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: Disclosed is a high-strength steel plate having a predetermined chemical composition, in which a microstructure of the steel plate at a depth of one-fourth to one half the thickness from a surface has an area fraction of bainite of 90% or more, an average lath width of bainite of 3.5 ?m or less, and a maximum equivalent circle diameter of martensite-austenite constituents in bainite of 3.0 ?m or less. The steel plate exhibits high strengths and good drop weight properties and is useful as structural materials for offshore structure, ships, and bridges, as well as materials for pressure vessels in nuclear power plants.

Abstract: The multistep fluid control valve comprises a valve case having a plurality of valve seats. A valve stem is provided in the valve case and is capable of being continuously or stepwise displaced axially. At least one valve body is shiftably mounted on the valve stem it is urged toward the corresponding one of the valve seats, but normally arrested at a position clear of the valve seat. This valve body closes the valve seat when the valve stem is moved a predetermined amount. At least one further valve body is provided axially in line with the valve stem so as to cooperate with a corresponding one of the valve seats. The further valve body is actuated by a further stepwise movement of the valve stem so that the corresponding valve seat is opened or closed by the further valve body.