压力对纯铜超声焊接界面行为的影响

以0.8 mm厚的纯铜为研究对象,进行了超声焊接接头试验分析,研究了焊接压力对焊接过程及接头强度的影响规律. 界面间运动传递力学分析表明,焊接压力通过界面粘—滑运动影响界面的能量输入,进而影响焊接接头的成形过程. 结果表明,焊接压力直接影响压电换能器的功率输出,从而影响输入焊接界面的能量,致使焊接区域的变形程度不同;焊接压力存在临界值,低于临界值时,焊接接头拉伸剪切力随焊接压力增大而增大,但强度较低;高于临界值时,随着焊接压力的增大,焊接接头拉伸剪切力基本保持不变.     

导电聚合物复合材料的产热特性及电阻焊接工艺

以丙烯腈-丁二烯-苯乙烯塑料(ABS)为基体,导电聚苯胺(PANI)和导电炭黑(CB)作为填充剂制备了导电聚合物基复合材料,测试分析了聚合物复合材料在不同焊接电压下焊接界面处温度随焊接时间的变化规律,并以其作为加热电阻研究了聚碳酸酯(PC)的电阻焊接工艺.结果表明,焊接电压和焊接时间对焊接效果的影响很大.选定较为合适的功率,在一定焊接时间内可以达到适合的焊接温度,接头的焊接界面处聚合物电阻片与母材有互融出现,形成了很好的接合,其接头强度达到了25.4MPa.探索了采用导电聚合物为产热器件进行塑料电阻焊接的新方法.     

超声-TIG复合焊接装置的研制与应用

不锈钢中厚板材TIG焊接时,存在焊接熔深浅,单道难以实现全熔透的问题.针对这一问题,研制了一套超声-TIG复合焊接装置,以实现借助高密度超声能量增加焊接熔深和提高焊接效率.该装置通过控制电路输入电压调节超声频率,并以主电路来控制超声输出功率.超声输出功率在0～1000W之间可连续调节.应用所研制的复合焊接装置,采用平板堆焊方法,对5mm厚度304不锈钢板进行了熔深对比试验,发现高能量密度超声可以起到增加焊接熔深的作用;并且和现有增加焊接熔深方法相比,试验过程简单,控制方便,满足设计和使用要求.     

激光束—电阻缝焊（LB—RSW）复合焊接研究

基于提出的LB-RSW复合焊接方法的基本概念,研究了"激光束-电阻缝焊(LB-RSW)"复合焊接系统的结构形式和基本组成,自主研制了专用的多功能电阻缝焊机,并与Nd:YAG激光器和焊接机器人组成了LB-RSW焊接试验系统;工艺试验表明,LB-RSW比单独激光焊有更大的深/宽比和拉剪力,显著提高了激光对高反射率材料的加工能力和工程应用范围;进行了LB-RSW中RSW温度场和电流场的数值模拟和热成像测量.结果表明,数值模拟技术和红外热成像技术是研究复合焊接过程的有效手段.     

5052铝合金压印-电阻点焊复合连接可行性研究

为了提高压印连接接头的强度,改善电阻点焊对铝合金连接不稳定的问题,对5052铝合金压印-电阻点焊复合连接的可行性进行了探究性试验。在焊接时间和焊接压力保持不变的情况下,将焊接电流(23-27 k A)视为唯一变量,探究了焊接电流的最优值。利用超声波水浸聚焦入射法对复合连接接头的成形性进行了检测;使用MTS材料试验机对试样进行了拉伸-剪切试验,得到了压印-电阻点焊复合连接接头的最大静拉伸载荷、失效形式及能量吸收值。结果表明:压印-电阻点焊复合连接可以实现对5052铝合金接头的有效连接且接头形貌可以利用超声C扫描进行检测;在焊接时间和焊接压力不变的情况下,适当增大焊接电流,接头的最大静拉伸载荷和能量吸收能力均有所提高,焊接电流的最优值均为25 k A;当焊接电流继续增加,接头内部结构遭到破坏。     

