Flux-cored arc welding (FCAW) is a wire-fed process like gas metal arc welding (GMAW/MIG). However, what makes FCAW a unique process is the filler metal. FCAW uses a tubular wire that generates slag during welding. While removing the slag after welding can be inconvenient, the slag is critical for the process to achieve good weld quality and provide unique benefits compared to MIG and other welding processes.
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When it is time to select a flux-cored wire for your application, you may find that there is an extensive list of wires to choose from. Selecting the best wire—one that is easy-to-use and produces a high-quality weld deposit with suitable mechanical and chemical properties—requires a basic understanding of the basic wire types and capabilities.
In addition to producing a slag during welding that helps to remove base metal impurities, flux-cored wires generate gases that serve to displace the atmosphere around the molten weld metal. This displacement protects the weld metal from atmospheric gases such as oxygen and nitrogen that can lead to porosity or harm mechanical properties.
Self-shielded flux-cored wires produce sufficient gaseous shielding, so no assistance (external shielding gas) is required. Self-shielded wires are suitable even in breezy conditions, such as outdoor construction and repairs. Remember that using these wires indoors can be challenging from an environmental health and safety perspective, even when strong ventilation is used.
Some self-shielded wires offer sufficient weld toughness—an ability to absorb energy before fracture—that makes them well-suited for structural fabrication in seismic areas and demand-critical welds on bridges and similar structures.
Of course, flux-cored wires also exist for “light-duty” applications around the house, garage, or farm and ranch. While these wires may not be as tough, they often provide more-than-adequate mechanical properties and are easier to use and available in diameters that complement commercial and light-industrial equipment. In addition to the local welding supply, it is often possible to find these wires at hardware and farm supply stores.
Not all flux-cored wires are self-shielded, meaning that an external shielding gas (supplied in cylinders similar to those used when MIG welding) is required to achieve acceptable weld quality; these gas-shielded wires are not capable of providing sufficient atmospheric displacement on their own. The process using these wires is often abbreviated as FCAW-G (for gas-shielded).
The trade-off to needed external shielding gas is that the gas-shielded wires are often much more user friendly than the self-shielded wires while still providing improved tolerance to poor base metal conditions—rust, weldable primer, and mill scale—than MIG welding. FCAW-G is especially popular in the railcar, shipbuilding, and heavy equipment fabrication industries.
Common shielding gases for gas-shielded include 100% carbon dioxide and 75% argon/25% carbon dioxide. 100% carbon dioxide is a lower-cost option that typically offers improved base metal penetration, while the argon/carbon dioxide shielding gases usually provide a smoother arc and reduced weld spatter.
In certain applications, it is possible to position the work (by hand, sometimes using equipment) so that the weld joint is roughly parallel with the ground. This is known as welding “in position.” Since the effect of gravity is not as detrimental, it is often possible to weld at higher amperages. This translates to improved deposition rates, welding travel speeds, and in many cases, improved welding productivity.
Some flux-cored wires are limited to welding in position only. The slag of these wires tends to freeze slower than those wires that are capable of welding in the flat, horizontal, vertical, and overhead positions, but a slow freezing slag often provides a very smooth weld bead contour and good penetration. Typically, these “flat and horizontal only” wires are available in larger diameters to allow the use of very high currents. A 3/32” wire, for example, is typically used between 350 and 500 amps!
If work cannot be positioned, resulting in weld joints in the vertical and overhead positions, an “all-position” flux cored wire must be used. Here, the slag is designed to freeze quickly to support the molten metal and prevent it from dripping or sagging when reasonable welding parameters are used.
Some flux-cored wires are suitable for welding lower-strength carbon steels. In contrast, others are designed for welding higher-strength low alloy (HSLA) steels that derive strength and toughness from elements such as nickel, chromium, and molybdenum, among others. Specialty wire manufacturers even make flux-cored wires designed for welding stainless steels, exotic nickel-based alloys, and tool steel compositions.
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Some available alloys are even designed for surfacing instead of joining so that exposed areas of base metals are more abrasion or impact resistant.
Flux-cored arc welding is an expansive process with many wire types: gas-shielded, self-shielded, all-position, in-position, carbon steel, HSLA steel, stainless steel, and more. If you ever feel overwhelmed by the sheer number of flux-cored wires in the welding marketplace, consider turning to AWS or CWB filler metal specifications. Often, these technical documents have electrode classification systems that help you compare products and descriptions of the intended uses of certain wire classifications.
Gas-shielded flux core wire was introduced in , followed in by self-shielded wires. All of the flux core wires in this guide are self-shielded wires that don’t require gas. These wires are great for use in simple, inexpensive wire feed welding machines that don’t have gas hookups.
The classification system for flux core wire was established by the American Welding Society and looks like this:
E – Means electrode wire.
7 – This digit indicates tensile strength x 10,000 PSI or 70K PSI
1 – indicates all-position wire, and 0 means flat and horizontal positions.
T – means tubular or flux core wire.
1 – All the wires in this guide use a 1 here. It refers to settings and methods.
1 – Means self-shielded wire. C means CO2, and M means gas mixture.
E71T-11 wire has the best performance for high volume, fast-paced production environments and requires less skill to use. When welding vertically, its fast freezing characteristics provide the fastest metal deposition rates, up to 7 pounds of steel per hour in automatic systems. E71T-11 is the most-used welding wire globally, common in shipbuilding, structural steel, and fabrication.
The ability to put different chemical mixes into tubular wire creates performance enhancements over solid wire. There are slag forming materials that shield the weld pool from porosity and help to support the weld puddle when welding vertically. Metal powders such as alloys to increase mechanical strength and iron to improve metal deposition rate make for stronger, cleaner welds on rusty or scaly materials.
The factors that affect the choice of flux core wire diameter include the type of feed wheels in your machine and the size of the nozzle tips in the MIG gun. There are also process factors to consider, like amperage settings and material thickness. Smaller diameter wires will require lower amperage rates for good results. The higher amperage rates associated with larger diameters can result in burn through, requiring higher feed rates to make up for the heat.
Read: Difference between .030 and .035 flux core wire
Depending on your application, different wires may weld differently, even with an identical AWS classification. Wires by different brands don’t have the same alloy mix nor the same chemicals and ratios in the flux core mixture. There will also be less consistent quality from spool to spool with the inexpensive brands because many don’t make their own wire, they order it in, and each lot could be made by a different manufacturer.
By contrast, the industry-leading American and European names make their own wire with more consistent quality. For instance, Lincoln wire is generally considered very high quality but can cost significantly more because of expensive quality control processes to maintain consistency from roll to roll. Be sure to buy stainless wire for stainless steel, aluminum wire for aluminum, and carbon wire for mild steel. Try some before you buy it any time you can because some perform better on dirty or painted materials than other brands do. Spatter amounts can differ with the same wire on different welding machines.
Some professional-grade MIG welders have precision feeding mechanisms with smoothly finished grooved wheels for feeding solid wire to use with gas shielding. Some inexpensive wires don’t feed well in these machines. It can be worthwhile to change the feed rollers for a flat profile with knurled surfaces for a higher grip. The size of a spool your welder can fit is also something to keep in mind.
With everything taken into account, including spatter production, feeding concerns by users, and cost of the wire, we’ve chosen Hobart Fabshield .030 E71T-11 as Our Favorite.
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