Study of the bulging of continuously cast slabs

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• Langue: English
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Commission of the European Communities
technical steel research
Steelmaking
STUDY OF THE BULGING
OF CONTINUOUSLY CAST SLABS
Report
EUR 8963/111 EN
Blow-up from microfiche original Commission of the European Communities
technical steel research
Steelmaking
STUDY OF THE BULGING
OF CONTINUOUSLY CAST SLABS
J.Y. LAMANT<1>, M. LARRECOJ1', Z. SMARZYNSKM1», J.L HENSGEN<1>,
C. ROSSARD·2», J.D. WEBER <3>, J.C. DHUYVETTER <4>
(D IRS1D - Station d'Essais, F-57210 Maizières-les-Metz
• (2) IRSID - F-78105 St-Germain-en-Laye
(3) Université de Metz, Laboratoire de Mécanique, F-57000 Metz
(4) USINOR - F-59 Dunkerque
IRSID
185, rue du Président Roosevelt
F-78105 SAINT-GERMAIN-EN-LAYE
Contract No 7210-CA/306
(1.5.1979-30.4.1982)
FINAL REPORT
Directorate-General
Science, Research and Development
1985 EUR 8963/III EN Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Information Market and Innovation
L-2920 LUXEMBOURG
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>ECSC-EEC-Euratom, Brussels· Luxembourg 1 -
ABSTRACT
This paper presents a theoretical and experimental study of
slab bulging in a continuous caster.
Two m ι fhawititoii1 models of the visco-plastic behaviour of
the solidified shell under the action of ferrostatic pressure have been
developed, in the static and cinematic case. We have determinated visco-
plastic behaviour laws described by <J- λίτ) £n έ with tensile tests
at low deformation rafte -and high temperature for different steel grades·.
*.* With'the results of the Cinematic model, we have established,
in the case of steel for heavy plates (0.18 % C), the relation summarizing
the influence of different parameters (roll pitch (1 in mm), metallurgical
height (H in m), casting speed (v in m/min), solidified thickness (h in
mm) and surface -temperature (Τ in °40) on the bulging deflection ( % in
mm) as follows :
. '" -Ι? M2"25 I6*10
ò = 7.86 10 exp (0.0046 T)
,,0.57 .5.26
N h
Another application of this model shows that, in the case
of large width (above 1.5 m) slab casting on a curved machine (R = 12.2 m),
the bulging deflection is always below 1.5 mm on the whole metallurgical
length if the guide rolls are chosen non divided and with diameters varying
from 260 to 420 mm.
* The experimental part is composed of the conception of a
physical modelization with a small scale model using modelling clay (plasti­
cine) as simulation material and the measurement of bulging on the slab
continuous caster No. 12 at USIN0R Dunkerque.
. The results of the measurements made on the plasticine model
agree with thes given by the mathematical models and show that
the boundary conditions at the slab-roll contact position are identical.
. The measurements on the industrial machine show that :
the bulging deflection is periodic due to the geometry of the support
structure and depends on the deformations in the upstream part of the
machine. Its mean value is almost equal to the roll eccentricity, i.e.
