In electric arc furnace (EAF) steelmaking, the properties of slag directly affect refining efficiency, metal recovery, and furnace lining life. Proper control of slag composition and quantity is essential for ensuring steel quality and reducing production costs.
Main Requirements for Slag in EAF Steelmaking
- Good electrical conductivity and suitable melting point: The slag should have strong conductivity and a moderate melting point, allowing stable fluidity at high temperature. Its viscosity should not change drastically with slight variations in composition.
- Facilitating refining reactions: Slag must provide favorable conditions for key metallurgical reactions during steelmaking, such as deoxidation, desulfurization, and dephosphorization.
- Easy separation of slag and steel: Proper slag composition ensures smooth and complete separation from molten steel, minimizing metal loss.
- Low erosion of furnace lining: The slag should be formulated to reduce damage to refractory materials, thereby extending furnace service life.
- Economical and accessible flux materials: The raw materials used for slag formation should be abundant, low-cost, and easy to obtain, supporting sustainable steelmaking operations.
Why Can’t the Slag Volume Be Too Much or Too Little?
The amount of slag in EAF steelmaking must be carefully controlled:
- Excessive slag: The melting of slag depends on FeO in its composition, typically requiring more than 14% FeO to maintain fluidity. Too much slag can trap iron droplets, causing significant metal loss during tapping. Excess slag also increases power and oxygen consumption, worsens reaction kinetics, and may lead to issues such as difficult decarburization or excessive foaming.
- Insufficient slag: If slag is too thin, the arc coverage effect is poor, reducing heat efficiency. It also fails to suppress metal splashing during oxygen blowing, leading to further steel loss.
Therefore, slag in electric arc furnace steelmaking must be kept within an optimal range—not too much and not too little. With balanced slag quantity and proper slag properties, EAF steelmaking can achieve efficient, stable, and economical operation.
