October 24, 2008


An Induction Furnace uses induction to heat a metal to its melting point which is based on the theory of Electro Magnetic Induction. Depending on their frequency (50 Hz - 250 kHz) these can be divided to three types:

  1. High Frequency
  2. Medium Frequency
  3. Low Frequency

Their capacities range from less than 1kg to 100MT, which are used for re-melting of iron & steel (steel scrap), copper, aluminium, precious metals and alloys. Even most modern foundries use this type of furnaces and now more iron foundries are replacing Cupolas with Induction Furnace to melt cast iron as the former emit lots of dust & other pollutants. The Steel making via Induction Furnace route has certain advantages & disadvantages:

Advantages of Induction Furnace

  1. It has no electrodes and electric arcs which allow productions of steel & alloys low in carbon and occluded gases without any quality problem.
  2. Low melting losses & alloying elements.
  3. High power efficiency, therefore, cost-effective.
  4. Precise control of the operating parameters.

Disadvantages of Induction Furnace

  1. Refining in Induction Furnace is not as intensive or effective as in Electric Arc Furnace (EAF).
  2. Life of Refractory lining is low as compared to EAF.
  3. Removal of S & P is limited, so selection of charges with less impurity is required.

Induction Furnaces are classified generally into two categories:

  1. Channel type induction furnace
  2. Coreless type induction furnace
Channel Type Induction Furnace design


1. Channel Type Induction Furnace

These furnaces basically consist of a vessel to which one or more inductors are attached. The inductor is actually a transformer whereby the secondary winding is formed with the help of a loop of liquid metal confined in a closed refractory channel. In the furnace the energy is transformed from the power system at line frequency through a power supply to the inductor and converted into heat. One advantage of this type of furnace is that the vessel or upper case can be built in any practical size & shape to suit the application, but the disadvantage are like -
a. Power input limitation per inductor.
b. Necessity to maintain a liquid heel in the furnace always to avoid problems related to operational parameters and refractories.
For the above reasons Channel type Induction furnaces (Fig.) are treated as a receiver or holding vessel for homogenization of liquid metal with limited capability of melting.

Coreless Type Induction Furnace

2. Coreless Type Induction Furnace
These furnaces (Fig.) are designed like a cylindrical crucible surrounded by a power coil in which energy is supplied either directly from the network (line frequency) or through a frequency converter. The magnetic field generated by the coil carries the energy to the charge.
Related Articles
=> Refractory Lining of Induction Furnaces [Read]

=> The Function of a Furnace and Kiln used in Ceramic and other Industries [Read]
=> Refractories for Reheating Furnaces [Read]
=> Refractory Resistance to Carbon Monoxide (CO) Attack [Read] 
=> Blast Furnace - Refractory Lining Pattern [Read]
=> MIDREX - The Most Widely accepted Direct Reduction (DR) Process of Ironmaking [Read]
=> COREX® : An Innovative Ironmaking Metallurgical Process [Read]
=> Iron Making in Mini Blast Furnace (MBF) [Read]
=> Use of Kyanite as Refractory Raw Material [Read]
=> HYL III and SL/RN - The two widely accepted Direct Reduction (DR) Processes of Ironmaking [Read]


  1. Hello, the following i need technical clarification.
    Can we melt Aluminium Alloy Like LM25 in medium frequency induction furnace. What should be the linig material and i need the malting procedure for Aluminium alloy melting in Induction furnace.

  2. Hello Anand, Yes you can melt Aluminium Alloy which you mentioned. To know about refractory lining material required for melting of Aluminium and its alloys please refer to our article Refractory Lining for Induction Furnace . There it has been given all in detail.

  3. In addition to advantage of induction furnace, induction heating eliminates the inconsistencies and quality issues associated with open flame, torch heating and other methods. Once the system is properly calibrated and set up, there is no guess work or variation; the heating pattern is repeatable and consistent. With modern solid state systems, precise temperature control provides uniform results; power can be instantly turned on or shut off. With closed loop temperature control, advanced induction heating systems have the capability to measure the temperature of each individual part. Specific ramp up, hold and ramp down rates can be established & data can be recorded for each part that is run.

  4. Very great brief info you shared here about furnaces inductions, really marvelous appreciate this work.

  5. Hello! we are using ramming material of induction furnace is made from quartz sand, we want to hot patching the wall of induction furnace, pl give me your idea what kind of material we should use, or if you have composition of this material, pl send it to me. tks!