| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a low cost steel for vacuum carburizing or vacuum carbo-nitriding. <P>SOLUTION: The steel for vacuum carburizing or vacuum carbo-nitriding has a chemical composition containing, by mass, 0.10-0.25% C, 0.35-1.5% Si, 0.4-1.5% Mn,≤0.025% P, 0.015-0.05% S, 0.50-2.0% Cr, 0.010-0.050% Al, 0.012-0.025% N, and the balance Fe with impurities, in which≤0.0012% O and≤0.003% Ti, are contained, and satisfying [910-203×C<SP>0.5</SP>+44.7×Si≤860], [2.0≤(0.31×C<SP>0.5</SP>)×(0.7×Si+1.00)×(3.33×Mn+1.00)×(2.16×Cr+1.00)≤3.5] and [0.2×(S/Mn)+P≤0.030], wherein the maximum equivalent circle diameter of the oxide and compound inclusion consisting mainly of the oxide and nitride and compound inclusion consisting mainly of the nitride, which are expressed by [(πLW/4)<SP>0.5</SP>] at the time of 99% of the accumulated distribution function estimated with an extreme value statistics method, provided that the long diameter of the inclusion in cross section parallel to the longitudinal direction is denoted as L(μm) and the short diameter is denoted as W(μm), is≤35μm. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
