Design, Manufacturing and Testing of controlled Stir Casting Furnace

DESIGN, MANUFACTURING AND TESTING OF INDUCTION FURNACE A PROJECT REPORT Submitted by

FRANCIS. T

(103378044)

GIPSON PEREIRA

(103378049)

MOHAMED ASHIQ.M

(103378086)

MANIVANNAN.N

(103378077)

in partial fulfillment for the award of the degree of

BACHELOR OF TECHNOLOGY In

MECHANICAL ENGINEERING

BHARATHIYAR COLLEGE OF ENGINEERING AND TECHNOLOGY KARAIKAL PONDICHERRY UNIVERSITY: PUDUCHERRY 605014 APRIL 2013 1

BHARATHIYAR COLLEGE OF ENGINEERING AND TECHNOLOGY KARAIKAL DEPARTMENT OF MECHANICAL ENGINEERING

BONAFIDE CERTIFICATE Certified that this project report “DESIGN, MANUFACTURING AND TESTING OF INDUCTION FURNACE” is the bonafide work of

FRANCIS. T (103378044) GIPSON PEREIRA (103378049) MOHAMED ASHIQ.M (103378086) MANIVANNAN.N (103378077) who carried out the project work under my supervision.

SIGNATURE

SIGNATURE

Prof .S.RAVICHANDRAN HEAD OF THE DEPARTMENT

Mr. S . GUNABALAN SUPERVISOR Associate professor Mechanical Department Bharathiyar College of Engineering And Technology, Karaikal

Mechanical Department Bharathiyar College of Engineering And Technology, Karaikal

Submitted for the university examination held on.......................................... INTERNAL EXAMINER

EXTERNAL EXAMINER

PONDICHERRY UNIVERSITY: PUDHUCHERRY APRIL 2013

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ACKNOWLEDGEMENT We would like to acknowledge all the people who have contributed to a great extent towards the initialization, the development and success of our project. Our sincere thanks go to Dr. Jayaraman, Principal, Bharathiyar College of Engineering & Technology, Karaikal for extending the college facilities for the successful completion of our project and for his kind patronage. We also thank Prof .S.Ravichandran, Professor & Head of the Department, Department of Mechanical Engineering, Bharathiyar College of Engineering & Technology, Karaikal for extending the excellent laboratory facilities, ideas and encouragement towards our project. We cordially thank Mr. S. Gunabalan, Associat Professor of Mechanical Department, Department of Mechanical Engineering, Bharathiyar College of Engineering & Technology for providing innovative ideas and expert guidance for the successful completion of our project.

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ABSTRACT Aluminum are the important structural material in aerospace and car industries, as well as in some other areas. Their main characteristics are small specific weight, good mechanical properties, good processing and resistance to corrosion. Based on great marketing interest of Aluminum, the investigation of technological parameters of workout of Aluminum on a laboratory and pilot-plant scale is carried out. In this project a part of results on design and definition of melting, alloying and casting conditions of aluminum are presented. These investigations involve alloying temperature, alloying time, amount of alloying elements, and sequence of their adding and casting temperature on the chemical composition, microstructure and mechanical properties are investigated.

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INTRODUCTON

Metal melting is the process of producing a liquid metal of the required composition at the required rate, and with required amount of superheat while incurring the minimal cost. It is one of the most important foundry practices, as it decides the quality of the casting. There are number of methods available for melting foundry alloys such as pit furnace, open hearth furnace, rotary furnace, cupola furnace, etc. The choice of the furnace depends on several factors, primary among them are the compositional range of the material to be melted, the fuel or energy used to melt the charge, the degree of refining and control over the process and type and size of the melting unit. Induction heating is widely used in metal industry because of its good heating efficiency, high production rate, and clean working environments. The development of high-frequency power supplies provided means of using induction furnaces for melting metals in continuous casting plants.

Rather than just a furnace, a coreless induction furnace is actually an energy transfer device where energy is transferred directly from an induction coil into the material to be melted through the electromagnetic field produced by the induction coil . A typical parallel resonant inverter circuit for induction furnace . The phase controlled rectifier provides a constant DC current source. The H-bridge inverter consists of four thyristors and a parallel resonant circuit comprised capacitor bank and heating coil. Thyristors are naturally commutated by the ac current flowing through the resonant circuit

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FURNACE A furnace is a device used for heating. The name derives from Latin fornax, oven. In American English and Canadian English usage, the term furnace on its own refers to the household heating systems based on a central furnace (known either as a boiler or a heater in British English), and sometimes as a synonym for kiln, a device used in the production of ceramics. In British English, a furnace is an industrial furnace used for many things, such as the extraction of metal from ore (smelting) or in oil refineries and other chemical plants, for example as the heat source for fractional distillation columns.

The term furnace can also refer to a direct fired heater, used in boiler applications in chemical industries or for providing heat to chemical reactions for processes like cracking, and is part of the standard English names for many metallurgical furnaces worldwide.

The heat energy to fuel a furnace may be supplied directly by fuel combustion, by electricity such as the electric arc furnace, or through induction heating in induction furnaces. A furnace is a device that produces heat. Not only are furnaces used in the home for warmth, they are used in industry for a variety of purposes such as making steel and heat treating of materials to change their molecular structure. Central heating with a furnace is an idea that is centuries old. One of the earliest forms of this idea was invented by the Romans and called a hypocaust. It was a form of under-floor heating using a fire in one corner of a basement with the exhaust vented through flues in the walls to chimneys. This form of heating could only be used in stone or brick homes. It was also very dangerous because of the possibility of fire and suffocation. Furnaces generate heat by burning fuel, but early furnaces burned wood. In the seventeenth century, coal began to replace wood as a primary fuel. Coal was used until the early 1940s when gas became the primary fuel. In the 1970s, electric furnaces started to replace gas furnaces because of the energy crisis. Today, the gas furnace is still the most popular form of home heating equipment. Wood and coal burning furnaces required constant feeding to maintain warmth in the home. From early morning to late at night, usually three to five times a day, fuel needed to be put in the furnace. In addition, the waste from the ashes from the burnt wood or coal must be removed and disposed.

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RAW MATERIALS Today's modern furnace uses stainless steel, aluminized steel, aluminum, brass, copper, and fiberglass. Stainless steel is used in the heat exchangers for corrosion resistance. Aluminized steel is used to construct the frame, blowers, and burners. Brass is used for valves, and copper in the electrical wiring. Fiberglass is used insulate the cabinet.

