Metal Vapor Behavior in GTA Welding of a Stainless Steel Considering the Marangoni Effect

A gas tungsten arc in helium was modeled taking into account the contamination of the plasma by metal vapor from the weld pool. The whole region of gas tungsten arc atmosphere including the tungsten cathode, arc plasma and weld pool was treated using a unified numerical model. The anode was of a low sulfur stainless steel or a high sulfur stainless steel. A viscosity approximation was used to express the diffusion coefficient in terms of viscosity of shielding gas and metal vapor. The transient two-dimensional distributions of the temperature, velocity of plasma flow and iron vapor concentration were predicted, together with the weld penetration at the atmospheric pressure. The distribution of the iron vapor is obviously different between the case of a low sulfur stainless steel anode and the case of a high sulfur stainless steel anode. © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Application of fuzzy logic to spatial thermal control in fusion welding

This paper considers the problem of sensing and controlling torch position in the pulsed gas metal arc welding (P-GMAW) process. The attitude and positional control described is essential to the production of quality welds with a specified geometry. For constant current arc welding processes, as normally employed with P-GMAW, the arc voltage signal variations that occur as a function of changes in the contact-tube-to-work distance can be used to automatically control the welding system with respect to bead placement and proper sidewall fusion. However, the arc voltage signals are uncertain and noisy because of many inherent disturbances associated with the electrode tip, droplet formation, droplet detachment, and droplet transfer through the arc. To deal with the nonlinear time-varying process with its inherent stochastic disturbances associated with the metal transfer, the theory of fuzzy sets was used as a general framework to interpret the uncertain arc signals and provide logic for control. The fuzzy logic controller weld joint tracking system was implemented and tested with pulsed gas metal arc welds under a variety of conditions. The goal was to obtain quick and accurate response to tracking errors in the presence of disturbances. A series of experiments was conducted to evaluate the performance of the fuzzy logic controller. The experimental results show that the fuzzy logic controller was found to be suitable for these purposes and better than methods based on signal averaging and bipolar decision levels under these criteria.     

Synchronous weld pool oscillation for monitoring and control

A novel approach for inducing and monitoring oscillations in a molten weld pool is presented. Recent research efforts have illustrated that the weld pool resonates at natural frequencies that are related to its dimensions and state of penetration. This phenomenon may be used to monitor the weld pool, particularly its depth of penetration, in a closed-loop feedback control system. The approach used to induce pool oscillations was to excite the weld pool with current pulses synchronized to the natural oscillations of the pool. Implementation of this synchronous weld pool pulsing technique was based on the use of a phase-locked loop (PLL) system. The natural weld pool oscillations are used as the reference frequency source and a pulsing circuit is controlled by the PLL oscillator, so that the arc current pulses repeatedly impact the pool after a fixed number of reference oscillation periods. An optical sensor detects the pool oscillations which are amplified, filtered, and limited to eliminate amplitude variations from the optical signal. A model of the weld pool is developed which uses a fluid droplet formulation for the relation of weld pool geometry and other physical parameters to the natural frequencies of the weld pool. Comparison of the weld pool's actual resonant frequency with the expected resonant frequency as predicted by weld pool geometry models and measurements of the pool width (or area) allows assessment of the state of penetration of the weld pool into the workpiece     

脉冲GTAW焊过程辩识及PID控制

针对脉冲GTAW焊溶池动态过程，利用面积法、Laplace变换的极限理法及最小二乘法对焊接速度与溶池背面熔宽模型进行了辩识。结果表明，面积法更适用于熔池动态过程辩识；对辩识所得到的二阶熔池模型进行了PID控制器设计，并针对起焊时的时滞采用Smith预估器予以补偿，实验结果表明，Smith预估器时滞具有很好的补偿效果。     

不同纵向磁场对大电流真空电弧中阳极活动影响的仿真研究

纵向磁场对阳极活动的控制效果对于大电流真空电弧成功开断十分关键。采用建模仿真的方法,分析不同纵向磁场强度对阳极活动的影响。基于大电流真空电弧模型,仿真得到不同纵向磁场强度下输入阳极的能流密度分布,并以此作为阳极活动模型的边界条件,得到不同磁场强度下的阳极熔化、蒸发情况。仿真结果表明:对于工频电流(50 Hz)电弧,阳极温度的最大值出现7 ms时刻附近;随着纵向磁场的增大,阳极表面温度、饱和蒸汽压、阳极蒸汽流量都相应减小;随着纵向磁场的增大,熔化半径增大,但是熔化深度减小,改善了阳极的烧蚀情况。     

Stability against tilt of a glass sheet submerged in molten metal with electromagnetic force

