Contribution of metal vapor mass at periphery part of pulsed arc to electromagnetic force in weld pool

The arc welding has been used in various welding methods because it is inexpensive and high in strength after welding. However, it is a problem that accidents such as collapse of the bridge occur because of the welding defects. The welding of low cost and high productivity is required without the welding defects. The pulsed TIG welding is inexpensive and capable of high‐quality welding. The electromagnetic force contributing to penetration changes because the transient response of arc temperature and iron vapor generated from anode occurs. However, the analysis of pulsed TIG welding with metal vapor has been elucidated only metal vapor concentration near anode with transient phenomenon and heat flux. Thus, the theoretical elucidation of penetration depth with control factor has not been researched. In this paper, the contribution of metal vapor mass at the periphery part of pulsed arc to the electromagnetic force in the weld pool is elucidated. As a result, the iron vapor mass at periphery part decreased with increasing the frequency. The iron vapor was stagnated at axial center within one cycle. The electromagnetic force to the penetration depth direction in weld pool increased at axial center. Therefore, the metal vapor mass at periphery part plays an important role for the electromagnetic force increment at axial center.     

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.     

不锈钢半自动(MAG)焊在核电厂建设中的应用

对采用半自动(MAG)气体保护焊来焊接不锈钢水箱的工艺进行了研究,并且对试验结果进行了分析,试验结果表明:焊缝经NDT检测合格,金相照片和力学性能良好.该焊接工艺成功应用于核电厂不锈钢水箱的安装焊接中,焊接接头质量合格,外现成型良好,焊接效率高.     

核电站控氮不锈钢Z2CN19-10焊接技术

控氮不锈钢因材质性能优良被广泛应用于核电站设备制造中,深入研究该钢种的焊接技术,对制造相关核电设备具有重要的意义.在分析了控氮不锈钢的焊接特点基础上,对其所采用的焊条电弧焊和埋弧焊工艺进行了试验和研究.通过选用合理的焊接材料、坡口型式和焊接工艺参数,可获得良好的焊缝质量,也使焊接接头具有良好的综合力学性能和抗晶间腐蚀能...     

Anode attachment and received heat of argon torch plasma with high lateral airflow as function of current

The torch plasma arc has useful characteristics of high energy and high current. The mode of torch plasma arcs can be flexible, even if the arc is exposed to the lateral gas. In this paper, we measured the input power, heat power, and heat efficiency of the torch plasma arc to the anode in order to determine the current effect on the anode attachment of plasma torch arc with high lateral air velocity, varying from 0 to 80 m/s at a plasma Ar flow rate of 12 slm. As a result, the input power increases with lateral gas velocity such as from about 8000 W to 16,000 W and the heat efficiency decreases with the lateral gas velocity such as from about 50% to 25% at the current I=150 A and appearance plasma length L_a=1 cm. These results could be applied to providing the electrical power from the ground to high‐speed mobiles, v.v., and to reducing an anode surface erosion by the anode spot movement. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(2): 29–35, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20479     

管道内部氩气浓度对焊缝成型的影响

通过采用氩气分析仪对不锈钢、马氏体钢等高合金钢在焊接过程中充氩的浓度大小进行测定,讨论氩气浓度的大小对不锈钢、马氏体钢等高合金钢焊缝内部质量的影响。试验表明：氩气浓度的大小对焊缝根部的保护效果有很大的影响,管道内部氩气浓度是制约焊缝内部质量的关键,是保障焊接质量的重要环节。     

大气压微等离子体放电特性研究

通过减小电极孔径到微米量级来实现高气压甚至大气压放电的现象已成为研究热点。笔者利用不锈钢空心针作为放电阴极,不锈钢网作阳极,进行了大气压微等离子体放电实验研究。实验测量了大气压微放电的伏安特性曲线。实验发现,大气压直流微放电存在不同的放电模式:空心阴极放电和反常辉光放电,随着电流的增加,放电越来越强烈。实验研究了放电电压随压强和气体流量的变化关系。结果显示,随着体系压强的增加,电离过程增多,放电电压逐渐降低。随着流量的增加,气体流动状态由层流状态逐渐过渡到紊流状态,引起放电电压先降低后增加。     

气液滑动弧放电降解4-氯酚溶液的研究

用10kV高压产生直接与废水接触的气液滑动弧放电非平衡等离子体降解水中4-氯酚。实验研究表明:由于液滴的存在改变了电极间的介电常数和局部电场,气液滑动弧放电的电压波形比纯气流滑动弧放电更加不规则,起弧电压更低:从溶液COD降解效果来看,当不锈钢作为电极材料时, 4-氯酚降解效果比铝和铜电极材料好;当空气作为载气时,经过76min的等离子体处理,溶液的COD值由1679.2mg／L降到190mg／L,相当于COD降解率为88．68％;增大气液混合比能够提高4-氯酚的降解效果;同时检测了H2O2和O3的生成量和溶液pH、电导率的变化。     

低压断路器电弧仿真试验和研究

介绍了二维电弧磁流体动力学模型的建立方法,分析了产气材料、金属蒸汽、灭弧室结构等不同因素对电弧特性的影响。仿真试验结果验证了仿真方法和模型的正确性,为低压电器灭弧室的优化设计提供了理论基础。     

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.     

