焊接位置对激光-电弧复合焊接底部驼峰的影响

目的 通过改变焊接位置来抑制底部驼峰的形成进而降低生产成本。方法 使用高速摄像机观察平向焊接和横向焊接2种不同焊接位置下熔池的匙孔和底部驼峰的形成过程,并对底部凸起受到的金属蒸气反冲压力、熔融金属重力以及表面张力进行受力分析。结果 在S355J2W耐候钢的激光-电弧复合焊接平焊过程中,受金属蒸气反冲作用力的影响,熔融金属迅速从匙孔底部排出,流入匙孔底部凸起区域,底部凸起的增长速度极快,仅需7.5 ms即可形成大尺寸的驼峰。而在横向焊接中,匙孔前壁凸起数量减少,导致金属蒸气反冲压力减小,匙孔排出的熔融金属量减少,底部凸起的增速减缓,在13.6 ms时才达到最大高度,使驼峰在底部熔池凝固之前难以形成。结论 采用横向焊接的方式可以有效避免驼峰的产生,降低生产成本。同时,该方式在焊缝背部成形效果方面也表现良好,为优化焊接工艺提供了重要参考。     

电子束焊接动态过程仿真分析

基于有限差分理论的入射电子束服从高斯分布，在有限平板中匙孔理想化为旋转抛物面的基本假设，利用C Builder快速开发软件，在WindowsNT平台上综合OpenGL图形接口及多线程技术开发了电子束焊接动态过程仿真系统EBWSIM。结果表明：该系统通过友好的图形用户界面可实现工艺参数。材料参数，约束控制，视点追踪等焊接过程与移动热源焊接匙孔及其三维温度场的可视化实时交互，并能够实时仿真电子束深熔焊各点的热循环，焊缝横截面，热影响区分布，焊缝钉形缺陷和匙孔曲面的形成过程，模拟结果与实验数据吻合较好。     

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。     

焊管CO2气体保护焊单面焊双面成形焊接工艺

焊管的单面焊双面成形焊接工艺是在接缝间隙处依靠控制熔池金属的操作技术来实现单面焊接,正、反双面成形。焊接时随着电弧热源的稳定,液态金属熔池沿前线熔化,沿后端线结晶,高温液态熔池处于悬空状态。选用100％C02气体保护焊,熔深好,焊缝成形美观,便于单面焊双面成形。焊管的单面焊双面成形焊接工艺焊缝质量好、焊接速度快、节省了焊接材料而且焊缝内部的质量容易达到探伤质量的求。     

CO气体保护焊单面焊双面成形工艺与应用

引言 焊管的单面焊双面成形焊接工艺是在接缝间隙处依靠控制熔池金属的操作技术来实现单面焊接,正、反双面成形。焊接时随着电弧热源的稳定,液态金属熔池沿前线熔化,沿后端线结晶,高温液态熔池处于悬空状态。选用100％CO2气体保护焊,熔深好,焊缝成形美观,便于单面焊双面成形。焊管的单面焊双面成形焊接工艺焊缝质量好、焊接速度快、节省了焊接材料而且焊缝内部的质量容易达到探伤质量的要求。     

药芯焊丝电弧焊(FCAW)的焊接电流对Fe-Cr-C合金堆焊金属组织与耐磨性的影响

采用自制药芯焊丝在3种焊接电流条件下堆焊获得了相应堆焊试样,对其显微组织进行了观察,并对相结构进行了分析。在此基础上,分析了焊接电流对堆焊金属硬度及耐磨性的影响。然后采用数值模拟方法对不同焊接电流的堆焊熔池温度进行了计算,并采用热力学软件对不同焊接电流堆焊金属在冷却过程中的CCT曲线进行了预测。结果表明,随着焊接电流的增加,堆焊熔池温度显著升高,堆焊金属的淬透性增加,从而使冷却后的堆焊金属中的马氏体含量增加,而残余奥氏体含量降低,导致堆焊金属的硬度和耐磨性均显著提升。     

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。     

压铸AZ91D镁合金TIG焊接气孔研究

对压铸AZ91D镁合金进行TIG自熔焊接,研究焊接电流对压铸镁合金气孔的影响,探讨焊缝中不同区域的气孔形貌特点及形成机理。结果表明:焊接气孔主要集中在焊缝近表面和熔合线附近;焊接接头的凸起面积、熔化区面积以及气孔率均随着焊接电流的增大而增加。在焊缝近表面主要是氢致气孔,其H主要来自母材;在焊缝中心,气泡受向上的流体力和浮力作用,气孔问题并不严重;在半熔化区,气泡受阻碍其上浮运动的流体力作用,且液态金属黏度较大,气泡很难上浮逸出到熔池表面,从而滞留在半熔化区成为大气孔。     

