Precipitation hardening martensitic stainless steel and steam turbine component made thereof

Patent metadata

Field	Value
Publication number	US-9873930-B2
Application number	US-201113292126-A
Country	US
Kind code	B2
Filing date	Nov 9, 2011
Priority date	Nov 9, 2010
Publication date	Jan 23, 2018
Grant date	Jan 23, 2018

Abstract

It is an objective of the present invention to provide a precipitation-hardening martensitic stainless steel having well-balanced properties of high mechanical strength, high toughness and good corrosion resistance properties. There is provided a precipitation-hardening martensitic stainless steel comprising: 0.10 mass % or less of C; 13.0 to 15.0 mass % of Cr; 7.0 to 10.0 mass % of Ni; 2.0 to 3.0 mass % of Mo; 0.5 to 2.5 mass % of Ti; 0.5 to 2.5 mass % of Al; 0.5 mass % or less of Si; 0.1 to 1.0 mass % of Mn; and the balance including Fe and incidental impurities, in which the mass % content of the Ti (represented by [Ti content]), the mass % content of the Al (represented by [Al content]) and the mass % content of the C (represented by [C content]) satisfy relationships of “0.5≦[Ti content]≦2.5” and “0.5≦[Al content]+2[C content]≦2.7”.

First claim

What is claimed is:

1. A precipitation-hardening martensitic stainless steel consisting of:
0.10 mass % or less of C;
13.75 to 15.0 mass % of Cr;
7.0 to 10.0 mass % of Ni;
at least one of Mo and W, wherein the sum of Mo and W is 2.0 to 3.0 mass %;
0.52 to 2.5 mass % of Ti;
0.5 to 2.5 mass % of Al;
0.5 mass % or less of Si;
0.1 to 1.0 mass % of Mn;
at least one of Nb and Ta, wherein the sum of Nb and Ta is 0.05 to 0.5 mass %;
0.5 to 1.0 mass % of Co;
0.5 to 1.0 mass % of Re; and
the balance being Fe and incidental impurities;
wherein the precipitation-hardening martensitic stainless steel has a uniform martensite structure with no δ-ferrite phase and residual austenite phase; a tensile strength of 1200 MPa or more; a 0.02% proof stress of 800 MPa or more; and a Charpy impact strength of 25.0 J/cm 2 or more, and
wherein the precipitation-hardening martensitic stainless steel has been subjected to a solution heat treatment at 900° C. to 950° C. followed by an aging heat treatment at 520° C. to 580° C.

2. The precipitation-hardening martensitic stainless steel according to claim 1 , wherein the incidental impurities are at least one of: 0.1 mass % or less of P; 0.1 mass % or less of S; 0.1 mass % or less of Sb; 0.1 mass % or less of Sn; and 0.1 mass % or less of As.

3. A long blade with a length of 48 to 60 inches made of the precipitation-hardening martensitic stainless steel according to claim 1 for a 3600 rpm steam turbine.

4. A rotor comprising the long blade according to claim 3 .

5. A steam turbine comprising the rotor according to claim 4 .

6. A thermal power plant comprising a 3600-rpm steam turbine,
wherein the 3600-rpm steam turbine comprises a rotor,
wherein the rotor comprises a long blade, and
wherein the long blade has a length of 48 to 60 inches and is made of the precipitation-hardening martensitic stainless steel according to claim 1 .

7. A precipitation-hardening martensitic stainless steel consisting of:
0.10 mass % or less of C;
13.75 to 15.0 mass % of Cr;
7.0 to 10.0 mass % of Ni;
both Mo and W, wherein the sum of Mo and W is 2.0 to 3.0 mass %;
0.52 to 2.5 mass % of Ti;
0.5 to 2.5 mass % of Al;
0.5 mass % or less of Si;
0.1 to 1.0 mass % of Mn;
at least one of Nb and Ta, wherein the sum of Nb and Ta is 0.05 to 0.5 mass %; and
the balance being Fe and incidental impurities;
wherein the precipitation-hardening martensitic stainless steel has a uniform martensite structure with no δ-ferrite phase and residual austenite phase; a tensile strength of 1200 MPa or more; a 0.02% proof stress of 800 MPa or more; and a Charpy impact strength of 25.0 J/cm 2 or more, and
wherein the precipitation-hardening martensitic stainless steel has been subjected to a solution heat treatment at 900° C. to 950° C. followed by an aging heat treatment at 520° C. to 580° C.

Assignees

• Oikawa Shinji
• Yoda Hideo
• Arai Masahiko
• Doi Hiroyuki
• Mitsubishi Hitachi Power Sys

Inventors

• Oikawa Shinji
• Yoda Hideo
• Arai Masahiko
• Doi Hiroyuki

Classifications

• C22C38/18 Primary

  containing chromium · CPC title

• C21D6/00

  Heat treatment of ferrous alloys · CPC title

• C21D2211/008

  Martensite · CPC title

• C21D6/02

  Hardening by precipitation · CPC title

• C22C38/48

  with niobium or tantalum · CPC title