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.
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