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。     

TC4合金等离子–MIG复合焊过程温度场的数值模拟

目的 研究TC4合金在等离子-MIG复合焊(Plasma–MIG Hybrid Welding)过程中的温度场特性,探究不同电弧功率对熔池形貌的影响。方法 进行了2组4 mm TC4合金板堆焊试验,根据实验结果提出了一种改进的复合热源模型并进行了相应的仿真分析。结果 仿真与实验获得的焊缝截面相吻合;等离子电流的增大使熔池尺寸增大且余高减小,等离子电弧功率的变化对熔池宽度的影响相对较小。结论 等离子–MIG复合电弧对工件的热作用非常集中,更易实现深熔焊、焊接效率更高;所提出的热源模型适用于TC4合金等离子–MIG复合焊温度场模拟。     

钛合金表面激光熔覆TiC/NiCrBSi涂层温度场有限元模拟

为在钛合金表面获得优质激光熔覆涂层,用有限元方法研究了激光熔覆工艺对熔池温度场分布和凝固后熔覆层组织的影响,考虑相变潜热、辐射对流散热以及温度对热物理性能的影响等因素,建立三维有限元模型模拟了Ti6Al4V合金表面激光熔覆TiC/NiCrBSi复合涂层过程中的温度场,并结合熔覆过程的温度场分布,对涂层的形貌、结合区、基...     

TC4合金空心阴极真空焊接熔池动态行为的数值模拟

建立了空心阴极真空电弧焊(Hollow Cathode Vacuum Arc Welding, HCVAW)焊接TC4钛合金板(5mm厚)熔池中流体流动和传热过程动态行为的物理、数学模型,并对焊接过程进行了数值模拟计算和工艺试验、通过计算,找出了焊接速度和焊接电流等工艺参数对焊缝成型的影响规律,并计算出焊接过程中工件上的温度场分布和熔池中的流场分布,计算结果与实验结果基本相符.     

TC4金字塔点阵结构的激光焊接及其平压性能

基于用高温节点下压法成形的TC4钛合金芯体,用面芯激光焊接制备了钛合金金字塔点阵结构。用响应曲面法优化激光焊接参数,实现了点阵结构面芯连接,分析焊接节点的微观组织并进行了点阵结构平压实验。结果表明：激光功率对焊接效果有显著的影响。点阵结构面芯激光焊接的优化工艺参数为：上面板的焊接功率为1.4 kW,下面板的焊接功率为1.2 kW,离焦量为30 mm,停留时间为1 s。在激光焊接热影响区发生了马氏体转变,分布着大量的针状马氏体;熔焊区的组织为粗大β相+针状α相。在焊接节点处,从熔焊区到母材的显微硬度随着马氏体相的减少而降低。根据平压实验结果分析了金字塔点阵结构变形和破坏的规律,桁架杆失效断裂发生在热影响区。用激光焊接制备的TC4钛合金点阵结构,其平压强度为3.09 MPa,平压模量为153.25 MPa。     

低温对TC4脉冲激光焊接接头组织和性能的影响

在-120~25℃温度范围内对TC4钛合金薄板脉冲激光焊接接头进行了拉伸试验,并对拉伸断裂后的显微组织进行了观察,研究了低温对TC4钛合金脉冲激光焊接接头组织和力学性能的影响。试验结果表明:随着温度的降低,TC4钛合金脉冲激光焊接接头的显微组织并未出现明显变化,拉伸强度升高而延伸率下降,呈延性断裂模式。在低温拉伸过程中,TC4钛合金脉冲激光焊接接头母材区域的α相中有滑移带形成,预示变形机制仍然是位错滑移机制。     

