INDUCTION MELTING FURNACE



 WHAT IS AN INDUCTION MELTING FURNACE ?

An induction melting furnace is a type of electrical furnace , wherein the heating is done by induction of electric current within the charge itself without having direct contact with the induction coil.

An induction furnace consist of water cooled hollow copper tubing arranged in different shape according to the requirement; mostly cylindrical shape copper coil is used in the melting industry. Through this copper coil an Alternating Current at high frequency is passed ,because of which a reversing magnetic field is created according to the lenz law.When we put any conductor (charge to be melted ) in this magnetic field an induced cicular current called Eddy Current is generated within the charge.

An induction generator consist of two coils called primary coil and secondary coil ; Primary coil takes in current at high voltage , low ampere and fixed frequency. Secondary coil converts this current to low voltage ,high ampere and high frequency, this high ampere and high frequency current is then provided to the copper coil discussed in the previous paragraph.

HOW DOES HEATING OCCUR BY INDUCTION ?

heating in induction furnace occur due to two major effect namely

  1.   Eddy Current heating :- in this heating occur by ohmic heating or joule's heating due to the restivity of the charge to the induced electric current.
  2.  Hysteric Heating :- heating (energy ) is produced within the charge by the alternating magnetic field generated by the coil modifying the charge's magnetic polarity. 

This loss is though limited only to the magnetic material , that also only upto the curie temperature , heating beyond which the material losses it's magnetic properties and hence the hysteric heating becomes nil.

Frequency also plays a major role in the heating process though not directly; frequency determines the depth upto which the induction current can reach by an effect called 'Skin Effect'. According to the skin effect the depth of penetration is inversely proportional to the frequency of the alternating current.Thus for purpose of surface treatment or smaller mass of material higher frequency is desired whereas for deeper penetration and larger melt size lower frequency is desired.

KEY FEATURES WHICH MAKES INDUCTION FURNACE SO UNIQUE AND DESIRABLE:-

  • An induction heating is considered as a green technology because the heating is done only of the charge and no other components is heated ,because of which incessant waste of energy is avoided.
  • Also in induction heating there is no release of any type of gases or fumes making it safe for the long term use without harming the health of the workers.
  • as there is no direct contact of the heating element we get a very clean melt with no contamination which is highly desired in the jewellery industry like gold,silver,platinum melting ,laboratory application or where precise control of the composition is required.
  • Induction furnace also provides us with the facility of automatic stirring which is highly desired for homogeneous melting and alloying.
  • Induction furnace can be frequently turned on and off according to the requirement without any  damage to the machinery. 
  • The melting temperature that can be reached in induction furnace is only limited by the refractory materials' temperature resistivity.
  • One of the very desired feature of induction furnace is its heating time; the heating time of induction melting is least as compared to any conventional or other heating method. 
  • Also induction heating furnaces are readily available in variants right from few grams to tons of kgs.

APPLICATION OF INDUCTION MELTING FURNACES:-

Induction furnaces can be utilised in,

  • Small size laboratory for melting small quantity of Materials for testing purposes. 
  • Manufacturing unit dealing with precious metals like Gold,silver,copper,platinum,brass, etc.
  • Jewellery manufacturing units.
  • Heat treatment industries where custom heating of parts is desired.
  • Large scale refining industries like  iron and steel industry melting metals in huge quantities.
  • Any industry desiring cleaner operation with homogeneous mixing can use induction furnace. 
  • Non conductive material industry can also use induction furnace if combined with conductive crucible.


No comments