PrefaceThis edition represents a major revision of this encyclopedia@ changing its orientation to the authoritative information base of the American Welding Society@ and providing access to its resources.Welding technology becomes more complex with every passing year@ and has expanded to an extent that defies containment between the covers of a book. This encyclopedia presents as much information as is practical@ but it is impossible to provide an exhaustive report on every welding process@ variation@ application@ technique or material involved in the welding industry.The Editor hopes Jefferson??s Welding Encyclopedia will be a helpful resource to those who need authoritative welding information at their fingertips@ and that it will be an effective starting point for those pursuing further scientific or engineering information. Following are some significant additions to the Eighteenth Edition:Welding terms and definitions standardized by the American Welding Society are presented dictionary-style throughout the encyclopedia. They are identified by reference to Standard Welding Terms. Standard definitions are printed in italics.Consensus standards@ codes@ specifications@ recommended practices@ classifications@ methods@ and guides for welding processes and applications documented by AWS are appropriately referenced. Standards of related organizations are referenced when applicable.U.S. customary units are converted to the International System of Units (SI); conversion figures are appropriate to the application.Nineteen appendixes have been included; most of these supply technical information from major American Welding Society documents. Appendix 1 contains historical notes of interest to the welding community.A buyer??s guide is provided; companies or organizations listed were exhibitors at the 1996 AWS International Welding and Fabricating Exposition in Chicago.The primary editorial effort is directed to presenting new and updated material@ although some of the basics of early welding processes are retained from previous editions@ and much of the instructional material remains. An effort is made to meet the needs of persons associated with various areas of welding@ and persons at many levels of expertise who are working with available equipment@ old or new.Most of the information available to the welding industry@ and in this book@ is the result of a continuous sharing of information involving every sector of the industry and spanning several generations. Contributors include research and development groups from manufacturers of welding equipment and consumables@ universities@ fabricators and job shops@ as well as individual welders. All who are involved in the welding industry are grateful to those who have contributed and those who are continuing to develop and share technology. In that same spirit@ we welcome comments@ as well as contributions of further information.?