What are the types of welded joints?

Main types of welded joints:

Metal welding is used in many industries. The durability of any structure depends on how this work is carried out. The quality of welding is influenced by how correctly the type of connection and seam are selected. There are a number of classifications and types of joints. The main types and elements of welded joints should be considered.

Security measures

Welding is a dangerous activity for human health and life. Therefore, it is impossible to do without the use of personal protective equipment during such work. Welding is accompanied by a number of harmful factors: radiation, gases, molten drops of metal. Therefore, the following set of PPE will be required:

• Costume. Made from canvas fabrics.
• Welding boots or boots. In this case, the laces must be closed.
• Glasses, welder's mask.
• Respirator for welding gases.
• Canvas mittens.

As you can see, you will need a fairly serious set. But it is he who will help protect against burns, loss of vision, and poisoning. Therefore its use is necessary.

Definition of Welding

Very often, on a construction site or in production, it is necessary to permanently connect metal planes and parts. For this purpose, welding is used, during which a seam is formed. Such a joint becomes permanent due to the process of melting the metal itself and filler materials (electrodes).

The main types of welded joints consist of the seam itself, the fusion zone, the heat-affected area, and the adjacent material. Parts are joined at the intermolecular or interatomic level under the influence of high temperatures. There are different types of welded joints. GOST 5264-80 contains detailed information about each of them.

Below we will look at all this in more detail.

Butt

This type is the most popular. It is used everywhere. Moreover, welding can be carried out with any type of edges. It can be one-sided or two-sided, with a removable lining, non-removable or without it.

It is used for the following edge options: flanging of two parts or one, without it, as well as in the absence of beveled edges. But that is not all. The edge can also be interlocking, with one-sided and two-sided, symmetrical and asymmetrical, curved and broken bevels, and so on.

Butt welded joint types are distinguished by their diversity and versatility. It is important to follow the work technology in order to obtain a high-quality seam.

Angular

This joining of parts is used when working with corner structural elements. Sometimes it becomes difficult to grip hard-to-reach places. Therefore, there is some limitation on the edges that need to be joined. Welding can be one-sided or two-sided. Suitable for the following types of edges:

• No bevel.
• With flanging on one edge.
• With one-sided and two-sided bevel.
• With bevel on both edges.

As you can see, a number of joining elements are eliminated due to the complexity or impossibility of fastening them using corner types of welded joints.

Tavrovoe

This type in cross-section looks like a T-shaped connection of parts. But it is also typical for parts, when connecting which a small angle of inclination of one surface to another was used. Welding can be one-sided or two-sided. When working with such joining, prepare the following row of edges:

• No bevel.
• With one-sided and two-sided options on one edge. They can be symmetrical or asymmetrical.
• With a curved one-sided and two-sided bevel of one plane.

T-type welded joints also allow you to work with a limited view of planes.

Lap and end connection

The first joining is used in cases where it is necessary to fasten parts overlapping. Edges without bevels are preferred by craftsmen using this type. The type of welded joint, end, is rarely used. But still it is allocated to a separate group.

In this way, the end sides of the parts are connected. Remember that a different type of seam may be used for each joint. For the convenience of working with the table, which lists all types of welded joints, GOST introduced their letter designation.

Every welder should become familiar with their main characteristics.

Classifications of seams

There are several classification options:

• By location relative to the surface - one-sided and two-sided.
• By purpose - working (operation of welded surfaces under load), non-working (without it).
• By length - short (up to 250 mm), medium (up to 1 m), long (over a meter).
• According to the configuration - rectilinear, curvilinear.
• In width - filament (the width is equal to the diameter of the electrodes or it is significantly smaller), widened (obtained by oscillatory movements of the electrodes).

The types of welds and joints have several more classifications that should be considered in detail.

By position in space

This classification highlights the following provisions:

• Lower. The angle of work relative to the horizon is from 0 to 60°.
• Vertical. The angle relative to the ground is from 60 to 120°.
• Ceiling. The operating angle ranges from 120 to 180°.

Position in space can influence both the quality of the seam and the choice of the type of joining.

By degree of continuity

The following types of welds and connections are distinguished in this classification: continuous (do not have gaps along their entire length) intermittent (performed with interruptions). The second option is more typical for corner and T-joints. Intermittent, in turn, can be:

• Chain, when identical intermittent chains of seams are made on both sides.
• Checkered, when the seams on one and the other side are applied with a shift relative to each other.
• Pointed. Performed with dots in a checkerboard pattern on both sides.

Continuous seams can withstand heavy loads. They are less susceptible to corrosion, so they are often used for working surfaces.

According to the type of welded joint obtained

This classification distinguishes the following types of seams:

• Stykova.
• Angular. It is used in T-joints, butt joints, and corner joints.
• Proflavnoy. Characteristic for T-joints and lap joints. In this case, the thickness of the surfaces should be no more than 10 mm.
• Electric rivets. Also used for T-joints and lap joints. The first surface is drilled first. The second one is welded through it. If the thickness of the first surface is no more than 3 mm, it is not drilled. Such sheets are punched through welding. The structures are strong, but not dense.
• End They are used for adhesion of the side surfaces of parts (ends).

As you can see, the types of welds and joints are interrelated according to this classification. They even have a number of the same names.

