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Fundamental studies related to the mechanisms of inclusion removal from steel

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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. (32-2) 29-53453; fax (32-2) 29-65987 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.
A great deal of additional information on the European Union is available on the Internet.
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 Contact Angle for (a) The Fe/Si02 and (b) and (c) Fe/Al203 Systems
37.et of the Concentration of S, Se and Te in Molten Iron on the Contact Angle for the
Fe/Al203 System at 1600°C<44)
38(a) Sketch of the Sessile Drop Equipment
38(b) Typical Sessile Drop Showing Contact Angle
39. Schematic Diagram of the Levitated Drop Apparatus Used to Determine Surface Tension
40. Surface Tension as a Function of Temperature for (a) Steel B, (b) Steel A, (c) Steel C and (d)
Steel D
41. The Dependence of the % Soluble Oxygen (% O) upon the Concentration of the Alloying
Element (M) in Fe-M-0 Systems at 1600°C; Concentration of O in Fe where (dy/dT) = 0
42. Thee of the Soluble Sulphur (% S) upon then of the Alloying
Element (M) in Fe-M-S Systems at 1600°C;n of S in Fe where (dy/dT) = 0
43. The Surface Tension of Austenitic Steels as a Function of the Total Sulphur Content
44.een of Ferritic Steels as an of the Totalrt
45. The Temperature Coefficient (dy/dT) as a Function of the Total Sulphur Content
46. Ternary Interfacial Energy Diagram, X, Slags from CaO + A1203 + Si02 System;
• Manganese Silicates
47. Schematic Drawings Showing the Profile of the Metal Sessile Drop as a Function of Time;
A is the Initial Stage; B-D Represent Stages where Mass Transfer of Sulphur Occurs and E
Represents the Final State of the Steel
48. Electron Beam Button Melting (EBBM) Technique (NPL)
49. Variation in Melting Parameters During Typical EBBM Experiment
50. Diagram of Lévitation Apparatus
51. Reactor Tube for a Cold Crucible
52. Photograph of the Button from Steel 9D16J
53. Alumina Agglomerates in Raft Area
54. Large Raft in Button
55. Central Area of Button
56. Inclusion Raft inn
57. 9D16J Button
58. 9D17Jn
59. Section of Button, 9D17J, Showing Solidification Pattern
60.n of Button, 6A16N, Showing Macrostructure
61.n of, 8U8N1,ge
62. Inclusions from Sample 9D16J
63.s frome 9D17J
64.s from Sample 6A16N
65. Inclusions frome 8U8N1
66. Effect of Pressure on Carbon Deoxidation of Steel Samples
Al. 1 Photographs of (a) Ceramic Monoliths and (b) Ceramic Foam Filters
Al .2 Schematic Drawing Showing (a) The Different Transport Mechanisms which can Transfer
a Particle from the Streamline to the Filter and (b) Transport Mechanism Operating
within the Pores
Al .3 A Schematic Diagram Illustrating the Different Flow Regimes Operating in Cellular and
Granular Filters Al.4 Schematic Drawing of the Three Types of Filtration Processes (a) Screen, (b) Cake and (c)
Depth or Deep Bed Filtration
Al. 5 Comparison of Filter Pore Sizes with Typical Inclusion Sizes
Al.6 Schematic Drawings of Capture Processes
Al.7 Stereological Parameters of Ceramic Foam
Al.8 The Effect of Mean Window Size (I) upon (a) The Mean Cell Size and (b) The Macroscopic
Internal Surface Area of Ceramic Foams
Al.9 The Efficiency of Inclusion Removal as a Function of the Interstitial Velocity of the Metal
ALIOey ofnl as an of the Channel Reynolds Number
Al.11 The Effect of the Melt Residence Time (L/U) upon the Efficiency of Inclusion Removal
Using Filters of 5 and 10 cm
Al.12 The Filtration Efficiency as a Function of the Metal Velocity for Ceramic Foam and a 5 cm
Bed of Tubular Alumina
