Untitled research work

The development of three wires submerged arc welding techniques was carried out to produce line-pipes in the large diameter and heavy-wall-thickness from 20 to 50 mm by UOE process. Some con-siderations on the polarity or the phase of the transformer connections, the stream of a molten metal, the deposition rate and the flux consumption were studied to clarify the following.(1) A leading arc is directly occurred at a base metal and shows the gouging action. An arc voltage fluctuation of a leading arc is most stable in three wires. The molten metal is pushed out backward by a plasma and a magnetic force around a leading arc. The middle arc makes the stream of a molten metal slow down due to the collision against a leading stream, and the stream is changed to the transverse direction of bead to extend the bead width. An arc voltage fluctuation of middle arc is larger than others. An action of trail arc is to form a good bead appearance without an undercut. An arc voltage fluctuation of trail arc exists between a leading and a middle one.(2) The fluctuation of an arc voltage and the deflection angle of DC leading arc in a transformer con-nection of DC-AC-AC are bigger than those of the AC-AC-AC connection. A leading arc in the Scott connection between a leading and a middle wire is apt to incline toward a middle arc and encourages the backward stream of a molten metal, so that the bead toe results the wavy shape. A leading arc in the reverse V connection between a leading and a middle arc is apt to incline forward to relieve the back-ward stream of a molten metal, so that this connection is suited to be applied to a high current and/or a high heat input welding. (3) A deposition rate of wire is proportional to the sum of three wire's current, and independent on the kind of fluxes. A cross sectional area and a flux consumption are directly proportional to the heat input.