Manual welding is performed by a person using a tool that receives energy from a special source. The textbook deals with arc welding - fusion welding, in which heating is carried out by an electric arc. Consumable-electrode arc welding is performed with an electrode, which melts during welding and serves as a filler metal. Summing up these three definitions, we can say that manual arc welding with a consumable electrode is performed by the welder using a tool that receives energy from a special source; The electrode being melted during welding, fixed in the tool, serves as a filler metal introduced into the weld pool in addition to the molten base metal. This type of welding currently occupies the first place in the construction and installation industry in terms of the volume of welding works performed.
In the initial period of the introduction of welding, steel electrode rods were used, chopped from wire and covered with a dried chalk solution to facilitate the initiation and burning of the arc. Currently, electrodes are used (Fig. 1.3) with rods made of wire of a certain chemical composition, coated on electrode coating presses with a special coating made up of components that protect the arc metal being melted from the harmful effects of air and provide the required composition and mechanical properties of the welded joint. In addition, the electrode coating improves the stability of the arc burning, the molten metal is covered with slag and gases formed during the melting of the coating and reacting with the metal. A large number of coated electrodes of various grades for manual welding of steels and non-ferrous metals have been developed and manufactured by the industry.
Rice. 1.3. Manual coated consumable electrode welding
1 - rod; 2 - coating; 3 - base metal
To form a welded joint, the welder strikes the arc at the place of the future seam and maintains its combustion, melting the edges of the base metal and the electrode. The space between the parts to be welded is filled with liquid metal of the edges and the electrode, the metals are mixed in one bath and a seam is formed. The welder moves the electrode towards and along the seam, forming a connection between the parts of the metal to be welded.
At submerged arc welding(fig. 1.4) the arc burns under a layer of welding flux. Welding is performed with automated welding installations: arc excitation, supply of electrode wire or filler metal and relative movement of the arc and the product are carried out by mechanisms without direct human participation according to a given program. The welding arc melts the base metal of the product, wire and flux, forming a weld pool covered with a layer of molten flux. The arc burning under the submerged arc is reliably protected by a layer of flux from the air and is not visible to the welder. The composition of the powdery flux is selected so that, in addition to being protected from air, when melted, it performs metallurgical processing of the molten metal, ensuring its required quality. The productivity of submerged arc welding is significantly higher than manual welding, since this type of welding allows the use of high welding currents, as a result of which the mass of the deposited metal per unit time is several times greater than in manual arc welding with covered electrodes. Submerged arc welding is especially common in building construction factories. It is also used in the installation of structures for the bathroom welding of reinforced concrete reinforcement.
Rice. 1.4. Automatic submerged arc welding
1 - electrode wire; 2- "welded product; 3 - welding flux; 4 - arc; 5 - welding bath; 6 - molten flux; 7 - molten metal
Gas shielded arc welding(Fig. 1.5) - this is a welding in which the arc and molten metal, and in some cases the cooling seam to prevent contact with air, are in a shielding gas supplied to the welding zone using special devices. This type of welding is widely used in the manufacture of building structures and, to a lesser extent, during installation. For welding in the manufacture of structures, carbon dioxide is used as a protective gas. Welding in carbon dioxide (Fig. 1.5, a) is usually carried out with a consumable electrode, which is a thin wire fed through hoses together with gas through a torch into the welding zone by a special mechanism. This type of welding is called mechanized arc welding. Manual argon-arc welding (Fig. 1.5, b) is performed using a special torch through which a shielding gas is supplied (argon or its mixture with helium and other gases). A non-consumable electrode from a tungsten rod is fixed in the torch, which has a high melting point (4500 ° C) and therefore almost does not melt and is little consumed during welding. In the latter case, it is mechanized welding.
