Flux Core vs MIG Welder — Which is the Best Option?

Welding joins pieces of metal together via a strong metallic bond, but this is only a simple overview, and there is much more to it than this. For instance, there are different types of welding best suited for your project.

Today, we’re going to be looking at two of the most commonly used types of welding: Flux Core and MIG welder operations. Read on to learn more about each type as we try to get to the bottom of the Flux Core/MIG welder debate.

What Is Flux Core Welding?

Also known as Flux Core Arc Welding, or FCAW, this form of welding utilizes a tubular wire with a hollow core. This hollow space within the wire is filled with flux, giving FCAW the first part of its name. The second part — Arc — refers to the arc between the continuous wire electrode of the welding device and the piece of material that is being welded.

FCAW can be carried out with or without a shielding gas, and this represents the two primary types of flux core welding. Self-shielded welding utilizes a longer electrode, extending the distance between the end of the unmelted electrode and the contact tube. The flux buildup itself will also provide shielding from atmospheric contamination.

When used with shielding gas, the length of the electrode is shorter, and a protective shield of gas is used to prevent this contamination. Gas-shielded flux core welding may be used in controlled environments, while self-shielded FCAW is typically used in locations where wind might blow the shield gas away, such as during outdoor welds.

What Is MIG Welding?

MIG stands for Metal Inert Gas. With this form of welding, a continuous solid wire electrode is fed through a welding gun, and an arc is created from this electrode to the material that is being welded. The arc will then melt both the metal material in the electrode and the material in the weld pool, forming a connection between the two.

This type of welding will also require a shielding gas to protect the weld, simply because atmospheric contamination may cause a failure in the join. This is a key difference between Flux Core Welding and MIG Welding, as FGAW offers both gas-shielded and self-shielded options.

Understanding Shielding Gases

While Flux Core Arc Welding can be implemented both with or without shielding gases, these substances are still important to both types of welding. Different shielding gases may be deployed in particular applications or when welding specific types of metal. Learn more about some of the most common types of shielding gases used in welding.

CO2 — CO2, or carbon dioxide, offers deeper penetration than other forms of shielding gas and may also be available more cheaply at higher volumes. Deoxidizing elements may also be required to remove the oxygen that is released from the molecule.
Ar and CO2 Mixture — Ar, or Argon, may be added to the CO2 shielding gas. As Argon is a noble gas, it will not react with carbon dioxide, and the two gases will remain chemically separate. This mixture may be used to reduce spatter from the weld puddle and also to increase the strength of the join, although the gas mixture is typically more expensive to source than pure CO2.
Ar and O2 Mixture — CO2 may corrode some forms of metal, so both Flux Core and MIG welders may require a different type of shielding gas. O2, or oxygen, may be added to the inert gas Argon to achieve the same benefits as the Ar/CO2 mixture without corrosion. Stainless steel is one example of a metal material that can be corroded by the presence of CO2. Typically, this mixture uses more Argon, which may make it even more expensive and difficult to source than the CO2 gas or Ar/CO2 option.

The Advantages of Flux Core Welding

Take a look at a quick summary of the key benefits of FGAW welding.

FGAW provides better penetration than MIG welding — i.e. the welded join extends more deeply into the material that is being welded.
FGAW is better suited for those who need to weld outdoors, particularly in windy conditions. This is because the self-shielded option can still be applied even if there is wind to blow away a shielding gas.
FGAW may be a more portable option than MIG welding, as there is no need for an additional shielding gas connection.
FGAW may have a more straightforward learning curve for welders who are still in training.
FGAW uses the same type of welding machine as the MIG process.
FGAW uses flux to create a secondary level of protection, even when the shielding gas is applied. This may be preferable to welders looking for additional peace of mind.
FGAW systematically deoxidizes the base metal, which makes it well-suited to welding ferrous metal materials.

The Disadvantages of Flux Core Welding

There are some disadvantages to using the Flux Core Arc Welding method.

FGAW may leave slag buildup on the surface of the welded metal, which could need cleaning and removal after you have finished welding.
FGAW depends upon tubular wires within the electrode, which may be more expensive to source than solid wires.
FGAW’s tubular wires are also flux-cored, so additional flux will also need to be sourced. This can potentially add to the overall cost of the project and may also contribute to project complexity.
FGAW produces toxic fumes when the flux disintegrates. These fumes will need to be dealt with to ensure a safe working environment.
FGAW can leave pockets of gas trapped in the welding join, which may expand to create holes when the metal cools and hardens.

The Advantages of MIG Welding

MIG welding also has its own specific advantages.

MIG welding can complete jobs at higher speeds due to a higher rate of deposition.
MIG leaves behind no slag on the join.
MIG makes it easier to see the weld pool during use.
MIG can be utilized fairly easily, with only a small amount of training beforehand.
MIG does not require shielded flux cored wire or filler metal, so the material cost may be lower than with FCAW.

The Disadvantages of MIG Welding

There are downsides to this type of welding too.

MIG setup may be more expensive, even though ongoing material costs will be cheaper.
MIG is a difficult process if you want to do quality welds outdoors.
MIG requires some set-up for more advanced welding techniques, and this may require additional training.
MIG increases exposure to radiation, so additional safeguards will need to be taken.

Choosing the Right Approach: Flux Core vs MIG Welder

Whether you are using MIG welding or Flux Core weld techniques, you can get strong results provided your materials and technique are sound. So, the question of Flux Core vs MIG welder is not really about welding quality and is more about what you plan to weld and where you plan to do it.

Metal Thickness

Metal thickness is an important consideration when choosing MIG welding or Flux Core weld. As discussed above, FCAW provides high levels of penetration, so creating strong bonds on thick pieces of metal is a common application for this form of welding. Thinner metal, however, is less suited to this sort of penetration, so MIG welding might be more suitable.

Metal Type

Some metals may be more suited to MIG and Flux Core welding, respectively. For example, stainless steel and some types of nickel alloy may be better welded with Flux Core equipment.

When it comes to welding mild steel, MIG welding is a great choice. Much simpler than TIG welding, it focuses on the task itself without the necessity of additional steps. Furthermore, with many welding machines offering MIG welding as one of their multi-process options, you can enjoy easy and efficient welding without compromising quality or precision.

The Flux Core Arc Welding process is a little more complex, as the welding wire feed, welding implement, and filler material all need to be considered. That said, both MIG and Flux Core Arc Welding can achieve good results on a mild steel project.

Welding Location

The location of the weld is an important part of the Flux Core/MIG welder debate. The shielding gas in an arc welder is not suitable for welding outdoors simply because the gas will be blown away by any wind or movement of air, leaving the weld pool exposed to atmospheric contaminants.

As such, a gas-shielded Flux Core welder will need to be used exclusively indoors, out of the wind. The self-shielded version of the Flux Core Arc Welder may be suitable for outdoor use. This can be a problem from MIG welding, as this form of welding does not feature a self-shielding option. It is difficult to effectively operate any sort of gas-shielded welder out of doors.

Work with Process Equipment and Controls on Your Project

Here at Process Equipment and Controls, we have a long history of metal fabrication and structural engineering success. This places us among the experts when it comes to welding. To discover more about what we can achieve for you and your project, get in touch today. Schedule your consultation, and let’s discuss what you need.

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