Steel material and oil-well steel pipe

Patent metadata

Field	Value
Publication number	US-10550962-B2
Application number	US-201716076705-A
Country	US
Kind code	B2
Filing date	Feb 20, 2017
Priority date	Mar 4, 2016
Publication date	Feb 4, 2020
Grant date	Feb 4, 2020

Abstract

The steel material according to this invention contains, in mass %, C: 0.15 to 0.45%, Si: 0.10 to 1.0%, Mn: 0.10 to less than 0.90%, P: 0.05% or less, S: 0.01% or less, Al: 0.01 to 0.1%, N: 0.01% or less, Cr: 0.1 to 2.5%, Mo: 0.35 to 3.0%, and Co: 0.50 to 3.0%, and satisfies expressions (1) and (2), and contains 90% or more of tempered martensite by volume ratio:

C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15−Co/6+α≥0.50  ( 1 )

(3C+Mo+3Co)/(3Mn+Cr)≥1.0  ( 2 )

Effective B=B−11(N−Ti/3.4)/14  ( 3 )

where, α in expression (1) is 0.250 when effective B (mass %) defined by expression (3) is 0.0003% or more, and is 0 when the effective B is less than 0.0003.

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: 0.10 to 1.0%,
Mn: 0.10 to less than 0.90%,
P: 0.05% or less,
S: 0.01% or less,
Al: 0.01 to 0.1%,
N: 0.010% or less,
Cr: 0.1 to 2.5%,
Mo: 0.35 to 3.0%,
Co: 0.50 to 3.0%,
Cu: 0 to 0.5%,
Ni: 0 to 0.5%,
Ti: 0 to 0.03%,
Nb: 0 to 0.15%,
V: 0 to 0.5%,
B: 0 to 0.003%,
Ca: 0 to 0.004%,
Mg: 0 to 0.004%,
Zr: 0 to 0.004%, and
rare earth metal: 0 to 0.004%,
with a balance being Fe and impurities, and satisfying expressions (1) and (2),
wherein the microstructure comprises, by volume ratio, 90% or more of tempered martensite:
C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15 −Co/6+α≥0.50   (1 )

(3 C+Mo+3 Co)/(3 Mn+Cr)≥1.0   (2 )

Effective B=B−11(N−Ti/3.4)/14   (3)

where, α in expression (1 ) is 0.250 when effective B (mass %) defined by expression (3 ) is 0.0003 % or more, and is 0 when the effective B is less than 0.0003%, where a content (mass %) of a corresponding element is substituted for each symbol of an element in expression (1) to expression (3).

2. The steel material according to claim 1 , wherein the chemical composition contains one or more types of element selected from a group consisting of:
Ca: 0.0003 to 0.004%,
Mg: 0.0003 to 0.004%,
Zr: 0.0003 to 0.004%, and
rare earth metal: 0.0003 to 0.004%.

3. An oil-well steel pipe comprising:
a chemical composition according to claim 1 , and
a wall thickness of 15mm or more.

4. The steel material according to claim 1 , wherein the chemical composition contains one or more types of element selected from a group consisting of:
Cu: 0.02 to 0.5%, and
Ni: 0.02 to 0.5%.

5. The steel material according to claim 4 , wherein the chemical composition contains one or more types of element selected from a group consisting of:
Ti: 0.003 to 0.03%,
Nb: 0.003 to 0.15%, and
V: 0.005 to 0.5%.

6. The steel material according to claim 5 , wherein the chemical composition contains:
B: 0.0003 to 0.003%.

7. The steel material according to claim 6 , wherein the chemical composition contains one or more types of element selected from a group consisting of:
Ca: 0.0003 to 0.004%,
Mg: 0.0003 to 0.004%,
Zr: 0.0003 to 0.004%, and
rare earth metal: 0.0003 to 0.004%.

8. The steel material according to claim 5 , wherein the chemical composition contains one or more types of element selected from a group consisting of:
Ca: 0.0003 to 0.004%,
Mg: 0.0003 to 0.004%,
Zr: 0.0003 to 0.004%, and
rare earth metal: 0.0003 to 0.004%.

9. The steel material according to claim 4 , wherein the chemical composition contains:
B: 0.0003 to 0.003%.

10. The steel material according to claim 9 , wherein the chemical composition contains one or more types of element selected from a group consisting of:
Ca: 0.0003 to 0.004%,
Mg: 0.0003 to 0.004%,
Zr: 0.0003 to 0.004%, and
rare earth metal: 0.0003 to 0.004%.

11. The steel material according to claim 4 , wherein the chemical composition contains one or more types of element selected from a group consisting of:
Ca: 0.0003 to 0.004%,
Mg: 0.0003 to 0.004%,
Zr: 0.0003 to 0.004%, and
rare earth metal: 0.0003 to 0.004%.

12. The steel material according to claim 1 , wherein the chemical composition contains one or more types of element selected from a group consisting of:
Ti: 0.003 to 0.03%,
Nb: 0.003 to 0.15%, and
V: 0.005 to 0.5%.

13. The steel material according to claim 12 , wherein the chemical composition contains:
B: 0.0003 to 0.003%.

14. The steel material according to claim 13 , wherein the chemical composition contains one or more types of element selected from a group consisting of:
Ca: 0.0003 to 0.004%,
Mg: 0.0003 to 0.004%,
Zr: 0.0003 to 0.004%, and
rare earth metal: 0.0003 to 0.004%.

15. The steel material according to claim 12 , wherein the chemical composition contains one or more types of element selected from a group consisting of:
Ca: 0.0003 to 0.004%,
Mg: 0.0003 to 0.004%,
Zr: 0.0003 to 0.004%, and
rare earth metal: 0.0003 to 0.004%.

16. The steel material according to claim 1 , wherein the chemical composition contains:
B: 0.0003 to 0.003%.

17. The steel material according to claim 16 , wherein the chemical composition contains one or more types of element selected from a group consisting of:
Ca: 0.0003 to 0.004%,
Mg: 0.0003 to 0.004%,
Zr: 0.0003 to 0.004%, and
rare earth metal: 0.0003 to 0.004%.

Assignees

• Nippon Steel & Sumitomo Metal Corp
• Nippon Steel Corp

Inventors

• Arai Yuji

Classifications

• C22C38/00

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title

• C21D8/10

  during manufacturing of tubular bodies · CPC title

• F16L9/00

  Rigid pipes · CPC title

• C21D9/085

  Cooling or quenching · CPC title

• Y10T428/13

  Hollow or container type article [e.g., tube, vase, etc.] · CPC title