Bulging Distortion of Austenitic Stainless Steel Sheet on the Partially Penetrated Side of Non-Penetration Lap Laser Welding Joint

Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded austenitic stainless steel parts is limited owing to the micro bulging distortion that occurs on the back surface of the partial penetration side.In this paper,non-penetration lap laser welding experiments,were conducted on galvanized and SUS304 austenitic stainless steel plates using a fiber laser,to investigate the mechanism of bulging distortion.A comparative experiment of DC01 galvanized steel-Q235 carbon steel lap laser welding was carried out,and the deflection and distortion profile of partially penetrated side of the sheets were measured using a noncontact laser interferometer.In addition,the cold-rolled SUS304 was subjected to heat holding at different temperatures and water quenching after bending to characterize its microstructure under tensile and compressive stress.The results show that,during the heating stage of the thermal cycle of laser lap welding,the partial penetration side of the SUS304 steel sheet generates compressive stress,which extrudes the material in the heat-affected zone to the outside of the back of the SUS304 steel sheet,thereby forming a bulge.The findings of these experiments can be of great value for controlling the distortion of the partial penetrated side of austenitic stainless steel sheet during laser non-penetration lap welding.

Visual sensing and morphological image processing of weld pool in laser spot welding

A visual sensing system was established to monitor the weld pool in laser spot welding. The top-hat and bottom-hat transformation algorithms based on mathematical morphology were used to compensate for non-uniform contrast of weld pool edge. Moreover, the canny edge detector was applied to extract the weld paol profile. The edge detected results show that the morphological operation is obviously superior to the traditional contrast enhancement method. In addition, the combination of dilation and erosion was applied to eliminate the irrelevant edge details, and the smooth weld pool edge was acquired. Based on the image processing technology described above, the dynamic process of weld pool diameter during laser spot welding was obtained.

Fatigue Resistance and Failure Behavior of Penetration and Non-Penetration Laser Welded Lap Joints

Penetration and non-penetration lap laser welding is the joining method for assembling side facade panels of railway passenger cars,while their fatigue performances and the difference between them are not completely understood.In this study,the fatigue resistance and failure behavior of penetration 1.5+0.8-P and non-penetration 0.8+1.5-N laser welded lap joints prepared with 0.8 mm and 1.5 mm cold-rolled 301L plates were investigated.The weld beads showed a solidification microstructure of primary ferrite with good thermal cracking resistance,and their hardness was lower than that of the plates.The 1.5+0.8-P joint exhibited better fatigue resistance to low stress amplitudes,whereas the 0.8+1.5-N joint showed greater resistance to high stress amplitudes.The failure modes of 0.8+1.5-N and 1.5+0.8-P joints were 1.5 mm and 0.8 mm lower lap plate fracture,respectively,and the primary cracks were initiated at welding fusion lines on the lap surface.There were long plastic ribs on the penetration plate fracture,but not on the non-penetration plate fracture.The fatigue resistance stresses in the crack initiation area of the penetration and non-penetration plates calculated based on the mean fatigue limits are 408 MPa and 326 MPa,respectively,which can be used as reference stress for the fatigue design of the laser welded structures.The main reason for the difference in fatigue performance between the two laser welded joints was that the asymmetrical heating in the non-penetration plate thickness resulted in higher residual stress near the welding fusion line.

LASER WELDING OF BEARING PROTECTIVE WASHERS

Spot laser welding was applied for fastening of protective bearing washers.Corresponding technology and laser welding plants are described. Correlation between appearance of the spot welds and their quality was discovered. Mechanism of the welding distortion has been revealed.

Welding of shape memory alloy to stainless steel for medical occluder

Dissimilar metal joining between NiTi shape memory alloy（SMA） and stainless steel was conducted.A cluster of NiTi SMA wires were first joined with tungsten inert gas（TIG） welding process,then the NiTi SMA TIG weld was welded to a stainless steel pipe with laser spot welding process.The microstructure of the welds was examined with an optical microscope and the elemental distribution in the welds was measured by electron probe microanalysis（EPMA）.The results show that TiC compounds dispersively distribute in the NiTi SMA TIG weld.However,the amount of TiC compounds greatly decreases around the fusion boundary of the laser spot weld between the NiTi SMA and stainless steel.Mutual diffusion between NiTi shape memory alloy and stainless steel happen within a short distance near the fusion boundary,and intermetallic compounds such as Ni3Ti＋（Fe,Ni）Ti appear around the fusion boundary.

