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Laser welding of a lean duplex stainless steel
Outokumpu Stainless AB, Avesta Research Centre.
Esab AB.
Nordic Laser Production AB.
Nordic Laser Production AB.
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.

Place, publisher, year, edition, pages
2007. 335-344 p.
Keyword [en]
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: urn:nbn:se:kth:diva-9297ISBN: 978-0-912035-88-8 (print)OAI: oai:DiVA.org:kth-9297DiVA: diva2:54601
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
In thesis
1. Welds in the lean duplex stainless steel LDX 2101: effect of microstructure and weld oxides on corrosion properties
Open this publication in new window or tab >>Welds in the lean duplex stainless steel LDX 2101: effect of microstructure and weld oxides on corrosion properties
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
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:nbn:se:kth:diva-9299 (URN)978-91-7415-109-1 (ISBN)
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

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