tubes in high tensile steel with excellent toughness at low temperature and resistance to corrosion under tension from sulphides.

摘要

Embodiments of the present disclosure comprise carbon steels and methods of manufacturing pipes having a wall thickness greater than or equal to about 8 mm and less than or equal to about 35 mm there from. In one embodiment, a steel composition is provided that yields an average austenite grain size greater than about 15 µm. Based upon this composition, a quenching sequence has been determined that provides a microstructure of greater than or equal to about 60% by volume, and less than or equal to about 40% by volume lower bainite, without substantial formation of ferrite, upper bainite, or granular bainite. After quenching, the pipe may be subjected to tempering. The yield strength of the quenched and tempered pipes may be greater than about 550 MPa (80 ksi) or 625 MPa (90 ksi) and mechanical property measurements find the quenched and tempered pipes suitable for 550 MPa (80 ksi) grade and 625 MPa (90 ksi) grade.