| 摘要 |
PROBLEM TO BE SOLVED: To provide a case-hardening steel which shows good forgeability even when it is cold-forged, suppresses coarsening of crystal grains attributable to heating for carburization and is excellent in a fatigue characteristics. SOLUTION: The case-hardening steel has composition containing, by mass%, 0.05-0.40% C,≤1.0% Si,≤1.0% Mn,≤0.03% P,≤0.03% S,≤2.0% Cr,≤0.1% Al, 0.05-0.30% Ti, 0.1-0.5% Cu, 0.002-0.02% Sb,≤0.0060% N,≤0.0020% O and the balance Fe with inevitable impurities, wherein≥30 pieces/μm<SP POS="POST">2</SP>of Ti-containing precipitates having a diameter of≥30 nm are present, and a ratio, by number, of Ti precipitates having a diameter of 5-50 nm to the total Ti precipitates is≥50%. COPYRIGHT: (C)2012,JPO&INPIT |