钛合金窄间隙激光填丝焊接工艺及接头组织性能分析

采用自主研发的Ti-Al-V-Mo系钛合金药芯焊丝为填充金属,进行TC4钛合金板窄间隙激光填丝焊接工艺实验,研究激光功率、摆动参数、焊接速度和送丝速度等工艺参数对焊缝成形的影响规律;借助高速摄像系统研究焊接过程羽辉及等离子体特性,并对获得的焊接接头组织性能进行分析。研究结果表明：采用激光功率4.0 kW、圆形摆动模式、摆动频率100 Hz、摆幅2 mm、焊接速度0.42 m/min、送丝速度0.6 m/min的工艺参数组合下得到的焊缝成形良好,无明显外观缺陷;当焊丝末端与液态熔池接触距离为0 mm时,过渡方式为液桥过渡,可以实现焊丝熔化金属向熔池的稳定、有序过渡;该焊接工艺获得的20 mm厚TC4钛合金板窄间隙激光填丝焊接头组织性能良好。     

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。     

T型接头旋转激光+GMAW复合焊熔池动态行为数值分析模型

目的 研究T型接头旋转光纤激光+GMAW复合焊熔池的温度场和流态特征,揭示气孔缺陷的产生及抑制机理。方法 依据光学、电磁学、传热学及流体动力学机理,建立T型接头旋转光纤激光+GMAW复合焊熔池数值分析模型。使用Fluent软件对旋转频率分别为50 Hz和100 Hz的T型接头旋转激光+GMAW复合焊进行温度场以及流态特征的模拟,对比不同频率下T型接头横、纵截面,从工艺和焊缝成形角度出发,针对不同频率对熔池、小孔成形以及气孔抑制的影响进行讨论。结果 当旋转频率为50 Hz时,纵截面内小孔最大深度为5.4 mm,横截面熔池内小孔开口直径相对较大,旋转一周后,小孔远离气泡,气泡无法逸出,形成气孔;当旋转频率为100 Hz时,纵截面内小孔深度显著降低,熔池体积明显减小,横截面内小孔最大开口直径和深度均降低,熔池尺寸也有所减小,在时间为0.097 s时,小孔上方区域出现的顺时针涡流不仅能抑制气孔,还能改善熔池的下垂以及立板焊趾处的咬边。结论 随着旋转频率的增大,小孔的最大开口直径和深度均降低,还对熔池具有搅拌作用,使熔池体积变小。     

等离子弧焊接熔池和小孔形成过程数值分析

目的 研究等离子弧焊接穿孔过程中熔池内部的金属流动情况和小孔动态变化过程。方法 通过“传热-熔池流动-小孔”之间的相互耦合关系,建立了等离子弧焊接穿孔过程的数值分析模型,通过VOF方法追踪了小孔界面,采用FLOW-3D软件模拟了等离子弧焊接熔池和小孔的形成过程,定量计算了等离子弧焊接温度场、熔池流场及小孔形状;分析了等离子弧焊接熔池和小孔行为;并通过等离子弧焊接实验数据验证了模拟结果。结果 当焊接时间为0~1.0 s时,小孔深度曲线与熔深曲线几乎相同,小孔底部紧贴熔池底部;在2.8 s以后,小孔深度曲线与熔深曲线有一定距离,小孔深度曲线在一定范围内波动,等离子弧焊接电弧挖掘作用到达极限,电弧压力与其他力达到平衡状态。模拟的焊缝熔深为8.04 mm、熔宽为13.20 mm,实验测得的焊缝熔深为8.00 mm、熔宽为13.42 mm。结论 构建的随小孔动态变化的曲面热源模型和电弧压力模型可以描述等离子弧焊接过程中的电弧热-力分布;模拟出了等离子弧焊接熔池和小孔动态演变过程;模拟得到的等离子弧焊接焊缝形貌与实验测得的焊缝形貌基本吻合。     

Melt pool vorticity in deep penetration laser material welding

In the present study, the vorticity of melt motion in the keyhole and weld pool has been evaluated in case of high power CO₂ laser beam welding. The circulation of vorticity is obtained as a function of Reynolds number for a given keyhole volume which is linked to Mach number variation. The shear stress and thermal fluxes present in the turbulent pool are linked to diffusivity and Prandtl number variation. It was shown that below a critical value of Rayleigh number, the conduction mode of melt transfer signifying beam absorption becomes dominant. Above this value, convective heat transfer indicates melting and evaporation occurring in the weld pool during laser welding. The evaporative recoil pressure expels the liquid while surface tension and hydrostatic pressure help to retain the melt in the keyhole cavity in this high power laser beam welding. The understanding of several hydrodynamic phenomena occuring in the weld pool is valuable not only for understanding basic mechanistic aspects but also for process optimization involved in laser beam welding.     

