A Submerged Arc Welding (SAW) option that combined the advantages of AC and DC Submerged Arc Welding was not possible until now.A high speed one-side submerged arc welding process of welding speed up to 1.5m/ min (16mm) has been developed for shipping of double-hull VLCC. In the new process, welding wires and fluxes as same as for a ordinary process are used. Electrode numbers are increased from three to four. Leading two electrodes fuse a root of a groove and form a underside (uranami) bead. Trailing two electrodes shape a good surface appearance bead and penetration. In case of 16mm thickness plate, total 3,000A welding current of leading two electrodes and total 1,500A of trailing electrodes are necessary to obtain good one-side weld. The new system has been practically applied to block assembly lines
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