Abstract
This paper describes a non-destructive approach to measure the distribution of brittle transition temperature of welded steel plate by means of hardness measurement at low temperature. The transition temperature in this hardness test is defined as the intersections of two linear stages in the description of the logarithmic Vickers hardness versus the reciprocal of absolute temperature. The two intersections were found in the range between room temperature and -196°C. The higher one is called as the first discontinuity temperature and the lower is the second discontinuity temperature. Both the temperatures are plotted as a function of distance from the center of welding, and compared with the result by usual Charpy impact test. The hardness method has a special advantage for the case to change the properties in various ways in the narrow range as the heat affected zone by welding.
The characteristics of the three stages in the temperature dependency of hardness are discussed from the observations of the deformations around the Vickers indentations by means of microscope and roughness meter.
