lecture 120310 steel 01 thermodynamics-of-steelmaking jhlee
TRANSCRIPT
8/13/2019 Lecture 120310 Steel 01 Thermodynamics-Of-Steelmaking JHLEE
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Thermodynamics of SteelmakingAn Introduction
Prof. Joonho Lee, Korea University
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8/13/2019 Lecture 120310 Steel 01 Thermodynamics-Of-Steelmaking JHLEE
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What is Steelmaking? Steelmaking is composed of
“Basic Oxygen Steelmaking” and“Secondary Steelmaking”.
What are they?
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WHAT IS
BASIC OXYGENSTEELMAKING?
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Basic Oxygen Steelmaking The purpose of the Basic Oxygen Steelmaking
(BOS) is to refine the hot metal produced inthe blast furnace into raw liquid steel, which
may be subsequently refined in the secondary
steelmaking shop.
%C %Mn %Si %P %S %OTemp.
/ oC
Hot
metal4.7 0.2-0.3 0.2-1.5 0.06-0.12 0.02 0.0
1350-
1400
Steel 0.05 0.1 0.0 0.01-0.02 0.01-0.02 0.061620-
1720
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History of Steelmaking
Bessemer (1850):air blowing
Thomas (1879):basic (dolomitic)
lining and a basic
flux
At Linz and Donawitz
in Austria (1879):
oxygen blowing
Bottom blow oxygen
steelmaking process
(1970s): tuyeres wereprotected by propane
or natural gas, or fuel-
oil
Mixed blowing process
(late 1970s): Ar or N2
blowing from bottom
Hot metal
dephosphorization in
Japan (early 1980s):
adding CaO and iron
ore mixtures
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BOF Facilities
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BOF Operation
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Oxidation Degree in Steelmaking
Iron oxide
De-O
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WHAT IS
SECONDARYSTEELMAKING?
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Solubility of Oxygen0.2 wt% O in liquid
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Impurities? Carbon comes from cokes and refractory
Sulfur comes from cokes Phosphorus comes from iron ore
Nitrogen comes from atmosphere Hydrogen comes from water vapor
Oxygen comes from steelmaking
As the quality of resources decreases, the
amount of impurities increases!
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Tolerable Maximum Inclusion Sizes
and Impurity Elements
(Emi,
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Efforts to decrease impurities
(After Sasabe)
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Typical Facilities for Secondary Refining
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Function of Secondary Refining
Process
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Process Integration for Clean Steel
Production
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THERMODYNAMICS OF
LIQUID STEEL FORDEOXIDATION
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Activity
ii X a ii X a
iii X a ii X a
1i
iii X a
1i
iii X a
1i
ii X a
Solutions
Two different types of solutions
Ideal solutions Non-ideal solutions
Two different typesRaoult’s law
Positive deviation Negative deviation
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Henrian Standard
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1 wt% Standard
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Mole Fraction vs. wt%
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Henrian vs. 1 wt% Standards
For further study, see “Chemical Thermodynamics for Metals and Materials” by
Prof. Hae-Geon Lee (1999)
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Interaction Coefficients
B B B
X f a
A-B solution
B
B B f f
A-B-C solution
C
B
B
B B f f f
A-B-C-D solution
D
B
C
B
B
B B f f f f
D
B
C
B
B
B B f f f f
In general
D
B
C
B
B
B B f f f f lnlnlnln
Taylor-series
000
lnlnlnln
DC B X D
D D
X C
C C
X B
B B B
X
f X
X
f X
X
f X f
D
D
BC
C
B B
B
B B X X X f ln
0
ln
j X j
i j
i X
f
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Interaction Coeff. for 1 wt% Std.
)%()%()%(log Dwt eC wt e Bwt e f D
B
C
B
B
B B
A
B
B
A
A
B
B
A B
A e M
M
e
B
A
B
S B
A
M
M e
3.230
where A, B: solutes, S: solvent
For further study, see “Steelmaking Data Sourcebook” by JSPS 19th committee on
Steelmaking (1984) & “Fundamentals of Steelmaking Metallurgy” by Brahma
Deo & Rob Boom (1993)
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Oxygen in Steel (Case Study)Fe(l) + O = FeO(s)
2Al + 3O = Al2O3(s)
K =aFeO
hO aFe
K =a
Al2O3
hAl2 hO
3
At a given temperature and for known slag
activity data, the value of hO can be calculated.From the activity of Al2O3, the value of hAl can
be calculaed.
Log hAl = log[wt%Al] + eAlAl [wt%Al] + eAl
C [wt%C] + eAlO [wt%O]
Log hO = log[wt%O] + eOAl [wt%Al] + eO
C [wt%C] + eOO [wt%O]
For a fixed value of [wt%C], it is possible to solve [wt%Al] and [wt%O].
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Deoxidation Equilibrium
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THERMODYNAMICS OF
SLAG FOR STEELREFINING
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Classification of Oxides
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Acid Oxide: Silicate
(Karpoor & Frohberg, 1970)
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How to Change the Silicate Structure?
(Waseda, 1980)
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Addition of Basic Oxide
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Basicity, Activity of Oxygen Ion
B = log aO2-
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Capacity Concept Carbonate capacity (Wagner)
2322 COOCO
223
2
23
)%( 2
3
COCO
O
CO p
COmass
f
aK C
*23
23
CO
CO
CarbonC
C B
Carbonate capacity in a reference slag
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Sulfide Capacity
2
22
2 2
1
2
1
OS OS
2/1
2
2
2
2
2
2 )%(
S
O
S
O
S p
p
S mass f
aK
C
*2
2
S
S
Sulfur
C
C B
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INCLUSIONS
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Investigation of Inclusions
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Origin & Cause of Macro Inclusions
Small spherical inclusion Octahedral inclusion
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Small spherical inclusion Octahedral inclusion
Small polyhedral inclusion Large polyhedral inclusion
a ter Dekkers 2002
Plate like inclusion Dendrite
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Plate like inclusion
Cluster Aggregate
a ter Dekkers 2002
Formation of dendrite tips during secondary metaluurgy Overgrowth during secondary metallurgy
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Formation of dendrite tips during secondary metaluurgy Overgrowth during secondary metallurgy
Cluster from tundish Cluster from clogging materials
a ter Dekkers 2002
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Morphology of Alumina Inclusions
after Dekkers, 2002
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Tundish Configuration
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SEN(Submerged
Entry Nozzle)
M
o u l d
Tundish
Mould FluxLiquid Slag
SEN Clogging
(Building up of
Inclusions)
Alumina Inclusions
Nozzle Clogging
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Alumina Inclusions at SEN
after Dekkers, 2002
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Clustering of Alumina Inclusions
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Steel Evolution Never Stop!
Fig. History of the development of cold rolled deep drawing steel sheet (after Emi)
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Concluding Remarks
Crystal growth & Solidification theory
Mechanism of materials at high temp.
Physical Properties (statistical mechanism)
Thermodynamics (statistical thermodynamics)
Reaction kinetics
Heat and mass transferFluid dynamics
Smelting and refining
technology
Phys. & math. Modeling
Computer simulation
Casting & solidification
technology
JFE 21st Foundation