TIG Welding Tips – How to Weld
TIG welding, or Tungsten Inert Gas, also referred to as GTAW (Gas Tungsten Arc Welding), is considered by most to be the best method of welding. It is very clean; TIG produces the least amount of fumes and slag. TIG welds can enhance the aesthetics of just about any project. A good TIG welder can create incredible-looking welds that are very strong. But all of this comes with a very serious learning curve. TIG welding takes all the fundamentals of shielded electrical welding and breaks it down into its primary forms -- shielding gas, electrical arc, and filler metal. Where MIG welding is almost automated, TIG is the exact opposite -- you control the arc and the filler metal at the part you are welding. One hand feeds the filler metal, the other controls the torch, while a foot (in most cases) controls the arc. You are not just operating the machine, you are part of it.
Most hobbyists are scared of TIG welding. We've all heard the stories about how tough it is to learn, that the machines are expensive, and it takes so long to complete a weld. While there are grains of truth to all of that, the reality is that TIG welding is not that tough to learn, and, as with anything, practice makes perfect. Will your first TIG welds look like a stack of dimes laid over? No. They might not even hold two pieces of metal together, but after some practice, you will get better. There are a few tips and tricks to getting started with TIG welding, and we call them the "TIG Commandments".
Tip #1 -- Cleanliness is next to Godliness
Other types of welding can be performed through all kinds of contaminants, but TIG welding requires a critically clean surface, especially when dealing with aluminum. All aluminum alloys have a coating of oxidation on the surface. It is a natural barrier that forms within minutes of exposure to air. Removing it is easy. There are two methods: scrubbing or chemical. Scrubbing is done with a stainless steel wire brush or wheel, applied to the area to be welded. The chemical process uses a liquid that is sprayed on, left to sit for a minute, and then wiped off. Removing the oxidation from aluminum is critical because the oxide coating melts at a considerably higher temperature than the base metal, meaning the aluminum underneath will have long melted before the coating. That can be a really big problem, leading to holes, pits and other issues with the weld.
TIG welding requires a Tungsten Rod (Electrode) in the torch. This is what provides a nice, stable arc. Selecting the right type and diameter of tungsten for the metal you are welding is critical. There are 4 types of Tungsten: pure, thoriated ceriated and lanthanated.
Pure Tungsten (EWP) is typically used in welding aluminum. This provides the stable arc with AC welding and can be used with either Argon, Helium, or mix shielding gas. Pure Tungsten electrodes are marked by a green tip. Pure tungsten has the highest consumable rate of all the types, but they are cheaper too. This type of electrode forms a natural balled tip, making them excellent for aluminum. DC welding is not recommended with this electrode, as the arc is unstable with DC.
Thoriated electrodes (EWTh-2) are marked with a red tip. Thoriated tungsten is the main type of electrode used in DC TIG welding when aluminum is not involved. These can be used in AC applications in thin sheet metal; nothing thicker than .060”. Thoriated electrodes emit a slight radiation, which means you might NOT want to keep one in your pocket. What that really means is take care of the dust when grinding thoriated tungsten.
Ceriated tungsten (EWCe-2, grey tip) requires less amperage for welding, making it an excellent electrode for thin sheet metal. Ceriated tungsten can be used on all types of metals. It is an excellent one-electrode option for the casual TIG welder. These electrodes do not like higher temperatures. Ceriated tungsten is best used in DC welding, but will work in AC applications.
Lanthanated electrodes (EWLa-1.5) are noted with a blue tip. This type of tungsten lasts longer than thoriated electrodes, with excellent arc starting and stability. The addition of the lanthana helps the electrode maintain its tip shape during the welding process (we will get into that later), making it excellent for steel and stainless. These electrodes are also AC compatible.
Tip #3 -- Know Thy Metal
The type and thickness of metal you are working with determines the function of your TIG. The filler rod must match the metal you are working with. All rods are noted by a code. Until you become an expert, there are really just a few filler rods that you need. If you are welding critical joints for things such as high-pressure tanks, then you need to use very specific filler materials, if you are just welding together a gas tank, there is a lot more leeway. Remember, critical welds require exact knowledge of the base metal. This is just a general welding guide. When in doubt, ask your local metal supply shop.
ER 70S-2 -- This is the typical mild steel filler rod used in TIG welding. It can be used to weld any mild steel, and is suitable for 4130 chromoly (roll cages, frames, etc)
4043 aluminum -- For general aluminum welding, this is the rod you will use.
Aluminum bronze -- TIG welding copper? You need this. Another cool feature of this type of filler rod is that it is great for welding cast iron and for cross-welding steel to copper.
Hastelloy W -- This is what many TIG welders call the “Wonder Rod”. It works for any type of steel: stainless, chromoly, tool steel, all of it. If you are unsure of what kind of steel you have, this one will get the job done.
