High cleanliness bearing steel with excellent rolling fatigue life in hydrogen environment

摘要

PROBLEM TO BE SOLVED: To provide a steel for high cleanliness shaft bearing excellent in rolling motion fatigue life in a hydrogen intrusion environment and less in life deterioration compared to rolling motion fatigue life in a normal environment in absent of hydrogen.SOLUTION: There is provided a steel for shaft bearing containing, by mass%, C:0.13 to 0.35%, Si:0.20 to 0.65%, Mn:0.50 to 1.20%, P:0.030% or less, S:0.030% or less, Cr:2.30 to 3.50% and further one or two kind selected from Ni:0.10 to 0.50%, Mo:0.03 to 0.50% and the balance Fe with inevitable impurities, and having a structure with an estimated value of maximum inclusion diameter in 30000 mm, which is estimated by an external statistical process with conducting a measurement of the maximum inclusion diameter of a non-metal inclusion in a steel material cross section of 100 mmat 30 locations of 50 μm or less, total of Si, Mn, Cr, Ni and Mo dissolved in a parent phase at 100 to 300 μm from a steel material outermost surface when the steel is applied to carburization hardening tempering or carbonitriding hardening tempering of 3.0% or more and remained γ amount of 25 to 50 vol.% and the balance martensite.SELECTED DRAWING: Figure 2