In one of the glass sheet tempering processes in which a glass sheet is submerged in molten metal with electromagnetic force by a linear induction motor (LIM), it is necessary to keep the glass sheet vertical in the center of the molten metal tank, because a glass sheet warps unless both sides are uniformly cooled. This paper describes the concept of the center of the buoyancy force on a glass sheet in molten metal, introduced in order to discuss its stability against tilt. If the center of the buoyancy force of a glass sheet is higher than its center of gravity, it is stable against tilt. Numerical simulation of electromagnetic fluid flow is performed to evaluate the center of the buoyancy force. The stability conditions are the following (where τ is the pole pitch of the LIM): (1) The shortest length of a glass sheet is 2τ/3 shorter than that of the LIM. (2) The lowest limit of the center of gravity of a glass sheet is τ/3 higher than the center of the LIM. © 1999 Scripta Technica, Electr Eng Jpn, 126 (3): 64–72, 1999     

TIG焊时的熔池形状及尺寸

焊接件在焊接过程中由于热输入导致的温度分布决定了焊接件的最终质量,熔池形状及尺寸的研究是预测焊接过程中温度场的一部分。在前人理论研究的基础上,通过对ＴＩＧ焊时熔池尺寸的实际测量,对大量的实验数据进行归纳、整理得出了熔池形状、尺寸与焊接规范的关系表达式。     

焊弧的电磁辐射研究

焊弧是大功率的用电负载；手工电弧焊中焊工距焊弧较近，研究焊弧的电磁兼容问题是有实际意义的，本文分析了焊接的形成机理，论述了焊弧电磁辐射的计算方法，给出了三维图形，对焊弧的辐射进行了测量，并对各个结果作了分析比较。     

SUPER304H奥氏体耐热钢焊接材料匹配与接头性能研究

分析了新型奥氏体耐热钢SUPER304H的焊接性及其焊接材料的匹配问题;采用NICRO82和ARCOS625镍基合金焊丝,TIG焊接方法焊制了该钢管接头,经过对试件接头力学性能、耐晶间腐蚀性能及组织特征等的分析和试验,表明SUPER304H钢采用镍基焊接材料焊接是可行的。     

考虑电极烧蚀影响的低压断路器电弧运动特性仿真及实验

以磁流体动力学(magnetic hydro-dynamics,MHD)为基础建立了考虑电极烧蚀影响的低压断路器中电弧的数学模型。在传统的质量、动量和能量守恒方程的基础上增加了铜蒸气的浓度方程,考虑电极烧蚀对气体的热动力学特性和传输系数的影响,针对阴极和阳极不同特点分别建立了电弧与阴极和阳极作用的数学模型。利用基于有限容积法的商业软件对上述模型进行求解,得出灭弧室内温度场、浓度场、气流场、电位场的分布情况。仿真结果表明,由于电极附近“双漩涡”的存在,使得Cu蒸气浓度最大的区域位于弧根后方靠近电极的区域;考虑Cu蒸气影响时计算得到的电弧电压为比未考虑Cu蒸气影响时减小12.3%;考虑Cu蒸气影响所得到的电弧平均运动速度比未考虑Cu蒸气影响时减少21.3%。实验结果验证了仿真模型的合理性。     

Investigate Weld Quality of Gas Metal Arc Welding Process Through Online Monitoring of Input Parameters

Gas metal arc welding (GMAW) is also referred as the metal inert gas (MIG) welding which is a process of welding done by the formation of an electric arc between the consumable wire electrode and the workpiece. Through the welding process, a continuous flow of inert gas is supplied, and it avoids the weld being subjected to react with at-mospheric air. The process can be automatic or semi-automatic where the main input parameters like current and the voltage can be direct and constant, respectively. Not only the current and voltage the welding quality depends on some more input parameters such as arc gap, velocity, and temperature. In this paper, we explain about a setup which is capable of real-time monitoring of input parameters mentioned above and selecting the best MIG welding parame-ters for the mild steel. The setup is composed of several sensors and microcontrollers for the collection and the measurement of the input parameters. The samples were categorized according to the federate and the voltage ad-justment of the selected welding machine. Then the final objective was to identify the samples of the weld with dif-ferent parameter changes which are monitored through the system. For the analysis, the samples were subjected to tensile and hardness tests, and microstructure tests to find the dependence of the input parameters which effect for the weld quality. Finally, the experimental results verified the effectiveness of the system for the selection of the quality weld.     

Generation of Anode Spot in Low‐Current DC Vacuum Arcs by the Effect of Embedded Magnet in the Anode

Experiments were conducted with the aim of keeping low‐current DC vacuum arcs stable. A permanent columnar magnet was embedded in the anode and a permanent disk‐shaped magnet was arranged behind the anode. As result, the arc plasma is strongly constricted to a column and a light emitting point appeared on the anode surface. Generation of the anode spot was confirmed by detecting anode metal vapor and ions using mass and spectroscopic analyses under low‐current arcs of less than 20 A. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Analysis and Improvement of Modeling of Electromagnetic Actuator for Medium Voltage Gas Insulated Switchgear

