Basic properties of high intensity electric arcs used in steelmaking. Period 1st October 1973 to 30th September 1975 FINAL REPORT

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Industrial research and development

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• Electrical equipment
• History of ferrous metallurgy
• Sciences et techniques

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• Publié par: DIRECTORATE-GENERAL-FOR-THE-INFORMATION-SOCIETY-AND-MEDIA
• Nombre de lectures: 105
• Langue: English
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COMMISSION OF THE EUROPEAN COMMUNITIES
steel research reports
Basic properties of high intensity
electric arcs used in steelmaking
Blow-up from microfiche original
EUR 5716 e 1977 COMMISSION OF TUE EUROPEAN COMMUNITIES
steel research reports
BASIC PROPERTIES OF HIGH INTENSITY ELECTRIC
ARCS USED IN STEELMAKING
British Steel Corporation, London
Contract No. 6210.93/8/801
Published by: Commission of the European Communities
Directorate General "Scientific and
Technical Information and Information
Management"
Bâtiment Jean Monnet - Kirchberg
Luxembourg (Grand Duchy of Luxembourg)
1977 EUR 5716 e ECSC Convention
No. 6210.93/8/801
BASIC PROPERTIES OF HIGH INTENSITY ELECTRIC
ARCS USED IN STEELMAKING
CARACTERISTIQUES..DES ARCS ELECTRIQUES À HAUTE INTENSITE
UTILISES DANS LA FABRICATION D'ACIER
GRUNDSÂTLICHE EIGENSCHAFTEN DER BEI DER HERSTELLUNG
VON STAHL ANGEWANDTEN HOCHINTENSITATSLICHTBÖGEN
Period 1st October 1973 to 30th September 1975
FINAL REPORT
FR/24/76 FR/24/76
CONTENTS Page
SUMMARY xiii
1. INTRODUCTION 1
1.1 The Electric Arc in an Arc Furnace 1
1.2 Laboratory Facilities Used for the Study of
High Current Arcs
2. HEAT TRANSFER CHARACTERISTICS OF HIGH POWER ARCS 6
2.1 Convective Energy Transfer by the Arc Flame
2.2 Radiated Energyr from the Arc Column
and Arc Flame 17
2.3 General Discussion 28
3. ELECTRODE EROSION IN ELECTRIC ARC FURNACES 35
3.1 Introduction 3
3.2 Summary of Previous Tip Erosion Measurements 3
3.3 An Investigation into Tipn Rate of 230 mm
Electrodes in an Experimental Furnace 39
3.4 An Examination of the Effects of Slag on
Electrode Tip Erosion Rates 43
3.5 Measurements of Tip Erosion Rate on a Production
Furnace 4
3.6 A Model of Electrode Tip Erosion due to Radiation
from the Arc Column 55
3.7 The Determination by Simulation of the Mass Loss
Rate and Profile of an Electrode at Stages during
59 its Erosion
67 3.8 Discussion
REFERENCES 70
APPENDIX 1 The Directionality of the Arc Flames in a
3-phase Arc Furnace^
APPENDIX 2 Calculation of Radiation Loadings on 'Hot'
and 'Cold' Spots in the Refractory Walls 75
APPENDIX 3 The Chemical Erosion of Graphite by Slag7 X 4 Calculation of Electrode Erosion Mechanisms 78
APPENDIX 5 The Automatic Camera 80 X 6 The Arc as a Radiator2
APPENDIX 7 Computer Model of Electrode Consumption -
Method and Theory .3 FR/24/76
Tables
1. Measurements of Arc and Arc Flame Characteristics for 5 MVA
Production Arc Furnace.
2. Power Densities received by the Water-cooled Calorimeter
for Different Operating Conditions.
3. Results of Tip Erosion Rate Measurements for a 230 mm diameter
Electrode.
4. Electrode Wear Measurements for Different Slag/Metal Conditions.
5. Results of Analysis of Slag Samples.
6. Analysis of Tip Wear Measurements - Stocksbridge 17 ton Furnace.
7. Calculations of Graphite Evaporation Rate.
Figures
1. Laboratory Furnaces for the Study of High Powered Arcs.
