Nippon Steel Sumitomo Metal Corporation

Nippon Steel Corporation

Toyota Jidosha Kabushiki Kaisha

Toyoda Jidosha Kabushiki Kaisha

Isuzu Motors Limited and Nippon Steel Corporation

Isuzu Motors Limited

Hiromasa Takada

Shinya Teramoto

Manabu Kubota

Osamu Ohyama

Motohide Mori

Suguru Yoshida

Atsuo Tanaka

Hiroyuki Mizuno

Makoto Okonogi

Hideo Kanisawa

Hitoshi Sakuma

Masahiro Toda

Yoshiro Koyasu

Masami Suzuki

Takashi Hirano

Hirohito Eto

Masayuki Shibata

Tetsuro Hashiguchi

Yoichi Taniguchi

Junichi Nakatsuka

Tetsuroh Hashiguchi

Kazuhiro Fujimura

Satoshi Koganemaru

Takeshi Komoto

Shinsaku Fukuda

A rolled steel bar for machine structural use includes a predetermined chemical composition comprising, by mass %, C: 0.45% to 0.65%, Si: higher than 1.00% to 1.50%, Mn: higher than 0.40% to 1.00%, P: 0.005% to 0.050%, S: 0.020% to 0.100%, V: 0.08% to 0.20%, Ti: 0% to 0.050%; Ca: 0% to 0.0030%, Zr: 0% to 0.0030%, Te: 0% to 0.0030%, and a remainder including Fe and impurities, wherein the impurities include: Cr: 0.10% or lower, Al: lower than 0.01%, and N: 0.0060% or lower. In the rolled steel bar for machine structural use, K1 obtained from 'K1=C+Si/7+Mn/5+1.54&#xd7;V' is 0.95 to 1.05, K2 obtained from 'K2=139&#x2212;28.6&#xd7;Si+105&#xd7;Mn&#x2212;833&#xd7;S&#x2212;13420&#xd7;N' is more than 35, a Mn content and a S content satisfy Mn/S&#x2265;8.0, and a total decarburized depth of a surface layer is 500 &#x3bc;m or less.

Rolled steel bar for machine structural use and method of producing the same

A rolled steel bar for machine structural use includes a predetermined chemical composition comprising, by mass %, C: 0.45% to 0.65%, Si: higher than 1.00% to 1.50%, Mn: higher than 0.40% to 1.00%, P: 0.005% to 0.050%, S: 0.020% to 0.100%, V: 0.08% to 0.20%, Ti: 0% to 0.050%; Ca: 0% to 0.0030%, Zr: 0% to 0.0030%, Te: 0% to 0.0030%, and a remainder including Fe and impurities, wherein the impurities include: Cr: 0.10% or lower, Al: lower than 0.01%, and N: 0.0060% or lower. In the rolled steel bar for machine structural use, K1 obtained from 'K1=C+Si/7+Mn/5+1.54&#xd7;V' is 0.95 to 1.05, K2 obtained from 'K2=139&#x2212;28.6&#xd7;Si+105&#xd7;Mn&#x2212;833&#xd7;S&#x2212;13420&#xd7;N' is more than 35, K3 obtained from &#x201c;K3=137&#xd7;C&#x2212;44.0&#xd7;Si&#x201d; is 10.7 or more, a Mn content and a S content satisfy Mn/S&#x2265;8.0, and a total decarburized depth in a surface layer is 500 &#x3bc;m or less.

Steel for forging having high strength and superior machinability due to controlled cooling immediately after shaping by hot forging followed by tempering and having a lower specific gravity than ordinary steel for forging use, the steel containing C: 0.05 to 0.50%, Si: 0.01 to 1.50%, Mn: 3.0 to 7.0%, P: 0.001 to 0.050%, S: 0.020 to 0.200%, Al: 3.0 to 6.0%, Cr: 0.01 to 1.00%, and N: 0.0040 to 0.0200% and having a balance of Fe and unavoidable impurities.

Low specific gravity steel for forging use excellent in machineability

The present invention provides a steel part for machine structural use whose fatigue strength and toughness are improved and a manufacturing method thereof. A steel part made of a steel containing, in mass %, C: 0.05 to 0.20%, Si: 0.10 to 1.00%, Mn: 0.75 to 3.00%, P: 0.001 to 0.050%, S: 0.001 to 0.200%, V: exceeding 0.20 to 0.25%, Cr: 0.01 to 1.00%, Al: 0.001 to 0.500%, and N: 0.0080 to 0.0200%, and a balance being composed of Fe and inevitable impurities, in which a steel structure contains a bainite structure having an area ratio of 95% or more, a bainite lath width is 5 &#x3bc;m or less, V carbide having an average grain diameter of not less than 4 nm nor more than 7 nm dispersedly exists in the bainite structure, and an area ratio of V carbide in the bainite structure is 0.18% or more.

