Inert gas-shielded welding arc behavior and metal transfer characteristics

An investigation of inert gas-shielded 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 + 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 + 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 + oxygen shielding gas. The transients or disturbances were frequently associated with drop severance from the filler wire and with formation of undesirable spatter. Electrical disturbances were not present in similar arcs in argon or argon + oxygen shielding gases.