| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel used in parts for machinery superior in the rolling fatigue life. SOLUTION: The steel for use in the machine parts needing a surface hardness of 58 HRC or higher contains 6 ppm or less oxygen, 0.008 mass% or less sulfur, and non-metallic inclusions having a diameter of 20μm or larger in a number of 12 or less when the steel material of 300 mm<SP>3</SP>by volume has been inspected with an ultrasonic detector. COPYRIGHT: (C)2008,JPO&INPIT
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