A procedure for extrapolating Charpy transition temperature from the data at other temperatures and in the case of incomplete transition curves

A procedure for extrapolating Charpy transition temperature of ferritic structural steels from the data at other temperatures has been developed based on generic equations describing the toughness dependencies of the Charpy ductile-to-brittle transition behaviour on material’s yield strength and upper-shelf toughness. These equations have been derived from an extensive data base comprising 510 different structural steels of the yield strengths ranging from 210 to 1 105 MPa and the upper-shelf toughness in the range of 38 to 335 J. As a case study, the procedure was applied to the assessment of Charpy-V data for SA-106 GrB grade unalloyed structural steels, with the aim at evolving a scheme for the estimation of Charpy-V transition temperature (T _40J /T _27J ) of a given steel at −29 °C from the Charpy data available at other temperatures. It was demonstrated that the procedure is capable of estimating whether a material will fulfil the 40 J (longitudinal), or 27 J (transverse), impact toughness requirement at −29 °C and, in the case the material fails to meet this requirement, providing an acceptance criterion in terms of an estimate to a temperature where the toughness requirement should become fulfilled. Using the present procedure, the analysed materials were characterised into three groups: those fulfilling the impact toughness criterion of 40 J at −29 °C, those that failed but met the corresponding acceptance criterion at comparatively low temperatures around −20 °C, and those that failed and exhibited comparatively high transition temperatures no more than −6…−13 °C. This way, the procedure not only screens those materials fulfilling the specified toughness requirement, but provides the end user with further knowledge on whether the failed material is likely to benefit from additional tests, or should some limitations be accepted for its further use.