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Coiled tubing is a new type of petroleum pipe with a single length of several kilometers and can be repeatedly bent to achieve multiple plastic deformations. Coiled tubing and its operating equipment are called "universal operating machines." In foreign countries such as the United States and Canada, coiled tubing has become an essential petroleum equipment for oilfield operations. At present, the longest coiled tubing is 9000m long. The core technology for the manufacture of this special tubing is:
Due to the severe service environment, there are high requirements for the mechanical properties and corrosion resistance of coiled tubing materials. To optimize the chemical composition of the material, it is necessary to achieve full-process clean control of smelting and rolling to minimize inclusions. And S, P and other harmful elements.
After the work hardening and the Bauschinger effect caused by dislocation proliferation and other factors work together, the transformation law of the tube strength is controlled.
Through the heat treatment of the pipe body, the best control of the structure and performance is achieved, especially high strength and plasticity and low residual stress.
4. Welding technology
For low-carbon microalloyed steels, currently HFW welding technology is mainly used. It is necessary to study the optimal welding process parameters (such as current, voltage, frequency, welding speed, forming angle, extrusion amount, etc.), and study the weld seam and heat treatment technology of the weld seam.
In order to achieve continuous production of HFW welded pipes, the plates must first be lengthened. Currently, TIG, MAG and plasma welding are mainly used for the butt jointing of plates. The method being studied is the friction stir welding method.
The coiled tubing may cause local damage during use. The damage or defect must be removed and the pipes connected by welding. The traditional docking method generally uses manual TIG welding, and the welding quality is difficult to control. At present, the automatic welding technology is used.
7.New manufacturing technology
For example, CVR technology, that is, continuous tubes using the same specifications of tube blanks, is heated online to 940 ° C by intermediate frequency induction, and thermomechanical rolling is used to optimize or seamlessize HFW welds on the one hand, and to achieve variable wall thickness or Reducing. In addition, there are special stainless steel continuous tube laser welding technologies.