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Ways of welding of rails (Electrocontact, electric arc, gas pressure and aluminothermic welding). Electric arc welding of rail joints Welding of rails by manual arc welding

Ways of welding of rails (Electrocontact, electric arc, gas pressure and aluminothermic welding). Electric arc welding of rail joints Welding of rails by manual arc welding

Even discarded or end-of-life rails are a desirable asset for any prudent homeowner. After all, a rail that is strong and resistant to corrosion can replace any metal beam.

However, the installation of structures from this type of rolled metal is very difficult. Heavy rails require strong welds. Railway workers use a special thermite composition for these purposes. Well, in everyday life, special electrodes are needed for welding railroad rails. And in this article we will describe exactly such products with which you can join the rails in any way convenient for you.

"Rail" electrodes

When deciding which electrodes to weld the rails with, it is worth taking into account the thickness of a given grade of rolled metal. Therefore, only special electrodes of the UONI series, designed for joining thick structures, can be a source of filler material in the process of rail welding. Moreover, for welding rails, the “junior” representatives of this series are sufficient - electrodes UONI 13/45 and 13/55, with which workpieces from high-carbon or low-alloy steels can be joined.

Electrodes UONI 13/45 and 13/55 differ from other sources of filler material by a special flux (coating), which includes ferromanganese ores, graphite, silicon and other materials.

Thanks to this multi-component mix, stable burning of the arc is ensured, which transfers high temperature to the welding zone, and the formation of pores in the weld is suppressed. The composition of the electrode wire is also interesting. It is made of an iron-carbon alloy alloyed with nickel and molybdenum. Wire diameter - 2-5 millimeters.

As a result, based on the special composition of the flux and filler material, the UONI series provides not only a high speed of operation, but also a no less high strength of the weld.

Preparation of the electrode for welding

Electrodes for rail welding - work in very difficult conditions. After all, the thickness of the joined edges in this case can be equal to several tens of centimeters.

Therefore, special requirements are imposed on the quality of such electrodes, namely:

There should be no large cracks on the coating of such electrodes.
The humidity of the coating must correspond to a certain value.

And if the compliance of the electrode with the first requirement can be checked visually, then with humidity everything is much more complicated. Therefore, before welding, all electrodes from the UONI series are subjected to mandatory calcination (drying) in a special installation.

This procedure looks like heating the product to a temperature of 350-400 degrees Celsius. Moreover, the electrodes are loaded into the already heated "oven" and "languish" in it for about 1-2 hours.

After such preparation, the electrodes can be used in any position, forming with their help both lower, and ceiling, and vertical seams with direct current, and reverse polarity of the connection.

The only "contraindication for use" for the UONI series is welding from top to bottom.

steelguide.ru

Method for welding rail joints

The invention relates to the field of welding, namely to the welding of railway rails. On the edges of the rails (1) and (2) or the edge of one of the rails, a transverse cut is made along the vertical plane from the head to the beginning of the rail sole. A horizontal cut is made along the end surface of the rails or rail perpendicular to the previously made cut and the end surface of the sole is chamfered at an angle of 45° to form a blunt (3) at the base of the sole. Install the rails with the required technological clearance (4). The welding wire is inserted into the gap together with the insulated end tip of the electrode holder of the semi-automatic welding machine. Electric arc welding is carried out continuously along the entire height of the rail using lateral forming overlays-moulds in the welding zone at a welding current that ensures the formation of a liquid pool in the entire volume of the technological gap. The liquid bath at the root of the weld is obtained by melting the edges of the base metal of the rails. The mechanical properties of the weld and the productivity of the process are increased, and the work of the welder is also facilitated. 2 ill.

The invention relates to electric arc welding methods of a railway track and can be used primarily for semi-automatic arc welding of rails.

A method of automatic welding of joints of a railway track is known, in which rails are welded using an electric arc welding machine (see Japan No. 08-00328 A, class B23K 31/00, publ. 09.01.1996).

However, this method of welding cannot be used in conditions of various wear of the working surfaces of the head of the rail track and requires high qualification of welders.

The closest known in terms of its technical essence and the achieved result is the method of welding railway track rails selected as a prototype, including trimming the edges of the rails or the edges of one of the rails, installing the rails with the necessary technological gap, introducing the welding wire inside the gap and arc welding using side forming mold overlays in the welding zone at the welding current, which ensures the formation of a liquid pool in the entire volume of the technological gap (see USSR author's certificate No. 78136, class V23K 9/02, 1942).

In the known method, the rails are installed with a gap between the edges to be welded from 9-14 mm. With such a gap, the weld is obtained mainly due to the melting of the electrode material. The welded edges heat up so much that a common pool of molten metal is formed, which is maintained in a liquid state during the entire welding period. As forms that form the outer side of the welded joint, graphite plates can serve, the inner surface of which is made in the form of a rail. The size and shape of the reinforcement of the weld depends on the size and shape of the corresponding recess that is made in the mold.

The ends of the rails are cut with a rail cutter along a plane perpendicular to the axis of the rail. Bevel edges before welding do not produce. The gap between the ends of the rails of the order of 9-14 mm does not allow welding the edges of the sole of the rails, therefore, a forming lining is used to form the reverse side of the weld root. The weld is obtained mainly due to the melting of the electrode material, the molten mass of which fills the gap between the ends of the rail sole and the forming lining.

The most significant disadvantage of this method is the frequent change of the electrode (the length of the electrode used for manual welding of rails is 450 mm). After the electrode burns out, the welding process is interrupted. A hard protective slag crust forms on the surface of the weld. To continue the welding process, it is necessary to re-ignite the arc, melt the slag and continue the process. Periodic interruption of the arc leads to the formation of defects such as lack of penetration, slag inclusions, gas pores in the weld. These defects are the reason for the low mechanical properties of the welded joint.