钛种板与铜耳的电阻钎焊技术

为实现钛种板与紫铜铜耳的焊接,采用自行改制的交流电阻焊机,使用银基钎料对钛板与紫铜进行电阻钎焊工艺试验.结果表明,选择合理的电阻钎焊工艺参数,可以实现钛与紫铜的良好焊接.焊缝微观结构通过光学显微镜、EPMA等进行分析,发现焊缝结合紧密连续,无明显焊接缺陷,钎料和母材元素相互扩散充分.另外对焊接电流、焊接时间、焊接压力等参数对接头力学性能的影响进行研究,结果在最佳工艺参数下得到的接头抗剪强度可达70 MPa以上.现有条件下使用功率为200 KVA的电阻焊机可以实现搭接面积为70 mm ×50 mm的钛种板和铜耳的焊接,并满足一定条件下的使用要求,直接应用于工业生产.     

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.     

焊接能量对铝/铜超声波焊接接头显微组织的影响

进行了1 mm厚铝/铜异种金属超声波焊接试验研究,分析了不同焊接能量输入对接头形貌、接合区塑性变形、原子扩散的影响.结果表明,工件在高频振动作用下,连接界面间会发生漩涡状塑性变形,形成局部机械自锁,有助于实现超声波接头的有效连接.焊接能量较小时,结合区域塑性变形量小,局部区域无法形成连接;焊接能量过大时,接合区域会出现空穴.SEM和EDS分析表明,能量过高时(2000 J),接触界面区域会形成薄金属间化合物层,其主要成分为Al₄Cu₉.     

铝合金激光-小功率脉冲MIG电弧复合热源焊接特性分析

针对5A06铝合金,通过一系列对比数据综合分析了MIG焊和激光MIG复合热源焊接技术在焊缝熔深、焊缝成形、焊接速度、焊接热输入等方面的优缺点.结果表明,在MIG平均电流小于200 A的小功率脉冲MIG电弧区域内,等热输入且等焊接速度条件下,激光-MIG复合热源焊接技术与MIG相比可以提高焊缝深宽比1～2倍,增加焊缝熔深0.43～2.5倍;等热输入且等平均焊接电流条件下,与MIG相比,激光MIG复合热源焊接技术可以提高焊接速度0.6～1.5倍,增加焊缝熔深0.5～5.9倍;激光MIG复合热源焊接技术可以用高于MIG焊0.6～6.5倍的焊接速度和更小的焊接热输入获得与MIG同样的焊缝熔深;与MIG焊相比,激光MIG复合热源焊缝的铺展性更好,更适合于高速焊接;MIG复合2 kW的激光能量后会增加平均电弧电压、减小平均电流.     

钉头管电阻点焊工艺研究

钉头管是一种通过在光管上焊接钉头来达到增加换热面积的传热元件,是石油化工企业管式加热炉中的重要组件.本文通过金相显微镜和扫面电镜对钉头管的电阻点焊工艺进行研究,测量了不同焊接电压(电流)下焊接接头接触面积,对各参数的焊接接头进行显微组织分析,并对最佳参数的焊接接头进行断口分析.结果表明,在焊接电压为4.64V,通电时间为0.44s时,焊接接头的接触面积最大(达106.18 mm~2,占整个焊接接头的93.9%)且未形成焊瘤,接头的显微组织最为均匀,断口为韧窝断口.     

Mechanical properties and interface morphology of Mg/Al ultrasonic spot weld bonding welds

This paper investigates the mechanical properties and interface morphology of Mg/Al ultrasonic spot welding (USW) joint, adhesive bonding (AB) joint and ultrasonic spot weld bonding (USWB) joint. The peak load and fracture energy of USWB joint increased significantly compared to that of USW joint and AB joint. The USWB joint presented a hybrid fracture mode which was composed of the delamination failure at adhesive/Mg interface, cohesive failure within the adhesive and cleavage failure in the weld zone. The interface morphology suggested that USWB joint exhibited fewer defects in the cured adhesive matrix and elevated connection density of adhesive/metal interface, which improved joint strength and altered the fracture mode.     

