高铬镍奥氏体焊丝Ar/He/CO2保护脉冲GMAW电弧形态与熔滴过渡

为解决高强度Cr-Ni奥氏体焊丝脉冲GMAW电弧挺度不足,熔滴过渡不稳定的问题,文中采用高速摄像手段对Ar/He/CO₂不同组合气体保护下的脉冲GMAW电弧形态与熔滴过渡进行了对比研究,以期优化混合气体成分.结果表明,氩气弧熔滴过渡容易,但电弧漂移、挺度差;氦气和CO₂气体的加入可提高电弧挺度、增大电弧能量、熔滴过渡变为1脉多滴,先一个大滴,接着几个小滴;氦气的比例越大,第一个熔滴的尺寸越大;CO₂气体可克服阴极斑点漂移,但比例不能超过5%;40% Ar+58% He+2% CO₂三元组合的电弧挺度大,熔滴过渡均匀平稳,是奥氏体焊丝脉冲GMAW厚板焊接较理想的混合气体组分.     

保护气体成分对双丝旁路耦合电弧GMAW旁路熔滴过渡形式的影响

双丝旁路耦合电弧GMAW的旁路焊枪选择了正极性接法即焊丝接电源负极,旁路熔滴仅依靠重力向熔池过渡,旁路熔滴尺寸较大且过渡过程并不稳定.针对这一问题,采用已建立的双丝旁路耦合电弧焊接过程信号控制与高速摄像采集系统,采集了纯氩气保护时旁路熔滴过渡形式,并分析了旁路熔滴尺寸较大且过渡过程不稳定的原因.在此基础上,采用80% Ar+20% CO₂为保护气体进行了焊接试验.结果表明,焊接过程中,保护气体中的O元素在旁路熔滴表面形成了氧化膜,旁路电弧在旁路熔滴表面的氧化膜上稳定燃烧,从而使电磁收缩力重新作用在旁路熔滴上并促进旁路熔滴向熔池过渡,因此焊接过程中旁路熔滴尺寸明显减小,熔滴过渡过程更加稳定.     

熔化极气体保护焊熔滴过渡分析

利用高速摄影图像与电信号波形观察熔化极气体保护焊的熔滴过渡,分析了影响熔滴过渡的主导因素。结果表明,CO2气体保护焊时熔滴沿非轴向排斥过渡,氩气保护焊时熔滴沿轴向过渡;焊接电流对熔滴过渡方式的转变起主导作用,随着焊接电流的增大,CO2气体保护焊中依次出现短路过渡和大滴排斥过渡,熔滴尺寸依次增大,过渡频率依次减小,氩气保护焊中依次出现短路过渡、大滴过渡、射滴过渡、射流过渡和旋转射流过渡,熔滴尺寸逐渐减小,过渡频率逐渐增大;氩气保护焊中,由滴状过渡转变为喷射过渡的临界电流约为170 A。     

电弧焊的熔滴过渡现象综述

主要介绍了实心焊丝和药芯焊丝气体保护焊时的熔滴过渡形态,采用不同的保护气体和不同的焊接电流时会出现不同的过渡形态.常见的熔滴过渡形态有颗粒过渡和短路过渡,颗粒过渡又分为滴状过渡和喷射过渡;喷射过渡时又有几种不同的形态.     

等离子-MIG焊熔滴过渡的研究

为了分析等离子-MIG焊熔滴过渡过程中等离子弧和MIG弧对熔滴过渡形态的影响,利用示波器研究了等离子-MIG焊接铝合金时不同熔滴过渡形式的特征,包括电弧电压波形的变化及熔滴过渡临界电流的研究.研究结果表明:等离子-MIG焊的熔滴过渡形式以滴状过渡和射流过渡为主;滴状过渡到射流过渡的临界总电流约为280～300A;等离子-MIG焊中,MIG电流对熔滴过渡产生决定性影响;等离子-MIG焊与MIG焊比较,显著的降低了熔滴过渡向射流过渡转变的临界点.     

面向工程应用的BA-GMAW熔滴过渡形态

综述了涉及工程应用的潜弧熔化极气体保护焊(Buried arc gas metal arc welding,BA-GMAW)熔滴过渡形态特征.结果表明,在大电流和相应的焊接参数下,BA-GMAW工艺的熔滴过渡形态有3种,即呈滴状过渡、摆动过渡和旋转过渡.BA-GMAW电弧空腔中电弧形态属于连续、敞开、非活动型;电弧空腔...     

超声-MAG复合焊接熔滴过渡受CO_2含量的影响

介绍了一种新型MAG焊熔滴调控的方法,基于前期研究,首次将超声驻波场引入MAG焊.在不同保护气体成分(CO2含量)条件下,探索研究超声对MAG焊熔滴过渡的影响.结合高速摄像拍摄的电弧与熔滴图像,研究了电弧长度以及熔滴导电区域夹角变化,结果表明,低CO2含量条件下超声作用更加明显,但随着CO2含量增加,特别是超过20%时,短路过渡中超声对电弧压缩效果趋于恒定并最低.滴状过渡中阻碍熔滴过渡的电磁力逐渐增强,最终也抵消了超声的促进作用.显示出超声作用效果对CO2含量的选择性.最后利用纯CO2保护的超声-MAG复合焊试验验证了试验的有效性.     