Fig 1.5. Gas shielded manual non-consumable electrode welding
without filler wire (i), with filler wire (b) 1 - torch; 2- welding zone; 3- consumable electrode; 4 - non-consumable electrode; 5 - shielding gas; 6 - filler metal
Electroslag welding(Fig. 1.6) developed and introduced into production by the Institute of Electric Welding. E.O. Patona. This welding is carried out by fusion, which uses the heat generated by the passage of an electric current through the molten slag. It is used to connect steel parts with a thickness of 25-30 to 1000 mm or more, located in a vertical or inclined position up to 30 °. Parts are assembled with a gap of 20 mm or more, depending on the thickness of the parts and fixed.
Rice. 1.6. Electroslag welding
1 - details 2 - copper plate; 3 - slider; 4 - molten metal; 5 - slag; 5 - welded seam; 7 - electrode wire
On the one hand, the copper plate is pressed over the entire length of the joint, and on the other hand, the cooled copper slider moved during welding. Initially, an arc is struck on an additional entry bar fixed at the lower edges of the parts to be joined, and a pool of molten metal and slag is created. Then the electrode wire is immersed in the slag, and the electric current, passing through the slag into the metal, continues to melt the wire and the edges of the metal. There is an arc-free electroslag process of welding parts with the formation of a weld by a copper plate and a slide. The entire welding process is automated: feeding the electrode wire into the gap, moving the slider upward, filling the gap with molten metal and slag, maintaining the optimal level of metal and slag, maintaining the adopted welding mode. Electroslag welding is used at factories of building metal structures and at construction sites in the manufacture and installation of elements of steel structures for blast furnace casings, various containers, etc.
Forced seam welding(Fig. 1.7, a) by the method of keeping the molten metal from flowing out is similar to electroslag welding, however, in this type of welding, an arc process takes place, and not an electroslag one. Welding is carried out on automated welding installations and is possible in all positions. During the welding process, molten metal is retained and formed by cooled sliders. When welding, flux-cored wire is used, which is made (Fig. 1.7, b) from a thin steel strip, simultaneously filled with flux powder and rolled on a special machine with crimping rollers. This type of welding is used for metal with a thickness of 10-30 mm in the construction of tanks, pipelines and other structures.
Rice. 1.7. Forced seam welding
a - the position of the powder wire during welding; b - manufacture of flux-cored wire; 1 - molten metal; 2 - slider; 3 - powder wire; 4- steel tape; 5 -flux; 6 - squeezing rollers
Gas welding- fusion welding, in which the heat of a flame of a mixture of gases burned with a torch is used for heating. For welding, flammable gases are used, most often acetylene (C 2 H 2) or its substitutes - propane-butane mixtures, natural gas, hydrogen, coke oven and other gases, as well as flammable liquids (gasoline, kerosene). The high temperature of the welding flame is achieved by burning flammable gas or liquid vapors in oxygen. The temperature of the acetylene-oxygen flame reaches 3100-3200 ° C, propane-oxygen flame 2600-3750 ° C, hydrogen oxygen 2400-2600 ° C, etc.
Oxygen is a colorless, transparent, odorless gas. It is obtained by separating atmospheric air in special separating apparatuses. The atmosphere contains 20.95% oxygen. It liquefies at atmospheric pressure and a temperature of minus 182.9 ° C. For welding and cutting it is supplied in gaseous form in cylinders with a volume of 40 dm 3 containing 6 m 3 of oxygen at a pressure of 15 MPa. Compressed oxygen, in contact with oil or other fats, oxidizes them at a high rate, which leads to their ignition and explosion. Therefore, oxygen cylinders must be protected from contamination, as well as shock and heating, since cylinders are explosive.
Acetylene is a colorless gas with an unpleasant odor, explosive at a pressure of 0.15-0.2 MPa and temperatures up to 200 ° C. A small spark is enough to explode. Supplied in cylinders filled with a special porous mass impregnated with acetone, in which acetylene is dissolved. The acetylene pressure in the cylinder should not exceed 1.9 MPa at 20 ° C. For welding or cutting, the cylinder must be installed vertically to avoid entrainment of acetone along with acetylene. A 40 dm 3 cylinder contains 5 m 3 of dissolved acetylene. To provide oxygen and acetylene to large welding shops, oxygen is delivered in liquid form in special tanks, then degassed and supplied to welding stations through gas pipelines, and acetylene is extracted from calcium carbide (CaC 2) in stationary acetylene generators and fed to the shop through pipelines. Hydrogen is supplied in cylinders with a volume of 40 dm 3 under a pressure of 15 MPa, propane-butane mixtures - in cylinders in liquid form.
