Q1. What do you mean by hybrid processes?

Write the metallurgical Superiority of hybrid blowing

process over LD and OBM process

Ans- All such processes wherein gas phase is introduced from both top and bottom of the vessel are known as
hybrid process of steel making .Hybrid process is a term applied to any such mixed blowing process where N2 & Ar
may be chosen as the inert stirring media separately or together judiciously .for experimental purposes the natural
stirring medium has been introduced in the beginning from top through auxiliary pipes it is now inversely introduced
from bottom through porous refractory phase or tuyers.

The oxygen bottom-blowing process is also known by the name OBM (Oxygen Bottom Maxhuette—
Maxhuette was the steel works in Germany where bottom-blowing trials were first undertaken) or Q-BOP
(Q standing for Quiescent/Quiet—the state of the bath vis-àvis LD steelmaking) or LWS (Loire, Wendel and
Sprunck—the names of three companies in France who developed this process). In the OBM/Q-BOP
process, the oxygen tuyeres are cooled by injecting hydrocarbon gas through an outer pipe surrounding
the oxygen pipe. Most bottom blown processes use methane or propane as the hydrocarbon coolant, but
fuel oil was employed in LWS converters. A principal advantage of bottom-blowing processes is that they
operate closer to equilibrium, encourage early formation of a fluid slag, reduce the oxygen content of the
steel tapped, and decrease the height requirements of the converter building since no top lance
equipment needs to be provided. Therefore, it became possible to retrofit bottom-blown converters in the
existing open hearth shops from the late 1970s with less capital cost in comparison to BOFs. The essential
feature of bottom-blown steelmaking is that the entire requirement of oxygen (50–55 Nm3 per tonne
liquid steel) is introduced through the bottom of the steelmaking vessel using tuyeres, canned porous
elements, or refractories with controlled porosity. Sometimes, lime is also introduced along with oxygen, in
which case only tuyeres can be employed . The oxygen bottom-blowing process (Figure 3.2) is also known
by the name OBM (Oxygen Bottom Maxhuette— Maxhuette was the steel works in Germany where
bottom-blowing trials were first undertaken) or Q-BOP (Q standing for Quiescent/Quiet—the state of the
bath vis-àvis LD steelmaking) or LWS (Loire, Wendel and Sprunck—the names of three companies in France
who developed this process.

A principal advantage of bottom-blowing processes is that they operate closer to equilibrium, encourage
early formation of a fluid slag, reduce the oxygen content of the steel tapped, and decrease the height
requirements of the converter building since no top lance equipment needs to be provided. Therefore, it
became possible to retrofit bottom-blown converters in the existing open hearth shops from the late 1970s
with less capital cost in comparison to BOFs.

Q.2. Is it important to do argon purging in ladle metallurgy to improve the quality of steel give the
suitable region in support of your answer.

Ans- Argon Purging Systems (APS), applicable to purging induction melting furnaces and induction power
ladle systems, help to reduce metallic inclusions to improve the overall purity of the melt. These systems
are an economical way to produce alloy steels.  Scrap is melted down in the melting furnace and after
the tapping, the liquid metal having a temperature of 1600 to 1650oC is charged into the Ladle.
The liquid metal either slag or with slag is weighted and transferred with the help of charging
crane to the LRF plant. First sample and temperature is taken from ladle. According to this
analysis and measured temperature pre-calculation of Ferro-alloys, additives and Argon gas is
effected to start from bottom of ladle process with using Argon purging system. To carry out
Argon gases are blown in Ladle through porous plug installed in the bottom side. As international
technology makes remarkable progress into the world of alloys & super alloys, the requirement
for cleaner steel homogeneous chemical composition coupled with the need for reducing the
production cost as well as increasing productivity has led to the development of more efficient
metallurgical tools in the secondary metallurgical process become a necessity for mini steel plant.
The process concerns itself with production of wide range of steels & high grade alloys steels.

The recognized benefits are:

 To make any type of qualitative steel production.

 Homogenization of melt for chemical analysis.
 Improvement of purity in terms of gaseous impurities.
 To reduce on metallic inclusions

Q.3. Write the different parameters, which will improve the mixing time in combined blowing processes.

