Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Shinya Nakajima

Masayuki Abe

Jun Maki

Kazuhisa Kusumi

Toshiyuki Kanda

Noriyuki Suzuki

Kunio Hayashi

Nobuhiro Fujita

Manabu Takahashi

Hironori Sato

Yuzo Takahashi

Masahiro Ohgami

Norihiro Fujita

Masahiro Oogami

A method is proved for hot pressing hot rolled steel sheet, cold rolled steel sheet, Al-based plated steel sheet or Zn-based plated steel sheet, where the hot pressed sheet can exhibit a strength of at least about 1200 Mpa, and my be prevented from exhibiting hydrogen embrittlement. The steel sheet may include between about 0.05 to 0.5 wt % C, and/or it may be plated with an Al-based or Zn-based plating material. The steel sheet may be heating to a temperature greater than an Actemperature and not more than about 1100&#xb0; C. before pressing. An atmosphere can be provided during heating which contains not more than about 6 vol % of hydrogen and a dew point of not more than about 10&#xb0; C. The exemplary methods may be used to form high strength parts which may be used, e.g., in automobiles.

Hot pressing method for high strength member using steel sheet and hot pressed parts

High-strength parts and a method for producing them can be provided, where such parts exhibit hydrogen embrittlement resistance and strength after high-temperature forming. For example, the atmosphere in a heating furnace can contain less than about 10% hydrogen and/or have a dew point of about 30&#xb0; C. or less. The amount of hydrogen penetrating a steel sheet during heating can thereby be reduced. After forming, quench hardening in a die assembly and post-working can be performed. Post-working can include shearing followed by re-shearing or compression forming; punching with a cutting blade having a continuously reduced base width; punching with a tool having a curved blade and a protrusion at the tip of the cutting blade, where the curved blade may include a shoulder portion of given radius and/or angle; fusion cutting; etc. Tensile residual stresses after punching can be reduced and resistance to hydrogen embrittlement can be improved.

High strength part and method for producing the same

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Kitakyushu, Japan

Shinya Nakajima