What is welding. Where modern welding is used What is welding in simple words

Welding

Welder at work

Welding- this is a technological process of obtaining a permanent connection by establishing interatomic and intermolecular bonds between the parts of the product to be welded during their heating (local or general), and / or plastic deformation.

Welding is used to join metals and their alloys, thermoplastics in all areas of production and in medicine.

Various energy sources are used in welding: electric arc, electric current, gas flame, laser radiation, electron beam, friction, ultrasound. The development of technologies now makes it possible to carry out welding not only in industrial enterprises, but in field and installation conditions (in the steppe, in the field, on the high seas, etc.), under water and even in space. The welding process is associated with a fire hazard; electric shock; poisoning with harmful gases; damage to the eyes and other parts of the body by thermal, ultraviolet, infrared radiation and splashes of molten metal.

Classification of metal welding

The temperature in the welding arc column ranges from 5000 to 12000 K and depends on the composition of the gaseous medium of the arc, material, electrode diameter and current density. The temperature can be approximately determined by the formula proposed by Academician of the Academy of Sciences of the Ukrainian SSR K. K. Khrenov: Tst = 810 × Uact , where Tst is the temperature of the arc column, ; Uact - effective ionization potential, .

Arc welding

The source of heat is an electric arc that occurs between the end of the electrode and the workpiece to be welded when the welding current flows as a result of closing the external circuit of the electric welding machine. The resistance of the electric arc is greater than the resistance of the welding electrode and wires, so most of the thermal energy of the electric current is released precisely into the plasma of the electric arc. This constant influx of thermal energy keeps the plasma (electrical arc) from decaying.

The released heat (including due to thermal radiation from the plasma) heats the end of the electrode and melts the surfaces to be welded, which leads to the formation of a weld pool - the volume of liquid metal. In the process of cooling and crystallization of the weld pool, a welded joint is formed. The main varieties of electric arc welding are: manual arc welding, non-consumable electrode welding, consumable electrode welding, submerged arc welding, electroslag welding.

TIG welding

Known in English literature as en: gas tungsten arc welding ( GTA welding, TGAW) or tungsten inert gas welding (TIG welding, TIGW de:wolfram-inertgasschweissen ( WIG).

The electrode used is a rod made of graphite or tungsten, whose melting point is higher than the temperature to which they are heated during welding. Welding is most often carried out in a shielding gas environment (argon, helium, nitrogen and mixtures thereof) to protect the seam and electrode from the influence of the atmosphere, as well as for stable arc burning. Welding can be carried out both without and with filler material. Metal rods, wire, strips are used as filler material.

Semi-automatic gas-shielded wire welding

In English-language foreign literature, it is referred to as en: gas metal arc welding ( GMA welding, GMAW), in German literature - de: metallschutzgasschweißen ( MSG). Separate welding in an inert gas atmosphere ( metal inert gas, MIG) and in an active gas atmosphere ( metal active gas, MAG).

A metal wire is used as an electrode, to which current is supplied through a special device (conductive tip). The electric arc melts the wire and the wire is fed automatically by the wire feeder to ensure a constant arc length. Protective gases (argon, helium, carbon dioxide and mixtures thereof) are used to protect against the atmosphere, which are supplied from the welding head along with the electrode wire. It should be noted that carbon dioxide is an active gas - at high temperatures it dissociates with the release of oxygen. The released oxygen oxidizes the metal. In this regard, it is necessary to introduce deoxidizers (such as manganese and silicon) into the welding wire. Another consequence of the influence of oxygen, also associated with oxidation, is a sharp decrease in surface tension, which leads, among other things, to more intense metal spatter than when welding in argon or helium.

Manual arc welding

In English literature, it is called en: shielded metal arc welding ( SMA welding, SMAW) or manual metal arc welding (MMA welding, MMAW).

Manual (TIG) and semi-automatic (MIG, MAG) pulse welding of aluminum is a more complex process than arc welding of ferrous metals. The reason for this is the unique properties of aluminum alloys, for which they are valued.

Submerged arc welding

In English-language foreign literature, it is referred to as SAW. In this type of welding, the end of the electrode (in the form of a metal wire or rod) is fed under the flux layer. The arc burns in a gas bubble located between the metal and the flux layer, which improves the protection of the metal from the harmful effects of the atmosphere and increases the depth of penetration of the metal.

Flame welding

Flame soldering

Acetylene-oxygen flame (temperature about 3150 ° C 2-3 mm from the core)

Welder, 1942

The source of heat is a gas torch formed during the combustion of a mixture of oxygen and combustible gas. Acetylene, MAF, propane, butane, blue gas, hydrogen, kerosene, gasoline, benzene, and mixtures thereof can be used as fuel gas. The heat released during the combustion of a mixture of oxygen and combustible gas melts the surfaces to be welded and the filler material to form a weld pool. The flame may be oxidative, "neutral" or restorative(carburizing), this is controlled by the ratio of oxygen and combustible gas.

• In recent years [ When?] as a substitute for acetylene, a new type of fuel is used - liquefied gas MAF (methyl acetylene-allene fraction). MAF provides high welding speed and high quality of the weld, but requires the use of filler wire with a high content of manganese and silicon (SV08GS, SV08G2S). MAF is much safer than acetylene, 2-3 times cheaper and more convenient for transportation. Due to the high combustion temperature of gas in oxygen (2927 °C) and high heat release (20,800 kcal/m³), gas cutting with MAF is much more efficient than cutting with other gases, including acetylene.

• Of great interest is the use of cyanide for gas welding, due to its very high combustion temperature (4500 ° C). An obstacle to the expanded use of cyanide for welding and cutting is its increased toxicity. On the other hand, the efficiency of cyanogen is very high and comparable to an electric arc, and therefore cyanogen represents a significant prospect for further progress in the development of flame treatment. The flame of cyanogen with oxygen, flowing from the welding torch, has a sharp outline, is very inert to the metal being processed, is short and has a purple-violet hue. The metal being processed (steel) literally “flows”, and when using cyanide, very high welding and metal cutting speeds are acceptable.

