Steel material
The steel material according to the present disclosure consists of, in mass %, C: 0.15 to 0.45%, Si: 0.05 to 1.00%, Mn: 0.05 to less than 0.80%, P: 0.030% or less, S: 0.0100% or less, Al: 0.100% or less, Cr: 0.30 to 1.50%, Mo: 0.25 to 2.00%, Ti: 0.001 to 0.015%, N: 0.0100% or less, O: 0.0050% or less, V: 0 to 0.05%, Nb: 0 to 0.010%, B: 0 to less than 0.0005%, Ca: 0 to 0.0100%, Mg: 0 to 0.0100%, and rare earth metal: 0 to 0.0100%, with the balance being Fe and impurities. In the steel material, the grain size number of prior-austenite grains is less than 7.0, Formula (1) to Formula (4) described in the specification are satisfied, the yield strength is 896 MPa or more, and the absorbed energy at −10° C. is 95 J or more.
1. A steel material consisting of, in mass %,
C: 0.15 to 0.45%,
Si: 0.05 to 1.00%,
Mn: 0.05 to less than 0.80%,
P: 0.030% or less,
S: 0.0100% or less,
Al: 0.100% or less,
Cr: 0.30 to 1.50%,
Mo: 0.25 to 2.00%,
Ti: 0.001 to 0.015%,
N: 0.0100% or less,
O: 0.0050% or less,
V: 0 to 0.05%,
Nb: 0 to 0.010%,
B: 0 to less than 0.0005%,
Ca: 0 to 0.0100%,
Mg: 0 to 0.0100%,
rare earth metal: 0 to 0.0100%,
Ni: 0 to 0.50%, and
Cu: 0 to 0.50%,
with the balance being Fe and impurities,
wherein:
a grain size number of prior-austenite grains is less than 7.0;
on a precondition that a content of each element is within a range described above, Formula (1) to Formula (4) are satisfied;
a yield strength is 896 MPa or more; and
an absorbed energy at −10° C. is 95 J or more:
{C+Mn/5+(Cu+Ni)/15+(Cr+Mo+V)/5+10×B}×(7.0/GN) 0.45 ≥0.678 (1)
{Mn/5.5+10×Ti+1.2×V+15×Nb+200×B}×(7.0/GN) 0.45 ≤0.240 (2)
10×Ti+V+10×Nb≥0.015 (3)
(10×Ti+1.2×V+30×Nb)/Mo≤0.205 (4)
where, a content in mass % of a corresponding element is substituted for each symbol of an element, and the grain size number is substituted for “GN”.
2. The steel material according to claim 1 , wherein:
a number density of Mn sulfides having an equivalent circular diameter of 5.0 μm or more is 10/100 mm 2 or less; and
an absorbed energy at −10° C. is 100 J or more.
3. The steel material according to claim 1 , containing one or more types of element selected from the group consisting of:
V: 0.01 to 0.05%,
Nb: 0.001 to 0.010%,
B: 0.0001 to less than 0.0005%,
Ca: 0.0001 to 0.0100%,
Mg: 0.0001 to 0.0100%,
rare earth metal: 0.0001 to 0.0100%,
Ni: 0.01 to 0.50%, and
Cu: 0.01 to 0.50%.
4. The steel material according to claim 2 , containing one or more types of element selected from the group consisting of:
V: 0.01 to 0.05%,
Nb: 0.001 to 0.010%,
B: 0.0001 to less than 0.0005%,
Ca: 0.0001 to 0.0100%,
Mg: 0.0001 to 0.0100%,
rare earth metal: 0.0001 to 0.0100%,
Ni: 0.01 to 0.50%, and
Cu: 0.01 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 2 , wherein:
the steel material is an oil-well steel pipe.
7. The steel material according to claim 3 , wherein:
the steel material is an oil-well steel pipe.
8. The steel material according to claim 4 , wherein:
the steel material is an oil-well steel pipe.