Bainite - from Nano to Macro Symposium on Science and Application of Bainite 1/2 June 2017 Dorint Hotel, Wiesbaden, Germany

Reproduced with the permission of AWT and Prof. Dr.-Ing. Hans-Werner Zoch Bainite - from nano to macro Symposium on science and application of Bainite 1/2 June 2017 Dorint Hotel, Wiesbaden, Germany Honoring Professor Sir Harshad K. D. H. Bhadeshia Proceedings Bainite – from nano to macro, Wiesbaden (Germany), 1/2 June 2017 Copyright © 2017 Arbeitsgemeinschaft Wärmebehandlung und Werkstofftechnik e. V. All rights reserved. No part of the contents of this publication may be reproduced or transmitted in any form by any means without the written permission of the publisher. Arbeitsgemeinschaft Wärmebehandlung und Werkstofftechnik e. V. Paul-Feller-Str. 1 28199 Bremen Germany <a href="/goto?url=http://www.awt-online.org" target="_blank">www.awt-online.org </a>image sources: bulk nanostructured steel (coloured micrograph) Source: Garcia-Mateo, Caballero, Bhadeshia; Dorint Hotels & Resorts; Harshad K. D. H. Bhadeshia; Wiesbaden Marketing GmbH. Bainite – from nano to macro, Wiesbaden (Germany), 1/2 June 2017 International Committee H. Altena (Austria) S. Denis (France) I. Felde (Hungary) B. Haase (Germany) S. Hock (UK) P. Jacquot (France) Ch. Keul (Germany) B. Kuntzmann (Switzerland) V. Leskovśek (Slovenia) K. Löser (Germany) S. Mackenzie (USA) D. Petta (Italy) H.-W. Raedt (Germany) R. Schneider (Austria) B. Smoljan (Croatia) P. Stolař (Czech Republic) G. Totten (USA) E. Troell (Sweden) B. Vandewiele (Belgium) H.-J. Wieland (Germany) Bainite – from nano to macro, Wiesbaden (Germany), 1/2 June 2017 Sponsors of Bainite – from nano to macro Bainite – from nano to macro, Wiesbaden (Germany), 1/2 June 2017 Foreword Bainite – from nano to macro Symposium on science and application of bainite honoring Prof. Sir Harshad K. D. H. Bhadeshia, Tata Professor for Metallurgy and Director of SKF University Technology Center at the University Cambridge, UK and Professor for Computational Metallurgy at Pohang University of Science and Technology, Korea. Today the knowledge about mechanisms and kinetics of the formation of “bainite” has expanded significantly compared to the early years of first detection of this microstructure. The research around this fascinating steel microstructure for years is bound to the name of an outstanding metallurgist, Professor Sir Harshad K. D. H. Bhadeshia. Honoring his most fruitful work on kinetics, characterization of bainite and developing bainitic steel grades and their thermal treatment, the German Association of Heat Treatment and Materials Technology (Arbeitsgemeinschaft Wärmebehandlung und Werkstofftechnik – AWT) rewards Prof. Bhadeshia with its highest scientific distinction, the Adolf-Martens-Medal, named according to the discoverer of another important microstructure, martensite. The Certificate of the Medal reads: The Adolf-Martens-Medal is awarded to persons from science and industry, which with their work broadened significantly the decisive knowledge about heat treatment of components and characterization of materials. The Adolf-Martens-Medal will be granted at most once a year by the managing board of the association. This citation in its distinguished meaning perfectly meets the achievements of our honoured scientist, Prof. Bhadeshia. AWT with pleasure dedicates this symposium on “bainite – from nano to macro” to Sir Harry, how his friends around the world call him. With his keynote lecture to this conference on “Atomic mechanism of the bainite transformation” he also will demonstrate his admirable capabilities as an outstanding speaker. Looking into history: It was the work of Charles E. Bain, who in about 1928 while being employed at the Research Laboratory of U.S. Steel Corp., began first investigations on isothermal austenite to pearlite transformation using the eutectoid 0.8 