Gas cylinders are painted in different distinctive colors: oxygen - blue, acetylene - white, hydrogen - dark green, liquid combustible gases - red.
It should be borne in mind that a mixture of acetylene and other flammable gases with air and especially with oxygen is explosive, therefore oxygen cylinders must be stored separately from flammable gas cylinders and ensure that there is no gas leak from the cylinders.
When oxygen and combustible gases are used for welding, the pressure is reduced by means of special reducing devices fixed to the outlet fitting of the cylinder valve.
For gas welding (Fig. 1.8), a gas-oxygen torch flame is used, into which gas flows through hoses. Filler wire is usually used to form the weld. Welding is carried out manually and is used in construction for plumbing work to connect pipes of small diameter, air ducts made of metal of small thickness, as well as during repair work.
Rice. 1.8. Gas welding
1 - gas-oxygen flame; 2 torch, 3 filler wire
Thermite welding- welding, in which the combustion energy of the thermite mixture is used for heating. This welding (Fig. 1.9) is used to join the joints of reinforcing steel, rails, wires, etc. The parts to be welded are placed in a special refractory mold. Then thermite powder, consisting of aluminum and iron scale, is poured into the crucible located above the joint and ignited. Burning at temperatures above 2000 ° C, thermite forms a liquid metal from the scale, which melts the edges of the parts and welds them. It is possible to add filler metal during welding in the form of a rod and stir the bath with this rod for better removal of slag and gas inclusions and the formation of a seam. The use of pre-prepared thermite cartridges for welding wires and busbars significantly increases its productivity.
Rice. 1.9. Thermite welding
1 - parts to be welded; 2 - refractory mold, 3 - crucible; 4 - electrode
Plasma welding- This is fusion welding, in which heating occurs with a compressed arc (Figure 1.10). Plasma is an ionized and heated gas. To obtain it, a gas jet is fed under pressure into a plasma torch nozzle - a torch for welding or cutting with a compressed arc, in which a tungsten electrode is fixed. Passing through the arc in the nozzle, the gas heats up, ionizes, while the walls of the nozzle increase the pressure on the arc, and it leaves the nozzle in the form of plasma with a temperature of up to 40,000 ° C. The plasma jet cuts metal well, therefore, in the construction industry, plasma torches are used mainly for cutting steel and non-ferrous metals. For welding, this type is mastered only when used in automated installations.
Rice. 1.10. Plasma welding
1 - arc; 2 - plasmatron nozzle; 3 -electrode
contact welding- welding with the use of pressure, in which the heat generated in the contact of the parts to be welded is used during the passage of an electric current. This type of welding, in turn, is divided into several types: spot resistance welding, projection welding, seam resistance welding, butt flash butt welding and resistance welding.
Spot resistance welding(Figure 1.11, a), is a welding in which a welded joint is obtained between the ends of the electrodes 4 and 5, supplying current and transmitting the compression force. The place of contact 1 of the parts to be joined is melted by the heat generated during the passage of an electric current, the electrodes are compressed by force, resulting in a welded point 6. Spot welding is widely used in the manufacture of reinforcing meshes, at the intersection of rods. To connect intersecting rods of spatial reinforcement structures, special suspended welding pliers are used.
Rice. 1.11. contact welding
a - spot, b seam, c - butt welding, 1 - welded joint, 2, 3 - parts to be joined, 4, 5 - electrodes, 6 - welded point; 7 - compression force
Embossed welding- this is resistance welding, in which a welded joint is obtained in separate sections, due to their geometric shape, including projections. This type of welding is used to connect reinforcement bars with flat embedded plates, for which one or two protrusions are made on the plates or on the bars. Resistance welding is carried out by passing current and compressing the rod with the plate with special electrodes, as a result of which the places where the protrusions adjoin the rod are heated to melting, and when compressed, spot welded joints are formed.
