In this paper, maximum value of energy to break at Charpy impact test as a criterion of fracture toughness of AISI 316/A387 Gr.91 weld joints with ERNiCrMo-3 filler metal were obtained by optimization of pulesd current gas tungsten arc welding process parameters. The selected parameters were peak current, background current, frequency and on time percentage that were changed in three levels. Therefore a L9 orthogonal array of Taguchi design including nine experiments for four parameters with three levels (34) was used. Analysis of signal to noise (S/N) ratio indicated that optimized values of peak current, background current, frequency and on time percentage were 120A, 90A, 10Hz and 80%, respectively. The welded specimen with optimized parameters showed an energy to break at Charpy impact test value of 65J at -20°c. The obtained results also demonstrated that the most influence on energy to break values belonged to background current, frequency, peak current and on time percentage, respectively.
