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Clean forming of stainless steel and titanium products by lubricious oxides
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Tribomaterial)
2012 (English)In: Proceedings of NORDTRIB, Trondheim: NTNU , 2012Conference paper, Published paper (Refereed)
Abstract [en]

Big social benefits can be attained through increased use of stainless steel or titanium in new sheet metal applications. Unfortunately, forming of these materials is often a challenging and costly operation, that can lead to environmental and health problems when solving the technical limitations. One possible method to overcome these problems is to use an oxide layer with optimised properties to reduce friction during forming, either as a substitute to lubricants, or acting as a conversion layer for environmental friendly lubricants. The most beneficial group of oxides for low friction is called lubricious oxides with a rutile crystal structure. Oxides of Ti, Mo, V, and Zn can build rutiles under certain contact temperatures during rolling and forming. The aim of this investigation is to evaluate if oxides designed on metal sheets display a lubricious effect under conditions similar to industrial forming processes. Preliminary evaluations show a beneficial influence of two oxides types, on stainless steel and on titanium. More work is needed to test the lubricating effect in other forming operations and to analyse the sustainability aspects for products manufactured with this alternative surface.

Place, publisher, year, edition, pages
Trondheim: NTNU , 2012.
Keyword [en]
lubricious oxides, friction, sheet metals, sliding contact, forming
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Tribo Materials
Identifiers
URN: urn:nbn:se:uu:diva-198746ISBN: 978-82-14-05270-1 (print)OAI: oai:DiVA.org:uu-198746DiVA: diva2:617648
Conference
15th Nordic Symposium on TribologyTrondheim 13-15 June 2012; Trondheim, Norway
Available from: 2013-04-24 Created: 2013-04-24 Last updated: 2014-03-04Bibliographically approved
In thesis
1. The Positive Effect of Nitrogen Alloying of Tool Steels Used in Sheet Metal Forming
Open this publication in new window or tab >>The Positive Effect of Nitrogen Alloying of Tool Steels Used in Sheet Metal Forming
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sheet metal forming processes are mechanical processes, designed to make products from metal sheet without material removal. These processes are applied extensively by the manufacturing industry to produce commodities such as heat exchangers or panels for automotive applications. They are suitable for production in large volumes.

A typical problem in forming operations is accumulation of local sheet material adherents onto the tool surface, which may deteriorate the subsequent products. This tool failure mechanism is named galling. The aim of this work is to explain the mechanisms behind galling and establish factors how it can be reduced.

The focus of this work is on the influence of tool material for minimum risk of galling. Experimental tool steels alloyed with nitrogen were designed and manufactured for systematic tribological evaluation. Reference tool materials were conventional cold forming tool steels and coated tool steels. The sheet material was austenitic stainless steel AISI 304, which is sensitive for galling. A variety of lubricants ranging from low to high viscous lubricants were used in the evaluation.

The properties of the tool materials were characterized analytically and their tribological evaluation included industrial field tests and several laboratory-scale tests. The testing verified that nitrogen alloying has a very positive effect for improving galling resistance of tool steels. Tool lives comparable to the coated tool steels were achieved even with low viscous lubricants without poisonous additives.

The hypothesis used for the explanation of the positive effect of nitrogen alloying is based on the critical local contact temperature at which the lubrication deteriorates. Therefore, the contact mechanism at the tool-sheet interface and the local energy formation were studied systematically. Theoretical considerations complemented with FEA analysis showed that a small size of hard particles with a high volume fraction gives low local contact loads, which leads to low frictional heating. Also, an even spacing between the hard particles and their frictional properties are of importance. Nitrogen alloyed tool steels have these properties in the form of small carbonitrides.

The finding of this work can be applied to a wide range of applications that involve sliding metal contacts under severe tribological loading.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 56 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1045
Keyword
galling, nitrogen, tool steel, sliding contact, metal forming
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Tribo Materials
Identifiers
urn:nbn:se:uu:diva-198747 (URN)978-91-554-8673-0 (ISBN)
Public defence
2013-06-12, Sal 2001 Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2013-05-21 Created: 2013-04-24 Last updated: 2013-08-30Bibliographically approved

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Conference websitehttp://orbit.dtu.dk/en/publications/clean-forming-of-stainless-steel-and-titanium-products-by-lubricious-oxides(f276633d-8d99-4729-a7a7-47644a4c481d).html

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Heikkilä, Irma

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