mass-% plain carbon steel. Varying transformation temperature he detected slower and faster kinetics and established the valid until today C-shaped transformation start and finish curves, often so called pearlite nose in the Temperature-TimeTransformation diagrams (TTT). When further lowering the isothermal holding temperature, he observed a new microstructure, which first was called “martensite-troostite”, sometime later also Bainite – from nano to macro, Wiesbaden (Germany), 1/2 June 2017 detected by Wever and Lange and named “Zwischenstufe”. Bain and his young metallurgist coworker, E. S. Davenport published about this new microstructure in 1929, which was later named “bainite”, honoring the fundamental research of Charles E. Bain. Even at that time already the favorable strength-ductility-relationship of bainitic steels was reported, which today finds various application in severe industrial applications. Especially the rolling bearing industry introduced this new heat treatment process into production as to prevent hardening cracking of large cross section rings. Further the generation of favorable compressive residual stresses within the surface regions of isothermal treated parts in the lower bainite range up to now is very useful in applications, where surface stresses cause a component to fail. In the bearing business bainitic components even compete with casehardened designs sometimes. Bringing the basic knowledge of bainitic microstructure development to industrial processes another name has to be mentioned, Prof. Otto Schaaber. Having been the first director of IHT – Institute of heat treatment technology, Bremen (now IWT – Institute of Materials Technology), among others he developed the “Schaaber-Dilatometer”, which allowed to study in-situ the microstructure evolution from austenite to bainite. Although research on bainite has a history of almost 90 years, still some observations are not fully clarified up to now. And the development is just going on, as Prof. Bhadeshia and some of his co-workers will report during this symposium as the nanostructured bainite. Recent developments deal with steel grades which allow a continuous transformation into bainite during cooling down from forging temperature to ambient temperature. The so-called “bainitic forging steels” also will be addressed by several speakers from the fundamentals to industrial application. The longest tradition in isothermal transformation to bainite without doubt has the bearing industry as contributions of the leading bearing manufacturers will demonstrate, including research results of multi-step bainitic treatments which lead to significant reductions in process time. Transferring the transformation mechanisms to casehardening opens up new possibilities to adjust case-core-properties by the so called carboaustempering procedure. The very time-consuming isothermal treatment, which can take up to 10 hours or more, require a reliable process technology which also will be presented. An interesting process variant, the dry bainitizing without salt baths was developed some years ago, too. All processes lacked the necessary online information, how the microstructure evolution occurs. The development of the socalled bainite-sensor “switches on the light” and allows to in-situ monitor the formation of bainite fractions, the remaining retained austenite portions and – very important – the precise finish of the process. In-situ observation by eddy current sensors or within an X-ray diffractometer offers great chances to better understand and control the processes. The complex transformation and its many influencing parameters finally calls for a suitable simulation, which also will be addressed. Not precisely a bainitic transformation as described before but also an isothermal transformation from austenite to the so-called ausferrite is the process that leads