How MIG Welders and the Welding Process Works


MIG welding is an incredibly popular and lucrative hobby or job.

Whether you are looking to do MIG welding as a hobby or professionally, however, you need to know how the process works. That being said, it isn’t just as simple as turning on a nozzle and firing away. There is a lot of intricacy to preparing a MIG welder, accessories, your welding environment, and yourself before welding a piece of metal. You have to be insightful and understand the art and science of a well-handled MIG welder and materials, and for that you need to know the basics of welding preparation and methodology.

With that in mind, let’s take a closer look at how MIG welders work and what you need to get the most out of it.

1. Safety Precautions

Before we start getting into the different welding steps themselves, you should first make sure that you are ready to weld, which means getting the right welding gear and taking the proper safety precautions.

Every welder needs to wear a welding helmet with a darkened visor while welding. The welding flame with which you’ll be working can burn incredibly brightly and as hot as the surface of the sun.

Among the other safety precautions you’ll need to take include:

  • Leather boots or shoes
  • Loose clothing that you don’t mind getting dirty, which also covers your whole arms and legs
  • A flame-resistant jacket
  • Leather gloves
  • Safety glasses

2. A Look at the Equipment

Next, you’ll want to have a look at your welding equipment. This is where we start getting into how it all works, even if we aren’t quite ready to set to work just yet.

Some things you’ll want to check ahead of time (and we’ll see why as we go through the process) include:

  • The cables, which must be free of frayed wires, crimping, or any other form of damage
  • The polarity, with MIG welding typically using DC electrode positive (aka reverse) polarity
  • The tension, which should not be too little or too much, lest it cause wiring problems
  • The consumables, which should not be dirty or damaged at the start of the welding process, lest they splatter or shatter under the heat
  • The gas flow, which is essential for shielding purposes

3. MIG Versus TIG Welding

Now we’re finally ready to get welding, right? Well, not quite. First we need to determine what type of welding we’re going to do. While there are many types of welding out there, two of the most common – and, thus, the ones covered here – are MIG and TIG welding.

MIG welding involves making use of electricity from a continuous electrode. The electricity passes through the heating gun in such a way as to heat the metals, causing them to melt together, thus welding them. A MIG welder needs to constantly pull the trigger on their welding gun. Doing so feeds the consumable electrode, which is responsible for working on the metal pieces.

Doing this creates an arc between the gun and the metal being welded. Eventually, that metal reaches its melting point and can be molded into the shape you wish. However, you will want to make use of filter materials to make sure that things don’t melt over.

TIG welding, on the other hand, makes use of tungsten and inert gas along with a nonconsumable electrode. This is used to heat the base metal. Tungsten has a very high melting point, so you don’t have to worry about the electrode itself melting. Just press it in place and fire away.

On the one hand, this gets rid of the need for filler materials as mentioned with MIG welding. The electrode’s arc is all that is necessary to meld the different metals together. That being said, you can still add external filler rods to create welding beads, which can potentially make the actual mechanics of the welding process operate more smoothly.

4. The Welding Process Begins

Now it’s finally time to start the welding process in earnest. Our knowledge of MIG and TIG welding can help us discern what’s going on with the actual welding process itself, as described below.

The name of the game in welding is heating something up so much that it is able to melt metals with ease. In some cases, this means creating plasma, which is a super-heated state of matter formed when gas is heated so much that it starts to take on new properties. Plasma is excellent for cutting and is used for many of the most essential welding jobs.

What is MIG Welding? >> Check out the video below

On the other hand, many more common welding tasks make use of arc and torch welding, which utilize principles and materials similar to those mentioned above with MIG and TIG welding.

In arc welding, an electrical arc – such as is generated by the electrodes mentioned above – are used to melt the filler material. This is done to create welding joints.

Related reading: What is a Multi-Process Welder, and When do You Use It?

To do this, you need grounding wire. You will need to attach this wire to the welding material or whatever other metal surface you plan on welding. In addition to the ground wire you have the electrode lead, which should be placed against the metal that you are trying to weld.

Once you have that welding material in position, you’ll want to pull the lead away from the material. This generates an arc, which creates the sparks which are so customary to the welding profession. The electric arc is then prepped and ready to melt the pieces and filler material. That filler material is often necessary to help join pieces together, unless you are using a TIG welding process that is able to eschew filler materials altogether.

You will want to operate these welders with a great deal of caution. It takes a keen eye and steady hands to be able to operate a welder of this kind, especially when feeding the filler. The metal filler rod will melt, and you’ll need to keep feeding new filler into the process. What’s more, you’ll need to do all of this without any sudden movements that might disrupt the arc or the flow of the metal. Doing so can cause scorching, beading, warping, and other signs of a poor weld.

