Inductive Melting and Holding Fundamentals Plants and Furnaces Process Engineering

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1 Erwin Dötsch Inductive Melting and Holding Fundamentals Plants and Furnaces Process Engineering

2 Inductive Melting and Holding

4 III Erwin Dötsch Inductive Melting and Holding Fundamentals Plants and Furnaces Process Engineering VULKAN VERLAG

5 IV Bibliographic information published by Deutsche Nationalbibliothek Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data is available on the Internet at ISBN Vulkan-Verlag GmbH Huyssenallee 52-56, D Essen, Fed. Rep. of Germany Tel.: +49 (0) , Internet: All rights reserved. No part of this book covered by the copyrights hereon may be translated, reproduced or copied in any form or by any means graphic, electronic, or mechanical, including photocopying, taping, or information storage and retrieval systems without written permission of the publisher. The listing of utility names, trade names, descriptions of goods etc. without special marking or designation in this book does not allow the presumption that such names are considered free in the sense of the trademark and trademark protection laws and can, consequently, be used by any person. This book was prepared with much care and devotion. Nonetheless, authors and publishing company do not assume responsibility for the correctness of data, comments, suggestions and possible printing errors. Managing Editor: Dipl.-Ing. Stephan Schalm s.schalm@vulkan-verlag.de

6 FOREWORD V FOREWORD In the foreword to his book "Inductive melting", published in 1966 by Verlag W. Girardet, Essen, which was to become the standard work of its day, K.-H. Brokmeier (Dr.-Ing.) wrote "Inductive melting is an application in a state of rapid development". He was right: Much progress has been made in the field of induction engineering since that was written more than 40 years ago. The time has therefore come to present - in summary form - the current state-of-the-art of this technology, still young and open to new developments, as it is deployed in manufacturing and processing metal. This is what this book sets out to do. The work focuses mainly on the metallurgical processes involved in melting, holding and pouring using induction systems. The fundamentals of inductive power transmission and the design of induction plants are described to the extent necessary to understand the production processes. The same applies to the sections on melting metallurgy, the targeted deployment of which is made possible by inductive melting. Based on these deliberations, the chapters on operating the systems themselves should be understandable and useful both for interested newcomers and for "old hands" in this field. In conclusion, a few personal notes: My thanks go to my first boss in Dortmund, Mr Karl-Heinz Brokmeier, to whom I primarily owe my knowledge of the interplays described in this book and who made my first steps in industry easy after many years at university, to Mr Franz Neumann, for all he taught me about cast iron metallurgy and to our technical head of the furnace business in Dortmund for many years, Mr Fritz Hegewaldt, who encouraged my positive attitude towards the engineering profession and to whom I owe most of my technical knowledge. I would furthermore like to thank the General Manager of ABP Induction Systems GmbH, Mr Wolfgang Andree, who made it possible for me to write this book and, above all, who has given me the opportunity to remain in daily contact with the interesting discipline of inductive melting and holding. In this context, I would also like to thank all my colleagues at ABP for all the pleasure I have gained in working together with you over the years. Last but not least, thanks go to my wife, Dorothee, whose mental support and technical writing skills have been invaluable in composing this book. May the reader find it useful. Dortmund 2009 Dr.-Ing. Erwin Dötsch

7 VI PREFACE PREFACE Inductive melting and holding is a major area of application in electro-thermal processes and one of the best-earning, high-performance sectors for inductive applications. After the rapid growth of inductive melting based on line frequency engineering in the 1960s, the technology enjoyed renewed growth in the 1980s in the wake of the development of suitable medium-frequency energy supplies. The importance of induction melting in iron foundries, in steel works and in metal works for non-ferrous applications continues to rise rapidly throughout the world. Yet the development of heavy-duty induction melting furnaces, executed both as induction crucible furnaces and as induction channel furnaces, also increases the risks in the works if the furnaces are not constructed and operated properly. Modern plants must furthermore fulfil the latest requirements of the iron, steel and non-ferrous industries, these needing to be considered in the design and construction of furnaces. The "energy efficiency" of process heating plants nowadays presents a new challenge for induction furnaces, for which new ideas have to be developed. The specialist literature available on these topics is extremely limited or has already become rather outdated. The expert knowledge required for designing and constructing induction furnaces is today preserved in the heads of a handful of specialists. The majority of these, however, will be retiring from professional life shortly, if they have not done so already. Although the theories of inductive melting are still taught at some universities or are even being further researched there, the applied practice of design and construction in consideration of the different metallurgical applications continues to be rather uncharted territory. I therefore particularly welcome the author's initiative to fill this gap. In this work, he presents the expert knowledge, in detail and oriented to practice, that he has gained through his many years of experience in the field of induction melting, both in plant construction and in the various areas of application. The book will provide excellent support not only for numerous specialists in the trade, but also for many students in their daily studies, in research and development and in practical applications. I would like to thank Vulkan Verlag, the publishers who agreed to print and distribute this important, ground-breaking work, and also ABP Induction Systems GmbH, which made its compilation possible. I hope that all established and up-and-coming engineers and students working in this field will profit greatly from this book. Prof. Dr.-Ing. Bernard Nacke Managing Director of the Institute for Electroprocess Engineering at Leibniz University in Hannover

