INDUCTION FURNACE STEEL MAKING

Induction Furnace


Induction process is the first patented in steady heating which is done by electric magnetic induction. The furnace is generally used only for remelting and compositional adjustment.

Furnace Construction :

Induction furnace consists of an annular channel surrounding a core of laminated iron sheets. The is surrounded by the primary winding. The crucible with spout usually made of magnesite bricks. The crucible is placed centrally inside a tubular cupper coli with water cooling arrangement. The crucible is packed in position by ramming by heat insulating refractory material. The copper coil carries high frequency primary current. The size of the furnace that is the crucible vary from a few kilo to several tonnes, however 0.5 to 10t capacity furnaces are more popular. The charge material inside the crucible acts as secondary current.

Working Principle :

● When high frequency alternative current passed through the primary copper coil, A strong electro magnetic field from around. This electro magnetic field is induced to the metallic charge inside the reactor. Due to induction, equivalent amount of Eddy current flow within the charge material. By which resistance of this Eddy current surface of the charge material got heated and melting starts. The melt zone is proceeds towards the centre of the metal charge and finally melting is completed. The melt is super heated and made ready for pouring.

● Due to excellent sintering action and very low oxidation loss of metals and alloys, makes the process useful in recovery and the well grade scrap to produced the same or nearly the same type of steel without much of external margin alloy addition.

● The process is equally suited to produce any type of alloys steels on a small scale. It is practically only the commercial process for making steel on small scale which is commonly used in alloy steel foundaries. The crucible can be enclose in a vacuum chamber and thereby better quality steels produced on a small scale. This is known as vacuum induction melting.

Charge Materials :

The charge for induction furnace process consist of well grade steel scrap of 100% required composition because it is only melting process and what ever may charge, that is the final output of same composition.

Process Operation :

High frequency induction furnace
High frequency induction furnace

Charging :

To start the process the crucible is at first charged with light scraps at the bottom and then followed by heavy scraps. Charging is done manually or using mechanical charging device or cranes. Heavy scrap is charged at the top to avoid oxidation at the top.

Melting :

After charging the furnace is switched on through which high frequency current is passed with the help of water cooled primary copper coil. A heavy alternative secondary current is induced in the metal charge due to electro magnetic induction. The charge offers the resistance to induced current to flow which generates heat with resistance heating principle. This induction heating melts the solid charge. Magnetic stirring takes places after melting which homogenised the bath. Then melting is completed with a very short period.

Tapping :

After melting the melt is deoxidized, if required with addition of ferro alloys. The furnace is the tilled to pour the liquid metal in to the ladle.

Advantage:

1. It is suitable for melting a small quantities of charge.
2. Cleanly process is maintain in an induction furnace.
3. Magnetic stirring helps in homogenized the melt.
4. Alloy addition like Ni, Co, Cr, W, Mo, V, Ti etc can be melt easily.
5. Shorter time of melting.
6. Melting is economically.

Limitations :

1. Initial installation cost is higher.
2. Due to faster melting no composition analysis time is available.
3. Charge material should be of selective composition.
4. Refining is seldom perform.

Application :

1. It is used for melting generally special alloys and high alloy steels
2. It is used in laboratory for research work in melting.
3. It is used in vacuum melting furnace.





References :
1. Modern Steel Making :  Dr R.H. Tupkary and V.R. Tupkary.
2. Ironmaking and Steelmaking Theory an d Practice : A. Ghosh and A. Chatterjee
3. Steel Making : A.K.Chakravorty

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