变电极力对管板单面电阻点焊质量的影响

根据管板单面电阻点焊结构特点,建立了采用伺服焊枪的管板单面电阻点焊试验系统.针对管板焊接过程中变形大、形成环形熔核质量不可靠等问题,提出了基于改变焊接过程中电极力来提高焊点质量的方法,并研究变电极力对管板焊焊点强度及焊接变形影响的规律.结果表明,通电阶段熔核生成初期减小电极力,可明显提高焊点拉剪强度,减小焊接变形;冷却阶段减小电极力对焊点质量也有所提高,但影响较小.研究结果对管板焊接工艺参数的制定及单面电阻点焊在车身焊装中广泛安全的应用具有重要意义.     

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.     

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...     

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.     

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.     

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.     

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.     

0.5～3毫米不锈钢钨极氩弧点焊

前言钨极氩弧点焊,是利用钨极电弧作热源,在氩气保护下对薄板进行点焊的方法。在点焊过程中,依靠电弧热量把上下板熔化成焊点,从而把上下板点焊在一起(图1)。焊点的几何尺寸见图2。这种方法在某些地方可以代替或部分代替电阻点焊(接触点焊)。与接触点焊比较,钨极氩弧点焊有如下特点: 1、可以进行单面点焊,背面无需放置电极或垫板,因此,特别适用于点焊不能接近背面的结构; 2、焊点质量与接触点焊的质量相近; 3、设备简单,制造容易; 4、操作方便,机动灵活,对结构的形     

B340LA低合金高强钢电阻点焊工艺试验优化与分析

在1.0 mm厚B340LA低合金高强钢电阻点焊工艺窗口范围内,以峰值拉剪力、失效能耗和熔核大小为考核指标,利用正交试验方法系统地研究了通电时间、焊接电流和电极压力等工艺参数对焊点质量的影响。结果表明,影响焊点质量的主次顺序为通电时间焊接电流电极压力,优选工艺参数组合为:通电时间8 cyc、焊接电流8.3kA和电极压力0.35kN,并试验验证了优选工艺参数组合条件下的点焊接头质量较高,飞溅较少。     

基于嵌入式系统的电阻点焊飞溅信息在线判读

钢材的电阻点焊过程中,动态电阻的变化表征了丰富的焊接质量信息.采用嵌入式系统实时监测焊接过程动态电阻的变化有利于提高对焊接质量的认识.设计了嵌入式监测系统,系统同时监测焊接电流、电极间压力和电极间的电压、电极位移信号.分析了双相钢DP600焊接过程中的动态电阻变化与焊点熔核之间的关系,并阐明用焊点两端的电压信号替代动态...     

Numerical analysis of single sided spot welding process used in sheet to tube joining

Abstract

As a new kind of lightweight structure, hydroformed tubes are now widely used in vehicle bodies. The single sided spot welding (SSSW) is a variation of resistance welding used in joining hydroformed closed tubular parts and vehicle structures. During the process of SSSW, large deformation and complex contact status of the workpieces occur because there is no inside support. The time variation of the contact region and pressure distribution changes the flow paths for electric current timely and brings a fierce shunting at the position far away from the axis line, which prevents the heat concentration at the faying surface of workpieces. The characteristics of SSSW different from those of classical resistance welding mentioned above make it difficult to determine rational welding processing parameters for SSSW. In the present paper, a comprehensive structural–thermoelectric model is established. Using the incrementally coupled analysis of finite element analysis, the electrical, thermal and mechanical aspects of sheet to tube process using SSSW are investigated. The mechanical characteristic of specimens during the squeeze and welding progress, the electric current density transient distribution, the nugget formation process, and the effects of welding parameters for SSSW are discussed. It is found that ring nugget is obtained by sheet to tube SSSW. Modifying electrode force during welding cycle is a valid method to obtain acceptable nugget with shorter welding time or less energy. The calculated results of nugget size and location are in good agreement with those of experimental observations.     

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.     

Technique for the determination of a wire-electrode tool shift value during the process of the conical four-coordinate electroerosion treatment

The problems of obtaining an exact conical surface of workpieces as a result of the displacements of the wire-electrode tool (WET) during the process of treatment from a specified position are explored in this paper. The method of determination and correlation of the real position of the cutting-wire area electrode is developed, forming the necessary inclination angle and obtaining exact conical surfaces.     

电火花加工精度的提高措施

通过对电极的优化设计制造、工件定位的精度保证、工件的定位加工3个方面提高电火花加工的精度。详细讨论了如何降低和消除电极加工精度误差、电火花加工机的几何精度误差、工件电极的校正精度误差、定位精度误差等对电火花加工精度的影响,从而提高电火花加工精度。     

Kinetics of the nucleation and growth of nickel particles in α-alanine-containing electrolytes

Kinetics of the nucleation and growth of nickel particles in an α-alanine-containing solution is studied with the use of voltammetry and chronoammetry. The electrochemical crystallization of nickel on a copper electrode is found to proceed according to the instantaneous nucleation mechanism. The main kinetic characteristics of the nucleation process are calculated. Partial curves of the metal deposition and hydrogen evolution are constructed.     

浅谈Cimatron E的快速电极设计

介绍了通过使用Cimatron E进行快速电极设计，提升电极设计效率、提高电极设计的安全系数，降低设计用时成本，其用途广泛，适用于各种复杂工件，简单实用，安全高效。     

TiO2粉末介质介入铝合金电阻点焊熔核形核电阻特征分析

以TiO2粉末作为添加介质进行铝合金电阻点焊. 焊接过程中利用实时传感技术对电阻点焊熔核形核过程的电极电压与焊接电流信号进行实时检测,通过对检测信号的计算和分析得到熔核形核动态电阻曲线,研究TiO2粉末介质对熔核形核与生长过程电阻特征的影响. 结果表明,随着TiO2粉末介质的介入,熔核形核动态过程发生变化,表现出不同的动态电阻特征. 由动态电阻曲线提取的接触电阻、终了电阻和形核电阻热效应3个特征值均能反映TiO2粉末介质对熔核形核质量特征的影响,且终了电阻、形核电阻热与焊点最大承载力高度线性相关,可作为检测熔核形核质量的依据.     

铝合金电阻点焊的熔核形成过程

点焊过程中熔核形成过程对焊接结构的强度和耐用性具有非常重要的影响.文中采用高速摄像技术研究了焊接电流和电极压力对铝合金电阻点焊形核过程的影响.结果表明,铝合金电阻点焊熔核首先在工件/工件接触面中心处形成,然后沿着水平方向生长,同时垂直方向也有少量的生长,一直扩展到电极头端面直径.熔核尺寸在点焊前80 ms时迅速长大,120 ms后基本保持不变,表明过长的焊接时间是没有必要的.随着电极力的增加,工件会经历较大的塑性变形,导致没有熔核形成.因此常规点焊时,不应采用过高的电极压力.     

电火花加工电极材料的选择

介绍电火花加工中电极材料受到各种干扰因素的影响,干扰因素直接或间接造成了电极材料损耗,研究发现,电极材料损耗越小,加工件的精度越高,通过试验将5种电极材料在电火花加工过程中的损耗进行对比研究,确定了W-Cu合金作为电火花加工用电极材料损耗最小,加工件加工精度最高。