Man has been able to melt metal ever since the Iron Age; but, for centuries the processes were slow and not all that efficient and the manufacture of metal implements was, correspondingly both expensive and limited in scope. The application of heat into the process is a key factor; heat is usually required to extract the base metal from the ore and further heat (in a number of different processes) is required to improve the qualities of the base metal and shape it into its desired configuration for whatever purpose the manufactured metal implement has to perform.
The Furnace
Early melting wasn’t much more than placing the ore or extracted base metal into a fire pit and hoping it would eventually get hot enough to suit your purpose. When it became known that iron could have much more uses if its chemical composition was modified so as to convert it into what we now know as steel, the development of an efficient Metal Melting Furnace become essential.
Until Bessemer invented the converter named after him, the common method for producing steel was to start with carbon-free wrought iron and heat it together with charcoal in a long stone box. This process took up to a week to complete and only small batches could be made at a time. Obviously, the mass production of steel that enabled the Industrial Revolution could not take place until a better, quicker Metal Melting Furnace could be made available.
Of the improvements that followed, one drew upon the ancient fire pit method and became known as the open hearth furnace; like Bessemer’s, it could produce bulk steel; but, it was a slower process which, however, allowed the quality of the finished steel to be improved. Both processes had a long and useful history from the mid 19TH Century through to the end of the 20TH, most open hearth furnaces were made redundant by the early 1990s, mainly due to their slow operation; they were replaced by basic oxygen or electric arc furnaces.
Iron and steel are not the only metals that we need to melt and/or modify by heat in furnaces and similar improvements occurred across the board. As a closing note; an industrial Metal Melting Furnace is an enclosed chamber in which metal can be heated to very high temperatures; it should not be confused with the domestic furnace in our homes which is basically a boiler for our central heating systems.