• Significant progress in the development of flame treatment using liquid fuels can be achieved by the use of acetylenedinitrile and its mixtures with hydrocarbons due to the highest combustion temperature (5000 °C). Acetylenedinitrile is prone to explosive decomposition under strong heating, but in mixtures with hydrocarbons it is much more stable. At present, the production of acetylenedinitrile is very limited and its cost is high, but with the development of production, acetyledinitrile can significantly develop the fields of application of flame treatment in all its fields of application.

Electroslag welding

Flash butt welding of plastics

The heat source is a flat heating element coated with PTFE. Welding is divided into 5 stages: heating under pressure, heating the mass, withdrawing the heating element, welding, solidification.

Welding with embedded heaters

It is applied to welding of polyethylene pipes. The heat source is the resistance elements soldered in the welded socket. When welding with embedded electric heaters, polyethylene pipes are interconnected with the help of special plastic fittings, which have a built-in electric spiral made of metal wire on the inner surface. The production of a welded joint occurs as a result of the melting of polyethylene on the surfaces of pipes and parts (couplings, bends, saddle tees) due to the heat generated by the flow of electric current through the spiral wire, and subsequent natural cooling of the joint.

Thermomechanical class

contact welding

When welding, two successive processes occur: heating of the welded products to a plastic state and their joint plastic deformation. The main varieties of contact welding are: contact spot welding, butt welding, relief welding, seam welding.

Spot welding

In spot welding, the parts are clamped in the electrodes of the welding machine or special welding tongs. After that, a large current begins to flow between the electrodes, which heats the metal of the parts at the point of their contact to melting temperatures. Then the current is turned off and "forging" is carried out by increasing the compression force of the electrodes. The metal crystallizes when the electrodes are compressed and a welded joint is formed.

Butt welding

The blanks are welded along the entire plane of their contact. Depending on the grade of metal, the cross-sectional area of ​​the workpieces and the requirements for the quality of the joint, butt welding can be performed in one of the ways.

Resistance butt welding

The blanks installed and fixed in the butt machine are pressed against one another with a force of a certain magnitude, after which an electric current is passed through them. When the metal in the welding zone is heated to a plastic state, precipitation occurs. The current is turned off before the end of precipitation. This method of welding requires machining and careful cleaning of the surfaces of the ends of the workpieces.

The uneven heating and oxidation of the metal at the ends of the workpieces reduce the quality of resistance welding, which limits its scope. With an increase in the cross section of the workpieces, the quality of welding decreases especially noticeably, mainly due to the formation of oxides in the joint.

Flash butt welding

Flash-butt welding of a gas pipeline pipe with a diameter of 1420 mm in Pskov at the TESO plant

It consists of two stages: melting and precipitation. The workpieces are placed in the clamps of the machine, then the current is turned on and they are slowly brought together. In this case, the ends of the workpieces touch at one or more points. In places of contact, jumpers are formed, which instantly evaporate and explode. Explosions are accompanied by a characteristic ejection of small drops of molten metal from the joint. The resulting metal vapors play the role of a protective atmosphere and reduce the oxidation of the molten metal. With further convergence of blanks, the formation and explosion of jumpers occur in other parts of the ends. As a result, the workpieces are heated in depth, and a thin layer of molten metal appears on the ends, which facilitates the removal of oxides from the joint. In the process of reflow, the workpieces are shortened by a given allowance. Reflow must be stable (continuous current flow in the absence of a short circuit of the workpieces), especially before upsetting.

During upsetting, the rate of convergence of workpieces is sharply increased, while carrying out plastic deformation for a given allowance. The transition from melting to upsetting should be instantaneous, without the slightest interruption. The precipitation begins when the current is on and ends when the current is off.

Butt welding by continuous flashing provides uniform heating of the workpieces over the cross section, the ends of the workpieces do not require careful preparation before welding, it is possible to weld workpieces with a cross section of complex shape and a large area, as well as dissimilar metals, and allows obtaining a stable quality of joints. Its significant advantage is also the ability to relatively easily automate the process.

Flash butt welding is used to connect workpieces with a cross section of up to 0.1 m². Typical products are elements of tubular structures, wheels, rails, reinforced concrete reinforcement, sheets, pipes.

relief welding

Reliefs are preliminarily created on parts for welding - local elevations on the surface several millimeters in diameter in size. During welding, the contact of the parts occurs along the reliefs, which are melted by the welding current passing through them. In this case, plastic deformation of the reliefs occurs, oxides and impurities are squeezed out. After the welding current stops flowing, the molten metal crystallizes and the joint is formed. The advantage of this type of welding is the possibility of obtaining several high quality welded joints in one cycle.

Diffusion welding

Welding is carried out due to diffusion - mutual penetration of atoms of welded products at elevated temperature. Welding is carried out in a vacuum unit, heating the joints to 800 °C. Instead of a vacuum, a shielding gas environment may be used. The diffuse welding method can be used to create joints from dissimilar metals that differ in their physical and chemical properties, to manufacture products from multilayer composite materials.

The method was developed in the 1950s by N. F. Kazakov.

Forge welding

The first type of welding in history. The connection of materials is carried out due to the occurrence of interatomic bonds during plastic deformation with a tool (forging hammer). Currently, it is practically not used in industry.

Welding with high frequency currents

The source of heat is a high-frequency current passing between the welded products. During subsequent plastic deformation and cooling, a welded joint is formed.

Friction welding

There are several friction welding schemes, coaxial appeared first. The essence of the process is as follows: on special equipment (friction welding machine), one of the parts to be welded is installed in a rotating chuck, the second is mounted in a fixed caliper, which has the ability to move along the axis. The part installed in the chuck starts to rotate, and the part installed in the caliper approaches the first one and exerts a sufficiently large pressure on it. As a result of the friction of one end against the other, the surfaces wear out and the layers of metal of different parts approach each other at distances commensurate with the size of the atoms. Atomic bonds begin to act (general atomic clouds are formed and destroyed), as a result, thermal energy arises, which heats the ends of the blanks in the local zone to the forging temperature. Upon reaching the required parameters, the cartridge stops abruptly, and the caliper continues to press for some more time, as a result, an integral connection is formed. Welding takes place in the solid phase, similar to forging.

