镀锌钢板插入辅助材料电阻点焊研究

针对镀锌钢板点焊电极寿命较短的问题,点焊时在电极与工件之间插入辅助材料,使电极与工件隔离。在10周波(硬规范)和40周波(软规范)两种焊接时间下,试验了不同的辅助材料:低碳钢、紫铜片、单面镀铜低碳钢和双面镀铜低碳钢的焊接电流范围。结果表明:镀层在工件侧的单面镀铜低碳钢作为辅助材料时,采用软规范电流范围7.20～9.36kA;镀层在电极侧的单面镀铜低碳钢作为辅助材料时,采用硬规范电流范围8.19～8.45kA,采用软规范电流范围13.60～13.72kA;双面镀铜低碳钢作为辅助材料,采用硬规范电流范围9.88～10.40kA,采用软规范电流范围13.60～13.96kA,能得到要求焊点直径。试验中的其他材料不适合作辅助材料。     

Seal spot welding of steel and aluminium alloy by resistance spot welding: dissimilar metal joining of steel and aluminium alloy by Zn insertion

This research concerns a dissimilar metal joining of steel and aluminium (Al) alloys by means of zinc (Zn) insertion. The authors propose a joining concept for achieving strong bonded joints between Zn-coated steel and Al alloys. A eutectic reaction between Zn in the Zn coating and uniform Al–Fe intermetallic compound (IMC) layer at the joint interface, leading to a strong bonded joint. The ultimate aim of this research was to apply this joining concept in the resistance spot welding process for manufacturing vehicle bodies. As a practical issue characteristic to joints of dissimilar metals, anticorrosion measures against electrochemical corrosion must be undertaken. If there is moisture near a joint interface of dissimilar metals, electrochemical erosion will progress. Therefore, a sealing function that could prevent moisture intrusion is required. By applying the above-mentioned welding process to a set of metals with thermosetting resin spread in between, we realized seal spot welding, which not only prevented moisture intrusion but also retained high tensile strength. In this research, first, a cyclic corrosion test was performed on the seal spot-welded joint of galvanized (GI) steel, a steel grade widely distributed in Japan, and Al alloy was bonded by seal spot welding, and the following topics are discussed. Complete removal of sealant from the joint interface is the key to realizing the high tensile stress joint, because remaining sealant will lead to reduction in tensile strength. Therefore, heat generation at the interface was monitored by measuring electrical current and potential difference between the two electrodes, and a precise temperature control was performed. Moreover, the bonding process was clarified by stepwise analysis of the joint interface using optical microscopy, and a guideline for producing strong joints was proposed. And finally, a TEM observation also confirmed that the interface structure of the seal spot-welded joint was the same as joints without the resin; a thin and uniform Al–Fe IMC layer was formed and a strong metallurgical bonding was achieved.     

Dissimilar spot welding of aluminium alloy and galvannealed steel by metal flow-application of friction anchor welding to aluminium alloy and Zn-coated steel

ABSTRACT

Lap joints of an upper Al alloy (1.0-mm-thick A5052) and lower hot dip galvanized steel (1.2-mm-thick GI steel) were welded by a novel spot welding process for dissimilar metal lap joints using a new tool with the tip made of spherical ceramics, i.e. ‘Friction Anchor Welding.’ As a result, the rotating tool was plunged only to 1.3–1.4 mm from the Al alloy surface, and accordingly, a steel projection was not formed in the Al alloy sheet. Further, the Al alloy near the rotating tool was removed. However, near this removed area, the Zn layer on the GI steel melted and was removed by friction heat, and consequently, the GI steel and the Al alloy were welded. Thus, the tensile shear strength reached about 2.6 kN/point.     

Resistance spot welding aluminium to magnesium using nanoparticle reinforced eutectic forming interlayers

Successful joining of dissimilar metals such as Al and Mg can provide significant advantages to the automotive industry in the fabrication of vehicle bodies and other important components. This study explores dissimilar joining of Al–Mg using a resistance spot welding process to produce microstructurally sound lap joints and evaluates the impact of interlayer composition on microstructural evolution and the formation of intermetallic compounds within the weld nugget. The results indicated that mechanically sound joints can be produced, with fine equiaxed and columnar dendrites within the weld nugget. The presence of intermetallic compounds was also confirmed by the variation in the microhardness values recorded across the weld zone.     