DESIGN The original gas furnace consisted of a heat exchanger, burner, gas control valve, and an external thermostat, and there was no blower. Natural convection or forced air flow was used to circulate the air through large heating ducts and cold air returns to and from each room. This system was very inefficient—allowing over half of the heated air to escape up the chimney. Today's gas furnace consists of a heat exchanger, secondary heat exchanger (depending on efficiency rating), air circulation blower, flue draft blower, gas control valve, burners, pilot light or spark ignition, electronic control circuitry, and an external thermostat. The modern furnace is highly efficient—80-90%, allowing only 10-20% of the heated air to escape up the chimney. When heat is requested from the thermostat, the burners light and throws heat into the primary heat exchanger. The heated air then flows through the secondary heat exchanger (90% efficient furnace only) to the exhaust flue and chimney. The average furnace has three heat exchangers each producing 25,000 BTUs for a total of 75,000 BTUs. A flue draft blower is placed in the exhaust flue to supercharge the burners and increase efficiency. The heat exchangers perform two functions: transfer heated air from the burners to the home and allow dangerous exhaust

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THE MANUFACTURING PROCESS 1. The primary heat exchanger is formed from two separate pieces of 409 stainless steel sheet. Each half is formed into shape by a 400 ton hydraulic press. The two halves are then fused together by a 25 ton hydraulic press.

2. The secondary heat exchanger is formed from 29-4°C stainless steel tubing and fins. The fins are welded to the tubing to form a radiator type configuration. 3. The primary heat exchanger is crimped to the secondary heat exchanger through a transition box. The flue draft blower is attached to the secondary heat exchanger.

4. The burners are constructed of aluminized steel and arrive at the plant preformed. They are then attached to a plate on the input side of the primary heat exchanger. There is one burner for each heat exchanger in the furnace.

5. The vendor supplied gas control valve is mounted to the heat exchanger and burner assembly. It is connected to the burner through a pipe.

6. The air circulation blower housing is formed through the same hydraulic press formation as the primary heat exchanger. The vendor supplied motor and squirrel cage rotor are connected and attached to the blower housing with brackets.

7. A plate is then attached for mounting the blower assembly to the heat exchanger assembly. Another mounting plate containing the vendor supplied furnace control circuitry and transformer are attached to the blower housing.

8. The air circulation blower assembly is then mounted to the heat exchanger assembly with screws and nuts. 9

9. The cabinet consists of two doors and the cabinet housing. The cabinet housing is supplied as a flat pre-painted sheet of steel and placed in a hydraulic press to form a three sided configuration. Sheets of fiberglass insulation are glued to the sides of the cabinet.

10. The cabinet is installed around the furnace assembly and secured with screws and nuts. The doors are installed on the front of the cabinet assembly. The completed assembly is boxed and prepared for shipment.

QUALITY CONTROL Each completed furnace undergoes an extensive series of tests. Checks for proper operation of the flue draft and air circulation blowers are performed. The gas valve is checked for proper operation. The heat output of the furnace in BTUs is measured. A dielectric test is performed for shorts. By products/Waste Scrap metal from cutting and forming operations are collected and sent to recycling plants for reclamation. Any excess piping is either reused or discarded. Defective steel sheets can be sent back tot he manufacturer and reformed, depending on the extent of the damage. The majority of the components of the furnace are able to be recycled.

Furnaces can also be classified according to the molten metal ; 1. Gray Cast Iron •

Cupola

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Air furnace

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Rotary furnace

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Electric arc furnace 10

2. Steel •

Open hearth furnace.

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Electric furnace.

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Arc furnace

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High frequency induction furnace

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Converter

3. Non-ferrous metals  Crucible furnaces (Al ,Cu) •

Pit type

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Tilting type

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Non-tilting or bale out type

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Electric resistance type (CU)

 Pot furnaces (fuel fired) (Mg & Al) •

Stationary

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Tilting

 Reverberatory furnaces (fuel fired ) (Al & Cu) •

Stationary

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Tilting

 Rotary furnaces 11

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Fuel fired

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Electrically heated

 Induction furnaces (Al & Cu) •

Low frequency

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High frequency

 Electric Arc furnaces (Cu)

TYPE OF FURNACE 1. Induction furnace 2. Cupola furnace 3. Open Hearth furnace 4. Electric furnace

Common Types of Metal Melting Furnaces Furnace Type

Induction Furnace

Raw Materials

Scrap iron or non-ferrous metals

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Outputs

Process

Molten iron or non-ferrous metals

Induction furnaces are the most common type used by both ferrous and non-ferrous foundries. Copper coils heat the metal using alternating currents. The flux reacts with impurities.

Cupola Furnace

Open Hearth

Electric Furnace

Iron ore, scrap iron, lime, coke

Non-ferrous metals, flux

Scrap iron, flux

Molten iron

Molten nonferrous metals

Molten iron and steel

Alternative layers of metal and coke are fed into the top of the furnace. The metal is melted by the hot gases from the coke combustion. Impurities react with the lime and are separated. Reverberatory furnaces melt metals in batches using a pot-shaped crucible that holds the metal over an electric heater or fuel-free burner. The flux reacts with impurities

Electric arcs from carbon electrodes melt the scrap metal. The flux reacts with impurities.

1. INDUCTION FURNACE

Introduction The development of Induction Furnaces starts as far back as Michael Faraday, who discovered the principle of electromagnetic induction. However it was not until the late 1870’s when De Ferranti, in Europe began experiments on Induction furnaces. In 1890,Edward Allen Colby patented an induction furnace for melting metals. The first practical usage was in Gysinnge, Sweden,by Kjellin in 1900 and was similar to the Colby furnace with the primary closest to the core. The first steel made in an induction furnace in the United States was in 1907 in a Colby furnace near Philadelphia. The first induction 13

furnace for three –phase application was built in Germany in 1906 by Rochling-Rodenhauser. Original designs were for single phase and even two phases were used on the three phase furnace. The two basic designs of induction furnaces, the core type or channel furnace and the coreless, are certainly not new to the industry. The channel furnace is useful for small foundries with special requirements for large castings, especially if off-shift melting is practiced. It is widely used for duplexing operations and installations where production requirements demand a safe cushion of readily available molten metal. The coreless induction furnace is used when a quick melt of one alloy is desirable, or it is necessary to vary alloys frequently. The coreless furnace may be completely emptied and restarted easily, makes it perfect for one-shift operations. Induction furnaces have increased in capacity to where modern high-power-density induction furnaces are competing successfully with cupola melting. There are fewer chemical reactions to manage in induction furnaces than in cupola furnaces, making it easier to achieve melt composition. However, induction melting is more sensitive to quality of charge materials when compared to cupola or electric arc furnace, limiting the types of scrap that can be melted. The inherent induction stirring provides excellent metal homogeneity. Induction melting produces a fraction of the fumes that result from melting in an electric arc furnace (heavy metal fumes and particulate emissions) or cupola (wide range of undesirable gaseous and particulate emissions as a result of the less restrictive charge materials). A new generation of industrial induction melting furnaces has been developed during the last 25 years. The development of flexible, constant power-tracking, medium-frequency induction power supplies has resulted in the widespread use of the batch melting methods in modern foundries. These power units incorporate heavy duty silicon-controlled rectifiers that are able to generate both the frequency and the amperage needed for batch melting and are able to achieve electrical efficiency levels exceeding 97%, a substantial improvement over the 85% efficiency typical of induction power supplies of the 1970s. The new designs allow maximum utilization of furnace power throughout the melting cycle with good control of stirring .Some of the largest commercial units are capable of melting at nearly 60 tons per hour and small furnaces with very high power densities of 700 to 1,000 kWh/ton can now melt a cold charge in 30 to 35 minutes.

