基于概率密度分布图的双丝脉冲焊稳定性定量评价

为减少双丝脉冲焊焊接过程稳定性评价的主观性,提出一种基于概率密度分布图的定量评价方法.在分析电流参数对概率密度分布影响的基础上,设计了峰值概率密度比K_DT、峰值概率和K_S、区间概率K_P三个分项指标,从而获得最终量化指标单路评价指标C_pdf,双丝评价指标TC_pdf.为验证方法的有效性,选择电参数和稳定性均不同的电流信号进行了试验.结果表明,设计的量化指标准确反映了不同双丝焊信号的稳定程度,焊接过程稳定性的定量评价得以实现.为工艺分析、智能控制参数优化提供决策参考.     

药芯焊丝CO_2焊工艺评价及远程监测系统研究

药芯焊丝CO2焊在我国船舶制造企业中大量应用,其焊接过程的稳定性评价与监控具有重要意义。通过对准1.4 mm药芯焊丝CO2焊三种不同焊接规范试验和过程稳定性试验,提取了短路过渡频率、断弧频率和瞬时短路频率作为评价其焊接过程稳定性的量化指标;搭建了基于单片机和无线Zigbee技术的药芯焊丝CO2焊远程监测系统,传输焊接过程量化特征信息,从而实现对其焊接过程的远程监测。通过试验证明,该系统具有良好的可扩展性,并能满足造船、冶金机械等行业实际焊接生产的质量监测和工艺评价需求。     

YAG激光焊接脉冲能量作用效应的声发射特征参数表征

对304不锈钢进行脉冲激光焊接试验,基于激光热源与工件相互作用所释放的声发射信号,研究利用声发射事件的平均峰值-振铃计数特征分布图评估焊接稳定性的方法.结果表明,脉冲激光对材料的作用越稳定,平均峰值-振铃计数特征分布图的散点分布聚集性越好;脉冲激光对材料的作用稳定性越差,平均峰值-振铃计数特征分布图的散点分布越发散.激光脉冲峰值功率增加时,对应声发射事件平均峰值和振铃计数均随之增加,反映出振铃计数对峰值功率变化而引发的焊接稳定性变化更为敏感.因此平均峰值-振铃计数特征分布图能够较为准确地表征激光焊接过程稳定性.     

基于电弧电压概率密度铝合金脉冲MIG焊稳定性分析

针对铝合金脉冲MIG焊过程稳定性评估问题,提出了基于电弧电压信号概率密度的分析方法.利用焊接过程电弧电压信号概率密度分布中的第一个峰值与第二个峰值的比值作为评价铝合金脉冲MIG焊过程稳定性的指标,通过对80组焊接试验中的电弧电压信号进行概率密度计算得到每一组概率密度分布中两个峰值的比值以此建立铝合金脉冲MIG焊过程稳定性评价体系.电压概率密度分布中两个峰值的比值越小,焊接过程越稳定;反之越不稳定.     

Study on DSP controlled CO2 arc ignition

CO2焊是一种生产效率高、成本低的高效焊接方法.传统的CO2焊采用接触式短路引弧,引弧时间长、成功率不高、稳定性差.分析了影响和提高引弧成功率的因素,并以DSP控制焊机为平台,设计了一种通过限制引弧过程焊接电流来进行引孤的方法.该引孤方法中,焊接过程中的电流为被控制对象,在电压为空载及以上,短路刚发生即电流不为零时就对电流进行控制,使整个引弧过程中电流值不大于给定峰值,从而达到限制引弧电流的目的.试验证明,该方法引孤时间短、一次性引孤成功率高、稳定性好,为后续CO2焊接稳定可靠的进行提供了有利条件.     

基于U-I周期重复率的CO_2弧焊稳定性机器判定方法

目前,焊接生产效率已得到了很大的提高,传统的人工经验判定方式难以完成如此高速度高强度焊接生产情况下的焊接质量监测任务。本文提出一种基于U-I周期重复率的CO2弧焊稳定性机器判定方法。该方法通过计算U-I工作点的周期重复率来判定焊接过程的稳定性,理论上符合焊接规律,实际上切实可行,能满足机器化焊接生产情况下的监测需求。     