8 CONTENTS VII CONTENTS FOREWORD... V PREFACE... VI 1. INTRODUCTION FUNDAMENTALS Inductive Power Transmission Induction Furnace Structural Shapes Induction Crucible Furnaces Electrical Efficiency Field Line Bath Agitation Bath Meniscus Hight Bath Flow Induction Channel Furnace Efficiency Factor Electromagnetic Field and Melt Flow COMPONENTS OF A CRUCIBLE FURNACE PLANT Furnace Body Refractory Lining Quartzite Dry Masses Spinel-Forming Dry Masses Refractory Technology Coil and Transformer Yokes Tilting Frame and Furnace Cover Power Supply Line and Medium Frequency Connection Parallel and Series Resonant Converters Circuit Feedback Optimizing Power Utilization by Tandem 34 Arrangement Frequency Selection Electromagnetic Leakage Fields Peripherals Recooling Devices Furnace Cooling Circuit... 38

9 VIII CONTENTS Electrical System Cooling Circuit Frost Protection and Water Quality Waste heat utilization Charging Devices Skimming Devices Process Control Systems Overall Layout COMPONENTS OF CHANNEL FURNACES Furnace Vessel Design for Holding Design for dosed pouring Design for Melting Refractory Lining Inductors Structural shapes Refractory Lining Power Supply Line Frequency Power Supply Converter Power Supply Cooling Devices ELECTROMAGNETIC STIRRERS AND PUMPS FURNACE DESIGN AND ENERGY REQUIREMENTS Characteristic Data for Melting in Crucible Furnaces Furnace Power Consumption Specific Enthalpy Electrical Losses Thermal Losses Furnace Efficiency Design of Furnace Power Specific Power and Furnace Limit-Rating Frequency of the Coil Current Energy Requirements Electricity Price and Load Management Characteristic Data for Channel Furnaces Melting Non-Ferrous Metals Holding and Superheating of Iron Melts... 86

10 CONTENTS IX 7. MELTING METALLURGY OF IRON AND NON-IRON MATERIALS Cast Iron Iron-Carbon Diagram Cast Iron Types Oxygen Content of the Melt and C/Si Isotherms Inoculation and Nucleation Magnesium Treatment Sandwich Process Tundish Cover Process Converter Process (Georg-Fischer System) Wire Flushing Process Inmold Process Other Processes of Mg Treatment Desulfurization Monitoring the Melt Wedge Test Piece Thermal Analysis Cast Steel Aluminium Primary and Secondary Aluminium Cast and Wrought Alloys Quality of the Aluminium Melt Treatment of the Melt Copper Materials Copper Production Copper Types and Alloys Oxidizing and Reductive Melting OPERATION OF INDUCTION PLANTS IN IRON FOUNDRIES Melting in Induction Crucible Furnaces Process Engineering Features Induction Furnace Versus Cupola Furnace Line Frequency (LF) or Medium Frequency (MF) Crucible Furnaces Charge Materials Steel Scrap Pig Iron Return Material

11 X CONTENTS Cast Iron Scrap Chips Additives Producing the Melt Making up the Charge and Charging Adjustment of the Target Composition of the Melt Heating to Tapping Temperature Processor-Controlled Melting Run Deposit and Bridge Formation Extraction of Fumes Melting Zinc-Coated Scrap Melting Chips Charging Loose Chips Melting Chip Briquettes Melting Sponge Iron Production Characteristic Properties Melting Process Profitability Downtime Procedure Refractory Behavior Chemical Erosion Infiltration Via the Liquid or Vapor Phase Crucible Monitoring Duplicating, Holding and Combined Holding/Melting in the Crucible Furnace Holding in the Channel Furnace Integrating the Storage Furnace into the Production Cycle Characteristic Features of the Channel Furnace Method of Furnace Operation Commissioning Operational Procedures Automatic Process Monitoring Inductor Change Dealing with Disturbances Inductor Monitoring Wear Behavior of the Refractory Lining Erosion Infiltration Crack Formation Clogging Energy Consumption and Profitability

