In all application fields for hot rolled strip products for direct processing, e.g.
construction and engineering but also crane and truck industry, there is a strong customers demand for grades with increased strength levels and well balanced formability. At voestalpine Stahl GmbH these requirements were met with the development of the high strength microalloyed steel grade ALFORM700M and the ultra high strength steel grade ALFORM900M with a minimum yield strength (YS) of 700 MPa and 900 MPa, respectively. In the present paper investigations on the steel grades ALFORM700M and ALFORM900M are introduced. To explain the evolution of the obtained complex microstructures consisting of bainitic ferrite, bainite and martensite alloy design and industrial production process is discussed on
the base of dilatometric experiments and TEM investigations. The formation of precipitates is studied by using a numerical model, chemical methods and mechanical testing after heat treatment. Mechanical and mechanic-technological properties of the two steel grades are compared. Furthermore, some processing aspects as weldability an bending behaviour are highlighted. Finally, some typical applications for this high and ultra high strength steel grades are presented.
The beneficial combination of thermomechanical Abstract: rolling and subsequent martensitic transformation is described as convenient method to receive ultra high strength hot rolled material with well balanced ductility and toughness. Using examples from laboratory experiments and investigations on hot rolled material produced in industrial scale the influence of austenite conditioning on the material behaviour after quenching with and without subsequent tempering is shown. Using this method for production of strip and cut length sheets or plates yield strength levels from 900MPa to 1100MPa can be reached with very low carbon contents between 0.08 and 0.17 m%. Therefore excellent welding behaviour is obtained.
Ultrahochfeste thermomechanisch gewalzte Stähleverbesserte Eigenschaften und AnwendungenDie Kombination aus thermomechani-Zusammenfassung: schem Warmwalzen und nachfolgendem Härten wird als geeignete Methode zur Erzeugung von ultrahochfesten warmgewalzten Stahlsorten vorgestellt, die hohen Anforderungen an Dehnung und Zähigkeit genügen. Mithilfe von Ergebnissen aus Produktionsversuchen im Labor, aber auch im großtechnischen Maßstab, wird der Einfluss der Austenitkonditionierung auf die Werkstoffeigenschaften sowohl mit als auch ohne nachfolgender Anlassbehandlung dargestellt. Durch die Anwendung dieser Produktionsmethode für die Fertigung von Warmband und Tafelblech können Streckgrenzenlagen zwischen 900 MPa und 1100MPa mit C-Gehalten zwischen 0,08m% und 0,17m% dargestellt werden. Daraus resultierend ergibt sich ein problemloses Verhalten beim Schweißen.
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