Method of manufacture

A method of electron beam welding (EBW) two components together along a joint 28 by moving the electron beam relative to the joint along an oscillating path that traverses the joint. Preferably the wavelength of the oscillating path 44a is greater than the diameter of the instantaneous weld pool 48 formed by the electron beam when it impinges on the components. The electron beam may therefore be moved sequentially along a plurality of oscillating paths 44a, 44b, 44c which are out of phase from one another, each of the oscillating paths extending the length of the joint, so that the entire joint is welded. The oscillating paths are preferably defined by harmonic functions or square waves and may have the same amplitude and wavelength. They may be produced by tilting, i.e. deflecting, the electron beam as it is moved relatively along the joint. Welding is preferably effected in a vacuum chamber surrounding the joint, with an electron beam gun mounted thereto. The method may be applied to the manufacture of pressure vessels for nuclear power plants, i.e. nuclear reactors.