Subir BiswasDebasish Sarkar

Introduction to Refractories for Iron- and Steelmaking

Introduction to Refractories for Iron- andSteelmaking

Subir Biswas • Debasish Sarkar

Introduction to Refractoriesfor Iron- and Steelmaking

Subir BiswasRefractory Technology Group,R&D and Scientific ServicesTata Steel (India)Jamshedpur, Jharkhand, India

Debasish SarkarDepartment of Ceramic EngineeringNational Institute of Technology RourkelaRourkela, Odisha, India

ISBN 978-3-030-43806-7 ISBN 978-3-030-43807-4 (eBook)https://doi.org/10.1007/978-3-030-43807-4

© Springer Nature Switzerland AG 2020This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of thematerial is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation,broadcasting, reproduction on microfilms or in any other physical way, and transmission or informationstorage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodologynow known or hereafter developed.The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoes not imply, even in the absence of a specific statement, that such names are exempt from the relevantprotective laws and regulations and therefore free for general use.The publisher, the authors, and the editors are safe to assume that the advice and information in thisbook are believed to be true and accurate at the date of publication. Neither the publisher nor the authors orthe editors give a warranty, expressed or implied, with respect to the material contained herein or for anyerrors or omissions that may have been made. The publisher remains neutral with regard to jurisdictionalclaims in published maps and institutional affiliations.

This Springer imprint is published by the registered company Springer Nature Switzerland AGThe registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Subir Biswas dedicates this book to the lovingmemory of his Parents & Parents in Law.

&

Debasish Sarkar dedicates this book with agreat sense of Devotion to “Lord Krishna”.

Preface

Despite several classic literatures including books, journal papers and internetresources, extensive demand motivated to fulfil the gap in between bookish knowl-edge and shop-floor experience, and thus we decided to write this textbook forstudents and professionals. In-depth thought process instigated to make an excellentlink in between fundamental concepts of refractories and their judicious use of ironand steel making, prime focus of this book. So, it provides a bridge between ceramistand metallurgist in the perspective of manufacturing of iron and steel for both small-and large-scale industries. It covers basic understanding on refractory selection andoperational process to mitigate the production effort. In this context, the entire bookhas been divided into 12 chapters, starting from “Refractories for Iron and SteelPlant” (Chap. 1) followed by “Iron and Steel Making Process” (Chap. 2); “BlastFurnace Refractory” (Chap. 3); “Hot Stove and Hot Air Carrying System” (Chap. 4);“Refractory Practice in EAF” (Chap. 5); “Refractory for Hot Metal Transport andDesulfurization” (Chap. 6); “BOF Refractory” (Chap. 7); “Refractory for SecondaryRefining of Steel” (Chap. 8); “Refractory in Ladle Flow Control and PurgingSystem” (Chap. 9); “Refractory for Casting” (Chap. 10); “Modern RefractoryPractice for Clean Steel” (Chap. 11); and “Advance Material Design and InstallationPractices” (Chap. 12). We believe that such concise literature is effectively helpfulfor a wide range of community including students, academia, researchers, novicegraduate trainees, senior managers, raw material processing, refractory manufac-turers, refractory procurement personalities and last but not least iron and steelmanufacturers.

Chapter 1

Refractories are the essential lining materials for working interfaces and backup zoneof furnaces throughout the manufacturing of iron and steel, in specific sequential andconsecutive operation of forming, holding, mixing and transporting hot metal, liquidsteel and slag. Despite refractory–metal direct interactions, refractory has to

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successively experience high temperature and corrosive environment through flues,stack or shaft and ducts. Prior to consider the refractories, recent market trend,designing parameters including predominant mechanical and thermal behaviourare explicitly discussed to provide a better insight of the subject. In this consequence,this chapter deals with the classification and description of acidic, neutral and basicrefractories for different environment and application zone for iron and steel-makingprocesses. Modern class of both shaped and unshaped refractories are highlightedstarting from raw materials to installation practice. Refractory corrosion mechanisminfluenced by blast furnace slag, primary and secondary steel-making slag areanalysed in order to understand and develop next-generation refractories.

Chapter 2

With extensive changing in the operating practice due to stringent control in productquality, introduction of new product mix and demand for high productivity, it isindeed to upgrade the refractory quality to cope up with the changed environmentand refractory life improvement. Hence, starting with the master plan, it was decidedto provide a brief introduction on modern iron and steel-making practice along withbackground of refractory choice to amalgamate the relation of refractory perfor-mance with changed escalating demand on safe performance. As small blast furnaceshave been closed and replaced by large size furnaces, open-hearth steel making hasbeen replaced by high productive basic oxygen furnaces (BOF), RH (RurhstahlHeraeus)—degasser is the most popular device for making ultra-low carbon steel.Additional composition adjustment by sealed argon bubbling with oxygen blowing(CAS–OB) has started to operate in many integrated and large size steel plant toproduce high quality alloy steel, the operating processes of those equipment havebeen discussed in detail.

Chapter 3

Blast furnace is likely to continue as the most efficient route to produce pig iron forits high productivity and cost optimization, for many years to come. Although asmall part of iron making has been supplemented by alternate iron-making processlike direct reduced iron (DRI) and smelting reduction; however, the replacement ofblast furnace for steel making is a distant dream. Thus, the refractory for modernblast furnace including cast house refractories is a critical issue and is discussed.Different refractory maintenance practices prolong campaign of blast furnace lifewith improved productivity, and thus their key features are enrolled. Starting fromthe reduction of coke rate to effective hot metal through runner is a challenging taskto the operator in the mind of production cost reduction and in turn, efficiency ofblast furnace is analyzed.

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Chapter 4

Hot stove is a thermal heat regenerator to produce and supply constant hot air to blastfurnace. The present demand of increased hot metal productivity through blastfurnace route requires high hot blast temperature more than 1200 �C, and it requiresto optimize and upgrade the quality and design of refractory. Thus, the design ofstove and their checkers have undergone major changes and demands in installationof superior quality refractories. Advantages in changed design and upgrade refrac-tory quality from alumina dome to silica, installation of ceramic burners are extrav-agantly explained in this chapter. Latest development in stove design is topcombustion stove that can deliver hot air more than 1300 �C; it is obvious that thisoperational feature has economic benefit over the conventional one. Detailed dis-cussion has been done on critical refractory application in those type of stoves thateventually help to generate knowledge on how one can use effectively hot blast morethan 1300 �C for as large as 5000 m3 blast furnace.

