The Casting Powders Book

550 Pages·2017·19.812 MB·English

by  Kenneth C. Mills, Carl-Åke Däcker (auth.)

Kenneth C. Mills
Carl-Åke Däcker
The Casting
Powders Book
The Casting Powders Book
Å ä
Kenneth C. Mills Carl- ke D cker
(cid:129)
The Casting Powders Book
123
Kenneth C.Mills Carl-ÅkeDäcker
RoyalSchoolof Mines SwereaKIMAB AB
Imperial CollegeLondon Kista
London Sweden
UK
ISBN978-3-319-53614-9 ISBN978-3-319-53616-3 (eBook)
DOI 10.1007/978-3-319-53616-3
LibraryofCongressControlNumber:2017933543
©SpringerInternationalPublishingAG2017
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Foreword
Swedish steelmakers have a long-standing commitment to product development.
Thisdemandsthatimprovedskillsmustbedevelopedinthesteelshop,inorderto
manufacture steel products free from defects and process problems. This is par-
ticularly important in the casting operation where it is necessary to optimise the
processparametersespecially,forthenewproductsunderdevelopment.Themould
powder is the key factor affecting casting process control and product quality and
has attracted considerable research effort in Sweden and other parts of the world
over the last 15–20 years. However, many of the parameters affecting continuous
casting are interactive; thus, changing one casting parameter can have a knock-on
effect on other parameters. Furthermore, there is an absence of collated and
structureddataforcastingpowders;thishasprovedamajorobstacletoresearchers
in steel plants, research institutes and universities. This is particularly apparent
when new researchers enter the complex world of mould powders and continuous
casting.
The Swedish Steel Producers identified the need for a comprehensive book on
continuous casting powders. This was discussed in 2012 at a meeting of the
Swedish Steel Producers’ Association by its CEO, Bo-Erik Pers, the Chairman
of the Technical Area on Casting and Solidification, Bo Rogberg, the research
manager, Lars-Henrik Österholm and Carl-Åke Däcker, Manager of Process &
Material Department, Swerea KIMAB. Following this meeting, Carl-Åke Däcker
was tasked with contacting Prof. Ken Mills (Imperial College) with a view to
writing a book on casting powders.
The project of writing a book on mould powders and slags was discussed at a
meeting inLondoninAugust2012between Ken Mills andCarl-ÅkeDäcker,who
have both participated in a significant number of ESCS and RFCS projects
involving mould powders. The idea of a combined effort was persuasive since it
would bring together Ken Mills’ knowledge of academic research on mould
powderswithCarl-ÅkeDäcker’smorepracticalexperienceinSwedishsteelplants.
The Swedish Steel Producers’ Association (Hugo Carlsson Foundation) provided
the necessary funding to take on the project and to provide supervision of the
progress by a reference group.
v
vi Foreword
Thebookisnotmeanttobereadfrombindertobinderandeachchapterisstand-
alone with its own abstract, introduction and reference list. For that reason, the
authorshavetriedtominimisetheamountofsearchingthereadermustdo,through
the various chapters, for figures, tables, etc. However, providing all the relevant
information comes at the expense of some repetition.
Acknowledgements
WewishtothanktheSwedishsteelmakersandSwereaKIMABfortheircontinual
support. We also acknowledge the additional funding and enthusiastic support
of the Technical Area on Casting and Solidification (TO 24).
WealsothankSwereaKIMAB,anditsCEO,StaffanSöderberg,forfundingand
support and the Materials Department, Imperial College, London for their support.
Wewouldliketogivespecialthankstothereferencegroupthatwasformedatthe
beginning of the book project. They attended a number of meetings and provided,
support,critical discussion andimportant technical input throughout the project:
– Tomas Sohlgren and Anders Lagerstedt, (SSAB Special Steels in Oxelösund).
– Arashk Memarpour, (Sandvik Materials Technology).
– Fatemeh Shahbazian, (Swerea KIMAB).
We also wish to thank the following for their help:
(cid:129) Klaus Schultz and Dirk Eckhard (Imerys) and Claudio Valadares and Omar
Afrange (Carbox, Brazil) for their inputs on Chap. 8 “Manufacture of mould
fluxes”.
(cid:129) KCM would like to thank the late, Dr. Adrian Normanton, Vince Ludlow,
Dr. Shahid Riaz and Dr. Bridget Steward ( Tata Steel/Corus) for many infor-
mative discussions.
(cid:129) Pavel Ramirez-Lopez (Swerea MEFOS), Peter Andersson (Swerea KIMAB),
Brian Thomas (University of Illinois), Masahiro Susa and Miyuki Hayashi
(Tokyo Institute of Technology), Qian Wang and Bing Xie (Chonquing
University), Masayuki Kawamoto and M Hanao (NSSMC), Koichi Tsutsumi
(JFE Steel Corporation), JW Cho (Gift, POSTECH) and Dr. Begona Santillana
(Tata Steel, IJmuiden) for providing important information and valuable dis-
cussions on various points arised during the project.