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INDUCTION HEATING: Induction heating is a form of non-contact heating for conductive materials. The principle of induction heating is mainly based on two well-known physical phenomena: 1. Electromagnetic induction 2. The Joule effect

1) ELECTROMAGNETIC INDUCTION The energy transfer to the object to be heated occurs by means of electromagnetic induction. Any electrically conductive material placed in a variable magnetic field is the site of induced electric currents, called eddy currents, which will eventually lead to joule heating.

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2) JOULE HEATING Joule heating, also known as osmic heating and resistive heating, is the process by which the passage of an electric current through a conductor releases heat. The heat produced is proportional to the square of the current multiplied by the electrical resistance of the wire.

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Induction heating relies on the unique characteristics of radio frequency (RF) energy - that portion of the electromagnetic spectrum below infrared and microwave energy. Since heat is transferred to the product via electromagnetic waves, the part never comes into direct contact with any flame, the inductor itself does not get hot and there is no product contamination.

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Induction heating is a rapid, clean, non-polluting heating. The induction coil is cool to the touch; the heat that builds up in the coil is constantly cooled with circulating water.

FEATURES OF INDUCTION FURNACE •

An electric induction furnace requires an electric coil to produce the charge. This heating coil is eventually replaced.

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The crucible in which the metal is placed is made of stronger materials that can resist the required heat, and the electric coil itself cooled by a water system so that it does not overheat or melt.

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The induction furnace can range in size, from a small furnace used for very precise alloys only about a kilogram in weight to a much larger furnaces made to mass produce clean metal for many different applications.

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The advantage of the induction furnace is a clean, energy-efficient and wellcontrollable melting process compared to most other means of metal melting. 17

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Foundries use this type of furnace and now also more iron foundries are replacing cupolas with induction furnaces to melt cast iron, as the former emit lots of dust and other pollutants.

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Induction furnace capacities range from less than one kilogram to one hundred tonnes capacity, and are used to melt iron and steel, copper, aluminium, and precious metals.

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The one major drawback to induction furnace usage in a foundry is the lack of refining capacity; charge materials must be clean of oxidation products and of a known composition, and some alloying elements may be lost due to oxidation (and must be re-added to the melt).

A. Domestic Steel Sector Scenario 1) Present Scenario : After 2 years of depressed market, the steel market has suddenly shown Competitiveness. It is noted that induction-melting furnaces in various parts of the country are at present operating to near capacity. However, the power is not supplied to the units fully. Revolution is taking place to make steel in India by utilising various technologies. India is therefore, emerging as a country with innovative idea to make steel, which is not followed by other countries in the world. In the first decade of twenty first century, major existing integrated steel plants will face a challenge in producing Long products from Induction Furnaces in producing steel economically and efficiently.

The iron and steel sector has been experiencing a slowdown in the last few years. The major reasons for the slow growth in the steel sector during the last few years include:(a) Sluggish demand in the steel consuming sectors (b) Overall economic slowdown in the country (c) Lack of investment by Government/private sector in major infrastructure projects. sector investment is yet to materialise in the core sectors of the economy. This has also contributed to slowing down demand for steel. 18

(d) Cost escalation in the input materials for iron and steel. In the national steel policy recently announced by the Govt. of India, it is expected that FDI in the steel industry along with domestic investment will take place in large integrated steel plants. So, all the focus and of the steel policy is on the Primary Steel Sector while completely ignoring the Secondary Steel Sector. Induction melting furnaces in India were first installed to make stainless steel from imported SS Scrap. Butin years 81-82 some entrepreneurs, who were having small size induction furnaces making stainless steel, experimented in making mild steel from steel melting scrap, they succeeded. More firms in northern India produced steel (Pencil Ingots) by using 500 kg to 1 tonne induction furnaces. The power consumption was found to be about 700 kWh/tonne, which was nearly 100 units less than EAFs. Bigger size Induction furnaces were then installed first in North India and then in other states of India. By 1985-86, the technology of making mild steel by Induction Furnace route was mastered by Indian Technicians. Induction furnace manufacturers saw the potential and started manufacturing bigger size/capacity furnaces. By 1988-89 period 3 tonne per charge induction furnaces were installed (became standard) all over India. The chemistry of melt was adjusted by adding mill scale, if opening carbon of bath was more. Good quality of steel melting scrap was used. In 1991-92, the Government license and control on steel making and rolling was removed. Then more induction furnaces were installed all over India. The use of sponge iron made it possible to adjust chemistry of melt. Thus good quality of Mild Steel pencil ingots are being produced with no tramp elements. 2) Ferrous Scrap: The word “Ferrous” comes from the Latin word “Ferrum”. Most people associate scrap with waste or rubbish. However, our Industry prefers to refer to ourselves as “Recyclers”, who play a very important role, in not only feeding the Steel Industry but also protecting the environment by converting waste into wealth for society. Indian Steel Mills mainly import Shredded or Heavy Melting grades only. HMS is nearly 65% of the imports. 3) Global Requirement For Scrap: With global steel production at 1 billion tonne mark, merchant scrap requirement is estimated in the current year at 318 million tonnes. By the year 2010, requirement for merchant scrap is likely to go up to 388 million tonnes. As the GDP 19

grows in developing countries, the generation of merchant scrap will increase and additional processing capacities and scrap yards will have to be installed to meet the demand for quality scrap needed for the increasing steel demand.

