No single filler metal is suitable for every job. The mechanical and chemical properties of the base material, the required welding position, the available equipment, and the welding operator's skill set, among other considerations, all factor in making the best selection.

Goto sino welding to know more.

When you are seeking to increase productivity through higher deposition rates, flux-cored wires often are a viable option. These wires are known for high performance and weld quality in industries ranging from general fabrication and manufacturing to construction, offshore, and shipbuilding.

Flux-cored wires have unique welding characteristics and requirements, advantages, and limitations. Knowing these can help you determine whether they are the right choice.

Flux Core Wire Uses, Types, and Characteristics

Flux-cored wire comes in self-shielded and gas-shielded varieties, some of which are designated for all-position welding (for example, American Welding Society [AWS] E71T-1C), or for flat and horizontal applications (E70T-1C). Both types are gas-shielded and produce a slag that helps protect the liquid weld metal during cooling, but this slag must be removed after welding and between passes.

These wires are available for various base materials, including mild steel, low-alloy steel, stainless steel, and nickel alloys. For steel welding, they are available in tensile strengths of 70 KSI for mild steel, as well as 80 to 120 KSI and higher for welding high-strength, low-alloy steel.

Self-shielded flux-cored wires (FCAW-S) produce their own shielding gas when the arc initiates, eliminating the need for an external gas cylinder and making them suitable for use in portable and remote applications. These wires tend to produce slightly higher levels of smoke and spatter than gas-shielded flux-cored wires, but many classifications offer good impact toughness, even at lower temperatures.

Self-shielded flux-cored wires are often employed in lieu of shielded metal arc welding (SMAW) electrodes as a means to increase productivity since they are continuously fed and don't require repeated downtime for changeover. They are generally available in diameters from 0.035 to 7/64 in.

Gas-shielded flux-cored wires (FCAW-G) require an external shielding gas of either 100 percent CO2 or a blend of argon and CO2. They tend to have a higher operator appeal, meaning they are easier to control and to use to produce an aesthetically pleasing weld. They typically are used in a shop setting. When used outside, FCAW-G wires may require a barrier, either a tent or some other means to protect the weld pool, so that the shielding gas doesn't blow away.

Typically available in diameters from 0.035 to 7/64in., these wires can be used instead of solid wires to enhance productivity through higher deposition rates; welding operators can add more weld metal to a joint in less time, especially in out-of-position applications.

Pound for pound, FCAW-G wires typically are less expensive than FCAW-S varieties, which contain additional core materials and alloying elements, but do not require the additional expense for the shielding gas. FCAW-S wires also have a lower efficiency, about 65 percent compared to FCAW-G, which have 75 to 85 percent efficiency. These efficiencies also are lower than solid wires', because a portion of the wire is lost in the slag-forming agents that are discarded during the welding process. These factors should be considered when choosing a welding process.

Both types of wires are classified by usability designators defined by AWS'a number from 1 to 14 or the letter G or GS, which indicates the wire's polarity and operating characteristics.

FCAW-G Shielding Gases

FCAW-G wires have varying shielding gas requirements, and each type provides specific characteristics. Wires with a "C" designation in their AWS classification ' for example, E70T-1C H8 ' operate with only CO2. Those with a "M" designation, such as E71T-1M, require a shielding gas mix of CO2 and argon, usually a 75/25 percent balance.

Some wires are considered dual-gas and have a "C/M" designations that allows them to be used with both types of gases.

Care should be taken when considering a shielding gas change. While the wire may operate with either shielding gas, altering the gas is considered an essential variable change that can require new welding procedures and testing before use.

Wires operating with 100 percent CO2 offer more weld penetration, but also tend to create more spatter, whereas wires for mixed gases have reduced spatter and smoke, along with a smoother bead appearance. Once again, it is worthwhile to weigh out cost when choosing between the two types of classifications and shielding gases. CO2 is less expensive, but will likely generate a weld that requires more time and labor to remove spatter. Conversely, mixed gases are more expensive, but the welds need less cleaning after completion.

