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

摘要

A forged steel for components for nuclear power plants meets a specific chemical composition. The grain size number of a metal structure thereof is 4.5 to 7.0 in terms of ASTM grain size number. It is preferred that the content of N is 0.0100 mass% or more when the mass ratio (A1/N) of the content of A1 to the content of N is 1.93 or more, and that the content of A1 is 0.022 mass% or more when the mass ratio (A1/N) of the content of A1 to the content of N is less than 1.93. The forged steel for components for nuclear power plants exhibits excellent strength, toughness and hydrogen cracking resistance even after being subjected to a stress relief heat treatment subsequent to welding.