Choosing the right filler metal can significantly influence the quality of the finished weld, but there isn&#;t a one-size-fits-all solution for every job. Key factors to consider when making the choice include your required welding position; available welding equipment; base material type or grade, size, and thickness; and operator skill level.

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Gas-shielded flux-cored arc welding (FCAW) wires can provide higher deposition rates than other filler metals, resulting in increased productivity for many applications. These wires are also a good match for applications across many industries, such as shipbuilding, structural steel, and general fabrication and manufacturing.

Understanding the characteristics and benefits of gas-shielded flux-cored wires can help you decide if they are the right fit for your welding operation.

Flux-Cored Welding Wire Basics

The common rutile-based American Welding Society (AWS) E71T-1 gas-shielded flux-cored wires tend to be very appealing because they are easy to control and produce an aesthetically pleasing weld. When deciding on the right wire for the job, it&#;s important to first consider a few flux-cored wire basics.

Know the weld position. Some flux-cored wires are designed for all-position welding (such as an AWS E71T-1C), while others are designated for flat and horizontal positions (like an AWS E70T-1C).

Pair with the base metal. Flux-cored wires are available for welding a variety of base materials, including mild steel, low-alloy steel, nickel alloys, and stainless steel. The wires for welding steel are available in tensile strengths of 70 KSI for mild steel and 80 to 120 KSI for high-strength/low-alloy steels.

Check the designators. Flux-cored wires have usability designators defined by AWS that indicate their polarity and operating characteristics. These designators can be a number (from 1 to 14) or a letter (G or GS).

Watch the slag. Flux-cored wires produce a slag that protects the molten weld puddle as it cools. You must remove the slag in between passes and after the final pass to avoid inclusions that could lead to defective welds.

Choose a shielding gas. FCAW with gas-shielded flux-cored wires requires an external shielding gas. Common options are 100% carbon dioxide or a CO2 and argon gas mix.

Flux-Cored Welding Wire Shielding Gases

What are the basics of matching a flux-cored wire with a shielding gas? Each type of shielding gas yields different characteristics in FCAW. It&#;s also important to know the specific shielding gas requirements of the flux-cored wires you&#;re using.

Use only 100% CO2 with wires with a C designation in their AWS classification, such as E70T-1C H8.

Wires with an M designation, such as E71T-1M, require a mixed shielding gas of CO2 and argon, often a 75%/25% ratio.

Wires that have both C and M designations are dual-gas wires that can be used with either gas type.

Wires paired with 100% CO2 provide more weld penetration but also tend to result in more weld spatter, which takes more time to clean. Using a mixed gas with flux-cored wire results in less weld spatter and a smoother bead appearance. A mixed gas is more expensive than straight CO2, so you should weigh the costs &#; including time and money spent on cleanup &#; when making the choice.

Also, be aware that making a change in your shielding gas may require new welding procedures and testing prior to use, depending on the application.

Equipment Requirements for FCAW Wire

Beyond choosing the right filler metal for the job, achieving the best results from flux-cored wires also requires having the proper equipment and using it correctly.

FCAW wires operate with a standard constant voltage (CV) power source that can be set to either straight polarity (direct current electrode negative, or DCEN) or reverse polarity (direct current electrode positive, or DCEP). The correct polarity setting depends on the wire formulation. Check the filler metal manufacturer&#;s recommendations before setting up your equipment.

Because flux-cored wire is softer than solid wire, it can be easily crushed or deformed if you use the wrong drive rolls. Be sure to choose V-knurled drive rolls for the wire feeder as they will provide you with smooth wire feeding and consistent weld quality.

Storage Tips for Flux-Cored Welding Wire

Once you have the proper filler metal and equipment in place, following a few best practices also can help you optimize results.

Use a drag technique while welding. A good drag angle for flat, horizontal, and overhead positions is generally around 10 to 30 degrees. For vertical-up welds, you should target a gun angle of 5 to 15 degrees.

Maintain a steady and appropriate travel speed. This will keep the weld pool from getting ahead of the arc, which could lead to slag inclusions.

Watch your stick-out. Improper stick-out can result in burnback, worm-tracking, incomplete slag coverage, and difficult slag removal. Be sure to check the stick-out recommendations for each wire. Depending on the wire diameter and type, the recommended stick-out may exceed 2 in. Stick-out is also important because it provides a level of resistive heating of the wire, which helps increase the deposition rate.

Store filler metals properly. You should store flux-cored wires in a clean, dry area. Exposure to moisture or other contaminants can damage the wires, resulting in poor weld quality. In addition, keep the wires in their original packages until you&#;re ready to use them. For wires in use, remove the spool from the wire feeder at night and store it in a plastic bag to reduce chances of problems from moisture exposure.

Maintain storage temperature. It&#;s also a good idea to maintain the same temperature in the storage area as in your welding area. Condensation can form on wires if you move them from a cold storage room to a warm fabrication environment. This can lead to rusting of the wire and potential wire feeding problems or porosity in the weld. If it&#;s not possible to maintain the same temperature in both the storage area and the weld cell, allow the wire to acclimate to the weld cell temperature for 24 hours before welding with it.

Optimize Welds With Flux-Cored Welding Wire

As with any new welding process or filler metal, training is an important step toward success. If you&#;re new to using gas-shielded flux-cored wires, you may want to seek out additional training or certifications to help you master the process.

Following the required work procedures and parameters for a specific application can also help you achieve the results you want with flux-cored wire. With proper technique and best practices, these wires can deliver improved productivity, better weld quality, and reduced downtime.

Flux Core Wire Types

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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.

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.

Primary FCAW Wire Types: Self-Shielded and Gas-Shielded

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 Welding (FCAW-S)

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.

Gas-Shielded Flux Cored (FCAW-G)

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-Position & All-Position Flux Cored Wires

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.

Weld Deposit Composition: So Many FCAW Wires!

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.

Some available alloys are even designed for surfacing instead of joining so that exposed areas of base metals are more abrasion or impact resistant.

Conclusion

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.

If you&#;d prefer to save the reading for another time, don&#;t hesitate to contact Red-D-Arc. We are a knowledgeable team who can rent you the best equipment and advise on the optimal consumables&#;such as flux-cored wire&#;you will need for your flux-cored welding application.

Red-D-Arc, an Airgas company, rents and leases welders, welding positioners, welding-related equipment, and electric power generators &#; anywhere in the world. Our rental welders, positioners and specialty products have been engineered and built to provide Extreme-Duty&#; performance and reliability in even the harshest environments, and are available through over 70 Red-D-Arc Service Centers, strategically located throughout the United States, Canada, the United Kingdom, France, and the Netherlands, as well as through strategic alliances in the Middle East, Spain, Italy, Croatia, and the Caribbean. From our rental fleet of over 60,000 welders, 3,700 weld positioners, and 3,700 electric-power generators, we can supply you with the equipment you need &#; where you need it &#; when you need it.

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