Abstract: Z-parameter method based on the Larson-Miller relationship is proposed to assess remaining life of a 1Cr5Mo steel. The non-linear master curve of stress δ vs. LarsonMiller parameter P of the steel can be expressed as: P=29.608-5.085logδ. A familyof curves parallel to the master curve can be expressed as: P=29.608-Z-5.085loyδ, where the value of Z represents the magnitude deviated from the master curve. A relationship between the value of Z-parameter and the level of spheroidization E (microstructural degradation) can be expressed as: Z=0.203(E-1).

Key words: life assessment, spheroidization, carbides