This study aimed to improve the acting magnetic force of an electromagnetic actuator for medium voltage gas insulated switchgear. First, a mathematical model was constructed based on the physical phenomena of an electromagnetic actuator in the fields of electric, magnetic, and mechanical energy. Then, ANSYS finite element software was used to calculate changes in the distribution of the magnetic field intensity and magnetic flux density of the electromagnetic actuator. The ANSYS simulation results were validated by numerical values derived from Matlab and experimentation. The factors influencing normal thrust were determined, including setting different working clearances, changing the size of the iron yoke of the electromagnetic actuator, magnetic material ratio, and the configuration of the movable axle center. The optimal characteristics were obtained by integrating the improved design. The integrated simulation of the improved iron yoke, silicon steel, and coil position was compared with the original model. The results suggested that the magnetic force significantly improved at a working clearance of 19.1, 10, and 2 mm, respectively, which nearly doubled the magnetic force of the original design.     

基于磁路分析的轴向混合磁轴承径向承载力解析计算

研究轴向混合磁轴承实现五自由度悬浮时,需要计算径向承载力与磁轴承结构参数以及永磁体参数之间的关系。为了解决轴向混合磁轴承缺乏径向承载力解析数学模型的问题,该文在分析轴向混合磁轴承磁路以及各部分磁导的基础上,结合稀土永磁体的工作特性,用虚位移法得出了轴向混合磁轴承的径向承载力解析数学模型。模型表明,在小径向位移时,该型的混合磁轴承径向承载力随着径向位移增加而增加,近似线性关系,径向承载力和刚度随轴向气隙增大而减小;磁轴承径向承载力随永磁体的有效长度增加呈现先增大后趋近饱和。利用有限元方法对径向承载力进行仿真计算,仿真结果与模型计算结果基本吻合。     

一种金属粉芯型CO2气体保护堆焊药芯焊丝的研制

研制了一种金属粉芯的CO2气体保护堆焊药芯焊丝，由于药芯中主要是各种合金粉末和少量的造渣剂和稳弧剂，因而焊接过程较一般焊丝要稳定，并且在气-渣联合保护下，降低了有益合金元素的烧损，又因为形成的渣极薄，因而可连续多层堆焊而无需清渣。随着制造工艺的不断完善，这种药芯焊丝必将有着十分广泛的应用前景。     

双管件电磁约束成形的电磁分布与均匀性变形研究

管件电磁胀形因其在轻质工领域具有成形极限高、回弹小等优点而得到广泛研究.然而传统电磁胀形过程中,存在轴向变形非均匀的问合金加题,制约了这一金属加工技术的发展.为此文中在驱动线圈和成形工件引入一约束管件来改善电磁力的分布特性,构建了基于双管件电磁约束成形方法.仿真结果表明,通过调节约束管的高度和电导率可以使成形工件取得比较高的轴向变形均匀度.此外,电磁力和成形速率的对比分析进一步表明采用基于双管件电磁约束成形方法时轴向均匀变形长度为36.3 mm,该值是传统电磁胀形方法下的2倍.显然,通过合理的引入一约束管件亦可以调节电磁力的分布规律,该研究为改善电磁力分布方式的创新提供了新的研究思路.     

高压电抗器油管路焊缝质量检测分析

变电设备中存在大量焊接制造产品,如变压器、电抗器、G IS设备等,外壳、管路采用焊接工艺制造。由于制造厂家注重产品电气性能,对产品的焊接质量要求不高,金属焊接部件出厂试验合格,但运行不久便出现开裂、泄漏等情况。文章针对某高压电抗器油管路焊缝质量检测中存在问题,提出了相应防范措施。     

基于双集磁器结构的管件电磁胀形研究

针对管件端部效应导致轴向变形不均匀,制约管件电磁胀形技术发展的问题,首次提出一种基于双集磁器结构的管件电磁胀形方法。首先通过采用双集磁器结构实现对管件电磁力分布的调控,然后建立管件电磁胀形电磁-结构二维轴对称模型,最后研究分析集磁器结构对电磁力分布和管件成形均匀性的影响。仿真结果表明,基于双集磁器结构的管件电磁胀形可为管件提供“凹型”分布的径向电磁力,与传统线圈相比采用双集磁器结构时所提供的算例能够显著增大管件胀形的均匀范围,从而有效解决管件轴向变形不均匀的问题。     

接触器用交流电磁铁三维磁场分析和静特性优化

用ANSYS软件分析了接触器用双E型交流电磁铁三维工频磁场 ,根据交流电磁吸力平均值的直流等效原理 ,分两步计算了衔铁吸力 ,利用ANSYS优化设计方法对铁心厚度进行了优化。讨论了动静触头初始接触处的电磁铁静特性配合问题     

操作油管对接焊缝焊接方法研究

针对贯流式水轮机操作油管对接焊缝的焊接质量问题,对钨极氩弧焊焊接工艺进行了研究,实验结果表明,焊缝成型好、表面无缺陷、焊缝RT探伤合格,完全满足操作油管的强度要求。