2. Water-cooled Furnace for Arc Studies.
3. Refractory Lined Furnace for Arc Studies.
4. Furnace Electrical Connections for (a) AC Operation,
(b) DC Operation.
5. Correlation of Arc Flame Lengths with Arc Characteristics for
a 5.5 MVA Production Furnace.
6. Factors Influencing the Direction of the Electric Arc.
7. Frequency Distribution of Flame Direction.
8. Experimental Arrangements for Photographing Arc Flame.
9. Photograph of the Flame Associated with a 6 kA Arc.
10. Calorimeters for Measuring Flame Power (a) Low Sensitivity,
(b) High Sensitivity.
11. Recording of Arc Current, Arc Voltage and Calorimeter Output.
12. Variation of Measured Power Density with Arc Voltage for a
Range of Arc Calorimeter Distances.
13.n of Measured Power Density with Arc Calorimeter
Distance (constant Current and Voltage).
14. Schematic Diagram of Apparatus for Axially Resolved Arc
Radiation Measurements.
15.c Diagram ofs for Total Arc Column Radiation
Measurements.
16. Variation of the Total Arc Radiation for a Graphite Arc
with (a) Arc Current, (b) Arc Voltage.
17.n of the Total Arcn for a Steel Arc with
(a) Arc Current, (b) Arc Voltage.
18. Axially Resolved Radiation Measurements.
19. Variation of Arc Column Radiation with Axial Position in the
Arc Column.
ii FR/24/76
20. Apparatus for the Measurement of Arc Flame Radiation.
21. Variation of Flame Radiance with Distance from the Arc for a
Range of Arc Powers.
22.n of Flame Radiance with Arc Voltage for a Range of
Arc Currents and Distances from the Arc.
23. Overall Energy Balance for a 8 kA, 143 V ac Arc.
24. Comparison of Valchev's and Hepworth's Erosion Rate Measurements.
25. Tip Erosion Rate Measurements.
26. Variation of Tip Erosion Rate with Arc Current and Arc Power
for a 230 mm diameter Electrode.
27. Arc Power/Current Characteristics for Stable Arc.
28. Erosion Rates at Electrode Tip as a Function of Arc Current.
29.ns ate Tip as Functions of Tip Angle.
30. Tip Angle as a Function of Current.
31. Average Side Loss Rate as a Function of Arc Voltage.
32. Position of Camera Relative to Electrode under Examination.
33. Typical Electrode Tip Photographs.
34. Diagram Illustrating the Parameters Measured from Arc Tip
Photographs.
35. Tip Erosion Plotted Against Arcing Time (Stocksbridge Ή' Furnace)
36. Graph Relating Arc Radiation with Radiation Flux at the
Electrode Surface.
37. Variation of Graphite Evaporation Rate with Temperature
(Clarke and Fox).
38. Graph of Surface Power Dissipation againste for a
Graphite Surface.
39. Evaporation Rate in Annulus Described by Radius "R" and r Plus
dr on the Electrode Surface.
40. Variation of Evaporation Rate with Arc Current (0-12 kA).
41.n ofn Rate with Arct (0-50 kA).
42. Electrode Surface Oxidation Rate Profile at Various Stages of a
Cast.
43. Variation of Arc Current and Tip Erosion Rate at Various Stages
of Cast.
44. Computer Print-out of the Calculated Electrode Consumption for
Craigneuk Arc Furnace.
45. Calculated Electrode Profiles for Craigneuk Arc Furnace.
46. Comparison of True Electrode Consumption and Linear Electrode
Consumption for Seven Furnace Casts.
Fig.A.l Current Paths in a 3-phase Arc Furnace 2 Polar Diagram Illustrating Locus of Arc Force Vector in
Horizontal Plane.
Fig.A.3 Calculation of Radiation Loadings on 'Hot' and 'Cold'
Spots in the Refractory Walls.
Fig.A.4 Electrode Wear (exaggerated) showing Separation into
Various Types of Loss.
Fig.A.5 The Automatic Camera Assembly.
iii