Low-temperature tensile properties, notch and fracture toughness of steels for use in nuclear power plant Original Research Article

The tensile and toughness properties of eight steels with yield stresses of 265–1003 MPa in plates of thickness 20–60 mm and a microstructure of polygonal ferrite and pearlite, quenched-and-tempered ferrite and pearlite, and tempered martensite were determined in the interval from ambient temperature to the nil-ductility temperature (NDT)−20 °C. It was found that the yield stress and tensile strength were increased after strain ageing and testing at the NDT±20 °C. Uniform elongation was greatly diminished after strain ageing and it was slightly increased at the NDT±20 °C. The reduction of area was only slightly decreased after strain ageing, even at testing temperatures down to NDT−20 °C. The greatest notch toughness was found for the steel with a microstructure consisting of quenched-and-tempered ferrite and pearlite. A new equation is derived which relates notch and fracture toughness in the temperature range NDT±20 °C and is valid for the lower shelf-notch toughness region.