GB778785A - Method of applying hard-facing metals - Google Patents

Abstract

778,785. Making oil well tools; welding by fusion. UNION CARBIDE & CARBON CORPORATION. Jan. 14, 1955 [Feb. 18, 1954], No. 1239/55. Classes 83 (2) and 83 (4). A method of hard facing a metal workpiece W comprises fusing successive portions of the workpiece with an electric arc formed between an electrode E and the workpiece, shielding the arc and the fused metal P with a stream containing inert gas and projecting a stream of hard facing particles through the gas stream into the fused metal, the electrode and the stream of particles being continuously oscillated transversely to the welding path. In the preferred embodiment, hard metal carbide particles are supplied by a hopper H and a vibratory dispenser V to a flexible tube T which, together with the electrode E, is oscillated at a frequency of 40 to 120 cycles per minute by an eccentric K and a motor M so as to distribute the particles uniformly and increase the width of the deposited band. The workpiece W is a section of oil well tool joint mounted in a turning fixture and provided with grooves G to receive the particles, The electrode E is preferably non-consumable and of thoriated tungsten, and to prevent wandering of the arc and undercutting at the weld edges, is provided with a pointed end which melts to a form providing maximum current density at the point of discharge. It may be vertical, as shown, or inclined at an angle c, the optimum range of which is from 0 to 15 degrees. The tip of the electrode is located forward of a vertical centre line O-Y by an angle a which is chosen to suit the peripheral speed of the workpiece and may have a value between 0 and 20 degrees. The angles a and c control the contour of the band of hard facing material. A nozzle N supplies the shielding gas, which may contain argon or helium, while alternating current with super-imposed high frequency or direct current is supplied to the electrode E. To prevent cracking in the matrix surrounding the particles, the workpiece is preheated and a ferrous wire may be fed into the fused metal P or ferrous particles may be mixed with the carbide particles. The Specification gives details of welding speeds, particle sizes &c. for the production of facing bands with a width of # to ¥ inch. Reference has been directed by the Comptroller to Specification 718,866.