Fundamental studies related to the mechanisms of inclusion removal from steel

Directorate-General For Research And Innovation European Commission

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Industrial research and development

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• Sciences et techniques

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• Publié par: DIRECTORATE-GENERAL-FOR-RESEARCH-AND-INNOVATION-EUROPEAN-COMMISSION
• Nombre de lectures: 55
• Langue: English
• Poids de l'ouvrage: 6 Mo

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ISSN 1018-5593
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European Commission
technical steel research
Steelmaking
Fundamental studies related
to the mechanisms of inclusion
removal from steel
STEEL RESEARCH EUROPEAN COMMISSION
Edith CRESSON, Member of the Commission
responsible for research, innovation, education, training and youth
DG XII/C.2 — RTD actions: Industrial and materials technologies —
Materials and steel
Contact: MrJ.-L. Martin
Address: European Commission, rue de la Loi 200 (MO 75 1/10),
B-1049 Brussels — Tel. [phone]; fax [phone] European Commission
technical steel research
Steelmaking
Fundamental studies related
to the mechanisms of inclusion
removal from steel
G. Hassal, K. Mills
British Steel pic
9 Albert Embankment
London SEI 7SN
United Kingdom
Contract No 7210-CF/804
1 July 1987 to 30 June 1990
Final report
Directorate-General
Science, Research and Development
1998 EUR 17894 EN LEGAL NOTICE
Neither the European Commission nor any person acting on behalf of the Commission
is responsible for the use which might be made of the following information.
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It can be accessed through the Europa server (http://europa.eu.int).
Cataloguing data can be found at the end of this publication.
Luxembourg: Office for Official Publications of the European Communities, 1998
ISBN 92-828-2592-2
© European Communities, 1998
Reproduction is authorised provided the source is acknowledged.
Printed in Luxembourg
PRINTED ON WHITE CHLORINE-FREE PAPER CONTENTS
Page
1. INTRODUCTION 31
2. ASSESSMENT OF INCLUSION AND BUBBLE SIZES IN LIQUIDS,
INCLUDING METALS {
2.1 Inclusions And Inclusion Behaviour In Liquid Steel 3
2.2 Clean Steel3
2.3 Bubble Properties In Different Liquids
2.4 Bubbles In Liquid Metals5
2.5 Summary8
3. THE FUNDAMENTALS OF INCLUSION REMOVAL BY
FILTRATION AND FLOTATION
3.1 Introduction
3.2 Filtration Of Solid Inclusions With Ceramic Filters 39
3.3n Of Liquid Inclusions With Ceramic Filters 41
3.4 Flotation Of Inclusions By Gas Bubbling2
3.5 Summary 47
4. BUBBLE-LIQUID-INCLUSION INTERACTIONS
4.1 Introduction
4.2 Entrainment Within The Wake Of A Bubble8
4.3 Effects Of Gas-Liquid Coupling9
4.4 Physical Modelling Experiments 50
4.5 Mathematical Modelling4
4.6 Hot Modelling5
4.7 Summary6
5. INTERFACIAL AND WETTING CHARACTERISTICS 5
5.1 Introduction g
5.2 Contact Angles7
5.3 Surface Tension Measurements
5.4 Discussion 5
5.5 Summary ß\
61
6. EVALUATION OF STEEL CLEANNESS
6.1 Introduction 61
6.2 Experimental2
6.3 Examination Of Electron Beam Melted Buttons 63
6.4n Of Levitated Drop And Cold Crucible Melted Samples 65
6.5 Discussion And Conclusions
6.6 Summary6
7. CONCLUSIONS9
8. FUTURE WORK8
9. REFERENCES
TABLES 74
FIGURES 91
APPENDICES 147 LIST OF TABLES
1. Influence of Size of Oxide Inclusions. Oxygen Content of Steel 100 mm. All Inclusions are
Supposed to be Spherical, Equal in Size and of AI2O3M
2. Rate of Rise of Spherical Inclusions of Different Sizes and Densities in Liquid Steel
3. Minimum Size of Bubbles Forming in Various Gas/Liquid Systems^10)
4. Value of (Surface Tension/Liquid Density)05 for Different Liquids
5. Calculated Equivalent Spherical Bubble Diameter Above which Spherical Cap Bubbles
will be Present in Different Liquid Metals
6.d Terminal Velocities of Minimum Equivalent Sphere Diameter Spherical Cap
Bubbles in Various Liquids
7. Critical Equivalent Sphere Bubble Diameters and Volumes for Argon Bubble
Disintegration
8. The Densities of Inclusions, kg nv3
9. Volume of Spherical Cap Air Bubbles at 25°C
10. Dimensions of Spherical Cap Air Bubbles of Varying Volume
11. Velocities ofl Cap Airs ofge in Water
12. Volume of Spherical Cap Helium Bubbles
13. Helium Bubble Dimensions in Water
14. Velocities of Spherical Cap Helium Bubbles in Water
15. The Conditions Favouring Filtration and Flotation Efficiency
16(a) Reported Contact Angle Measurements of'Pure Fe' on Various Oxides
16(b) Mean Values of the Contact Angle for 'Pure Fe' on Various Oxides at 1600°C
17. Contact Angle Measurements for Sulphides on 'Pure Fe'
18.tes of 'Pure Fe' on Carbon and Carbides
