Honda Motor Co., Ltd.

Sumitomo Metal Industries, Inc.

Saga Tekkohsho Co., Ltd.

Daido Steel Co., Ltd.

Tetsuya Asai

Hideki Imataka

Masaki Amano

Hitoshi Matsumoto

Yoshihiro Takitani

Daisuke Suzuki

Katsuhiro Tsukiyama

Takehiko Egawa

Hayato Onda

Katsunori Daido Steel Co Ltd Takada

Makoto Daido Steel Co Ltd Hobo

Kazuyoshi Daido Steel Co Ltd Kimura

There is provided a screw treated by a chemical conversion coating of trivalent chromium having a torque characteristic approximately equivalent to a screw of a hexavalent chromate treatment. For the purpose, on a surface of a bolt, a zinc plating layer is formed by a zinc plating treatment. On the layer, a chemical conversion coating of trivalent chromium is also formed by a treatment of chemical conversion coatings of trivalent chromium. The coating is formed to be thin and soft so that the zinc-based plating layer can be exposed on the surface due to rubbing off of the chemical conversion coating of trivalent chromium at a contact portion to a fastened member of the bolt by tightening the bolt.

Screw and screw fastening structure

A hot forged non-heat treated steel for induction hardening, comprising by mass percent, C: 0.35 to 0.45%, Si: 0.20 to 0.60%, Mn: 0.40 to 0.80%, S: 0.040 to 0.070%, Cr: 0.10 to 0.40%, Ti: 0.020 to 0.100%, Ca: 0.0005 to 0.0050%, B: 0.0005 to 0.0030%, O: 0.0015 to 0.0050%, Mo: 0 to 0.05%, P: 0.025% or less, V: 0.03% or less, Al: 0.009% or less and N: 0.0100% or less, and the balance being Fe and impurities, with Fn1=C+(Si/10)+(Mn/5)+(5Cr/22)+1.65V&#x2212;(5/7S)+1.51&#xd7;(Ti&#x2212;3.4N)&#x2266;0.63, Ca/O&#x2266;1.0, and 25.9&#xd7;Fn1+27.5&#xd7;(Ti&#x2212;3.4N)&#x2212;7.9&#x2267;5.7, has more excellence in the machinability than a conventional steel and also has fatigue strength equal to or more than that of a conventional steel, while using the steel product in a hot forged state as a starting material.

Hot forged non-heat treated steel for induction hardening

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Wako, Japan

Tetsuya Asai