Induction Furnace Report

MORNING STAR POLYTECHNIC COLLEGE CHUNKANKADAI

ELECTRIC INDUCTION FURNACE

A Project Report In partial fulfillment of the requirement for the award of diploma In

MECHANICAL ENGINEERING Project guided by Mr.T.KAMILLAS FRANKLIN,M.E Submitted By NAME J.AJEESH P.AJIN RAJ P.ALAN BINO SUGIHAR R.ALEX A.ALEX MON A.M.ANAND

SL.NO 12208566 12208568 12208570 12208571 12208572 12208573

DIRECTORATE OF TECHNICAL EDUCATION, TAMILNADU 2013-2014

MORNING STAR POLYTECHNIC COLLEGE CHUNKANKADAI

Department Of Mechanical Engineering CERTIFICATE This is to certificate that the project entitled “ELECTRIC INDUCTION FURNACE” is a bonafide work done by……………………………….. reg.no………………………........ of final year diploma in mechanical engineering, during the year 2013-2014.

Guide Of The Department

Head

Mr.T.KAMILLAS FRANKLIN,M.E Mr.T.KAMILLAS FRANKLIN,M.E

Submitted For The Board Examination Held At Morning Star Polytechnic College On …………………..

Internal Examiner External Examiner Place : Chunkankadai Date :

ELECTRIC INDUCTION FURNACE

INTRODUCTION

INTRODUCTION An induction furnace is an electrical furnace in which the heat is applied by induction heating of metal. The advantage of the induction furnace is a clean, energy-efficient and wellcontrollable melting process compared to most other means of metal melting. Most modern 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. Induction furnace capacities range from less than one kilogram to one hundred tonnes capacity and

are

used

melt iron and steel, copper, aluminium and precious

to metals.

Since no arc or combustion is used, the temperature of the material is no higher than required to melt it; this can prevent loss of valuable alloying elements. 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). 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.

1

-

Melt

2

-

water cooled

3

-

yokes

4

-

coil

crucible

A preheated, one-tonne 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 tonnes of metal respectively. 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.

DIAGRAM

DIAGRAM

COMPONENTS

COMPONENTS    

Crucible Inductor coil and shell Cooling system Tilting mechanism.

CRUCIBLE A crucible is a container that can withstand very high temperatures

and

and pigment production

is as

used well

as

for

metal, glass,

anumber of

modern

laboratory processes. While crucibles historically were usually made from clay,[1] they can be made from any material that withstands temperatures high enough to melt or otherwise alter its contents. Crucibles and their covers are made of high temperatureresistant materials, usually porcelain, alumina or an inert metal. One of the earliest uses ofplatinum was to make crucibles. Ceramics

such

as alumina, zirconia,

and

especially magnesia will tolerate the highest temperatures. More recently, metals such as nickel and zirconium have been used. The lids are typically loose-fitting to allow gases to escape during heating of a sample inside. Crucibles and their lids can come in high form and low form shapes and in various

sizes, but rather small 10–15 ml size porcelain crucibles are commonly used for gravimetric chemical analysis. These small size crucibles and their covers made of porcelain are quite cheap when sold in quantity to laboratories, and the crucibles are sometimes disposed of after use in precise quantitative chemical analysis. There is usually a large mark-up when they are sold individually in hobby shops.

INDUCTOR COIL AND SHELL An inductor, also called a coil or reactor, is a passive twoterminal electrical component which resists changes in electric currentpassing through it. It consists of a conductor such as a wire, usually wound into a coil. When a current flows through it, energy is stored temporarily in a magnetic field in the coil. When the current flowing through an inductor changes, the

time-varying magnetic field induces a voltage in the conductor, according to Faraday’s law of electromagnetic induction, which opposes the change in current that created it. An inductor is characterized by its inductance, the ratio of the voltage to the rate of change of current, which has units of henries (H). Inductors have values that typically range from 1 µH (10−6H) to 1 H. Many inductors have a magnetic core made of iron or ferrite inside the coil, which serves to increase the magnetic

field

and

thus

the

inductance.

Along

with capacitors and resistors, inductors are one of the three passive linear circuit elements that make up electric circuits. Inductors are widely used in alternating current (AC) electronic equipment, particularly in radio equipment. They are used to block AC while allowing DC to pass; inductors designed for this purpose are called chokes. They are also used in electronic filters to separate signals of different frequencies, and in combination with capacitors to make tuned circuits.

