Can I use MIG wire in a flux core welder?

Yes, you can use MIG wire in a flux core welder, but adjustments and additional equipment may be required.

Understanding Welding Wires

Welding wires play a pivotal role in determining the quality, efficiency, and cost of welding projects. Different types of wires offer unique advantages, influencing the welder’s choice based on the specific requirements of the task.

The Basics of MIG Wire

Metal Inert Gas (MIG) welding, commonly referred to as Gas Metal Arc Welding (GMAW), utilizes a continuously fed wire electrode to produce the weld. The primary features of MIG wire include:

  • Material Composition: Typically made from mild steel, but variants can be found in stainless steel, aluminum, and other metals.
  • Diameter Range: MIG wires are available in various diameters, from 0.023 to 0.045 inches. The choice often depends on the thickness of the material being welded.
  • Cost: The average price of MIG wire ranges from $5 to $20 per pound, depending on quality, material, and brand.
  • Speed: MIG welding is recognized for its speed, allowing welders to lay down a large amount of material in a short span of time.
  • Quality: Offers a clean and spatter-free weld, reducing post-weld cleanup efforts.

Features of Flux Core Wire

Flux-cored arc welding (FCAW) uses a wire that is filled with flux materials. This type of wire has gained popularity due to its versatility and some inherent advantages:

  • Self-shielding: The flux inside the wire produces its own shielding gas when burned, eliminating the need for external gas tanks.
  • Material: Commonly made from a combination of mild steel and flux compounds.
  • Welding Speed: Generally slower than MIG due to its flux content but offers deeper penetration.
  • Efficiency: It is particularly effective for welding thicker materials.
  • Cost: Flux core wire is typically more expensive, with prices ranging from $8 to $30 per pound.
  • Advantages: Ideal for outdoor welding since it’s less sensitive to wind and atmospheric conditions.

Key Differences Between MIG and Flux Core Wires

  • Shielding Mechanism: While MIG relies on external shielding gases like argon or carbon dioxide, flux core wire has its internal shielding mechanism due to the flux content.
  • Speed & Efficiency: MIG is faster but might not offer the same penetration as flux core, especially on thicker materials.
  • Cost Differences: Flux core wire is generally pricier than MIG wire, with a difference of about $3 to $10 per pound based on the brand and quality.
  • Applications: MIG is preferred for clean and cosmetic welds, especially on thinner materials. In contrast, flux core is chosen for outdoor conditions and thicker material welds.
  • Quality & Cleanup: MIG usually offers cleaner welds with less spatter, whereas flux core might require more post-weld cleanup due to slag.

The Flux Core Welding Process

Flux core welding, a subset of arc welding, has emerged as a favored technique for many welders. It integrates the flux within the wire, which upon melting, produces the shielding gas and slag to protect the weld pool from contaminants.

How Flux Core Welding Works

Flux core welding utilizes a special wire that’s filled with flux. When the arc is struck between this wire and the workpiece, the flux melts and transforms, performing two primary functions:

  1. Shielding Gas Production: As the flux burns, it releases gases that shield the weld pool from atmospheric contamination, specifically oxygen and nitrogen. This ensures a cleaner weld and reduces the chances of weld defects like porosity.
  2. Formation of Slag: Post gas production, a layer of slag forms on the weld bead’s surface. This slag solidifies and protects the cooling weld from contaminants and the surrounding environment. It is usually chipped off after the welding is complete.

The power required for flux core welding typically ranges from 20 to 550 amperes, depending on the material’s thickness and the specific job requirements.


Advantages and Disadvantages of Flux Core Welding


  • Versatility: Works well on rusty or dirty materials without the need for intense pre-cleaning.
  • Deep Penetration: Offers a deeper weld penetration, making it ideal for thicker materials.
  • Outdoor Usability: The self-shielding nature makes it less susceptible to wind or atmospheric contaminants, making it a good choice for outdoor welding.
  • Cost Efficiency: Despite the higher wire cost (ranging from $8 to $30 per pound), savings are made from not having to purchase external shielding gases.


