Primer on Flat Rolling Primer on Flat Rolling Second Edition John G. Lenard Department of Mechanical and Mechatronics Engineering University of Waterloo Waterloo, Ontario, Canada AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD PARIS • SAN DIEGO • SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Elsevier The Boulevard, Langford Lane, Kidlington, Oxford, OX5 1GB, UK 225 Wyman Street, Waltham, MA 02451, USA First edition 2007 Second edition 2014 Copyright © 2014, 2007 Elsevier Ltd. All rights reserved No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. 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Dedication For Elisa-Chaya, whose smile makes my day Preface to the Second Edition In the first edition of this book, I wrote that the process of flat rolling has not changed for centuries, not since Leonardo da Vinci rolled soft metals on his hand-driven mill. While the process hasn’t changed in the last few years, either, there have been numerous, important innovations. The first edition was intended to present the basic ideas of flat rolling and that objective also has not changed in the second edition. Several chapters have been added, however, expanding on the fundamental concepts. In Chapter 1, various rolling processes À not only flat rolling, exclusively À have been described. In a new Chapter 2, Don Adair, the manager of Flat Rolling Operations at Quad Engineering of Toronto and Edwin B. Intong, former technical manager for Electrical & Automation, US Steel Engineers and Consultants, present a history of the development of different generations of hot strip mills. The changes are highlighted and their importance is pointed out. In an interesting section, the innovations, introduced in recent times, are listed. Another new addition, Chapter 3, prepared by Dr J.B. Tiley, hot rolling consultant, discusses current trends of roll design, focusing on the development of new materials for work rolls and back-up rolls with the objectives of reducing roll wear and enhancing roll life. Chapter 4, unchanged, describes the basic ideas of flat rolling. Chapter 5 deals with mathematical modelling of the process. Section 3.8 in the first edition, dealing with Neural Networks, has been removed. While the use of neural networks created some excitement some years ago, this didn’t continue, as engineers prefer to use statistical methods for control and predictions. Chapter 6, Advanced Finite Element Modelling is new. It is the result of the cooperative research of Dr G. Krallics, Z. Be´zi, M. Szucs˝ of the University of Miskolc, Miskolc, Hungary and the present author. It is acknowledged that finite element modelling of flat rolling has often been dealt with in the literature. Details of some of these models are given and a new model that accounts for all three components of the flat rolling system À the roll, the rolled strip and its interface À is introduced. Its predictive ability is pre- sented by comparing its computations to experimental results. Chapter 7, Simulation and Reduction of Local Buckles in Cold Rolling, goes somewhat beyond the basics. It was prepared by Dr Yuli Liu, chief process engineer, manager of Process Engineering and Development of Quad Engineering Inc. An advanced mathematical model, consisting of several modules, is given in some detail. The chapter is of some importance as it deals with problems of shape and dimensional inaccuracies in the rolling process. However, using the model is neither easy nor immediate. A potential user must refer to the original publications. xii Preface to the Second Edition Chapter 8 is unchanged. A new section, Nanotribology, is now included in Chapter 9, Tribology. The topic is briefly described. Chapter 10 is unchanged, as well. Most of the first edition dealt with steels. In the second edition, a presentation of hot rolling of aluminium alloys (Chapter 11) broadens the scope of the book. This portion has been prepared by Dr Mary Wells of the University of Waterloo. The rest of the first edition is repeated. None of Chapters 12À15 has been changed. A well-acknowledged chapter in the first edition presented problems and their solutions; this chapter has been repeated unchanged. Advice for Instructors There are several topics mentioned in this book, the thorough understanding of which needs a broad and varied background. The instructor should be aware of the prepara- tion of the audience and make sure that the following subjects are understood well before starting on the presentations of the book’s contents. A brief quiz during the first lecture and the discussion of the results are often helpful in finding out what needs to be reviewed. In the present writer’s experience with rolling mill engineers, this background may have been there in the listeners’ college or university days but if such knowledge has not been used daily for some considerable time, gaps are certain to exist. It is strongly recommended that at least the first six lectures be devoted to a review of the following. The ideas involved with the strength of materials should be mastered first. These include the theory of elasticity and the analysis of stress and strain; the idea of equilibrium, static and dynamic. Principal directions, principal stresses and strains also need to be appreciated. Boundary conditions, surface and body forces should be clarified and it may be helpful to assign, and then discuss in class, some esoteric examples such as the free-body diagram of a tooth while it is being extracted or the forces and torques acting on a rail car wheel in motion. Identifying and sketching the loads on a bullet in flight would also pose a challenge. If these are well understood, their application during the course should become easy. The difference between engineering and true stresses and strains should be made clear. Strain rates and the conditions under which they remain constant in a test need to be mentioned. The theory of plasticity is used throughout the book without developing the basic ideas. ElasticÀplastic boundaries, the yield and the flow criteria, the associated flow rules, the constancy of volume and the compatibility equations should be presented as part of the review. The stress and strain tensors should be mentioned in addition to the tensor invariants. Basic ideas from the field of metallurgy are needed. The grain structure of metals, the carbon equilibrium diagram, the hardening and restoration mechanisms and the hot and cold response of metals to loading are all used in many of the developments in the course. It would be helpful for the students to have actually mounted, polished and etched a piece of metal for metallographical examination. Preface to the Second Edition xiii Some time should be devoted to a discussion of Tribology as well. Viscosity, Reynold’s equation, lubricant and emulsion chemistry are all necessary here. As a last comment to the instructors, nothing replaces the actual hands-on exper- imentation. Having a well-instrumented rolling mill and conducting some carefully designed experiments would lead to immeasurable benefits. Some care needs to be exercised in assigning the problems from Chapter 11. Many of them are fairly straightforward and require the application of the ideas presented in the text. Many of them, however, require extensive reading and may well lead to some frustration. A discussion of the solution in class is often highly appreciated. Seminars or class discussions are suggested when dealing with Chapters 7À10. These may require advance preparation so the discussions would not become pro- fessorial presentations. State-of-the-art reviews have been found helpful. John G. Lenard, 2013 Preface to the First Edition I have been dealing with problems of the flat rolling process for the last 30 years. This included mathematical modelling, experimentation, consulting, publishing in technical journals and presenting my research at conferences and in industry, as well as lecturing on the topic at levels, appropriate for second- and third-year undergraduate students, graduate students and practicing engineers and technolo- gists of aluminium and steel companies.