电子束焊接熔池周期性波动的数值模拟

为了更深入地探究电子束焊接过程中的机理问题,利用数值软件Fluent,对10mm厚的2219铝合金电子束焊接熔池进行三维瞬态模拟。分析电子束焊接进入准稳态后熔池中涡流的变化规律和产生原因,并结合电子束与匙孔壁面相互作用进行讨论。结果表明:电子束焊接进入准稳态后熔池呈周期性波动;根据液态金属流动情况可将焊接熔池分为3个区域,区域Ⅰ中的液态金属维持了熔池体积的稳定,区域Ⅱ中的涡流起到扩大熔池表面的作用,区域Ⅲ中的涡流促使匙孔坍塌;通过对电子束与匙孔壁面的耦合分析可知,电子束在匙孔壁面上并不是均匀分布的,这造成了匙孔底部具有一定的滞后性。     

单束与双束串行激光填丝焊特性对比

以铝合金为研究对象,研究了双束串行激光填丝焊不同能量比对焊缝成形及焊缝气孔率的影响,并与单束激光填丝焊工艺进行对比。进一步借助高速摄像机对双束串行激光填丝焊能量比R为20/80以及单束激光填丝焊的熔池、匙孔以及等离子体的变化进行对比分析,获得了双束串行激光填丝焊能量比R为20/80时焊缝气孔率降低的原因。结果表明,对于双束串行激光填丝焊,当能量比R为20/80时焊缝气孔率较低。与单束激光填丝焊相比,双束激光填丝焊能量比R为20/80的焊缝气孔率降低了38%,而且焊接过程中焊丝熔化后沿熔池边缘流入,可大幅降低对匙孔的冲击作用,匙孔始终处于张开状态,焊接过程中等离子体的形态波动相对较小,表明焊接过程的稳定性较好。     

电子束钎焊温度场PID控制系统

为了将电子束应用于精密构件及热敏感性材料钎焊,以适应复杂形状曲线钎焊缝的要求,采用电子束扫描轨迹编辑及在线调节、钎焊温度实时采集及PID控制器构建真空电子束钎焊温度闭环控制系统.研究表明:本控制方法可实现在焊接过程中电子束按设定轨迹对工件进行扫描加热的同时,对被加热工件温度进行在线检测及实时调节.采用电子束扫描轨迹编辑及在线调节可以适应各种形状曲线钎焊缝、特殊材料及热敏感性材料的钎焊要求;只要适当选取PID参数,采用PID控制器可以对钎焊温度进行有效控制.该方法提高了电子束钎焊温度控制的精确性和适应性,有利于钎焊质量的提高.     

CuNi90/10合金电子束焊接工艺研究

对10 mm厚CuNi90/10合金进行电子束焊接试验。液态金属表面张力较小，导致焊接工艺窗口较窄，较大的热输入将导致正面下凹，单面焊双面成形效果不如钛合金的；采用优化的参数可实现正面轻微下凹，同时保证背面成形基本良好。按照优化参数进行试板电子束焊接，并进行GTAW盖面。对焊接试板进行了射线检测和渗透检测，均满足NB/T 47013—2015的Ⅰ级标准；对焊接接头按照NB/T 47014—2011进行了力学、工艺性能测试，测试结果均满足标准要求。电子束焊接区域柱状晶特征明显，焊缝冲击性能优良，冲击功可达200 J以上，同时焊缝区硬度相比母材的有所下降。电子束焊接区域为典型的大深宽比形貌，焊缝区为枝晶α,热影响区为孪晶α;富镍α表现为较亮形貌，富铜α表现为较暗形貌。     

铝锂合金电子束焊接数值模拟分析及工艺优化

采用组合热源模型对Al-Li合金电子束焊接温度场分布进行数值模拟分析,通过热-力耦合,模拟计算得到接头区域的残余应力分布.结果表明,Al-Li合金电子束焊接温度场沿焊接方向呈椭圆形分布,电子束热源中心的温度最高,其附近区域的等温线分布密集,随着与热源中心的距离增大,等温线分布逐渐稀疏,焊缝区存在较大的温度梯度,较好地模拟出了电子束焊缝的钉形分布特征.接头的残余应力分布模拟结果显示,残余应力主要集中于焊缝区,由于修饰焊的热作用,焊缝上部具有相对较大的应力值.利用模拟计算得到的结果进行焊接工艺及参数优化,焊接工艺试验表明,试验焊缝形貌与模拟熔池形貌相吻合,进一步验证了模拟计算结果的可靠性.     