  • Slag Cleanup: The formation of slag necessitates post-weld cleaning, which can be time-consuming.
  • Wire Cost: As mentioned, the wire tends to be more expensive than other types, which can affect the project’s budget.
  • Weld Appearance: While the weld is strong, it might not be as aesthetically pleasing as other welding forms, such as MIG.

Using MIG Wire in a Flux Core Welder

The topic of using MIG wire in a flux core welder is a prevalent debate in the welding community. While both MIG and flux core wires serve the same primary purpose – to provide filler metal in arc welding processes – they’re designed for different setups and have distinct characteristics.

Compatibility Considerations

When considering the use of MIG wire in a flux core welder, the primary focus should be on the welder’s compatibility.

  • Shielding Gas: MIG wire requires an external shielding gas to protect the weld pool. If the flux core welder is set up for gasless welding, then an external gas cylinder and the necessary regulators would need to be added.
  • Wire Feed Speed: Flux core welders are often designed to handle the specific feed speed and characteristics of flux core wire. Using MIG wire might require adjusting the feed speed due to its different diameter and composition.
  • Power Settings: The power requirements for MIG wire can differ from flux core wire. Users might need to adjust the amperage based on the MIG wire’s specifications and the material being welded.

Potential Issues and Challenges

Switching to MIG wire in a primarily flux core setup isn’t without challenges:

  • Weld Quality: Without the proper shielding gas flow, welds can become porous or contaminated.
  • Burnback: MIG wire might burn back into the contact tip if the feed speed isn’t set correctly, causing interruptions during welding.
  • Cost Implications: Purchasing external gas cylinders and regulators can significantly increase the welding project’s costs. An average gas cylinder might cost anywhere from $50 to $250, depending on its size and gas type.
  • Adjustment Time: Welders accustomed to flux core welding may need time to adjust their techniques and settings for MIG wire.

Recommendations for Successful Welding

For those determined to use MIG wire in a flux core welder, here are some steps to ensure success:

  • Equipment Check: Ensure the welder can accommodate external gas tanks. If not, consider upgrading or modifying the setup.
  • Choose the Right Gas: For steel welding with MIG wire, a common choice is a mix of 75% argon and 25% carbon dioxide. Ensure the flow rate is consistent, typically between 20 to 25 cubic feet per hour.
  • Regular Maintenance: Clean the welder’s liner and change the contact tip to match the MIG wire diameter.
  • Practice: Before starting on the main project, practice on scrap material to fine-tune settings and get a feel for the MIG process in a flux core setup.

Flux Core Welding Basics

Safety Considerations

Safety remains paramount in any welding operation. When using MIG wire in a flux core welder, specific safety precautions ensure that the process remains hazard-free. Proper understanding of equipment and personal protective measures can prevent injuries and provide an efficient welding environment.

Precautions When Using MIG Wire in a Flux Core Welder

  • Gas Safety: Ensure that gas cylinders are securely fastened to prevent tipping. Regularly inspect for leaks using soapy water. Remember, gases like argon are heavier than air and can displace oxygen, leading to asphyxiation in confined spaces.
  • Electrical Safety: Always inspect equipment for damaged cords or plugs. A typical welding process might involve 20 to 550 amperes, which can be deadly if mishandled. Maintain a dry workspace, and use insulated tools to prevent electrical shocks.
  • Ventilation: Proper ventilation is essential, especially when welding in confined spaces. Some metals release toxic fumes when welded. For instance, welding galvanized steel can release zinc fumes, which can lead to metal fume fever.
  • Fire Safety: Clear the welding area of flammable materials. Sparks can travel up to 35 feet from the welding space, so maintain a radius clear of combustibles. Have a fire extinguisher readily available.
  • Equipment Calibration: Regularly calibrate and check the welder settings. An improperly calibrated welder can result in weld defects or increased spatter, which can be a fire hazard.

