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There are many advantages to using a TIG weld for certain welding projects. Because this type of weld allows for much deeper penetration of the welding filler, it makes it a suitable weld type for pressure vessels and other metal seams/joints that need to be x-rayed to code. What many welders aren’t aware of is that you can TIG weld off an inverter welder in many cases.
So how can TIG welding be performed with an inverter welder? In TIG welding with an inverter welder, a sharpened tungsten rod is used to scratch-start the TIG arc, and the filler rod is kept in straight argon shielding gas used at a rate of roughly 8-10 liters per minute to prevent contamination.
TIG welding off an inverter welder may seem complicated, but with a few steps of preparation, it doesn’t have to be. Anyone who has performed basic oxy-fuel welding can get their head around a TIG weld. Read on to find out more about how to use an inverter welder to pull it off.
What is TIG Welding?
For those that are unfamiliar with the term, TIG welding is the shorthand for tungsten inert gas welding, a method of welding where an electrical arc is produced off a non-consumable tungsten electrode and shielded with inert gas from oxidation and contamination. This shielding gas is usually pure argon, but sometimes a mixture of helium and argon is used.
TIG welding is slower and more difficult than its rival, MIG (metal inert gas) welding, but offers a much more precise bond.
It can also be used at lower amperages than MIG welds, which means it can be used on exotic metals that can’t tolerate higher amperages, and on thinner metals without burning through and compromising the structural integrity of the materials.
Inverter welders are powered by inverting AC power (which is what is run through most residential buildings) into useable DC power. DC power affects the quality of a weld in two ways:
- Positive DC current: Higher penetration into the steel base of the weld
- Negative DC current: a Higher level of filler deposit for welding thin sheet metals
What Projects Should TIG Welds be Used on? Who Should TIG Weld?
TIG welds with an inverter welder are an excellent choice for thinner materials, as TIG welding requires getting the pieces of connecting metal hot enough to form atomic bonds where they meet. In contrast, MIG welding uses a filler wire to connect the two parts of metal with a seam.
Using a TIG weld on a thicker material can still get the job done but can lead to heat stress cracking and other cosmetic or structural issues.
TIG welding is known for being a little more complicated and harder to pick up than MIG welding, and MIG welding is usually recommended for newer welders who are inexperienced since it is not as forgiving of beginner’s mistakes as other welding methods.
TIG welding requires a very firm grasp of the following variables mid-weld:
- Electric current
Not properly monitoring or manipulating any of these operator variables during the weld can lead to the weld failing (best case scenario) or the welder becoming injured (worst case scenario).
For this reason, a TIG weld with an inverter welder should only be attempted by someone comfortable and well-versed with the electrical and metallurgic concepts involved in welding.
TIG welding is a good option for steel or stainless projects, but should not be used with aluminum, which requires an AC current. Some TIG units do have an option for AC, but since inverter welders are designed to convert AC into DC current, many of them do not have this option.
Supplies Needed for TIG Welding with an Inverter Welder
To do TIG welding with an inverter welder, a few basic welding supplies are needed.
It’s better to get all these supplies together before beginning the weld, as welding is a precise craft, and you don’t want to be scrambling around mid-weld trying to find something you forgot to locate near your workbench.
Here are some of the supplies you’ll need to TIG weld with an inverter welder:
- Tungsten electrode
- Inverter welder w/high-frequency unit
- Torch (electrode holder)
- Shielding gas (either argon or helium)
- Filler safety rod
- Welding helmet
- Welding gloves
- Protective welding jacket or apron
Some of the protective gear required for a TIG weld might seem unnecessary, especially for experienced welders. Still, welding requires working with molten metal and arcs so bright they can burn your eyes. In a hobby or profession like welding, protective equipment is crucial.
Make sure that you are outfitted in your protective gear before the start of the weld and keep all tools at close hand to avoid having to get up. As stated earlier, TIG welding requires exact control over the elements involved, so you don’t want to get distracted.
How to TIG Weld with an Inverter Welder
Like other types of stick welding, TIG welding with an inverter welder has a series of steps that need to be performed for the weld to go smoothly. The first thing you need to do is run your stick out.
