What is GMAW (MIG Welding) and How Does it Work?

Updated: 22 Nov 2023


Gas metal arc welding (GMAW) is the process of welding that joins two pieces of metal together. It uses the electrical supply, shielding gas, and electrode filler for jointing the metal pieces.

It’s also known as wire welding, which acts as an electrode and filler material due to the consumable wire. It’s completely different from the tungsten arc welding (GTAW). The TIG welding joints the metal surface directly using a tungsten electrode for heating and joints.

GMAW generates the heat to melt the wire and metal, which allows the theme to make it together and create a durable, long-lasting weld.

This article will explore everything about the MIG welding process, its advantages and disadvantages, how it works, and other career opportunities to save your life.

What Is Gas Metal Arc Welding?

MIG welding is the fundamental process of metal joining that uses a constant voltage direct current power supply to create an electric arc that fuses metal with a filler wire feed through a welding torch.

A special wire is passed through the welding tools, making the two metal pieces stick together. When a special gas is blown over the melted metals, everything will be cleaned. It doesn’t work with the metal and filler materials.

MIG welding is specially used for heavy projects such as home improvements, fabrication work, etc. It’s faster than the TIG welding. It does the jobs more quickly with less cost.

Gas Metal Arc Welding (GMAW)
MIG Welding Diagram
Source: https://weldguru.com/mig-welding/

How Does MIG Welding Work?

MIG welding is very straightforward, so anyone can easily understand it. If you want to know how MIG welding works, learning its flow is too easy.

The welders always do the MIG welding on the direct current, which means that it is unidirectional and its flow of charge is in one direction.

If we talk about the battery, it requires a complete electrical circuit to work. Let’s discuss how you can utilize it for the welding process.

When a wire spool is loaded onto the machine, the wire is fed through the driver rollers, contact tip, torch liner, and nozzle.

There will be a torch trigger or button that will feed the wire continuously when it’s pressed. Pressing the torch trigger will start the gas according to the needs fed through the nozzle.

The wire comes in contact with the two parts: heat source and filler materials. The wire will pass through the copper, which the welding current will electrically charge.

You can transfer the filler metal from the wire using different ways, but it’s recommended to do it using short circuit mode.

MIG Welding Settings (Voltage & Wire Feed Speed)

The MIG welding has two settings options, which you need to do for a perfect weld.

Voltage Control:

The voltage control is essential for welding. It especially determines how much heat is in the weld. It will entirely control the heat in the weld.

Depending on your requirements, you can adjust the voltage control to lower and higher settings. Keeping the voltage settings higher will produce more heat, and lower settings will produce less heat.

Some people keep the voltage settings too low so the wire won’t burn, which doesn’t create a proper weld. You need enough heat if you want to melt the wire and look for a perfect weld.

Wire Feed Speed Adjustment

It controls the rate at what rate wire is added to the weld. It may be in inches or millimeters per minute. What more will you do? It will cool the weld, and less wire will create a hotter weld.

Most welding machines come with complete instructions and guides if you still need clarification about the settings and adjustments. They will provide the recommended settings for the different types of metal.


Getting the correct polarity is essential because a poor polarity will impact the weld quality. Setting the wrong polarity during welding may leave an excessive spatter and uncontrollable arc that damages the weld.

The MIG welding will run on the positive polarity where the current is positively charged and runs from negative to positive. It’s called the direct current electrode positive (DCEP).

You must plug the polarity cable into the positive (+) and the earth clamp into the negative (-) mount to do its setup.

If your welding machine doesn’t have a Euro connection, you can plug it directly into the dense connector. Otherwise, the polarity cable will act as a torch if your machine comes with a Euro quick-connect plug.

Selecting the Right Filler Wire

While selecting the electrode wire, there are two factors you need to consider. Make sure that the base and filler metals match. Besides this, the correct wire size is essential during selection. 

Metal Matching:

  • The filler metal must match the base of the metal. Are you using mild steel? It would be better if you use the mild steel filler wire.
  • Some people need clarification about the grade, but according to experts, they have experience that matches the metals and ignore what type of grade your metal is.

Consider Wire Thickness

  • Another important crucial point is to consider the thickness of the filler wire. The thin enough wire will melt quickly, but make sure it’s thick enough to make a strong joint together.
  • If you need clarification about how much it’s thicker and thinner, according to most welding experts, the common wire size is 0.8mm, suitable for different types of welding.
  • If you’re doing a project on thinner material, you can go for 0.6mm wire; otherwise, try 0.9mm wire for a strong joint for thicker things.
  • If you want a successful GMAW welding process, consider the metal match and the right size wire factors.

Understanding Shielding Gas in Welding

It plays an essential role in welding to protect the weld externally. It depends on the welding and what type of metal you want to weld so that it will affect the welding process differently.

