A bolt is provided that has high strength and excellent hydrogen embrittlement resistance characteristics. A bolt according to an embodiment of the present invention consists of, in mass %, C: 0.32 to 0.39%, Si: 0.15% or less, Mn: 0.40 to 0.65%, P: 0.020% or less, S: 0.020% or less, Cr: 0.85 to 1.25%, Al: 0.005 to 0.060%, Ti: 0.010 to 0.050%, B: 0.0010 to 0.0030%, N: 0.0015 to 0.0080%, O: 0.0015% or less, Mo: 0 to 0.05%, V: 0 to 0.05%, Cu: 0 to 0.50%, Ni: 0 to 0.30%, and Nb: 0 to 0.05%, with the balance being Fe and impurities. The bolt satisfies Formula (1) and Formula (2), and has a tensile strength of 1000 to 1300 MPa and satisfies Formula (3). 4.9≤10C+Si+2Mn+Cr+4Mo+5V≤6.1 (1) Mn/Cr≤0.55 (2) [dissolved Cr]/Cr≥0.70 (3)
1. A bolt having a chemical composition consisting of, in mass %:
C: 0.32 to 0.39%,
Si: 0.15% or less,
Mn: 0.40 to 0.65%,
P: 0.020% or less,
S: 0.020% or less,
Cr: 0.85 to 1.25%,
Al: 0.005 to 0.060%,
Ti: 0.010 to 0.050%,
B: 0.0010 to 0.0030%,
N: 0.0015 to 0.0080%,
O: 0.0015% or less,
Mo: 0 to 0.05%,
V: 0 to 0.05%,
Cu: 0 to 0.50%,
Ni: 0 to 0.30%, and
Nb: 0 to 0.05%,
with a balance being Fe and impurities, and satisfying Formula (1) and Formula (2),
wherein the bolt:
has a tensile strength of 1000 to 1300 MPa, and
satisfies Formula (3);
4.9≤10C+Si+2Mn+Cr+4Mo+5V≤6.1 (1)
Mn/Cr≤0.55 (2)
[dissolved Cr]/Cr≥0.70 (3),
where, a content (mass %) of a corresponding element is substituted for each symbol of an element in Formulae (1) to (3); in a case where a corresponding element is at an impurity level, “0” is substituted for the symbol of the corresponding element in Formula (1); and a dissolved Cr amount (mass %) in the bolt is substituted for [dissolved Cr] in Formula (3).
2. The bolt according to claim 1 , containing one or more types of element selected from a group consisting of:
Mo: 0.01 to 0.05%,
V: 0.005 to 0.05%,
Cu: 0.03 to 0.50%, and
Ni: 0.03 to 0.30%.
3. The bolt according to claim 1 , containing:
Nb: 0.0015 to 0.05%.
4. The bolt according to claim 2 , containing:
Nb: 0.0015 to 0.05%.
5. The bolt according to claim 1 , wherein:
when a P content in an outer layer from a surface of the bolt to a depth of 50 μm is taken as Ps (mass %), and a P content at a central axis of the bolt is taken as Pc (mass %), the bolt satisfies Formula (4):
Ps/Pc≤1.2 (4).
6. The bolt according to claim 2 , wherein:
when a P content in an outer layer from a surface of the bolt to a depth of 50 μm is taken as Ps (mass %), and a P content at a central axis of the bolt is taken as Pc (mass %), the bolt satisfies Formula (4):
Ps/Pc≤1.2 (4).
7. The bolt according to claim 3 , wherein:
when a P content in an outer layer from a surface of the bolt to a depth of 50 μm is taken as Ps (mass %), and a P content at a central axis of the bolt is taken as Pc (mass %), the bolt satisfies Formula (4):
Ps/Pc≤1.2 (4).
8. The bolt according to claim 4 , wherein:
when a P content in an outer layer from a surface of the bolt to a depth of 50 μm is taken as Ps (mass %), and a P content at a central axis of the bolt is taken as Pc (mass %), the bolt satisfies Formula (4):
Ps/Pc≤1.2 (4).