Electron beam welding (E.B.W.)
|Fig. 22-9 Electron beam welding.|
|Fig. 22-10 Examples of T.I.G. and E.B. welds.|
29. This system, which can use either low or high voltage, uses a high power density beam ofelectrons to join a wide range of different materials and of varying thickness. The welding machine ref. fig. 22-9, comprises an electron gun, optical viewing system, work chamber and handling equipment, vacuum pumping system, high or low voltage power supply and operating controls. Many major rotating assemblies for gas turbine engines are manufac- tured as single items in steel, titanium and nickel alloys and joined together i.e., intermediate and high pressure compressor drums. This technique allows design flexibility in that distortion and shrinkage are reduced and dissimilar materials, to serve quite different functions, can be homogeneously joined together. For example, the H.P. turbine stub shafts requiring a stable bearing steel welded to a material which can expand with the mating turbine disc. Automation has been enhanced by the application of computer numerical control (C.N.C.) to the work handling and manipulation. Seam tracking to ensure that the joint is accurately followed and close loop under bead control to guarantee the full depth of material thickness is welded. Focus of the beam is controlled by digital voltmeters. See fig. 22-10 for weld examples.