Steel part for machine structural use and manufacturing method thereof

The present invention provides a steel part for machine structural use whose fatigue strength and toughness are improved and a manufacturing method thereof. A steel part made of a steel containing, in mass %, C: 0.05 to 0.20%, Si: 0.10 to 1.00%, Mn: 0.75 to 3.00%, P: 0.001 to 0.050%, S: 0.001 to 0.200%, V: exceeding 0.25 to 0.50%, Cr: 0.01 to 1.00%, Al: 0.001 to 0.500%, and N: 0.0080 to 0.0200%, and a balance being composed of Fe and inevitable impurities, in which a steel structure contains a bainite structure having an area ratio of 95% or more, a bainite lath width is 5 &#x3bc;m or less, V carbide having an average grain diameter of not less than 4 nm nor more than 7 nm dispersedly exists in the bainite structure, and an area ratio of V carbide in the bainite structure is 0.18% or more.

The present invention provides a steel part for machine structural use whose fatigue strength and toughness are improved and a manufacturing method thereof. A steel part made of a steel containing, in mass %, C: 0.05 to 0.20%, Si: 0.10 to 1.00%, Mn: 0.75 to 3.00%, P: 0.001 to 0.050%, S: 0.001 to 0.200%, V: 0.05 to 0.20%, Cr: 0.01 to 1.00%, Al: 0.001 to 0.500%, and N: 0.0080 to 0.0200%, and a balance being composed of Fe and inevitable impurities, in which a steel structure contains a bainite structure having an area ratio of 95% or more, a bainite lath width is 5 &#x3bc;m or less, V carbide having an average grain diameter of not less than 4 nm nor more than 7 nm dispersedly exists in the bainite structure, and an area ratio of V carbide in the bainite structure is 0.18% or more.

A steel tie rod end includes a shaft portion and first and second fitting portions. A minimum area portion having a small radially cross-sectional area is provided for the shaft portion, and 90% or above of a steel structure of the minimum area portion is formed of martensite or tempered martensite. The surface hardness of the minimum area portion and the average hardness of the radial cross section of the minimum area portion are 600 Hv or below, and the average hardness of the radial cross section of the first fitting portion and the average hardness of the radial cross section of the second fitting portion are 300 Hv or below. A method of manufacturing a steel tie rod end includes a quenching process of heating only a prospective shaft portion by high frequency to an austenitizing temperature and then rapidly cooling the prospective shaft portion by water or cooling medium.

Steering tie rod end made of steel and method of manufacturing the same

The present invention provides a fine grain surface layer steel part having a high proof strength ratio equal to or higher than that of conventional quenched and tempered materials, that is, a fine grain surface layer steel part containing, by mass %, C: 0.45% to 0.70%, Nb: 0.01% to 0.60%, Si: 0.10% to 1.50%, Mn: 0.40% to 2.0%, P: 0.10% or less, S: 0.001% to 0.15%, and N: 0.003% to 0.025% and having a balance of Fe and unavoidable impurities, where the surface layer and inside at all or part of the part have structures of different average particle sizes of ferrite crystal grains surrounded by high angle grain boundaries of a misorientation angle of 15 degrees or more and a method of production of that part comprising warm forging locations where strength is required to a predetermined shape at 1000&#xb0; C. to 800&#xb0; C. during which working so as to give an equivalent strain of 1.5 or more.

Fine grain surface layer steel part and method of production of same

A steel for machine structural use which realizes excellent fracture splitability and fatigue strength in its as-hot forged formed articles, and which comprises, based on weight, 0.2 to less than 0.35% of C, 0.1 to 1.1% of Si, 0.1 to less than 0.3% of Mn, 0.01 to 0.2% of P, 0.01 to 0.2% of S, greater than 0.2 to 0.5% of V, 0.01 to 0.1% of Ti, 0.005 to 0.02% of N and the balance of Fe and unavoidable impurities. The steel further comprises, if necessary, one or at least two of the following elements in the following amount or amounts: 0.005 to 0.05% of Al and/or 0.05 to 0.5% of Nb, 0.1 to 0.5% of Cr and 0.1 to 0.5% of Mo.

Steel for machine structural use excellent in fracture splitability and

Non-tempered steel for mechanical structure

A steel for machine structural use, essentially having the following chemical composition:

Steel for machine structural use and machine parts made from such steel

Microalloyed steel for hot forging free of subsequent quenching and

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Tokyo, Japan

Hiromasa Takada