HOW ARE GRAPHITE ELECTRODES CONSUMED IN EAF STEELMAKING?

The consumption of graphite electrodes is mainly related to the quality of the electrodes themselves, but also to the steelmaking operation and process (such as the current density through the electrodes, the smelting steel, the quality of scrap steel and the oxygen duration of the block friction, etc.).

(1) The top part of the electrode is consumed. The consumption includes sublimation of graphite material caused by high arc temperature and loss of chemical reaction between the electric extreme part and molten steel and slag, and the consumption of the electric extreme part is also related to whether the electrode is inserted into the molten steel to carburize.

(2) Oxidation loss on the outer surface of the electrode. In recent years, in order to improve the smelting rate of electric furnace, oxygen blowing operation is often used, which leads to the increase of electrode oxidation loss. Under normal circumstances, the oxidation loss of the outer surface of the electrode accounts for about 50% of the total consumption of the electrode.

(3) Residual loss of electrodes or joints. A small section of electrode or joint (i.e., residue) that is continuously used to connect the upper and lower electrodes is prone to fall and increase consumption.

(4) Loss of electrode breakage, surface peeling and falling blocks. These three types of electrode losses are collectively referred to as mechanical losses, where the cause of electrode breakage and falling off is the controversial point of the quality accident identified by the steel mill and the graphite electrode production plant, because it may be due to the quality and processing problems of the graphite electrode (especially the electrode joint), or it may be a problem in the steelmaking operation.

The inevitable electrode consumption such as oxidation and sublimation at high temperature is generally called “net consumption”, and the “net consumption” plus mechanical loss such as breaking and residual loss is called “gross consumption”. At present, the single consumption of graphite electrode per ton of electric furnace steel in China is 1.5~6kg. In the process of steel smelting, the electrode is gradually oxidized and consumed into a cone. Often observing the taper of the electrode and the redness of the electrode body in the process of steel making is an intuitive method to measure the oxidation resistance of the graphite electrode.