The method is quite economical. Automated friction welding installations consume 9 times less electricity than resistance welding installations. Parts are connected in seconds, with virtually no gas emissions. With other advantages, a high quality of welding is obtained, since porosity, inclusions, and shells do not occur. With the constancy of the modes provided by the automation of the equipment, the constancy of the quality of the welded joint is ensured, which, in turn, makes it possible to exclude expensive 100% control while ensuring quality. The disadvantages include:

• the complexity of the required equipment;
• a narrow range of application of the method (bodies of revolution are butt welded);
• impossibility of application in non-production conditions;
• diameters of welded parts from 4 to 250 mm.

The method allows welding dissimilar materials: copper and aluminum, copper and steel, aluminum and steel, including those that cannot be welded by other methods.

The idea to weld parts by friction was expressed by the turner-inventor A. I. Chudikov. In the 1950s, using a simple lathe, he was able to firmly connect two mild steel rods.

To date, there are several friction welding schemes: such as axial, stirring (allowing welding of stationary parts), inertial, etc.

mechanical class

Explosion welding

Welding is carried out by approaching the atoms of the products to be welded to the distance of action of interatomic forces due to the energy released during the explosion. Using this welding method, bimetals are often obtained.

Ultrasonic welding of metals

Welding is carried out by approaching the atoms of the metal products being welded to the distance of action of interatomic forces due to the energy of ultrasonic vibrations introduced into the materials. Ultrasonic welding is characterized by a number of positive qualities, which, despite the high cost of equipment, determines its use in the production of microcircuits (welding of conductors with contact pads), precision products, welding of various types of metals and metals with non-metals.

Cold welding

Scheme of spot cold welding

Cold welding is a connection of homogeneous or inhomogeneous metals at a temperature below the minimum recrystallization temperature; welding occurs due to plastic deformation of the welded metals in the joint zone under the influence of mechanical force. Cold welding can be butt, spot and seam.
The strength of the joint depends significantly on the compression force and the degree of deformation of the parts being welded.

Welding in art

Welding is often seen as a subject of socialist realism.

Electric welder. Bust at the Museum of Socialist Art in Sofia	Welding in space on a postage stamp. 2006

see also

Notes

Literature

	Welding at Wikimedia Commons

Welding is a method of joining parts of a homogeneous material: plastic to plastic, metal to metal. During welding, the contact surfaces are melted or tightly compressed. In the contact zone, two materials are fused into one. The result is a strong tight connection between the two surfaces.

Welding is the joining together of parts made of the same material to form a single structure.

Fusion welding of metals is used for high-quality hermetic connection of critical parts: pipeline elements, car (bus, plane) body, metal garage walls and gates, sports horizontal bar supports, fittings inside a concrete wall and much more. What types of welding use modern welding technologies? How is metal welding performed?

Types of welding of metal surfaces

Welding of metals can be carried out with the melting of contact surfaces or with their compression. In this case, the welding processes are called:

• fusion welding (or melting);
• welding by plastic deformation.

The deformation connection can be performed with or without heating. The deformation of surfaces without heating is called cold welding. Under tight compression, the atoms of different materials are at close range and form interatomic bonds. Surfaces are connected.

In fusion welding, the surfaces to be joined are locally heated and melted. Often a third (filler) material is used that melts and fills the gap between the two metals. In this case, interatomic bonds are formed in the liquid melt between the base material and the additive (molten electrode). After cooling and solidification, a continuous welded joint is formed.

Local heating of parts for welding can be carried out by electric current or burning gas. Accordingly, according to the method of local heating, welding is divided into two types:

• electrical (including electroslag, electrobeam, laser);
• gas.

The names are determined by the heat source used. Electricity can work either directly or indirectly. When used directly, electricity heats the metal and filler electrode due to the passage of current through them or the appearance of an arc. In indirect use, various energies derived from the effects of electricity work: the energy of molten slag through which current passes, the energy of electrons in an electric field, the laser beam that occurs when electricity is applied.

Welding of metal surfaces can be performed manually or automatically. Some types of welded joints are possible only with the use of automation (for example, electroslag or seam), others are available for manual welding devices.

Electric welding is represented by two methods:

• electric arc;
• electrocontact.

Let us analyze in more detail how the surfaces are connected in the arc and contact welding methods.

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Electric arc welding of metals and electrocontact

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Work of an electric arc

This type of welding uses the heat of an electric arc for heating. The arc formed between metal surfaces is a plasma. The interaction of metal surfaces with plasma causes their heating and melting.

Electric arc welding can be performed using a consumable electrode or its non-consumable type (graphite, coal, tungsten). The consumable electrode is both the exciter of the electric arc and the supplier of the filler metal. With a non-consumable electrode, a rod is used to initiate the arc, which does not melt. The filler material is introduced into the welding zone separately. When the arc burns, the additive and the edges of the parts melt, the formed liquid bath after solidification forms a seam.

In some technological processes, the joining of surfaces occurs without the supply of filler material, only by mixing the two base metals. This is how welding with a tungsten electrode is performed.

If the electric arc does not burn freely, but is compressed by a plasma torch, while an ionized gas plasma is blown through it, then this type of welding is called plasma welding. The temperature and power of plasma welding are higher, since when the arc is compressed, a higher temperature of its combustion is achieved, which makes it possible to weld refractory metals (niobium, molybdenum, tantalum). The plasma gas is also a protective medium for the joined metals.

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Molten metal protection and fusion by electrical contact

If, during arc burning, metal surfaces are protected from oxidation by gas or vacuum, then such a connection is called welding in a protective environment. Protection is necessary for welding reactive metals (zirconium, aluminum), critical parts made of alloyed alloys. It is possible to protect welding with other substances: flux, slag, flux-cored wire. Accordingly, the welding methods used were named: submerged arc welding, electroslag welding, vacuum welding. All these are varieties of the electric arc method that use a different protective environment to prevent the oxidation of the melt, changes in its chemical composition and loss of the properties of the welded joint.

Electrocontact welding uses the heat generated at the point of contact between the two surfaces to be welded. This is how spot welding is performed: the parts are pressed against each other with force until they touch at several points. The points of contact will be the places of maximum resistance and the greatest heating of the surface. Due to this heating, the melting and connection of metal elements at the points of contact occurs.

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Technology of electric arc welding of metals

The technology of welding metal using an electric arc consists in a sequence of actions to organize the operation of the welding machine and the direct execution of welding.

