KI-NA-25329-EN-N EU The use of (advanced) high strength sheet (A)HSS in forming, shearing and punching applications places increasing demands upon tool materials, particularly in terms of wear performance. A range of tool and sheet steel materials has been studied within the Duratoolproject. Tribological tests were used to assess wear and friction in forming. High volume forming, shearing and punching trials were also conducted. The tribological findings indicate that conventional tool materials do not Mass production perform well in terms of adhesive wear or abrasive wear for steels of tensile strengths above 800 MPa and that more advanced tool materials and coatings must be considered. Tool roughness and lubrication should be controlled to of high strength steel with durable tooling (Duratool) Mass production forming forming of high strength steel with minimise adhesive wear. A finite element model has been developed to predict abrasive tool wear in durable tooling forming. The model can be used to simulate tool wear and changes in subsequent part geometry. Studies show that changes in part geometry due to tool wear are significant for (A)HSS. (Duratool) For best performance in shearing, the process should be optimised. A cutting clearance equal to 5 % of sheet thickness and a shear angle of 1 ° is suitable for all sheet strengths. High volume shearing trials show that edge quality is more dependent on sheet ductility than tool wear. High strength steels produce a good edge with small burrs simply due to their reduced ductility, despite incurring increased tool wear. In punching trials, conventional tool steels were found to work well to 200 000 strokes for low carbon and mid-range high strength steels. For more demanding AHSS grades, only PM tool steels offered acceptable performance. The results of the project have been summarised in the form of tool selection guidelines. 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EUROPEAN COMMISSION Directorate-General for Research and Innovation Directorate G — Industrial Technologies Unit G.5 — Research Fund for Coal and Steel E-mail: [email protected] [email protected] Contact: RFCS Publications European Commission B-1049 Brussels European Commission Research Fund for Coal and Steel Mass production forming of high strength steel with durable tooling (Duratool) Louisa Carless-Elliott and Gerard Krusemeijer Corus Technology BV Wenckebachstraat 1, IJmuiden, THE NETHERLANDS Dominique Kircher Arcelor Research SA Voie Romaine, Maizières-lès-Metz, FRANCE Irma Heikkila KIMAB AB DrottningKristinasvag 48, Stockholm, SWEDEN Daniel Eriksson SSAB Tunnplåt AB781 84 Borlänge, SWEDEN Emile van der Heide TNO Industrie De Rondom 1, Eindhoven, THE NETHERLANDS Berne Högman Uddelholm Tooling AB17 Värmlandslän, Hagfors, SWEDEN Riccardo Porta Centro Sviluppo Materiali SpA Via di Castel Romano 100, Rome, ITALY Grant Agreement RFSR-CT-2003-00032 1 September 2003 to 31 May 2007 Final report Directorate-General for Research and Innovation 2013 EUR 25329 EN LEGAL NOTICE Neither the European Commission nor any person acting on behalf of the Commission is responsible for the use which might be made of the following information. The views expressed in this publication are the sole responsibility of the authors and do not necessarily reflect the views of the European Commission. Europe Direct is a service to help you find answers to your questions about the European Union Freephone number (*): 00 800 6 7 8 9 10 11 (*) Certain mobile telephone operators do not allow access to 00 800 numbers or these calls may be billed. More information on the European Union is available on the Internet (http://europa.eu). Cataloguing data can be found at the end of this publication. Luxembourg: Publications Office of the European Union, 2013 ISBN 978-92-79-24934-1 doi:10.2777/5904 © European Union, 2013 Reproduction is authorised provided the source is acknowledged. Printed in Luxembourg Printed on white chlorine-free paper CONTENTS 1. FINAL SUMMARY 5 1.1 INTRODUCTION 5 1.2 TOOL MATERIALS (WP1) 5 1.3 FORMING PERFORMANCE (WP2 AND WP4) 6 1.4 SHEARING PERFORMANCE (WP3 TASKS 1 AND 3)) 10 1.5 PUNCHING PERFORMANCE (WP3, TASK 2) 12 1.6 ABRASIVE TOOL WEAR MODEL (WP5) 13 1.7 TOOL SELECTION GUIDELINES (WP6) 15 2. INTRODUCTION AND BACKGROUND 17 2.1 BACKGROUND TO THE PROJECT 17 2.2 SOLVING THE PROBLEM OF TOOL WEAR 17 