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THE COMTHERM ON-LINE TECHNICAL MANUAL

METAL MELTING

In order to form castings in a foundry or casting plant it is necessary to melt the metal and heat it to a suitable temperature for pouring into a mould or pattern. The furnaces used for metal melting are of three types, crucible furnaces, hearth furnaces or shaft (tower) furnaces.

Crucible furnaces usually consist of an insulated and cladded refractory enclosure containing a container (crucible) manufactured from a high temperature carbon or iron material. These furnaces are most commonly used for melting metal in small batches involving relatively low temperature metals and alloys. Fig. MM-1a illustrates some examples of crucible furnaces.

Hearth and shaft furnaces are usually restricted in use to applications were larger quantities of molten metal and higher temperatures are required. Hearth furnaces are particularly associated with the iron and steel making industries. Examples of hearth furnaces and shaft (tower) furnaces are illustrated in Fig. MM-1b and Fig. MM-1C respectively.

In most cases the gas burner and combustion engineer will only experience applications involving crucible furnaces and will only encounter hearth or tower furnaces on rare occasions. When gas fired the hearth and tower furnaces are fitted with air blast nozzle mix burners; often using preheated air or oxygen to help fuel efficiency.

Crucible furnaces can be fitted with nozzle mix air-blast burners for higher temperature applications, although with low temperature metal melting, special industrialised packaged burners can be fitted.

Examples of gas burners applied to crucible furnaces are illustrated in Fig. MM-1d.

Refer to the non-ferrous metals and ferrous metals web pages for data regarding metals and for graphs showing melting points, latent heats and total heat capacities of metals refer to Fig. MM-2a , Fig. MM-2b and Fig. MM-3a .

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  Metal Melting

  None Ferrous Metals
  Ferrous Metals



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