The electric furnace method stands as the predominant approach for smelting continuous cast steel and iron alloys, with electric furnace-produced ferroalloys accounting for over 70% of the total ferroalloy output.
Electric furnaces can be broadly classified into two types: submerged arc furnaces and electric arc furnaces, the latter also known as refining furnaces. When carbon is employed as a reducing agent to produce ferroalloys, the electric furnaces are commonly referred to as ore reduction furnaces, specifically submerged arc furnaces.
During the smelting process in a submerged arc furnace, a mixture of raw materials is introduced through the furnace mouth, with the electrode root buried within the charge. Heating is achieved through the electrical resistance heat generated by the electric arc and the current passing through the charge. Molten iron and slag are periodically discharged through the tap hole, ensuring a continuous production process.
Submerged arc furnaces can be further categorized based on the amount of slag produced into two operations: the micro-slag method and the slag-containing method. In the production of ferrosilicon and high-silicon ferrochrome, where raw materials are of high purity and contain fewer impurity oxides, no flux is added during the smelting process. Consequently, the amount of slag generated is minimal, leading to the adoption of the micro-slag method. The primary raw materials for this method include silica, coke, and steel scraps, with carbon ferrochromium used in the production of silicon chromium.
Conversely, in the production of carbon ferromanganese, carbon ferrochrome, silicomanganese alloy, and other alloys, the ore used contains numerous impurities and oxides, necessitating the addition of flux to form slag. As a result, the amount of slag produced is substantial, often exceeding the weight of the alloy, hence the term slag method. In addition to ore and reducing agents, raw materials for the slag method frequently require the addition of flux.
Owing to the use of carbonaceous reducing agents, submerged arc furnaces are limited to producing high-carbon alloys (excluding silicon alloys). For the production of ferroalloys containing silicon, primarily siliceous alloys (as reducing agents), electric arc furnaces are typically employed, which share similarities with steel-making electric arc furnaces.
The raw materials utilized in electric arc furnace production primarily consist of ore, including concentrates or purer oxides, siliceous reducing agents, and flux. The charge is introduced into the furnace either through the top or the door. The entire smelting process can be segmented into arc ignition, charging, melting, refining, and tapping stages. The smelting process is driven by the exothermic heat from the arc and the heat generated by the silicon oxidation reaction. The tapping time is contingent on the silicon content in the alloy, and production is carried out intermittently.
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