(cid:129) Mariana Ursu Däcker for valuable discussions, information and literature
regarding silicate chemistry.
vii
viii Acknowledgements
Finally, Ken Mills would like to thank his wife Margaret for her constant love,
support and understanding throughout the project.
Kenneth C. Mills
Carl-Åke Däcker
Contents
1 Introduction and Overview ..... .... .... .... .... .... ..... .. 1
1.1 Introduction ... .... ..... .... .... .... .... .... ..... .. 2
1.2 The Continuous Casting Process for Steel . .... .... ..... .. 2
1.3 The Introduction of Casting Powders. .... .... .... ..... .. 4
1.4 Mould Powder Behaviour in the Mould... .... .... ..... .. 6
1.5 Slag Film and Slag Rim Characteristics... .... .... ..... .. 7
1.5.1 Slag Film . ..... .... .... .... .... .... ..... .. 7
1.5.2 Slag Rim.. ..... .... .... .... .... .... ..... .. 9
1.6 Casting Conditions.. ..... .... .... .... .... .... ..... .. 10
1.6.1 Casting Speed (V ) ... .... .... .... .... ..... .. 10
c
1.6.2 Metal Flow..... .... .... .... .... .... ..... .. 11
1.6.3 Mould Dimensions ... .... .... .... .... ..... .. 12
1.6.4 Oscillation Characteristics.. .... .... .... ..... .. 12
1.6.5 Steel Grade..... .... .... .... .... .... ..... .. 12
1.6.6 Ar Flow Rate ... .... .... .... .... .... ..... .. 13
1.7 Physical Properties of Mould Slags .. .... .... .... ..... .. 13
1.8 Fluctuations in the Process. .... .... .... .... .... ..... .. 14
1.9 Definitions .... .... ..... .... .... .... .... .... ..... .. 14
1.9.1 Powders, Slags, Fluxes.... .... .... .... ..... .. 14
1.9.2 Powder Consumption Terms.... .... .... ..... .. 14
1.9.3 Temperature .... .... .... .... .... .... ..... .. 15
1.9.4 Viscosity.. ..... .... .... .... .... .... ..... .. 16
References .. .... .... .... ..... .... .... .... .... .... ..... .. 16
2 Slag Infiltration, Lubrication and Frictional Forces.. .... ..... .. 19
2.1 Introduction ... .... ..... .... .... .... .... .... ..... .. 20
2.2 Powder Consumption (Q).. .... .... .... .... .... ..... .. 21
2.2.1 Various Powder Consumption Terms . .... ..... .. 22
2.2.2 Measurement of Powder Consumption .... ..... .. 23
2.2.3 Methods Used to Understand Slag Infiltration
Mechanisms .... .... .... .... .... .... ..... .. 23
ix
x Contents
2.2.4 Problems Arising from Poor Powder
Consumption.... .... .... .... .... .... ..... .. 30
2.2.5 Optimum Casting Conditions ... .... .... ..... .. 30
2.2.6 Factors Affecting Powder Consumption ... ..... .. 32
2.3 Slag Infiltration During the Oscillation Cycle... .... ..... .. 41
2.4 Empirical Equations for Calculating Powder Consumption . .. 44
2.4.1 Frictional Forces. .... .... .... .... .... ..... .. 45
2.4.2 Factors Affecting Frictional Forces in the Mould . .. 48
2.5 Summary . .... .... ..... .... .... .... .... .... ..... .. 54
References .. .... .... .... ..... .... .... .... .... .... ..... .. 55
3 Heat Transfer in the Mould and Shell Solidification . .... ..... .. 59
3.1 Introduction ... .... ..... .... .... .... .... .... ..... .. 60
3.1.1 Heat Flux . ..... .... .... .... .... .... ..... .. 62
3.2 Horizontal Heat Flux ..... .... .... .... .... .... ..... .. 62
3.2.1 Heat Transfer Mechanisms Involved
in Horizontal Heat Transfer. .... .... .... ..... .. 63
3.2.2 Interfacial Thermal Resistance (R ) .... ..... .. 65
Cu/Sl
3.2.3 Factors Affecting the Horizontal Heat Flux. ..... .. 71
3.2.4 Measurement and Calculation of Heat Fluxes.... .. 80
3.3 Shell Solidification and Growth. .... .... .... .... ..... .. 85
3.4 Variability in Heat Flux... .... .... .... .... .... ..... .. 87
3.4.1 Variations in Heat Flux (q ) During the
Hor
Oscillation Cycle. .... .... .... .... .... ..... .. 88
3.4.2 Thermal Gradient Variations Arising from Metal
Flow and Other Causes.... .... .... .... ..... .. 88
3.4.3 Mould Level Variations ... .... .... .... ..... .. 91
3.4.4 Carbon Content of Steel ... .... .... .... ..... .. 92
3.4.5 Thermal Gradients in the Mould. .... .... ..... .. 94
3.4.6 Fracture of Slag Films. .... .... .... .... ..... .. 95
3.5 Vertical Heat Flux .. ..... .... .... .... .... .... ..... .. 96
3.5.1 Heat Transfer Mechanisms Involved in Vertical
Heat Transfer ... .... .... .... .... .... ..... .. 96
3.5.2 Factors Affecting Vertical Heat Transfer... ..... .. 97
3.6 Summary . .... .... ..... .... .... .... .... .... ..... .. 102
References .. .... .... .... ..... .... .... .... .... .... ..... .. 103
4 How to Manipulate Slag Behaviour in the Mould ... .... ..... .. 109
4.1 Introduction ... .... ..... .... .... .... .... .... ..... .. 110
4.2 Vertical Heat Flux and Thermal Insulation of Bed... ..... .. 111
4.2.1 Vertical Heat Flux.... .... .... .... .... ..... .. 111
4.2.2 Thermal Insulation of the Bed .. .... .... ..... .. 114
4.2.3 Measurements of Thermal Insulation of Powders . .. 116
4.2.4 Ways of Improving the Thermal Insulation
of the Bed. ..... .... .... .... .... .... ..... .. 116