The technical result from the use of the present invention is an increase in the mechanical properties of the weld; reduction of rail welding time; saving expensive welding materials, as well as facilitating the work of the welder.

The specified technical result is achieved by the fact that in the method of welding the rails of a railway track, including cutting the edges of the rails or the edges of one of the rails, installing the rails with the necessary technological gap, introducing the welding wire into the gap and arc welding using side forming overlays-molds in the welding zone on welding current, which ensures the formation of a liquid pool in the entire volume of the technological gap, when cutting the edges of the rails or the edges of one of the rails, a transverse cut is made along the vertical plane from the head to the beginning of the rail sole, a horizontal cut along the end surface of the rail perpendicular to the previously made cut and removed on the end surface of the sole there is a chamfer at an angle of 45° with the formation of a bluntness at the base of the sole, and electric arc welding is carried out continuously along the entire height of the rail using a semi-automatic welding machine with an electrode holder equipped with an insulated end tip, which is inserted with the welding wire into the technological gap, while the formation of liquid baths in the root of the seam are carried out by melting the edges of the base metal of the rails.

The proposed welding method can be implemented in two versions.

Figure 1 shows a welded joint with the preparation of the edge of one of the rails, figure 2 - welded joint with the preparation of 2 edges of the rails.

In Fig.1 marked: 1 - rail (without edge processing), 2 - rail with a prepared edge, 3 - blunting, 4 - gap between the edges, α - angle between the edges.

In Fig.2 marked: 1, 2 - rails with a prepared edge, 3 - blunting, 4 - the gap between the edges, α - the angle between the edges. The angle α between the edges is in the range of 30-60°.

In the first version of the welding method with preparation of the edge of one of the rails, the edges of the rails or the edge of one of the rails are preliminarily machined, maintaining a gap between the ends of the rails of 22-25 mm. On the welding holder, instead of the usual mouthpiece, a special tip (insulated end nozzle) is installed, which allows welding into a narrow gap along the entire height of the rail. The tip with the wire is inserted into the gap and welding is carried out using forming mold plates in the welding zone at a current strength that ensures the formation of a liquid pool in the entire volume of the gap. To increase the strength of the welded joint, the ends of the rails are prepared by cutting them along a vertical plane making an angle of 45° with the longitudinal axis of the rail, so that the weld experiences a minimum load when the wheel rolls over the surface of the rail head. Welding is carried out in a continuous, semi-automatic arc method.

Weld railroad rails tapa R65. The edges of the rail are prepared from two ends or from one end, maintaining a gap between the ends of the rails of 22-25 mm. The surfaces of the ends of the rails before welding are cleaned to a metallic sheen. A copper lining is installed under the sole of the rails to be welded, forming the reverse side of the seam, and fixed with a clamp. The sole of the rail is welded with a self-shielding flux-cored wire with a diameter of 1.6 mm, at a current strength of 190-200 A. Side copper molds - molds are installed on the neck and head of the rails and fixed with a clamp. Weld the neck and head of the rail.

The proposed method makes it possible to obtain a weld with mechanical properties that are equivalent to the properties of the base metal, while the obtained mechanical properties of the weld increase the service life of the rails to the service life of the rails installed in the track without welding.

In the second variant of the welding method with the preparation of 2 rail edges, the rail edges or the edge of one of the rails are preliminarily machined, while a transverse cut is made along the vertical plane from the head to the beginning of the rail foot, and then a horizontal cut is made along the end surface of the rail perpendicular to in relation to the previously made cut and at the end of the sole, a chamfer is chamfered with a bluntness at the base of the rail sole, rails are installed with the necessary technological gap, an electrode is inserted into the gap and welding is carried out using a semi-automatic welding machine and using molds at the welding site at a current strength that ensures the formation of a liquid pool in the entire volume of the gap, and the liquid bath at the root of the weld is obtained by melting the edges of the base metal.

The edges of the rails or the edge of one of the rails are preliminarily machined, a transverse cut is made along the vertical plane from the head to the beginning of the rail sole and a horizontal cut is made along the end surface of the rail perpendicular to the previously made cut, and at the end of the sole, a chamfer is removed with a bluntness at the base of the rail sole , and the liquid bath at the root of the weld is obtained by melting the edges of the base metal.

Welded railway rails tapa R65. In mechanical workshops, distances are measured for a piece of rail 3 m or more in accordance with TU 32 TsP-670-88 and the edges of the rail are prepared from both ends for installation in place of the defective rail. In this case, a transverse incision is made along a vertical plane from the head to the beginning of the rail sole. Then, a horizontal cut is made along the end surface of the rail perpendicular to the previously made cut, and at the end of the sole, a chamfer is removed at an angle of 45° with a bluntness of 2 mm at the base of the rail sole. Markings are made on the rail from which the defective section is removed. A defective piece of rail is cut off, equal in size to the prepared one, and a piece of rail with edges prepared for welding is installed in this place. The gap between the rails is 2 mm. The ends of the rails before welding are cleaned to a metallic sheen.

Under the sole of the welded rails, a copper lining forming the reverse side of the seam is installed and fixed with a clamp. The root of the seam is welded with an electrode of the UONI - 13/65 brand with a diameter of 3 mm, a current of 140-160 A, followed by filling the gap between the ends of the rail foot with an electrode of the UONI - 13/65 brand, with a diameter of 5 mm, a current of 250-280 A.

Lateral copper molds are installed on the neck and head of the rails and fixed with a clamp. The neck and head of the rail are welded with electrodes of the UONI - 13/65 brand, 5 mm in diameter, current 250-280 A.