工艺参数对Cu/Al大功率超声波焊接微观组织和力学性能的影响

尽管大功率超声波焊接可以更好的焊接较高的导电、导热性的材料,但是对焊接机理的认识还很少. 为了深入明晰焊接过程以及得到高质量的Cu/Al焊接接头,研究了不同夹紧力、焊接时间、焊接振幅以及焊头形状对Cu/Al大功率超声波焊接的界面温度、中间相生长和接头力学性能的影响. 结果表明,随着夹紧力的增大,界面中间相厚度先增大后减小. 随着焊接振幅的下降,界面温度的降幅增大且中间相厚度呈现近似线性下降. 最优的焊头齿数为9个,焊头齿数的增多和减少均会导致界面温度降低和焊接裂纹产生. 为获得较高的Cu/Al大功率超声波焊接质量,焊接振幅应设置为最高. 对焊接接头的拉伸断口进行扫描电镜测试表明,Cu/Al超声波焊接接头的断裂模式是韧性-脆性复合断裂. 研究结果为优化超声波焊接工艺参数提供了指导.     

附加超声对6061-T6铝合金/Q235钢搅拌摩擦焊搭接工艺优化

采用超声振动强化搅拌摩擦焊接工艺实现了6061-T6铝合金和Q235钢异种金属的有效连接,考察了超声能量对焊缝成形、接头组织、力学性能以及焊接载荷的影响.结果表明,施加超声能量可以显著改善焊缝表面成形,增加铝/钢界面区和焊核区的宽度.超声振动细化了焊核区和热力影响区的晶粒组织,改变了搭接接头的断裂机制和断裂位置,提高了...     

HAZ development and accelerated post-weld natural ageing in ultrasonic spot welding aluminium 6111-T4 automotive sheet

By careful hardness measurements, supported by electron microscopy, it has been shown that there is a clearly observable heat-affected zone (HAZ) when ultrasonic spot welding (USW) aluminium automotive alloys like AA6111-T4, the severity of which depends on the welding energy. In contrast, it has been previously reported that because of the low-energy input with USW no HAZ can be detected. Immediately after welding, softening is seen in the weld zone relative to the normal T4 starting condition. However, this is rapidly recovered by natural ageing, which masks the presence of a HAZ, and the weld strength over long natural ageing times significantly exceeds that of the parent T4 material. This behaviour is caused by dissolution of the solute clusters and Guinier–Preston zones present in the T4 sheet due to the high weld temperatures, which were recorded to reach over 400 °C at the weld interface, followed by accelerated post-weld natural ageing. Interestingly, the weld zone was found to naturally age faster, and to a more advanced state, than the parent material. Modelling has been used to demonstrate that a large excess vacancy concentration can potentially be generated by the high-strain-rate dynamic deformation in USW, which can accelerate the natural ageing response seen in the weld.     

铝/铜异种金属电阻热辅助超声波缝焊工艺特性

1060纯铝箔作为中间层,通过电阻热辅助超声波缝焊的方式实现1 mm厚度6061铝合金和T2紫铜异种金属焊接,分析了焊接过程中电阻热对铝/铜焊接接头焊缝成形、界面形貌、温度场以及力学性能的影响. 结果表明,采用单独超声波缝焊焊接铝/铜异种金属时,因产生的焊接能量较小,接头连接界面处仅局部区域位置形成连接,接头拉剪强度为45 MPa. 但在电阻热辅助超声波缝焊过程中,电阻热的加入能够有效预热工件,令待焊材料表面发生软化,在高频振动作用下,接头连接界面处形成有效连接. 同时,引入电阻热提高了铝/铜界面处温度,由单独超声波缝焊的140 ℃增加至190 ℃,界面处原子扩散距离增加,获得焊接接头的拉剪强度增加至75 MPa,相对前者接头拉剪强度提高67%.     

