Remaining life assessment of a CrMoV steel using the Z-parameter method

A Z-parameter method based on the Larson-Miller relationship is proposed to assess the remaining life of a CrMoV steel. It is found that the non-linear master curve of stress sigma vs Larson-Miller parameter P of the steel can be expressed as: P = 26.68 - 2.49 log sigma - 0.01sigma. A family of curves parallel to the master curve can be expressed as: P = Z - 2.49 log sigma - 0.01sigma, where the value of Z represents the deviation from the master curve which corresponds with the deterioration in rupture-properties. The deterioration in rupture properties is connected with the degradation of microstructure, namely the spheroidization of carbides in the pearlitic steel. A relationship between the value of the Z-parameter and the level of spheroidization E can be expressed as: Z = 27.32 - 0.54E. A normal distribution is supported for the value of the Z-parameter by both normal probability plotting paper and Shapiro-Wilk normality tests. (C) 2004 Elsevier Ltd. All rights reserved.