2.3 THE DURATOOL PROJECT 18 2.4 PARTNERS 18 2.5 THE RESEARCH WORK 19 3. WP1 MATERIAL SPECIFICATIONS AND REQUIREMENTS 21 3.1 TASK 1.1: SELECTION OF SHEET MATERIALS 21 3.2 TASK 1.1: SELECTION OF TOOL MATERIALS 21 3.3 TASKS 1.2 AND 1.4 PRODUCTION OF MATERIALS AND TEST SAMPLES 27 3.4 TASK 1.3: DETERMINATION OF SELECTED MATERIAL PROPERTIES 27 4. WP 2 TRIBOLOGICAL ASSESSMENT FOR FORMING APPLICATIONS 29 4.1 TASK 2.1: ANALYSIS OF CRITICAL CONTACT SITUATIONS DURING FORMING 29 4.2 TASK 2.2: SLIDER ON SHEET (TNO) 31 4.3 TASK 2.2: BENDING UNDER TENSION TEST (KIMAB) 40 4.4 TASK 2.3 FRICTIONAL STABILITY OF THE SELECTED SYSTEMS (CORUS) 49 4.5 TASK 2.4: ENHANCED SHEET SURFACES (ARCELOR) 55 4.6 TASK 2.5: ADHESIVE WEAR TESTS (CSM) 60 4.7 TASK 2.6: OVERALL ANALYSIS OF WP2 RESULTS 62 5. WP3 PUNCHING AND SHEARING WITH DURABLE TOOLING 65 5.1 TASK 3.1: REDESIGN AND EVALUATION OF A PUNCHING AND SHEARING TEST 65 5.2 TASK 3.2: HIGH VOLUME PUNCHING 71 5.3 TASK 3.3: HIGH VOLUME SHEARING 79 5.4 SUMMARY OF WP3 WITH RESPECT TO TOOL SELECTION GUIDELINES 83 6. WP4 FORMING WITH WEAR RESISTANT TOOLING 85 6.1 TASK 4.1: EFFECT OF TOOL MATERIALS ON SLIDING BEHAVIOUR [CSM]. 85 6.2 TASK 4.2: DESIGN OF HIGH VOLUME EXPERIMENTS [ARCELOR]. 87 6.3 TASK 4.3: VALIDATION OF THE RESULTS IN A SEMI-INDUSTRIAL ENVIRONMENT [ARCELOR]. 90 7. WP5 FORMING MODEL INCORPORATING TOOL WEAR 95 7.1 TASK 5.1: TOOL WEAR MODEL (CORUS, TNO) 95 7.2 TASK 5.2: STUDY OF THE EFFECT OF DRAW-IN RADIUS WEAR ON PRODUCT GEOMETRY 98 7.3 TASK 5.3: INITIAL VALIDATION OF FORMING SIMULATIONS (CORUS) 101 7.4 TASK 5.3: VALIDATION USING ARCELOR SEMI-INDUSTRIAL TRIAL DATA (CORUS) 104 7.5 TASK 5.4: VISUALISATION OF THE RESULTS IN MS POWERPOINT (CORUS) 105 8. WP6 COMMUNICATION AND ADMINISTRATION 107 8.1 TASK 6.2-3: TOOL SELECTION GUIDELINES 107 8.2 TASK 6.4: HTTP://DURATOOL.C-S-M.IT/ 107 9. CONCLUSIONS 109 3 10. LIST OF FIGURES 111 11. LIST OF TABLES 114 12. LIST OF REFERENCES 115 4 MASS PRODUCTION FORMING OF HIGH STRENGTH STEEL WITH DURABLE TOOLING RFCS Agreement No. RFS-CR-03032 Final report for the period 1st September 2003 – 31st May 2007 1. FINAL SUMMARY 1.1 Introduction The application of HSS has been shown in FE studies to lead to higher forces, pressures and mechanical loading conditions (Task 2.1). This places increasing demands on tool materials, particularly in terms of their durability and wear performance. A range of tool materials have been studied within DURATOOL using tribological tests to assess wear and friction in forming and in long term tests of shearing and punching performance. 1.2 Tool materials (WP1) Several types of iron-based tool materials are used for the forming, punching and shearing of sheet steel. The traditional choice has been cast iron, although with the increasing use of advanced high strength steels (AHSS), the performance of this relatively soft material may not be sufficient and so harder tool steels must be considered. Tool steels contain carbide forming elements to improve wear resistance by increasing hardness. Several techniques are used to do this, each of which result in a different size and distribution of carbides. The finest microstructure is obtained using powder metallurgy (PM); a much coarser structure is produced by casting. Coating a conventional tool can also improve performance. Again, many techniques are available for this. A conventional method is electrolytic deposition of a hard chrome layer. The project tested a selection of tool materials and coatings representing a large range of manufacturing techniques and expected performance levels ( Table 1 and Table 2). The diagram in Figure 1 displays families of sheet steels in terms of their formability and strength. Galvanised and uncoated steels from the groups highlighted in red were selected for the DURATOOL study in order to provide a wide range of steel types at a range of strength levels for analysis. Type of material Major Typical alloying hardness elements HRC / HV GGG70L Cast Iron C 40 / 375 SVERKER 21 Tool steel C-Cr 59 / 700 SLEIPNER Tool steel Cr-Mo 62 / 750 Coating type Typical Hardness CALDIE Electro-slag remelt Cr-Mo-V 61 / 725 Chrome Electrolytic 800-1100 HV ROLTEC SF Spray formed Cr-Mo-V 62 / 750 Plasma Nitride Diffusion 1000-1500HV VANADIS 4 Powder metallurgy Cr-Mo-V 60 / 700 EXTRA TiC CVD Up to 4500 HV VANCRON 40 Powder metallurgy Cr-Mo-W-V 61 / 725 TiAlN PVD 2800 HV Table 1.