STEEL
According to an aspect of the present invention, there is provided a steel containing, by mass %, C: 0.08% to 0.12%, Si: 0.05% to 0.50%, Mn: 1.00% to 3.00%, P: 0.040% or less, S: 0.020% or less, Cr: 1.0% to 2.5%, Cu: 0.01% to 0.50%, Ni: 0.75% to 3.20%, Mo: 0.10% to 0.50%, Nb: 0.005% to 0.050%, Al: 0.010% to 0.100%, N: 0.0050% to 0.0150%, V: 0% to 0.300%, Ca: 0% to 0.0100%, Zr: 0% to 0.0100%, Mg: 0% to 0.0100%, and a remainder including Fe and impurities, in which a number density of Mn sulfides having an equivalent circle diameter of more than 5 m is 0 pieces/mm 2 to 10 pieces/mm 2 , and an average aspect ratio of the Mn sulfides having an equivalent circle diameter of 1.0 m to 5.0 μm is 1.0 or more and 10.0 or less.
1 . A steel comprising, by unit mass %,
C: 0.08% to 0.12%;
Si: 0.05% to 0.50%;
Mn: 1.00% to 3.00%;
P: 0.040% or less;
S: 0.020% or less;
Cr: 1.00% to 2.50%;
Cu: 0.01% to 0.50%;
Ni: 0.75% to 3.20%;
Mo: 0.10% to 0.50%;
Nb: 0.005% to 0.050%;
Al: 0.010% to 0.100%;
N: 0.0050% to 0.0150%;
V: 0% to 0.300%;
Ca: 0% to 0.0100%;
Zr: 0% to 0.0100%;
Mg: 0% to 0.0100%; and
a remainder including Fe and impurities,
wherein a number density of Mn sulfides having an equivalent circle diameter of more than 5 μm is 0 pieces/mm 2 to 10 pieces/mm 2 , and
an average aspect ratio of the Mn sulfides having an equivalent circle diameter of 1.0 μm to 5.0 μm is 1.0 or more and 10.0 or less.
2 . The steel according to claim 1 comprising, by unit mass %,
V: 0.010% to 0.300%.
3 . The steel according to claim 1 comprising, by unit mass %, one or more selected from the group consisting of
Ca: 0.0005% to 0.0100%;
Zr: 0.0005% to 0.0100%; and
Mg: 0.0005% to 0.0100%.
4 . The steel according to claim 2 comprising, by unit mass %, one or more selected from the group consisting of
Ca: 0.0005% to 0.0100%;
Zr: 0.0005% to 0.0100%; and
Mg: 0.0005% to 0.0100%.