What “Stickout” Is and How to Run It
In TIG welding, the electrical stick out is defined as the distance between the contact tip and the unmelted end of the tungsten electrode. This distance is also referred to as the amount of wire in resistance. Electrical stick out influences a lot of factors in a weld, including the following:
- Melt-off rate: Melt-off rate is the weight or length of the electrode/wire/rod/powder melted in a specified unit of time
- Penetration: Penetration is the depth to which the fusion line in a weld penetrates the base metal; the deeper the penetration on a weld, the stronger the welding bond
- Weld bead shape: Weld bead shape is essential for good fusion in a weld, and subsequently the structure of the resulting weld bond depends on it
For TIG welding, stick-out should be roughly half the diameter of the inner diameter of the shielding cup in a standard setup. The specific length will range from the welding setup to set up, but this rule of thumb serves as a good standard for most of them. Experimentation with the welding rig will further inform the welder of optimal stick out to maintain a good weld.
One way to increase the length of stick out you can use without sacrificing weld quality is to incorporate a TIG glass lens.
These lenses help with holding the tungsten steady and ensures proper electrical transfer while simultaneously improving shielding coverage and accessibility to the joint being welded.
Using Sharpened Tungsten in a TIG Weld on an Inverter Welder
TIG welding can be done with an inverter welder either with or without filler wire, but when using sharpened tungsten wire, you should be careful that the tungsten doesn’t stick. If it does, you’ll have to stop and re=sharpen your tungsten to avoid contamination.
Accidentally contaminating the tungsten electrode in a TIG weld can occur in a few different ways:
- Dipping the tungsten electrode into the molten weld puddle
- Touching the tungsten electrode to the filler rod
Contaminating your tungsten during a TIG weld is one of the most common mistakes you can make. Luckily, all you need to do is re-sharpen your tungsten on a bench grinder, and you’ll be back in the saddle. To sharpen or re-sharpen your tungsten for TIG welding, perform the following:
- Grind the tungsten in a bench grinder dedicated to tungsten (don’t use a bench grinder used to grind steel, or you will introduce contaminants to your tungsten)
- Grind the tungsten lengthwise, being sure to leave the tip of the tungsten about twice the diameter of the electrode.
- Cut off the tip of the tungsten cone, so it doesn’t detach and contaminate your next weld.
The tungsten necessary for use in DC-based TIG welding isn’t just any tungsten, either.
You will need to use thoriated tungsten, which can be quite toxic and should be handled carefully. Thoriated tungsten has been treated with thorium, which is a radioactive compound. This radioactivity is inert and shielded during regular welding use but can be emitted and inhaled during tungsten grinding.
Scratch or Tap Starting an Arc
This is a major way in which TIG welding differs from MIG welding. When using a TIG welder, the torch is live as soon as you switch the welder on. There is no button to start the arc, so to do so, you’ll have to either tap start or scratch start an arc.
Tap Starting an Arc for TIG Welding with an Inverter Welder
One way to start an arc in TIG welding is to tap start an arc. This is done by sharply tapping the rod against the metal you’re working on will both remove any extra flux from the end of the tungsten rod and will also create electrical contact needed to begin an arc.
This movement must be performed decisively and sharply, only making contact for a moment before pulling the rod back. This action must also be performed in a light way. If you’re too slow with your tap or use too much pressure, this can cause the tungsten to stick.
If your tungsten sticks, congratulations, you’ve messed up the TIG weld. Go back to the previous section of this how-to guide, re-sharpen your tungsten, and try again. One advantage of TIG welding on an inverter welder is that if your rod sticks, the inverter welder should reduce voltage automatically.
If you are reasonably new to TIG welding, it can be smart to practice tap starting a weld on scrap metal until you have built up confidence in doing so before beginning a serious weld.
Scratch Starting an Arc for TIG Welding with an Inverter Welder
Another way to start an arc for a TIG weld other than tap starting is to scratch start a weld. This is where you move the rod against the metal to remove extra flux and initiate electrical contact. When scratch starting an arc, the rod should be lifted from the metal as soon as it begins sparking.
When scratch starting an arc, move the rod back and forth in a small scratching motion to remove the flux coating. Try not to scratch in a long motion, as this can start your welding arc further from your desired start point than necessary.
