Effect of temperature on impact toughness of nuclear grade low-carbon tubular steel

Abstract In this study, the low-temperature impact toughness and tensile properties of nuclear grade low carbon tubular steel were systematically studied. A comparative discussion was conducted on the quantitative relationships between temperature and impact energy absorption, as well as between temperature and various tensile properties, by analyzing the microstructure and mechanical properties at the fracture surface. The results show that the impact toughness of steel decreases with a decrease in temperature, while the impact fracture mode gradually changes from the toughness mode to the brittle mode. Meanwhile, the dimples in the radial zone were larger than those in the fiber zone, whereas the shear lip zone exhibited the highest number of dimples during the ductile impact fracture of the test steel. A combination of quasi-cleavage planes and intergranular cracks was shown in brittle fractures. The reliability of the ductile-brittle transition temperature (DBTT) fitted by the Boltzmann function is well verified based on the change results of low-temperature impact toughness and tensile properties and on the analysis of macro and micro fracture characteristics of the fracture. The result not only enhances the understanding of material fracture behavior, but also provides a scientific basis for material selection in practical applications.