Patent Number: 
Section: claims

1. A jet pump beam made of improved heat-treated nickel base alloy, produced by preparing a precipitation-strengthened nickel base alloy material having a component composition containing by mass %, Ni: 50.0% to 55.0%, Cr: 17.0% to 21.0%, Nb+Ta: 4.75% to 5.50%, Mo: 2.8% to 3.3%, Ti: 0.65% to 1.15%, Al: 0.2% to 0.8%, C: 0.08% or less, Mn: 0.35% or less, Si: 0.35% or less, S: 0.015% or less, P: 0.03% or less, Cu: 0.30% or less, B: 0.001% or less, and Co: 0.05% or less, and Fe and inevitable impurities constituting a remaining part,the nickel base alloy material having been subjected to solution heat treatment at a temperature of 1010° C. to 1090° C., andthe nickel base alloy material having a γ″ phase (Ni3Nb) precipitate formed by subjecting the nickel base alloy material to age-hardening heat treatment at a temperature of 694° C. to 714° C. for 5 to 7 hours after the solution heat treatment. 2. The jet pump beam according to claim 1, produced from an improved heat-treated nickel base alloy material obtained by forming the nickel base alloy material into a product shape by machining or product processing after the solution heat treatment, and subsequently subjecting the material to the age-hardening heat treatment. 3. A method for producing a jet pump beam made of improved heat-treated nickel base alloy, comprising the steps of: preparing a precipitation-strengthened nickel base alloy material having a component composition containing by mass %, Ni: 50.0% to 55.0%, Cr: 17.0% to 21.0%, Nb+Ta: 4.75% to 5.50%, Mo: 2.8% to 3.3%, Ti: 0.65% to 1.15%, Al: 0.2% to 0.8%, C: 0.08% or less, Mn: 0.35% or less, Si: 0.35% or less, S: 0.015% or less, P: 0.03% or less, Cu: 0.30% or less, B: 0.001% or less, and Co: 0.05% or less, and Fe and inevitable impurities constituting a remaining part;forming the nickel base alloy material into a product shape by machining or cold working after subjecting the nickel base alloy material to solution heat treatment at a temperature of 1010° C. to 1090° C.; andsubjecting the nickel base alloy material formed into the product shape to age-hardening heat treatment at a temperature of 694° C. to 714° C. for 5 to 7 hours, thereby to precipitate a γ″ phase (Ni3Nb) in the nickel base alloy material. 4. The method for producing a jet pump beam according to claim 3, wherein the jet pump beam made of improved heat-treated nickel base alloy is produced by roughly forming the nickel base alloy material into the product shape by die forging after melting the nickel base alloy material, subjecting the roughly formed nickel base alloy material to the solution heat treatment at a temperature of 1010° C. to 1090° C., finishing the nickel base alloy material by the machining or the cold working, and subjecting the finished nickel base alloy material to the age-hardening heat treatment at a temperature of 694° C. to 714° C. for 5 to 7 hours, thereby to precipitate a γ″ phase (Ni3Nb) in the nickel base alloy material. 5. A jet pump beam used in a jet pump for forcibly circulating high-temperature and high-pressure water within a reactor pressure vessel of a boiling water reactor, the jet pump beam comprising:a body made of an elastic material;a vertical threaded hole provided in a center portion of the body, into which a head bolt is screwed; anda body top portion support surface for supporting a head bolt fixing device,wherein the body is made of precipitation-strengthened nickel base alloy having a component composition containing by mass %, Ni: 50.0% to 55.0%, Cr: 17.0% to 21.0%, Nb+Ta: 4.75% to 5.50%, Mo: 2.8% to 3.3%, Ti: 0.65% to 1.15%, Al: 0.2% to 0.8%, C: 0.08% or less, Mn: 0.35% or less, Si: 0.35% or less, S: 0.015% or less, P: 0.03% or less, Cu: 0.30% or less, B: 0.001% or less, and Co: 0.05% or less, and Fe and inevitable impurities constituting a remaining part, and the nickel base alloy material is subjected to solution heat treatment at a temperature of 1010° C. to 1090° C., and subjected to age-hardening heat treatment at a temperature of 694° C. to 714° C. for 5 to 7 hours after the solution heat treatment, to thereby precipitate γ″ phase (Ni3Nb) in the nickel base alloy material and provide a jet pump beam made of an improved heat-treated nickel base alloy material.