Development of High-Strength Heavy-Wall Sour-Service Seamless Line Pipe for Deep Water by Applying Inline Heat Treatment

High strength heavy wall sour service seamless line pipe suitable for deep water applications has been developed by Sumitomo Metal Industries, Ltd.,. This paper describes the concept of developing these pipes applying inline heat treatment technology, equipped in a newly constructed, medium-size seamless mill. Increasing hardenability through inline heat treatment achieved higher strength (X70) for heavy wall pipe (40mm) even though carbon equivalent was lower than in a conventional Q&T process. Good toughness was obtained by the control of microalloying elements such as titanium or sulfur. The produced pipe passed the hydrogen-induced cracking (HIC) test conducted according to NACE TM 0284 solution A. Controlling the microstructure and suppressing maximum hardness, utilizing the uniform quenching facility during inline heat treatment, contributed to the test result. Satisfactory data on weldability for practical use were also obtained.Copyright © 2004 by ASME