to austempered ductile iron (ADI), with very promising properties but ambitious in process control. Also this heat treated cast iron will be presented and the beneficial properties and narrow process windows described. The comprehensive presentation on all aspects of isothermal or continuous transformation of austenite to bainite and related materials shall provide state-of-the-art knowledge and recent developments for all participants of this symposium. We wish to thank all participants for their appearance and fruitful discussions. We further explicitly would like to thank all speakers, authors and co-authors for their excellent contributions to this symposium. Our gratitude also goes to the members of the international committee for their support. Finally we gratefully acknowledge the excellent organizational assistance of Mrs. S. Müller, Mrs. H. Dietz and Mrs. Y. Lübben. <ul style="display: flex;"><li style="flex:1">Dr.-Ing. Michael Lohrmann </li><li style="flex:1">Prof. Dr.-Ing. Hans-Werner Zoch </li></ul>Chairmen of the Symposium on Science and Application of Bainite Wiesbaden, Juni 1st, 2017 <ul style="display: flex;"><li style="flex:1">Bainite – from nano to macro, Wiesbaden (Germany), 1/2 June 2017 </li><li style="flex:1">VI </li></ul>Contents Session 1: Fundamentals and new findings on bainite mechanisms <ul style="display: flex;"><li style="flex:1"><a href="#10_0">Atomic mechanism of the bainite transformation </a></li><li style="flex:1"><a href="#10_0">2</a></li></ul>H. K. D. H. Bhadeshia, University of Cambridge, Materials Science and Metallurgy, U. K. <ul style="display: flex;"><li style="flex:1"><a href="#20_0">New Insights into carbon distribution in bainitic ferrite </a></li><li style="flex:1"><a href="#20_0">12 </a></li></ul>Rosalia Rementeria, Carlos Garcia-Mateo, Francisca G. Caballero, Spanish National Center for Metallurgical Research (CENIM-CSIC), Madrid, Spain Session 2: Steels and steel developments for bainitizing and their characterization <ul style="display: flex;"><li style="flex:1"><a href="#30_0">Microalloyed Engineering Steels with Improved Performance </a></li><li style="flex:1"><a href="#30_0">22 </a></li></ul>Wolfgang Bleck1, Margarita Bambach2, Vera Wirths3, Andreas Stieben1, Steel Institute, RWTH Aachen 1 2University, Aachen, Germany, Chair of Materials and Physical Metallurgy, Brandenburg University of Technology Cottbus-Senftenberg, Germany, 3BGH Edelstahl Siegen GmbH, Siegen, Germany <ul style="display: flex;"><li style="flex:1"><a href="#0_0">Bainite and superbainite in long products and forged applications </a></li><li style="flex:1"><a href="#0_0">32 </a></li></ul><a href="#0_0">43 </a>Thomas Sourmail, Asco Industries CREAS, Hagondange, France <a href="#0_0">Taming the bainite for use in bright bar applications </a>Hans Roelofs1, Mirkka Ingrid Lembke2, 1Swiss Steel AG, Emmenbrücke, Switzerland, 2Steeltec AG, Emmenbrücke, Switzerland <ul style="display: flex;"><li style="flex:1"><a href="#0_0">Development and Application of high Strength Bainitic Forging Steel </a></li><li style="flex:1"><a href="#0_0">52 </a></li></ul><a href="#0_0">57 </a>Oliver Rösch, Georgsmarienhütte GmbH, Georgsmarienhütte, Germany <a href="#0_0">Low Distortion Bainitic Steel for Automotive Applications </a>1Till Schneiders1, Frank van Soest2, Drago Duh2, Hans-Günter Krull2, Deutsche Edelstahlwerke, Witten, Germany, 2Deutsche Edelstahlwerke, Krefeld, Germany Session 3: Heat treatment processes and properties of bainitic components <a href="#0_0">Bainitic Bearings for Demanding Applications </a>Werner Trojahn1, Markus Dinkel2, 1Schaeffler AG, Schweinfurt, Germany, 2 Schaeffler AG, Herzogenaurach, Germany <a href="#0_0">66 </a><ul style="display: flex;"><li style="flex:1"><a href="#0_0">75 </a></li><li style="flex:1"><a href="#0_0">Development of a two-step bainitizing procedure to enhance fatigue strength economically </a></li></ul>Brigitte Clausen1, Juan Dong1, Klaus Burkart1, Hans-Werner Zoch1,2, 1 Stiftung Institut für Werkstofftechnik, Bremen, Germany, 2MAPEX Center for Materials and Processes, University of Bremen, Germany CarboBain: case hardening by carbo-austempering – a systematic evaluation of transformation <ul style="display: flex;"><li style="flex:1"><a href="#0_0">kinetics, microstructure and residual stresses </a></li><li style="flex:1"><a href="#0_0">88 </a></li></ul>Matthias Steinbacher1, Hans-Werner Zoch1,2, Stiftung Institut für Werkstofftechnik Bremen, Germany, 12MAPEX Center for Materials and Processes, University of Bremen, Germany <ul style="display: flex;"><li style="flex:1">Bainite – from nano to macro, Wiesbaden (Germany), 1/2 June 2017 </li><li style="flex:1">VII </li></ul>Session 4: Process equipment and control <a href="#0_0">Process Technology and Plant Design for Austempering </a>Herwig Altena1, Klaus Buchner2, Aichelin Holding GmbH, Mödling, Austria,, 2Aichelin GesmbH, Mödling, <a href="#0_0">100 </a>1Austria <ul style="display: flex;"><li style="flex:1"><a href="#0_0">Batch furnace line with integrated salt quench for austempering </a></li><li style="flex:1"><a href="#0_0">108 </a></li></ul><a href="#0_0">114 </a><a href="#0_0">123 </a>Herbert Hans, Ipsen International GmbH, Kleve, Germany <a href="#0_0">Dry bainitizing – a clean approach to achieve bainitic microstructures </a>Volker Heuer, Klaus Loeser, ALD Vacuum Technologies GmbH, Hanau, Germany <a href="#0_0">Dry austempering: A new technology for future automotive requirements </a>1Eric Dabrock1, László Hagymási2, Frank Sarfert3, Hagen Kuckert3, Eberhard Kerscher4, Robert Bosch <ul style="display: flex;"><li style="flex:1">2</li><li style="flex:1">3</li></ul>GmbH, Stuttgart, Germany, Robert Bosch GmbH, Stuttgart, Germany, Robert Bosch GmbH, Renningen, Germany, 4Materials Testing, University of Kaiserslautern, Kaiserslautern, Germany <ul style="display: flex;"><li style="flex:1"><a href="#0_0">New bainite sensor technology allows for a detailed view on material transformation </a></li><li style="flex:1"><a href="#0_0">133 </a></li></ul>Heinrich Klümper-Westkamp1, Jochen Vetterlein2, Hans-Werner Zoch1, Wilfried Reimche3, Oliver <ul style="display: flex;"><li style="flex:1">1</li><li style="flex:1">2</li></ul>Bruchwald3, Hans Jürgen Maier3, Stiftung Institut für Werkstofftechnik, Bremen, Germany, Flowserve Hamburg GmbH, Hamburg, Germany, 3Leibniz Universität Hannover, Garbsen, Germany Inline application of bainite sensor technology for characterizing phase transformation during <ul style="display: flex;"><li style="flex:1"><a href="#0_0">cooling </a></li><li style="flex:1"><a href="#0_0">141 </a></li></ul><a href="#0_1">151 </a>Wilfried Reimche1, Oliver Bruchwald1, Sebastian Barton1, Hans Jürgen Maier1, Heinrich Klümper- <ul style="display: flex;"><li style="flex:1">1</li><li style="flex:1">2</li></ul>Westkamp2, Hans-Werner Zoch2, Leibniz Universität Hannover, Garbsen, Germany, Stiftung Institut für Werkstofftechnik, Bremen, Germany <a href="#0_1">In-situ Investigation of Bainite Formation with fast X-Ray Diffraction (iXRD) </a>Andreas Kopp, Timo Bernthaler, Dieter Schmid, Gaby Ketzer-Raichle, Gerhard Schneider, Materials Research Institute, Aalen University, Aalen, Germany Session 5: Fundamentals and simulation of bainite transformation Bainitic transformation analysis in carbon and nitrogen enriched low alloyed steels: kinetics and <ul style="display: flex;"><li style="flex:1"><a href="#0_0">microstructures </a></li><li style="flex:1"><a href="#0_0">162 </a></li></ul><a href="#0_0">172 </a>Julien Teixeira1,2, Simon D. Catteau1,2,3, Hugo P. Van Landeghem1,2, Jacky Dulcy1, Moukrane Dehmas1,2, 1Abdelkrim Redjaïmia1,2, Sabine Denis1,2, Marc Courteaux3, Institut Jean Lamour – UMR 7198 CNRS – 2Université de Lorraine, Nancy CEDEX, France, Labex DAMAS “Design