Steel material suitable for use in sour environment

Patent metadata

Field	Value
Publication number	US-11891680-B2
Application number	US-202017414727-A
Country	US
Kind code	B2
Filing date	Feb 13, 2020
Priority date	Feb 15, 2019
Publication date	Feb 6, 2024
Grant date	Feb 6, 2024

Abstract

A steel material according to the present disclosure has a chemical composition consisting of, in mass %: C: 0.15 to 0.45%, Si: 0.05 to 1.00%, Mn: 0.01 to 1.00%, P: 0.030% or less, S: 0.0050% or less, Al: 0.005 to 0.100%, Cr 0.55 to 1.10%, Mo: 0.70 to 1.00%, Ti: 0.002 to 0.020%, V: 0.05 to 0.30%, Nb: 0.002 to 0.100%, B: 0.0005 to 0.0040%, N: 0.0100% or less, O: less than 0.0020%, and the balance being Fe and impurities, and satisfying Formula (1) described in the specification. A grain diameter of a prior-austenite grain is 15.0 μm or less, and an average area of precipitate which is precipitated in a prior-austenite grain boundary is 12.5×10 −3 μm 2 or less. A yield strength is 758 to 862 MPa.

First claim

The invention claimed is:

1. A steel material comprising:
a chemical composition consisting of, in mass %:
C: 0.15 to 0.45%,
Si: 0.05 to 1.00%,
Mn: 0.01 to 1.00%,
P: 0.030% or less,
S: 0.0050% or less,
Al: 0.005 to 0.100%,
Cr: 0.55 to 1.10%,
Mo: 0.70 to 1.00%,
Ti: 0.002 to 0.020%,
V: 0.05 to 0.30%,
Nb: 0.002 to 0.100%,
B: 0.0005 to 0.0040%,
N: 0.0100% or less,
O: less than 0.0020%,
Ca: 0 to 0.0100%,
Mg: 0 to 0.0100%,
Zr: 0 to 0.0100%,
rare earth metal: 0 to 0.0100%,
Cu: 0 to 0.50%,
Ni: 0 to 0.50%,
Co: 0 to 0.50%, and
W: 0 to 0.50%,
with the balance being Fe and impurities,
and satisfying Formula (1),
wherein
in the steel material, a grain diameter of a prior-austenite grain is 15.0 μm or less,
an average area of precipitate which is precipitated in a prior-austenite grain boundary is 12.5×10 −3 μm 2 or less, and
a yield strength is 758 to 862 MPa:
Mo/Cr≥1.90  (1)

where, content in mass % of a corresponding element is substituted for each symbol of an element in Formula (1).

2. The steel material according to claim 1 , wherein
the chemical composition has, in mass %:
Ca: 0.0001 to 0.0100%, and/or
Mg: 0.0001 to 0.0100%, and/or
Zr: 0.0001 to 0.0100%, and/or
rare earth metal: 0.0001 to 0.0100%.

3. The steel material according to claim 1 , wherein
the chemical composition has, in mass %:
Cu: 0.02 to 0.50%, and/or
Ni: 0.02 to 0.50%.

4. The steel material according to claim 1 , wherein the chemical composition has, in mass %:
Co: 0.02 to 0.50%, and/or
W: 0.02 to 0.50%.

5. The steel material according to claim 1 , wherein the steel material is an oil-well steel pipe.

6. The steel material according to claim 1 , wherein the steel material is a seamless steel pipe.

7. The steel material according to claim 2 , wherein
the chemical composition has, in mass %:
Cu: 0.02 to 0.50%, and/or
Ni: 0.02 to 0.50%.

8. The steel material according to claim 2 , wherein the chemical composition has, in mass %:
Co: 0.02 to 0.50%, and/or
W: 0.02 to 0.50%.

9. The steel material according to claim 3 , wherein the chemical composition has, in mass %:
Co: 0.02 to 0.50%, and/or
W: 0.02 to 0.50%.

10. The steel material according to claim 7 , wherein
the chemical composition has, in mass %:
Co: 0.02 to 0.50%, and/or
W: 0.02 to 0.50%.

Assignees

• Nippon Steel Corp

Inventors

• Otome Yohei
• Kamitani Hiroki
• Soma Atsushi
• Oe Taro
• Komatsubara Nobuaki
• Arai Yuji
• Takabe Hideki

Classifications

• C21D8/10

  during manufacturing of tubular bodies · CPC title

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C21D1/26 Primary

  Methods of annealing · CPC title

• C22C38/32 Primary

  with boron · CPC title

• C21D1/25

  Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten") · CPC title