New findings in welding of structural steels

Abstract

Gas shielded arc welding is the most widely applied welding process in industry. H2 (1.0425) structural steel chosen can be welded very cost-effectively with VAC 60 welding wires in CO2 shielding gas. With only the replacement of a highly oxidising gas, i.e. CO2, with a less oxidising gas mixture, i.e. Ar+18% CO2, a nicer appearance of the weld face and a higher weld quality may be obtained. Still higher quality of welds may be accomplished by employing pulsed arc welding of structural steels. In the study and development of the existing welding process, special attention was paid to the metal transfer. In pulsed arc welding with VAC 60 wire in the protective gas mixture of Ar+18% CO2, the metal transfer is very smooth and uniform in a very wide range of welding parameters. Because of the low oxidising capability of the Ar+18% CO2 gas mixture and the very short time of droplet formation, however, in pulsed arc welding major chemical processes in the droplet will occur only in welding with a higher average welding current (281 A). Less alloyed surfacing welds with silicon and manganese will provide higher quality only because of the surfacing weld dilution resulting from the parent-metal fusion, i.e. penetration. In pulsed arc welding, a pulse shape and energy and base current may efficiently affect the degree of penetration.