Overview
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Graphite electrodes are primarily used in the production and recycling of steel.

During the process, steel scrap is melted in a large crucible (furnace) by an electric arc. This is the genesis of the name “Electric Arc Furnace” (EAF). The arc is a channel of ionized air through which electric current passes from the electrode into the steel scrap. A similar phenomenon occurs during a thunderstorm with the rapid discharge of electricity that we know as lightning.

In the steel mill, the furnace is loaded with steel scrap. Then, one column (direct current furnace) or three columns (alternating current furnace) consisting of multiple graphite electrodes screwed on top of each other, is introduced and the arc is ignited. The arc is maintained for a few minutes so that a generated temperature of around 3500 degrees Celsius can rapidly melt the scrap in the furnace. The molten steel is then poured off for further processing. This procedure is known as tapping. Typical cycle times, i.e., the time between two taps, are between 45 and 90 minutes.

Approximately one-third of the world’s steel is produced via EAF, making it the largest recycling process globally. Compared to steel made using a basic oxygen furnace (BOF), the EAF process bypasses around 80% of direct CO2 emissions per ton of steel.

But why do electrodes have to be made of graphite? If the electrodes that conduct the current were made of metal, like many electrical devices, it would simply melt like the scrap does. Other materials, like ceramic, can withstand the heat, but are not good conductors of electricity. It’s essential to have a material that can conduct an electric current without melting when exposed to elevated temperatures. Graphite is an excellent solution.

Despite its extraordinary properties, the graphite electrode is consumed during the melting process – primarily through oxidation. As the electrode wears down, it must be replaced by a new one. The quality of an electrode is typically measured by the rate of consumption per liquid ton of steel melted. The lower the consumption rate, the better for electric steelmakers.