焊接参数对TC4薄板焊接过程的影响

目的 揭示焊接参数对TC4薄板焊接过程中温度场、位移场及应力场的影响规律。方法 基于有限元（FEM）模拟方法,运用Fortran语言对焊接热源及焊接参数进行定义,以模拟不同焊接参数下TC4薄板的TIG对接焊过程。结果 在稳弧阶段,温度场为一组以焊接方向为长轴的椭圆,且存在温度梯度,随着焊接速度的增大,温度场峰值、温度场温度梯度、熔池宽度和熔池体积逐渐减小,而焊接效率和焊接电流对温度场的影响与焊接速度刚好相反;随着焊接速度的增大,薄板最大变形量逐渐减小,焊接角变形及挠度变形逐渐得到改善,而焊接效率和焊接电流对位移场的影响与焊接速度刚好相反。在稳弧阶段,焊缝位置的残余应力为拉应力,两侧为压应力,随着焊接速度和焊接电流的增大,纵向残余拉应力逐渐增大,焊缝处高应力集中区的宽度逐渐减小,而焊接效率对应力场的影响与焊接速度刚好相反。在高焊接速度、中等焊接效率、低焊接电流参数条件下,可获得熔池体积小及熔池宽度窄的焊缝,有利于减小焊后残余应力与变形。结论 上述研究结果可为TC4薄板的焊接过程提供一定的理论指导。     

TG合金空心阴极真空焊接熔池动态行为的数值模拟

建立了空心阴极真空电弧焊（Hollow Cathoda Vacuun Arc Welding,HCVAW)焊接TC4钛合金板（5mm)熔池中流体流动和传热过程动态行为的物理,数学模型,并对焊接过程进行了数值模拟计算和工艺试验,通过计算,找出了爆接速度和爆接电流等工艺参数对爆缝成型的影响规律,并计算出焊接过程中工作上的温度场分布和熔池中的流场分布,计算结果与实验结果基本相符。     

40Cr轴面激光熔覆Ni60数值模拟

目的 针对激光熔覆过程中熔池内部复杂的传热和对流现象,分析激光功率和扫描速度对熔池内部温度场、流场演变和分布的影响.方法 采用双椭球热源模型,建立了40Cr轴面基体激光熔覆Ni60粉末过程的三维温度场流场数值模型,并进行试验验证.结果 熔覆过程形成了近似椭球体的熔池,最高温度位于移动光斑中心偏后方,达到了2080.4 ...     

激光粉末床熔融WC-12Co硬质合金温度场模拟EICSCD

结合有限元软件ANSYS建立三维有限元热模型,利用APDL命令及生死单元方法实现对高斯热源的施加和WC-12Co硬质合金打印过程的模拟,得到WC-12Co硬质合金在激光粉末床熔融(LPBF)成形过程中的温度场分布,研究不同工艺参数(激光功率、扫描速度)对温度场分布及熔池特征的影响。结果表明:WC-12Co硬质合金在LPBF过程成形时,利用有限元能够有效模拟其成形过程。位于热源前部的等温线比尾部更为密集,温度梯度更大;而扫描路径终端边缘处熔池中心的温度最高。随着激光功率的增大和扫描速度的减小,熔池宽度、深度和长度均相应增大。通过相关实验分析不同工艺参数对晶粒尺寸的影响,发现晶粒尺寸随扫描速度的增加而减小,随激光功率的增加而增大;但过高的激光功率会引起一定的热裂纹现象发生。     

A transient finite element simulation of the temperature and bead profiles of T-joint laser welds

Laser welding is a high power density welding technology, which has the capability of focusing the beam power to a very small spot diameter. Its characteristics such as high precision and low and concentrated heat input, helps in minimizing the micro-structural modifications, residual stresses and distortions on the welded specimens. In this study, finite element method (FEM) is adopted for predicting the bead geometry in laser welding of 1.6 mm thick AISI304 stainless steel sheets. A three-dimensional finite element model is used to analyze the temperature distribution in a T-joint weld produced by the laser welding process. Temperature-dependent thermal properties of AISI304 stainless steel, effect of latent heat of fusion, and the convective and radiative boundary conditions are included in the model. The heat input to the model is assumed to be a 3D conical Gaussian heat source. The finite element code SYSWELD, along with a few FORTRAN subroutines, is employed to obtain the numerical results. The T-joint welds are made using a Nd:YAG laser having a maximum power of 2 kW in the continuous wave mode. The effect of laser beam power, welding speed and beam incident angle on the weld bead geometry (i.e. depth of penetration and bead width) are investigated. Finally, the shapes of the molten pool predicted by the numerical analysis are compared with the results obtained through the experimentation. The comparison shows that they are in good agreement.     