12 CONTENTS XI 8.4 Pouring with Pressure-Actuated Pouring Furnaces Variants and Features of the Teapot Pouring Device Use of Heated and Unheated Pouring Devices Pouring Mg Treated Melts Deposite Formation Caused by Suspended Oxides Magnesium Vaporization Magnesium Reactions with Metal Oxides and Sulfur Practical Experience Pouring with Intermediate Ladles Stopper for Automatic Pouring Pouring in a Regulated Closed-Circuit Integrated Inoculations Process Monitoring Continuous Supply of Molten Iron Melting Cycle in a Tandem Plant Plant Concepts for a Continuous Supply of Molten Iron Channel Furnace as Buffer Tandem Plant as Melting and Buffer Unit Pouring Furnace as Buffer Optimised Design of the Melting and Pouring Plant MELTING CAST STEEL IN INDUCTION CRUCIBLE FURNACES Frequency and Gas Absorption Adjusting the Target Composition INDUCTION CRUCIBLE FURNACES IN MINI STEEL WORKS Induction Furnaces Versus Electric Arc Furnaces Requrements on the Melting Operations Producing Different Types of Steel Structural Steel Alloyed Steels Example of an Induction Melting Plant to Produce Structual Steel Billets Production Figures Layout of the Induction Plant

13 XII CONTENTS 11. INDUCTION SYSTEMS IN THE ALUMINIUM INDUSTRY Crucible Furnaces in Foundries Metallurgical Process Engineering Benefits Duplicating in a Crucible Furnace Refractory Behavior Melting Aluminium Chips Melting in Works for Semi-Finished Product Shops Examples of Establihed Production Plants Behavior of the Inductor Refractory Lining INDUCTION PLANTS FOR COPPER MATERIALS Induction Furnaces in Copper Fondries Melting Pouring Copper Materials with Pressure-Actuated Pouring Furnaces Inductive Melting in Semi-Finished Product Shops Channel Furnaces with High-Performance Inductors Application of Crucible Furnaces Melting Brass Chips Recycling Cable Wastes Flexible Melting of Copper Alloys INDUCTION PLANT FOR MELTING ZINC Re-Melting Zinc Cathodes Producing Zinc Alloys Galvanized Strip LITERATURE INDEX

$All you ever wanted to know on Refractory Materials REFRACTORY MATERIALS Design, Properties, Testing Gerald Routschka, Hartmut Wuthnow (Editors) The book aims to provide in a compact format basic$

14 All you ever wanted to know on Refractory Materials REFRACTORY MATERIALS Design, Properties, Testing Gerald Routschka, Hartmut Wuthnow (Editors) The book aims to provide in a compact format basic knowledge and practically oriented information on specific properties of refractory materials, on their testing and inspection, and on interpretation of test results. Tables and illustrations are used to clarify fundamental concepts on a comparative basis. This pocket-format manual provides an overview of the diverse range of modern refractories and their application-relevant properties. Its main feature is a series of practice-derived articles by well-known authors in the field on the various material groups and their characteristic property data. The content has deliberately been kept concise and instructive, abstracting and more detailed works are referenced. ORDERFORM FAX: +49 (0) 201 / Ex. Pocket Manual Refractory Materials Design-Properties-Testing Editor: Gerald Routschka und Hartmut Wuthnow 3. edition 2008, 625 pages, plastic, (EUR) 60,00 ISBN Date of Publication: Company Name Street address/p.o.b. Postcode/Zip, Town/City Phone Fax Preferred payment method Standing order Bill I will receive a 10,- credit note after using the secure and safe payment method by standing order. Vulkan-Verlag GmbH Leserservice Postfach Essen Bank name, Town/City Bank account number Giro account number Date Signature

Inductive Melting and Holding Fundamentals Plants and Furnaces Process Engineering

Erwin Dötsch Inductive Melting and Holding Fundamentals Plants and Furnaces Process Engineering Inductive Melting and Holding III Erwin Dötsch Inductive Melting and Holding Fundamentals Plants and Furnaces