Nippon Steel Corporation

Toyota Jidosha Kabushiki Kaisha

Satoru Okawa

Masato Yuya

Tatsuhiko Abe

Manabu Kubota

Motoichi Murakami

Yuichiro Kajiki

Hiroaki Tahira

Yusuke Morita

Takeshi Fukui

Kison Nishihara

Yusuke Inukai

A crankshaft with improved seizure resistance is provided. A crankshaft () is a crankshaft including journals () and pins (), having a chemical composition of, in mass %: 0.35 to 0.40% C; up to 0.70% Si; 1.00 to 2.00% Mn; up to 0.50% Cr; up to 0.050% Al; up to 0.020% N; up to 0.020% P; 0.005 to 0.200% S; and balance Fe and impurities, each of the journals () and pins () having a surface microstructure containing tempered martensite in not less than 80 volume % and a surface hardness not higher than HV 450.

Crankshaft

A crankshaft with improved seizure resistance is provided. A crankshaft having journalsand pinsincludes a compound layer containing iron and nitrogen on its surface, wherein, in the compound layer, for both the journalsand pins, the porosity area ratio of the thinner one of a region from the surface to a depth of 3.0 μm and a region across the total thickness of the compound layer is not higher than 10.0%, and both the journalsand pinshave such a surface geometry that the arithmetical mean deviation of the primary profile, Pa, is not larger than 0.090 μm.

Crankshaft and method of manufacturing the same

Provided are a roughly-shaped steel material for a nitrided part, and a nitrided part obtained by nitriding the roughly-shaped steel material for a nitrided part, having a determined chemical composition, in which the portion with a diameter or width ranging from 60 to 130 mm of the roughly-shaped steel material for a nitrided part has a microstructure at a depth of 14.5 mm from a surface including, in terms of area fraction: tempered martensite and tempered bainite in total: from 70 to 100%; remaining austenite: from 0 to 5%; and a balance: ferrite and perlite; and has a microstructure at a depth of 15 mm or more from the surface including, in terms of area fraction: tempered martensite and tempered bainite in total: from 0 to less than 50%; remaining austenite: from 0 to 5%; and a balance: ferrite and perlite.

Roughly-shaped steel material for nitrided part, and nitrided part

Growing community of inventors

Tokyo, Japan

Satoru Okawa