The development and improvement of high-strength steel grades up to grade X100 with good toughness and sour service properties as well as welding performance becomes more and more important due to enhanced material and design requirements. Over the last years Vallourec & Mannesmann Tubes and Salzgitter Mannesmann Forschung have developed new high strength steels up to grade X90 or even X100. These new developments are presented. Seamless quenched and tempered pipes with wall thickness up to 38mm of these steels exhibited good toughness and sour service properties. The strength levels for steel grades up to X90 were safely reached and the hardness level was low with respect to the chosen alloying concepts. The steel grades showed good toughness properties with the average Charpy impact values clearly above 200J at -40 deg C for the grades X80 and X90 and above 300J at-60 deg C for the grade X70. The CTOD results for grade X70 were excellent and for the grades X80 and X90 adequate with respect to the increased strength levels. Due to the relatively low Carbon equivalent, the mechanical properties of the first welding tests showed good weldability. Welding tests on grade X70 material were very promising, showing a good weldability. Further welding tests are performed at the moment on X80 and X90 pipe material. It has to be stated that the alloying concept as well as the heat treatment play an important role concerning the combination of mechanical properties and corrosion resistance. The alloying concept as well as the production process was optimised using both, simulation techniques like computational thermodynamics and traditional laboratory and industrial trials.
High strength seamless line pipes up to grade X100
Drei R International ; 49 , Special 1: Pipeline Technology ; 18-21
2010
4 Seiten, 4 Bilder, 1 Tabelle, 3 Quellen
Article (Journal)
English
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