COOLING SYSTEM Metalcasting cooling systems normally operate quietly in the background and receive regular attention only from the maintenance personnel tasked with keeping them running. The goal for this article is to provide useful insights into the design and operation of effective and efficient induction melt shop cooling systems, with real-world illustrations drawn from a new

system installed at Chassix Columbus Casting Operation, Columbus, Ga. Chassix is a $1.2 billion global company headquartered

in

Southfield,

Mich.,

serving

automotive

customers from 25 locations in eight countries. Its Columbus facility melts 240,000 tons of ductile iron per year.

COOLING SYSTEM BASICS Induction furnaces of all types and sizes normally are cooled by water flowing through the furnaces’ coils, which are made of heavy copper tubing. These coils generate high levels of heat, principally from the enormous electrical currents flowing through them and only to a much lesser extent from heat produced by the molten metal held in the furnace. Induction power supplies also require water cooling of their electrical components. Without an effective cooling system, induction furnaces will not operate. At its most basic level, an induction furnace cooling system includes pumps circulating water through the furnace to absorb heat and on to a cooling tower where that heat is released. But to be safe and effective, a cooling system must incorporate a variety of vital subsystems. These include:  Filters and other devices to keep the water clean and flowing.

 Heat exchangers, inline heaters and cold water diversion valves to maintain the optimal water temperature.  Automatic city water makeup to keep the cooling system full.  Flow sensors, pressure gauges, thermometers, water meters,

and

other

monitoring

and

control

devices needed to be sure it’s all working properly.  An emergency backup system to maintain furnace cooling in the event of pump failure or power outage. Because cooling systems are so essential, when the system at Chassix was no longer able to meet its needs, the management team moved quickly to repair or replace it. According to Darold “Jack” Roop, senior project engineer, Chassix, the problems with the old cooling system had increased considerably when new furnaces were installed to support growth in the company’s casting business. “We added three 12.5 metric tons per hour, medium frequency induction furnaces for batch melting, along with their power supplies, compressors and hydraulics,” Roop explained. “But our cooling system lacked the capacity to handle this new load. Due to inadequate cooling, the furnaces frequently overheated and tripped out. Several coils were burned up. We did not have sufficient cooling to allow us to run all of our furnaces at the same time. This reduced our metal production and limited our ability to fully benefit from the new melting capacity we had just added.” Chassix determined repairs to the existing cooling system would not provide the cooling capacity needed, so it set up and

funded a project to replace much of the system. Chassix project manager Frank Burton oversaw the creation of the new cooling system. “Our cooling tower was old, the wood was rotting and falling apart and its three pumps had to run all the time to provide needed cooling,” he said. “There was no redundancy. If one pump failed, production had to be shut down until the pump could be replaced. Shutting down was a slow process. The only emergency backup was city water, and that outflow presented environmental concerns.”

DESIGNING AN INDUCTION MELT COOLING SYSTEM Very small induction furnaces used in labs or for melting small quantities of precious metals may be cooled by direct connection to an incoming city water recirculated back through the furnace. This is the basis of most cooling systems. To design a cooling system for an induction melt shop, first you must determine the heat load on the system, taking into account the size of each furnace, the power applied, the metal melted, type of melting (batch or heel), holding and pouring times and the heat loads added by non-furnace ancillary equipment. These calculations can be complex. The new cooling system for Chassix was based on heat load calculations for the facility’s wide variety of furnace sizes, melting processes and ancillary equipment used to support them. These included:

 Three 12.5-metric-ton, medium frequency induction batch melting furnaces.  Five 10-ton line frequency induction heel melting furnaces.  Two 17-ton line frequency induction heel melting furnaces.  Ancillary systems including air compressors, hydraulic pumps and air conditioners. The calculations also had to take into account the need for backup

capacity

to

maintain

cooling

during

equipment

maintenance or repair and to support future growth. “I was looking for a new cooling system that would be reliable and offer the redundancy to enable it to continue running even with a pump failure,” Burton said. “I also wanted a system that would provide not just the capacity to cool all of our furnaces and equipment running at the same time, but that would have the additional capacity to support anticipated future growth.” The next step in the overall cooling system design is to make adjustments for the desired incoming water temperature from the tower to the process, the outgoing water temperature from the process to the tower and the climatic data for the foundry location. line and use a city drain for the outflow. Most other size furnaces require a pump or pumps to push cooling water through the furnace and a cooling tower of some kind to remove the heat from the water, which is then

