Volume 31, Issue 3 (May 2003)

    Application of Stress Relaxation Test Methodology for Predicting Creep Life of a Large Steam Turbine Rotor Steel (1CrMoV)

    (Received 11 April 2002; accepted 16 December 2002)

    CODEN: JTEOAD

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    Abstract

    The technique proposed here adopts short-term stress relaxation testing (SRT) to determine the metallurgical life of 1CrMoV large rotor steel. SRT has been performed at two temperature levels of 550°C and 600°C, on samples taken from the core region of a large rotor. At 550°C, five initial prestrains ranging from 0.2–1.0% strain were applied, while at 600°C, the specimens were relaxed from 0.6% and 0.8% prestrains. All test durations were kept between 4 to 5 h. To validate the results, a few conventional creep tests have been conducted at same temperature levels and at different stresses. The initial data, stress versus time, were converted into stress versus inelastic strain rate and the creep life was predicted with the help of the Monkman-Grant relationship (ˊεs × tr) = C), where the value of the constant C is taken from experimental creep data. The comparison of creep life, predicted through SRT, with the actual creep data revealed that they were agreeing extremely well at higher test temperature, i.e. 600°C. The computed SRT data have delivered higher activation energy (600 kJ mol−1) than conventional creep testing (344 kJ mol−1). Detailed SEM and TEM studies revealed that degradation and/or development of microstructures had taken place and was commensurable to long-term creep exposure. Therefore, the methodology has the capacity to assess the inherent creep strength of any material.


    Author Information:

    Bose, SC
    Deputy Manager and Senior Managers, Metallurgy Dept., Corporate R & D, Bharat Heavy Electricals Limited, Vikasnagar, Hyderabad,

    Singh, K
    Deputy Manager and Senior Managers, Metallurgy Dept., Corporate R & D, Bharat Heavy Electricals Limited, Vikasnagar, Hyderabad,

    Jayaraman, G
    Deputy Manager and Senior Managers, Metallurgy Dept., Corporate R & D, Bharat Heavy Electricals Limited, Vikasnagar, Hyderabad,


    Stock #: JTE12427J

    ISSN: 0090-3973

    DOI: 10.1520/JTE12427J

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    Author
    Title Application of Stress Relaxation Test Methodology for Predicting Creep Life of a Large Steam Turbine Rotor Steel (1CrMoV)
    Symposium , 0000-00-00
    Committee E28