Flux Cored Welding Wire

Flux cored welding wire is designed for high-deposition welding applications using the flux-cored arc welding (FCAW) process. Unlike solid wire, flux core wire contains internal flux that produces shielding during welding, allowing for strong weld penetration and reliable performance in fabrication, construction, and structural welding environments.

Flux core wire is commonly used for heavy fabrication, outdoor welding, and applications where wind or environmental conditions make shielding gas difficult to control. Both self-shielded and gas-shielded FCAW wires are available depending on the welding process and material requirements.

WeldingMart supplies professional flux cored welding wire from trusted manufacturers including Lincoln Electric, providing dependable FCAW filler metals for fabrication shops, industrial manufacturing, and structural welding operations.

Flux Core Welding Wire for MIG / Flux Cored Arc Welding (FCAW)

Flux core welding wire is the go-to filler metal for fabricators, construction crews, and maintenance welders who need higher deposition rates, reliable arc performance, and the flexibility to weld in demanding environments. Whether you're running a production shop in the Midwest or tacking steel decking on a windy job site, flux cored wire cuts your cleanup time, boosts productivity, and lets you push through conditions that would shut down solid MIG wire setups. At WeldingMart—located in Appleton, WI—we stock 97+ SKUs from Lincoln Electric, Hobart, ESAB, Forney, and other trusted brands so you can find exactly the wire your welding process demands. Orders ship same day when placed before 3 PM CT, and free freight kicks in at just $99.

What Is Flux Cored Wire? The Basics

Flux cored wire is a tubular filler metal with a powdered flux compound packed into its hollow core. When the arc melts the wire, that flux core vaporizes and forms a shielding cloud and a protective slag blanket over the weld pool. The slag floats contaminants to the surface and slows cooling, which results in improved weld quality compared to unprotected bare wire deposits.

Unlike solid MIG wire—which relies entirely on external shielding gas to protect the weld puddle—flux cored wire generates its own shielding compounds from within. That built-in design is what makes FCAW one of the most versatile welding processes in commercial and industrial fabrication today.

The two most common types of flux cored wire are self shielded FCAW (FCAW-S) and gas shielded flux cored (FCAW-G). Understanding the differences between these forms is the first step toward choosing the right wire for your job.

Self Shielded Flux Cored Wire (FCAW-S): No Gas Required

Self shielded flux cored wire generates all of its own protection from the flux inside the wire. No external shielding gas is required. This makes self shielded FCAW exceptionally portable—you need only a power source, a wire feeder, and a spool of wire. There's no cylinder to drag around, no regulator to set, and no worries about your gas coverage collapsing in windy conditions.

Self shielded FCAW is the wire type of choice for outdoor structural steel erection, pipe laying, and field repair work. Lincoln Electric's Innershield product line is arguably the most recognized family of self shielded flux cored wires in North America. These wires are classified by the American Welding Society (AWS) and carry an AWS classification that tells you the tensile strength, welding positions, and usability characteristics of each product.

Most self shielded fcaw wires run on direct current electrode negative (DCEN), also called straight polarity. This is the opposite of what most MIG welders use, so check your machine settings before you strike an arc. Self shielded FCAW wires tend to produce more spatter and a thicker slag than gas shielded flux cored wires, but their portability and performance in windy conditions more than compensate for the extra cleanup on outdoor and field jobs.

Key characteristics of self shielded flux cored wires:

No external shielding gas needed — ideal for outdoor and field welding
Excellent performance in windy conditions where gas coverage is difficult
Typically runs on straight polarity (DCEN)
Higher spatter levels and heavier slag compared to gas shielded types
Great for general fabrication, structural steel, and pipeline work
Available in multiple diameters to match your machine output

Gas Shielded Flux Cored Wire (FCAW-G): Higher Deposition Rates, Cleaner Welds

Gas shielded flux cored wire relies on external shielding gas—typically 100% CO₂ or a 75/25 argon/CO₂ mix—to protect the weld pool from atmospheric contamination. The gas shielded process combines the protection of external gas shielding with the productivity advantages of the flux core itself. The result is a wire that can provide higher deposition rates than solid MIG wire while still producing clean, low-porosity weld beads.