Challenge to Welding and Joining Technology for Applying Multi-material in Electric Vehicle Production

Advanced high strength steel,aluminum alloy and plastic materials are used in the right places for the purpose of reducing the weight of EV(electric vehicle)bodies and in-vehicle parts,and multi-material structures are advancing.Therefore,it is difficult to handle the welding and joining processes of automobile structures by the conventional arc welding and resistance spot welding,which have been applied to steel joining,and various joining processes are being applied depending on the material.Under above mentioned background,the authors have developed some unique joining processes for multi-materials that are used in the right place.This paper introduces the dissimilar metal joining between the galvanized steel and aluminum alloy by laser arc hybrid process,the metal/thermoplastic dissimilar material joining using laser process and the solid-state resistance spot joining process of advanced high strength steel for EV body structural parts.Moreover,the authors describe the high-speed plasma jet GTA(Gas Tungusten Arc)welding process of copper applied to electrical components such as motors.

激光功率对3/4H SUS301和SUS316异种不锈钢激光点焊成形特征及组织性能的影响

采用准连续激光器对测力传感器的3/4H SUS301弹性体和SUS316支撑体进行异种不锈钢激光焊接,探讨了激光功率对点焊接头成形特征和力学性能的影响。研究表明,采用准连续激光模式,在脉冲时间为2 ms、激光功率为180 W至270 W范围内,弹性体焊后的角变形量随着激光功率的增大而增大,激光功率为270 W时弹性体焊后的角变形远低于传感器容许的变形量。当激光功率为210W时,在焊接界面处产生气孔缺陷,焊接功率增大至270 W时,在匙孔底部形成严重的气孔缺陷。焊缝内部以胞状晶方式生长,从熔合区两侧向焊缝中心生长为粗大的柱状晶,焊缝中心为等轴状的树枝晶,随着激光功率的增大,等轴晶区域的宽度减小。焊缝区承受较高的焊接热量使得焊缝区内形变组织发生不完全再结晶,致使形变诱发马氏体相变被抑制,α'马氏体含量降低。点焊接头的剪切力随着激光功率先增大后减小,当激光功率为250 W时,接头的剪切力达到最大值0.49 kN,远高于行业要求。

激光螺旋点焊的断裂行为与断口研究

为研究激光螺旋点焊的断裂行为和断口特征,以期为高性能激光点焊的应用提供理论支持。采用振镜搭载机器人的激光螺旋焊接系统对1 mm厚汽车用高强钢进行焊接,设计了一种类阿基米德螺旋线扫描路径以使焊点热输入均匀分布,并对焊接接头的断裂行为进行分析。研究发现,在拉剪力的作用下,激光螺旋点焊主要发生的断裂失效形式为单面焊点撕出断裂和双面焊点撕出断裂,裂纹的萌生及扩展均是沿着熔合区和热影响区交界处。粗晶热影响的大角度晶界比例相对较少,为18.69%,KAM均值最大为0.65,存在的应力应变相对较大,使得裂纹更倾向于在粗晶热影响区萌生和扩展。

基于机器视觉跟踪的船舶小组立焊接过程中焊点提取技术研究

针对船舶分段小组立焊接工艺要求,开展了基于机器视觉跟踪引导焊接中焊点提取技术的研究。首先,介绍了焊点提取技术的国内外研究现状;其次,分析了焊接工件的常用接头形式;再次,采用自主研制的视觉跟踪引导传感器采集了工件的激光线图像,基于灰度重心法提取了激光光心重心;最后,基于斜率平均值法计算了光心的斜率,提取了光心轮廓单调区间,基于突变点的几何特性提取了最大跨度单调区间,确定了焊点坐标。最终开展了小组立零件的焊接实验,取得了较好的焊接质量。

高水头大容量机组通风槽板制造技术

为了提升高水头大容量水轮发电机组定子通风槽板的质量和性能,对激光焊接工艺进行了改进,对影响焊接质量的相关因素进行了试验,发明了新型分体式定位夹具,改进了原有破坏性试验的检测方法,研发了专用打磨设备以实现对焊点凸起的控制,经过不断的试验、分析和工艺改进,解决了生产过程中面临的诸多难题,并在多个水电项目上进行了应用,保证了电机铁心装压的质量,通风冷却效果良好,为日后更高水头、更高容量的水电机组研发奠定了基础。