According to the profile data of the section

If you cut any butt joint, you can accurately determine the type of seam using this classification:

• Convex. Used for products subject to static load. Considered enhanced. When making such a seam, a large number of electrodes are used.
• Concave. Characteristic for structures with dynamic and alternating loads. Considered weakened.
• Normal. Recommended use is the same as for concave.

T- and corner types of welded joints imply another type of seam - a special one. If you look at it in section, you will see that one of the legs will be larger, i.e. you get an isosceles triangle. Used for products with variable load. Reduces tension.

In the direction of the efforts made

This classification is related to welding technology. So, the seams are:

• Longitudinal. The force is directed along the axis of the seam.
• Transverse. The direction of force is transverse.
• Combined. Sometimes structures require a combination of several types of efforts. For example, both transverse and longitudinal.
• Oblique. The force is applied at an angle.

By number of layers

There are only two types of seams in the context of this classification: single-layer and multi-layer. In addition, they are single-pass and multi-pass. If everything is clear with the first option, then the second is characterized by the presence of several new definitions:

• Passage. In simple words, this is a one-time pass through the joint by welding.
• Roller. This is the name given to part of the melted metal obtained in one pass. By the way, the seam layer can consist of one or several rollers made at the same level.
• The root of the seam. This is the furthest roller from the facing level.

A multi-layer, multi-pass type of seam in a welded joint is used to bond thick materials and reduce the heating zone. The same classification identified additional types of welds and joints. GOST designated them as:

• Podvarochny. A smaller part of the preparatory double-sided seam. This is done to prevent burn-through when performing other levels. Or lastly it is applied to the root of the seam.
• Facing. The name itself speaks for itself. Performed for the front part of a multi-level seam. Improves appearance.

Multi-row seams are usually complex. They require accuracy and professionalism.

Unacceptable errors

Types of welded joints and types of welds should be performed according to technology. The quality of work is directly related to the further operation of products and structures. The following errors should not be allowed when welding:

• Undercut, burn. Formed by prolonged heat exposure at one point.
• Lack of penetration. Thermal exposure is not long enough, resulting in the formation of a poorly cleaned base. The design turns out to be unreliable.
• Slag inclusions. May appear due to poor-quality electrodes.
• Pores. Formed as a result of splashes of hot metal. The welding temperature should be adjusted.
• Cracks. They can appear when joining different types of metal. They may have different melting points.
• Cavities. Formation under the influx of voids. This is fraught with the appearance of cracks during operation.
• Non-fusion. Reasons: insufficient temperature for welding, poorly cleaned surface, lack of penetration.

All this may further affect the quality of metal structures and products.

Quality control

Welding work requires quality control. This can be done in several ways:

• Visual inspection. It will help to detect visible errors: pores, cracks, slag inclusions.
• Measurement. Using measuring instruments, the length and width of the seam are controlled. Compliance with the technical specifications and GOST is checked.
• Leak test. Required for some types of structures. It is checked using a special crimp test.
• Control and measuring instruments. New technologies have found their application in this area.
• Laboratory research. Tested by physical and chemical reactions.

Of course, the quality of work depends on the experience and qualifications of the welder himself. He will easily determine the possibility of performing a particular type of work, the compatibility of the material, select the required connection and seam, and perform the work at the proper level. A good welder has always been and will always be valuable. But this is learned both theoretically and practically. For some it takes years.

Conclusion

As stated earlier, welding is a complex technological process that requires professional skills and knowledge. We should also not forget about personal protective equipment. They will help avoid burns to the cornea of ​​the eye and thermal effects that are harmful to the skin. If you need to use welding for complex structures, it is better to trust a professional. And all because the reliability of the structure itself will depend on the quality of the work performed in the future.

To gain experience, it is better to start with simple products. In this case, welding technology and safety precautions must be strictly observed. It should be understood that edge preparation plays an important role. Therefore, you should thoroughly clean the surface before starting work. Also, upon completion, the seam should be cleaned of slag. Sometimes it turns out uneven. This cannot be seen behind the layer of slag that remains from the electrode.

So, we have found out the main types of welds and joints.

Source: https://BusinessMan.ru/new-osnovnye-tipy-svarnyx-soedinenij.html

Welding seams

Welds are sections of a welded joint formed as a result of crystallization (solidification) of molten metal or as a result of plastic deformation during pressure welding or a combination of crystallization and deformation.

The separation of the concepts of welding joint and welding seam is necessary because the latter, as the connecting part of the elements being connected, determines the geometric shape, continuity, strength and other properties of the metal directly at the welding site.

The properties of a welded joint are determined by the properties of the metal of the weld itself and the zone of the base metal adjacent to the weld, with a changed structure and, in many cases, with changed properties of the heat-affected zone.

It is also necessary to take into account some part of the base metal adjacent to the heat-affected zone and determining the stress concentration at the point of transition from the weld metal to the base metal and plastic deformations in the heat-affected zone, which affects the nature and distribution of forces acting in the welded joint.

Criteria for classification

Welding seams are divided depending on:

- on the shape of the section;

- on the nature of the mating of the welded parts;

- in appearance;

— on implementation;

- by the number of layers;

— by the number of passes;

- from the length;

- in the direction of the current force;

— by position in space;

- according to the intended purpose;

— on the operating conditions of the welded product;

- by the method of holding molten metal;

- by type of welding;

- according to the material used for welding.