Chapter 5

Owing to several advantages including flexibility to produce several grades steel,precise control, cleaner environment and minimum installation space, many ministeel plants are producing steel through electric arc furnace (EAF) route. Thisprotocol is benefited to use sponge iron and higher share of scrap utilization. EAFsupports 35% high quality alloy steel production around the globe. Different con-structional and operational features, side wall and bottom/hearth refractory proper-ties and refractory design for bottom tapping are discussed in the perspective ofeffective steel processing. Despite the use of three carbon electrodes in EAF, onlyone electrode-based direct current (DC) arc furnace is highlighted. Refractorycorrosion mechanism in the presence of different impurities and subsequent slaginteraction are discussed through relevant phase diagrams in order to select therefractory depending on steel compositions. Eventually, the state-of-the-art operat-ing practice and refractory performances are summarized.

Chapter 6

Continuous steel production demands uninterrupted iron supply for steel vessels.Limited 60–80-ton hot metal ladle has several disadvantages, and thus high capacityup to 300-ton torpedo ladle is being introduced to overcome the hot metal ladlelimitations. Herein, explicitly focused on the design aspects, competitive early daysand recent refractory lining, plausible refractory deterioration factors and operationalinfluence on the refractory performance to operate the torpedo ladle effectively.

Preface ix

Torpedo ladle refractory development and lining modules for higher campaign,effect of insulation refractories, refractory maintenance protocols, and future chal-lenges are encountered to improve the working environment. Despite torpedo ladle,desulphurization in hot metal ladle and in situ process reactions with refractories,and wear mechanisms are discussed to fulfil the knowledge gap.

Chapter 7

Is it BOF a “heart” of any steel sector? If yes, it is mandate to take extra care to keepit healthy through refractory management, lining practice and effective operationalprotocols. In this backdrop, this chapter concentrates on the refractory designing forthe vessel and tap hole sleeve, and analyse probable wear mechanism throughternary phase diagram. Influence of gas purging and slag splashing on the refractorylife of different zones, followed by zonal lining concept and role of antioxidant arealso being discussed systematically. Topics of this chapter concerns on state-of-the-art refractory maintenance practice to prolong campaign life and optimization ofcost. Importance of protective slag coating on refractory performances, break-through in achieving vessel life >20,000 heats by introducing slag splashing andits influence in refractory performance have been explained in detail. MgO-Crefractory lining wear is an inevitable circumstance and is discussed in considerationof refractory–slag interaction, reduction of MgO, metal infiltration with respect tocritical pore diameter, thermal stress and spalling phenomena, impact caused bycharging and mechanical erosion and abrasion. Basic philosophy has beenhighlighted to improve the MgO-C refractory for BOF lining. Herringbone vesselrelining and maintenance practice by gunning and patching are emphasized toimprove the BOF lining life.

Chapter 8

Modern steel ladle is used not only to merely transport liquid steel from BOF tocaster, but also to act as a reactor vessel where refining of steel takes place to reduceimpurities, carbon, alloy addition and killing (Al, Si, bi-metal) of steel to reduceoxygen and other gasses; this comprehends the necessity and critical role of refrac-tories. Substantial modification and development have been brought into the refrac-tory quality to eliminate carbon (C) and oxygen pick-up into steel from refractorylining for ladle furnace (LF) and CAS–OB processes. Thus, refractory design in steelladles, energy saving issues, variation of thermal conductivity with respect toconventional graphite and nanocarbon, thermal stress-assisted cracks and refractoryfailure are discussed. RH–Degasser is in limelight to produce ultra-low C and highalloyed steel with an efficient productivity. Most suitable refractory practice hasbeen suggested in consideration of slag–refractory interaction that eventually facil-itate prolong ladle life and high quality steel.

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Chapter 9

Continuous strive towards new technology introduced reliable flow control systemsthat enable safe and prolong tapping liquid steel from ladle to tundish with consistentand high casting rate. Thus, synchronization of operational parameters, appropriaterefractory and analysis of probable failure are essential and encountered. Erosion ofbore and corrosion of sliding surface of the slide plates, radial cracking of plates andmetal leakage are the most critical issues as addressed with mention of optimizerefractory quality of plates and nozzles to prolong casting time. In order to homog-enous the molten steel, gas purging is an important aspect and thus different types ofpurging plugs, their design, refractory quality and the effect of casting sequences hadalso been discussed. Thermal-stressed failure and premature wear that may reducethe operational safety and promote shop-floor safety hazards are also highlighted.

Chapter 10

Continuous casting (con-cast) demands uninterrupted product length whereas in-gotprocess is popular for batch process. In modern production protocol, in-got castingprocess is limited and more than 90% of global steel production follows continuouscasting of slab, bloom, billet, thin slab, etc. A brief understanding including mould,pouring, choice of refractory and their failure, advantages and disadvantages ofin-got casting are discussed. In spite of batch process, exhaustive con-cast in specificoperational features, and refractory design and failures are delivered in the perspec-tive of minimizing casting defects and higher yield of finished steel. Tundish is theindispensable component in the con-cast process, and it is the refractory lined lastvessel before solidification of molten steel in the mould, in which different refrac-tories in hot face and in backup for easy de-sculling are described. Causes ofclogging, usage of anti-clogging refractory materials in sub-entry nozzle and other“black refractories” with latest design of inert gas purging in SEN had beenmentioned.

Chapter 11

Ductility facilities reforming but elastic modulus provides the strength of steel. It alldepends on constituents and phases in steel. The previous discussion emphasizessteel production is a multi-step process that has to pass through the exhaustiveenvironment and thus possibilities of inclusions despite targeted compositions.This drawback reduces the steel performance, and therefore modern amenitiesdemand clean steel for an extensive range of applications. An excellent choice ofnew class of modern refractory is required to avoid contamination and maintain

Preface xi

desired properties of steel. Detailed discussion is concentrated on probable inclu-sions by refractories, the stability of refractory oxides to produce clean steel and lowcarbon-containing refractories through the adoption of nanotechnology like usingnanocarbon and graphene. Magnesia–alumina–graphite refractories and spinelrefractory are highlighted in view of the carbon reduction in a ladle and continuouscasting refractories to make clean steel. Several operational features and refractorychoice for large tundish including hydrogen pick-up minimization in steel throughnon-aqueous resin-bonded dry-vibrating mass (DVM) is encountered and the ben-efits of using dry vibratable mass replacing basic spray material for easy de-scullingand achieving longer sequence life are discussed.

