摘要:
The present invention provides a steel for nitrocarburizing having excellent mechanical workability before nitrocarburizing, and showing excellent fatigue properties after nitrocarburizing, which is suitable for applying in mechanical structural components for automobiles etc. prepared by adjusting the composition so that it contains in mass%, C: 0.01 % or more and less than 0.10 %, Si: 1.0 % or less, Mn: 0.5 % to 3.0 %, P: 0.02 % or less, S: 0.06 % or less, Cr: 0.3 % to 3.0 %, Mo: 0.005 % to 0.4 %, V: 0.02 % to 0.5 %, Nb: 0.003 % to 0.15 %, Al: 0.005 % to 0.2 %, and Sb: 0.0005 % to 0.02 %, and the balance including Fe and incidental impurities, and setting the area ratio of bainite phase to the whole microstructure to more than 50 %.
摘要:
According to the present invention, it is possible to obtain steel for nitrocarburizing having a predetermined chemical composition, a bainite area ratio exceeding 50 % and excellent machinability by cutting before nitrocarburizing, and having strength and toughness equivalent to conventional steel, such as SCr420 carburized steel material, and excellent fatigue properties after nitrocarburizing.
摘要:
Steel parts for a machine structure which have a chemical composition in mass % that C: 0.3 to 0.7 %, Si: 0.3 % or less, Mn: 0.2 to 2.0 %, Al: 0.005 to 0.25%, Ti: 0.005 to 0.1 %, Mo: 0.05 to 0.6 %, B: 0.0003 to 0.006 %, S: 0.06 % or less, P: 0.020 % or less, O: 0.0030 % or less and the balance: Fe and inevitable impurities, has a hardened layer formed by induction hardening at least on a part of the surface thereof, wherein the hardened layer has an average old austenite grain diameter of 7 mum or less and it has non-metal inclusions comprising an oxide having a maximum diameter of 15 mum. The above parts exhibit excellent fatigue strength, and thus are suitable for a drive shaft, a constant-velocity universal joint, and the like.
摘要:
The present invention provides a machine structural part composed of 0.3% to 0.7% of C, 0.30% or less of Si, 0.2% to 2.0% of Mn, 0.005% to 0.25% of Al, 0.005% to 0.1% of Ti, 0.05% to 0.6% of Mo, 0.0003% to 0.006% of B, 0.06% or less of S, 0.020% or less of P, 0.0030% or less of O on a mass basis, and the balance being Fe and unavoidable impurities. In addition, the machine structural part has a hard layer on at least a part of a surface thereof formed by induction quenching, an average prior austenite grain diameter of the hard layer is 7 µm or less, and the maximum diameter of a non-metal inclusion composed of oxides is 15 µm or less. Since having a high fatigue strength, this machine structural part is suitable for an automobile drive shaft, constant velocity joint, and the like.