Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Friction stir welding of copper canisters for nuclear waste
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

The Swedish model for final disposal of nuclear fuel waste is based on copper canisters as a corrosion barrier with an inner pressure holding insert of cast iron. One of the methods to seal the copper canister is to use the Friction Stir Welding (FSW), a method invented by The Welding Institute (TWI).

This work has been focused on characterisation of the FSW joints, and modelling of the process, both analytically and numerically. The first simulations were based on Rosenthal’s analytical medium plate model. The model is simple to use, but has limitations. Finite element models were developed, initially with a two-dimensional geometry. Due to the requirements of describing both the heat flow and the tool movement, three-dimensional models were developed. These models take into account heat transfer, material flow, and continuum mechanics. The geometries of the models are based on the simulation experiments carried out at TWI and at Swedish Nuclear Fuel Waste and Management Co (SKB). Temperature distribution, material flow and their effects on the thermal expansion were predicted for a full-scale canister and lid. The steady state solutions have been compared with temperature measurements, showing good agreement.

Microstructure and hardness profiles have been investigated by optical microscope, Scanning Electron Microscope (SEM), Electron Back Scatter Diffraction (EBSD) and Rockwell hardness measurements. EBSD visualisation has been used to determine the grain size distribution and the appearance of twins and misorientation within grains. The orientation maps show a fine uniform equiaxed grain structure. The root of the weld exhibits the smallest grains and many annealing twins. This may be due to deformation after recrystallisation. The appearance of the nugget and the grain size depends on the position of the weld. A large difference can be seen both in hardness and grain size between the start of the weld and when the steady state is reached.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 39 p.
Keyword [en]
Materials science, Friction Stir Welding (FSW), Copper, Welding, Finite Element Method (FEM)
Keyword [sv]
Materialvetenskap
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-318ISBN: 91-7283-974-0 (print)OAI: oai:DiVA.org:kth-318DiVA: diva2:8948
Supervisors
Note
QC 20101207Available from: 2005-07-19 Created: 2005-07-19 Last updated: 2010-12-07Bibliographically approved
List of papers
1. Microstructure and temperature development in copper welded by the FSW-process
Open this publication in new window or tab >>Microstructure and temperature development in copper welded by the FSW-process
2003 (English)In: 4th International Symposium on FSW, Park City, USA, April, 2003, 2003Conference paper, Published paper (Refereed)
Abstract [en]

The use of Copper canisters with cast iron inserts is one of the proposed methods for long time deposition of nuclear fuel waste. The joining of the lid and possibly the base of the canister can be performed with Friction Stir Welding (FSW). A thorough understanding of the microstructure development in these welds is of major importance, since defects must be avoided. The microstructure and hardness profiles were investigated for two FSW conditions, at the beginning of the weld when there are essentially cold conditions, and when the steady state is reached. In cold welds the features of the nugget are very similar to that observed when FSW-joining aluminium. However, when the welding conditions reach the steady state, the nugget gets wider and the hardness is lower than in the cold weld.

Electron Back Scatter Diffraction (EBSD) visualisation has been used to determine the grain size distribution of, twins and misorientation within grains. The orientation maps show a fine uniform equiaxed grain structure. There is no major misorientation within the grains in the nugget or at the root, but 25 mm from the weld centre the misorientation is large. This confirms that this area lies within the Thermal Mechanical Affected Zone (TMAZ) and is partially recrystallised.  The root has many more annealing twins than the nugget. This indicates that the nugget has experienced deformation after recrystallisation. A model has been used to correlate heat flow to the grain size and the hardness distributions.

Keyword
friction stir welding, microstructure, defect, void, copper, process parameter
National Category
Materials Engineering Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-12010 (URN)
Note
QC 20100716Available from: 2010-02-16 Created: 2010-02-16 Last updated: 2010-12-07Bibliographically approved
2. Microstructure development in copper welded by the FSW-Process
Open this publication in new window or tab >>Microstructure development in copper welded by the FSW-Process
2004 (English)In: SCIENTIFIC BASIS FOR NUCLEAR WASTE MANAGEMENT XXVII / [ed] Oversby VM, Werme LO, Warrendale: Materials Research Society , 2004, Vol. 807, 483-488 p.Conference paper, Published paper (Refereed)
Abstract [en]

To ensure safe storage of nuclear fuel waste, copper canisters are proposed as corrosion barrier. One alternative for sealing the copper canisters is Friction Stir Welding (FSW). During the joining process friction heat and mechanical deformation appear between the rotating tool and the material being welded. Liquid metal will not form, since this is a solid state welding process. Three distinct microstructural zones are developed namely the nugget, the thermomechanically affected zone (TMAZ) and heat-affected zone (HAZ). The nugget is in the centre of the weld, where the pin is located and where severe plastic deformation occurs that leads to recrystallisation. Surrounding the nugget, the TMAZ is only partially recrystallised, due to lower temperature increase and deformation compared to the nugget. The third zone, HAZ, surrounds the TMAZ. The initial nugget can have a classic round aluminium nugget image, when the welding conditions are cold, but the steady state nugget, is wider near the shoulder and shorter in the weld root.

