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

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

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.

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

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

Inclusion Modification Calcium Treatment Adding calcium Lowered melting point Enhanced castability

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

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

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

Spinels!! (shsh….it’s a bad word!)

Al2O3.MgO Spinel inclusions

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

Change in composition slag during processing of steel Proces Time

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)

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. 41-55.

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

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

Does top slag impact Ca Content of steel too?

Representative study plot for heat processed in LMF2

Example of results, sample S1 and M1

Example of Results samples M2

Sample M3

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

Process Conditions and Inclusions Chemistry

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

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

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

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

PEACE