In steelmaking, the formation of foamy slag plays a vital role in electric arc furnace (EAF) operations. It not only stabilizes the electric arc and reduces power consumption but also enhances metallurgical reactions, thereby improving overall steelmaking efficiency.
Basic Process of Foamy Slag Formation
When a large amount of gas enters the slag and becomes dispersed, multiple discontinuous gas–liquid interfaces are created inside the slag. If the surface tension of the slag is relatively low and the interfacial free energy remains small, the system’s energy is maintained at a lower level. Under these conditions, the tiny gas bubbles dispersed within the slag will not easily merge, which allows stable foamy slag to form.
Inside the foamy slag, gas bubbles are separated by thin liquid films. These films are strengthened, delaying the release of bubbles. As the bubbles rise under pressure, the slag volume changes continuously, promoting slag foaming.
To ensure the stability of the slag-covered arc during steelmaking, the foamy slag must maintain a certain surface tension. This requires the slag to have appropriate viscosity and a sufficient amount of suspended solid particles. Classic studies show that when the binary basicity is controlled within 1.8–2.5, both the foaming ability and the presence of suspended particles are optimized, ensuring stable foamy slag formation.
Basic Conditions for Foamy Slag Formation
In both EAF steelmaking and converter steelmaking, two fundamental conditions must be met for foamy slag to form:
1. Presence of Gas with Sufficient Energy
Gas generation within the slag, such as CO formation, provides the necessary driving force for bubble creation and slag foaming.
2. Proper Physical and Chemical Properties of the Slag
The slag must have suitable basicity, viscosity, and suspended solid particles to stabilize bubbles and extend their lifetime.
Only when these two conditions are satisfied can slag effectively foam, allowing foamy slag to contribute to energy savings, electrode protection, and improved metallurgical reactions in steelmaking.