Numerical simulation of variable polarity vertical-up plasma arc welding process

Three-dimensional transient governing equations were developed based on conservation laws of energy, momentum and mass. These equations described physical phenomena of convection in weld pool and heat transfer in workpiece during variable polarity vertical-up plasma arc welding process. Boundary conditions for the developed governing equations were given. Welding energy input for variable polarity vertical-up plasma arc welding process was quantitatively expressed. Free surface deformation of the keyhole molten pool was coupled into calculation. Effect of wire filling on the geometry of molten pool and weld reinforcement was considered in the simulation. Correlations of temperature and thermophysical properties for aluminum alloy 2219 were quantitatively established. A control volume based finite difference method was used to solve the discrete governing equations. Moreover, dynamic evolutions of geometrical profile, dimension and fluid flow for the molten pool and keyhole were simulated through the developed computational routines, which achieved transient solution of fluid flow field coupling with thermophysical properties, temperature field and weld pool free surface deformation. Besides, the effect of the workpiece thickness on the moments of keyhole formation and stable keyhole establishment was analyzed, and thermal cycles for the main welding stage were calculated. In addition, experiments via variable polarity vertical-up plasma arc welding technique were conducted, and the established models were experimentally verified through weld cross-section profiles.     

CLAM钢穿孔等离子超声电弧焊接激励频率的优化

为了优化超声电弧焊接激励频率,针对穿孔等离子超声电弧焊接熔池进行了计算机模态分析.根据穿孔等离子弧焊接特点,利用特定的数值分析模型,通过ANSYS软件计算超声电弧焊接熔池模态,分析与模态频率相对应的熔池响应情况.最后,分别施加不同大小的超声电弧频率,以3组4.5 mm厚的中国低活化马氏体(CLAM)钢板为实验材料进行平板对接焊试验.结果表明:在谐振条件下,焊缝区面积增大,组织的细化效果较好,界面棒状碳化物生长得到抑制,同时焊缝区硬化现象得到显著改善;利用这种方法基本达到了超声电弧频率优化的目的.     

Physical and Thermal Processes During Electron Beam Welding

Complicated processes of the seam formation during electron beam welding are described. The physical processes in the weld pool and in the vapor-plasma mixture emitted in the cavity into the liquid metal created by intensive high energy beam are discussed. The dynamics of the liquid metal in the weld pool are interconnected with the energy distribution of the electron beam in the cavity which influences the weld depth and width and controls the defect formation in the weld such as pores (blow holes), non-uniformity of the weld root (spiking) and rippled weld surface. The moving heating source, working in the weld pool of metal samples is steady only as a first approximation due to the molten pool dynamics. A more exact heat model of the electron beam welding must take into account the unstable nature of beam transport within vapors and gas plasma in the cavity as well as the variations of energy dissipation on the crater walls and of heat transfer through molten metal of the weld pool.     

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.     

Influence of gravity state upon bubble flow in the deep penetration molten pool of vacuum electron beam welding

The governing equations of two-dimensional bubble flow model for gas–liquid two-phase system in deep penetration molten pool of vacuum electron beam welding were developed according to the laws of mass and momentum conservation. The separation models of gas and liquid convections in bubble flow were formed by regarding the gas phase in molten pool as a particle phase, and the vacuolar fraction, velocity slip, pressure gradient and other factors were introduced into the models. The influences of the gravity state upon the convection of bubble flow and the distribution of cavity-type defects in molten pool of AZ91D magnesium alloy were studied by the method of numerical simulation based on the mathematical models. The results showed that the gravity is an important factor to drive the convection of the bubble flow in the deep penetration molten pool during vacuum electron beam welding. The gravity has an impact on the gas distribution in molten pool, thus affects the distribution of cavity-type defects in weld. Because of the gravity contributing to driving the convection of bubble flow, it is conducive to the escape of gas phase in molten pool and reducing the air rate. A larger convection velocity of gas phase is helpful to the escape of gas phase, thus reduce the tendency of cavity-type defects.     

变极性等离子弧穿孔熔池受力及焊缝成形稳定性

通过YB005-01型压力变送器测定相同参数条件下正极性等离子电弧力大于反极性等离子电弧力,并建立了铝合金VPPA焊接穿孔熔池受力模型,分析了在不对称正、反极性等离子电弧力的作用下,穿孔溶池稳定性及其焊缝成形机理.同时进一步分析铝合金VPPA力学特性,掌握了焊接电流和离子气流量等重要焊接参数对其影响.经穿孔焊工艺实验,...