Classification

Depending on the cross-sectional shape, welding seams can be:

butt; corner; slotted (electric riveted).

Depending on the nature of the mating of the welded parts, the following types of welded joints are distinguished:

— butt connections;

- corner connections;

- T-joints;

— lap joints;

- end connections.

https://www.youtube.com/watch?v=qBf24cIxYuU

Welding seams are divided into:

- normal (flat)

- convex (reinforced)

- concave (weakened).

Convex weld Normal weld Concave weld

Convex welds work better under static (constant) loads, but they are not economical. Normal and concave welds are better suited for dynamic and alternating loads, since due to a smoother transition from the base metal to the weld, the likelihood of stress concentrations leading to weld failure is reduced.

According to the execution, welding seams can be one-sided or two-sided.

Single-sided seam Double-sided seam

Depending on the number of layers, welding can be single-layer or multi-layer; depending on the number of passes, welding can be single-pass or multi-pass.

Single layer, single pass Multilayer Multipass

A multi-layer weld is used when welding thick metal, and also to reduce the heat-affected zone.

Pass - a single movement of a heat source in one direction during welding or surfacing. A bead is a portion of the weld metal that has been deposited in one pass.

Weld layer - weld metal consisting of one, two or more beads that are placed at the same level of the cross-section of the weld. When welding, each layer of a multilayer butt weld, except for the reinforcement and back weld, is annealed when the next layer is applied. As a result of this thermal effect, the structure and mechanical properties of the weld metal are improved.

Depending on the length, welds can be continuous or intermittent. Butt seams are usually made continuous. Fillet welds can be made:

- continuous;

- one-sided intermittent;

— double-sided chain;

— double-sided chess;

- point.

In the direction of the current force

According to this criterion, welds are divided into:

- longitudinal (flank) - the direction of the acting force is parallel to the axis of the weld;

- transverse (frontal) - the direction of the acting force is perpendicular to the axis of the weld;

- combined - a combination of longitudinal and transverse seams;

- oblique - the direction of the acting force is placed at an angle to the axis of the weld.

According to their position in space, seams are divided into:

According to their intended purpose, welding seams are divided into

- durable;

- dense (sealed);

- durable and dense.

Depending on the operating conditions of the welded product, seams are divided into:

- workers intended directly for loads;

- non-working (binding or connecting), used only for connecting parts of a welded product.

The width of the welds is divided into

- thread welds with a seam width equal to or slightly greater than the diameter of the electrode, are performed without transverse oscillatory movements of the welding electrode;

- normal with width

- widened, which are performed with transverse oscillatory movements of the electrode.

According to the method of holding molten metal, the seams of welded joints are divided:

— on seams made without linings and pillows;

— on removable and remaining steel pads;

— on copper, flux-copper, ceramic and asbestos linings;

- on flux and gas cushions.

According to the weld configuration:

 — straight;

— ring;

— vertical;

— horizontal;

According to the type of welding, the seams of welded joints are divided into:

— arc welding seams (GOST 5264-80);

— seams of automatic and semi-automatic submerged arc welding (GOST 8713-79);

— gas-shielded arc welding seams (GOST 14771-76);

— electroslag welding seams (GOST 15164 - 78);

- electric riveted seams (GOST 14776 - 79);

- contact electric welding seams (GOST 15878 - 79);

— gas welding seams;

- seams of soldered joints.

According to the material used for welding, the seams of welded joints are divided into welding seams:

— carbon and alloy steels (GOST 5264-80; 14771-76; 15164-78; 8713 - 79, etc.);

— compounds of non-ferrous metals (GOST 16038 - 70; 14806 - 69);

— bimetal compounds (GOST 16098 - 70);

— connections of vinyl plastic and polyethylene (GOST 16310-70).

Source: https://blog.svarcom.net/technologia-svarki/svarnye-shvy.html

Types of weld defects and reasons for their formation

Novice welders who independently repair metal structures and parts often make welding defects that reduce the strength of the seams. They crack, let water through, and break under load. There are ways to identify and eliminate defects in welds and joints that reduce the strength of mounted structures and welded parts.

The review presents all types of consequences of technology violations and methods for restoring damaged areas.

Reasons for the formation of defects

Welding defects arise for objective and subjective reasons. Each type of rolled metal product is characterized by weldability. This indicator depends on the component composition of the alloy and the method of production of rolled products. For poorly welded parts, a large percentage of defects is immediately included in the technological maps.

Main types of defects in welded joints:

• violation of the integrity of the metal;
• deformation of structures or parts due to internal stresses;
• violation of the shape of the weld seam bead;
• non-compliance with the geometric parameters of the surfacing bead;
• structural changes in the metal (grain size in the phase transition region of the welded joint).

External defects are not as dangerous as internal, invisible ones. They are detected using non-destructive testing methods. Making critical welds yourself is risky. It's better to turn to professionals.

The main reasons for violating the integrity of the weld seam beads and the thermal influence zone:

• poor-quality processing of joints: poorly cleaned scale, rust, remnants of an oxide film, greasy stains, dirt;
• the use of surfacing wire or electrodes that do not match the base metal;
• welding machine malfunction;
• incorrect setting of operating parameters: current, voltage on the welder regulators;
• incorrect placement of parts, the coefficient of linear expansion is not taken into account;
• non-compliance with the interval between the electrode and the workpiece, a certain arc length is not maintained.

