Ferroalloy Refining Electric Furnace

Refining furnaces, also known as secondary refining furnaces or ladle refining equipment, are used for deep treatment of molten steel from primary furnaces (EAF, converter, etc.). They aim to improve molten steel purity, adjust composition and temperature, and meet the production requirements of continuous casting and high-quality steel.

The ferroalloy refining electric furnace is the main equipment for producing medium-carbon, low-carbon, and micro-carbon ferroalloys. It performs desiliconization refining on high-silicon and low-carbon ferroalloy intermediate products to obtain ferroalloy products with required compositions. This equipment combines the advantages of electric arc furnaces and submerged arc furnaces, using electric arc heating method, equipped with three electrodes (graphite electrodes or continuous self-baking electrodes). Its capacity is generally expressed by transformer capacity (kVA) rather than tonnage,  because the same refining furnace can produce different types and quantities of refined ferroalloys using different raw materials.

Unlike a Submerged Arc Furnace (SAF)—also known as a reduction furnace—which operates with submerged arcs, the Ferroalloy Refining Electric Furnace employs an open arc heating method and is equipped with a control system similar to that of a steelmaking EAF. It combines the flexibility of an EAF with certain economic advantages of an SAF.

Ferroalloy refining electric furnaces can be divided into two types: fixed type and tilting type, with significant differences in structural features and application scope:
 

The core working principle of a Ferroalloy Refining Electric Furnace is desiliconization refining, also known as the Electro-Silicothermic Process.
 

I. Raw material preparation: The main raw materials are high-silicon, low-carbon ferroalloy intermediate products (such as silicomanganese and silicon-chromium alloys), combined with fluxes like manganese ore, chromium ore, and lime.

II Arc heating: An arc is generated by three electrodes (graphite or self-baking electrodes) to provide the high temperature required for the desiliconization reaction.

III. Desiliconization reaction: Under conditions of high temperature and high basicity slag (CaO/SiO₂ ratio of 1.6~1.8), the silicon in the intermediate products reacts with the added ores (manganese ore, chromium ore). The silicon is oxidized and enters the slag, thereby reducing the carbon content of the final product.

IV. Tapping: After refining is completed, the molten metal is discharged into a ladle via the tilting device or tapping spout. The molten metal is then cast into ingots to obtain the final product.