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Synopsis: An investigation of inert gasshielded consumable electrode arc behavior and metal transfer characteristics was undertaken on aluminum and steel in flat, vertical, and overhead welding positions with the use of argon, argon-f-5-per-cent(%) oxygen, helium and helium+ 5% oxygen shielding gases. Arc and metal transfer behavior were observed with high-speed motion pictures with the use of intense supplementary illumination to facilitate photography.Electrical behavior of the arc was examined during production of a considerable number of weld beads by recording oscilloscope traces of arc current or voltage on the high-speed pictures of the arc. Thus, relationships were observed between current transients and arc physical behavior. Arcs shielded with argon or a mixture of argon-|-5% oxygen, known commercially as sigma grade argon, were more stable and operated with less spatter than similar arcs in helium or helium-f-5% oxygen. Although addition of oxygen to argon was desirable, addition of oxygen to helium shielding gas did not improve arc behavior or metal transfer. Numerous large transients occurred in current and voltage of reverse polarity (RP) arcs in helium and helium-hoxygen shielding gas. The transients or disturbances were fre quently associated with drop severance from the filler wire and with formation of undesirable spatter.Electrical disturb ances were not present in similar arcs in argon or argon-(-oxygen shielding gases. D URING the past few years, consider able information from various sources has appeared about welding arc behavior with the use of consumable and nonconsumable electrodes in several shielding gases on a variety of base metals. Research to provide informa tion has been in progress at the Linde Air Products Company Laboratories con tinuously in connection with develop ment of Heharc* and sigma welding. This discussion is the third in a series of papers deaUng with the behavior of inert gas-shielded welding arcs.The first paper discussed voltage dis tribution in the arc core, heat transfer measurements and metal transfer be havior in steel, and aluminum welding with argon shielding. ^ More detailed * Registered trade-mark of the Union Carbide and Carbon Corporation. D. M. YENNINONMEMBER AIEE information on metal transfer was given in a second paper in which the mech anism of metal transfer in pure argon and in argon +5% oxygen mixtures, with the use of straight and reverse polarity on steel, stainless steel, and aluminum, was discussed.2 Information on metal trans fer appeared recently in an article de scribing research with coated electrodes.^ Investigation of arc and metal transfer behavior has now been extended to arcs shielded with argon, sigma argon, helium, and helium +5% oxygen mixtures op erating on steel and on aluminum in flat, vertical, and overhead welding. How ever, only a limited amount of data is presented for aluminum welding because the sigma-process behavior on this base metal has rapidly become well known. Currently, a large amount of research attention is being...

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