Simulation of nitrogen transport and desorption in laser welds of 21Cr–6Ni–9Mn stainless steel

Abstract

Loss of nitrogen is a concern when welding nitrogen strengthened stainless steel alloys. Building on the current understanding of the underlying mechanisms, a three-dimensional simulation of conduction mode laser weld pool development using the volume of fluid technique was developed. Weld pools formed by a moving Gaussian heat input for two different laser power densities were simulated and the transport and surface desorption of nitrogen was tracked using nitrogen macroparticles. The penetration depth and width of the weld pool predicted by the simulation was comparable to the data derived from macrographs of welds made on nitronic 40 alloy. Additionally, the 25–32% predicted decrease in nitrogen composition of the weld fusion zone by the new rate law is comparable to the literature.

Keywords:

• Laser welding
• Nitronic 40
• 21Cr–6Ni–9Mn high nitrogen stainless steel
• Nitrogen transport
• Nitrogen desorption and loss
• Conduction mode laser welding
• Computational modelling

Acknowledgements

The authors would like to acknowledge the financial support and research opportunity from Los Alamos National Laboratories in conjunction with the National Science Foundation Industry/University Collaborative Research Center: Center for Integrative Materials Joining for Energy Applications (I/UCRC CIMJSEA). Funding was in part from National Science Foundation award no. 1034729. The authors would also like to give special thanks to Stephen Tate and Dr Stephen Liu at Colorado School of Mines for performing welds on Nitronic 40 and nitrogen content analysis as well as all their help with this work. The authors thank Dr Avraham Benatar for his help and advice on this manuscript. Additionally, thanks to Dr Sudarsanam S. Babu for the research opportunity as part of his I/UCRC center.