Sammendrag
The exploration of oil and gas fields in the arctic brings several challenges in the use of structural steels concerning their low-temperature properties. Among others, fatigue behavior needs also to be considered for arctic applications, despite little attention to fatigue at low temperature has been given so far. This paper summarizes a set of fatigue crack growth rate tests performed both at room temperature and at -60 °C, with the latter representing the possible design temperature relevant for the most extreme arctic areas. Accordingly, the material under investigation is a 420 MPa structural steel, one of the probable candidate materials to be used for structural purpose here.
Since weldments are the most susceptible to fatigue failures, the fatigue crack growth measurements have been performed not only on parent metal, but they have been extended also to weld thermal simulated Coarse Grained Heat Affected Zone (CGHAZ) and Intercritically Reheated Coarse Grained Heat Affected Zone (ICCGHAZ). The resulting fatigue crack growth curves are compared to the fatigue assessment curves indicated in BS 9710:2013. Data indicates that, for all the material under investigation, the fatigue properties are improved at -60 °C when compared to room temperature
Since weldments are the most susceptible to fatigue failures, the fatigue crack growth measurements have been performed not only on parent metal, but they have been extended also to weld thermal simulated Coarse Grained Heat Affected Zone (CGHAZ) and Intercritically Reheated Coarse Grained Heat Affected Zone (ICCGHAZ). The resulting fatigue crack growth curves are compared to the fatigue assessment curves indicated in BS 9710:2013. Data indicates that, for all the material under investigation, the fatigue properties are improved at -60 °C when compared to room temperature