电极点蚀形貌对铝合金电阻点焊的影响

采用有限元分析和物理模拟相结合的方法,研究了环形和孔形两种电极点蚀形貌对铝合金AA5182电阻点焊的影响.结果表明,环形点蚀使两试件间接触半径增大,电流幅值基本不变而峰值略外移,所得熔核直径略有增大;孔形点蚀使试件间接触半径增大更为显著,电流密度降低,且由于此时界面中部没有电流流过,材料不能熔化,只能形成环形熔核.孔形点蚀使点焊接头强度大大降低,其对接头强度的不利影响远大于环形点蚀.     

铝合金电阻点焊电极寿命及其烧损原因分析

针对铝合金电阻点焊存在电极烧损和寿命短等缺点,结合国内外相关工作的研究状况,从铝合金点焊电极端面存在的问题、铝合金点焊电极烧损及其影响因素、铝合金点焊电极端面铜铝合金化等方面,分析总结了铝合金点焊电极烧损与寿命短的原因。结果表明:铝合金电阻点焊电极端面与工件界面铜铝合金化是电极烧损及寿命短的主要原因;而探索控制电极端面铜铝合金化反应的措施,是减弱电极烧损程度,提高铝合金电阻点焊电极寿命的重要途径。     

铝合金与低碳钢的复合电极电阻点焊接头特性

针对铝/钢难以焊接这一课题,研发了基于复合电极的电阻点焊新工艺,并对铝合金A6061与低碳钢Q235进行了点焊. 介绍了复合电极的设计、制造流程,观察分析了结合界面区反应层形貌及分布等微观组织特点,探讨了焊接电流对熔核尺寸和接头抗剪载荷的影响. 在结合界面上观察到了反应层的生成,其厚度随位置的变化而变化. 焊接接头熔核直径与抗剪载荷随焊接电流的增加而增大. 结果表明,在铝合金与低碳钢的电阻点焊中,镶嵌式复合电极的使用能够起到抑制界面反应层在焊点中央区域生长的效果.     

大电阻介质下的铝合金电阻点焊

在介绍大电阻介质材料的制备及其在铝合金点焊中的应用方法的基础上,以LF21防锈铝合金点焊为例,经金相试样分析及扫描电镜分析,对比研究了在不同的焊接电流下,应用介质材料与未应用介质材料时的熔核形貌、缺陷及组织.结果表明,未加入大电阻介质的点焊熔核均出现气孔和未熔合缺陷;而加入大电阻介质,形核效果良好,有个别小气孔但未出现影响焊点力学性能的未熔合缺陷.此外,加入大电阻介质降低了对焊件表面质量的要求,从而提高了铝合金点焊质量的稳定性;可降低焊接电流,导致较低的电极温度从而提高了电极寿命.     

CrZrCu电阻点焊电极焊接镀锌钢板失效原因分析

为分析CrZrCu电阻点焊电极焊接镀锌钢板失效快的原因,文章通过统计电极端部直径的变化趋势,利用扫描电镜、X衍射仪、显微硬度计对焊点及失效电极端面物相和横截面硬度进行了分析.结果发现在焊接镀锌钢板时,导致CrZrCu电极失效的原因表现为,电极的粘连使得电极材料磨损加快,以及电极端部的合金化使得焊接接触区的电阻发生较大的变化,同时也因为合金化导致硬度变低,进而加快了电极的塑性变形使得电极失效较快.     

铝合金直流点焊时电极的不对称烧损研究

对铝合金直流点焊时正、负电极的不对称烧损现象进行了试验研究,并通过对焊接过程中电参数曲线的分析,指出其原因在于正、负电极与铝板接触区域产热的不同。     

基于非对称电极的铝合金/钢电阻点焊

采用非对称电极点焊铝合金A6061与低碳钢Q235,观察接合界面区反应层形貌及分布等微观组织特征,探讨焊接电流、焊接时间与电极压力对熔核尺寸和接头抗剪力的影响。在接合界面上观察到反应层的生成,其厚度随界面的位置的变化而变化。在22 k A的焊接电流条件下获得的接头抗剪力达到5.51 k N。结果表明,在铝合金与低碳钢的电阻点焊中,不对称电极的使用有效地提高了焊接接头强度。     

镀锌钢板电阻点焊电极的失效分析

采用光学显微镜、X射线衍射等方法研究了铬锆铜电极在点焊镀锌钢板时的失效形式,对电极内部组织及其硬度、导电性能在焊接过程中的动态变化进行了监测、分析.结果表明:铬锆铜电极的失效形式主要是塑性变形、合金化和坑蚀;随点焊进行,电极内部发生再结晶和析出相长大,导致电极头部显微硬度明显降低.但对导电性能影响不大;铬锆铜电极失效后端面合金化产物为Cu5相似文献   

铝合金电阻点焊研究现状及工业应用

铝合金作为一种新型节能材料,被广泛应用在航空航天、汽车工业等领域,其特点是低密度、高比强度、导热导电性能优异、抗腐蚀性强等.阐明了铝合金电阻点焊存在的难点,并进行了相关的原理性解释,归纳总结了国内外关于铝合金电阻点焊的相关研究现状,探讨未来铝合金的电阻点焊研究方向与研究重点,并列举了铝合金的电阻点焊在汽车工业与其他产业中的应用.     

