ArticlePDF Available

Induction Furnace -A Review

Authors:

Abstract and Figures

A new generation of industrial induction melting furnaces has been developed during the last 25 years. Present practices followed in Induction Furnaces are discussed in this paper. Through a literature review account of various practices presently being followed in steel industries using Induction Furnaces has been carried out with a view to gather principal of working. Apart from this a pilot study has also been carried out in few industries in India. We provide some recommendations for the productivity improvement .Due to non availability of the proper instrumentations the effect of the ill practices can not be precisely judged. If this is properly measured, the percentage of productivity improvement in steel melting Induction Furnace can be calculated.The review is carried out from the literature in the various journals and manuals.
Content may be subject to copyright.
Vivek R. Gandhewar et al. / International Journal of Engineering and Technology Vol.3 (4), 2011, 277-284
Induction Furnace - A Review
Vivek R. Gandhewar1*, Satish V. Bansod2, Atul B.Borade3
1,3 Mechanical Engineering Department, Jawaharlal Darda Inst. of Engg. & Tech. Yavatmal, India
2 Mechanical Engineering Department ,Prof.Ram Meghe Institute of Technology & Research, Badnera
Rl.(M.S.),India
*Corresponding author (e-mail:vivek.gandhewar@rediffmail.com, Contact no:
09763702569 )
AbstractA new generation of industrial induction melting furnaces has been developed during the
last 25 years. Present practices followed in Induction Furnaces are discussed in this paper. Through a
literature review account of various practices presently being followed in steel industries using Induction
Furnaces has been carried out with a view to gather principal of working. Apart from this a pilot study
has also been carried out in few industries in India.
We provide some recommendations for the productivity improvement .Due to non availability of the
proper instrumentations the effect of the ill practices can not be precisely judged. If this is properly
measured, the percentage of productivity improvement in steel melting Induction Furnace can be
calculated.The review is carried out from the literature in the various journals and manuals.
Keywords- Induction Furnace, molten metal , productivity, Melt rate
I. 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 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 (10).
Induction furnaces have increased in capacity to where modern high-power-density induction furnaces are
competing successfully with cupola melting (Fig.1). 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. (4)
ISSN : 0975-4024
August - September 2011
277
Vivek R. Gandhewar et al. / International Journal of Engineering and Technology Vol.3 (4), 2011, 277-284
Fig.1:Schematic of induction furnace
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. (3)
The iron and steel sector has been experiencing a slow down 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 slow down 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.
(d) Cost escalation in the input materials for iron and steel. .(7)
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.(1)
Induction melting furnaces in India were first installed to make stainless steel from imported SS Scrap. But
in 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.(3)
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
ISSN : 0975-4024
August - September 2011
278
Vivek R. Gandhewar et al. / International Journal of Engineering and Technology Vol.3 (4), 2011, 277-284
scrap is likely to go up to 388 million tonnes. As the GDP 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.(2)
II. CONSTRUCTION AND WORKING
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.
Fig. 2: 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
A. 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.
B. 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.(5)
C. Input And Output Paameters Of The Induction Furnaces:
In order to study the prevailing practices in steel plants using Induction Furnaces, the following parameters
have been identified as
ISSN : 0975-4024
August - September 2011
279
Vivek R. Gandhewar et al. / International Journal of Engineering and Technology Vol.3 (4), 2011, 277-284
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. (3)
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.(5)
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.(8)
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.
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 sulfides plus a host of other compounds, which may include alumina,
calcium oxides and sulfides, rare earth oxides and sulfides and spinels and fosterites. (4)
III.TYPES OF INDUCTION FURNACES
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..(4)
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.
C. Pressure Pour Furnace:
A pressure pour is, in essence, a channel furnace, as described above, that is carefully sealed so that the
metal can be moved out of the furnace by way of pressurizing the chamber above the molten metal bath in the
furnace.
D. Safety Implications:
Accident investigation reports indicate that most foundry accidents happen due to one of the following
reasons:
• The introduction of wet or damp metal into the melt, causing a water/molten metal explosion
• Lack of operator skill during temperature taking, sampling or the addition of alloying compounds, causing
metal splash.