热成形钢激光局部软化组织与性能研究

为了降低热成形钢连接位置的硬度,提高塑性,采用高斯激光光束快速扫描试样表面,利用高温回火原理使材料的强度、硬度降低,成功实现了局部区域的材料软化。结果表明,软区组织为回火索氏体,扫描速率越慢,软区硬度越低;温度为800℃、扫描线速率为2 mm/s时,软区硬度为230 HV,是母材硬度的47.92%,软区抗拉强度降低767 MPa,是母材的50.53%,其断后伸长率17.36%,是母材的188.08%;软化拉伸试样为韧性断裂,杯锥状断面;软化后点焊不会改变焊核的硬度,可以加宽热影响区,避免其硬度骤降骤升的情况,改善热影响区应力集中的情况,防止焊点出现界面断裂,软化后能提高焊点断裂最大位移60%,最大能量吸收功提升了10.14%。本研究证明了激光软化热成形钢具有可行性,对热冲压汽车零件局部软化有一定指导意义。

激光点焊等离子体光信号同轴监测及其特性分析

激光焊接时产生的等离子体包含了许多可以反映焊接质量的相关信息。通过光电传感器采集等离子体的光信号可以有效监控激光焊接质量。本文搭建了激光点焊等离子体光信号的同轴监测系统,并对激光点焊过程中采集的光信号进行了短时能量分析。试验结果表明,在焊接起始阶段,工件表面对激光有较强的反射作用。当母材形成熔池以后,等离子体浓度逐渐增加,焊接过程趋于稳定,此时等离子体的光信号强度达到最大。随着焊接时间的增加,熔池发生塌陷,等离子体的稳定性变差,光信号的强度变弱且波动变大。工件被焊穿的瞬间,等离子体光信号强度明显减小。

热冲压成形超高强钢焊接技术的进展

超高强钢在减小车身质量的同时能保证汽车的安全性。热冲压成形超高强钢尺寸精度高、使用寿命长,已被广泛应用于汽车制造领域。目前热冲压成形钢常用的焊接技术为电阻点焊和激光焊接等。为避免热冲压成形过程中表面氧化和脱碳,通常在钢板表面预制Al-Si镀层。然而镀层的存在会导致焊接接头力学性能降低。概述了可热冲压成形的超高强度钢及其镀层技术、热冲压成形钢常用的焊接技术以及焊缝组织和焊接接头的性能,探讨了改善热冲压成形超高强度钢焊接接头性能的途径。

激光光斑尺寸对激光焊接熔池、匙孔行为的影响

在激光焊接中,激光光斑半径的大小直接影响激光功率密度,不同的激光功率密度对熔池流场和小孔的三维形状有影响。然而,关于激光光斑尺寸对激光熔池和小孔行为的影响的研究很少。基于Fluent软件建立了激光焊接热-流耦合模型,研究了激光光斑尺寸下激光焊接过程的匙孔三维瞬态行为及熔池流场。研究结果表明,随着光斑半径的增大,匙孔的深度明显变小。光斑半径分别为0.1 mm和0.15 mm时,焊接过程中均会出现匙孔底部闭合的情况,当光斑半径为0.2 mm时,匙孔未出现闭合的情况,匙孔的稳定性有所提高。随着光斑半径的增大,熔池最大流动速度波动相对较小,熔池尺寸逐渐增大。

光纤激光工艺参数对Q235钢穿透点焊缝形状和尺寸的影响

为了研究光纤激光工艺参数对穿透点焊缝形状和尺寸的影响,采用单因素试验方法,进行了不同激光功率、摆动幅度和焊接时间下的穿透点焊试验,分析了激光的功率密度分布、点焊缝的形状和尺寸的变化规律。结果表明,光纤激光光斑内的功率密度分布影响点焊缝的形状和尺寸。随着激光功率的增大,未摆动高斯光束形成点焊缝的形状由抛物线状逐渐转变为钟铃状,点焊缝的熔宽、熔深、深宽比和熔宽比都随之增大。光束摆动增大了激光与材料的作用面积,改变了功率密度分布和点焊缝的形状和尺寸。随着摆动幅度的增大,点焊缝的形状由钟铃状逐渐转变为碗盆状,点焊缝的熔深和深宽比都逐渐减小而熔宽比逐渐增大。当激光功率密度不变时,焊接时间对点焊缝的形状影响不大。随着焊接时间的增大,点焊缝的熔深和熔宽都逐渐增大,但深宽比基本保持不变。

