FORGED STEEL MATERIAL FOR NUCLEAR POWER GENERATION DEVICES, AND WELDED STRUCTURE FOR NUCLEAR POWER GENERATION DEVICES

摘要

PROBLEM TO BE SOLVED: To provide a forged steel material for nuclear power generation devices, which exhibits excellent strength, toughness and hydrogen embrittlement crack resistance even after being subjected to stress relief annealing after being welded, and to provide a welded structure for nuclear powder generation devices, which is constituted by using a plurality of forged steel materials for nuclear power generation devices and welding the forged steel materials.SOLUTION: The forged steel material for nuclear power generation devices meets a specified chemical component composition, wherein the crystal grain size of a metallic structure is 4.5-7.0 in terms of the grain size number as determined in accordance with ASTM. It is preferred that the content of N is 0.0100 mass% or more when the mass ratio of the content of Al to the content of N, (Al/N) is 1.93 or more, and that the content of Al is 0.022 mass% or more when the mass ratio of the content of Al to the content of N, (Al/N) is less than 1.93.