Study on arc characteristics and their influences on weld bead geometry in narrow gap GMAW of 5083 Al-alloy

As an efficient process, narrow gap gas metal arc welding (NG-GMAW) was employed to join thick plates of 5083 Al-alloy. In this paper, arc characteristics in NG-GMAW of 5083 Al-alloy and their influence on the weld bead geometry were studied with synchronous acquisition system for various groove types, welding modes, welding current levels, and swing frequencies. The arc profiles were measured and appear to be entirely different compared with that in bead-on-plate GMAW process, meanwhile the arc size changes with varied welding mode, welding current, and arc swing frequency. Arc characteristics highly affect the weld bead geometrical parameters such as bead width, welding penetration, sidewall penetration, and weld surface concavity. Linear regressions were made between the arc characteristics and the weld bead geometrical parameters both in swing and non-swing arc process. It showed that a negative linear correlation exists between welding penetration and arc length, sidewall penetration, and arc warpage, while a positive linear correlation exists between weld surface concavity and arc warpage in non-swing arc process. In contrast, a non-linear correlation exists among them and the variation tendency remains the same in swing arc process.     

铝合金MIG+激光复合焊接工艺研究

研究轻量化轿车用3A21铝合金M IG 激光复合焊接工艺,探讨工艺参数对焊缝成型的影响规律及激光与电弧的复合作用。试验结果表明,采用M IG 激光复合焊接工艺可以显著提高熔深和焊速,达到采用小功率激光焊机实现铝合金的激光焊接。在比较宽的工艺参数范围内M IG YAG激光复合焊接铝合金具有焊缝成型美观等优点,熔深和焊速均显著提高,大大提高生产率。     

Prediction of pulsed GTAW penetration status based on BP neural network and D-S evidence theory information fusion

This paper used multi-sensor information fusion technology in pulsed gas tungsten arc welding. Arc sensor, visual sensor, and sound sensor were used simultaneously to obtain weld current, voltage, weld pool image, and weld sound information about the pulsed gas tungsten arc welding process, and special algorithms were designed to extract the respective signal features of different sensors’ information. Then D-S evidence theory was used to fuse the different signal features to predict the penetration status about the welding process. Aimed at the difficulty of obtaining basic probability assignment in D-S evidence theory, back-propagation (BP) neural network was used to obtain the basic probability assignment. Experiments were done to obtain data for training the BP neural network and test the prediction reliability of D-S evidence theory information fusion, and comparison results showed that D-S evidence theory could effectively use the information obtained by different sensors and obtain better prediction result than single sensor.     

基于周期平均值外特性的脉冲MIG焊弧长稳定性研究

通过对脉冲熔化极惰性气体保护(Metal inert gas,MIG)焊脉冲平均电流电压变化率的计算,提出脉冲周期平均值外特性曲线,并对弧焊电源脉冲周期平均值外特性曲线和电弧静态性曲线的动态稳定工作点进行详细分析,得出利用脉冲平均值外特性控制脉冲MIG焊的控制策略。同时运用双闭环控制实现了基于弧压反馈的I/I模式控制数字化弧焊电源,此电源能在送丝速度稳定情况下自适应弧长扰动变化,实现脉冲弧焊过程一脉一滴熔滴过渡。通过弧长阶跃试验表明,脉冲弧焊过程中焊丝熔化速度快速跟踪弧长变化,具有良好的弧长动态调节性能,保持弧长动态稳定,即焊接过程稳定,焊缝成形良好,同时验证了分析过程正确性和设计过程的可行性。     

Mathematical models for control of weld bead penetration in the GMAW process

This paper presents the effects of welding process parameters on weld bead penetration for the gas metal arc welding (GMAW) process. Welding process parameters included wire diameter, gas flow rate, welding speed, arc current and welding voltage. The experimental results have shown that weld bead penetration increased as wire diameter, arc current and welding voltage increased, whereas an increase in welding speed was found to decrease the weld bead penetration. However, the weld bead penetration is not affected significantly by gas flow rate changes. Mathematical equations for study of the relationship between welding process parameters and weld bead penetration have also been computed by employing a standard statistical package program, SAS.     

