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Lesson 1
The Basics of Arc Welding
Lesson 2
Common Electric
Arc Welding Processes
Lesson 3
Covered Electrodes for Welding
Mild Steels
Lesson 4
Covered Electrodes for Welding Low Alloy Steels
Lesson 5
Welding Filler Metals for Stainless Steels
Lesson 6
Carbon & Low Alloy
Steel Filler Metals -
Lesson 7
Flux Cored Arc Electrodes Carbon Low Alloy Steels
Lesson 8
Hardsurfacing Electrodes
Lesson 9
Estimating & Comparing Weld Metal Costs
Lesson 10
Reliability of Welding Filler Metals
© COPYRIGHT 1998 THE ESAB GROUP, INC. LESSON II 2.3 GAS TUNGSTEN ARC WELDING Gas Tungsten Arc Welding* is a welding process performed using the heat of an arc established between a nonconsumable tungsten electrode and the work piece.  See Figure 5. The electrode, the arc, and the area surrounding the molten weld puddle are protected from the atmosphere by an inert gas shield.  The electrode is not consumed in the weld puddle as in shielded metal arc welding.  If a filler metal is necessary, it is added to the leading the molten puddle as shown in Gas tungsten arc welding produces exceptionally clean welds no slag is produced, the chance inclusions in the weld metal is and the finished weld requires virtually no cleaning.  Argon and Helium, the primary shielding gases employed, are inert gases.  Inert gases do not chemically combine with other elements and therefore, are used to exclude the reactive gases, such as oxygen and nitrogen, from forming compounds that could be detrimental to the weld metal. Gas tungsten arc welding may be used for welding almost all metals — mild steel, low alloys, stainless steel, copper and copper alloys, aluminum and aluminum alloys, nickel and nickel alloys, magnesium and magnesium alloys, titanium, and others.  This process is most extensively used for welding aluminum and stainless steel alloys where weld integrity is of the utmost importance.  Another use is for the root pass (initial pass) in pipe welding, which requires a weld of the highest quality.  Full penetration without an excessively high inside bead is important in the root pass, and due to the ease of current control of this process, it lends itself to control of back-bead size.  For high quality welds, it is usually necessary to provide an inert shielding gas inside the pipe to prevent oxidation of the inside weld bead. * Gas Tungsten Arc Welding (GTAW) is the current terminology approved by the American Welding Society, formerly known as "TIG" (Tungsten Inert Gas) welding. FIGURE 5 TRAVEL DIRECTION TORCH SHIELDING GAS NOZZLE INERT GAS SHIELD WORK PIECE TUNGSTEN ELECTRODE ARC FILLER METAL GAS TUNGSTEN ARC WELDING