Types of welds used in welding steel structures
Each structure, whether steel, concrete or composite, is an object created by combining many elements in order to build a solid, indivisible and properly functioning whole. In today’s article, we will focus on welding steel structures and the types of welds used in their creation. What are they and what is their use? You will find the answer to this questions below.
What is welding?
This question probably appears in the mind of every novice engineer who is just starting his adventure in the welding industry. Welding is nothing more than one of the methods of point joining or surface of two materials, in this case metals, using very high temperature, in order to bond them together. This operation can be performed with or without a welding filler. As for the heat source, it is of course the welding arc.
Weld - what is it?
Now that you know what welding is all about, we will focus a little more on the subject of welds. A welded joint or a weld, colloquially known as a weld, is a kind of joint that will be created as a result of the process of physical joining two materials through their local melting and solidification. Binders are most often used to join steel and plastics. Sometimes the joint is filled with a special additive material that fuses with the main material (the so-called welding filler material). Each of the basic types of welds is briefly characterized below.
Types of welds
Depending on the type of weld, we divide into:
- marginal welds
Marginal joints are usually used to join very thin sheets – their thickness should not exceed 3 mm. In this case, it is necessary to properly prepare the sheet, which should be slightly bent. As for the welding process itself, it does not require the addition of a welding filler. This type of weld is usually found in butt joints and rebate angle joints.
- butt welds
These are the welds that are formed between the wall of one element which is the thickness and the other element. They can be in the form of full or incomplete remelting. If the weld is fused into the base material along the entire thickness of a given element, then full remelting should be made. Otherwise, i.e. in a situation where the weld does not cover the entire thickness of the joint, then it is called a partial or incomplete remelting weld. Butt welds are usually found in angular and butt joints. It is recommended to avoid the use of intermittent butt welds and the formation of eccentricities – characteristic elements in the form of a circle bent into a ring guide. They are most often used for butt joining sheets, pipes and bars.
- hole welds
Hole welds are the most specific type of all welded joints. As the name suggests, in this case, the welding process focuses on filling the designated round or oval-shaped holes in one of the sheets of the connecting element with adhesive. These openings can be provided with oblique walls, which additionally facilitate fusion of the adhesive. Extremely important in this case are the dimensions and spacing of the holes, the diameter or width of which should be 8 mm greater than the thickness of the sheet. As for the spacing of the opening welds, it is recommended here that it should be adjusted in terms of maintaining the stability of the structure. Hole welds occur in lap joints. Usually used to strengthen fillet welds connecting wide elements.
- field joints
Field welds are divided into equilateral and non-equilateral. They are made in the groove between the two non-tapered walls of the joined elements. In the case of this type of weld, their face can be flat, concave or convex. Field welds are usually found in rebate and angle joints. They are used primarily for overlapping joining sheets and other elements set at an angle.
- intermittent field welds
As you can easily guess, this is a special type of field welds, characterized by the segmental appearance of welds in a staggered or symmetrical arrangement. Unfortunately, their disadvantage is that they are highly susceptible to corrosion, so they are not recommended for use in such places. Moreover, such welds should not be performed also in the case of dynamic loads, in the zones of abrupt changes in stiffness, and in the situation of simultaneous occurrence of normal and tangential stresses.
- circumferential field welds
The use of such welds is only possible if they are intended to prevent separation and bulging of the lap portions, and also when they are subjected to shear. Depending on the shape of the whole, its diameter or width should be at least four times bigger that the thickness of the sheet. Sharp edges should be avoided, and also in this case it is worth paying attention to the spacing of the welds so that it is optimally adjusted in terms of stability.
- ridge welds
Ridge welds, as well as edge welds, are used for joining thin sheets. They are performed both on the parallel parts of the sheet and its previously folded edges. As for the thickness of the weld, it should be equal to the sum of the height of the welded joint and the depth of the fusion line.
- spot welds without holes
Point welds, similarly to hole welds, are used to strengthen field welds connecting wide plates. This type of weld is created by fusing one of the elements and fusing into the other, directly below it. They appear mainly in lap joints.
- line welds without holes
Line welds without a hole are formed by the accumulation of point welds. In this case, the welds touch each other or overlap directly, creating the so-called linear welds