Sensing controlled pulse key-holing condition in plasma arc welding

According to the strategy of controlled pulse key-holing, a new sensing and control system was developed for monitoring and controlling the keyhole condition during plasma arc welding (PAW). Through sensing and processing the efflux plasma voltage signals, the quantitative relationship among the welding current, efflux plasma voltage and backside weld width of the weld was established. PAW experiments show that the efflux plasma voltage can reflect the state of keyhole and backside weld width accurately. The closed-loop control tests validate the stability and reliability of the developed keyhole PAW system.     

PAW受控脉冲穿孔状态的检测与控制

根据受控脉冲穿孔的控制策略,研制出等离子弧焊接(PAW)小孔状态的检测与控制系统,采用等离子弧尾焰电压作为表征小孔状态的传感检测信号,对不同焊接电流作用下的焊接过程进行实时监测,系统可以同时采集焊接电流和尾焰电压信号,并对信号进行分析、处理,建立了焊接电流、尾焰电压和背面熔宽三者之间的定量关系曲线.结果表明,尾焰电压信号能够迅速准确地反映出小孔状态和焊缝背面熔宽.根据检测试验得到的数据,建立穿孔型PAW焊接闭环控制系统,通过对普通平板和改变散热条件工件进行闭环控制焊接试验,获得了适当的焊缝背面熔宽及良好的焊缝质量,证明了该系统运行稳定、可靠.     

Determination of arc pressure and current density on the molten pool surface in plasma arc welding

A unified numerical model is developed to couple the plasma arc, weld pool and keyhole in a self consistent way. The plasma arc/anode interface and the melt/solid interface are treated specially, the VOF method is used to trace the moving keyhole wall, and the fluid flow and heat transfer in both the plasma arc and weld pool are numerically simulated. The distributions of current density and arc pressure on the weld pool surface during the keyhole formation process are analyzed using the coupled model. The predicted arc pressure and current density are compared with the experimentally measured results, and both are in good agreement.     

数控逆变焊机电流波形控制技术

针对采用大规模集成电路LSI芯片的新型逆变气体保护焊机及其输出电流波形控制技术进行讨论。根据选用的保护气体种类,优化直流焊接模式的电流输出,采用"改进型冷桥过渡CBT-EX"的熔滴过渡控制方式对短路过渡进行处理,大大降低了飞溅的发生量。实现了从薄板焊接的低电流领域到厚板焊接的高电流领域的高品质焊接。根据焊接母材材质,优化脉冲波形,获得"一脉一滴"理想的熔滴过渡形式,减少了飞溅量,提高了焊接速度。     

Effects of current waveform parameters during droplet transfer on spatter in high speed waveform controlled Short-circuiting GMAW

Aim at improving the stability of the Short-circuiting Gas Metal Arc Welding （GMAW-S） process for the enhanced speed usage, effects of current waveform parameters during short-term on the welding stability have been investigated by experimental method. The welding power source used for the research is an inverter with a special current waveform control. It is shown that the spatter decreases at first then increases with each increase of the low current period, current increase rate and the maximum current limit. The test results are provided for welding of 1 mm and 3 mm mild steel at speed of 1.2 m/min. The stable GMA W-S process under high speed welding condition has been achieved by optimizing the parameters.     

脉冲电流波形对Tandem双丝MIG焊力学性能影响

双丝脉冲MIG焊作为高效化的不锈钢焊接方法,是目前焊接行业研发的热点之一,但是如何选择和调节双丝MIG焊的电流波形参数依旧是一个难点. 为了优化不锈钢焊接的焊接方法,提高焊接效率,文中以双相不锈钢为焊接工件,通过电流波形参数对比试验,研究了双丝梯形波双脉冲焊,双丝矩形波双脉冲焊以及双丝单脉冲焊对焊接质量的影响. 结果表明,在相同热输入的条件下,双丝梯形波双脉冲焊焊接稳定性好于双丝矩形波双脉冲焊和双丝单脉冲焊,且前者的焊接成形质量更高,可看到更多的鱼鳞纹,同时使不锈钢接头的的拉伸强度和硬度以及韧性显著提高.     

Simulation of droplet transfer process and current waveform control of CO_2 arc welding

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Study on arc characteristics and behavior of metal transfer in pulse current flux-cored arc welding of mild steel

The variation in arc characteristics and behavior of metal transfer with the change in pulse parameters has been studied by high speed video camera during pulse current flux cored arc weld deposition. A comparative study of similar nature has also been carried out during flux-cored arc weld deposition in globular and spray transfer modes. The effect of pulse parameters has been studied by considering their mean current and arc voltage. The arc characteristics studied by its root diameter, projected diameter and length, and the behavior of metal transfer noted by the metal transfer model and the droplet diameter have been found to vary significantly with the pulse parameters. The observation may help in understanding the arc characteristics with respect to the variation in pulse parameters which may be beneficial in using pulse current FCAW to produce desired weld quality.     

Numerical analysis of weld pool geometry in pulsed current plasma arc welding

Numerical analysis of weld pool shape and size is of great significance for selection and optimization of the process parameters in pulsed current plasma arc welding (PAW). In this paper, a mathematical model and relevant algorithm are developed to determine the temperature profiles and weld pool geometry in pulsed current PAW through employing an adaptive heat source model. The volumetric heat source consists of semi-ellipsoid at upper part and a conic body at lower part along the workpiece thickness direction. The dynamic variation features of weld pool shape during a pulse cycle are numerically simulated. The calculated weld cross-section is consistent with the measure one.     

