| 摘要 |
A case hardening steel wire which has a chemical composition containing, in mass%, 0.10-0.24% of C, 0.16-0.35% of Si, 0.40-1.00% of Mn, 0.005-0.050% of S, 1.65-1.90% of Cr, 0.015-0.060% of Al, 0.005-0.060% of Nb, 0.0130-0.0250% of N, 0-0.20% of Cu, 0-0.20% of Ni, 0-0.20% of V and 0-0.0050% of Ca with the balance made up of Fe and impurities, and which satisfies 15 ≤ Mn/S ≤ 150, 0.75 ≤ Cr/(Si + 2Mn) ≤ 1.40 and 0.30 ≤ Si × Cr ≤ 0.65. Elements among the impurities satisfy P ≤ 0.020%, Ti ≤ 0.005%, Mo ≤ 0.03% and O ≤ 0.0020%. The hardness (HV) of the portion from the surface to the depth of 50 μm is 250 or less. In the portion from the surface to the depth of half the radius, the total number of Al precipitates and Nb precipitates having circle-equivalent diameters of 100 nm or more and the total number of Al precipitates and Nb precipitates having circle-equivalent diameters of 5 nm or more but less than 100 nm are 100 precipitates/100 μm2 or less and 100 precipitates/25 μm2 or more, respectively. |