A method for welding rails of a railway track, which includes cutting the edges of the rails or the edges of one of the rails, installing the rails with the necessary technological gap, introducing the welding wire into the gap and arc welding using side forming overlays-molds in the welding zone at a welding current that ensures the formation of a liquid pool in the entire volume of the technological gap, characterized in that when cutting the edges of the rails or the edges of one of the rails, a transverse cut is made along the vertical plane from the head to the beginning of the rail sole, a horizontal cut along the end surface of the rail perpendicular to the previously made cut and removed on the end surface of the sole chamfer at an angle of 45° with the formation of a blunt base at the base, and electric arc welding is carried out continuously along the entire height of the rail using a semi-automatic welding machine with an electrode holder equipped with an insulated end tip, which is inserted with the welding wire into the technological gap, while the formation of a liquid pool at the root of the weld carried out by melting the edges of the base metal of the rails.

www.findpatent.ru

Ways of welding rails (Electric contact, electric arc, gas pressure and aluminothermic welding), page 2

Welding of rails by the second method - flashing with preliminary intermittent heating consists of an intermittent heating stage, a continuous flashing stage; stages of upsetting and welding, stages of cooling of welded joints. In this method, in contrast to the first method, heating of the metal of the rails is carried out by repeated cyclic closing and opening of the rail ends. Electrocontact welding provides the highest quality of welded joints. The quality of welded joints is determined by the degree of plastic deformation and heating of the rail metal. In this regard, the priority is the obligation to strictly ensure the welding modes approved by the Main Directorate of the track of the Ministry of Railways.

7.3. Arc welding

In electric arc welding, the rails are connected by the metal of the electrode, which is melted from the heat of the arc discharge.

Electric arc welding of joints does not require the application of sedimentary pressure. For this welding, alternating current from a transformer or direct current from a mobile welding unit is used.

The best method of electric arc welding is the bath method, in which the ends of the rails, cut perpendicular to the longitudinal axis, are installed without a fracture in the plan, and in the profile with an elevation of 3-5 mm, and in this position they are fixed with a gap of 14-16 mm.

An electrode is inserted between the ends, through which a current of 300-350 amperes is passed. The molten metal of the electrode fills the gap between the ends along the entire section of the rail.

To prevent the molten metal of the electrode from spreading, inventory copper molds are used to close the gap from below and from the sides. Welded joints are ground around the entire perimeter of the rail. The quality of the welded joint depends on the electrodes and their coating, the constancy of the liquid state of the metal until the end of the welding process, and the thoroughness of the seam processing.

Electric arc welding is used only for rails laid on station tracks, except for main and receiving-departure ones.

7.4. Gas pressure welding

Gas pressure welding provides metal connection at a temperature

below the melting point with the application of pressure.

The main advantage of gas-pressure welding of rails is the high quality of the joint and the obtaining of a homogeneous metal structure in the joint zone, therefore this type of welding is especially beneficial when applied to heavier types of rails.

Before welding, the ends of the two rails are attached tightly to each other and together with the joint, the ends of both rails are simultaneously cut with a circular saw on a rail-cutting machine or with a mechanical hacksaw, which ensures the tightness of the ends and the purity of the metal. Immediately before welding, the ends of the rails must be thoroughly washed with carbon tetrachloride or dichloroethane. Preparation before welding consists in preheating the ends of the rails.

To heat the rail, multi-flame burners of the MG-50R type are used,

MG - 65R, MG - 75R. Multi-flame burner type MG - R65 is shown in Figure 1.3.

Fig. 7.3: Multi-flame burner MG-R65 (a) and its barrel (b):

1 - upper part of the burner; 2 - pads with holes for gas; 3 - the lower part of the burner; 4 - gas pipeline; 5 and 9 - pipelines for running water; 6 - gas bracket connecting 1 and 3; 7 - gas distribution chamber; 8 - cord with nipple; 10 - extension connecting the barrel with the mixing chamber; 11 - mixing chamber; 12 - burner barrel; 13 and 14 - fittings for supplying gas to the barrel.

The ends of the rails are clamped with a hydraulic press and heated to a temperature of 12000C by a system of multi-flame burners oscillating along the joint (50 oscillations per minute). At the same time, the rails are compressed with the force set by the calculation (10 - 13 tons) until a draft of a given value (about 20 mm) is obtained.

For welding, universal gas-pressing machines SGP - 8U or MGP - 9 are used.

After welding, the joint is processed, and then it is normalized.

7.5. Aluminothermic welding

The creation of high-speed highways and a seamless track sets high quality standards for rails, especially at their junctions. Aluminothermic welding of rails fully meets these standards.

Aluminothermic welding of rails is intended for joining together in any combination of volume-hardened, surface-hardened and non-thermally hardened rails.

Welding of joints of rail lashes and joints (except insulating) of turnouts laid on wooden or reinforced concrete sleepers and beams can be carried out on the main, receiving-departure, station and hump tracks of the railways of the Russian Federation, on the access roads of industrial enterprises, as well as in the subway .

This process is based on the thermite reaction, discovered in 1896 by Professor Hans Goldschmidt, which is a chemical reaction to reduce pure iron from its oxide using aluminum with the release of a large amount of heat:

Fe2O3 + 2Al => 2Fe + Al2O3 + 849 kJ

The thermite reaction occurs in the crucible within a few seconds after the thermite portion is ignited, consisting of a mixture of aluminum powder, iron oxide, steel particles that dampen the reaction, and alloying additives necessary to obtain steel of the desired quality. The reaction takes place at temperatures above 2000°C with final layer-by-layer separation of the reaction products: liquid steel (bottom) and light slag (top).

