A multi-level model for the analysis and prediction of creep and creep fracture of 2.25Cr–1Mo steel tubes

The creep and creep rupture properties of 2.25Cr–1Mo steel tubes have been analysed using the Wilshire equations. The observed behaviour patterns are then discussed in terms of the dislocation processes governing creep strain accumulation. A suitable statistical framework for analysing both the single and multi batch data available on this material is then specified. It is shown that ignoring the hierarchical nature present in many creep data bases, which has been the approach until now when using the Wilshire equations, leads to a serious and significant underestimate of the predicted safe life for this material. The model allows accurate predictions of long-term properties by extrapolation of short-term results for this steel.