2 000 MPa级热成形钢双光斑激光 焊接接头成形研究

目的探究焊接参数对PHS2000型热成形钢焊接接头宏观形貌的影响,利用双光斑激光焊接工艺减少焊接缺陷,得到形貌良好的焊接接头。方法使用德国通快公司的TruDisk 5000型双光斑激光器对2000 MPa级热成形钢进行激光焊接。使用金相显微镜对不同参数下焊接接头正面和背面的宏观形貌及焊缝横截面的熔深和熔宽进行研究。结果随着激光功率从3500 W增大到4400 W,焊接接头成形良好,熔深大体呈增大趋势,深宽比先下降后上升再下降;随着焊接速度从50 mm/min增大到250 mm/min,熔深、熔宽基本降低,深宽比总体呈下降趋势;随着芯环比的提高,焊缝背面成形变差,熔深在芯环比为55%~65%时较理想,深宽比总体呈W形上升;当离焦量为0 mm时,焊缝背部出现了较为严重的烧损变色,并且在焊缝两侧产生了飞溅。而随着离焦量降低到−4 mm,烧损变色情况得到改善。结论激光功率和芯环比对焊接接头成形的影响较为显著。得到了成形良好的焊接接头,且在激光功率为4700 W、焊接速度为150 mm/min、芯环比为65%、离焦量为−2 mm的焊接参数下,1.4 mm厚2000 MPa级热成形钢双光斑激光焊接接头的成形效果最佳。

激光螺旋点焊和电阻点焊DC06镀锌钢接头组织和性能

对比研究了激光螺旋点焊和电阻点焊工艺对DC06镀锌钢接头成形、微观组织和力学性能(显微硬度和剪切性能)的影响规律.结果表明,两种工艺均能获得成形良好的焊接接头,激光螺旋焊接头微观组织主要为铁素体(F)和少量渗碳体(Fe3C);电阻点焊接头微观组织主要为贝氏体(B)和铁素体(F).由于内外散热不均匀,激光螺旋点焊熔核区中心形成不同硬度的等轴晶,周围为具有明显取向的柱状晶,硬度值为130~160 HV10;电阻点焊熔核区冷速相近,无明显硬度梯度,硬度在190 HV10左右.激光螺旋点焊拉剪承载载荷为10.14 kN,比电阻点焊的8.82 kN提升了13.02%.接头失效形式分析发现:激光螺旋点焊和电阻点焊的失效形式分别为撕出型和拔出型,激光螺旋点焊由于热影响区组织塑性较好,接头受到拉剪作用时更易产生大角度转动而吸收更多的能量,具有更好的力学表现.最后,还对搭接间隙和锌镀层对激光螺旋点焊接头力学性能的影响进行讨论.

1250 MW核电半速汽轮发电机定子通风槽板制造工艺

介绍了1250 MW核电半速汽轮发电机定子通风槽板的产品结构及尺寸特点,阐述了其生产工艺,对影响产品质量的相关因素进行了说明。分析对比了各种焊接方法,经过试验、分析和工艺改进,解决了生产过程中面临的诸多难题,保证了产品质量,实现了核电重要部件的国产化。

铝合金在汽车车身的应用及连接技术研究

概述了几种常见的连接技术在铝合金汽车车身领域的应用,介绍了这几种连接技术的工艺原理和最新研究进展,为铝合金及其连接技术在汽车车身的日常应用和后续发展提供参考。

动力电池1060铝合金薄板可调环形光斑激光搭接焊工艺优化

激光焊接为动力电池铝合金薄板焊接提供了有效技术手段,然而传统激光焊接工艺在高焊接速度要求下易产生飞溅、气孔等缺陷,影响构件的服役性能.文中开展可调环形光斑激光搭接焊工艺调控研究,阐明了中心-环形激光功率对焊缝成形的影响规律,在此基础上,确定了无飞溅、少气孔、大搭接面熔宽的高速稳定焊接工艺窗口.在上述工艺窗口范围内,以小熔深波动与大搭接面熔宽作为目标,基于Kriging模型与NSGA-Ⅱ遗传算法开展多目标工艺参数优化.经验证,在焊接速度70 mm/s以上,焊缝成形质量进一步得到提升,搭接面熔宽提高8.89%、熔深波动小于10%、无明显成形缺陷.