In Russia, VNIIZhT together with foreign companies Snaga (Slovakia), Electro-Termite (Germany), Reltech (Czech Republic and France) perform work related to thermite welding of rail elements in the area of connecting tracks. When laying a seamless track, the thermite method of rail welding (Fig. 1.4.) plays a leading role. At present, in the turnout area, it is the main method of connecting rails. It is a cost-effective technology with great application flexibility. In most cases, welding can be carried out without closing the stage. The technology of the company "Electro-Termite", having received the greatest distribution in comparison with other companies, represents two main methods of electro-thermite welding on the Russian market, namely the so-called SoBoS method (SoWoS) and the SkFau method (SkV) (Fig. 1.5) .

vunivere.ru

Electrodes for welding railroad rails

People who carry out large-scale construction or are simply used to doing everything powerfully, then they, for sure, are faced with the problem of rail welding. Welding rails is a problem because they have a large diameter and, as a result, create obstacles for comfortable welding. Therefore, for welding rails, you need to use high-quality electrodes that allow you to be completely confident in the quality of the welded product.

One of those electrodes that can be used for welding rails are UONI 13/45 or UONI 13/55. Yes, indeed, UONI welding electrodes are an excellent choice for welding such thick structures as rails.

UONI electrodes are used for welding critical metal structures, when high demands are placed on the metal seam in terms of impact strength. Many professional welders recommend UONI electrodes for welding structures operating under loads, pressure and other environmental influences.

Welding with UONI electrodes makes it possible to obtain high quality metal, which has high resistance to cracking and hydrogen content. Welding with UONI electrodes can be performed in all spatial positions. For welding, you need to use a direct current of reverse polarity.

The material for the manufacture of welding electrodes UONI is Sv-08A welding wire, which fully complies with state standards adopted in our country. On the surface of the coating of the welding electrodes of the UONI, small cracks are allowed, which may be on the coating of the welding electrode. However, if the coating of the welding electrode is severely damaged, then you need to check where you store them, because moisture can damage the welding electrode.

There are some features in the coatings of UONI welding electrodes that require mandatory calcination before use. The calcination of the UONI electrodes is carried out at a temperature of 350 to 400 degrees Celsius.

Baking electrodes before welding makes it easier to work with them and allows you to make the welding seam applied by them more durable. Also, baking or drying the electrodes at a specified temperature makes them less susceptible to moisture.

As you can see, the use of UONI welding electrodes allows for high quality welding. Thanks to their high quality and welding features, you can start welding rails in a short time.

Welding rails is a difficult job, so in order for you to be able to do it as quickly and efficiently as possible, you need to use UONI electrodes. Also, in order for you to bake the UONI electrodes and store them in a suitable place, it is best for you to purchase a special oven for baking electrodes.

When carrying out installation, as well as repair work on the railway track, crane installations, and other conditions where rails are used, a special welding technology is used. Since, under the described conditions, special strength is required, as well as resistance to various kinds of loads, the welding of railway rails belongs to a separate category of welding.

Arc welding

It should be noted that one of the most common methods used in welding rail strips and rail joints is electric arc welding. In this case, the rails are laid in the required position, and the space between their joints is gradually filled in layers with the necessary welding material. The latter is melted by the temperature of the arc discharge. For welding the ends of railway rails in this way, alternating current supplied from a transformer or direct current obtained from a mobile welding unit can be used.

The best option is the bath method. In this case, the ends of the rails, previously cut perpendicular to their longitudinal axis, are mounted without a fracture. In this case, the profile should have an elevation of 3 to 5 millimeters. In this position, the rails must be fixed with a gap of 14 to 16 mm.

An electrode is inserted between the ends of the railroad rails, through which a current of 300-350 amperes is passed. As a result, the molten metal of the electrode fills the gap between the ends, evenly over the entire cross section.

To prevent metal spreading, various methods are used to close the gap between the rails. After welding, the place of work is polished around the entire perimeter.

Thermite welding

The technology of this type of welding consists in the reaction that occurs when iron oxide and aluminum come into contact. Steel, which occurs under the described conditions at temperatures above 2000 degrees, must be poured into a fire-resistant form, which is completely identical to the geometry of the rail itself.

Thermite technology was discovered back in 1896 by the famous professor Hans Goldschmidt. In fact, thermite technology is the reduction of iron from oxide using aluminum. In this case, the thermite reaction is characterized by the release of a large amount of heat.

Thermite technology is also called aluminothermic rail welding, as it uses aluminum. Interestingly, the thermite reaction occurs within only a few seconds after the thermite portion is ignited. In addition to iron and aluminum oxide, this mixture includes steel particles that dampen the reaction, as well as alloying additives. The latter serve to obtain steel of the required quality and parameters. Interestingly, at the end of the reaction, a layer-by-layer separation into liquid steel and light slag is carried out, which is on top.

Thermite technology allows connecting surface-hardened, volume-hardened, and also non-thermally hardened rails in any combination. Thermite welding makes it possible to meet the high requirements that are put forward today for high-speed highways and seamless tracks.

Gas pressure welding

This technology is based on the connection of metals at a temperature that is in the range below the melting point, but at high pressure. The main "advantages" of this technology:

Homogeneous structure of the metal in the area of the junction of railway rails;
High quality of the resulting connection.

Due to the advantages described above, this type of welding is very effective when welding heavy railroad rails. Before the actual welding, the ends of the railway rails are tightly attached to each other. In this case, with the help of a circular saw of a rail-cutting machine or a mechanical hacksaw, the ends of both rails are simultaneously cut through. As a result, the maximum purity of the metal is ensured, as well as a high tightness of fit. Before the welding process itself, the ends are washed with carbon tetrachloride. Dichloroethane can also be used for these purposes. The preparatory stage before welding itself consists in heating the ends of the rail, for which multi-flame burners are used.

After that, the ends of the rails must be clamped with a hydraulic press, followed by heating to 1200 degrees using the same multi-flame burners. The latter carry out oscillatory movements along the formed joint. The frequency of these oscillations is 50 oscillations per minute. Along with this, the rails are compressed with a force of 10 to 13 tons, which is set by special calculations. The result is a draft of about 20 mm. To carry out the described actions, universal gas-pressing machines are used.

