Coiled tubing is a new type of oil pipe that can be several kilometers long and can be repeatedly bent and plastically deformed.
The introduction of the manufacturing technology of stainless steel coiled tubing can be divided into the following core processes:
1. Chemical elements
Due to the harsh service environment, there are high requirements for the mechanical properties and corrosion resistance of coiled tubing materials. For the optimization design of the chemical composition of materials, it is necessary to realize the clean control of the whole process of smelting, rolling, etc., and minimize inclusions and S, The amount of harmful elements such as P.
After the work hardening caused by factors such as dislocation proliferation and the Bauschinger effect work together, the transformation law of the tube strength is controlled.
3. Heat treatment
The pipe is heat-treated to achieve optimal control of structure and properties, especially high strength and high plasticity as well as low residual stress.
4. Welding technology
For low-carbon micro-alloyed steel, HFW welding technology is mainly used at present, and the optimal welding process parameters (such as current, voltage, frequency, welding speed, forming angle, extrusion amount, etc.) need to be studied, and the welding seam and weld heat treatment technology should be studied.
5. Plate butt joint
To realize the continuous production of HFW welded pipes, the plates must be lengthened. The current plate butt joints mainly use TIG, MAG, and plasma welding methods. The method currently being studied is friction stir welding.
6. Pipe butt joint
During use, the coiled tubing may cause local damage. The damaged or defective parts must be cut off and the pipes connected by welding. The traditional butt joint method generally uses manual TIG welding, and the welding quality is difficult to control. Currently, fully automatic welding technology is used.
7. New Manufacturing Technology
For example, CVR technology can use continuous tubes of the same specification, heat them to 940°C through medium frequency induction, and then use thermomechanical rolling to realize HFW weld seam optimization or seamlessness on the one hand, and variable wall thickness on the other hand. Or variable diameter, in addition, special stainless steel continuous pipe welding technology and so on.