DSP控制CO_2焊引弧研究

CO2焊是一种生产效率高、成本低的高效焊接方法。传统的CO2焊采用接触式短路引弧,引弧时间长、成功率不高、稳定性差。分析了影响和提高引弧成功率的因素,并以DSP控制焊机为平台,设计了一种通过限制引弧过程焊接电流来进行引弧的方法。该引弧方法中,焊接过程中的电流为被控制对象,在电压为空载及以上,短路刚发生即电流不为零时就对电流进行控制,使整个引弧过程中电流值不大于给定峰值,从而达到限制引弧电流的目的。试验证明,该方法引弧时间短、一次性引弧成功率高、稳定性好,为后续CO2焊接稳定可靠的进行提供了有利条件。     

基于自相关分析的电弧焊熔滴过渡过程稳定性的定量评价

文中提出了基于自相关分析的定量评价方法,从电弧焊的电压电流信号中提取自相关函数峰值间距变异系数,作为电弧焊熔滴过渡过程稳定性评价的量值.结果表明,该方法所得的结果与人工分析判定的结果一致,切实可行.此外,该方法所提取的量值与其它量值联合使用,还较好地实现了CO2弧焊电源动特性的自动化评定.其准确率达97.4359%,已接近实际应用的要求.     

基于MATLAB的激光-脉冲MIG复合焊过程稳定性评价

因焊接质量与焊接过程的稳定性有直接关系,且焊接过程中采集到的电信号数量庞大,难以实现有效数据的快速提取,文中提出一种基于MATLAB的激光-脉冲MIG复合焊焊接过程稳定性评价方法.采用电流周期T的均值与标准差评价焊接过程的周期性,峰值电流与基值电流的差值d的均值与标准差来衡量焊接过程的波动性,综合这两方面来评价焊接过程的稳定性.文中进行四组激光-脉冲MIG复合焊验证试验,其电流信号、电弧形态、熔滴过渡和焊缝形貌的分析结果与该评价方法所得结果一致,证明文中提出的评价方法是有效可靠的.     

人工神经网络在CO2气体保护焊实时监测中的应用

利用人工神经网络的训练结果可以对焊接过程的各类特征参数进行合理评价.利用LVQ神经网络模型,根据实验采集分析得到的CO2气体保护焊不同焊接工艺条件下焊接电流和焊接电压的概率密度分布曲线以及短路过渡时间和燃弧时间等的时间频数分布曲线,在Matlab神经网络工具箱中开发出焊接过程神经网络识别器,可以自动识别焊接过程中各种干...     

基于时频分析的CO2焊接电弧信息提取

利用Choi-Williams分布二次型时频分析方法研究CO2焊接过程所采集的电弧电压信号,获得信号的时频分布图。通过时频图像信息提取,进一步获得焊接过程特征信息,即信号的能量谱密度和瞬时频率估计。结果表明,利用Choi-Williams分布可以描述弧焊过程中电弧电压信号的时频能量分布。在时频分析基础上进行电弧信息提取,可以得到短路、断弧等物理现象的时间特征及瞬时频率信息。电弧特征信息的奇异点表现出明显不同的瞬时频率特性,以此界定电弧物理过程。     

Obtaining residual stress along weld beads by means of analytical and experimental methods

In CO₂ arc welding of solid wire, metal transfer phenomena and spatter generation are investigated with rectangular pulse current, and a low spatter CO₂ arc welding process with high frequency pulse current is developed. The optimal conditions of high frequency pulse CO₂ arc welding are in the range of peak current: 450–550 A and pulse frequency: 450–750 Hz. These high frequency pulse currents have the effect of droplet oscillation due to resonance between applied pulse frequency and the natural frequency of the droplet. The droplet is transferred consistently every 9–11 pulses and the average interval of metal transfer is about 16 ms which is reduced to half that of conventional CO₂ arc welding. This average droplet weight is 34 mg, showing a large reduction in comparison with that of the conventional method. As a result, total spatter weight is reduced by 70% in comparison with the conventional method, and especially, large spatters more than 0.5 mm in diameter are reduced from 1.5 to 0.2 g/min.     

CO2短路过渡焊接熔池三维瞬态数值模拟

考虑CO₂短路过渡焊接过程中的随机性,建立了考虑熔滴熔池短路时刻、熔滴初始大小等因素的熔滴自适应模型. 此外,采用非对称高斯热源模型来考虑电弧热流密度沿焊接方向的非对称性,结合附加源项法考虑电弧压力、电磁力和浮力,采用连续表面张力模型计算表面张力,采用VOF方法追踪熔池表面,采用焓-孔隙度法考虑熔化凝固过程中的糊状区的动量损失,建立了CO₂短路过渡焊接熔池的三维瞬态模型. 利用该数学模型计算6 mm厚低碳钢板的CO₂短路过渡焊接熔池的温度场和流场的瞬态发展,模拟和试验结果的短路间隔时间概率密度分布及焊缝成形吻合良好.     

