EAF roof's introduction and influence factors

Introduction to EAF roof

The EAF roof is a spherical structure with electrode holes and smoke exhaust holes. The outer ring part is called the main furnace cover, and the middle part is called the small furnace cover (also known as the triangular area). The furnace cover can be removed during charging. The smelting process of electric furnace is extremely complex, and the service conditions of prefabricated parts in triangular area are very harsh. It is mainly affected by electrode arc radiation, rapid cooling and heating, chemical erosion of molten steel and slag, impact wear of high-speed air flow formed during dust removal, unreasonable furnace cover structure and other factors.

Influence factors of water cooled EAF roof 

1. Arc radiation

During electric furnace smelting, the arc temperature generated by electrode discharge is more than 3000 ℃, which causes severe melting loss on the working face of small furnace cover. In the arcing stage, the arc is exposed above the charge, close to the furnace top, and the heat radiation is large. The longer the arc, the greater the power, the greater the radiant heat to the furnace top, and the faster the furnace top is damaged. General steel mills require lower power transmission during arcing to control the arc length; In the process of drilling, large voltage and large current power supply are gradually used to protect the furnace cover.

2. Quench and heat

Arc heating, tapping and furnace cover rotating to the outside of the furnace, resulting in rapid cooling and heating, resulting in thermal stress on the furnace cover and spalling of the working face.

The high-speed air flow formed by the dust extraction system impacts and wears the working face of the furnace cover. When the pumping force is insufficient, most of the flue gas and flame generated by scrap melting escape from the gap between the electrode and the electrode hole, and the air flow is violently washed for a long time, resulting in serious hole expansion of the electrode hole. When the main furnace cover is spherical or arc-shaped, the working surface of the small furnace cover will be eroded in an arc. Therefore, the operator shall regularly clean the sundries in the flue of the dust removal system to avoid blocking the flue and affecting the dust removal effect.

3. Chemical erosion

Molten steel and slag splashed to the working face of the furnace cover, and some chemical components reacted with the working face and penetrated into the working face to form a metamorphic layer. When the temperature changes suddenly, the thermal stress causes the metamorphic layer to peel off, then forms a new working face and suffers cyclic damage. The higher the distance between the molten pool liquid level and the working face of the small furnace cover, the smaller the splashing effect and the smaller the impact of chemical erosion. The height is generally more than 1.5m.

4. Molten iron blending ratio

Molten iron contains high silicon and sulfur, which is easy to form acidic substances such as silicon oxide and a small amount of sulfur oxide in oxidizing atmosphere, aggravating the damage to the small furnace cover. The higher the proportion of molten iron, the greater the impact.

5. Electrode spray water

Spraying water on the electrode not only reduces the electrode consumption, but also reduces the temperature around the electrode hole, so as to inhibit the high-temperature melting loss to a certain extent. If this measure is not adopted, the damage of electrode hole will be aggravated, mainly manifested as hole expansion.