of Alloy Metals for Low-mass Structures”, Université de Lorraine, France, 3PSA Peugeot-Citroën, Centre Technique de Belchamp, Voujeaucourt, France <a href="#0_0">Modeling of bainitic transformations under high stresses </a>Martin Hunkel, Diego Said Schicchi, Stiftung Institut für Werkstofftechnik, Bremen, Germany Session 6: Ausferritizing of cast iron (Austempered ductile iron – ADI) <ul style="display: flex;"><li style="flex:1"><a href="#0_0">Virtual optimization of process and material properties for ADI </a></li><li style="flex:1"><a href="#0_0">183 </a></li></ul><a href="#0_0">192 </a>Erik Hepp, Corinna Thomser, MAGMA Gießereitechnologie GmbH, Aachen, Germany <a href="#0_0">Is ADI with Bainite Optimized? </a><ul style="display: flex;"><li style="flex:1">1</li><li style="flex:1">2</li></ul>Arron Rimmer1, Eike Wüller2, ADI Treatments Ltd., West Bromwich, U.K., SIEMENS AG, Voerde, Germany <ul style="display: flex;"><li style="flex:1">Bainite – from nano to macro, Wiesbaden (Germany), 1/2 June 2017 </li><li style="flex:1">1</li></ul>1. Fundamentals and new findings on bainite mechanisms <ul style="display: flex;"><li style="flex:1">Bainite – from nano to macro, Wiesbaden (Germany), 1/2 June 2017 </li><li style="flex:1">2</li></ul>Atomic mechanism of the bainite transformation H. K. D. H. Bhadeshia University of Cambridge, Materials Science and Metallurgy, U. K., [email protected] Abstract I have on previous occasions shown how we can be surprised and delighted by new discoveries in steels, which at the same time may be useful. However, my focus in this lecture is purely on some basic science so that a well-founded understanding of mechanisms can lead to ever greater advances. The composite structure that is known colloquially as bainite is arguably the most interesting of all of the essential microstructures that occur in steels, where the manner in which atoms move is seminal to the design of steels. Therefore, I take the liberty to indulge myself and talk only of theory on this occasion. Keywords Atomic mechanism, bainite, shape deformation, local equilibrium, thermodynamic, dissipations 1 Introduction Bainite is not a phase, rather, it can be an aggregate of phases consisting predominantly of platelets of ferrite but with a sprinkling of minority phases such as carbides or residual austenite [Davenport 1930, Bhadeshia 2015b]. It is lovely structure that has advantages including the fact that it can be generated uniformly in huge components such as steam turbines [Colbeck, Rait 1952], or can be used microscopically as a surface treatment to enhance tribological properties [Zhang et al. 2008]. The structure is amenable to careful control – for example, its scale can be regulated from hundreds of micrometres to tens of nanometres [Bhadeshia, Honeycombe 2017]. Such variations are reflected in properties, emphasising the versatility of the structure. There are cases where the structure has such a high energy absorbing capacity that the Charpy toughness cannot in fact be measured because the energy absorbed is off the upper limit of the scale at subzero temperatures [Zhu et al. 2016]. A number of the industrial advances that have been made in recent years have relied on the theoretical understanding of the bainite transformation. The theory therefore is not simply fodder for academic debate. Any completely satisfactory theory of a phase transformation must explain in quantitative detail the known set of observations. It should also be able to venture into previously unknown domains so that experiments can be done to verify its ability to generalise. Some of its predictions may lead to previously unknown consequences, which is when it becomes thrilling.

Bainite - from Nano to Macro Symposium on Science and Application of Bainite 1/2 June 2017 Dorint Hotel, Wiesbaden, Germany

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