Seamless coiled tubing manufacturing technology

Seamless steel coiled tubing is a kind of new oil pipe，several kilometers long, being bend repated,and generating plastic deformation many times. Coiled tubing and its operation equipments are called "universal operating machine". In foreign countries such as the United States, Canada and other countries, coiled tubing has become an essential oil equipment in oilfield operations. Currently the longest coiled tubing is 9000m long. And for this particular pipe, the core manufacturing technologies are as below:

1, The chemical elements
Due to the harsh environment,there are some higher requirements for the properties of the coiled tubing material mechanical and corrosion resistance. To optimize the design of the chemical composition of the material,we must also implement clean control of the whole process of smelting, rolling, etc, to minimize the containing of inclusions and S, P and other harmful elements.

2, Processing
after the combined effects of working hardening caused by the proliferation of dislocation and Bauschinger effects, take control of the transformation law of tube intensity.

3, Heat treatment
To achieve optimal control of microstructure and properties through the tube heat treatment, especially for the high strength and high ductility and low residual stress.

4, Welding Technology
For low carbon microalloyed steels, HFW welding technology is currently used. What need to study is the optimal welding parameters (such as current, voltage, frequency, welding speed, forming angle, extrusion volume, etc.), welds technology and weld heat treatment technology.

5, Plate butt
To achieve continuous production of HFW pipe, you must first take a long plate. Currently,butt plate is mainly using TIG, MAG and plasma welding methods. What is under study is friction stir welding methods.

6, Pipe butt
Coiled tubing may suffer local damage when in use, injury or defective parts must be cut off, and the rest parts are connected by welding. The traditional methods, which is commonly using manual TIG butt welding, but the welding quality is difficult to control, what is popular used currently is making automatic welding technology.

7, New manufacturing technologies
CVR technology, which uses a continuous tube of the same specifications, heated to 940 ℃ through online medium frequency induction and rolled by thermo-mechanical.On the one hand, to achieve seamless HFW weld optimization , on the other hand to achieve variable wall thickness or reducers. In addition, there are special stainless steel continuous tube laser welding technology.