Application of high strength MnMoNi steel to pressure vessels for nuclear power plant

Recent increase in output of nuclear power plant has been attained by enlar gement of major components such as pressure vessels. Such large components have: almost reached a size limit from the points of manufacturing capacity and cost in both forgemasters and fabricaters. In order to solve this prob lem, it must be beneficial to apply design by use of material of higher str ength, which brings reduction of pressure vessel thickness and weight. The Japan Steel Works Ltd. (JSW) has many manufacturing experiences of large in tegrated forgings made from high strength MnMoNi steel with tensile strengt h level of 620 MPa for steam generator (SG) pressure vessel, and has perfor med confirmation tests of its material properties. This paper describes the confirmation test results such as tensile and impact properties, nil-ducti lity transition temperature (NDT-T), static and dynamic fracture toughness, weldability including under-clad cracking (UCC) sensitivity, as well as me tallurgical factors which influence on such material properties. (C) 2001 E lsevier Science B.V. All rights reserved.