Patent ID: 11952648
Assignee: TENARIS COILED TUBES, LLC
Field: Materials, metallurgy (Chemistry)
Classification: CPC C  E | IPC C  E

Claim 22:
23. A method of forming and heat treating a tube, the method comprising:
providing a plurality of steel strips to be welded together, each of the steel strips including from about 0.010 wt. % to about 0.025 wt. % titanium and from about 0.0010 wt. % to about 0.0025 wt. % of boron;
welding the plurality of steel strips together end-to-end to form a plurality of end-to-end welded strips and longitudinally welding the plurality of end-to-end welded strips to form a tube having a first microstructure and comprising:
a first tube section with a substantially constant inner diameter, outer diameter, and wall thickness, said first portion of coiled tubing having a first microstructure; and
a second tube section with a wall thickness that is different than the wall thickness of the first tube section;

after forming the tube, performing a continuous and dynamic heat treatment process (CDHT) comprising a continuous quench and temper heat treatment along the tube, wherein heating rate is modified to compensate for the change in wall thickness from the first tube section to the second tube section, thereby resulting in a tube with a second microstructure comprising at least 80% tempered martensite across (a) the plurality of steel strips, (b) the plurality of end-to-end welds, and (c) the plurality of longitudinal welds,
wherein the second microstructure is more homogeneous than the first microstructure; and
coiling the first portion of coiled tubing to form a coiled tube.