In this article, we’ll talk about Induction Heating Furnaces. Basically, the main principle of induction melting is that a primary coil generates a high voltage electrical source.
Then, the high voltage produces a low voltage high current in the secondary coil (the metal).
In simpler words, induction heating is a way or method to transfer heat energy.
Induction Heating Furnaces Types:
Well, there are 2 main induction heating furnaces types which are:
- The coreless induction furnaces.
- The channel induction furnaces.
We’re going to discuss each type of induction heating furnaces in further details, so you completely understand the differences…
First of all, we are going to talk about the coreless induction heating furnaces. Basically, its heart is made of a coil which has a hollow section of heavy charge. Also, it has a copper tubing of high conductivity that is made into a helical coil.
We use a magnetic shielding and steel shell to contain the coil shape to avoid the heating of the supporting shell. Basically, the coil is water cooled to protect it and avoid overheating.
The water is cooled and recirculated in a cooling tower to cool the coil. The trunnions support the shell where the furnace tilts to make pouring easier.
So, the crucible is set by driving a granular refractory between a hollow internal former and the coil. But, first, the hollow internal former is melted away by the first heat produced from the sintered lining.
Then, the power cubicle converts the frequency and voltage required for electrical melting or of the main supply. You can use different frequencies for induction melting ranging from 50 cycles per second up to 10,000 cycles per second. Of course, 50 cycles per second is the main frequency, while 10,000 cycles per second are the high frequency.
A higher operating frequency will generate a greater maximum amount of power that you can practically apply to a furnace. Consequently, this will lower and reduce the amount of turbulence induced.
The electrical currents going through the induction coil and the interaction of the magnetic field produce a stirring action in the molten metal.
Now, the molten metal will rise upwards as the stirring action forces it to in the center. As a result, this will cause the characteristic meniscus on the surface and exterior of the metal.
Basically, there are 2 main factors that affect the degree of stirring action. The factors are the frequency and power applied and the shape and size of the coil. Also, the viscosity and density of the molten metal affect the degree of stirring.
One of the important things is the stirring action within the bath since it helps with the mixture of alloys. Moreover, the stirring action helps with homogenizing of temperature throughout the furnace and melting the turnings.
An increase in the gas pickup, oxidation of alloys, and lining wear could result from excessive stirring.
Finally, you should that the coreless induction heating furnaces are a great replacement for the crucible furnace. It’s the best type of furnace to use if you want melt alloys with high melting points.
Commonly, we use the coreless induction furnace to melt all types of irons, steel, and various non-ferrous alloys. The coreless furnace makes a perfect option for alloying and remelting.
The best thing about it is its high degree of controlling and maintaining the chemistry and temperature as the induction current generates good circulation.
The second type of induction heating furnaces is the channel induction furnace which has a refractorily lined steel shell.
Now, this steel shell contains a molten metal. Then, there’s an induction unit that is connected by a throat and attached to the steel shell. This induction unit makes the melting element of the furnace.
Basically, the induction unit has an iron core in the shape of a ring around which a primary induction coil wounds. This is results in the formation of a simple transformer where the molten metal loops involve the secondary component.
Then, the metal circulates into the furnace main well by the heat generated within the loop. A valuable stirring action in the melt is affected by the current of the molten metal.
Ordinarily, we use the channel induction heating furnaces as a superheating and holding unit for greater melting point alloys (cast iron).