Honda Motor Co., Ltd.

Nippon Steel Sumitomo Metal Corporation

Daido Steel Co., Ltd.

Akihito Ninomiya

Yoshinari Okada

Masayuki Horimoto

Shinichiro Kato

Takahiro Miyazaki

Hideki Imataka

Masaki Amano

Naoyuki Sano

Yasushi Matsumura

Tetsuya Shimomura

Katsuya Yamaguchi

Masaomi Nakaoka

The invention provides a carburized part which has excellent medium-cycle fatigue strength in particular subjected to surface-hardening treatment by carburization. The invention provides a carburized part including a carburized layer formed by performing carburizing treatment to a steel, the steel including, in terms of % by mass: 0.15% to 0.25% of C, 0.15% or less of Si, 0.4% to 1.1% of Mn, 0.8% to 1.4% of Cr, 0.25% to 0.55% of Mo, 0.015% or less of P, and 0.035% or less of S, with the remainder being Fe and unavoidable impurities, and the steel satisfying the following relation; 0.10&#x2266;[Mo]/(10[Si]+[Mn]+[Cr])&#x2266;0.40, in which [M] represents a content of element M in terms of % by mass.

Carburized part, method for manufacturing thereof, and steel for carburized part

A method for producing a steel component by performing the treatments of the following sequentially steps 1 and 2 to a steel material containing, by mass %, C: 0.15 to 0.25%, Si: 0.01 to 0.10%, Mn: 0.50 to 0.80%, S: 0.003 to 0.030%, Cr: 0.80 to 1.20%, Mo: 0.30 to 0.45%, Al: 0.015 to 0.050%, and N: 0.010 to 0.025%, wherein Cr/Mn is 1.3 to 2.4, the balance being Fe and impurities, and contents of P and O among the impurities are P: not more than 0.010%, and O: not more than 0.0020%:

Method for producing steel component

A method for producing a carbonitrided member comprising the steps of carburizing a steel part having a composition of, by mass percent, C: 0.10 to 0.35%, Si: 0.15 to 1.0%, Mn: 0.30 to 1.0%, Cr: 0.40 to 2.0%, S: 0.05% or less with the balance being Fe and impurities in a carburizing atmosphere of 900 to 950&#xb0; C. The carburized steel part is carbonitrided in a carbonitriding atmosphere with the temperature of 800 to 900&#xb0; C. and the nitrogen potential of 0.2 to 0.6%. The carbonitrided steel part is qhenched and then shot peened. The shot peening treatment may be further performed while heating to a temperature not higher than 350&#xb0; C. or immediately after heating to a temperature not higher than 350&#xb0; C. After quenching, the shot peening treatment may be further performed after tempering in the temperature range exceeding 250&#xb0; C. and not higher than 350&#xb0; C.

Method for producing carbonitrided member

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Saitama, Japan

Akihito Ninomiya