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Showing posts with label Induction Furnace. Show all posts
Showing posts with label Induction Furnace. Show all posts

Induction Furnaces | Channel Type and Coreless Induction Furnaces - Advantages and Disadvantages

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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 generally of two types:

  1. Channel type induction furnace
  2. Coreless type induction furnace
https://www.industry.guru - Channel Type Induction Furnace

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 are treated as a receiver or holding vessel for homogenization of liquid metal with limited capability of melting.

https://www.industry.guru  - Coreless Induction Furnace

Coreless Type Induction Furnace
These furnaces 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 Installation Procedure and Heating Schedule to be followed after starting an Induction Furnace | Furnace Operation

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Installation of refractories in any furnace is a tricky process and after the lining is done the most important thing is the heating schedule. That means how the furnace after repairing or with new refractory lining should be started, what should be the rate of heating (rising temperature) and holding time at any particular temperature. You cannot start the furnace by raising its temperature to peak at one go, as otherwise the refractories will be damaged or even the refractory lining may fall apart. The furnace starting heating schedule depends on various aspects including, thermal conductivity of the refractories used.


Here is a step-by-step guide for installation of Refractories (Ramming Masses, etc.) in Induction Furnace also the heating schedule that should be followed after starting the furnace:


 Read: 

1. Scrub all loose materials and clean the furnace.

2. Before using heat the refractory material (Ramming mass) at about 100OC to make it free from moisture. Spread the material at the furnace bottom to about 50 - 60 mm thick layer at each time. Then ram the layer uniformly using a suitable rammer. The material has to be rammed layer by layer to get maximum compaction. Before ramming, little bit poking with a rod help to drive away the air-pockets trapped within the loose refractory material spread.

3. Place the steel former on the rammed bottom. Then fix the steel iron block at the center of the steel former to get uniform thickness throughout the furnace wall.

4. For ramming the upper portion of the side-wall just above the induction coil, mix the dry refractory material with 1-1.5% Sodium Silicate solution and 3-4% water.

5. Best results can be achieved by following the heating schedule for the furnace as mentioned hereunder -

Furnace Heating Schedule | Furnace Operation

Furnace Temperature

Rate of Heating with Holding Time

Ambient temp to 100OC

@ 30OC / hr.

Hold at 100OC.

4-6 hr depending upon the lining thickness.

100O - 800OC.

@ 50OC / hr.

Hold at 800OC.

2 - 3 hr.

800O - 1400OC.

@ 100OC / hr.

Hold at 1400OC.

4 - 6 hr.

1400OC to furnace operating temperature.

@ 100OC / hr.


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