While the process above, known as arc welding, is among the most common forms, it is also worth touching on torch welding here. This usually makes use of an oxyacetylene torch to melt the filler and prime material along with the welding rod. Once again, you will have to control both the torch as well as the rod at once, making hand-eye coordination and the ability to multitask that much more important.

This method makes use of burning acetylene gas and oxygen rather than electricity. On the one hand, this is a lot less common today, and many modern welding setups make use of electricity instead. On the other hand, this type of welding allows you to weld if you do not have access to electricity, it can be highly portable, and is still used in some repair work today.

5. Holding Things Together

Of course, all of this begs the question – just what are you welding, anyway, and how? You already know that you can weld a wide variety of metals, from aluminum to stainless and mild steel, but that still doesn’t explain how these pieces are actually welded together.

Unless you’re just melting things into one another or creating some hodge-podge creation, chances are good that you are welding different joints together to create something made from their constituent parts. In that case, you need to know how welding joints hold together.

There are several common types of welding joints, including:

  • Butt Joint: Connecting the ends of two parts at a 180 degree angle.
  • T Joint: Connecting the ends of two parts at a 180 degree angle, over which you place another part which connects at a 90 degree angle between the two, forming a “T” shape.
  • Corner Joint: A connection where the edges of two corners touch but not the butt ends, leaving room for something else to be welded into place there.
  • Edge Joint: A connection between two parts at a slight angle (30 degrees or less.)
  • Cruciform Joint: A joint that fits one of two parts at right angles on top of or in between one another in such a way as to create a “Plus Sign” or “Crucifix” shape.
  • Lap Joint: A connection between overlapping parts at various angles.

This is where all that talk of filler material becomes so important. You obviously don’t want to warp the edges of the prime material you are welding. As such, using filler material can help ensure that you weld different prime materials together in various joint configurations without the risk of warping them.

6. The Pros and Cons

One of the most important things to consider when it comes to the welding process is which one is right for you, which is to say which one is right for the job at hand. Different welding tasks require different approaches. MIG, TIG, and torch welding all have pros and cons that need to be considered carefully to get the most out of your welding experience.

Some of the pros of torch welding include:

  • It is lightweight and portable, making it a good option for welders on the go
  • It is able to cut through thick materials
  • It does not take a lot of skill to operate this type of welder compared to MIG and TIG welding

Some of the cons of torch welding are:

  • This type of process is less common nowadays, so you may find fewer articles and support
  • The gas, once it has been combined, only cuts iron-based steels
  • If you aren’t careful (ie, use a correct cutting tip) the process can warp thinner metals
  • The process and heating tip use a huge amount of oxygen-acetylene

Among the pros for MIG welding are:

  • The ability to join together a wide range of different metals
  • The ability to work with metals in a wide range of thicknesses
  • Good beading on your weld
  • Reduced splatter compared to torch welding
  • A popular form with lots of support
  • Easier to learn compared to other methods of welding

Some cons to consider with MIG welding are:

  • While it can handle many thicknesses, MIG welding is primarily meant for medium-thick metals
  • Because it uses inert gas and external shielding gasses, it is less portable than other methods
  • Still splatters more than TIG welding

Some pros for TIG welding include:

  • Less splatter than torch or MIG welding, making it more detail-friendly
  • Can be used for a wide range of industrial and hobbyist applications
  • The electrodes being non-consumable means they might last longer

Some cons for TIG welding are:

  • More complex than other methods of welding
  • More time-consuming than other methods of welding
  • The inert gas required can be expensive

Related reading: Do Welders Make Good Money? | Highest Paying Welding Jobs

7. The Gas

Last, but not least, it is important to note that with MIG and TIG welding especially, you’ll need shielding gas. These, too, will vary depending on the type of welding you’ll be doing. This gas is essential for making sure that you do not scorch the metal while helping to control the process.

By using shielding gasses, you can weld faster, cleaner, and won’t have to replace your electrodes quite as often.

Among the most commonly used types of shielding gasses are oxygen, helium, argon, and CO2.

In Conclusion

So, where does all of that leave us? Hopefully with a better understanding of not just how different welders operate, but of how the overall welding works from start to finish.

Part of what makes welding such a fabulous field is the interconnectedness of its parts. From the electrodes and consumables to the arc itself to the shielding gas and everything in between, it all fits together like the notes of a symphony.

When you know what you’re doing, MIG welding makes you feel like a true metal maestro.

David Harper

David is the Co-Founder and Senior Editor at David's an experienced fitter and tuner/welder who's passionate about helping others develop in life through new skills and opportunities.

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