Types of weld defects

A complete classification of possible violations of the external and internal structure of welds is presented in GOST 30242-97. The occurrence of external defects in welds is often accompanied by deep-seated damage to the structure of the alloy. They are possible using any welding method and are divided into external, internal and through. It is worth talking about each type of defect in welded joints in more detail.

External

Identified by visual inspection. Most external defects in welds are eliminated during operation.

The cause of cracks is non-compliance with the temperature regime. Hot ones are formed at high temperatures above 1100°C. Cold with insufficient surface heating (up to 200°C). When cracks occur, the metal becomes less ductile and collapses under load.

Cracks appear due to non-compliance with temperature conditions

Undercuts are the most common defective defects in weld beads: depressions are visible between the surfacing and the part. Causes:

• the arc voltage is too high, the welded workpieces become thinner;
• one part is boiled more strongly, the melt pool moves away from the center of the gap.

When undercutting, the strength of the connection decreases, and the weld has to be passed through again.

Burn-throughs are typical for welding thin-walled products. Experienced welders can avoid them. Uncertain control of the electrode often leads to burnout. Excessive current is another reason.

Fistulas are large shells that look like a funnel. They worsen the appearance of the weld and are immediately visible. They are eliminated by secondary penetration.

The crater is characterized by the looseness of the metal and its shrinkage. They often cause cracks on the surface. They occur in the area of ​​lack of fusion when the electric arc is disconnected or separated from the surface of the workpiece.

If a crater is found, it must be cleaned and re-welded.

Sagging is excess metal that has spilled out: the surfacing spreads without forming a reliable weld, there is no durable diffuse layer. The electric arc does not have time to melt the workpiece due to insufficient voltage. Another reason is poorly cleaned edges; the remaining scale does not melt.

Source: https://svarkaprosto.ru/tehnologii/defekty-svarnyh-shvov

Types of welded joints: types, control methods, quality control

Welding is widely used for joining elements made of ferrous and non-ferrous metals and their alloys. The types of welded joints are determined by the welding method, the location of parts, the thickness of the material and the requirements imposed by operating conditions. The welding method depends on the melting point of the metal, its thermal conductivity and ability to react with oxygen and nitrogen.

The welding process is influenced by many factors, including the skill level of the worker. Welding and control are mandatory elements of the technological process. To check the quality, non-destructive testing is used, which includes scanning the seam, etching, and external inspection. The destructive method of cutting and etching allows you to accurately examine all zones, their structure and the quality of the seam.

What is this?

A permanent connection obtained as a result of melting the edges of the combined parts and the electrode is called welded joints and seams . The result is one part made from two or more elements. It can be processed by cutting or heat treated to stabilize the structure.

Heating and melting can be done in several ways:

• electric arc welding,
• gas burner,
• resistance welding.

Heating and creation of a weld pool by the temperature of the electric arc occurs from the electrode and wire. The edges of the parts being joined are sure to melt. In addition to these, an electrode, wire or filler material melts.

The gas burner controls the melting rate of the base material and filler rod.

When resistance welding with high currents, spot heating occurs and the heated metal is joined due to strong compression.

Types of welding joints are selected depending on the requirements for tightness and strength of the seam, and the operating conditions of the welded product.

Options

The parameters of a butt and fillet weld are different . In both cases, this includes the thickness of the parts being connected; the size of the convexity or concavity of the surface of the deposited metal is entered into the drawing. When assembling for welding, a gap is maintained between the elements being connected.

When checking butt welds, the penetration depth is measured, from the surface of the part to the bottom of the seam. The convexity protrudes above the plane of the surfaces being welded.

Thickness is determined as the sum of the penetration depth and convexity values. It is maximum along the longitudinal axis.

In the parameters of the corner connection, the technological and controlled size is the leg . These are the dimensions of the sides of the angle formed by the line connecting the extreme points of the seam material to the parts. The ratio of dimensions determines the equilateral and offset connection.

By method of execution

Welds are divided into single-sided and double-sided. According to the method of execution: welded in one pass and multi-layer .

They can be applied in one row on thin parts, in several layers if the width of the material being joined is more than 5 mm.

One-sided multi-layer seams connect parts with a thickness of 8 - 25 mm or more, if the metal structure is hollow inside and there is no possibility of welding on the other side. For example, a large cross-section pipe. In other cases, if increased strength and tightness are required, melting is carried out from 2 sides.

By degree of convexity

The convexity is determined relative to the line formed by the points of contact of the seam. For corner joints this is a leg. For a butting connection, the plane of the parts. Seams are classified according to the degree of convexity:

• normal,
• convex,
• weakened.

The optimal height is 2 - 3 mm above the surface of the part or the hypotenuse line of the leg. Convex ones protrude beyond the plane boundary more strongly.

Loose or concave seams are less strong but more flexible. They are used for corner joints. Due to its frequent use in welding the hulls of sea vessels, it is called a ship weld.

By length

The length is taken not from the total length of the connection, but from the nature of the execution:

Solid ones are performed on products that must be sealed or parts operating under heavy loads.

