How are graphite electrodes consumed in electric furnace steelmaking?
The consumption of graphite electrodes is mainly related to the quality of the electrode itself, as well as the steelmaking operation and process (such as the current density through the electrode, the type of steel being smelted, the quality and block size of the scrap steel, and the duration of oxygen blowing).
(1) Electrode end consumption. Its consumption includes the sublimation of graphite material caused by high arc temperature, as well as the loss of chemical reactions between electrode ends and molten steel and slag. The consumption of electrode ends is also related to whether electrodes are inserted into molten steel to increase carbon.
(2) Oxidation loss on the outer surface of the electrode. In recent years, in order to improve the smelting rate of electric furnaces, oxygen blowing has been widely used, which has led to an increase in electrode oxidation loss. In general, the oxidation loss on the outer surface of the electrode accounts for about 50% of the total electrode consumption.
(3) Residual loss of electrodes or connectors. A small section of electrode or connector (i.e. residue) that is continuously used to connect the upper and lower electrodes is prone to falling off and increasing consumption.
(4) Loss of electrode breakage, surface peeling, and chipping. These three types of electrode losses are collectively referred to as mechanical losses, among which the reason for electrode breakage and detachment is a controversial point in the determination of quality accidents between steelmaking plants and graphite electrode production plants, as it may be due to issues with the quality and processing of graphite electrodes (especially electrode joints), or operational issues in steelmaking.
Electric furnace steelmaking plants generally refer to inevitable electrode consumption such as oxidation and sublimation at high temperatures as "net consumption", and "net consumption" plus mechanical losses such as breakage and residual losses as "gross consumption". At present, the graphite electrode consumption per ton of electric furnace steel in China is 1.5-6kg. During the steelmaking process, the electrodes are gradually oxidized and consumed into cones. Observing the taper of the electrodes and the redness of the electrode body during the steelmaking process is an intuitive method to measure the oxidation resistance of graphite electrodes.