Al.13 The Filtration Efficiency as a Function of the Interstitial Melt Velocity for a Ceramic
Foam Filter and for a 5 cm Bed of Tubular Alumina
Al. 14 The Effect of Melt Interstitial Velocity on the Efficiency of Inclusion Removal for Tabular
and Monolithic Filters
Al. 15 The Effect of Total Surface Area on the Efficiency of Inclusion Removal
Al.16 Thet of Filter Type on (a) The Number and (b) Volume Efficiency of Removal of A1203
Particles as a Function of Particle Size Using the Filters with the Same Length and the
Same Melt Velocity
Al. 17 The Relationship of (a) Number and (b) Volume Efficiency as a Function of Alumina
Particle Size Showing the Effect of Melt Velocity for Tests where the Filter Lengths were
Identical for the Two Types of Filter
Al.18 Experimental and Calculated (Dotted Lines) Efficiencies of Ceramic Foam Filters for
Different Melt Velocities
Al.19 The Distribution of Inclusion and Capture in a Sandwich Filter Consisting of 20 and 40 ppi
Foam Filters
Al.20 Qualitative Expression for Different Particle Capture Mechanisms
Al.21 Typical Pressure-Time Relationship for a Constant Rate of Cake Filtration
Al .22 Schematic Drawing of the Model of the Dimensionless Unit Cell
Al.23 The Calculated Initial Filter Efficiencies as a Function of Melt Velocity
Al.24 Theoretical Collection Efficiency as a Function of (a) Filter Depth (L) and (b) Particle Size
(di) for Different Inclusion Densities Relative to Al
Al.25 The Efficiency ofn Removal as a Function of the Bulk Melt Velocity
Al.26 The Three Regimes of Filtration in the Typical Run; Total Capture; Onset of Release and
Transitional Zone; No Capture
Al.27 The Effect of Interstitial Forces on the Dimensionless Retained Volume (V*)
A1.28 The Critical Hold-up Volume (V*) as a Function of Bulk Melt Velocity
Al.29 The Instantaneous Efficiency (IE) as an of Reynolds Number
Al.30 The Effect of the Viscosity of Inclusion Phase On the Inclusion Retention Volume (V*) as a
Function of Bulk Melt Velocity
Al.31 Schematic Diagram Showing the Pathways of Capture and Release of Liquid Inclusions in
a Filter Bed
Al.32 The Inclusion Retention Volume V* at the First Release as a Function of the Adhesion
Tension (ψ) (and Contact Angle) for a Filter with a Grain Size of 6 mm
Al.33 The Effect of Wettability on the Inclusion Retention Volume (V*), the Parameter t*
Represents the Total Volume of Inclusions Fed to the Filter up to a Certain Time
Al.34 The Inclusion Retention Volume for the Steady State, Vss, as a Function of the Adhesion
Tension (and the Contact Angle)
Al.35 The Instantaneous Efficiency (IE) as a Function of Time Showing the Effect of Wettability
on the Release of Inclusions Al.36 The Contact Angle of Mercury as a Function of Potential in 0.05 M Na2S04
Al.37 Rate of Ascent of Bubbles as a Function of Bubble Size in Aqueous Solutions of Sodium
Decyl Sulphate (1) Distilled Water, (2) 10-6 Mole Litre-1, (3) 1.2x10-5 Mole Litre-l, (4) IO-3
to IO-4 Mole Litre1. The Dotted Line Corresponds to 'Solid' Bubbles in Distilled Water
Al. 38 Calculated Rising Velocity of Bubbles and their Associated Reynolds Numbers as a
Function of Bubble Size
Al.39 Schematic Drawing Showing Inertial Impaction of Particle on a Gas Bubble
Al.40 The Calculated Gas Sparging Rate for 99.9% Particle Removal by Inertial Impaction as a
Function of Bubble Size
Al.41 Schematic Drawing Showing Peripheral Interception of a Particle by Gas Bubble
Al.42 The Flotation of Particles as a Function of Particle Diameter for Differente Sizes
Al.43 (a) The Ternary Interfacial Energy Diagram Showing the Various Regions where Various
Modes of Bubble/Particle Attachment Occur, (b) Shows the Significance of the Angles, and
(X = γΙΜ/Σγ) Y = (γΙ0/Σγ and Ζ - ΥΜ0/Σγ)