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
Welds in the lean duplex stainless steel LDX 2101: effect of microstructure and weld oxides on corrosion properties
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Duplex stainless steels are a very attractive alternative to austenitic grades due to their higher strength and good corrosion performance. The austenitic grades can often be welded autogenously, while the duplex grades normally require addition of filler metal. This is to counteract segregation of important alloying elements and to give sufficient austenite formation to prevent precipitation of chromium nitrides that could have a negative effect on impact toughness and pitting resistance. The corrosion performance of the recently-developed lean duplex stainless steel LDX 2101 is higher than that of 304 and can reach the level of 316. This thesis summarises pitting resistance tests performed on laser and gas tungsten arc (GTA) welded LDX 2101. It is shown here that this material can be autogenously welded, but additions of filler metal, nitrogen in the shielding gas and use of hybrid methods increases the austenite formation and the pitting resistance by further suppressing formation of chromium nitride precipitates in the weld metal. If the weld metal austenite formation is sufficient, the chromium nitride precipitates in the heat-affected zone (HAZ) could cause local pitting, however, this was not seen in this work. Instead, pitting occurred 1–3 mm from the fusion line, in the parent metal rather than in the high temperature HAZ (HTHAZ). This is suggested here to be controlled by the heat tint, and the effect of residual weld oxides on the pitting resistance is studied. The composition and the thickness of weld oxide formed on LDX 2101 and 2304 were determined using X-ray photoelectron spectroscopy (XPS). The heat tint on these lean duplex grades proved to contain significantly more manganese than what has been reported for standard austenitic stainless steels in the 300 series. A new approach on heat tint formation is consequently presented. Evaporation of material from the weld metal and subsequent deposition on the weld oxide are suggested to contribute to weld oxide formation. This is supported by element loss in LDX 2101 weld metal, and nitrogen additions to the GTA shielding gas further increase the evaporation.

 

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , vi, 37 p.
Keyword [en]
Duplex stainless steel, welding, weld metal, HAZ, nitrogen, manganese, austenite formation, phase balance, precipitates, pitting resistance, heat input, solidification, element loss, evaporation, deposition, weld oxides, discoloration, mechanical properties, thermo-mechanical simulation, Geeble, GTA, laser, LOM, SEM, EDS, TEM, Leco, EPMA, ferroxyl test, XPS, post weld cleaning, pickling
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-9299ISBN: 978-91-7415-109-1 (print)OAI: oai:DiVA.org:kth-9299DiVA: diva2:54604
Presentation
2008-10-03, Sal 408, KTH, Brinellvägen 23, Stockholm, 10:00 (English)
Supervisors
Note
QC 20101126Available from: 2008-10-17 Created: 2008-10-17 Last updated: 2010-11-26Bibliographically approved
List of papers
1. Weld oxide formation on lean duplex stainless steel
Open this publication in new window or tab >>Weld oxide formation on lean duplex stainless steel
2008 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 50, no 9, 2620-2634 p.Article in journal (Refereed) Published
Abstract [en]

Weld oxides have a strong influence on corrosion resistance, but have hitherto only been studied to a limited extent for duplex stainless steels. X-ray photoelectron spectroscopy (XPS) has here been used to study heat tint formed on gas tungsten arc (GTA) welds on the commercial duplex grades LDX 2101 (EN 1.4162/UNS S32101) and 2304 (EN 1.4362/UNS S32304) welded with and without nitrogen additions to the shielding gas. The process of heat tint formation is discussed in terms of transport phenomena to explain the effect of atmosphere, temperature and composition. The oxides formed were found to be enriched in manganese and corrosion testing shows that nitrogen has a strong influence on the weld oxide. A mechanism is proposed including evaporation from the weld pool and subsequent redeposition.

