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The mechanical and metallurgical effects of skin passing and tension levelling

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84 pages
Mechanical working (rolling mills)
Industrial research and development
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ISSN 1018-5593
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* *
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European Commission
technical steel research
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Mechanical working (Rolling mills)
The mechanical and metallurgical effects
of skin passing and tension levelling
STEEL RESEARCH European Commission
technical steel research
Mechanical working (Rolling mills)
The mechanical and metallurgical effects
of skin passing and tension levelling
T. de la Rue
British Steel pic - Welsh Technology Centre
Port Talbot
West Glamorgan SA13 2NG
United Kingdom
Contract No 7210-EA/822
1 July 1990 to 30 June 1992
Final report
v * Directorate-General XII
Science, Research and Development
1996 EUR 15849 EN 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.).
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
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1996
ISBN 92-827-7123-7
© ECSC-EC-EAEC, Brussels • Luxembourg, 1996
Reproduction is authorized, except for commercial purposes, provided the source is acknowledged
Printed in Luxembourg SUMMARY
THE MECHANICAL AND METALLURGICAL EFFECTS OF SKIN PASSING AND TENSION
LEVELLING
British Steel pic
ECSC Agreement No. 7210.EA/822
Final Summary Report
An exercise has been carried out to investigate the mechanical and metallurgical effects of skin passing
and tension levelling. The investigation was hampered by a lack of suitable cut sheet orders, nevertheless
five coils were processed using different levels of skin passing and tension levelling. Full width x 2m
length samples were taken at each processing stage for measurement of shape, gauge profile, surface
texture, tensile mechanical properties and formability properties.
The investigation showed that for EDD steel qualities low levels of tension levelling gave a significant
improvement in strip shape, but that levels as low as 0.5% increased strip hardness and the 0.2% proof
stress and reduced the work hardening coefficient ni such that the material may be rendered unsuitable
for its intended use.
The transverse gauge profile of strip is not affected by skin passing at 0.4-0.8% extensions or by additional
tension levelling up to 1.5% extension. Tension levelling up to 0.5% has no effect on surface texture and
skin passing at 0.4% has only a marginal effect when compared to the texture obtained at 0.8% skin pass
extension.
Combinations of 0.4% skin passing and low levels of tension levelling, up to 0.5% resulted in strip with
similar mechanical and formability properties to those of the normal 0.8% skin pass material and would
fully satisfy the property and texture specifications for EDD exposed part applications. Limited residual
surface stress measurements using a Stresscan 500C system showed that the technique may after further
study offer some use for the on-line determination of strip shape.
A number of investigations were also carried out into plant problems. They related to the design and
operating set up of roller and tension levellers on various units. The pilot tension leveller rig was
successfully used to simulate plant practices in a number of these investigations. CONTENTS
PAGE NO.
1. INTRODUCTION 1
1.1. Background to Research Programme
1.2. Summary of Intendede
2. PLANT INVESTIGATIONS INTO THE EFFECTS OF SKIN PASSING AND 2
TENSION LEVELLING
2.1. Final Acceptance Trial of an Inspection Line Tension Leveller
2.2. Plant Production Trial Coils 3
2.3. Investigations into Various Plant Problems 6
2.4. Use of Pilot Tension Leveller Rig in Plant Problem Investigations 8
3. CONCLUSIONS 9
4. RECOMMENDATIONS 10
5. REFERENCES
TABLES1
FIGURES 28
APPENDICES
I Off-Line Shape Assessment 53
II Details of Tensile Testing5
IIIs of Modified Stretch Draw Test7
IV LIST OF TABLES
1. Shape Assessment of Tension Leveller Final Acceptance Trial Coil.
2. Transverse Gauge Characteristics of Tension Leveller Final Acceptance Trial Coil.
3. Mechanical Properties - Tensile Test Results for the Tension Leveller Final Acceptance Trial
Coil.
4. Shape Assessment of Trial Coils 82076 and 82078.
5.et of Trial Coils 16528,16637 and 17430.
6. Transverse Gauge Characteristics of Trial Coils 82076 and 82078.
7.e Gauges of Trial Coils 16528,16637 and 17430.
8. Surface Texture Characteristics of Trial Coils 82076 and 82078.
9.e Textures of Trial Coils 16528,16637 and 17430.
10. Mechanical Properties: Tensile Test Results for Coil 82076.
11.l: Tensile Test Results for Coil 82078.
12. Mechanical Properties: Tensile Test Results for Coil 16528.
13.l: Tensile Test Results for Coil 16637.
14. Mechanical Properties: Tensile Test Results for Coil 17430.
15. Modified Stretch Draw Results for Coils 82076 and 82078: Lubricated Condition.
16.d Stretch Draw Results for Coils 82076 and 82078: Dry Condition.
17. Modified Stretch Draw Results for Coils 16528,16637 and 17430: Dry Condition.
V LIST OF FIGURES
1. Off-Line Shape Measurement on the Coil used for the Final Acceptance Trial of the Tension
Leveller (Skin Pass Only).
2.e Shape Measurements on the Coil Used for the Final Acceptance Trial of the Tension
Leveller (Skin Pass and Tension Levelling).
3. Relationship Between Flatness Index and Total Wave Height for a 2m Long Sample.
4. Rockwell B Hardness Values Across the Width of the Tension Leveller Final Acceptance
Trial Coil Samples.
5. Transverse Gauge Profiles of the Tension Leveller Final Acceptance Trial Coil Samples.
6. Description of Original and Modified Processing Routes and Sampling Positions for the Plant
Trial Coils.
7. Histograms of Degree of Flatness After Each Process for Coils 82076 and 82078.
8.s of Degree of Flatness After Each Process for Coils 16528,16637 and 17430.
9. Off-Line Shape Measurements for Coil 82076 at Various Processing Stages.
10.e Shapes for Coil 82078 at Various Processing Stages.
11. Off-Line Shape Measurements for Coil 16528 at Various Processing Stages.
12.e Shapes for Coil 16637 at Various Processing Stages.
13. Off-Line Shape Measurements for Coil 17430 at Various Processing Stages.
14. Transverse Gauge Profiles for Trial Coils 72086 and 72088 at Various Processing Stages.
15.e Gauge Profiles for Trial Coils 16528, 16637 and 17430 at Various Processing
Stages.
16. Residual Surface Stress Differences for Coil 16528 at Various Process Stages.
17.l Surface Stresss for Coil 16637 at Various Process Stages.
18. Residual Surface Stress Differences for Coil 17430 at Various Process Stages.
19. Equivalent Surface Stress to Cause Curvature in D.R. Tinplate.
20. Residual Longitudinal Stress in Straight Strip After Four Bends of Decreasing Curvature.
21. Relationship Between Roll Penetration and Effective Radius of Curvature.
22. Present Setting of Roller Levellers ("Wedge").
23. Modified Setting of Roller Levellers.
VI 24. Effects of Springback in D.R. and S.R. Tinplate During Tension Levelling.
25. Pilot Tension Leveller Rig.
26. Relationship Between Tension Stress, Penetration and Radius of Curvature of 3.1mm
Hot Dipped Galvanised Material for a 45mm Diameter Bending Roll.
VII

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