基于工程应用的CW-GMAW熔滴过渡形态表征

综述了涉及工程应用的冷丝熔化极气体保护焊（Cold wire gas metal arc welding, CW-GMAW）熔滴过渡形态特征。结果表明,在大电流、强规范、富氩混合气体保护下,CW-GMAW工艺的熔滴过渡形态呈喷射过渡;当电流较小、电弧电压较低时,可能为滴状过渡,甚至在弧压很低时,呈现短路过渡形态。该工艺电弧发生偏向冷丝的位移,弧长变短甚至发生短路,与冷丝送进速率比增高及冷丝在电弧中产生大量金属蒸气时弧柱电阻下降有关。在具有富氩混合保护气体的相同工艺参数下,CWGMAW转变电流比GMAW降低了4%～7%。焊接工艺参数对CW-GMAW和GMAW工艺熔滴过渡形态的影响规律大致相近,但前者因涉及冷丝送进速率比和电极焊丝送进速度,以及它们的匹配等,使焊接电流的影响更为复杂。     

埋弧焊熔滴过渡形态与焊接工艺质量的关系

探讨埋弧焊熔滴过渡形态与焊接工艺质量的关系。结果表明,在单丝埋弧焊中,渣壁过渡是熔滴的主导过渡形态,在双丝埋弧焊中,可能存在渣壁和喷射多种过渡形态,但不会有短路过渡形态。影响埋弧焊熔滴过渡的多种因素中,焊接电流是改变过渡形态的决定因素。单丝埋弧焊中,通过工艺参数变化建立了熔滴过渡形态与焊接工艺质量间的关系,其内在联系主要是熔滴尺寸、电弧力和熔滴冲击力变化。在双丝埋弧焊中,渣壁、喷射和滴状过渡对焊接质量参数的作用各异,前后焊丝过渡形态的位置匹配对焊接质量参数影响强烈。     

单丝高熔敷率MAG焊接工艺的研究

从提高焊接电流和电孤热熔化焊丝等效电压的角度出发,提出了两种新型的单丝高熔敷率MAG焊接工艺-细丝大电流MAG焊和直流正接MAG焊,并借助高速摄像手段分析了这两种焊接工艺的电孤行为、熔滴过渡机制以及焊缝成形特点.试验结果表明,通过选择合适的保护气体体φ(Ar)98%+φ(O2)2%使得电弧烁亮区包覆了大部分液锥和全部的液流束且熔滴过渡基本在电弧烁亮区内部进行,可获得稳定的细丝大电流MAG焊;同样选择φ(Ar)98%+φ(O2)2%的保护气,能够获得电弧较为稳定、焊接飞溅较小、焊缝成形良好的直流正接MAG焊.     

The measurement of metal droplet temperature in GMA welding by infrared two-colour pyrometry

The temperature of metal droplets is essential for clarifying the phenomenon of metal droplet transfer and the melting behaviour of wire; also, it governs the emission of fumes. On the other hand, in situ measurement of the temperature of a metal droplet formed at the tip of a wire during welding was difficult. Hence, this temperature was obtained in many experiences of measurements by such a way that several numbers of metal droplets were collected in a calorimeter to measure the amount of heat content of metal droplet and the heat was converted to temperature. With this way, however, the reliability of the measurement is not necessarily high because the heat loss of the metal droplet during the time when detaching from the wire tip and entering into the calorimeter has to be estimated properly. In this research, two-colour pyrometry has been conducted to obtain the temperature of metal droplets, in which metal droplets have been photographed by a high-speed camera during arc welding, two wavelengths (950 and 980 nm) of light in the infrared range have been selected from the thermal radiation light emitted from the metal droplet at the instant of arc extinguishment by using an imaging spectroscope, and the temperature has been obtained from the intensity ratio of the two waves of light. Consequently, in CO₂ arc welding, it has been revealed that the constricted arc causes high-heat input density locally at the arc root portion of a metal droplet and thereby the arc root portion exhibits a higher temperature. By contrast, in MAG (80% Ar–20% CO₂) arc welding, it has been disclosed that because the arc covers metal droplets, the temperature distribution in a metal droplet is relatively uniform and the average temperature is lower than in CO₂ arc welding.     

保护气体对440MPa HSLA钢GMAW焊缝组织及韧性的影响

采用不同保护气体对440 MPa级低合金高强钢(HSLA钢)进行气保焊焊接,通过光学显微镜(OM)、透射电镜(TEM)、扫描电镜(SEM)和电子背散射衍射技术(EBSD)对焊缝微观组织及夹杂物形貌进行了观察,研究了保护气体组成对焊缝组织及韧性的影响,并分析了不同成分保护气体对焊缝夹杂物大小、数量及其成分的影响.结果表明,保护气体为100％ CO2,焊缝金属韧性较差;保护气体(体积分数)为80％ Ar+20％ CO2和90％ Ar+ 10％ CO2,焊缝金属韧性较好.100％ CO2气体保护焊焊缝组织主要为铁素体和贝氏体,混合气体保护焊(20％ CO2和10％ CO2)焊缝组织主要为针状铁素体和少量侧板条铁素体.随着保护气体中CO2含量的减少,焊缝金属中夹杂物数量、尺寸均降低,且成分发生变化.对于440 MPa级HSLA钢,合理的保护气体组成可以得到良好的焊接质量.     

