Until now, to satisfy both requirements of the high tensile properties and the low temperature toughness, thick-walled X-80 and greater grade line pipes were developed by plate-UOE pipe manufacturing process. These were introduced bainite single phase transformed at very low temperature with ultra low carbon steels to keep coarse hard secondary phase away to improve the toughness. On the other hand, by hot rolled sheet to ERW (electric resistance welding) pipe manufacturing process, X-80 line pipe steel with bainitic microstructure made by low stop-cooling temperature was also studied. The ERW process can gain higher production rates, however, it was difficult to obtain bainite microstructure with good toughness because coiling process is indispensable. In hot rolling, stop-cooling is necessary before coiling at 500 - 700 deg C generally. The stop-cooling temperature of hot rolled sheet is very higher than that of plate, which is less than 350 deg C. So it was difficult to obtain good toughness by the lower bainite microstructure as same as the plate-UOE processed pipes by the ERW process. In this paper, solution of above issue was studied and a new microstructure for X-80 ERW line pipes, which has precipitation hardened bainitic ferrite microstructure, with low Pcm value for good weldability was developed. It was achieved that reduction of carbon content to the extremely low level causes excellent low temperature toughness.
Development of API X-80 grade electric resistance welding line pipe with excellent low temperature toughness
Entwicklung von widerstandsgeschweißten Leitungsrohren der Güte API X-80 mit ausgezeichneter Tieftemperaturzähigkeit
2005
7 Seiten, 12 Bilder, 2 Tabellen, 4 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
Experimental Research on Fracture Toughness of High Grade Line Pipe
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