Chapter 12

Design terminology is not only confined in a particular shape rather performance ofapplied components depend on the geometry and material design, together. In earlydays, industrial furnaces and vessels were made out of brickwork, but clean steelasks for total package including refractory composition, shape and installationpractice for continuous and long period operation without interruptions for repairs.In order to accomplish steel sector demand, latest jointless monolithic especiallycolloidal silica-bonded cement-free castable, alumina-oxi-carbide-bonded castable,magnesia containing castable, chrome-free castable are encountered and analysed.Despite different classic endless lining protocols, installation and repair methodol-ogies are systematically discussed. Uniform microwave-assisted heating and dryingopens up a new installation practice for endless working lining that is capable ofreplacing partial damage zone without major replacement of original lining. Advan-tages of flame gunning over conventional wet gunning differentiate the performanceof refractory lining and also reduction of down time of the equipment for repair andmaintenance. Ceramic welding process is emphasized in which base refractory hotsurface is being repaired through metal powder at elevated temperature, and exo-thermic reaction facilitates permanent bond and repairs the defective refractoryzones.

In brief, this book has been written after gathering 25 years of hard-earnedknowledge and is full of amalgamation of introductory knowledge to advancerefractory practice in the outlook of iron to low carbon content steel manufacturing.So, we hope that it can serve the purpose as a textbook and will also provide a quickanswer to repeatedly posed question in real-life application.

Jamshedpur, Jharkhand, India Subir BiswasRourkela, Odisha, India Debasish Sarkar

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Acknowledgements

We would like to convey our heartfelt thanks to our parents and family members fortheir constant endorsement and motivation throughout the journey of writing thebook. We would like to thank our students and friends for their uninterrupted co-operative actions in manuscript preparation. Thanks to PhD scholar Sarath ChandraKatakam, Laboratory of Materials Processing and Engineering, Department ofCeramic Engineering, National Institute of Technology, Rourkela, Odisha, India,for his sincere help to complete the manuscript.

We would like to acknowledge Tata Steel Ltd, Jamshedpur; NIT Rourkela,Odisha, India; Department of Science and Technology (DST/TSG/Ceramic/2011/142-G, EEQ/2017/000028), India; and Board of Research in Nuclear Sciences(BRNS, 2012/34/46/BRNS), India, for their support.

We would like to thank all the researchers for their contributions to the scientificsociety, which are the building blocks of the conceptual knowledge of this textbook.

Eventually, our sincere apology to those whose names are inadvertently notmentioned.

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Why This Book?

This book provides unique and exhaustive topics compared to the existence ofrefractory books and discusses elaborately to accomplish the demand of students,shop-floor professionals, researchers and academia. Understanding the raw materialselection, refractory design, tailor-made refractory development, refractory proper-ties and their mode of applications are encountered in compliance with the objectivesof iron and steel making. Cumulative information under one umbrella resolves abridge-gap; main focus of this book. Thus, the book is considered as:

• A textbook for UG/PG students to understand the modern refractory practices ofiron and steel making

• Amalgamation of interdisciplinary knowledge to boost up the refractory research• Exhaustive modern iron and steel-making information enables refractory selec-

tion protocols• Refractory installation and performance analysis for blast furnace to continuous

casting refractories• Excellent knowledge resource for R&D and shop floor to solve the refractory

failure problems

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Contents

1 Refractories for Iron and Steel Plant . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.1 Scenario of World Steel Production and RefractoryDemand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.2 Modern Refractory Practices . . . . . . . . . . . . . . . . . . . . 31.2 Definition and Classification of Refractories . . . . . . . . . . . . . . . 51.3 Refractory Design Parameters and Testing . . . . . . . . . . . . . . . . 7

1.3.1 Density and Porosity . . . . . . . . . . . . . . . . . . . . . . . . . 81.3.2 Permanent Linear Change . . . . . . . . . . . . . . . . . . . . . . 91.3.3 Crushing Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.3.4 High-Temperature Deformation Under

Compressive Load . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.3.5 Deformation in Bending . . . . . . . . . . . . . . . . . . . . . . . 111.3.6 Elastic Modulus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121.3.7 Mechanical Stress Assisted Crack Propagation . . . . . . . 131.3.8 Thermal Stress Assisted Crack Propagation . . . . . . . . . 131.3.9 Thermal Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . 151.3.10 Thermal Expansion Behaviour . . . . . . . . . . . . . . . . . . 161.3.11 Thermal Stress and Shock . . . . . . . . . . . . . . . . . . . . . . 171.3.12 Wear Behaviour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191.3.13 Difference Between Corrosion, Erosion

and Abrasion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191.4 Shaped Refractories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

1.4.1 Silica Refractories . . . . . . . . . . . . . . . . . . . . . . . . . . . 211.4.2 Alumina-Silicate Refractories . . . . . . . . . . . . . . . . . . . 241.4.3 High-Alumina Refractories . . . . . . . . . . . . . . . . . . . . . 301.4.4 Magnesite Refractories . . . . . . . . . . . . . . . . . . . . . . . . 391.4.5 Dolomite Refractory . . . . . . . . . . . . . . . . . . . . . . . . . . 431.4.6 MgO-C Refractories . . . . . . . . . . . . . . . . . . . . . . . . . . 471.4.7 MgO–Cr2O3 Refractories . . . . . . . . . . . . . . . . . . . . . . 49

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1.4.8 Spinel Refractories . . . . . . . . . . . . . . . . . . . . . . . . . . . 561.4.9 Silicon Carbide Refractories . . . . . . . . . . . . . . . . . . . . 591.4.10 Zircon and Zirconia Refractories . . . . . . . . . . . . . . . . . 65

1.5 Monolithic Refractories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 681.5.1 Types of Monolithic Refractories . . . . . . . . . . . . . . . . 691.5.2 Castables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701.5.3 Calcium Aluminate Cement (CAC) . . . . . . . . . . . . . . . 761.5.4 Spinel-Containing Castable . . . . . . . . . . . . . . . . . . . . . 771.5.5 Ramming Masses and Plastic Monolithics . . . . . . . . . . 801.5.6 Application Methodology . . . . . . . . . . . . . . . . . . . . . . 83

1.6 Corrosion of Refractory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 861.6.1 Basic Corrosion Concept . . . . . . . . . . . . . . . . . . . . . . 861.6.2 Slag Viscosity and Penetration . . . . . . . . . . . . . . . . . . 871.6.3 Slag–Refractory Interaction . . . . . . . . . . . . . . . . . . . . . 891.6.4 Primary and Secondary Slags . . . . . . . . . . . . . . . . . . . 921.6.5 Effective Use of Iron/Steel slags . . . . . . . . . . . . . . . . . 96