Ans- In the combined steel making process, O2 required to refine the steel is blown through the top mounted lance
while the inert gas (N2 or Ar) needed for the bottom stirring process is introduced into the melt through bottom
stirring bricks for improving the process conditions by optimized mixing. The flow rate and type of stirring gas
depends on the process phase and steel grade. A faster and better approaching of the metal slag equilibrium is
achieved because of the bottom stirring. Equilibrium and mixing time depend on type, number, location of stirrers,
and flow rate. Stronger stirring shifts the thermodynamic equilibrium to the desired direction and reduces the mixing
time. A shift-over from N2 to Ar is normally required, depending on the final steel chemistry. The valve station as the
central part of the bottom stirring system allows individual flow control per individual purging plug.

Like in the top blowing process, O2 is injected through multi holes lance to the molten steel bath in the combined
blowing process. The metal droplets are generated as a result of jet impact and the shearing action of the gas flow
from the impact region where the jet strikes the metal surface and the gases are deflected upwards. This effect of jet
liquid interaction is described in terms of three modes namely (i) dimpling, (ii) splashing, and (iii) penetrating.

The amount of iron droplets splashed into the gas and the slag influences metallic yield, refractory wear and the
progress of decarburization. There is an effect of gas and liquid properties on the depth of depression of the bath
and the critical depth marks the onset of splashing. The splashing increases up to a certain jet momentum beyond
which it decreases. The direction of splashes is dependent on lance nozzle angle, lance height, profile of the jet cavity
estimated from its depth and diameter and overlap of the O2 jet.

Many experiments have been carried out to modify the lance tips in order to control splashing or spitting in the BOF
converter. The importance of proper design of nozzle diameters and inclination angles is necessary for an optimum
pressure distribution of the O2 jet. Different studies have shown that the top blowing with bottom stirring of the
converter bath gives superior performance than only the top blowing in BOF converter with respect to splashing and
spitting.

Q.4 Is it possible to remove phosphorous and carbon together in LD process, how?

Ans- LD slag is one of the highest produced wastesfrom different steelmaking industries.It can be reused in the blast
furnace as flux due to its high calcium content, but the high phosphorus content restricts its use. Therefore,
phosphorus removal from LD slag is necessary to make it more valuable. Phosphorus removal from LD slag is
one of the applications in the mineral biotechnology. Several microorganisms are known to help in dissolving the
insoluble inorganic phosphate so that both dissolved phosphorus and slag residue have valuable usage. These are
known as Phosphorus Solubilizing Microorganism (PSM). They are including bacteria (Pseudomonas, Bacillus,
Erwinia, etc.), Fungal (Aspergillus, Penicillium, Fusarium, etc.), yeast, and actinomycetes species. They convert the
unavailable phosphate to its dissolved form through different acid formation, chelation and H 2S generation removal
of phosphorus from LD slag is an important method. In the industrial biotechnology microbial removal of
phosphate from the LD slag is a promising method. In the agriculture industries, phosphorus is an essential
nutrient for the growth of crops and plants. Conversion of unavailable form of inorganic phosphate to its available
form is being carried out by microbial action in the natural environment. It was found that the temperature of the
bath gradually rises from 1250–1450°C initially to about 1600–1680°C at the end of the blow essentially because of
exothermic oxidation of Si, C and Fe. Silicon dissolved in iron gets eliminated in the form of silica right from the start
of the blow. Silicon is the first element to get oxidised owing to the much higher stability of SiO2 as compared to the
other oxides. To make sure that this silica is assimilated in the slag as soon as it is formed (otherwise it would attack
the basic vessel lining), lime addition is also begun right from the start of the blow. Once silicon is removed,
oxidation of carbon dissolved in the bath to CO starts and continues almost throughout the blow. Significant removal
of phosphorus occurs primarily towards the end of the blow.

Q.5. Dephosphorization and decarburization are not possible together in basic Bessemer processes but it
is possible in LD processes why?

