L51676 Evaluation of Modern X70 and X80 Line Pipe Steels

Nine sections of advanced high strength line pipes, Grades X70 and X80 have been evaluated during this study. Six of those pipes were Grade X70 and three were Grade X80. Four of the X70 pipes were fabricated from microalloyed steels that were controlled rolled; the other two X70 pipes were controlled rolled plus accelerated cooled. Two of the controlled-rolled X70 pipes were produced from plates from the same slab of continuously cast steel; one was fabricated by the pyramid-rolling process and the other was fabricated by the U-O-E process. Two of the Grade X80 steels were produced from plate that was controlled rolled; one of those was accelerated cooled after controlled rolling. The third X80 pipe was produced from a microalloyed steel plate that was fabricated into pipe, ERW welded, and then heat treated by austenitizing, spray quenching, and tempering. The information obtained from the evaluations of these pipes is summarized in the following sections.