To permanently connect metal parts to each other by welding, various types of welded joints are used.
Permanent connection of parts made from metal blanks and obtained by melting their edges with an electric arc or gas. At the same time, additional metal is deposited; this can be a molten electrode or a rod specially supplied to the heating zone. As a result of these manipulations, a weld seam is formed at the junction of the workpieces.
Various types of welding are used to connect metal parts. The list of welding technologies is quite large, but the main types include:
- electric arc;
- gas-flame;
- plasma;
- laser and many others.
Main types of welding joints
All issues related to welding are, one way or another, standardized. One of the fundamental documents is GOST 2601-92. This document normalizes the terms and basic concepts in the field of welding. The same document also defines the main types of connections using welding. These include:
Butt
The ends fit tightly to each other. This is a widely used type of connection that can be obtained using various welding technologies. Butt welds have a number of advantages compared to others - high speed of work, and correspondingly high productivity of work performed. Minimum material consumption. High strength of the welded joint, of course, is achieved in full compliance with all technological norms and rules. But the use of a butt joint requires preliminary preparation of the edges, that is, to prepare a chamfer, in addition, it is necessary to ensure the accuracy of the installation of the workpieces.
This type is used for joining sheets, pipes and long products.
Overlapping
With this assembly method, the workpieces are positioned so that their planes are parallel to each other and at the same time partially overlap each other. Connections of this type are most often used when performing spot and resistance welding. In other cases, when making such a weld, the consumption of the metal itself and electrodes increases unjustifiably. When making an overlap joint, there is no need to pre-cut the edges. But in any case, the sheets must be cut using special equipment, for example, mechanical scissors. To avoid corrosion that may occur between sheets of metal, it is advisable to weld such a connection along its entire length.
It is advisable to use such fastening of workpieces if their thickness does not exceed 10 mm.
Angular
The workpieces are positioned relative to each other at a certain angle, and the seam lies at the point of their contact.
Corner connections can be single- or double-sided. They are used when merging parts from sheet metal, shaped products and pipes. The angle can be different, it all depends on the purpose of the structure. A slight complication is that it is necessary to cut the edges of the adjacent workpiece.
Tavrovoe
The end of one workpiece is adjacent to the plane of another, most often at a right angle.
A part installed vertically must have a cut edge. Thus, the adjacency of one part to another is ensured. By the way, when preparing it for welding, depending on the thickness, preliminary cutting of the edge may be required. If the metal is quite thick, for example, over 20 mm, then the chamfer must be removed from both sides of the workpiece. This approach will ensure penetration of the connection.
Tortsovoye
This is a form of merging of surfaces in which the edges of the workpieces being welded are adjacent to each other and the resulting part resembles a cross-section of a sandwich.
Connections made by welding have become widespread in industry and construction. Welding is widely used to replace forged and cast parts.
Technological features of welding work
Any job has its secrets, which for the most part are owned by professionals, and welding is no exception. For example, when making a T-joint consisting of sheets of different thicknesses, the electrode holder should be installed so that the angle between it and the thick sheet is 60 degrees.
Another feature of the T-type design is that the sheets are installed in a “boat”, that is, the angle between the workpiece and the horizontal plane should be 45 degrees. With this form of installation of workpieces, the electrode can be installed strictly vertically. As a result, the welding speed increases and the likelihood of defects such as undercutting decreases; by the way, this is the most common defect in a T-weld. Depending on the thickness of the metal, it may be necessary to make several passes with the electrode. Boat welding is used when using automatic welding.
Classification by connection location
In addition to the above qualifications, welds can be classified according to other characteristics. One of these is by the degree of convexity.
Welds can be divided into:
- normal;
- convex;
- concave.
This parameter largely depends on the parameters of the welding materials and the modes of the welding machine. If a long arc is used when welding, the seam will come out smooth and wide. When using a short arc, the width of the seam will decrease and it will become convex. We must not forget that the speed of movement of the electrode and, of course, the shape and dimensions of the edge cut have a great influence on the quality and geometry of the seam.
Welds can be classified according to their position in space. That is, they can be located - below, vertically and on the ceiling.
The optimal location of the weld seam is considered to be lower. This type of seam is recommended to be used when developing working documentation for products. The welder, when processing the lower seam, stands on top of it and perfectly sees both the movement of the electrode and the process of formation of the seam.