Resistance seam welding(Fig. 1.11.6), in which the connection of the parts to be welded occurs between the rotating roller electrodes 4 and 5, supplying current and transmitting the compression force. Points 1 overlap each other to form a continuous seam. This type of welding is used to connect building structures made of thin metal, air ducts, pipe liners, etc.
Flash butt welding(Fig. 1.11, c) is butt resistance welding, in which the heating of the metal is accompanied by the flashing of the ends. The parts to be welded are fixed in the jaws of a contact butt machine, to which an electric current is supplied. When parts are brought together with a small force between the ends, strong heating occurs, accompanied by sparks and splashes, as a result of which the ends melt, then the parts quickly come together by force, the current is turned off, and a welded joint is formed, surrounded by an extruded burr consisting of oxidized burnt metal, which is cleaned. For parts with a large cross-section, in order to reduce the electrical and mechanical power of the machine, butt welding with preheating is used by periodically bringing the parts together with low pressure and heating the joint with a small current. After heating to a certain temperature, the current is increased and flash welding is performed. This type of welding is used for joining reinforcing bars and connecting pipes.
Resistance butt welding- contact butt welding, in which the heating of the metal is carried out without melting the butt ends. The welding scheme is similar to that shown in Fig. 1.11, c. First, they squeeze the parts with sponges, and then turn on the current. Contact resistance is created between the ends, individual protrusions at the ends are crumpled under the influence of temperature, and further heating occurs due to the resistance of the parts. When the temperature of the metal at the ends approaches the melting temperature, welding occurs under the influence of the compressive force with the formation of a smooth thickening.
Electron beam welding(Fig. 1.12) - fusion welding, in which the energy of accelerated electrons is used for heating. An electron gun is used to obtain a welding beam of electrons. It consists of a tungsten or cermet cathode, which is located in the focusing head, at some distance there is an accelerating anode electrode with a hole. When a low voltage alternating current is passed, a heated cathode emits (emits) an electron flow, which, passing through the anode hole, acquires a powerful acceleration, and then is formed by a magnetic lens and a deflecting magnetic system, as a result of which a narrow compacted electron beam is formed directed to a small area of the product ... The positive potential of the anode reaches several tens of thousands of volts. Upon impact on the surface of the metal, the energy of the electrons turns into heat, melting the metal with a narrow seam. Welding is performed in a vacuum created in a special chamber where the gun and the product are placed; it is mainly used to combine refractory, reactive metals. Occurs sporadically in the construction industry.
Rice. 1.12. Electron beam welding
1 - cathode, 2 - focusing head, 3 - anode, 4 - electron flux, 5 - magnetic lens, 6 - magnetic system, 7 - electron beam, 8 - product
Laser welding- fusion welding, in which laser radiation energy is used for heating. This welding is based on the use of radiation of light energy, specially enhanced by the interaction of photons with the atoms of the system. It is not yet used in the construction industry, but in the future it is possible to introduce it for special types of welding.
Ultrasonic welding- welding by pressure, carried out under the influence of ultrasonic vibrations - for joining plastic parts.
Plasma, oxygen-arc and air-arc separation and surface cutting of metals are used for heat treatment of steel and non-ferrous metals. Plasma cutting is carried out with plasma torches for cutting sheets of rolled steel, aluminum and other non-ferrous metals. This is mainly mechanized cutting; plasma torches are used for manual cutting.
In oxygen-arc cutting, a hollow (tubular) electrode with an outer diameter of 6-10 mm and a length of up to 400 mm, covered with a special coating, is used. Oxygen is supplied under pressure through the electrode tube. The cutter, holding the electrode in a special holder, turns on the current, ignites the arc from the edge of the cut metal and, moving the electrode along the cut line, gradually melts the metal, which burns in a stream of oxygen and is blown out by it, forming a cut. Oxygen arc cutting is used mainly for underwater work.
