Fiber Laser Welding in a Controlled Inert Gas Atmosphere: An Experimental and Numerical Investigation

In fusion welding, thermo-chemical reactions may take place among surrounding atmosphere particles and molten weld pool at high temperature gradients. The atmosphere particles such as oxygen, hydrogen and nitrogen may become part of final weld joint that severely affects the weld joint quality and weld metal properties. Therefore, the welding atmosphere and protection of weld pool plays a noticeable role on the quality of the final weld joint. Henceforth, in this chapter, fiber laser welding of austenitic stainless steel plates have been examined in two different ambient atmospheres. Firstly, the experiments are conducted in open atmosphere and in argon ambient atmosphere to study the characteristic difference between them. The experimental investigation specifies that the weld bead dimensions and aspect ratio are higher in case of argon atmosphere as compared to open atmosphere. The microstructures of heat affected zone (HAZ) and fusion zone (FZ) at both atmospheric conditions are analyzed. It is obvious from the experimental results that the top surface profile is smoother and very clear in case of welds at argon atmosphere. Moreover, in this work, the authors also reported an efficient conduction mode finite element based heat transfer model of linear fiber laser welding process using a volumetric heat source. The calculated weld bead dimensions using finite element model are compared with the experimentally measured results at similar process variables. Relatively fair agreement of the experimental results with model results entitles the robustness of the modeling approach followed here and reported in this work.