After welding is completed, the resulting joint is processed. After that, it is also normalized.

Results

So, there are three key rail welding technologies. Each of them has its own "pros" and "cons". However, it should be noted that aluminothermic welding meets all the most stringent modern requirements for seamless railway tracks. Therefore, its use is fully justified in the construction and repair of modern highways.

Rail welding

When working with crane installations and performing the installation of the railway track, it becomes necessary to connect and weld the rails. In this case, a special technology is used, which provides a special connection strength and resistance to increased loads. It must be said that such work belongs to a separate category of welding work, the features of which we will discuss in this article.

Welding can be performed by the following technologies:

Thermite.
Electric arc.
Gas pressure welding.

Each of these technologies has its own specific disadvantages and advantages. Let's talk in more detail about such welding methods.

Electric arc welding of rail joints

To date, this technology has become the most widespread, which is explained by the simplicity of the equipment, the ease of the work itself and the quality of the connection made. When performing welding work, the rails are laid in the desired position, after which the space between the joints is layer-by-layer filled with welding material. The melting of the welding material is ensured by the high temperatures of the arc discharge. If it is necessary to weld the ends of the rails, alternating current from the transformer is used. It is also possible to use mobile welding machines powered by direct current.

When using electric arc technology, it is possible to weld rail joints using the bath method, in which rails cut perpendicular to their axis are mounted inside the bath. In the bath, their high-quality welding is carried out with each other. With this welding method, the rails are fixed with a gap of no more than 16 millimeters. The elevation of the profile can vary in the range of 3-5 millimeters.

When using the bath method, an electrode is placed between the ends, through which an electric current with a power of about 350 amperes is supplied. The electrode quickly fills the gap between the connected rails, evenly distributing the molten material over the entire section. This method eliminates the spreading of metal, while ensuring the highest quality closing of the gap between the connected metal elements. After welding is completed, it will be necessary to grind the connecting seam around the perimeter.

Aluminothermic rail welding

Thermite welding method is based on the property of aluminum oxide and iron to react with each other at high temperatures. Such thermite welding is also called aluminothermic technology. To perform this welding, a high-temperature-resistant form is used, which is identical in appearance to the geometry of the rails. This form must withstand temperatures of more than 2000 degrees, at which aluminum and iron come into contact.

This welding technology was discovered at the end of the 19th century. However, due to its technological complexity, it has received distribution only relatively recently. The main difficulties in performing such thermite welding are that the reaction of aluminum oxide and iron occurs only at temperatures of several thousand degrees. Accordingly, it was necessary to heat both the rails themselves to such extreme temperatures, and to use an appropriate form that could not melt and retain its geometry.

To join metals, it is necessary to set fire to the thermite mixture, which quickly burns out with the formation of high temperature. Such thermite portion contains not only oxides of aluminum and iron, but also a variety of alloying additives. Such additives are necessary to obtain the most durable connection with the desired parameters of resistance to mechanical stress. During such a temperature reaction, a layer-by-layer separation of light slag and liquid steel occurs. In this case, the slag is on top and subsequently easily removed from the joint.

The thermite method of rail welding allows joining volume-hardened and surface-hardened materials. It must be said that with the help of this technology a strong and durable connection is provided, therefore the thermite welding method has found application in the manufacture of jointless high-speed railway lines.

Gas press technology

This original rail joining technology uses a temperature below the melting point, but high pressure ensures a quality rail joint. Among the advantages of this welding technology, the following can be noted:

Excellent indicators of the quality of the connection made.
Homogeneous structure of the railway pavement joint.
High performance.
Minimum consumption of welded materials.

Such gas-pressure welding is widely used when connecting heavy railroad rails. When performing, special equipment is used, which allows to ensure the highest possible pressure of the connected rails. Metal products are tightly pressed against each other, after which, using a special clamp, the ends are heated, and due to high pressure, the rails are connected to each other. In the process of such work, it is necessary to ensure the washing of the elements to be welded with carbon trichloride. This allows for the connection of metal elements at the molecular level.

The operating temperature for gas-pressing technology is about 1200 degrees. For such work, multi-flame burners and powerful hydraulic presses are used. For high-quality heating of the junction, multi-flame burners are used, which carry out numerous oscillations in the area of the welded joint, which makes it possible to heat the metal qualitatively. The hydraulic press used to connect the rails provides a pressure of 13 tons or more. The shrinkage of the rails when they are connected by this technology is about 20 millimeters.

Conclusion

Currently existing technologies make it possible to obtain a durable, reliable and resistant to mechanical stress connection. The choice of this or that technology is made depending on the available equipment and the specific types of rails to be connected. It must be said that a high-quality choice of such equipment used and following the entire work technology will allow you to guarantee high-quality rail welding.

svarkagid.com

High-quality welding of rail joints

10th of November
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28 rating

Main characteristics
Practical recommendations
Additional points

Welding of rail joints is in high demand today. As you know, when the rolling stock passes prefabricated joints, they begin to get upset at a high speed. In this case, the smooth running disappears, due to which the upper coating of the railway track is destroyed. And this option will help correct the situation.

Scheme of butt welding.

Main characteristics

It is required to lay rail tracks that have welded joints on any type of track, resulting in a seamless rail.

The rail thread is torn precisely in the places where the joint is formed. Such a gap, even with the installation of butt plates, has a great influence on the rigidity of the structure, and subsidence begins to increase.

