On-line calculation of time optimal pass sequences for cold rolling on Sendzimir mills

European Commission Directorate-General For Research And Innovation

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Industrial research and development

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• Publié par: EUROPEAN-COMMISSION-DIRECTORATE-GENERAL-FOR-RESEARCH-AND-INNOVATION
• Nombre de lectures: 311
• Langue: English
• Poids de l'ouvrage: 2 Mo

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ISSN 1018-5593
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European Commission
technical steel research
Mechanical working (rolling)
On-line calculation of time optimal pass
sequences for cold rolling on Sendzimir mills
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: Mr. J.-L. Martin
Address: European Commission, rue de la Loi 200 (MO 75 1/10),
Β-1049 Brussels — Tel. [phone]; fax [phone] European Commission
i eß&k jø&t
Mechanical working (rolling)
On-line calculation of time optimal pass
sequences for cold rolling on Sendzimir mills
O. Davies, P. Yates, J. Woodisse
British Steel, Swinden Technology Centre
Moorgate
Rotherham S60 3AR
United Kingdom
Contract No 7210-EA/823
1 August 1990 to 31 July 1993
Final report
Directorate-General
Science, Research and Development
1998 EUR 17881 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 92-828-3127-2
© European Communities, 1998
Reproduction is authorised provided the source is acknowledged.
Printed in Luxembourg
PRINTED ON WHITE CHLORINE-FREE PAPER CONTENTS PAGE
1. INTRODUCTION 7
2. OPTIMISATION SOFTWARE 8
2.1 Schedule Optimisation g
2.2 Evaluation of the Objective Function 11
2.3 Operational Constraints4
2.4 Software Testing 15
3. STAINLESS STEEL YIELD STRESS DETERMINATION 16
3.1 The Temperature Dependence of Stainless Steel Yield Stress 1
3.2 Annealing Treatment7
3.3 Investigation of Anisotropy of Stainless Steel Yield Stress8
3.4 Conclusion and Implications to Rolling Mill Scheduling 19
4. ROLLING FORCE MEASUREMENT ON SENDZIMIR MILLS 20
4.1 Measurement of Roll Separating Force 21
4.2 Monitoring Sendzimir Mill Rolling using Torque Telemetry 24
5. ANALYSES OF MILL DATA 25
6. INSTALLATION OF OPTIMISED SCHEDULING7
7. CONCLUSION8
REFERENCES9
TABLES 31
FIGURES 4LIST OF TABLES
1. Data used in Optimisation Program OPTI
2. Cold Rolling Model Input Parameters
3. Optimised Schedule Results and Computation Times
4. (a) Percentage Chemical Analyses ofType302XD Hot Band Material
(b)els of Type 302AA Hot Bandl
5. Mechanical Properties of Softened and Descaled 302AA Grade Stainless Steel Hot Band
6. Details of Cold Rolling Experiments, Starting Hardness 139-141 VPN
7.s of Cold Rolling, Starting Hardness 145-162 VPN
8. Details of Cold Rolling Experiments, Starting Hardness 160-182 VPN
9. 302XD Bright Annealed Rolling Schedules LIST OF FIGURES
1. Schematic of Optimisation Programme Modules
2. Total Strip Gauge Reduction Displayed as a Function of the Individual Pass Reductions
3. Schematic of Optimisation Search Space
4. True Stress ν Natural Strain Type 302XD Longitudinal Results of Tensile Tests
5.e Stress ν Natural Strain Type 302XD Transverse Results of Tensile Tests
6. True Stress ν Natural Strain Type 302XD Transverse Results of Tensile Tests at Different
Temperatures
7. True Stress ν Natural Strain Type 302XD Longitudinal Results of Tensile Tests at Different
Temperatures
8. Proportion of Martensite in the Tensile Test Specimens Against Test Temperature - Values
Determined by Ferriscope Measurement
9. Graph of Annealing Time in Furnace ν Final Hardness Values
10. Comparison of Cumulative Roll Separating Force with Initial Hardness
11. True Stress ν Strain Curves for Various Initial Hardnesses
12. Yield Stress of Grade 302AA Stainless Steel Obtained by Compression Testing
13. Ratio of Compressive and Tensile Yield Stress ν % Reduction
14. Sketch of a 63 inch Sendzimir Mill Housing
15.h of simplified Geometry Developed for Mathematical Modelling
16. Undeformed Mesh
17. Deformed Mesh (Magnified Displacement)
18. Vertical Strain Component (E22) as Viewed from the Front of the Mill
19.l Straint (E22) as Viewed from Mill Interior
20. Prototype Load Sensor
21. Gauge Output ν Applied Strain
22. Strain Sensor Output During Rolling
23. Screwdown Pressure Signal ν Gauge Output for Bottom Back-Up roll Eccentric Positions
24. Sendzimir Mill Torque and Speed Signals
25. Weighted Histogram of Torque Output for a Six Pass Schedule
