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
Testing and modelling of creep in copper friction stir welds
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0002-8494-3983
2009 (English)In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847Article in journal (Other academic) Submitted
Abstract [en]

Specimens cut from friction stir welds in copper canisters for nuclear waste have been used for creep experiments at 75°C. The specimens were taken from a cross-weld position as well as heat affected zone and weld metal. The weld specimens exhibited shorter creep lives than the parent metal specimens by a factor of three in time. The cross weld and HAZ specimens were shorter by an order of magnitude when compared to the weld metal. The creep exponent was in the interval 50 to 69 implying that the material was well inside the power-law breakdown regime. The ductility properties expressed as reduction in area were not significantly different in the weld zones and all the rupture specimens demonstrated valu esexceeding 80%. The stationary creep rate for the parent metal was consistent with a previously developed model. The primary creep was successfully modelled. Weld reduction factors have been obtained by comparing the results from base metal tests and weld tests. Measured values at 75 °C for are about 6% for friction stir welds and 14% for electron beam welds.

Place, publisher, year, edition, pages
2009.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-12075OAI: oai:DiVA.org:kth-12075DiVA: diva2:300986
Note
QS 20120315Available from: 2010-03-02 Created: 2010-03-02 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Mechanical Properties of Welds at Creep Activation Temperatures
Open this publication in new window or tab >>Mechanical Properties of Welds at Creep Activation Temperatures
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Welds in materials intended for service at temperatures above the creep activation temperature often develop damage before the base metal. The weld is a discontinuity in the material and stresses and strains often accumulate in the weld. Knowledge of the properties of the weld is essential to the safe operation of the component containing the weld. The work in this thesis has been aimed at the study of welds in service at high temperatures: The work is divided into two main chapters. The first chapter deals with welds in stainlesssteels and dissimilar metal welds and includes three papers, and the second chapter dealswith welds in copper intended for nuclear waste disposal, also including three papers. Common to both parts is that the temperature is high enough for most of the damage in the welds to result from creep.

In the first part the role of the weld microstructure on the creep crack propagation properties has been studied. Experiments using compact tension specimens have been performed on service exposed, low alloyed heat resistant steels. The results show good correlation with the crack tip parameter, C*, during steady state creep crack growth. The test methodology has also been reviewed and sensitive test parameters have been identified. The results from the creep crack propagation tests on service exposed material has been modeled using uniaxial creep data on both new and ex-service material. The development of the weld microstructure in a dissimilar metal weld between two heat resistant steels has also been investigated. A weld was made between one ferritic and one martensitic steel and the development of the microstructure during welding and post-weldheat treatments has been studied. The results show that the carbon depleted zone that develops near the weld metal in the lower alloyed steel depends on the formation and dissolution of the M23C6-carbide. Variations of the weld parameters and the post-weld heat treatment affect the size and shape of this zone. The process has been successfully modeled by computer simulation.

The second part focuses on oxygen free copper intended for nuclear waste disposal containers. The containers are made with an inner core of cast nodular iron and an outer core of copper for corrosion protection. The copper shell has to be welded and two weld methods has been tested, electron beam welding and friction stir welding. Creep specimens taken from both weld types have been tested as have base metal specimens. The technical specifications of the waste canisters demand that the creep ductility of both the copper shell and the welds has to be as high as possible. The creep test results show that base material doped with at least 30 ppm phosphorus has high creep ductility, and friction stir welds made from this material has almost as high creep strength and creep ductility. Copper without phosphorus does not exhibit the same ductility. The creep properties evaluated from testing has been modeled and extrapolated for the intended purpose

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. 69 p.
Keyword
creep, creep crack propagation, OFHC copper, welds, nuclear waste disposal, creep modeling
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-12077 (URN)978-91-7415-567-9 (ISBN)
Public defence
2010-03-05, Sal E3, Lindstedtsvägen 3, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC20100719Available from: 2010-03-02 Created: 2010-03-02 Last updated: 2010-07-19Bibliographically approved

Open Access in DiVA

No full text

Authority records BETA

Sandström, Rolf

Search in DiVA

By author/editor
Andersson-Östling, Henrik C.M.Sandström, Rolf
By organisation
Materials Science and Engineering
In the same journal
Materials Science and Technology
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 59 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