Suitability study of Endless Strip Production technology for fabrication of api grades

Abstract

Production of hot rolled strip for oil and gas transport pipelines requires a fine and homogeneous
microstructure and careful choice of chemical composition in order to meet strength, toughness, and
weldability requirements. Whilst hot rolled coils to grade X80, produced by conventional continuous casting
and hot rolling, are a commercial reality, there is great interest in producing API grades manufactured by the
alternative (and more economical) thin slab direct rolling route.
The current work has assessed the feasibility of producing hot rolled strip of grades X65-X70 using the endless
strip production layout (ESP), originally developed at Arvedi. The study was carried out using a metallurgical
modelling system based on empirical equations describing austenite evolution, transformation and mechanical
properties. Using this approach it was possible to study the effects of initial slab thickness, reduction ratio and
chemical composition on the mechanical properties of strips in a thickness range of 10 to 20 mm. In this way,
for each grade, the optimum rolling schedules, microstructures and chemical compositions could be obtained.