Equipment Requirements for Flux Core Wire

Gaining the best results from flux-cored wires is as much a matter of selecting the right wire for the job as it is having the proper equipment and training to weld with them. Both FCAW-S and FCAW-G operate with a standard constant-voltage (CV) power source set for straight polarity (direct-current electrode negative, or DCEN) or reverse polarity (direct-current electrode positive, or DCEP), depending on the wire formulation.

A common mistake made when setting up equipment to operate FCAW-S is selecting the wrong polarity on the welding power supply. While many wire welding processes operate using DCEP, the majority of FCAW-S wires are designed to operate on DCEN. Always consult the filler metal manufacturer's recommendations for operation.

FCAW-S wires often are paired with a voltage-sensing wire feeder. The welder can set the voltage at the power source but then control the wire feed speed (and therefore amperage) at the feeder. This feature is helpful on large job sites; fewer trips to the power source allows for more welding time. In the event that the welder varies the contact-tip-to-work distance (CTWD), voltage-sensing wire feeders also can help regulate the subsequent voltage variations.

Both wire types require V-knurled drive rolls in the wire feeder to provide smooth wire feeding and consistent weld quality. Flux-cored wire is softer than solid wire and can easily be deformed or crushed if incorrect drive rolls are used.

Proper Technique

During the welding process, welders should employ a drag technique. A good drag angle for flat, horizontal, and overhead positions is between 15 and 45 degrees. For vertical-up welds, a gun angle of 5 to 15 degrees works well. A steady and fast enough travel speed keeps the weld pool from getting ahead of the arc, which could lead to slag inclusions.

Welders using flux-cored wires should be sure to use the correct stick-out or electrode extension; self-shielded wires are particularly sensitive to this variable. Depending on the wire diameter and type, the manufacturer-recommended stick-out could exceed 2 in.; check the requirements for each wire.

Improper stick-out can cause issues such as burnback, worm tracking, incomplete slag coverage, and difficult slag removal. Stick-out also is crucial because it provides a level of resistive wire heating, which helps increase the deposition rate. The increase in resistance allows less current to pass through the arc, permitting higher wire feed speeds to be used, and thus increasing the deposition rate.

Storage Requirements

As with any filler metal, it's important to store FCAW-G and FCAW-S wires in a clean, dry area. Damage from moisture or other contaminants can lead to poor weld quality and likely void the product warranty.

It's a good idea to maintain the same temperature in the storage area as in the welding area. Moving wires from a cold storage room to a warmer weld cell may cause condensation to form on the wires. This condensation can cause the wire to rust and potentially cause porosity and wire feeding problems. If maintaining the same temperature in both spaces is not feasible, allow the wire to acclimate to the temperature of the weld cell for 24 hours before welding.

It also is important to keep the wires in their original vacuum- or hermetically sealed packages until ready for use. For wire already in use, take precaution to remove the spool from the wire feeder, place it in a plastic bag, and store it properly. Remember to remove any wire still inside of the gun if that equipment won't be used for a long period of time. Flux-cored wires, especially in humid climates, can rust inside the gun, requiring the removal and replacement of the entire welding gun liner.

Final Thoughts on Flux Core Wire

Training is key when using any type of filler metal. Welders new to using flux-cored wires may need additional training and/or certifications for their particular application, for example, converting from an SMAW electrode to an FCAW-S wire for a structural application.

Another example would be converting from an FCAW-G wire to an FCAW-S. While both wires are known as flux-cored, they are in different AWS classifications, and this change could potentially require additional testing and qualification.

Always follow the required work procedures and operating parameters for a given application and flux-cored wire. Combined, proper technique and operation can lead to better weld quality and productivity, while also reducing costly downtime.

Flux Core Wire Types

Share this

| Print this

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.

Want more information on Flux Cored Wire Self-shielded? Feel free to contact us.

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.

Share this

| Print this

If you are looking for more details, kindly visit Cast Iron Stick Electrodes.