Representation of the High-Temperature Tensile Behavior of Reannealed Type 304 Stainless Steel by the Voce Equation

Tensile tests were performed on a reference heat of type 304 stainless steel (heat 9T2796) in the laboratory reannealed condition. Testing temperatures ranged from 25 to 760 deg C (77 to 1400 deg F) and strain rates were varied from 1.5 × 10⁻⁶ to 8.3 × 10⁻²/s. Several models were developed to represent the tensile curves, and each model was restricted to a specific range of applicability. For the inelastic strains below 0.001 a Ludwik-type formulation was developed; it was independent of strain rate but applicable for temperatures up to 760 deg C. For the strain range 0.001 to 0.05 a second Ludwik-type formulation was developed with minimal strain rate dependence, and the model was restricted to temperatures not exceeding 593 deg C (1100 deg F). For inelastic strains above 0.001 an alternative model was based on the Voce equation. The Voce model was applicable for all temperatures and strain rates and for strains to the uniform strain at the ultimate strength. The ability of the Voce model to represent tensile behavior at strain rates well below those that are practical in the laboratory experimentation was checked by comparing predicted ultimate tensile strength data against creep strength data for minimum creep rates corresponding to the tensile strain rates. The agreement was good. The ability of the Voce model to predict uniform strain behavior was also examined. In the creep range the Voce model overestimated uniform strains for temperatures below 649 deg C (1200 deg F) and underestimated them for temperatures above 649 deg C (1200 deg F).