厚板铝合金搅拌摩擦焊匙孔补焊接头组织与性能

研究了35mm厚板铝合金搅拌摩擦焊匙孔补焊工艺,应用光学显微镜、扫描电镜、显微硬度仪及电子拉伸试验机等对接头的组织与性能进行了研究。结果表明,采用铝合金块材填充匙孔后进行FSW焊接,获得成型良好、表面光滑的焊缝;未加填充材料的匙孔位置,焊缝表面出现沟槽缺陷。FSW焊接一次接头的前进侧焊核区与热力影响区之间存在"吻接"缺陷;FSW焊接二次和三次接头的前进侧和后退侧过渡区均连接良好,二者组织无明显差别;FSW焊接一次和二次接头显微硬度分布呈W型,硬度最低值均出现在前进侧热影响区分别为56HV和60HV;采用搅拌头旋转速率为720r/min,焊接速率为180mm/min焊接工艺条件下,FSW焊接一次、二次和三次接头抗拉强度分别达到173、210和205MPa。     

TC4合金电子束焊接接头微观组织研究

对不同工艺参数电子束流焊接TC4钛合金焊缝显微组织进行分析,结果表明:电子束流工艺参数的改变对焊缝的相组成没有影响,却使得焊缝形状及其显微组织分布发生了改变,产生了焊缝显微组织梯度.焊缝夹角越大,焊缝上中下各部位马氏体针尺寸梯度越大.焊缝中显微硬度比母材硬度高HV30～50,热影响区中显微硬度呈梯度分布.     

汽车用铝钢无匙孔搅拌摩擦点焊接头组织及界面特征研究

随着轻量化技术的发展，镀锌钢板与铝合金等异种金属连接在现代汽车工业中的应用越来越多，回抽式无匙孔搅拌摩擦点焊具有热输入低、焊缝晶粒细小、接头力学性能高等优点，在铝合金等轻金属焊接领域具有很大的优势。本工作使用回抽式搅拌摩擦点焊技术，成功实现了0.7 mm厚的镀锌钢板与2 mm厚的铝合金板的无匙孔搅拌摩擦点焊连接。在不同的焊接转速下，对铝钢异种金属进行无匙孔搅拌摩擦点焊实验研究，分析了无匙孔搅拌摩擦点焊接头的剪切性能、断口形貌、各区微观组织、界面区特征及连接机理。研究结果表明，转速为1 200 r/min、压入量为0.2 mm、焊接时间为15 s时焊接接头最佳，具有最好的力学拉伸性能，断裂位置为热机影响区；通过扫描电镜(SEM)和能谱分析(EDS)对接头的微观形貌以及断口形貌进行观察分析发现，在搅拌区接头界面形成了约6μm厚的金属间化合物，为AlFe₃、Al₁₃Fe₄、AlFe；各位置处金属间化物的形貌与厚度不同，断裂方式为混合断裂机制，界面处的连接为机械结合和冶金结合两种接合方式。     

基于机器学习的薄板等离子弧搭接焊的熔深预测

在等离子弧搭接焊中,搭接焊接头的焊缝熔深是评价焊接质量的关键指标之一,而焊接过程中的热输入信息和熔池图像信息都与焊缝熔深有密切关系。本文通过建立304L不锈钢薄板等离子弧搭接焊数据采集系统,利用LabVIEW实时检测电信息,采用视觉传感技术实时获取薄板等离子弧搭接焊过程中的熔池图像,并通过图像处理方法获得熔池的几何参数信息,结合焊接工艺参数,选择峰值电流、峰值电压、焊接速度、离子气流量、保护气流量、熔池宽度和熔池后端长度作为输入量,焊缝熔深作为输出量,建立了基于支持向量机回归和BP神经网络的熔深预测模型。实验验证表明,采用径向基函数的支持向量机回归模型可以有效地对焊缝熔深进行预测,并具有很好的泛化能力,可为进一步实现在线优化焊接工艺参数提供依据。     