As a result, when the rolling stock passes through the rail joint, the wheel hits the end head of the receiving rail. Due to numerous blows to the butt joints, the undercarriage of the cars, as well as the laid rails, begins to wear out quickly. Due to strong impacts of the wheelset on the running rail, rail heads are chipped and crushed. Typically, such defects are found 60 cm from the junction. The rails begin to break in the bolt holes, the linings are bent, the butt bolts are deformed. All of the above disadvantages do not apply to a seamless path, and it has several positive qualities:

Scheme of the design of contact welding.

almost 30% reduction in the cost of maintenance of the rail track;
energy is saved significantly, fuel consumption is reduced by about 10%;
increases the service life of the upper tracks,
rolling stock can operate much longer;
passengers experience greater comfort when the train moves;
the operation of auto-blocking and electrical circuits becomes more reliable.

Due to such positive qualities, the seamless version was adopted by all the main railway lines in the world.

Sometimes the choice of a certain type of butt welding depends on the cost of work and productivity. Such a choice entails the appearance of welding joints in especially critical structures, the quality of which is at a very low level.

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To obtain an excellent weld, a material with good weldability is required. Basically, weldability characterizes the properties of the metal, the existing reaction to the welding process, as well as the ability to obtain such a welding joint that will meet all specified technological requirements.

When the parts are made of a material that is freely weldable, no special conditions are required to obtain a high-quality seam. But for parts made of poorly weldable material, additional technological conditions are required. Sometimes a special type of welding is used, which is much more expensive and more complicated. Moreover, the execution of works requires strict adherence to the technological process.

Welding of rails is in demand today, as the rail thread breaks and the undercarriage of the cars wears out quickly.

The composition of steel for rails includes a lot of carbon, almost 82%. This material belongs to the group of materials with poor weldability. When welding, cracks may appear, which is completely unacceptable on the rails. They concentrate stress, which can lead to the destruction of the butt joint and the collapse of the composition.

Today, two types of welding of rail joints are known:

contact;
aluminothermic.

Resistance welding has become widespread, however, it has several serious drawbacks and limitations when repairing railway tracks is carried out:

welding requires special rail welding machines, which are very expensive;
duration of equipment delivery and its subsequent evacuation;
to carry out the work, it is necessary to involve numerous teams;
for lack of a large amount of time, it is necessary to constantly perform work without observing the technological process, as a result of which the joint is of very poor quality;
it is impossible to weld the joint directly in the place where the arrows are translated.

Contact welding of joints loses to aluminothermic welding of rails. For it you need to have:

complex and very expensive equipment;
numerous brigade;
breaks in train traffic.

Aluminothermic welding of rails is done very quickly. The operation takes about half a minute. If you count the preparatory work and the final processing of the weld, it takes about 45 minutes.

I must say that such welding allows you to simultaneously weld several joints, as a result, the time spent on work is reduced.

Rail joints with different shapes of butt ends.

Three people are needed to weld the joint. Their training takes place in the shortest possible time. The mass of the used equipment reaches 350 kg. For welding, when aluminothermic welding is used and other special operations are carried out, autonomous fuel supply sources are used.

To carry out aluminothermic welding of rails, engineers created portable miniature equipment that can operate offline right in the floor.

Technologists were able to choose a certain composition of the thermite solution and its granularity. This helped to achieve a thermite reaction in which no explosions occur, no decay is observed, and the most optimal speed and the desired temperature of all materials involved in the reaction are maintained.

Aluminothermic welding consists of several basic technological steps:

initial high-temperature heating;
final welding of rails.

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A special multi-flame burner is used as heating.

The operation takes approximately 7 minutes. Control over heating and its termination is carried out visually. Here it is very important that the heating is performed by a highly qualified welder.

Scheme of electrocontact welding.

Such preheating is an important component of the technological process in aluminothermic welding of rails. As a result, non-fusion does not occur, and the occurrence of hardening structures is minimized. When a welding operation is performed, the parameters of residual stresses of the weld and heat-affected zone are noticeably reduced, and cracks do not occur.

After the rail has passed the heating stage, welding work is performed, and the thermite mixture ignites. The thermite ignition reaction begins. It is automatically released into the inter-joint rail gap.

After long experiments, it was proved that the main technological parameters that affect the quality of the future weld can be considered;

preheating time;
the power of the gas flame used.

To obtain a seamless rail track using the aluminothermic method, it is allowed to use used rails, as well as their new modification. For such a welding operation, apply:

hardened rails;
non-reinforced rails;
open-hearth rails;
Bessemer rails.

It is possible to weld rails of various railway tracks in this way: station, access and even turnouts.

But remember: the rails to be welded must be of the same type and have the same shelf life group.

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rail welding

In the railway industry and in construction, equipment is used that moves along rails. As a rule, it has a fairly large weight, and, accordingly, the metal is faced with large loads. In order for the products to withstand all the difficulties of operation, rail welding must take place exactly with the prescribed technologies, since this is a complex process. On the one hand, the problems are added by the large diameter of the products, which does not allow them to be boiled to the full depth, which would ensure higher quality. On the other hand, the welded joint will always be the weakest point of the structure and must be strengthened.

rail welding

Welding of rail joints can take place both in manual and automatic mode. After it, it is always necessary to carry out processing of the material in order to achieve a smooth surface. Thus, for a quality process to be carried out, it is required:

Use professional equipment;
It is necessary to select suitable consumables;
Provide better weldability conditions due to fluxes and other means;
Maintain precise welding conditions;
Carefully process the resulting connection so that the rails are serviceable.

Weldability properties

Over the problem, which is the welding of crane rails, as well as their other varieties, people have been working for a long time. After all, the products themselves are made from hardened steel, which is often processed mechanically. Any hardening treatment adds complexity to weldability and to any other heat treatments. However, modern technology can achieve acceptable results. One of the most affordable options among the electrodes that can be freely found on sale are UONI 13/45 and UONI 13/55. These are products for working with critical structures, powerful frames made of metal structures, and they are also suitable for rails. But this is far from the only method, although it is the simplest of all possible.

