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Study of issues in difficult-to-weld thick materials by hybrid laser arc welding.

机译：研究混合激光电弧焊难以焊接的厚材料问题。

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摘要

There is a high interest for the high strength-to-weight ratio with good ductility for the welds of advanced alloys. The concern about the welding of thick materials (Advanced high strength steels (AHSS) and 5xxx and 6xxx series of aluminum alloys) has stimulated the development of manufacturing processes to overcome the associated issues. The need to weld the dissimilar materials (AHSS and aluminum alloys) is also required for some specific applications in different industries. Hence, the requirement in the development of a state-of-the-art welding procedure can be helpful to fulfill the constraints. Among the welding methods hybrid laser/arc welding (HLAW) has shown to be an effective method to join thick and difficult-to-weld materials. This process benefits from both advantages of the gas metal arc welding (GMAW) and laser welding processes. The interaction of the arc and laser can help to have enough penetration of weld in thick plates. However, as the welding of dissimilar aluminum alloys and steels is very difficult because of the formation of brittle intermetallics the present work proposed a procedure to effectively join the alloys. The reports showed that the explosively welded aluminum alloys to steels have the highest toughness, and that could be used as an "insert" (TRICLAD) for welding the thick plates of AHSS to aluminum alloys. Therefore, the HLAW of the TRICLAD-Flange side (Aluminum alloy (AA 5456)) to the Web side (Aluminum alloys (AA 6061 and AA 5456)) and the TRICLAD-Flange side (ASTM A516) to the Web side (AHSS) was studied in the present work. However, there are many issues related to HLAW of the dissimilar steels as well as dissimilar aluminum alloys that have to be resolved in order to obtain sound welds. To address the challenges, the most recent welding methods for joining aluminum alloys to steels were studied and the microstructural development, mechanical properties, and on-line monitoring of the welding processes were discussed as well. The heat and mass transfer and the issues in joining of dissimilar alloys by the hybrid laser/arc welding process (HLAW) were explicitly explained in details. A finite element model was developed to simulate the heat transfer in HLAW of the aluminum alloys. Two double-ellipsoidal heat source models were considered to describe the heat input of the gas metal arc welding and laser welding processes. An experimental procedure was also developed for joining thick advanced high strength steel plates by using the HLAW, by taking into consideration different butt joint configurations. The geometry of the weld groove was optimized according to the requirements of ballistic test, where the length of the softened heat affected zone should be less than 15.9 mm measured from the weld centerline. Since the main issue in HLAW of the AHSS was the formation of the pores, the possible mechanisms of the pores formation and their mitigation methods during the welding process were investigated. Mitigation methods were proposed to reduce the pores inside in the weld area and the influence of each method on the process stability was investigated by an on-line monitoring system of the HLAW process. The groove angle was optimized for the welding process based on the allowed amount of heat input along the TRICLADRTM interface generated by an explosive welding. The weld was fractured in the heat affected zone of the aluminum side in the tensile test. The microharness was shown that the temperature variation caused minor softening in the heat affected zone satisfying the requirement that the width of the softened heat affected zone in the steel side falls within 15.9 mm far away from the weld centerline. The microstructure analysis showed the presence of tempered martensite at the vicinity of the weld area, which it was a cause of softening in the heat affected zone.
机译：人们对高强度重量比和先进合金焊缝的良好延展性非常感兴趣。对厚材料（高级高强度钢（AHSS）以及5xxx和6xxx系列铝合金）的焊接的关注刺激了制造工艺的发展，以克服相关问题。对于不同行业中的某些特定应用，还需要焊接异种材料（AHSS和铝合金）。因此，开发最新焊接工艺的要求可能有助于满足这些约束条件。在焊接方法中，混合激光/电弧焊（HLAW）已被证明是一种将厚而难焊接的材料连接起来的有效方法。该工艺既受益于气体保护金属电弧焊（GMAW）的优势，又受益于激光焊接的优势。电弧和激光的相互作用可以帮助厚板中的焊缝有足够的熔深。然而，由于异种铝合金和钢的焊接由于形成脆性金属间化合物而非常困难，因此本工作提出了一种有效接合合金的方法。报告显示，爆炸焊接铝合金与钢具有最高的韧性，可以用作将AHSS厚板焊接到铝合金的“插入件”（TRICLAD）。因此，TRICLAD法兰侧（铝合金（AA 5456））到腹板侧（铝合金（AA 6061和AA 5456））的HLAW和TRICLAD法兰侧（ASTM A516）到腹板侧（AHSS）的HLAW在当前工作中进行了研究。但是，为了获得良好的焊缝，必须解决与异种钢以及异种铝合金的HLAW相关的许多问题。为了应对这些挑战，研究了将铝合金与钢连接的最新焊接方法，并讨论了焊接工艺的显微组织发展，力学性能和在线监控。详细地详细解释了通过激光/电弧混合焊接（HLAW）进行的传热和传质以及异种合金的接合问题。建立了有限元模型来模拟铝合金在HLAW中的传热。考虑了两个双椭圆形热源模型来描述气体金属电弧焊和激光焊接过程的热量输入。考虑到不同的对接接头构型，还开发了使用HLAW连接厚的高强度高强度钢板的实验程序。根据防弹测试的要求，对焊接坡口的几何形状进行了优化，其中从焊接中心线开始测量的软化热影响区的长度应小于15.9 mm。由于AHSS的HLAW的主要问题是孔的形成，因此研究了焊接过程中孔形成的可能机理及其缓解方法。提出了缓解方法以减少焊接区域内部的气孔，并通过HLAW过程的在线监测系统研究了每种方法对过程稳定性的影响。基于爆炸焊接产生的沿TRICLADRTM界面允许的热量输入量，针对焊接工艺优化了坡口角度。在拉伸试验中，焊缝在铝侧的热影响区断裂。显微线束表明，温度变化在热影响区产生了轻微的软化，满足了钢侧软化热影响区的宽度距离焊接中心线不超过15.9毫米的要求。显微组织分析表明，在焊接区附近存在回火马氏体，这是热影响区软化的原因。

著录项

  • 作者

    Mazar Atabaki, Mehdi.;

  • 作者单位

    Southern Methodist University.;

  • 授予单位 Southern Methodist University.;
  • 学科 Mechanical engineering.;Materials science.;Electrical engineering.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 323 p.
  • 总页数 323
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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