Metal-Dependent Gas Selection

It depends on the type of metals that you are welding. It requires specific gas selections for a perfect welding result. If you are doing a welding project for stainless steel, then 75% argon and 25% CO2 is the better option.

It will enhance the penetrations and combine the two pieces with the stabilized welding arc that will be durable and long-lasting. 

Do you want to weld aluminium? According to experts, pure argon gas is the perfect option for effective shielding.

Variety of Shielding Gasses

There are different varieties of shielding gasses available worldwide. Each is used in specific welding projects, depending on the requirements. 

If you want to ensure the durability of welding, then it’s essential to select the suitable shielding gas for your welding project.

What Are The GMAW Equipment

The MIG welding joints parts of the metal by using wire electrodes and shielding gas. There are several pieces of equipment necessary during the welding project. Some of the main components of GMAW welding are given below.

  1. Power Source: A welding machine provides the voltage and current to start welding. The voltage and current may be constant or vary depending on the welded materials.
  2. Welding Gun: Sometimes, it’s also called the welding torch. The handling device holds the electrode wire and delivers it to the workpiece area.
  3. Consumable Electrode Wire: It uses the consumable wire electrode, usually made from the same materials as the workpiece. The welding gun feeds this electrode wire, creating a durable welding of two pieces.
  4. Shielding Gas: There are several types of shielding gas. Some common gasses are carbon dioxide (CO2), argon, and a mixture of other gasses. The selection of the shielding gas depends on the specific project. It’s the best option to help you protect the weld pool.
  5. Wire Feeder: The feeder feeds the consumable electrode wire from the spool to the welding gun. It will give the supply to the wire during the welding process.

Additional GMAW Equipment

MIG Wedling (GMAW) settings and system
MIG Welding Process
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1. Regulator and Gas Cylinder

The regulator is used to adjust the flow rate of the welding. During the welding, it’s important to maintain the proper flow gas rate for a durable weld. The gas cylinders have shielding gas that can be utilized depending on the requirements.

2. Ground Clamp

Do you want to create an electrical circuit? Ground clamp is the best option for it. It is attached to the workpiece to help the welding machine create an electrical circuit required for the welding.

3. Welding Table or Workpiece

It is essential to have a proper welding table to position the two pieces you want to weld together securely. The welding table will help you better weld in the desired position.

4. Safety Equipment

This is the most important thing you should consider while welding. During welding, you should consider all the safety gear to protect yourself from injury. According to welding experts, you should wear a welding helmet, safety glasses, gloves, and protective clothing.

Advantages of MIG Welding

Several advantages of gas metal arc welding (GMAW) are given below.

  1. Ease of Use: Mig welding is easy to use, so a beginner and expert, everyone can benefit from it. You can easily set up all its equipment and start the welding project as a beginner.
  2. Minimal Cleanup: Welding the two pieces together produces minimal spatter that can be cleaned easily. Its easy cleaning process reduces its effective cleaning cost.
  3. High Deposition Rates: The high deposition rates mean it joins metal pieces quickly and efficiently. 
  4. Versatility: You can weld several materials using mig welding, such as stainless steel, metal, carbon, and different alloys. MIG welding is better for both if you want to weld thin or thicker materials.
  5. All-Position Welding: You can do the MIG welding at every position in the different welding projects. You can weld the materials flat, horizontally, vertically, and in other positions according to your wish.
  6. Continuous Welding: I love this point because you can consistently do the welding without interruption or stop due to the continuous electrode wire. Some welding types don’t allow you to weld things continuously.    
  7. High Weld Quality: When you weld the two metals correctly, it will be a very high-quality weld that doesn’t separate easily. You will be in love with the MIG welding durability.
Disadvantages of MIG Welding

With advantages, MIG welding has many disadvantages you should consider before welding.

  1. Limited Penetration: If you have a project requiring deep weld penetration, MIG welding is not recommended for this type of welding. 
  2. Material Sensitivity: The MIG welding is unsuitable for dirty or rusted surfaces. 
  3. Gas and Wind Sensitivity: As discussed above, MIG welding uses shielding gas, which winds may cause. Sometimes, it affects the weld quality. It’s a challenging task if you want to do welding outside.
  4. Limited Portability: MIG welding is less portable than other welding processes because it needs a cylinder and power source.
  5. The Cost: For the first time you want to do a MIG welding setup, it’s very costly. People may not purchase all its setup on an average budget, but one of my friends purchased its equipment nowadays, making enough money from welding projects.
  6. Limited on Thin Materials: MIG welding is not the best option for the less than 1mm thin materials. It may lead to a burn or other excessive distortion.

What Type of Power Source Is Used For GMAW

GMAW uses a constant power voltage source. Some people are confused about wire feeders or CV welding machines, but don’t be confused because a constant voltage power source also refers to these two.

Constant Voltage Power Source

A constant voltage power source is used in the MIG welding process. They are used because they maintain the consistency of voltage during the welding. Depending on the welding project, you can adjust the voltage setting according to your choice. 

