Welding is a complex craft that requires patience, attention to detail, and creativity. To do their job successfully, welders must have a deep understanding of the various techniques and practices used in the industry, including the types of welded joints.
The term “weld joint design” refers to the way metal parts are joined or aligned with one another. The design of each joint affects the quality and cost of the finished weld. Selecting the most suitable joint design for a welding job requires special care and skill.
What is Welding Joint?
A welding joint is a point or edge where two or more pieces of metal or plastic are joined together. They are formed by welding two or more workpieces (metal or plastic) according to a particular geometry.
There are five types of joints referred to by the American Welding Society: butt, corner, edge, lap, and tee. These configurations may have various configurations at the joint where actual welding can occur.
Types of Welding Joint
According to AWS, there are five basic welding joint types that are commonly used in the industry:
- Butt joint welding
- Tee joint welding
- Corner joint welding
- Lap joint welding
- Edge joint welding
The term weld joint design refers to the way pieces of metal are put together or aligned with each other. The five basic joint designs are butt joints, lap joints, tee joints, outside corner joints, and edge joints. illustrates the way the joint members come together.
1. Butt Joint Welding
A butt weld is one of the simplest and most versatile types of welded joints. The joint is made simply by placing two pieces of metal together and then welding them along the join.
In a butt joint the edges of the metal meet so that the thickness of the joint is approximately equal to the thickness of the metal. The metal surfaces are usually parallel with each other, although there can be some difference in thickness or misalignment of the plates. Butt joints can be welded from one side or both sides with some form of groove weld.
Types of butt weld joints
Butt welds are made in different ways, and each serves a different purpose. Typical examples of butt weld joints include:
- Square butt weld. The square butt weld is primarily used for projects where metals are 3/16 inches or less in thickness. The square butt weld joint is quite strong, but it is not recommended if the finished structure is subject to shock loads or fatigue with prolonged use.
- Grooved butt weld. If you want to weld metals more than 3/16 inches thick, you will likely need to use the grooved butt joint. The grooving of the metal plates is used to give the connection the necessary strength. Thicker metals have more space to apply the filler and the grooving of the sheets results in a more permanent bond.
- V-butt welding. The single V butt weld is more common on frames 1/4 “to 3/4” thick. The tapered angle for the connection is generally about 60 degrees for the plate and 75 degrees for the pipe. You can prepare the metal with the help of a special chamfering machine or a cutting torch. The V-shaped weld seam is more expensive to manufacture than a square butt joint. You will also need more filler material for this weld than for the square joint.
- Double V butt welding. The double V butt weld is great for a wide variety of projects. Its main advantage is that metals greater than 3/4 inch thick can be grooved on either side. However, it can be used on thinner metal plates where load resistance is critical.
2. Tee Joint Welding
Tee welds are created when two parts intersect at a 90 ° angle. This causes the edges to converge in the center of a panel or component in a T-shape. Tee joints are considered a type of fillet weld and can also be formed when a tube or pipe is welded to a base plate.
Tee joints are usually not grooved unless the base metal is thick and the welding on both sides cannot withstand the load the joint must bear. A common defect that occurs in Tee joints is the rupture of lamellae, which occurs due to a limitation of the joint. To prevent this from happening, welders often use a stopper to prevent joint deformation.
3. Corner Joint Welding
Corner joint welding refers to instances in which two materials meet in the “corner” to form an L-shape. You can use corner joints to construct sheet metal parts, including frames, boxes, and similar applications.
To complete this joint, begin by tacking the outside edges, then make the same curved zig-zag weaving motion we made for our filleted tee weld.
Corner joints can be hard because you can’t often rest your hand on your material to steady your torch hand. You may want to practice a dry run along the joint to make sure you’re going to be able to weld comfortably, I’ve gone as far as clamping a vice grip to another piece of material to create a hand rest.
The styles used for creating corner joints include V-groove, J-groove, U-groove, spot, edge, fillet, corner-flange, bevel-groove, flare-V-groove, and square-groove or butt.
4. Lap Joint Welding
Lap welding joints are essentially a modified version of the butt joint. They are formed when two pieces of metal are placed in an overlapping pattern on top of each other. They are most commonly used to join two pieces with differing thicknesses together. Welds can be made on one or both sides.
In a lap joint the edges of the metal overlap so that the thickness of the joint is approximately equal to the combined thickness of both pieces of metal. The distance the surfaces overlap each other may vary from a fraction of an inch to several inches or even feet.