•Dropping large pieces of charge material into a molten bath, causing metal splash
• Improper attention to charging, causing a bridging conditions
ISSN : 0975-4024
August - September 2011
280
Vivek R. Gandhewar et al. / International Journal of Engineering and Technology Vol.3 (4), 2011, 277-284
• Failure to stand behind safety lines, causing a tapping situation
• Coming into contact with electrical conductors, overriding safety interlock switches or coming into contact
with incompletely discharged capacitors, causing electric shock or electrocution
• Lack of operator training (5)
IV. TECHNOLOGY ABSORPTION AND GAPS
A. Need For Adoption Of Foreign Technology Using DRI As Raw Material
Of late, main problems faced by steelmakers are short supply, fluctuating prices together with extremely
heterogeneous nature and presence of tramp elements of steel scrap. Use of direct reduced iron (DRI) as a partial
replacement to scrap, to some extent does help in overcoming this hurdle. However, unlike scrap and even pig
iron, DRI is characterized by high porosity, low thermal and electrical conductivities which, in turn, poses
problems in its melting.(6)
With the scarcity of scrap and production of DRI in the country, an inherent difference in the process
between the advanced countries and India has been created. The Indian technologists/engineers will have to
meet the situation with intelligent adaptation of the available technology.There are however a few companies in
the world that use DRI as metallic input in their EAF divisions and have mastered this technology. They are ;
i) Krakatau, Indonesia (using gas based DRI)
ii) Sidbec Dosco, Canada ( using coal based DRI)
iii) New Zealand Steel, New Zealand (using coal based DRI)
iv) ISCOR, South Africa (using gas based DRI)
v) Vespasiano, Brazil (using gas based DRI)
vi) HSW, Germany (using gas based DRI) Equipment suppliers like Mannesmann Demag have considerable
experience in steel making with DRI in AC EAF's. The companies mentioned above could also be approached
for process know-how.(11)
B. Technological Up gradation
The old slogan that in Induction Melting Furnaces you do not “make” steel but only “melt” which is like
“Garbage in” and “Garbage out” has been proved wrong. The ingenuity of making all types of steels has been
mastered by technologists of Induction melting Furnaces..(3)
Over the past 30 years, the U.S. foundry industry has seen a significant change in melting methods and
associated molten metal handling systems. Further, there has been a steady and continued deterioration in the
quality of metallic scrap and other iron unit feed stocks. The net result is that slag generation and slag related
melting problems have become relatively widespread in recent years. A search of the foundry technical
literature to gain a better understanding of methods and practices needed to improve slag control over the past
30 years will produce only a handful of technical articles. A new flux, Redux EF40L, has been developed that
controls build-up in melting furnaces without adverse effects on refractory Linings. (9)
The newer power supplies improve the overall melting efficiency and furnace production at lower operation
and fixed costs. Induction furnaces have benefited from improvements in the following areas:
Scrap Charging Systems: Scrap sorting and charging systems that achieve higher density charges show increase
in efficiency through increase in coil efficiency and shortening of melting time.
Furnace Designs: Newer furnaces with more efficient and larger power supplies (KWh capacity per ton) reduce
energy consumption.
Furnace Covers: The use of furnace cover is critical to energy efficiency once the metal is molten. The simplest
system is to keep a slag on the molten metal, reducing radiation losses from the top surface.
Harmonics Controls: Harmonics problem, or feedback of electrical equipment on the power source, can be
caused by the high power of the furnace power supplies. These power interface problems include low-power
factor, high-frequency harmonics, line voltage notching, and inter-harmonic distortions. Special technologies
and equipments have been developed to minimize the negative influence of induction furnaces on the power
supply.
ISSN : 0975-4024
August - September 2011
281
Vivek R. Gandhewar et al. / International Journal of Engineering and Technology Vol.3 (4), 2011, 277-284
Multiple-Output Power Supplies: Dual-output or “butterfly” operations utilize a single power supply and two
furnaces with mechanized or electronic switching. This results in continuous and completely controllable power
to two furnaces at the same time.
