Abstract: 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 (Al/N) of the content of Al to the content of N is 1.93 or more, and that the content of Al is 0.022 mass % or more when the mass ratio (Al/N) of the content of Al 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.

Abstract: 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 (Al/N) of the content of Al to the content of N is 1.93 or more, and that the content of Al is 0.022 mass % or more when the mass ratio (Al/N) of the content of Al 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.

Abstract: The invention provides a ferritic heat-resistant steel having excellent high-temperature oxidation resistance, especially excellent steam oxidation-resistant characteristics. In high-Cr ferritic heat-resistant steel, ultra-fine oxide particles having a size of not larger than 1 ?m are formed just below the oxide films and formed on the steel base, whereby the adhesiveness between the films and the base is enhanced. The ferritic heat-resistant steel contains Cr in an amount of from 8.0 to 13.0% by weight, and at least one of Rh and Ir in a total amount of from 0.3 to 5.0% by weight.

Abstract: The invention provides a ferritic heat-resistant steel having excellent high-temperature oxidation resistance, especially excellent steam oxidation-resistant characteristics. In high-Cr ferritic heat-resistant steel, ultra-fine oxide particles having a size of not larger than 1 &mgr;m are formed just below the oxide films and formed on the steel base, whereby the adhesiveness between the films and the base is enhanced. The ferritic heat-resistant steel contains Cr in an amount of from 8.0 to 13.0% by weight, and at least one of Rh and Ir in a total amount of from 0.3 to 5.0% by weight.

Abstract: The invention provides a ferritic heat-resistant steel having excellent high-temperature oxidation resistance, especially excellent steam oxidation-resistant characteristics. In high-Cr ferritic heat-resistant steel, ultra-fine oxide particles having a size of not larger than 1 &mgr;m are formed just below the oxide films and formed on the steel base, whereby the adhesiveness between the films and the base is enhanced. The ferritic heat-resistant steel contains Cr in an amount of from 8.0 to 13.0% by weight, and at least one of Rh and Ir in a total amount of from 0.3 to 5.0% by weight.

Abstract: High chromium ferritic steel containing chromium (Cr) in amount of 7˜12 weight %, one or two elements of molybdenum (Mu) and tungsten (W) as a solid-solution strengthening element, and one or more of elements for forming a MX carbonitride(s) is heat-treated at a temperature higher than both solid-solution temperature of the element(s) for forming the MX carbonitride(s) and a precipitation starting temperature of 6 ferrite for 5 seconds or longer, cooled at a rate of 0.5° C./s or faster, and subsequently tempered.

Abstract: The invention provides a ferritic heat-resistant steel having excellent high-temperature oxidation resistance, especially excellent steam oxidation-resistant characteristics. In high-Cr ferritic heat-resistant steel, ultra-fine oxide particles having a size of not larger than 1 &mgr;m are formed just below the oxide films and formed on the steel base, whereby the adhesiveness between the films and the base is enhanced. The ferritic heat-resistant steel contains Cr in an amount of from 8.0 to 13.0% by weight, and at least one of Rh and Ir in a total amount of from 0.3 to 5.0% by weight.