Flux Core Welding: How To, What Is It, Tips

Did you know that there are different types of welding for you to choose from, the same way there are different plasma cutters on the market?

Many novice welders are surprised by this fact. They thought that all welding is just the same, not realizing that their differences lie in the small details. And for those who want to learn how to weld, this can be overwhelming.

So if you want to learn, where do you even start? What welding type should you study first?

A lot of welders would say that MIG welding is the easiest to learn and is most suitable for beginners. But there are also others that claim flux core welding is better because the learning curve is a lot easier even when compared to MIG welding.

If you are planning to do your welding outdoors and can’t be bothered with all the necessary prep work in most welding types, then flux core welding is right for you.

Don’t know how to do it? We’ve got you covered!

In this article, we will explain what it is, how to do it, and some important tips to help you master it.

What is Flux Core Welding?

To start with, you first need to know what exactly flux core welding is and how it is different from other welding types, particularly MIG welding.

Also referred to as FCAW, flux core arc welding is one of the types that involve the creation of an electric arc and the use of welding wire. Because this wire is directly attached, it is constantly being fed to the welding gun when in operation.

This welding process starts with the creation of an electric current when the base metal and wire meet while the equipment is in operation. Once they separate, there is a resulting electric arc hot enough to fully melt the wire and partially melt the base metal. This now creates a molten pool of the wire and metals. When this pool cools down, it solidifies and the weld joint is formed.

Flux core welding only requires minimal equipment, namely your chosen flux core welder with the welding gun attached, your workpiece, and the right welding wire. This is generally much simpler than the setup required in other welding machines, specifically the more popular TIG welders and MIG welders.

Flux Core vs MIG: Are They the Same or Is One Better Than the Other?

If you already have some background when it comes to welding, particularly in MIG welding, you may have noticed that flux core welding shares some similarities. After all, they both involve a wire directly fed to the welder.

Its entire process is a lot like MIG welding and that is why they are often confused with each other.

So, are flux core and MIG welding just the same? If not, which one is better?

The answers to those questions depend mainly on one thing: the shielding gas.

Did you notice that this gas was never mentioned when we discussed what flux core welding is? That is because this is where the difference between the two becomes obvious.

MIG welding, also known as metal inert gas welding and gas metal arc welding (GMAW) also involves continuous wire feeding to the welder. However, it requires the use of a shielding gas that will protect the welded area from contamination. This shielding gas is also continuously being released at the same time as the wire.

You might think that having a shielding gas is a lot better, so why bother with flux core welding? While it does not use a separate shielding gas, its alternative serves the same function.

The wire used in flux core welding has a hollow center that is filled up with flux, unlike the solid wire used in MIG welding. As this wire melts, this flux now creates its own version of the shielding gas to protect the metals from contamination while welding.

Essentially, both MIG and flux core welding have components that prevent the contamination of the metals while welding – they just do it differently. MIG welding requires the use of a separate tank for the shielding gas that should be connected to the welder, but flux core welding does not.

This is the main difference between the two. But because of their similarities, some MIG and flux core welders allow you to do both welding types using a single welder.

There are also other noteworthy differences between the two, such as:

  • MIG welding is limited to welding thin metals or those of medium thickness, while flux core welding can work with thicker materials
  • FCAW allows you to weld faster than MIG welding, which means you can do a lot more with it
  • MIG welding creates a neater looking weld and weld beads, while flux core welds can get porous and create “wormholes” on the weld
  • Fumes and spatter are present more in FCAW than in MIG welding
  • The shielding gas used in MIG welding makes it suitable for indoor welding only, while FCAW allows you to weld both indoors and outdoors
  • While welding generally involves preparing the base metals prior to welding, FCAW is more forgiving in that aspect. The wires used in FCAW contains de-oxidizing elements, which makes it capable of welding materials even with rust, oil, and other contaminants present
  • The overall cost ends up cheaper when MIG welding is used because the wire used in FCAW is more expensive than the solid wire in MIG welding
  • MIG welding has deeper penetration, while it is rounder in FCAW and requires you to remove the slag present after welding

If you were to pit flux core versus MIG welding to know which one is better, you will not get a straight answer. Both have their own advantages in specific situations, that is why we cannot judge if one is better than the other overall.

But if weld strength is your primary concern, don’t worry because they are equal in that aspect.

What Is It Used For?

Because of its similarities with MIG welding, people assume that flux core welding can also be used for the same applications. While they can often be used interchangeably, FCAW is more often used for industrial applications.

This welding type is seen as more cost-efficient because it can be done automatically or semi-automatically, welds much faster, has better weld penetration on thicker metals (e.g. nickel-based and iron alloys and structural steel), and does not require a thorough cleaning before you can start welding.