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.     

Dissimilar spot welding of aluminium alloy and hot dip galvanised steel by metal flow: application of friction anchor welding to aluminium alloy and Zn-coated steel

Lap joints of an upper Al alloy (1.0 mm-thick A5052) and lower hot dip galvanized steel (1.2 mm-thick GI steel) were welded by a novel spot welding process for dissimilar metal lap joints using a new tool with the tip made of spherical ceramics, i.e. ‘Friction Anchor Welding’. As a result, the rotating tool was plunged only to 1.3–1.4 mm from the Al alloy surface, and accordingly, a steel projection was not formed in the Al alloy sheet. Further, the Al alloy near the rotating tool was removed. However, near this removed area, the Zn layer on the GI steel melted and was removed by friction heat, and consequently, the GI steel and the Al alloy were welded. Thus, the tensile shear strength reached about 2.6 kN/point.     

薄镀锌钢板点焊超声谐振检测

研究了低频超声探头的谐振特性,并将这种谐振特性用于镀锌薄板的点焊检测中.采用接触式低频探头对点焊进行检测时,检测探头能够接收到未焊薄基板产生的半波谐振高频信号,这些半波谐振信号的高频部分处于探头频带外的奇数次谐振频率附近.通过小波包变换的方法可以将这些高频信号从检测信号中分离出来并用于点焊的质量评价.分析小波包变换中各尺度信号,获取了能够评价焊核质量的超声波特征值并将这些特征值与点焊力学性能联系起来,提供了一种能够定量评价点焊质量的超声无损评价方法.此外,采用低频探头对点焊进行检测较之普通检测方法将大大降低检测成本.     

镀锌钢板点焊电极寿命预测

采用连续点焊试验与数值模拟相结合的方法预测电极寿命,即利用镀锌钢板连续点焊试验得出电极端面直径随焊接点数增加的规律,并用ANSYS软件模拟不同电极端面直径下点焊区域温度场,得出对应的熔核直径.综合试验及模拟结果得出焊接点数与熔核直径的关系,在定义了保证焊点质量的临界熔核直径情况下,即可得出相应的临界电极端面直径和连续点焊可焊点数,从而预测电极寿命.结果表明,两种方法得出的熔核直径的误差不超过15%.此方法对实际生产过程中的电极修整及更换周期制定具有一定的指导作用.     

Effect of aluminium sheet surface conditions on feasibility and quality of resistance spot welding

A study investigating the effect of sheet surface condition on resistance spot welding (RSW) of aluminium has been carried out. This concentrates on two automotive aluminium alloys; AA5754 and AA6111, used for structural and closure applications respectively. The results show the marked effect that surface condition can have on the RSW process. For AA5754 sheet incomplete removal of a ‘disrupted surface layer’ prior to surface pretreatment is shown to have a detrimental effect on the RSW process. The solid wax lubricant used to assist metal forming leads to unpredictable changes in contact resistance, and consequently affects the process stability. For AA6111 closures the final surface topography can influence the RSW process. Standard ‘mill’ and electro-discharge textured (EDT) finish sheet surfaces were examined and preliminary results suggest that both are suitable for welding. The successful application of RSW of aluminium sheet requires careful consideration of the sheet surface condition. This requires close collaboration between material suppliers and automotive manufacturers.     

Resistance spot welding of PA2 and D16 aluminium alloy sheets

Abstract

Technologies which make it possible to improve the working properties of surface layers of castings, while utilising traditional materials, are increasingly being used in industrial applications. The life of fabrications can be extended as necessary. It is also possible to manufacture fabricates with working properties that are normally unobtainable in the case of traditional construction materials and technology.     

