Method to obtain a continuous casting apparatus and continuous casting apparatus thus obtained

A method to obtain a continuous casting apparatus to cast, through the casting cavity (13) of a crystallizer (14) of a mold (11), a cast product (P) with a polygonal cross section (S1, S2, S3, S4, S5, S6, S7), wherein said method provides to determine the minimum containing length (LC) of a containing device (21) with rollers, located downstream of said mold (11) and configured to contain the deformation of said cast product (P) with a containing device (21) with rollers, said minimum containing length (LC) being determined, on each occasion, as a function at least of the width (W) of the side of the polygon, of a maximum admissible deformation camber (f) of said side of the polygon outside the mold (11), and of the casting speed (Vc).