转轮用高屈强比高韧性不锈钢焊接接头微观组织与性能

本文针对应用于大型转轮的高屈强比高韧性铸造不锈钢的焊接接头组织及力学性能进行了研究,结果表明,焊后经过480℃退火处理后接头微观组织均为单相板条马氏体,接头拉伸性能良好,而接头焊缝区域的韧性较差;而经过590℃退火处理后,微观组织除板条马氏体外,在靠近热影响区的母材、热影响区存在少量铁素体。接头强度降低,而接头各区域的冲击韧性良好。     

负极板浸硼酸液的控制及硼酸池的改进

本文分析了负极板浸硼酸的作用机理,试验了浸不同温度硼酸液对负极板氧化铅的影响和补加硼酸量的方法,针对不锈钢硼酸池存在的铁含量较高等问题,进行了优化改进。     

直流氩弧焊在铝及铝合金件缺陷修复中的应用

电力系统生产企业在遇到铝及铝合金件缺陷修复焊接时，可以利用现有直流氩弧焊设备，工具和操作技术，配备焊粉，焊丝等材料，采用直流正接手工钨极氩弧焊方法解决，介绍了对油泵机缸体铝锰合金铸造件缺陷补焊修复的技术工艺，且弥补了若采用交流氩弧焊和气灶施焊时存在不足。     

开距对不同状态下真空电弧特性影响的仿真分析

仿真分析了开距对真空开关中不同状态下真空电弧特性的影响。对于小电流扩散态真空电弧,随着开距增大,电弧的扩散程度增大,离子温度、电子温度和等离子体压力增大;对于超音速收缩态真空电弧,随着开距的增大,电弧的收缩程度增大,离子温度、电子温度和等离子体压力增大,阳极轴向电流密度和能流密度的分布更不均匀;对于离子处于亚音速状态的大电流真空电弧,随着开距的增大,极间等离子体的损失增多。对于3种不同状态的真空电弧而言,随着开距的增大,电弧电压和注入阳极的能流密度都增大。同时,可以发现,建模与仿真是理解真空电弧微观过程的一种有效方法。     

AP1000堆芯补水箱的焊接

针对中国国内首个先进非能动压水堆AP,1000项目浙江三门1号及2号堆芯补水箱（CMT）的制造,介绍了CMT的设计参数、结构特征、材料特征和所依据的规范技术条件。介绍了CMT主体材料SA-508Gr.3Cl.1低合金钢、SA-336GrF316LN不锈钢及采用的相应焊接材料的主要性能。说明了CMT的焊接要求和焊接工艺特点,并就筒体窄间隙埋弧自动焊工艺、大接管马鞍形窄坡口埋弧自动焊工艺、筒体内壁不锈钢堆焊工艺、接管-安全端异种金属镍基合金焊接工艺等重要接头的焊接工艺作了详细阐述。     

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。     

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。     

不锈钢焊缝中超声传播特性及TOFD检测方法研究

为提高对不锈钢焊缝内部缺陷的超声检测能力,开展了关于焊缝超声波传播特性及其超声衍射时差法(TOFD)的研究工作。通过调整探头间距(PCS)改变检测声束方向,分析检测声束与柱状晶夹角对检测信号信噪比的影响,提出基于超声TOFD技术的焊缝一次波、二次波检测方法;鉴于二次波检测中特征波结构的复杂性,建立了特征波传播模型以识别二次波特征信号。研究结果表明,焊缝中传播的超声波声束呈现明显的各向异性特征,柱状晶与检测声束的夹角是检测信噪比的关键影响因素;与探头置于焊缝根部侧和余高侧相对应,需分别采用一次波和二次波检测方法进行TOFD检测;当检测声束与柱状晶夹角在35°~48°且检测区域具有较高声压时,可有效提高对焊缝缺陷的检测能力。基于声波传播的各向异性特征提出的超声TOFD一次波和二次波检测方法对于提高奥氏体不锈钢焊缝的超声检测能力具有重要作用。     

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     

大电流真空电弧磁流体动力学模型与仿真

为了对大电流真空电弧进行深入研究,以真空电弧双温度磁流体动力学模型为基础,通过计算流体动力学软件FLUENT,采用控制容积法,对大电流真空电弧特性进行了仿真研究。对于大电流真空电弧而言,等离子体的流动处于亚音速状态,因此,在阴极和阳极边界条件的选择上将区别于超音速流动的真空电弧。同时对等离子体密度、轴向电流密度、等离子体速度、马赫数、离子温度、电子温度、离子压力、等离子体压力以及注入阳极的能流密度分布的形成机理进行了分析。从仿真结果可以发现,大电流真空电弧等离子体压力的最大值出现在阴极附近,等离子体将在压力梯度的作用下从阴极到阳极做加速运动,这一点明显区别于超音速流动的真空电弧。另外,仿真结果与高速CCD照片也是吻合的。