Method and device for arc welding

850,428. Welding by fusion. COMMISSARIAT A L'ENERGIE ATOMIQUE. Nov. 19, 1958 [Nov. 21, 1957], No. 37261/58. Class 83 (4). In a method of arc seam welding members in a vacuum, the gap between the members and the welding-electrode is ionized to enable the arc to be started or re-started by an electron beam focused on the members and operative only when no arc exists. The members 3 are mounted on a support movable relatively to a tungsten electrode 1 , in a chamber 4 that is evacuated by a pump 5. The secondary windings of high and low voltage transformers 6, 7, respectively, having primaries connected in parallel across the supply, are connected in series with the members 3 and the electrode 1 . Also connected to the secondary of the highvoltage transformer is a cathode 1 and a focusing electrode 2 which direct an electron beam on to the members 3 to ionize the gap. A triode 13 in a control circuit 11 is biased to conduct by a voltage derived from a resistance 12 in parallel with the arc. The output of the triode 13 energizes the saturating winding 10 of a saturable reactor having an impedance winding 9 in circuit with the primary of the high-voltage transformer 6 which energizes the cathode 1. When the arc strikes the triode 13 ceases to conduct and the impedance winding 9 prevents the transformer 6 from supplying current to the cathode to maintain the electron beam. The method may be applied to the welding of magnesium, beryllium and their alloys and zirconium.