Isothermal compression tests of 316LN stainless steel at temperatures ranging from 1000 to 1200 degrees C and strain rates from 0.01 to 10 s(-1) were performed on Gleeble thermo-simulation machine. Based on hyperbolic sine function, the constitutive equations of 316LN stainless steel and hot processing maps during the hot deformation process were established. The flow stresses were corrected via considering the temperature rise induced by plastic deformation and friction during the test process. In addition, by taking the influence of strain on flow stress into account, a unified constitutive model for predicting flow stress was proposed. The flow stress predicted by the constitutive equations shows good agreement with the corrected stress when R is 0.992 and ARRE is 4.43%. According to the dynamic material model presented by Prasad, hot processing maps for hot working condition were established based on the effect of power dissipation and instability coefficient associated with various kinds of temperatures and stain rates. Subsequently, efficiency of power dissipation and instability coefficient were interpreted based on hot processing maps under a series of strains, temperatures and strain rates. The results show that efficiency of power dissipation increases gradually with the increasing temperature and the decreasing stain rate, and it is noted that the maximum of efficiency of power dissipation is 0.38. An optimum zone for 316LN stainless steel is obtained and verified effectively by the analysis of microstructure.
