PIECE TRES RESISTANTE ET PROCEDE POUR LA FABRICATION DE CELLE–CI

N° de brevet: EP1790422 (A1)
Date de publication: 2007-05-30
Inventeur(s): KUSUMI KAZUHISA [JP];SATO HIRONORI [JP];ABE MASAYUKI [JP];FUJITA NOBUHIRO [JP];SUZUKI NORIYUKI [JP];HAYASHI KUNIO [JP];NAKAJIMA SHINYA [JP];MAKI JUN [JP];OOGAMI MASAHIRO [JP];KANDA TOSHIYUKI [JP];TAKAHASHI MANABU [JP];TAKAHASHI YUZO [JP];
Demandeur(s): NIPPON STEEL CORP [JP];
Classification: B21D28/00;B21D28/14;C21D9/46;C21D1/74;C22C38/00;C22C38/04;C22C38/38;
N° de demande: EP20050785864 20050915 
Numéro(s) de priorité: WO2005JP17441 20050915;JP20040267797 20040915;JP20040267795 20040915;JP20040267792 20040915;JP20040309779 20041025 
A high-strength part that excels in hydrogen embrittlement resistance and strength after high-temperature forming; and a process for producing the same. The atmosphere in a heating furnace before forming is regulated to one of 10% hydrogen volume fraction and 30°C dew point. As a result, the amount of hydrogen penetrating in a steel sheet during heating is reduced. After forming, there are sequentially carried out quench hardening in die assembly and post-working. As the method of post-working, there can be mentioned shearing followed by re-shearing or compression forming of sheared edge portion; punching with a cutting blade having a gradient portion at which the width of blade base is continuously reduced; punching with a punching tool having a curved blade with a protrudent configuration at the tip of cutting blade part, the curved blade having a shoulder portion of given curvature radius and/or given angle; fusion cutting; etc. Consequently, the tensile residual stress after punching is reduced and the performance of hydrogen embrittlement resistance is improved.

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