The EBT (Eccentric Bottom Tapping) electric furnace modifies the traditional electric furnace's tapping trough into a tapping box, with the tapping opening oriented vertically downward at the base of this box. The lower section of the tap hole is equipped with an opening and closing mechanism to control the flow of molten steel. Additionally, the top center of the tap box features an operation port, facilitating the maintenance and operation of the tap hole filler.
The EBT electric furnace offers several key advantages, primarily centered around achieving slag-free tapping and enhancing the usable area of the water-cooled furnace wall:
Reduced Tapping Tilt Angle: By minimizing the tilt angle required for tapping, the EBT design simplifies the electric furnace's tilting mechanism, reduces resistance in the short network, increases the usable area of the water-cooled furnace wall, and extends the furnace body's lifespan.
Retained Steel and Slag Operations: Slag-free tapping improves steel quality and benefits subsequent refining processes. Retaining some steel and slag within the furnace supports efficient smelting and energy conservation.
Bottom Tapping: Tapping from the furnace bottom results in lower tapping temperatures, reduced power consumption, minimized secondary oxidation, improved steel quality, and increased ladle lifespan.
Owing to these numerous advantages, EBT electric furnaces have rapidly gained global popularity. Modern electric furnace constructions, particularly those paired with external refining furnaces, mandate slag-free tapping, making EBT the preferred choice.
During tapping, the furnace is tilted approximately 5° towards the tapping side. The tapping mechanism is then activated, causing the tapping filler to automatically fall under the static pressure of the molten steel, allowing the steel to flow into the ladle for automatic pouring. When the molten steel reaches about 95% of the required volume, the furnace is quickly tilted back to prevent slag from entering the ladle. During this back-tilting process, approximately 5% of the molten steel and a small amount of slag flow into the ladle. After tapping, the furnace is shaken to leave 10%-15% of the steel and 95% of the residual slag inside. The tap hole is then inspected and maintained, closed, refilled, scrap steel is loaded, and arc melting is restarted.
The smelting process in an EBT electric furnace has evolved from a comprehensive steelmaking setup that encompassed melting, oxidation, reduction refining, temperature and composition control, and quality assurance, to a more streamlined chemical steel equipment setup that retains only melting, heating, and essential refining functions (such as dephosphorization and decarburization). Process operations requiring lower power are transferred to the ladle refining furnace.
The ladle refining furnace provides optimal refining conditions for the initial molten steel, enabling strict control over its composition, temperature, inclusions, and gas content to meet increasingly stringent steel quality requirements. Dephosphorization and even partial decarburization are advanced to the melting period as much as possible, while the oxidation refining and heating period after melting focuses solely on carbon control and avoids adding ferroalloys that are prone to oxidation and are added in larger quantities during charging. This approach is particularly beneficial for shortening the smelting cycle, reducing consumption, and enhancing productivity.
The EBT electric furnace adopts steel and slag retention operations. At the onset of melting, a pre-existing molten pool, supplemented by enhanced oxygen blowing and bottom blowing and stirring, creates favorable conditions for advanced metallurgical reactions. From the perspective of improving productivity and reducing consumption, electric furnaces are required to achieve the shortest melting time, fastest heating rate, and minimal auxiliary time (such as furnace repair, feeding, electrode replacement, steel tapping, etc.) to attain optimal economic benefits.
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