PRCI Report 201

L51676e

Battelle Memorial Institute

Need: The demand for high-strength, high-toughness line pipe has resulted in the development of new types of steels for gas-transmission line pipe. These types of steels have resulted from the continuing research on improved steel refining processes and the use of microalloy additions and controlled thermomechanical processing on steels that was initiated about 30 years ago. Consequently, steels with radically different chemical compositions from those of the conventionally hot-rolled carbon-manganese steels (X52 steels of the 1950's) and processed using highly advanced hot rolling and subsequently cooling methods have been used
by pipe producers to satisfy these demands.

Benefit: 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.

Result: This study demonstrates that a variety of desirable properties can be achieved as a function of the chemical compositions and the processing applied to steel used to fabricate line pipes. Many combinations of steel composition, processing, and resulting properties are possible; however, the responses to such phenomena as strain aging and environmental-induced damage also vary. It is believed that a pipe purchaser should carefully consider the service requirements for Grade X70 and X80 line pipes and then specify appropriate performance requirements to assure that the pipe supplied is suitable for the intended service.

Product Details

Published:

04/01/1992

Number of Pages:

101

File Size:

1 file , 4.5 MB