MIG Welding vs. MAG Welding: The Differences


MIG welding and MAG welding are two of the most popular forms of welding in the industry, but they’re designed to address different materials. Even though they sound similar, these two welding techniques are not interchangeable. 

MIG welding and MAG welding differ in the gases used to shield them. MIG welding uses inert gases and MAG welding uses active gas mixtures. MIG welding is used for non-ferrous metals such as aluminum while MAG welding is used for welding steel. 

It’s important to know the difference between MIG welding and MAG welding to know which type of welding is best for your project. Read on and learn more about these welding techniques and how they differ from one another. 

The Main Difference Between MIG and MAG Welding


MIG welding and MAG welding are similar in many ways, but the biggest way they differ is in their shielding gas. In welding, the shielding gas is a gas used at the welding torch to help prevent the weld from oxidizing due to the oxygen in the surrounding atmosphere. Shielding gas replaces the atmosphere around the weld to keep it pure. 

MIG welding is welding that is performed with inert gases. Inert gases are chemically neutral and are not reactive chemically with other gases or elements. These include elements such as carbon dioxide, helium, and argon. 

In contrast to MIG welding torches, MAG welding torches use an active gas mixture that contains various gas elements such as carbon dioxide, argon, and oxygen. The reason for the difference between the two is because the metals that are welded in MIG welding are more sensitive to oxidation than the metals used in MAG welding. 

What is Shielding Gas in MIG and MAG Welding? 


Shielding gas is an important part of achieving a good weld. These gases are designed to provide a protective bubble of gas against the surrounding atmosphere to keep the tungsten electrode in the welding torch from becoming corroded. (Source: Science Direct)

Shielding gas is fed into the welding assembly from a tank with a flow meter that helps to throttle the gas and keep it calibrated to a certain level. Keeping the gas shield consistent around the end of the welding assembly is what helps ensure that the weld remains uncontaminated. 

Shielding gases include the following elements: 

  • Argon
  • Helium
  • Carbon Dioxide 

Shielding gases are used to protect against three major atmospheric hazards: nitrogen, oxygen, and water. These two elements can lead to contamination and corrosion of the weld site, which can decrease the quality of the weld or even prevent it from forming an acceptable seal. 

Since industrial welding is held to very high safety standards, especially in pressurized metals, the quality of the weld is paramount. A failed weld in the bottom of a steel ship, for example, can lead to the ship foundering and sinking if it begins to take on water. 

What Is MIG Welding?


MIG welding is a type of welding that is primarily used on aluminum and other non-ferrous metals. This is because it is shielded with inert gases that help protect these delicate metals from becoming contaminated during the welding process. Aluminum especially is very volatile during the welding process and has to be handled carefully to achieve a good weld. 

MIG welding uses a heated tungsten electrode to weld two base metals together. The electrode creates a melted area where the two metals can be fused together without the threat of being separated. MIG welding is strong enough that it is used in many kinds of industrial practices. 

Supplies Needed for MIG and MAG Welding


MIG welding requires many of the same supplies that MAG welding does. However, they do require slightly different materials. Here’s a list of the items needed to perform MIG and MAG welding (Source: Home Depot): 

  • MIG/MAG welding assembly: The MIG welding assembly typically includes the welding power source as well as the welding torch itself. 
  • Welding tips: The welding tip on a welding torch becomes worn quickly through repeated use, so having backups is a good idea in case you need to replace the tip mid-job. 
  • Welding wire: Welding wire is the tungsten wire that is fed through the welding torch to form the superheated electrode that allows it to melt the weld pool. 
  • Shielding gas: Shielding gas is hooked up to the welding torch via a valve-operated system and adjusted so that it forms a consistent protective barrier around the welding site. In MIG welding, the shielding gas primarily used is argon. 
  • Wire brush: Wire brushes are used in welding to scrub away slag and other corrosion that may form during the welding process. 
  • Metal grinder: A metal grinder is used to clean metal in more difficult to reach spots than a wire brush can access. 
  • Ventilation system: When performing MIG welding indoors, the area is well-ventilated. Welding can create noxious fumes and the gases used by shielding equipment displace oxygen in the air. 

There are other accessories you can add to a welding workshop that will also refine the welding process. However, the materials listed above are the basics you need to get started in a MIG welding project. 

