There are two types of flux-cored wire electrodes: gas-shielded and self-shielded. As its name implies, the gas-shielded type of flux-cored wire requires an external shielding gas. The self-shielded variety does not.
The flux coating on gas shielded flux-cored wires solidifies faster than the molten weld material. Consequently, a sort of shelf is created which holds the molten pool when welding overhead or vertically up. Gas-shielded flux wires work well when welding thicker metals. They also work well for welding out-of-position applications. Slag removal is easy with this type of wire.
Self-shielding flux-cored wires do not require an external shielding gas. With this type of electrode, the weld pool is protected as gas is generated when the flux from the wire is burned. Because the self-shielding wire produces its own protective shield and doesn’t require an external gas tank, it is more easily carried about.
Advantages of Flux-Cored Wire Electrodes
There are several advantages of using flux-cored wire electrodes. These advantages include but are not limited to:
- They allow for a high deposition rate.
- They work well outdoors and in windy conditions.
- With the right filler materials, these electrodes can make FCAW an “all-position” process.
- Typically, flux-cored wires create clean, strong welds.
Disadvantages of Flux-Cored Wire Electrodes
There are concerns with any type of welding method. Regardless of the process and type of electrode used, there is the possibility of creating an incomplete fusion between the base metals. Slag inclusion or cracks in the welds may also result.
Additional problems that may arise when using flux-cored electrode wires include:
- A melted contact tip may occur if the electrode contacts the base metal and fuses the two together.
- If gases do not escape the welded area before the metal hardens, the weld may develop holes and become porous.
What are the differences between flux-cored electrode wire and solid electrode wire? Is one type of electrode better than the other for welding? What are the advantages and disadvantages of each type of wire?
Solid Wire Electrodes
Solid wire electrodes are used in Metal Inert Gas Welding. Such electrodes require a shielding gas, which is delivered from a pressurized gas bottle. The shielding gas protects the molten weld pool from atmospheric contaminants.
Solid wire electrodes are often made of mild steel which is plated with copper to prevent oxidation and to aid in electrical conductivity. The copper plating also helps to increase the life of the welding contact tip.
Solid wires are the best choice when working on thin materials, such as sheet metal. They should produce nice, clean welds.
Solid wire electrodes do not work well in wind. Exposing the shielding gas to the wind can compromise the integrity of the weld.
Which Wire is the Best Choice?
When comparing the flux-cored wires to the solid wires, it would be wise to note that the best choice is dependent upon the welding job and location. Both types of wires can produce sound welds with good weld bead appearances, when done correctly.
For thicker metals and outdoor jobs, the flux-cored wire electrodes work best. For thinner metals and jobs performed out of the wind, solid wire electrodes can work quite well.
Solid wire electrodes used in MIG welding are not as portable as flux-cored wires. This is due to the necessity of a shielding gas in MIGW.
Both solid wire electrodes and flux-cored wire electrodes are relatively easy to use. However, flux-cored wire electrodes are more costly.
About the Flux-Cored Arc Welding (FCAW) Process
Flux-Cored Arc Welding was introduced in the 1950s. It is a process that is very closely related to Metal Inert Gas Welding. Both processes use similar equipment and continuous wire feeds, and both MIGW and FCAW use the same type of power supply. Flux-Cored Arc Welding typically uses a shielding gas similar to the MIGW process. However, Flux-Cored Arc Welding may also be performed without a shielding gas. Additionally, this type of welding is a much more productive process than MIG welding. In fact, FCAW is the most productive of the manual welding processes.
How FCAW Works
During the Flux-Cored Arc Welding process, an electric arc is used to unite a continuous filler metal electrode with the base material. (Note: The MIG welding method uses a solid metal electrode, whereas, the FCAW process uses a hollow tubular electrode that is filled with flux.) The flux-filled metal wire electrode automatically feeds through the center of the gun using the same type of equipment that is used in Metal Inert Gas Welding. The use of the gas shield supplied by the gun protects the weld pool from oxidation during the welding process. The flux that is inside the electrode forms a slag (smelting refuse) that covers and protects the weld from the atmosphere. The shield that is provided by the flux allows the welding procedure to be more easily executed outdoors, even in the wind.
