Study On Microstructure And Properties Of CT90 Coiled Tubing Butt Weld Joint

Coiled tubing technology is considered an advanced method of oil and gas field operations in today's world.With the development of coiled tubing technology to a higher level in China,like drilling,deep well operations and so on,the tube to tube butt welding in the field is the unique means to ensure the length and solve the segmented transport of coiled tubing that required large diameter,high strength.CT90 coiled tubing is used extensively and the highest strength level in the engineering,at present,its tube butt welding technology research is still in the beginning stage.This paper is based on China National Petroleum Corporation major engineering project——<Field test of side drilling technology and equipment for coiled tubing>,aimed at QT900 tube butt welding,which is CT90 coiled tubing and 2 inch diameter,made in the United States,by TIG welding technique;researched of QT900 coiled tubing grain growth,and the effect of grain size on mechanical properties of materials by means of heat treatment;modified calculation method of welding thermal cycle theory,provides a convenient method for thermal cycle curve acquisition;applied welding thermal simulation technology,studied on the micro-structure and mechanical properties of HAZ,under different heat inputs;used automatic pulse TIG welding in all positions,obtained the welded joints,which strength equivalent of the QT900 coiled tubing base material,provides the basis for the development of butt welding process of CT90 coiled tubing.