Place, publisher, year, edition, pages
Warrendale: Materials Research Society, 2004
Series
Materials Research Society Symposium Proceedings, ISSN 0272-9172 ; 807
Keyword
Materials Science, Multidisciplinary
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-12008 (URN)000225038400079 ()2-s2.0-12844266096 (Scopus ID)1-55899-752-0 (ISBN)
Conference
27th Symposium on Scientific Basis for Nuclear Waste Management Kalmar, SWEDEN, JUN 15-19, 2003
Note
QC 20100716Available from: 2010-02-15 Created: 2010-02-15 Last updated: 2011-10-31Bibliographically approved
3. Finite element modelling of temperature distribution in friction stir welding process and its influence on distortion of copper canisters
Open this publication in new window or tab >>Finite element modelling of temperature distribution in friction stir welding process and its influence on distortion of copper canisters
2004 (English)In: SCIENTIFIC BASIS FOR NUCLEAR WASTE MANAGEMENT XXVIII, 2004, Vol. 824, 57-62 p.Conference paper, Published paper (Refereed)
Abstract [en]

In an effort to enhance safety for long time disposal of waste nuclear fuel, friction stir welding has been developed as one alternative to seal copper canisters. To avoid the formation of voids and cracks during the welding process, an understanding of the heat and material flow and thereby the evolution of the microstructure, is of great importance. Finite element modelling has been used to simulate the heat and material flow as well as thermal expansion during the friction stir welding process. A model involving heat transfer, material flow, and continuum mechanics has been developed. The steady state solutions have been compared with experimental temperature observations as well as analytical solutions, showing good agreement. Temperature distribution is affected by the welding speed. For a given reference point perpendicular to the welding direction, a lower welding speed corresponds to a higher peak temperature. The plunging position of welding tool influences the temperature distribution and therefore the displacement distribution of the weldment.

Series
MATERIALS RESEARCH SOCIETY SYMPOSIUM PROCEEDINGS, ISSN 0272-9172 ; 824
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-12011 (URN)000224543500009 ()2-s2.0-14944346646 (Scopus ID)1-55899-774-1 (ISBN)
Conference
28th Symposium on the Scientific Basis for Nuclear Waste Management held at the 2004 MRS Spring Meeting San Francisco, CA, APR 13-16, 2004
Note
QC 20100719Available from: 2010-02-16 Created: 2010-02-16 Last updated: 2011-10-31Bibliographically approved
4. Finite Element Modelling of Friction Stir Welding on Copper Canister
Open this publication in new window or tab >>Finite Element Modelling of Friction Stir Welding on Copper Canister
2004 (English)In: 5th International Friction Stir Welding symposium, 2004Conference paper, Published paper (Refereed)
Abstract [en]

In an effort to enhance safety for long time deposit of waste nuclear fuel, friction stir welding has been tentatively used to seal copper canisters. To avoid the formation of voids and cracks during the welding process, and to understand the heat and material flow as well as the evolution of the microstructure, are of great importance. Finite element modelling has been used to simulate the friction stir welding process.

A model involving heat transfer, material flow, and continuum mechanics has been developed. The steady state solutions have been compared with experimental temperature observations as well as analytical solutions, showing good agreement. Temperature distribution is affected by the welding speed. For a given reference point perpendicular to the welding direction, a lower welding speed corresponds to a higher peak temperature. The plunging position of welding tool influences the temperature distribution and therefore also the thermal distortion of the weldment.

Keyword
friction stir welding, FSW, copper, finite element modelling
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-12012 (URN)
Conference
5th International Friction Stir Welding symposium, Metz, France, 14-16 September, 2004
Note
QC 20100719Available from: 2010-02-16 Created: 2010-02-16 Last updated: 2010-12-07Bibliographically approved

Open Access in DiVA

fulltext(1164 kB)6395 downloads
File information
File name FULLTEXT01.pdfFile size 1164 kBChecksum MD5
72c7485f7acec1dbf3d0120594b8c487c528a0d82177cbc7fb55bdb8766e1c04ef8782b0
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Källgren, Therese
By organisation
Materials Science and Engineering
Materials Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 6395 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1225 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf