旁路耦合微束等离子弧焊增材制造的热过程

针对旁路耦合微束等离子弧焊电弧增材制造中的热物理过程,利用K型热电偶测量堆垛过程中不同焊接速度、不同旁路电流和不同堆垛顺序下的热循环曲线,分析研究堆垛成型时各参数对热过程的影响。结果表明:随着焊接速度的增大,母材热输入减小;在合适的旁路电流区间内,增加旁路电流,母材热输入减少;且同向堆垛散热性要优于往复堆垛。精确控制旁路电流、合理规划堆垛路径可较好地控制旁路耦合微束等离子弧焊电弧增材制造的热过程。     

新型微束等离子弧焊接电源的研制

鉴于高频电弧具有较强的自收缩作用及较好的电弧稳定性的特点 ,研制了调制型脉冲微束等离子弧电源 .本电源可通过对高频电流的低频脉冲调制调节电弧对焊缝的热输入 ,同时具有电弧能量密度大、主弧空载电压低及起始电流递增和熄弧电流递减等功能 ,适用于铜、钛、不锈钢等金属薄件、微细件的焊接 .     

喷涂工艺参数对NICrBSi涂层显微组织和性能的影响

采用微束等离子喷涂系统制备了NiCrBSi涂层。研究了电弧功率、喷涂距离和等离子气体流量对涂层显微组织和性能的影响。试验结果表明,NiCrBSi涂层的致密程度与显微硬度随电弧功率和气体流量的增加而增加。当喷涂距离超过40mm时,喷涂距离对涂层显微硬度没有显著影响。采用微束等离子喷涂工艺制备的NiCrBSi涂层显微硬度可达HV0．2700。     

横向稳态磁场作用下微束等离子电弧数值分析

为分析外加横向稳态磁场作用下电弧特性与电弧对工件热、力输入的变化规律,本文建立了微束等离子电弧三维模型,将外加磁场简化为背景场添加至模型,使用有限元分析软件COMSOL进行求解计算.结果表明:外加横向稳态磁场作用下,喷嘴内部各项特性均未发生较大变化,喷嘴下方电弧等离子体在洛伦兹力的作用下向x负方向移动,电弧温度、等离子...     

高频逆变真空电弧蒸发电源

高频逆变真空电弧蒸发电源是现代电力电子技术与微电子技术的综合产物，因其具有高效节能、形小体轻、真空电弧稳定等特点，势必发展成为新一代电弧蒸发电源。本文就其主要工作原理、设计计算、实验数据等进行了分析研讨，并举电路实例供参照     

高频逆变真空电弧蒸发电源

高频逆变真空电弧蒸发电源是现代电力电子技术与微电子技术的综合产物，因其具有高效节能、形小体轻、真空电弧稳定等特点，势必发展成为新一代电弧蒸发电源。本文就其主要工作原理、设计计算、实验数据等进行了分析研讨，并举电路实例供参照     

双弧脉冲MIG焊耦合电弧特性的数值模拟研究

针对双弧脉冲MIG焊热源稳定性差的问题,本文对双弧脉冲MIG焊耦合电弧进行瞬态数值模拟,分析了不同脉冲电流参数下耦合电弧形态、温度和压力的分布及变化规律。研究表明：耦合电弧呈驼峰状,脉冲电流发生跳变时,耦合电弧伸展或收缩,并逐渐稳定,峰值电流越小,越快达到稳定;增大脉冲电流,耦合电弧温度和电弧压力随之升高;保持总电流不变,减小主弧电流,增大旁弧电流,主弧温度和电弧压力减小,旁弧温度和电弧压力增大,当旁弧电流足够大时,耦合电弧温度和电弧压力呈双峰分布。数值模拟结果与双弧脉冲MIG焊工艺实验结果吻合良好,模拟结果对调控双弧脉冲MIG焊脉冲电流参数,改善其耦合电弧稳定性及工艺性能具有重要意义。     