Vertical or ceiling welds can only be performed by welders of certain qualifications. The ceiling location of the seam is the most labor-intensive and unsafe job.
Qualification of welded joints by length
Permanent connections obtained by welding can be divided into continuous and intermittent. The first ones are performed where it is necessary to ensure the tightness of the connection or where, due to strength requirements, it is impossible to use the second option (intermittent)
Normative base
Welding joints can be classified according to different parameters - the geometry of the seam, the type of connection, and much more. When designing a product in which welding seams will be used, the designer must first of all be guided by the results of strength calculations. And only after that choose the method of joining the workpieces.
In their work, designers and manufacturers must be guided by the following documents:
- GOST 2601-84;
- GOST5264;
- GOST15878;
- GOST 15164.
Based on the data from these regulatory documents, it is necessary to determine the geometry of the seam and the type of welding. Only then should the criteria for edge separation, if required, be established. At the last stage, the permissible and maximum deviations of the seam dimensions are determined.
Welding defects
Welding work is considered particularly responsible. And this is understandable. Welding is also used in the manufacture of pressure vessels, pipelines and boilers. And the performance and, most importantly, the safety of the equipment depends on the quality of the connection. Almost all industries and construction sites. Where welding is used, various quality control methods are used. In accordance with the requirements of GOST 3242-79, several control methods are provided for monitoring welded joints. Among them are:
- Visual, it is used when monitoring non-essential connections.
- Ultrasonic - it is used to control various types of connections.
For particularly critical ones, for example, on bridge structures or high-pressure pipelines, the welder must leave a personal stamp.
Welds and connections
A permanent connection that was made by welding is called welded. It consists of several zones (Fig. 77):
Weld seam;
Fusion;
Rice. 77. Welded joint zones: 1 – weld; 2 – fusion; 3 – thermal influence; 4 – base metal
Thermal influence;
Base metal.
According to their length, welded joints are:
Short (250–300 mm);
Medium (300–1000 mm);
Long (more than 1000 mm). Depending on the length of the weld, the method of its execution is chosen. For short connections, the seam is carried out in one direction from beginning to end; for the middle sections, it is typical to apply a seam in separate sections, and its length should be such that a whole number of electrodes (two, three) are enough to complete it; long joints are welded using the reverse-step method discussed above.
By type, welded joints (Fig. 78) are divided into:
1. Butt. These are the most common joints used in various welding methods. They are preferred because they are characterized by the lowest intrinsic stresses and deformations. As a rule, sheet metal structures are welded using butt joints.
Rice. 78. Types of welded joints: a – butt; b – tee; c – angular; g – overlap
Rice. 78 (end). d – slotted; e – end; g – with overlays; 1–3 – base metal; 2 – cover: 3 – electric rivets; h – with electric rivets
The main advantages of this connection, which can be counted on subject to careful preparation and adjustment of the edges (due to the blunting of the edges, burn-through and leakage of metal during the welding process are prevented, and maintaining their parallelism ensures a high-quality, uniform seam), are the following:
Minimum consumption of base and deposited metal;
The shortest time period required for welding;
The completed connection can be as strong as the base metal.
Depending on the thickness of the metal, the edges during arc welding can be cut at different angles to the surface:
At a right angle, if connecting steel sheets with a thickness of 4–8 mm. In this case, a gap of 1–2 mm is left between them, which makes it easier to weld the lower parts of the edges;
At a right angle, if metal with a thickness of up to 3 and up to 8 mm is connected using one- or two-sided welding, respectively;
With one-sided bevel of edges (V-shaped), if the metal thickness is from 4 to 26 mm;
With a double-sided bevel (X-shaped), if the sheets have a thickness of 12–40 mm, and this method is more economical than the previous one, since the amount of deposited metal is reduced by almost 2 times. This means saving electrodes and energy. In addition, double-sided bevels are less susceptible to deformation and stress during welding;
The bevel angle can be reduced from 60° to 45° if you weld sheets with a thickness of more than 20 mm, which will reduce the volume of deposited metal and save electrodes. The presence of a gap of 4 mm between the edges will ensure the necessary penetration of the metal.