INDUCTION ELECTRICAL SYSTEM CONFIGURATION: Induction furnaces require two separate electrical systems: one for the cooling system, furnace tilting and instrumentation, and the other for the induction coil power. A line to the plant’s power distribution panel typically furnishes power for the pumps in the induction coil cooling system, the hydraulic furnace tilting mechanism, and instrumentation and control systems. Electricity for the induction coils is furnished from a three-phase, high voltage, high amperage utility line. The complexity of the power supply connected to the induction coils varies with the type of furnace and its use. A channel furnace that holds and pours liquefied metal can operate efficiently using mains frequency provided by the local utility. By contrast, most coreless furnaces for melting require a medium to high frequency power supply. Raising the frequency of the alternating current flowing through the induction coils increases the amount of power that can be applied to a given size furnace. This, in turn, means faster melting. A 10 ton coreless furnace operating at 60 Hz can melt its capacity in two hours. At 275 Hz, the same furnace can melt the full 10 ton charge in 26 minutes, or four times faster. An added advantage of higher frequency operation is that furnaces can be started using less bulky scrap and can be emptied completely between heats. The transformers, inverters and capacitors needed to “tune” the frequency required for high-efficiency induction furnaces can pose a serious electrical hazard. For this reason, furnace power supplies are housed in key-locked steel enclosures, equipped with safety interlocks.

CONSTRUCTION AND WORKING

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Current flowing in one direction in the induction coil induces a current flow in the opposite direction in the metal charge. This current heats the metal and causes it to melt Combustion furnaces and induction furnaces produce heat in two entirely different ways.In a combustion furnace, heat is created by burning a fuel such as coke, oil or natural gas. The burning fuel brings the interior temperature of the furnace above the melting point of the charge material placed inside. This heats the surface of the charge material, causing it to melt. Induction furnaces produce their heat cleanly, without combustion. Alternating electric current from an induction power unit flows into a furnace and through a coil made of hollow copper tubing. This creates an electromagnetic field that passes through the refractory material and couples with conductive metal charge inside the furnace. This induces electric current to flow inside the metal charge itself, producing heat that rapidly causes the metal to melt. Although some furnace surfaces may become hot enough to present a burn hazard, with induction, you heat the charge directly, not the furnace.

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Induction Electrical System Configurations: Induction furnaces require two separate electrical systems: one for the cooling system, furnace tilting and instrumentation, and the other for the induction coil power. A line to the plant’s power distribution panel typically furnishes power for the pumps in the induction coil cooling system, the hydraulic furnace tilting mechanism, and instrumentation and control systems. Electricity for the induction coils is furnished from a three-phase, high voltage, high amperage utility line. The complexity of the power supply connected to the induction coils varies with the type of furnace and its use. A channel furnace that holds and pours liquefied metal can operate efficiently using mains frequency provided by the local utility. By contrast, most coreless furnaces for melting require a medium to high frequency power supply. Raising the frequency of the alternating current flowing through the induction coils increases the amount of power that can be applied to a given size furnace. This, in turn, means faster melting. A 10 ton coreless furnace operating at 60 Hz can melt its capacity in two hours. At 275 Hz, the same furnace can melt the full 10 ton charge in 26 minutes, or four times faster. An added advantage of higher frequency operation is that furnaces can be started using less bulky scrap and can be emptied completely between heats. The transformers, inverters and capacitors needed to “tune” the frequency required for high-efficiency induction furnaces can pose a serious electrical hazard. For this reason, furnace power supplies are housed in key-locked steel enclosures, equipped with safety interlocks. A. Safety Implications: Typically, the induction coil power supply and the other furnace systems are energized from multiple electric services. This means that foundry workers cannot assume that the power to the furnace coil has stopped because service has been interrupted to the furnace’s cooling system or hydraulic pumps. Review the lock out/tag out section provided in this safety guide. B. Input And Output Parameters Of The Induction Furnaces: In order to study the prevailing practices in steel plants using Induction Furnaces, the following parameters have been identified as

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1) Raw Material: Induction Furnaces are using Steel melting scrap, Sponge Iron & Pig Iron/Cast Irons. On an average the ratio of these items is 40% sponge Iron + 10% Cast Irons or Pig Iron. The technology of melting these input materials varies according to the availability of raw materials and location of the plant and inputs of sponge iron consumed is as high as 85 % as charge mix on bigger furnaces. 2) Power Supply: An A.C.current from the transformer is fed to the rectifier of the furnaces electronic circuit. This converts A.C. to D.C, voltage is smoothed out by a D.C. choke, and then fed to the inverted section of the furnace. Here the D.C is converted to a high frequency A.C. current and this is fed to the coil. 3) Refractory Lining: The material used for lining is crushed quarts. This is a high purity silica material. The linings are of two types, acidic lining and basic lining. 4) Water: The cooling system is a through-one-way- flow system with the tubular copper coils connected to water source through flexible rubber hoses. The inlet is from the top while the outlet is at the bottom. The cooling process is important because the circuit of the furnace appears resistive, and the real power is not only consumed in the charged material but also in the resistance of the coil. This coil loss as well as the loss of heat conducted from the charge through the refractory crucible requires the coil to be cooled with water as the cooling medium to prevent undue temperature rise of the copper coils. 5) Molten Metal : The molten metal is the desired output of the Induction furnace. The quantity depends upon the capacity of the furnace, and the quality depends upon the raw material and alloy composition. The tapping temperature depends upon the type of steel, as well as the distance of end use of the molten metal. 6) Waste Heat: The surface of the molten metal bath is exposed to atmosphere. This results in the major thermal energy loss through radiation. The Coils of furnace are water cooled this also results in heat loss. 7) Slag : During the operation of electric induction melting furnaces, non metallics are produced from the various sources described earlier. Depending on the specific process being used and the type of iron or steel being melted, the composition of the slag will vary. 23

8) Slag Composition: The composition of furnace and ladle slags is often very complex. The slags that form in electric furnace melting are the results of complex reactions between silica (adhering sand on casting returns or dirt), iron oxide from steel scrap, other oxidation by products from melting, and reactions with refractory linings. The resulting slag will thus consist of a complex liquid phase of oxides of iron, manganese, magnesium and silicon, silicates and sulphides plus a host of other compounds, which may include alumina, calcium oxides and sulphides, rare earth oxides and sulphides and spinel’s and fosterites.

ADVANTAGES OF INDUCTION FURNACE: Induction furnaces offer certain advantages over other furnace systems. They include: Higher Yield. The absence of combustion sources reduces oxidation losses that can be significant in production economics. Faster Start-up. Full power from the power supply is available, instantaneously, thus reducing the time to reach working temperature. Cold charge-to-tap times of one to two hours are common. Flexibility. No molten metal is necessary to start medium frequency coreless induction melting equipment. This facilitates repeated cold starting and frequent alloy changes. Natural Stirring. Medium frequency units can give a strong stirring action resulting in a homogeneous melt. Cleaner Melting. No by-products of combustion means a cleaner melting environment and no associated products of combustion pollution control systems. Compact Installation. High melting rates can be obtained from small furnaces. Reduced Refractory. The compact size in relation to melting rate means induction furnaces require much less refractory than fuel-fired units

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Better Working Environment. Induction furnaces are much quieter than gas furnaces, arc furnaces, or cupolas. No combustion gas is present and waste heat is minimized.

