By using the Taguchi method with an L16 (45) orthogonal array, the conditions of the double loop electrochemical potentiokinetic reactivation (DL‐EPR) technique have been optimized to evaluate the different degrees of the precipitates among the sensitized AISI 316LN austenitic stainless steels. The optimum conditions under the highest resolution of DL‐EPR were approved to be 1.2 M sulfuric acid, 0.05 M potassium thiocyanate, 0.8 M sodium chloride, 40 mV/min scan rate, and 40 °C. Analysis of variance (ANOVA) was used to determine the effect of the control parameters on the degree of sensitization (DOS) difference. As a result of ANOVA, the sulfuric acid concentration had the most significant effect on the DOS difference among the five factors. The percent contributions of sulfuric acid (H2SO4), potassium thiocyanate (KSCN), sodium chloride (NaCl), scan rate, and temperature to the DOS difference were 53.22, 5.33, 21.74, 4.92, and 14.79%, respectively. Finally, the maximum DOS difference (6.7908) obtained from the confirmation experiment showed an approximate 11 times improvement.

The hot deformation behavior of AISI 316LN austenitic stainless steel was studied through isothermal hot deformation tests conducted on Gleeble 1500 thermo-simulation machine. By using Taguchi method with an L16 (4 3 ) orthogonal array, the hot deformation conditions including deformation temperature, strain rate and strain were optimized for obtaining minimum mean grain size of the steel. Analysis of variance was used for determining the effect of the hot deformation parameters on the mean grain size. The results suggested that the strain had the most significant effect on the mean grain size among the three factors. The percent contributions of deformation temperature, strain rate and strain to the mean grain size were 0.80 %, 2.45 % and 93.32 %, respectively. Finally, the confirmation experiment under the optimum conditions, i.e., 1050°C temperature, 0.01 s -1 strain rate and 0.7 strain was carried out. The observational mean grain size (11.4 μm) is approximately twelve times smaller than that of the initial microstructure.Keywords: 316LN / austenitic stainless steel / gleeble / hot deformation / taguchi method / grain size Schlüsselwörter: X2CrNiMoN17-11-2 / austenitischer Stahl / Gleeble / Warmumformung / Taguchi Methode / Korngröße

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