In the present study, an ultrafine grained 304L stainless steel with the average grain size of 300 nm was produced by a combination of cold rolling and annealing. 93% cold rolling and nnealing was performed at 700?C for 2h. Weldability of the UFG sample was studied by Nd: YAG laser welding under different welding conditions. Taguchi experimental design was used to optimize the effect of frequency, welding time, laser current and laser pulse duration on the resultant microstructure and mechanical properties. X-ray Diffraction (XRD), Optical Microscope (OM), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and microhardness measurement were used to characterize the sample after thermomechanical processing and laser welding. The results showed that the ultrafine grained steel had yield strength of 1000 Mpa and total elongation 48%, which is almost three times higher than coarse grained sample strength. The microstructure of the weld zone was found as a mixture of austenite and delta ferrite. The optimized parameter was selected frequency 55Hz, current 160A, weld time 30s and pulse duration 4 ms. The microhardness of the optimized welded sample (315 HV 0.5 ) was found to be close to the UFG base metal (350 HV) and was not seen any defect. Then parameters were modelling with neural network. Relation of parameters of welding, mechanical and tribologycal properties was investigated with neural network. Keywords : Ultrafine grained stainless steel, Laser welding, Nd: YAG laser welding, Taguchi experimental design, neural network.