FCAW-G is the dominant choice for high-production shop fabrication, heavy equipment manufacturing, shipbuilding, and any application where weld quality standards are strict. Because the external gas shielding gives you more precise control over the arc and the weld puddle, you can dial in travel speed, heat input, and bead profile more tightly than with self shielded FCAW.

Gas shielded flux cored wires also offer all position welding capability when you select the right AWS classification. An E71T-1 wire, for example, is designed for flat and horizontal positions as well as vertical and overhead welding, making it one of the most widely used flux cored wires in structural and general fabrication shops. FCAW-G wires are sometimes called shielded fcaw or gas shielded flux cored wires to distinguish them from their self shielded cousins.

FCAW G wires use external gas shielding and produce:

Lower spatter and smoother weld bead appearance than self shielded types
Better puddle control for critical structural applications and code work
Excellent deposition rates — often higher than comparable solid wire
Reduced porosity when proper gas flow is maintained
Compatibility with CO₂, argon/CO₂ blends, and other shielding gas mixtures

How to Choose Between Self Shielded and Gas Shielded Flux Core

When choosing between self shielded and gas shielded flux cored wire, consider these factors:

Work environment: If you're welding outdoors or in areas with poor draft control, self shielded FCAW wins. Wind will blow external shielding gas away and cause porosity in gas shielded flux cored wires. Self shielded fcaw is engineered to hold up in those conditions.
Weld quality requirements: For critical structural applications, X-ray quality welds, or code-governed work, gas shielded flux cored (FCAW-G) typically delivers superior weld quality. The arc is more controllable and the bead is cleaner.
Positions: Many FCAW-G wires are all position welding capable, while some FCAW-S wires are limited to flat and horizontal positions. Always check the AWS classification on the package.
Equipment on hand: Self shielded FCAW only requires a power source and wire feeder. FCAW-G requires the same plus proper equipment for gas delivery—regulator, hose, and cylinder.
Deposition rates needed: Both types provide higher deposition rates than stick welding (SMAW). For maximum productivity on heavy plate, large-diameter gas shielded flux cored wires running in flat position can deliver exceptional deposition rates.
Material type: Most flux cored wires are designed for mild steel and low-alloy steel applications, though specialty wires exist for stainless steel, hardfacing, and even aluminum in some forms.

Key Specs to Understand When Buying Flux Cored Wire

Wire Diameter

Wire diameter is one of the most critical specs to match to your machine and application. Common diameters for flux cored wire include .030", .035", .045", .052", 1/16", and larger. Smaller diameters work well for thinner materials and lighter-duty machines. Larger diameters are used for heavy plate and high-deposition applications where the power source can sustain higher amperage. Always confirm your wire feeder and gun liner are sized to match the wire diameter you select.

AWS Classification

The American Welding Society establishes the AWS classification system for flux cored wire. The classification tells you minimum tensile strength, the welding positions the wire is rated for, the type of external shielding gas required (if any), and the usability characteristics of the filler metal. For example, E71T-1C/M means: E=electrode, 7=70,000 psi tensile, 1=all position welding, T=tubular (flux cored), -1=usability designation, C=CO₂ shielding gas, M=mixed gas. Learning to read the AWS classification is the fastest way to sort through your wire choices.

Polarity

Gas shielded flux cored wires almost always run on DCEP (direct current electrode positive, reverse polarity). Self shielded flux cored wires commonly run on direct current electrode negative (straight polarity / DCEN). Running the wrong polarity is one of the most common setup mistakes with FCAW. Always check the wire data sheet before adjusting your machine.

Shielding Gas

For FCAW-G wires, the choice of shielding gas affects arc characteristics, spatter levels, and mechanical properties. 100% CO₂ is the most economical option and produces deep penetration. A 75/25 argon/CO₂ blend reduces spatter and tends to produce a smoother arc. Some premium FCAW-G wires specify a C25 blend or other gas mixes—always follow the wire manufacturer's recommendation. Using the wrong shielding gas can introduce porosity, increase spatter, or degrade mechanical properties.

