High-strength pipeline steels, such as X100 steel, experience strain ageing upon coating application. This is indicated by the presence of Luders strain during yielding, an increased yielding strength, decreased elongation and the high Y/T ratio. However, strain ageing would not alter the microstructure of the steel. Strain ageing affects (increases) the susceptibility of X100 steel to SCC, especially at the CP or more negative potentials. It is suspected that hydrogen evolution is enhanced at the cathodic potential, and hydrogen is involved in the cracking process. Hydrogen could induce blistering and cracking of high-strength steels even in the absence of external stress. The hydrogen-induced crack is associated with the inclusion. The hydrogen permeation rate, hydrogen diffusivity, hydrogen apparent solubility, sub-surface hydrogen concentration and hydrogen trapping density in X80 and X100 steels are determined. Compared to α-Fe, X80 and X100 pipeline steels are capable of trapping much more hydrogen at reversible trapping sites such as dislocations, grain boundaries, M/A islands, etc. Hydrogen would also be trapped at irreversible traps such as inclusions to induce hydrogen-induced cracking (HIC).


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    Title :

    Strain ageing of high-strength steels in the northern area and the associated technical challenges in development of high-strength steel pipeline technologies


    Additional title:

    Reckalterung von hochfesten Stählen in nördlichen Regionen und die damit zusammenhängenden technischen Herausforderungen bei der Entwicklung von hochfesten Stahl-Pipelinetechnologien


    Contributors:


    Publication date :

    2013


    Size :

    6 Seiten, 7 Bilder, 26 Quellen


    Type of media :

    Conference paper


    Type of material :

    Storage medium


    Language :

    English




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