The main aim is to obtain a better knowledge of the behaviour during rolling of the billets produced by horizontal continuous casting. The project will also study the development of the different structures found in the same cross-section of the horizontally cast billet. The development of defects will be studied to determine those that remain and those that disappear as a function of their nature and the degree of reduction in different passes. The result will help to define the most suitable reduction plan to minimize defects in rolled products.