Nobuhiko Ibaraki

Influence of Si on nano sub-structure of cementite lamellae in pearlitic steel wires

Abstract Microstructures of hot dip galvanized pearlitic steel wires were investigated by TEM to understand the influence of Si on sub-structure of cementite lamellae in pearlitic steel wires. The following conclusions were obtained: 1. 1) Each single crystal cementite lamella turned into aggregation of nano sub-structure after cold drawing and blueing over 673K. 2. 2) The diameter of the nano sub-cementite is controlled by blueing temperature and Si content.

Development of 1600 N/mm2 Class Ultra-High Strength Bolts

Many different bolts are employed in automobiles for different purposes and uses, and their strength generally ranges from 700 N/mm 2 to 1200 N/mm 2 . Automobiles face the issue of making improvements in fuel economy as anenvironmental measure, and there is consequently a requirement to lighten component parts. The creationof higher-strength bolts is an important factor in achieving lighter weight. Increasing the strength, however, can also bring about an increased incidence of delayed fracture, and the conventional solution used to require the application of special steels such as expensive maraging steel. The present development addressed this issue by focusing on high carbon steel rod, which had been considered less susceptible to delayed fracture, although heading was also considered to be difficult. Heading techniques were therefore devised that made it possible not only to form bolts from this material, but also to provide satisfactory strength. The result was successful development of 1600 N/mm 2 class high strength bolts.

Hochfester Walzdraht für die Herstellung von Aufhängungsfedern mit hervorragender Korrosions- Ermüdungsbeständigkeit

Dieser Beitrag von Kobe Steel befasst sich mit der Entwicklung eines neuen Aufhangungsfederstahls UHS 1900, der fur eine maximale Schubspannung von 1200 MPa ausgelegt ist und sich durch hervorragende Korrosionsermudungs-Charakteristika auszeichnet. Diese wurde durch erhohten Widerstand gegen Lochfraβkorrosion und Wasserstoffsprodigkeit erreicht. Der Korrosionswiderstand wurde durch Zulegieren von Kupfer, Nickel und Chrom verbessert. Der Widerstand gegen Wasserstoffsprodigkeit wurde erhoht, indem Titan hinzugefugt wurde, was zur Entstehung von Wasserstoff-Einfangstellen fuhrte.