Abstract
This study deals with the generation of isochronous stress-strain curves for modified 9Cr-1Mo steel. Material property data ($s_{y}$, D, and m) from tensile tests and strain-time curves from creep tests were obtained at 550 ${^{\circ}C}$. On the basis of the experimental data, the creep curves were characterized by Garofalo’s creep model. The three parameters of $P_{1}$, $P_{2}$ and $P_{3}$ in Garofalo’s model could be optimized properly by a nonlinear least square fitting analysis. The three parameters showed a good stress dependency with a linear relation. However, the $P_{3}$ parameter, which represents the steady state creep rate, exhibited two-slope behavior with different stress exponents at a transient stress of about 250 MPa. The results verify that the long-term creep curves for G91 steel can be modeled by Garofalo’s model with only several short-term creep data. When the modeled creep curves are used, long-term isochronous curves of up to $10^{5}$ h can be successfully constructed.