Air arc cutting of steel is used more often. In this type of cutting, the metal melted by the arc of a carbon or graphitized electrode is blown out with a jet of compressed air, thus separating or surface cutting is carried out. Control questions
- What is called welding?
- What is the difference between consumable and non-consumable electrodes, their meaning?
- What types of fusion welding do you know?
- What are the electrode coating and shielding gas used for?
- What is the difference between arc and electroslag welding?
- What is Plasma?
- It is required to join two steel parts by welding, the gap between them is 4 mm, the thickness is 5 mm. In what ways is their welding possible?
- It is required to cut pieces of copper sheet 10 mm thick and 400 mm long. How can you do this?
Currently, there are several methods of joining metal structures in the world, which are detachable and one-piece. Detachable connection methods are bolted connections using high-strength bolts, which are widely used in construction and repair work. In particular, bolted joints are used in the installation of floor trusses in industrial construction.
Permanent joints of metal structures include riveting and welding. Despite its centuries-old history, the connection of structures and parts of products using rivets is still used in industry to this day. However, the most modern and widespread method of joining metal structures is electric and gas welding.
Welding is a technological process of permanently joining materials, including metals and thermoplastics, by local or general heating. Since the discovery of the method of joining metal by electric welding, it has gone through a dynamic path of its development, in which many scientists of physics and metallurgy took part. Electric welding by the method of production is divided into the least complex manual electric arc welding, which is widespread almost everywhere from industry and agriculture to construction, repair and domestic use, as well as semi-automatic and automatic electric welding in stationary conditions in workshops and workshops.
One of the widespread and demanded method of electric welding in construction and when performing various repair work is manual electric arc welding, which is used in the manufacture and installation of metal structures, including non-standard ones. In addition, electric arc welding is used in the manufacture and installation of metal frames, various designs and sizes of trusses, beams, in the production of interfloor floors. The greatest advantage of manual welding is its mobility, that is, the ability to work in any conditions with the use of the simplest welding equipment - welding transformer in the presence of power supply. In the absence of power supply networks, any generators of electric current are used. Currently, a wide selection of welding machines of various capacities and for various applications is presented on the construction services market.
One of the main requirements when performing welding is to protect the seam from atmospheric air, the oxygen of which contributes to the oxidation of the weld metal. Such protection is carried out by special additives of welding electrodes or welding in inert gases. The most common inert gas welding is TIG welding, which is used for delicate welding jobs where the aesthetic appearance of welded structures is needed, such as internal stairs, various fences and other structures.
Welding work may only be carried out by companies that have the appropriate authorization. In their staff, companies must have highly qualified professionals welders who have an attestation certificate and admission to perform welding. Welding works are widely used for laying and repairing external engineering networks - water supply, heating networks, gas pipelines and other networks.
For the laying and repair of internal communications, gas welding is used using a combustible gas such as acetylene with oxygen. Together with manual electric arc welding, gas welding is also the most common in construction.
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Welding works are widely used in almost all sectors of the national economy - from microelectronics to the space industry. The connection of individual metal parts, the creation of metal structures and finished products is used in the manufacture of ships and land vehicles, in the construction of bridges, dams, flyovers and skyscrapers, etc. Everywhere we are surrounded by artistically executed metal fences, benches and balconies. To create such parts, electrodes are used, half of the produced range of which is used in manual electric arc welding. This is the most common type of welding. In addition, there are gas, electroslag, thermal, contact, diffusion ultrasonic and other types of welding.
A special feature of manual electric arc welding is that it uses electrodes, which are sheathed metal rods to supply current to the parts to be joined. In this case, an electric arc is formed between the electrode and the surface to be welded, forming a weld pool. The slag coating protects the seam from weathering. The correct selection of electrodes when welding various surfaces is of great importance, since the metal used in them participates in the formation of the weld. During the melting process, it is necessary to feed the rest of the rod to the joint by hand. The widespread use of this type of welding in construction is associated with its versatility. This allows welding in any position. Since the electrodes are available in numerous versions, it is possible to use them for welding various types of steel.