Ans- A major limitation of the process, however, was that it could not remove sulphur and phosphorus
present in hot metal. These harmful impurities often caused fractures during hot working of the products
(known as hot shortness). The oxygen content of Bessemer steel was also inordinately high. In 1864,
Mushet found that deoxidation of liquid steel using ferromanganese after tapping into a ladle, lowered the
oxygen level. This also increased the Mn content of steel, which contributed towards preventing hot
shortness arising from high levels of sulphur. As far as phosphorus was concerned, in the original Bessemer
process, hot metal made only from low phosphorus Swedish iron ores was refined. In spite of these
shortcomings, the acid Bessemer process was predominant up to around 1910. The phosphorus issue was
tackled following the invention of the Thomas process by Sidney G. Thomas in England in 1879. The basic
Bessemer process or the Thomas process involved the use of a basic oxide (burnt dolomite or magnesite)
lining in the vessel. Basic oxides (e.g. CaO) as flux were added during the blow to form a basic slag of high
CaO content. This type of basic slag was capable of removing phosphorus in the form of calcium
phosphate. This allowed production of steel with acceptable levels of phosphorus even from hot metal
containing medium-to-high phosphorus

In case of the LD furnaces phosphorus partition (LP) between slag and metal at converter turndown for
large number of heats at Tata Steel for each tuyere arrangement. Theratio RP, as defined below, was
employed for assessment.

At slag–metal phosphorus equilibrium, LP = LP (at equilibrium), and RP = 1. If kineticlimitations

do not allow attainment of equilibrium, then RP is lower than 1. RP as function of turndown temperature
for various tuyere arrangements. Since the turndown slag contains some undissolved lime particles and
this is not determined in routine slag analysis data, two values of free lime, viz. 0% and 10%, were
assumed. that with better mixing by change of tuyere arrangements, RP values increased, i.e.
dephosphorisation was more efficient. These findings also are in conformity with evidences cited earlier.
Q.6. What do you mean by active and inactive sites in the removal of carbon from the melt?

Ans- As the carbon level is lowered in liquid steel, the level of dissolved oxygen theoretically increases
according to the relationship %C × %O = 0.0025. This means that, for instance, a steel with 0.1 percent
carbon, at equilibrium, contains about 0.025 percent, or 250 parts per million, dissolved oxygen. The level
of dissolved oxygen in liquid steel must be lowered because oxygen reacts with carbon during solidification
and forms carbon monoxide and blowholes in the cast. This reaction can start earlier, too, resulting in a
dangerous carbon monoxide boil in the ladle. In addition, a high oxygen level creates many oxide inclusions
that are harmful for most steel products. Carbon oxidation is a heterogeneous reaction at the solid surface,
since Tb>Ti. The carbon surface absorbs oxygen molecules and desorbs CO or CO2. Surface oxidation
reactions produce CO or CO2, a reduction reaction produces CO, and a CO volume reaction produces CO2

Q.7. Why Mn reversion will takes place in LD convertor during refining of Steel? Explain with suitable
reason.

Ans- The invention relates to the refining of steel and has particular reference to the refining of steel by a
process in which a stream of hot gases is directed onto the upper surface thereof. The invention
particularly provides for a method of controlling the manganese content of the melt at turn-down of a
steel refining process by at least a two stage process in which the refining is carried out using a gas stream
comprising the products of combustion of a fuel and uncombined oxygen by varying the proportions of
combustion products to uncombined oxygen in a first stage in which the gas stream is relatively poor in
uncombined oxygen and in a subsequent or second stage in which the gas stage is relatively rich in
uncombined oxygen and varying the duration of the first stage so that with a relatively long first stage a
low manganese reversion is obtained and by providing a relatively short first stage a high manganese
reversion to the melt at turn-down is obtained.
[Mn] + [O] ↔ (MnO) .....(8)

[Mn] + (FeO) ↔ (MnO) + Fe .....(9)

Initially, the bath manganese level falls as a result of oxidation, but later, a slightly reversion, followed by a
second fall occurs. These changes in the manganese content of the bath are attributed to the combined
effects of rising temperature and variable slag composition, on the activities of manganese and ferrous
oxides, suggesting that the reaction is close equilibrium. This view is supported by the observation that at
the end of blowing, the manganese content was found to be 82% of the equilibrium value when lump lime
was used and 85% of the equilibrium value when powdered lime is injected

Q.8. What JFN number? Explain the term super sonic region, subsonic core, and potential core ,show
with a suitable diagram.

