New High Strength Steels having a Bainitic microstructure (HSBS) have been designed for large truck parts or smaller automotive parts produced by hot forging and controlled cooling. These steels can be used: - when other traditional micro alloyed steel grades cannot meet the requirements of the new parts designed for weight reduction. - when subsequent savings (cost, energy) are desired while maintaining equivalent or improved properties compared to quenched and tempered parts. In this case, these grades are an alternative to heat treated alloyed grades, such as NiCrMo or CrMo grades. - if the forger is not equipped with heat treatment facilities. - for parts with a new design, for example parts with shapes that could be sensitive to cracking or to distortion, if a classical quenching process is applied after forging. The bainitic steel grades presented are readily applicable to parts that do not need induction hardening treatment after machining, some however are specially designed for parts requiring this treatment. This presentation deals with the characteristics: mechanical properties, machinability, quenchability, hardenability Jominy and induction hardening characterisation and finally fatigue behaviour, of the new bainitic grades developed in our R&D centre. The CCT diagrams of a selection of these grades are presented and illustrated with numerous microstructures. Comparison between the microstructures observed on parts and those obtained after laboratory simulations are shown. Finally, our recommendations to achieve the parts are explained with a focus on the forging process control as well as on the machining process.
New generation of High Strength Bainitic Steels (HSBS) for large forging and automotive components
2008
14 Seiten, 14 Quellen
Conference paper
English
Abkühlungsgeschwindigkeit , Aushärten , Automobilbau , bainitischer Stahl , Fahrzeugbauteil , gehärteter Stahl , Gewichtsverringerung , hochfester Stahl , Induktionserwärmung , Induktionshärten , kontinuierliche Abkühlungskurve , Leichtbauweise , Materialermüdung , mechanische Festigkeit , mikrolegierter Stahl , Mikrostruktur , Prozesssteuerung , Schmiedestahl , Schmiedestück
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