A guide tube structure for flux concentration is provided. The discharge guide tube comprises a central orifice that extends from a source of metal to an outlet in the discharge guide tube for directing a stream of melt therethrough; a structure that generates an electromagnetic field in the discharge guide tube; and an interior discharge guide tube flux concentration configuration that is capable of concentrating at least one of heat, electromagnetic field, and electromagnetic flux onto the stream of melt that flows through the central orifice. The electromagnetic field is applied at a substantially constant level.