FORGED STEEL AND WELDED STRUCTURE FOR COMPONENTS FOR NUCLEAR POWER PLANTS

摘要

This 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 ratio of the content of Al to the content of N (Al/N) is 1.93 or more by mass, and that the content of Al is 0.022 mass% or more when the ratio of the content of Al to the content of N (Al/N) is less than 1.93 by mass. The forged steel material for nuclear power generation devices exhibits excellent strength, toughness and hydrogen embrittlement resistance even after being subjected to stress relief annealing after welding.