What Is Butt Welding? – Basics of Butt Welding Technique and Joint Types

What is butt welding

Butt welding is one of the easiest welding techniques used for joining side by side parallel parts of workpieces. The base materials could be of the same or different thickness and diameter.

It’s the most widely used joining technique for the pre-fabrication of piping systems and creating metal frameworks for factories. Not just that, it’s also a popular welding method for flanges, valves, rail lines, and equipment fittings.

Butt welding is highly cost-effective as you don’t necessarily need any additional components such as shielding gas to make the joints. In this guide, I’ll break down every important detail you need to know about butt welding to kickstart your DIY projects.

Let’s get right to it:

How to Form a Butt Weld?

How to Form a Butt Weld

This kind of joints are forged by holding two workpieces end-to-end and applying heat to melt the electrode which deposits into the gap. Then the molten edges are pressed together to form the joint. Butt welding can be accomplished with the combination of both heat and pressure.

You can either hold the parts of the assembly on a workbench or with the help of a tack weld.

Tack weld is a kind of temporary joint made to keep the weld pieces properly aligned when the butt welding is being performed.

Professional metal fabricators generally use electric arc welding, electric resistance, or high-energy beam welding to form butt joints. For small-scale or non-commercial projects, you can do butt welding using an MIG welder or a brazing torch for copper pieces.

Edge Preparation for Butt Welding

To create strong, reliable butt welds, you must make sure the filler metal penetrates deep inside the weld pieces. That’s why you need to leave at least 2-3 mm or ⅛” gap between the root pieces.

Full penetration is easier with thin pieces of metals, so when working with ultra-thin metals, you may avoid leaving any gap between the pieces.

Conversely, when creating different types of grooves with components thicker than 3/16”, you must first do the edge preparation. You can prep the metal components using a cutting torch, beveling, or chamfering machine.

Edge preparation widens the gap, allowing the molten filler metal to penetrate deep enough into the thick-walled components to yield strong joints.

The most important takeaway here is that if the gap is too big or too small for the metal thickness, the welds won’t be up to the mark.

Filler Material for Butt Welding

Flux-cored TIG rods are the standard choice for filler material for butt welding. When you strike the arc, the filler material melts, creating a pool of molten metal that flows into the passage between the weld pieces to form a joint.

With an MIG welder, you will need a continuous cast copper wire rod. If you are opting for the traditional method of butt welding metal boxes with a blow torch, choose a tin paste solder rosin flux for the job.

A Quick Rundown of the Different Types of Butt Welding Techniques

Butt welding can be done both manually or with the help of auto welding machines. Below I have explained the two most commonly used butt welding techniques for heavy-duty industrial projects and DIY applications:

  • Flash Butt Welding (FBW)

Flash Butt Welding is a type of electrical resistance welding technique. It is the most widely used welding method for building railway tracks. The welder performs this process mainly for joining thick metal pieces of various sizes and complex shapes such as rail lines and heavy-duty pipes.

For flash welding, the base materials are positioned end-to-end. When you apply high voltage current to metal, the gap between the workpieces generates resistance heat, creating the arc for melting the metal.

Once the arc reaches a specific temperature, the flashing begins. It burns off the surface material, revealing a clean joint surface. Once the molten metal starts to cool down a bit, the soft metal pieces are pressed together to produce the joint.

  • Resistance Butt Welding

Like flash butt welding, resistant butt welding is also a kind of Resistance Welding (RW) process that is mostly used for joining workpieces of identical sizes and shapes.

Resistance butt welding

It is a quick, reliable, and simple welding method for joining up to 16 mm metal rods, window frames, specific fixtures, and welding automobile wheel rims.

In this case, the weld pieces are held in electrode clamps that are supported by two platens – one fixed and one movable.

The goal is to make a weld in the cross-section between two pieces in one clean movement.

In resistance butt welding, the metal piece ends touch each other to create resistance against the passage of current. This, in turn, creates contact resistance that heats the pieces.

When the welding temperature is around 925°C, the melted ends are pressed together to form the joint.

Different Types of Butt Weld Joints Listed and Explained

There are several types of butt weld joints, depending on how the workpieces are aligned, prepared, and welded.

  • Grooved Butt Joint

When joining metal sheets thicker than 3/16” work components, you need to bevel the end faces to allow the filler material to flow down the root gap.

This process is also known as edge preparation and is essential to ensure clean, strong joints.

Grooved butt welds can be further divided into two types: single-groove (grooved on only one side) and double-groove (grooved on both sides). Thicker pieces are always double grooved to create strong welds.

Certain thin materials, especially of mismatched diameters, have to be grooved on only one side. There are several other kinds of groove joints named after the shapes they form, e.g. V-groove, double V-groove, J-groove, and U-groove.

  • Square Butt Joint

You can form square butt joints of metal sheets that are less than 3/16” in thickness. There’s no need for edge preparation. You only have to make sure to leave enough root gap for the molten filler material to deposit into.

The process is fairly simple, hence beginner-friendly, but not super reliable. Square butt joints can break apart if subjected to heavy loads. Therefore, I definitely won’t recommend it for structures meant for heavy weight-bearing.

Advantages of Butt Welding:

  • The simplest and the most economical form of welding methods for joining parallelly position workpieces.
  • Can be combined with arc brazing process to join two pieces of copper.
  • Suitable for joining a huge variety of metals such as steel, stainless steel, copper, aluminum, titanium, and nickel alloys.
  • You can easily apply subsequent welds on the joint area using butt welding technique.
  • Allows you to run the machine continuously instead of having to pause every few minutes to get a new supply of metal.
  • Can be performed with the help of MIG welder, arc welder, auto welding machines as well as a standard propane torch.

Disadvantages of Butt Welding: 

  • Not as sturdy as the other, more complex welding joints such as tee joint and lap joint.

The Bottom Line

That was pretty much everything you needed to know about butt welding before attempting the technique. Butt welds are omnipresent.

From your home’s piping system to your bicycle’s wheel rims, down to the railway tracks in your towns- everything uses butt welding, mostly with the combination of other joining methods.

Now that you know the basics, what’s stopping you from getting started with that long overdue project?

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