| 摘要 |
PROBLEM TO BE SOLVED: To provide a carburizing steel having improved torsion fatigue characteristics useful for, for example, materials of machine parts, particularly shafts, used in a driving system of an automobile. SOLUTION: The carburizing steel superior in the torsion fatigue characteristics is made of a steel which comprises 0.1-0.5% C (% means mass%, hereafter), 0.5% or less Si, 2.0% or less Mn, 0.035% or less S, 0.015% or less P, more than 0% but 3% or less Cr, 0.005-0.06% A1, and 0.005-0.030% N, while making the contents of Cr and Mn satisfy the relation of "Cr/ (Cr+Mn)≤0.6 "; and has a line fraction of a secondary phase [standard deviation / average line fraction] in an amount of 0.30 or less, when measured with a method indicated in a specification body. COPYRIGHT: (C)2004,JPO
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