The preparation consists in installing the welding inverter, and performing the necessary beveling of the edge (surface preparation).

After the welding machine is installed at the welding site, the contact wire is attached to one of the contact metal surfaces with the help of a “crocodile” (the design of the connecting terminal). Turn on the welding machine and set its strength with a current regulator. The current strength is regulated by the size of the electrode and the thickness of the parts to be welded. For an electrode with a diameter of 3 mm, the current strength should correspond to 80-100 A.

If the metal surface is painted or oxidized with a layer of rust, it must be scratched with a wire brush to ensure proper contact in the joint.

The type of connection of contact surfaces is determined:

• butt;
• overlap;
• angular;
• tee;
• end.

Let us consider in more detail the features of welding various types of joints. A butt joint often requires preliminary preparation of the edges of the surfaces to be welded: bevels are made along their edges. V-shaped bevels are made along the edges of sheets with a thickness of 5 to 15 mm, X-shaped bevels - on sheets with a thickness of more than 15 mm. Removing the V-shaped edge at the junction of surfaces allows you to get a recess along which welding is performed. X-shaped edges suggest the presence of a recess and the execution of welds on both sides of the connection.

Corner and tee joints can also be made with beveled edges (with surface groove) or without bevels and grooves (depending on the thickness of the welded section).

T-joints and corner joints allow you to connect parts of various thicknesses. In this case, the position of the electrode should be more vertical to the surface, which has a greater thickness.

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Welding electrodes: types and selection

The electrode for welding is a metal rod coated with a coating. The coating composition is designed to protect the weld metal from burning out during oxidation. The flux displaces oxygen from the molten metal, which prevents oxidation, and releases a protective gas, which also prevents oxidation. The composition of the coating includes the following components:

Scheme of the electrode for welding: 1 - rod; 2 - section of the transition; 3 - coating; 4 - contact end without coating; L is the length of the electrode; D is the coating diameter; d is the nominal diameter of the rod; l is the length of the end stripped from the coating

• ignition and combustion stabilizers (potassium, sodium, calcium);
• slag-forming protection (spar, silica);
• gas-forming (wood flour and starch);
• refining compounds (for removing and binding sulfur and phosphorus, impurities harmful to metal welding);
• alloying elements (if the seam needs special properties);
• binders (liquid glass).

Industrially produced electrodes have a diameter of 2.5 to 12 mm; for manual welding, 3 mm electrodes have received the greatest use.

The choice of electrode diameter is determined by the thickness of the surfaces to be welded, the required penetration depth. There are tables that give the recommended values ​​for the diameters of the electrodes, depending on the thickness of the surfaces to be melted. It is necessary to know that a slight decrease in the diameter of the electrode is possible, while the process time increases. The smaller diameter electrode allows better control of the process, which is important for a novice welder. A thinner electrode can be moved more slowly, which is important in the learning process.

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Arc Welding Characteristics: Definition and Significance

Before starting welding, the optimal characteristics of the welding process are determined:

1. Current strength (adjustable on the welding machine). The current strength is determined by the diameter of the electrode and the material of its coating, the location of the seam (vertically or horizontally), and the thickness of the material. The thicker the material, the greater the current required to heat it through to melt. Insufficient current strength does not melt the weld cross section completely, as a result there are lack of penetration. Too much current will cause the electrode to melt too quickly, when the base metal is not yet melted. The recommended current value is indicated on the packaging of the electrodes.
2. Current properties (polarity and gender). Most welding devices use direct current, it is converted from current by a rectifier built into the machine. With direct current, the flow of electrons moves in one (specified by polarity) direction. Polarity during welding determines the direction of movement of the electron flow. The existing polarities are expressed in the connection of the electrode and the workpiece:

• straight line - the part to "+", and the electrode to "-";
• the reverse is the part to “-”, the electrode to “+”. Due to the movement of electrons from “minus” to “plus”, more heat is released on the positive “+” pole than on the negative “-”. Therefore, the positive pole is placed on an element that requires more significant heating: cast iron, steel with a thickness of 5 mm or more. Thus, straight polarity provides deep penetration. When connecting thin-walled parts and sheets, reverse polarity is used.

1. Arc voltage (or arc length) is the distance maintained between the tip of the electrode and the metal surface. For an electrode with a diameter of 3 mm, the recommended arc length is 3.5 mm.

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How arc welding is performed: technology

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Start welding: arc ignition sequence

To initiate an arc, a new electrode is inserted into the clamp and tapped against a hard surface to remove the coating on its working end. Under the slag there is a metal additive, the slag itself serves as insulation and closes the additive from ignition. After that, the electrode rod is brought closer to the metal surface at the minimum possible distance, 3-5 mm, avoiding touch. In this case, the electrode is held at an angle to the surface of the metal to be welded. The technology of welding metals with an electrode regulates the angle of inclination of the electrode in the amount of 60-70ºC. Visually, such an angle is perceived as almost vertical, with a slight slope.

To ignite the arc, an electrode is struck on the surface of the metal, like lighting a match on a box of sulfur.

If the electrode is too close to the metal surface to be welded, sticking and a short circuit will occur. For those who start cooking, the electrode sticks often. As you gain the skill of correctly positioning the electrode over the metal, maintaining the optimal sticking distance should not occur. A stuck electrode can be torn off by tilting it to the other side or turning off the welding machine.

If the electrode sticks too often, the current may not be strong enough and should be increased.

With the optimal correct distance of the electrode from the place of welding (about 3 mm), an arc is formed with a temperature of about 5000-6000ºC. After ignition of the arc, the electrode can be slightly raised from the working surface by a few millimeters.

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Electrode movement and weld pool

When the electrode and the base material melt, a weld pool (pool of molten metal) is formed.

The electrode and arc, together with the weld pool (molten metal zone), move smoothly along the connection line. The speed of movement of the electrode is determined by the rate of melting of the metal and its color change. Rapid movement of the electrode is carried out when working with thin sheets that heat up quickly and easily form a weld pool. The slow movement of the electrode is used on thick massive joints.

The shape of the electrode movement (straight, zigzag, loops) is determined by the width of the weld and the depth of penetration. The electrode can move in a straight line (evenly) with a small welding width. It can move in loops, zigzag, if it is necessary to weld a sufficient width and depth of the connection. Options for electrode movement are shown in Figure 1.

