Modelling the effect of welding current on resistance spot welding of DP600 steel

Experiments were made for welding current variation between 6 kA and 12 kA. Microstructure and mechanical performance under tensile-shear tests were recorded and compared. Welding current effect on micro-properties was very slight while nugget size was highly dependent on welding current. Expulsion phenomenon existed at 12 kA welding current and the unsatisfactory partial interfacial failure was detected. Nugget formation and temperature distribution were analysed numerically. Comparisons with experimental results showed that the nugget size deviation was within 10% and the nugget shape was well predicted.     

轨道车辆不锈钢电阻点焊工艺试验

针对轨道车辆常用不锈钢材料3 mm X2CrNi N18-7,采用NIDS-50-815电阻点焊机进行电阻点焊,焊后根据产品标准进行外观检验、剪切拉伸试验、凿铲试验、剥离试验和宏观检验。试验结果表明,电阻点焊技术在轨道车辆不锈钢材料的应用良好,能够获得满足产品要求的焊接接头。     

不锈钢电阻点焊过程中的动态电阻变化规律分析

对利用自动数据采集技术获取的不锈钢点焊过程中的动态电阻信息进行系统研究.结果表明,不锈钢点焊过程中动态电阻能够灵敏且有规律地反映点焊工艺参数的变化,蕴含着丰富的点焊质量信息.焊接过程中动态电阻变化与熔核生长过程具有明显的对应关系,动态电阻曲线的拐点时间及终点值等特征量分别与熔核出现时间和最终熔核尺寸有很强的相关性.点焊过程喷溅会导致动态电阻骤降,其动态电阻变化率曲线在相应位置出现尖峰,为喷溅的自动识别提供了依据.     

焊接工艺对2205双相不锈钢焊接接头综合性能的影响

采用等离子弧焊打底 TIG焊盖面及等离子弧焊打底 MIG焊盖面焊接工艺焊接了2205双相不锈钢,研究了2205双相不锈钢的焊接性,并对焊后固溶处理与未进行固溶处理的焊件组织特征、力学性能及抗腐蚀性进行了比较,研究了不同焊接热输入和固溶处理工艺对焊接接头综合性能的影响.     

不锈钢车侧墙点焊铜台的爆炸焊工艺

采用爆炸焊工艺制造不锈钢车侧墙点焊铜台,代替了采用螺钉连接铜台合金板与基材获得的铜钢结构,避免了频繁点压铜台导致铜垫下陷的问题,提高了铜台的制作质量和产品质量。爆炸焊技术选用15 mm厚度合金铜板,节约成本50%以上,减少了合金铜板磨削时间,焊接区域能实现可靠、均匀的冶金连接,熔合率达95%以上,导电率达60%以上。     

时效不锈钢舱体的电子束焊与电阻点焊

时效不锈铜以其强度高、韧性好、焊接性能优良的优异综合性能成为空空导弹舱体制造中最主要的结构材料.分析了某型号空空导弹舱体的结构特点和时效不锈铜的焊接性,介绍了舱体制造时所采用的焊接、旋压、热处理这三大关键技术,着重阐述了电子束焊和电阻点焊技术在舱体制造中的应用,详细说明了焊接参数的调试原则和控制焊接缺陷及焊接变形的方法与措施.检验与探伤、拉伸结果表明:首批试制的时效不锈钢舱体的尺寸精度和焊缝与焊点的焊接质量、力学性能符合设计要求,工艺方案完全适合于舱体的加工.     

基于Ta过渡层的钛与不锈钢电阻点焊

以Ta作为中间过渡层对纯钛与不锈钢SUS304进行电阻点焊。观察分析接合界面区反应层形貌及分布等微观组织特征,探讨焊接电流对熔核尺寸和接头抗剪力的影响。在接头中的Ta/SUS304界面生成了FeTa和含Fe量不同的Fe-Fe_2Ta共晶组织。在焊接电流为14 kA时,获得的接头抗剪力最大,为7.4 kN。结果表明,在钛与不锈钢的电阻点焊中,使用中间过渡层Ta能够有效提高焊接接头的强度。     