Ans- JFN number- The Mach Number can be as high as 2.5, when the Supersonic Jet emerges from the nozzle. In the
potential core (length three to seven times nozzle diameter), the velocity is constant. Then the jet starts entraining
the surrounding fluid (in this case, the gaseous converter atmosphere). This Jet Entrainment causes lateral expansion
of the jet and decreases the jet velocity to make it finally subsonic. Beyond a distance about 25–30 nozzle diameters,
the supersonic jet becomes fully subsonic

The jet ultimately impinges on the liquid metal bath surface to form a cavity. The impingement of the jet and the
dissipation of the jet momentum causes circulation of the liquid bath in the upward direction at the vessel central
axis. The intensity of jet-bath interaction is expressed in terms of the Jet Force Number (JFN) defined as:

Gas pressure ( pd ) × Nozzlediameter ( dn)

JFN =
Lance height ( L)

where L, the height of the lance tip above the bath surface, is a key operating variable in the BOF process. With
changing JFN (say, by changing L), the following behaviour of the liquid bath at the impact zone has been observed.
At low JFN, dimpling with a slight surface depression . At medium to high JFN, splashing with a shallow depression .
At high JFN, penetrating mode of cavity with reduction in splashing.

In the steelmaking by basic oxygen furnace (BOF), the removal of impurities such as carbon, silicon, manganese, and
phosphorus etc. is carried out by oxidizing them with high purity oxygen (O2).  For this purpose, a water-cooled lance
is used for the injection of a high velocity stream of O2 onto the molten bath. The velocity or momentum of the O2
jet results in the penetration of the slag and metal to promote oxidation reactions over a relatively small area. The
most important part of the lance is the nozzle. The functions of the nozzle are (i) supply and distribution of O2, (ii)
production of a gaseous jet, (iii) induce bath agitation, and (iv) produce metal droplets. The jet velocity and
penetration characteristics are functions of the nozzle design.

Lance nozzle has a convergent-divergent (CD) design. The CD nozzle is also known as laval nozzle and is
characterized by a flow passage whose cross sectional area decreases in the direction of the flow, attains a minimum
cross section area and then increases further in flow direction. The minimum cross section area of the flow passage
is called the throat of the nozzle. The CD nozzle design helps in accelerating the gas velocity to the supersonic
velocities. The gas flow jet is sub-divided into potential core, supersonic, and subsonic regions. Within the core
region, the velocity is constant. At the end of supersonic region the velocity becomes Mach 1. Downstream the
velocity is sub sonic. The jet interacts with the converter environment and produces a region of turbulent mixing.
The entrainment process increases the mass flow rate and the jet diameter and decreases the mean axial velocity as
the distance from the nozzle exit increases. The impact force on the slag melt surface is reduced with increasing
lance height. The jet length and the spreading angle are affected by the gas temperature and pressure as well
condition of metal slag mix in the converter. A supersonic core remains for a certain distance from the nozzle.
Supersonic jets spread at an angle of around 10 degrees to 14 degrees.

Q.9. How multi nozzle lances are superior than single nozzle lances in LD process?

Ans- The lance tips can have either (i) single hole, or (ii) multiple holes. In a single hole lance tip the design
of the laval type lance tip nozzle is simple. It comprises of contracting section, throat opening, and
expanding section. At the throat section, which is at the inter section of the contracting and expanding
sections, the cross section area is smallest. Throat opening diameter is the critical diameter and the area at
the throat is the critical area. Presently single hole lance tips are no more under use.

Multi holes lance tips are most popular in converter steelmaking these days. In case of these lances, the
lance tips can contain from three number laval type nozzles to nine number laval type nozzles. These
lances are at angle to centre line of the lance. Four holes to six holes lances are more popular. These lances
produce multiple strand supersonic jet at the nozzle outlet. Metallurgical process performance of these
lance tips is very superior. However manufacturing of these lance tips is more complex. Normally
components of these lance tips are manufactured separately and then assembled and welded. In this way
the manufacturing is easy, dimensions are accurate and the operating performance is good. However for
longer life of these nozzles, the high temperature of steels is to be avoided, there is to be good slagging
and low position blowing is to be avoided. The important parameters in the design of multi holes lance tips
are (i) O2 flow rate, (i) theoretical pressure of O2, (iii) Mach number of nozzle outlet, (iv) nozzle angle and
spacing, (v) expanding section and length of expanding section, (vi) throat opening section dimensions, and
(vii) dimensions of contracting section .In the 1950s when the top blown converter size was limited to 50 t
maximum then a single hole lance nozzle was being used for the blowing of the O2. With the passage of
time the converter size went on increasing. This has necessitated increase of number of holes in the lance
nozzle for better distribution of O2 over a larger surface of the bath in the converter. Presently 5 holes to 6
holes lances are very common. Even 8 holes lances are under use
Q.10. Why cold pig iron is not preferably charged in LD furnaces as a raw material but scrap and ore can
be charged as a raw material?

