| abstract |
A bainite type non-refined steel for nitriding, which has a chemical composition in wt % (wt/wt): C: 0.05 to 0.8, Si: 0.01 to 2.5 %, Mn: 0.1 to 3.5 %, P: 0.001 to 0.2 %, S: 0.01 to 0.2%, Cr: 1.0 to 3.5 %, V: 0.1 to 0.5 %, Al: 0.001 to 0.020 %, Ca: 0.0005 to 0.02 % and O: 0.0005 to 0.01 %, provided that ([Mn] - 55[S]/32 + [Cr]) > 2.0, balance: inevitable impurities and Fe, and sulfide based inclusions containing 1.0 wt % of Ca which are present in contact with oxide based inclusions containing 8 to 62 wt % of CaO occupy a visual field of 2.0 X 10-4 mm2 or more per the total visual field of 3.5 mm2. The steel for nitriding has not been refined and secures a desired strength and hardness, and further, exhibits machinability superior to or same as a steel containing Pb, though it has no Pb. |