电弧超声对改善电弧喷涂雾化效果的研究

把电弧超声方法引入到喷涂领域，对电弧喷涂的热源施加高频调制之后，喷涂电弧可以激发出超声波。超声波的空化效应、机械效应和热效应加强了喷涂材料的雾化效果。从能量的角度研究了电弧超声的应用使喷涂粒子的粒度变小，飞行速度加快，制备出的涂层强度提高，孔隙率降低的机理。它是改善电弧喷涂层质量的一种新的方法。     

电弧放电法制备纳米碳管

纳米碳管的制备方法主要有三种：电弧放电法、激光烧蚀法和有机物催化热解法,首先综述了近年来应用电弧放电方法制备纳米碳管的研究进展,然后概述了中国科学院金属研究所在普通电弧法的基础上发展起来的大量制备单壁纳米碳管的氢等离子电弧方法。     

变极性等离子弧穿孔熔池受力及焊缝成形稳定性

通过YB005-01型压力变送器测定相同参数条件下正极性等离子电弧力大于反极性等离子电弧力,并建立了铝合金VPPA焊接穿孔熔池受力模型,分析了在不对称正、反极性等离子电弧力的作用下,穿孔溶池稳定性及其焊缝成形机理.同时进一步分析铝合金VPPA力学特性,掌握了焊接电流和离子气流量等重要焊接参数对其影响.经穿孔焊工艺实验,...     

Dynamics studies of cathode spots in a vacuum-arc discharge with ring electrodes

The effect of an external pulse magnetic field with axial and radial components on electric characteristics of the discharge and the configuration of cathode spots of a vacuum arc discharge with ring electrodes is studied experimentally. For arc currents within the range of 0.05–2 kA, shots of the cathode spots at different instants of time are obtained. The dependences of the number of the spots on the discharge current and the mean current per spot are determined. It was found that the expansion rate of the cathode spots area depends significantly on the instant value of the discharge current. It is shown that, when the pulse magnetic field is applied, the discharge voltage increases and the discharge current and number of the cathode spots decreases. It was found that the current interruption is a probability process. The probabilities of the current interruption depending on the maximal value of the external pulse magnetic field induction are determined.     

Effect of system parameters on size distribution of 304 stainless steel particles produced by electrical discharge mechanism

An electrical discharge machine (EDM) can be used to produce Uranium Carbide (UC) microspheres. This material is useful for dispersed nuclear fuel fabrication. To obtain empirical data about the process parameters for UC modeling, 304 stainless steel (304 SS) was used to produce microspheres. Particle size effects were analyzed via three parameters; arc intensity, dielectric medium, and pulse width. Results indicate that the size and yield of the particles are dependent on all three parameters. The yield of larger particles increased with increasing arc current. Particle size distribution decreased with decreasing pulse width.     

锁孔TIG焊接技术的研究进展

锁孔TIG焊接技术具有不开坡口、单面焊双面成形的特点,尤其适用于中厚板焊接。首先介绍了锁孔TIG焊的基本原理,然后分析了目前锁孔TIG焊接波形控制技术的研究现状,主要包括恒流锁孔TIG焊、单脉冲锁孔TIG焊和高低频双脉冲锁孔TIG焊。针对现有锁孔TIG焊接技术存在热输入量过大、接头组织晶粒粗大等缺点,重点介绍了一种新型的快频脉冲TIG焊接技术,它通过快频脉冲电流产生的电磁场对电弧进行压缩,控制焊接过程的热输入量,达到提高焊接质量的目的。与传统脉冲电弧相比,快频脉冲电弧的收缩效果更为明显,可细化焊接接头组织,将快频脉冲焊接技术应用于锁孔TIG焊是今后研究的热点和主要发展方向。     

