Preface

More than 50 years have passed since a laser beam was first recognized by the irradiation of a pulsed ruby laser. Since then many characteristic lasers such as high-power CO₂ lasers, fiber-delivered YAG lasers and short-wavelength Excimer lasers have been utilized in various industries. Recently, high-efficiency diode lasers, high-quality disk lasers and high-power, high-brightness and compact-sized fiber lasers have been developed and are receiving considerable attention. Moreover, the second or third harmonic solid-state laser, called the green or ultra-violet laser, and the ultra-short pulse laser, often referred to as a femtosecond (fs) or nanosecond (ns) laser, have been developed to search for new applications. Accordingly, a variety of laser materials processing techniques including removal processes such as cutting and drilling, joining processes such as welding, brazing and soldering, surface modification treatments such as transformation hardening, cladding and annealing, have now been developed. Especially recently, peripheral apparatuses such as jigs and fixtures, monitoring systems and focusing optics, have been incorporated into the automation lines for welding, cutting and drilling to improve these processes. Thus laser processing is expected to continue to be an indispensable technology for the twenty-first century.

Among laser materials processing technologies, laser welding is especially noted in conjunction with recent advances in laser apparatuses. An understanding of laser welding mechanisms and phenomena is required for its proper application. Consequently, this book, which includes various laser or hybrid welding processes, welding of various kinds of materials, metallurgical, chemical and mechanical aspects, is planned to appeal to students, engineers, scientists and professors concerned with, or interested in, laser welding. The book is divided into four parts: established laser welding technologies, laser welding of various materials, emerging laser welding technologies and applications of laser welding, covering almost all topics on laser welding.

The editor would like to express his appreciation for the cooperation and contribution of all the authors. Also, the editor would like to thank Ms Rachel Cox, Ms Anneka Hess, Ms Laura Pugh and Ms Sarah Lynch at Woodhead

Publishing Limited for their encouragement, help and hard work. The editor really hopes that this book is essential and useful to everyone who is concerned with laser welding, from beginners to experts or professionals, and that laser welding technologies will be more and more utilized and advanced all over the world.