机械产品焊接过程中受控脉冲穿孔等离子弧焊接小孔动态行为分析

将视觉传感器应用于受控脉冲穿孔等离子弧焊接技术,检测小孔的动态行为,为调整机械产品的焊接工艺参数提供依据。结果表明:一个脉冲周期会对应产生一个小孔,每个小孔都依次经历了出现、长大、缩小和闭合,且小孔位置偏移量由刚穿孔时的最大逐渐变为闭合时的最小。     

低压环境对等离子弧穿透能力的影响

设计了一套水冷铜阳极电弧力测试装置,测量了不同环境压力下等离子弧在穿透一定厚度工件后电弧压力的径向分布情况,研究了焊接电流、环境压力对于穿透电弧压力的影响规律. 结果表明,等离子穿透电弧压力在电弧中心区域最大,沿着径向从中心至边缘迅速减小. 在同一环境压力下,随着焊接电流的增加,等离子穿透电弧压力增大;当焊接电流相同时,在一定的压力范围内,随着环境压力的降低,等离子穿透电弧压力显著增大,且环境压力变化对于等离子穿透电弧压力的影响比焊接电流变化对其的影响更显著.     

高频脉冲变极性焊接电源及电弧压力分析

采用变极性和高频脉冲电路叠加,设计了一套变极性和高频脉冲复合电流输出特性的焊接电源,将高频脉冲电弧特性引入变极性焊接过程.建立电弧压力数学模型,结合具体工艺试验,分析了高频脉冲电流对于变极性焊接电弧特性的改善.结果表明,在相等电流有效值的情况下,电弧压力随脉冲频率的提高而增加,高频脉冲电流频率达到5kHz附近时,弧柱区电弧压力较常规直流电弧提高2倍左右,电弧的挺度和能量密度都有所增加,为进一步研究高频脉冲变极性焊接方法在铝合金焊接中的应用提供了理论依据.     

Numerical analysis of transient keyhole shape in pulsed current plasma arc welding

Based on the characteristics of ＂one keyhole in a pulse＂ in pulsed current plasma arc welding （PAW） , the transient variation process of weld pool in a pulse cycle is simulated through the establishment of corresponding heat source model. And considering the effects of gravitational force, plasma arc pressure and surface tension on the weld pool surface, the dynamic change features of the keyhole shape in a pulse cycle are calculated by using surface deformation equation. Experiments are conducted and validate that the calctdated weld fusion line is in good agreement with the experimental results.     

熔化极气体保护焊电流与电压调节

在应用熔化极气体保护焊的基础上,分析焊接电流和电弧电压对焊缝成形的影响,探究焊接电流与电弧电压匹配对焊接电弧特性的影响规律,总结正确调节焊接电流与电弧电压的基本方法和操作技能,正确调节焊接电流与电弧电压是熔化极气体保护焊技术推广与应用的关键因素。     

高速CO2焊电流波形控制系统

针对高速CO2焊焊缝成形差、飞溅大的问题,提出了一种新型的焊接电流波形控制方法,在短路阶段控制短路电流和电流上升率,在燃弧阶段采用大恒流 小恒流的两段恒流法来控制燃弧能量.根据该控制原理,设计了基于单片机控制的高速焊系统和控制软件.探讨了波控参数对焊缝成形的影响,并通过大量试验对波控参数进行优化.试验结果表明,该系统采用两段恒流控制法对电流波形实时控制,可精确控制燃弧能量,有效地改善焊接工艺性能,满足了高速CO2焊的控制要求.     

不锈钢活性剂等离子弧焊焊接电弧

针对活性剂等离子弧焊焊接过程,对焊接电弧外形的变化,焊接电弧电压与活性剂之间的关系进行了研究,采用红外热像伪着色法测定了活性剂等离子弧焊焊接电弧温度场,并建立了活性剂等离子弧焊焊接电弧热流密度径向分布模型.研究结果表明,活性剂等离子弧焊焊接电弧收缩,弧尾翼消失,尾焰加大,电弧穿透力增强,电弧电压升高;活性剂等离子弧焊焊接电弧的温度分布比较紧凑,温度场外形窄,温度分布范围较集中,电弧径向温度梯度较大;电弧径向温度分布呈现正态Gauss分布模式;使用活性剂后的焊接接头性能与未使用活性剂焊接接头相当.     

Simulation analysis of double arc in plasma arc welding

Aimed at plasma arc welding, a mathematic model was established according to the theory of magnetic fluid dynamics. The model was numerically analyzed by ANSYS software. The temperature, current density and plasma velocity distributions of normal arc had been simulated and compared with those of double arc. The results show that the appearance of double arc has made the temperature of the nozzle rise up to 5 000 K. The appearance of side arc could make the current density of the main arc decrease, and also make the maximal temperature of the arc reduce.     

Ti-6Al-4V合金的动态控制等离子焊接(英文)

介绍了一种新的动态控制等离子焊接工艺。该工艺能够在保持完全焊透的情况下减少对被焊材料的热输入。利用该工艺对Ti-6Al-4V合金实施平板对焊。利用光学显微镜、扫描电镜(SEM)和显微硬度计对焊接接头的显微组织、断口形貌和显微硬度进行表征。与钨极电弧焊接和常规的等离子焊接相比较,使用本工艺提高了焊接质量,其原因在于:1)由于热输入的减少,焊缝中先析出的β相晶粒大幅度减少,从而使马氏体的形成得到抑制;2)焊接接头具有更好的韧性和更高的硬度。