The single steel for a nuclear power generator of the present invention satisfies a predetermined chemical composition and the grain size of the metal structure is 4.5 to 7.0 in terms of particle size according to ASTM. When the mass ratio of Al and N (Al / N) is 1.93 or more, when the N content is 0.0100 mass% or more and less than 1.93, the Al content is preferably 0.022 mass% or more. Such a single steel material for nuclear power generation equipment is excellent in strength, toughness and hydrogen cracking resistance even after stress relieving annealing after welding.
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