When welding metal of different thicknesses, the edge of the thicker material is beveled more strongly. If the parts or sheets to be joined by arc welding are of significant thickness, cup-shaped edge preparation is used, and with a thickness of 20–50 mm, one-sided preparation is carried out, and with a thickness of more than 50 mm, two-sided preparation is carried out.
The above is clearly shown in table. 44.
2. Lap welds, most often used in arc welding of structures whose metal thickness is 10–12 mm. What distinguishes this option from the previous connection is that there is no need to prepare the edges in a special way - just cut them off. Although the assembly and preparation of metal for lap joints is not so burdensome, it should be taken into account that the consumption of base and deposited metal increases compared to butt joints. For reliability and to avoid corrosion due to moisture getting between the sheets, such joints are welded on both sides. There are types of welding where this option is used exclusively, in particular with spot contact and roller welding.
3. T-bars, widely used in arc welding. For them, the edges are beveled on one or both sides or are dispensed with without bevel at all. Special requirements are imposed only on the preparation of a vertical sheet, which must have an equally trimmed edge. For one- and two-sided bevels, the edges of a vertical sheet provide a gap of 2–3 mm between the vertical and horizontal planes in order to weld the vertical sheet to its full thickness. A one-sided bevel is performed when the design of the product is such that it is impossible to weld it on both sides.
Table 44
Selecting a butt joint depending on the thickness of the metal
5. Slotted, which is used in cases where an overlap seam of normal length does not provide the necessary strength. There are two types of such connections - open and closed. The slot is made using oxygen cutting.
6. End (side) in which the sheets are placed one on top of the other and welded at the ends.
7. With overlays. To make such a connection, the sheets are joined and the joint is covered with an overlay, which, naturally, entails additional metal consumption. Therefore, this method is used in cases where it is not possible to make a butt or overlap weld.
8. With electric rivets. This connection is strong, but not tight enough. For this, the top sheet is drilled and the resulting hole is welded in such a way as to capture the bottom sheet as well.
If the metal is not too thick, then drilling is not required. For example, with automatic submerged arc welding, the top sheet is simply melted by the welding arc.
The structural element of a welded joint, which during its execution is formed due to the crystallization of molten metal along the line of movement of the heating source, is called a weld. The elements of its geometric shape (Fig. 79) are:
Width(b);
Height(h);
Leg size (K) for corner, lap and T-joints.
The classification of welds is based on various characteristics, which are presented below.
Rice. 79. Elements of the geometric shape of the weld (width, height, leg size)
1. By connection type:
Butt;
Angular (Fig. 80).
Rice. 80. Corner seam
Fillet welds are practiced for some types of welded joints, in particular lap, butt, corner and overlay joints.
The sides of such a seam are called legs (k), zone ABCD in Fig. 80 shows the degree of convexity of the seam and is not taken into account when calculating the strength of the welded joint. When performing it, it is necessary that the legs are equal, and the angle between the sides OD and BD is 45°.
2. By type of welding:
Arc welding seams;
Automatic and semi-automatic submerged arc welding seams;
Gas-shielded arc welding seams;
Electroslag welding seams;
Resistance welding seams;
Gas welding seams.
3. According to the spatial position (Fig. 81) in which welding is performed:
Rice. 81. Welds depending on their spatial position: a – bottom; b – horizontal; c – vertical; g – ceiling
Horizontal;
Vertical;
Ceiling.
The easiest seam to make is the bottom seam, the most difficult is the ceiling seam.
In the latter case, welders undergo special training, and it is easier to make a ceiling seam using gas welding than arc welding.
4. By length:
Continuous;
Intermittent (Fig. 82).
Rice. 82. Intermittent weld
Intermittent seams are practiced quite widely, especially in cases where there is no need (strength calculations do not involve making a continuous seam) to tightly connect products.
The length (l) of the joined sections is 50–150 mm, the gap between them is approximately 1.5–2.5 times larger than the welding zone, and together they form the seam pitch (t).
5. According to the degree of convexity, i.e. the shape of the outer surface (Fig. 83):
Normal;
Convex;
Concave.
The type of electrode used determines the convexity of the weld (a‘). The greatest convexity is characteristic of thinly coated electrodes, while thickly coated electrodes produce normal seams, since they are characterized by greater fluidity of the molten metal.
