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Tribology in Metal Working
Dalarna University, School of Technology and Business Studies, Materials Technology.
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on the tribological performance of tool surfaces in two steel working operations, namely wire drawing and hot rolling. In all forming operations dimensions and surface finish of the products are of utmost importance. Forming basically includes three parts – forming conditions excluded – that may be changed; work material, tool and (possibly) lubricant. In the interface between work material and tool, the conditions are very aggressive with – generally or locally – high temperatures and pressures. The surfaces will be worn in various ways and this will change the conditions in the process. Consequently, the surface finish as well as the dimensions of the formed product may change and in the end, the product will not fulfil the requirements of the customer. Therefore, research and development in regard to wear, and consequently tribology, of the forming tools is of great interest.

The investigations of wire drawing dies focus on coating adhesion/cohesion, surface characteristics and material transfer onto the coated steel both in laboratory scale as well as in the wire drawing process. Results show that it in wire drawing is possible to enhance the tribological performance of drawing dies by using a lubricant together with a steel substrate coated by a polished, dual-layer coating containing both hard and friction-lowering layers.

The investigations of hot rolling work rolls focus on microstructure and hardness as well as cracking- and surface characteristics in both laboratory scale and in the hot strip mill. Results show that an ideal hot work roll material should be made up of a matrix with high hardness and a large amount of complex, hard carbides evenly distributed in the microstructure. The surface failure mechanisms of work rolls are very complex involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation.

This knowledge may be used to develop new tools with higher wear resistance giving better performance, lower costs and lower environmental impact.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. , 52 p.
Keyword [en]
tribology, friction, wear, metal working, coatings, wire drawing, hot work rolls
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
Stålformning och ytteknik
Identifiers
URN: urn:nbn:se:du-11730OAI: oai:DiVA.org:du-11730DiVA: diva2:589436
Presentation
2012-12-14, Clas Ohlson, Skomakargatan 1, Borlänge, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2013-01-18 Created: 2013-01-18 Last updated: 2013-01-18Bibliographically approved
List of papers
1. Tribological testing of some potential PVD and CVD coatings for steel wire drawing dies
Open this publication in new window or tab >>Tribological testing of some potential PVD and CVD coatings for steel wire drawing dies
2011 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 273, no 1, 55-59 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to investigate the possibility to replace cemented carbide wire drawing dies with CVD or PVD coated steel dies. Material pick-up tendency, friction and wear characteristics of four different commercial coatings – CVD TiC and PVD (Ti,Al)N, CrN and CrC/C – in sliding contact with ASTM 52100 bearing steel were evaluated using pin-on-disc testing. The load bearing capacity of the coating/substrate composites was evaluated using scratch testing. The results show that the friction characteristics and material pick-up tendency of the coatings to a large extent is controlled by the surface topography of the as-deposited coatings which should be improved by a polishing post-treatment in order to obtain a smooth surface. Based on the results obtained in this study, three different coatings – CrC/C, TiC and dual-layer TiC/CrC/C – are recommended to be evaluated in wire drawing field tests. CrC/C and TiC are recommended due to their intrinsic low friction properties and material pick-up tendency in sliding contact with steel. The dual-layer is recommended in order to combine the good properties of the two coatings CrC/C (low shear strength) and TiC (high hardness).

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2011
Keyword
Drawing die; PVD coating; CVD coating; Material transfer
National Category
Tribology
Research subject
Stålformning och ytteknik
Identifiers
urn:nbn:se:du-6239 (URN)10.1016/j.wear.2011.06.020 (DOI)000297902500010 ()
Available from: 2012-01-24 Created: 2012-01-24 Last updated: 2015-06-16Bibliographically approved
2. Microstructural, mechanical and tribological characterisation of roll materials for the finishing stands of the hot strip mill for steel rolling
Open this publication in new window or tab >>Microstructural, mechanical and tribological characterisation of roll materials for the finishing stands of the hot strip mill for steel rolling
2013 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 307, no 1-2, 209-217 p.Article in journal (Refereed) Published
Abstract [en]

The microstructure, mechanical and tribologicalproperties for three different materials, High Speed Steel, High Chromium ironand Indefinite Chill iron, used for hot strip mill work rolls have beenevaluated. Microstructural characterisation was performed using light opticalmicroscopy, scanning electron microscopy and energy dispersive X-rayspectroscopy. The mechanical and tribological properties were evaluated usingmicro Vickers indentation and scratch testing in combination with post-testmicroscopy. The microstructures of the investigated materials were found to berather complex with a number of secondary phases andalso materials with similar nominal composition display significant differenceswith respect to distribution, size and morphology of carbides. Scratch testing,including detection of friction coefficient, acoustic emission and penetrationdepth, gives valuable information concerning the mechanical and tribologicalresponse on a microscopic level of the investigated materials. Type,amount, distribution, size and morphology of the secondary phases in thematerials have a strong impact on the surface deformation and wear mechanismsduring scratching. Cracking and chipping are frequently observed in connectionto the ridges surrounding the scratches. However, cross-sectional analyses ofthe scratched microstructures reveal that cracking of the brittle carbidephases may extend to significant depths, >100 µm, reducing the mechanicalstrength of the material. Based on the results, it is believed that a moreisotropic microstructure, e.g. obtained via a powder metallurgy process, withfiner carbides would result in improved properties and performance in a hotrolling application.

Place, publisher, year, edition, pages
Elsevier, 2013
Keyword
Work roll materials; Microstructure; Scratch testing;Surface deformation; Wear
National Category
Metallurgy and Metallic Materials
Research subject
Stålformning och ytteknik
Identifiers
urn:nbn:se:du-11443 (URN)10.1016/j.wear.2013.09.002 (DOI)000328523800026 ()
Available from: 2012-12-13 Created: 2012-12-13 Last updated: 2015-06-29Bibliographically approved
3. An investigation of worn work roll materials used in the finishing stands of the hot strip mill for steel rolling
Open this publication in new window or tab >>An investigation of worn work roll materials used in the finishing stands of the hot strip mill for steel rolling
2013 (English)In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, Vol. 227, no 8, 837-844 p.Article in journal (Refereed) Published
Abstract [en]

The surface failure characteristics of different work roll materials, i.e. High Speed Steel, High Chromium Iron and Indefinite Chill Iron, used in the finishing stands of a hot strip mill have been investigated using stereo microscopy, 3D optical profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the surface failure mechanisms of work rolls for hot rolling are very complex, involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation. Despite the differences in chemical composition and microstructure, the tribological response of the different work roll materials was found to be strongly dependent on second phase constituents such as the size, morphology and distribution of different carbide phases and graphite (in the case of Indefinite Chill Iron) which was found to promote cracking. Cracking and chipping of the work roll surfaces, both having a negative impact on work roll wear, are strongly influenced by the presence of carbides, carbide networks and graphite in the work roll surface. Consequently, the amount of carbide forming elements as well as the manufacturing process must be controlled in order to obtain an optimised microstructure and a predictable wear rate.

Place, publisher, year, edition, pages
Sage Publications, 2013
Keyword
Work rolls, hot strip mill, surface failure, wear, cracking
National Category
Manufacturing, Surface and Joining Technology
Research subject
Stålformning och ytteknik
Identifiers
urn:nbn:se:du-11444 (URN)10.1177/1350650113478333 (DOI)000321702800004 ()
Available from: 2012-12-13 Created: 2012-12-13 Last updated: 2015-06-29Bibliographically approved

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