Figure 1. Ways of moving the electrode.

The convexity of the seam after solidification of the weld pool is determined by the position of the electrode during welding. If the electrode is located almost vertically, the seam will be even, and the penetration will be deep. A more inclined location of the electrode forms a convex surface of the welded joint and a decrease in the depth of penetration. Too much tilt of the electrode places the arc in the direction of the seam, making the welding process difficult to control.

For a quality connection, the molten bath must have thin edges, be sufficiently liquid and obediently move behind the electrode.

The bathtub in the light filter (through dark glass) looks like an orange surface with ripples. The appearance of an orange color of the bath (drops of liquid melt) can be regarded as an indicator for further movement of the electrode. That is, if an orange color appears, then we move the electrode further by a few millimeters.

At the end of penetration, it is necessary to increase the size of the weld pool. To do this, the electrode must be held over this point for a few seconds longer.

If through penetration of the material occurs, it is necessary to reduce the current value and take another electrode (smaller diameter). The burnt holes are allowed to cool, slag is knocked off from them and then brewed.

After welding, it is necessary to tap the weld with a hammer. This will remove scale from it and visually check the welded joint for the absence of discontinuities or lack of penetration.

There are 50 types of welding. While we are writing this material, maybe this number is increasing. It is difficult and stupid to cover a complete classification in one article, so let's look at at least 4 main types of metal welding.

What is welding like? Main types

Manual arc

Gas

semi-automatic

Welding allows you to connect parts together with a dense or spot seam. The choice of method affects the quality, accuracy of the seam and the cost of the work. GOSTs for welding operations describe the designation according to international standards of devices and materials for quality control.

Types of welding

View	Principle of operation
Electric (electric arc) submerged arc	The welding arc burns out between the welding material and the electrode wire under a layer of loose fluxes. Due to the heat of the arc, the surfaces to be welded and the wire with flux melt.
Thermite	Products are placed in a fire-resistant container, and powder (termite) is poured into the upper strobe, where there is a seam. At 2000° the metal melts and fills the seam. This seam is then welded.
Ultrasonic	The effect of mechanically induced vibrations (ultrasonic frequencies) on the part to be welded.
Cold	Fusion of crystals under high pressure.
Electroslag	A welding arc appears under the flux. The flux melts and an electrically conductive slag appears, which has a high ohmic resistance. Due to the latter, metals are welded. Plus: no need to use heat treatment; flux savings. Minus: possible deformations.
Contact	Metals are heated, passed through an electric current and deformed. Contact welding is used in mechanical engineering in the mass production of parts.
Plasma	Non-standard welding technology. The moving arc is heated, which, due to this unusual property, sharply increases the temperature. Plasma welding is considered the most convenient type of aluminum welding, since the temperature with it is much lower than with gas. This means that it will practically not deform the aluminum part.

All models and types of devices that have received a certificate from NAKS can be used. Below are a few abbreviations.

1. MP - mechanized consumable electrode welding;
2. MADP - mechanized argon arc welding with a consumable electrode;
3. ЗН - welding with embedded heaters;
4. RD - manual arc welding with coated electrodes;
5. AF - automatic submerged arc welding;
6. MADPN - mechanized argon-arc surfacing with a consumable electrode.

Manual arc view

Welding is carried out with stick electrodes, which gradually melt and leave behind a bonding seam. The required distance is made between the metal surface and the electrode for its melting.

This is called the arc, which maintains a distance of about three millimeters. It decreases over time, so it is difficult for a beginner welder to maintain the same gap.

When welding several objects, they are first spot-fixed so that they do not move apart, otherwise the welding will be uneven, and the seam will stretch - on the one hand it will be of a set size, and on the other - wider.

IMPORTANT! Uneven welding can cause metal to burn through.

When welding plates with a thickness of more than two mm between each other, it is imperative to make a small gap between them. Hold the electrode at an angle of 45°. This will ensure that the welding slag comes out. The straighter its angle, the more likely it is to burn through the metal.

Before starting welding, the electrode must be brought as close as possible to the place where the seam is applied. Failure to do so may result in the welding site being lost when putting on the welding helmet.

When fastening two surfaces, it is necessary to melt the edge of the first and second. Remember that the electrode also melts. We mix the melted edges of the surfaces to be welded and the electrode. To do this, you need to make small movements to the left and right.

If the electrode is led straight, then only one part of the surface will melt, which means the seam will be unreliable.

This method is often used in reinforced concrete structures (reinforcement welding), when installing fences and gates, in various types of pipe welding.

IMPORTANT! If the work takes place at a height or just the cable at the holder is very long, then it will pull, and this may interfere with the correct seam. To do this, hold it in your other hand or hang it on a hook.

Semi-automatic welding

PS advantages (compared to manual or arc):

1. versatility - you can cook both structural and stainless steel, as well as other metals (cast iron, aluminum);
2. ease of learning - you can quickly learn how to work with the type of welding;
3. can be used for thin metals;
4. high speed of work;
5. convenience - slag does not interfere with seeing the result of the work: the master sees how the metal melts and can change the settings.

To work with this type of welding, you will need a power source (or the machine itself), a special wire and shielding gas.

IMPORTANT! When choosing an electrode wire, you need to ensure that it is close in chemical composition to the metal being welded or exceeds its properties in order to obtain a high-quality seam.

We recommend a wire for welding ST-3 08G2S steel with a diameter of 0.6 to 1.2 mm.

For working with metal with a thickness of 1 to 4 mm, a wire with a cross section of 0.8 mm is suitable. For larger metal thicknesses, choose 1 or 1.2 mm wire.

IMPORTANT! Welding without gas is prohibited unless special flux-cored wire is used. Then the protective gas is formed during the melting and combustion of a special powder composition.

It is allowed to use both pure CO2 and mixed CO2 + Ar gas (carbon dioxide and argon). Pure carbon dioxide is the cheapest and most available.

Cons: strong spattering of the metal, not a very beautiful appearance of the seam.

By adjusting the inductance, with such welding, it is possible to change the quality of penetration and the width of the seam. If it is reduced, the arc will be colder. The result of the work is a thin seam and deep penetration. By increasing the inductance, the arc gets hotter, resulting in a smooth, wide bead and less deep penetration.

