Effects of nitrogen, oxygen and hydrogen gases added to argon gas on MIG-welding of aluminum alloys

Abstract

Studies were made on the effects of nitrogen, oxygen, and hydrogen gases added to argon gas on the weldability and properties of MIG welds of aluminum alloys.Tests were carried out to observe appearance, shape and depth of penetration, mechanical properties, porosities, structures and other properties of welds. The results obtained were as follows;(1) The addition of nitrogen was considered to be effective in practical application for increasing the depth of penetra tion, tensile strength, and refining of the structure in welds.In commercially pure aluminum, it decreased the porosities of welds with no formation of scale on bead surface; while, in Al-Mg alloys, it formed the brown scale on bead surface and the porosities were not always decreased.(2) The addition of oxygen was considered to be adaentageous in practical application, because it increased the depth ofpenetration and decreased the porosities of welds. However, its addition of above 5% was harmful owing to the puckering and formation of excessive oxide film (white scale) on the bead surface.(3) The addition of hydrogen was harmful, because it remarkably increased the porosities, resulting in decreasing of the mechanical properties of welds.