SEAMLESS STEEL PIPE TO BE USED AS A STEEL CATENARY RISER IN THE TOUCHDOWN ZONE

摘要

The invention relates to an SCR with upset ends, consisting of a novel chemical composition having a low carbon content and a microstructure, and to a method for producing said SCR. Said method improves the fatigue life of the SCR by creating a single component with the riser pipe section in the touchdown zone. The SCR with upset ends and a low carbon content obtains its desired properties by means of the heat treatment to which it is subjected. The novel chemical composition having a low carbon content and microstructure comprise, in weight percentage, between 0.04 and 0.10 of carbon, between 0.40 and 0.70 of manganese, between 0.15 and 0.35 of silicon, between 0.40 and 0.70 of chrome, between 0.40 and 0.70 of molybdenum, between 0.10 and 0.40 of nickel, a maxiumum of 0.008 of nitrogen, between 0.010 and 0.045 of aluminium, a maximum of 0.005 of sulphur, a maximum of 0.020 of phosphorus, between 0.003 and 0.020 of titanium, between 0.020 and 0.035 of niobium, no more than 0.10 of vanadium, no more than 0.20 of copper, a maximum of 0.020 of tin, and the equivalent of a maximum of 0.43 of carbon and no more than 0.23 of PCM, with a yield strength of at least 4569.5 kg/cm2, an utimate tensile strength of at least 541 3.1 kg/cm2, and a YS/UTS ratio lower than 0.89 in the material forming the body of the pipe, the transition zone and the upset end.