Intermittent creates less tension. It is used in lightly loaded structures, for example, reinforcement for pouring concrete slabs. Located nearby, it receives low pressure in one direction. Concrete bears the main load. The rods keep it from collapsing when it bends.

In the direction of the acting force and the vector of action of external forces

Division in the direction of the actual force is a conventional method of classification . During operation, even if the structure is stationary, several multidirectional forces act on each of its elements. To calculate the strength, choose the largest of them.

The flank connection is located along the edges of the part parallel to the force vector. A frontal shot, on the contrary, creates a direct goal with the direction of the acting force. If the angle is not 90⁰, then the connection is oblique.

The most durable is the combined connection. It forms flanking formations in combination with other species.

According to the shape of the products being welded

The configuration of the parts being welded determines the shape of the seam . The majority and variety of welded joints occur in straight seams of sheet material and flat parts.

Ring welds are used to weld pipes, bushings and other cylindrical products. The position of the joint can be vertical and welded in a circle with a continuous seam in one spatial position. Such seams are made on short parts that can be installed vertically.

Pipelines of various diameters are made with a transition in position from the ceiling to horizontal through vertical.

Dependence on the thickness of the working material and the length of the joint itself

The connected elements can be different in size. Welds are made depending on the thickness.

Preparing parts for welding includes cutting the edges and giving them a certain configuration:

• smooth – thickness up to 5 mm,
• X or V-shaped – thickness 3 – 25 mm,
• U-shaped for parts with a wall thickness of more than 25 mm.

Both edges are cleaned and cut off during butt welding. V-shaped stripping is done with one-sided welding. If welding is done from 2 sides, then it looks like X - V-shaped cuts connected at the tops.

The U-shaped stripping, rounded at the bottom, is convenient for use when multi-layer welding on one side.

In T-joints, the corner of the part that is welded with its end at an angle to the main element is cleaned.

Chairman of the acceptance committee, military representative Rogozhin N.V.: “Long seams, especially around the perimeter of the part, are applied in several stages. To avoid overheating, cook in small sections.

For example, first to the left of each corner, then several short seams in the middle of each section, alternately on different sides. After welding to the right of the corner, fill in the remaining areas. Welding of large, critical products can be carried out simultaneously by several welders.

Then they are distributed evenly, at the same distance, and continuous seams are welded in one direction, in a circle.

The welding card of the product includes the names of the welders, the suture pattern, and the start and end times of the work. Each worker puts a mark against his section of the seam.”

Types of control

For welds, control methods are used:

• visual inspection,
• non-destructive,
• destructive.

It is important for the worker to know what parameters should be controlled during the welding process so that the product is of high quality. These are the modes specified in the technology: current, voltage, welding speed.

Preliminary

Oil and dirt may coat the surface of the parts being welded. They degrade the quality of the connection.

Before starting work, you should check the correctness of chamfering and assembly of the structure. In addition, the welder himself checks the connection of the device and what mode the device is set to.

Current

During the welding process, the current strength and wire feed speed are controlled. The flux should coat the hot metal evenly.

Final

After cooling, the seam is visually inspected for defects such as undercuts, tops, cracks, and lack of penetration. After this, physical and chemical control is done .

To determine discontinuities and micropores, substances with high fluidity, such as kerosene, are used. On one side, the joints are smeared with chalk, on the other, liquid is applied.

After this, the product undergoes non-destructive testing.

Control methods

All control methods are divided into non-destructive and destructive . Non-destructive methods are incorporated into the technological process of manufacturing products. Destruction of parts allows you to see the micro and macro structure. It is carried out periodically. The frequency depends on the degree of responsibility of the product.

Destructive

The destructive method of testing welds allows you to see the main zones located symmetrically from the center to the sides:

• alloy of metal parts and electrode,
• fusion line,
• transition zone,
• metal parts.

The joint is cut crosswise, planed, ground and etched. After this, the structure of the material and the slightest defects can be seen through the microscope.

Inspection of macrosections etched with nitric acid allows you to control the quality of welding, see the microstructure of all zones, and determine the continuity of the metal. Metallography shows the depth of penetration and the degree of melting. The main stresses pass close to the seam, along the transition zone. Its width and condition of the edges indicate the quality of the seam and the correctly selected technology.

Chemical analysis

The shavings for chemical analysis are taken mainly from the seam itself. Based on the results of the study, it is determined how much of the base material and filler material melted.

Mechanical tests

In addition to testing cut samples for strength, flexibility, tension, vessels and pipelines are subjected to hydraulic testing. Liquid is pumped inside under high pressure. Tapping with a hammer of a certain weight is carried out and inspected for the presence of emerging moisture.

Non-destructive

Magnetic flaw detection is often used in production . The magnetized part is dipped into a special powder and inspected. Uneven coverage indicates defects.

The ultrasonic wave is reflected from the lower boundary of the metal. Passing through the metal, it will show all the pores and cracks.

The service life of the product and the safety of nearby people depend on the quality of the weld. The method of control and the frequency of its implementation are indicated in the technology.

Source: https://greendom74.ru/svarka/kakie-byivayut-svarochnyie-soedineniya-i-shvyi-vidyi-i-parametryi

What are the types of welded joints?