Spool Size

Flux cored wire is available on spools ranging from 2 lb. mini-spools to 33 lb. production spools and 50 lb. or larger drums. For shop production welding, larger spool sizes reduce changeover time and improve productivity. For field or maintenance welding, smaller spools are easier to handle and transport.

Common FCAW Wire Types and Applications

E71T-1 — The Workhorse FCAW-G Wire for Mild Steel

E71T-1 is one of the most widely used gas shielded flux cored wires in general fabrication. It runs on CO₂ or mixed shielding gas, delivers all position welding capability, and produces clean weld beads with low slag inclusions. E71T-1 is ideal for structural steel, general purpose welding on mild steel, and any job where consistent weld quality and good travel speed are required. This is the first wire most fabrication shops reach for when they want to move from solid wire to flux cored for improved productivity.

E71T-8 and Other Self Shielded Innershield Wires

Lincoln Electric's Innershield line includes several self shielded fcaw wires designed for structural and field applications. E71T-8 wires are all position welding capable, run on DCEN (straight polarity), and meet demanding AWS and code requirements for critical structural applications. These wires are commonly specified by engineers and inspectors on bridge, building, and heavy civil construction projects. They produce a fast-freezing weld pool that supports overhead and vertical-up welding, and they are designed to perform without external gas shielding even in windy conditions.

E70T-4 and Large-Diameter FCAW-S Wires

For high-deposition flat and horizontal positions welding on heavy plate, E70T-4 and similar large-diameter self shielded flux cored wires provide exceptional deposition rates. These are the wires that make the big productivity case for FCAW on structural fab and heavy equipment manufacturing. They are not designed for all-position work—they run only in flat and horizontal positions—but in those positions they produce deposition rates that far exceed what stick welding (SMAW) or solid MIG wire can achieve.

Low-Hydrogen and Low-Alloy FCAW Wires

For applications requiring controlled hydrogen content and higher strength, low-hydrogen flux cored wires are available in both self shielded and gas shielded variants. These filler metal choices are used in critical structural applications such as offshore structures, pressure vessels, and high-strength steel fabrication. The low-hydrogen characteristics reduce the risk of cracking in high-restraint joints and are essential when the base metal or service conditions demand it.

All Position Welding with Flux Cored Wire

One of the most attractive characteristics of properly selected flux cored wire is all position welding capability. Fast-freeze flux formulations allow the weld pool to solidify quickly enough to support vertical-up and overhead welding without the puddle sagging or running. This is in contrast to some solid wire modes and large-diameter FCAW wires limited to flat and horizontal positions only.

When you need all position welding in structural or pipe work, look for wires classified with a "1" in the third position of the AWS classification (e.g., E71T-1, E71T-8). These are specifically tested and certified for all positions. When selecting an FCAW wire for overhead or vertical-up welds, also pay attention to adjusting your travel speed and wire feed rate—faster travel and lower heat input typically yield the best results in out-of-position welding.

FCAW vs. Stick Welding (SMAW) vs. Solid MIG Wire

Flux cored arc welding (FCAW) sits between stick welding and solid MIG wire in many ways, combining benefits from both welding processes:

vs. Stick Welding (SMAW): FCAW wires provide higher deposition rates than SMAW electrodes. The continuous wire feed eliminates stub loss and electrode changeover, which means more arc-on time and improved productivity. FCAW also tends to produce less worm tracking and more consistent weld beads than stick welding in many applications.
vs. Solid MIG Wire: Flux cored wires provide higher deposition rates and better performance on dirty or rusty base materials than solid MIG wire. The slag protect the weld bead during cooling, which can improve mechanical properties. The downside: slag removal is an extra step, and the initial equipment setup requires more attention to detail.

In many applications, switching from solid MIG wire to flux cored wire on mild steel or low-alloy steel will deliver improved productivity without sacrificing weld quality.

