High performance microalloyed line pipe steel China

The demand for energy has become a bottle neck for development of China. Economical delivery of natural gas through pipelines is an urgent problem that needs to be solved. Gas pipeline construction has stimulated development of high performance pipe steels since 2000 in China. The super tough X-70 Acicular Ferrite/Bainite pipe steel with yield strength YS>530 – 630 MPa used in the West – East gas transmission project, essentially corresponds to X80 grade steel elsewhere. However, to delivery natural gas from the Western most reservoirs to Eastern China using the present pipe steel cannot be competitive as compared with practices overseas. Recent research elsewhere gives us inspiration. Exxon Mobil and BP redesigned the pipeline to operate at higher pressure using Grade X 100 or X 120 high strength pipe steels to achieve comprehensive cost savings. A series of development works was done before applying this new idea. Research on the steel went going deeply into the relationship between the substructure domain size, high angle boundaries and the TMCP schedule. This innovation on high grade pipe steel also involved new types of welding consumables and welding techniques special for the high strength steel. In order to assure the integrity of pipelines laid in geologically unstable regions, the pipeline was designed using based strain principles and special pipe having higher deformability. Research on ductile fracture prevention of the steel pipe considered toughness and the installation of composite crack arresters. Developments concerning oxide metallurgy to dramatically improve the toughness of the pipe girth welding joint is worthy of mention. (AU)