不锈钢电弧铆焊焊点组织及力学性能

采用电弧铆焊的方法对3 mm+5 mm厚的0Cr18Ni9不锈钢钢板采用搭接形式实现连接. 通过优化焊接电流及其作用时间的参数匹配,以期得到最佳的焊点显微组织和力学性能. 采用X射线检测焊点缺陷的存在,使用金相显微镜研究焊点熔深和熔核尺寸的变化,使用电子万能试验机测试焊点的抗剪力. 结果表明,电弧铆焊焊点呈蘑菇状,与基体圆滑过渡,成形良好,无气孔、裂纹等宏观缺陷. 随着第一段和第二段焊接电流的增大,焊点的熔深和熔核尺寸,及焊点抗剪力随之增大. 优化的工艺参数下,熔深尺寸可达4.07 mm,熔核尺寸可达7.73 mm,抗剪力可达23.654 kN,满足生产需求.     

不锈钢轨道车辆用电阻点焊设备的组成与应用

针对不锈钢轨道车辆的材料的性能,适合采用电阻点焊技术进行焊接.分别从电阻点焊的工作原理、焊接设备的整体结构形式、焊接系统、走行系统、控制系统、焊接监测系统、润滑系统、冷却系统、焊钳结构、点焊电极、设备焊接能力、设备的辅助装置等方面分析了电阻点焊设备各系统的组成与应用,指出了生产不锈钢轨道车辆用电阻点焊设备的基本组成、应...     

Effect of joint design on the failure behaviour of three-stack-up austenitic stainless steel resistance spot welds

Tensile shear tests were carried out on three-stack-up austenitic stainless steel resistance spot welds having four types of joint design. Mechanics-based criteria were applied to reveal the difference in the stress state at the microstructural level. Optical microscopy and scanning electron microscopy showed evidence of the different stress states for different joint designs. Nugget rotation generated combined tensile/shear stress at the microstructural level. The peak load and the energy absorption of the joints reduced with the growth of the normal component of the global loads. Joints for which both interfaces bear the load were more prone to failure in pull-out mode.     

Electrical-thermal interaction simulation for resistance spot welding nugget process of mild steel and stainless steel

A three-dimensional finite difference electrical-thermal model for resistance spot welding nugget process of mild steel and stainless steel is introduced. A simulation method of the interaction of electrical and thermal factors is presented. Meanwhile, calculation method of contact resistance and treatment method of heater structure is provided. The influence of the temperature dependent material properties and various cooling boundary conditions on welding process was also taken intoaccount in the model. A method for improving the mild steel and stainless steel joint was analyzed in numerical simulation process. Experimental verification shows that the model prediction agrees well with the practice. The model provides a usefultheoretic tool for the analysis of the process of resistance spot welding of mild steel and stainless steel.     

轨道车辆不锈钢车体电阻点焊缺陷产生及预防工艺

结合生产实际情况,介绍了不锈钢电阻点焊基本原理、冷作硬化不锈钢板电阻点焊的工艺特性、轨道车辆不锈钢车体电阻点焊常见缺陷类型,如:焊核直径不符合要求、缩孔、飞溅、未熔合、熔透率不达标、过烧、焊点外观不良等。分析缺陷产生的原因并制定预防措施,如焊接电流、电极压力、通电时间、工件装配及电极形状材质等影响因素。通过相应的工艺手段,提升焊点质量,保障产品的焊接和商品化质量。     

不锈钢点焊热过程的协同控制策略

着重探讨了协同控制法应用于不锈钢点焊过程控制的特殊性、必要性与适用性.针对动态电阻单调下降的不锈钢材料,以工艺试验确定的实际熔核形成起点,把焊接热过程明确划分为未形核与形成熔核两个阶段.进而,在这两个阶段中分别采用恒流控制和基于给定动态电流滞后角特性的模型化控制技术,即协同控制策略.结果表明,该监控策略能够保证不锈钢材料电阻点焊热过程的形核起点稳定,从而确保了阈值法控制的可靠性,焊接品质优良.     

