Method and apparatus for isothermal holding of wire when a wire is

Abstract

The present invention is drawn to a method and apparatus for holding wire at a specified temperature for a specified period of time by a direct-resistance heating device which applies such voltage as to generate Joule's heat in the wire, sufficient to offset the quantity of heat that would tend to be released from the heated wire during unforced cooling, after the travelling wire is heated rapidly to a specified temperature throughout its cross section. A temperature-holding apparatus, employed subsequent to the heating of wire, may either supply power directly to a wire through feeding wheel electrodes or entail a combination of a shell type transformer and a hollow annular holding furnace incorporating guide rollers, and having wheel electrodes electrically connected by a lead, disposed outside of the inlet and outlet of the holding furnace incorporating guide rollers, and producing secondary current in the multiple-wound wire in the furnace with the lead as a return, depending upon the holding time desired. The latter form of the apparatus imparts an advancing force and curl to the wire so that thick and inflexible wire can be placed in the holding furnace, and rollers are provided to create a desired number of turns in the wire in the holding furnace.