Hybrid Laser Arc Welding

Hybrid laser-arc welding (HLAW) is a combination of laser welding with arc welding that overcomes many of the shortfalls of both processes. This important book gives a comprehensive account of hybrid laser-arc welding technology and applications. The first part of the book reviews the characteristics of the process, including the properties of joints produced by hybrid laser-arc welding and ways of assessing weld quality. Part two discusses applications of the process to such metals as magnesium alloys, aluminium and steel as well as the use of hybrid laser-arc welding in such sectors as ship building and the automotive industry. With its distinguished editor and international team of contributors, Hybrid laser-arc welding is a valuable source of reference for all those using this important welding technology. Reviews arc and laser welding including both advantages and disadvantages of the hybrid laser-arc approach Explores the characteristics of the process including the properties of joints produced by hybrid laser-arc welding and ways of assessing weld quality Examines applications of the process including magnesium alloys, aluminium and steel with specific focus on applications in the shipbuilding and automotive industries

Laser and hybrid laser-arc welding are used at present in modern industry, having many advantages over traditional welding technology. Sectors such as the automotive industry, shipbuilding, aviation and space industry, chemical machinery, defense industry, and so on cannot be imagined without these technologies. Possibility of dramatic increase of weld joint properties, robustness, and high level of process automation makes the technology of laser and hybrid material processing a prospective part of the industry. At the same time, physical complexity of these processes, their cross-science nature, and necessity in high-level skilled stuff require many efforts for wide and successful industrial implementation. Present manuscript, devoted to discussion of physical peculiarity of laser and hybrid laser-arc welding of metals, approaches to physical-based design of technological equipment, as well as examples of industrial applications of laser and hybrid welding concerning the possibility to control welded metal structure and properties, is one of the steps on this way.

The welding of Ni-base alloy Inconel 690 is commonly required during the construction and refurbishing of nuclear power plants with plate thicknesses varying between 1 mm to greater than 25 mm. However, during conventional multi-pass welding of Alloy 690 in this thickness range, micro-cracking in the form of ductility dip cracking (DDC) and solidification cracking can occur, causing significant delays in an already expensive industry. Hybrid laser-arc welding can significantly reduce the number of passes necessary to weld thick sections and, at the same time, lower the risk of forming DDC and solidification cracking. Significant advantages can be achieved by welding with laser and arc energy sources in close proximity. The high intensity laser forms a vapor cavity, or keyhole, leading to a large increase in weld depth, and welding speed is typically higher during laser welding. On the other hand, an arc creates a wide weld pool, which is useful for bridging gaps between plates, and can add material to the weld with a consumable electrode. However, hybrid laser-arc welding can lead to unique defects not found in conventional arc welding, including keyhole porosity and root defects. Porosity from keyhole instability and collapse can lead to very large bubbles (> 1 mm) becoming trapped as pores in the weld metal during partial penetration welds, while, during full penetration welds, weld metal can fall out of the weld and solidify as nuggets, a form of root defect. The solidification microstructure, root defect formation, keyhole porosity, and keyhole dynamics are studied in-depth using a combination of tools including a three dimensional heat transfer and fluid flow model, X-ray computed tomography, and inline coherent imaging. The results of this work produced a solidification map for Alloy 690, clarified the phenomena affecting root defect formation, developed hybrid welding solutions to keyhole porosity, and documented the keyhole growth rates during laser welding.

As a fabrication technology, welding presents a number of technical challenges to the designer, manufacturer, and end-user of the welded structures. Both weld residual stress and distortion can significantly impair the performance and reliability of the welded structures. They must be properly dealt with during design, fabrication, and in-service use of the welded structures. There have been many significant and exciting developments on the subject in the past ten to fifteen years. Measurement techniques have been improved significantly. More importantly, the development of computational welding mechanics methods has been phenomenal. The progresses in the last decade or so have not only greatly expanded our fundamental understanding of the processes and mechanisms of residual stress and distortion during welding, but also have provided powerful tools to quantitatively determine the detailed residual stress and distortion information for a given welded structure. New techniques for effective residual stress and distortion mitigations and controls have also been applied in different industry sectors. Processes and Mechanisms of Welding Residual Stress and Distortion provides a comprehensive summary on the developments in the subject. It outlines theoretical treatments on heat transfer, solid mechanics and materials behavior that are essential for understanding and determining the welding residual stress and distortion. The approaches for computational methods and analysis methodology are described so that non specialists can follow them. There are chapters devoted to the discussion of various techniques for control and mitigation of residual stress and distortion, and residual stress and distortion results for various typical welded structures are provided. The second half of the book looks at case studies and practical solutions and provides insights into the techniques, challenges, limitations and future trends of each application. This book will not only be useful for advanced analysis of the subject, but also provide sufficient examples and practical solutions for welding engineers. With a panel of leading experts this authoritative book will be a valuable resource for welding engineers and designers as well as academics working in the fields of structural and mechanical engineering.

Laser-Arc Processes and Their Applications in Welding and Material Treatment presents a comprehensive and timely overview of laser-arc processes for material joining and treatment, which is a current and developing research area. The authors review existing methods for combined welding and associated processes and describe theoretical investigations of the stationary combined discharge induced by focused laser radiation of CW CO2-lasers affecting the DC arc plasma. The volume also details the main principles of integrated plasma torches together with their applications in the joining and treatment of materials.