Tungsten Inert Gas (TIG) welding, also known as Gas Tungsten Arc Welding (GTAW), is a precise and clean welding process highly valued for its ability to produce high-quality, aesthetically pleasing welds. This method uses a non-consumable tungsten electrode to create the arc and a separate filler metal to join materials. TIG welding is a two-handed process that requires coordination and practice but offers exceptional control over the weld.
This guide will walk you through the essential steps, from setting up your equipment to perfecting your technique.
Part 1: Safety and Preparation
Safety is paramount in any welding operation. TIG welding produces intense UV and IR radiation, so proper personal protective equipment (PPE) is non-negotiable.
- Essential Safety Gear:
- Welding Helmet: An auto-darkening helmet with a shade rating of #9 to #13 is recommended.
- Protective Clothing: Wear flame-resistant, long-sleeved clothing. A welding jacket is highly recommended. Avoid synthetic fabrics, which can melt and cause severe burns.
- Welding Gloves: Choose thin, flexible TIG welding gloves. They are designed to provide dexterity for handling the filler rod while still offering heat protection.
- Respirator/Ventilation: Welding fumes can be harmful. Always weld in a well-ventilated area and consider a respirator, especially when welding certain alloys.
- Preparing the Workpiece: TIG welding is highly intolerant of contaminants. A “squeaky clean” surface is crucial for a strong weld and to prevent porosity.
- Cleaning: Use a wire brush (dedicated to that specific metal type), a grinder, or a solvent (like acetone) to remove all rust, dirt, oil, and paint.
- Clamping: Securely clamp the parts to be welded together. Use tack welds to hold the pieces in place before starting the full weld.
Part 2: Equipment Setup
Properly setting up your TIG welding machine is the foundation for a successful weld.
- Tungsten Electrode Selection:
- The type and size of the tungsten electrode depend on the base metal and welding current.
- DC Welding (Steel, Stainless Steel): Use a pointed tip. A common choice is 2% Ceriated (Grey) or 2% Lanthanated (Gold).
- AC Welding (Aluminum): Use a balled tip, or a pointed tip with a modern AC TIG welder with balance control. A common choice is pure Tungsten (Green).
- Grinding the Tungsten Electrode:
- Use a bench grinder dedicated only to tungsten. Grinding on a wheel used for other metals can contaminate the tungsten, leading to a poor arc.
- Grind the tungsten in a linear direction, parallel to the length of the electrode, to a long, sharp point. The length of the pointed cone should be about 2 to 2.5 times the diameter of the electrode. This helps produce a stable, focused arc.
- For AC welding, you may need to “ball” the tip, which can be done by melting the tip slightly with the AC arc on a piece of scrap metal.
- Machine Settings:
- Polarity:
- DCEN (DC Electrode Negative): Used for steel, stainless steel, copper, and most other metals. This concentrates 70% of the heat on the workpiece for deep penetration.
- AC (Alternating Current): Used for aluminum and magnesium. The alternating current provides a cleaning action that breaks up the aluminum oxide layer.
- Amperage: Set the amperage according to the material thickness. It’s often best to start with a slightly lower setting and increase it as needed.
- Shielding Gas: TIG welding requires a shielding gas to protect the weld puddle from atmospheric contaminants.
- Gas Type: Pure Argon is the most common shielding gas for a wide range of materials.
- Flow Rate: Set the gas flow rate to around 15-20 cubic feet per hour (CFH) and adjust it as needed.
- Polarity:
Part 3: Welding Technique
Once your equipment is set up and your workpiece is prepared, you can begin the welding process.
- Get Comfortable: TIG welding requires a steady hand. Find a comfortable position and rest your hands or elbows on the workbench to provide stability. Do a “dry run” to ensure your movement is smooth and unimpeded.
- Torch Angle:
- Hold the torch at a 15-20 degree angle from the workpiece, pointing in the direction of travel.
- Maintain a consistent arc length (the distance between the tungsten tip and the workpiece), typically 1/8 to 3/16 inches. Avoid touching the tungsten to the workpiece, as this will contaminate the tip and require re-grinding.
- The Welding Process:
- Start the Arc: Use the foot pedal or a fingertip control to initiate the arc. The high-frequency start will create an arc without needing to scratch-start.
- Form the Puddle: Hold the arc in one spot until a molten puddle forms. The puddle should be about 1/4 inch wide.
- Add Filler Metal: With your other hand, gently dab the filler rod into the leading edge of the puddle. The heat from the puddle, not the arc, should melt the filler rod.
- Travel: Move the torch and continue dabbing the filler rod to create a uniform bead. Maintain a steady, consistent movement.
- End the Weld: Slowly release the foot pedal to gradually decrease the amperage, which helps prevent crater cracks. Continue to hold the torch over the end of the weld to allow the shielding gas to protect the cooling metal (post-flow).
Part 4: Common Problems and Troubleshooting
- Porosity: Caused by trapped gas in the weld.
- Solution: Ensure the workpiece is clean, check your shielding gas flow rate, and make sure there are no leaks in your gas line.
- Contaminated Tungsten: Occurs when the tungsten touches the workpiece or the filler rod.
- Solution: Immediately stop and re-grind the tungsten electrode. Practice maintaining a consistent arc length.
- Arc Wandering/Instability:
- Solution: The tungsten may be improperly ground. Re-grind the tungsten, ensuring the grind marks are lengthwise. Also, check for proper gas flow.
- Poor Penetration:
- Solution: Increase the amperage or slow down your travel speed.
With practice, TIG welding can become a rewarding skill for creating strong, high-quality welds on a variety of materials.