Lap welds are usually joined by making a fillet weld along the edge of one plate, joining it to the surface of the other. There are several alternate ways of welding lap joints where the weld is made through one or both pieces of metal joining the lap in the center of the overlap.
Some examples of this would be plug welds, seam welds, and stir welds. Welds can be made on one side or both sides of the joint.
Potential drawbacks to this type of welding joint include lamellar tearing or corrosion due to overlapping materials. However, as with anything, this can be prevented by using the correct techniques and modifying variables as necessary.
5. Edge Joint Welding
Edge welding Joints are often applied to sheet metal parts that have flanging edges or are placed at a location where a weld must be made to attach to adjacent pieces. Being a groove type weld, Edge Joints, the pieces are set side by side and welded on the same edge.
In an edge joint, the metal surfaces are placed together so that the edges are even. One or both plates may be formed by bending them at an angle. The purpose of a weld joint is to join parts together so that the stresses are distributed. The forces causing stresses in welded joints are tensile, compression, bending, torsion, and shear.
The ability of a welded joint to withstand these forces depends upon both the joint design and the weld integrity. Some joints can withstand certain types of forces better than others. The welding process to be used as a major effect on the selection of the joint design. Each welding process has characteristics that affect its performance.
Welding Joint Design
Welding drawings and specifications usually tell you exactly which joint design will be used for all of the welds to be made. Often a welding engineer or designer has determined the best type of joint to be used.
However, on small projects or on some repair welding jobs, you will be making the decision as to the joint design to be used. The way the pieces of metal fit together may determine the joint design that must be used.
Joints on every weldment are not as easily determined. If you are the one choosing the weld joint design, you must consider a number of factors. Some of the factors involve the type and thickness of the metal being welded, the welding position, welding process, finished weld properties, and any code requirements.
The selection of the best joint design for a specific weldment requires that you carefully consider all of the various factors. Each factor, if considered alone, could result in a part that might not be able to be fabricated or meet the strength requirements.
For example, a narrower joint angle requires less filler metal, and that results in lower welding costs. But if the angle is too small for the welding process being used, the weld cannot be made strong enough.
A large weld may be stronger, but it may result in the part being distorted so badly that it becomes useless. The purpose of a welded joint is to join parts together so that the completed weldment can withstand the stresses.
The forces acting on a weld cause stress. Forces cause stresses in five ways: tensile, compression, bending, torsion, and shear. If the stresses are excessive, the part can fail. The ability of a welded joint to withstand these forces depends both upon the joint design and the weld integrity.
Some joints can withstand some types of forces better than others. Some of the factors that affect the selection of a specific weld joint design include welding process, edge preparation, joint dimensions, metal thickness, metal type, welding position, codes or standards, and cost.
Advantages of Welding Joints
- The welded joint has high strength, sometimes more than the parent metal.
- Different materials can be welded.
- Welding can be performed anyplace, no need for enough clearance.
- They give a smooth appearance and simplicity in design.
- They can be done in any shape and any direction.
- It can be automated.
- Provide a complete rigid joint.
- Addition and modification of existing structures are easy.
Disadvantages of welding Joints
- Members may become distorted due to uneven heating and cooling during welding.
- They are permanent joints, to dismantle we have to break the weld.
- High initial investment
Application of Welding Joints
Welding is widely used for the fabrication of pressure vessels, bridges, building structures, aircraft and space crafts, railway coaches, and general applications in shipbuilding, automobile, electrical, electronic, and defense industries, laying of pipelines, and railway tracks, and nuclear installations.
- Fabrication of sheet metal.
- Automobile and aircraft industries.
- Joining ferrous and non-ferrous metals.
- Joining thin metals.
There are five basic welding joint types commonly used in the industry, according to the AWS:
1. Butt joint welding.
2. Tee joint welding.
3. Corner joint welding.
4. Lap joint welding.
5. Edge joint welding.
The five basic weld joints include the butt joint, the lap joint, the tee joint, the corner joint, and the edge joint. The butt joint occurs when two members are placed side-by-side or butted together.
They are formed by welding two or more workpieces (metal or plastic) according to a particular geometry. There are five types of joints referred to by the American Welding Society: butt, corner, edge, lap, and tee. These configurations may have various configurations at the joint where actual welding can occur.
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