镀锌钢板点焊电极寿命研究

通过在不对电极进行更换和修磨的情况下，对2种镀锌钢板进行连续点焊的电极寿命试验，探索焊接过程中电极直径的增加规律和影响因素，以及对熔核尺寸的影响，并简单分析电极在长时间焊接后的合金化程度。     

热镀锌钢板点焊的点蚀对电极使用寿命的影响

热镀锌钢板点焊时电极磨损严重,点蚀特征变化明显.建立点焊过程中的电极端面接触电阻模型与接触热阻模型,分析点蚀变化对电极使用寿命的影响,并进行相应试验验证.结果表明.点蚀的产生与发展使电极端面接触电阻与接触热阻增大,导致电极端面温度升高、电极使用寿命降低.试验研究表明,热镀锌钢板点焊的点蚀区域在高温高压下容易产生微裂纹,镀锌层金属元素沿微裂纹渗八电极的内部,加速了电极失效.     

电阻点焊电极压力在线监测

针对电阻点焊压力信号的在线测量,设计了一种可以直接安装在焊接电路中的应变式点焊电极压力传感器。选用抗磁应变片,采取电桥线路补偿法以及测试应变片和补偿应变片感应电势相互抵消等措施,实现温度补偿和降低通电电流对压力传感器输出信号的干扰。测试结果表明,设计的压力传感器可以实时反映点焊压力的实际变化;采取的补偿和抗干扰措施,能够保证大电流通电焊接条件下传感器压力信号的较小干扰输出。     

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.     

Numerical study of electrode geometry effects on resistance spot welding

Abstract

This work numerically investigates the geometrical effects of the electrode containing a coolant hole on transport variables during resistance spot welding. The model accounts for transient magneto-fluid mechanics, heat and species transport, bulk resistance in workpiece, and film and constriction resistances at contact interfaces. The computed results show that electrode cooling due to the coolant hole influences transport processes during not only freezing and cooling periods but also heating and melting periods. Electrode cooling can be interpreted by thermal resistance, depending on the shapes of the electrode and coolant hole within the growing thermal diffusion layer. Major factors affecting electrode cooling are different in distinct time stages. In most cases, enhanced electrode cooling due to the coolant hole decreases the electrode temperature and nugget growth rate. A decrease in the electrode face radius strongly increases nugget growth rate and workpiece temperature and decreases electrode temperature, whereas its effect on cooling rate is insignificant. The optimum design and sensitivity analysis of the electrode shapes subject to required cooling rate, nugget growth rate and welding time are revealed.     

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.     

镀锌钢板电阻点焊涂层电极与普通电极寿命分析

为增加镀锌钢板电阻点焊电极寿命,在普通铬锆铜电极表面沉积镍和金属陶瓷涂层后,研究涂层电极与无涂层普通电极的寿命.结果表明,相同条件下,涂层电极使用寿命大约是普通电极使用寿命的2.5倍;涂层电极抗塑性变形能力明显高于普通电极;普通电极端面有明显坑蚀、裂纹、合金层、自愈合层,而电极表面涂层能有效防止镀锌钢板电阻点焊过程中由...     

Surface modified long-life electrode for resistance spot welding of Zn-coated steel

In order to increase the life of conventional copper electrodes in resistance spot welding of Zn-coated sheet steel, a multi-layer Ni/(TiC_P/Ni)/Ni composite coating was deposited onto the copper electrode top surface by electro-spark deposition. Scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction and micro-hardness tests were employed to characterize the microstructure and property of the coating. The results showed that the copper electrodes with a dense Ni/(TiC_P/Ni)/Ni coating slightly increased the resistance of the weld system and hence the welding current could be reduced to produce a weld with the same button size as that made by uncoated electrodes at a high welding current. The coating was gradually cracked during welding under the action of welding force, forming Ni/(TiC_P/Ni)/Ni composite islands which were strongly adherent to and further, punched into copper substrate. The coating could significantly reduce the alloying between copper electrode substrate and molten Zn. As a result, coated electrode showed a much longer life than an uncoated electrode even though the welding current for coated electrode was lower than that for uncoated one.     

Effects of electrode contact condition on electrical dynamic resistance during resistance spot welding

This study systematically investigates the effects of electrical resistance at the workpiece/electrode interface or electrode face on temperature dependent dynamic resistance during resistance spot welding (RSW). To evaluate temperature transport equations of mass, momentum, energy, species and magnetic field intensity in workpieces, the energy and magnetic equations in the electrode are solved. Contact resistances composed of constriction and film resistances are functions of hardness, temperature, electrode force and surface conditions. The results show that dynamic resistance is complicated due to different variations of film and constriction resistances with temperature at not only the faying surface but also the electrode face in the early stage, i.e. shorter than around 3 cycles. Dynamic resistance in this stage is fortunately insignificant to transport processes. When the power is off, dynamic resistance depends on competition between decreased bulk resistance and increased constriction resistance at the electrode face. Decreased constriction resistance at the electrode face reduces dynamic resistance and temperature.     

热镀锌钢板连续点焊时电极损耗对焊接质量的影响

镀锌钢板电阻点焊时由于锌层的影响电极损耗非常严重。以厚0.8mm家电用热镀纯锌钢板DX51D+Z为研究对象,探究在正交试验优化焊接参数后,热镀锌钢连续点焊时焊接接头质量变化的规律和电极损耗的特点。结果表明,当采用I=11 kA、P=2 500 N、T=13 cyc的点焊工艺参数组合可获得力学性能最佳的点焊接头;连续点焊试验初期(150点前)焊点力学强度稳定且焊点成形较好,焊接后期(150～300点)接头力学强度波动大,焊接状况不稳定;电极损耗至失效是接头质量急剧下降的主要原因,电极失效形式为头部塑性变形、端面坑蚀和Cu-Zn合金化,在本试验条件下,Cr-Zr-Cu电极焊至150点后显现不稳定现象,电极寿命约280点;失效电极端面的Cu-Zn合金层约65μm。