The fifth major type of welding connection is the corner joint. As its name implies, this joint is used to connect two parts together to form a corner. This weld type is extremely useful and can be preformed with either a high or low energy density welder. There are a total of four common sub types of corner joint, each, as usual, with its own advantages and disadvantages.
The first common corner joint sub type is made but beveling both parts, usually at 45 degrees for a 90 degree joint, then placing the two faces together, and melting the outside edge. This is usually done with a low energy density welder but a high-energy density welder can be used. A weld bead may also be added to the inside of the corner to reinforce the weld. This weld is fairly fast and easy to create, but can have problems with strength due to the relatively low area of the weld, as well as aesthetic appearance.
The second type of corner joint is essentially a butt weld between two pieces that are perpendicular rather than complainer. This weld can be done with a low energy density welder if the parts are small enough, but is usually done with a high energy density beam. This allows deep penetration and can form a weld that is as strong as the base material. This advantage of strength is countered by the joints increased proneness to deformation, as well as the increased difficulty and equipment cost of the weld. As in the case in normal butt joints, the edges may be machined prior to welding to improve fit, alignment or welding properties.
The third type of corner weld is the melt though weld. In this weld, the corner is assembled and the beam is used to melt through the top component and into the lower component. This type of weld works best when the top piece is relatively thin compared to the bottom piece, allowing it to be melted through with minimal energy input. This type of weld is preformed exclusively with high energy density sources. This weld can be made easily without the need to precisely follow a joint, but it can be week due to the very low cross sectional area of the weld. If necessary, multiple passes can be made if the bottom piece is sufficiently thick, improving the weld strength.
The final major type of corner joint is truly a flange joint. This is used for making corners in plates or foils that are too thin for the other types of weld. To make this type of joint, one a 90-degree flange is made in one of the components. This flange is then aligned to the other piece to be welded, and the welder is run over the edges of the two parts. This melts the edges together and forms the weld bead. This method can be used with either a high or low energy density source and is fast and reliable, but tends to make extremely week joints due to the leverage and odd stress angles that the flange causes.