基于电弧传感器的焊缝自动跟踪系统的研究

研制电弧传感器的焊缝自动跟踪系统 ,采用具有先进性能的开关型MIG MAG脉冲焊接电源 ,将电流和电压信号同时用作传感信号 ,通过电弧的扫描 ,既实现了焊接过程的自动跟踪 ,又解决了打底焊道的熔透问题 ,大大提高了产品焊接质量。     

Analysis of weld pool dynamic during stationary laser–MIG hybrid welding

A mathematical model was established to simulate the weld pool development and dynamic process in stationary laser–metal inert gas (MIG) hybrid welding. Surface tension and buoyancy were considered to calculate liquid metal flow pattern; moreover, typical phenomena of MIG welding such as filler droplets impinging weld pool, electromagnetic force in the weld pool, and typical phenomena of laser beam welding such as recoil pressure, inverse Bremsstrahlung absorption, and Fresnel absorption were all considered in the model. The laser beam and arc couple effect was introduced into this model by the plasma width during hybrid welding. Transient weld pool shape and complicated liquid metal velocity distribution from two kinds of weld pool to a unified weld pool were calculated. Furthermore, the simulated weld bead geometries were in good agreement with experimental measurement.     

TIG-MIG双面对称焊焊缝成形机理研究

就纯铝中薄板,通过单面TIG、MIG和TIG-MIG双面对称焊工艺试验对比,利用ANSYS有限元计算软件进行了TIG-MIG双面对称焊熔池的数值模拟,研究了TIG-MIG双面对称焊的熔池特征及焊缝成形规律。研究表明,TIG-MIG双面对称焊的热源静态累积效应和动态热阻效应使得此焊接方法熔深大大增加,TIG、MIG熔池在焊接过程中发生交汇并在电弧力、熔池表面张力和重力等作用下达到平衡,并由此形成焊缝反面成形。TIG-MIG交汇熔池的稳定性决定焊缝的反面成形特征。     

Nd:YAG激光+脉冲MAG电弧复合热源焊接参数对焊缝熔深的影响

试验研究Nd:YAG激光 脉冲MAG电弧复合热源焊接过程中焊接参数对焊缝熔深的影响.研究结果表明,复合热源焊缝熔深随电弧功率和激光功率的增大而增大,随焊接速度的增大而减小,并且在相同参数下,复合热源焊缝熔深稍大于激光焊缝熔深而显著大于脉冲MAG焊缝熔深.对于不同焊接电流,光丝间距在0～3 mm内复合热源焊缝取得最大熔深,且取得最大熔深的光丝间距与焊接电流大小有关;复合热源焊缝熔深在离焦量为2 mm时取得最大值.试验结果分析表明,在激光 电弧复合热源焊接过程中激光功率不仅决定复合热源焊缝熔深,而且可以极大地提高焊接速度:MAG电弧也可提高Nd:YAG激光焊的热效率.     

等离子弧焊接穿孔行为的声信号传感

使用高精度传声器采集穿孔型等离子弧焊接过程中的声音信号 ,围绕焊接过程中出现的“小孔效应” ,开展了等离子弧焊接熔透的声音信号传感方法的研究。结果表明 ,焊接过程中的声音信号在熔池的过渡阶段产生了剧烈的低频振动 ,与熔池的振动有关 ,说明声音信号的低频段分量中包含有熔池穿孔状态的信息。频域分析表明 ,声音信号的低频段分量 (0～ 10 0Hz) ,在熔池处于不同阶段时有明显的变化 ,熔池处于过渡阶段时其值大 ,穿孔后小 ,未穿孔时居中。据此 ,设计出了声音信号的A算法 ,用于识别焊接过程中熔池的穿孔状态 ,该算法可靠性较高 ,为等离子弧焊接熔透质量监测及闭环控制提供了前提条件     

不锈钢AA-TIG焊接法

针对不锈钢,提出一种新型活性TIG焊方法——电弧辅助活性TIG焊,即AA-TIG焊。采用CO2+Ar作为小电流钨极电弧的保护气体进行单弧AA-TIG焊,分别研究小电流钨极电弧和正常TIG焊工艺参数对焊缝熔深的影响,并针对试验范围内的最佳焊接规范研究不锈钢AA-TIG焊的焊缝成形、焊缝显微组织、化学成分和焊缝性能。采用AA-TIG焊可以单道焊透10mm厚的不锈钢板材,单面焊双面成形。与传统TIG焊相比,焊缝组织和化学成分几乎没有变化,焊缝的耐Cu/CuSO4腐蚀性能和低温冲击韧度都满足相关标准要求。     