不锈钢与钛合金纳秒激光焊接工艺研究

目的 针对不锈钢与钛合金异种金属焊接时,容易产生间化合物,导致焊点拉力低的现象,通过纳秒激光焊接工艺来提高不锈钢与钛合金异种金属焊接的焊点拉力.方法 采用纳秒光纤激光器进行304不锈钢与TC4钛合金的焊接实验,通过激光运行螺旋线组成焊点,并对工艺参数进行正交试验,得到焊点拉力最大的工艺参数.结果 当激光功率为90 W,...     

Hybrid laser/arc welding of thick high-strength steel in different configurations

In this investigation, hybrid laser/arc welding (HLAW) was employed to join 8-mm-thick high-strength quenched and tempered steel (HSQTS) plates in the butt-and T-joint configurations. The influences of welding parameters, such as laser power, welding speed, stand-off distance (SD) between the arc of gas metal arc welding, and the laser heat source on the weld quality and mechanical properties of joints, were studied to obtain non-porous and crack-free fully-penetrated welds. The weld microstructure, crosssection, and mechanical properties were evaluated by an optical microscope, and microhardness and tensile tests. In addition, a finite element model was developed to investigate the thermal history and molten pool geometry of the HLAW process to join the HSQTS. The numerical study demonstrated that the SD had a paramount role in good synergy between the heat sources and the stability of the keyhole. For the butt-joint configuration, the results showed that, at a higher welding speed (35 mm/s) and optimum SD between the arc and laser, a fully-penetrated sound weld could be achieved. A non-porous weld in the T-joint configuration was obtained at a lower welding speed (10 mm/s). Microstructural evaluations indicated that the formation of residual austenite and the continuous network of martensitic structure along the grain boundary through the heat affected zone were the primary reasons of the softening behavior of this area. This was confirmed by the sharp hardness reduction and failure behavior of the tensile coupons in this area.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-017-0193-6     

Simulation of temperature distribution in single metallic powder layer for laser micro-sintering

Simulation of temperature distribution in single metallic powder layer for laser micro-sintering (LMS) using finite element analysis (FEA) has been proposed, taking into account the adoption of ANSYS μMKS system of units, the transition from powder to solid and the utilization of moving laser beam power with a Gaussian distribution. By exploiting these characteristics a more accurate model could be achieved. The effects of the process parameters, such as laser beam diameter, laser power and laser scan speed on the temperature distribution and molten pool dimensions have been preliminarily investigated. It is shown that temperature increases with the laser power and decreases with the scan speed monotonously. For the laser beam diameter during single-track, the maximum temperature of the powder bed increases with the decrease in the laser beam diameter, but far from the center of the laser beam area, the temperature increases with the laser beam diameter. The molten pool dimensions in LMS are much less than that in classical selective laser sintering (SLS) process. Both molten pool length and width decrease with the laser beam diameter and the laser scan speed, but increase with the laser power. The molten pool length is always larger than the molten pool width. Furthermore, the center of molten pool is slightly shifted for the laser multi-track.     

