Abstract
Plate steels for linepipe are in continuous development. High strength levels can be reached by combining advanced alloying and accelerated cooling concepts. Toughness is another important property, and the Battelle drop weight tear test must be passed at low temperatures, sometimes in combination with hydrogen induced cracking/sulphide stress corrosion cracking resistance. Such features can only be realised through appropriate steel and plate production. Steel grades based on ferrite–pearlite structures are nowadays applied up to a certain strength level. Such structures can even be used to produce plates with excellent property profiles. Other concepts are applied to obtain acicular ferrite/bainite microstructures. This paper describes alloying and plate processing and relates them to the microstructure and properties. Plates for pipes for onshore and offshore applications are covered. The first is a grade X60 steel for deepwater application, using the reel lay technique. Examples of grade X65 steel for offshore and grade X70 steel for onshore use follow. Finally, results for a sour service steel order using grade X65 are presented.
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