母材成分对DP590钢电阻点焊接头性能的影响

通过对两种强度相近、母材化学成分不同的DP590双相钢电阻点焊接头的强度、断口及熔核TEM分析,揭示了母材化学成分对双相钢点焊接头强韧性的影响规律及机理.结果表明,母材碳含量越高,接头正拉强度及韧性越差,其主要机理是,在电阻点焊不平衡的急速冷却条件下,随着母材碳含量的增加,在点焊熔核及熔合区形成了板条状或片状的孪晶马氏体亚结构,从而降低了接头的韧性.     

热处理工艺对TRIP980钢板点焊性能的影响

采用不同焊接工艺对TRIP980钢板进行点焊试验,研究了焊接电流、焊前预热及焊后热处理工艺对点焊性能的影响. 结果表明,随着焊接电流的增大,焊点的熔核直径和拉剪力均增大,但当电流过大而发生飞溅时,焊点的熔核直径和拉剪力开始减小. 焊前预热工艺可提高点焊飞溅电流,进而可以获得更大的熔核直径及拉剪力. 在对焊点进行焊后热处理的情况下,当焊接电流与焊后热处理电流之间的冷却时间超过900 ms时,可显著改善熔核组织,降低熔核硬度,提高焊点拉剪力.     

钛与低碳钢的电阻点焊

采用电阻点焊方法对纯钛与低碳钢Q235进行焊接试验，利用扫描电子显微镜观察分析了熔核区组织特性，探讨了焊接电流对熔核尺寸和抗剪载荷的影响. 结果表明，受焦耳热的影响熔核直径随焊接电流的增加而增加，抗剪载荷则随焊接电流的增大而呈先升后降的变化趋势，焊接电流为8 kA时所得接头的抗剪载荷最大，约2.85 kN. 在钢侧熔核区观察到了靠近钢侧厚度约为30～50 μm的TiFe2+α-Fe共晶组织层和粗大TiFe柱状晶；钛侧熔核区主要由靠近钛侧约12 μm厚的TiFe+α-Ti共晶组织层和TiFe柱状晶构成，且观察到了宏观分层现象.     

热补偿电阻点焊铝合金接头的性能

采用热补偿电阻点焊的方法焊接铝合金A5052板,分析了焊接电流、焊接时间及电极压力等焊接参数对熔核尺寸与接头抗剪强度的影响,并分析了接头抗正拉强度与焊接电流的关系.铝合金的热补偿电阻点焊接头抗剪力及熔核直径随焊接时间延长而增大,随电板压力的增大而减小.当焊接电流为12kA时,接头拉剪力达到最大值,约5.5 kN.试验结...     

Ni在钢/铝电阻点焊中的作用

以DC01钢板与5082铝合金板为基材,在电极压力3 kN、焊接时间300 ms、保持时间100 ms条件下,研究了电阻点焊中焊接电流(9~12 kA)及Ni镀层对接头剪切力、正拉力、界面相组成的影响。结果表明,随焊接电流的提高,熔核尺寸增大,接头力学性能提高。剪切力比正拉力高一个数量级。在10 kA焊接电流下,镀Ni钢/铝接头的剪切力和正拉力均比钢/铝直接焊接时强度明显提高,这与钢/铝界面形成了Al 3Ni合金相,抑制了脆性Fe 2Al 5金属间化合物的生成有关。     

预涂导电密封胶的轨道车辆不锈钢车体电阻点焊工艺试验

根据某不锈钢车辆上下侧墙板搭接结构形式,采用涂导电密封胶的电阻点焊技术,实现结构连接的同时保证了车辆密封.为验证该工艺的可靠性,采用预涂导电密封胶的电阻点焊技术分别对三种搭接结构试件进行焊接试验.焊后根据相关标准分别对三种搭接结构进行电阻点焊接头试验,包括外观检验、剥离试验、剪切拉伸试验和金相检验,并对点焊接头的表面凹...     