Keyword
Stainless steel, EPMA, XPS, Oxidation, Pitting corrosion
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-9294 (URN)10.1016/j.corsci.2008.06.024 (DOI)000260358900023 ()
Note
QC 20101126 Uppdaterad från submitted till published (20101126).Available from: 2008-10-17 Created: 2008-10-17 Last updated: 2017-12-07Bibliographically approved
2. Laser welding of a lean duplex stainless steel
Open this publication in new window or tab >>Laser welding of a lean duplex stainless steel
2007 (English)In: 26th International Congress on Applications of Lasers and Electro-Optics, ICALEO 2007: Congress Proceedings, 2007, 335-344 p.Conference paper, Published paper (Refereed)
Abstract [en]

Nd:YAG laser welding and laser gas tungsten arc (GTA) hybrid welding of the lean duplex stainless steel LDX 2101® (EN 1.4162, UNS S32101) were performed with and without filler wire and nitrogen additions to the shielding gas. The high energy density associated with laser welding of duplex stainless steels can affect the mechanical strength and corrosion resistance negatively. The high solidification rates and cooling rates characteristic of laser welding may cause ferritization and chromium nitride precipitation. However, due to the balanced composition of LDX 2101, the austenite reformation in the weld metal and the heat affected zone (HAZ) was satisfactory as confirmed by tensile test results, corrosion performance in terms of critical pitting temperature (CPT) and hardness measurements. Transmission electron microscopy (TEM) was conducted on simulated HAZs to study the effect of cooling rate on precipitate formation. Furthermore, Laser-GTA hybrid welding of the galvanized carbon steel Dogal® DP 600 onto LDX 2101 in lap joints was successful without porosity or liquid metal embrittlement (LME), and with sufficient tensile strength.

Keyword
Chromium nitride, Cooling rates, Corrosion performance, Critical pitting temperatures, Duplex stainless steel, Ferritization, Filler wire, Hardness measurement, High energy densities, Hybrid welding, Lap joint, Laser gas, Laser welding, Laser-GTA hybrid welding, Lean duplex stainless steel, Liquid metal embrittlement, Mechanical strength, Nd:YAG laser welding, Nitrogen additions, Shielding gas, Solidification rate, TEM, Tensile tests, Weld metal, Carbon steel, Chromium, Cooling, Corrosion resistance, Corrosion resistant alloys, Galvanized metal, Heat affected zone, Industrial applications, Laser beam welding, Liquid metals, Neodymium lasers, Nitrides, Scanning electron microscopy, Tensile strength, Tensile testing, Transmission electron microscopy, Tungsten
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-9297 (URN)978-0-912035-88-8 (ISBN)
Conference
26th International Congress on Applications of Lasers and Electro-Optics, ICALEO 2007, Orlando, FL; 29 October 2007 through 1 November 2007
Note
QC 20101126Available from: 2008-10-17 Created: 2008-10-17 Last updated: 2013-06-12Bibliographically approved
3. Corrosion resistance of welded lean duplex stainless steel
Open this publication in new window or tab >>Corrosion resistance of welded lean duplex stainless steel
2008 (English)In: Stainless Steel World America 2008, 2008Conference paper, Published paper (Other academic)
Keyword
duplex stainless steel, corrosion resistance, critical pitting temperature, CPT, welding, autogenous welding, gas tungsten arc welding, GTA, laser welding, laser hybrid welding, weldability, austenite formation, chromium nitride precipitates, weld metal, heat affected zone, HAZ
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-9298 (URN)
Note
QC 20101126Available from: 2008-10-17 Created: 2008-10-17 Last updated: 2013-06-12Bibliographically approved

Open Access in DiVA

fulltext(1761 kB)2550 downloads
File information
File name FULLTEXT01.pdfFile size 1761 kBChecksum SHA-512
bb398fb1bf1bbd4dc147811eb42aa010736e8fa4c16424e6bd6e60f4bcbb4933e307f08e49b916cc605a3748e8c51edd8ce35f3659e4525ff62560aa071ecadf
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Westin, Elin M.
By organisation
Physical Metallurgy
Materials Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 2550 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: 1162 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