Fabrication of Double Wall Tube by U-O Press Forming and Pulsed Gas Tungsten Arc-welding

Double walled tubes were trially fabricated by press‐forming and arc‐welding, as difficulty in fabrication was anticipated in the case of roll‐forming. U‐O press‐formed double walled sheets are TIG arc‐ welded. For determination of welding conditions, overlapped flat sheets were employed and butt‐welded including pulsed arc‐welding. Pulse from 1 to 100Hz is effective to obtain penetrated weld bead. With this, the double walled tube could be arc‐welded, which could not be achieved by conventional TIG arc‐welding.