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

2 Iron- and Steel-Making Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . 992.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 992.2 Overview on Blast Furnace Iron Making . . . . . . . . . . . . . . . . . 101

2.2.1 Basic Construction of Blast Furnace . . . . . . . . . . . . . . 1012.2.2 Blast Furnace Reactions to Produce Metallic Iron . . . . . 1042.2.3 Gaseous or Indirect Reduction of Iron Oxides . . . . . . . 1052.2.4 Direct Reduction of Iron Oxide by Solid Carbon . . . . . 1062.2.5 Other Reactions in Blast Furnace . . . . . . . . . . . . . . . . . 1072.2.6 Cooling System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1092.2.7 Cast House Practice . . . . . . . . . . . . . . . . . . . . . . . . . . 1172.2.8 Drainage of Hot Metal Through Trough

and Runners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1202.3 Modern Steel-Making Practices . . . . . . . . . . . . . . . . . . . . . . . . 121

2.3.1 Bessemer Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1212.3.2 Open-Hearth Process . . . . . . . . . . . . . . . . . . . . . . . . . 1222.3.3 Primary Refining Process Through BOF . . . . . . . . . . . 1232.3.4 Secondary Refining Process . . . . . . . . . . . . . . . . . . . . 128

2.4 Type of Processes and Special Consideration . . . . . . . . . . . . . . 1292.4.1 Ladle Furnaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1312.4.2 RH-Degasser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1372.4.3 CAS-OB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

3 Blast Furnace Refractory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1473.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1473.2 Demand on Refractory Lining . . . . . . . . . . . . . . . . . . . . . . . . . 148

3.2.1 Refractory Practice in Stack . . . . . . . . . . . . . . . . . . . . 152

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3.2.2 Refractory Practice in Bosh and Belly . . . . . . . . . . . . . 1553.2.3 Refractory Practice in TJ Area . . . . . . . . . . . . . . . . . . . 1583.2.4 Refractory Practices in Hearth . . . . . . . . . . . . . . . . . . . 161

3.3 Refractory Maintenance Practice . . . . . . . . . . . . . . . . . . . . . . . 1673.3.1 Robotic Stack Gunning . . . . . . . . . . . . . . . . . . . . . . . . 1683.3.2 Grouting Refractory . . . . . . . . . . . . . . . . . . . . . . . . . . 1713.3.3 TiO2 Injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

3.4 Consideration to Prolong Blast Furnace Campaign . . . . . . . . . . 1793.4.1 Designing Features . . . . . . . . . . . . . . . . . . . . . . . . . . . 1803.4.2 Quality Upgradation . . . . . . . . . . . . . . . . . . . . . . . . . . 1873.4.3 Monitoring of Refractory Condition . . . . . . . . . . . . . . . 1893.4.4 Thermal Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1963.4.5 Bottom Pad Cooling Layer . . . . . . . . . . . . . . . . . . . . . 1983.4.6 Blast Furnace Repair Processes . . . . . . . . . . . . . . . . . . 1983.4.7 Change of Stack Refractory . . . . . . . . . . . . . . . . . . . . 203

3.5 Cast House Refractory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2043.5.1 Tap Hole Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2053.5.2 Tap Hole Clay and its Performances . . . . . . . . . . . . . . 2063.5.3 Hot Metal Trough and its Design . . . . . . . . . . . . . . . . 2083.5.4 Refractory for Hot Metal Trough

and Iron Runners . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2113.5.5 Wear Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2133.5.6 Modern Refractory Practices . . . . . . . . . . . . . . . . . . . . 213

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

4 Hot Stove and Hot Air Carrying System . . . . . . . . . . . . . . . . . . . . . 2194.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2194.2 Design of Hot Blast Stove . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2214.3 Refractory Lining Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

4.3.1 High Alumina Refractory in Hot Blast Stove . . . . . . . . 2314.3.2 Silica Refractory in Hot Blast Stoves . . . . . . . . . . . . . . 2334.3.3 High-Temperature Corrosion Mechanism . . . . . . . . . . . 237

4.4 Hot Blast Carrying System . . . . . . . . . . . . . . . . . . . . . . . . . . . 2394.5 Failure of Stove Refractory and Repair Methodology . . . . . . . . 244References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

5 Refractory Practice in Electric Arc Furnace . . . . . . . . . . . . . . . . . . 2495.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2495.2 Features of an Electric Arc Furnace . . . . . . . . . . . . . . . . . . . . . 251

5.2.1 Roof Construction and Refractory Lining . . . . . . . . . . . 2525.2.2 Side Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2555.2.3 Bottom of Hearth . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2575.2.4 Refractory Design in Bottom Tapping . . . . . . . . . . . . . 260

5.3 Direct Current Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2615.4 Slag–Refractory Interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

Contents xix

5.4.1 Corrosion of Roof Refractory Liningin Presence of FeO . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

5.4.2 Chemical Erosion in Presence of TiO2 . . . . . . . . . . . . . 2635.4.3 Reaction with EAF Slag . . . . . . . . . . . . . . . . . . . . . . . 263

5.5 State-of-the-Art Operating Practice and RefractoryPerformances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266

6 Refractory for Hot Metal Transport and Desulfurization . . . . . . . . 2696.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2696.2 Torpedo Ladle Car . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270

6.2.1 Refractory Lining Practices . . . . . . . . . . . . . . . . . . . . . 2716.2.2 Refractory Lining Design . . . . . . . . . . . . . . . . . . . . . . 2796.2.3 Refractory Maintenance Practices . . . . . . . . . . . . . . . . 280

6.3 Desulphurization in Hot Metal Ladle . . . . . . . . . . . . . . . . . . . . 2836.3.1 Refractory Lining Practice . . . . . . . . . . . . . . . . . . . . . 2846.3.2 Wear Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

7 BOF Refractory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2897.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2897.2 Operating Conditions and Refractory Lining . . . . . . . . . . . . . . . 290

7.2.1 Gas Purging in Vessel . . . . . . . . . . . . . . . . . . . . . . . . 2947.2.2 Refractory Design in Vessel . . . . . . . . . . . . . . . . . . . . 2947.2.3 Refractory Design in Tap Hole Sleeve . . . . . . . . . . . . . 2997.2.4 Wear Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301