19.t Angles for 'Pure Fe' on Suicides
20. Contacte Measurements for 'Pure Fe' on Nitrides
21.t Angles for 'Pure Fe' on Borides
22. Chemical Composition of the Steels Used in this Investigation (Mass %)
23. The Contact Angle Measurements for Steels Α-D on AI2O3, S1O2 and MgO Plaques
24. Values of the Flotation Coefficient for Various Solid Inclusions in Different Molten Steels
25. Flotation Values for Various Solid Inclusions Based on Contact Values Cited in Tables 16
to 21
26. Calculated Values for the Interfacial Tension γΜΙ and the Non-Dimensional Parameters X,
Y and Ζ for Liquid Inclusions in Steel D
27. Details of the Techniques Used for the Evaluation of Alloy Cleanness
28. Typical Chemical Compositions of the Steels Used in EBBM Investigation
29.s of the Levitated Drop Experiments
30. Comparison Between Total Oxygen Content of Original Samples as Analysed and
Calculated from the Oxide Rafts after Remelting
A1.1 Details of Studies into the Factors Affecting Filter Efficiencies
Al.2 The Expression Used in the Calculation of Collection on Different Flow Regimes<A120<
A1.21.A1.1»
Al.3 Experimental Details of Filtration Experiments Involving Liquid Inclusions LIST OF FIGURES
1. Oxide Inclusions in Aluminium-Killed Steel (Al 0.010 to 0.060%)
2. Shape Regimes for Bubbles and Drops in Unhindered Gravitational Motion Through
Newtonian Liquids
3. Bubble Volume and Equivalent Sphere Diameter as a Function of Flow Rate at the Bath
Temperature in Metallic Systems
4. The Spherical Cap Bubble
5. Schematic Diagram Showing the Contact Angle Formed by Liquid, Gas and Solid Phases
(ΘΙΜ-GM)
6. The Calculated Velocities of Deoxidation Products with Various Densities Pj and
Diameters di in a Bath of Molten Steel
7. Schematic Illustration of Liquid Metal Withdrawal from a Particle that is Separated from
the Filter Wall (Left) and upon Contact (Right). The Liquid Metal Withdrawal without the
Simplifying Assumptions for the Calculation of Energy Reduction is Shown in the Centre;
HL = Liquid Metal Head
8. Energy Reduction Resulting from the Reduction of the Liquid Metal Film Separating a
Particle from the Filter Wall. The Effect of the Separating Distance D and Height X which
the Metal Withdraws To
9. Energy Reduction in the Particle Contact Region as a Function of the Height to which the
Liquid Steel Withdraws from the Particle, the Wetting Angle (Denoted a) and the Particle
Radius RL( = di)
10. A Sessile Drop of a Liquid Inclusion on a Filter and Surrounded by Metal (Denoted ΘΙΡ_ΙΜ)
11. The ISO-φ Contours in the CaO + Si02 + A1203 System at 1600°C
12. Calculated Versus Measured Interfacial Tension Values for Slag-Iron Systems at 1600°C
13. Perspex Physical Model for Study of Bubble-Particle Behaviour
14. Physical Model Showing Bubble Calibration Apparatus
15. Schematic Arrangement for Flow Visualisation Around Spherical Cap Bubbles
16. Velocities of Single Air Bubbles in Water of Different Equivalent Diameter in Columns of
Varying Diameter
17. Frequency and Amplitude of Spherical Cap Air Bubble Eccentricity in Water
18. Wake/Vortex Pattern Behindl Cap Aire (~10 cm3) inr (Relative to
Static Liquid)
19. Measured Particle Velocity Behind 10 cm3 Bubble
20. Particle Velocity vs Distanced Bubble. 10 cm3 Bubble
21. Experimental Arrangement Used to Study the Relative Lifting Effect of Streams of
Spherical Cap Bubbles
22. Apparatus Used for Dye-Injection Experiments
23. Schematic Diagram Showing Main Features of a Typical Experimental Trace. Area A is
the Area of Deflection Caused by the Injected Dye
24. Area ofn vs Bubble Volume for Most Accurate Data Points
25. Effect of 10 cm3 Spherical Cap Bubble Rising in Water - Bubble Moving
26. Calculated Velocity Profile Behind 10 cm3 Bubble
27. Water Velocity vs Distanced Bubble. Math Model: 10 cm3 Bubble
28.d Trajectories for 50 pm Neutral Density Particles Under the Influence of a
10 cm3 Bubble in Water
29. Calculated Relative Particle Lift as a Function of Bubble Volume for 50 pm Neutral
Density Beads in Water (x) and for 50 pm Alumina Particles in Steel (·)
30. Particle Lift for 50 pm Neutral Density Beads in Water as a Function of Bubble Volume as
Given by Calculation and by Experimentation
31. Tundish Gas Bubbling Brick Used in Pilot Plant Trials
32. i Scale Tundish Fitted with Gas Bubbling Block - Processed Image of Metal Surface 33. Process Image of Metal Surface in Tundish Showing Bubble on Point of Bursting
34. Schematic Drawing Showing How the Apparent Contact Angle can be Affected by the
Surface Roughness
35. The Contact Angle Between Liquid Fe and AI2O3 as a Function of Time, the Partial
Pressure of Oxygen in the Atmosphere is Also Shown(42>
36. The Effect of Po2 on the Con