硼钢与铝合金的新型电阻单元焊技术

文中使用了一种新型电阻单元焊技术,用来连接6061铝合金以及22MnMoB硼钢.“电阻单元焊”即在上板待焊区域预制工艺孔,将辅助单元塞入孔中,底部与上板持平,要求辅助单元与下板具有好的焊接性,最后使用电阻点焊机在辅助单元处进行焊接,试验中使用的辅助单元为Q235钢钉.研究了该工艺的接头力学性能、断口形貌、微观组织及硬度分布,并进行了电阻点焊试验作为对比.结果表明,传统的电阻点焊几乎无法连接硼钢及铝合金,而电阻单元焊新型工艺能够完成硼钢及铝合金的可靠连接,接头最大拉剪力达到7142 N,且塑性也十分优良.     

异种钢电阻塞焊工艺优化及接头性能分析

采用一种新型复合焊接工艺——电阻塞焊对1.5 mm等厚TRIP980高强钢/SPCC低碳钢板进行焊接,利用正交试验优化其焊接参数,随后增加焊前预热,分析对比无预热和焊前预热两种条件下较优焊接参数时接头的力学性能及组织、硬度特点.结果表明,各焊接参数对接头的拉剪载荷影响程度由大到小依次为焊接电流、填充物直径、焊接时间及电极力;在电极头端面直径为8 mm的条件下,填充物直径为5.5 mm时的接头力学性能优于其它直径;相同焊接参数时,焊前预热塞焊接头的拉剪载荷比无预热提高7%以上;两种条件下较优焊接参数时,焊前预热塞焊接头的熔核偏移量小于无预热,熔核和熔合区的硬度比无预热时有所下降,熔合区脆硬马氏体组织比无预热少;焊前预热塞焊接头断口为韧性断裂,无预热塞焊接头断口为脆性断裂;其主要机理是,预热减小了熔核区金属过热倾向,使熔核扩展均匀,熔合区脆硬组织减少,有利于接头强度的提高.     

外加磁场对非等厚铝合金电阻点焊熔核偏移的影响

针对两层板及三层板组合下的5052铝合金进行了外加磁场与常规情况下的电阻点焊,研究了外加磁场对铝合金点焊熔核偏移影响. 结果表明,外加磁场改善了两层板及三层板非等厚度铝合金的熔核偏移情况,尤其是针对熔核偏移较严重的板材厚度组合下,外加磁场改善熔核偏移的作用更加明显. 之后针对外加磁场和常规点焊情况的不同两层及三层板铝合金板厚组合式样进行了剪切拉伸测试. 结果表明,外加磁场在改善点焊熔核偏移的同时,提高了点焊接头的强度. 因此,外加磁场是一种改善非等厚度铝合金点焊熔核偏移及提高接头剪切拉伸性能的有效方法.     

Influence of polarity on mechanical properties of dissimilar resistance spot welds of DP 600/AISI 304 steels

The influence of polarity during resistance spot weld (RSW) of dissimilar lap joints on mechanical properties and failure mode is assessed in this work. A dissimilar lap joint was set using DP 600 dual phase steel with AISI 304 stainless steel. The experiments were performed on a medium-frequency direct current spot welding machine with proper data acquisition of voltage and welding current. Temperature evolution was also acquired by using IR camera. The mechanical properties of spot welds were evaluated by using a coach peel testing. The effect of welding current and welding time on mechanical properties was also evaluated. Correlations between polarity with the welding nugget size, failure mode, tensile strength, temperature evolution and dynamic resistance were analysed. The analysis confirmed that the polarity on dissimilar lap joints affects the behaviour of dissimilar RSWs.     

永磁体磁场对双相高强钢电阻点焊质量的影响

以1对中空圆柱形永磁体为磁场源,系统地分析了外加恒定磁场作用下,2.25mm厚热镀锌双相高强钢板(HDG-DP600)电阻点焊接头的力学性能、熔核尺寸及宏观晶粒组织走向.试验发现:在永磁体磁场作用下,热镀锌双相高强钢点焊接头的拉剪力较无外加磁场情况下提高了11.01%,接头的晶粒组织得到一定程度的细化,熔核形状"长而扁...     