The Drag Technique: Running Self Shielded FCAW

Using the Drag Technique for FCAW-S Wires

One important difference between self shielded flux cored wire and gas shielded MIG is gun angle. With self shielded fcaw, you use the drag technique—the gun is pointed back toward the completed weld (drag angle) rather than forward. This keeps the slag and flux shielding cloud behind the arc where it can properly protect the solidifying weld puddle. Using a push technique with self shielded wires will result in the arc running into the slag and producing poor weld quality.

Proper drag technique with FCAW-S also means maintaining a consistent contact-tip-to-work distance (CTWD). A longer stick-out is typical for self shielded flux cored wires—often ¾" to 1½" or more depending on the wire type—which affects arc voltage and deposition. Always check the wire data sheet for recommended CTWD and voltage settings.

Storage and Handling: Protect Your Wire Investment

Flux cored wire is sensitive to moisture. The flux inside the wire can absorb humidity from the air, which leads to porosity and potential cracking in the finished weld. To protect your wire:

Store flux cored wire in its original packaging until ready for use
Maintain appropriate storage temperature — most manufacturers recommend storing at room temperature in a dry environment
Reseal opened spools in plastic bags when not in use
Avoid storing wire in damp areas, unheated sheds, or environments with wide temperature swings that lead to condensation
Inspect wire for rust or surface damage before welding — damaged wire should not be used for critical structural applications

Moisture in the flux is one of the most common causes of porosity and hydrogen-induced cracking in FCAW welds. Proper storage practices protect both your investment and your weld quality.

Why Buy Flux Core Welding Wire from WeldingMart?

WeldingMart is a welding supply specialist based in Appleton, WI, serving professional welders, contractors, and fabrication shops across the country. When you order flux core welding wire from us, here's what you get:

Huge selection: 97+ flux cored wire SKUs covering self shielded flux cored, gas shielded flux cored (FCAW-G), mild steel, low-alloy, stainless, and hardfacing wires in a range of diameters and spool sizes.
Top brands: Lincoln Electric Innershield, Hobart, ESAB, Forney, and others — the same filler metal brands professional welders trust on the job.
Same-day shipping: Orders placed before 3 PM CT ship the same day. You get proper equipment and supplies fast, without waiting.
Free freight on orders $99+: Stock up on the wire choices you need most and save on shipping.
Expert knowledge: Our team understands the welding process from electrode to power source. We can help you select the right wire for your application, material, and machine.

Applications for Flux Cored Welding Wire

Flux core welding wire has many applications across a wide range of industries. Depending on whether you choose self shielded or gas shielded flux cored wire, FCAW is used for:

Structural steel fabrication: Both self shielded and gas shielded FCAW wires are used on building frames, bridges, and critical structural applications where code-compliant welds are required.
Heavy equipment manufacturing: High-deposition flux cored wires improve productivity on thick plate components in excavators, cranes, and agricultural machinery.
Shipbuilding: Gas shielded flux cored wires are a standard in shipyard fabrication for their high deposition rates and consistent weld quality on large steel assemblies.
Pipe welding: Self shielded FCAW is widely used for pipeline welding in the field, where portability and wind resistance are essential.
General fabrication and maintenance: For general purpose welding on mild steel, general fabrication, and repair work, flux cored wires offer a practical upgrade over stick welding with improved productivity and easier technique.
Outdoor construction: Self shielded fcaw is designed specifically for the outdoor environment, where external shielding gas is impractical or unreliable.

Frequently Asked Questions

What is the difference between self shielded and gas shielded flux cored wire?

Self shielded flux cored wire (FCAW-S) contains all the shielding compounds it needs inside the wire itself — no external shielding gas is required. This makes it ideal for outdoor and field welding in windy conditions. Gas shielded flux cored wire (FCAW-G) relies on external shielding gas (such as CO₂ or an argon/CO₂ blend) combined with the flux core to protect the weld pool. FCAW-G tends to produce lower spatter, better weld quality, and higher deposition rates, making it the preferred choice for shop fabrication and critical structural applications.

