In electric arc furnace (EAF) steelmaking, the properties of slag directly affect refining efficiency and metallurgical reactions. A frequently asked question is: does slag conduct electricity?
Structurally, most steelmaking slags are ionic crystals. In their solid state, these compounds block current flow and are almost non-conductive. However, under the high temperatures of steelmaking, combined with chemical reactions and the influence of the electric arc, the slag gradually melts and transforms into liquid form. At this stage, the originally stable ionic crystals dissociate into various ions or complexes, forming an electrolyte-like system. This gives slag significant electrical conductivity, which makes electric arc furnace steelmaking possible.
When voltage is applied, the charged ions and free electrons within the slag move together, enabling current conduction. However, the conductivity of slag is not constant; it gradually increases during the refining process. For example, during the oxidation and refining stage, lime is often added to remove phosphorus. If a large amount of lime covers the electrode tip, the electrode may fail to strike an arc because lime alone does not conduct well. In such cases, oxygen blowing is typically used to break up the lime layer, allowing the furnace to resume normal arc heating.
The electrical conductivity of slag is usually measured by its conductivity (γ or σ), which is the reciprocal of resistivity and expressed in S/m or S/cm. The magnitude of slag conductivity mainly depends on the number of ions in the slag and the interactions between positive and negative ions. The lower the “internal friction” resisting ion movement, the higher the slag’s ability to conduct electricity.
In summary, slag in electric arc furnace steelmaking does exhibit electrical conductivity, and this conductivity increases as temperature and metallurgical reactions progress. Understanding the conductivity of slag is essential for optimizing furnace operation, improving steelmaking efficiency, and ensuring better steel quality.