Crane rail welding

Welding of track rails is carried out in accordance with GOST 103-76. This includes several methods that differ in the principle of operation, complexity, technique used and other nuances. Each of them in its own way helps to deal with poor weldability of products. Also, their choice depends on the type of rails themselves, which will have to be amenable to future repairs.

Kinds

Railway industrial - are used for relatively short sections of tracks at various enterprises. These are broad-gauge options for which the RP75, RP65 and RP50 brands are used.
Narrow gauge railway - used in underground mines and narrow gauge railway. Here, brands such as P24, P18, P11 and P8 are used.
Mine for conductors in mines - are used to create jointless and link broad gauge track. Also used for turnouts. The grades P43, P38 and P33 are used here.
Frame - used for the construction of intersections and connections on the way. Here you need the brand PP65.
Crane - serve to create paths for the passage of a construction crane on the sites. There may be such brands as KR140, KR120, KR100, KR80 and KR70.
Ostroyakovye - serve for the upper structure in the railway track. Turnouts, circular support devices and so on are made of them. The grades OP75, OP65, OP50 and OP43 are suitable here.
Railway - standard products for creating seamless and link main track for railway transport. The brands P75, P65 and P50 are used here.
Trams with a gutter - used to create paths for trams. The brands T62 and T58 are used here.
Counter-rail - used in the upper structures of the railway track. These can be brands RK75, RK65 and RK50.
Antennae - crosses are made of them, which have a continuous rolling surface. Brand UR65.

Rail welding methods

There are various rail welding methods that are used today. Among them, it is worth highlighting the main ones:

Manual arc welding of rails is the easiest and most affordable method. It is suitable for connecting joints and lashes. Products are located with a small gap, which is gradually filled with molten metal. Here, an alternating or constant type of current is used.

Electric arc welding of rails by hand

One of the varieties of the previous version is the bath method. For this, a special bath is used, which delays the flow of the molten material. The ends are preliminarily cut perpendicular to their axis. Installation is carried out without fracture. The gap between the products should be about 1.5 cm. An electrode is placed in this gap, which is melted under current and welded to the base material.

Bathroom welding rail

Thermite welding of railroad rails is based on a chemical reaction between iron oxide and aluminum oxide. With their contact and under the influence of a temperature of more than two thousand degrees, the steel acquires a fire-resistant form. It is identical to the shape of the rail itself. This is an old method that has been used for over a hundred years.

Gas-pressure welding of crane rails involves incomplete melting, since the temperature of the working process does not reach the melting point of the metal. Welding of rail lashes is achieved here due to high pressure. The quality of the connection is quite high, and its structure is very homogeneous. It requires a tight fit of the ends of the product. On a rail cutter, a hacksaw cuts the ends of two products, which helps to clean the mating surface as much as possible. Before joining, the ends are treated with carbon tetrachloride. Next comes the heating and clamping of the blanks using a hydraulic press.

Gas press welding of rails

Modes

To obtain a high-quality connection, you must adhere to the appropriate modes. Each brand of products needs its own parameters, as they have different properties. Here are the most commonly used options:

Quality checking

Regardless of whether the procedure was carried out by a machine for welding rails or by a person, quality control is required. Measuring instruments are the primary method of control. Then the condition of the surface of the seam is checked, as it should be as even and smooth as possible. Then a number of non-destructive quality controls are carried out, but this is done after the metal has cooled and the surface has been treated.

Security measures

When welding rails with electrodes, you should use personal protective equipment, check the grounding and serviceability of the equipment. Avoid being close to molten metal unless necessary. If different machines are used, they should be checked for functionality before use. If any equipment has breakdowns or defects are noticed in consumables, then such things should not be used in the process.

One of those electrodes that can be used to weld rails, are SSSI 13/45 or SSSI 13/55. Yes, indeed, UONI welding electrodes are an excellent choice for welding such thick structures as rails.

UONI electrodes are used for welding critical structures from metal, when presented to a metal seam high demands on impact strength. Many professional welders recommend UONI electrodes for welding structures operating under loads, pressure and other environmental influences.

The material for the manufacture of welding electrodes UONI is the welding wire Sv-08A, which fully complies with state standards adopted in our country. On the surface of the coating of the welding electrodes of the UONI, small cracks are allowed, which may be on the coating of the welding electrode. However, if the coating of the welding electrode is severely damaged, then you need to check where you store them, because moisture can damage the welding electrode.

Baking electrodes before welding makes it easier to work with them and allows you to make the welding seam applied by them more durable. Also, baking or drying the electrodes at a specified temperature makes them less susceptible to moisture.

As you can see, the use of UONI welding electrodes allows for high quality welding. Thanks to their high quality and welding features, you can start welding rails in a short time.

Due to the relatively low strength characteristics, this method of welding is rarely used in tram facilities and on station tracks of railways. The advantage of the electric arc welding method is that it can weld rails on the way.

Joints welded by the electric arc method can be divided into two groups: 1) joints with welding of linings and linings; 2) joints welded over the entire cross section of the rails (bathroom method). The joints of the first group are not used in railway transport due to extremely low strength indicators, and they are rarely used in tram tracks.

Bath way '

The bath method for welding rail joints was developed by the Moscow Experimental Welding Plant.

Welding is carried out on direct or alternating current with electrodes with a diameter of 5 mm. Power is supplied from the standard - 76

0 electric welding equipment of STE-34 type; PS-500; PAS-400

Applied current 300-350 a. For welding use UONI-ІЗ/55А brand electrodes with a temporary resistance on - coated metal 55 kg/mm2.