Rice. 83. Welds that differ in the shape of the outer surface: a – normal; b – convex c – concave
It was experimentally established that the strength of the seam does not increase with increasing convexity, especially if the connection “operates” under variable loads and vibration. This situation is explained as follows: when making a seam with a large convexity, it is impossible to achieve a smooth transition from the seam bead to the base metal, so at this point the edge of the seam is, as it were, cut, and stresses are mainly concentrated here.
Under conditions of variable and vibration loads in this place, the welded joint may be subject to destruction. In addition, convex welds require increased consumption of electrode metal, energy and time, i.e. it is an uneconomical option.
6. According to configuration (Fig. 84):
Straight-line;
Ring;
Rice. 84. Welds of various configurations: a – straight; b – ring
Vertical;
Horizontal.
7. In relation to the acting forces (Fig. 85):
Flanking;
Face;
Combined;
Oblique. The vector of action of external forces can be parallel to the axis of the seam (typical for flank forces), perpendicular to the axis of the seam (for end forces), pass at an angle to the axis (for oblique ones) or combine the direction of flank and end forces (for combined ones).
8. According to the method of holding molten weld metal:
Without linings and pillows;
On removable and remaining steel pads;
Rice. 85. Welds in relation to the acting forces: a – flank; b – end; c – combined; g – oblique
On copper, flux-copper, ceramic and asbestos linings, flux and gas cushions.
When applying the first layer of a weld, the main thing is to be able to hold the liquid metal in the weld pool.
To prevent it from leaking, use:
Steel, copper, asbestos and ceramic linings, which are placed under the root seam. Thanks to them, it is possible to increase the welding current, which ensures through penetration of edges and guarantees 100% penetration of parts. In addition, the linings hold the molten metal in the weld pool, preventing the formation of burns;
Inserts between welded edges, which perform the same functions as gaskets;
Hemming and welding the root of the seam from the opposite side, without attempting to achieve through penetration;
Flux, flux-copper (for submerged arc welding) and gas (for manual arc, automatic and argon-arc welding) pads that are brought or fed under the first layer of the seam. Their goal is to prevent metal from flowing out of the weld pool;
Lock joints when making butt seams, which prevent burns in the root layer of the seam;
Special electrodes, the coating of which contains special components that increase the surface tension of the metal and do not allow it to flow out of the weld pool when making vertical seams from top to bottom;
A pulsed arc, due to which a short-term melting of the metal occurs, which contributes to faster cooling and crystallization of the weld metal.
9. On the side on which the seam is applied (Fig. 86):
One-sided;
Double-sided.
10. For welded materials:
On carbon and alloy steels;
Rice. 86. Welds, differing in their location: a - one-sided; b – double-sided
On non-ferrous metals;
On bimetal;
On foam and polyethylene.
11. According to the location of the parts to be connected:
At an acute or obtuse angle;
At right angles;
In one plane.
12. By volume of deposited metal (Fig. 87):
Normal;
Weakened;
Reinforced.
13. By location on the product:
Longitudinal;
Transverse.
14. According to the shape of the structures being welded:
On flat surfaces;
On spherical surfaces.
15. By the number of deposited beads (Fig. 88):
Single layer;
Multilayer;
Multi-pass.
Before welding, the edges of the products, structures or parts to be joined must be properly prepared, since the strength of the seam depends on their geometric shape
Rice. 87. Welds that differ in the volume of deposited metal: a – weakened; b – normal; c – reinforced
Rice. 88. Welds that differ in the number of welded beads: a – single-layer; b – multilayer; c – multilayer multipass
The elements of form preparation are (Fig. 89):
Edge cutting angle (?), which must be made if the metal thickness is more than 3 mm. If you skip this operation, then such negative consequences as lack of penetration along the cross-section of the welded joint, overheating and burnout of the metal are possible. Cutting the edges makes it possible to weld in several layers of small cross-section, due to which the structure of the welded joint is improved, and internal stresses and deformations are reduced;
Rice. 89. Elements of preparing cromo
Gap between edges to be joined (a). The correctness of the established gap and the selected welding mode determines how complete the penetration will be across the cross section of the joint when forming the first (root) layer of the weld;
The blunting of the edges (S) is necessary in order to give the root welding process a certain stability. Ignoring this requirement leads to burnout of the metal during welding;
The bevel length of the sheet if there is a difference in thickness (L). This element allows for a smooth and gradual transition from a thicker part to a thin one, which reduces or eliminates the risk of stress concentration in welded structures;
Offset of edges relative to each other (?). Since this reduces the strength characteristics of the connection, and also contributes to lack of penetration of the metal and the formation of stress spots, GOST 5264–80 establishes acceptable standards, in particular, the displacement should be no more than 10% of the metal thickness (maximum 3 mm).
