1. A device for induction heating of a billet of metal material having high electrical conductivity comprising:a tubular body comprising permanent magnets wherein each of the permanent magnets is arranged parallel to an axis of the tubular body, wherein the permanent magnets are arranged on a circumference of the tubular body centered on the axis of the tubular body and are angularly spaced apart from each other and arranged by alternating opposite polarities;
a billet support adapted to support the billet so that the billet is arranged in the tubular body and the billet faces the permanent magnets; and
a drive device with a motor that produces a relative rotation between the tubular body and the billet, wherein the relative rotation of the permanent magnets with respect to the metal material of the billet induces current in the billet that circulates within the billet itself, thereby obtaining a heating of the metal material; and
a cooling system integrally carried by the tubular body that provides a flow of cooling air on the circumference between two adjacent permanent magnets, wherein the cooling air flows in a channel located between said two adjacent permanent magnets.