The Suitability of Flux-Cored Arc Welding
Flux-Cored Arc Welding is a very flexible welding method. This type of welding is suitable for all position welding with the proper filler metal and flux composition. The high deposition rates of FCAW contribute to the productivity of this process, which provides quality welds with excellent weld appearance. It is often used for welding thicker sections and has the ability to produce a fully-penetrated weld on both sides of half-inch plate in a single pass.
The materials that work best with Flux-Cored Arc Welding are carbon steel, stainless steel, and low-alloy steels. Unfortunately, most non-ferrous metals, including aluminum, cannot be welded using the FCAW method.
Because of its high welding speed and the ability to be performed outdoors, even in windy conditions, Flux-Cored Arc Welding is frequently used in the construction industry.
Aspects of Flux-Cored Arc Welding
As its name implies, flux-cored arc welding is a type of automatic or semi-automatic arc welding process which uses a tubular electrode containing a flux rather than a solid electrode. This flux cored electrode makes FCAW the ideal choice for many of today’s welding requirements.
There are two types of flux-cored arc welding: one that requires an external supply of shielding gas and one that is self-shielding. The self-shielding type of FCAW gets its shielding gas from the continuously-fed tubular electrode. Not only does this electrode contain flux, it also contains ingredients that generate a shielding gas as the electrode comes into contact with the extreme heat of the welder. The gas protects the arc and the molten metal from the atmosphere.
Flux-Cored Arc Welding (FCAW) vs. Metal Inert Gas Welding (MIG)
Flux-Cored Arc Welding is a welding method that is somewhat unique compared to Metal Inert Gas welding. What primarily distinguishes FCAW from MIG welding is the type of wire electrode that is used and the way the molten metal is protected from the atmosphere.
The MIG welding process uses a continuous solid wire electrode, typically made of mild steel. An external gas supply is required to create a shield for protecting the molten pool. This is usually provided by a high-pressure gas cylinder.
As with MIG, FCAW requires electricity, filler metal, and some way to shield the molten metal from the air. In contrast to the MIG process, the flux-cored method uses a wire that contains an inner core made of materials that produce fluxing agents and shielding gases when burned by the heat of the welding arc. This type of wire eliminates the need for an external gas supply, because it has internal shielding properties.
Using the FCAW Method
Flux-Cored Arc Welding works better than MIG welding when working with thicker materials. In fact, FCAW is recommended only on materials that are no thinner than 20 gauge. When using the FCAW process on thicker metals, a good, strong weld can be produced in a single pass.
Because the flux-cored wire produces its own shielding gas during the welding process, FCAW works much better outdoors than does the MIG method. This internal shielding can even endure strong breezes. There is no need to carry a separate gas cylinder to the welding site, which makes FCAW more convenient.
One of the downsides of using FCAW is that the welding arc does make spatter. As a result, the finished weld gets covered with a slag which may have to be removed.
To begin the welding process using the flux-cored method, the welder first squeezes the trigger, which begins feeding the electrode continuously to the joint. As the electrode is fed through the wire feeder, it becomes electrically charged. When the wire reaches the metal joint, a short circuit occurs, which causes the electrode to heat up and begin to melt. As the wire electrode melts, the metal begins to melt, too. Together, the melting electrode and metal form a molten pool. The pool simultaneously melts the flux core of the electrode to create a protective shield from the environment and a slag that protects the weld from contamination.
Which Metals Work Best With FCAW
Most non-ferrous exotic metals, including aluminum, cannot be welded using the flux-cored method. However, flux-cored welding works well on most carbon steels, nickel-based alloys, cast iron, and some stainless steels.
