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Experimental and numerical studies on hybrid laser welding techniques of thick plates.

机译：厚板混合激光焊接技术的实验与数值研究。

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摘要

Autogenous laser welding is widely recognized as an important joining technology in diverse industries due to its advantages, such as less distortion, higher welding speed, deeper weld penetration, and ease of automation. It is mainly used to join the thin metal sheets like zinc-coated steel plates and alluminium alloys. In the case of welding of thick plates, autogenous laser welding is often disadvantageous. Limited by the laser power, a full weld penetration is hard to obtain in a single pass. The small laser focal spot restricts the gap tolerance of autogenous laser welding. The preparation of coupons is more complicated, leading to an increase in the manufacturing costs. Another disadvange of autogenous laser welding is its high cooling rate that likely causes an excessive hardening and high residual stress in the weld zone. The crack-susceptible metals are prone to produce the solidification cracks because of its rapid cooling rate in combination with its large depth/width ratio. Filler materials and an additional heat source are required to increase the weld penetration of autogenous laser welding, improve its gap bridging capability, and slow its cooling rate.;Laser welding assisted by a hot wire is one of promising solutions. The mechanical and microstructural properties of the welds could be adjusted by using an additional heat source and by selecting the proper filler wire. In order to study its welding characteristics, the dynamics of the molten pool during welding were visualized by using a high-speed charge-coupled device (CCD) camera assisted by a green laser. The effects of welding parameters, such as the position of the hot-wire tip with respect to the laser focal spot and the hot-wire voltage, were investigated to obtain sound welds with good quality. The temperature field and thermally-induced residual stress of laser welding assisted by a hot wire was investigated by using the FE method. An X-ray diffraction technique was used to measure the residual stress at the weld beads, and to verify the numerical results. The verified numerical results provided detailed information about the evolution and distribution of the residual stress during welding. The advantages of laser welding assisted by a hot wire were also investigated.;Hybrid laser-arc welding is another promising method to mitigate the disadvantages of autogenous laser welding. The synergetic effect between laser beam and electrical arc was investigated by using a spectral diagnostic technique assisted by a high-speed CCD camera. The spectrometer was used to study the plasma characteristics of the hybrid laser-arc welding. The CCD camera was applied to make the welding process visible and to monitor the interaction between laser beam and arc. The effects of two welding parameters on the synergistic effect, the welding current and the offset distance, were studied. Optimal values of the offset distance and welding current were found to obtain the maximum weld penetration. The effect of the arc on the mechanical and microstructural properties of the in the hybrid laser-arc welds was also studied. By using a 10 kW disk laser, hybrid laser-arc welding was used to weld the 17-4 PH stainless steel plates in a thickness up to 19 mm. The welding procedure was optimized to achieve the full weld penetration in a single pass. The effects of the welding parameters on the formation of porosity were investigated. The microstructural evolution and cracking susceptibility of 17-4 PH SS welds were studied to remove the solidification cracks along the weld centerline.
机译：自生激光焊接由于其具有的优点，例如变形少，焊接速度快，焊缝熔深和自动化容易等优点，被广泛认为是各种行业中的重要连接技术。它主要用于连接薄金属板，例如镀锌钢板和铝合金。在焊接厚板的情况下，自发激光焊接通常是不利的。受激光功率的限制，很难在一次焊道中获得完整的焊缝熔深。小的激光焦点限制了自生激光焊接的间隙公差。优惠券的准备更加复杂，导致制造成本增加。自生激光焊接的另一个缺点是其高冷却速度，这可能会导致焊接区域中的过度硬化和高残余应力。易受裂纹影响的金属由于其快速的冷却速度以及较大的深宽比而易于产生凝固裂纹。需要填充材料和额外的热源，以增加自发激光焊接的焊缝熔深，提高其缝隙桥接能力并降低其冷却速度。热线辅助激光焊接是一种有前途的解决方案。可以通过使用额外的热源并通过选择合适的填充焊丝来调节焊缝的机械和微观结构性能。为了研究其焊接特性，通过使用绿色激光辅助的高速电荷耦合器件（CCD）摄像机对焊接过程中熔池的动态进行可视化。研究了焊接参数的影响，例如热线焊头相对于激光焦点的位置和热线电压，以获得质量良好的合理焊接。利用有限元方法研究了热焊丝辅助激光焊接的温度场和热致残余应力。使用X射线衍射技术测量焊缝处的残余应力，并验证数值结果。验证的数值结果提供了有关焊接过程中残余应力的演变和分布的详细信息。还研究了热丝辅助激光焊接的优点。混合激光电弧焊是减轻自发激光焊接缺点的另一种有前途的方法。利用光谱诊断技术，借助高速CCD相机，研究了激光束与电弧之间的协同效应。该光谱仪用于研究混合激光电弧焊的等离子体特性。 CCD摄像机用于使焊接过程可见并监视激光束和电弧之间的相互作用。研究了两种焊接参数对协同效应的影响，即焊接电流和补偿距离。发现偏移距离和焊接电流的最佳值以获得最大的焊缝熔深。还研究了电弧对混合激光电弧焊的力学性能和显微组织性能的影响。通过使用10 kW圆盘激光器，使用混合激光电弧焊焊接了厚度最大为19 mm的17-4 PH不锈钢板。对焊接程序进行了优化，以在一次焊道中实现全部焊缝熔深。研究了焊接参数对气孔形成的影响。研究了17-4 PH SS焊缝的组织演变和裂纹敏感性，以消除沿焊缝中心线的凝固裂纹。

著录项

  • 作者

    Liu, Wei.;

  • 作者单位

    Southern Methodist University.;

  • 授予单位 Southern Methodist University.;
  • 学科 Engineering Mechanical.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 212 p.
  • 总页数 212
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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