GB1235350A - Improvements in or relating to arc-welding processes - Google Patents

Abstract

1,235,350. Welding by fusion. OSAKA TRANSFORMER CO. Ltd. 19 Dec., 1968, No. 60465/68. Heading B3R. [Also in Division G3] In arc-welding, e.g. by flux-submerged arc, using a consumable or non-consumable electrode, the welding parameters, e.g. arc current, voltage and position of the electrode transversely of the joint, are controlled in accordance with measurements obtained from one or more detectors located behind the joint. In one embodiment (Figs. 1, 2), a recessed short copper backing bar 5, which slides in contact with the work at the same rate and in the same direction as the traversing electrode 2, supports one or more detecting elements 6, e.g. thermocouples, which measure the temperature at a point or points of the bar. the results being fed to a control unit 8 which controls the welding parameters in accordance with the deviations of the results from predetermined values. In a modification (Fig. 3, not shown), a long backing bar 5 secured to the work is contacted by a sliding conductive plate 9 supporting the detecting elements 6, the plate 9 being driven in synchronism with the electrode. In a second embodiment (Figs. 4, 5, not shown), the recess in the backing bar is flux-filled whereby, when the molten slag results, the width and height of the penetration bead may be controlled by control of the welding parameters. Where a short sliding backing bar is used, flux is supplied continuously into the recess through an opening in the bar, e.g. by the use of a carrier gas. Where a long backing bar contacted by a sliding conductive plate is used, the entire recess is packed with flux. In a third embodiment (Figs. 6, 7, not shown), the backing bar is insulated by layers (11) from the work, and the recess is filled with a material having a high resistance at a low temperature and low resistance at a high temperature, reversion to the high resistance occurring on cooling from the high temperature. Materials having this property are stated to be submerged-arc fluxes, glass, glass powder, glass tape and glass fibre. The work, this material, the backing bar and a detector including a resistor and ammeter, are connected in series in a power supply circuit additional to that supplying the welding current. Detection of the current flowing in this circuit, due to the heating and hence variation in resistance in the material, or detection of the corresponding resistance of the material is used to control the welding parameters. Where a short sliding backing bar is used, the material may be continuously fed into the recess, and where a long backing bar contacted by a sliding conductive plate is used, the entire recess is filled with the material. In all embodiments the work may be moved while the backing bar or the conductive plate is held stationary, or the work may be held stationary and the backing bar or the conductive plate moved. In an example, a submerged-arc flux having the composition: is used.