Linepipe steels for sour, arctic and offshore applications, form a class of material by themselves. These linepipes are originated in the need to fulfill several special characteristics like adequacy for induction bending, toughness requirement at very low temperature to prevent a unstable crack propagation, and hydrogen induced cracking resistance.
These kind of linepipes are produced through clean steel practice, resulting in a low residuals content and a low non metallic inclusions rating. It is also very important to get a fine and uniform microstructure to guarantee good performance under sour environments, arctic and offshore conditions.
In the present paper, a practical test to assess fitness for service of special linepipes is presented. Two linepipes with diameters between 219 and 273 mm and Diameter/thickness (D/t) ratios from 10 to 20, intended for arctic service were studied. While linepipe of both large Diameter and D/t (above 50), have been studied, there has been very little work done for diameters below 420 mm and D/t ratios in the range of 10–20.
Full scale burst tests at −40°C and −60°C were carried out under controlled conditions. Actual crack propagation speed during burst tests at temperatures below −60°C, was tracked through an oscilloscope-computer data acquisition system. Weldability and hydrogen induced cracking performances were also studied.
Crack propagation speed in ceramic during quenching
