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The hidden secrets of welded joints: Do you know which welding methods are best for different metal thicknesses?
In metalworking, a welded joint is the joint or edge of one or more pieces of metal or plastic. These joints are formed from two or more workpieces welded according to a specific geometry. According to the definition of the American Welding Society, there are five types of welded joints: butt joints, corner joints, edge joints, lap joints and T-joints. These types come in a variety of configurations for the actual welding process and can be adjusted as needed.
Butt connector
Butt joints are structures in which two pieces of metal are placed parallel and welded together. This type of joint requires minimal preparation and is suitable for sheet metal that can be welded in a single pass. Common problems with butt joints include trapped welding slag, excessive porosity or cracks, which can weaken the weld. For strong welds, the goal is to use the least amount of weld material. This has led to the widespread use of butt joints in automated welding processes, as their relatively simple preparation makes them easier to automate.
Type
There are many types of butt joints, including single-sided butt joints, double-sided welded butt joints, and open or closed butt joints. A single-sided butt joint is welded from only one side, while a double-sided butt joint is welded from both sides and may have slightly different weld depths. A closed joint is when two pieces of metal are in contact with each other during the welding process, while an open joint is where a small gap exists before welding.
Square butt joint
Square joints are flat and parallel butt welding methods. The preparation of this type of joint is relatively simple, low cost, and provides satisfactory strength, but is limited by the thickness of the joint. Closed square joints are square joints with no gaps and are often used for gas or arc welding. For thicker joints, the edges of each joint must be prepared with a specific geometry to enable welding and ensure the soundness and strength of the weld.
Single-sided V welding is similar to a bevel joint, but has bevels on both sides.
V-shaped joint
Single V welding and double V welding are often used to weld thick metals. Double V joints are more commonly used when welding can be done from both sides. Compared with single V joints, double V joints require less filling material and are more favorable in resisting deformation forces.
J-type connector
Single-sided J-butt welding is where a J-shaped groove is formed in one piece of metal to accept the filler material, while the other piece is flat. Although J-joints are more difficult to prepare, a single J-joint provides a stronger weld on metals between half an inch and three-quarters of an inch and requires less filler material.
U-shaped connector
The edges of the welding surface of a single U-shaped butt weld appear J-shaped, but combine to form a U-shape. Double U-shaped joints have U-shapes above and below the prepared joint. Because U-joints are more expensive to prepare and weld, they are typically used on very thick substrates.
T-type connector
T-shaped welded joint is to weld two bars or plates together at a 90-degree angle to form a T-shape. This type of welding can be done by resistance butt welding or extrusion welding, and usually does not require any filler metal during the welding process.
Other connector types
Sheet metal often needs to be edge flanged to produce edge flange or corner flange welds. These welds usually do not require filler metal as the flange itself will melt and provide the required filler material. For example, pipes and tubes are usually made by rolling up metal sheets or plates and welding them together.
The choice of welded joint depends on the thickness of the material and the welding process used.
Standards and preparation
In welding practice, the welding surface needs to be prepared in advance to ensure the firmness of the welding. Preparation for most welded joints is relatively simple, but butt joints still require certain preparation. The most common preparation techniques include oxygen acetylene cutting, machining, chopping, grinding and air carbon arc cutting. Each technology has its specific advantages when used.
Did you know that the selection of welded joints varies depending on the thickness of the metal and the welding method?