Refractories: Push-out lining systems use a large plug to quickly remove the old lining for easy disposal. This
system reduces time and cost for periodic lining changes, lowers refractory dust, and is less likely to damage
back-up lining than manual refractory removal. (4)
V. PILOT STUDY OBSERVATIONS AND FINDINGS
The exhaustive literature review has been carried out for study of working principal of induction furnace, its
construction and to account the various practices followed in induction furnace operations.
A pilot study has also been carried out in few industries in India. These industries are using induction
furnaces as a part of the process. Following are the observations.
A. Melt Rate
Figure 3: Melt Rate in Kg/Min Vs kWh /Mt MS
From figure 3 we can conclude that, Though the furnace and other working parameters are same, there is a
variation in melt rate.
Remarkable variation in Specific power consumption is also observed. As the Melt rate increases the
specific energy consumption decreases.
B. Operating KW
0
100
200
300
400
KW
Time
Time Vs KW
Figure 4: Time Vs KW
As can be seen from the KW readings, the furnace doesn’t draw full power during this initial stage resulting
in increased energy losses and more time is required for molten metal to form at the base of the crucible to speed
up further melting.
C. Scrap Quality
Mostly the raw material is charged as per the availability, and no particular sequence or proportion is
followed.
Scrap is not sorted or graded. If the carbon content is found more while sampling, ,the melter usually prefer
to add sponge iron ( low carbon) or proceed for the excessive stirring. Both these results in greater specific
consumption.
D. Heat Tap To Tap Time
ISSN : 0975-4024
August - September 2011
282
Vivek R. Gandhewar et al. / International Journal of Engineering and Technology Vol.3 (4), 2011, 277-284
The time for a heat also depends upon the type of scrap. The time required for a heat is around 192 minutes
for the 2 heats which were monitored. The heat time increases to 300-320 minutes. Longer heat time translates
into more power input for same amount of metal.
E. Deslagging Practice
During deslagging the charging stops for nearly 3-5 minutes, the metal is overheated as metal input is zero
during this interval of 3-5 minutes. If the power supply is not lowered by operating the potentiometer, the
molten metal starts boiling due to excessive temperature. In this case the melter turn off the power supply, this
results in heat loss through water flowing through coil.
Once the metal temperature falls slightly the power is again kept on which consumes more energy. If the
slag sticks to the linings of furnace, it creates difficulty for charging the scrap, this also decrease the
performance of the furnaces. While removing the slag built up from the walls the lining may also damaged.
F. Metal Quantity
It is observed that frequently the level of molten metal at the time of tapping is below the lip of crucible.
VI. RECOMMENDATIONS
A. Initial Scrap Charging By Bucket
In usual practice just after the tapping of heat the initial charging is done manually by using shovels or
some big lumps of metal scrap or pressed bundles of low grade scrap. In some cases it is done with the help of
crane, the big metal box is filled with scrap is hanged with crane and it spread the scrap over the furnace surface.
Due to this practice though the furnace appears to be charged fully it is not a dense charge. After some time it is
observed that the furnace is not drawing the full power. This results in more time for heat and more energy
consumption. It is suggested that a charging bucket be used initially to charge the scrap into the crucible. This
enables the saving in charging time as well as the charge is in dense form due to compaction, so furnace will
draw full power from the beginning (Fig.5). Bucket charging also enables in reducing the furnace off time.
During off time the percentage losses are are higher as heat is carried away by cooling water and also being
dissipated by radiation and convention losses
Fig 5: Comparative graph showing the effect of bucket charging
B. Control On Furnace Power During De-slagging Operations
The power to the Furnace should be controlled during the period of de-slagging after judging condition of
the molten bath. As soon as no solid scrap remains in the bath or just before this, the power in the furnace is to
be reduced using potentiometer settings. This will avoid overheating of the molten metal and off time of the
furnace can be reduced.
C. Ensuring Full crucible before Tapping
It is recommended that the melter ensures the crucible is filled upto the maximum extent. The molten bath
is available at the end of heat which can melt the light scrap very fast and specific energy consumption is also
low for this last portion.
