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State of the art and developments in near-net-shape casting of flat steel products

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ISSN 1018-5593
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European Commission
technical steel research
Steelmaking
State of the art and developments in
near-net-shape casting of flat steel products European Commission
technical steel research
Steelmaking
State of the art and developments in
near-net-shape casting of flat steel products
Jean-Pierre Birat
Institut de recherches de la sidérurgie (IRSID)
Voie Romaine
F-57210 Maizières-les-Metz
France
Rolf Steffen
Verein Deutscher Eisenhüttenieute (VDEh)
Sohnstr. 65
D-40237 Düsseldorf
Germany
Stephan Wilmotte
Centre de recherches métallurgiques (CRM)
rue Ernest Solvay, 11
B-4000 Liège
Belgium
Agreement 7210-ZZ/556
Düsseldorf, Germany
March 1995
Final ECSC report
Directorate-General XII
Science, Research and Development
1995 EUR 16671 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
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1995
ISBN 92-827-5639-4
© ECSC-EC-EAEC, Brussels · Luxembourg, 1995
Reproduction is authorized, except for commercial purposes, provided the source is acknowledged
Printed in Luxembourg Preface
This study was financed by the European Coal and Steel Community
(ECSC) by Agreement 7210-ZZ/556 of Verein Deutscher Eisenhütten­
leute (VDEh), Düsseldorf
The authors responsible
for chapter 3, 4 and 5:
R. Steffen
Verein Deutscher Eisenhüttenleute
Sohnstr. 65
40237 Düsseldorf / Germany;
and within chapter 4 for the part 4.3:
R. Klima and M. Roder
Betriebsforschungsinstitut (BFI)
Sohnstr. 65
40237 Düsseldorf / Germany
for chapter 6:
J. P. Birat
Institut de Recherches de la Siderurgie (IRSID)
Voie Romaine
57210 Maizieres-les-Metz / France
for chapter 7 :
S. Wilmotte
Centre de Recherches Metallurgigues (CRM)
Rue Ernest Solvay, 11
4000 Liege / Belgium
The authors thank their colleagues of the ECSC Executive Commit­
tees C3 "Casting and Solidification" as well as T2 "P & D in
Continuous Casting" for important information regarding running
projects.
Ill Summary
In near-net-shape casting of steel thin slab casting (40 to 125
mm as-cast thickness) and strip casting (1 to 25 mm as-cast
thickness) are important technical developments which have the
potential to change the structure of the iron and steel indu­
stry.
The advantages of flexible minimills with lower investment costs
and the reduction of energy consumption as well as the possibi­
lities to improve as-cast structure and to achieve better physi­
cal and mechanical properties are competing against the high
surface guality and high productivity level of the conventional
slab casting-hot strip mill route of big integrated plants.
Thin slab casting is most advanced in a variety of technologies
that have been developed since 1986.
As-cast thickness of 50 mm with funnel-type mould, no in-line
deformation: CSP (SMS Schloemann-Siemag)
- As-cast thickness of 60 to 90 mm, soft reduction or in-line
reduction with liguid core: ISP (Mannesmann Demag Hüttentech­
nik MDH); FTSC (Danieli); CPR (Thyssen Stahl, Usinor-Sacilor,
SMS)
- As-cast thickness of 70 to 125 mm with planparallel mould; no
in-line deformation: Conroll (Voest-Alpine Industrieanlagen­
bau VAI and Davy Intern.); TSP (Tippins and Samsung); MTSC
(Sumitomo Metal Ind.).
The total production of all thin slab casters will arise to
about 30 mio t/a at the end of 1998, SMS with its CSP caster
currently is the leader in orders for thin slab casters. This
means that a considerable amount of production will shift from
hot strip mills of conventional steel plants to the new mini-
mills. As technology marches on the quality of via thin slab
produced steel grades will proceed towards high product demands,
and the intergrated steel plants will loose segments of their production staying with the production of high quality products.
But thin slab casting is not successful till now for all steel
grades to be covered. Special rolling strategies have to be de­
veloped for microalloyed steel, and for stainless steels expe­
riences show lower difficulties in the casting behaviour of fer-
ritic steel grades compared to austenitic steels.
Strip casting processes are now in the same situation as the
conventional continuous casting processes 20 years ago, but have
to compete with the highly developed processes of today. For ca­
sting steel products with 1 to 3 mm thickness about 10 demon­
stration plants are being developed or operational; twin-roll
casters are mainly used. Usinor-Sacilor together with Thyssen
Stahl and Clecim are leading the European scene (20 to 90 t,
3 mm χ 800 mm), whereas Nippon Steel is currently able to cast
already 3 mm strip of 1330 mm width. As these developments con­
centrate on casting stainless steel there is one plant in Au­
stralia (BHP, built by IHI) which will produce 2 mm carbon steel
strip of up to 19 00 mm width by twin-roll casting.
Due to rolls diameters technical feasible and the heat transfer
the annual production is limited to about 600 000 t/a; but this
means an adequate production rate for special steel grades like
stainless steels.
There is only one pilot development on casting of about 10 mm
thick strip by using a moving belt which should allow producti­
vities similar to conventional slab casting (Preussag Stahl, TU
Clausthal, Mefos). In-line rolling of this strip gives the po­
tential to achieve the deformation degree needed for a wide ran­
ge of product properties.
To improve surface quality is the most important task in all new
near-net-shape casting developments. For strip casting long term
testing is necessary to get a reliable view on production costs.
VI CONTENTS
1. Introduction and Aim of the study 1
2. Definitions 3
3. Metallurgical aspects 5
3.1 Heat transfer and casting speed
3.2 Solidification rate and structure 9
4. Thin Slab Casting 13
4.1 Past developments on processes with moving mould . 1
4.2 News ons with stationary mould 16
4.3 Energy consumption of hot strip production by thin
slab casting 35
4.4 Conclusion on thin slab casting 56
5. Thick Strip Casting 6
5.1 Past developments on moving mould processes .... 6
5.2 News on moving moulds. 6
5.3 Conclusion on thick strip casting 74
6. Strip Casting 77
6.1 Presentation of strip casting processes9
6.2 Basic process technology of strip casting processes 82
6.3 Process developments 112
6.4 Economics of strip casting processes and
future perspectives 140
6.5 Conclusion on strip casting5
7. Quality aspects in Near-Net-Shape Casting 153
7.1 The thin slab route 15
7.2 The strip route 169
7.3 Conclusions 18
8. General Conclusions 193
VII