What Is MAG Welding?


MAG welding is similar to MIG welding except that it is used on mild steel rather than non-ferrous metals. MAG welds still require a gas shield, but they are less susceptible to corrosion than aluminum and non-ferrous metals. This means that for the sake of practicality, MAG welds typically use an active gas mixture that is less expensive than most inert gas setups. 

At the end of the day, the only real differences between a MIG welding setup and a MAG welding setup are the type of shielding gases used and the type of metal that each type of welding is designed to address. 

How Does MIG and MAG Welding Work? 


Even though MIG and MAG welding are different in the type of shielding gases they use, they are both gas arc welding techniques that operate on basically the same principles. This is how an arc welding torch works (Source: Linde Gas): 

  • Wire is fed through the wire feeder in the welding assembly. 
  • The welding assembly creates an electric arc between the weld pool and the welding tip. The electricity in this arc is what causes the metal to become hot enough to fuse. 
  • The shielding gas is blown out in a protective cone around the end of the welding tip to keep atmospheric gases from interacting with the weld pool. 

Using this tool to put different base metals together, MIG and MAG welding can create a nearly unbreakable bond or joint between different metal pieces. The final tensile strength of the weld is determined by both the integrity of the weld and the base materials that are used.  

How to Choose a Shielding Gas?

The different shielding gases used in MIG and MAG welding all afford welders different properties during the weld itself. Some gases are better with certain metals than others. Below you’ll find an overview of the major shielding gases and how they affect a weld. (Source: Tregaskiss)

Carbon Dioxide

Carbon dioxide is one of the most common gases used in MAG welding because it is cheap and readily available. Carbon dioxide is frequently used in welding operations where the appearance of the weld is less important than keeping material costs down in construction. Carbon dioxide is ideal for deep penetration welds but is vulnerable to splatter and other quality issues. 

Argon
Argon is the shielding gas that is preferred when the appearance of the weld is an important factor in the final product. This expensive gas is known for producing a clean weld that requires a minimal amount of post-welding refinement. Another advantage of argon is that it is capable of a narrow and shallow weld, which makes it useful in dovetailing metals with butte or fillet joints. 

Oxygen
Oxygen is usually included in active shielding mixtures in small percentages (9% or less). Because this is a reactive gas that can lead to corrosion, oxygen is not used in welding projects on non-ferrous metals like aluminum that are known for rapid oxidation.

Helium
Like argon, helium is another shielding gas that is used primarily as a gas in MIG welding since it is inert and one of the strongest shields against atmospheric contamination. Helium is also one of the most expensive shielding gases due to its relative scarcity. Compared to other shielding gases, using helium as a shield results in a deep, wide welding pool. 

When choosing a shielding gas, there are a few different questions that the welder should take into consideration: 

  • What base metals are being used? 
  • Is a MIG or a MAG welding setup being used? 
  • How does the cost of the shielding gas affect the cost of the final product? 
  • What kind of joint is being welded? 
  • How clean are the materials being used? 

Since all welding operations are slightly different, it might take a welder some experimentation to find a gas mixture that they’re happy with. Many welders also swap back and forth between MIG and MAG welding depending on the project, so they’ll want to have supplies on hand for both welding setups.  

Safety Risks Involved with MIG and MAG Welding


Even though arc welding techniques like MIG and MAG welding are popular due to the strong bonds they’re capable of making, there are still some significant safety risks involved with both types of welding. There are no real differences between the risks involved in MIG and MAG welding. 

These are a few of the major risks involved with arc welding: 

  • Asphyxiation: If arc welding is performed in a small enclosed space, the shielding gases pushed by the assembly can eventually replace breathable oxygen with unbreathable gases such as carbon dioxide. This process is slow and the welder may not realize what is happening until they collapse of Hypoxia. This is why good ventilation is essential in welding.
  • Electrocution: Welding assemblies use high-voltage electricity that is easily capable of killing a person. MIG and MAG welding assemblies should be properly grounded and attached to a power source that is rated for the machine. Installing a MIG or MAG welding machine on an electrical outlet that isn’t rated for it can cause short circuits and fires. 
  • Fire: Welders should always keep in mind that MIG and MAG welding assemblies can heat materials to 10,000 degrees Fahrenheit. This means that anything left in proximity to an active welding operation is susceptible to combustion. This includes the spontaneous combustion of materials that are left even near a welder without direct contact. 
  • Blindness: MIG and MAG welding throws up slag and sparks that can blind the welding operator if one of the sparks hits them in the eye. (Source: Industrial Safety and Hygiene News) Welders are also susceptible to “welder’s eye” or photokeratitis, a condition caused by over-exposure to ultraviolet radiation that can gradually cause vision loss and permanent blindness. 
  • Burns: The heated materials used in arc welding can cause third-degree burns if they come into contact with the eyes or skin of a person. 

