An approach to detecting the brittle transition temperature of steels by means of hardness testing and its applications

This paper describes a new nondestructive approach to measuring the brittle transition temperature of several steels by means of hardness testing. The transition temperature in hardness tests is defined as the intersections of the two straight-lines in the plot of the logarithmic Vickers hardness vs. the reciprocal of absolute temperature. The transition temperature of hardness were discussed in comparison with the results of the usual tensile test and a specially instrumented Charpy impact test. It was concluded that the first and second transition temperatures of hardness were equivalent to the ductile transition temperature and brittle transition temperature respectively. The approach has been applied effectively as surveillance measures of (1) distributions of brittle transition temperatures of pre-strained welded steel plates, and (2) increases of the nil ductility transition temperature due to neutron irradiation for nuclear reactor vessel steels.