Electric Arc , Blast Furnace & Metal Casting Furnaces

By: Kent Klein

There are several types of casting furnaces which includeElectric Arc furnaces, Blast furnaces, Cornwall Iron Furnace, etc. Here’s aquick review of some of them.

Electric Arc Furnace:This furnace can be described as a furnace heating charged materials by theway of an electric arc. These furnaces exist in all the sizes-right, from thesmallest one having a capacity of around 1 ton to the largest one having acapacity of 400 tons. The former one is used in foundries to produce cast ironproducts, whereas the latter one is used for secondary steel making. The onesused by dentists and in research laboratories might be having capacity of a fewgrams only. The electric arc furnace can have temperatures risen up to 1800Celsius. The first electric furnaces came into being in 1907, at the hands ofPaul Heroult of French origin. The commercial part of these furnaces wasestablished in the United States of America. In the beginning, the specialtyproduct used in the making of spring steel and machine tools was electricsteel. Calcium Carbide was also prepared in these arc furnaces. It (calciumcarbide) was used in carbide lamps.

This furnace comprises of a refractory-lined vessel, normallywater-cooled in huge sizes, having a covering of a retractable roof, throughwhich the entry of graphite electrodes takes place. They might be one or manyin number. The furnace is divided into 3 sections: the shell, consisting oflower steel bowl and sidewalls, the hearth, consisting of refractory lining thelower bowl, and the roof, that can be water-cooled or refractory-lined, and caneasily be shaped into a spherical section or conical section (frustum). Arefractory delta is also supported by the roof at its center, by the way ofwhich graphite electrodes make an entry.

The process of operation starts with delivery of scrap metalto scrap bay which is located adjoining melt shop. After that, the loading ofscrap into huge buckets or baskets takes place. The next step is to carry thisbasket to the melt shop. The charging takes place here. After the completion ofcharging, let the electrodes be allowed to enter and placed onto scrap. Thiscauses the arc to be struck. Lower voltage is preferred for this part (ofoperation) to provide protection to the walls and roof against arc damage andexcessive heat. After having the electrodes reached the heavy melt, shieldingof arcs by scrap takes place. This enables a rapid formation of molten pool,thereby decreasing tap-to-tap times. Oxygen is also allowed to enter.

Blast Furnace:It can be referred to as a kind of metallurgical furnace, through which theprocess of smelting takes place. This produces metals, normally iron. Thesefurnaces trace their origin to China (around 500 BC). They were also found inBelgium and England later. They do not have any special mode of operation. Themetals get melted by heating only. Generally, iron is melted in these furnaces.The chemical reaction can be explained as follows:

??????????????? Fe2O3+ 3CO -> 2Fe + 3CO2

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