Thus, when preparing for welding, the following requirements must be met:
Clean the edges from dirt and corrosion;
Remove chamfers of the appropriate size (according to GOST);
Set the gap in accordance with GOST developed for a particular type of connection.
Some types of edges have already been discussed earlier (although they were considered in a different aspect) when describing butt joints, but nevertheless it is necessary to once again focus on this (Fig. 90).
The choice of one type of edge or another is determined by a number of factors:
Welding method;
Metal thickness;
The method of connecting products, parts, etc.
For each welding method, a separate standard has been developed, which specifies the form of edge preparation, the size of the seam and the permissible deviations. For example, manual arc welding is carried out in accordance with GOST 5264–80, contact welding – in accordance with GOST 15878–79, electroslag welding – in accordance with GOST 15164–68, etc.
Rice. 90. Types of edges prepared for welding: a – with bevel of both edges; b – with a bevel of one edge; c – with two symmetrical bevels of one edge; d – with two symmetrical bevels of two edges; d – with a curved bevel of two edges; e – with two symmetrical curved bevels of two edges; g – with a bevel of one edge; h – with two symmetrical bevels of one edge
In addition, there is a standard for the graphic designation of a weld, in particular GOST 2.312–72. To do this, use an inclined line with a one-way arrow (Fig. 91), which indicates the seam area.
The weld characteristics, recommended welding method and other information are presented above or below the horizontal shelf connected to the inclined arrow line. If the seam is visible, that is, it is on the front side, then the characteristics of the seam are given above the shelf, if invisible - below it.
Rice. 91. Graphic designation of welds
The symbols of a weld also include additional symbols (Fig. 92).
For various types of welding, letter designations are adopted:
Arc welding - E, but since this type is the most common, the letter may not be indicated in the drawings;
Gas welding – G;
Electroslag welding – Ш;
Welding in an inert gas environment – I;
Explosion welding – Vz;
Plasma welding – Pl;
Resistance welding – Kt;
Welding in carbon dioxide – U;
Friction welding – Tr;
Cold welding - X.
If necessary (if several welding methods are implemented), the letter designation of the welding method used is placed before the designation of one or another type:
Rice. 92. Additional designations of a weld: a – intermittent weld with a chain sequence of sections; b – intermittent seam with a checkerboard sequence of sections; c – seam along a closed contour; d – seam along an open contour; d – installation seam; e – seam with the reinforcement removed; g – seam with a smooth transition to the base metal
Manual – P;
Semi-automatic – P;
Automatic - A.
Submerged arc – F;
Welding in active gas with a consumable electrode - UP;
Welding in inert gas with a consumable electrode - IP;
Welding in inert gas with a non-consumable electrode - IN.
There are also special letter designations for welded joints:
Butt – C;
Tavrovoe – T;
Lap – N;
Angular - U. Using the numbers after the letters, the number of the welded joint is determined according to GOST for welding.
Summarizing the above, we can state that the symbols of welds develop into a certain structure (Fig. 93).
One way to connect parts of a material is welding. The method has found very wide application in various fields. Using this relatively cheap and at the same time reliable method, permanent connections are obtained. Taking into account the types of metals, each of which has its own welding characteristics, differences in work conditions and joint requirements, various types of welds and joints are distinguished.
Welding zones
The fusion zone with partially melted grains is 0.1−0.4 mm of the main metal. When the metal in this zone warms up, its structure becomes needle-like with high fragility and low strength.
The thermal zone is divided into four sections:
The main metal zone begins from a section heated to less than 450 °C. The structure here is similar to the structure of the base metal, but the steel loses its strength due to heating. Oxides and nitrides are released along the boundary, weakening the bond of the grains. The metal in this place becomes more durable, however, it receives less ductility and toughness.
