What are the 6 types of welds and when should you use each type?
Officially, there are 5 types of weld joints: butt, T-joint, lap, edge, and corner. However, many might consider tack welding to be a sixth—and very useful—type. The type of weld joint necessary depends on many factors, least of which is the amount of stress the weld may endure.
Interested in learning more about the 6 types of welds? Keep reading! We’ll discuss each type of weld in-depth, including when to use each one and for what applications. You’ve probably seen many of these welding joint types in your everyday life. You just haven’t stopped to consider and respect their usefulness.
It’s All About Positioning
Welding is defined as joining 2 separate pieces of metal together, through a process of melting material from both components and adding additional material. Welding 101 teaches us that. However, to simplify the welding process in so many words means we lose a certain amount of complexity associated with the task. Amperage, filler rod makeup, puddle size: these are all just minor examples of the thought process necessary to achieving proper welds. And that’s not even considering the metals sitting on the welding table in front of you.
Really, the correct type of weld joint in any given situation depends on how you are joining the 2 pieces of metal. Do you need to overlap them? Will there be an outside force or forces acting upon either (a) the 2 metals or (b) the joint itself? The answers to these questions can often mean the difference between a large structure withstanding large amounts of force or buckling under high/heavy pressure.
The 5 types of welding joints differentiate themselves based on how you join the 2 metal pieces. The positioning of the 2 in regard to one another often gives away which type of weld joint you’ll need to use, but there can often be multiple ways to achieve the same result. As we discuss each type, consider which factors and applications most closely fit your project.
While theorizing how a joint might react to stress can be easy for some, there’s no replacement for real-world stress environments. Ideally, you’ll want to create a few test pieces if you’re unsure of what weld joint to use, but a general rule of thumb states the stronger you can make it, the better.
The 6 Types of Weld Joints
Let’s take a closer look at each of those 5 types of welding joints, along with tack welds. If you’re already familiar with the 5 types, you’re probably aware of the usefulness of tack welds. However, if you’d like to learn more about tack welds specifically, skip down to the end of this section for more information. It’s crucial to know of these 5 types, but of all, tack welds will come in handy the most. In fact, you may find you use tack welds more often than you do any other kind of weld joint.
Butt Weld Joints
The first type of weld joint we’ll discuss is the butt weld. This is perhaps the most common type of weld joint because the 2 pieces of metal are joined on the same plane, butted up against each other. Think of putting one piece of bread right next to another on the table. The side which joins both pieces utilizes a butt weld. That is, when you’re actually joining metal. Not bread.
In using a butt weld joint, it’s crucial to consider the penetration and quality of your welds. Butt welds hold up best against lots of stress when done properly. While even the best butt welds will shrink across the seam of the joint, expert welders should use that contraction to their advantage. Pull the metals together tighter and the overall piece should be stronger than the 2 are separately.
If you’re looking to maintain a smooth surface, a butt weld is your go-to joint. Because butt welds require deep penetration and only work across one plane, it’s easy to weld your pieces and grind any excess bead flat. For this reason, butt welds are plentiful and often used in fabrication. WeldingGeek.com states butt welds are used in pipes, fittings, and frames, and if you look hard enough, butt welds shouldn’t be hard to spot. Butt welds are easy for automated welders since there’s very little skill involved, so you’re likely to have more butt welds in your life than you might imagine.
Perhaps one of the most visually self-explanatory weld joints, T-joints (sometimes written as tee-joints) meld one piece of metal across the flat surface of another piece of metal. Essentially, you have an upside-down “T” shape. You can also think of T-joint welds as having a pair of 90-degree angles opposite one another.
For this reason, among others, T-joints are most common in construction welding. The flat base allows for structural support. Because T-joints require welding on 2 sides of the work pieces, they are often stronger than other common types of weld joints. They may require gusseting in some cases. Drawing upon the high structural integrity of the triangle shape, gusseted T-joint welds could be stronger than even butt welds might be.
Lap Weld Joints
The easiest way to remember how lap weld joints look is to think of overlapping pieces of metal. While lap joints might not be the strongest joint out there, they are a great way to extend your work piece to get the job done.
Lap joints are typically welded across the longest seam of the 2 work pieces, at minimum. Depending on the application and stress factors, you might also want to place the weld bead all the way around the joint itself. Placing the bead across the longest seams ensures higher rigidity in the final piece. The individual pieces themselves cannot break away from one another without first encountering the welded joint.