电子束回扫间距对焊缝金属的可控细化作用

以焊缝中晶体主轴长度表述晶粒细化程度，研究了电子束扫描频率、焊接速率对Ａｌ－Ｍｇ合金焊缝金属晶粒细化的影响以及晶车化与焊缝金属硬度的关系，分析了电子束回扫间距对焊接金属晶粒的可控经作用，结果表明：回扫间距决定晶粒细化的可控程度，最佳回扫间距０．０４ｍｍ时，凝固组织可由粗大柱状晶转化为细小等轴晶，与无扫描焊接相比，晶体主轴长减少到无扫描焊接时的１／５；焊硬度提高８０％，接近母材水平。     

电子束焊接热冲击对GH4133A的微裂纹损伤研究

电子束焊接是一个复杂的强瞬态的热冲击过程,包括发生在表层的热过程和发生在一定深度的应力波与材料的交互作用。本文基于电子束焊接热冲击效应分析了高温合金电子束焊接接头影响区的微裂纹形成原因,研究了微裂纹损伤对GH4133A电子束接头高温力学性能的影响。结果表明,热冲击是高温合金电子束焊接热影响区的微裂纹损伤的主要原因,热冲击损伤效应导致接头力学性能的劣化。     

Improved mechanical properties of Ti–6Al–4V alloy by electron beam welding process plus annealing treatments and its microstructural evolution

In this study, we investigated the effect of post weld annealing treatments on the mechanical properties of a Ti–6Al–4V alloy following electron beam welding (EBW). The operational parameters used in this EBW process together with suitable annealing treatments appeared to substantially enhance the tensile properties of the Ti–6Al–4V weldment, suggesting that EBW is a promising method for industrial application. Moreover, we report for the first time that γ-TiAl + α₂-Ti₃Al formed in the fusion zone of the Ti–6Al–4V EBW weldment and exhibited the same lamellar structure, orientation relationship, deformation mechanism, and slip system as common Ti–Al-based alloys do. The presence of these intermetallic compounds affected the mechanical properties of the weldment. We discuss the related phase transformation, microstructural evolution, and characteristics of the precipitates formed.     

大厚度钛合金的电子束焊接技术研究现状

综述了大厚度钛合金电子束焊接技术的研究进展,主要介绍了电子束深熔焊的原理特点,接头成形及缺陷控制、组织性能和残余应力分布等方面国内外的研究情况,明确了大厚度钛合金电子束焊接技术研究尚需解决的突出问题并展望了未来研究的发展方向。     

Improved mechanical properties of Ti–15V–3Cr–3Sn–3Al alloy by electron beam welding process plus heat treatments and its microstructure evolution

Electron beam welding (EBW) and related heat treatments were carried out on Ti–15V–3Cr–3Sn–3Al (Ti-15-3) alloy plate materials. It was found that the operated parameters in the present EBW process together with suitable heat treatments significantly enhanced the mechanical properties as well as the elongations of the Ti-15-3 weldment, which may provide a promising way for further industrial application. Furthermore, the observed nano size phase of β, α, and here first reported TiCr₂ particle, may form from the solid solution matrix of the Ti-15-3 alloy. The possible mechanisms for these phase formation are discussed.     

Investigation on AISI 304 austenitic stainless steel to AISI 4140 low alloy steel dissimilar joints by gas tungsten arc,electron beam and friction welding

This paper presents the investigations carried out to study the microstructure and mechanical properties of AISI 304 stainless steel and AISI 4140 low alloy steel joints by Gas Tungsten Arc Welding (GTAW), Electron Beam Welding (EBW) and Friction Welding (FRW). For each of the weldments, detailed analysis was conducted on the phase composition, microstructure characteristics and mechanical properties. The results of the analysis shows that the joint made by EBW has the highest tensile strength (681 MPa) than the joint made by GTAW (635 Mpa) and FRW (494 Mpa). From the fractographs, it could be observed that the ductility of the EBW and GTA weldment were higher with an elongation of 32% and 25% respectively when compared with friction weldment (19%). Moreover, the impact strength of weldment made by GTAW is higher compared to EBW and FRW.     