Classification of welded joints and seams
Types of seams are divided into several categories depending on their characteristics. In appearance they stand out:
- Normal.
- Convex.
- Concave.
By type, welds can be single-sided or double-sided. According to the number of passes - single-pass and multi-pass. By the number of layers: single-sided and multilayer (when welding thick metals).
There are also varieties in length:
- One-sided continuous.
- Unilateral intermittent.
- Double-sided chain.
- Double-sided chess.
- Spot welds (created by resistance welding).
Types of seams according to the force vector:
- Transverse - the force is perpendicular to the seam.
- Longitudinal - force parallel to the seam.
- Oblique - force at an angle.
- Combined - signs of both transverse and longitudinal seams.
By spatial position:
According to their functions, seams are divided into the following:
- Durable.
- Durable and dense.
- Sealed.
Width:
- Thread seams whose width practically does not exceed the diameter of the electrode.
- Widened seams are made by transverse oscillatory movements of the rod.
Special connections
Butt. The most common option, representing an ordinary connection of end surfaces or sheets. Their formation requires a minimum of time and metal. They can be done without beveled edges if the sheets are thin. For thick products, you need to prepare the metal for welding, where you will need to bevel the edges to increase the depth of welding. This is relevant for a thickness of 8 mm or more. If the thickness is more than 12 mm, double-sided butt joints and beveled edges will be required. Most often these connections are made in a horizontal position.
Tavrovoe. T-joints are T-shaped and can be single- or double-sided. They can be used to connect products of different thicknesses. If the smaller part is mounted perpendicular, the electrode is tilted up to 60° during the welding process. To carry out a simpler version of boat welding, use tacks. This reduces the likelihood of undercuts. Usually the suture is applied per pass. Today, many machines for automatic T-welding are produced.
Angular. The edges of these joints (at different angles) are often bent so that the seam lies at the required depth. Double-sided welding makes the connection stronger.
overlap. This method is used to weld sheets less than 1 cm thick. They are laid overlapping each other and boiled on both sides. There should be no moisture between them. For better bonding, the joint is sometimes welded from the end.
Seam geometry
S - thickness of the workpiece.
E - width.
B - gap between workpieces.
H is the depth of the welded area.
T - thickness.
Q is the size of the convex part.
P is the calculated height corresponding to the perpendicular line from the point of penetration to the hypotenuse of the largest right triangle inscribed in the outer part.
A is the thickness of the fillet weld, which includes the value of the convexity and the design height.
K - leg is the distance from the surface of one workpiece to the corner boundary of the other.
Q - convexity of the deposited area.
Choice
The types of seams and welded joints differ in properties, and for each case the parameters of a successful combination are selected. The first step is to evaluate the spatial position. The easier the work is, the better the quality. It is easier to make horizontal seams, so they try to position the workpieces horizontally. Sometimes, to ensure quality, a part has to be turned over several times.
Welding in one pass helps to achieve better strength than in the case of multiple passes. So, a balance is required between convenience and number of aisles.
When the pieces are thick, the edges are cut and the surface is treated to add a clean finish. Butt-joint options are the simplest; it is preferable to choose them, since fixation is easier to ensure in order to avoid distortion of the geometry of the finished parts. In addition to choosing the type, attention is also paid to the temperature regime, because the cooking zones may shift and the product will not be fully cooked or will melt.
Welded metal joints are among the main methods of fastening structures used in everyday life and production. This is a very reliable method of obtaining a single design, which is also relatively cheap.
Bonds of this type are formed by melting the metal in the joint area and then crystallizing it as it cools. Their quality depends on the correct choice of operating mode of the electric welding machine, electrode, and seam penetration. This is regulated by current regulations and standards. They indicate all types of welds, as well as types of joints and their characteristics.
Numerous metals have their own welding characteristics, different work conditions, and requirements for fastening. For them, appropriate types of electric welded connections are used. When welding metal elements, the main types of electric welding fasteners are used, which are discussed below.
Classification
Welding joints are divided into several varieties, depending on their characteristics. The classification of welds covers the entire range of their uses. According to external parameters they are:
- convex type (with reinforcement);
- concave (weakened design);
- flat type (normal).
