The Smelting Electric Furnace

The Smelting Electric Furnace

The smelting electric furnace, also known as the EAF or arc furnace, is the melting heart of today’s green steel transformation processes.smelting electric furnace It is the main melting device for ferroalloys and the platinum group metals (PGM), but is increasingly used for primary steel production as well. This development is being driven by lower energy costs compared to blast furnaces and increasing focus on environmental performance.

The EAF is a fundamentally different technology than the traditional BF route to liquid steel.smelting electric furnace It is not only smaller and more flexible in terms of scrap ratio, but it can use a wider variety of raw materials, including direct reduced iron (DRI), which eliminates the need to first smelt coal. This opens up the opportunity to run the EAF on renewable power, which will bring near zero carbon steel production within reach.

Modern EAFs are characterized by shallow hearth designs and multiple supersonic oxygen injectors to enable efficient melt movement.smelting electric furnace However, as the EAF becomes the dominant route for primary steel production using DRI, larger quantities of iron are lost to the slag. This slag contains basic oxides such as CaO and MgO, which inhibit the activity of silicate ions in the smelting process. This reduces the effectiveness of oxygen addition and makes it more difficult to achieve the desired smelting conditions.

RHI Magnesita has extensive experience with the engineering and refractory design of large rectangular and round EAFs, and can offer a complete range of products for this application. Our refractory solutions are designed to achieve the specified thermal profile in the hearth and bath area, taking into account the specific cooling systems that are employed by each original equipment manufacturer involved. The general lining concepts for these smelters are based on high-fired, high-purity magnesia bricks for ferroalloys or magnesia chrome bricks for PGM, Ni, and Cu applications.

During the melting of raw material, the EAF is a highly turbulent environment. This creates significant heat loss through the walls, roof and refractory of the furnace as well as through the electrodes in contact with the molten metal. This can result in poor slag formation and poor metallic iron quality.

To minimise these losses, the refractory has to be capable of maintaining good electrical conductivity whilst having low porosity. This can be achieved through the combination of an appropriate binder, a mineral filler and a special grade of aggregate.

After the initial scrap charge is melted, additional charges can be added to maintain the required smelting temperature and density of the liquid steel. Once the smelting is completed, refining operations are carried out to check and correct the steel chemistry and superheat the molten metal. Typically, this produces a steel product ready to be cast. This is commonly done in a basic oxygen furnace, but the EAF can also perform this operation. The resulting "hot metal" is then fed into the continuous caster or ladle treatments. In this way, the EAF completes the green steel transformation.