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Galling in sheet metal forming
Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering. (Materialteknik)ORCID iD: 0000-0001-6029-2613
Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering. (Materialteknik)ORCID iD: 0000-0002-9441-2502
Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering. (Materialteknik)
Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.ORCID iD: 0000-0002-1225-0598
2008 (English)In: Proceedings of the IDDRG 2008 Conference: Best in class stamping, 16-18 June 2008, Olofström: Industriellt utvecklingscentrum i Olofström AB , 2008Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
Olofström: Industriellt utvecklingscentrum i Olofström AB , 2008.
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
URN: urn:nbn:se:kau:diva-3037ISBN: 978-91-633-2948-7 (print)OAI: oai:DiVA.org:kau-3037DiVA, id: diva2:126667
Available from: 2008-11-19 Created: 2008-11-19 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Wear mechanisms in sheet metal forming: Effects of tool microstructure, adhesion and temperature
Open this publication in new window or tab >>Wear mechanisms in sheet metal forming: Effects of tool microstructure, adhesion and temperature
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The general trend in the car body manufacturing industry is towards low-series production and reduction of press lubricants and car weight. The limited use of lubricants, in combination with the introduction of high and ultrahigh-strength sheet materials, continuously increases the demands on the forming tools. The major cause for tool failure during the forming process is transfer and accumulation of sheet material on the tool surfaces, generally referred to as galling. The adhered material creates unstable frictional conditions and scratching of the tool/sheet interface. To provide the means of forming new generations of sheet materials, development of new tool materialswith improved galling resistance is required, which may include tailored microstructures introducing specific carbides and nitrides, coatings and improved surface finish. In the present work, the galling wear mechanisms in real forming operations have been studied and emulated at a laboratory scale by developing a test equipment. The wear mechanisms, identified in the real forming process, were distinguished into a sequence of events. At the initial stage, local adhesive wear of the sheets led to transfer of sheet material to the tool surfaces. Successive forming operations resulted in growth of the transfer layer with initiation of scratching of the sheets. Finally, scratching changed into severe adhesive wear, associated withgross macroscopic damage. The wear process was successfully repeated in the laboratory test equipment in sliding between several tool materials, ranging from cast iron and conventional ingot cast tool steels, to advanced powder metallurgy tool steel, sliding against medium and high-strength steel sheets. By use of the test equipment, selected tool materials were ranked regarding galling resistance. The controlling mechanism for galling in sheet metal forming is adhesion. The initial sheet material transfer was found to occur, preferably, to the metallic matrix of the tool steels. Hence, the carbides in the particular steels appeared less prone to adhesion as compared to the metallic matrix. Therefore, an improved galling resistance was observed for a tool steel comprising a high amount of small homogeneously distributed carbides offering a low-strength interface to the transferred sheet material.Further, atomic force microscopy showed that nanoscale adhesion was influenced by temperature, with increasing adhesion as temperature increases. A similar dependence was observed at the macroscale where increasing surface temperature led to initiation of severe adhesive wear. The results were in good agreement to the nano scale observations and temperature-induced high adhesion was suggested as a possible mechanism.

Place, publisher, year, edition, pages
Karlstad: Karlstad University, 2008. p. 41
Series
Karlstad University Studies, ISSN 1403-8099 ; 2008:46
Keywords
Galling, sheet metal forming, wear, friction, adhesion, temperature
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-2911 (URN)978-91-7063-204-4 (ISBN)
Public defence
2008-12-12, Nyqvistsalen, 9C 203, Karlstads Universitet, Karlstad, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2008-11-20 Created: 2008-10-23 Last updated: 2011-11-24Bibliographically approved

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Bergström, JensKrakhmalev, PavelGåård, AndersLindvall, Fredrik

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