D. Scrap Preheating
The hot gases releasing after the complete melting of raw material, we can reuse these hot gases to heat the
scrap or raw material so that the moisture present in it get removed. And after this we can use this heated scrap
ISSN : 0975-4024
August - September 2011
283
Vivek R. Gandhewar et al. / International Journal of Engineering and Technology Vol.3 (4), 2011, 277-284
due to which it takes less time for complete melting and ultimately the cycle time decreases. Scrap preheating
has the potential to reduce energy required for melting operations. Preheating systems, such as a second furnace
is the most promising. More efforts for research is needed to develop a comprehensive energy transfer model
linking the furnace operation with gas generation and scrap preheating.
E. Minimum Holding Time
Steel melting energy efficiency can be improved if there is no time delay in holding the molten metal where
additional energy is required to maintain the temperature of the molten metal until it is poured.
F. Proper Scheduling Of Furnace
If the furnace can be scheduled so that it can operate at continues full power, the energy requirements for,
melting steel can be reduced substantially.
G. Quality Of Scrap
For better melting of raw material, dense charge should be provided to the induction furnace. e.g. for
increasing density of M.S. Scrap shredded machines can be used, also bundling press can be used to make
bundles of loose light weight scrap and tuning and boaring.
VII.CONCLUSION
Through the exhaustive review of literature, the basic operations of Induction Furnace and importance of
its individual parameters are studied. Pilot study is carried out in few industries in India, to verify the working
practices and parameters of the Induction Furnaces. It is found through observations that, there are many
differences in operations in various industries. In few cases lack of standardisation of process is also observed.
In this paper we are focusing on improving the efficiency of steel melting processes. After actually
watching all the steel melting process, we came to know that, what are the various losses and where heat is lost.
Hence for improving its efficiency and for reducing the losses we have made recommendation like Scheduling
of operations, Molten metal delivery, Preheating, No time delay in holding the molten metal, Reuse of hot gases,
Using the good quality raw material, Proper charging practice. If this comes in regular practice obviously it
helps to increase its efficiency. Material and energy losses during these process steps represent inefficiencies
that waste energy and increase the costs of melting operations. Modifying the design and/or operation of any
step in the melting process may affect the subsequent steps. It is, therefore, important to examine the impact of
all proposed modifications over the entire melting process to ensure that energy improvement in one step is not
translating to energy burden in another step.
Although these technologies require little or no capital for deployment, engineering assistance is needed for
the facility to reap its maximum benefits. For example steel melting energy efficiency can be improved if there
is no time delay in holding the molten metal where additional energy is required to maintain the temperature of
the molten metal until it is poured. If a furnace can be scheduled so that it can operate at continuous full power,
the energy requirements for melting steel can be reduced substantially. While reviewing the literature, it is
observed that till this time an attempt is not made by the concerns to study the impact of variation of one
parameter on others. Through the planned design of experimentation, the effect of individual parameters can be
studied and its overall effect on productivity can be found out.
REFERENCES
1. Presidential address on the occasion of xx annual general meeting & interactive seminar on 16th November 2005 at New Delhi overview
of iron and steel industry steel markets Asia conference 2005.
2. Ikbal Nathani ( November 15, 2005) importance of recycling and current ferrous scrap scenario. Ambassador, Indian sub-continent
bureau of international recycling Brussels.
3. www.steelworld.com
4. Advanced Melting Technologies: (November 2005 Energy Saving Concepts and Opportunities for the Metal Casting Industry BCS,
Incorporated 5550 Sterrett Place, Suite 306 Columbia, MD 21044 www.bcs-hq.com.
5. Information Brochure of Inductotherm Safety Information: An Inductotherm Group Company.
6. S.K. Dutta, A.B. Lele and N.K. Pancholi (October 2004) “Studies on direct reduced iron melting in induction furnace” Trans. Indian Inst.
Met. Vol.57, No. 5, October 2004, pp. 467-473 TP 1904.
7. www.steel.nic.in
8. Catalogue of Adore Multilane Products: Manufacturer of Ramming Mass.
9. R. L. (Rod) Naro(November 4, 2003) “Control of Slag and Insoluble Build-up in Melting Furnaces” An International Iron Melting
Conference Orlando, Florida.