According to the type of execution, they are found in one-sided, as well as double-sided, according to the number of passes with the electrode: single-pass, double-pass. In addition, there are single-layer and double-layer welding methods.
According to their length, suture fastenings are:
- unilateral with intermittent pitch;
- solid one-sided;
- spot (with contact electric welding);
- chain double-sided;
- double-sided checkerboard pattern.
Separation by spatial location:
- horizontal, lower;
- vertical, ceiling;
- into a boat;
- semi-horizontal design;
- semi-ceiling type;
- semi-vertical.
According to the force vector:
- longitudinal (flank) – the force has a vector parallel to the penetration;
- transverse - the force acts perpendicularly;
- combined - a type of frontal, as well as flank;
- oblique - the impact occurs at an angle.
According to their purpose and function, electric welding penetrations can be durable, as well as durable and tight, hermetically sealed. Based on their width, they are distinguished into thread type, which does not exceed the diameter of the electric welding electrode rod, and widened, performed using oscillatory movements when welding in the transverse direction.
To simplify the understanding of the classification and application of certain varieties, a special table has been compiled.
All types of seams have strict designations according to GOST. The drawings use special icons that contain complete information about the type of fastening and its method of execution. For those who are thinking of seriously engaging in welding work at a professional level, they should additionally study the drawing symbols of welded fasteners.
Types of welds
Depending on the material used, thickness, and design features, different types of welds are used. To do this, you need to undergo the necessary theoretical training. This will allow you to better understand the specifics of welding parts and avoid defects in work. Novice welders often do not sufficiently weld the joint areas, which affects the weak mechanical resistance of the joints. By choosing the right operating modes and types of welding, you can obtain welding seams of sufficient strength and quality. Welder training consists not only of practical training, but also of theoretical training with the study of requirements, norms and rules, as well as including the types of welding joints and equipment used. Knowledge of the principles of using certain electric welding fasteners, the techniques for producing them, the joints will be very strong and durable.
Butt
This connection option is the most used among other types of welding seams. This butt welding is used on end sections, pipes or sheet metal structures. To obtain it, a minimum amount of time, material and effort is spent. These butt joints have some seam features. On thin sheet metal, welding is carried out without bevel of edges.
Products with large thickness of joint sections require preliminary preparation of joints, which consists of beveling them to increase the depth of welding penetration. This is necessary when the thickness of metal products is over 8 mm and up to 12 mm. Thicker sections must be joined by double-sided welding with preliminary bevel of the edges. Butt welding is most often performed on products in a horizontal plane.
T-bar
These types of electric welding connections are made like a regular letter “T”. They connect objects of the same or different thickness, which determines the width of the weld seam. In addition, these types are used single- or double-sided, which is influenced by the characteristics of the fastening. When working with metal elements of varying thickness, the electrode is held in an inclined position at an angle of about 60 degrees. The welding process can be greatly simplified by using tacks, as well as boat welding. This method significantly reduces the occurrence of undercuts. The T-weld is applied in one welding pass. In addition to manual arc welding, automatic electric welding machines are widely used for this type.
Overlapping
This method is used for welding sheet metal with a thickness of up to 12 mm. The areas to be joined are overlapped and welded along the joints on both sides. Do not allow moisture to enter the interior of the structure being welded. To strengthen the bond, full welding is performed around the perimeter.
With this welding, the formation of a connecting joint occurs between the end of one product and the surface of another. With this type of welding seams and connections, the consumption of materials increases, which must be taken into account in advance. Before starting work, you should align the sheet structures and ensure that they are pressed well together.
Corner
These connections include fastenings of elements made at a certain angle to each other. They are characterized by the use of preliminary bevels to ensure the best weld penetration. This will increase the depth of the welding joint, which will increase the reliability of the structure. To enhance strength, double-sided welding of metal products is used, while gaps in the joined edges are not allowed. These types of electric welds are characterized by increased use of the volume of deposited metal.
Ceiling
Welding with a ceiling seam, the seam of which is located above the welder, is one of the most difficult types of electric welding work. It is applied by intermittent welding at a low electric current. Vertical and ceiling connections are very difficult, so not all welders can perform them with sufficient quality. They are used in places where it is not possible to change the position of the structures being welded. These are pipes, various metal structures, as well as ceiling beams and channels at construction sites. The specifics of making ceiling seams, the video of which will explain the nuances, can be mastered through constant practice.
