Properties of hand-welded laser joints

Abstract

Laser welding technology is a rapidly developing field of material joining. Compared to traditional welding methods, it has been relatively little studied. This article presents the results of tests on welded test joints made of stainless steel, using three types of shielding gases: nitrogen, argon, and a mixture of argon with hydrogen. Strength tests were conducted on hand-held laser welded joints, the chemical composition of welding fumes, and the corrosion resistance of test joints in neutral salt spray (NSS). Strength testing in a static tensile test showed that the welding process of X5CrNi18-10 (AISI 304) steel did not significantly reduce most parameters. None of the tested specimens fractured in the weld or in the HAZ zone, regardless of the type of shielding gas. The tensile strength for all specimens was at a similar level, only slightly lower compared to the steel before welding. The corrosion resistance test using the NSS test revealed a greater susceptibility to corrosion in welded joints made under a pure nitrogen shield. The first corrosion spots appeared after only 8 days of testing. The highest corrosion resistance was demonstrated by plates welded in a shielding gas mixture of argon with added hydrogen. An analysis of welding fumes was conducted for test joints welded. The content of manganese oxides, iron oxides, and nitrogen oxides was analyzed. Analysis of the content of manganese oxides and iron oxides in welding fumes showed a significantly higher concentration of these substances during welding in a nitrogen shield. The concentration of substances harmful to health was approximately 20% higher than during welding in an argon-hydrogen mixture shield. The results of the study indicate that the reducing properties of hydrogen have a beneficial effect on welders’ working conditions and on corrosion resistance, without reducing the strength properties of the welded joints.