10. Duncan, George, R., Electric Furnace Steelmaking, Iron and Steel Society,Inc, Book Crafters, Inc., Chelsea,MI, USA 1985,pp 161-166.
11. www.dsir.gov.in
URL visited:
http://www.steelworld.com/smii.htm
http://www.steel.nic.in/annual report(2002-03)
http://www.dsir.gov.in/reports/techreps/tsr154.pdf
ISSN : 0975-4024
August - September 2011
284
... In USA, beginning from 2010, the number of operating cupolas decreased in 2 times, at the same time the number of induction furnaces increased in 2.5 times. Remarkable is the fact, that among the world amount of induction furnaces more than 80 % belong to middle-frequency furnaces and can be used for any alloys obtaining, including cast iron [5,6]. Induction crucible furnaces of industry frequency (50 Hz) consist overwhelming majority of them. ...
... The nano-size inclusions should improve the mechanical and heat-resistant properties of the LGU. The described light-guide assemblage is placed on the axis of force block (4) with non-stick coating (5). Circular gap between loadbearing pipe and force block is also compacted by reinforcement material (2). ...
Article
The article is devoted to the question of the most effective for the full use of the induction furnaces technological flexibility continuous temperature control. The aim of the work is to create a light-guide technology for continuous temperature control of the processes of induction melting, treatment and pouring of liquid metal in metallurgy of machine building. The investigations of crucible and channel, melting, holding and pouring induction furnaces from the standpoint of light-guide thermometry have been developed. Materials, designs, as well as technologies of manufacturing, mounting and safe operation of the light-guide and auxiliary devices have also been investigated. Using the results of complex studies, the base light-guide thermometry system, general and particular methods of the light-guide temperature measurements have been developed. On the base of the Huygens construction, as well as the laws of geometric and crystal optics, techniques for calculation of the optical characteristics of the light-guide and focusing devices, as well as schemes of their optical joint have been developed. These techniques increase the metrological characteristics of the light-guide thermometry. Standard construction of the secondary part of thermometry system requires classical pyrometry methods application. These methods are acceptable for continuously operated metallurgical aggregates, where stable emissivity of the light-guide operating end takes place. The secondary part of thermometry system has been modernized in order to widen application field of light-guide thermometry on periodically operated metallurgical aggregates where emissivity of light-guide immersion end randomly changes. Modernized secondary part is purposed for spectral (multicolor) pyrometry methods realization. These methods minimize influence of the instability of emissivity of light-guide immersion end on methodical errors of temperature measurements. Research and industrial exploitation, at domestic and foreign enterprises, have shown obvious metrological advantages of the light-guide thermometry technology in comparison with known solutions. Implementation of the light-guide thermometry systems on induction furnaces has high technical-economic efficiency, including by reduction the spoilage of metal products and resource costs for production. Keywords: induction furnace, continuous temperature control, light-guide thermometry, amorphous, poly- and single-crystalline materials, measurement error, Huygens construction, technical-economic efficiency.
... Induction furnaces have been used since the first decade of the 20th century (USA and Germany), and a new generation of these furnaces was developed in the mid-1980s [1]. There are two main types of induction furnaces: coreless and channel [2]. ...
... where Iind eff is the effective current through the inductor. In the optimal case (described inductor completely filled with steel charge, go mal insulation, heating below the Curie temperature, frequency slightly lower resonant frequency, inverter in the optimal range, etc.), the following paramet measured and calculated: The equivalent series resistance of the inductor and the ferromagnetic charge is calculated according to the following equation [23]: (1) where N ind represents the number of turns of the inductor, while z ind and z ch represent the depths of Foucault's currents in the conductor of the inductor and in the batch, respectively. The first addend represents the equivalent series resistance of the inductor at 80 • C, and the second addend represents the equivalent resistance of the steel batch (reduced to the inductor side) at 800 • C. Based on the tables and calculations [41], z ind ≈ 1 mm and z ch ≈ 3.3 mm were obtained. ...