TECHNOLOGICAL PROCEDURES OF ELECTRON BEAM WELDING AND REPAIR

The most developed fields of electron beam welding (EBW) industrial application in the world are aerospace industry, nuclear power engineering, turbine manufactures, instrumentation, automobile industry, manufacture of bimetal strip. The expansion of EBW application is associated with the manufacturing of thick-wall steel structures. A short review of EBW techniques is given. The expediency of applying the electron beam facing of edges before welding the relatively contaminated plate materials is explained. The procedure of welded joint repair is presented. The acceptability of rewelding the defective weld areas is shown for the case of high-strength steel.     

Reduction of residual stress and deformation in electron beam welding by using multiple beam technique

The electron beam could be controlled by magnetic field for fast deflection, in which way multi-beam could be produced by deflection technique. The multi-beams run simultaneously for material processing with different heat input and positions. Therefore, it is possible to adjust the thermal effects and optimize the process. In this paper, the generation of multi-beams in electron beam welding (EBW) was investigated, and the processes of EBW with multi-beams were also investigated by both the numerical simulation methods, i.e., finite element analysis (FEA), and the experiments. The result shows that the residual stress of EBW could be minimized by using the multiple beam technique, and at the same time the welding deformation could also be reduced with the optimized parameters.     

Fatigue crack growth resistance of gas tungsten arc,electron beam and friction stir welded joints of AA2219 aluminium alloy

AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding (GTAW), electron beam welding (EBW) and friction stir welding (FSW) processes. The effect of three welding processes on fatigue crack growth behaviour is reported in this paper. Transverse tensile properties of the welded joints were evaluated. Microstructure analysis was also carried out using optical and electron microscopes. It was found that the FSW joints are exhibiting superior fatigue crack growth resistance compared to EBW and GTAW joints. This was mainly due to the formation of very fine, dynamically recrystallised grains and uniform distribution of fine precipitates in the weld region.     

Influence of welding parameters on microstructures and mechanical properties of electron beam welded aluminium–lithium plates

Abstract

The present work focused on the welding characteristics of electron beam welding (EBW) in 8090 Al–Li plates, evaluated in terms of strength or toughness degradation in post-weld impact and bending tests with loading rates of 10³, 10^-1, and 10^-4 s^-1. The influence of welding parameters, such as welding power, welding speed, and electron beam focus position, on the post-weld microstructures, porosity, and mechanical properties were examined. Although the joint efficiency for the maximum flexure strength (F_p ), or tensile strength, can be as high as 85–90%, the joint efficiency for the fracture absorption energy (E_t ) was only 20–40%, a level usually unsuitable for applications. It was found that changing the welding power and speed by a factor of 3 resulted in significant variation in E_t but only minor variation in F_p . Changing the welding focus position had little effect on post- weld mechanical properties. The abundant grain boundary precipitates in the welded specimens were thought to be the main cause of the degraded post-weld properties. Other microstructural factors included the δ′ precipitate and grain sizes. The volume fraction of porosity did not play any decisive role owing to the small size (<0·3 mm), low quantity (1–2%), and spherical shape of the EBW induced pores. Finally, given the same post-weld microstructures, the toughness degradation of the EBW specimens was worst under high rate impact loading.     

真空电子束焊机中的PLC应用技术

本文介绍了电子束焊机的组成及工作原理，并对电子束焊机的控制原理和使用进行分析，提出用三菱公司的FX系列的可编程逻辑控制器对电子束焊机进行逻辑控制，工作台控制则要用PLC的高速输出口和PLC特殊模块功能技术，实现了工作台的精密控制，结合电子束焊机对控制系统要求及焊接工艺需要，分别对控制软件的作用和软件构成进行了详细的说明，控制系统硬件及软件经过设备的运行表明，控制系统的硬件，软件功能完善，工作可靠。