1+2+3_Ferroalloys_Fundamentals_2020.pdf

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Ferroalloys, 4th Year_Students, Metallurg. Eng Dept, 2019/2020, Essam Ahmed, Dr Eng
Faculty of Petroleum and Mining Engineering
Suez University
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Ferroalloys
@ 17.03.2020
@ 24.03.2020
@ 31.03.2020
4th Year Students, Metallurgical and Materials
Engineering Department, 2019/2020
Dr. Eng. Essam Ahmed
essam.ahmed@suezuniv.edu.eg
Suez University
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Ferroalloys:
Definitions & Fundamentala
@17.03.2020
Part One

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Flashback @10.03.2020
 Alloys?
 Ferrous- vs. non Ferrous- alloys?
 Alloying Elements in Steels?
 Ferroalloys _ Egypt/Arab Market?
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Part One_Outlines
*. Ferroalloys: definitions
*. Fe-alloys vs. Pure metals
*. Fe-alloys Uses
*. Fe-alloys Classification
*. Reducing Agents in Fe-alloys Production
* . Physico-Chemicals in Fe-alloys

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1. Fundamentals
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Outlines_1. Fundamentals
1.1 Introduction
1.2 Utilization of Ferroalloys
1.3 Requirements needed from Ferroalloys
1.5 Physicochemical basis of oxides reduction during
manufacture of Ferroalloys
1.6 Selection of reducing agent
1.7 Metal recovery
1.8 Deoxidation power of Ferroalloys
1.4 Classification of Ferroalloys

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1.1 Introduction
• Definition of Ferroalloys
• Why Ferroalloys not pure metals?
Ferroalloys are alloys consisting of iron and other
specific elements such as Si, Mn, Cr, Ti, Mo, W, V
…etc.
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Why Ferroalloys not pure metals?
1. Simpler and cheaper than that of pure elements
2. Mn, Cr, Mo, W have higher specific gravity than
Fe,
3. Si and Ti have lower specific gravity than iron,
4. Cr, V, Mo and W have very high melting point
while their ferroalloys have much lower M.P

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1.2 Utilization of ferroalloys
• Ferroalloys are usually used by the steelmaker for two
main purposes:-
1. Deoxidation of steel
2. Alloying of steel
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1.2.1 Deoxidation of steel
Oxygen harmful effects:-
1. blowholes in the metal structure.
2. decrease the mechanical properties and enhance
the fatigue of the metal.
3. decrease the ductility of the metal.
4. cause the hot-shortness during the metal fabrication.
5. reduce the magnetic properties and electric
resistevity of metal.

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1.2.1 Deoxidation of steel
1.2.1.1 Deoxidation by diffusion (IR)
1.2.1.2 Deoxidation by precipitation (DR)
1.2.1.3 Deoxidation by synthetic slag
1.2.1.4 Vacuum deoxidation
1.2.1.5 Gaseous deoxidation or R.O.S.I. process
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1.2.1.1 Deoxidation by diffusion
extractive deoxidation or indirect deoxidation
Oxygen dissolves in both steel and slag.
Equilibrium between the two systems may be presented by
the equation:
[O] = (O)
The equilibrium constant of the reaction:
KFeO = a[O]/a(O)
or
a[O] = KFeO*a(O)

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Thus reduction of the oxygen activity (concentration) in steel
may be achieved by decreasing the oxygen activity in the slag.
When the oxygen activity in the slag is reduced oxygen ions
dissolved in steel begin to diffuse from the steel into the slag,
and the equilibrium conditions are restored. In other words,
deoxidation of slag results in deoxidation of the steel.
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This method relies on the idea that deoxidation of slag will
lead to the deoxidation of steel.
The chemical equilibrium equation used for this process is:
Reducing the activity in the slag will lower the oxygen
levels in the slag. Afterwards, oxygen will diffuse from
the steel into the lesser concentrated slag

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- need long time
- slag phase must be free from phosphorus oxide
+ clean metal free from (N.M.I.)
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1.2.1.2 Deoxidation by precipitation
or direct deoxidation
[FeO] + [R]  (RO) + Fe
* Adding the deoxidizer (in the form of big lumps) into the
liquid metal (bath). ” greater affinity for oxygen than iron“
+ very fast and need small time to take place
- the produced metal (after deoxidation) will contain some
quantities of N.M.I