Weld geometry
Having studied numerous types and methods of obtaining joints by welding, it is necessary to familiarize yourself with the geometry of the joints, which photos of welding seams will help with.
The main parameters of a seam joint include its width - e, welding thickness - c, convexity - q, gap - b, welding depth - h, and the thickness of the material being welded - S.
For corner joints, the following designations are used: convexity - q, thickness - a, leg - k and design height - p.
Various methods of applying welds, their numerous types, as well as the parameters of the prepared edges affect the volume of use of the deposited and base metals. Its quantity may differ markedly when any calculated values change.
Types of welding joints are characterized by a shape coefficient, which is calculated by the ratio of the width to the thickness of the seam joint. For butt fastenings, this parameter is in the range of 1.2-2 (limit values 0.8-4). The convexity coefficient is calculated by the ratio of width to convexity, the value of which should be from 0.8 to 4.
Welding metal materials at an angle relative to each other requires precise adherence to the geometry of the seam. The reliability of the connection, as well as its durability of use, directly depends on the quality of welding and compliance with the required parameters.
Types of control
The further operation of the structure depends on the high-quality execution of electric welded fastening. Various defects significantly reduce the strength and reduce the period of use of the product. To prevent defects, as well as to prevent emergency situations, various types of control of welds are used. These include an external inspection, which can visually determine violations, their types, as well as the use of special equipment to determine hidden defects in welds.
Control methods are divided into non-destructible and destructible. When using the first method, the strength of the welded joint is determined without changing its appearance or parameters. Destructible methods are used for mass production of structures using the same type of electric welding work. This makes it possible to accurately detect internal defects in welding joints.
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A welded joint is a structural element or section of a product in which two of its parts are connected into one using welding. In this case, individual parts of the connection can consist of either the same metal or dissimilar metals and their alloys.
Welded joints and their characteristics are a very important classification, on the basis of which the welding method used is determined and its modes are selected.
Types of welds.
A weld is a place where different elements of the same structure are fused. During welding, the metal in this place melts, and subsequently, as it cools, it crystallizes, which ensures the strength and tightness of the seam.
Welds can have different cross-sectional shapes. According to this parameter, welds are divided into
butt welding, the distinctive feature of which is that the individual elements of the product are applied to each other on the same plane before welding using the “butt” method.
- corner, in which the components of the structure are attached to each other at a certain angle.
- slotted or electric rivet - here individual structural elements are attached to each other in one part by installing a special welded rivet. In this case, the upper part is completely melted, and the lower part is partially melted.
Depending on what kind of weld is observed at the junction of two parts of the product, there are different types of welded joints, each of which has its own distinctive features and areas of application.
All welded joints can be divided into
- butt joints
- corner connections
- T-joints
- lap joints
- end connections.
Characteristics of welded joints.
Now let's take a closer look at the various welded joints and their characteristics.
Butt joint is an alloy of two parts of a product located on the same plane using welding technologies. In a butt connection, the parts touch each other with their end sides. There are different subtypes of butt joints:
Connection without bevel
Connection with curved edge bevel
V-Bevel Joint
X Bevel Joint
Gusset - this is an alloy of different components of a structure or different parts of one product, placed at a certain angle relative to each other. The weld seam is located in the place where the individual parts come into contact.
T-joint - this is an alloy of different elements of one product, where one structural part with its end end is attached to the side surface of the second part.
Lap welded joint - this is an alloy of different elements of the product, in which both elements are located on parallel planes in relation to each other and partly overlap each other.
End welded connection differs from other types in that its individual elements are welded to each other with their side surfaces.
The choice of the type of welded connection depends on the configuration of the final element and on the requirements for the connection. The result should be a functional product that can withstand high loads, not succumb to environmental influences and not exhibit fatigue failure. Often the durability of the resulting product depends on the quality of the welded joint and the correct choice of its type, so it is very important to carefully approach this stage of work and take into account not only where exactly and how the resulting product should work, but also what materials it is made of and their alloys it consists. In this case, both the qualifications of the welder himself and the qualifications of the craftsman involved in the design of the welded structure are equally important.