Process for utilizing slag (2, 2") which originates from the iron smelting industry and is obtained in steel works convertors and contains oxidic iron particles, with addition of a reducing agent and reduction of oxidic iron particles of the slag (2, 2") and also any other metal oxides present by means of this reducing agent, characterized by the combination of the following features: - charging of the slag (2, 2") into a reactor vessel, preferably into a tiltable laden reactor, onto a residual iron melt which contains dissolved carbon, slowly and continuously over a prolonged period of time, - electric heating of the slag and of the residual iron melt and also freshly formed iron melt over a prolonged period of time, - blowing-in of a carbon-containing reducing agent by means of gas, preferably inert gas, over a prolonged period of time by means of a lance into a region close to the interface between slag and iron melt or directly into the iron melt, with dissolution of carbon in the iron melt and with mixing of iron melt and slag, - dissolution of the carbon of the reducing agent in the iron melt and - reduction of oxidic iron particles of the slag to form metallic iron and CO over a prolonged period of time, - formation of a foamed slag by means of the CO formed over a prolonged period of time, - introduction of an oxygen-containing gas or of oxygen into the foamed slag and after-combustion of CO to CO 2 over a prolonged period of time, with the introduction being carried out in the upper half, preferably in the upper third, of the height of the slag, - flushing of the bottom of the reactor vessel with inert gas over a prolonged period of time, - discharge of the treated slag and optionally - subsequently discharge of iron melt leaving a residual iron melt containing dissolved carbon in the reactor vessel, with the term prolonged period of time referring to the period of time essentially from discharge of slag and optionally iron melt until the subsequent discharge of slag. - charging of the slag (2, 2") into a reactor vessel, preferably into a tiltable laden reactor, onto a residual iron melt which contains dissolved carbon, slowly and continuously over a prolonged period of time, - electric heating of the slag and of the residual iron melt and also freshly formed iron melt over a prolonged period of time, - blowing-in of a carbon-containing reducing agent by means of gas, preferably inert gas, over a prolonged period of time by means of a lance into a region close to the interface between slag and iron melt or directly into the iron melt, with dissolution of carbon in the iron melt and with mixing of iron melt and slag, - dissolution of the carbon of the reducing agent in the iron melt and - reduction of oxidic iron particles of the slag to form metallic iron and CO over a prolonged period of time, - formation of a foamed slag by means of the CO formed over a prolonged period of time, - introduction of an oxygen-containing gas or of oxygen into the foamed slag and after-combustion of CO to CO 2 over a prolonged period of time, with the introduction being carried out in the upper half, preferably in the upper third, of the height of the slag, - flushing of the bottom of the reactor vessel with inert gas over a prolonged period of time, - discharge of the treated slag and optionally - subsequently discharge of iron melt leaving a residual iron melt containing dissolved carbon in the reactor vessel,