Metal Casting Furnaces and Metal Casting Furnace Types Described

There are several types of casting furnaces which include Electric Arc furnaces, Blast furnaces, Cornwall Iron Furnace, etc. Here’s a quick review of some of them.

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

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

The process of operation starts with delivery of scrap metal to scrap bay which is located adjoining melt shop. After that, the loading of scrap into huge buckets or baskets takes place. The next step is to carry this basket to the melt shop. The charging takes place here. After the completion of charging, let the electrodes be allowed to enter and placed onto scrap. This causes the arc to be struck. Lower voltage is preferred for this part (of operation) to provide protection to the walls and roof against arc damage and excessive heat. After having the electrodes reached the heavy melt, shielding of 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 the process of smelting takes place. This produces metals, normally iron. These furnaces trace their origin to China (around 500 BC). They were also found in Belgium and England later. They do not have any special mode of operation. The metals get melted by heating only. Generally, iron is melted in these furnaces. The chemical reaction can be explained as follows:
Fe2O3 + 3CO -> 2Fe + 3CO2