A process for heat treating a carbon steel wire to obtain a fine pearlite structure is characterized by the following steps: (a) cooling the wire until the wire reaches a given temperature which is below the AC.sub.1 transformation temperature; (b) regulating the temperature of the wire to not more than 10.degree. C. above or below said given temperature by passing an electric current through the wire and effecting a modulated ventilation thereof; (c) cooling the wire.