26. Fourier Spectrum for Single Pass Torque Measurement 27. Work Roll Torque per Unit Width ν Input Gauge
28.k Roll Torque per Unit Width ν Total Fractional Reduction
29. Work Roll Torque per Unit Width ν Front Tension Stress for First Passes
30.k Roll 'Fitted' ν Measured Torque per Unit Width
31. Histogram of Residual Error/Mean Measurement Error
32. Calculated Yield Stress ν Reduction
33. (a) Fit to 40 Passes Residual Error for Remaining 25 Passes in Sample
(b) Fit to 50 Passes Residual Error for Remaining 15 Passes in Sample
(c) Fit to 60slr forg 5s ine
34. Work Roll Torque ν Input Gauge ON-LINE CALCULATION OF TIME OPTIMAL PASS SEQUENCES FOR COLD ROLLING ON
SENDZIMIR MILLS
British Steel pic
ECSC Agreement No. 7210.EA/823
FINAL TECHNICAL REPORT
1. INTRODUCTION
The aim of this project has been to test the feasibility of implementing the on-line calculation of time
optimised rolling schedules for Sendzimir rolling mills. Cold rolling is a complex physical process, which is
further complicated by the fact that hot rolled coils of stainless steel can have individual characteristics.
The variability in the properties of processed strip is generated by the natural fluctuations in processing
parameters that occur during casting, hot rolling, annealing, descaling and grinding. The variability of
hot rolled coil properties necessitates that on-line adaptive schedule calculations are performed during
subsequent cold rolling. The schedule calculations are therefore repeated after each pass. The new
calculations are based upon measurements of coil properties obtained during cold rolling, such that the
material in question is always rolled in an optimum manner.
Scheduling can be implemented in a number of different ways. Firstly, one can use a model to predict the
mill loadings and adjust the schedule until maximum rolling force and the minimum number of passes
have been achieved. The mill speed is free to vary from pass to pass at the discretion of the mill operators.
Adaption of the schedule is achieved by measuring roll separating force, from which the yield stress is
inferred and subsequent more accurate roll separating force are predicted. This approach is favoured for
reversing hot rolling mills, where rolling speed is limited. It would also be suitable for application on four-
high or Z-high cold rolling mills which have limited reduction and speed capability.
Alternatively, one can generate a model which predicts both the mill rolling force and maximum mill
speed throughout a schedule. A time optimum schedule may then be calculated which seeks to find the
balance between heavier draftings and faster rolling speeds. This approach is deemed to be applicable to
rolling on Sendzimir mills. These mills are generally equipped with powerful motors which allow rolling
speeds in the range 500-1000 m/min to be achieved. However, the rolling of quality stainless strip also
requires that certain criteria are obeyed regarding drafting, strip speed and tension. To achieve maximum
productivity of a high quality product, the schedule required must respect the rules applied, yet exploit the
available mill power. Schedule adaption can be implemented by using measured load data as a means of
refining the predictions made. However, it must be realised that adaption is also a means of error
correction. One cannot claim to have time optimised scheduling if the result on rolling requires
continuous large error correction. One must therefore aim to achieve suitable accuracy in the predictions
of the model such that adaption represents a small perturbation to the predictions.
The proposed solution to this problem is a computer software package capable of providing calculated
schedules within the time required to roll one pass. Thee developed must therefore contain all the
information required to predict the rolling forces generated at the work roll for any proposed reduction
sequence. The main elements of the proposed system are shown in Fig. 1. Essentially the system consists
of an optimising procedure, a model of the mill mechanics, and a model of cold rolling describing the
behaviour of stainless steel strip during rolling reduction.
The approach sought is both theoretical, in that the aim is an improved understanding of the cold rolling
processes, and practical, in that a focus has been retained on the overall aim of the project and its
importance to stainless strip manufacturers. Hence, both theoretical and empirical models of material
behaviour under deformation have been