7.3 Zonal Lining Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3117.3.1 Bottom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3127.3.2 Charging Side Wall . . . . . . . . . . . . . . . . . . . . . . . . . . 3127.3.3 Tapping Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3127.3.4 Trunnion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3137.3.5 Mouth and Cone . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

7.4 Vessel Relining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3157.4.1 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3157.4.2 Tear Out and Profiling the Old Lining . . . . . . . . . . . . . 3157.4.3 Bottom Lining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3167.4.4 Bottom Wear Lining with Herringbone

Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3167.4.5 Bottom Wear Lining with Concentric

Ring Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3177.4.6 Barrel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3177.4.7 Cones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318

7.5 Refractory Maintenance Practice . . . . . . . . . . . . . . . . . . . . . . . 3207.5.1 Gunning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3207.5.2 Patching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

xx Contents

7.5.3 Slag Splashing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3227.6 Modern Refractory Practice to Prolong Life . . . . . . . . . . . . . . . 324

7.6.1 Source of Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3257.6.2 High Crystalline Graphite . . . . . . . . . . . . . . . . . . . . . . 326

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327

8 Refractory for Secondary Refining of Steel . . . . . . . . . . . . . . . . . . . 3298.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3298.2 Refractory Design in Steel Ladles . . . . . . . . . . . . . . . . . . . . . . 330

8.2.1 Volume Stability/Expansion/Shrinkage . . . . . . . . . . . . 3318.2.2 Stress During Cooling . . . . . . . . . . . . . . . . . . . . . . . . 3338.2.3 Results of Tensile Stress . . . . . . . . . . . . . . . . . . . . . . . 334

8.3 Ladle Refractory Lining for Silicon-Killed Steel . . . . . . . . . . . . 3358.3.1 Slag–Refractory Interaction . . . . . . . . . . . . . . . . . . . . . 3358.3.2 Prospective Dolomite Refractory . . . . . . . . . . . . . . . . . 337

8.4 Ladle Refractory Design for Al-Killed Steeland Ca-Treated Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3398.4.1 MgO-C Refractories . . . . . . . . . . . . . . . . . . . . . . . . . . 3408.4.2 Alumina Spinel Refractory . . . . . . . . . . . . . . . . . . . . . 3418.4.3 Al2O3-MgO-C (AMC) Refractory . . . . . . . . . . . . . . . . 344

8.5 Refractory Used Under Vacuum . . . . . . . . . . . . . . . . . . . . . . . 3468.5.1 MgO and CaO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3478.5.2 Cr–O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3478.5.3 Al–O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3478.5.4 Si–O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3488.5.5 MgO–C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3488.5.6 RH Degasser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3498.5.7 Refractory Wear Mechanism . . . . . . . . . . . . . . . . . . . . 3498.5.8 CAS-OB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357

9 Refractory in Ladle Flow Control and Purging System . . . . . . . . . . 3599.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3599.2 Refractory for Slide Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360

9.2.1 Alumina Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3619.2.2 Al2O3-ZrO2-C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3629.2.3 Magnesite Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3639.2.4 Slide Plate Refractory for Ca-Treated Steel . . . . . . . . . 363

9.3 Wear Mechanism of Slide Plate . . . . . . . . . . . . . . . . . . . . . . . . 3649.3.1 Metal Sticking on Working Surface . . . . . . . . . . . . . . . 368

9.4 Refractory Design of Purging System . . . . . . . . . . . . . . . . . . . . 3689.4.1 Types of Refractory . . . . . . . . . . . . . . . . . . . . . . . . . . 3699.4.2 Wear Mechanism of Purging Plugs . . . . . . . . . . . . . . . 3729.4.3 Safe Operating Practices . . . . . . . . . . . . . . . . . . . . . . . 375

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375

Contents xxi

10 Refractory for Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37710.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37710.2 Ingot Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37710.3 Continuous Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380

10.3.1 Refractory Practice in Tundish . . . . . . . . . . . . . . . . . . 38310.4 Black Refractory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395

10.4.1 Mono-block Stopper (MBS) . . . . . . . . . . . . . . . . . . . . 39610.4.2 Ladle Shroud . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39610.4.3 Submerged Entry Nozzle (SEN) . . . . . . . . . . . . . . . . . 399

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406

11 Modern Refractory Practice for Clean Steel . . . . . . . . . . . . . . . . . . 40911.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40911.2 Inclusions from Refractories . . . . . . . . . . . . . . . . . . . . . . . . . . 41011.3 Ladle Refractory Practices for Clean Steel Production . . . . . . . . 412

11.3.1 MgO-C Refractory in Steel Ladle . . . . . . . . . . . . . . . . 41311.3.2 Low Carbon Containing MgO-C Refractory . . . . . . . . . 41411.3.3 Magnesia–Alumina–Graphite Refractories . . . . . . . . . . 41811.3.4 Spinel Refractory . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41911.3.5 Corrosion Mechanism of Castable Lining

in Steel Ladle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42111.4 Continuous Casting Refractories for Clean Steel . . . . . . . . . . . . 422

11.4.1 Tundish Refractory . . . . . . . . . . . . . . . . . . . . . . . . . . . 42311.4.2 Tundish Design and Operation for Clean Steel . . . . . . . 424

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425

12 Advance Material Design and Installation Practices . . . . . . . . . . . . 42712.1 Refractory Material Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 427

12.1.1 Colloidal Silica-Bonded Cement-Free Castable . . . . . . . 42912.1.2 Alumina-Oxi-Carbide-Bonded Castable . . . . . . . . . . . . 43112.1.3 Magnesia-Containing Castable . . . . . . . . . . . . . . . . . . 43312.1.4 Chrome-Free Refractory . . . . . . . . . . . . . . . . . . . . . . . 434

12.2 Best Installation Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43812.2.1 Endless Lining in Steel Ladle . . . . . . . . . . . . . . . . . . . 43812.2.2 Micro-wave Heating of Castables . . . . . . . . . . . . . . . . 44112.2.3 Flame Gunning and Ceramic Welding . . . . . . . . . . . . . 443

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447

xxii Contents

About the Authors

Subir Biswas is Head of Refractory Technology Groupat Tata Steel Ltd., Jamshedpur, India. He has held thisposition since 2009. Subir Biswas is graduated from theUniversity of Calcutta, India, in 1985 with B.Tech(Ceramic Technology) and joined Carborundum Uni-versal Ltd., India, as graduate engineer in R&D centerof super refractory division. He joined Tata Steel Ltd. in1996 and has moved through a number of positions ofrefractory maintenance, research and development iniron making and steel making. Subir was responsiblefor new refractory product development and technology,selection of refractories, application of modern refrac-tory in steel plants for over 30 years. He has vastexperience in development and manufacturing of spinel,silicon carbide, dolomite refractories and low-cementcastables. He worked on advanced characterization ofrefractories, quality assurance and modern installationtechniques of refractories in steel plant, and he wasinvolved in various expansion projects on refractoryinstallation in commissioning of blast furnaces andre-heating furnaces at Tata Steel. Subir is a life memberof Indian Ceramic Society and Indian Institute ofCeramics and he has published appreciable number ofjournal papers on refractories development and installa-tion of his credit.

xxiii

Debasish Sarkar Professor and Head, Department ofCeramic Engineering, National Institute of Technology,Rourkela, Odisha, India, has 25 years of academic,research and industrial experience and published75 peer-reviewed international journal papers and3 Korean patents. While national patent concerns, apatent on graphene fortified MgO-C refractory for lowcarbon steel in collaboration with Tata Steel Limited,Jamshedpur, India, and a patent on zirconia-toughenedalumina femoral head and acetabular socket for hipreplacement in collaboration with IISc. Bangalore,India, are in pipeline. Professor Sarkar has written twopopular books Nanostructured Ceramics: Characteri-zation and Analysis by CRC Press, USA, 2018, andCeramic Processing: Industrial Practices by CRCPress, USA, 2019; both grasp attention of global stu-dents, material research community and ceramic indus-tries. Debasish is professionally involved in Modelling,Design and Failure Analysis of Structural Ceramicsthrough association with empowered National and Inter-national experts.

xxiv About the Authors

Chapter 1Refractories for Iron and Steel Plant

1.1 Introduction

Incompatible marriage results in divorce. Thus, competency and understandingexpedite long life. Competitive marriage in “Refractory” and “Steel” can reducethe refractory consumption per ton of steel is a dream of all steel manufacturers. Inthis perspective, basic understanding comprising shaped and unshaped refractorieswith respect to market demand and practices, classifications, refractory designingparameters, high-temperature phase transformation behaviour and properties, effectof impurities, and corrosion phenomena are discussed. Furthermore, a brief globalsteel market scenario is emphasized.

1.1.1 Scenario of World Steel Production and RefractoryDemand

World Steel Association published Global 2018 crude steel production data. Theretrieved data for top ten steel-producing countries is given in Table 1.1. India isplaced in second among high output ten countries like China, India, Japan, UnitedStates, South Korea, Russia, Germany and Turkey, with a wide gap of steelproduction by China [1]. Growing demand in Asian countries provokes to increasethe production capacity; however, downward experience is observed in Japan steelsector economy during 2018. In order to fulfill such enormous steel production,billion tons of refractories are produced around the globe. Top players like RHI AG(Austria), VESUVIUS (UK), Magnesita (UK), KROSAKI (Japan), SHINAGAWA(Japan), Imerys (North France), HWI (USA), MORGAN CRUCIBLE (UK),SAINT-GOBAIN (France) and INTOCAST (Germany) primely monitor majorshare of the global refractory market [2].

© Springer Nature Switzerland AG 2020S. Biswas, D. Sarkar, Introduction to Refractories for Iron- and Steelmaking,https://doi.org/10.1007/978-3-030-43807-4_1

1

Moreover, the million refractory manufacturers are actively supplying differentclasses of refractories around the globe despite these giant participants. In currentreport, the anticipated refractory market growth volume is around 5% registered bycompound annual growth rate (CAGR) for the forecast duration of 2019–2024, asshown in Fig. 1.1. The prime philosophy is described as because of growingproduction of non-ferrous materials, increasing large infrastructure projects inemerging markets, and upcoming demand from the glass industries. However, theenvironmental awareness and laws restricts the disposal of refractories that eventu-ally may hinder the actual market growth.

In spite of other end-user industries, iron and steel sector consumes lion-sharemarket of refractories that can withstand a wide range of temperatures 260–1850 �Cwithout major alteration of their physical properties. The prime applications ofrefractories in the iron and steel industry include usage in internal linings of furnacesto make iron and steel, in furnaces for heating steel before further processing, invessels for holding and transporting metal and slag, in the flues or stacks conducted

Table 1.1 Recent steel production scenario for top ten countries

Top 10 steel-producing countries

Rank Country 2018(Mt) 2017(Mt) % 2018/2017

1 China 928.3 870.9 6.6

2 India 106.5 101.5 4.9

3 Japan 104.3 104.7 �0.3

4 United States 86.7 81.6 6.2

5 South Korea 72.5 71.0 2.0

6 Russia(e) 71.7 71.5 0.3

7 Germany(e) 42.4 43.3 �2.0

8 Turkey 37.3 37.5 �0.6

9 Brazil 34.7 34.4 1.1

10 Iran(e) 25.0 21.2 17.7

Source: World Steel Association

Fig. 1.1 A projected global refractories market revenue sharing by the different end-user industriesin the duration of 2019–2024 [2]

2 1 Refractories for Iron and Steel Plant

through hot gases, and others are listed. Change in global political scenario mayimprove the confidence and investment to fulfill the forecasted CAGR.

When we are addressing the refractory market in India as a second steel manu-facturer in world, steel sector consumes near to 70% refractories, and further it isexpected to increase to fulfill the cumulative steel production demand near to 300 mtin 2025. Indian refractory industry has potential to make promising product for steel-makers; however, couple of integral factors are indeed to synchronize to boost up theuse of domestic raw materials and refractory market [3].

Steps to be taken to facilitate this include:

• Correction in the trade duty structure of raw material and finished products.• Domestic procurement of products required in turnkey package.• Focus on making domestic products cost competitive.• Increase in export customer base for products made with domestic raw materials.

A win–win industrial environment is mandatory to establish continuous businessand effective outcome for refractory manufacturer and steel-making organization, assupplier like to try supply more, and end-user try to optimize the refractory con-sumption per ton of steel. In general, the long-term total refractory consumption forsteel making is expected to be in the range of 5–10 kg/ton, which essentially followsthe trend in Japan. However, current regional rates of specific refractory consump-tion (kg refractories/ton steel) are China 20 kg/t; Europe and Americas 10 kg/t; Japan8 kg/t and India 10 kg/t [2]. From this above discussion, one can envisage whyrefractory study is important in the perspective of iron and steel manufacturingaround the globe. This refractory practice is not confined in only shaped or unshapedrefractories, rather it can be classified in broader sense as acidic, basic and neutralrefractories that are extensively used in different regions, and discussedsystematically.

