Application of a modified hyperbolic sine creep rate equation to correlate uniaxial creep data vs. stress and temperature for creep resistant low chrome steel alloys

ABSTRACT

Modified hyperbolic sine minimum creep rate equations were used to correlate uniaxial minimum creep strain rate data of 1/2Cr-1/2Mo-1/4 V and Grade 22 steel alloys and to correlate creep life data of Grade 22 steel when coupled with the Monkman-Grant equation. Hyperbolic sine equations were selected because of their physical basis in dislocation creep and numerical stability. Both equations provided very good fits to minimum strain rate data over a wide range of temperatures and stresses. Reasonable correlations of a large Grade 22 creep life data set were obtained with goodness of fit nearly equivalent to those obtained with the Larson-Miller and Wilshire equations, and with more conservative predictions of long-term creep strength. However, all these equations provided a poor fit to the entire data set when only short-term data (t_r < 5,000 h) were correlated, and they predicted lower long-term creep rupture strengths vs. the full data set correlations.

KEYWORDS:

• Creep
• creep rupture
• minimum strain rate
• Monkman-Grant equation
• Larson-Miller equation
• Wilshire equation
• hyperbolic sine equation
• grade 22 steel
• 1/2Cr-1/2Mo-1/4V steel

Acknowledgments

This research was supported in part by the National Energy Technology Laboratory (NETL), sponsored by the U.S Department of Energy (DOE) Office of Fossil Energy (FE) Mickey Leland Energy Fellowship (MLEF) program, and administered by the Oak Ridge Institute for Science and Education (ORISE).

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Funding

This work was supported by the