电弧声信号与铝合金MIG焊缝塌陷的相关性

针对铝合金MIG焊过程热积累作用强容易产生焊缝突然塌陷从而导致焊接过程失败的问题,建立电弧声信号传感系统并以焊接电弧声为研究对象,运用小波分析方法研究焊接电弧声信号与焊缝塌陷的相关性。研究表明电弧声信号的能量变化与焊缝塌陷有着明显的对应关系,电弧声总能量随着焊缝开始塌陷而增加,对电弧声进行小波分解发现不同频带有着不同的变化规律。研究结果为铝合金MIG焊实时焊接塌陷缺陷的检测提供一种新型有效的方法。     

脉冲MIG焊建模仿真分析及弧长控制

针对脉冲MIG焊过程中的电弧稳定性问题,建立基于尖端不稳定熔滴过渡理论的焊丝熔化动态电弧模型,并对焊接过程中的电弧电压、电弧长度及熔滴过渡尺寸进行仿真,得到与实际焊接相似的电弧电压波形,分析脉冲电流下熔滴过渡频率及影响电弧稳定性的因素,且进行弧长稳定控制的仿真研究,在此基础上运用快速原型技术建立铝合金脉冲MIG焊控制系统,采用电弧电压反馈对铝合金脉冲MIG焊过程进行送丝调节的弧长控制试验。研究表明:所建立的铝合金脉冲MIG焊焊丝熔化动态电弧模型很好反映了实际焊接过程,揭示出脉冲MIG焊焊接过程中熔滴过渡时间间隔具有一定的不确定性和电弧长度的不稳定性,通过电弧电压反馈控制可显著改善铝合金脉冲MIG焊过程电弧系统的稳定性。     

CHARACTERISTICS OF DROPLET TRANSFER IN CO2 LASER-MIG HYBRID WELDING WITH SHORT-CIRCUITING MODE

LF6 aluminum alloy plates with 4.5 mm thickness are welded in this experiment.Welding is carried out by using the CO2 laser-MIG paraxial hybrid welding in flat position. The experimental results indicate that the inherent droplet transfer cycle time of conventional MIG arc is changed due to the interaction between CO2 laser beam and MIG arc in the short-circuiting mode of laser-MIG hybrid welding. Because of the preheating action of CO2 laser to electrode and base material, the droplet transfer frequency of MIG arc is increased in the hybrid welding process. When laser power is increased to a certain degree, the droplet transfer frequency is decreased due to the effect of laser-induced keyhole. Furthermore, through analyzing the MIG welding current and arc voltage waveforms and the characteristics of droplet transfer in the hybrid welding process, the effect of laser energy and the action point between laser beam and arc on the frequency of droplet transfer and weld appearance is investigated in details.     

Integrated design and process analysis of a blow molding turbo-charged pipe

These days, the trend in every manufacturing industry including welding is to automate the processes in order to increase productivity. To achieve this objective, it is therefore necessary to make use of models to relate the input parameters with the responses. This paper reports on the applicability of fuzzy logic to predict the weld bead penetration in submerged arc welding process as affected by input welding parameters. Fuzzy logic is a computer technique which allows expressing, evaluating, and simplifying complexities in regard to the relationships in a process by describing the dependencies between output and input parameters in a linguistic form. To develop the fuzzy logic model, the arc voltage, welding current, welding speed, electrode stick-out, and thickness of TiO₂ nanoparticles were taken as the input parameters and the weld bead penetration as the response. In order to generate experimental data, a five-level five-factor rotatable central composite design of experiments was employed. Experiments were performed, and the weld bead penetrations were measured. The predicted results using fuzzy logic were compared with the experimental ones. The correlation coefficient value obtained was 99.99 % between the measured and predicted values of weld bead penetration. The results show that the fuzzy logic is an accurate and reliable technique used in predicting the weld bead penetration due to its low error rate.     