Do I need a special welder to run flux cored wire?

Most standard MIG welders can run flux cored wire with minor setup changes. For self shielded FCAW, you typically need to switch polarity to DCEN (direct current electrode negative / straight polarity) and may need to adjust your drive rolls to knurled rolls designed for flux cored wire. For gas shielded flux cored wire, you'll also need a shielding gas setup. Always verify your power source and wire feeder are sized for the wire diameter you intend to run.

What shielding gas should I use with FCAW-G wire?

The most common choices are 100% CO₂ and 75% argon / 25% CO₂ (C25). CO₂ is more economical and provides deep penetration but produces more spatter. Argon/CO₂ blends reduce spatter and tend to improve arc stability. Some wires specify particular gas mixes for best results — always check the wire manufacturer's data sheet. Using the wrong shielding gas can lead to porosity, increased spatter, or poor mechanical properties in the finished weld.

What does the E71T-1 AWS classification mean?

In the AWS classification E71T-1: 'E' stands for electrode; '7' indicates minimum tensile strength of 70,000 psi; '1' means the wire is rated for all position welding; 'T' identifies it as a tubular (flux cored) wire; '-1' is the usability designator indicating specific flux characteristics and gas compatibility. Suffixes like 'C' (CO₂) or 'M' (mixed gas) indicate the shielding gas type. The American Welding Society classification system ensures you know exactly what you're getting before you run a bead.

Can I use flux cored wire outdoors?

Yes — self shielded flux cored wire is specifically designed for outdoor welding where windy conditions make external shielding gas impractical. The self-contained shielding process protects the weld pool without relying on gas coverage that can be blown away. Gas shielded flux cored wire is generally not recommended for outdoor welding in windy conditions because the shielding gas will disperse and leave the weld pool unprotected, leading to porosity and poor weld quality.

How do I prevent porosity when welding with flux cored wire?

Porosity in FCAW welds most commonly results from moisture in the flux, contaminated base metal, inadequate shielding gas coverage (for FCAW-G), or improper storage of the wire. To prevent porosity: store wire properly at stable storage temperature in a dry environment, clean base metal before welding, maintain correct contact-tip-to-work distance, use the recommended shielding gas at the correct flow rate (for FCAW-G), and always run the correct polarity for your wire type.

What is the drag technique and why is it important for self shielded FCAW?

The drag technique means angling the gun so it points back toward the completed weld as you travel forward. Self shielded flux cored wires require the drag technique because it keeps the arc in front of the slag and shielding cloud. If you use a push technique — pointing the gun forward toward the unwelded joint — the arc will run into the slag, producing worm tracking, porosity, and poor weld quality.

How do I choose the right wire diameter for my application?

Match wire diameter to your base metal thickness and your machine's output capacity. Smaller diameters (.030"–.035") work well for sheet metal and thin plate. Medium diameters (.045"–.052") are the most common choices for general fabrication on mild steel. Larger diameters (1/16" and above) are used for high-deposition work on heavy plate. Always verify that your wire feeder, drive rolls, and gun liner are matched to the wire diameter you select.

Is flux cored wire better than solid MIG wire?

It depends on the application. Flux cored wire generally provides higher deposition rates, better performance on dirty or painted surfaces, and the ability to weld outdoors without gas (with self shielded FCAW). Solid MIG wire typically produces less spatter, no slag removal, and is often preferred for thinner materials and very clean weld bead requirements. For high-production fabrication on structural steel and heavy plate, flux cored wire is often the more productive and cost-effective filler metal choice.

What brands of flux cored wire does WeldingMart carry?

WeldingMart stocks flux cored wire from Lincoln Electric (Innershield and UltraCore), Hobart, ESAB, and Forney, with 97+ SKUs covering self shielded flux cored wires, gas shielded flux cored wires (FCAW-G), and specialty wires in a range of diameters and spool sizes. All orders over $99 ship free, and same-day shipping is available on orders placed before 3 PM CT.