Reheat cracking susceptibility of new generation 2%CrMo(W)V P23 steel multipass welds made using matching and mis-matching filler metals

Pekka Nevasmaa, Jorma Salonen, Stefan Holmström

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

    Abstract

    In comparison with conventional creep resisting grade T/P22, the modified 2%Cr steels T/P23 and T/P24 show nearly twice the creep strength at typical service temperatures of about 520-570°C. The possibility of welding thin-wall boiler tubes without preheating or PWHT has promoted the use of T23 and T24 in practical boiler service. For thick-wall applications and multipass welds, welding consumables still require further development to improve creep strength and ductility. Susceptibility to reheat cracking and hydrogen cracking increase with the wall-thickness and structural rigidity of the component. Consequently, thick-wall sections generally require the use of PWHT and sometimes preheating as well. This paper is concerned with weldability of P23 pipe steel, with particular emphasis on reheat cracking sensitivity of simulated HAZ microstructures and thick-section multipass welds made using closely matching and mis-matching filler metals. The results demonstrate that the weld metal is far more critical than the parent steel HAZ, both in terms of reheat cracking sensitivity and ductility & toughness. In the as-welded condition, the weld metal exhibited excessive hardness of 380 HV and only diminutive Charpy toughness at room temperature. Adoption of the PWHT (760°C/2h) enhanced the weldment toughness; however, it also inevitably raises risk to reheat cracking in the weld metal that showed values of reduction of area (RA) no more than 2-3% in the BWI cracking test. The results imply that thick-section multipass welds made using filler metal with the chemical composition closer to P24 grade material are much less susceptible to reheat cracking than 'matching' P23 grade welds.
    Original languageEnglish
    Title of host publicationBALTICA VII - Life Management and Maintenance for Power Plants. Vol. 1
    Place of PublicationEspoo
    PublisherVTT Technical Research Centre of Finland
    Pages128-142
    ISBN (Electronic)978-951-38-6316-6
    ISBN (Print)978-951-38-6315-9
    Publication statusPublished - 2007
    MoE publication typeB3 Non-refereed article in conference proceedings
    EventBALTICA VII - International Conference on Life Management and Main-tenance for Power Plants - Helsinki-Stockholm, Finland
    Duration: 12 Jun 200714 Jun 2007

    Publication series

    SeriesVTT Symposium
    Number246
    ISSN0357-9387

    Conference

    ConferenceBALTICA VII - International Conference on Life Management and Main-tenance for Power Plants
    CountryFinland
    CityHelsinki-Stockholm
    Period12/06/0714/06/07

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  • Cite this

    Nevasmaa, P., Salonen, J., & Holmström, S. (2007). Reheat cracking susceptibility of new generation 2%CrMo(W)V P23 steel multipass welds made using matching and mis-matching filler metals. In BALTICA VII - Life Management and Maintenance for Power Plants. Vol. 1 (pp. 128-142). VTT Technical Research Centre of Finland. VTT Symposium, No. 246 https://www.vtt.fi/inf/pdf/symposiums/2007/S246.pdf