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1.2.1.3 Deoxidation by synthetic slag
Use pre-prepared synthetic slag, which is free from FeO
[10% CaO, 5% MgO, 60% SiO2, 15% Al2O3, 10% Na2O]
This slag has low oxidizing ability and high ability to
dissolve FeO and oxides
+ very active and rapid process
- some quantities of the slag droplets will be trapped in the metal bulk
as N.M.I
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1.2.1.4 Vacuum deoxidation
This method based on decreasing the pressure on the metal
surface, by vacuum to 1-10-3 mmHg.
decrease the partial pressure of CO in the system
[O] + [C] → COg
KP = PCO / [C]. [O]
 [O] = PCO / [C]. Kp
- needs special care and needs complicated equipments
and high costs
+ very high quality steels free from N.M.I

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1.2.1.5 Gaseous deoxidation (R.O.S.I. )
suggested by Prof. M. Elzeky and others
based on the idea of blowing a reducing gas (H2 or coke gas
or mixture of them) from the bottom of the ladle
Ladle
+ Very fast and active process
+ Can reach to very deep level of deoxidation
+ Need no special or complicated equipments.
+ Very economic process
+ High quality steels and special steels can be treated
+ Produce metal free from any N.M.I.
H2 + [O]

{H2O}
H2 + [FeO]  {H2O} + Fe
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1.2.2 Alloying of steel
A classification of steels based on alloying
elements
• Low-alloy steels
• Medium –alloy steels
• High –alloy steels
A classification of steels can be according to their
use, based on their properties
• Structural steel (HSLA, low C st, .....)
• Tool steel (e.g. High C st. , W-St., .....)
• Special alloy steel (e.g. st. st.)

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1.2.2 Alloying of steel
Cast Irons (CI)
1. melting point and fluidity of cast iron
2. degree of graphitization + the size and shape of the graphite
particles
3. depth of the chill or the case with which white CI
4. grain size of the structure
5. machinability
6. strength, hardness, impact resistance
7. Heat and corrosion resistance
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1.3 Requirements needed from Fe-alloys
• high percentage of alloying element.
• low percentage of carbon content.
• low percentage of impurities such as P, S
• low content of N.M.I.
• the ferroalloys should not introduce excessive
amounts of gases especially H2 in the bath.
• suitable size of ferroalloys (not too small / big)

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1.4.1 According to the place of production
1.4.2 According to the reducing agent used
1.4.3 According to the method of production
1.4.4 According to the quantity of slag formed
1.4.5 According to the using of fluxes
1.4.6 According to type of furnaces
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1.4.1 According to the place of production
1.4.1.1 Blast furnace ferroalloys
1.4.1.2 Electric furnaces ferroalloys
1.4.1.3 Ex-Furnace ferroalloys

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1.4.2 According to the reducing agent used
1.4.2.1 Carbon
1.4.2.2 Silicon
1.4.2.3 Aluminum
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1.4.3. According to the method of production
1.4.3.1 Continuous process (e.g. Blast F.)
1.4.3.2 Periodic process (e.g. Electric A.F.)

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1.4.4. According to the quantity of slag
formed
1.4.4.1 Slag process
1.4.4.2 Slagless process
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1.4.5. According to the using of fluxes
1.4.5.1 with flux
1.4.5.2 Fluxless

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1.4.6. According to type of furnaces
1.4.6.1 Ore-reducing furnaces
1.4.6.2 Refining furnaces
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Physicochemical basis of oxides
reduction during manufacture of Fe-
alloys
1. Reduction reactions occurring on the boundary of
two phases (metal and slag)
2. Reactions proceeding in metal phase with the
formation of carbide, silicate, intermetalloide …etc.
(reaction between iron and reducing agent)
3. Reactions proceeding in slag phase with the
formation of different slag compounds

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1.5.1 Reduction reactions occurring on the boundary of
two phases (metal and slag)
2(MeO) + [Si] = 2[Me] + (SiO2)………………………… (1)
The equilibrium constant :
K1 = (a2
Me . aSiO2) / (a2
MeO . aSi)
aMe activity of metal (Me), aSiO2 activity of SiO2
aMeO activity of metal oxide (MeO), aSi activity of silicon
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1.5.2 Reactions proceeding in metal phase with the
formation of carbide, silicate, intermetalloide …etc.
(reaction between iron and reducing agent)
[Fe] + [Si] = [FeSi] ………………………………......(2)
The equilibrium constant is:
K2 = (aFeSi) / (aFe . aSi)

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1.5.3 Reactions proceeding in slag phase with the
formation of different slag compounds
2(MeO) + (SiO2) = 2(MeO.SiO2)……………………(3)
The equilibrium constant is:-
K3 = (a2
MeO . SiO2) / (a2
MeO . aSiO2)
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If element forms several oxides with oxygen as in Fig. 2
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1.6.1 The role of iron in ferroalloys production
MeO + R = Me + RO
Me + Fe = Me. Fe
* Iron oxides, as a role, are easier reduced as compared to
the majority of other oxides. Iron dissolves in the reduced
elements and decreasing their activities and therefore the
reduction process becomes easier.
* Iron dissolves the reduced element (Me) and takes it off
from the zone of reaction (prevents the backward reaction
and makes the system far from equilibrium.

