Melting Procedure for High Frequency Induction Furnace:

The high-frequency induction furnace is fundamentally an air transformer in which the primary coil refers a coil of water-cooled copper tubing and the secondary coil refers the metal charge. Furnace capacity hardly ever exceeds 1 ton. Sketch of the furnace is illustrated in Figure 4. The shell of the furnace contains asbestos board, and it is supported on trunnions on which the furnace pivots while pouring. Inside the shell is placed the circular winding of copper tubing. Firebrick is located on the bottom portion of shell, and the space among that and the coil is rammed with grain refractory. The furnace chamber might be a refractory crucible, or it might consist of a rammed and sintered lining. The common practice is to ganister rammed around a steel shell that melts down with the first heat, leaving a sintered lining. Fundamental linings are frequently preferred, and in this case either the lining might be rammed, utilizing magnesia grain, or a clay-bonded magnesia crucible might be used.

The procedure consists of charging the furnace along steel scrap and then passing a high-frequency present through the primary coil, therefore inducing a much heavier secondary current in the charge, that results in heating the metal charge through resistance. As soon as a pool of metal is produced, very pronounced stirring action in the molten metal occur, which helps to accelerate melting. In this procedure, melting is fairly rapid, so much so that there is just a slight loss of the simply oxidized elements. If a capacity melt is needed, steel scrap is added up continually throughout the melting-down period. As soon as melting is complete, the wished superheat temperature is attained and the metal is deoxidized and tapped into ladles.

The time of melting based upon the weight of the charge, the size of the furnace and the power input. As a period of only 10 or possibly 15 min elapses through the time the charge is melted down till the heat is tapped, there is not adequate time for chemical analyses. Therefore the charge is typically carefully chosen from scrap and alloys of known composition so as to generate the desired analyses in the finished steel. A very close control of elements might be attained in this manner.

In most of the cases, no attempt is made up to melt under a slag cover, as the stirring action of the bath makes it hard to maintain a slag blanket on the metal. But, a slag cover is not essential since oxidation is slight.