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EP-4741522-A1 - FE-CR-NI ALLOY MATERIAL

EP4741522A1EP 4741522 A1EP4741522 A1EP 4741522A1EP-4741522-A1

Abstract

A Fe-Cr-Ni alloy material that has high strength and reduced strength anisotropy is provided. A Fe-Cr-Ni alloy material according to the present disclosure consists of, by mass%, C: 0.030% or less, Si: 0.01 to 1.00%, Mn: 0.01 to 2.00%, P: 0.040% or less, S: 0.0050% or less, Al: 0.01 to 0.50%, Ni: 28.0 to 36.5%, Cr: 19.0 to 27.5%, Mo: 2.00 to 6.00%, Cu: 0.01 to 3.00%, N: 0.010 to less than 0.220%, Co: 0.01 to 2.00%, and O: 0.010% or less, with the balance being Fe and impurities. In a microstructure, a standard deviation of the grain size numbers of austenite grains is 0.60 or less. The tensile yield strength is 758 MPa or more.

Inventors

  • OKADA, Seiya
  • KONDO, KEIICHI
  • NAKANE, Kazuya

Assignees

  • Nippon Steel Corporation

Dates

Publication Date
20260513
Application Date
20240628

Claims (3)

  1. A Fe-Cr-Ni alloy material consisting of, by mass%, C: 0.030% or less, Si: 0.01 to 1.00%, Mn: 0.01 to 2.00%, P: 0.040% or less, S: 0.0050% or less, Al: 0.01 to 0.50%, Ni: 28.0 to 36.5%, Cr: 19.0 to 27.5%, Mo: 2.00 to 6.00%, Cu: 0.01 to 3.00%, N: 0.010 to less than 0.220%, Co: 0.01 to 2.00%, O: 0.010% or less, V: 0 to 0.50%, Nb: 0 to 0.10%, Ti: 0 to 0.40%, W: 0 to 3.0%, Sn: 0 to 0.010%, Ca: 0 to 0.0100%, B: 0 to 0.0100%, Mg: 0 to 0.0100%, rare earth metal: 0 to 0.100%, and with the balance being Fe and impurities, wherein: in a microstructure, a standard deviation of grain size numbers of austenite grains is 0.60 or less; and a tensile yield strength is 758 MPa or more.
  2. The Fe-Cr-Ni alloy material according to claim 1, containing one or more elements selected from a group consisting of: V: 0.01 to 0.50%, Nb: 0.01 to 0.10%, Ti: 0.01 to 0.40%, W: 0.1 to 3.0%, Sn: 0.001 to 0.010%, Ca: 0.0001 to 0.0100%, B: 0.0001 to 0.0100%, Mg: 0.0001 to 0.0100%, and rare earth metal: 0.001 to 0.100%.
  3. The Fe-Cr-Ni alloy material according to claim 1 or claim 2, wherein: the Fe-Cr-Ni alloy material is a seamless alloy pipe for oil wells.

