消耗的测量平台.针对1G、2G和3G位置的直焊缝焊接,使用该平台测量了CMT弧焊焊接机器人在不同焊枪自转角作业过程中消耗的瞬时功率.计算并对比了机器人的平均功率,发现在这3种位置,改变焊接起点和终点的焊枪自转角,机器人在整个运动过程和焊缝段消耗的平均功率都有显著变化.机器人在焊缝段和整个运动过程中的功率消耗变化规律相似,存在着能量最优的起点和终点焊枪自转角.结果表明改变焊枪自转角,可以节省焊接机器人能量消耗.在1G、2G和3G位置,分别以各焊接位置所有焊枪自转角组合的平均值计算,最大可以减少11.1％、5.9％和8.3％的功率消耗.定义了功率消耗最小值附近区间表示取得功率最小值的难易程度,发现该区间概率很小,这进一步说明了焊枪自转角对机器人的功率消耗有显著影响,为了减少弧焊焊接中机器人的功率消耗,需要注意焊枪自转角的选择.最后,简述了焊枪自转角与机器人功率消耗,以及工件摆放位置与机器人功率消耗关联模型的建立思想,并给出了相关初步结果.该方面的研究对焊接机器人能量优化和实际焊接生产有着重要的指导意义.

以焊缝高宽比和深宽比作为优化目标,结合径向基函数神经网络和带精英策略的非支配排序的多目标遗传算法NSGA-Ⅱ,实现了多目标优化.建立了以焊接电压、送丝速度、焊接速度作为自变量,预测焊缝熔宽、余高和熔深的5种模型,即误差反向传播神经网络、遗传算法优化的误差反向传播神经网络、克里金插值法、径向基函数神经网络和二阶多项式回归模型.对比分析表明,径向基函数神经网络具有较高的预测精度和稳定性,最为合适.最后,利用NSGA-Ⅱ算法实现了以盖面焊和填充焊为应用场景的工艺参数多目标优化,试验证明了该优化方法的有效性.

以MAG焊焊接电压、焊接速度、送丝速度为可调工艺参数,开展了三因素三水平全因子平板对接焊和堆焊试验.基于试验数据建立了误差反向传播神经网络、径向基神经网络和克里金模型来预测焊缝余高、接头抗拉强度和冲击吸收能量.模型预测结果显示,所建立模型均能较好的预测焊缝性能,但是没有一个模型能同时最佳预测三种焊缝性能且各模型预测波动较大.为了进一步提升预测精度和稳定性,将误差反向传播神经网络、径向基神经网络和克里金模型以线性加权法组合.结果表明,组合模型能提升预测的精度和稳定性.基于组合模型,采用NSGA-II算法实现多目标优化,得到并验证了焊缝余高、接头冲击吸收能量和抗拉强度三者间的非劣解.验证结果表明焊接工艺多目标优化对实现焊缝综合性能整体最优以及焊接精细化应用具有较大的指导意义.

采用焊接电信号采集系统与高速摄像系统对SAF2507超级双相不锈钢CMT + P(冷金属过渡 + 脉冲)熔滴过渡过程进行观测研究. 分析了CMT与CMT + P过程在不同送丝速度WFS下的熔滴过渡行为、波形变化机理与能量输入特征,揭示了CMT + P熔滴过渡特性. 结果表明:CMT + P实际波形图与理论上有多处不同;熔滴形状与尺寸、过渡形式、熔池的波动状态、焊丝端部到工件的距离及飞溅等都能影响电压的波动,电压波形图可以用来指导分析熔滴过渡行为;脉冲阶段对热输入起主要影响作用,调节脉冲峰值电流、脉冲基值电流、脉冲个数,可实现热输入的控制.

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.

In order to meet the demand of robotic multi-pass welding of single V-groove with an uneven and irregular change of intersecting pipes, a novel method in which the weld was divided into several segments according to the change rate of cross-sectional area was put forward in this paper. It was effective to avoid repair welding and secondary processing for such complex joints. By controlling the welding parameters in each segment, the amount of filler metal changed with the cross-sectional area of weld groove; thus, the number of weld passes kept unchanged in each layer and the appearance of the weld remained flat. For each segment, the appropriate welding parameters were identified according to the target value of the size of welding seam through the second-order regression prediction model which was related to the width and height of weld seam. Finally, the feasibility of the welding trajectory was verified by virtual simulation. Welding experiment was carried out and the actual welding seam was basically consistent with the planning results. It was proved that this planning method for sectional welding of the welding seam according to the variation of cross-sectional area is feasible and can be applied to practical welding engineering.

