In the construction industry, when welding massive metal structures at the joints, serious loads occur, which, if the technology is not followed, carries the risk of collapse of the structure. This is relevant in the ship industry and mechanical engineering (when constructing large-sized automatic machines), in the construction of massive buildings. A quality connection must be initially calculated to avoid possible future deformations. The easiest way to check the correctness of the weld line is to find out the leg of the seam.
The leg of the weld is called the leg of a conditional triangle, which fits into the cross section. There is no single figure that would become an indicator of a reliable and high-quality seam when determining its leg. The larger the size of an isosceles triangle that can be entered instead of a seam, the greater the load it can withstand. Often this characteristic depends on the type of metal and the voltage limit to which itcan resist. An increase in the leg gives the opposite effect - the part is deformed and will not be able to work in the desired mode.
How to determine the size of the leg?
To determine the optimal welded joint, you need to calculate the seam, and also determine the leg of the seam during welding. The following factors are taken into account:
- thickness of metal blanks;
- position of parts relative to each other;
- type of seam used when joining.
For each product, the leg is selected individually, but here we are talking only about working with heavy loads. For private use of welding, fine calculations are not needed, but still professionals take into account the properties of the metal and try to make the seam strong and not harm the details. The leg of the seam is set along the edge if the two parts have the same thickness. If different, then the leg is determined by a thinner metal. It is important to choose and calculate its size correctly. After all, the maximum power that the part can resist depends on this. The leg of the weld is determined by the GOST 5264-80 standardization system.
The leg of the seam during welding is equal to the thickness of the sheets with an overlap joint, but at the same time it should not exceed 4 mm. If this parameter is greater, then you should take 40% of the metal thickness and add 2 mm. This way you can determine the maximum value of the leg of the seam.
How to choose a leg?
The leg of the seam is determined when welding reinforcement in the same way as when joiningany other elements of metal structures. The size depends on several parameters, including the position of the blanks, their length and thickness. Professionals use templates that welders have already developed before them. The main parameter is the length of the weld, because it is it that affects the strength of the future structure. Material consumption and the likelihood of deformation are the main dangers with a long seam. Much depends on the type of seam that will connect the parts.
Butt weld
A butt weld involves the following technology - to connect two butt welding elements (i.e., arrange the parts with the ends of the surfaces in the same or different planes). There are more than 30 types of butt joints, all of them are provided by GOST. In this case, the dependence on the thickness of the welded elements, equipment and welding technology is carried out. If the structure will be subjected to stress of a variable nature, then this method of junction is the most reliable. Various parts can be joined and welded. It can be not only sheets of metal, but also pipes, corners, channels. To weld two sheets, they do not even need to be in contact with each other - welding is carried out with a minimum distance of two blanks.
Splice
Op-joining is a welding method where parts are parallel and their edges overlap. Unlike a weld, there are only two types of overlap joints. The ends of the products can be welded withtwo sides or one. There is also a connection using an additional pad, which is welded to two parts, connecting them at the right angle. The parts are overlapped using two types of seams - end and frontal. The welding mode with this connection may be higher, since there is no danger of burning through the surfaces.
Corner connection
Welding of two parts, the edges of which are located at an angle relative to each other, occurs by the method of fillet connection. The standard distinguishes up to 10 types of such joints. Sometimes, for the strength and reliability of the weld, a special metal lining is used, which allows better joining of the elements and makes the structures more reliable. In load-bearing structures, this type of connection is rarely seen, therefore, calculations for such seams are not made. Nevertheless, if this type of welding is necessary, calculations are made by analogy with a tee joint and the type of weld must be taken into account.
T-weld joint
It often becomes necessary to connect elements that are located in different planes. The best solution in this case is a tee joint, where the end of one workpiece adjoins another at a right or other angle. The types of such connections differ within 9 types provided by GOST. A tee joint requires deep penetration at the junction, the seam is usually made by automatic welding, or the edges are prepared in advance, for example, with a fillet weld, which can be done manually, or butt. seam type,which the connection was made affects its calculation. This takes into account the fact that the weld, pre-treated, will be much stronger than the base metal.
Seam quality control
In any of the seams, one should not forget about the leg of the seam when welding, the formula of which is not complicated and consists in determining the thickness of the metal. If it is less than 4 mm, then the leg is taken equal to it, if more, then in the range of 40% - 45% of the thickness with an increase of 2 mm. The formula for calculating the leg: T=S cos 45º, here T is the required leg, and S is the hypotenuse or the width of the weld bead.
It is not difficult to control the connection of workpieces, while using visual and instrumental methods (using instruments). A tool has been developed that determines the leg of the seam during welding. How to measure the seam of interest to them? To do this, you need to attach the device to two parts of the workpiece, and direct the middle to the seam, then write down the indicators and carry out a simple calculation. Usually the seam turns out to be convex, but this is the most unreliable option. After all, it is in this form that tension is concentrated.
The ideal option is a concave seam, which is quite difficult to obtain. Here you need to observe the speed of welding, as well as to achieve the correct operation of the welding machine. Experienced craftsmen will be able to make such a seam. But more often it is obtained mechanically, simply by cutting off the unnecessary part of the seam.
