Patent GB-565219-A (GB)
Title: Improvements in or relating to electric arc welding
IPC: B23K9/14
Filed: 1943-03-05
Abstract: 565,219. Uniting by fusion. MARTIN, H., and MUREX WELDING PROCESSES, Ltd. March 5, 1943, No. 3629. [Class 83 (iv)] In electric arc welding an upper plate to a metal backing member, such as an under plate, through spots formed from the front surface of the plate and penetrating through the plate to the surface of contact between the plate and backing member, a coated metal electrode is supplied with such high values of electrical energy that when the arc is struck between the electrode and the surface of the upper plate, particles of the core wire are expelled violently from the electrode tip so that the coating forms an insulating cup beyond the tip, the electrode is then pressed against the work so thatthe cup is maintained in contact therewith and the arc is maintained under these conditions so that it penetrates the upper plate to form a cavity therein, whereupon weld metal is deposited until the cavity is filled up. When the arc is struck the confining effect of the cup on the arc facilitates the displacement of the metal of the plate immediately beneath the electrode and thus facilitates the formation of the hole in the plate. Part of the displaced metal is removed in the form of vapour or spray and part builds up round the periphery of the zone where the hole is being formed. The electrode is pressed down on to the -work, the cup acting as an insulating spacer and as the electrode burns away and metal is blown from the hole the electrode moves downwardly with the spacer -always in contact with the solid metal at the bottom of the hole. When the hole is of such size to ensure fusion of the underplate the travel of the electrode towards the work is discontinued so that the arc lengthens due to burning away of the electrode and when the cup comes away from contact with the molten metal built up round the periphery of the hole, the molten metal runs into the hole, which is filled by molten metal deposited from the core of the electrode. Eventually current value is so reduced that metal except in the form of vapour ceases to pass across the arc. The reduction in current may be facilitated by a retarded action choke coil or a series of choke coils or resist,ors inserted into the welding circuit by time-delayed contactors. When deposition of metal ceases, the arc flame melts over the surface of the small pool to facilitate escape of occluded gas or particles of slag before solidification. If the electrode coating contains metal powder to form a partial conductor of electricity, the arc may be struck with the coating material in contact with the work without dabbing the end of the electrode on to the work and then holding it off a short distance. The electrode 6 may be fixed in a holder 5 traversed by gravity on a guide bar 4, which together with a bar 8 is mounted on an insulated support 3 over the plates 1, 2 to be welded. When a hole of desired magnitude has been formed, travel of the electrode is discontinued by a stop 7 on the bar 8 and the hole is then filled up as described above. The holder may alternatively be positively actuated and the rate of travel then slowed down by a dashpot. A number of welding units may be fed off the same or separate phases of a three-phase current supply.