Personal Protective Equipment Recommendations

  • Welding Helmets: Invest in an auto-darkening welding helmet. These helmets darken automatically when they detect the bright light of an arc, protecting the eyes from harmful ultraviolet and infrared rays.
  • Gloves: Use thick, flame-resistant gloves, preferably made of leather. They protect hands from burns and electrical shocks.
  • Welding Jacket: Flame-resistant jackets or aprons made of leather or other fire-resistant materials can protect the body from sparks and spatter.
  • Safety Shoes: Wear high-top leather shoes or boots to prevent sparks from entering the shoes. Steel-toed variants provide added protection against dropped tools or metal pieces.
  • Respirators: Especially important when welding materials that emit harmful fumes. Ensure it fits well and doesn’t interfere with the welding helmet.
  • Ear Protection: Sparks can fly and enter the ear, causing burns or discomfort. Ear muffs or plugs can prevent this, especially in environments with high ambient noise.
  • Safety Glasses: Wear them under the welding helmet for added protection from flying debris or when chipping slag off welds.

Practical Applications and Scenarios

The decision between using MIG wire or sticking to flux core wire often comes down to the specific requirements of the task at hand. Both wires have their unique advantages, making them suitable for distinct applications. By examining real-world scenarios, we can better understand where each type of wire shines.

When MIG Wire is Preferable

  • Thin Materials: MIG welding is often the method of choice for welding thin metals. Its precise control and lower heat input prevent burn-through on materials like thin automotive panels.
  • Clean Welds: For projects where aesthetics matter, such as furniture or visible structural elements, MIG welding offers cleaner welds with minimal spatter and post-weld cleanup.
  • High Production Rate: In assembly lines or manufacturing setups, speed is of the essence. MIG welding, with its faster deposition rates, can significantly reduce production times.
  • Controlled Environments: In indoor, controlled environments where wind isn’t a concern, MIG welding provides consistent results, especially with the steady flow of shielding gas like a 75% argon and 25% carbon dioxide mix.
  • Cost Sensitivity: While the initial setup for MIG welding can be pricey, the cost per weld might be lower, especially when considering the time saved on post-weld cleanup. On average, high-quality MIG wire might cost between $5 to $20 per pound, but savings in labor and materials might offset this.

How To Weld Common Joints Using A Flux Core Wire MIG Welder

Benefits of Sticking to Flux Core Wire

  • Thicker Materials: Flux core welding, with its deeper penetration, is ideal for welding thicker materials, making it perfect for heavy-duty structures and equipment.
  • Outdoor Welding: The self-shielding characteristic of flux core wire makes it resistant to the effects of wind or other atmospheric contaminants. It’s a go-to choice for outdoor construction projects or repair tasks.
  • Rusty or Dirty Materials: Unlike MIG, flux core welding can handle materials that aren’t perfectly clean. This makes it invaluable in scenarios like farm equipment repairs, where removing every bit of rust or dirt isn’t feasible.
  • Versatility: Flux core welding is versatile in terms of positional welding. It’s easier to weld in vertical or overhead positions due to the slag that protects the weld pool.
  • Avoiding Gas-Related Issues: In scenarios where managing gas tanks is cumbersome or shielding gas can be blown away easily, flux core wire provides an edge. While the wire is generally more expensive, ranging from $8 to $30 per pound, the costs associated with gas tanks, regulators, and potential gas losses are eliminated.

What is the cost difference between MIG and flux core wires?

MIG wire usually costs between $5 to $20 per pound, while flux core wire is generally more expensive, ranging from $8 to $30 per pound.

Which wire offers faster welding speed?

MIG welding offers a faster deposition rate and is thus quicker than flux core welding.

Do I need an external shielding gas with MIG wire?

Yes, MIG wire requires an external shielding gas, often a mix of 75% argon and 25% carbon dioxide, to protect the weld pool.

How does flux core welding handle outdoor conditions?

Flux core welding is ideal for outdoor conditions since its self-shielding nature makes it resistant to wind and atmospheric contaminants.

What power settings do MIG and flux core welding typically require?

Both methods can operate between 20 to 550 amperes, but specific settings depend on material thickness and the particular task.

Can MIG wire handle rusty or dirty materials?

Flux core welding is better suited for materials that aren't perfectly clean, whereas MIG welding requires cleaner surfaces for optimal results.

Which method is preferable for welding thin materials?

MIG welding is often the method of choice for welding thin metals due to its precise control and lower heat input.

Is post-weld cleanup more challenging with flux core welding?

Yes, flux core welding results in slag formation, which requires post-weld chipping and cleaning, whereas MIG welding typically offers cleaner welds with minimal spatter.

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