What is the main difference between MIG and TIG welding? We look at the features and benefits of the different types of welding processes. Find out if MIG or TIG welding is right for you.
Is MIG Or TIG Welding Better?
Naturally, it depends on what you mean by "better". Depending on your goals, different welding projects will benefit from either MIG or TIG welding.
Since their introduction in the aerospace industry during the 1940s, both of these common welding methods have made themselves indispensable to professional and amateur welders around the world. However, if there's one thing to say in favour of one compared to the other, MIG welding is widely considered to be the easier form to pick up for learners.
The MIG process is considered easier because it provides a continuous wire feed and is typically a faster welding process compared to TIG welding.
You also don't need to heat the entire piece you're working on in order to form the weld when MIG welding. This not only makes MIG welding much easier but also makes it the ideal welding technique if you are working with thick materials or heavy structural metals.
Main MIG and TIG Welding Differences
Before the differences, some similarities between TIG and MIG welding are worth noting. Besides the similar sounding names, both of these welding techniques use an arc with a shielding gas as their essential welding methods. But it's the key differences that are important to remember when deciding which method to use when you are welding.
The main thing that distinguishes these techniques is the different electrodes used to create the welding arcs. MIG welding uses a solid feed wire that is consumed as it is automatically fed into the weld.
Conversely, TIG welding uses an electrode that isn't consumed alongside a hand-held filler rod that creates the welded joint. We'll take a closer look at the two processes to better understand the differences and which will be best depending on your particular project.
TIG Welding Process
Another similarity between MIG welding and TIG welding is that the second also has a couple of names. We've already used TIG welding, which stands for "Tungsten Inert Gas", while the second is GTAW, or "Gas Tungsten Arc Welding". However, this is where the differences between this arc welding process and MIG welding come in.
TIG welding uses a non-consumable electrode made of tungsten, meaning a different consumable filler material must also be used when creating a joint. You need to manually feed a rod of your filler material into the puddle in the weld area as your welding torch creates an arc with the tungsten electrode.
Similarly to the MIG wire electrode, the type and size of your TIG filler rod will differ depending on the type of weld you want to create and the metal you're welding.
The shielding gas is also different for TIG welding. While MIG welding uses a mix of argon and CO2, it is just argon for TIG welding. This is because CO2 creates tungsten oxide, which will quickly wear down your electrode.
It can also lead to tungsten oxide contaminants making their way into your weld. While MIG welding is relatively easier, TIG welding gives you greater control.
This is thanks to a foot pedal, which you use to alter the amperage of the welding torch. Doing this allows you to control the heat generated by the torch as you introduce it to the metal you are welding.
MIG Welding Process
There are, in fact, two names for this process. The one you'll be familiar with, and the one we've been using so far, is MIG, which stands for "Metal Inert Gas". The other is GMAW, which stands for "Gas Metal Arc Welding".
In either case, the welding process is the same, with an automatic or semi-automatic arc being used to create the weld. You also have a consumable wire electrode and shielding gas being fed into the welding torch, or welding gun, through a lead.
Depending on the type of metal you are welding, how thick it is and the type of joint you are creating, you will need to use different diameters and types of the electrode wire.
This is because the wire also serves as the weld filler metal. There are also different sizes of electrode wire spool, meaning you have to adjust your MIG welder's wire feed speed (WFS) to ensure the continuously fed weld metal arrives correctly at the joint.
Alongside choosing the right electrode wire and settings, you'll also need to choose the right shielding gas.
MIG shielding gas is typically a blend of argon and carbon dioxide at a ratio of 3:1, but again, depending on the metal you are welding and other factors, you may need to alter your shielding gas.
Difference between MIG and TIG Welds
Now that we've gone through how the MIG and TIG processes differ, it's time to discuss the differences in the two different welds they create.
This is ultimately the most important consideration when choosing between the two methods. There are also some big differences in these welds, so it is best to understand them thoroughly so you can make an informed decision.
Weld Strength
TIG welds are usually considered to be the strongest of the two. Thanks to the narrow arc TIG torches produce, this means you can penetrate deeper into the metal.
This means things like tack welds are much stronger when done with TIG welding equipment.
TIG beads are also much cleaner than MIG ones, with fewer defects or holes. These imperfections will weaken a weld, so the fewer, the better, and the stronger the weld will be. These factors that make TIG stronger sometimes mean it is the better method when working with thicker materials.
While this is the common attitude amongst many welders to the different weld strengths, it's not impossible to create a perfectly good weld with a MIG torch. Both welding methods can create welds that will last for years. There are even ways to create penetrative arcs with a MIG welder to match those of the TIG.
One way to do this is to cut a V-shaped groove into your joint before welding. It's also about the operation. A smooth travel speed with the right torch position will produce good weld strength with either technique.
Weld Speed
When it comes to speed, MIG welders are the clear winner.
TIG welders cannot move the weld puddle or supply as much of the filler material nearly as fast as a MIG welder, despite being able to create clean, smooth welds.
TIG welders also tend to overheat during lengthy welding sessions, meaning you may have to opt for a more expensive water-cooled torch.
On the other hand, MIG welders, with their constant supply of electrode material being automatically fed into the weld, combined with the round and broad arc, means heat can be dissipated more evenly.
This allows you to move the weld puddle much faster with air-cooled torches that are cheaper and easier to use. Therefore, if you're going to be doing a lot of welding, a good quality MIG welder is possibly the better choice.
Welding Gas
Shielding gasses help keep impurities in the air away from your weld puddle to avoid contamination, which could weaken your joint. But, again, the gasses used in MIG and TIG welding differ.
The non-consumable tungsten electrode used in TIG welding is very reactive when combined with CO2 or oxygen, so non-reactive argon is the essential shielding gas you need. Of course, depending on the welding job you are working on, you can blend it with hydrogen, nitrogen or helium for different effects.
In contrast, MIG welders can use argon and CO2 in a 75%/25% mix. This is because the small amount of carbon dioxide in the mix allows for better penetration and increases the stability of the MIG arc.
Again, you can alter the shielding gas when MIG welding. For example, if you are welding aluminium, it's possible to use 100% argon gas. Using 100% CO2 is possible and is much cheaper, but it does come with some disadvantages.
The flow rate is one of the most important things to remember about shielding gas. This must be properly set to achieve the best welds. For MIG welding, the proper rate is 35-50 cubic feet per hour. Conversely, TIG welding requires a gas flow rate of 15-25 cubic feet per hour.
Weld Aesthetics
When it comes to weld aesthetics, the TIG welder takes the top spot.
TIG welded joints can be incredibly clean and professional. There is rarely any spattering in the weld puddle, and joints only require minimal polishing or pickling to remove discolouration.
The smartly "stacked dimes" produced by a TIG welder are often considered the benchmark for aesthetically pleasing welds. This is especially important if the piece you're working on isn't going to be painted or coated, like when working with aluminium or stainless steel. In these cases, having a good-looking weld is more important than ever.
But all this isn't to say that you can't have a good-looking MIG weld. In the hands of experienced welders, a MIG torch can lay down some very pretty beads.
Of course, most welding projects don't require that much in the way of aesthetics so that you can create passable, strong welds with a MIG electric arc.
Again, if you're going to paint or coat the material once it's been welded, there's no need to shoot for perfection, and a MIG welder will get the job done.
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