The revenue produced by a pipeline depends on the rate that the fluid can be pumped along its length.It has been recognized for some time that the benefit-to-cost ratio increases with strength level.In this regard,the strength of high pressure pipeline steels has doubled in 40 years,from X60 in 1970 to approaching X120 today.The alloy design,rolling and cooling of plates for X100 + pipe applications will be presented and discussed.The metallurgy of attaining the strength and ductility while reducing brittle fracture by cleavage and increasing the ductile fracture crack arresting potential of these new steels will also be discussed.In this paper a low carbon steel of C.E.0.50 and Pcm of 0.21 was subjected to a TMCP simulation on a computer controlled laboratory mill.After rolling,the steel was immediately IDQ to various water - end temperatures followed by air cooling to RT.The resulting microstructure was a mixture of various types of bainite and MA microconstituent.The effect of processing on microstructure was assessed,and the tensile and CVN properties were determined and correlated to the final microstructure.