Aisin Takaoka Co., Ltd.

Nippon Steel Corporation

Toyota Jidosha Kabushiki Kaisha

Nippon Steel Sumitomo Metal Corporation

Masashi Ozawa

Shinichi Suzuki

Toshimasa Tomokiyo

Shuuji Souma

Katsuji Nakashima

Kiyohito Kondou

Hiroshi Sato

Kiyoshi Nonomura

Yuki Ishiguro

Hideaki Ikezawa

A current density changing portion is formed in a heating process on an upper base side with respect to a center portion of a flat metal plate in a direction of current flow, by passing current from a lower base side to the upper base side of the flat metal plate which is rectangular when viewed from above. As a result, a quenchable portion is formed on the upper base side with respect to the center portion of the flat metal plate in the direction of current flow, and a non-quenchable portion is formed on the lower base side with respect to the center portion of the flat metal plate in the direction of current flow. The flat metal plate is press-formed after the heating process, so a complex die cooling structure is not necessary during press-forming, which enables the die cost to be reduced.

Press-forming method and press-formed part

The high-strength quenched formed body contains a layer, in which Zn is a major component and which is formed of Fe: 30% by mass or less, in an amount of 30 g/mor more on the surface of an after-quenching formed-body steel material, and accordingly is good in corrosion resistance. A quenched formed body is produced by quenching a zinc-plated steel material, which includes a zinc-plated layer which contains each of Al and Si having alloying-retarding function and readily-oxidizing function independently or compositely, in an amount of 0.15% by mass or more, after heating it to 800&#xb0; C. or more and 950&#xb0; C. or less in an oxidizing atmosphere of oxygen: 0.1% by volume or more.

High-strength quenched formed body with good corrosion resistance

A high-strength quenched formed body containing a layer on the surface of an after-quenching formed-body steel material in which layer Zn is a major component and which layer contains 30% by mass or less of Fe, and which layer is present in an amount of 30 g/mor more. A quenched formed body is produced by quenching a zinc-plated steel material which includes a zinc-plated layer containing each of Al and Si having alloying-retarding function and readily-oxidizing function independently or compositely, in an amount of 0.15% by mass or more, after heating it to 800&#xb0; C. or more and 950&#xb0; C. or less in an oxidizing atmosphere containing 0.1% by volume or more of oxygen.

High-strength quenched formed body with good corrosion resistance and process for producing the same

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Toyota, Japan

Masashi Ozawa