Since magnetic properties of ferromagnetic steels have a good correlation with their mechanical properties, those mechanical properties will be evaluated by magnetic measurements. An apparatus for measurement of BH curves of Charpy impact test pieces was therefore developed in order to evaluate the integrity of nuclear reactor pressure vessels nondestructively. In this paper, the operation of developed apparatus is demonstrated together with calibration of coercive field. It is also clarified that the evaluation of coercive field of the Charpy impact test pieces will be possible with an accuracy of better than 36 A/m. Additionally, a relation between the coercive field and the ductile–brittlement transition temperature is discussed.