1.1.2 Modern Refractory Practices

Silica refractory is in forefront for coke oven, considered as the first region whererefractory used in a steel sector to make coke from coal, as coke is an essential feedfor blast furnace, but such refractory has limited interaction with iron or steel.Predominately, silica brick is the master component for coke oven lining; brief ofsuch refractory is discussed in Sect. 1.4.1. Despite selective information on silicarefractory, all other refractories are critically considered and analysed in the per-spective of application zone, interaction with solid, liquid or gas during processingof iron and steel, probable installation, failure, etc. Application zone, subzone andtype of all probable refractories are listed in Table 1.2 that provide an overall ideaabout essential demand of refractories in modern installation practice for iron andsteel industries.

1.1 Introduction 3

Table 1.2 Modern refractory practices starting from iron manufacturing to steel casting

Vessels/zones/components Subzone

Type of refractories

Shaped Unshaped

Blast furnace Stack Al2O3, SiC, Si3N4-bonded SiC,Graphite

–

Bosh Al2O3, SiC, Si3N4-bonded SiC,Graphite

–

Belly SiC, Si3N4-bondedSiC, Sailon-bondedSiC, Graphite

–

T J Area Carbon blocks,Sialon-Bonded SiC

–

Hearth Carbon blocks withceramic cup bricks

–

Tap hole – Tap hole clay

Trough High Al2O3 bricks Trough castable, ram-ming mass

Hot stove Inner lining/checkers

Silica, HA bricks,Insulation bricks

Ramming mass,castables

Burner Mullite, Mullite-andalusite bricks

Castables

Hot blasttransport

HA bricks, Insula-tion bricks

Castables

EAF Roof Basic (Magnesite,Mag-Chrome), HAbricks, Precastblocks

Gunning castables

Side wall MgO-C bricks, Car-bon (C) blocks

Ramming masses, cast-ables (back up)

Hearth MgO-C bricks, Cblocks

Tapping spout Precast blocks Ramming masses

Torpedo ladle Vessel lining ASC, AC, HAbricks, Insulationbricks, insulationboards

Castable in mouth,Ramming masses andcastable in intermediatelining

BOF Vessel MgO-CMag-Chrome,Magnesite

Carbon ramming mass

Tap hole sleeve Basic refractoryprecast

Ramming masses

Secondaryrefining

Si killedsteel

Slag zone MgO-C, Dolomite

Metal zone Dolomite Castable in back up

Bottom Dolomite, Al2O3-MgO-C (AMC)

Ramming mass, castablein back up

Al killedsteel

Slag zone MgO-C

Metal zone MgO-C, AMC, Spi-nel,Mag- chrome inback up.

Castable

(continued)

4 1 Refractories for Iron and Steel Plant

1.2 Definition and Classification of Refractories

Classification of refractories are prerequisite to understand why alumina-silicaterefractory is a suitable practice for blast furnace, but MgO-C brick for BOF.However, such classification depends on the refractory composition, slag chemistry,physical properties and mode of applications.

In consideration of different class of refractories used in iron making to steelcasting, a cumulative representation of different class of refractories has been givenin Fig. 1.2. Base composition of pyramid represents oxide refractories, but anupward direction signifies non-oxide refractories such as SiC and carbon-basedrefractories, whereas peak point is for carbon block only [4]. However, a basicidea on both shaped and unshaped refractories and their characteristics with respectto composition, temperature and application can provide in-depth understanding offuture discussion.

In shaped refractories, prime products are unfired, fired, fusion cast and insulating(porous) bricks, in which first set of dense refractory is using for working lining.

Table 1.2 (continued)

Vessels/zones/components Subzone

Type of refractories

Shaped Unshaped

Bottom AMC, Ramming mass

Ca killedsteel

Slag zone MgO-C Castable (back up)

Metal zone Spinel, MgO–C

Bottom AMC Basic ramming mass

RH-Degasser Upper vessel Mag-Chrome

Lower Vessel Mag-Chrome (directbonded, rebonded)

Basic ramming mass

Snorkels Direct-bonded andrebondedMag-Chrome

Castable andRamming mass.

Flow control and purgingsystem

Slide plate, Wellblocks, Ladle andcollector nozzle

Al2O3-C, HAAl2O3-ZrO2-C

–

Insert ZrO2 –

Casting Ingot HA bricks andshapes

Ramming mass

Continuous Tundish Dam and wear pre-castPrecast flow controldevise.

Backup castable lining,hot face spray, dryvibratable mass

Black refractory Mono-block stop-per, shroud, subentry nozzle

–

1.2 Definition and Classification of Refractories 5

However, insulating brick possesses low thermal conductivity and provides thermalbarrier in the backup lining. Predominate unshaped refractories are castables, gun-ning mixes, ramming mixes, patching and coating materials. Castables are made ofwide size range of refractory aggregates and mixed with cement as bond. Theaggregate is mixed with water and casting is done to form rigid mass in lining. Inmodern refractory practice, no-cement castable is also introduced where different solis used to cast and form in situ high-temperature phases. Some lightweight porouscastable is also used as backup lining to maintain the thermal barrier. Gunning mixesare mixer of refractory particles which consist of binders and easily stick to theapplied surface after gunning. This may be either cold or hot gunning. Rammingterminology refers a pneumatic ramming is required during application of binder(organic or inorganic) added refractory aggregates that eventually become hardthrough formation of ceramic bond. Mortar is a binder-added relative finer refractorymass applied through trawling that helps to join within two shaped refractories.Analogous to the mortar, the patching and coating materials are employed throughspraying. Despite such class of refractories, insulating alumino silicate ceramicdrawn fibres produce several refractory articles including blankets, felt, rope,2–10-mm-thick papers, etc.

Only definite design practice is not enough to select refractory, rather cumulativeaccepting the high-temperature thermo-mechanical properties and chemical compat-ibility with iron and steel aids to select and develop new class of refractories. Forexample, more often acidic silica refractory has high abrasion resistance at hightemperature and high mechanical strength under load. It possesses very goodspalling resistance >600 �C, however, experience poor thermal shock resistance<600 �C. It has excellent corrosion resistance to acid slag and to iron oxide.

