of kinetics of Inclusions Transformations in Ladle Metallurgical Furnace for the Production of LCAK Steels Departmental Seminar Presentation Mahshid Fathi May 272011 1 Outline Objectives Introduction ID: 315072
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Study of kinetics of Inclusions Transformations in Ladle Metallurgical Furnace for the Production of LCAK Steels
Departmental Seminar PresentationMahshid Fathi- May 27/2011
1Slide2
OutlineObjectivesIntroduction
Ladle Metallurgical FurnaceNon Metallic Inclusions and Inclusion EngineeringLiterature Review:Role of slag on formation of
spinels
Experimental results
SummaryFuture workAcknowledgement
2Slide3
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 transformationsWith focus on Spinels and calcium aluminates
Validation of the model by experimental results.
3Slide4
4
Significant control challenges:
-Elevated temperatures
-Dusty environment
-Electrical arcing
-Complex multi component slag/metal systems
Ladle Metallurgical FurnaceSlide5
5Slide6
Non Metallic Inclusions during refiningOxides and sulfidesMostly oxides,
deoxidation productsBy adding Al in LCAK steelsInitially Al2
O
3
oxide ParticlesHigh melting point, solid (above 2000C)Remain in the steel
Degrade mechanical properties
Cause problem in casting
6Slide7
Inclusion Modification Calcium Treatment
Adding calciumLowered melting pointEnhanced castability
7Slide8
CaO-Al2O3 binary system
8
P.C.
Pistorious
, R.J.
Fruehan
, 2009 Slide9
Mass Transfer steps in steelmaking bathAssumption 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
9Slide10
Mass Transfer Metal- Inclusion
Initial alumina inclusion
content and size
levels of Sulfur
levels of OxygenCalcium feed rates
Presence of multiple pumping source of dissolving element as in MgO.Al2O3
spinels
10Slide11
11
Spinels
!!
(
shsh
….it’s
a bad word!)
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Al2O3.MgO Spinel inclusions
12Slide13
Possible sources of dissolved Mg to form Spinels
:
13
Refractory
Alloying additions
Top slagSlide14
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Change in composition slag during processing of steel
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Proces
TimeSlide16
Multi-Component Reaction Model
Work based on the model of Robertson et al. (1984)
Local equilibrium assumed at the slag-metal interface
Generalized equilibrium reaction can be stated as:
where:
Metal
Slag
[Mn]
[O]
(MnO)
16Slide17
System represented by series of differential equations:Reaction are coupled using flux density equations:
Newton-Raphson subroutine used to solve overall oxygen balanceInterfacial concentrations were determined and trajectories updated
Kinetic Model Formulation
Metal:
Slag:
Robertson, D.G.C., Deo, B., and Ohguchi, S., 1984, Ironmaking and Steemaking, Vol. 11, No. 1, pp. 41-55.
17Slide18
Effect of slag(FeO+ MnO
) content on average inclusion content
Kevin Graham, Thesis, 2009
18Slide19
Effect of Top Slag on Mg Content of Steel
Kevin Graham, Thesis, 2009
19Slide20
Does top slag impact Ca Content of steel too?
20Slide21
Representative study plot for heat processed in LMF2
21Slide22
Example of results, sample S1 and M1
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Example of Results samples M2
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Sample M3
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Sample M4
MgO+CaO+L
SP
L
MgO+L
SP+L
S
Sample M4
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Process Conditions and Inclusions Chemistry26Slide27
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
27
Heat #
dS
up to M3
Max %
MgO
inc
100548
0.0194
5
100541
0.0198
8
100545
0.0201
11
100543
0.0204
16Slide28
SummaryKinetics 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 modelThere 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 parametersSlag carryover from EAFSlag conditioningAdditionsComposition
Time of additionImpact 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 inclusionsCalcium 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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Future WorkSlide30
AcknowledgementsMy Supervisor Dr. Gordon IronsDr. Ken Coley and Dr. Chris Swartz
Steel Research Centre, John ThompsonArcelor Mittal Dofasco Team, Don Holdridge, Steve Waterfalls, Dongsheng Liao
My sister, Shideh Fathi
All of you, my friends in MSE
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PEACE