| 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:0.05 to 1.00%, Mn:0.30 to 1.50%, S:0.015 to 0.080%, Cu:0.02 to 0.35%, Cr:0.50 to 1.50%, Al:0.005 to 0.080%, V:0.005 to 0.080%, Ti:0.120 to 0.300%, N:0.0080% or less, and if needed, any one or more kind of Ni, Mo, Nb, B and Sb, and the balance Fe with inevitable impurities, containing ferrite and pearlite with an area ratio of 80% or more in a structure after hot-forging, and having 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, and 50/μmor more of carbide or carbonitride containing Ti having a diameter of 50 nm or less. |