Energy parameters in a mathematical model of a dynamic welding arc

Summary

This paper describes a method for experimental determination of the dynamic characteristics of an arc sensor in GMA (MIG/MAG) welding in droplet transfer mode. The method basically involves a vibration device being used to excite sinusoidal waveforms of the torch height as well as data processing by means of an FIR digital low-pass filter and dispersive Fourier transformation (DFT). The experimental results show that the sensitivities of the arc sensor are much greater than in DC open arc welding. The response of the welding current to torch height variation is maximised at around 3 Hz. Although the response continues up to a higher level when the frequency exceeds around 5–6 Hz, the SN ratio is poorer than that at 3 Hz. The response of the welding current shows a phase lag relative to the torch height variation. The response of the welding voltage, however, shows a phase advance relative to the torch height variation, and the response increases with an increasing variation frequency of the torch height, but its SM ratio is much poorer than that of the welding current.

To clarify the effects of shielding gases on the arc sensor, experiments using four types of shielding gas - pure Ar, Ar + 10% CO₂, Ar + 20% CO₂, and CO₂ — were conducted. The results show that, contrary to those obtained in open arc welding, the responses in short-circuiting arc welding using pure Ar are higher than those using Ar and CO₂ mixed gases.

Simulations using an arc sensor model proposed by the authors are also run for short-circuiting arc welding and the results analysed. The analytical results based on this model show the theoretical and experimental results to be similar qualitatively but to disagree quantitatively. The theoretical results further show that not only the average short-circuit frequency, but also the rate of change of the short-circuit frequency induced by variation of the arc length strongly affect the sensitivities of the arc sensor.     

Visualization of gas metal arc welding on globular to spray transition current

The transfer modes in gas metal arc welding have important effects on welding quality. However, present study of metal transfer modes is not yet fully understood. In this study, welding arcs was visualised using the optical emission spectroscopy technique. The carbon steel wire electrode was used for welding with 80% Ar?+?20% CO₂ shielding gas. The results showed that the globular to spray transition current was 330–350?A. During globular to spray transition, argon,CO₂ and Fe plasma tended to gradually change from localising near the arc axis to a two-layer structure having 11,000?K in high-temperature region away from the arc axis and around 7000?K in low-temperature region near the arc axis.     

单道多层电弧增材制造成形控制理论分析

文中采用冷金属过渡（CMT）技术,围绕船用高强钢的电弧增材制造（WAAM）开展研究. 分析不同比例的保护气体对单道单层形貌尺寸的影响. 结果表明,单道单层的润湿铺展能力随着保护气中CO₂含量的增加而提高,并建立了能够准确预测80%Ar + 20%CO₂混合气体保护下单道单层截面轮廓的全周期余弦函数模型. 依据单道多层电弧增材的成形特点,利用面积关系并根据几何形貌建立了单道多层抬升量h的预测模型,抬升量h预测值的相对误差不超过3.50%. 通过建立抬升量预测模型,为单道多层的电弧增材成形控制提供了理论支撑.     

环保焊枪吸烟对小电流CO2气体保护电弧焊的影响

采用环保焊枪进行了小电流二氧化碳气体保护电弧焊平焊位置焊接,通过分析焊接过程中电弧形貌、电流电压和熔滴过渡方式变化以及焊缝成形、焊缝金属拉伸力学性能和X射线探伤结果,评估了吸烟功率变化时的吸烟效果以及吸烟行为对于焊接过程和焊缝质量的影响规律. 结果表明,使用环保焊枪可以显著降低小电流二氧化碳气体保护电弧焊时飘散在周围空间中的焊接烟尘. 吸烟过程虽然使得短路过渡熔滴频率略有增加,悬挂熔滴和电弧的稳定性略为变差,但对焊缝成形和焊接缺陷都无影响,焊缝金属屈服强度略有减小,抗拉强度略有增加.     

水下高压空气环境下GMAW电弧特性试验

采用高压试验舱模拟水下高压干式焊接环境,以压缩空气为气源进行加压,通过防燃爆试验验证在0.1~0.7 MPa范围内,在CO2和混合气(80%Ar+20%CO2)作为保护气源的情况下,可以进行正常的GMAW焊接过程.在此基础上,通过试验研究了高压空气环境下GMAW电弧特性,分别考察了环境压力、焊接电流、焊丝伸出长度和保护气种类及流量对焊接电弧特性的影响规律,并给出试验结果.借助最小二乘法对试验数据进行拟合,得出了高压空气环境下GMAW电弧电压的数学模型.