Melting of Charged Scrap in the Electric Arc Furnace

Melting of Charged Scrap in the Electric Arc Furnace

The melting stage represents the core of electric arc furnace (EAF) steelmaking. Modern EAF designs prioritize maximizing melting efficiency through optimized energy input, which can be supplied both electrically and chemically.

Electrical Energy Input  

Electrical energy is delivered via graphite electrodes and typically serves as the primary melting energy source. Operation begins on an intermediate voltage setting, allowing the electrodes to bore into the scrap. Light scrap is often placed on top to speed up this initial penetration, during which roughly 15% of the scrap melts. Once the electrodes are sufficiently buried, the furnace switches to a high-voltage, long‑arc setting. This maximizes power transfer to the scrap while minimizing radiation damage to the roof. A molten metal pool soon forms in the hearth. Although the arc is initially erratic, it stabilizes as the furnace heats up and the molten pool expands, enabling higher average power input.

Chemical Energy Input  

Chemical energy supplements the melting process through:

- Oxy‑fuel burners that combust natural gas with oxygen (or oxygen‑enriched air), heating the scrap via flame radiation and convection.

- Oxygen lancing, where oxygen is injected—often through a consumable pipe—to thermally “cut” scrap by oxidizing hot iron, releasing intense localized heat.

Once a molten bath is established, oxygen can be lanced directly into the steel. This promotes exothermic reactions with elements such as carbon, silicon, manganese, aluminum, and phosphorus, generating additional heat to melt remaining scrap. The resulting metallic oxides report to the slag. The reaction of oxygen with carbon produces carbon monoxide, which either combusts in the furnace or is extracted and treated by the off‑gas system.

Charging and Process Control  

After sufficient scrap has melted to accommodate a second charge, the furnace is recharged. When the final charge is nearly melted, the exposed sidewalls require protection from intense arc radiation. This is achieved either by lowering the voltage or, more effectively, by creating a foamy slag that buries the arc, shields the refractory, and improves thermal efficiency.

Transition to Refining  

Once full melting is achieved (“flat bath” conditions), temperature measurement and bath sampling are conducted. Chemical analysis determines the required oxygen blowing rate for the refining stage and allows preliminary calculation of bulk alloy additions, which are finalized after refining.

Through coordinated use of electrical and chemical energy, along with careful process control, the EAF efficiently converts scrap steel into a molten bath ready for subsequent refining and tapping.

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