Description

TECHNICAL FIELD The present disclosure relates to an alloy material, and more particularly relates to a Fe-Cr-Ni alloy material. BACKGROUND ART In oil wells and gas wells (hereinafter, oil wells and gas wells are collectively referred to simply as "oil wells"), alloy materials for oil wells which are typified by oil country tubular goods are used. Many oil wells are sour environments that contain hydrogen sulfide, which is corrosive. As used in the present description, the term "sour environment" means an acidified environment containing hydrogen sulfide. In some cases, sour environments also contain carbon dioxide, and not just hydrogen sulfide. Materials used in such sour environments are required to have excellent corrosion resistance. Examples of materials which are required to have excellent corrosion resistance include 18-8 stainless steel materials such as SUS304H, SUS316H, SUS321H, and SUS347H, and Fe-Cr-Ni alloy materials represented by Alloy 800H, which is defined as NCF800H by the JIS Standard. Fe-Cr-Ni alloy materials have excellent corrosion resistance in comparison to 18-8 stainless steel. Fe-Cr-Ni alloy materials are also more excellent in economic efficiency in comparison to a Ni-base alloy material represented by Alloy 617. Therefore, Fe-Cr-Ni alloy materials may in some cases be used as alloy materials for oil wells for use in a sour environment. Japanese Patent Application Publication No. 2-217445 (Patent Literature 1) and International Application Publication No. WO2015/072458 (Patent Literature 2) each proposes an alloy material for oil wells that has excellent corrosion resistance. Patent Literature 1 discloses an alloy material which is a Fe-Cr-Ni alloy that consists essentially of Ni: 27 to 32%, Cr: 24 to 28%, Cu: 1.25 to 3.0%, Mo: 1.0 to 3.0%, Si: 1.5 to 2.75%, and Mn: 1.0 to 2.0%, and the following elements whose amounts are controlled as follows: N: 0.015% or less, B: 0.10% or less, C: 0.10% or less, Al: 0.30% or less, P: 0.03% or less, and S: 0.02% or less, with the balance being Fe and impurities. It is disclosed in Patent Literature 1 that this alloy material has high strength, galling resistance, and corrosion resistance under stress. Patent Literature 2 discloses an alloy material that is an Ni-Cr alloy material having a chemical composition consisting of, by mass%, Si: 0.01 to 0.5%, Mn: 0.01 to less than 1.0%, Cu: 0.01 to less than 1.0%, Ni: 48 to less than 55%, Cr: 22 to 28%, Mo: 5.6 to less than 7.0%, N: 0.04 to 0.16%, sol. Al: 0.03 to 0.20%, REM: 0.01 to 0.074%, W: 0 to less than 8.0%, Co: 0 to 2.0%, one or more of Ca and Mg: 0.0003 to 0.01% in total, and one or more of Ti, Nb, Zr, and V: 0 to 0.5% in total, with the balance being Fe and impurities, and in which C, P, S, and O in the impurities are as follows: C: 0.03% or less, P: 0.03% or less, S: 0.001% or less, and O: 0.01% or less, and a dislocation density ρ satisfies the formula (7.0 × 1015 ≤ ρ ≤ 2.7 × 1016 - 2.67 × 1017 × [REM(%)]). It is disclosed in Patent Literature 2 that this alloy material is excellent in hot workability and toughness, and is also excellent in corrosion resistance (stress corrosion cracking resistance in environments in which the temperature is a high temperature of more than 200°C and which contain hydrogen sulfide), and has a yield strength (0.2% proof stress) of 965 MPa or more. CITATION LIST PATENT LITERATURE Patent Literature 1: Japanese Patent Application Publication No. 2-217445Patent Literature 2: International Application Publication No. WO2015/072458 SUMMARY OF INVENTION TECHNICAL PROBLEM In recent years, oil wells are being made deeper, and consequently there is a need to increase the strength of alloy materials for oil wells. In other words, in regard to Fe-Cr-Ni alloy materials for which use as alloy materials for oil wells is assumed, there has been a need for the Fe-Cr-Ni alloy materials to have high strength. Furthermore, recent oil wells include an increased number of inclined wells in addition to vertical wells that are drilled straight down vertically. An inclined well is formed by drilling in such a way that the extending direction of the well is bent from vertically downward to the horizontal direction. By including a portion that extends horizontally (horizontal well), an inclined well can cover a wide range of strata in which a production fluid such as crude oil or gas is buried, and can thus increase the efficiency of producing a production fluid. On the other hand, when used for such kinds of inclined wells, the alloy material may be loaded with a compressive force. For such cases, it is preferable that not only the tensile yield strength, but also the compressive yield strength of the alloy material is high. That is, it is preferable that a Fe-Cr-Ni alloy material which is expected to be used in an inclined well not only has high strength, but also has a reduced strength anisotropy of the alloy material. However, in the aforementioned Patent Literatures 1 and 2, as t