At present, due to the emergence of new grades of rail -) steel with increased strength data, it is recommended to use UONI-13 / 85u electrodes with temporary resistance of the deposited metal. 85 kg / mm2 -

The assembly of joints for welding, as a rule, is carried out on shpa - iax. The ends of the rails are cut along the square by mechanical means or gas. After cutting with gas, the ends of the rails must be cleaned of scale.

The joint must be aligned in the vertical and horizontal planes, after which it rises by 1.0-1.5 mm per 1 lin. m.

The joint lift is adjusted with wooden wedges, and the check is made with a special steel meter ruler with pins at the ends adjustable in length.

The gap between the welded rails should be 12-15 mm or 1.5 of the electrode diameter, taking into account the thickness of the coating layer. .

Technologically, rail joint welding can be divided into two main operations: base welding, neck and head welding.

* Welding of the sole is carried out on the remaining (steel) or removable copper plate. The length of this plate is 20 mm longer than the width of the rail sole, and the width of the plate is 40 mm.

Several variants of such plates are used:

1) steel (St. 3) 5-6 mm thick; the plate is placed under the joint and pressed tightly;

2) combined, a steel plate 2 mm thick is laid under the joint, and a copper lining under it;

3) a copper plate with a groove filled with several butts of UONI-13/55 A electrodes is pressed directly under the joint.

The best results are obtained by using copper and combined plates. *

The sole of the rail is the most sensitive place of the welded joint, where the low quality of the deposited metal and other welding errors are especially pronounced.

With the bath method of welding, it is important to keep the liquid deposited metal and slag in the inter-butt gap. For this, special reusable copper molds are used: the lower ones are for welding the soles and the side ones are for welding the neck and head.

Outside, the forms have a rectangular shape. Their inner contour corresponds to the shape of the section of the rail with which they are mated. There is a recess along the axis of the mold, which is filled with liquid deposited metal during welding to form a butt reinforcement.

When installing the forms, their axis is combined with the joint gap, and the side forms, in addition, are also fixed with a clamp.

The gap at the junction of the molds with the surface of the rails should not exceed 1 mm. Otherwise, the edges of the molds must be coated with refractory clay. When welding the sole, the seam starts from the edge of the plate and, making oscillatory movements across the joint gap, leads it to the other end, carefully welding the corners between the ends of the rails and the plate.

The second suture should be applied in the opposite direction, also starting from the edge of the plate.

When making the following passes, care must be taken to ensure that the liquid bath of molten metal is located along the entire length of the sole.

During welding, the oscillatory movements of the electrode must be performed quickly. Finish welding of the sole should be in the center of the joint, due to which the seam is obtained with a slope from the center to the edges, which corresponds to the profile of the rails -

In the sole of the joint, the weld should have a reinforcement of 2-3 mm, and the edges of the sole should overlap with a smooth seam.

The surface of the seam after welding the sole must be cleaned of slag.

After the side molds have been installed, the subsequent welding should immediately begin to prevent significant cooling of the joint.

The welding arc is excited at the end of the welding of the sole, i.e., at the base of the neck, and is carried out, continuously filling the entire gap with weld metal.

Finishing the welding of the joint, it is necessary to weld on the tread surface a profitable part with a thickness of 4-5 mm, which compensates for shrinkage during the crystallization of the joint.

After welding, when the joint is still red, its surface should be sealed by forging.

The disadvantages of the bath welding method are hot cracks and lack of fusion. Hot cracks sometimes appear when welding rails made of Bessemer steel containing an increased amount of harmful impurities - sulfur, phosphorus, nitrogen. The same defects can be at acceleration of processes of welding of rails of heavy types.

Lack of penetration and slag inclusions, on the contrary, are obtained at slow welding speeds -

If any defects are found, subsequent welding can be carried out at a joint temperature of at least 300°.

7.3. Arc welding

In electric arc welding, the rails are connected by the metal of the electrode, which is melted from the heat of the arc discharge.

Electric arc welding of joints does not require the application of sedimentary pressure. For this welding, alternating current from a transformer or direct current from a mobile welding unit is used.

An electrode is inserted between the ends, through which a current of 300-350 amperes is passed. The molten metal of the electrode fills the gap between the ends along the entire section of the rail.

Electric arc welding is used only for rails laid on station tracks, except for main and receiving-departure ones.

7.4. Gas pressure welding

Gas pressure welding provides metal connection at a temperature

below the melting point with the application of pressure.

To heat the rail, multi-flame burners of the MG-50R type are used,

MG - 65R, MG - 75R. Multi-flame burner type MG - R65 is shown in Figure 1.3.

Fig. 7.3: Multi-flame burner MG-R65 (a) and its barrel (b):

The ends of the rails are clamped with a hydraulic press and heated to a temperature of 1200 0 C by a system of multi-flame burners oscillating along the joint (50 oscillations per minute). At the same time, the rails are compressed with the force set by the calculation (10 - 13 tons) until a draft of a given value (about 20 mm) is obtained.

For welding, universal gas-pressing machines SGP - 8U or MGP - 9 are used.

After welding, the joint is processed, and then it is normalized.

7.5. Aluminothermic welding

The creation of high-speed highways and a seamless track sets high quality standards for rails, especially at their junctions. Aluminothermic welding of rails fully meets these standards.

Aluminothermic welding of rails is intended for joining together in any combination of volume-hardened, surface-hardened and non-thermally hardened rails.

Fe 2 O 3 + 2Al => 2Fe + Al 2 O 3 + 849 kJ

The thermite reaction occurs in the crucible within a few seconds after the thermite portion is ignited, consisting of a mixture of aluminum powder, iron oxide, steel particles that dampen the reaction, and alloying additives necessary to obtain steel of the desired quality. The reaction takes place at a temperature above 2000 o With the final layer-by-layer separation of the reaction products: liquid steel (bottom) and light slag (top).