How To Weld Sheet Metal With Flux Core Welder – Step by Step Guide

Last Updated on: by Richard Boyer

Normally, highly-skilled welders make perfect welds with efficient tools and techniques. When using arc welding machines, it's important to have proper eyes and hand coordination. However,  there are common problems of sheet metal welding with the flux-cored technique. 

How to Weld Sheet Metal With Flux Core

This technique has some positives too. In this article, you will learn how to use flux core welding machines with challenges.

What Is Flux Core Welding (FCAW)?

The flux-cored welding process was developed in the mid-1950s. It's an automatic electric arc welding process that uses a flux-filled encore, and hollow (wired) electrodes. Also, it might come with self-shielded gas that protects the weld. However, the Flux-core arc welding (FCAW) machine continuously feeds its electrode into the joint with flux.

While the FCAW is not prone to cold lapping, the process comes with high weld-metal deposition rates. It's not ideal to use flux-cored processes for very thin (below 20 gauge) materials. Instead, this self-shielded flux-cored process is ideal for welding dense portions of steel materials.

It's important to know that Flux-core arc welding (FCAW) is different from shielded metal arc welding (SMAW) and MIG welding techniques. Most times, the FCAW comes with a built-in shielding feature. However, FCAW machines require metal fillers (wire) as electrodes for their arc, but they work differently.

The Advantages Of Flux-Cored Welding Process

  • Flux-cored welding is ideal for outdoor procedures
  • It's suitable for underwater welding, shipbuilding, pipeline fabrication, and general repairs
  • The machine is portable, and its welding process penetrates base metals very well
  • The flux-cored process is great with thicker metal sheets (at least 20 gauge)
  • It's suitable for welding dirty metal surfaces and can withstand the wind

Disadvantages Of Flux-Cored Welding Process

  • It's not suitable for welding thin metal sheets
  • This process produces welds that aren’t very attractive. So, flux-cored welders switch to the MIG process (indoors) for finer welds.
  • It produces a slag on weld area, but you can chip off the slag.

How To Weld Sheet Metal With Flux Core

Types Of FCAW Welding Process

During infrastructural projects, the weldability for fabricating steel structures need high wire feed speed. The FCAW welding process offers amazing chemical and mechanical properties for heavy-duty fabrications. However, this flux-cored welding process has different types. 

The Self-shielded Flux-cored Welding

This type of FCAW is also called the no-shielding gas process because it doesn't need an external shielding gas. It's a wire welding process with a core of multiple fluxes. Usually, the hollow (consumable) electrode houses its flux core. During welding, heat from the electrode produces inert gas that protects the weld pool.

Advantages Of Self-Shielded Flux-Cored Welding Process

  • This FCAW welding machine is portable
  • Welders can penetrate base metals with high intensity
  • There's no need for any external shielding gas like Argon to protect the weld pool
  • The self-shielded flux-cored process is ideal in windy conditions.
  • It's easier and faster to set up this type of FCAW process

Disadvantages Of Self-Shielded Flux-Cored Welding Process

  • Creates more noxious fumes that are excessive
  • There will be porous weld pools when welders lack the skill to set up or choose the right electrode for a self-shielded flux-cored machine
  • This process is not ideal for thin materials (less than 20 gauge)
  • It creates a bad weld when you use the welding gun from a wrong angle
  • This type of FCAW process generates slag and spatter, and welders need to clean the weld after their task

The Gas Shield Flux-Cored Welding Process

This type of FCAW welding is also called the 'dual shield' process. It has a unique shielding method that's ideal for fabricating structural steels. Since wind and moisture are bad for welding tasks, this FCAW process is your ideal choice during these conditions. These FCAW welding machines use consumable electrodes that protect the flux from environmental impacts.

According to experts, this process integrates gas metal (GMAW) welding methods. Their reason is that it uses an external shielding (inert) gas, and a flux-cored electrode. Usually, the inert shielding gas is a blend of 25% carbon dioxide and 75% of argon. However, you can use only carbon dioxide for this process.

Advantages Of Gas Shield Flux-Cored Welding Process

  • You'll get consistent mechanical accuracy with fewer weld defects
  • This FCAW shielding method doesn't need an extra inert gas tank
  • When you weld with this process, there's more ease of movement (increased mobility)
  • It's ideal for welding out-of-position metals.
  • Welders don't have to struggle to clean the slag formed by the flux
  • It's ideal to use this process for welding thicker (more than 20 gauge) sheets of metal
  • This gas shield process allows welders to have a higher production rate. They wouldn't need to insert new electrodes like the SMAW method 

Disadvantages Of Gas Shield Flux-Cored Welding Process

  • It produces more fumes than MIG welding machines.
  • When welders use this process indoor, they will need a well-ventilated space
  • The flux-cored process is more expensive than simple welding methods.

More Reading: Fix An Exhaust Leak Without Welding

How To Weld With Flux-Cored Welding Process

1) Safety is an important part of any welding project. Normally, exposures to metal particles and UV radiation can affect our organs. Ensure to use the right personal protective equipment (PPE). The PPE includes a flame-proof long-sleeve jacket, leather gloves, auto-darkening helmet, safety boots, and glasses.

2) Welders require special techniques to avoid downtime from wire feed failures. One of these malfunctions is called a burnback. The burnback condition happens when the wire fuses with the contact tip and forms a ball. Usually, insufficient feed speed from a wire causes the burnback.

3) Insufficient space between the base metal and the welding gun can cause a burnback. To prevent the problem, please ensure an ideal feed speed. Additionally, keep a distance (at least) 1.25 inches between the contact tip and base metal.

4) The problem of birdnesting causes poor weld quality. During FCAW welding, this condition tangles the wire and prevents it from being fed. Also, this condition can extinguish the arc intermittently. To prevent the problem, please attach special drive rolls like the U-groove and knurled V to the wire feeder.

5) During the FCAW welding process, the core could stick on the weld area. This condition occurs with a molten flux and wrong placement of weld beads.

6) Use the right travel angle and speed techniques. It's between 15 and 45 degrees for horizontal, flat, and overhead positions. Also, the ideal drag angle for vertical positions is between 5 and 15 degrees.

7) Maintain a 'drag' angle that's recommended for your type of FCAW gun. This instruction can improve welder's visibility.

8) After the FCAW welding process, clean the weld area that has been covered with slag.

Final Note

Understand how to weld metal pieces with FCAW technique can make your projects fast. It's important to choose the right welding process. As a professional welder, familiarizing yourself with the right tool makes you more skillful. During projects, you can provide value with FCAW welding machines. Get a reliable FCAW machine and boost your confidence!

Richard Boyer
 

Richard wants to educate you, inform you, and prepare you to make the best decision you can concerning welding related items.

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