Bearing part
A bearing part according the present invention includes, as the chemical composition, by mass %, C: 0.95% to 1.10%, Si: 0.10% to 0.70%, Mn: 0.20% to 1.20%, Cr: 0.90% to 1.60%, Al: 0.010% to 0.100%, N: 0.003% to 0.030%, P: 0.025% or less, S: 0.025% or less, O: 0.0010% or less, and optionally Mo: 0.25% or less, B: 0.0050% or less, Cu: 1.0% or less, Ni: 3.0% or less, and Ca: 0.0015% or less, and a remainder including Fe and impurities; metallographic structure includes a retained austenite, a spherical cementite and a martensite; an amount of the retained austenite is 15% to 25%, by volume %; an average grain size of prior-austenite is 8.0 μm or less; and a number density of a void having a circle equivalent diameter of 0.02 μm to 3.0 μm is 2000 mm −2 or less in the metallographic structure.
1. A bearing part comprising, as a chemical composition, by mass %,
C: 0.95% to 1.10%,
Si: 0.10% to 0.70%,
Mn: 0.20% to 1.20%,
Cr: 0.90% to 1.60%,
Al: 0.010% to 0.100%,
N: 0.003% to 0.030%,
P: 0.025% or less,
S: 0.025% or less,
O: 0.0010% or less, and
optionally
Mo: 0.25% or less,
B: 0.0050% or less,
Cu: 1.0% or less,
Ni: 3.0% or less, and
Ca: 0.0015% or less, and
a remainder including Fe and impurities,
wherein a metallographic structure includes a retained austenite, a spherical cementite and a martensite,
wherein an amount of the retained austenite is 15% to 25%, by volume %,
wherein an average grain size of a prior-austenite is 8.0 μm or less, and
wherein a number density of a void having a circle equivalent diameter of 0.02 μm to 3.0 μm is 2000 mm −2 or less in the metallographic structure.
2. The bearing part according to claim 1 comprising, as the chemical composition, by mass %, one or more of
Mo: 0.01% to 0.25%,
B: 0.0001% to 0.0050%,
Cu: 0.1% to 1.0%,
Ni: 0.05% to 3.0%, and
Ca: 0.0003% to 0.0015%.
3. The bearing part according to claim 1 ,
wherein a Vickers hardness is 750 Hv or more, and
wherein a rolling contact fatigue life in a contaminated environment is 5.0×10 6 or more, the contaminated environment being an environment where 1 g of an iron powder having a hardness of 750 Hv to 800 Hv and a particle size of 100 μm to 180 μm is mixed into 1 L of a lubricating oil.
4. The bearing part according to claim 2 ,
wherein a Vickers hardness is 750 Hv or more, and
wherein a rolling contact fatigue life in a contaminated environment is 5.0×10 6 or more, the contaminated environment being an environment where 1 g of an iron powder having a hardness of 750 Hv to 800 Hv and a particle size of 100 μm to 180 μm is mixed into 1 L of a lubricating oil.