Shizuo Ukita

High-speed DCEN TIG welding of very thin aluminium sheets with magnetic arc control

The TIG welder is generally used for butt welding of thin aluminium sheets. When industrial very thin aluminium sheets of less than 0.4 mm thickness as used in the manufacture of heat exchangers are being welded, however, butt welding by the conventional TIG welder is extremely difficult. This is due to the greater thermal conductivity and thermal expansion coefficient of aluminium base metal as compared with other materials such as steel. For this reason, the base metal and weld periphery is preheated by the arc during arc welding. Because of the very thin gauge of the material being welded, strain deformation generated just ahead of the welding zone causes butt weld misalignment. Particularly in the case of AC or wire-plus DCEP polarity, a largediameter pure tungsten electrode is used, making arc concentration difficult. Under these conditions, it is therefore difficult to achieve successful welding. Some of the authors have investigated butt welding of very thin aluminium sheets by the two techniques of:

Effects of shielding gas flow properties on ultra‐high‐speed DCEN TIG welding of ultra‐thin aluminium sheets

Summary Butt‐welding of O.3 mm ultra‐thin aluminium sheets using a conventional inverter‐controlled TIG welder at the ultra‐high welding speed of 12 000 mm/min has been developed by nozzle improvements. The following welding process features were found and nozzle improvements appropriately sought: By use of DCEN polarity and fine 2% Th‐W electrodes of 1.0 and 1.6 mm dia., arc spreading can be prevented and the heat responsible for base metal strain can be prevented from flowing into the zone not yet welded. Butt‐welding is performed by the technique of clamping the aluminium base metal between two 30 mm thick Cu plates and allowing the heat from the base metal to escape to the Cu plates. Butt‐welding becomes more difficult when the welding speed exceeds 6 000 mm/min. This is due to the fact that, as the welding speed increases, the arc is progressively dragged backwards (towards the bead formation zone), being dislodged from its position inside the stable shielding gas atmosphere, resulting in arc instabi...

Oxygen and Nitrogen contents of Multilayer Weld Metal by Submerged Arc Welding

This study was made on the oxygen and nitrogen contents and notch toughness of the multilayered weld metal produced by submerged arc welding.The results obtained are summarized as follows.(1) The oxygen content of multilayered weld metal increased as the number of layered weld metal increased.(2) The nitrogen content of multilayered weld metal is almost constant irrespective of the number of layered weld metal.(3) The silicon content of multilayered weld metal increased as the number of layered weld metal increased, and the oxygen content of multilayered weld metal shows the similar tendency.(4) The manganese content of multilayered weld matal increased by MnO included flux, and decreased by flux without MnO as the number of layered weld metal increased.(5) The carbon content of multilayered weld metal decreased as the number of layered weld metal increased.(6) The impact value of multilayered weld metal is roughly constant, but the value of last layered weld metal decreased slightly.(7) The oxygen and nitrogen contents of weld metal does not change remarkablly irrespective of heat treatment.(8) The oxygen content of weld metal increased as the welding current increased, but the nitrogen content in weld metal decreased as the welding current increased, and the impact value of weld metal generally decreased as the welding current increased.