GB826106A - Improvements in the arc cutting of fusible bodies - Google Patents

Abstract

826,106. Cutting by fusion. UNION CARBIDE CORPORATION. Feb. 19, 1958 [Feb. 20, 1957; June 17, 1957], No. 5351/58. Class 83 (4). [Also in Group XI] In the constricted-arc cutting of metals using an inert gas shielded non-consumable electrode E, Fig. 6, and a nozzle 138 with a constricted orifice 140, a stream of gas which is chemically active to the workpiece is introduced into the outer portions of the inert gas stream prior to its discharge through the orifice 140. The electrode E of thoriated tungsten is held in a collet H and is surrounded by a shielding gas tube 126 of refractory material into which the shielding gas, which may be nitrogen, argon, helium, hydrogen or mixtures thereof, is admitted from a pipe 110. Inlet and outlet conduits 112, 117 for cooling water lead to a water jacket J; the current supply lead 115 passes within conduit 117. A chemically active gas such as oxygen, air, carbon dioxide or water vapour is admitted through conduit 136 outside the tube 126 and into nozzle 138 which has a water jacket 144. For starting the cutting arc by ionizing the gas, a pilot arc is established by a high-frequency current supply between the electrode and nozzle. This current supply is stopped after the cutting arc has been established using direct current between the electrode and workpiece. An electric control circuit including solenoidactuated valves for the gases and water is described, Fig. 7 (not shown) and this enables the cutting action to be stopped if the torch runs off the edge of the workpiece or is raised or the water supply is interrupted or decreased. In other embodiments the shielding gas tube 126 is omitted and the active gas is admitted through ports in the constructed orifice, Fig. 1 (not shown) or in the nozzle between the orifice and electrode, Fig. 2 (not shown). The active gas may be water vapour admitted through a porous metal or ceramic lining to the orifice, Fig. 5 (not shown) or in another embodiment, Fig. 4, it may be atmospheric air admitted through lateral passages 40 between a main copper nozzle portion 12 and an annular portion 30 insulated from each other and supplied independently with current through resistors 36, 38 from a source S. The workpiece 16 need not be connected in the current circuit. Specific examples are given for cutting mild steel and aluminium and references are included to the cutting of magnesium, carbon steel, stainless steel, nickel and copper.