Ans- Scrap, cold pig, iron ore, manganese ore, and hot metal are used as charge in open hearth furnaces.
The proportion of the solid charge consisting especially of scrap (in various forms) is seldom less than 70%,
and a lot of time (at least 3–4 hours) is consumed in the process of charging and melting these solids. In
fact, in any open hearth shop, extensive stock yard facilities have to be provided for scrap storage in large
heaps. When oxygen contacts blast-furnace iron, a great amount of heat is released by the ensuing
exothermic reactions, especially the oxidation of silicon to silica, so that using only blast-furnace iron would
result in a liquid steel temperature too high for casting. Therefore, before the hot metal is added, a specific
amount of scrap is charged into the furnace. Melting this scrap consumes about 340 kilocalories per
kilogram, effectively cooling the process.

A typical BOP charge, therefore, consists of about 75 percent liquid iron and 25 percent scrap.
This requires a reliable supply of low-cost iron with a uniform chemical composition, which is attainable
only by keeping the operating condition of a blast furnace as constant as possible; this in turn requires a
consistent iron consumer. There are also certain iron properties—for example, the silicon and sulfur
content—that are selected to optimize the blast furnace and BOF operations and to produce steel at
minimal cost. Such interdependence requires that blast furnaces and BOFs work within a well-integrated
operating system.

Q.11. What is secondary steel making write its importance to improve the quality of Steel?

Ans- Secondary steelmaking has become an integral feature of virtually all modern steel plants. The advent of the
continuous casting process, which requires stringent quality control is one of the main reasons for the growth of
secondary steelmaking. The harmful impurities in steel include: sulphur, phosphorus, oxygen, nitrogen and
hydrogen. The latter three elements occupy interstitial sites in the iron lattice and hence, are known as interstitials.
The principal effect of these impurities in steel is loss of ductility, lower impact strength and poorer corrosion
resistance. Once refining of the molten metal bath in the furnace is completed, liquid steel is tapped into a ladle.
Earlier, the only operations carried out in the ladle were deoxidation by ferromanganese, ferrosilicon, etc. followed
by minor alloying additions. In the last fifty years, the situation has changed dramatically. At present, the ladle is
used as a reactor (rather than as a containing vessel) where a variety of secondary processing of liquid steel is carried
out. This includes: degassing, desulphurisation, reheating, etc. as well as deoxidation. All these unit processes can be
grouped into the broad category of secondary steelmaking. Without resorting to secondary steelmaking, it is not
possible to produce all the sophisticated qualities of steel in use today. With secondary steelmaking having become a
standard feature of modern steel plants, BOS and EAF steelmaking are now classified as primary steelmaking
processes

Q.12. Describe metallurgical superiority of continuous cast product over ingot cast product

Ans- Even though ingot casting of steel is now not extensively practised, this separate chapter is being included in
this book for some important reasons. Except for steel cast in foundries, ingot casting was the only method of casting
steel for more than 100 years, till the advent of continuous casting. Therefore, extensive investigations and studies
have been made on the science and technology of solidification processing, with major emphasis on ingot casting of
steel as well as other metals and alloys. This has without doubt contributed significantly towards the present day
understanding of the physicochemical phenomena during freezing of liquids, and has laid the foundation for the
growth of the continuous casting process. Therefore, some coverage of ingot casting is required, without which
knowledge of casting will be incomplete. Ingot moulds are made of cast iron, having various cross sections such as
square, round, polygonal, etc. depending on the end-use of the product. There are various mould designs,
such as:Narrow-end-up, or wide-end-up

Open bottom, closed bottom, or plugged bottom With, or without hot top.

