The Japan Steel Works, Ltd. (JSW), the worlds leading supplier of clad steel pipe, has been fabricating welded clad steel pipe for many oil and gas producers worldwide since 1978. These pipes have been used for transporting natural gas, including sour gas conditions without any service failures. Since the 1990s there has been a growing demand for clad steel pipe, particularly for higher pressure gas service. In such conditions there is a demand for a combination of high strength steel with excellent toughness of the steel and weld portion to give the required low temperature toughness. Combined with these enhanced mechanical properties, the steel has to maintain excellent weldability. Therefore, there was a drive for upgrading of the base metal from API 5L-X65 to X70, while maintaining low temperature toughness and weldability and hence higher toughness X70 grade clad steel pipe development was carried out. Clad steel needs to achieve both corrosion resistance of the Corrosion Resistant Alloy (CRA) such as TP316L or Alloy825, and strength and toughness of the carbon steel base material. It is necessary to choose the most suitable chemical composition, hot rolling and heat treatment condition and welding technology for fulfillment these requirements. The low temperature toughness of the carbon steel base metal and weld heat affected zone (HAZ) was improved by grain refining during the water quenching from austenitizing temperature. It is considered that the sensitive controlling of alloy element amount contributes to this grain refining process from the experimental results in the laboratory. The girth welding technology of the X70 grade clad steel pipe was developed in collaboration with Serimax, France. As the conventional welding consumables for clad pipe (such as TP.309LMo or Alloy625) did not satisfy X70 grade material properties, Duplex Stainless Steel (DSS) and Alloy686CPT were applied as the girth welding consumables. This paper summarizes the material properties obtained and fabrication results of the newly developed high toughness X70 grade clad steel pipe including longitudinal and girth welds.
Development of high toughness X70 grade clad steel pipe for natural gas transportation pipelines
Entwicklung eines plattierten Rohres aus Stahl X70 mit hoher Zähigkeit für den Erdgastransport
2007
13 Seiten, 11 Bilder, 2 Tabellen, 8 Quellen
Conference paper
English
Clad Steel Pipe for Corrosive Gas Transportation
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