Study of kinetics of Inclusions
Transformations in Ladle Metallurgical
Furnace for the Production of LCAK
Steels
Departmental Seminar
Presentation
Mahshid Fathi- May 27/2011
1

• Objectives
• Introduction
– Ladle Metallurgical Furnace
– Non Metallic Inclusions and Inclusion Engineering
• Literature Review:
– Role of slag on formation of spinels
• Experimental results
• Summary
• Future work
• Acknowledgement
2

Objectives
• Investigation of the impact of processing parameters on the kinetics of transformations of inclusions formed after deoxidation of the LCAK steels and during the Ca treatment in full scale
Industrial Ladle.
• Development of a mathematical model for the kinetics of inclusions transformations
– With focus on Spinels and calcium aluminates
• Validation of the model by experimental results.
3

Significant control challenges:
-Elevated temperatures
-Dusty environment
-Electrical arcing
-Complex multi component slag/metal systems
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• Oxides and sulfides
• Mostly oxides, deoxidation products
• By adding Al in LCAK steels
• Initially Al
2
O
3 oxide Particles
– High melting point, solid (above 2000C)
• Remain in the steel
• Degrade mechanical properties
• Cause problem in casting
6

• Calcium Treatment
• Adding calcium
– Lowered melting point
– Enhanced castability
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P.C. Pistorious, R.J. Fruehan, 2009
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Mass Transfer steps in steelmaking bath
• Assumption of equilibrium at the interface
• 1-Transfer of reactants from the metal phase to the slag/metal interface
• 2-Chemical reaction at the slag-metal interface (very fast in steelmaking T)
• 3-Transfer of products away from the slag metal interface
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Mass Transfer Metal- Inclusion
• Initial alumina inclusion content and size
• levels of Sulfur
• levels of Oxygen
• Calcium feed rates
• Presence of multiple pumping source of dissolving element as in MgO.Al2O3 spinels
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(shsh….it’s a bad word!)
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Al
2
O
3
.MgO Spinel inclusions
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Possible sources of dissolved Mg to form
Spinels:
Refractory
Alloying additions
Top slag
13

14

slag
Proces Time
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• Work based on the model of Robertson et al. (1984)
• Local equilibrium assumed at the slagmetal interface
• Generalized equilibrium reaction can be stated as: xM
 yO

M O y
[ Mn
 
MnO )
[ Ca
 
CaO )
[ Mg
 
MgO )
Slag
 
FeO )
Metal
[ ] [ ] ( SiO
2
)
[ ] [ ] ( TiO
2
)
2[ Al O Al O
3
)
(MnO)
[Mn] [O] where:
K
M a
 h
M x y h
O
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• System represented by series of differential equations:
Metal: dX dt i 


 i k A
V m




X i b 
X i
*
 Slag: dX i  
 i k A

 dt  V sl


X i
* 
X i b

• Reaction are coupled using flux density equations: k C
Vm

X b
M

X
*
M

 k sl
C
Vs

X
* 
X b

• Newton-Raphson subroutine used to solve overall oxygen balance
• Interfacial concentrations were determined and trajectories updated
Robertson, D.G.C., Deo, B., and Ohguchi, S., 1984, Ironmaking and Steemaking, Vol. 11, No. 1, pp.
41-55.
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Effect of slag(FeO+ MnO) content on average inclusion content
Kevin Graham, Thesis, 2009
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Effect of Top Slag on Mg Content of Steel
Kevin Graham, Thesis, 2009
19

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Representative study plot for heat processed in LMF2
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Sample
M3
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Sample
S
L
SP+L
MgO+L
SP
MgO+CaO+L
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Process Conditions and Inclusions Chemistry
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• there seems to be a close relationship between the Max MgO as seen in M3 of heats with the amount Sulfur decreased from its initial value to the value it reached in M3
Heat # dS up to M3 Max % MgO inc
100548
100541
100545
100543
0.0194
0.0198
0.0201
0.0204
11
16
5
8
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• Kinetics of inclusions transformations are controlled by mass transfer in metal
• Composition of both metal and slag changes during the processing which can be described by the multi-component kinetic model
• There is a strong relation between the chemical composition of slag and the injection of Mg in the metal and forming spinel inclusions
• There can be a link between the conditioning of slag specially for desulfurization and increase of
MgO level in steel
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• Continuing the study on impact of industrial process parameters
– Slag carryover from EAF
– Slag conditioning
– Additions
• Composition
• Time of addition
• Impact of initial size and distribution of inclusions
• Kinetics of oxygen removal, measurements of total oxygen
• Investigation of the impact of refractory and other possible sources of Mg to form spinel inclusions
• Calcium is injected as wire into the steel, and the rates of dissolution need to be determined.
• Completion of the model
• Validation with the experimental data
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• My Supervisor Dr. Gordon Irons
• Dr. Ken Coley and Dr. Chris Swartz
• Steel Research Centre, John Thompson
• Arcelor Mittal Dofasco Team, Don
Holdridge, Steve Waterfalls, Dongsheng
Liao
• My sister, Shideh Fathi
• All of you, my friends in MSE
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