Article
Full-text available
This paper presents the development of a piece of induction hardening equipment based on the foundations of the design, starting from zero. It was intended for steels in general, and was tested on unalloyed low- and medium-carbon steels, whereas the results for EN 1C60 steel are shown in this study. The EN 1C60 steel showed average results, and was chosen as a representative of a wider group of engineering steels. The main objective of this work was to develop a flexible system for mild steel hardening that can be used for various hardening depths and steel types. The system design’s priorities were the use of standard electronic components to avoid supply chain disruptions and to achieve high energy efficiency. The construction of the prototype in full detail is also presented. The optimal process parameters are listed, as well as the procedure of their obtaining by using the appropriate simulation method. The key parameters were adjusted in consecutive steps. This study resulted in high matching between the model predictions and experimental results. The basic goal of this research was achieved, with the system having a minimum energy efficiency of 75.3%, a most frequent energy efficiency of 90% and a maximum energy efficiency of 95.1%.
... Based on this score, processes were ranked and ordered, as shown in Table 2. This ranking helps identify processes with the highest carbon emissions (hotspots) for small-and medium-scale industries, as presented in Table 3. Research indicates that current induction furnaces can achieve electrical efficiency levels exceeding 97% (Gandhewar, Bansod, and Borade 2011). ...
Article
Full-text available
In response to concerns about depleting natural resources, organisations are developing eco-friendly products and services. This study examines the role of manufacturing industries and services in sustainable resource utilisation, focusing on the Micro, Small, Medium Enterprises (MSME) sector, a significant contributor to global Gross Domestic Product (GDP). Using Life Cycle Assessment (LCA) methodology, the research identifies hotspots within the production processes of three companies manufacturing bathroom fittings, specifically the ‘Wall mixer’ component used in households and hotels. The study calculates In response to concerns about depleting natural resources, organisations are developing eco-friendly products and services. This study examines the role of manufacturing industries and services in sustainable resource utilisation, focusing on the MSME sector, a significant contributor to global GDP. Using Life Cycle Assessment (LCA) methodology, the research identifies hotspots within the production processes of three companies manufacturing bathroom fittings, specifically the ‘Wall mixer’ component used in households and hotels. The study calculates CO2 equivalents for each phase of the product lifecycle, identifying average gate-to-gate process values across the companies. This comparison reveals specific hotspots, with a significant one identified, leading to recommendations for industries to prioritise this issue for immediate energy savings. The primary focus is to establish an initial benchmarking system to reduce CO2 equivalents in cradle-to-gate or gate-to-gate systems. Implementing these measures is expected to reduce the carbon footprint, energy consumption, and raw material usage, ultimately enhancing profitability for the three companies. equivalents for each phase of the product lifecycle, identifying average gate-to-gate process values across the companies. This comparison reveals specific hotspots, with a significant one identified, leading to recommendations for industries to prioritise this issue for immediate energy savings. The primary focus is to establish an initial benchmarking system to reduce CO2 equivalents in cradle-to-gate or gate-to-gate systems. Implementing these measures is expected to reduce the carbon footprint, energy consumption, and raw material usage, ultimately enhancing profitability for the three companies.
... Induction furnaces are still not widely adopted. This technology requires optimization and improvements to process practices [147,148], but appears promising, mainly for processes that require temperatures above 2000°C. • Solar thermal could play an important role by supplying a part of the heat demand. ...
Article
Full-text available
Electrification scenarios dominate most plans to decarbonize the global economy and slow down the unfolding of climate change. In this work, we evaluate from a primary power perspective the impacts of electrifying the power, transport, residential and commercial sectors of the economy. We also investigate the electrification of industrial intense heat processes. Our analysis shows that, in terms of primary power, electrification can result in significant savings of up to 28% of final power use. However, actual savings depend on the sources of electricity used. For intense heat processes, these savings are very sensitive to the electricity sources, and losses of over 70% of primary power can occur during the conversion of heat to electricity and back to heat. Overall, this study highlights the potential benefits and limitations of electrification as a tool for reducing primary power consumption and transitioning to a more sustainable energy system.
