Critical hardness for HSC in deposit welding on steel line pipes under cathodic protection

Noritake Oguchi, Hiroyuki Lnoue, Junichi Sakai, Shigeru Komukai

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    1 Citation (Scopus)

    Abstract

    Repairing corrosion-damaged areas of operational steel line pipes by deposit welding performed without stopping the gas flowing inside is a common practice. However, this repair method tends to considerably increase the hardness of the weld metal and the HAZ, and it poses the risk of HSC under cathodic protection. In this study, the HSC susceptibility of the welding area was examined using welded full-scale C-ring specimens. The specimens were prepared from X42, X60, and X65 steel line pipes, whose outer diameter and longitudinal length were 610mm and 100 to 110mm, respectively, and whose nominal thickness was 10.3 to 15.1mm. Deposit welding was applied to the middle of each specimen's outer surface, and then a bolt through the specimen was tightened until the welded part was subjected to yield stress. The welded surface of the welding and its surrounding area were exposed to a test solution whose pH was adjusted to 7, and a cathodic current of 20mA/cm2 or 4mA/cm 2 was applied for 500hours. Cracks appeared in the weld metals on the C-ring specimens to which a cathodic current of 20mA/cm2 had been applied. However, the propagation of the cracks ceased at the boundaries between the weld metal and the HAZ, and no cracks initiated in the HAZ. The maximum hardness of the HAZ was about 300 to 400Hv. These levels of hardness are far greater than 260Hv, which is the value obtained from experiments carried out using slow strain rate testing and is widely used in Japan as a criterion of hardness for avoiding HSC in the HAZ.

    Original languageEnglish
    Title of host publicationProceedings of the Biennial International Pipeline Conference, IPC
    Pages371-376
    Number of pages6
    Volume2
    DOIs
    Publication statusPublished - 2007
    Event2006 6th International Pipeline Conference, IPC 2006 - Calgary, AB
    Duration: 2006 Sep 252006 Sep 29

    Other

    Other2006 6th International Pipeline Conference, IPC 2006
    CityCalgary, AB
    Period06/9/2506/9/29

    ASJC Scopus subject areas

    • Engineering(all)

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  • Cite this

    Oguchi, N., Lnoue, H., Sakai, J., & Komukai, S. (2007). Critical hardness for HSC in deposit welding on steel line pipes under cathodic protection. In Proceedings of the Biennial International Pipeline Conference, IPC (Vol. 2, pp. 371-376) https://doi.org/10.1115/IPC2006-10227