Detailed Introduction to Five Key EBT Smelting Processes

1. EBT Rapid Melting and Heating Operation

The rapid melting and heating capabilities are paramount in an electric arc furnace (EAF), particularly following the initial charge of scrap into the furnace. To swiftly melt the scrap steel and elevate the molten steel temperature to the tapping point, the EBT EAF typically employs a series of advanced operations. These include supplying maximum possible power, utilizing oxygen lance nozzles for melting, oxygen blowing and stirring, bottom blowing for mixing, and implementing foam slag and other intensified smelting and heating technologies. These measures collectively ensure efficient and rapid heating of the molten steel.

2. Dephosphorization Operation in Electric Furnaces

Dephosphorization within an electric arc furnace is primarily achieved by meticulously controlling slag oxidizability, lime content, and temperature. The main processes involved encompass:

• Enhanced Oxygen Blowing and Combustion: This step boosts the oxidizability of the primary slag, facilitating effective dephosphorization.
• Pre-formation of Foamed Slag: Highly oxidizing and basic foamed slag is prepared in advance, leveraging its low melting temperature to enhance dephosphorization capacity.
• Timely Release of High-Phosphorus Slag: Initial slag with elevated phosphorus levels is promptly released and replaced with fresh slag to prevent phosphorus reversion during temperature increases and tapping.
• Injection Operation for Strengthened Dephosphorization: Lime and fluorite powder are directly injected into the molten pool with oxygen, achieving a dephosphorization rate of up to 80% and concurrent desulfurization at nearly 50%.
• Slag-Free Tapping Technology: This technique strictly controls slag volume, minimizing post-tapping phosphorus levels. Typically, slag volume is maintained at 2 kg/t, with phosphorus reversion limited to ≤0.001% for slag containing 1% P2O5.

The tapping phosphorus content is comprehensively determined based on product specifications, alloying requirements, and other factors, generally kept below 0.02%.

3. Decarburization Operation in Arc Melting Furnaces

High carbon content is intentionally incorporated into electric furnace charging for several reasons:

• Reduced Iron Burning Loss: During the melting period, carbon oxidizes before iron, minimizing iron loss.
• Accelerated Melting: Carburizing lowers the melting point of scrap steel, speeding up the melting process.
• Enhanced Slag-Steel Reaction: The carbon-oxygen reaction stirs the molten pool, promoting slag-steel reactions and early dephosphorization.
• Further Dephosphorization and Homogenization: During the refining heating period, active carbon-oxygen reactions expand the slag-steel interface, facilitating further dephosphorization, homogenizing liquid steel composition and temperature, and aiding gas and inclusion flotation.
• Foam Slag Formation: Active carbon-oxygen reactions contribute to foam slag formation, increasing heat transfer efficiency and accelerating heating.

4. Alloying in Electric Heat Furnaces

Alloying in an EBT electric furnace is typically completed in the ladle during tapping. Alloys that are resistant to oxidation and have high melting points, such as Ni, W, Mo, and other ferroalloys, can be added to the furnace post-melting. However, when steel retention operations are employed, the impact of retained steel on the composition of molten steel in subsequent heats must be considered.

During tapping, the tapping temperature should be adjusted according to the alloy addition amount. Proper ladle preheating and heat compensation within the ladle can enhance alloy yield without causing low-temperature issues. Alloying in the ladle during tapping serves as pre-alloying, with final accurate alloy composition adjustments made in the refining furnace. Pre-alloying ensures smooth composition adjustments during refining, preventing deviations beyond the middle limit of specifications.

5. Temperature Control in Excentric Bottom Tapping Electric Arc Furnaces

Effective temperature control is crucial for successful metallurgical processes. For instance, dephosphorization requires not only highly oxidizing and basic slag but also optimal temperature coordination, emphasizing the importance of early-stage dephosphorization when lower temperatures favor the process. During the oxidation refining period, higher temperatures (>1550°C) are necessary to induce active carbon-oxygen boiling. To ensure smooth post-treatment and pouring, the initial molten steel from the electric furnace must possess a certain degree of superheat, compensating for temperature losses during tapping, external refining, and liquid steel transportation, depending on the specific processes employed.
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