In most practices, pouring of liquid steel is done from the top. Bottom pouring, i.e. feeding
the mould through a bottom opening, is practised only in special cases where ultra pure cast products are required.
Cast iron moulds have an advantage since the coefficient of thermal expansion of cast iron is different from that of
steel. Upon cooling, steel contracts more than the cast iron mould, which assists detachment. The conical shape of
the moulds facilitates pulling-out of only the mould by a stripping crane, thus separating the mould from the
solidified ingot. In this context, the narrow-end-up mould is the most convenient

The advantages of continuous casting (over ingot casting) are:

It is directly possible to cast blooms, slabs and billets*, thus eliminating blooming, slabbing mills completely, and
billet mills to a large extent.

Better quality of the cast product.

Higher crude-to-finished steel yield (about 10 to 20% more than ingot casting).

Higher extent of automation and process control.

Better consistency in the quality of the cast products and higher productivity are other advantages of continuous
casting over ingot casting. All these advantages have contributed to substantial savings of capital and operating costs
per tonne of steel. The capital cost is lower since less equipment is involved and the cast product is closer to the final
product; the operating cost savings arise out of lower manpower and energy as well as higher yield. Henry Bessemer
first propagated the concept of continuous casting of steel in 1846. However, it took more than hundred years to
make continuous casting a reality. It was initially successful in casting non-ferrous metals in the 1930s. However, it
was more difficult to apply it to steel because of the higher melting temperature and lower thermal conductivity. The
first pilot plant for continuous casting of steel was installed in Germany in 194

Q.13. write short notes on the followings

1. AOD process- Argon–Oxygen Decarburisation. The process was patented by the Industrial Gases Division of the
Union Carbide Corporation (now known as Praxair Inc.). In an AOD converter, argon is used to dilute the other
gaseous species (O2, CO, etc.). Hence, in some literature, it is designated as Dilution Refining Process. After AOD,
some other dilution refining processes have been developed. Lowering of the partial pressures, such as the partial
pressure of carbon monoxide, is achieved either by argon or by employing vacuum. The combination of EAF and AOD
is sufficient for producing ordinary grades of stainless steels and this combination is referred to as a Duplex Process.
Subsequent minor refining, temperature and composition adjustments, if required, can be undertaken in a ladle
furnace. Triplex refining, where electric arc furnace melting and converter refining are followed by refining in a
vacuum system, is often desirable when the final product requires very low carbon and nitrogen levels. About 65–
70% of the world’s total production of stainless steel is in the austenitic variety,made by the duplex EAF–AOD route.
If the use of AOD converters even in the triplex route is included, the share of AOD in world production would
become as high as 75–80%.

2. VOD process- Vacuum-oxygen decarburisation (VOD) where oxygen lancing is done under vacuum was originally
developed for stainless steel refining, but is now used for the production of ultra-low carbon steels (ULC) as well.
Similarly, RH–OB, where oxygen is blown into the RH chamber, is used for the production of ULC steels. Besides
degassing and decarburisation, modern vacuum degassers are used to carry out various other functions such as
desulphurisation, heating, alloying and melt homogenisation. Injection of argon below the melt is a must for good
homogenisation, fast processing and inclusion removal. The carry over slag from steelmaking converters has to be
modified by the addition of deoxidisers and CaO.
3. MRP process

4. CLU process

5. VAR process

6. Injection metallurgy- IM is practised in secondary steelmaking not only for the removal of sulphur from metal,
but also for inclusion modification. In Chapter 16, the description of IM processes has already been presented and
hence, will not be repeated. The processes may be broadly classified into the following two categories:

1. Continuous injection of solid powdered reagents into molten steel along with a stream of argon, through a lance
immersed from the top.

2. Continuous injection (i.e. feeding) of powdered regents, encased in a steel tube immersed inside molten steel.
This is known as Cored Wire Feeding.

Q.14. Discuss the importance of tundish in continuous casting processes. Is it possible to cast steel
without tundish give suitable reason?

Ans- The tundish is a shallow, refractory-lined vessel that is located in between the ladle and the
continuous casting mould. Liquid steel flows from the ladle into the tundish and from the tundish into the
mould. A tundish is a must in continuous casting for proper regulation of the rate of flow into the mould. A
detailed description of the tundish and its metallurgical aspects will be taken up in. At this juncture, it will
suffice to state that proper design and operational control of the tundish is extremely important for the
final cleanliness of steel. It is worth mentioning here that proper metallurgical control is required even in
the casting mould (both for continuous as well as for ingot casting) to ensure meticulous fine control of
steel cleanliness.
Q.15. Write the main points to be considered in a stainless steel making by electric Arc furnace.

