What is Flux-Cored Arc Welding? Understanding it Thoroughly

• Dual Shield

Also called FCAW-G, the ‘G’ denoting that it is to be used with shielding gas. The best polarity to be used with Dual Shield is DCEP (Direct Current Electrode Positive). This essentially means that about ⅔ of the heat from the arc will be focused on melting the electrode wire, while ⅓ of the heat will be focused on the workpiece. FCAW-G is called Dual Shield welding because it has two complementary ways that the weld is ‘shielded’ during welding.

The flux burns and creates a protective slag. At the same time, the shielding gas which is emitted from the gas diffuser on the welding gun helps protect the weld from outside contaminants such as oxygen. But an important thing to remember with Dual Shield FCAW is that though there are two methods of shielding the weld, both are required since the wire is designed to be used with shielding gas. If you run out of gas in the middle of welding, you can expect to see pinholes and slag inclusions in your weld! The two most common shielding gases that are used for Dual Shield are 100% carbon dioxide or less common, a mix of 75% carbon dioxide and 25% argon. The reason the mix is less common is that it is more expensive.

• Self-Shielded (Innershield)

Innershield is Lincoln Electric’s brand name for what we know as self-shielded FCAW (FCAW-S). It uses DCEN (Direct Current Electrode Negative) as its polarity. This means that about ⅔ of the heat from the arc is concentrated on the workpiece while ⅓ of the heat is burning the electrode. Unlike Dual Shield, the wire for Self-Shielded FCAW does not require a shielding gas. It is intended to be used without shielding gas. Between these two wires, this is the preferred method for those who work outdoors. Ironworkers and people who do a lot of mobile welding repairs tend to prefer Self-Shielded.

• Other Variables

These two wires that are listed are simply the two largest categories for Flux-Cored welding wire. The most common FCAW wires are geared toward welding mild steel. But others are high in nickel and are designed for welding special alloys. All of these wires come in a variety of sizes as well. In a fabrication setting, the selection will usually depend upon the WPS (Welding Procedure Specification). Wire diameter can affect the deposition rate and depending on the setting of the machine, can make or break the proper weld size.

• Dual Shield

Dual Shield welding is most often used in fabrication shops, especially those that deal with structural steel. Since it has such a high deposition rate and effective weld penetration, it has all but completely replaced Stick welding in a fabrication setting. FCAW for fabrication is one of the easier processes to learn. Most of the welding can be done in the horizontal or flat position. When the welds required are out of position, unless the workpiece is massive, it can be rotated to facilitate welding in the flat or horizontal position.

• Self-Shielded

Innershield is the preferred choice for welding outside. This makes it the favorite for those exposed to the weather. Since it is designed to be used without shielding gas, it can be used in high winds. Often in a construction setting like the erection of a skyscraper or other tall office building, Self-Shielded welding will be used in conjunction with Stick welding. This is because Self-Shielding welding uses more equipment. If the work is to be done up high, though the deposition rate is much lower, it is oftentimes easier to throw a small Arc welder in the scissor lift. Carrying the MIG equipment can be a hassle in certain situations since it’s a more complicated setup.

• Efficiency

FCAW is one of the most efficient welding processes out there. It’s used by fabricators and construction workers alike. The primary reason that it is used so widely is its efficiency. The deposition rate can be 10 times higher than Stick welding. Since the filler metal runs off of a wire-feeder, this also means that you will not have to make as many stops and starts. With SMAW, 14-inch rod electrodes will not get you as many passes as FCAW.

• Facility

Depending upon the application, this is one of the easiest welding processes to learn. While no welding process is easy to learn, welding instructors often recommend that their students get their certification in FCAW-G since it is one of the easier tests to pass and it opens up more job opportunities. FCAW uses a welding gun as used in standard MIG welding. The arc is relatively stable due to the CV current. The welding gun is easier to control than a 14-inch electrode hanging out of a stinger (Stick electrode holder). 

• Environment Specific

While it is true that FCAW can be used outside with Self-Shielded, and indoors with Dual-Shield, there are cases where this rule does not apply. The carbon-dioxide or other shielding gas can be blown away even from a mild breeze blowing into the shop or work area. This can be remedied in a variety of ways.

Even though Self-Shielded can be used outdoors, even in inclement weather, it is not a safeguard against water. A little moisture near the weld zone is not going to hurt, but it’s not recommended that you weld over a puddle of water either.

• Defects

Okay, so defects are a problem in all welding processes. They are almost exclusively due to user error. But there is an additional downside to flux-cored arc welding defects. If you weld fast, you make mistakes equally fast. There’s nothing worse than laying a root pass in overhead for a groove weld only to find out that it was full of porosity because you ran out of gas. This means you will have to grind, or carbon-arc gouge the weld out and start over. Not fun to do if you’re working overhead! Common defects with FCAW are undercut (where the base metal is penetrated but not filled in) slag inclusions (pockets of flux stuck in the weld), porosity (pinholes in the weld appearance), and lack of fusion.