Characterisation of ferritic stainless steel by Barkhausen techniques

Magneto-acoustic emission (MAE) and magnetic Barkhausen noise (MBN) sensing techniques were developed and employed to characterise plastically deformed and heat-treated AISI 430 ferritic stainless steel samples. These results have been compared to the mechanical hardness, coercivity and residual stress of the samples. MAE and MBN were shown to decrease with increasing permanent material deformation. It was found that the inverse of MAE (absolute energy) and MBN (RMS) are linearly proportional to hardness. With increased deformation, the resultant change in dislocation density was found to effect material coercivity. It has been shown that the inverse of MAE absolute energy and MBN have an exponential relationship to the change in material coercivity. The results are explained in terms of the different mechanisms that effect dislocation-domain wall interactions. A new measurement parameter has been developed for microstructural characterisation called MAE absolute energy and has proved to be a useful quantitative method in MAE waveform measurement.     

双相钢电阻点焊应力与变形行为数值分析

文中对DP600电阻点焊过程进行了数值模拟,分析了预压、焊接和维持阶段热力学行为.结果表明,熔核尺寸预测值与试验结果基本保持一致.相比于其它位置,熔核中心点温度在焊接阶段升高较快,而在维持阶段则下降较为缓慢.在焊接过程中,电极/工件和工件/工件接触面的接触压强变化明显,并通过工件热膨胀变形行为进行解释.在焊接阶段结束时,熔核中心区域由于热膨胀不匹配而产生径向压应力状态,这由工件的热膨胀不匹配而产生.焊点温度在维持阶段迅速下降,中心区域的压应力因此得到部分释放.另外,在模型中可以观察到与试验结果较为一致的工件间缺口及劈尖形区域.     

Ferritic–austenitic stainless steels dissimilar resistance spot welds: metallurgical and failure characteristics

The paper addresses the microstructure and failure characteristics of dissimilar resistance spot welds between austenitic stainless steel and ferritic stainless steel. The fusion zone (FZ) of dissimilar welds exhibited complex microstructure consisting of ferrite, austenite and martensite. The development of this triplex structure in the FZ was explained by analysing the phase transformation path and austenite stability. Results showed that all dissimilar welds failed in partial thickness–partial pull-out failure mode. It was shown that the fraction of the nugget fracture of the weld is reduced by increasing the FZ size improving the mechanical performance of the weld. Peak load and energy absorption of the similar and dissimilar welds were compared and analysed.     

伺服焊枪点焊双相高强钢的焊点质量在线评价方法

点焊双相高强钢的焊点质量稳定性差,阻碍其在车身制造中的应用. 利用伺服焊枪进行压痕深度在线提取的可行性分析. 结果表明,伺服焊枪精度能够满足压痕深度在线采集要求. 分析压痕深度随焊接点数变化规律,初期焊接阶段压痕深度变化速率较大,随着焊接点数增加,压痕深度变化速率逐渐减小,直至处于稳定波动状态. 进行压痕深度与焊点质量关系分析,板厚15%～25%范围内的压痕深度符合焊点质量要求. 基于压痕深度的伺服焊枪焊点质量在线检测评价可有效解决传统点焊质量检测的离线性、滞后性问题.     

不锈钢点焊动态电阻曲线频谱与熔核的关系

运用快速离散傅里叶变换(FFT)方法,分析了不锈钢1Cr18Ni9Ti点焊动态电阻曲线的频谱特征,并通过对6个焊点的熔核直径的解剖验证,发现了动态电阻曲线幅频图中0 Hz及3.1 Hz处的幅频值与熔核直径成正比,3.1 Hz处的幅频值随熔棱尺寸变化的曲线斜率较小,0 Hz处的幅额值随熔核尺寸的变化更为敏感.     

铝合金与不锈钢电阻点焊接合界面区的组织特性

采用热补偿工艺垫片电阻点焊法对铝合金A5052与不锈钢SUS304异种材料进行了焊接．通过电子显微镜对接合界面区进行了观察,并分析了所生成反应物的微观结构及分布等组织特性．结果表明,一锯齿状反应层在接合界面生成,其主要由Fe2Al5和FeAl3组成;反应层厚度随焊接电流以及界面上位置的变化而变化．另外,在界面附近的铝合...