| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide steel for a machine component which regulates the contents of oxygen, sulfur and Al in the steel, the average composition ratio of an MgO-AlObased oxide and the number ratio of the MgO-AlObased oxide in the total oxides, and has excellent Llife and rolling fatigue life.SOLUTION: In steel excellent in rolling fatigue life, the content of oxygen is 8 ppm or less; the content of sulfur is 0.008% or less; the content of Al is 0.005 to 0.030%; the number of non-metallic inclusions detected in the steel material per 1000 mmwith ultrasonic flaw detection, having the inclusion diameter of 20μm or more and less than 100μm, is 12.0 pieces or less; the number of non-metallic inclusions detected in the steel material per 2.5 kg with ultrasonic flaw detection, having the inclusion diameter of 100μm or more, is 2.0 pieces or less; the mass% ratio MgO/AlOin an MgO-AlObased oxide present in the steel is 0.25 to 1.50; and the number ratio of the MgO-AlObased oxide in the total oxide based inclusions is 70% or more.</p> |
