Effect of shielding gas composition and pulsed current frequency on geometry and nitrogen content of 304L austenitic stainless-steel welds

This study investigated the effects of pulsed current frequency and shielding gas composition on the weld metal geometry and nitrogen content. Austenitic stainless-steel sheets were welded by gas tungsten arc welding using 0, 0.5, 1, 2, 5, and 10 vol.% of nitrogen gas in argon shielding gas and pulse frequencies of 40, 80, 120, 160, and 200 Hz. Weld sections were recorded using a stereomicroscope. Weld depth and cross-section of the weld metal were measured by ImageJ${}^{\circledR }$ software and their changes were recorded. Nitrogen analysis tests were performed on the weld metal and, the results were analyzed. Investigations revealed that by increasing the nitrogen content of the shielding gas up to 10 vol.%, the nitrogen content of the weld metal almost doubles at the maximum nitrogen level. This increase was more considerable at higher current frequencies. Also, by increasing the pulsed current frequency, the weld pool and the weld metal depth-to-width ratio increased to 37 % and 44 %, respectively, at the maximum level of shielding gas nitrogen. In addition, at the frequency of 200 Hz, increasing nitrogen led to an 86 % and 72 % increase in the weld pool and the weld aspect ratio, respectively.