Effect of manganese content and microstructure on the susceptibility of X70 pipeline steel to hydrogen cracking

► Increasing the hydrogen content decreases the fracture toughness (JQ) linearly. ► X70 strip exhibits higher JQ than MX70 strip before and after hydrogen charging. ► The normalized X70 transfer bar shows much lower JQ than the hot rolled strips. ► The fracture morphology changed from ductile to bri...

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Bibliographic Details
Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2012-08, Vol.551, p.40-49
Main Authors: Hejazi, D., Haq, A.J., Yazdipour, N., Dunne, D.P., Calka, A., Barbaro, F., Pereloma, E.V.
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Fractography
Fracture toughness
Fractures
Hydrogen charging
Inclusions
Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology
Metals. Metallurgy
Microstructure
Pipeline steel
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Summary:► Increasing the hydrogen content decreases the fracture toughness (JQ) linearly. ► X70 strip exhibits higher JQ than MX70 strip before and after hydrogen charging. ► The normalized X70 transfer bar shows much lower JQ than the hot rolled strips. ► The fracture morphology changed from ductile to brittle with increasing hydrogen. ► Simulated CGHAZ structures show low JQ which decreases with increasing hydrogen. The influence of composition and microstructure on susceptibility to hydrogen induced cracking (HIC) was investigated in high strength pipeline steels, with Mn contents of 1.2% (standard, X70), and 0.5% (medium, MX70). The HIC resistance of the simulated coarse grained heat affected zone microstructures and normalized X70 transfer bar was also investigated. Notched and fatigue pre-cracked samples were charged with hydrogen prior to three point bend tests. The conditional fracture toughness JQ was determined. The results are discussed in relation to grain size, microstructure, composition and the type and distribution of non-metallic inclusions and precipitates.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2012.04.076