TIG焊接时熔池外激振荡与熔透的关系

用脉冲电流冲击熔池,使熔池产生有规律的振荡,造成孤长和电弧电压有规律的变化,检测电弧电压变化量及其变化规律,发现熔池振荡频率与熔池尺寸有一定的对应的关系。本文介绍了能产生冲击电流的晶体管电源及熔池振荡信号检测系统。研究了电弧参数如弧长、脉冲电流幅值,脉冲电流持续时间等对产生熔池振荡的影响。研究了熔池振荡特性与熔池尺寸的关系,发现随着熔池上面和背面宽度的增加,熔池振荡频率下降,找出了不同板厚熔池尺寸与其振荡频率的关系,把熔池振荡特微做为熔透控制信号,是一条可行的途径。     

Metallurgical characterization of arc-conditioned carbon coating on copper electrodes

During arc discharge between two parallel electrodes, the electrode surface is eroded by the arc. Carbon coating of the electrode surface often results in a decreased erosion. The surface structure of the arc-conditioned carbon-coated copper electrode was metallurgically characterized by the use of (1) scanning electron microscopy and (2) Auger in-depth profiling. Two different types of a.c. conditioning with varying pulse characteristics were studied.It was found that the peak current density, the pulse duration and the total number of pulses were the most important parameters in determining the metallurgical structure of the conditioned electrode surface. The vapor arcs which were produced by pulses with a high current density and short pulse duration were most effective in compacting the carbon coating and promoting good adhesion between the carbon and the copper electrode. The compaction and the adhesion are effected by a high ionic beam pressure on the cathode reaching up to 1000 atm.A lower degree of carbon penetration was effected when surface melting was produced by thermionic arcs which have a lower current density and longer pulse duration. In this case, carbon adhesion is due to the mechanical entrapment of carbon powder in the thin molten copper layer produced on the electrode surface by the arcs.     

Dynamics of cathode spots in an axial magnetic field on the fall of a current pulse in a high-current vacuum arc

The cathode attachment of a high-current vacuum arc on the fall of a current pulse was studied. Contacts generating an axial magnetic field were used. The revealed transformation of the attachment shape near zero current was explained quantitatively in a way that was in satisfactory agreement with experimental results.     

Tri-Arc与Tandem双丝电弧焊的工作原理对比分析

目的 介绍一种称为Tri-Arc的新型双丝电弧焊接方法。方法 将Tri-Arc双丝电弧焊与应用较广的Tandem双丝电弧焊的系统构成和焊接电流波形进行对比分析。结果 Tri-Arc和Tandem两种双丝电弧焊接方法所使用的双丝焊枪相近,双电源相位同步控制和U/I脉冲控制方式类似。Tri-Arc和Tandem两种双丝电弧焊接方法的差异在于:Tandem双丝电弧焊的2个电弧是相对独立的,而Tri-Arc双丝电弧焊的2个电弧是相互耦合的,因此Tri-Arc双丝电弧焊又具有旁路耦合电弧的某些特点。结论 这种新型的Tri-Arc双丝电弧焊不仅具有与Tandem双丝电弧焊一样的高焊丝熔敷率,而且具有比Tandem双丝电弧焊更低的焊接热输入。     

Development of a High-Current Vacuum Arc in a Rod Electrode System

The development of a high-current pulse electric discharge in a rod electrode system with the current amplitude changing from 10 to 100 kA is investigated using a sectional model of a vacuum chamber with the simultaneous recording of the electrical characteristics of the discharge, of the glow of discharge plasma, and of the spots on the electrodes. A phenomenon is revealed of a rapid transition of the discharge from the ignition unit to interrod gaps on reaching an instantaneous value of current from 5 to 9 kA. A correlation is established between the moment of appearance of an abrupt drop of voltage across the vacuum arc and the moment of formation of a new discharge channel in the interrod gap. It is demonstrated that various vacuum arc modes in the interrod gap and the multiplication of discharge channels in all interrod gaps are observed with increasing current. The effect of the rate of current increase on the development of the vacuum arc is investigated.