TIG stands for tungsten inert gas. The American Welding Society (AWS) calls this method of welding gas tungsten arc welding (GTAW). Heli-arc welding is another name for this common procedure used throughout the welding industry.
TIG welding uses tungsten electrodes, which have a very high melting point. When doing TIG welding aluminum, the electrode gets hot but does not melt, which means that it’s a non-consumable electrode. The tungsten will not last forever, but it will not melt and become part of the weld as it does in other welding processes, such as MIG and stick welding.
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Basics of TIG Welding
A TIG torch contains a tungsten electrode that is held in a collet, which is then tightened into place. By loosening the end cap, the tungsten electrode can move up and down in the collet, allowing more or less of the tip to be exposed. Once the end cap is tightened, it holds the electrode in place.
TIG welding works by melting the base metal of the two pieces that are being joined together. An electric arc forms between the base metal and the electrode. The heat generated from the arc then melts the two parts, combining them. The amount of heat applied is controlled using a foot pedal or a thumb wheel on the torch.
The type of current used to generate the heat is DC or direct current. This is similar to a battery in which one side is positive and the other is negative. The negative side of the direct current is the tungsten electrode. The positive side is the metal that is being welded together. Therefore, this is called DCEN for direct current electrode negative. Straight polarity is another term often associated with this procedure. The heat generated while TIG welding is projected onto the metal. Aluminum TIG welding uses AC, or alternating current, to break up the oxide film that covers the piece.
The tungsten electrode torch is connected to a battery, which transfers the electric current to the weld piece. The weld piece then has a work lead connected to the end of it to transfer the current back to the battery, thus completing the circuit.
Filler metal can be used in a TIG weld but does not have to be used. You will want to make sure that any filler metal alloy that you use is compatible with the base metal and also has the necessary strength to do the job properly.
The molten metal is protected by a shielding gas, such as argon or helium, to prevent it from reacting with the oxygen in the atmosphere. The shielding gas is stored in high-pressure cylinders which use a regulator to adjust the pressure to a usable level. The gas comes out of a hose connected to the torch at the point of the weld.
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Specifics of TIG Welding Aluminum
When TIG welding aluminum, the type of current changes to alternating instead of direct current. In this type of weld, the positive and negative sides continually switch back and forth between the electrode and the piece being welded. This means that there is more heat on the electrode, and this fluctuation produces a cleaning effect on the workpiece. The high temperature on the target section creates a bubbling effect that cleans away the oxide that is always on aluminum. If the oxide is not removed, you will not get a strong weld. The alternating current helps to control the oxides.
Tips for General Welding
- Make sure your hand position is comfortable when you are welding. Some people hold the torch like a pencil. Others use an overhand grip, but you should use whatever grip or angle is most comfortable for your hand and arm position.
- Practice with the torch to make sure you have enough room as your hand travels along the weld. You don’t want to stop because you run out of table or hose.
- Practice left- and right-hand welding to be ready for any welding situation.
- Wear a glove on the hand holding the torch for protection from the heat, but it is also a good idea to use a glove on your other hand to protect it from ultraviolet (UV) radiation. Long-term exposure to UV rays can damage exposed skin.
Tips for TIG Welding Aluminum
- Since TIG welding aluminum is more difficult than steel welding, do not attempt it until you have several hours of arc welding experience. You will need to understand the basics of working with steel before moving on to aluminum. Once you master aluminum, steel becomes much easier.
- Aluminum is expensive, so practice doing a lap-and-T-joint combination, and then stack the weld with additional bead practice to get the most out of your practice material.
- Practice doing an aluminum welding drill, in which you attempt many single beads on one piece of aluminum. You should practice a variety of different techniques in this drill: loose ripple and weave beads, forward and backward welding, short and long arcs, tapered and rounded electrodes, tight and lose ripples, manual and automatic pulse settings, and different torch angles.
- Use a TIG finger heat shield. This extra protection for your fingers allows you to maintain a long weld without getting your hand or fingers burned. The heat shield fits over your welding gloves to provide an additional layer of protection. Other essential safety equipment should be used at all times as well: welding mask, respirator, and gloves and boots to protect hands and feet.
- While the TIG welder cleans oxide from the aluminum as you make the bead, it is best to clean as much of the oxide off the project piece and the filler rod before beginning to weld. This will save you time and energy during the welding process. One way to remove the oxide is by using a safe chemical, such as a heavy-duty degreaser or denatured alcohol. To manually remove the oxide, use a soft-bristled brass brush. Stainless steel brushes may leave fine scratches on the surface of the aluminum.
- Use the correct gas combination. Helium, the preferred choice in the past, burns hotter and boosts the amperage of your torch. However, new methods suggest using an argon and helium blend that increases the arc voltage and allows a more stable welding arc for optimal performance.
- TIG welding aluminum heats up quickly, so you will need to be attentive to the bead. If it begins to look grainy, the area is too hot and the aluminum will not solidify quickly, which affects the weld. The work area needs to be cooled before continuing.
- Have a bucket of water next to your workbench to cool the metal frequently. You will probably need to dunk the metal into the water after every two or three beads to prevent it from getting too hot.
- Bend the filler rod to a 90-degree angle toward the top to prevent the rod from poking you in the eye when you flip your helmet to inspect the weld.
- When welding, it is best to maintain a tight arc without too much torch angle for the best effect, and control the flow of gas. Knowing how tungsten affects the arc is important in keeping the arc tight. A long taper will permit the heat to concentrate in one small area; therefore, decreasing the taper allows the arc to spread out more. A round profile allows the heat to flare out. Practice using different tapers to see which works best for your needs.
- Do not add any filler rod until you see the shiny, wet puddle of melted TIG welding aluminum. Keep the filler rod as close to the gas as possible. This takes lots of practice. Also, the filler rod shouldn’t be too thin, since that will make it more difficult for you to weld. Work with thicker filler rod until you gain experience.
- Purchase and use the best tools from trusted suppliers. Poor-quality tools will only result in poor-quality welds. Indications of reduced quality in tools include flaking paint, bent electrodes, and fluctuating diameters.
- There are many impressive and informative videos on YouTube that can help welders learn both basic and advanced techniques. The benefit of these videos is that you can see precisely what the trained welder is doing as he describes the steps. Use these videos as part of your overall self-education program for learning welding techniques.
TIG welding aluminum is an arc welding process that uses a non-consumable tungsten electrode. The filler metal from a filler rod is added separately by hand, and the shielding gas is stored in cylinders. TIG welding aluminum differs from working steel because of aluminum’s oxide layer that must be considered before and during a weld. Since aluminum is more difficult to weld than steel, learning how to handle TIG welding aluminum properly will make welding other metals considerably easier. Training programs are available throughout the country, and there are many online training videos available for anyone to examine.