NI-BASE ALLOY LARGE MEMBER, NI-BASE ALLOY WELDED STRUCTURE MADE OF SAME, AND METHOD FOR MANUFACTURING STRUCTURE THEREOF
A Ni-base alloy large-size member comprises a base material having strip-shaped carbide segregation, and a homogeneous modified layer formed on a welding groove surface by treatment using Friction stir processing and solution treatment. In addition, a Ni-base alloy welded structure is manufactured by welding the Ni-base alloy large-size member with other member constituting the Ni-base alloy welded structure, such as a member formed of ferrite steel or another Ni-base alloy large-size member under the condition that weld penetration depth is shallower than the thickness of the modified layer.
1 . A Ni-base alloy large-size member constituting a Ni-base alloy welded structure, comprising:
a base material of the member, having strip-shaped carbide segregation; and
a modified layer formed on a welding groove surface of the member by treatment using Friction stir processing and solution treatment.
2 . The Ni-base alloy large-size member according to claim 1 , wherein
thickness of the modified layer is 2 mm or more.
3 . A method for manufacturing a Ni-base alloy welded structure by welding the Ni-base alloy large-size member according to claim 1 , wherein
welding is performed in such a way that weld penetration depth is shallower than the thickness of the modified layer.
4 . The method for manufacturing a Ni-base alloy welded structure according to claim 3 , wherein
thickness of the modified layer is 2 mm or more.
5 . A welded type steam turbine rotor manufactured by the method for manufacturing a Ni-base alloy welded structure according to claim 3 .
6 . A welded type steam turbine rotor, comprising:
a high-temperature rotor part formed of the Ni-base alloy large-size member according to claim 1 ; and
a low-temperature rotor part formed of ferrite steel,
wherein the high-temperature rotor part is welded with the low-temperature rotor part under the condition that weld penetration depth is shallower than the thickness of the modified layer.
7 . A large-size pipe made of Ni-base alloy constituting boiler piping of a steam turbine plant, comprising:
a base material of the large-size pipe, having strip-shaped carbide segregation; and
a modified layer formed on a welding groove surface of the large-size pipe by treatment using Friction stir processing and solution treatment, and thickness of the modified layer is 2 mm or more.