What are the Melting Stages in Electric Arc Furnace Steelmaking?

What are the melting stages in electric arc furnace steelmaking?

The traditional electric arc furnace steelmaking process is generally divided into three phases: melting, oxidation, and reduction. With the advancement of smelting technology, some of the reduction phase tasks are gradually being completed by refining outside the furnace.

The melting phase, from the time the power is applied to the complete melting of the charge, is called the melting phase. Its primary task is to quickly melt the entire charge, primarily removing some phosphorus. To accelerate charge melting and conserve energy, oxygen blowing is generally used during the melting phase to assist melting.

After the charge is completely melted, samples are taken for analysis, and the oxidation phase begins. This phase aims to minimize the phosphorus content in the molten steel, remove gases (nitrogen and hydrogen) from the steel through carbon-oxygen reactions, and heat the molten steel to a temperature slightly above the tapping temperature.

To accomplish these tasks, lime and ore must be added to the furnace, and oxygen blowing and slag flow must be performed. At the end of the oxidation phase, the oxidizing slag must be removed. With technological advancements, the oxidation method of adding ore has been largely phased out due to the high heat absorption and increased energy consumption of the ore.

After a power outage to remove the oxidized slag, new slag is created using lime and fluorite, and the reduction phase begins.

The main tasks of the reduction phase are to remove sulfur from the steel, deoxidize it, and adjust the chemical composition and temperature of the molten steel.

During the reduction phase, carbon powder and ferrosilicon powder are evenly added to the slag surface in batches, striving to whiten and maintain the slag color. Ferromanganese, ferrosilicon, and the ferroalloys required for the steel grade are also added to the molten pool. For final deoxidation, aluminum blocks are inserted into the molten steel.