about 1 mm ;
- the measurements agree with the results of the cinematic model ;
- the axial segregation increases with the bulging deflection, and bulging
intensity does not depend on the solidification structure. - 3 -
CONTENTS
Page
INTRODUCTION 7
1. BIBLIOGRAPHIC STUDY 9
1.1 Defects created by bulging 9
9 1 Internal cracks
1.1 Different types of internal cracks 10
1.2 Influence of operating parameters on the proportion
of internal cracks in the broad faces 11
1.3 Mechanism of formation of internal cracks 13
1.4 Criteria for the occurrence of internal cracks 14
2 Centre segregation 15
2.1 Experimental results 16
2.2 Mathematical modelling of the formation of centre
17
segregation
1.2 On-site measurement of bulging 19
1.3 Mechanical modelling of bulging 21
21 1.3.1 Elastic models
22 1.3.2 Elasto-plastic models
1.3.3 Viscous models 23
2. MATHEMATICAL MODEL OF BULGING, DEVELOPED AT IRSID 27
2.1 Mechanical behaviour of steel at high temperature 27
2.2 Mathematical models, developed by IRSID, of the bulging of
continuously cast steel slabs 30
2.2.1 Method of calculation 31
2.2.2 Static model 35
2.2.3 Kinetic model 35 4 -
Page
2.3 Results of the calculations of bulging 37
2.3.1 Results obtained with the kinetic model
2.3.1.1 Influence of the boundary conditions on steel 18M5 38 2 Comparison of the calculations with the available
measurements 39
2.3.1.3n of thes with some other
results taken from the literature 40
2.3.1.4 Profile of bulging on machine no.12 at USINOR
Dunkerque 41
2.3.2 Results obtained with the static model4
2.3.3 Overall model of the bulging of slabs5
2.3.4 Discussion of the results9
3. PHYSICAL MODELLING OF BULGING 5
3.1 Definition of the mock-up of bulging1
3.1.1 Choice of a material for simulating the behaviour
of steel
3.1.2 Dimensioning of the mock-up2
3.1.3 Description of thep3
3.1.4 Similitude study 54
3.2 Realisation of trials on the mock-up
3.2.1 Experimental method5
3.2.1.1 Uniformity of the base-plate thickness 5
3.2.1.2 Influence of the width of the vessel
3.2.1.3 Influence of aging of the Plasticine6
3.2.1.4 Waiting time between tests made with the same vessel 5
3.2.2 The progress of a static test 5
3.2.3 Thes of a kinetic test
3.3 Method of analysing the tests7
3.3.1 Influence of the true weight of the Plasticine 5
3.3.2e of the elasticity of theePage
3.3.3 Influence of the quality of the Plasticine 59
3.3.4 Determination of the laws of mechanical behaviour
of Plasticine 5
3.4 Results of the tests using the mock-up 60
3.4.1 Bulging profiles obtained on the mock-up
3.4.2 Determination of the boundary conditions2
3.4.3 Influence of various test parameters on the bulging
deflection 6
3.4.4 Comparison of measurements and values calculated
using the mathematical model5
3.5 Discussion of the results6
4. MEASUREMENT OF THE BULGING OF SLABS IN A STEELWORKS 69
4.1 Principle and realisation of the measurement of bulging
4.1.1 Principle of the measurement 70
4.1.2 Choice of measuring technology
4.1.3 Making the measurement1
4.2 Method of analysis of the bulging deflection3
4.2.1 Example of the direct recording of data 7
4.2.2 Calculation of the instantaneous bulging deflection 7
4.2.3 Observations made concerning thegn4
4.3 Programme of tests carried out 76
4.4 Results of the measurements made7
4.4.1 Behaviour of rolls6 and8 during the period of the
tests 7
4.4.2 Influence of various parameters on the bulging deflection 80
4.4.3 Comparison of measured and calculatedg deflections 82
4.5 Study of the behaviour of the slab during the casting process 82
4.5.1 Measurement of slab thickness at the exit from the machine 82
4.5.2 Monitoring of a casting carried out with roll 78 out of
alignment 83
4.6 Relation between the bulging deflection, the solidification
structure, and centre segregation4 - 6
Page
4.6.1 Relationship between centre segregation and
solidification structure 85
4.6.2 Relation between solidification structure and the
bulging deflection
4.6.3 Relation between the bulging deflection and the centre
segregation6
4.7 Synthesis of the results obtained7
5. CRITICAL STUDY OF THE VARIOUS TECHNICAL SOLUTIONS TO THE PROB­
LEM OF BULGING 89
5.1 Technical solutions to the problem of bulging 8
5.2 The calculations made : 90
5.2.1 Assumptions made for the bulging calculations 91
5.2.2 The model of deformation of the rolls 92
5.2.3 Bulging profiles obtained on an industrial machine3
5.2.4 Choice of criteria for the threshold of harmfulness
of bulging 93
5.2.5 Choice of mechanical criterion 94
5.3 Presentation of the results obtained5
5.3.1 Influence of the mechanical criterion on the profile
of roll diameters
5.3.2e of the bulging criteria on the profile of
the roll spacings
5.3.3 Influence of casting speed 97
5.3.4e of surface temperature8
5.4 Tentative definition of optimal geometry of the machine 9
5.5 The role of deformation not connected with bulging 100
5.5.1 Strains imposed by misalignment 10
5.5.2s due to straightening or bending1
5.5.3 Influence of these strains on the profile of roll 0 102
5.6 Synthesis of the results 104
6. CONCLUSION6
REFERENCES
FIGURES
APPENDICES