In construction, electrodes produced by the specialized company "SpetsElektrod" are widely used. Such brands as ANO-4. OZL-8, MR-3, MR-3s, UONI-13/45, OZS-12, TsT-11 have deservedly gained wide popularity due to their high performance characteristics. This association produces electrodes, the price and quality of which will appeal to any customer. The company constantly renews its production facilities and creates new samples. The old brands of electrodes are also being improved. You can familiarize yourself with and purchase SpetsElektrod products on the company's website. Here you can also find special welding electrodes, the price and characteristics of which are presented in the catalog of welding equipment. A wide assortment, tireless work with clients, attractive prices and high quality of products are the main basis of the activity of the "SpetsElectrod" company.
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Welding works in the manufacture of building structures
The section provides information on welding, welding and weldable materials, on qualification requirements for workers. Methods for increasing labor productivity and organization of welding production are given. Methods of welding metal structures, as well as methods of quality control of welded joints are described. For workers in construction and installation organizations.
Foreword Capital construction, one of the most important branches of the national economy, must ensure the creation and accelerated renewal of the fixed assets of the national economy, intended for the development of social production and the solution of social problems.
Welding work is an important technological process during construction and installation work. The complexity and responsibility of these works is constantly increasing in connection with the use of new steel grades and with the increased requirements for the quality of welded joints. The quality of welding depends not only on the timing of putting industrial and residential facilities into operation, but also on their further trouble-free operation.
To fulfill the tasks facing builders, in particular welders, it is necessary to increase labor productivity and quality of work by introducing advanced equipment and advanced forms and methods of labor, improving the organization of work, and improving the qualifications of workers.
Stroyizdat has published the following books on welding from the series "Improving the skills of workers in the construction and building materials industry" Doronin Yu. V., Khanapetov MV One-sided welding in construction.
Mechanized and manual methods of one-sided welding of carbon and low-alloy steels using new flexible and rigid backing strips are considered. The design of forming pads is given, their production and field of application are described, a feasibility study for the introduction of this type of welding is given.
For workers and foremen of construction and installation organizations.
Khanapetov M.V. Welding of structures with an additional powdery additive.
High-performance methods of automated submerged-arc welding and electroslag welding with powdered filler metal are considered. Recommendations are given on the choice of welding equipment, welding technology. The methods of restoring parts with a recumbent electrode with an additional powdery filler metal, as well as quality control of welded joints are discussed.
For workers in construction organizations.
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Welding in construction
Today, welding is more than actively used in industrial and residential construction, as well as in the process of laying roads and power lines, creating oil and gas pipelines. Moreover, each of these processes involves the use of its own type of welding: electroslag, butt, gas-flame, thermite, laser ...
If you delve into the history of the issue, it is worth noting that the welding process in construction began to be used really widely in the first half of the twentieth century. The prerequisites for this were: the invention of first electric arc, then contact, and even later gas welding; improvement of welding materials (wire, electrodes, welding machines, etc.) and equipment; proven higher efficiency of the use of welded structures, comparable to structures made of stone and concrete.
Today, the most widely demanded in the implementation of various construction works, the so-called electric arc welding. It is worth noting that this type of welding connects various metal structures to each other during construction and (or) repairs by creating a so-called electric arc (a powerful eclectic discharge that combines electrodes and welded structures).
Manual electric arc welding is used most often in construction today. Anyone who wants to try this technology on their own for the first time is recommended to buy electrodes with a special coating, which forms a special protective layer during melting.
In general, it is worth noting that in the process of implementing construction work for different alloys and metals, different electrodes are used (most often you will be offered to buy high-quality electrodes ANO-21, ANO-4, OZL-8, MR-3s, MR-3, OZS -12, UONI-13/55, TsT-11). In addition, these modern materials on the market are also presented for specialized purposes - for cutting and for surfacing. Moreover, it is important to take into account that the final quality of the welding itself, in particular, of finished construction objects, in general, determines the initial quality of these very electrodes.
