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    Evaluation of the Modified 9Cr-1Mo Steel Forging by French Laboratories

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    The use of Oak Ridge National Laboratory's (ORNL) modified 9Cr-1Mo steel in liquid metal fast breeder reactor (LMFBR) steam generators (SGs) could present significant advantages as compared with the other ferritic steels envisaged or used for this application.

    Novatome (France) received from ORNL a specimen of this steel obtained from a National Forge Co. (NF) saddle forging.

    The evaluation of this specimen by French laboratories covers the topics deemed the most significant to confirm the advantages of this steel for a LMFBR-SG application. Namely: tensile, creep, impact properties, tensile and impact behavior after heat treatment performed to simulate very thick forgings, fatigue, stress corrosion cracking, fracture mechanics, and aging behavior.

    Our results confirm that the impact properties of modified 9Cr-1Mo steel are excellent, at least up to a simulated thickness of 300 mm (12 in.), even after step cooling. They also confirm that this steel has among the highest mechanical properties and creep resistance, as compared with other ferritic steels envisaged or used for LMFBR-SG applications.

    On the basis of these first satisfactory results, we are encouraged to continue the characterization of this steel in France. This work is proceeding, on the one hand, on the NF forging and, on the other hand, on a forged-rolled thick plate manufactured in France. This characterization program will last 5 years.


    forgings, chromium molybdenum steels, mechanical properties, microstructure, heat treatment, fast nuclear reactors, breeder reactors, boiler plate

    Author Information:

    Gelpi, A
    Consulting engineer, Framatome, Paris-La Défense,

    Committee/Subcommittee: A01.06

    DOI: 10.1520/STP17366S