Energy Conservation. Overall energy efficiency in induction melting ranges from 55 to 75 percent, and is significantly better than combustion processes.

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.

TYPES OF INDUCTION FURNACE •

CORELESS INDUCTION FURNACE

•

CHANNEL INDUCTION FURNACE

a) Coreless Induction Furnaces: The coreless induction furnace is a refractory lined vessel with electrical current carrying coils surrounding the refractory crucible. A metallic charge consisting of scrap, pig iron and ferroalloys are typically melted in this vessel. b) Channel Furnaces : In a channel furnace, induction heating takes place in the “channel,” a relatively small and narrow area at the bottom of the main bath. The channel passes through a laminated steel core and around the coil assembly.

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CORELESS INDUCTION FURNACE:

A coreless induction furnace is actually an energy transfer device where energy is transferred directly from an induction coil into the material to be melted through the electromagnetic field produced by the induction coil. The coreless induction furnace consists basically of a crucible, inductor coil, shell, cooling system and tilting mechanism. The crucible is formed from refractory material, which the furnace coil is lined with. This crucible holds the charge material and subsequently the melt. The choice of refractory material depends on the type of charge, i.e. acidic, basic or neutral. The durability of the crucible depends on the grain size, ramming technique, charge analysis and rate of heating and cooling the furnace . Principles are: The principle of induction heating is based on the following two laws: 1. Electromagnetic induction 2. The joule effect

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The high frequency induction furnaces use the heat produced by eddy currents generated by a high frequency alternating field. The inductor is usually made of copper in order to limit the electric losses. Nevertheless, the inductor is in almost all cases internally water-cooled. The furnace consists of a crucible made of a suitable refractory material surrounded by a water cooled copper coil. In this furnace type, the charge is melted by heat generated from an electric arc. The coil carries the high frequency current of 500 to 2000 Hz. The alternating magnetic field produced by the high frequency current induces powerful eddy currents in the charge resulting in very fast heating. Various configurations are available, with two or three electrodes high melting capacity (25 to 50 tons/hr) and they are used primarily for casting steel. These currents also provide certain amount of agitation to the melting charge resulting in efficient mixing. Molten metal can be poured by tilting the furnace.

Advantages: • Induction furnace does not need electrodes like electric arc furnace. • Better control of temperature • Better control of composition of the melt

Disadvantages: • An induction installation usually implies a big investment that must be considered and compared to alternative heating techniques. • Induction heating is preferably used for heating relatively simple shapes.

Materials to be casted: • Steel • Steel alloys

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CHANNEL INDUCTION FURNACE; •

The channel induction furnace consists of a refractory lined steel shell which contains the molten metal. Attached to the steel shell and connected by a throat is an induction unit which forms the melting component of the furnace.

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The induction unit consists of an iron core in the form of a ring around which a primary induction coil is wound.

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This assembly forms a simple transformer in which the molten metal loops comprises the secondary component.

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The heat generated within the loop causes the metal to circulate into the main well of the furnace.

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The circulation of the molten metal effects a useful stirring action in the melt.

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Channel induction furnaces are commonly used for melting low melting point alloys and or as a holding and superheating unit for higher melting point alloys such as cast iron.

2.CUPOLA FURNACE

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For many years, the cupola was the primary method of melting used in iron foundries. The cupola furnace has several unique characteristics which are responsible for its widespread use as a melting unit for cast iron.

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Cupola furnace is employed for melting scrap metal or pig iron for production of various cast irons. It is also used for production of nodular and malleable cast iron. It is available in good varying sizes. The main considerations in selection of cupolas are melting capacity, diameter of shell without lining or with lining, spark arrester.

Shape A typical cupola melting furnace consists of a water-cooled vertical cylinder which is lined with refractory material.

Construction •

The construction of a conventional cupola consists of a vertical steel shell which is lined with a refractory brick.

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The charge is introduced into the furnace body by means of an opening approximately half way up the vertical shaft.

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The charge consists of alternate layers of the metal to be melted, coke fuel and limestone flux.

•

The fuel is burnt in air which is introduced through tuyeres positioned above the hearth. The hot gases generated in the lower part of the shaft ascend and preheat the descending charge.

Various Zones of Cupola Furnace

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Various numbers of chemical reactions take place in different zones of cupola. The construction and different zones of cupola are : 1. Well The space between the bottom of the tuyeres and the sand bed inside the cylindrical shell of the cupola is called as well of the cupola. As the melting occurs, the molten metal is get collected in this portion before tapping out. 2. Combustion zone The combustion zone of Cupola is also called as oxidizing zone. It is located between the upper of the tuyeres and a theoretical level above it. The total height of this zone is normally from 15 cm. to 30 cm. The combustion actually takes place in this zone by consuming the free oxygen completely from the air blast and generating tremendous heat. The heat generated in this zone is sufficient enough to meet the requirements of other zones of cupola. The heat is further evolved also due to oxidation of silicon and manganese. A temperature of about 1540°C to 1870°C is achieved in this zone. Few exothermic reactions takes place in this zone these are represented as: C + O2 → CO2 + Heat Si + O2 → SiO2 + Heat 2Mn + O2 → 2MnO + Heat

3. Reducing zone Reducing zone of Cupola is also known as the protective zone which is located between the upper level of the combustion zone and the upper level of the coke bed. In this zone, CO2 is changed to CO through an endothermic reaction, as a result of which the temperature falls from combustion zone temperature to about 1200°C at the top of this zone. The important chemical reaction takes place in this zone which is given as under. CO2 + C (coke) → 2CO + Heat 30

Nitrogen does not participate in the chemical reaction occurring in his zone as it is also the other main constituent of the upward moving hot gases. Because of the reducing atmosphere in this zone, the charge is protected against oxidation.

4. Melting zone The lower layer of metal charge above the lower layer of coke bed is termed as melting zone of Cupola. The metal charge starts melting in this zone and trickles down through coke bed and gets collected in the well. Sufficient carbon content picked by the molten metal in this zone is represented by the chemical reaction given as under.

3Fe + 2CO → Fe3C + CO2 5. Preheating zone Preheating zone starts from the upper end of the melting zone and continues up to the bottom level of the charging door. This zone contains a number of alternate layers of coke bed, flux and metal charge. The main objective of this zone is to preheat the charges from room temperature to about 1090°C before entering the metal charge to the melting zone. The preheating takes place in this zone due to the upward movement of hot gases. During the preheating process, the metal charge in solid form picks up some sulphur content in this zone.

