Laser weld pool management through diffractive holographic optics
Laser weld pool management through diffractive holographic optics
复制标题
通过衍射全息光学进行激光焊池管理
DOI：
10.1179/1743284711y.0000000050
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发表时间：
2012
影响因子：
1.8
通讯作者：
Sara C. Noden
中科院分区：
文献类型：
--
作者：
J. Kell;J. Tyrer;R. Higginson;John Jones;Sara C. Noden
摘要 传导激光焊接涉及通过暴露于高功率激光感应光和受控热传导来引发熔池。现有的焊接技术通常提供足够的能量来连接部件，但无法真正控制熔池。这个过程总是会导致邻近区域甚至熔池本身过热，通常会造成不可避免的影响，例如“烧穿”。目前的工作提出了一种程序，其中构思了所需的熔池形状，并设计了定制的光束辐照度分布来匹配。光束不是由传统透镜整形，而是由衍射全息光学元件 (DHOE) 整形。 DHOE 利用全息术通过相长干涉和相消干涉完全创建高度复杂的三维能量分布。该技术允许将新颖的光束辐照度分布应用于传导模式激光焊接，并将熔池横向轮廓成形为特定设计。全息传导激光焊接已被证明是成功的，代表着行业向前迈出的重要一步，正如本例中低碳钢和不锈钢的情况所证明的那样。研究表明，熔化区特别受照明激光束轮廓形状的影响，因此许多焊缝呈现出高度新颖的焊接轮廓。使用定制的光束辐照度分布可以控制流向工件的热流，从而可以更好地控制由于表面张力效应而导致的材料迁移。许多焊缝表现出独特的表面凝固模式，与所使用的光束轮廓直接相关。 DHOE 还具有许多额外的优点，例如增加了可用景深，允许不太严格的设置公差。通过使用光学显微镜、电子显微镜、电子背散射衍射和能量色散（X 射线）光谱，对这些焊缝样品进行了全面的金相分析。这些技术提供了对晶体尺寸、形状、方向和相位的深入分析。通过将DHOE纳入激光焊接工艺，不仅熔池形状变得可控，而且晶体生长也受到很大影响。通过使用 DHOE 创建的光束分布，可以减少传统激光焊接的许多不良属性，使焊池的微观结构更接近母材的微观结构。
Abstract Conduction laser welding involves initiating a melt pool by exposure to high power laser induced light and controlled thermal conduction. Existing welding techniques generally provide enough energy to join the component but have no real control over the melt pool. This process can invariably lead to overheating in adjacent areas or even the melt pool itself, often causing unavoidable effects, such as ‘burn through’. The present work presents a procedure in which a desired melt pool shape is conceived, and a bespoke beam irradiance distribution is designed to match. The beam is shaped not by conventional lenses but by a diffractive holographic optical element (DHOE). The DHOE utilises holography to wholly create highly complex three-dimensional energy distributions through constructive and destructive interference. This technique allows novel beam irradiance distributions to be applied to conduction mode laser welding, with the melt pool transverse profile being shaped to a specific design. Holographic conduction laser welding has been shown to be successful and represents a significant step forward in the industry, as demonstrated in this case in both mild and stainless steels. The fusion zone is shown to be particularly influenced by the shape of the illuminating laser beam profile, and many of the welds demonstrate a highly novel weld profile because of this. The use of a bespoke beam irradiance distribution allows control of the heat flow to the workpiece, and this allows greater control over material migration due to surface tension effects. Many of the welds demonstrate unique surface solidification patterns directly linked to the beam profile used. The DHOE also presents a number of additional advantages, such as an increased usable depth of field, allowing for less stringent set-up tolerances. Comprehensive metallography has been performed on samples of these welds through the use of optical microscopy, electron microscopy, electron backscatter diffraction and energy dispersive (X-ray) spectroscopy. These techniques offer in depth analysis of crystal size, shape, orientation and phase. By incorporating DHOEs into a laser welding process, not only does the melt pool shape become controllable, but also the crystal growth is highly influenced. Many of the undesirable attributes of a conventional laser weld are reduced by using a beam distribution created by a DHOE, bringing the microstructure of the weld pool closer to that of the parent material.