Fig. 1.2 Cumulative representation of probable refractories w.r.t. chemical compositions

6 1 Refractories for Iron and Steel Plant

Depending on the alumina content, high-alumina (neutral) brick experiences volumestability at high temperature, thermal expansion is low up to below 80% Al2O3

(major phase mullite), but high above 80% Al2O3 (corundum phase), good load-bearing capacity and resistance to acid slag, but relatively less resistance to basicslag. Basic refractories, more popular magnesite-based refractories, exhibit highrefractoriness, high basic slag corrosion resistance, high strength and refractorinessunder load. Furthermore, non-oxide SiC is an excellent choice for high-temperatureapplication, but in the presence of oxygen it oxidizes rapidly beyond 800 �C. It hasalso excellent abrasion resistance, thermal shock resistance and corrosion resistancetowards hot metal and acid slag, as well. In consideration of different physical,thermal, mechanical, thermo-mechanical properties, are elaborated to understandhow one can select the designing parameters for particular choice of application.

1.3 Refractory Design Parameters and Testing

Refractories are non-metallic and inorganic ceramic materials, composed of oxides,nitrides and carbides or combination of them and which can withstand very hightemperature (1400 to as high as>2500 �C), can prevent corrosion to liquid metal andslag and are resistant to hot abrasion and erosion. Other essential properties ofrefractory materials are:

• Resistance to thermal fluctuation.• Resistance to high-temperature deformation (creep).• Volume stability at elevated temperature.• High load-bearing capacity.

While considering the critical definition of refractory materials, background ofabove features is considered and discussed that eventually support to comprehendthe refractory selection for particular zone of interest. In brief, the resistance tothermal fluctuation of refractory depends on the elastic modulus, work of facture,thermal expansion coefficient and thermal conductivity, and resistance to high-temperature deformation (creep) is controlled by the fundamental properties likethermo-elastic behaviour, deformation under load at high temperature (RUL) andon-site operating temperature analogous to PCE. The volume stability at elevatedtemperature associates with permanent linear change (PLC), reversible thermalexpansion (RTE), as well as the operating temperature, and finally high load-bearingcapacity depends on apparent porosity, bulk density, crushing strength, linearchange, refractory composition (presence of glassy phase), etc. However, theseproperties are further controlled by the composition, microstructure, porosity contentand their distribution. Basic philosophy staring from the physical properties tocritical thermal and thermo-mechanical properties is encountered in order to empha-size as a backbone of refractory properties and enable “refractory design” forparticular zone of interest during iron and steel making.

1.3 Refractory Design Parameters and Testing 7

1.3.1 Density and Porosity

Rapid inspection of bulk density (BD) and apparent porosity (AP) assures the first-stage quality control of shaped and unshaped refractories. Standard testing protocolspecifies a method for the determination of the bulk density, apparent (open)porosity, and true (open + closed) porosity of dense shaped refractory products.Closed porosity comes across as particular voids entrapped within the matrix anddifficult to penetrate conventional liquid like water or kerosene in normal atmo-spheric pressure and temperature, whereas Archimedes process easily estimates theopen porosity content, only. In brief, following equations are used to determine theseparameters:

The bulk density,

ρb ¼ m1

m3 � m2Þð � ρliq g=cc ð1:1Þ

The apparent porosity,

ρa ¼m3 � m1Þðm3 � m2Þð � 100% ð1:2Þ

The true porosity,

ρt ¼ρtheoretical � ρbÞð

ρtheoretical� 100% ð1:3Þ

where m1 is the mass of the dry test piece, m2 is the apparent mass of the suspendedtest piece, m3 is the mass of the soaked test piece, ρliq is the theoretical density andρtheoretical is the theoretical density.

High-dense compact enhances the elastic modulus and load-bearing capacity andavoids early-stage corrosion aggravated by molten metal. However, the porous bodyreduces the thermal conductivity that facilitates insulation properties for backuplining. In this context, the influence of density and porosity on different mechanicaland thermo-mechanical properties is summarized in consecutive sections. Severalfabrication techniques fulfilled the desired density or porosity; nevertheless, thestarting raw material size grading and composition are critical parameters forsintered density. Appropriate coarse-to-fine ratio provides highest tapping densitythat accomplishes appreciable room temperature pressing or casting green density. Inorder to achieve desired density, modification on particle grading or pressing moduleor workmanship is desired. However, composition plays a serious role during high-temperature processing or in situ application temperature. For example, high alkalicontent produces low eutectic phase in alumina-silicate refractories as well asdifferent degree of grain orientations alter the resultant microstructure, resulting inthe formation of weak region and early stage of failure through metal penetration in

8 1 Refractories for Iron and Steel Plant

weak or porous zone. It is worthy to remember that the resultant refractory density orporosity (size, shape and distribution) amends at service temperature and strictlydepends on the composition. In cumulative, the green density depends on initialstage of particle grading; however, sintered density regulates by grading, composi-tion and temperature, where true porosity is always higher than apparent porosity.Despite refractory density and porosity, the operating condition and metal chemistryare responsible parameters to achieve high metal throughput.

1.3.2 Permanent Linear Change

Continuous pore removal provokes shrinkage, and in situ phase transformationresults in either expansion or shrinkage, depending on the coefficient of the thermalexpansion (CTE) behaviour of new phase. Permanent linear change (PLC) soundsirreversible dimensional change and in obvious it is critical at definite temperaturefor a particular set of composition. Usually, the PLC is measured by Eq. (1.4), where

PLC %ð Þ ¼ Lf�LiLi

� 100 %ð Þ ð1:4Þ

where Li ¼ initial sample length before heating, Lf ¼ final sample length afterheating.

In order to describe the importance of such physical properties on refractorylining, let us consider the utility of high-alumina brick in hot metal ladle at 1550 �C.The high-alumina bricks are widely used in backup of steel ladle where the bricks areexperiencing the temperature as high as 1400 �C. Expansion of the bricks in eachcycle is preferable to keep the ring tight and bricks would not allow falling from therefractory lining. The PLC value is the utmost important factor to adjust the mortarjoints also and the value to be maintained at 0.1% expansion. The stable mullite(3Al2O3.2SiO2) phase is formed in high-alumina bricks, which involves3–5 � 10�6/K thermal expansion. Recent development is the use of spinel(MgAl2O4) forming bricks in steel ladle, which provides +ve PLC during repeatedheating.

1.3.3 Crushing Strength

Terminology indicates the capability to withstand load-bearing strength; in otherwords, the refractory is subjected to survive an optimum compressive strength beforecrushing or failure. However, the importance of such data is started from green brickfabrication where an essential strength is required to handle prior to different stage oftransportation and firing to obtain high degree of crushing strength under compres-sive (load/area) mode of loading. It is generally measured as the fracture load at room

1.3 Refractory Design Parameters and Testing 9