Ring and wall block of electric arc furnaces

Electric arc furnace or EAF furnace is included in the group of electric furnaces. Today, this furnace is the most common type of steel furnace and is widely used in the steel and cast iron production industry. Also, this type of furnace is used to melt scraps and refine their parts. The temperature required to melt the metal is provided by the conversion of electrical energy into thermal energy. This energy conversion happens with the help of an electric arc.

What is electric arc?

In 1802, the electric arc was discovered by Petrov with two charcoals attached to the two ends of the battery. When two charcoal heads are placed at a short distance from each other, a dazzling light is created between them, which creates intense heat. An electric arc is actually a column of gases ignited by electrons separated from the cathode. For this reason, the arc temperature is very high.

What is an electric arc furnace?

Furnaces that are used for melting steels, especially simple carbon steels, are called electric arc furnaces. The electric arc furnace is called Electric Arc Furnace in English and is also called EAF furnace for short.

In these furnaces, the arc created between the electrodes and the furnace load converts electrical energy into thermal energy. This energy conversion increases the temperature up to 15,000 degrees Celsius, thus providing the necessary temperature for melting. In 1878, Sir William Siemens built the electric arc furnace. The Siemens design was based on melting using an arc created between two horizontal electrodes.

The EAF furnace, with a design close to what is used in industry today, was first developed in 1890 by Herault. Although this furnace was first introduced by Siemens, Herault built the first direct arc furnace. In the design of this furnace, three-phase electricity and three electrodes were used. By passing through these electrodes, the electric current creates an arc between the electrodes and between the electrodes and charges the  furnace  , providing the necessary heat to melt the melt.

Electric arc furnace components include body, electrodes, electrode regulators, furnace roof, furnace floor, walls, melt discharge chamber, slag removal valve, reactor and transformer.

How does the electric arc furnace work?

At the beginning of the EAF furnace start-up, you should first have a basin for molten iron. After charging this area according to the percentage of composition elements and with the help of scraps and sponge iron, electrodes are installed above and from the roof of the furnace. Electrodes may also be placed inside the melt.

The current performs the melting operation by passing through the electrodes and entering the furnace load and creating very high heat. The length of the arc depends on the length of the electrode. Therefore, to increase the length of the electrode, the length of the arc can be reduced or increased and in this way, the necessary heat can be provided.

In the stages of steel production by EAF furnace, scrap is first placed in the furnace and after reaching the temperature of 1550 degrees Celsius and melting them, it is time to charge sponge iron. To be more precise, iron scraps are thrown into the furnace by an electromagnetic magnet. Then materials such as iron ore and coke are added to help the slag flow. After adding lime and fluorine as furnace slag, the steel production stage begins.

Types of electric arc furnaces in terms of electric current path

Melting with electric arc furnace is done in two direct and indirect ways. The electric arc is created either between two electrodes or between the electrode and the charge. As mentioned above, Siemens offered the indirect arc furnace and Herault the direct arc furnace.

Indirect arc furnace

This type of EAF furnace is used for melting non-ferrous metals or melting cast iron. The placement of positive and negative electrodes in this type of arc furnace is horizontal. In this type of electric arc furnace, the arc is created between the electrodes (double or triple electrodes) and the heat between the two charges will melt this area. In the figure below, you can see the schematic of this type of furnace. Today, the use of this type of furnace is less in the industry.

Indirect arc furnace

In a direct arc furnace, an arc is created between the electrode(s) and the bottom and wall, melting the charge in the area. Today, this type of electric arc furnace is widely used in steelmaking. In the design of this furnace, the arc temperature can reach up to 4000 degrees Celsius.

This type of furnace is used in single electrode, two electrode and three electrode types. Of these, the three-electrode type is the most used for melting steel at high tonnages. These electrodes are made of graphite. They can be considered the most important part of an electric arc furnace.

Previous Post

Alumina base refractories

Next Post

Processing specialized monthly

Leave a Reply

Your email address will not be published. Required fields are marked *

The reCAPTCHA verification period has expired. Please reload the page.

Latest products