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
Influence of Reduced Cooling Time on the Properties of Resistance Spot Welds
2008 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 52, no 3-4, 43-53 p.Article in journal (Refereed) Published
Abstract [en]

Reducing the cooling time in a resistance spot welding schedule offers two possible advantages. The first is decreased weld cycle time, which is of great importance in particular to car body assembly lines performing hundreds of millions of spot welds each year. Decreasing each resistance spot weld cycle time by a mere 0.1 s leads to substantial cost savings. The second advantage is the possibility to reduce the hardness in the weld metal and thereby improve fracture behaviour. Reducing the cooling time leads to reduced cooling rate of the weld metal and potentially a softer material. Two and three-sheet joint combinations of martensitic, dual phase, transformation induced plasticity (TRIP), complex phase and hardened boron steels were investigated in this study. The joints were evaluated by shear-, peel and cross-tension testing as well as metallographical examinations and hardness measurements. With knowledge of the materials weldability, and evaluation of the behaviour when welding with reduced cooling time, it was possible to develop optimised weld schedules and thereby increase productivity. It is recommended that the programming of the hold time in the power sources is modified in order to enable full flexibility in setting of the hold time /cooling time. This study showed that the cooling time could be reduced significantly without endangering the joint integrity.

Place, publisher, year, edition, pages
Springer-Verlag, 2008. Vol. 52, no 3-4, 43-53 p.
National Category
Manufacturing, Surface and Joining Technology
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-167984DOI: 10.1007/BF03266631OAI: oai:DiVA.org:kth-167984DiVA: diva2:813650
Note

QC 20150526

Available from: 2015-05-25 Created: 2015-05-25 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Challenges in Resistance Welding of Ultra High Strength Steels
Open this publication in new window or tab >>Challenges in Resistance Welding of Ultra High Strength Steels
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Increasing the use of Ultra High Strength Steels (UHSS) in vehicle bodystructures is important for reducing weight and cutting CO2 emissions. This thesis investigates challenges in resistance welding that can be a barrier to implementing UHSS as a replacement for low strength steels in vehicle structures. Empirical research has been performed to offer new approaches for improved joint strength and to increase knowledge on cracking mechanisms in resistance projection welding and resistance spot welding of UHSS. By optimising the current build-up phase and peak current during the first milliseconds of weld time, it was shown that the strength could be improved by up to two-fold for projection welded joints. An approach to improve the ductility and strength of resistance spotwelds in UHSS using reduced cooling time was unsuccessful. The reduced cooling rate after weld metal solidification did not fully create the desired softened microstructure. The study on the surface cracking mechanism in resistance spot welded dual-phase UHSS showed that cracking is linked to the galvanization method. It is proposed that formation of aluminium oxide layers on the electrode tips increases the surface temperature and thereby increases the probability for liquid metal embrittlement and surface cracking.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xvii, 59 p.
Series
TRITA-IIP, ISSN 1650-1888 ; 15:02
Keyword
Resistance welding, spot welding, surface cracks, nut welding, UHSS, projection welding
National Category
Manufacturing, Surface and Joining Technology
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-167985 (URN)978-91-7595-577-3 (ISBN)
Presentation
2015-06-03, M311, Brinellvägen 68, KTH, Stockholm, 10:00 (Swedish)
Opponent
Supervisors
Funder
XPRES - Initiative for excellence in production research
Note

QC 20150526

Available from: 2015-05-26 Created: 2015-05-25 Last updated: 2015-05-26Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Tolf, Erik
In the same journal
Welding in the World
Manufacturing, Surface and Joining Technology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 40 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