伺服焊枪在板管单面电阻点焊中的应用

针对板管单面电阻点焊可焊性范围较窄,焊接质量难以保证的问题,分析了伺服焊枪电极位置、运动速度和电极力可控特性在板管单面电阻点焊中的应用前景.结果表明,伺服焊枪的软接触特性可以避免冲击力对焊接工件的影响,从而保证板管良好的接触状态;利用伺服焊枪的可变电极力特性,在焊接过程中减小电极力,能够有效提高接头的抗剪强度,降低焊接变形,改善焊点外观,并且拓宽可焊性范围.伺服焊枪为板管单面点焊的焊接质量提供了有力保障,在板管单面电阻点焊中具有广阔的应用前景.     

变电极力对管板单面电阻点焊形核的影响

根据管板单面电阻点焊结构特点,建立了轴对称有限元模型.通过结构、热电场的全耦合,分析了恒定电极力作用下,管板单面点焊的形核过程和特点,其焊接过程结构件的大变形导致形成的焊点质量不可靠.利用伺服焊枪通电过程中可实时改变电极力的特性,研究焊接过程中力的变化对焊点形状的影响规律.结果表明,单面电阻点焊焊接通电过程中改变电极力,在同等焊接工艺参数的情况下可增大焊接件间的连接宽度,减小焊接变形,提高焊点质量,为管板焊接在车身上广泛安全的应用提供理论依据.     

变电极力作用下的电阻点焊质量分析

热镀锌低碳钢板在车身内外板上获得了广泛应用.在传统的气动焊枪作用下,采用恒定的电极力焊接时,点焊质量不稳定.然而变电极力对镀锌钢板电阻点焊质量的影响很大.因此利用伺服焊枪能够精确控制电极力的特点,运用正交试验设计方法,深入分析了点焊过程中三个阶段电极力,即预压力、焊接力和锻压力对点焊质量的影响,得到了最优的变电极力参数.结果表明,点焊过程中的锻压力是影响点焊质量的重要因素,其次是焊接力,而预压力是最次要因素;最优的变电极力参数能够明显提高热镀锌低碳钢板的焊点拉剪力和熔核直径,这为基于电极力检测的点焊质量实时评价和电极力控制方面的研究奠定了基础.     

基于二维DIC技术的电阻点焊板件变形分析

结合二维数字图像相关技术(DIC),针对焊接电流、通电时间及电极力对电阻点焊过程中工件翘曲变形量的影响规律进行了深入研究和讨论. 结果表明,利用二维DIC技术获得的工件变形过程与电阻点焊各个阶段相吻合,而且具有较高的精确度. 随着焊接电流和通电时间的增大,熔核形成造成的翘曲变形增大;随着电极力的增大,熔核形成造成的翘曲变形减小,同时电极下压造成的变形增大.二维数字图像相关技术在电阻点焊过程中的首次尝试为电阻点焊工艺的研究和焊接质量的提高提供了新的方法,对电阻点焊工艺的发展和完善具有重要意义.     

基于ANSYS的管板单面电阻点焊数值模拟

针对管板单面电阻点焊工艺,建立其焊接过程的热、电、力耦合有限元分析模型,研究了焊接过程中的接触状态变化、温度场分布和焊接变形过程,揭示了环状熔核的生成机理,并利用金相试验和电极位移曲线对模型进行了验证.结果表明,计算结果与试验结果基本相符,证实了数值模型的正确性和适用性.研究结果可为管板单面点焊焊接机理和质量监控方法研...     

管板单边电阻点焊环状焊点力学性能分析

电阻点焊接头的焊接强度由母材和熔核的材料属性及几何特征决定.管板单边电阻点焊由于其焊接结构的特殊性,生成熔核的外形为环状,其强度不能用传统的圆形焊点强度经验公式计算.环状熔核的特征影响因素复杂,物理试验存在不确定性,通过大量试验方法难以建立焊接强度和影响因素之间的关系.基于拉剪试验原理,采用计算机模拟试验和试验设计方法,设计试验并统计得出低碳钢焊接强度和环状熔核几何特征因素之间的关系,并对其影响规律做了深入研究,为环状熔核质量的评估提供了依据.     

双相钢电阻点焊接头断裂形式研究

针对双相钢电阻点焊过程焊接工艺窗口窄、易出现熔核断裂的问题,文中通过焊点力学性能与微观金相试验,研究了不同焊接工艺参数变化时对双相钢焊点质量的影响规律,建立其焊接工艺窗口,分析了双相钢熔核断裂的成因及焊接参数对熔核断裂的影响规律.研究表明,对于一定板厚的试件,临界熔核直径将是决定双相钢点焊接头是否出现熔核断裂的重要参数之一,并给出避免熔核断裂的合理焊接工艺参数.     

管板单边电阻点焊形核过程有限元模拟

根据管板单边电阻点焊结构特点,建立了轴对称有限元模型.通过结构、热电场的全耦合,分析了焊接过程中接触面压力变化规律,单边焊熔核形成过程以及形核特点等.结果表明,单边点焊和传统点焊焊接过程有很大的不同.单边点焊焊接过程中工件变形严重,电极和板以及板和管子间接触状态变化复杂,熔核形成需要电流大、时间长,且最终形成环状熔核.与金相试验比较,管板单边焊熔核特征的计算结果与试验结果相符合,证实了所建模型的正确性和适用性.为研究单边点焊过程中焊接参数对熔核形成过程的影响规律及确定合理的管板焊接参数奠定了基础.     

DP780双相钢电阻点焊的数值模拟及试验验证

为了提高实际生产中的焊点质量,探究影响焊点质量的因素,针对厚度分别为1.6和2.0 mm的DP780样片组,建立电阻点焊过程的轴对称有限元模型,采用融合力场、热场、电场及微观组织结构的耦合分析模型模拟点焊熔核形成过程,研究点焊加热及冷却过程中的温度场分布特点,确定熔核尺寸和抗剪强度指标.通过试验测定实际点焊接头的熔核尺寸以及抗剪强度.结果表明,模拟预测的熔核尺寸、失效剪切力与试验值之间误差分别为2.05%和13.6%;焊接过程中的飞溅是导致误差的主要原因.     

压水堆新型燃料组件骨架压力电阻点焊工艺研究

压水堆新型燃料组件有别于AFA 3G型燃料组件,骨架采用导向管内外管"管中管"代替了AFA#3G型导向管缓冲段的新型设计,"管中管"与端部格架焊舌片采用压力电阻点焊工艺进行连接。通过对Zr4合金导向管外管单管段与焊舌片、导向管内外管双管段与焊舌片的点焊工艺进行分析,研究了焊接电流及电极压力对焊点剪切强度、熔核尺寸的影响规律。结果表明:Zr4合金薄壁管材两层及三层压力电阻焊时,焊接电流对熔核尺寸及剪切强度影响最大;随着焊接电极压力的增加,焊点的剪切强度和熔核尺寸均呈下降的趋势,但焊接压力的适当提高有利于形核的稳定性。     

Experimental study of single sided sheet to tube resistance spot welding

Abstract

To reduce weight and improve performance, hydroformed tubes are being widely used in automotive structure fabrication and the single sided sheet to tube resistance spot welding (SSRSW) is considered as a feasible method for joining a tube to other parts. However, in the sheet to tube SSRSW process, it is difficult to assure welding quality because of large welding deformation due to a lack of support inside the tube. The present paper investigates the influences of welding parameters, such as electrode force and welding current, on the welding deformation and quality of the sheet to tube SSRSW using electrode displacement and tensile shear tests. The effects of different electrode force patterns on the welding quality are investigated utilising the force characteristics of a servo gun. It is found that the welding deformation is influenced by both the electrode force and the welding current, and the tensile shear strength declines with larger electrode force and higher welding current. However, the tensile strength could be enhanced significantly and the welding deformation decreased greatly by reducing the electrode force in the welding stage or holding stage. In order to decrease manufacturing cost and improve weld quality, the reduced electrode force is recommended for the sheet to tube SSRSW process.     

Application of electrode force change in single sided resistance spot welding using servo gun

Abstract

Single sided resistance spot welding (SSRSW) is considered as a feasible method to join hydroformed or closed section parts to others in vehicle productions. Unfortunately, it is difficult to guarantee the weld quality utilising conventional air gun. Because of a lack of support inside the closed section parts, the impact of electrode driven by pneumatic gun will cause large deformation of the workpieces at the welding stage and will lead to a crack around weld region after welding completion. In addition, poor weldability is another pressing problem for welding operations. Servo gun with new gun driven method has some merits such as realising the soft touch between electrode and workpieces and changing electrode force during the welding process which are greatly suitable to the sheet to tube joining. Based on the characteristics of servo gun, the present paper investigates a new method to increase the weld quality of sheet to tube joining with SSRSW method. By adjusting the electrode force during the welding process, weld strength would be increased, weld deformation be decreased and weldability lobe curve be widened. The results verify that servo guns can provide high assurance for welding quality of sheet to tube joining and have broad prospect in SSRSW.     

工艺参数对板管间接点焊过程的影响

针对板管间接点焊过程中焊接变形较大,引起接头质量难以保证的问题.通过采集电极位移曲线,研究板管间接点焊过程中膨胀量和变形量的变化规律,分析不同焊接工艺参数(焊接电流、电极力和焊接时间)对该点焊过程的影响.结果表明,板管间接点焊焊接阶段,膨胀过程与变形过程相互耦合;保持阶段,在电极力作用下,焊接变形进一步加大,最大变形量随着电极力的增大和焊接热输入的增多而线性增加.发生喷溅时,电极位移曲线出现阶梯状畸变,可利用位移曲线斜率的变化评判该点焊的喷溅现象.研究结果为板管间接点焊过程在线监测与质量控制提供理论指导.     

Cold welding sealing of copper-water micro heat pipe ends

The quality of micro heat pipe(MHP) is strongly affected by sealing technology. Based on the analysis of requirements of sealing technology, a cold welding technology was presented to seal MHP. In the cold welding process, compression force was used to flatten micro groove copper(MGC) tube. Then the bonding of MGC tube was reached because of intensively plastic deformation of MGC tube under pressure. It is found that the plastic deformation area of the cold welding of MGC tube can be divided into three sections. The deformation of micro grooves in each section was investigated; the influence of the dimensions of cylindrical heads on the weld joint shape and strength was studied; and a comparison between smooth copper tube and MGC tube was done. The results show that a groove compression stage exists in the cold welding of MGC tube besides a flattened stage and a melting stage.     

管板单边电阻点焊过程预压接触分析

通过建立轴对称有限元模型,对管板单边电阻点焊预压过程中电极与板以及板与管间接触行为进行了研究,系统分析了预压阶段接触区域范围及接触压力分布的影响因素.研究发现,管板焊接过程预压阶段的接触压力分布与传统点焊过程预压阶段接触压力分布有很大的不同.在电极和板以及板和管之间均形成环状接触区,可能导致焊后形成环状熔核;预压过程中,电极和板间接触区不受压力变化影响,板和管间接触区则受压力影响明显;接触区域大小和电极端面直径、管板厚度等因素均有关系.试验表明,所建模型的模拟结果与实际是相吻合的,为今后管板电阻点焊工艺参数优化及车身轻量化中管板厚度比优化提供有效依据.     

Development of single-side resistance spot welding technology applying in-process welding current and electrode force controls

An indirect resistance spot welding process with single-side electrode access was developed for automotive applications. The variable controls of electrode force and welding current during welding were studied in order to achieve the promotion of weld nugget formation and the suppression of expulsion without sacrificing the productivity and design flexibility of automobiles. The welding experiments were performed on lapped test coupons of 0.7-mm-thick cold-rolled sheet with tensile strength of 270 N/mm² and 1.6-mm-thick cold-rolled sheet with tensile strength of 980 N/mm² using a resistance spot welding system consisting a servo-motor-controlled welding gun and an inverter DC power supply. Welding experiments verified that the occurrence of expulsion and formation of molten nugget were significantly influenced by the heat generation and melting process at an initial period during welding and manageable by applying the variable patterns of electrode force and welding current. When welding was performed under the large shunting condition simply with the constant force and current pattern of 400 N in electrode force, the appropriate current range was less than 1 kA. On the other hand, it extended to 2.6 kA when performed with the variable force and current pattern of 800 N in force and 4 kA in current at the first stage and 400 N in force at the second stage, confirming the fact that the variable pattern successfully suppressed the expulsion and promoted the nugget formation. Numerical simulations were conducted to compare the difference in welding phenomena between the constant force and current pattern and the variable force and current pattern and clarified that the effect of variable force and current pattern on the promotion of nugget formation and the suppression of expulsion.     

铝合金电阻点焊接头质量特征信息分析

为了研究电阻点焊接头质量,分析了铝合金2A12电阻点焊过程中的电极力、电极位移和焊接电流三组动态数据,并绘制了动态数据三曲线图.结果表明,在焊接过程中合格焊点的电极力曲线变化情况是:开始有轻微下凹现象,然后是小幅增长并伴随轻微波动,最后有向下倾斜的趋势,每个阶段不足或过度,则有不合格焊点产生.电极位移曲线的上升率直接与能量供应率有关,电极位移最大时刻与加载锻压力时刻之间的曲线形状与金属熔化量和软化区大小有关.     

Effect of variable electrode force on weld quality in resistance spot welding

Abstract

Resistance spot weldability is defined as the acceptable welding current ranges as determined by the weld lobe in resistance spot welding. Nowadays many studies have focused on the effect of welding current and welding time under constant electrode force on the weld quality and weldability. There is little research on the influence of variable electrode force on the weld quality and weldability because of the difficulty in controlling variable electrode force using pneumatic gun. In the present study, first, the influence of three stages of electrode force, including squeeze force, welding force and forging force, on the quality of welds is analysed. Then a design of experiment approach is applied to analyse the influence of the three stages of electrode force on welding quality and thus to obtain optimum parameter of variable electrode force by controlling the electrode force with servo gun. The comparisons of tensile shear strength, nugget size, weld lobe width and wear rate of electrode tip between variable force and constant force are carried out. The results show that the weld quality and weldability can be increased evidently using optimum parameter of variable electrode force without accelerating the electrode wear rate.