When welding metal, the torch must be held at 60 ° to the plane of the seam, and the distance from the nozzle to the welding surface is 7-20 mm.

Before starting the welding process, you need to bite off the tip of the wire sticking out of the nozzle, because a ball is formed on it, which does not conduct current well. When welding surfaces, they must be cleaned of paint or rust.

IMPORTANT! If distinct clicks are heard during operation, it means that the welding machine is set to a high value of the welding voltage or insufficient wire feed speed. At a high feed rate, the wire will not have time to melt.

The application of various seams requires machine settings. Welding of thin metals occurs spot. Do not weld with a continuous seam to avoid warping.

Gas welding

The set of gas welding equipment includes:

1. oxygen hose of the first category for supplying acetylene under pressure of 0.63 MPa;
2. oxygen hose of the third category for supplying oxygen under pressure up to 2 MPa;

Before use, you need to clean the metal from rust and paint. Setting the pressure on the acetylene cylinder is done by opening the cylinder screw counterclockwise. The adjusting screw is screwed in clockwise, look at the pressure gauge.

Its working pressure is 0.2 MPa. To set the pressure on the oxygen cylinder, turn the screw counterclockwise. Then screw the adjusting screw clockwise into the gearbox and look at its pressure gauge. The pressure should be 0.5 MPa.

To set the working flame on a gas burner, open the acetylene screw, then light the flame. Make sure that the flame does not break away from the tip of the gas burner. After that, adjust it with a screw with oxygen.

The flame should represent the core, the recovery zone, and the torch.

To make a weld pool, you need to position the torch at 90 ° to the base metal. The distance between the core of the flame and the surface should be 1.3 mm.

As in the previous cases, the torch must be moved left and right to melt the edges of the surfaces to be welded.

After the metal has warmed up and the weld pool is ready, we position the torch at an angle of 45 ° and feed the filler rod. It can be fed dropwise or so that it is constantly in the weld pool. At the same time, make slight movements to the left and right.

Weld Requirements

It should be dense, and the scales should be uniform. Width 5-6 mm, height 1-2 mm. After the end of work, the gas burner closes: first, the acetylene propeller, then, after the burner is purged, the oxygen one.

The balloons are closed one by one. Acetylene first. We close the screw on it, then unscrew the adjusting screw from the gearbox. Oxygen closes similarly.

After closing the cylinders, it is necessary to release the residual pressure from the sleeves. The screws on the burner open: first acetylene, then oxygen. On the pressure gauges of both cylinders, you will see how the pressure drops. After the release of the remaining pressure, close.

Safety precautions when working with gas welding

• it is better to choose hoses of class 3. They withstand pressure up to 40 atmospheres;
• fastening on fittings should be carried out using clamps, but not wire;
• fire safety valves are installed on hoses, reducers and burners: they prevent the flame from passing inside the hose and getting into the cylinder, thereby preventing a gas explosion;
• if the burner suddenly starts to melt, you don’t need to throw it and run away - near it you need to bend and pinch the hoses with your hand, and then close the screws on the burner; if not in time, then on the balloon.

Argon welding

It is applied to connection of non-ferrous metals or the alloyed steel.

Comprises:

1. welding machine for operation from alternating or direct current;
2. cylinder with argon;
3. flow meter and gas flow regulator;
4. burner with regulator and air cooling;
5. inert gas hose;
6. reducer;
7. tungsten rods (DC and universal).

Before welding, tungsten rods are sharpened so that the risks are located vertically, and not horizontally. Then it is inserted into the burner and closed with a nozzle. Under each metal there is a nozzle of the required number.

IMPORTANT! A standard gas bottle lasts approximately 14 hours at a flow rate of 7 l/min. Before welding, the metal surface is cleaned and degreased with acetone or solvent.

To work with different metals, including the thickness, different arcs are installed - even, medium and high-frequency pulse. It makes it possible to work on thin materials, because the arc is interrupted and does not burn through them.

During welding, a filler wire is fed. Welding occurs in the same way as the previous ones. By surfacing the edges of the metals to be welded and welding the wire into the gap between them.

We must not forget that the electrode in the burner is always energized, so you need to handle it carefully.

Model	Description
	Designed for arc welding. Small dimensions (56x42 cm) and weight (5.2 kg). Works with electrodes with a diameter of 4 mm.
	Inverter weighing 5.87 kg. Works with electrodes with a diameter of 1.6-5 mm. IGBT technology, which increases the efficiency of the unit.
	Antistick system, which independently reduces the current when the electrode sticks to the metal.
	Designed for surfacing and arc welding. Plus: during welding, the metal practically does not splatter.
	Electricity consumption is almost 30 percent less compared to analogues.
	Automatic overload protection, neat seam. Efficiency 85%.

Due to its PFC technologies, it can operate at a voltage of 100 V, which is very convenient in country conditions. It copes well with arc welding, it is possible to connect to a generator. By reducing the electromagnetic field, electricity consumption is reduced by almost 30%.

It is worth paying attention to the model, which has a “hot start” function (you can plug it into the network and start working immediately) and an anti-sticking function for electrodes in metal. The device can operate at a voltage of 170 V.

After the concept of "metal welding" has become firmly established in modern everyday life, there is practically no industry left where it would not be used. Construction on an industrial and small scale has become the main industry where metal bonding is used. This is due to the advantages of welding: process acceleration, joint strength, economic component. In a word, all the qualities in which fruitful work should go.

The question - where welding is used - is almost rhetorical. The areas in which metals are joined are so vast that they have already passed the earthly meaning - special technologies allow you to weld structural elements while in outer space. Mechanical engineering and the automotive industry cannot do without welded technologies. Agricultural production and design offices are another of the many industries where the connection of structures by welding elements is applicable. We must not forget about the conductors of natural resources - gas, water, oil and others. Welded pipeline structures are also used for them.