... Earlier it was assumed that in induction furnace we can't make steel but only melt which is like "Garbage in" and "Garbage out". This thought has been proven wrong and now all types of steels are being manufactured by technologists through induction furnace route [2].The Ministry of steel, Government of India published a report in which it has been mentioned that the total crude steel production in India during the year 2021-2022 was 118.134 MT and out of which 28% was the contribution of induction furnace route [3].The plain carbon steel and construction quality steels are mostly produced through induction furnace route [4]. ...
Article
Full-text available
The industries who are using induction melting furnace to produce steel does not carry out any refining process, the steel produced by induction route was considered to be of inferior quality and not suitable for critical applications. Thus, in this work a methodology has been designed to produce steel from induction routes of similar quality as the steel produced through electric arc furnace and Basic Oxygen Furnace. In this new design a ladle refining furnace was implemented after induction melting. In this process the removal of phosphorous was achieved by addition of calcium oxide as a flux to maintain the basicity of the ladle refining furnace. The phosphorous has been removed in great extent and degree of dephosphorization has been achieved up to 78-85%. The extent of phosphorous removal was achieved by maintaining dephosphorization index and basicity in best possible range and is found to be in line with the design of experiment framed by Taguchi method. Taguchi method was used to find the best possible combination of degree of dephosphorization, dephosphorization index and V-ratio to remove the phosphorous from steel.
Article
Full-text available
Direct reduced iron (DRI)-based steelmaking requires high-grade iron ore (Fe > 65 wt-%). However, a swift decline in ore grade has forced steelmakers to use lower-grade ores for DRI making, creating challenges in subsequent processes dealing with high gangue content for steelmaking. Hence, an intermediate melting/smelting furnace has been proposed to treat high gangue content from the DRI before transferring hot metal into an electric arc furnace (EAF)/basic oxygen furnace (BOF) for steelmaking. This study investigates and models the performance and charge behaviour in a melter/smelter with respect to the gangue content, DRI carbon content and temperature. The results showed that the specific energy consumption (SEC) and off-gas production increase with increasing temperature, carbon in DRI and gangue content. At 90 wt-% metallisation ratio (MR) using the lowest-grade ore (gangue 16 wt-%), the SEC at 1300 °C was calculated to be 706 kWh/tHM compared to 850 kWh/tHM at 1600 °C using 3.5 wt-% carbon. The MR is predicted to profoundly impact the SEC, as the increasing MR decreases the SEC markedly. At 90 wt-% MR, the SEC using the lowest-grade ore was 805 kWh/tHM, decreasing to 684 kWh/tHM using 100 wt-%MR. Increasing MR, carbon in DRI and temperature decreases slag production consistently while increasing with the increasing gangue. Using hot DRI onsite is predicted to significantly reduce the SEC compared to cold DRI. Overall, the energy demand from cold DRI is predicted to be 120 kWh/tHM higher than hot DRI. Increasing the scrap-to-DRI ratio is predicted to decrease the energy demand, that is, every 1.0 wt-% increase in scrap decreases the SEC by 2.5 kWh/tHM.
Article
Full-text available
This project involved the design and construction of an electric heat treatment furnace using locally sourced materials. The design process included extensive research on existing designs, the creation of detailed CAD models, and the careful selection of refractory materials. All materials used for the design and production were locally sourced in Warri, Nigeria. The fabrication process encompassed cutting, drilling, welding, and assembling the components, resulting in a high-quality and durable furnace. The heat treatment furnace, designed and fabricated, successfully achieved a performance of 1,000°C. The furnace was lined with a refractory composed of clay and white cement in a ratio of 3:1, with a thickness of 150mm. Additionally, an initial lining layer of 100mm fire-resistant rock-wool, capable of withstanding temperatures up to 1,400°C, was applied. To monitor and control the temperature, a digital temperature and time control/monitor unit, along with a temperature sensor, were installed in the furnace. The project was successfully completed at a cost of N247,200.00, significantly cheaper than imported alternatives, and proved efficient during testing.