WORKING

WORKING The heart of the coreless induction furnace is the coil, which consists of a hollow section of heavy duty, high conductivity copper tubing which is wound into a helical coil. Coil shape is contained within a steel shell and magnetic shielding is used to prevent heating of the supporting shell. To

protect it from overheating, the coil is water-cooled, the water bing recirculated and cooled in a cooling tower. The shell is supported on trunnions on which the furnace tils to facilitate pouring. The crucible is formed by ramming a granular refractory between the coil and a hollow internal former which is melted away with the first heat leaving a sintered lining. The power cubmicle converts the voltage and frequency of main supply, ot that required for electrical melting. Frequencies used in induction melting vary from 50 cycles per second (mains

frequency)

to

10,000

cycles

per

second

(high

frequency). The higher the operating frequency, the greater the maximum amount of power that can be applied to a furnace of given capacity and the lower the amount of turbulence induced. When the charge material is molten, the interaction of the magnetic field and the electrical currents flowing in the induction coil produce a stirring action within the molten metal. This stirring action forces the molten metal to rise upwards in the centre causing the characteristic meniscus on the surface of the metal. The degree of stirring action is influenced by the power and frequency applied as well as the size and shape of the coil and the density and viscosity of the molten metal. The stirring action within the bath is important as it helps with mixing

of

alloys

and

melting

of

turnings

as

well

as

homogenising of temerature throughout the furnace. Excessive

stirring can increase gas pick up, lining

wear and oxidation of

alloys. The coreless induction furnace has largely replaced the crucible furnace, especially for melting of high melting point alloys. The coreless induction furnace is commonly used to melt all grades of steels and irons as well as many non-ferrous alloys. The furnace is ideal for remelting and alloying because of the high degree of control over temperature and chemistry while the induction current provides good circulation of the melt.

ADVANTAGES

ADVANTAGES

• Safe operation • Pollution can be reduced • Electric induction is used to melt the material • Less power consumption

APPLICATIONS

APPLICATIONS

• Automobile industry • Aluminum melting furnace • Industrial application

CONCLUSION

CONCLUSION

The development of this project from the theoretical aspects to its practical application is

of

immense

contribution.

The

Induction

furnace design and subsequently its fabrication should be promoted considering the abundant power sources, less maintenance cost and labor requirements.

REFERENCES

REFERENCES 1. Percy, John. Natural Refractory Materials Employed in the Construction

of

Crucibles,

Retorts,

Forunaces

&c. Metallurgy. London: W. Clowes and Sons, 1861. 208– 09. Print. 2. Jump up^ Pigott, Vincent C. "The Neolithic (C.A 7500–5500 B.C) and Caltholithic (C.A 5500–3200 B.C) Periods." The Archaeometallurgy of the Asian Old World. Philadelphia: UPenn Museum of Archaeology, 1999. 73–74. Google Scholar. Web. 3. Jump up^ Rehren T. & Thornton C. P, 2009, A truly refractory crucible from fourth millennium Tepe Hissar, Northeast Iran, Journal of Archaeological Science, Vol. 36, pp2700–2712 4. ^ Jump up to:a

b

Hauptmann A., 2003, Developments in

copper Metallurgy During the Fourth and Third Millennia B.C. at Feinan, Jordan, P. Craddock & J. Lang, Eds, Mining and Metal Production Through the Ages, British Museum Press, London, pp93–100 5. ^ Jump up to:a

b

Rehren Th., 2003, Crucibles as Reaction

Vessels in Ancient Metallurgy, Ed in P. Craddock & J. Lang, Mining and Metal Production Through the Ages, British Museum Press, London pp207–215 6. Jump up^ Rehren Th., 1999, Small Size, Large Scale Roman brass Production in Germania Inferior, Journal of Archaeological Science, Vol. 26, pp 1083–1087 7. Jump up^ Craddock P., 1995, Early Metal Mining and Production, Edinburgh University Press Ltd, Edinburgh

8. ^ Jump

up

to:a

b

Rehren,

Th.

and

Papakhristu,

O.,

2000, Cutting Edge Technology – The Ferghana Process of Medieval crucible steel Smelting, Metalla, Bochum, 7(2) pp55–69 9. Jump up^ Martinon-Torres M. & Rehren Th., 2009, Post Medieval crucible Production and Distribution: A Study of Materials and Materialities, Archaeometry Vol.51 No.1 pp49–74