Ans- The process of electric arc furnace steelmaking is about 100 years old .Through decades of efforts till
about 1970, electric furnace steelmaking practices got significantly standardised. This is what is denoted by
the term conventional—it is practised even now in smaller and relatively older units.EAF steelmaking
involves most of those stages, with the exception of the following:

Hot metal is not used in conventional practice

The refining and finishing practices differ widely.

The basic purpose of refining in EAFs is two-fold:

Removal of undesirable impurities (C, Si, P, S, N, H, etc.)

Finishing the bath so as to ensure maximum alloy recovery. The reactions in primary steelmaking and their
physicochemical aspects. the reactions of silicon and sulphur, and hence need not be repeated. EAFs
produce a wide variety of steels. Therefore, depending on the type of the solid metallic charge and the
grade of steel to be produced, the refining practice differs considerably

1.Since EAF steelmaking is primarily scrap/DRI based and both these materials have relatively low levels of
residual impurities, the extent of refining is much less than in BOH steelmaking.
2. As a process, EAF is far more versatile than BOH and can make a wide range of steel grades.

3. Sorting out of scrap and choosing the proper scrap grade are important for EAF steelmaking, since the
extent of refining has to be managed accordingly. For this purpose, scrap may be classified into the
following categories:

(a) scrap containing clements that cannot be removed by oxidation during refining, such as Cu, Ni, Sn, Mo,
W, etc.

(b) scrap containing partially oxidisable elements, such as P, Mn , Cr, etc.

(c) scrap containing completely oxidisable elements, such as Al, Si, Ti, V, Zr, etc.

(d) scrap containing volatile elements, such as Zn, Cd, Pb, etc. Scrap of type (b) and (c) can be tackled easily
during refining. Type (d) scrap would require some special attention. However, type (a) scrap gives rise to
problems like undesirable residuals in the final steel. This is where DRI scores over scrap—it is totally free
from all the above undesirable element

Q.16. Write the main points to be considered in a stainless steel making by electric Arc furnace.

Ans- The process of electric arc furnace steelmaking is about 100 years old .Through decades of efforts till
about 1970, electric furnace steelmaking practices got significantly standardised. This is what is denoted by
the term conventional—it is practised even now in smaller and relatively older units.EAF steelmaking
involves most of those stages, with the exception of the following:

Hot metal is not used in conventional practice

The refining and finishing practices differ widely.

The basic purpose of refining in EAFs is two-fold:

Removal of undesirable impurities (C, Si, P, S, N, H, etc.)

Finishing the bath so as to ensure maximum alloy recovery. The reactions in primary steelmaking and their
physicochemical aspects. the reactions of silicon and sulphur, and hence need not be repeated. EAFs
produce a wide variety of steels. Therefore, depending on the type of the solid metallic charge and the
grade of steel to be produced, the refining practice differs considerably

1.Since EAF steelmaking is primarily scrap/DRI based and both these materials have relatively low levels of
residual impurities, the extent of refining is much less than in BOH steelmaking.

2. As a process, EAF is far more versatile than BOH and can make a wide range of steel grades.

3. Sorting out of scrap and choosing the proper scrap grade are important for EAF steelmaking, since the
extent of refining has to be managed accordingly. For this purpose, scrap may be classified into the
following categories:

(a) scrap containing clements that cannot be removed by oxidation during refining, such as Cu, Ni, Sn, Mo,
W, etc.

(b) scrap containing partially oxidisable elements, such as P, Mn , Cr, etc.

(c) scrap containing completely oxidisable elements, such as Al, Si, Ti, V, Zr, etc.
(d) scrap containing volatile elements, such as Zn, Cd, Pb, etc. Scrap of type (b) and (c) can be tackled easily
during refining. Type (d) scrap would require some special attention. However, type (a) scrap gives rise to
problems like undesirable residuals in the final steel. This is where DRI scores over scrap—it is totally free
from all the above undesirable element