Ni-based alloy pipe or tube for nuclear power

Patent metadata

Field	Value
Publication number	US-10550451-B2
Application number	US-201615739631-A
Country	US
Kind code	B2
Filing date	Jun 21, 2016
Priority date	Jun 26, 2015
Publication date	Feb 4, 2020
Grant date	Feb 4, 2020

Abstract

An object of the present invention is to provide an Ni-based alloy pipe or tube for nuclear power with reduced rate of SCC crack propagation. The Ni-based alloy pipe or tube for nuclear power according to the present invention is an Ni-based alloy pipe or tube having a wall thickness of 15 to 55 mm, having a chemical composition of, in mass %: 0.010 to 0.025% C; 0.10 to 0.50% Si; 0.01 to 0.50% Mn; up to 0.030% P; up to 0.002% S; 52.5 to 65.0% Ni; 20.0 to 35.0% Cr; 0.03 to 0.30% Mo; up to 0.018% Co; up to 0.015% Sn; 0.005 to 0.050% N; 0 to 0.300% Ti; 0 to 0.200% Nb; 0 to 0.300% Ta; 0% or more and less than 0.03% Zr; and the balance being Fe and impurities, wherein the Ni-based alloy pipe or tube has a microstructure being an austenite single phase, and the chemical composition satisfies the following equation, Eq. (1):

−0.0020≤[N]/14−{[Ti]/47.9+[Nb]/92.9+[Ta]/180.9+[Zr]/91.2}≤0.0015  Eq. (1).

For the element symbols in Eq. (1), the contents of the corresponding elements in mass % are substituted.

First claim

The invention claimed is:

1. An Ni-based alloy pipe or tube for nuclear power having a wall thickness of 15 to 55 mm, having a chemical composition of, in mass %:
0.010 to 0.025% C;
0.10 to 0.50% Si;
0.01 to 0.50% Mn;
up to 0.030% P;
up to 0.002% S;
52.5 to 65.0% Ni;
20.0 to 33.0% Cr;
0.03 to 0.25% Mo;
up to 0.018% Co;
up to 0.015% Sn;
0.005 to 0.050% N;
0 to 0.300% Ti;
0 to 0.200% Nb;
0 to 0.300% Ta;
0% or more and less than 0.03% Zr; and
the balance being Fe and impurities,
wherein the Ni-based alloy pipe or tube has a microstructure being an austenite single phase, and
the chemical composition satisfies the following equation, Eq. (1):
−0.0020≤[N]/14−{[Ti]/47.9+[Nb]/92.9+[Ta]/180.9+[Zr]/91.2}≤0.0015  Eq. (1),

wherein, for the element symbols in Eq. (1), the contents of the corresponding elements in mass % are substituted.

2. The Ni-based alloy pipe or tube for nuclear power according to claim 1 , wherein a rate of corrosion evaluated in accordance with ASTM A 262 C is 1 mm/yr or lower.

3. The Ni-based alloy pipe or tube for nuclear power according to claim 1 , wherein the chemical composition includes one or two or more elements selected from the group consisting of, in mass %:
0.005 to 0.300% Ti;
0.001 to 0.200% Nb;
0.001 to 0.300% Ta; and
not less than 0.001% and less than 0.03% Zr.

4. The Ni-based alloy pipe or tube for nuclear power according to claim 3 , wherein a rate of corrosion evaluated in accordance with ASTM A 262 C is 1 mm/yr or lower.

5. The Ni-based alloy pipe or tube for nuclear power according to claim 1 , wherein the alloy pipe or tube has been subjected to a solution heat treatment and a second heat treatment following the solution heat treatment, wherein the second heat treatment is performed at 690 to 720° C. for 5 to 15 hours.

6. The Ni-based alloy pipe or tube for nuclear power according to claim 1 , wherein:
the Ni-based alloy pipe or tube for nuclear power has a grain boundary with a plurality of grain-boundary precipitate particles precipitated thereon;
an average of major-axis lengths of the plurality of grain-boundary precipitate particles is 0.8 μm or smaller; and

a number of ones of the plurality of grain-boundary precipitate particles having a major-axis length of 0.8 μm or larger per micrometer of the grain boundary is less than 3.0.

7. The Ni-based alloy pipe or tube for nuclear power according to claim 6 , wherein the grain-boundary precipitate particles includes both a carbonitride and M 23 C 6 , and has no Cr-depleted layer.

8. The Ni-based alloy pipe or tube for nuclear power according to claim 7 , wherein a rate of corrosion evaluated in accordance with ASTM A 262 C is 1 mm/yr or lower.

9. The Ni-based alloy pipe or tube for nuclear power according to claim 6 , wherein a rate of corrosion evaluated in accordance with ASTM A 262 C is 1 mm/yr or lower.

10. The Ni-based alloy pipe or tube for nuclear power according to claim 6 , wherein the chemical composition includes one or two or more elements selected from the group consisting of, in mass %:
0.005 to 0.300% Ti;
0.001 to 0.200% Nb;
0.001 to 0.300% Ta; and
not less than 0.001% and less than 0.03% Zr.

11. The Ni-based alloy pipe or tube for nuclear power according to claim 10 , wherein a rate of corrosion evaluated in accordance with ASTM A 262 C is 1 mm/yr or lower.

12. The Ni-based alloy pipe or tube for nuclear power according to claim 10 , wherein the grain-boundary precipitate particles includes both a carbonitride and M 23 C 6 , and has no Cr-depleted layer.

13. The Ni-based alloy pipe or tube for nuclear power according to claim 12 , wherein a rate of corrosion evaluated in accordance with ASTM A 262 C is 1 mm/yr or lower.

Assignees

• Nippon Steel & Sumitomo Metal Corp
• Nippon Steel Corp

Inventors

• Takeda Kiyoko
• Kinomura Shoji

Classifications

• C22C19/05

  with chromium · CPC title

• C22F1/00

  Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working (apparatus for mechanical working of metal B21, B23, B24) · CPC title

• C22F1/10

  of nickel or cobalt or alloys based thereon · CPC title

• C22C19/055 Primary

  with the maximum Cr content being at least 20% but less than 30% · CPC title

• C22C19/053

  with the maximum Cr content being at least 30% but less than 40% · CPC title