(a) TIG Welding Process:
Tungsten Inert Gas (TIG) welding, also known as GTAW (Gas Tungsten Arc Welding), is a meticulously controlled arc welding process that uses a non-consumable tungsten electrode and an inert shielding gas. Here’s how it works:
- Preparation: Clean the weld area thoroughly to remove any contaminants that could compromise the weld quality.
- Setup: Choose the appropriate tungsten electrode and shielding gas (e.g., argon) based on the material being welded. Set the welding current and flow rate.
- Initiation: Create an arc between the tungsten electrode and the workpiece using a high-frequency start or by touching the tip momentarily and retracting.
- Welding: Hold the torch at the desired angle and distance from the joint. Add filler metal (a separate rod or wire) manually to the molten pool created by the arc, building the weld bead layer by layer.
- Travel Speed: Move the torch along the joint seam at a controlled pace, maintaining the arc and adding filler metal as needed.
- Finishing: Allow the weld to cool completely, then remove any slag (residue) with a wire brush or other cleaning tools.
TIG welding offers exceptional control and precision because the filler metal is not continuously fed, allowing the welder to manipulate the molten pool directly.
(b) AC Current for Aluminum:
When welding aluminum, AC current is often preferred over DC current for several reasons:
- Penetration: The alternating polarity of AC creates a cleaning action during the positive cycle, breaking up the tenacious oxide layer (aluminum oxide) that forms on the surface. This allows for deeper weld penetration compared to DC.
- Cathode Cleaning: During the negative cycle, the aluminum melts and cleans the tungsten electrode, preventing contamination and maintaining a stable arc.
- Weld Quality: The combined cleaning and penetration effects of AC lead to cleaner welds with reduced porosity and improved visual appearance.
Though DC can be used for specific aluminum applications, AC generally offers better overall performance and ease of welding.