In recent years, there has been development of several significant pipeline projects for the transmission of oil and gas from deep water environments. The production of gas transmission pipelines for application demands heavy wall, high strength, good lower temperature toughness and good weldability. To overcome the difficulty of producing consistent mechanical property in heavy wall pipe Shougang Steel Research in cooperation with the Shougang Steel Qinhuangdao China (Shouqin) 4.3m heavy wide plate mill research was conducted.
This paper reports on the experience with the research and development of pipeline up to 40.5mmin wall thickness grade 485FDU intended for applicationsin the Middle East‐India deep water environments. The plate was produced at Shougang Steel’s 4.3m heavy wide plate mill in Qinhuangdao China (Shouqin). Alloy design and processing strategy along with production parameters are introduced. The achieved mechanical properties in both plate and pipe are reported. The pipe tensiletest results in transverse and longitudinal directions achieved yield strength and ultimate tensile strength of 525∼555MPa and 625∼650MPa respectively, which are higher than plate yield and ultimate tensilestrengths of 475∼515MPa and615∼640MPa respectively. The increase of strength during pipe making is due to the creation of a fine uniform grain bainite and polygonal ferrite microstructure from the alloy/processing design. Even with this DNV485FDU strength level and heavy wall the low temperature fracture toughness achieved was excellent. Drop weight tear testing(DWTT) of pipe body (19mm thickness samples, two sides average thinning) achieved an average of 95% shear at –27°C. And crack tip opening displacement (CTOD) of pipe body achieved an average of 1.84mm at –10°C. All of these results demonstrated that the heavy wall 40.5mm DNV485FDU production at Shougang Steel’s 4.3m wide heavy plate mill (Shouqin)can meet the technical specifications of “3500m Deep Water Pipeline Development” and DNV‐OS‐F101.