Transgranular stress corrosion cracking (TGSCC) can develop in pipelines under normal operating conditions when a coating breaks down and ground water comes into contact with the outside surface. An investigation was carried out on API X-60 steel specimens with multiple edge cracks to determine transgranular stress corrosion crack (TGSCC) growth rates in simulated ground water (NS-4 solution). Loading and environmental conditions were similar to those for buried natural gas pipelines in service. Specimens were loaded statically or cyclically in cantilever bending with the maximum crack tip stress intensity factor (Kmax varying from 34 MPa.m0.5 to 38 MPa.m0.5. Static tests were carried out for periods extending to 111 days. For the cyclic tests, which lasted up to 378 days, the stress ratio (R = minimum/maximum load) was controlled between 0.5 to 0.9, with frequencies ranging from 40 cycles/day to 5000 cycles/day. TGSCC with crack features similar to those found in the field was produced successfully in the laboratory. Depending upon the loading conditions and test period, the crack growth varied from approximately 10 to 1800 micron, corresponding to maximum average crack growth rates from 6.1x10-10 mm/s to 2.6x10-7 mm/s. For a low R ratio and high frequency, the observed growth was the result of corrosion fatigue. Under the conditions of a static load or high R ratio and low frequency, growth was caused by TGSCC. A superposition model for crack growth was proposed and applied to the experimental data, giving good agreement between the predicted and observed crack growth rates.


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    Title :

    Transgranular stress corrosion cracking of X-60 pipeline steel in simulated ground water


    Additional title:

    Transkristalline Spannungsrißkorrosion des X-60 Röhrenstahles in simuliertem Grundwasser


    Contributors:
    Zhang, X.Y. (author) / Lambert, S.B. (author) / Sutherby, R. (author) / Plumtree, A. (author)

    Published in:

    Corrosion, Houston ; 55 , 3 ; 297-305


    Publication date :

    1999


    Size :

    9 Seiten, 17 Bilder, 1 Tabelle, 20 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English