A SEAMLESS STEEL TUBE FOR USE AS A STEEL CATENARY RISER IN THE TOUCH DOWN ZONE

摘要

A seamless steel tube for a steel catenary riser with upset ends may be formed of a material including, in weight per cent: carbon 0.04-0.10; manganese 0.40-0.70; silicon 0.15-0.35; chromium 0.40-0.70; molybdenum 0.40-0.70; nickel 0.10-0.40; nitrogen 0.008; aluminum 0.010-0.045; sulfur <= 0.005; phosphorus <= 0.020; titanium 0.003-0.020; niobium 0.020-0.035; vanadium <= 0.10; copper <= 0.20; and tin <= 0.020. The material may have a carbon equivalent of 0.43 maximum, a composition parameter of no more than 0.23, a yield strength of at least of 65000 psi, an ultimate tensile strength of at least 77000 psi, and a yield strength to ultimate tensile strength ratio below 0.89. The material may have a microstructure that is homogeneous at midwall and is mainly bainite and at least one of acicular and non-polygonal ferrite.