Steel pipe
A steel pipe, consisting of, in terms of mass %: from 0.06% to 0.25% of C, 0.50% or less of Si, 1.00% to 1.80% of Mn, 0.030% or less of P, 0.020% or less of S, 0.08% or less of Al, 0.008% or less of N, 0.080% or less of Nb, and a remainder consisting of Fe and unavoidable impurities, wherein a compressive residual stress at an outer surface measured by an X-ray method is 250 MPa or more, and a compressive residual stress at a position at a depth of 1 mm from the outer surface measured by the X-ray method is 70% or more of the compressive residual stress at the outer surface measured by the X-ray method.
1. A steel pipe, consisting of, in terms of mass %:
0.06% to 0.25% of C,
0.50% or less of Si,
1.00% to 1.80% of Mn,
0.030% or less of P,
0.020% or less of S,
0.08% or less of Al,
0.008% or less of N,
0.080% or less of Nb, and
a remainder consisting of Fe and unavoidable impurities,
wherein a compressive residual stress at an outer surface measured by an X-ray method is 250 MPa or more,
a compressive residual stress at a position at a depth of 1 mm from the outer surface measured by the X-ray method is 70% or more of the compressive residual stress at the outer surface measured by the X-ray method, and
having a wall thickness of from 7 mm to 17 mm, wherein a ratio of the wall thickness to an outer diameter (wall thickness/outer diameter) is from 0.07 to 0.12.
2. A steel pipe, consisting of, in terms of mass %:
0.06% to 0.25% of C,
0.50% or less of Si,
1.00% to 1.80% of Mn,
0.030% or less of P,
0.020% or less of S,
0.08% or less of Al,
0.008% or less of N,
0.080% or less of Nb,
0.080% or less of V,
0.030% or less of Ti,
0.50% or less of Cu,
0.50% or less of Ni,
0.50% or less of Cr,
0.50% or less of Mo,
0.0040% or less of B,
0.005% or less of Ca,
0.005% or less of REM and
a remainder consisting of Fe and unavoidable impurities,
wherein a compressive residual stress at an outer surface measured by an X-ray method is 250 MPa or more,
a compressive residual stress at a position at a depth of 1 mm from the outer surface measured by the X-ray method is 70% or more of the compressive residual stress at the outer surface measured by the X-ray method, and
having a wall thickness of from 7 mm to 17 mm, wherein a ratio of the wall thickness to an outer diameter (wall thickness/outer diameter) is from 0.07 to 0.12.
3. A steel pipe, comprising, in terms of mass %:
0.06% to 0.25% of C,
0.50% or less of Si,
1.00% to 1.80% of Mn,
0.030% or less of P,
0.020% or less of S,
0.08% or less of Al,
0.008% or less of N,
0.080% or less of Nb, and
a remainder comprising Fe and unavoidable impurities,
wherein a compressive residual stress at an outer surface measured by an X-ray method is 250 MPa or more,
a compressive residual stress at a position at a depth of 1 mm from the outer surface measured by the X-ray method is 70% or more of the compressive residual stress at the outer surface measured by the X-ray method, and
having a wall thickness of from 7 mm to 17 mm, wherein a ratio of the wall thickness to an outer diameter (wall thickness/outer diameter) is from 0.07 to 0.12.
4. The steel pipe according to claim 1 , wherein, in a case in which a full thickness specimen is subjected to a pipe axis direction tensile test, a ratio of yield strength to tensile strength is 80% or more, and yield elongation is exhibited.
5. The steel pipe according to claim 1 , wherein the steel pipe is an electric resistance welded steel pipe.
6. The steel pipe according to claim 1 , wherein one or more of the following are satisfied:
Al: 0.001% to 0.08%,
N: 0.002% to 0.008%, or
Nb: 0.008% to 0.080%.
7. The steel pipe according to claim 2 , wherein, in a case in which a full thickness specimen is subjected to a pipe axis direction tensile test, a ratio of yield strength to tensile strength is 80% or more, and yield elongation is exhibited.
8. The steel pipe according to claim 2 , wherein the steel pipe is an electric resistance welded steel pipe.
9. The steel pipe according to claim 2 , wherein one or more of the following are satisfied:
Al: 0.001% to 0.08%,
N: 0.002% to 0.008%, or
Nb: 0.008% to 0.080%.
10. The steel pipe according to claim 3 , further comprising, in terms of mass %, one or more of:
0.080% or less of V,
0.030% or less of Ti,
0.50% or less of Cu,
0.50% or less of Ni,
0.50% or less of Cr,
0.50% or less of Mo,
0.0040% or less of B,
0.005% or less of Ca, or
0.005% or less of REM.
11. The steel pipe according to claim 3 , wherein one or more of the following are satisfied:
0.001% to 0.08% of Al,
0.002% to 0.008% of N, or
0.008% to 0.080% of Nb.
12. The steel pipe according to claim 10 , wherein one or more of the following are satisfied:
0.001% to 0.08% of Al,
0.002% to 0.008% of N, or
0.008% to 0.080% of Nb.