To prevent the rod from sticking, it should be pulled away as soon as sparks are seen, then returned to a normal welding arc length. Avoid excessive amounts of pressure, as this encourages sticking.
Scratch starting an arc is similar to tap starting an arc but is prone to sticking if a welder is not fast enough or is inexperienced with starting an arc in this manner. However, scratch starting can be a good choice for rods that are harder to start.
Gas Shielding in TIG Welds Using Inverter Welders
Another major issue people have trying to TIG weld using an inverter welder is insufficient inert gas shielding, which leads to materials contamination. For TIG welding, you should be using either pure argon or an argon-helium mix.
If you TIG weld with argon-carbon dioxide, you will immediately contaminate and ruin your weld. For this reason, having adequate gas shielding during a TIG weld is vital. To ensure proper gas shielding for a TIG weld, observe the following procedure:
- Set your gas flow rate. The correct gas flow rate for a TIG weld using an inverter welder would be 8-10 liters per minute. It is just as important not to set your flow rate too high as it is to set your flow rate high enough–high flow rates of shielding gas can cause turbulence that introduces ambient airborne contaminants.
- Check fittings and hoses for any leaks. If you’re observing a contaminated weld and you think your shield should be adequate, check your setup for leaks. To check for leaks, run soapy water over the hoses and fittings. If there is a leak, you should see bubbles at the leaking seam.
Other Common Problems TIG Welding with an Inverter Welder
While TIG welding can be easily learned by anyone with some basic background in welding techniques and concepts, there are a few issues that TIG welders run into that can strike any welder, novices and experts alike.
Here are some of the common problems you run into during TIG welding with an inverter welder:
- TIG welding aluminum with a DC current: DC is not ideal for welding aluminum, and instead, an AC current should be used. TIG welding aluminum with a DC current leads to contamination.
When TIG welding aluminum, make sure that all oxide compounds are burned away, and the weld spot is perfectly shiny before introducing filler wire to prevent contamination. TIG welding in AC can remove these oxides but be aware that it also dulls the tungsten and can increase etching.
- Lack of fusion in the weld root: If your weld is suffering a lack of fusion or lack of structural integrity at the root of a T-joint or fillet weld, this can be caused by a couple of different operator errors including feeding the filler into the weld improperly, or holding the arc too far from the surface of the metal.
To prevent this problem while TIG welding, avoid trying to weld too quickly or feed filler into the weld too quickly. You should also decrease the length of your arc.
- Craters: Some TIG welders have a crater control function embedded in them to avoid this unsightly welding error, which is caused by reducing the power of the weld too quickly.
To avoid this problem during a TIG weld, you should continue to feed filler into the welder as you slowly reduce the incoming current to prevent cooling the weld too fast.
- Grainy weld: A grainy weld appearance is usually indicative of defects in the filler wire or rod material, rather than the quality of the welding job itself. Before beginning a TIG weld, be sure to verify your filler metal type and clean the filler thoroughly to remove any possible contaminants such as moisture, oil, or grease.
In TIG Welding on an Inverter Welder, the Name of the Game is Arc Control
When TIG welding on an inverter welder, one of the most important skills you can learn to become a better TIG welder is arc control–this means from the moment you tap or scratch out the arc to the moment you kill the switch.
Along with learning proper gas shielding, it’s crucial to a successful, strong, and aesthetically pleasing TIG weld.
To control your arc properly in a TIG weld, you need to keep the arc as short as possible. While it might feel more natural to lengthen the arc as it allows you to see the contact and weld puddle better, it is better to move your head or reposition your body rather than the torch.
Any adjustment of the arc length mid-weld is going to decrease the consistent look of your weld bead and can also cause structural problems in more severe cases. When first learning to TIG weld, it can be helpful to practice many welds in different positions on scrap metal before attempting any serious welding project.
TIG Welding is for Every Welder
Anyone familiar with MIG welding can jump on the TIG welding train, and there’s no need to get an industrial-grade TIG welding power source to do it. Anyone with an inverter welder, a TIG torch, an argon tank, and a regulator can do it.
With an inverter welder and the right tools, it is easy to perform high quality, strong, precise TIG welds on thin and exotic metals from the comfort of your workshop.