In the framework of the development of a microalloyed grade for truck crankshaft as a replacement of the hardened tempered alloyed grade 34CrNiMo6, Mittal Steel R&D and ThyssenKrupp Automotive have made a study based on a medium carbon and high manganese grade. Different chemical compositions (with the addition of various microalloying elements (V, Mo, Si, B, etc) were explored (on Laboratory Ingots). Subsequently the different microstructures obtained on forged bars (ferrite pearlite, bainite and mixed pearlite/bainite) were characterized. After one year of investigations, a new grade CRIE A7 was set up: it is a medium carbon microalloyed grade with a mixed microstructure of pearlite/bainite after forging. An industrial heat was cast at Mittal Steel Ruhrort, crankshafts were forged at ThyssenKrupp Gerlach Company (USA) and ThyssenKrupp Gerlach (Germany), and machined and treated at ThyssenKrupp Mavilor (France). For this new grade, no problem appears in the forging process. However, due to the high mechanical properties of this grade, a study was necessary to determine the machining conditions particularly regarding the deep drilling operation. The crankshafts microstructures, depend on the true cooling rate at a localized point but the level of hardness is relatively homogeneous throughout one kind of crankshaft. Machining these structures is difficult due to the high mechanical properties but one can propose the drilling conditions that are suitable for all the structures present on the crankshafts. This new grade has high mechanical properties on 'as forged' crankshafts (UTS around 1200 MPa), and good induction hardened behaviour.The fatigue tests are in progress and the results are promising.


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    Title :

    Development of an 'as forged' microalloyed steel with high torsional fatigue strength for truck crankshafts


    Additional title:

    Entwicklung eines geschmiedeten mikrolegierten Stahls mit hoher Drehungsermüdungsfestigkeit für Kurbelwellen von Lastkraftwagen




    Publication date :

    2005


    Size :

    8 Seiten, 6 Bilder, 3 Tabellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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