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What is a MIG Welder? Everything You Should Know

Last updated on June 21st, 2023

Metal Inert Gas (MIG) welding also known as Gas Metal Arc Welding (GMAW) is one of the most popular and versatile welding methods.

It has revolutionized the welding industry with its ease of use, high efficiency, and ability to weld a wide range of materials.

MIG welding offers several advantages to other welding methods but like all methods, it also comes with its own drawbacks.

In this comprehensive guide, I will be sharing some of the most important aspects of MIG welding. If you are new to the world of welding and don’t know much about this method, then you have come to just the right place.

So, without any further ado, let’s dive into the amazing details of this welding process.



MIG Welding—Gas Metal Arc Welding

MIG welding uses a consumable wire electrode and shielding gas to create a joint. The wire electrode is continuously fed through a welding gun while the inert gas is used to shield the welding area and protect it from contamination.

The arc is formed between the wire electrode and the workpiece which generates the heat and melts both the wire and base metal to create the welding pool. The molten metal then solidifies and creates a strong and durable bond.

MIG welding always uses the Direct Current Electrode Positive (DCEP) polarity, which means the ground clamp is always attached to the negative terminal of the welding machine.

Hence, when you pull the trigger on the MIG torch or welding gun, an arc will be generated which will feed the wire into the joint.

The arc is generated when the wire touches the base metal, which shorts the electric circuit, and the process is known as short-circuiting.

Upon first contact, the tip of the wire and a small part of the base metal will be melted, but as you continuously press the welding wire into the base metal, it will generate the arc continuously and hence creating the weld pool and forming the joint.

If you are familiar with TIG welding, then you might notice the major difference between the two. In the former method, the filler metal was fed externally, while in this case, the wire acts both as an electrode and the filler material.

Related:Who Invented the MIG Welder? A Journey Through History

Types oWho Invented the MIG Welder? A Journey Through History by Sheila Jamesf MIG Welding

There are four major metal transfer methods that can classify as types of MIG welding. The manner or method through which you transfer the filler material from the electrode to the weld pool determines this process.

1. Short-Circuiting or Dip Method

I have already explained this method above while explaining MIG welding. It is the most common method used for this process.

Short-Circuiting is used for low-current operations where the wire is dipped into the weld pool to create the arc which melts both the wire and the base metal.

Whenever you touch the wire with the base metal, it will create a short circuit. Hence, you will have control of the weld. This method is mostly used for thinner materials.

2. Spray or Droplet Method

This method is ideal for thicker materials and requires the use of high welding current. In this method, you will spray the molten droplets into the metal to create the weld.

It requires a much higher voltage, and the wire does not need to make contact with the weld pool.

The tip of the filler wire is already in a molten state from the voltage and will transfer to the weld pool in the form of a spray or small droplets.

If the voltage is low, it would prevent the formation of large droplets at the top of the wire which would transfer erratically and ruin the weld joint.

3. Pulsed-Spray

To deal with the shortcomings of the above two methods, the pulsed-spray method was developed. It comes with the benefits of both short-circuit transfer and spray transfer.

In this method, the pulsing current is used to transfer the molten metal. The heat input will be reduced but you will have more control of the welding process.

This method was developed to stabilize the open arc at low current levels. This method has little to no spatter, high resistance, and a lack of fusion defects.

In short, it has more advantages than other methods and comes with 98% electrode efficiency.

4. Globular

It is one of the less-used methods that is used for welding thicker materials. This method involves slower wire feed that uses larger droplets of molten metals to transfer across the arc.

This method is mainly used when the current density is relatively lower. The arc length is kept longer to ensure that the large droplet of molten wire detaches itself before it contacts the molten metal.

The inert gas will not only protect the weld pool but also ensure that there is less spatter. On the downside, it can only be used in flat or horizontal positions.

MIG Welding Equipment

The following equipment is used in the setup of a MIG Welding machine:

1. The Welding Machine

A MIG welder is used to supply a constant voltage or current. The welder comes with an integrated wire feeder.

However, if your welding machine does not come with a wire feeder, then you can get a dedicated machine for the task.

2. MIG Torch or Gun

The choice of MIG torch will depend on the duty cycle required which in turn depends on the thickness of the metal you will be welding.

Usually, the welding torch will come with the welding machine, but you might need to get an upgraded one depending on your use.

3. Shielding Gas Tank and Regulator

You will need to get a shielding gas tank and regulator depending on the specific application. The size and type of gas will also depend on the type of metal you are going to weld.

4. Welding Wire

There are various types of welding wires depending on the specific type of material you will be welding with a MIG welder. You will need a solid MIG wire, which will also act as filler material.

5. Safety or Protective Gear

Safety should be your top priority engaging with a welding machine. You must purchase proper safety equipment to protect your skin from the risks of welding.

The safety gear will include a welding helmet, gloves, boots, and fire-resistant apparel. Never compromise on your safety under any circumstances.

Related: What Should Be the Gas Pressure for MIG Welding?

Importance of Shielding Gas in MIG Welding

Shielding gas is mainly responsible for protecting the weld pool from any sort of contamination.