Wire Feed System

A separate wire feeder system is used to supply the electrode wire continuously. This wire feeder is connected to a constant voltage source and controls the speed of the wire entering the welding arc.

Voltage and Wire Feed Speed

The welders can easily adjust the voltage and wire feed speed to control the heat output. If you are using a higher voltage setting, then it will produce hotter arcs. The wire feed speed will determine the amount of wire added to the weld pool.

What Are The 4 Processes of MIG Welding

There are four different processes of MIG welding, which are given below.

1. Short-Circuit Transfer (Short-Circuiting MIG)

Short Circuit Transfer Mode example
Short Circuit Transfer Mode
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It is the easiest use of the MIG welding process using the low voltage. The short circuit transfer method uses the consumable electrode wire that touches the shorts and base materials.

The electrode wire makes contact with the workpiece, creating a short circuit. During the welding, when a short circuit occurs, the wire melts and forms a tiny droplet; later, they are transferred to the weld pool.

If you are welding materials, then a short circuit is the best option that produces low heat. It’s commonly used for light fabrications.

2. Spray Transfer

mode of spray transfer
Spray Transfer Mode
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If you use the spray arc transfer method, small droplets of molten metal from the consumable electrode are sprayed onto the weld joint. This is a pure CV (constant voltage) process in which a constant flux of weld metal is sent through the arc into the base metal.

If you are doing a thicker materials welding project, it’s the best option to provide high deposition rates. It produces high heat and less spatter compared to the short circuit transfer.

3. Globular Transfer

It’s similar to the short circuit transfer, where the consumable electrode wire arcs and touches the base and short material. Only there is a small difference between both. How long does the consumable electrode melt?

In this method, wire is heated longer, creating a large volume of weld metal that drips into the weld joints. This consumes a lot of heat, and there is also the risk of poor melting due to spatter distorting the molten pool.

4. Pulse MIG Welding

pulse mig welding transfer droplet example
Pulse MIG Welding
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The pulsed MIG transfer method is a modified version of the spray arc method that exploits the advantages of all transfer methods while minimizing their disadvantages. Pulsed MIG welding requires a particular power source that applies voltage multiple times per second.

It’s more versatile, allowing you to easily control the heat output and reduce distortion, which is a suitable option for different types of materials.

Frequently Ask Questions:

How Hot Does a MIG Welder Get?

Mig welding provides extremely high temperatures at the welding arc, up to 3,000 degrees. We can’t tell the exact parameters because they depend on different factors.

It depends on what type of materials you want to weld, welding parameters, and any other specific welding process.

Can I MIG weld Without Gas?

You can MIG weld without gas using Flux-Cored Arc Welding (FCAW). FCAW is a variation of MIG welding that uses a special type of flux-cored wire. This flux core acts as an electrode and a shielding agent, eliminating the shielding gas’s needs.

What type of Wire is Used for MIG Welding?

There are two different types of wires used for the MIG welding process.

  1. Solid Wire: The solid wire is made of stainless steel, mild steel, and other alloy. It does not have a flux core, so you require a separate shielding gas to protect the weld pool from atmospheric contamination.
  2. Flux-Cored Wire: The flux core wire is an electrode consisting of the flux compound inside the electrode. If the wire melts and acts as a welding arc, it forms an oxygen gas for the weld protection.
Is MIG Welding Steel AC or DC?

MIG welding using the direct current (DC) power sources. You can lower the frequency and precisely control the heating of the welding according to your own choice. If you have thinner materials, you can use low heat for welding, and for a big project, go for a higher heat welding, making the two pieces together strongly.

What is the best Angle for MIG Welding?

The best and recommended MIG welding position is between 35 and 45 degrees and pointed upwards. If you want to move in a circle while welding, it will help you distribute the heat equally to both sides of the joints.

Final Verdict:

MIG welding is the versatile welding process of joining the two metals. It is easy to use and has the ability to produce high-quality welds. If you weld something using MIG welding, you will love its durability and longevity.

MIG welding relies on different things, such as wire electrodes, shielding gas, and power sources, to join metals together.

While doing big or small projects with MIG welding, it’s essential to consider the safety precautions to reduce the risk of injury. You can easily set up all the welding equipment as a beginner and expert.

Do you want to master MIG welding? It’s important to consider parameters such as voltage, wire feed speed, and shielding gas selections. If you have good knowledge about these three things, then you are an expert in MIG welding.

Try to understand the MIG welding equipment, such as the welding gun, power source, shielding gas, and wire feeder. If you have all the knowledge, it will empower you as a welder to make an informed decision in selecting the right tools and materials for your projects.

Abu Bakar

Abu Bakar

Hello, Abu Bakar here, the Mastermind Behind Welding Villa. Test my years of experience through my well-written blogs, where I have covered the overall experience of welding materials and shown all the aspects of Welding, their types and equipment.

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