Building has always been the profession of creatives in every era of human history. Whether that be the building of the pyramids, the Eiffel Tower, or the Empire State building, every type of constructive truly is an art form. In current times, our most commonly used building materials are concrete and steel.

Considering building with steel, we could not accomplish it without expert welders who make possible all the wonderful structures, products, and other physical items that we enjoy in our age of human history. So, what do welders know that the typical citizen may not be aware of?

Well, the very first thing that comes to mind is the specific welds that are possible, and the two fundamental types of these welds are the fillet weld and the butt weld. Butt welding is typically combining two pieces of metals together, usually done on pipes.

Today let’s inspect what is a butt weld, specifically and figure out what it does, and what the distinct types or techniques of butt welding are possible. The first area that is important to talk about is what really is a butt welding and the differences between the joints?

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What Is Butt Welding?

Well, when talking about this type of weld, we are looking at the way we join together two metal pieces. What is a butt weld?

A butt weld is a common welding joint that combines two pieces or sheets of metal end to end, that are leveled, i.e. on the same axis and/or parallel to one another. The two pieces are typically flat surfaces/circular pipes that are combined to become a strong single piece of metal through the correct application of butt weld techniques, of which there are four main types. These types of butt welds are the square joint, v joint, u joint, and the j joint.

To create a strong butt weld you first choose the proper joint type needed to make sure you achieve full penetration of both metal faces and that the gap between the two, typically set at about 1/8th of an inch apart, can be filled fully with whatever your filler material is while maintaining the proper angle.

Once prepared, you will simply create an arc and heat up a point between the two pieces until they both become molten. Then, while adding filler material to the gap and maintaining the molten pool, you push at the proper angle and move the pool along the entire seam evenly. Once you reach the end you should have pushed out any contaminants into the upset and have created one continuous and single piece of metal out of your original two sides of material.

When done correctly the butt welding finish is smooth and pleasing surface without unnecessary grinding or brushing to remove uneven areas in your welded seam. Both sides of front and back will have an equally smooth face, that only the perfect butt weld can create.

Single-sided welding is when the welds are done from one area.

Image Credit: https://www.svets.se/download/18.274ebf1415b8cd45d523c10b/1510575524112/Part+05+-+Risks+with+the+new+standard+EN+ISO+2553+2014.pdf

Double-sided welding is when the welds are done on both sides of the material, they require more precision and specific angled cuts in order to have a clean fit. (See the video above at 9:06)

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Different Types Of Butt Welding Joints:

This butt weld joint is best if used on metals of a 3/16-inch thickness or less. This is because of the level of penetration required in thicker metals to fill the joint and create a strong weld. A square joint weld is the simplest type of joint weld for butt joints because it requires no major preparation of the material.

The V Joint Butt Weld:

The next type of butt weld joint to consider is the simple V joint butt weld. This welding joint is created by cutting or grinding your edges of the material to be joined into a V shape by creating a beveled edge of about 60 degrees into each side of the base material. When put together the gap between the two pieces should make a V shape when viewed from the end of the pieces. This type of joint is best for materials of around a ¼ inch thick or more. This is because it allows for a full penetration into the material, which helps create a stronger weld than would otherwise be possible.

Also, there is a double V joint that is used in much thicker material, say around 3/8 inch or larger. This is done by beveling from both sides of the material so that the end of each side of the material to create the butt joint each makes a V shape on their own. When combined the two ends make an hourglass shape in their gap. This joint is then welded together with a bead going down each side of the material that penetrates to the middle of the pieces. This type is used so you can create a strong weld even in thick material that would otherwise not be possible to fully penetrate with a single-sided weld with your filler material.

The U Joint Butt Weld:

Like the V joint, we use the U joint when combining thicker materials end to end, i.e. butt to butt. This type of joint is made by grinding a curved groove into each side of the material that resembles a C shaped groove on each material's end. When combined, and viewed from the end of the pieces, these two grooves create the U shape that makes up the joint’s namesake. We use this type of butt weld in the connection of thicker metal materials because it offers you the ability to create full penetration. This type takes more filler material to create a strong weld than would a V joint but is sometimes easier to work with, in the long run.