ER308L -- When welding stainless steel, the most common type is 304 stainless. The 308 rod works very well.
Tip #4 -- AC/DC
The type of current used in the welding process makes a big difference in the end result. AC current is a push/pull action, an important function in welding aluminum and magnesium. Aluminum melts at 660°C, However the oxide doesn’t melt until over 2000°C. The AC current constantly breaks off the oxide layer by thermal cycling (that push/pull action). DC current can’t penetrate the oxide layer because the DC current only flows in one direction. Steel does not oxidize as fast or as easily as aluminum, and the oxides that form are not as dissimilar from the base metal. Copper and steel can all be welded via DC current.
One side note. AC welding is much louder that DC, so don’t get spooked when the machine cracks out a loud hum when you fire-up on some aluminum. It should not be so loud that it runs you out of the room, but it is much louder than DC TIG work, which is almost silent.
Tip #5 -- Spare the rod, spoil the weld – shaping the tip
You can’t just slap an electrode into the torch and go. The tip must be ground to shape. For most steels, a sharp tip is sufficient. The trick here is to grind the tip about 2 times the width of the rod. A 1/8” rod should be sharpened from 1/4” to the tip. This helps focus the arc. Thin sheet metals need a sharp tip, where thicker materials and high-current applications do better with a truncated tip.
Aluminum welding is typically done with a rounded tip. This is achieved by rolling the end to balled tip. Always grind the tip straight on, so the grind marks run parallel with the rod and not at 90°. Grinding at 90° will create horizontal grooves that will create an unstable arc. Tungsten can become contaminated when grinding, which is bad news for your welds. Purchase a dedicated tip grinder, preferably diamond or borazon. Do not use this to grind anything else. You can even use a chemical sharpener.
Tip #6 -- Fancy Footwork – working the pedal
TIG welding is not a drag race, so the foot pedal should not be floored start to finish. The foot pedal controls the amperage of the arc; it is in essence a throttle for the arc itself. When you first trigger the arc, the pedal should be full on. Then when the weld puddle forms, back off the pedal. Too much pedal will cause wide welds, burn through, and other issues. Each weld is different, so there is no one set way to do it, but once the puddle has formed and the welding has begun, you will find a rhythm for the foot pedal that coincides with the addition of the filler material.
Tip #7 -- Motion of the Ocean – torch control
Where MIG welding can be done using different torch techniques, TIG requires a set style. The torch should always be pushed along the weld. Pulling the torch will result in too much heat going through the previously made weld, which can cause warping and burn through. With TIG, you want to push the heat towards the unwelded joint. Each weld should start with the torch positioned at 90° from the joint, and then after the weld puddle forms, move the torch to 70°. Filler rod is added at a low angle, around 20-30° from the material being welded. The exception to the degree rule is in a T-joint, which we will discuss later. Unlike MIG welding, the torch does not need to be moved in the C-pattern; the foot control and manual filler rod control eliminate the need for that. If you are welding without filler rod, however, a C-pattern may help complete the weld.
Tip #8 -- Remember the Alamo(nium) – temperatures and aluminum
Aluminum does not change color with temperature. Additionally, aluminum transfers heat much better than steel, meaning a smaller part will get very hot without showing any appreciable sign of being hot. TIG Welding Gloves are much thinner than MIG gloves. This is because you need the dexterity to control the torch and the filler rod. Even with gloves on, it can burn you. Pay attention to what you are working with and always put safety first.
Another issue with TIG welding is that the amperage is lower than with MIG, which can cause issues with auto-darkening helmets. You need a welding helmet that will register lower amperage arcs to safely function.
Tip #9 -- Joint Venture – Different joints need different welds
Different types of joints require different techniques. Where you focus the arc, and how and where you add the filler material, all differ depending on the style of joint you are working with. Here are the 4 most common types of welding joints:
A basic butt joint (two pieces placed together in a flat plane) is the most simple to make. Form the weld puddle at 90°, tilt the torch to 70° and continue.
Lap joints, where one piece is lying on top of the other, are pretty much the same, except that you want to focus the arc just past the edge of the top piece, as the edge will melt faster than the face. Dip the filler rod at the edge so that you get a smooth joint.
Outside c orner joints require more filler material to ensure a good weld. The torch angles are the same as a butt joint.
T-joints are the most difficult. First, the tungsten electrode needs to be positioned far enough past the cup of the torch so that it can reach the inside of the corner. As with a lap joint, you need to focus the heat into the face of the material, as opposed to the edge of the second piece.
TIG welding is most certainly a mix of art and science. The science is straightforward, and there is much more art involved. Just like anything else, practice is most important; you will only get better with time. Most local trade schools offer night classes for adults, and many welding supply shops even hold evening or weekend workshops. Even 20 minutes of personal training with a professional can do wonders for your TIG-welding abilities.
Contributing Eastwood Customer: