This text equips the reader with an understanding of the essential scientific and technical basis of welding, whilst not losing sight of the practicalities of the process. The approach is suited to students who intend to go on to supervise and inspect welding work, and as a background book for craft welders wanting to deepen their understanding of the process, or as an introduction for undergraduate engineers. The second edition has been fully updated to take into account the new developments in welding technology as well as changes in safety requirements, and those arising from the harmonization of British and European standards, most particularly with European practice and terminology.