Benefits of FCAW
FCAW has several advantages over other welding methods. For instance, Flux-cored arc welding has a higher deposit rate than MIG welding. In fact, it can deposit at least three times the amount of weld per hour than MIG welding. There are also fewer restarts with FCAW, decreasing the chance of defects in the restart area.
In addition to having a high deposit rate, flux-cored arc welding can be performed outdoors, even in windy conditions, and still produce a strong, quality weld. This benefit makes FCAW a popular choice in the construction and farming industries.
The electrode used in FCAW sticks out longer than the wire used in gas metal arc welding. This allows the welder to see and control the molten puddle much easier.
Flux-cored electrodes contain deoxidizers that reduce or eliminate porosity in welds.
The FCAW process can be performed in all positions with the right consumable electrode.
Flux wires for FCAW range in size from 0.035 inch to 1/8 inch in diameter. The most commonly used wire in FCAW measures 0.045 inch in diameter. The larger wire makes it possible for the welder to weld at a higher current level.
A porous weld is a weak weld. Although FCAW wires contain deoxidizers, it is still a good idea to properly clean the weld area to ensure prevention of weld porosity. This means removing dirt, oil, rust, paint or coating, grease, and any other debris from the metal.
To get the desired weld results, maintaining the proper heat input is typically necessary. This can be achieved by keeping a consistent travel speed of the weld, as well as a consistent current or voltage.
Additional Aspects of FCAW
Flux-cored arc welding cannot be used to weld non-ferrous exotic metals, including aluminum. However, FCAW works well on most carbon steels, nickel-based alloys, cast iron, and some stainless steels.
Self-shielding electrodes emit toxic fumes. When working with this type of electrode, the welder needs to have proper ventilation in the work area or to use a protective, sealed mask that provides fresh air.
Flux-Cored Arc Welding Techniques
The techniques used in flux-cored arc welding are much the same as those used in other welding methods—especially MIG welding. The electrode type, the flux type, the metal thickness, and the welding position will help determine which technique might work best on a certain project.
The backhand technique is often used with self-shielded flux-cored arc welding. This technique is achieved by passing the electrode along the welding site in the direction opposite that of welding.
When using the backhand technique, the handle of the welder is dragged like a stick welder. This technique works well when welding in the flat and horizontal positions. It may also be an option when welding in the 4G position to avoid being hit by spatter.
The backhand welding method creates a weld that is high and narrow—one that penetrates deeply. A disadvantage of using the backhand technique is that the weld puddle is a bit harder to see. As in stick welding, you need to keep an eye on the weld puddle size behind the crater.
The forehand welding technique is often used with gas-shielded flux-cored arc welding. The forehand process requires the electrode to be moved along the work site in the same direction as the welding.
The forehand method is often used when working with thinner metals. It may be the best method to use when welding in the vertical up position and for overhead fillet welds (4F). The forehand technique can also be used in the flat and horizontal positions.
Unlike the backhand method, the forehand welding technique makes it easy to see the weld puddle. As a result, it is also easier to see the weld joint and to keep from wandering off the joint.
With the forehand technique, it is important to try to keep the travel angle just right, so as to prevent excessive accumulation of spatter.
Stringer Bead and Weave Bead Techniques
The stringer bead welding technique is one in which the weld beads are deposited in a straight line. When using the weave bead technique, the weld beads are deposited in a zigzag formation.
The forward weld travel speed of the stringer bead method is faster than that of the weave bead method. This faster travel speed reduces the amount of heat input, which is desirable when welding T-1 steels.
The straight bead technique works well in any position. If welding in the vertical position, however, a partial weave may be preferable. Although the partial weave can make the welding process easier in this position, the weave total should not exceed twice the electrode diameter.
In FCAW, the stringer bead method is more commonly used. The weave bead method may be used occasionally, but most flux cored electrodes are designed for stringer beads.
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www.millerwelds.com (The Miller Electric Manufacturing Co.)