Investigation on the Effect of Activating Flux on Tungsten Inert Gas Welding of Austenitic Stainless Steel Using AC Polarity

The TIG welding has a high disadvantage against the substantially high productivity welding procedures. This is why there were continuously going on several trials to improve the productivity of the TIG welding. The Activated Tungsten Inert Gas welding (ATIG welding) is one of these trials. Application experiments of ATIG welding on austenitic stainless steel plates will be presented. The main problems which appear when using the ATIG welding are the choosing of tungsten electrode, the suggested fitting of parts for the joining, portioning of the activating flux and the sensitivity for the measure of flux. They are extremely important to apply the ATIG welding and the results will be presented by this work. In the second half of this paper the comparison of the productivity differences between TIG and ATIG welding; mechanical properties, microstructure and corrosion resistance of welded joints will continue. Finally the evaluating the results and trying to classify the ATIG welding amongst the modern and most productive welding procedures is detailed. Furthermore advises for using the ATIG welding for suitable applications are represented.

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Experimental Investigations for Reducing Effect of Sensitization in Tungsten Inert Gas Welding

Volume 6: Materials and Fabrication, Parts A and B ◽

10.1115/pvp2008-61078 ◽

2008 ◽

Author(s):

Rupinder Singh ◽

Sehijpal Singh

Keyword(s):

Mechanical Properties ◽

Stainless Steel ◽

Corrosion Resistance ◽

Austenitic Stainless Steel ◽

Inert Gas ◽

Experimental Investigations ◽

Welding Parameters ◽

Work Piece ◽

Tungsten Inert Gas Welding ◽

Stainless Steel 316L

Stainless steels are considered to have very good resistance to general and localized corrosion due to their chromium content. This property of corrosion resistance constitutes the main criterion for selecting austenitic grades of steels for service in the chemical, nuclear and aerospace industries although their mechanical properties are relatively modest. However, this resistance can degrade when structural components manufactured from these steels are used in a chemically aggressive environment, especially when service involves exposure to high temperatures like in welding. This exposure gives rise to precipitation of chromium carbides producing chromium depletion at grain boundaries that brings about the inter-granular corrosion or sensitization of these materials. Austenitic stainless steel (316L) is one of the corrosion resistance material used extensively in the oil production, chemical and power generation industries for transportation and reservoir of corrosive products. In spite of its corrosion resistance property there exist severe problems of sensitization. In the present work an effort has been made to reduce the effect of sensitization in Tungsten Inert Gas welding of Austenitic stainless steel (316L). Three welding procedures (namely conventional, back step and skip welding) in Tungsten Inert Gas welding have been used to control exposure time of the weld pool to higher temperatures, in order to study the effect of sensitization on mechanical properties (such as tensile strength, yield strength, percentage elongation and hardness). The results of this study suggested that the better mechanical properties were attained by the skip welding procedure and recommended welding parameters are 90 Amp current and 10 L/min of gas flow rate for a 5 mm thick work piece. Noticeable change in amount/extent of sensitization was observed using a scanning electron microscope (SEM) analysis within the various welding specimens prepared using the various procedures. Further mechanical properties (like strength and hardness) have been correlated with the extent of sensitization, which show remarkable decreases when the amount/extent of sensitization increases.

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