High-strength steel material for oil well and oil well pipes

Patent metadata

Field	Value
Publication number	US-2016168672-A1
Application number	US-201414904967-A
Country	US
Kind code	A1
Filing date	Jul 24, 2014
Priority date	Jul 26, 2013
Publication date	Jun 16, 2016
Grant date	—

Abstract

There is provided a high-strength steel material for oil well having a chemical composition consisting, by mass percent, of C: 0.60-1.4%, Si: 0.05-1.00%, Mn: 12-25%, Al: 0.003-0.06%, P: <0.03%, S: ≦0.03%, N: <0.1%, Cr: ≧0% and <5.0%, Mo: ≧0% and <3.0%, Cu: ≦0% and <1.0%, Ni: ≧0% and <1.0%, V: 0-0.5%, Nb: 0-0.5%, Ta: 0-0.5%, Ti: 0-0.5%, Zr: 0-0.5%, Ca: ≧0% and <0.005%, Mg: ≧0% and <0.005%, B: 0-0.015%, the balance: Fe and impurities, wherein Nieq [=Ni+30C+0.5Mn] is 27.5 or higher, a metal micro-structure is a structure consisting mainly of an FCC structure, a total volume fraction of ferrite and α′ martensite is less than 0.10%, and a yield strength is 862 MPa or higher.

First claim

1 . A high-strength steel material for oil well having a chemical composition consisting, by mass percent, of
C: 0.60 to 1.4%, Si: 0.05 to 1.00%, Mn: 12 to 25%, Al: 0.003 to 0.06%, P: 0.03% or less, S: 0.03% or less, N: less than 0.1%, Cr: 0% or more and less than 5.0%, Mo: 0% or more and less than 3.0%, Cu: 0% or more and less than 1.0%, Ni: 0% or more and less than 1.0%, V: 0 to 0.5%, Nb: 0 to 0.5%, Ta: 0 to 0.5%, Ti: 0 to 0.5%, Zr: 0 to 0.5%, Ca: 0% or more and less than 0.005%, Mg: 0% or more and less than 0.005%, B: 0 to 0.015%, the balance: Fe and impurities, wherein Nieq defined by the following Formula (i) is 27.5 or higher, a metal micro-structure is a structure consisting mainly of an FCC structure, a total volume fraction of ferrite and α′ martensite is less than 0.10%, and a yield strength is 862 MPa or higher;
Nieq=Ni+30C+0.5Mn   (i)

where, the symbol of an element in the formula represents the content (mass %) of the element contained in the steel material, and is made zero in the case where the element is not contained.

2 . The high-strength steel material for oil well according to claim 1 ,
wherein the chemical composition contains, by mass percent, one or two elements selected from Cr: 0.1% or more and less than 5.0% and Mo: 0.1% or more and less than 3.0%.

3 . The high-strength steel material for oil well according to claim 1 ,
wherein the chemical composition contains, by mass percent, one or two elements selected from Cu: 0.1% or more and less than 1.0% and Ni: 0.1% or more and less than 1.0%.

4 . The high-strength steel material for oil well according to claim 1 ,
wherein the chemical composition contains, by mass percent, one or more elements selected from V: 0.005 to 0.5%, Nb: 0.005 to 0.5%, Ta: 0.005 to 0.5%, Ti: 0.005 to 0.5% and Zr: 0.005 to 0.5%.

5 . The high-strength steel material for oil well according to claim 1 ,
wherein the chemical composition contains, by mass percent, one or two elements selected from Ca: 0.0003% or more and less than 0.005% and Mg: 0.0003% or more and less than 0.005%.

6 . The high-strength steel material for oil well according to claim 1 ,
wherein the chemical composition contains, by mass percent, B: 0.0001 to 0.015%.

7 . The high-strength steel material for oil well according to claim 1 ,
wherein the yield strength is 965 MPa or higher.

8 . Oil well pipes, which are comprised of the high-strength steel material for oil well according to claim 1 .

9 . Oil well pipes, which are comprised of the high-strength steel material for oil well according to claim 2 .

10 . Oil well pipes, which are comprised of the high-strength steel material for oil well according to claim 3 .

11 . Oil well pipes, which are comprised of the high-strength steel material for oil well according to claim 4 .

12 . Oil well pipes, which are comprised of the high-strength steel material for oil well according to claim 5 .

13 . Oil well pipes, which are comprised of the high-strength steel material for oil well according to claim 6 .

14 . Oil well pipes, which are comprised of the high-strength steel material for oil well according to claim 7 .

Assignees

• Nippon Steel & Sumitomo Metal Corp
• Nippon Steel & Sumitom Metal Corp

Inventors

• Kobayashi Kenji
• Tomio Yusaku

Classifications

• C21D8/0236

  Cold rolling · CPC title

• C22C38/58 Primary

  with more than 1.5% by weight of manganese · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C22C38/16

  containing copper · CPC title

• C22C38/46

  with vanadium · CPC title