FEATURES OF PHYSICAL AND METALLURGICAL PROCESSES DURING WELDING OF THIN-WALLED ALUMINUM ALLOY STRUCTURES USING LASER RADIATION

Abstract

This paper aims to study features of physical and metallurgical processes during welding of thin-walled structures made of aluminum alloys using laser radiation, including the effect of concomitant heating provided by a compressed electric arc of direct action, as well as the influence of distance between a center of anode region of compressed arc of a non-consumable electrode and an axis of laser radiation, on reduction of laser energy losses. To perform the study, modes of laser and laser-plasma welding are selected and correspondent experiments are carried out to determine the effect of specified distance, as well as metallographic analysis of experimental results is made. It is determined that applying the concomitant plasma heating in laser welding makes it possible to increase the penetration depth by 15–65% compared to conventional laser welding, including by improving radiation absorption. To improve absorption of radiation during laser-plasma welding, it is recommended that distance between a center of anode region of compressed arc of a non-consumable electrode and an axis of laser radiation should not exceed 1.0 mm, and in hybrid welding it should not exceed 0.5 mm. During laser welding of 7075 alloy, it is possible to obtain joints with sufficiently narrow seams with minimal energy input and lifetime of a melt pool. However, typical defects such as microcracks 10 –20 µm long in HAZ and oxide film inclusions in the root part of the remelted metal may occur. The use of concomitant local plasma heating during laser welding of 7075 alloy may provide reduction in graininess and increase in uniformity of hardness of joints in combination with elimination of formation of microcracks and oxide inclusions, which makes laser-plasma welding method more preferred.