Induction furnace

Electric furnace using induction heat

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An induction furnace is an electrical furnace in which the heat is applied by induction heating of metal.[1][2][3] Induction furnace capacities range from less than one kilogram to one hundred tons, and are used to melt iron and steel, copper, aluminum, and precious metals.

The advantage of the induction furnace is a clean, energy-efficient and well-controlled melting process, compared to most other means of metal melting.

Most modern foundries use this type of furnace, and many iron foundries are replacing cupola furnaces with induction furnaces to melt cast iron, as the former emit much dust and other pollutants.[4]

Induction furnaces do not require an arc, as in an electric arc furnace, or combustion, as in a blast furnace. As a result, the temperature of the charge (the material entered into the furnace for heating, not to be confused with electric charge) is no higher than required to melt it; this can prevent the loss of valuable alloying elements.[5]

The one major drawback to induction furnace usage in a foundry is the lack of refining capacity: charge materials must be free of oxides and be of a known composition, and some alloying elements may be lost due to oxidation, so they must be re-added to the melt.

Types

In the coreless type,[6] metal is placed in a crucible surrounded by a water-cooled alternating current solenoid coil. A channel-type induction furnace has a loop of molten metal, which forms a single-turn secondary winding through an iron core.[7][8]

Operation

An induction furnace consists of a nonconductive crucible holding the charge of metal to be melted, surrounded by a coil of copper wire. A powerful alternating current flows through the wire. The coil creates a rapidly reversing magnetic field that penetrates the metal. The magnetic field induces eddy currents, circular electric currents, inside the metal, by electromagnetic induction.[9] The eddy currents, flowing through the electrical resistance of the bulk metal, heat it by Joule heating. In ferromagnetic materials like iron, the material may also be heated by magnetic hysteresis, the reversal of the molecular magnetic dipoles in the metal. Once melted, the eddy currents cause vigorous stirring of the melt, assuring good mixing.

An advantage of induction heating is that the heat is generated within the furnace's charge itself rather than applied by a burning fuel or other external heat source, which can be important in applications where contamination is an issue.

Operating frequencies range from utility frequency (50 or 60 Hz) to 400 kHz or higher, usually depending on the material being melted, the capacity (volume) of the furnace and the melting speed required. Generally, the smaller the volume of the melts, the higher the frequency of the furnace used; this is due to the skin depth which is a measure of the distance an alternating current can penetrate beneath the surface of a conductor. For the same conductivity, the higher frequencies have a shallow skin depth&#;that is less penetration into the melt. Lower frequencies can generate stirring or turbulence in the metal.

A preheated, one-ton furnace melting iron can melt cold charge to tapping readiness within an hour. Power supplies range from 10 kW to 42 MW, with melt sizes of 20 kg to 65 tons of metal respectively.[citation needed]

An operating induction furnace usually emits a hum or whine (due to fluctuating magnetic forces and magnetostriction), the pitch of which can be used by operators to identify whether the furnace is operating correctly or at what power level.[citation needed]

Refractory lining

There is a disposable refractory lining used during casting.

See also

• Electric arc furnace&#;for another type of electric furnace, used in larger foundries and mini-mill steelmaking operations

References

Further reading

Contact us to discuss your requirements of induction melting furnace platinum. Our experienced sales team can help you identify the options that best suit your needs.

Today, every industry is moving towards energy-saving and clean ways of doing things. Therefore, the induction furnace has become popular because of its ability to conserve heat and energy without polluting the environment with gases and loud noises. Let us look at how the furnace works and understand how each component contributes to the process.

WHAT IS INDUCTION MELTING?

Induction melting is the induction heating of a metal, typically within a crucible until the metal becomes molten using an induction furnace. Once the metal has fully melted, the liquid is then poured into an ingot mold or cast into a component at a foundry, or into smaller precise parts such as dental and jewelry castings.

An Induction melting furnace uses a copper induction heating coil that delivers an alternating magnetic current to the metal within the coil. This alternating magnetic current creates a resistance in the metal, causing it to heat and eventually to melt. Induction furnace technology does not require any flame or gasses that can be harmful to the environment to melt metals.

An induction furnace is therefore preferred in most modern foundries because it does not produce dust and other pollutants. The ability to melt the metals at regulated temperatures allowing them to retain their alloying elements, makes this furnace a better option,

How Does an Induction Melting Furnace Work?

There are four essential components in an induction melting furnace. The first one is the crucible, which is usually nonconductive and is used to hold the charge of the metal for melting. Next goes the yokes, which protect the copper coil from damage when it produces the magnetic field that induces the circular electric currents.

The water-cooled coil is the third component, made of copper wire and has a powerful alternating current flowing through it.

The best thing about this furnace is that heat originates from the furnace&#;s charge and is not an external heat source. That works well when you do not want to contaminate the metal you are melting. That characteristic puts the induction furnace ahead of any other heating process because there is very little heat lost.

The frequencies used in an induction furnace range between 50 to 400 kHz. However, it could go higher depending on the melting speed, type of material, and the volume of the furnace. If the volume of the melts is smaller, then the frequency of the furnace will be higher. Lower frequencies have higher penetration into the metal, referred to as skin depth.

Advantages of Using An Induction Melting Furnace

Less Heat Loss

Unlike traditional heating equipment, induction furnaces do not use heat conduction to heat the melt. It uses induction heating, which heats the metal and has thermal insulation materials to reduce heat loss. Therefore, an induction melting furnace offers less energy loss and higher thermal efficiency than other heating methods.

Produces High-quality Metals

This type of heating has no external heat sources because the heat comes from within the charge itself. Therefore, the chances of contamination are slim. Any metals melted in the furnace will be pure and high-quality. This benefit works best for most high-end products from metals like gold and silver.

The temperatures are also controlled, which keeps off excess heat and maintains the alloying elements of the metals. The induction furnace also uses electromagnetic force, which stirs the molten metal and ensures its uniform composition. Without the electromagnetic force, there would be no automatic mixing, and other forms of mixing may not be as effective or uniform as the automatic one.

Fast Speed of Melting

Melting in an induction furnace is fast because of the controlled temperatures and the high thermal efficiency. It is an excellent way to melt high volumes of metal as each melting session will take a considerably short time. You can maximize production and still retain the high quality of the metals you melt. This melting process is good for both ferrous and non-ferrous metals.

Less Environmental Pollution

The impact of induction melting furnace on the environment is small because it only produces a small noise. It is also a clean melting process, meaning no dust or gases are made. These aspects make it favorable for any environment and working space.

When you compare it to other melting methods, it has the least environmental impact and is, therefore, safe to use. Employees using the furnace will be able to work in a safe environment that has little to no dust or other gas emissions. This furnace allows you to do your job without endangering your life or the environment.

Cost-effective Way of Melting Metals

Now that this process melts metals fast and does not produce unnecessary high temperatures, the furnace life extends, giving you value for money. It saves you maintenance costs, which makes it relatively cost-effective.

This furnace uses no electrodes or fuel, making it easy and affordable. It also takes up less space because compact design

6. Easy to Automate Operations

You can achieve higher production volumes without affecting the quality when you automate your induction heating process. The design of the machine makes it easy to integrate communication between the material handling and the heating process.

Conclusion

An induction melting furnace is efficient in melting most metals. Its versatility and efficiency make it the most preferable in today&#;s foundries. It is also energy-saving, making it a much better option than other traditional melting processes.

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