Induction furnace Features and uses

An induction furnace is an electric furnace in which heat is applied by inductively heating metal.Induction furnaces range in capacity from less than one kilogram to a hundred tons and are used to smelt steel,copper,aluminum,and precious metals.Advantages of induction furnaces over most other methods of melting metals are cleanliness,energy savings and a well-controlled melting process.Most modern foundries use this type of furnace,and many iron foundries are replacing cupola furnaces with induction furnaces for melting cast iron because the former emit a lot of dust and other pollutants.Induction furnaces do not require an electric arc (like an electric arc furnace) or combustion (like a blast furnace).As a result, the charge (the material that goes into the furnace to heat, not to be confused with the charge) doesn't get hotter than it needs to melt it; this prevents the loss of valuable alloying elements.A major disadvantage of using induction furnaces in foundries is the lack of refining capacity:the charge must be free of oxides and of known composition,some alloying elements may be lost to oxidation and must therefore be re-added to melt. 

Type

In the coreless type,the metal is placed in a crucible surrounded by a water-cooled AC electromagnetic coil.Channel induction furnaces have a loop of molten metal passing through an iron core to form a single-turn secondary winding.

Operation

An induction furnace consists of an insulated crucible containing the metal to be melted,surrounded by a ring of copper wire.A strong alternating current flows through the wire.The coil produces a rapidly opposing magnetic field that penetrates metal.The magnetic field induces eddy currents in the metal through electromagnetic induction,that is,circular currents.Eddy currents flow through the resistance of a bulk metal,heating it by Joule heating.In ferromagnetic materials such as iron,the material may also be heated due to hysteresis (an inversion of the molecular magnetic dipoles in the metal).Once melted,vortexing causes vigorous agitation of the melt,ensuring good mixing.An advantage of induction heating is that the heat is generated inside the charge of the furnace rather than by burning fuel or other external heat source,which can be important in applications where contamination is an issue.Operating frequencies range from mains 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 desired melting rate.In general,the smaller the melt volume,the more frequently the furnace will be used; this is because skin depth is a measure of how far below the surface of a conductor an alternating current can penetrate.For the same conductivity,higher frequencies have a shallower skin depth,ie less penetration into the melt.Lower frequencies create agitation or turbulence in the metal.A preheated one-ton furnace of molten iron can melt cold charges ready for tapping within an hour.Power sources range from 10 kW to 42 MW with melt sizes from 20 kg to 65 tonnes of metal respectively.A running induction furnace will often hum or whine (due to fluctuating magnetic forces and magnetostriction),the tone of which can be used by the operator to determine if the furnace is functioning properly or the power level.

Features and uses

Electric furnace

In an induction furnace, a coil carrying an alternating current surrounds a metal vessel or chamber.Eddy currents are induced in the metal (electric charge), and the circulation of these currents generates extremely high temperatures to melt the metal and create alloys of precise composition.

In Steel: Induction Melting

Induction furnaces for professional steelworks and foundries are cylindrical,open-top,tiltable refractory crucibles with water-cooled induction coils mounted on the outside around the side walls.The coils are powered by alternating current, which induces eddy currents in the metal charge,which generate heat.The refractory walls of the crucible.

Processing Alloys

Metallurgy:Process done electrically, by induction heating or arc melting.Induction melting takes place in a crucible,while in arc melting,molten droplets drop from an electric arc onto a water-cooled base and freeze immediately.

Material Processing

Material processing, the series of operations that transform industrial materials from a raw material state into a finished part or product.Industrial materials are defined as those used in the manufacture of "hard" goods,such as more or less durable machines and equipment produced for industry and ) in contrast. Manual material processing is as old as civilization.Mechanization began with the Industrial Revolution in the 18th century,and in the early 19th century,basic machines for shaping, shaping and cutting were developed,mainly in England.Since then, the variety and number of material processing methods,techniques and machinery have increased.Immediately after raw materials are extracted from minerals or produced from basic chemicals or natural substances,the cycle of manufacturing processes that transform materials into parts and products begins.Raw metals are usually produced in two steps.First, the raw ore is processed to increase the concentration of the desired metal; this is called beneficiation.Typical beneficiation processes include crushing,roasting,magnetic separation,flotation and leaching.Second,additional processes such as smelting and alloying are used to produce metals that will be processed into parts that are eventually assembled into products.In the case of ceramic materials,natural clay is mixed and blended with various silicates to produce raw materials. Plastic resins are chemically produced in powder,granule,putty or liquid form.Synthetic rubber is also manufactured through chemical techniques and,like natural rubber,is produced in forms such as sheet,sheet,crepe and foam for the manufacture of finished components.The processes used to transform raw materials into finished products perform one or both of two main functions: first,they form the material into the desired shape,and second,they change or improve the material's properties.Forming and shaping processes can be divided into two broad categories - those that work on liquid materials and those that work on solid or plastic materials.When it comes to metals, glass, and ceramics,the processing of liquid materials is usually called casting; when applied to plastics and some other non-metallic materials,it is called forming. 

Most casting and forming processes involve four main steps: 

1. Making an accurate model of the part.

2. Making a mold from the model.

3.introducing liquid into the mold.

4. Removing the hardened part from the mold.Sometimes finishing is required.A solid material is formed into a desired shape by the application of force or pressure.The material to be processed can be in a relatively hard and stable state,in the form of rods,flakes,pellets,powders,or soft,plastic,and putty.Solid materials can be hot or cold formed.

The processing of solid metals can be divided into two main stages:

First,raw material in the form of ingots or billets is thermally worked,usually by rolling, forging or extrusion,into smaller shapes and sizes; second,these shapes are passed through a One or more smaller-scale hot or cold forming processes into final parts and products.After the material is formed, it is often further altered.In material processing,the process of "removal" is the process of removing a piece or part of a body of material to obtain a desired shape.Although removal processes are applicable to most types of materials,they are most widely used on metallic materials.Material can be removed from a workpiece by mechanical or non-mechanical means.There are many metal cutting processes.In nearly all of these,machining involves pressing a cutting tool against the material to be formed.The tool is harder than the material being cut and removes unwanted material in the form of chips.Thus,the elements of machining are the cutting device,the device for holding and positioning the workpiece,and usually the lubricant (or cutting oil).

There are four basic non-machining removal processes

1. In chemical grinding, the metal is removed by the etching reaction of a chemical solution on the metal; although usually applied to metals, it can also be used on plastics and glass. 

2. Electrochemical machining utilizes the reverse principle of metal plating, since the workpiece is not built up by the plating process, but is corroded away in a controlled manner by the action of an electric current. 

3. EDM and grinding use high-energy sparks or electrical discharges to corrode or cut metals.

4. Laser processing uses a strong beam of laser light to cut metal or refractory materials.