A weld is a line of molten metal at the edges of two joining structures, resulting from the action of an electric arc on the steel. The type and configuration of welds is selected individually for each case; its choice depends on factors such as the power of the equipment used, the thickness and chemical composition of the alloys being welded. Such a seam also occurs when welding polypropylene pipes with a soldering iron.

This article discusses the types of welds and the technology for their implementation. We will study vertical, horizontal and ceiling seams, and also learn how to clean them and check for defects.

1 Classification of welds

Classification of seams into varieties is carried out according to many factors, the main of which is the type of connection. According to this parameter, seams are divided into:

Let's consider each of the presented options in more detail.

1.1 Butt connection

This connection method is used when welding the end parts of pipes, square profiles and sheet metal. The connecting parts are placed so that there is a gap of 1.5-2 mm between their edges (it is advisable to fix the parts with clamps). When working with sheet metal whose thickness does not exceed 4 mm, the seam is laid only on one side; in sheets of 4-12 mm it can be either double or single, with a thickness of 12 mm or more - only double.

https://www.youtube.com/watch?v=ZbnEIr5ITFc

Methods for cutting seams

If the wall thickness of the parts is 4-12 mm, mechanical cleaning of the edges and sealing of the edges using one of the following methods is necessary. It is recommended to join particularly thick metal (from 12 mm) using X-shaped stripping; other options are unprofitable due to the need for a large amount of metal to fill the resulting seam, which increases the consumption of electrodes.

However, in some cases, the welder may decide to weld thick metal in one seam, which requires filling it in several passes.
Seams of this configuration are called multilayer; the technology for welding multilayer seams is shown in the image. to menu

1.2 Lap joint

The lap joint is used exclusively when welding sheet metal 4-8 mm thick, while the plate is welded on both sides, which eliminates the possibility of moisture getting between the sheets and their subsequent corrosion.

The technology for making such a seam is extremely demanding in terms of maintaining the correct angle of inclination of the electrode, which should vary in the range of 15-40 degrees.
In case of deviation from the norm, the metal filling the seam will move from the joint line, which will significantly reduce the strength of the connection. to menu

1.3 T-seam

The T-joint is made in the shape of the letter “T”; it can be made on both sides and on one side. The number of seams and the need for cutting the end part of the part depends on its thickness:

• up to 4 mm - one-sided seam without cutting the ends;
• 4-8 mm - double, without cutting;
• 4-12 mm - single with one-sided cutting;
• more than 12 mm - double-sided, double cut.

One type of T-joint is a fillet weld, used to connect two sheets of metal that are perpendicular or inclined towards each other.

2 Types of seams according to spatial position

In addition to classification according to the type of connection, seams are divided into varieties depending on the position in space according to which they occur:

Vertical seam from bottom to top

The problem with making vertical seams is the sliding of the molten metal downwards, which occurs due to gravity. Here it is necessary to use a short arc - keep the end of the electrode as close to the metal as possible.

Welding vertical seams requires preliminary work - stripping and cutting, which are selected based on the type of connection and the thickness of the metal.

After preparation, the parts are fixed in the required position and a rough connection is made with transverse “clamps” that prevent the workpieces from moving.

Welding a vertical seam can be done both top-down and bottom-up; in terms of ease of operation, the latter option is preferable. The electrode must be held perpendicular to the parts being joined; it is permissible to rest it on the edges of the weld crater. The movement of the electrode is selected based on the required thickness of the seam; the strongest joint is achieved when the electrode is moved transversely from side to side and with loop-shaped oscillation.

On vertical planes, horizontal type seams are laid out from left to right or from right to left. Welding horizontal seams is complicated by the pool flowing down, which requires maintaining a significant angle of inclination of the electrode - from 80 to 90 0. To prevent an influx of metal in such positions, it is necessary to move the electrode without transverse vibrations, using narrow rollers.

The speed of movement of the electrode is selected so that the center of the arc passes along the upper boundary of the seam, and the lower contour of the molten pool does not reach the upper end of the previous roller. Particular attention here must be paid to the upper edge, which is most susceptible to the formation of various defects. Before starting welding of the last bead, it is necessary to clean the formed seam from slag and carbon deposits.

The most difficult to perform are the ceiling seams. Since in this spatial position the molten pool is held solely by the surface tension of the metal, the seam itself must be made as narrow as possible. The standard width of the roller is no more than twice the width of the electrodes used, and in this case it is necessary to use electrodes with a diameter of up to 4 mm.

When laying a seam, the electrode must be held at an angle of 90 to 130 0 to the planes being connected. The roller is formed by oscillatory movements of the electrode from edge to edge, while in the extreme lateral position the electrode is delayed, which avoids undercuts. Please note that welders without experience are not recommended to tackle ceiling seams.

Source: https://vi-pole.ru/kakie-byvajut-vidy-svarnyh-soedinenij.html

What are the types of welded joints - Metalworker's Handbook

Metal welding is used in many industries. The durability of any structure depends on how this work is carried out. The quality of welding is influenced by how correctly the type of connection and seam are selected. There are a number of classifications and types of joints. The main types and elements of welded joints should be considered.

Types of welding seams and application methods

The basis of the welding process is the connection of metal elements and parts made of other materials by melting their edges. The place where the elements join is a seam, the art of performing which is the main thing for any welder. During the welding process, various types of element connections and welds are used, the choice of which is regulated by the conditions and requirements for welding.

