The Influence of the Shielding Gas to the Static and Dynamic Strength Properties of Laser Welded Workhardened Nitrogen Alloyed Austenitic Stainless Steel

Abstract

As an interstitial atom, nitrogen strengthens the structure of austenitic stainless steel (ASS). It therefore has been used to increase the strength of ASS. On the other hand, work hardening of ASS is a common method to increase the strength of the sheet product. When a work-hardened structure is welded, the strength properties decreases at the melted zone and the heat-affected zone (HAZ) of the weld. The nitrogen content can also be reduced by the effect of the heat input of the weld. Because the width of the soft area of the HAZ depends on the energy input of the weld, the strength of the weld depends on energy input. Therefore, laser welding provides better strength to the welded structure. The role of the shielding gas is also significant. Argon shielding gas is inert, but nitrogen used as a shielding gas can strengthen the weld metal and HAZ microstructure. In this study, the effect of different shielding gases in the laser welding of AISI 201 LN TR type work-hardened ASS are tested and the results are reported. Both non-destructive material and destructive material tests are performed. According to the results of the tensile test, the use of nitrogen as a shielding gas strengthens the laser-welded structure. The results of the low-cycle fatigue test show that fatigue strength improves when nitrogen is used as the shielding gas.