Holding furnaces are heat hearth-type furnaces. The transfer of heat to the metal is by heat radiation from the glowing ceiling and walls as well as from SiC heating tubes themselves.
There exist two types of these furnaces:
holding furnaces which maintain the temperature of aluminium alloys
combines furnaces in which it is also possible to melt ingots
The combined stationary furnace can be employed as a universal foundry plant in which it is possible to cary out melting, temperature maintenance and refining of the material as well as preparation of the metal for casting.
The furnace has been designed so that it has three chambers:
.an antechamber for charging
a chamber withheating elements
an antechamber for takink the alloy
The chamber accommodating elements is seperated by a partion wall from the charging chamber and the casting chamber. This chamber accommodating heating elements is on its lateral side provided with an opening closed by a door which serves to treat the molten metal as well as to treat the furnace with salts against oxide formation and growth (corundum) on the¸internal wall faces of the furnaces and visually the state oh heaters.
Advantages of the stationary furnaces with SiC heating elements:
high heat efficiency of the furnace
minimum consumption of electric power for melting and temperature maintenance
low percentage of burnout
possibility to treat the furnace with salts against corundum formation on the furnace walls
minimal interruptions due to the replacement of heating elements
possibility to start the furnace with frozen alloy
lower maintenance costs in comparison to conventional electric resistant heartg-type or crucible melting furnaces