Study of plastic deformation and interface friction process for ultrasonic welding

Ultrasonic spot welding (USW) is attracting increasing attentions in joining of dissimilar metals. Previous experimental results show that material plastic deformation and interface friction plays key role for joint formation process. In the present study, experimental and theoretical analysis was carried out to study USW of copper and aluminium. Evolution of interface friction and surface deformation was obtained quantitatively. Meanwhile, theoretical analysis was proposed to research material flow and contact behaviour between faying interfaces of specimens. Conclusions can be made that interface friction resulted in tremendous plastic deformation, which was beneficial for joint formation. Growth rate of plastic deformation decreased as welding proceeds. Compression stress and cyclical shear stress induced by ultrasonic vibration determined direction and degree of material flow.     

Macrostructures and mechanical properties of ultrasonic-assisted friction stir welding joint of 2024-T3 aluminium alloy

In friction stir welding of aluminum alloys, tunnel defect may occur due to insufficient plastic material flow caused by lower heat input in the weld region. The inadequacy in heat input is due to improper selection of friction stir welding tool and process parameters. Ultimately, such defects degrade the properties of weld and may pose serious concerns towards the integrity and safety of the weld component. In order to improve the properties of weld joints, an ultrasonic-assisted friction stir welding device has been configured where ultrasonic energy is transferred from an ultrasonic unit directly into one of the workpieces near the tool. Using this configuration, ultrasonic-assisted friction stir welding was conducted on 6 mm thick 2024-T3 aluminum alloy sheets. The macrostructure and mechanical properties of these welds were compared with the welds of this alloy prepared by conventional friction stir welding using identical process parameters. The results show that the welding speed can be increased while satisfactory weld quality is still ensured. The ultrasonic energy transferred in this configuration could enlarge the volume of weld nugget zone. Also, the influence of ultrasonic energy on the suppression or elimination of the tunnel defect is quite apparent. However, any beneficial effects of ultrasonic vibration on the tensile strength and the elongation of the joint were less obvious in this configuration.     

超声振动辅助E40钢水下湿法焊接组织与性能

文中针对常规水下湿法焊接过程中焊缝力学性能低的问题,设计了超声振动辅助水下湿法焊接的方法. 通过超声辐射端将超声振动能量施加在电弧前方的待焊区域,进而通过工件将超声能量传递到熔池中,对比研究了超声振动对焊缝成形、微观组织及力学性能的影响. 结果表明,超声振动能够减小焊缝截面不对称,增加焊缝深宽比,使熔池发生强烈的搅拌作用,具有细化晶粒的作用,并降低熔合区处柱状结晶的倾向. 与常规水下湿法焊接相比,超声振动辅助水下湿法焊接抗拉强度明显提高,达到母材的92.4%;焊缝区显微硬度升高,热影响区硬度值变化较小.     

Process robustness of single lap ultrasonic welding of thin, dissimilar materials

Fusion welding processes, such as resistance welding and laser welding, face difficulties in welding thin layers of dissimilar materials. Ultrasonic welding overcomes many of these difficulties by using high frequency vibration and pressure to input energy into the affected area to create a solid state weld. This paper presents a process robustness study of ultrasonic welding of thin metal sheets. Quality of the welded joints is evaluated based on mechanical tests and the quality criterion is then applied to evaluate the weldability. These results were used to determine both the optimal weld parameters and the robust operating range.     

Mechanical properties of martensitic stainless steel weld/adhesive hybrid bonds

Hybrid weld-adhesive bonding (AB) was used as an approach to improve the mechanical properties of martensitic stainless steel resistance spot welds. The weld fusion zone in both techniques was composed of predominantly martensite and δ-ferrite. It was found that the presence of adhesive does not induce excess hardening effect in the fusion zone. It was shown that hybrid AB/resistance spot welding) i.e. weld-bonding) technique can double the peak load and energy absorption of the joints compared to those of the resistance spot welds. To obtain high performance weld-bonded joints, heat generation during welding should be controlled to produce weld bonds with large fusion zone size, but without detrimental effect on the adhesive strength.