Creep strain, damage and life prediction for welded 0.5CMV steel

Juhani Rantala, Pertti Auerkari, Stefan Holmström, Jorma Salonen, Anssi Laukkanen

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientific

    Abstract

    Creep damage as cavitation and cracking has historically occurred somewhat earlier in the inspections of steam lines made of 0.5CMV steel, when compared to other low alloy steels. The difference has been attributed to modest creep ductility of 0.5CMV steel, and has resulted in attention paid to inspection and maintenance. As the steel is still being used in vintage plants, it is of interest for users while also serving as a model material that can show some essential features of long term creep in much shorter laboratory testing. Particularly challenging service can combine welded thick-wall components with pre-existing fabrication defects, resulting in an unfavorable combination of high stresses, multi-axial loading, and locally weak material. Examples are shown of the observed damage evolution in welded 0.5CMV steam line material in front of a crack-like defect. Long-term multi-axial loading does not necessarily result in type IV failure of welds, but can also induce creep damage and cracking close to the fusion line. This particularly applies to welds with undermatching weld metal such as those made with consumables corresponding to 2.25Cr-1Mo steel. With the LICON approach, it has been shown that this IIIa type of damage can be reproduced in about 5 000 h of multi-axial creep testing, while in plant such damage may require more than 100 000 h of service. The microstructural features of the observed damage and a comparison of uniaxial and CT test data suggest that the LICON approach of life prediction could be applied also for welded components where the location of maximum damage deviates from the type IV position.
    Original languageEnglish
    Title of host publicationBaltica VIII
    Subtitle of host publicationLife Management and Maintenance for Power Plants
    Place of PublicationEspoo
    PublisherVTT Technical Research Centre of Finland
    Pages176-192
    Volume2
    ISBN (Electronic)978-951-38-7594-7
    ISBN (Print)978-951-38-7593-2
    Publication statusPublished - 2010
    MoE publication typeB3 Non-refereed article in conference proceedings
    EventBALTICA VIII - International Conference on Life Management and Maintenance for Power Plants - Helsinki-Stockholm, Finland
    Duration: 18 May 201020 May 2010

    Publication series

    SeriesVTT Symposium
    Number265
    ISSN0357-9387

    Conference

    ConferenceBALTICA VIII - International Conference on Life Management and Maintenance for Power Plants
    CountryFinland
    CityHelsinki-Stockholm
    Period18/05/1020/05/10

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  • Cite this

    Rantala, J., Auerkari, P., Holmström, S., Salonen, J., & Laukkanen, A. (2010). Creep strain, damage and life prediction for welded 0.5CMV steel. In Baltica VIII: Life Management and Maintenance for Power Plants (Vol. 2, pp. 176-192). VTT Technical Research Centre of Finland. VTT Symposium, No. 265 https://www.vtt.fi/inf/pdf/symposiums/2011/S265.pdf