New developments in advanced welding

Electron beam welding

U. D I L T H E Y, RWTH-Aachen University, Germany

7.1 Introduction

The history of electron beam technology goes back to the year 1869 when Hittdorf discovered electron beams. Thomson, in 1897, found out about their negative electron charge. In 1905, Pirani was first to use electron beams for fusion tests with metals (Schiller et al., 1977).

The principle of the technology is based on a beam of electrons that are accelarated by a high voltage and can so be used as a tool for treatment of materials such as in welding. Currently electron beam welding is firmly established in many manufacturing fields; especially in joining technology the electron beam has been generally accepted for its reliability and efficiency. The thickness of materials that can be joined ranges from thin plates of thicknesses of fractions of millimetres to thick plates of more than 150 mm in steel and over 300 mm in aluminium. Almost all electrically conductive materials can be welded and many such may be joined. The high power density ranges up to 108 W/cm2 (typical of electron beam welding) and the connected depth-to-width ratio of the weld ranges up to 50:1. These figures allow a large variety of possible applications of the joining process. As the electron beam is electromagnetically deflectable and effectively lacking in mass, progress in the field of control techniques and increased processor performances have extended the variety of applications and these are still increasing. In some cases electron beam welding is carried out in a vacuum chamber (with high or low vacuum) and in others the electron beam can be applied under normal atmospheric conditions. The different variations in conditions for electron beam welding are shown in Fig. 7.1.