Flux Core Welding: Understanding Its Preparation And Functions

Flux core welding comes as a viable process with a history dating back to the 1950s. It appears as an alternative to shielded metal arc welding. Moreover, it uses a consumable electrode tube containing flux as the welding agent. Since then, welders used it on a variety of projects, from steel erection to bridge construction.

What is Flux Core Welding?

Dual Shield Flux Core Welding Vertical Up Project Showing the root pass, two stringers, and 3 cover passes

Flux core welding, also known as Flux core arc welding (FCAW) or tubular electrode welding, remain as an automatic or semi-automatic arc welding method.  Here, the arc between a continuously-fed electrode tube wire and the workpiece generates the heat for welding. The tubular electrode contains the flux, which melts during welding.

The usage of flux core welding started in the 1950s. Although, most people thought of it as an entirely new method.  It proves its use through the new electrode utilized in a MIG (melting inert gas) welding machine on the theories & basic practices of welding.

In fact, MIG welding and flux core welding appear similar. Both MIG and FCAW have automatic and semi-automatic capabilities. They both use continuous electrode feeds with the same type of power supply and both have a high production rate.

Self-Shielded Versus Gas-Shielded Flux Core Welding

There remain two types of FCAW – self-shielded and gas-shielded. Self-shielded FCAW has frequent outdoor applications, where the wind blows away the shielding gas. It doesn’t require any external shielding gasses such as carbon dioxide (CO2) or argon.

Instead, the tubular electrode contains flux and other ingredients. Also, when they come in contact with high temperatures, create their own shield to protect the weld pool from getting contaminated. The benefits of this method include the fact that it uses dirty or rusty metal.

And, it comes easily to carry around. Yet, still powerful enough to go through the base metal. There exists few disadvantages self-shielded FCAW. It produces too much noxious smoke, which, among other things, make it hard to see the weld pool.

The Flux Core Welding and Your Job

Fully-Geared Men Doing Flux Core Welding on a structural support beams in the Grand Central Terminal Biltmore Room

FCAW produces slag that has to be chipped off. Uses of self-shielded FCAW include repairing heaving equipment, building bridges and other outdoor construction projects. Learning these in welding schools come handy and ensures skill efficiency.

With gas-shielded FCAW, an external source provides the shielding glass. Sometimes referred to as “dual shield” welding, this type of FCAW comes better used for welding thicker metals. Metals come out of position or metals in a closed environment.

Some of the benefits of using gas-shielded FCAW include the fact that it produces better welds with fewer defects. The slag gets easier to remove and operators appear more productive. They don’t have to stop to get a new electrode constantly. One of its disadvantages, unlike the self-shielded FCAW, it does not work outdoors.

Before Getting Started With Flux Core Welding

As with any repair or construction job, make sure you have the proper equipment and safety gear. This includes steel-toed leather boots, full-length denim pants without cuffs, and welding helmet. A background of welding symbols surely helps.

Also, prepare a flame-resistant jacket, forearm length leather gloves and skull cap or bandana to protect your head.  Be sure to remove anything fire hazard before starting any project.

Prepare the Metal

Surprisingly, flux core welding seems more forgiving of dirty surfaces. It always occurs as a good idea to clean the metal you’re going to be working on as much as possible. Wipe off any rust or chipped scales to keep them from contaminating the weld. A good metal brush or a similar tool should be able to get the job done.

You also want to clean the part of the base metal where the ground clamp attachment. Inadequate contact with the ground clamp means likely to be resistance in the welding circuit. This leads to poor quality.

Prepare the Equipment

Men Preparing and Checking Metals for Flux Core Welding Job

Primarily, checking your cables remain as the first thing to do when getting your equipment ready. Specifically, connect tightly all your cables. Also, remove any knots and objects that block the way. Unraveling the cord or moving any obstacles in the middle of your project feels inconvenient.

Next, decide whether you need to use DC electrode negative or straight polarity. Then, look on the inside of the machine next to the drive rolls.

