Static and dynamic fracture mechanics characteristics of a fine grain low alloy structural steel

A fine grain, low alloy steel was used for the construction of a spherical PWR full pressure containment vessel. Fracture mechanics data had to be established for brittle fracture safety evaluation purposes. Compact Tension (CT) Specimens of the 2T-geometry and with thickness of the actual plates from 32 to 50 mm have been tested under quasistatic loading for the corresponding wall thickness and ST specimens for higher wall thickness. Internal clip gages according to ASK AN 220 have been applied for COD and J evaluation. In addition, Charpy-type specimens, manufactured and pre-cracked according to ASTM E 399-74 (Instrumented pre-cracked Charpy type) have been tested. An instrumented Schnadt type pendulum, with two different velocities (ratio 50/1) was used. Pendulum, measurement and registration equipment was according to ASK AN 425. Dynamic initiation K(Ic) and J(Ic) have been determined using peak or maximum load. Fracture mechanics data originating from CT and IPCT specimens are plotted against temperature; depending on the testing materials, results of both types of specimens fall in the same scatter band or outside. Rate sensitivity seems to be materials dependent (e.g. normalised, quenched and tempered base metal, weld metal or heat affected zone)