Fracture behaviour, structure and mechanical properties of A508 Gr. 4N Class 3 Grade Steel

Recent increase in output of nuclear power plant has been attained by enlargement of most major components such as pressure vessels. Such large components have almost reached a size limit from the points of manufacturing capacity. In order to solve this problem, it must be beneficial to apply by use of material of higher strength, which brings reduction of pressure vessel thickness and weight A508 Grade 4N is a high nickel pressure vessel steel with relatively high yield strength and a relatively low transition temperature. A study was undertaken to evaluate conventional as well as unconventional material properties of forging made of in our institute. This paper describes results of mechanical properties, structure and fracture behavior including nil-ductility transition temperature.