This paper is a brief history on the development of pipelines steels since the API 5L X42 steel, developed in 1948 by hot rolling followed by heat treatment. Subsequently different developments were made to increase the strength and toughness of these materials, and to improve their weldability. Among them, the addition of microalloying elements, producing HSLA steels and thermomechanical processing routes during hot rolling. Initially the route used was the controlled hot rolling (TMCR), together with microalloying element such as Nb for X60 steel and Nb plus V for X65 and X70 steels, associated with a reduction in carbon content. Later, the thermomechanical controlled process (TMCP) manufacturing route was implemented together with carbon reduction and addition of Nb and Ti for X80 steels, and additions of Mo, Nb, B and Ti for X100. The reduction of carbon was also motivated to improve the weldability of theses steels and, for this reason; they are welded by various welding processes such as SMAW. Recent developments with GMAW with controlled short circuit transfer on the root and filling passes with FCAW has given encouraging results.
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