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Title

DEVELOPMENT AND APPLICATION OF HEAVY-GAUGE X80 SSAW PIPE WITH OPTIMIZED HTP PROCESSING

Authorship

Yongqing, Zhang; Tao, Niu; Zongyue, Bi; Aimin, Guo

Yongqing, Zhang

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Tao, Niu

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Zongyue, Bi

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Aimin, Guo

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DOI

10.5151/9785-9785-32207

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Abstract

Over the two decades years, big achievements have been made for the development and application of high-strength and low-alloy steels with thermomechanically rolling and cooling in China, among which the most typical application case is the development and application of X80 coil and spiral welded pipe used for the Second West-East Pipeline trunk line. In order to increase deliverability from 30 billion cubic meter to 38 or 45 billion cubic meter annually, X80 welded pipe with higher thickness and larger diameter was required, and X80 welded pipe with the diameter of 1422mm and the thickness of 21.4mm was employed. However, almost all X80 welded pipes with such size for already constructed pipeline were supplied by X80 LSAW pipe made of plate, instead of X80 SSAW pipe made of coil. Based on traditional two-stage rolling experiences, some people thought it is impossible to produce 21.4mm thick X80 coil on commercial scale. In order to meet demanding requirements, optimized rolling and cooling schedule besides low carbon and high niobium alloy design made it possible to break the ceiling of 18.4mm in thickness. Up to now, about 500,000 tons X80 coil and spiral welded pipe with 21.4mm in thicknes have been produced and applied to China's section of Russia-China East line. What is more, burst test results demonstrated more excellent performance to resist crack propagation than that of longitudinal X80 welded pipe. In this paper, metallurgical design, production data and microstructure analysis before and after pipe making would be presented.

Keywords

Nb-bearing X80 steel, spiral welded pipe, low-temperature coiling