6. Stack The empty portion of cupola above the preheating zone is called as stack. It provides the passage to hot gases to go to atmosphere from the cupola furnace.

Charging of Cupola Furnace •

Before the blower is started, the furnace is uniformly pre-heated and the metal and coke charges, lying in alternate layers, are sufficiently heated up. 31

•

The cover plates are positioned suitably and the blower is started.

•

The height of coke charge in the cupola in each layer varies generally from 10 to 15 cms. The requirement of flux to the metal charge depends upon the quality of the charged metal and scarp, the composition of the coke and the amount of ash content present in the coke.

Working of Cupola Furnace

32

•

The charge, consisting of metal, alloying ingredients, limestone, and coal coke for fuel and carbonization (8-16% of the metal charge), is fed in alternating layers through an opening in the cylinder.

•

Air enters the bottom through tuyeres extending a short distance into the interior of the cylinder. The air inflow often contains enhanced oxygen levels.

•

Coke is consumed. The hot exhaust gases rise up through the charge, preheating it. This increases the energy efficiency of the furnace. The charge drops and is melted.

•

Although air is fed into the furnace, the environment is a reducing one. Burning of coke under reducing conditions raises the carbon content of the metal charge to the casting specifications.

•

As the material is consumed, additional charges can be added to the furnace.

•

A continuous flow of iron emerges from the bottom of the furnace.

•

Depending on the size of the furnace, the flow rate can be as high as 100 tones per hour. At the metal melts it is refined to some extent, which removes contaminants. This makes this process more suitable than electric furnaces for dirty charges.

•

A hole higher than the tap allows slag to be drawn off.

•

The exhaust gases emerge from the top of the cupola. Emission control technology is used to treat the emissions to meet environmental standards.

•

Hinged doors at the bottom allow the furnace to be emptied when not in use. 33

Type of Molten Metal •

Cupola is employed for melting scrap metals or (over 90 %) of the pig iron used in the production of iron castings.

•

Gray Cast iron, nodular cast iron, some malleable iron castings and some copper base alloys can be produced by Cupola Furnace.

Heat Energy Source •

The cupola is a tubular furnace which produces cast iron by melting scrap and alloys using the energy generated from the oxidation (combustion) of coke, a coal derivative.

Advantages •

It is simple and economical to operate.

•

A cupola is capable of accepting a wide range of materials without reducing melt quality. Dirty, oily scrap can be melted as well as a wide range of steel and iron. They therefore play an important role in the metal recycling industry

•

Cupolas can refine the metal charge, removing impurities out of the slag.

•

From a life-cycle perspective, cupolas are more efficient and less harmful to the environment than electric furnaces. This is because they derive energy directly from coke rather than from electricity that first has to be generated.

•

The continuous rather than batch process suits the demands of a repetition foundry.

•

Cupolas can be used to reuse foundry by-products and to destroy other pollutants such as VOC from the core-making area.

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•

High melt rates

•

Ease of operation

•

Adequate temperature control

•

Chemical composition control

•

Efficiency of cupola varies from 30 to 50%.

•

Less floor space requirements comparing with those furnaces with same capacity.

Limitations •

Since molten iron and coke are in contact with each other, certain elements like si, Mn are lost and others like sulphur are picked up. This changes the final analysis of molten metal.

•

Close temperature control is difficult to maintain

3. OPEN HEARTH FURNACE Open hearth furnaces are one of a number of kinds of furnace where excess carbon and other impurities are burnt out of pig iron to produce steel. Since steel is difficult to manufacture owing to its high melting point, normal fuels and furnaces were insufficient and the open hearth furnace was developed to overcome this difficulty. In 1865, the French engineer Pierre-Émile Martin took out a license from Siemens and first applied his regenerative furnace for making steel. Their process was known as the SiemensMartin process, and the furnace as an "open-hearth" furnace. Most open hearth furnaces were closed by the early 1990s, not least because of their slow operation, being replaced by the basic oxygen furnace or electric arc furnace. While arguably the first primitive open hearth furnace was the Catalan forge, invented in Spain in the eighth century, but it is usual to confine the term to certain nineteenth century 35

and later steelmaking processes, thus excluding bloomeries (including the Catalan forge), finery forges, and puddling furnaces from its application.

Open hearth working

A. gas and air enter B. pre-heated chamber C. molten pig iron D. Hearth E. heating chamber (cold) F. gas and air exit. The open hearth process is batch process and a batch is called a "heat". The furnace is first inspected for possible damage. Once it is ready or repaired, it is charged with light scrap, such as sheet metal, shredded vehicles or waste metal. Once it has melted, heavy scrap, such as building, construction or steel milling scrap is added, together with pig iron from blast 36

furnaces. Once all steel has melted, slag forming agents, such as limestone, are added. The oxygen in iron oxide and other impurities decarburize the pig iron by burning the carbon away, forming steel. To increase the oxygen contents of the heat, iron ore can be added to the heat. The process is far slower than that of Bessemer converter and thus easier to control and take samples for quality control. Preparing a heat usually takes 8 h to 8 h 30 min to complete into steel. As the process is slow, it is not necessary to burn all the carbon away as in Bessemer process, but the process can be terminated at given point when desired carbon contents has been achieved The furnace is tapped the same way a blast furnace is tapped; a hole is drilled on the side of the hearth and the raw steel is let to flow out. Once all the steel has been tapped, the slag is skimmed away. The raw steel may be cast into ingots; this process is called teeming, or it may be used on continuous casting for the rolling mill. The regenerators are the distinctive feature of the furnace and consist of fire-brick flues filled with bricks set on edge and arranged in such a way as to have a great number of small passages between them. The bricks absorb most of the heat from the outgoing waste gases and return it later to the incoming cold gases for combustion.

4. ELECTRICAL FURNACE Electric arc furnaces (EAF) are often used in large steel foundries and steel mills. The metal is charged into the furnace, with additives to make recovery of slag easier, and heat to melt the metal is produced with an electric arc from three carbon or graphite electrodes. The electric arc furnace is lined with refractories which slowly decompose and are removed with slag. Electric arc furnaces also usually employ air emissions equipment to capture most air pollution . Furnace operations are discussed in detail below.

Furnace Operations The electric arc furnace operates as a batch melting process producing batches of molten steel known as "heats". The electric arc furnace operating cycle is called the tap-to-tap cycle and is made up of the following operations: Furnace Charging

37

The first step in the production of any heat is to select the grade of steel to be made. Preparation of the charge bucket is an important operation, not only to ensure proper melt-in chemistry but also to ensure good melting conditions. The scrap must be layered in the bucket according to size and density to promote the rapid formation of a liquid pool of steel in the hearth while providing protection for the sidewalls and roof from electric arc radiation. Other considerations include minimization of scrap cave-ins which can break electrodes and ensuring that large heavy pieces of scrap do not lie directly in front of burner ports which would result in blow-back of the flame onto the water cooled panels. The charge can include lime and carbon or these can be injected into the furnace during the heat. Many operations add some lime and carbon in the scrap bucket and supplement this with injection.

