STEEL MATERIAL AND EXPANDABLE OIL COUNTRY TUBULAR GOODS
There is provided a steel material having a chemical composition consisting, by mass percent, of C: 0.6-1.8%, Si: 0.05-1.00%, Mn: >25.0-45.0%, Al: 0.003-0.06%, P: ≦0.03%, S: ≦0.03%, Cu: 0.5-3.0%, N: ≦0.10%, V: 0-2.0%, Cr: 0-3.0%, Mo: 0-3.0%, Ni: 0-1.5%, Nb: 0-0.5%, Ta: 0-0.5%, Ti: 0-0.5%, Zr: 0-0.5%, Ca: 0-0.005%, Mg: 0-0.005%, REM: 0-0.01%, B: 0-0.015%, the balance: Fe and impurities, and satisfying [0.6<C−0.18V<1.44], wherein a metal micro-structure is consisting of an austenite single phase, a yield strength is 241 MPa or higher, and a uniform elongation is 40% or higher.
1 . A steel material having a chemical composition consisting, by mass percent, of
C: 0.6 to 1.8%,
Si: 0.05 to 1.00%,
Mn: more than 25.0% and 45.0% or less,
Al: 0.003 to 0.06%,
P: 0.03% or less,
S: 0.03% or less,
Cu: 0.5 to 3.0%,
N: 0.10% or less,
V: 0 to 2.0%,
Cr: 0 to 3.0%,
Mo: 0 to 3.0%,
Ni: 0 to 1.5%,
Nb: 0 to 0.5%,
Ta: 0 to 0.5%,
Ti: 0 to 0.5%,
Zr: 0 to 0.5%,
Ca: 0 to 0.005%,
Mg: 0 to 0.005%,
REM: 0 to 0.01%,
B: 0 to 0.015%,
the balance: Fe and impurities, and
satisfying the following formula (i),
wherein a metal micro-structure is consisting of an austenite single phase,
a yield strength is 241 MPa or higher, and a uniform elongation is 40% or higher;
0.6<C−0.18V<1.44 (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 steel material according to claim 1 ,
wherein the chemical composition contains, by mass percent,
V: 0.03 to 2.0%.
3 . The steel material according to claim 1 ,
wherein the chemical composition contains, by mass percent,
one or more elements selected from
Cr: 0.1 to 3.0%,
Mo: 0.1 to 3.0% and
Ni: 0.1 to 1.5%.
4 . The steel material according to claim 1 ,
wherein the chemical composition contains, by mass percent,
one or more elements selected from
Nb: 0.005 to 0.5%,
Ta: 0.005 to 0.5%,
Ti: 0.005 to 0.5%,
Zr: 0.005 to 0.5%,
Ca: 0.0003 to 0.005%,
Mg: 0.0003 to 0.005%,
REM: 0.001 to 0.01% and
B: 0.0001 to 0.015%.
5 . Expandable oil country tubular goods, which are comprised of the steel material according to claim 1 .
6 . The expandable oil country tubular goods according to claim 5 , which are seamless oil country tubular goods.
7 . Expandable oil country tubular goods, which are comprised of the steel material according to claim 2 .
8 . Expandable oil country tubular goods, which are comprised of the steel material according to claim 3 .
9 . Expandable oil country tubular goods, which are comprised of the steel material according to claim 4 .
10 . The expandable oil country tubular goods according to claim 7 , which are seamless oil country tubular goods.
11 . The expandable oil country tubular goods according to claim 8 , which are seamless oil country tubular goods.
12 . The expandable oil country tubular goods according to claim 9 , which are seamless oil country tubular goods.