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1.6.2 Reducing agents
1.6.2.1 Carbon
Main characteristics;-
1. one of the products of reaction is gaseous CO =
easily withdrawn from the reaction zone, =
the reduction reaction to occur to quite complete extent
2. the reduction by carbon is an endothermic reaction =
furnaces are usually needed to provide the required
external heat for occurring the reaction.
3. the reduction reaction will accompanied by carbide
ormation (alloys with high carbon content produced)
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1.6.2. Carbon
MeO + 2C  MeC + CO
MeC + MeO (under vacuum)  2Me + CO

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1.6.2.2 Silicon
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1.6.2.3 Aluminum

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1.7 Metal recovery
F = C + 2 – P
F is No. of degree of freedom
C is No. of components
2 is the external factors i.e. Temp. and pressure
P is No. of phases
* For any reaction , to determine the different factors which
may effect on this reaction by using the phase rule:
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* The Fe-X production processes are usually taken place at
the atmospheric pressure (i.e. at one atm.)
So for Fe-X production conditions
F = C + 1 - P
* For the general reduction reaction
(MeO) + [R] = [Me] + (RO)
C= 3 (???), P = 2 (slag + alloy), hence F = ?
1.7 Metal recovery

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1.7 Metal recovery
1.7.1 Effect of Temperature
1.7.1.1 For the endothermic reactions
High temperature is not desirable because:
* increase the energy consumption
* increase the attack of furnace lining (decrease lining life)
* increase the metal losses as a result of evaporation
increasing of T help the considered reaction to take place
But
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1.7 Metal recovery
1.7.1.2 For the exothermic reactions
* The decreasing of T help the considered reaction to takes place

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
F = - RT ln K = - 4.575 T log K ………….. (2)
..log K = - (F) / 4.575 T
log K = - (H) / (4.575 T) + (S) / 4.575
log K = A / T + B
MeO + R = Me + RO +

H
The free energy change for this reaction is:
F = H - TS …………………………………(1)
HT = H298 + CP dT
ST = S298 + CP/T dT
* The theoretical T of beginning of the reduction reactions:
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1.7 Metal recovery
1.7.2 Effect of phases composition
1.7.2.1 Composition of slag phase (1. T & 2. Ch. %)
1. The increasing of T leads to decrease the slag viscosity =
gives better chance for the slag components to interact with the
metallic phase components
2. The fluxes addition to the slag to give better chemical and
physical properties.

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1.7 Metal recovery
1.7.2.1 Composition of slag phase ( Ch. %)
Excessive addition of fluxes = increase the amount of the slag:
1. more power consumption to heat and melt this large amount
2. more losses for leading oxides and element
3. more attack for the lining of the furnace i.e. decrease of
the lining life
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1.7 Metal recovery
1.7.2.2 Composition of metallic phase
It is found that the recovery of the leading element from its
oxide increases with decreasing its percentage in the alloy (i.e.
decreasing its activity in the products which help the reduction
reaction to increase its completeness)

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Generally if R is the deoxidizer
X [R] + y [O] = z RO (s,l,g)
K = (az
RO) / (ax
[R] . ay
[O]
a[O] = {(az
RO) / (ax
[R] .K)}1/y ……….(1)
According to Henery’s law:
a[O] =  = %wt[O]
Supposing ideal behavior 
 = 1
 is activity coefficient and a[O]  %wt[O] ……………….(2)
[%O] = {(az
RO) / (ax
[R] .K)}1/y…….(3)
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1.8.1 Standard and real deoxidation power

a[O]st = [%O]st = {(az
RO) / (ax
[R] .K)}1/y…….(4)
a[O]r = a[O]st - (-a[O]s.s)
a[O]r = a[O]st + (a[O]s.s)……(5)
[%O]r  [%O]st
[%O]r = [%O]st + a[O]s.s ……(6)

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END
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Fe-Si Alloys
Next Lecture title

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“END”
THANKS FOR YOUR ATTENTION

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