Investigation of induced magnetic force on liquid nugget during resistance spot welding

Abstract

This paper investigates the source, magnitude and direction of magnetic force on the liquid nugget during resistance spot welding (RSW). High speed photography was used to observe the nugget formation process during half-sectioned RSW of steel (ferromagnetic substance) and aluminium alloy (paramagnetic substance). The induced magnetic force acting on half-sectioned and regular nugget was afterwards analysed and calculated. The results show that in the case of steel RSW, the magnetised workpieces generated a very strong magnetic field around the spot welding zone, while weak magnetic field appeared in the case of aluminium alloy RSW. This strong magnetic field causes a strong convection in the liquid nugget of steel even when the welding current is low. This strong convection will promote that the dimensions of nugget in the steel RSW become larger and closer to rectangle (observed on the cross-section) than in the aluminium alloy RSW.     

Optimization design of resistance spot welding parameters of magnesium alloy

By means of the quadratic regression combination design process, the regression equations of nugget diameter and tensile shear load of spot welded joint were established. Effects of welding parameters on the nugget diameter and the tensile shear load were investigated. The results show that effect of welding current on nugget diameter is the most evident. And higher welding current will result in bigger nugget diameter. Besides, interaction effect of electrode force and welding current on tensile shear load is the most evident compared with others. The optimum welding parameters corresponding to the maximum of tensile shear load have been obtained by programming using Matlab software, which is 4, 7 kN electrode force, 28 kA welding current and 4 cycle welding time. Under the condition of the optimum welding parameters, the joint having no visible defects can be obtained, nugget diameter and tensile shear load being 6. 8 mm and 3 256 N, respectively.     

The comparison between laser screw welding and resistant spot welding of lap joint with large thickness ratio

The present paper investigates the welding forming, microstructure and shear tensile test of lap joints with large thickness ratio which were fabricated by laser screw welding(LSW) and resistant spot welding(RSW). The comparison was conducted on two kinds of lap joints, galvanized sheet and hot pressed steel(GS-HPS), galvanized sheet and high strength steel(GS-HS). The microstructure and fracture morphology were analyzed by optical microscope. It was demonstrated that with large thickness ratio the sound lap joint of GS-HS could be obtained by LSW regardless of the irradiation of laser beam from thick metal to sheet or otherwise, and the morphology shows it is better when the laser is irradiated on the thick metal. Nevertheless, when the laser beam was applied on thick metal of HPS, blind hole or blowhole was formed in the center of joint, which is attributed to the shrinkage during solidification of the molten pool. Small pores or dispersed porosity appeared on the faying face of the joint without predetermined gap which provides the degassing. However, the increase of predetermined gap could reduce the shear strength and nugget size. Two kinds of joints made by LSW have superior shear strength than those made by RSW when the laser were applied on galvanized sheet.     

高强镁合金点焊接头性能

采用电阻点焊方法对高强镁合金Mg₉₆Zn₂Y₂进行了焊接.通过扫描电子显微镜对接头微观组织进行了观察,分析了接头的组织,研究了焊接电流对接头熔核直径及抗剪载荷的影响.在此基础上探讨了接头组织对接头性能的影响.结果表明,接头熔核直径与抗剪载荷均随焊接电流的增大而增大,接头最大抗剪强度约为142 MPa;接头熔核区第二相呈细网状分布,其α-Mg晶粒发生了粗化,直径约为30 μm.熔核区这些组织特征被认为是接头弱化的主要原因.     