However, it also performs a number of other important functions, such as the formation of arc plasma, stabilization of arc roots on the metal surface, and ensuring a smooth transfer of molten droplets to the weld pool.

Two types of shielding gasses are used in MIG welding: Inert Gasses like Argon and Helium, or a mixture of inert gasses with active gasses.

Technically, the use of active gas makes the process of Metal Active Gas welding, or MAG short, but the term MIG is used for both processes because of a lack of apparent difference.

The mixture of active gasses is used to influence the weld pool and create the desired effect in welded material.

Inert gasses do not interact with welded metal but modifying it can get professional welders specific results which they require in complex projects.

For non-ferrous materials like Aluminum, Copper, or Nickel alloys, inert gasses are used while for Steel and its alloys, CO2 or a mixture of inert and active gasses are used in MIG welding.

Related: Which is the Best Gas For MIG Welding? Explained With Images

Advantages of MIG Welding

MIG welding has tons of advantages and that is why it is one of the most popular welding methods worldwide. Here’s a quick look at some of the benefits of MIG welding.

  • It is used in welding a wide range of materials.
  • Compatible with materials of varying thicknesses.
  • Both the machine and equipment are readily available at very affordable prices.
  • The electrode efficiency of this method is much higher compared to other types of welding.
  • High welding speed and productivity
  • The excellent metal deposition rate
  • Easily adaptable for automation and robotic applications.
  • Can be used in any position or angle.
  • Multiple metal transfer modes
  • The resulting welding bead has an excellent appearance.
  • The hydrogen deposit is much lower.
  • Requires lower heat input than other types of welding.
  • The minimum spatter of the welding process makes cleaning a lot easier.
  • Less amount of welding fumes is produced during the process.
  • A cost-effective welding process.
  • Comparatively easy to learn as compared to TIG welding.
  • Less downtime during operation since the welding wire is itself the filler wire.
  • Excellent for tack and spot welds.

Drawbacks of MIG Welding

Like any other welding method, MIG welding also comes with some limitations or drawbacks. Here’s a look at some of the limitations a welder has to face when using this method:

  • Produces more spatter and fumes than the TIG welding process.
  • Only suitable for indoor welding applications. Outdoor welding in windy situations may blow the shielding gas away. So, it is not used outdoors.
  • The resulting weld is not as clean as compared to TIG welds.
  • Requires continuous replacement of welding wire because it is constantly consumed.
  • Limited arc control functions.
  • Often challenging to use in hard-to-access corners.
  • Gas is always required in MIG welding.
  • You cannot MIG weld without filler material.
  • Troubleshooting problems may present some difficulties.

Applications of MIG Welding

MIG welding is used in a wide range of industries. It is one of the most common welding processes.

In the automotive industry, welders use it in creating welds in all sorts of vehicles including light to heavy and small to large vehicles. MIG welding is capable of creating good-quality welds.

In addition to this, the process is also used in the piping industry because of its high productivity and flexibility. It is easier to automate and is often used in that aspect to increase productivity in industries.

Adding to this, this welding method is also used in the railway industry to weld railway tracks. Since the tracks are very thick, this process is much more efficient than other types of welding.

Moreover, it is also used in sheet metal welding. Manufacturing plants and the construction industry also have a wide range of applications in MIG welding.

Last but not least, MIG welding is also used widely in general repairs as compared to TIG welding because of its economic and cost-effective nature.

Related: How to MIG Weld Stainless Steel? Tips for Best Results

Frequently Asked Questions

What is a MIG welder used for?

Metal Inert Gas welding is a popular welding process that is used for joining metal pieces together. The process uses a consumable wire electrode and is a contact welding method where the wire is touched to the base metal to create the arc.

What is the difference between TIG and MIG welding?

TIG welding uses a non-consumable tungsten electrode while MIG welding uses a consumable wire electrode. In the former, the filler metal is fed externally, whereas, in the latter, the wire electrode itself acts as the filler metal.

What is MIG welding in simple terms?

In simple terms, it is a cost-effective and efficient welding process where a consumable wire electrode is melted and used as filler material to weld metal pieces together while shielding gas protects the weld from contamination.

Does MIG welding require gas?

Yes, you cannot MIG weld without using gas. A shielding gas is required to protect the weld pool from atmospheric contamination. Not using gas will ruin the weld. This is one of the reasons the method cannot be used outdoors.

Is MIG welding AC or DC?

DC is more commonly used in MIG welding because it provides higher stability and better control over the welding process. However, AC polarity is also used in the welding process, but its use is very limited.

Which gas is used for MIG welding?

Most commonly, a mixture of argon and carbon dioxide is used in the welding process because it provides the best arc stability and coverage for a wide range of materials. However, the gas used may vary depending on the specific application.

Wrapping It Up!

To sum it all up, MIG welding is a popular and versatile welding process. It is more cost-effective than TIG welding and more efficient than Stick welding.

Like all other welding methods, MIG welding also comes with its own pros and cons. However, it can be established that it has more benefits than other welding methods.

I hope the above guide was helpful in providing you with a detailed insight into What MIG welding is and also into its basics.

If you have any questions, you can drop them in the comments section below and I will get back to you as soon as I can. Happy Welding!

Sheila James

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