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。     

铝合金T型接头激光+GMAW复合焊残余应力数值分析

目的 研究激光+GMAW复合焊中不同激光功率参数对铝合金T型接头残余应力的影响,从而提高焊接性能。方法 分别考虑了热弹塑性理论、传热学以及T型接头几何特性,建立了铝合金T型接头激光+电弧复合焊残余应力的数值分析模型。采用双椭球体热源模型表征电弧热输入与熔滴晗,采用锥体热源模型对激光深熔焊进行描述。基于所建立的T型接头模型,使用ANSYS有限元软件对12 mm厚铝合金激光+ GMAW焊T型接头残余应力进行模拟计算,并研究其分布特征;使用X射线衍射法对T型接头处的残余应力进行测量从而对所建模型的准确性进行验证。同时,对比了不同激光功率下铝合金T型接头对残余应力的影响规律。结果 当激光功率分别为2、3、4、5 kW时,铝合金T型接头路径L3上的纵向残余应力最大值分别为270、263、258、251 MPa,米塞斯-等效应力最大值分别为265、261、257、250 MPa。结论 后焊的焊缝A对焊缝B有明显的热处理作用,使应力明显降低;在T型接头焊缝及近缝区,横向残余应力和厚度方向残余应力峰值均比纵向残余应力峰值小,且随着激光功率的增大,焊缝及近缝区拉应力峰值不断减小。     

Nd:YAG激光与半导体激光复合焊接对铝合金焊缝组织和性能的影响

目的 提高铝合金的焊缝抗拉强度,解决铝合金焊接过程中的裂纹缺陷。方法 采用脉冲Nd:YAG激光与半导体激光复合焊接铝合金,先用Nd:YAG激光形成焊接熔池,然后用半导体激光对熔池进行加热保温,获得无裂纹的焊缝,并对焊缝进行抗拉强度测试。结果 与单独的Nd:YAG激光焊接相比,Nd:YAG激光与半导体激光复合焊接的铝合金焊缝抗拉强度提高了50%,达到193MPa,为母材抗拉强度的90%。结论 2束激光的结合延长了熔池的冷却凝固时间,从而有效避免了热裂纹,减少了焊接缺陷,提高了焊接质量。     

Influence of welding parameters on lap joint between Al and Ti alloys using low power fiber laser

Fiber laser beam welding has always been a user‐friendly and flexible method to join dissimilar materials despite differences in thermal coefficient. Many industrial applications such as automotive has replaced the conventional joining methods towards this because of the flexibility and reduction in time consumption. In the present study, dissimilar titanium alloy; Ti6Al4 V and aluminum alloy; AA2024‐0 were laser welded through a lap joint technique using a low power Yb‐fiber laser without any additional filler. The influence of welding speed on weld morphology was investigated using optical microscopy (OM) and scanning electron microscope (SEM). The cross‐section of the joints revealed that the fusion zone (FZ) and heat affected zones (HAZ) are wider when welding speed decreases with lower laser power. This result shows that the low power fiber laser has sufficient energy to melt the base materials, forming a liquid bridge to facilitate the smooth flow of molten metal between the top and bottom layer. Therefore, at lower welding speeds with constant low laser power, it was shown that there are possibilities of laser welding between two non‐ferrous metals.     

超薄铝合金胶粘接及激光焊接工艺研究

目的为了解决厚度为0.05 mm的铝合金在激光焊接过程中,材料发生变形导致的焊穿或者虚焊问题。方法采用在下层铝合金材料表面均匀涂覆粘胶剂,将上下2层铝合金材料进行预固定,然后采用激光焊接,形成焊缝。通过控制涂覆粘胶剂的次数,得到胶层厚度为11.2μm,对涂覆粘胶剂的铝合金进行激光焊接实验。结果当激光平均功率为150W,焊接速度为100mm/s,离焦量为2mm时,焊缝剪切强度最大,为124 MPa,达到母材剪切强度的82%。结论通过粘胶剂预固定后,在激光加热过程中,可以很好地克服材料的变形,让上下材料形成熔池,熔池冷却凝固后熔合在一起形成焊缝,可以解决材料发生变形导致的焊穿或者虚焊问题。