Foaming of Slagging in Steelmaking

Steel slag is a waste of steel making which produced during by separating the molten steel with impurities from steel furnace. The slag appears as a molten liquid melt and is a complex solution of silicates and oxides.

The foamed slag greatly increases the boundary area of the steel-slag two-phase, improves the kinetic conditions of the dephosphorization reaction, and accelerates the dephosphorization reaction speed. However, serious foaming of slag should be avoided to prevent splashing.
Molten slag with a large number of tiny bubbles is foamy. Such slag is called foaming slag. According to measurements, the volume of bubbles in foamed slag is usually larger than the volume of molten slag. It can be seen that the slag in the foam slag exists in the form of a liquid film of bubbles. In addition, the foam slag is often rich in metal droplets.

After the slag is foamed, the contact area between the three phases of steel, slag, and gas is greatly increased, which can accelerate the oxygen transfer process and the physicochemical reaction between steel and slag. The foaming makes the volume of slag significantly increase without increasing the amount of slag, and the thickness of the slag layer increases exponentially. Metal yield. These effects of foam slag are particularly prominent in converter steelmaking. In electric furnace steelmaking, the thickness of foam slag is generally required to be more than 2.5 times the length of the arc column to achieve submerged arc operation.

The reasons for making the slag foamy are more complicated. At present, the research is not thorough enough, but there are two conditions that must be met. This is the external condition of slag foaming. Blowing gas into the slag or passing a large amount of gas in the molten pool can promote slag foaming. Second, the slag itself must have a certain degree of foaming. There are two standards for measuring the slag foamability, the duration of the foam and the amount of foam slag. Together, these two standards represent the stability of foam slag.