Safety Precautions 

As you can see, there are many risks involved with being a MIG or a MAG welder. This is why safety precautions should always be taken in the welding shop no matter which arc welding technique you’re using. To prevent accidents while performing MIG and MAG welding, welders should observe the following: 

  • Always wear protective gear: The protective gear needed for all arc welding operations includes a welding helmet with a shield, a welding apron, and welding gloves. This protective gear may seem tedious to wear, but it’s well worth the trouble compared to the trouble of losing your sight or suffering from a slag burn. 
  • Always weld in a ventilated area. Ventilation prevents the build-up of toxic fumes and can help make sure that the room has a fresh source of breathable oxygen at all times. To see the proper way to ventilate a welding operation, see the safety standards for ventilation shown by the National Ag Safety Database.
  • Never arc weld on closed containers. Tanks, barrels, drums, and other containers are vulnerable to explosion during the welding process. Explosion occurs when the heat from the welding assembly raises the air temperature inside the container, raising the air pressure until it is high enough to cause an explosion. Containers are also more likely to contain fuel or oxygen fumes. 
  • Check your power source. Do not plug a welding assembly into a wall outlet that is not rated for high-voltage operations. In some cases, welders may have to rewire a new power source into their workshop to have a safe and stable electrical circuit. Inspecting the welding assembly to ensure that it is undamaged and properly welded before each operation can prevent accidents.
  • Clear the workshop of all combustible materials. This includes items like oily rags, fabric, wood, or paper. Making sure that welding materials aren’t contaminated with oil, gas, or other flammable fluids can also help prevent a fire. 

Keeping a safe welding operation in MIG and MAG welding leads to a safer work environment and can also lead to a better weld. The less worried the welder is about getting blinded, burned, or electrocuted, the better they can focus on the job at hand. 

Can MIG and MAG Welding Be Performed on the Same Torch?


MIG welding and MAG welding can both be used on the same arc welding equipment as long as the inert gas mixture used in MIG welding is swapped out for an active gas mixture setup instead. These gas tanks are easily hooked into the welding setup and can be used interchangeably depending on what type of materials you’re trying to weld. 

Can MAG Welding Be Used for Aluminum?

While MAG welding is possible on some aluminum and aluminum alloys, using an active gas mixture increases the threat of the weld becoming contaminated by atmospheric elements. However, MAG welding is still used in aluminum fitting where production cost is a factor.

The biggest issue with welding aluminum is that this metal has a high level of thermal conductivity and melts at a low temperature (1220F), and these traits make it unpredictable to work with while welding. Without a strong shielding gas, gas inclusions can end up in the welding pool and cause it to become brittle once cooled. This ultimately affects the integrity of the entire weld.

When working with aluminum, shielding with argon or helium is the best option to end up with a strong, good-looking weld. Incorporating any active gas mixture that has oxygen can create corrosion and cause the weld to fail. (Source: Firmly Welded

Final Thoughts


There are more similarities between MIG and MAG welding than there are differences, but the differences between the two are important when it comes to choosing your shielding gas. Choosing the right shielding gas for your operation and making sure that your welding setup is secure regardless of which technique you use are vital for getting a good weld safely.

If you liked this article, have a look at my other articles I wrote about the topic!

Your Feedback is much appreciated!
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Alexander Berk

A bit about myself: I am a certified international welding engineer (IWE) who worked in different welding projects for TIG, MIG, MAG, and Resistance Spot welding. Most recently as a Process Engineer for Laser and TIG welding processes. To address some of the questions I frequently got asked or was wondering myself during my job, I started this blog. It has become a bit of a pet project, as I want to learn more about the details about welding. I sincerely hope it will help you to improve your welding results as much as it did improve mine.

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