Ferroalloys_Fundamentals.pptx

Ferroalloys, 4th Year_Students, Metallurg. & Mater. Eng Dept, Essam Ahmed, Dr Eng
Faculty of Petroleum and Mining Engineering
Suez University
1
Ferroalloys
4th Year Students, Metallurgical and Materials
Engineering Department, 2020/2021
Essam Ahmed, Dr. Eng.
essam.ahmed@suezuniv.edu.eg

Suez University
2
Ferroalloys:
Definitions & Fundamentala
Part One

Suez University
3
Flashback
 Alloys?
 Ferrous- vs. non Ferrous- alloys?
 Alloying Elements in Steels?
 Ferroalloys _ Egypt/Arab Market?

Suez University
4
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

Suez University
5
1. Fundamentals

Suez University
6
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

Suez University
7
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.

Suez University
8
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

Suez University
9
1.2 Utilization of ferroalloys
• Ferroalloys are usually used by the steelmaker for two
main purposes:-
1. Deoxidation of steel
2. Alloying of steel

Suez University
10
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.

Suez University
11
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

Suez University
12
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)

Suez University
13
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.

Suez University
14
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

Suez University
15
- need long time
- slag phase must be free from phosphorus oxide
+ clean metal free from (N.M.I.)

Suez University
16
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

Suez University
17
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

Suez University
18
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

Suez University
19
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

Suez University
20
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.)

Suez University
21
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

Suez University
22
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)

Suez University
23
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

Suez University
24
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

Suez University
25
1.4.2 According to the reducing agent used
1.4.2.1 Carbon
1.4.2.2 Silicon
1.4.2.3 Aluminum

Suez University
26
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.)

Suez University
27
1.4.4. According to the quantity of slag
formed
1.4.4.1 Slag process
1.4.4.2 Slagless process

Suez University
28
1.4.5. According to the using of fluxes
1.4.5.1 with flux
1.4.5.2 Fluxless

Suez University
29
1.4.6. According to type of furnaces
1.4.6.1 Ore-reducing furnaces
1.4.6.2 Refining furnaces

Suez University
30
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

Suez University
31
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

Suez University
32
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)

Suez University
33
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)

Suez University
34

Suez University
35
If element forms several oxides with oxygen as in Fig. 2

Suez University
36
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.

Suez University
37
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)

Suez University
38
1.6.2. Carbon
MeO + 2C  MeC + CO
MeC + MeO (under vacuum)  2Me + CO

Suez University
39
1.6.2.2 Silicon

Suez University
40
1.6.2.3 Aluminum

Suez University
41
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:

Suez University
42
* 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

Suez University
43
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

Suez University
44
1.7 Metal recovery
1.7.1.2 For the exothermic reactions
* The decreasing of T help the considered reaction to takes place

Suez University
45

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:

Suez University
46
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.

Suez University
47
1.7 Metal recovery
1.7.2.1 Composition of slag phase ( Ch. %)
Excessive addition of fluxes = increase the amount of the sla
1. more power consumption to heat and melt this large amou
2. more losses for leading oxides and element
3. more attack for the lining of the furnace i.e. decrease of
the lining life

Suez University
48
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)

Suez University
49
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)

Suez University
50
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)

Suez University
51
END

Suez University
52
Fe-Si Alloys
Next Lecture title

Suez University
53
“END”
THANKS FOR YOUR ATTENTION

Ferroalloys_Fundamentals.pptx

Recommended

Recommended

More Related Content

Similar to Ferroalloys_Fundamentals.pptx

Similar to Ferroalloys_Fundamentals.pptx (20)

Recently uploaded

Recently uploaded (20)

Ferroalloys_Fundamentals.pptx