Important conditions for a productive welding process in all areas

1. The design of the required product. It is no secret that it is not difficult even for a student to weld a simple pipe to another. Whereas the labor-intensive process of erecting grandiose structures requires responsibility at the development stage. Everything is taken into account - conditions of use, tools, safety precautions and so on.
2. Organization of the process. Now, at the time of technological progress, enterprises, public or private, are striving to equip the welding process with the latest technology. Workplaces are being modernized, as are the machines. There is no longer a need to pull large and bulky cables - technical innovations have made it possible to create compact devices that allow welding products in any hard-to-reach areas.
3. Competence in processes. Businesses of all sizes need skilled workers in the fields that cover metal welding. To do this, management often resorts to continuing education courses to assess the competence of their own employees, to improve their skills.

Features of the welding process in certain areas

The finished product depends on how complete the work on welding metal structures is. Quality depends not only on advanced equipment, but also on welding methods and materials.

Some features of welding with semiautomatic devices and transformers

Torch for semi-automatic consumable electrode welding: 1 - mouthpiece; 2 - replaceable tip; 3 - electrode wire; 4 - nozzle.

MMA welding is applicable in most areas of the construction industry. Do not do without them and installation, industrial scale. But nevertheless, the work with electrodes is not the most effective - too much consumption of both metal and electrodes. The percentage of loss will be up to 30% of the mass of the rod. It is best to use such welding in areas that do not provide for an automated process or in places that are difficult to access in terms of location.

Welding machines must also meet the working conditions.

Bulky transformers are good for stationary use. While manual semi-automatic machines are gaining popularity with their mobility and success in any field. In addition, transformer types are difficult in the practice of beginner welders due to the instability of the arc, which cannot but affect the quality of work. In the case of welding responsibility, for example, load-bearing or technically important structures, it is easier and better to do the work with a rectifier, which will quickly respond to current changes.

It is worth knowing that the use of manual arc welding can be unstable due to the magnetic field that occurs as a result of connecting polar products to each other.

That is, when melting metal with elements that have some magnetism, one should take into account the peculiarity of such work - the arc may deviate from the pool being welded and the seam will lie crooked.

The quality of the seams in any welding application must be at its best. Especially when it comes to responsible work (roads, pipelines, etc.). Stations are too dependent on the supplied electricity, their use can lead to seams that do not meet the requirement. Semiconductor rectifiers that have a voltage stabilizer in their design will best cope with such work, which is why the work is carried out continuously. However, welders claim that transformers (of a long-standing year of manufacture) are much more reliable in terms of durability than semiconductors and machines.

Electronic devices are used where accuracy is important and artificial air cooling is present. All kinds of relays, transistors and microcircuits will facilitate the work.

Safety is important when working with any type of automatic welding machine. Therefore, work in high-risk conditions (at height, in water or in a confined space) should provide for built-in current limiters in the apparatus. The qualification of the welder must meet the highest requirements.

Types of welding for various jobs

1. Melting of thick-walled metals up to 400 mm (bridge structures, wagons, reinforced concrete reinforcement tanks) is carried out using submerged arc welding. Such equipment is equipped with various power sources and accelerates work up to 300 m/h.
2. Ordinary. Under workshop conditions, welding takes place by means of a consumable electrode in carbon dioxide. Such welding is characterized by the absence of spatter, and is used in riveting or in the manufacture of hot steel structures.
3. Fixed joints of pipelines and highways of resource value are welded using flux-cored wire. This method is also good for structures whose assembly does not have accuracy for electronic components occupying various spatial positions.
4. Structures and products can be made of non-ferrous metal, which is known to be softer than alloy steels or carbon steels, titanium can be an exception. Such elements are best cooked with consumable or non-consumable electrodes in an inert gas.
5. Many designs combine several metals, so different welding technologies will be used.
6. Relatively new electron-beam and plasma welding. Became popular in construction. It is used for melting hard and active metals, where the long-term process is unacceptable. Minimum oxygen, allows you to get first-class seams.

Welding: scope

The construction of cottages, houses, renovation of apartments and offices also requires the presence of welding. They are especially associated with redevelopment. Any welding that does not require bulky equipment and special calculations is suitable here. Usually, a manual arc is used, but it is not suitable for supporting reinforcement due to the small depth of welding and low current. Electroslag welding is suitable for vertical joints, and the metal can vary in thickness up to 20 mm.

Welding masterpieces: features

Welding can become an art.

Nowadays, metal installations, which are of artistic value, are not uncommon. Typically, such facilities are located in squares or driveways.

Along with artistic forging, the use of welding has also found its place here. Some compositions are admirable, at first glance it is impossible to determine the position of the welding seams - they are so skillfully hidden.

It is easy to learn the basics of welding, if there is a desire, but only a true professional can constantly improve his own skills. The scope of welding is so vast that it is impossible to cover everything and describe in detail - it is everywhere.

In construction, engineering, outside the earth, in the form of art. Some of its subspecies are also used in high-precision medicine. And this means that it is difficult to overestimate the scale in which welding is involved.

The welding process forms an inseparable connection of various parts of any metals due to the formation of new interatomic bonds.

It consists in creating local or widespread heating, plastic deformation, or the simultaneous action of both factors. Modern welding technologies are represented by almost a hundred types of automated and manual welding.

There are three varieties or types of welding. According to the method of obtaining the energy of the connection, it is divided into thermal, thermomechanical and mechanical.

Thermal welding includes processes using an electric arc, gas, plasma and other sources of thermal radiation. It is thanks to him that heating and welding occur.

In thermomechanical types, in addition to thermal energy, pressure is used to obtain an inseparable connection.

In mechanical heat is obtained by friction, pressure, ultrasound or explosion.

Types of welding work are diverse and their classification is made according to different criteria. The classification goes according to the method, according to the continuity of the welding process, the degree of mechanization, the gases used. In addition, there are technological features that are individual for each type of welding.

Types of welded joints are described in detail in GOST (state standards). In addition, there are a large number of GOSTs describing the types of welding, methods for controlling welds, safety measures in the production of welding work.

Thermal welding of materials

Thermal processes are based on the melting of the parts to be joined due to thermal energy. There are several types of thermal welding:

• electric arc (in shielding gases, submerged arc, etc.);
• electroslag;
• electron beam and beam (laser);
• plasma;
• gas;
• thermite.

received the widest application. But other types are also in demand in various modern areas of production and in domestic conditions.