Two step friction stir spot welding between aluminium and carbon steel sheets

A two step friction stir spot welding has been developed to join a 2?mm thick low carbon steel sheet and a 3?mm thick aluminium sheet. In the first step, a consumable aluminium tool is used to develop frictional heat and plasticise the aluminium layer from the tool which fills the cavity in the aluminium sheet, progressively. In the subsequent step, the plasticised layer is squeezed by a non-consumable forming tool made of high carbon steel with an inverted semi-hemispherical profile. To understand the efficacy of the contact area of the plasticised metal, five different tool rotational speeds were used. The integrity of the joint was evaluated by different mechanical and metallurgical examinations.     

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.     

Resistance welding of aluminium and aluminium alloys

Special features of the process of resistance welding of aluminium and its alloys and also equipment manufactured by the CEA and supplied by Weber Comechanics are described.     

SPAH590高强度板电阻点焊工艺

通过对SPAH590高强度板的点焊试验,确定了可行的焊接工艺和焊接参数,获得了外观良好和性能合格的接头,解决了SPAH590高强度板点焊工艺的问题.     

Novel dissimilar spot welding of aluminium alloy and steel sheets by friction stirring

Friction stir spot welding (FSSW) has been applied to a dissimilar metal lap joint of an aluminium alloy and steel by stirring only the upper aluminium alloy sheet. Therefore, FSSW cannot be used to weld a lap joint composed of three or more sheets and a lap joint with an adhesive interlayer. In the present work, we propose a novel spot welding process for dissimilar metal lap joints using a new tool with the tip made of spherical ceramics. When this process is applied to the lap joint of the aluminium alloy and steel, the tool can be plunged into the lower steel sheet, then a steel projection is formed in the aluminium alloy sheet. The height of this steel projection increases with the plunge depth, and accordingly, the weld strength increases; the tensile shear strength and the cross tensile strength reached about 3.6 and 2.3 kN/point, respectively.     

镀锌钢板电阻点焊的多元非线性回归模型

为了研究用于家用轿车车身制造的镀锌钢板电阻点焊工艺,采用多元非线性回归正交组合的方法设计试验.试验将电阻点焊熔核形状参数和焊接接头抗剪强度作为考察指标,将焊接电流、电极压力、通电时间、预热电流四个参数,以及各参数之间的交互作用作为影响指标的考察因素,得到可预测熔核形状和焊接接头力学性能的四元二次回归数学模型,并通过方差分析对模型进行优化.结果表明,优化的回归数学模型可实现焊接接头熔核成形及力学性能较为准确的预测.在模型的基础上研究各参数及各交互作用对焊点质量的影响规律,从而可实现电阻点焊工艺参数的优化设计.     

两种铝合金的点焊组织模拟与试验分析

AA754和AA6082是两种具有不同强化机制的铝合金材料,在电阻点焊加热过程中,两种铝合金材料的组织会发生不同类型的转变.通过采用不同的计算模型,使用有限元软件对两种铝合金点焊后不同焊接组织的分布进行了模拟和预测.通过焊接试验研究,对两种铝合金的点焊组织的形态和分布进行了观察.结果表明,所采用的两种计算模型可以有效的预测和反映出两种铝合金点焊组织变化过程中的一些现象.仿真结果和试验结果都显示出两种铝合金的点焊组织有着明显不同的特征.     

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。     

汽车用钢板电阻点焊工艺参数优化选择

焊装车间多采用多层板搭接进行电阻电焊,而电阻电焊过程的不确定性因素较多。为了用较少的试验次数得到满足生产要求的试验结果,以板厚0.8 mm+1.4 mm+1.8 mm的三层低碳钢板搭接为研究对象,分析各因素对多层板材搭接焊点熔核质量的影响,获得了最优焊接工艺参数。试验结果表明:板厚为0.8 mm+1.4 mm+1.8 mm的三层低碳钢板搭接最佳焊接工艺参数为多脉冲软规范焊接参数,即三周波,焊接电流8.8/11.1/9.6 k A、焊接时间5/19/5 cyc、电极压力3 k N,得到各层搭接板之间熔核直径大于等于φ6 mm。