| ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ KAWASAKI STEEL TECHNICAL REPORT No.4 ( December 1981 ) Special Issue on Steel Pipe ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ |
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Development of Large Diameter High Strength Line Pipes for Low Temperature Services
Chiaki Shiga, Taneo Hatomura, Jun-ichi Kudoh, Akio Kamada, Keisuke Hirose, Toshihiro Sekine |
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Synopsis : Large diameter high temperature line pipes of X65, X70, and X80 grades for the arctic gas transmission use have been developed by using controlled-rolled steel plates and by adopting a quench and temper treatment after forming the pipe. A combination of high strength and toughness without an increase in alloying elements can be provided by strictly controlled rolling of low C, low S, high Mn, and Nb- and V-bearing steel. Rolling in the dual phase (Α+Ώ) temperature range between Ar3 and "Ar3 - 40" can produce fine bainite and fine deformed ferrite grains in the ferrite-pearlite matrix, which is very effective in improving both strength and toughness of the plate and the pipe. By adopting the controlled rolling and the subsequent quench and temper treatment for low C and Mo- and Nb-bearing steel, BDWTT 85% shear FATT is significantly improved. This is due to the very fine microstructure of the plate which consists of fine ferrite and martensite island. The rolled steel plate of this type is proved to be useful for quenched and tempered pipes. The CVT, CV100 and BDWTT energy values of the pipes tested are much greater than those necessary for arresting unstable ductile fracture which have been shown in Battelle's full scale burst experiments. |
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