Jfe Steel Corporation

Naoya Ihara

Kimihiro Nishimura

Masayuki Kasai

Takashi Iwamoto

Provided is a steel for nitrocarburizing that ensures mechanical workability before nitrocarburizing treatment. A steel for nitrocarburizing comprises: a chemical composition containing, in mass %, C: &#x2265;0.02% and &#x3c;0.15%, Si: &#x2264;0.30%, Mn: 1.5-2.5%, P: &#x2264;0.025%, S: &#x2264;0.06%, Cr: 0.5-2.0%, Mo: 0.005-0.2%, V: 0.02-0.20%, Nb: 0.003-0.20%, Al: &#x3e;0.020% and &#x2264;1.0%, Ti: &#x3e;0.0050% and &#x2264;0.015%, N: &#x2264;0.0200%, Sb: 0.0030-0.010%, with a balance being Fe and inevitable impurities, satisfying Expression (1) or (2); and a steel microstructure where an area ratio of bainite phase is &#x3e;50%, a prior austenite grain size is &#x2264;100 &#x3bc;m, &#x2265;300/&#x3bc;mTi precipitates with an equivalent circular particle size of &#x2264;30 nm disperse, Sb segregates to prior austenite grain boundaries.

Steel for nitrocarburizing and nitrocarburized component, and methods of producing same

Provided is a steel for nitrocarburizing that can ensure hardened case depth by suppressing precipitation of Cr, V, and Nb in a part of the surface layer very close to the surface. The provided steel comprises: a specific chemical composition satisfying 9.5&#x2264;([Cr]/52+[V]/50.9+[Nb]/92.9+M)&#xd7;10&#x2264;18.5, with the balance being Fe and inevitable impurities; and a steel microstructure in which an area ratio of bainite phase with respect to the entire microstructure is more than 50%.

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Tokyo, Japan

Naoya Ihara