What is the White Slag Process?

What is the White Slag Process?

As the name suggests, the white slag process is the process of producing white slag. White slag is a type of alkaline slag commonly produced in electric furnace steelmaking. After cooling, the slag appears white. The alkalinity of the white slag is high (between 2 and 4), with less than 1% iron oxide and approximately 60% calcium oxide.

The white slag production process involves adding calcium carbide, carbon powder, ferrosilicon powder, or other additives to the furnace after thin slag is formed. This stirring reduces the iron oxide and manganese oxide in the slag to metallic iron and manganese. As the oxides in the slag decrease, the slag gradually turns white.

Oxygen from the molten steel beneath the white slag diffuses into the slag, reducing the oxygen content in the steel.

The white slag process requires the addition of CaC2 to the thin slag after the oxygen melting period of steelmaking. Once the slag is white, sampling and analysis are begun to adjust the alloy composition. The slag is then maintained white for 30 minutes.

The primary task of the reduction period is to remove oxygen and sulfur from the molten steel, adjust the alloy, and bring the steel temperature to the tapping temperature. White slag formation is a reduction measure employed during the diffusion deoxidation phase at the end of steelmaking. Therefore, to ensure adequate deoxidation, the white slag process requires a 30-minute maintenance period from slag formation to tapping.

This 30-minute maintenance period not only prolongs smelting time and increases power consumption, but also makes alloy adjustment difficult due to the extended reduction period. Consequently, processes requiring longer white slag maintenance periods are gradually being phased out. In their place, the fast white slag process, which offers strong deoxidation, generally allows for a reduction period of around 20 minutes, reducing energy consumption and improving operating efficiency.

Additionally, a shortened reduction period significantly reduces steel aspiration, which also benefits quality, achieving high quality, high yield, and low energy consumption.