HIC tests (Hydrogen Induced Cracking) were performed for eight types of X65 linepipes in various environments in which H2S partial pressure was in the range of 1x10-5 to 0.1 MPa and pH was in the range of 2 to 5. The conditions governing HIC occurrence were investigated and the following results are obtained: (1) (H)(in Fe) was formulated as a function of ppHpS and pH ((H)(in Fe) = 3.1 + 0.56logP(H2S) - 0.17pH). (2) CAR (crack area ratio) of HIC increases with an increase in (H)(in Fe). (3) (H)(crit) was expressed as a function of the length of MnS and the maximum hardness of center-segregation zone for the investigated TMCP steels (log(H)(crit) = (1.2 - 0.0020Hv) - 1/4log(a(crit))). HIC initiated in the lower critical hydrogen concentration for CR steel. CR steels are also expected to follow this equation, while first term (1.2 - 0.0020Hv) of this equation for CR steels is supposed to be lower than that for TMCP steels. (4) If the maximum hardness of center-segregation zone and the size of MnS are given, whether KIC occur or not can be predicted for a given environmental condition.
The condition of HIC occurrence of X65 linepipe in wet H2S environments
Bedingungen für das Auftreten von wasserstoffinduzierter Rißbildung in X65-Pipelinerohren in feuchter H2S-haltiger Umgebung
Corrosion, 1999 ; 429/1-429/14
1999
14 Seiten, 13 Bilder, 3 Tabellen, 10 Quellen
Conference paper
English
Microstructure and strength dependence of occurrence of HIC in linepipe steels
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