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Effects of nitrogen and hydrogen in argon shielding gas on bead profile, delta-ferrite and nitrogen contents of the pulsed GTAW welds of AISI 316L stainless steel

Auswirkungen von Stickstoff und Wasserstoff im Argon-Schutzgas auf das Nahtprofil, den δ-Ferritanteil und den Stickstoffgehalt von gepulsten Wolfram-Inertgas-Schweißungen eines AISI 316L Stahls
Panyasak Phakpeetinan, Amnuysak Chianpairot, Ekkarut Viyanit, Fritz Hartung and Gobboon Lothongkum
From the journal Materials Testing

Abstract

The general effects of 1, 2, 3 and 4 vol.-% nitrogen and 1, 5 and 10 vol.-% hydrogen in argon shielding gas on weld bead profile (depth/width ratio: D/W) and the δ-ferrite content of AISI 316L pulsed GTAW welds were investigated. The limits for imperfections for the quality levels of welds were based on ISO 5817 B. The plates with a thickness of 6 mm were welded at the flat position and the bead on plate. Increasing hydrogen content in argon shielding gas increases the D/W ratio. Excessive hydrogen addition to argon shielding gas will result in incompletely filled groove and excessive penetration of weld. Increasing welding speed decreases the weld-metal volume and the D/W ratios. Nitrogen addition to argon shielding gas has no effect on the D/W ratio. The addition of a mixture of nitrogen and hydrogen to argon shielding gas on the D/W ratio does not show any interaction between them. An effect on the D/W ratio can be exclusively observed as a function of hydrogen content. Increasing hydrogen content in argon shielding gas increases the δ-ferrite content of weld metal. Increasing either nitrogen content in shielding gas or welding speed decreases the δ-ferrite content of weld metal. The nitrogen addition increases the weld metal nitrogen content, however, the hydrogen addition leads to a decrease of weld metal nitrogen content.

Kurzfassung

Die allgemeinen Auswirkungen von 1, 2, 3 und 4 vol.-% Stickstoff sowie 1, 5 und 10 vol.-% Wasserstoff im Argon-Schutzgas auf das Nahtprofil (Tiefe-zu-Weite-Verhältnis: D/W) und den δ-Ferritanteil von gepulsten WIG-Schweißungen des Stahls AISI 316L wurden untersucht. Die Grenzen für Unregelmäßigkeiten für die Qualitätsstufen der Schweißungen basierten auf der ISO-Norm 5817 B. Die Platten mit einer Dicke von 6 mm wurden in der Wannenposition auftragsgeschweißt. Ein zunehmender Wasserstoffanteil im Argon-Schutzgas erhöht das D/W-Verhältnis. Eine exzessive Wasserstoff-Zugabe führt zu einer vollständig gefüllten Nahtvorbereitung und einer exzessiven Durchschweißung. Die Erhöhung der Schweißgeschwindigkeit setzt das Schweißbadvolumen herab ebenso wie die D/W-Verhältnisse. Eine Stickstoff-Zugabe hat keine Auswirkungen auf das D/W-Verhältnis. Die Zugabe eines Stickstoff-Wasserstoff-Gemisches zum Argon-Schutzgas zeigte keine Wechselwirkung zwischen diesen und bezüglich des D/W-Verhältnisses. Eine Auswirkung auf das D/W-Verhältnis kann ausschließlich in Abhängigkeit des Wasserstoffgehalts beobachtet werden. Eine Erhöhung des Wasserstoffgehalts im Argon-Schutzgas erhöht den δ-Ferritanteil im Schweißgut. Eine Erhöhung entweder des Stickstoffgehalts oder der Schweißgeschwindigkeit setzt den δ-Ferritanteil im Schweißgut herab. Die Stickstoff-Zugabe erhöht den Stickstoffgehalt im Schweißgut, wenngleich eine Erhöhung der Wasserstoff-Zugabe zu einer Abnahme des Stickstoffgehalts im Schweißgut führt.


*Correspondence Address, Assoc. Prof. Dr. Gobboon Lothongkum, Innovative Metals Research Unit, Department of Metallurgical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, 10330, Thailand. E-mail:

Panyasak Phakpeetinan, born in 1980, received his Bachelor Degree in Production Technology from King Mongkut's University of Technology, North Bangkok, Thailand in 2004, and his Master Degree in Metallurgical Engineering from Chulalongkorn University, Bangkok, Thailand, in 2008. His research interest is welding of metals.

Dr. Amnuysak Chianpairot, is a researcher at the Failure Analysis and Surface Technology Lab, Materials Reliability Research Unit, National Metal and Materials Technology Center (MTEC), Pathaumthani, Thailand. He received his Master Degree in Metallurgical Engineering from University of California, Berkeley, USA, in 2001 and his PhD in Metallurgical Engineering from Chulalongkorn University, Thailand, in 2012. His research interests are corrosion and failure analysis.

Dr.-Ing. Ekkarut Viyanit, born in 1972, is a researcher and Head of the Failure Analysis and Surface Technology Lab, Materials Reliability Research Unit, National Metal and Materials Technology Center (MTEC), Pathaumthani, Thailand. He received his Dr.-Ing. Degree in Materials Engineering from Helmut-Schmidt University, Hamburg, Germany, in 2005. His areas of expertise include corrosion protection, failure analysis and joining of metals.

Prof. Dr.-Ing. Fritz Hartung is a visiting professor in the Department of Metallurgical Engineering, Faculty of Engineering, Chulalongkom University, Bangkok, Thailand. He received his Master and Dr.-Ing. Degrees in Mechanical Engineering from University of Technology Magdeburg, Germany, in 1969 and 1975, respectively. He was the Head of Department of Materials Technology and Welding, Trier University of Applied Science, Germany, from 1993 to 2010, and Professor at the University Dortmund, Germany, from 1993 to 2002. His areas of expertise are welding and metal joining.

Assoc. Prof. Dr.-Ing. Gobboon Lothongkum is a member of the Innovative Metals Research Unit, Associate Professor and Head of the Department of Metallurgical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand. He received his Dr.-Ing. Degree from Helmut Schmidt University of the Federal Armed Force in Hamburg, Germany, and the International Welding Engineer Certificate of the International Institute of Welding (IIW) in 1994 and 2006, respectively. His research interests are corrosion and welding of metals and alloys, development of stainless steels and high temperature materials.


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Published Online: 2016-05-23
Published in Print: 2016-06-01

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