While it involves using a more expensive welding wire, FCAW also allows various industries to cut costs especially if plenty of welding is needed.

Some of its common applications include:

  • Shipbuilding and other shipyard-related applications
  • Underwater welding
  • General repairs
  • Manufacturing
  • Welding of pipelines
  • Indoor and outdoor welding, including in a windy environment
  • Agriculture, such as those involving farming equipment
  • Automobiles
  • Welding metals with dirty surfaces, especially those that can no longer be easily cleaned
  • Anything involving mild steel

While you can use flux core welding for various metals with varying thicknesses, it is recommended that you use it on metals with a minimum thickness of 20 gauge. But you plan to weld on thinner materials, you will get better results through MIG welding.

How to Flux Core Weld

If you consider yourself a novice, learning how to flux core weld is one of the essentials you should know first. In fact, both manufacturers and seasoned welders claim that mastering it will only take you about an hour on average. And once you master it, you can easily move on to learning the other types.

Flux core welding does not involve complicated steps, but what is important is to properly set up your equipment. After that, it is basically a point-and-shoot process. If MIG welding is called the “hot glue gun” of welding, you can also think of flux core welding as such.

The general process of flux core welding semi-automatically involves the following:

  1. Once you set up your equipment, including connecting the appropriate welding wire to it, you may opt to clean first the surfaces of your base metals
  2. Secure the materials using clamps or anything similar
  3. Switch on the welder and adjust it to the recommended settings, depending on your materials. Most welders come with a chart that you can use as your reference.
  4. Squeeze the trigger to start welding. The speed of travel will depend on the material being welded.

But when it comes to automatic flux core welding, the machine will do everything for you. You only need to monitor its operation.

Flux Core Welding Techniques

Flux core welding can be done in all positions, but there are also specific techniques recommended for specific purposes and situations. In particular, there are four techniques available: forehand, backhand, weave bead, and stringer bead.

Forehand Technique

Typically used for welding thin materials, the forehand technique involves moving the electrode over the weld site following the direction of welding, as if you are pushing it away. While it can be used in both horizontal and flat positions, it is more ideal for overhead fillet and vertical up welding positions. Splatter is quite common but you can lessen it by using the right angle of travel.

This technique also gives you a better view of the molten pool created and the joint itself, making it easier for you to weld. If you are using a flux core arc welder that is gas-shielded, this is the technique that you should use.

Backhand Technique

In contrast, the backhand technique is similar to stick welding, which requires moving the electrode along the welding site but in the opposite direction of welding. Also known as the drag technique, this is the most popular FCAW technique and is used if you require a deeper weld penetration.

You can only use this technique in the 4g, horizontal, and flat positions. And if you want to minimize spatter, use this technique in the 4g position. Also, the molten pool is not as visible with this technique since you are doing a pulling motion.

Weave Bead Technique

Traditional welding involves traveling in a straight path but in the weave bead technique, you create the weld beads in a zig-zag direction. This technique is rarely used in FCAW welding but when used, it is done in a vertical position only.

Stringer Bead Technique

For the stringer bead technique, weld beads are made following a straight line. It requires faster weld travel to lessen the heat input on the base metals. Another commonly used FCAW technique, this can be also be done in any position.

Note that these four flux core welding techniques are all easy enough to learn, even for beginners.

Welding Sheet Metal with Flux Core

Sheet metal may be one of the more complicated materials to weld, but it is possible with flux core welding. However, it is complicated to do so because this material is heat-sensitive. You need to have adequate heat control when welding, which is hard to achieve with FCAW.

Still, welding sheet metal via flux core welding is doable and follows its usual procedures. But because it is more suitable for welding thicker materials, you typically need to start with the lowest settings available.

Also, it may be hard to get the right settings in one go, so do a test weld first on scrap sheet metals before you start welding on the actual workpieces.

Once the sheet metal becomes warped or distorted, which can easily happen when using the wrong settings, it will be very difficult and time-consuming to remedy the issue. That is why you need to prevent it from happening in the first place.

Flux Core Welding Aluminum

Aluminum is another material that can be a challenge to work with. This is because it has properties that make it complicated to weld using any type.

Flux core welding involves the use of a welding wire that matches or at least closely resembles the base material to be welded. If you plan to weld aluminum via FCAW, this means you need to use an aluminum welding wire.

But does that even exist? No.

Simply put, you cannot weld aluminum using FCAW. But if you need to do so, you need to use other welding types.

Want to keep reading? Here’s a great article on another topic we’ve covered – how to use a plasma cutter.

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