Welding laser beams is one of the essential parts of in automobile manufacturing used for joining plates. In this paper, for the first time, simulation of of joining stainless steel to low carbon steel was carried out. For this purpose, at first, thermal analysis was carried out by finite element method and of temperature profile and the dimensions of the melting area was gained as results. This was followed by mechanical analysis. The thermal analysis results were stored in a mechanical element as history to obtain the thermal conditions of the material. As results of this analysis, the strain of elastic and plastic as well as the amount of residual stress The results show that low carbon steel passes through in , because of higher thermal conductivity. Also, low carbon steel saves more residual stress due to higher yield stress. For validation of simulated model, two plates of 304 stainless steel with similar parameters the simulated model by laser welding. Comparing the results obtained from the experimental model with the simulated model shows a very good agreement.

Pulsed laser welding have a wide application in welding of thin sheet because of high intensity of its localized heat source. In the current study, 3 experimental tests with low, medium, and large level of energy and also, the 3D finite element simulation of Nd:YAG pulsed laser welding in thin sheet AISI316L have been done. Thermal analyzes were done with ABAQUS software in transient heat transfer. In order to increase the accuracy of thermal model, heat losses were considered as convection, radiation, and thermal conduction. 3 thermal models with different heat flux distribution as Gaussian surface, Gaussian volume, and conical volume were used. The main aim of this study is the selection of best thermal model between 3 mentioned thermal models to estimate the melt pool geometry with high accuracy. In addition, with defining and applying the shape factor in 3 thermal models, the finite element analyses were carried out in order to enhance the precision of estimated melt pool geometry. After thermal analysis, the melt pool geometry dimensions are extracted for each of the mentioned thermal models and compared with experimental results. Results show that thermal analysis with Gaussian surface model have the melt pool geometry accurately just in welding with low energy. Also, the conical model could estimate the melt pool geometry in all levels of energy with acceptable accuracy. Therefore, the pyramidal thermal model can be selected as the most suitable model for simulating pulsed laser welding in thin steel sheets.

The Nd: YAG pulsed laser welding process with different speed and shielding gas was applied on 2205 duplex stainless steel. The effects of different parameters on the microstructural evolutions and mechanical properties were investigated. Four different zones with different secondary austenite contents were observed in the weld microstructure. By changing the shielding gas from argon to nitrogen, the secondary austenite percentage was not significantly varied. The secondary austenite fraction was showed about 38% reduction with increasing the welding speed. The weld penetration depth decreased with changing the shielding gas from argon to nitrogen (about 26% and 14% reduction at speed of 3.8 and 8.3 mm/s, respectively) and increasing the welding speed (about 43% and 34% reduction under shielding gas of argon and nitrogen, respectively). The variations in microhardness values along the weld line were correlated to the microstructural characterizations. Changing the welding speed had no significant effect on the microhardness variations, but changing the shielding gas from argon to nitrogen caused a significant increase of microhardness.