Z-Parameter Method for Life Prediction in Low Carbon Steels
In this paper, a Z-parameter method is proposed to relate creep rupture data and microstructure deterioration of three low carbon steels: Cr5Mo, 12Cr1MoV and 20 steels. A new analytic expression of the Larson-Miller parameter verse stress is supposed as: P =Z + C1 lgσ + C2 σ, where C1 and C2 are constants which determine the shape of the curves and related to materials, and the value of parameter Z represents the magnitude deviated from the master curve which corresponds with the deterioration in rupture properties. As the deterioration in rupture properties closely connects with the degradation of microstructure, namely the spheroidization of carbides in pearlite style steel, a linear relationships have been found between the value of Z-parameter and the level of spheroidization E which can be expressed as: Z = a1 + a2 E.
Young-Jin Kim, Dong-Ho Bae and Yun-Jae Kim
S. Q. Han et al., "Z-Parameter Method for Life Prediction in Low Carbon Steels ", Key Engineering Materials, Vols. 297-300, pp. 1758-1763, 2005