Effect of process parameters on SPRC35 spot welded automotive panels

This paper presents an experimental study on the resistance spot weldability of SPRC35 (steel plate re-phosphorised cold rolled) sheets. The sheets were joined by using resistance spot welding as lap joint. The weld nugget diameter and tensile shear force were investigated. Tensile-shear tests were applied to the welded specimens to understand the tensile shear force that the joint can withstand. Mathematical models were developed for both nugget diameter and tensile shear force. Use of automatic mode, will increase the dependence on the use of equations to predict the nugget diameter. The developed models have been checked for their adequacy and significance by the F test and t test respectively. The results obtained from the mathematical models have been optimized and also tested using conformity test runs.     

钛合金胶接点焊与电阻点焊接头性能对比分析

分别对1.5 mm厚的钛合金板进行胶接点焊和电阻点焊连接,获得了不同焊接电流下的胶接点焊和电阻点焊接头,从熔核的C扫描图像、接头的失效载荷和断口形貌等方面,对比分析了胶接点焊和电阻点焊的接头强度及失效样貌. 结果表明,通过观察A扫描信号的变化与C扫描图像的特征,能够很好的划分接头的热影响区、熔合区、熔核区以及检测出接头的熔核直径和焊接缺陷. 随着焊接电流(7.0～10.0 kA)的逐渐增大,接头熔核直径及失效载荷呈递增趋势;当焊接条件相同时,胶接点焊接头的熔核直径普遍大于电阻点焊接头,但接头的强度相当. 当电流在7.0～8.5 kA时,接头强度不足,熔核区的断口处出现大小不等的韧窝,呈现出韧性断裂特征;当电流为10.0 kA时,接头强度较高,主要呈现出韧性断裂与准解理断裂特征.     

一种先进热冲压钢的电阻点焊工艺多元非线性回归设计

采用多元非线性回归正交组合设计了试验方案,研究了点焊工艺参数对一种先进热冲压钢焊接接头质量的影响.将点焊接头抗剪切强度与点焊熔核直径作为影响接头质量的主要考察指标.以电极力、焊接电流及焊接时间作为工艺参数,并分析三者之间的相互制约关系.通过正交理论设计了9组试验,根据回归设计理论,建立三元二次非线性回归方程并进行了剩余标准差计算.结果表明,回归模型能够实现对点焊接头抗将剪切强度与点焊熔核直径的有效预测.绘制了其三维视图,在模型的基础上研究点焊工艺参数对焊缝质量的影响规律.     

Dissimilar metal joining of aluminium to zinc-coated steel by ultrasonic plus resistance spot welding – microstructure and mechanical properties

Vehicle body structures are increasingly utilising multi-materials designs with advanced high strength steels (AHSS) and aluminium alloys. A robust process for joining aluminium alloys to AHSS based on resistance spot welding (RSW) is essential to widespread application of such bi-metallic structures in fuel-efficient vehicles. In this study, ultrasonic plus RSW was applied to join AA6022 to Zn-coated dual-phase steel DP980. During solid-state ultrasonic spot welding, an interface structure comprising multilayer, Al–Zn and Zn–Fe intermetallics formed due to alloying of aluminium with steel coating. Such structure was subsequently melted into the aluminium nugget, and new Al–Fe intermetallics formed during RSW. Ultrasonic plus resistance spot-welded joints had superior fracture energy than direct resistance spot-welded joints.     

TRIP980高强钢电阻点焊接头的组织及力学性能

采用电阻点焊对TRIP980高强钢进行焊接. 通过单因素法和焊后回火优化了焊接参数和工艺,研究了较优焊接参数和工艺时的接头熔核显微组织及力学性能,结果表明,优化参数为9.5 kA,22 cycle,3 kN,接头熔核为粗大的马氏体组织,接头硬度为617.1 HV,最大拉剪载荷为17.8 kN;在此基础上增加焊后回火,回火电流6.3 kA、回火时间13 cycle,接头组织显著细化,接头硬度降低至574 .0 HV,接头最大拉剪载荷提高到19.5 kN,增幅为9.6%,断口形式由原先的界面断裂转变为纽扣断裂.