Joints and seams

If you intend to master welding, then first of all you need to understand what seams and joints are.

https://www.youtube.com/watch?v=yww-vPMWEAA

Welding joints refer to the way in which the parts to be welded are connected. There are several main types, the use of which allows you to join any elements:

• Butt;
• Angular;
• Tavrovoe;
• End;
• With rivets.

Classification of welds

Welding work involves a wide variety of welds and joints. Types of welds can be distinguished according to various characteristics. Let's introduce some of them:

• According to external features: concave, convex, flat. Concave ones impart some weakness to the completed connection; convex ones, on the contrary, are considered reinforced and are used when it is necessary to create a strong weld that is resistant to heavy loads;
• According to the method of execution: one-sided or two-sided. Welding can be done both on both sides (which is much more common, as it gives the part greater strength) or on one side;
• By number of passes: single-pass and multi-pass. The latter are distinguished by their large size and strength;
• According to the number of welded layers: single and multilayer. The latter are used for welding work with thick metals;
• By length: point, chain, checkerboard, intermittent, solid. This characteristic reflects the method in which the welded joint was made along the entire seam. Spot welding is typical for resistance welding. The remaining names refer to the length of the smaller seams that form the longer main one;
• In the direction of impact: transverse (the impact is perpendicular), longitudinal (the impact is parallel to the seam), combined (combines transverse and longitudinal), angular (the force is applied at an angle);
• In terms of functionality: durable, dense, airtight. This characteristic is associated with the further operation of the part, which dictates the need to follow special requirements;
• In width: thread (the seam is equal to the diameter of the electrode) and expanded (created by oscillatory movements).

This classification represents an almost complete encyclopedia of types of welding methods.

It is necessary for a professional to know and be able to use them; for an amateur, it is enough to master the basic types of welding seams, which are quite sufficient for welding almost all types of joints.

Types of welded joints

Let's move on to the types of welded joints, that is, how the welded parts are connected. There are several main varieties:

1. The butt method is the most popular and frequently used type.
   It is characterized by minimal internal stress and is least likely to deform during welding. It is characterized by high strength, sufficient to operate the product under dynamic and static loads. The butt method represents the mating of the ends of two elements. If the metal sheets are quite thin, then they do not require preliminary preparation before welding. Thicker metal must be prepared by beveling its edges for deeper welding. This rule works when the workpiece thickness is more than 8 mm. If the metal is more than 12 mm thick, then the edges must be beveled on both sides and a two-sided connection must be made. Welding work is carried out in a horizontal plane.
2. The overlap joint has a scope of application in the construction industry, where it is used in arc welding with a thickness of metal elements up to 12 mm. Metal does not require preliminary preparation, but it is important to ensure that no water gets between the elements. It is recommended to weld from both sides;
3. An angle connection allows you to weld elements at any angle to each other. To make the weld more secure, the edges of the parts being joined are usually beveled, which allows for deeper welding. Welding on both sides also adds strength to the product;
4. The T-bar method is used to create building elements (trusses, beams, etc.) representing the letter “T”. Depending on which method was used, it can be one-sided or two-sided; elements of different thicknesses are often welded. Welding along the entire perimeter usually occurs in one step. The modern market offers devices for T-bar installation in automatic mode;
5. A riveted connection implies obtaining a sufficiently strong composite element. Holes are made in the upper element using a drill or other method and through them the upper element is welded to the lower one. There are different types of rivet seams, among them the most common are those in which rivets are used - special elements for fastening two parts;
6. The end method involves welding two elements that are aligned at their ends. In this case, one element is at an angle to the other and is welded to one of its side planes.

The listed types of welded joints and seams have a detailed description and execution diagrams, which are given in GOST standards for welding work.

Let's sum it up

Knowledge of the types of joints and seams in welding work is basic and provides the basis for the application of welding skills in practice. This theoretical experience allows you to correctly select the required type of joining of elements and the method of their welding, which will guarantee the resulting part the strength characteristics that are planned during its creation.

Sergey Odintsov

Source: https://steelfactoryrus.com/vidy-svarochnyh-shvov-i-sposoby-naneseniya/

Main types of welding

Electric welding is divided into 2 main classes: non-arc and arc.

Non-arc welding is more often called contact welding. In resistance welding, electrodes that supply current are applied directly to the metal being welded. A short but very powerful current discharge (thousands of amperes) is supplied through the metal located between the brought electrodes. In this case, fusion occurs only between the applied electrodes.

If the electrodes are located directly opposite each other, then the welded joint is a spot weld. Although spot welding is not the only type of contact welding, it is the most common. Therefore, the concepts of “spot welding” and “resistance welding” are often used as synonyms. Spot welding voltage is a few volts.

Therefore, resistance welding is used primarily for fastening thin sheet metal. For example, in the automotive industry.

In construction, electric arc welding has become much more widespread. In electric arc welding, there is a small gap between the current source (electrode) and the metal being welded, which is filled with an electric arc.

It is a mistake to assume that this is an air gap. This is a gap of ionized gas that conducts current. Arc welding, as we imagine it today, is impossible without gas.

The gas can simply be supplied from a separate cylinder, or it can be formed as a result of burning of the electrode coating.

