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Five Most Common Types of Weld Joints

Date: 10-07-2023
MMA Welding Welding MIG Welding

5 Most Common Types of Weld Joints - Alphaweld

It's vital to choose a suitable joint type to get the most out of your welds. The five most common weld joints are the butt, lap, edge, "T" (tee), and corner joint.

They have pros and cons, but the joint selection mainly comes down to the application, time and resource constraints, welded thickness, welder's skill, welded material, and the forces the weld needs to endure in service.

5 Most Common Weld Joints

You should always choose a weld design that requires the least amount of filler metal to meet the strength requirements. Otherwise, unnecessary internal stresses will remain, and you risk distortion and burn-through.

Every joint should be designed to avoid stress raisers and minimise residual stresses, while enduring the forces like tension, compression, shear, bending, and torsion, depending on the application. But you should also account for the joint's corrosion resistance and the ability for crevices and irregularities to form in chemically aggressive environments.

Butt Joint

Butt joint configuration is the most commonly used weld joint type for plate and pipe welding applications. Both welded pieces should be of similar (preferably the same) thickness and placed in the same plane so that their edge faces run parallel to each other to form a butt joint. You can weld it from one or both sides for improved weld strength.

However, to achieve the best butt joint weld quality, bevelling the edges of one or both pieces is often required. You can grind or gouge the joint ends during the edge preparation to form the following butt joint types:

• U-groove
• V-groove
• Single or double bevel
• J-groove
• Square butt joint (no edge preparation)

While bevelling or gouging a groove improves weld penetration and strength, it requires additional filler metal. So, you can limit the edge preparation to one edge only at a steep angle (e.g. 60 degrees) to reduce the heat input when weld distortion must be avoided. 

Sometimes it's necessary to create a root opening between the welded pieces to ensure maximum penetration and alignment. You can use a welding gauge, like the GAL Single Purpose Hi-Lo gauge, to accurately measure the root opening. Using an even root opening along the entire joint line is vital. 

Lap Joint

A lap joint is formed when two sheets of metal overlap, and the weld is deposited in the intersecting joint(s). You should always weld both intersecting joints whenever possible to improve the structure's rigidity.

Lap joints are most commonly used to join thin metal sheets but can also connect medium-thickness plates. The thicker the plates, the more overlap is needed.

It's crucial to ensure complete overlap of the surfaces. The pieces should be as flush as possible, without any gaps. But this becomes a problem when welding thicker plates in the lap joint configuration due to the increased need for the arc amperage. So, keep the power output to the lowest possible and use a relatively fast travel speed to prevent warping and gaping between the pieces. Use high quality clamps to firmly clamp the pieces to a horizontal surface like the welding table to prevent warping and distortion. 

The lap joint is at a higher risk of lamellar tearing and corrosion due to overlapping materials. So, consider an alternative when used in a chemically aggressive environment or when the steel is likely to contain contaminations that contribute to lamellar tearing.

Tee Joint

A tee joint is shaped like the letter "T" and is formed by two welded members at 90-degree angles to one another. It's one of the strongest joints you can weld, especially when welded from both sides. Tee joints are applied in construction, structural tubing, manufacturing, and heavy-equipment repairs and production. Perhaps the best example of a tee joint is a typical steel "I" beam formed by welding the centre, vertical piece to two horizontal plates in double-sided tee joint configurations.

Tee joints are usually formed using a fillet weld along the edge where the pieces meet at a 90-degree angle. But, you can also bevel the vertical piece to improve weld penetration. Just keep in mind that it's crucial to place the weld on the joint side subject to stress. If the force is applied from the opposite side, the tee joint is likely to fail. If unsure about the force origin and propagation, weld both sides when possible to provide the most robust joint.

You'll see tee joints in almost all welding applications. They are the most straightforward to weld and have little to no downsides, depending on the application. It's easy to hold the vertical component of the tee joint at a 90-degree angle to the surface of the horizontal element using the StrongHand Multi Angle Magnet to tack the joint before welding. 

Edge Joint

Edge joints are used for welding sheet metal pieces that run parallel to one another at the meeting edges. These welds aren't designed to withstand stresses, so avoid applying this joint type for load-bearing or other stresses like torsion.

You can grind the edge joint welds to improve the finish quality if the weld aesthetics are important. Bevelling or gouging the edge joint into a V, U, or J groove can improve weld penetration, but you should still avoid this joint type for stress loading.

Corner Joint

Corner joints are constructed from pieces joined at 90-degree angles but take the shape of the letter "L," as opposed to the tee joints that form a joint resembling the letter "T." 

You can either weld an open or closed corner joint depending on the welded thickness and required weld strength. 

Open corner joint configuration meets the two plates at their edges so you can see the thickness of both elements. On the other hand, a closed corner joint won't let you see both pieces' thickness because one edge is completely flush with the edge of the other piece.

Corner joints can be prone to distortion depending on your travel speed and applied amperage. It's crucial to ensure an even fit up. Use magnets to hold the pieces at a right angle to one another, and consider using a jig fixture to hold the parts in place. 

Need Further Assistance with Weld Design and Fit Up?

If you need expert guidance on choosing the right joining tool for your project, the team at Alphaweld is here to help. Give us a call today on (08) 9456 8000 or email sales@alphaweld.com.au.