Development of low spatter CO2 arc welding process with high frequency pulse current

Abstract

Metal transfer phenomena and spatter generation in CO₂ arc welding with a solid wire were investigated, and a low spatter welding process using a high frequency pulse rectangular current was developed. The optimal conditions of high frequency pulse CO₂ arc welding were determined to be a peak current of 450–550 A and pulse frequency of 450–750 Hz. These high frequency pulse currents influenced the droplet oscillation due to resonance between the applied pulse frequency and the natural frequency of the droplet. A droplet was regularly transferred by 9–11 pulses, and the average interval of metal transfer was ～16 ms, which was half of that in conventional CO₂ arc welding. The average droplet weight is 34 mg, showing a large reduction in comparison with that of the conventional method. As a result, the total spatter weight was reduced by 70% in comparison with the conventional method, and particularly large spatters more than 0·5 mm in diameter were reduced from 25 to 3 mg s^?1.     

Effect of REM addition of wire on CO2 gas shielded arc phenomenon

Carbon dioxide (CO₂) gas shielded arc welding is the main arc welding method, but it generates a large amount of spatter during welding. The root cause of spatter lies in the fact that the droplet undergoes repeated irregular shaking. To solve this problem, spatter generation modes were clarified and the effects of polarity and rare earth metal (REM) addition of the wire on CO₂ gas shielded arc welding were investigated. As a result, when welding is performed with an electrode negative (DCEN) polarity using REM added wire, it was found that a conical arc plasma is formed, and the droplet which is transferred from the wire tip to the molten pool is fine and continuous, in what is termed ‘spray transfer’. Thus, spatter generation was reduced to 10% of amount of the conventional CO₂ gas shielded arc welding (from 0.058 to 0.005g/s).     

自保护药芯焊丝全位置焊接电弧稳定性分析与评价

采用高速摄像仪和汉诺威弧焊质量分析仪对三种市售X70管线用自保护药芯焊丝全位置焊接的熔滴过渡及电弧稳定性进行观察分析.结果表明,全位置焊接电弧稳定性为1号焊丝最好,3号居中,2号最差;电流变异系数比标准差更能准确地反映电弧稳定性;单凭平均短路时间不能作为判定电弧稳定性的依据,必须结合短路时间频次分布图才有意义;短路过渡时电弧电压概率密度分布为双驼峰形状,双驼峰处曲线的概率密度分布及整条曲线的收敛情况可作为评定电弧稳定性的重要参考依据.     

低热输入推拉送丝CO2焊接工艺

传统短路过渡过程熔滴过渡随机发生,短路与燃弧时间比例范围较大,燃弧与短路期间的能量分配比例也随之起伏不定.推拉送丝CO₂焊接系统利用焊丝的送进-回抽与波形控制相结合的控制方式,促使熔滴在较小的电流下进行过渡,实现稳定可控的短路过渡CO₂焊接过渡.通过焊接参数的合理选定,控制回抽焊丝强制熔滴过渡,可有效减小等效燃弧电流I_ea和等效燃弧电压U_ea,从而降低热输入量.当推拉送丝系统中焊丝的送进与回抽时间相等时,焊接过程中短路/燃弧的时间也大致相同,无较大波动,燃弧与短路能量分配比例也较为稳定,可以控制在一个较小的值.结果表明,采用相同送丝速度时,推拉送丝短路过渡燃弧期间能量远小于传统的短路过渡,采用推拉送丝CO₂焊接系统可实现过程精密控制的低热输入短路过渡的焊接过程.     

Effect of power source characteristic on CO2 short circuiting arc welding

Abstract

Some problems are reported concerning the observation of the weld pool and effects of the power source characteristic on arc stability in CO₂ short circuiting arc welding. First, the effect of a power source with a constant voltage characteristic on CO₂ short circuiting arc welding is investigated by analysing the behaviour of the voltage and the current. From the results of this analysis, the cause of spatter generation is identified. A new power source characteristic is then proposed to improve the stability and the self-regulation of the arc. By adjusting the power source characteristic, the metal transfer can be stabilised in the CO₂ short circuiting arc welding process, i.e. the present authors have developed a power source having a non-linear characteristic. Its performance is verified by carrying out experiments.