The most common technologies in construction are the following:

• MMA (in the domestic classification - manual arc welding, or MMA)
• TIG (argon arc)
• MIG-MAG (semi-automatic, wire).

MMA

The popularity of this type of welding is predetermined precisely by the absence of the need to carry a gas cylinder with you. The coating of the electrode is the “frozen” gas cloud. As soon as the electrode touches the metal and the resulting short circuit current melts the metal of the electrode, the coating around it will also melt. The resulting gas cloud will provide a conductive ionized environment for the arc and protect the molten metal from oxygen.

Electrodes are selected according to the type of metal and diameter. The type of metal is important, since during operation the metal of the electrode rod flows drop by drop into the metal being welded and fuses with it. For a strong connection, the metal of the electrode rod and the metal being welded must be identical. The packaging of electrodes always indicates which metals these electrodes are suitable for.

Once you have decided on the type of electrode, you need to decide on its thickness. Newbie question: why do we need electrodes of different diameters? It's simple. The thicker the electrode, the greater the current that can melt it. The same goes for the edges of the metal being welded. Therefore, the thickness of the electrode is selected to match the thickness of the metal being welded. For ferrous metals it is recommended:

MMA technology allows you to work with most common metals, with the exception of aluminum and alloys based on it. Although theoretically this is also possible with an assistant, if you ensure that the cleaned aluminum surfaces do not have time to be covered with a film before melting. But it is more correct, of course, to simply use welding technologies suitable for this.

TIG

Consumers of TIG welding are entirely professionals and advanced users, and almost all of them are not in the construction sector. TIG produces cleaner seams, but is far inferior to MMA in performance and ease of use.

For example, many “amateurs”, having honed their skills on MMA machines, are frustrated by failures during their first experience with TIG. It turns out that, unlike MMA, it is not easy to strike an arc with a TIG machine unless it is equipped with a device such as an oscillator.

(And almost all “2 in 1” devices are not equipped, of course). The welder strikes with a tungsten electrode - there is a spark, but the arc cannot be raised. But an experienced welder places a piece of coal under the electrode - and the arc starts without problems.

It is no coincidence that specialized TIG devices rarely exceed a 1% share of retail store sales.

In TIG welding, devices with the ability to switch to alternating current mode, the so-called, deserve special mention. AC/DC. These devices are the main equipment for welding aluminum. It is they who predominantly make up this very 1% of TIG in retail sales of welding equipment.

MIG-MAG

Semi-automatic wire welding is mainly used for welding sheet metal. Therefore, traditionally its main area of ​​application is body repair, as well as the construction of structures made of black sheet metal. Using wire instead of replaceable electrodes greatly improves productivity. Household devices use coils with a capacity of 1 and 5 kg, and professional ones use 5 or 15 kg.

The wire can be used both regular (without coating) and with coating (so-called flux). In the first case, it is necessary to use a gas cylinder (GAS mode). In the second, a cylinder is not required (NO GAS). Despite the fact that it is more convenient to work without a cylinder, uncoated wire is the leader in sales by a large margin. The reason is simple: it is much cheaper than flux. In addition, many professionals believe that the accuracy of the seams in the gas environment from the cylinder is higher.

Despite the fact that this type of welding also belongs to electric arc welding, the principle of the MIG-MAG device is fundamentally different from the principles of MMA and TIG. In MMA and TIG it is important to maintain current stability despite electrode fluctuations, in MIG-MAG it is important to maintain arc voltage stability.

And the strength of the welding current in MIG-MAG machines is a conditional indicator (although, according to the habit developed in MMA, most people focus on it). The strength of the welding current in MIG-MAG will depend on the set voltage, the diameter of the wire used, the gas used and the wire feed speed.

So, making a semi-automatic MIG-MAG out of an MMA device by attaching a wire feed unit and a torch will not work.

Text author: Yu. Shklyarevsky

Source: https://www.kuvalda.ru/blog/articles/polz/osnovnye-vidy-svarki.html

What are the types of welded joints? answer

Currently, welding has become one of the most popular technological processes for connecting various parts and structural elements. The process is so technologically advanced that it is sometimes difficult to make a complete classification of all types of such a process. They are classified into two groups: the weld itself and preparatory work (edge ​​preparation).

What are the types of welding seams and connections classification?

All types of welded joints are classified according to the following criteria.

By length

The total length of the contact segment is considered. The quality of work performed along the entire length determines the reliability of the resulting element. Welds are divided into three categories:

• short seams (length does not exceed 250 millimeters);
• medium category (length increases from 250 mm to 1 meter);
• long seams (their length exceeds one meter).

Weld seams by length

Types of welded joints and seams by relative position

The position of the parts being welded relative to each other divides all seams into main types:

• butt-welded metal sheets (they are called butt-welded);
• tee (after welding, tee seams are formed);
• angular (one element is welded to another at a certain angle);
• before welding, one part of the sheet is placed on another (lap type);
• welding two products end to end;
• the action is performed in such a way that the cross section forms a figure resembling a cross;
• free combination of several elements in an established order;
• welding using cutting technology (slot type).

Types of welded joints by location

Source: https://crast.ru/instrumenty/kakie-byvajut-tipy-svarnyh-soedinenij-otvet