L51690 Evaluation of Modern X-70 HFER Line Pipe

In recent years, several pipe mills have produced heavy-wall, large diameter pipe from plates of microalloyed steels that were controlled-rolled to develop properties to meet the API 5LX Grade 70 or Grade 80 requirements and that were electric resistance welded (ERW) using advanced techniques. The use of advanced electric seam-welding practices on the steels produced using advanced steel making and processing methods offers the possibility of obtaining high strength line pipe at a lower cost than pipes produced from similar steels but with double submerged arc seam welds. The present study was undertaken to evaluate the properties of the pipe body and the ERW seam-weld region of a recently produced heavy-wall X70 line pipe. This report describes the evaluation of that pipe. The mechanical properties of the weld zone from this pipe were evaluated and reported under Task 18-89. Those data are included in this report. A high-frequency electric resistance welded (HFERW) X70 line pipe was evaluated to assess the strength properties, fracture behavior, thermal stability, and susceptibility to environmentally induced degradation that may affect its behavior in gas transmission service. A 20-inch-(508 mm)-diameter by 0.500-inch-(12.7 mm)-wall high-frequency, electric-resistance-welded (HFERW) X70 line pipe was evaluated to assess the strength properties, fracture behavior, thermal stability, and susceptibility to environmentally induced degradation that may affect its behavior in gas transmission service. The steel from which the pipe was produced was processed using advanced steel-making practices that resulted in a low sulfur content and was microalloyed with Cb, V, and Ti. The steel was controlled rolled with 75 percent of the rolling reduction being accomplished at temperatures below 1418 F (770 C); the finishing temperature was 1328 F (720 C) and the steel was hot coiled after finishing. The seam weld was produced by high frequency electric resistance welding and the seam weld region was post-weld normalized.