Microstructure of X52 and X65 pipeline steels

The microstructure of two commercial pipeline steels X52 and X65 was examin ed to provide a foundation for the understanding of the IGSCC mechanism of pipeline steels. Observation of the microstructure was carried out using sc anning electron microscopy (SEM) and an analytical electron microscope. The microstructure of X52 and X65 pipeline steels shows banding of pearlite ri ch and ferrite rich areas. The ferrite grains were about 10 mu m in size wi th curved grain boundaries. There was carbide at the ferrite grain boundari es for X52 steel, and there was circumstantial evidence to suggest carbon s egregation at the boundaries. The pearlite colonies were consistent with nu cleation by a number of different mechanisms. (C) 1999 Kluwer Academic Publ ishers.