Then there is the double U joint. This butt weld joint is made by creating a C shaped groove from the outer edge of the material into the middle of the piece and one on each side. When looking at one side of the joint, i.e. one piece of metal, then it will look like a small bite was taken from each corner of the metal and creates a point in the middle. Then, when you combine the two pieces, the gap in between again resembles an hourglass shape. Except for this time, it looks like a regularly curved hourglass rather than a straight-edged one as in the double V joint. This type of joint is used in very thick metals so you can create the proper channel in each side for penetrating to the middle of the pieces of metal and create a strong joint by working your way down each side of the joint (front and back).

The J Joint Butt Weld:

The fourth and final type of butt weld joint is the J joint. This type is the most economical way of combining two thicker pieces of material because you will use less filler material from your welding. This is because the preparation for this type of joint involves only grooving one of the two pieces of metal you are connecting. When making the groove you just grind down one of the two pieces so you create the same shape you would have for a single U joint. Then, when you set the two pieces up to be welded, the gap between them looks like a J up against a straight-sided piece of metal. Since the groove your are going to be filling with welding material is only half the size of a regular U or V joint, it makes this the most economical option for welding together two thicker pieces of metal while maintaining the penetration required to create the strong bond you are seeking.

Then there is the double J joint type of butt weld. This type is for even thicker pieces of metal and is created by grooving both sides of one of the two pieces of metal. Just as you would if you prepared that piece for a double U joint, but instead of preparing by grooving both pieces, you are only doing this to one of them. So, when set up in position for the welding to take place, the gap between the two pieces, when viewed from one end of the metal, will look like a j and an upside-down j pressed up against the flat vertical wall of the other piece of metal. This is where it gets the name double J joint butt weld. The weld is created by running a bead down each canal the has been created by the J shaped grooves ground into the one end. 

These are the basic types of butt welds that are considered when we talk about joining two pieces of metal to each other side by side and parallel to one another. There may be other more specialized options or variations of these basic four but knowing these are important in creating strong and reliable welds of parallel pieces of metal.

Benefits of Using a Butt Weld

  • Butt welds are strong and secure welds that are versatile in their applications. They can be used in many situations such as end to end pipe connections or in continuously running rail systems.
  • They are easy to create once you know how to prep the materials for the type of joint you want and that will achieve full penetration with a level finish once the canal is filled with your filler material.
  • All of the various butt weld joint types can be used on an array of different metals including aluminum alloys, nickel alloys, all kinds of steel including stainless steel, titanium, and more.
  • A full-fledged forge weld is created, and any contaminants that got brought out during heating get pushed out into the upset. This means the risk of cracking and other issues that come about during solidification are minimized or even eliminated completely.
  • The joint is leakproof and solid, making it an excellent weld for piping and can create one continuous section of steel or other metal through multiple pieces of material.
  • Butt welding can be done using a variety of methods including flash, fusion, upset, and others. Each with its own advantages and disadvantages of their own and each with this a specific application that they are best used for.
  • These types of welded butt joints, if performed correctly, are very strong and also smooth on the surface. They are attractive looking welds that join two pieces of metal together until they are essentially one continuous piece.

What are Typical Filling Agents?

In order to create a strong joint between your materials, you will use a vise or clamp to fix them together. Many welders use a class 3 copper solution as their filling equipment of choice, conducting heat very well and giving strength and flexibility to your project.

How Do I Choose The Right One?

If you are looking to join together two different pieces of metal, you definitely will want to use a butt joint weld, but choosing the right kind for your needs is where it gets a little tricky.

Remember, a simple square butt weld is useful for thinner pieces of metal, where you want to use a V-shaped or double V-shaped butt weld for thicker pieces. As you learn about, what is a butt weld and gain more experience in the field, it will be easier for you to make the best possible choice for the different type of joints to preform.