The roof and electrodes are raised and are swung to the side of the furnace to allow the scrap charging crane to move a full bucket of scrap into place over the furnace. The bucket bottom is usually a clam shell design i.e., the bucket opens up by retracting two segments on the bottom of the bucket. The scrap falls into the furnace and the scrap crane removes the scrap bucket. The roof and electrodes swing back into place over the furnace. The roof is lowered and then the electrodes are lowered to strike an arc on the scrap. This commences the melting portion of the cycle. The number of charge buckets of scrap required to produce a heat of steel is dependent primarily on the volume of the furnace and the scrap density. Most modern furnaces are designed to operate with a minimum of back-charges. This is advantageous because charging is a dead-time where the furnace does not have power on and therefore is not melting. Minimizing these dead-times helps to maximize the productivity of the furnace. In addition, energy is lost every time the furnace roof is opened.

Melting 38

The melting period is the heart of EAF operations. Melting is accomplished by supplying energy to the furnace interior. This energy can be electrical or chemical. Electrical energy is supplied via the graphite electrodes and is usually the largest contributor in melting operations. Initially, an intermediate voltage tap is selected until the electrodes bore into the scrap. Usually, light scrap is placed on top of the

Principle of Metal Casting charge to accelerate bore-in. Approximately 15 % of the scrap is melted during the initial bore-in period. After a few minutes, the electrodes will have penetrated the scrap sufficiently so that a long arc (high voltage) tap can be used without fear of radiation damage to the roof. The long arc maximizes the transfer of power to the scrap and a liquid pool of metal will form in the furnace hearth. At the start of melting the arc is erratic and unstable. Wide swings in current are observed accompanied by rapid movement of the electrodes. As the furnace atmosphere heats up the arc stabilizes and once the molten pool is formed, the arc becomes quite stable and the average power input increases. Chemical energy is supplied via several sources including oxy-fuel burners and oxygen lances. Oxy-fuel burners burn natural gas using oxygen or a blend of oxygen and air. Heat is transferred to the scrap by flame radiation and convection by the hot products of combustion. Heat is transferred within the scrap by conduction. Large pieces of scrap take longer to melt into the bath than smaller pieces. In some operations, oxygen is injected via a consumable pipe lance to “cut” the scrap. The oxygen reacts with the hot scrap and burns iron to produce intense heat for cutting the scrap. Once a molten pool of steel is generated in the furnace, oxygen can be lanced directly into the bath. This oxygen will react with several components in the bath including, aluminum, silicon, manganese, phosphorus, carbon and iron. All of these reactions are exothermic (i.e., they generate heat) and supply additional energy to aid in the melting of the scrap. The metallic oxides that are formed will end up in the slag. The reaction of oxygen with carbon in the bath produces carbon monoxide, which either burns in the furnace if there is sufficient oxygen, and/or is exhausted through the direct evacuation system where it is burned and conveyed to the pollution control system. 39

Refining Refining operations in the electric arc furnace have traditionally involved the removal of phosphorus, sulphur, aluminum, silicon, manganese and carbon from the steel. In recent times, dissolved gases, especially hydrogen and nitrogen, have been recognized as a concern. Traditionally, refining operations were carried out following meltdown i.e., once a flat bath was achieved. These refining reactions are all dependent on the availability of oxygen. Oxygen was lanced at the end of meltdown to lower the bath carbon content to the desired level for tapping. Most of the compounds which are to be removed during refining have a higher affinity for oxygen than the carbon. Thus the oxygen will preferentially react with these elements to form oxides which float out of the steel and into the slag. In modern EAF operations, especially those operating with a "hot heel" of molten steel and slag retained from the prior heat, oxygen may be blown into the bath throughout most of the heat. As a result, some of the melting and refining operations occur simultaneously. Phosphorus and sulphur occur normally in the furnace charge in higher concentrations than are generally permitted in steel and must be removed. Unfortunately the conditions favourable for removing phosphorus are the opposite of those promoting the removal of sulphur. Phosphorus removal is usually carried out as early as possible in the heat. Hot heel practice is very beneficial for phosphorus removal because oxygen can be lanced into the bath while its temperature is quite low. Early in the heat the slag will contain high FeO levels carried over from the previous heat thus aiding in phosphorus removal. High slag basicity (i.e., high lime content) is also beneficial for phosphorus removal but care must be taken not to saturate the slag with lime. This will lead to an increase in slag viscosity, which will make the slag less effective. Sometimes fluorspar is added to help fluidize the slag. Stirring the bath with inert gas like argon is also beneficial because it renews the slag/metal interface thus improving the reaction kinetics.

FURNACE ATMOSPHERE The surrounding in the thermal enclosure (furnace) is termed atmosphere. The atmosphere consists of gases and is usually air. However, in some heat treatment, thermo‐mechanical processing, sintering etc special type of atmosphere is required to 40

•

Prevent oxide formation, if the heating material is prone to oxidation.

•

Decarburize steel.

•

Control the surface chemistry of steel which means the elements must not be oxidized or reduced during heating.

•

Produce “blueing” effect in steel. The blueing effect imparts a wear‐resistant and oxidation‐ resistant surface finish.

•

reduce oxides formed on the surface.

•

Make the surface hard by allowing carburizing or nitriding.

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PROTECTIVE ATMOSPHERE APPLICATION Composition(vol%) Atmosphere Lean exothermic

N2 86.8

CO2 10.5

CO 1.5

H2 1.2

42

CH4 1

Dew point 4.5

Applications. Bright annealing of Cu, sintering of ferrites

Rich exothermic

71.5

5.0

10.5

12.5

5

10

Bright annealing low C steel, silicon steels/Cu brazing, sintering

Dissociated NH3

25

‐

‐

75

‐

‐50 to +60

Brazing sintering bright annealing

34‐ 40

0.51

‐10 to +10

Hardening, carburizing with CH4, sintering brazing

‐60 ‐ 68

Natural for annealing

Endothermic 40‐ 45

Nitrogen H2

0‐0.5 20

99.9

99.9

Reducing, sintering

Ar or He : These are pure and inert gases and are used to prevent oxidation during welding of stainless steel , aluminum etc. and heat treatment of special steels.