Electric arc melting

Electric arc welding works by releasing energy in the arc due to the fact that the resistance of the arc is much greater than the resistance of the entire electrical circuit forming a closed loop.

Therefore, almost all thermal energy is released in the arc, heating it up to 4.5-6 thousand degrees and causing the melting of any metal. The arc occurs in the gap between the electrode and the metal to be welded, causing them to melt.

During cooling, an inextricable seam is created, the properties of which are related to the current, the composition of the additive, and many other factors.

Arc welding is performed with consumable and non-consumable rods (electrodes). The equipment uses inverter technology, which made it possible to create compact, productive devices.

When welding workpieces with an electrode, an arc is ignited between it and the joint surface. This is created due to a short circuit when the bar touches the metal, and its subsequent separation at a distance of 3-5 mm.

The arc melts the end of the electrode and the edges of the workpiece to be welded. A weld pool is created at the arcing point.

To obtain a weld, it is required to lead the electrode along the joint at a speed sufficient to melt the edges and the electrode, but not sufficient to burn the parts.

After cooling the metal, a welded seam is obtained that is comparable in strength to the base. The electrode can be in the form of a separate rod in the coating or filler wire on the feed mechanism.

When welding with a non-consumable rod, an electric arc occurs between it and the edges of the workpieces. The edges are melted, if necessary, and the filler wire in the resulting weld pool. The rod can be carbon or tungsten. An electrode of a non-consumable type usually works with (brass, bronze, cupronickel) and refractory metals.

Flux and gas protection

Submerged arc welding is usually performed automatically or in a semi-automated process (semi-automatic). In the first case, all processes are automated, in the second, the electrode feeding process is carried out automatically, and the torch movement is carried out by the welder.

The melt in the weld pool is protected by the slag melt from exposure to atmospheric air. The slag is obtained by melting the flux entering the bath. The type of welding using fluxes is very productive, in addition, a high-quality weld is obtained without pores and other shortcomings.

Welding in gas provides protection of the welding area from the harmful effects of water vapor, atmospheric oxygen and nitrogen.

This is achieved by supplying a jet of shielding gas through the torch nozzle into the welding zone, which makes it possible to displace atmospheric air. Used when using non-consumable and consumable electrodes. The result is a high-quality seam with high labor productivity.

Electroslag

Electroslag type of welding is carried out due to the fusion of the vertical edges of the product with the electrode. When an electric current passes through the varnish, heat is released. The arc is present only at the initial stage. Subsequently, the metal is melted due to the heat released by the slag.

Copper sliders are installed on both sides of the gap. They are cooled by water supply. A tray with flux is installed below. An arc is ignited between it and the electrode and a wire is fed there.

The electric arc melts the wire and flux, forming a weld pool over which a light liquid slag floats. As the edges and welding wire melt, the sliders move up the joint. The result is a quality seam. Thanks to this process, metals of great thickness can be welded in one pass.

Radiation

In industry, especially instrumentation and electronics, it is required to weld very small parts that have special requirements for the welding process. The choice of welding method in this case is small. Only a powerful light beam, a stream of electrons or plasma can cope with them.

To obtain a seam of excellent quality, a high-energy source is required. It can be a laser or other similar source of energy capable of concentrating huge thermal energy in a small area and for a short time. uses the energy of electrons accelerated to high speed. In the case of a laser, heating is carried out due to the energy of photons.

Plasma, gas, thermal reaction

The essence of the type of welding using plasma is the formation of a jet of ionized gas, which is a current conductor.

The plasma temperature reaches 30,000 °C, which allows you to melt any metals in the shortest possible time. The plasma energy depends on the welding current, operating voltage, gas consumption. Welding seams are of high quality, thin, without internal stresses.

Gas welding is carried out by burning combustible gas in oxygen and releasing a large amount of heat. This is one of the oldest types of welding.

The temperature of the gas flame is three thousand degrees. Due to this, the joints of the welded product are melted. The melting process takes a long time, which causes heating of large areas of the surface of the joined products. When cooled, it causes large stresses in the seam and the part itself.

Thermite welding uses the heat generated by burning a mixture of aluminum and iron oxides.

Thermomechanical welding of materials

Thermomechanical welding includes forging, contact and similar types. These methods of welding metal use simultaneously thermal and mechanical energy. This type includes the following technologies:

• blacksmith;
• contact;
• diffusion;

Forge welding is a method in which the products to be welded are first heated to the required temperature in a furnace, and then they are connected to each other with a hammer. If a press is used instead of a hammer, then this method is called a press.

The contact type has such a name due to the fact that welding is carried out at the point of contact of the parts to be joined. They are strongly pressed against each other with the help of special electrodes, and then a powerful current is passed through the pressure point.

At the point of contact, the greatest resistance is obtained, which causes the release of the main heat precisely at this point. Accordingly, this leads to the melting of the metal at the point of contact. With the help of contact, spot or seam welding is obtained.

Resistance welding has become widespread in mechanical engineering, especially in the automotive industry. This is due to the high productivity and efficiency of this type of welding. It is the easiest to automate and is widely used in robotic systems.

It is impossible not to mention the diffusion type of welding. Its essence lies in the preliminary heating of the workpieces and their subsequent connection with the help of deformation, which arises from mechanical pressure. In such a process, diffusion of atoms from one connected part to another occurs and an inseparable connection is obtained.

Mechanical welding of materials

With a mechanical welding method, an inseparable connection is obtained without an external heat source. The joining process occurs under the action of pressure, friction, explosion or something similar, which forms interatomic bonds between the welded products.

Friction welding occurs as a result of rapid rotations. It is a part so tightly pressed against another that during rotation there is strong friction and heating to melting. This ensures a reliable connection of the workpieces.

If we take two metal plates, clean them from impurities and press them hard, then at pressures of several tens of thousands of atmospheres, plastic deformation occurs, leading to the formation of interatomic bonds of two parts. The result is an unbreakable connection. This method is called cold welding.

In order for the forces of atomic interaction to arise, an explosion is sometimes used between two parts. At this moment, the parts to be welded approach each other so that atomic bonds arise, which ensure a reliable connection of the products.

Another type of welding is ultrasonic. The high frequency waves cause the atoms in the metal to vibrate, and these become so strong that they cause atomic interactions. The result is a reliable connection.