| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of manufacturing a case hardened steel and parts omissible of normalizing after hot forging and excellent in high temperature carburizability.SOLUTION: There is provide a case hardened steel containing, by mass%, C:0.10 to 0.35%, Si:0.50 to 1.50%, Mn:0.30 to 1.50%, S:0.030 to 0.080%, Cu:0.02 to 0.35%, Cr:0.15 to 1.50%, Al:0.050 to 0.100%, Ti:0.050 to 0.300%, N:0.0080% or less, and if needed, any one or more kind of Ni, Mo, V, B, Nb and Sb, and the balance Fe with inevitable impurities, having an area ratio of ferrite and pearlite of 80% or more, the particle size number of ferrite of 8.0 or less and there are total 5 or more/100 μmof Ti sulfide or Ti carbonitride having a diameter of 500 nm or less, 50/μmor more of carbide or carbonitride containing Ti having a diameter of 50 nm or less, and a value of X consisting of specific components, which is an index of a transformation initiation temperature of 840 or more. |
