Abstract: A charge of iron-containing metallic substance is melted in a melting vessel, and the molten metallic substance is passed through a body of carbonaceous material contained in a treating container for the metallic substance to be enriched with carbon. The treating container is gas-tightly sealed except for its communication with the melting vessel. At least oxygen is admitted into the treating container to partly and gradually burn the carbonaceous material and thus to heat the metallic substance passing through the body. The body may contain alloying elements and/or slag-forming constituents. The enriched molten metallic substance and slag which form a bath at the bottom of the treating container are discharged therefrom through respective discharging outlets which are provided with traps. The gases which are liberated during the passage of the molten metallic substance through the body of carbonaceous material are utilized for heating either the body or the charge of metallic substance in the melting vessel.