The Organization And Evolution Of X60 And X65 Subsea Pipeline

With the rapid development of China’s offshore oil industry,as a tool for conveying fluid medium,the long distance transportation subsea pipeline has many advantages With continuous,fast,large throughput and many other advantages,such as continuous,fast and large transportation volume,its construction is showing more and more strong momentum and demand is also increasing.High Strength,high toughness,corrosion resistance,low temperature submarine pipeline development has become the mainstream direction of pipe manufacturing enterprises.Among the offshore oil pipes,X60 and X65 steel grade pipes are used the most.In this paper,after a thorough understanding of the submarine pipeline classification,application environment,failure forms and production problems should be paid attention to,combined with the production experience of Baotou Steel Pipe Company,through the analysis and research of steel grade composition design,steel-making process,seamless tube rolling process and heat treatment process,the developed submarine Pipeline X60 and X65 have high strength,high toughness,corrosion resistance,low temperature resistance and good fracture toughness.In addition,the mechanical properties and microstructure of the material were studied,the ductile-brittle transition temperature,the resistance to hydrogen sulfide corrosion and the fracture toughness of the material were tested and evaluated:1.Based on the C-Mn-Cr-Mo steel system,the composition of the steel grades with trace alloying strengthening elements NB,V and TI is designed reasonably,the production process is complete and the process adaptability is strong,the production of X60,X65submarine pipeline product performance and dimensional accuracy to achieve the design goals.2.Through a series of low temperature impact tests,it is concluded that the ductile-brittle transition temperature of the steel pipe should be between-50°C to-60°C.3.The results of HIC and SSC tests show that the product has excellent corrosion resistance to H₂S,with no hydrogen bubbling,no fracture and no crack on the surface.4.The average value of CTOD test is 1.013 mm,which is much larger than the acceptance value of 0.2 mm.It shows that the material has good fracture resistance.5.Through the transmission electron microscope,it can be seen that Nb and Ti precipitates are distributed in the grains and are spherical in shape,with strong grain refinement and precipitation strengthening,and the spheroidization of the alumina inclusion after the calcification treatment in the smelting process reduces the stress concentration,improves the comprehensive mechanical properties of the product,and improves the corrosion resistance of the material to hydrogen sulfide.The development of this product not only meets the requirements of X60 and X65subsea pipelines,but also can be used to produce X42NS and X46NS anti-sulfur pipelines by normalizing,more conducive to production management.