The experimental set-up of Electron-beam welding.

In the electron-beam process, electrons are emitted from the heated filament called the cathode and then focused into a beam which is directed at the welding point. This electron beam is accelerated by a high difference of potential voltage between the work-piece and the cathode filament. The cathode within the electron-beam gun releases the electrons, which travel through a series of focusing lenses, causing the electrons to converge on one another to form the beam. The electrons are not free flowing but are instead greatly accelerated by the tremendous difference of potential voltage between the cathode and anode. The speed of these accelerated particles range from 30,000 to 1,20,000 miles/sec, depending upon the voltage of the unit.

          When the beam strikes the welding point, the kinetic energy of the high-speed electrons is converted into heat. The heat is great enough to melt and fuse the metal. The greater the kinetic energy, the greater the amount of heat released and by this energy the welding process is completed.

Ans.(b) The soldering is a method of joining similar or dissimilar metals by means of a filler metal (called solder) which melts at a relatively low temperature i.e. less than 427ºC. Although soldering is done below 427ºC generally the solde3rs used have a melting point between 180ºC to 270ºC.