基于不同送丝速度、电弧电压、焊丝伸出长的CO2焊短路过渡的电信号,计算焊接过程中的焊接电流变异系数和熔滴过渡频率,综合熔滴过渡频率和高速摄影图片来分析焊接过程稳定性,研究了焊接电流变异系数与焊接稳定性的定量关系.试验与数值分析表明在改变送丝速度Vf,电弧电压U和焊丝伸出长L的条件下,焊接电流变异系数v(Ⅰ)和焊接过程稳定性都成负相关关系,即焊接电流变异系数v(Ⅰ)越小,焊接过程越稳定,反之熔滴过渡频率f越小,焊接过程越不稳定.

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 in-tense 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.

The reel-lay method is one of the most effective procedures for installing submarine pipelines. During the reel-lay installation process, pipelines are subjected to large-scale plastic strain because of cyclic bending/ straightening processes. Thus, mechanical tests must be carried out to assess the effect of large-scale pre-strain on the girth weld of pipelines after cyclic bending/straightening processes. Tensile tests were performed on weld metals, the results showed that a slight increase in tensile and yield strength were caused by a pre-strain of 2.709% (maximum strain region). A single-edged notched tension (SENT) specimen was examined via the unloading compliance method to evaluate the fracture toughness for the base metal, weld metal and HAZ. The fracture toughness test results showed that the weld metal exhibited the lowest fracture toughness followed by the base metal and HAZ. The fracture toughness of the base metal, the weld metal and HAZ all decreased after the cyclic bending/straightening with a pre-strain of 2.709%.

The effects of electron beam welding and subsequent post-weld heat treatment at different temperatures on the microstructure evolution and pitting corrosion resistance of duplex stainless steel were investigated. The as welded joint exhibited poor pitting corrosion resistance, and pitting preferentially occurred at the ferrite grain in the weld. Heat treatment promoted austenite formation, Cr2N dissolution, and eliminated dendritic segregation, consequently improving the corrosion resistance of the welded joint. The optimal solution temperature range was 1050-1110 degrees C. The austenite in the weld was prone to selective corrosion after heat treatment owing to its lower pitting resistance equivalent number.

With the aim of developing highly conductive ink for flexible electronics on heat-sensitive substrates, Ag nanospheres and nanoplates were mixed to synthesize hybrid inks. Five kinds of hybrid ink and two types of pure ink were written to square shape on Epson photo paper using rollerball pens, and sintered at a low temperature (100 °C). The microstructure, electrical resistivity, surface porosity, hardness and flexibility of silver patterns were systematically investigated and compared. It was observed that the optimal mixing ratio of nanospheres and nanoplates was 1:1, which equipped the directly written pattern with excellent electrical and mechanical properties. The electrical resistivity was 0.103 μΩ · m, only 6.5 times that of bulk silver. The enhancement compared to pure silver nanospheres or nanoplates based ink was due to the combined action of nanospheres and nanoplates. This demonstrates a valuable way to prepare Ag nanoink with good performance for printed/written electronics.

The influences of electron beam (EB) welding and subsequent post-weld heat treatment (PWHT) at different temperatures on the microstructure evolution and low-temperature toughness of duplex stainless steel were investigated. The results showed that the rapid cooling in EB welding led to excessive ferrite formation, abundant Cr2N precipitation, and significant dendritic segregation in the weld, ultimately resulting in deterioration of toughness. PWHT promoted austenite formation and Cr2N dissolution, and eliminated dendrite segregation, which consequently restored the toughness of the weld. The annealing temperature had a very significant influence on the type and content of austenite, as well as toughness. The toughness was not determined solely by the ferrite/austenite ratio. Spheroidal intragranular austenite particles played an important role in improving toughness due to incoherent interface boundaries with the ferrite matrix and low-energy special grain boundaries. The most favourable annealing temperature for the studied EB weld was found to be 1080 degrees C, at which the weld had the highest impact toughness. (C) 2018 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.