ATMOSPHERE VOLUME REQUIREMENTS It depends on 1

Type and size of furnace

2

Environment and presence of draft

3

The nature and size of work pieces

4

Metallurgical process involve

5

Presence or absence of curtains at entrance and exit 43

APPLICATION FOR INDUCTION FURNACE Induction heating is used for an ever-widening range of industrial and scientific applications: material joining processes such as brazing, soldering and curing; material processes applications including hardening, forging, annealing and melting; and component assembly applications such as epoxy bonding and heat staking metal into plastic. Our engineers have also applied the technology for catheter tipping, hot heading and other component manufacturing processes. 1. Annealing Annealing and tempering are used to soften metal for improved ductility and machinability, as well as to relieve residual stress. In contrast to hardening, annealing involves a much slower heating step followed by gradual cooling of the metal. Tempering refers to a reheating and slow cooling of metal which has become too brittle as a result of a hardening process. 2. Bonding

Flexible, epoxy-based gaskets can be bonded to metal or other conductive material without a third bonding agent. Our Epoxy Bonding Systems are ideal for this application. Induction heating has been used for bonding gaskets to metal automotive parts, thermoplastic composite bonding, and rubber washer/bumper assemblies.

3. Brazing

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Brazing is the process of joining two or more pieces of metal or ceramic material with a molten filler metal such as silver, aluminum alloy or copper. Brazing requires a higher temperature than soldering but produces a very strong bond which withstands shock, vibration and temperature change. Brazing in a controlled vacuum or in an inert protective atmosphere can significantly improve overall part quality and eliminate costly part cleaning procedures. Please visit The Brazing Guide section of our website for in-depth information about brazing processes, materials, filler metals and equipment. 4. Forging and Hot Forming Industrial forging and hot forming processes involve bending or shaping a metal billet or bloom after it has been heated to a temperature at which its resistance to deformation is weak. Blocks of non-ferrous materials can also be used. 5. Fusing Nickel-Based Alloys to Steel This application involves heating a steel boiler tube assembly to fuse a nickel-based, hardsurfacing alloy which has been applied as a spray. The tube is coated with the alloy to provide corrosion resistance during use; wear-resistant nickel alloys are applied to new parts where wear or corrosion is anticipated, or to worn parts to replace metal lost through wear. 6. Hardening Steel

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Steel hardening consists of heating the material to a temperature over 723ºC (austenitic temperature) and then cooling the steel quickly, often with a quench of industrial water. The aim is to transform the structure of the steek in order to increase its hardness, its yield strength, and its breaking tension. The steels that are normally hardened with induction heating contain from 0.3% to 0.7% carbon. 7. Heat Staking When one piece of metal is designed to be inserted into a second piece, induction heating can be used to "shrink fit" the two pieces together. The first or larger piece containing the opening is heated to expand the size of the hole. The second piece is then inserted into the opening, and as the first piece cools and shrinks back to its original size, the resulting pressure holds the two pieces together in a strong bond. 8. Heat Setting This medical application involves heating nitinol stents to set proper size. The stents are slid over a correctly-sized mandrel, to which induction heating is then applied. Precise temperature control is required for this process.

9. Melting Hard metals can be melted with an induction heating furnace. The metal is placed on a non-conductive crucible; when induction heating power is applied, the eddy currents circulating within the metal effectively stir the molten mass as it melts. Very high quality, uniform melting can be achieved with precious metals, high quality steels and non-ferrous alloys. 10. Pre-Tinning Induction heating can be used to quickly pre-tin solder paste in a copper electrical connector. With the right combination of induction coil and temperature, the solder paste can be melted within 10 seconds. 46

11. Soldering/Desoldering Induction soldering is similar to induction brazing, but soldering is done at a lower temperature and the bond strength is not quite as high. One unusual application involves desoldering and removing a stainless steel lid which had previously been soldered to a stainless steel box. 12. Susceptor Heating A susceptor is a conductive metal material that is used to transfer heat to another piece of metal or non-conductive material. Susceptors are often made from graphite because it is highly resistive and very machinable, or alternatively from stainless steel, aluminum, or other materials. 13. Pre-Heating for Welding

Induction heating can be used very effectively to preheat conductive materials for forging, welding, hot forming and hot heading. For example, the tips of turbine engine blades can be placed in a specially designed induction coil and heated to the desired temperature for

47

welding repairs. The induction preheating step improves cycle time and reduces stress on the rest of the blade.

DESIGN ANALYSIS

48

LOAD APPLIED

DISPLACEMENT

49

MESHING

RESULT OF APPLIED LOAD 50

ELECTROMAGNETIC & THERMAL ANALYSIS MESHEING

51

ELECTROMAGNETISATION

HEAT GENERATION

52

JOULE HEAT GENERATION

MAGNETIC FLUX GENERATION

53

54

PRODUCTION DRAWING

55

56

57

58

59

60

PHOTOGRAPHY

61

Assembly

Crucible

62

CONCLUSIONS

• Transient Thermal analysis of mock-up induction furnace is being carried out in this study which is highly important for operation and control of the process. • Preliminary model : it will aid in improving the design. • The studies reveal that Aluminium -liner is effective in reducing the electromagnetic coupling between the coil and the vessel and thus prevents vessel from getting heated up by this effect. • The coil temperatures are above the acceptable temperature of copper material, hence different cooling technique is to be adopted. • These results will be compared with the experimental results which will be obtained during the operation of mock up facility.

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REFERENCES [1] E. J. Davies and P. G. Simpson, Induction Heating Handbook. Maidenhead, U.K.: McGraw-Hill, 1979. [2] D. A. Lazor, "Induction Related Considerations in Investment Casting", Modern Investment Casting Technical Seminar, pp 1-14, Pittsburg USA, March 27-29, 2001. [3] K.C. Bala, "Design Analysis of an Electric Induction Furnace for Melting Aluminum Scrap", AU Journal of Technology, vol(9), No(2):, pp83-88, Oct. 2005. [4] P. Dorland, J.D. Wyk, and O.H. Stielau, "On the Influence of Coil Design and Electromagnetic Configuration on the Efficiency of an Induction Melting Furnace", IEEE Trans on IA, Vol. 36, No. 4, July/Aug. 2000. [5] J. Lee, S. K. Lim, K. Nam and D. Choi, "Design Method of an Optimal Induction Heater Capacitance for Maximum Power Dissipation and Minimum Power Loss Caused by ESR", 11th IFAC Symposium on automation in Mining, Mineral and Metal processing, Nancy, France, September 2004. [6] A. K. Sawheny, A Course in Electrical Machine Design, J.C. Kapoor, 1981. [7] Lloyed H. Dixon, Jr. "Eddy Current Losses in Transformer Winding and Circuit Wiring", Texas Instruments Incorporated, 2003.

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