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| Crucible or low frequency induction furnaces are mainly used in melting copper and copper alloy. While gas absorption during the brass melting does nor matter, the loss amount of evaporated Zn, which is resulted from its low melting point, is critical Therefore more filter equipment has to be applied, and the filtered dust, which is usually composed of 40-60 percent of oxidized zinc, are required to be re-used. Low frequency induction furnace is divided into two types: crucible and channel types. |
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Crucible and Channel Type Furnaces
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Item
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Crucible Type
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Channel Type
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Structure
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Fundamental Structure
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Change Available
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Heating and Melting Chamber
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Unit Type
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Separate Type
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Furnace/Output Capacity
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6/ 3.5ton, 7.5/3.5 ton
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8/3.5 ton
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Life
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3~6 months
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12~24 months
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Remained Melt
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Unnecessary
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Necessary
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Workability
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Discontinuous
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Continuous
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Composition Change
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Easy
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Difficult
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Stirring Power
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Strong
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Weak
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Scrap Type
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Chip or Cluster
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Cluster
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Crucible Type Induction Furnace
The coiled crucible is heated by supplying electric current through the coil to melt metal. Cold material can be used in this type of furnace. This type is suited to small quantity batch production but its thermal efficiency is lower than channel type. Unit type of heating chamber shortens its life. Since remained melt is not necessary, it is easy to change composition and work discontinues operation. Stirring primarily occurs at the middle point of the coil where tesla is highest Therefore, input flux is compressed on crucible wall, causing decrease in wear resistance of refractory, oxidation of melt and rolling of oxide compound. Strong stirring power enables small cutting chips to be used in this type of furnace.
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Cannel Type Induction Furnaces
Metal is melted by making a ring at the point corresponding to the second coil of single phase AC transformer and supplying current through the first coil. The second current is induced in the metal to be heated and melted. Low frequency of 50-60 Hz is used. This type has higher capacity than the crucible type. It is easy to change the structure. Heating and melting chamber is separate type. The capacity of electric power is unlimited and the life of the furnace is 1-2 years. Since remained melt is required for the next operation, continuous melting with little change of composition is possible. Scrap of cluster type is used due to the weaker stirring power.
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