ELECTRIC ARC FURNACE

ELECTRIC ARC FURNACE

  

An arc furnace is a type of oven used in metallurgy . It uses the energy heat of the electric arc established between one (or more) electrode (s) of carbon and the metal to obtain a sufficient temperature to its melting .

Small (about one ton) or high capacity (up to 400 t ), it is mainly used for production of liquid steel (about 35% of world production) and also for the recycling of metals (for example to recover the zinc from dust and metallurgical wastes) (process called Electric Arc Furnace Dust (EAFD) by the Anglo-Saxon).

Dome of a rotary electric furnace steel

Miniature arc furnaces are used in some research laboratories. Some furnaces are used for reactions between solid and gas phases between.

It is found in other sectors, such as that of dentistry , with capacities from a few ounces.

Principle :

Principle: In an envelope refractory (not closed to exhaust vapors), a high voltage is applied between the electrodes ( graphite - carbon ) and the metal to melt. This tension brings out an electric arc . Electrical cables, the envelope, the roof (or the dome) and some elements are cooled with water or other coolant.

The temperature generated by the arc exceeds 1800 ° C and can reach 3600 ° C . A colder zone persists between the electrodes, a problem is usually solved by gas burners + oxygen or electromagnetic stirring of molten metal.

Filling a pocket by tilting the sole

Some ovens operate in DC and are then fitted with only one electrode.

Openings, or tilting of the furnace used to recover the molten metal and slag .

Energy 

It varies by age and quality of the oven and depending on the materials you walk inside.

A ton of steel to be produced in an electric arc furnace in theory requires about 440 kWh. The theoretical minimum required to melt one ton of scrap steel is 300 kWh (melting point 1520  ° C / 2,768 ° F). Make steel with an electric arc is therefore economical only where there is plenty of power with an electric grid stable and well developed.

Quality 

These ovens are cost-effective than using metallurgical wastes. These, often poorly controlled or rich impurities have affected the quality of steel products. Indeed, some chemical elements (such as copper , the tin , the molybdenum or chromium are very difficult to remove once dissolved in the liquid steel, which often are associated with scrap metal.

This difficulty controlling purity metal has limited the production of steel in electric furnaces with alloys less demanding:

for construction, long products (rebar, beams , ...) or flat ( sheet piling , siding , ...)

flat products for common equipment ( cans welded, furniture, ...)