Considering all of the above, in order for all construction work to be performed at the proper level, if you want to buy electrodes, you need to do this only from trusted sellers, for example, from the SpetsElectrod company, whose welding materials are always of the highest quality.
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Welding is the main type of joints in metal building structures. It has almost completely replaced other types of connections in the manufacture of structures and is widely used both in the factory and during installation on the construction site. Welding simplifies the structural form of the joint, saves metal, allows the use of high-performance mechanized methods, which significantly reduces the complexity of manufacturing structures. Welding joints have not only strength, but also water and gas tightness, which is especially important for sheet structures.
However, the internal residual stresses in the joint arising during welding complicate its operation and, in some cases, under the action of dynamic loads and low temperatures, contribute to brittle fracture. Welding is often difficult when assembling structures and joining several sheets into packages. Both of these circumstances in some cases complicate the use of welding and force us to turn to traditional bolted types of joints.
In construction, mainly electric arc welding is used: manual, automatic, semi-automatic and electroslag... Contact and gas welding is less commonly used. Other types of welding during the assembly and erection of building structures have not yet become widespread.
1. Manual arc welding universal and widespread, as it can be performed in any spatial position. It is often used for installations in hard-to-reach places where mechanized welding cannot be inflicted. The shallower penetration depth of the base metal and lower productivity of manual welding due to the reduced strength of the applied current, as well as the lower stability of the manual process compared to automatic submerged arc welding, are disadvantages of manual welding.
Electrodes used for manual welding are divided into several types according to the value of the ultimate resistance of the weld metal.
2. Automatic and semi-automatic welding submerged arc is carried out by an automatic machine with a welding wire feed d = 2-5 mm without coating. The arc is struck under a layer of flux, the flux melts, dopes the molten metal with impurities contained in it and reliably protects it from contact with air. The metal turns out to be clean with negligible amounts of harmful impurities - oxygen, nitrogen, etc. Due to good thermal protection, the molten metal under the flux layer cools slowly, is well freed from gas bubbles and slag and is distinguished by significant density and purity. High current strength (600-1200 A and more), used in automatic welding, and good heat protection of the seam provide deep penetration of the welded elements and high welding speed. Thus, good weld quality and high productivity are great advantages of automatic submerged-arc welding, and its use is desirable in all joints where possible.
The disadvantages include the difficulty of performing this welding in a vertical and overhead position and in cramped conditions, which limits its use at installation.
For short seams, semi-automatic welding with a semi-automatic hose is successfully used. The welding process is carried out with bare wire d> 3 mm submerged arc in the lower position or with a flux-cored wire rolled into a tube with a steel tape, inside which the flux is pressed, in any position. Flux-cored wire welding should be widely used in the installation of structures.
3. Electroslag welding is a type of fusion welding; this type of welding is convenient for vertical butt welds of metal with a thickness of 20 mm or more. The welding process is carried out with a bare electrode wire under a layer of molten slag, the weld pool is protected from the sides by copper sliders that form a seam, cooled by running water. The quality of the seam made in this way is very high.
4. Carbon dioxide welding conducted with a bare electrode wire d = 1.4-2 mm at a direct current of reverse polarity. Carbon dioxide at high temperatures actively interacts with steel, oxidizing it, which is compensated by the increased content of deoxidizers in the electrode wire. Welding in carbon dioxide environment, without requiring devices for holding the flux, can be performed in any spatial position. It ensures the production of high-quality welded joints from various metals with high labor productivity (15-20% higher than in semi-automatic submerged-arc welding).
Welding is used in order to obtain high-quality and reliable joints of metal products, which can have various shapes and compositions. Welding has found wide application in the production of construction work, in industrial construction, in private housing construction, in the construction of high-rise buildings, to obtain strong metal structures.
Welding works are carried out in two ways. The first method involves obtaining joints by plastic deformation - pressure. The second method is melting, this method involves connecting surfaces by melting them with an electric arc, plasma jet, gas torch. The method of welding is selected depending on what types of metal need to be connected, on its characteristics and properties. can be manual, automatic, semi-automatic.