Article
Vanadium is a critical metal that has been widely used in a broad variety of applications with almost no metal substitutes. However, the limited availability of its (vanadium) primary resources has raised concerns of supply security. In view of the criticality, recycling vanadium from secondary resources has been identified as a vital supply alternative. This article thus presents a comprehensive overview of metallurgical processes used in the recycling of vanadium from a variety of secondary resources, including spent HDS catalyst, spent SCR catalyst, fly ash, red mud, Bayer’s sludge, alloy scrap, tailings, etc. First, the physicochemical characteristics of these secondary resources are emphasized. Understanding the characteristics of vanadium-bearing secondary resources is important as it determines the recycling route. The metallurgical recycling processes of vanadium, which include aqueous- and thermal processes are discussed in depth, along with the theoretical backgrounds and fundamentals of each process. Also discussed are the industrial-scale processes and trend in research and development (R&D) for the respective secondary resources. Besides highlighting the status of recycling processes, the article also provides prospective directions for such resources.
Article
The medium frequency coreless induction furnace has gradually replaced the cupola in cast iron melting. However, induction coils at the bottom 1–6 turns can experience issues posing production and resulting safety risks. A kind of coil interturn breakdown failure caused by black attachment has occurred in our engineering practices. To explain the attaching and breakdown mechanism, an experimental investigation and detailed analysis of physical and chemical processes are performed. SEM, EDS and Fourier transform infrared spectrum results show that the attachment is primarily composed of free carbon, with a mass and atomic fraction of 62 and 71%, respectively. There were no C-H bonds in the powdered black attachment. The redox reactions of SiO2 and C, hydrogen and disproportionation reactions of CO and the ionization reactions of H2O contribute to the C transfers. The physical isolation of the Isoplan board, which prevents the mixture of CO, CO2, H2, H2O, and O2 from diffusing, causes C deposited only on the coil surface. The conductive carbon deposition in a moisture environment reduces the insulation degree of interturns and generates high-voltage discharge between adjacent coils. According to the findings, three improvement strategies are proposed and validated: (1) drilling holes in the Isoplan board; (2) unplugging the silicate insulating cloth in the lining sintering; and (3) as new lining is put into service, silicon steel sheets are prioritized for use as furnace charge.
Article
Full-text available
Of late, main problems faced by steelmakers are short supply, fluctuating prices together with extremely heterogeneous nature and presence of tramp elements of steel scrap. Use of direct reduced iron (DRI) as a partial replacement to scrap, to some extent does help in overcoming this hurdle. However, unlike scrap and even pig iron, DRI is characterized by high porosity, low thermal and electrical conductivities which, in turn, poses problems in its melting. Attempts were made to study melting of DRI in a laboratory size induction furnace using molten steel bath as hot heel. The induction stirring accelerates the transfer of heat and promotes the melting of DRI. The effect of partial replacement of scrap by DRI on various melting parameters has been studied. Also kinetic studies were made to evaluate net melting rate. It was revealed that since melting and refining are taking place simultaneously, the increasing proportion of DRI in the input charge increases net melting rate and metallic yield. It was concluded that higher proportion of DRI, as a replacement to scrap, contributes to improve mechanical properties with no segregation of carbon content and the decrease in sulphur and tramp elements in the product that improves steel quality.
Article
Powered by a rising world market and efficiency-enhancing technologies, electric furnace steelmaking has reached an all-time peak in North America. Arc furnaces melted 36.8 million tons of carbon, alloy and stainless steels last year, according to the American Iron and Steel Institute (AISI). Electric furnaces established new highs for carbon and stainless steels at nearly 29 million and 2.2 million tons, respectively. The article describes industry developments including modernization of plants at Chaparral Steel and Lukens Steel.
2005) importance of recycling and current ferrous scrap scenario. Ambassador, Indian sub-continent bureau of international recycling Brussels
  • Ikbal Nathani
Ikbal Nathani ( November 15, 2005) importance of recycling and current ferrous scrap scenario. Ambassador, Indian sub-continent bureau of international recycling Brussels.
Energy Saving Concepts and Opportunities for the Metal Casting Industry BCS
  • Melting Advanced
  • Technologies
Advanced Melting Technologies: (November 2005 Energy Saving Concepts and Opportunities for the Metal Casting Industry BCS, Incorporated 5550 Sterrett Place, Suite 306 Columbia, MD 21044 www.bcs-hq.com.