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

2. Outline 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

3. 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.

4. Ladle Metallurgical Furnace
Significant control challenges:
-Elevated temperatures
-Dusty environment
-Electrical arcing
-Complex multi component slag/metal systems

6. Non Metallic Inclusions during refining
Oxides and sulfides
Mostly oxides, deoxidation products
By adding Al in LCAK steels
Initially Al2O3 oxide Particles
High melting point, solid (above 2000C)
Remain in the steel
Degrade mechanical properties
Cause problem in casting

7. Inclusion Modification
Calcium Treatment
Adding calcium
Lowered melting point
Enhanced castability

8. CaO-Al2O3 binary system
P.C. Pistorious, R.J. Fruehan, 2009

9. 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

10. 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

11. Spinels!!
(shsh….it’s a bad word!)

12. Al2O3.MgO Spinel inclusions

13. Possible sources of dissolved Mg to form Spinels:
Refractory
Alloying additions
Top slag

15. Change in composition slag during processing of steel
Proces Time

16. 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)

17. Kinetic Model Formulation
System represented by series of differential equations:
Reaction are coupled using flux density equations:
Newton-Raphson subroutine used to solve overall oxygen balance
Interfacial concentrations were determined and trajectories updated
Metal:
Slag:
Robertson, D.G.C., Deo, B., and Ohguchi, S., 1984, Ironmaking and Steemaking, Vol. 11, No. 1, pp

18. Effect of slag(FeO+ MnO) content on average inclusion content
Kevin Graham, Thesis, 2009

19. Effect of Top Slag on Mg Content of Steel
Kevin Graham, Thesis, 2009

20. Does top slag impact Ca Content of steel too?

21. Representative study plot for heat processed in LMF2

22. Example of results, sample S1 and M1

23. Example of Results samples M2

24. Sample M3

25. Sample M4
Sample M4 S SP
SP+L L
MgO+L
MgO+CaO+L

26. Process Conditions and Inclusions Chemistry

27. 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
0.0194 5
100541
0.0198 8
100545
0.0201 11
100543
0.0204 16

28. Summary
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

29. Future Work
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

30. Acknowledgements 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

31. PEACE