The effect of section size on the transition fracture toughness of a silicon-killed CMn plate steel

Well founded, statistically-based equations are available for describing the transition fracture toughness of C-Mn steel in the size range 25-100mm thick. The statistical description accommodates the amount of any ductile tearing prior to cleavage and specimen size effects. In order to examine the extrapolation of these equations to smaller section sizes, fracture toughness tests have been performed on 10mm thick pre-cracked Charpy specimens and 13mm thick compact tension specimens. The influence of sidegrooving on the fracture toughness values obtained from the compact tension specimens was also investigated. The results showed that extrapolating the large specimen equation to smaller section sizes yielded conservative estimates of Fracture toughness. This was due, in part, to the broad range of compositions, heat treatments, etc. covered by the large specimen data. Sidegrooving was found to have a measurable reduction on the fracture toughnesses of the compact tension specimens.