THE conversion of the kinetic energy of a beam of electrons into heat on striking a metal work‐piece has been known for a very long time, a patent was in fact taken out for an electron beam melting device by Pirani in 1905. It was not, however, until the late 1950s that serious attempts were made to use more refined devices for welding. The main difference between the early melting machines and present day welding devices lies in the degree of power intensity due to beam focusing developments which lead to the discovery of a completely new welding mechanism.