The Steps

Speaking of the drive rolls, make sure that you use knurled drive rolls as opposed to standard drive rolls. Using knurled rolls in flux core welding wires remain softer than solid wires. Knurled rolls clamp down on the pliable wire without damaging it.

Then, check the tension in the wires. If the wires seem too tight or too lose, the wire feeding won’t work as it should.

Lastly, make sure your contact tips come in good shape. Do this by removing any leftover spatter and replacing the worn down ones. In addition, look for rust on contact tips and liners and throw them out if you spot any.

Avoiding Common Issues on Flux Core Welding

Man during a Flux Core Welding Job of a monumental sculpture inside a workshop

As with any project, you’re going to run into challenges. Notably, ensure to complete your project with a few setbacks as possible. So, do your best to prepare for them ahead of time. The least amount of surprises you face, the better off you become. Afterward, expect better quality outputs and welding projects in the future. 

Wire Feeding Issues

Wire feeding malfunctions remain as one of the primary causes of downtime during welding projects. Birdnesting and burn back comes as the two most popular types of feeding issues.

Birdnesting occurs on a tangle that prevents the wire from feeding properly. Burnback takes place when the wire gets burned at the end of the contact tip. Most likely, due to the wire feeding too slowly or the welding gun too close to the metal.

To prevent birdnesting, make sure to always use U- or V-groove drive rolls in your wire feeder. To avert burn back, ensure the right feed speed for your project. Hold the gun where the contact tip comes no closer than 1 ¼ inches to the metal.

Protect Against Slag

Accordingly, ensure the little slag included in the weld as possible. Accomplish this by improving your technique in four ways:

  • Ensure an accurate bead placement
  • Maintain the correct travel angle and speed
  • Make sure the correct weld heat input
  • Clean off any excess slag in between passes

Avoid Undercutting

Man Fully-geared Doing Flux Core Welding Job under a Truck

Undercutting happens when a groove melts in the base metal close to the bottom of the weld. But, the weld metal does not fill it up. Hence, this leads to cracking because it leaves a weak spot at the bottom of the weld.

To keep this from happening, use the appropriate voltage and welding current.  Make sure that your gun comes at the proper angle.

Prevent Insufficient Fusion

Obviously, improper fusing brings major problems in your metals. Limit this by making sure an appropriate heat input and work angle. Get the right work angle by placing the stringer bead in its correct spot at the joint and adjusting the work angle.

Or, open up the groove to access the bottom during welding as necessary. Make sure to wipe off any dirt, or debris that prevents the two metals from fusing.

Get Proper Penetration

Too much or too little heat during welding cause issues with penetration. Too little penetration happens when there’s only a shallow fusion between the base metal and the weld metal. To prevent this from occurring, choose a higher wire speed, select a higher voltage or decrease the travel speed.

On the other hand, prevent too much penetration where the weld melts through the metal and sits below it. So, do the exact opposite. If you notice over penetration, simply select a slower wire speed, bring down the voltage and use a faster travel speed.

Practice Makes Your Flux Core Welding Perfect

Instructor and a Student Observing on a Welding Class during a Flux Core Welding Job

Like anything else, a novice at welding feels challenging at first. Then, take some time to master the beginner’s welding techniques and deliver flawless output. Even individuals who have experience with welding still struggle with certain aspects.

The key is to continue to work at it, pay attention to your mistakes and try to fix them the next time around. Knowing all the rules only helps to a certain extent. After that, the more experience you have, the better off you’ll be.

Flux core welding has been used reliably to create high-quality welds for a long time. Many great projects have been completed using this method. So, whether you’re using self-shielded for an outdoor projector gas-shielded for an indoor project, you’re looking for an alternative to melding methods such as MIG.

Then you should give flux core welding a shot for your next job. As long as it’s an approved method for your project, you just need to be sure to figure out the equipment that you’ll need and have a solid grasp on the various techniques, and you’ll be on your way to a successful project.

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