Prediction of metal deposition from arc sound and weld temperature signatures in pulsed MIG welding

The weld deposition efficiency is an important economic factor like productivity and weld quality in gas metal arc welding (GMAW). There is a strong relationship between arc sound signals and arc stability (or deposition efficiency) in GMAW. In this work, the variation of weld deposition efficiency with various pulse parameters in pulsed metal inert gas welding was investigated. The arc sound signal along with current and voltage signals were acquired and analyzed in time domain as well as in frequency domain. The sound signal kurtosis and arc power were found to be highly correlated with welding process stability. The weld deposition efficiency was also related to weld surface peak temperature. Finally, an attempt was made to correlate the sound time domain as well as frequency domain features of sound signal with the deposition efficiency. The variation of pulse shape with the duty factor also influenced the deposition efficiency as evidenced by in fast Fourier transform analysis.     

变极性等离子弧焊接熔透信息的检测与分析

通过对铝合金3003变极性等离子弧穿孔立焊熔池振荡行为的研究,发现熔池振荡频率与焊接熔透之间的内在规律。在变极性电流的作用下,焊接熔池产生振荡,可以通过对电弧电压频谱分析获得熔池固有振荡频率。分别建立变极性等离子弧穿孔立焊未熔透及完全熔透熔池模型,并分析焊接电流的变化对熔池固有振荡频率的影响,发现焊接电流大小对其影响很小,可以忽略。为了验证该模型的准确性,进行理论与实测分析,结果表明,理论值与实测值相吻合。熔池固有振荡频率主要取决于熔池宽度、深度及材料密度等参数,而其他焊接参数对其没有直接影响。因此,熔池振荡频率可间接反映焊接熔透信息,为焊接质量自动控制提供了理论支持。     

Effect of laser on the welding process of short-circuiting transfer MIG welding of aluminum alloys

In this paper, the effect of laser on the welding process in metal inert gas (MIG) welding of aluminum alloys was studied exploiting high-speed imaging and welding electrical signals collecting. Bead-on-plate welding experiments were conducted using conventional short-circuiting transfer MIG welding and laser-short-circuiting transfer MIG hybrid welding. The obtained results point out that it took less time to strike the arc in laser-MIG hybrid welding, and the stability of arc striking was increased. When the laser was introduced into the arc atmosphere, the arc was compressed, and the welding energy was more concentrated. The arc cathode spot was fixed to the laser beam impinging spot, so the arc could burn stably. In laser-MIG hybrid welding, the droplet short-circuiting transfer stability and the weld appearance were improved significantly. Moreover, an analysis method of judging droplet transfer stability which bases on statistical techniques was proposed. By this method, it can be concluded that the short-circuiting transfer process became more stable in laser-MIG hybrid welding.     

面能量对激光—电弧复合焊接焊缝及熔滴过渡的影响

引入面能量的定义,从激光功率、电弧参数和焊接速度等方面来研究面能量的变化对焊缝熔深、熔宽、焊缝成形系数和熔滴过渡的影响,试图建立激光能量与电弧能量之间的最佳配比关系以及面能量与熔深的定量关系。采用高速摄像系统观测熔滴过渡模式和等离子体形态的变化,并采集焊接过程中的电弧和熔滴图像;利用激光共聚焦显微镜观察焊缝形貌,并测量焊缝熔宽、熔深等数据。试验研究发现:激光与电弧两热源之间存在最优匹配范围;电弧电压与焊接电流之间存在U(15 1)0.05I的关系式;焊接速度的降低与焊缝熔深的增加并非线性关系,可选择的焊接速度是一个区间,该区间内存在一个最佳的焊接速度,并对应一个最佳的面能量。因此,在具体的激光—电弧复合焊接中,需要根据板厚、接头形式等确定激光与电弧的能量参数,选择合适的面能量。     

Multisensor-based monitoring of weld deposition and plate distortion for various torch angles in pulsed MIG welding

Manufacturing companies often fail to maintain good weld quality due to poor arc stability and distortion after welding. Weld quality can be improved by reducing the transverse shrinkage and the angular distortion in butt welding. The welding deposition efficiency is also an important economic factor. In this work, various pulse voltage parameters have been varied along with welding torch angle in pulsed metal inert gas (P-MIG) welding. The experimental results revealed that the peak voltage is the dominant pulse voltage parameter. Various sensors were also used to monitor arc current, arc voltage, arc sound, and also weld temperature. A strong relationship between arc sound (as well as arc power) and transverse distortion (as well as metal deposition) was found to exist in P-MIG welding. The frequency domain features of welding arc sound were also extracted and correlated to the process characteristics.