Segregation and phase distribution during solidification of carbon, alloy and stainless steels

260 Pages·2016·5.99 MB·English

by  Howe A.A.

* *
Commission of the European Communities
technical steel research
Steelmaking
Segregation and phase distribution
during solidification of carbon,
alloy and stainless steels

Commission of the European Communities
technical steel research
Steelmaking
Segregation and phase distribution
during solidification of carbon,
alloy and stainless steels
A. A. Howe
British Steel pic
9, Albert Embankment
London SE1 7SN
United Kingdom
Contract No 7210-CF/801
(1 July 1986 to 30 June 1989)
Final report
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Directorate-General ti.c./^ZTAiSSSS
Science, Research and Development
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1991 FUR 1330? FN
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Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Telecommunications, Information Industries and Innovation
L-2920 Luxembourg
LEGAL NOTICE
Neither the Commission of the European Communities 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, 1991
ISBN 92-826-0518-3 Catalogue number: CD-NA-13302-EN-C
© ECSC-EEC-EAEC, Brussels • Luxembourg, 1991
Printed in Belgium
SEGREGATION AND PHASE DISTRIBUTION DURING SOLIDIFICATION OF
CARBON, ALLOY AND STAINLESS STEELS
SUMMARY
A major, new computer model of as-cast microsegregation has been created which can be applied to the
majority of carbon, alloy and stainless steels because of its ability to handle multicomponent compositions
and the peritectic reaction in a rigorous manner. Comparison of computed and experimental data has
shown strong correlation.
The program can operate on a 1, 2 or 3 dimensional primary (static) or secondary (coarsening) dendrite
arm representative basis, as desired, under variable cooling rate or heat extraction control. Subsequent,
sub-solidus interface motion and diffusive adjustment is readily considered on the same morphological
basis. The finite difference (FD) procedure uses second order interpolation for solute gradients at
interfaces, with the interface position independant of nodal planes. A third order interpolation procedure
is included for the remeshing of the FD array.
The basic concepts and computer model are fairly general to metallic alloys although the emphasis for
application is naturally on steel.
In addition to the central work on the derivation of new, numerical routines and their programming
within a FD formulation, important extensions have also been made on analytical equations for
microsegregation and the analysis of secondary dendrite arm coarsening. The implications for
macrosegregation have been discussed but only semi-quantitative treatments could as yet be added onto a
detailed treatment of microsegregation.
Multicomponent equlibrium data have been provided as a computerised database (MTDATA) which has
been assessed against experiment and alternative predictive techniques. It is a powerful and flexible
system although certain limitations have been highlighted where further work is required.

CONTENTS PAGE
1. INTRODUCTION 2
2. THEORY 3
2.1 Principles 3
2.2 Interface Modelling 3
2.3 Secondary Dendrite Arm Coarsening 4
2.4 Model Validity 6
2.5 Application of Peritectic Model to FeCrNi (Stainless) Alloys 8
2.6 Macrosegregation 11
3. ANALYTICAL MODELS 15
3.1 Theory/Literature Review 15
3.2 Proposed Extensions to Standard Formulation 18
3.3 The Peritectic Reaction 19
3.4 Simplified Peri/Eu-Tectic Equilibrium Data 20
3.5 Secondary Dendrite Arm Coarsening 21
4. NUMERICAL MODELS 28
4.1 Literature Review 28
4.2 Basis of Current Work 30
4.3 Model Alternatives 33
4.4 Model Facilities 35
4.5 The Peritectic Reaction 40
5. EXPERIMENTAL WORK 48
5.1 Scope of Study 48
5.2 Liquidus Experiments 49
5.3 Equilibration Furnace Experiments 53
5.4 Optical Metallography 55
5.5 Electron Metallography and Mass Spectroscopy 57
6. VALIDATION OF COMPUTED MICROSEGREGATION 60
6.1 Comparison with Jernkontoret Data 60
6.2 Further Comparison 64
7. DISCUSSION 66
7.1 Modelling Features 66
7.2 Equilibrium Data 66
7.3 Validation of Input Data 67
7.4 Validation of Model 67
7.5 Composition Guidelines 67
7.6 Alloy Design 68
7.7 Implications for Macrosegregation 68
7.8 Model Properties 68
7.9 Prospects for Future Work 69
8. SUMMARY AND CONCLUSIONS 70
9. REFERENCES 72
TABLES 77
FIGURES 95
APPENDIX 186
V-

LIST OF TABLES
1. Simplified Peritectic Data.
2. Empirical Formulae for Secondary Arm Spacings.
3. Values of the Parameter m (k-1) Used to Estimate the Influence of Solutes on the
Secondary Arm Spacings in Multicomponent Steels.
4. Composition of Austenitically Solidifying Steels.
5. Local Solidification Times and Secondary Arm Spacings.
6. Data Employed in Derivation of Figure 46.
7. Cast Composition, Wt. %.
7.1 Previous Work
7.2 Present Work
7.3 Related Work, Ref. 97
8. Calculation Schemes.
9. Liquidus and Primary Phase Predictions.
9.1 Low Alloy and Quasibinary Steels
9.2 High CrNi Alloys
10. Thermal Solidus Predictions.
11. Partition Coefficients.
12. Diffusivity Data.
13. Comparison of Computed Results with Jernkontoret Data for Critical Temperatures and
Extent of Peritectic Reactions.
14. Comparison of Computed Results with Jernkontoret Data for Segregation Ratios.
15. Comparison of Core (D) and Interdendritic (ID) Manganese Contents from Ref. 23.
LIST OF APPENDICES
1. National Physical Laboratory
The Segregation and Phase Distribution During Solidification of Carbon, Alloy and
Stainless Steels.
VII