Lap joints can be found in a variety of applications. WeldingGeek.com states you can find them in a lot of weight and exercise equipment, but these joints are not just exclusive to welding metals. According to Corrosionpedia.com, lap joints are used in woodworking and plastics as well. The most common use, however, is in the automotive field. Lap joints are used in vehicle frames and even aircraft fuselages. They can often be used to repair unibody automotive frames where they will be subjected to a static load. Because they aren’t the strongest joint of the 6 we’re focusing on, it’s not a good idea to expect too much of lap joints when stress levels are higher than normal.
Edge Weld Joints
Meld a butt joint, lap joint, and a corner joint weld together and you’ve got something close to what an edge joint looks like. To visualize what a common edge joint looks like, place your hands out in front of you, arms extended with your palms touching. Now, pull them towards you in a praying position, with your fingertips pointed upwards. Typically, you’d weld edge joints where your fingertips touch one another, and down the sides of your pointer and pinky fingers. Depending on the application and stresses involved, you might weld the seam on the inside of your knuckles as well.
Edge joints are not the strongest joints. In fact, you might be better off moving towards pieces that utilize a T-joint instead. With a T-joint, you don’t have to weld as much material and it’s easier to achieve deeper penetration. In some cases, however, edge joints are both necessary and unavoidable. In those instances, direct stress to other points of the final piece as much as possible. Edge joints do not hold up well to stress and are often the most replaced joint because of it.
Corner Weld Joints
As you might expect, corner joints come from welding the corners of 2 pieces of material together. There are 2 main types of corner welding joints: open and closed. Differentiating between the pair relies on, you guessed it, positioning.
In each instance, however, you’ll want to weld on the inside seam of the 2 pieces of material. While that’s bare minimum for a corner weld joint, applications might require you to stitch the pieces together along the entire joint surface. Depending on what the finished product will be used for, you may need to weld the seam in one pass, and/or both sides of the joint. Corners tend to take a lot of stress and wear and tear, so opting for a stronger joint from the get-go is in any welder’s best interest.
Some might even consider corner joints to be almost type of butt weld joint. However, butt welds join along a smooth surface. Corner weld joints add a second dimension to this equation, increasing the complexity. When welded (and ground down) properly, butt welds can easily become invisible to the naked eye. At the same time, corner joints could potentially fall into the same category. The best welders can make a joined piece look milled out of one chunk of metal.
As we mentioned, tack welding can be considered another type of weld joint. More part of the welding process than the finished product, tack welds can vary in size depending on your application. A tack weld holds work pieces together so that they line up correctly when welded. You can use other methods of holding your work in place, but sometimes tack welds are all you have in the area you’re working in.
Tack welds are essentially just small weld beads. They can be ground off if needed and don’t do too much to deface the pieces you’re working on. If you’re working on pieces that require a strong bond, thicker tack welds with high penetration are key. However, as long as the pieces you’re working on stay together, tack welds don’t have to perform beyond that critical step.
Knowing how many tack welds to use depends again on what you’re welding together. Generally, the fewer tack welds you add on, the better. Your grinder will thank you and you won’t waste welding materials. Most of the time, tack welds vary between ½ inch and ¾ inch. They sometimes measure around 1 inch in diameter, but anything beyond is excessive.
Tack welds are a great tool to use during the welding process and in fact, they may even become part of the final welds. The next time you find yourself in a pickle while welding, try out some tack welds. After all, you’ve already got all you need!
Which Weld Joint is Right for Me?
Now that you know the different types of weld joints, how can you accurately (and easily) choose between them? The answer lies within your specific application and the various factors that affect your work piece.
There are a few things to consider when choosing between weld joints. Obviously, in some instances the weld joint is chosen for you. If you have to join 2 pieces at a corner, there you go! Problem solved. All the same, perhaps you’re not even at the welding stage yet. Tweaking a design in the planning stage may even help you head off any dilemmas ahead of time. The more cognizant about these factors you can be, the better.
Another way to be sure of the correct weld joint choice is to consider what others have used in the past. What worked well for them, and what do they recommend for anyone working in the same application? You might prioritize strength over aesthetics. Look to welded structural components often covered up by things like drywall and insulation. If detail is a big deal to you, consider which weld joint will require the least amount of grinding.
Real World Applications
Knowing how to weld can open many doors in your life. After all, the welding business holds near unlimited potential for those willing to learn and most importantly, practice. Brushing up on which types of weld joints exist, and when to use each, is something you might consider part of your initial education. However, some welders might come to these joints later in their careers. No matter what, expanding your welding abilities only increases your proficiency and potential.
Now that you know a bit more about weld joints try them out! Whether it’s on a few test pieces or a project of your own, weld joints come in handy a lot. Happy welding!