Welding work is an integral part of construction or renovation work. Often construction work involves the installation of metal structures, communications, equipment and devices. During major repairs, it may be necessary to dismantle and install new engineering systems, perform a number of other welding and technical works. Installation of metal structures is not complete without welding.
In the course of his work, the welder is exposed to harmful gases, radiation of an electric arc, splashes from molten metal, in connection with safety requirements, the employee must be provided with personal protective equipment. A welding specialist must carry out work in overalls and special footwear. It is also supposed to use personal protective equipment for the head - helmets, berets, hats; face protection - welding masks, shields; face and eye protection means are goggles, as well as other protective equipment offered by NT-Svarka.
The most common types of work using this: installation and dismantling of heating systems, water supply systems, sewerage systems, installation and dismantling of heating devices, manufacturing, installation, transfer, repair of metal structures, welding of non-ferrous metal, production and installation of garage doors, fences, gratings.
The most common welding method in the construction industry is manual arc welding. It is used for the manufacture, repair and installation of metal structures of any shape, size and purpose.
Argon arc welding is used for delicate work such as fences, window bars, stairs. This welding method is used when the aesthetic aspect is of decisive importance.
The most popular method of welding is gas welding, usually this method is used for the installation of pipeline systems, minor repairs.
Regardless of the welding method, the work must be carried out by qualified specialists with the appropriate category, permission to, personal protective equipment.
The creation of a permanent connection of metals using an electric arc is called welding. In this way, one or more parts are assembled.
Today, welding is used in industry and construction. Welding work can be carried out anywhere, in different climatic zones, under extreme weather conditions. From space to welding of underwater objects.
It is impossible to imagine modern production without welding - too much has been created using this technology. From a garage to a large aircraft building plant, from a kettle to an airplane, one or another type of welding joints is used or has been applied everywhere.
New technologies for creating seams are introduced every year. Materials joining technologies are becoming more and more advanced. Often, when creating something new, one has to remember the well-forgotten old.
A striking example of this is today's news about the restoration of previously lost technology at the Kazan aircraft plant, ELU-24. This type of welding allows you to weld monolithic titanium-magnesium alloy plates of variable thickness. A unique, very high-tech welding used for the construction of airframe structures in the aircraft industry.
Welding machines are becoming more accessible for ordinary citizens. At the moment, they are common even among non-professionals. In many private houses, garages, there is equipment designed for welding, small works.
The wide demand gave rise to a large-scale offer - the range of welding equipment on the market is simply huge. From semi-professional to household.
Main types of welding
The main types of welding, the most common:
- manual;
- automatic;
- argon.
Of course, these are not all possible technologies, but some of the most widely used ones.
Each type of welding has its own pros and cons. Its subtleties and nuances. Each type requires one or another equipment, consumables.
Manual arc welding
Most used, common welding. Due to long-term use, technologies are well developed, therefore, it is universal. The welding process takes place using a standard electrode.
Its advantages - you can work in any position, which makes welding easier in places that are difficult to access. Often used in construction. The wide range of electrodes produced by the industry allows you to weld various grades of steel. Easy transportation of equipment.
Disadvantages - poor performance. The quality of the seams depends entirely on the qualifications of the welder who performs the work, which is an unpredictable factor.
Argon welding
Welding a seam using argon is called argon welding. Inert gas allows you to create weld joints using consumable electrodes. It is a convenient weld when joining alloy steels. Also suitable for welding non-ferrous metals.
With argon, well-formed welds are easily created using the ability to control the penetration depth of materials.
Argon welding is usually done with automatic machines. Especially for connecting non-swivel pipe joints.
The main disadvantage of this type is the low productivity of the manual mode. Automatic is not always possible, in particular for differently oriented short seams.
Semi-automatic welding
The type of creation of welded joints is massively widespread in the machine-building industry. Carbon dioxide is used for welding. Not demanding on the level of qualifications of a welder working on such equipment.
