Method of welding rail joints. How to weld rails Welding ordinary steel to a rail

7. RAIL WELDING METHODS

7.1. General provisions

Experience in operating continuous continuous track in domestic and foreign countries railways ah revealed not only its high technical and economic efficiency, but also the “weak” point of this progressive design, which is the leveling spans. In their zone, due to the rail joints, a higher dynamic impact of the rolling stock on the track is observed compared to the middle part of the track, disorders occur faster, and residual deformations accumulate more intensively. As a result, there is an increased failure of rails, fastenings, reinforced concrete sleepers, and splashes are formed. Specialists from various research institutes have made many attempts to improve leveling spans. The most drastic measure at the moment is considered to be reducing the number of leveling spans by increasing the length of the lines. With an increase in the average length of the string to 1500 m, it is possible to reduce the number of equalization spans by more than 60%, and with an increase to 5000 m – by an additional 20–25%. The explanation for the fact that at one time the railways of many countries and Russia in particular began to lengthen welded rail strands may be the desire to get rid of joints. When laying continuous track strands up to the length of a block section or section, one cannot do without the use of modern welding technologies, making it possible to create a continuous rolling surface (especially on high-speed lines), as well as to weld turnouts into rail strands.

Currently on the railways Russian Federation The following types of welding have become widespread:

Electric contact;

Gas press;

Electric arc;

Termite.

Usually, when welding strands into long and extra-long strands, 2 of them are most often used: aluminothermic and electric contact.

Different methods of welding rails differ significantly in technical and economic data. The most important indicators are: mechanical properties and consistency of joint quality, operational durability and cost of welded rails, productivity and labor intensity of the process, mechanization and automation of work.

The mechanical characteristics of welded rails make it possible to judge the quality and strength of joints under static, dynamic and cyclic loading, which are determined by testing standard and full-scale samples. The strength of the welded joint relative to the whole rail is presented in Table 7.1.

Table 7.1

7.2. Electric contact welding

The electric contact welding method is based on heating the welded ends of the rails with an electric arc created by a high current and low voltage. Welding of rails using the electric contact method is carried out using automated butt electric contact welding machines. In stationary conditions, welding is carried out on welding machines MSGR-500, MS-5002 and K-190 (Fig. 1.1), K-190M, K-190P, MSR-6301; on the way - by PRSM machines equipped with contact heads K-155, K-255, K-355. The modern self-propelled track rail welding machine PRSM - 4 is designed for electric contact welding of railway rail joints (Fig. 1.2). Welding of rails can be carried out both on the track directly along which the machine moves, and on rails laid along this track, inside or outside the track, at a distance of 2600 mm from the axis of the track. This machine can be used with interchangeable contact heads of various types (K-155, K-255 and others). Technical specifications PRSM-4 machines are presented in Table 1.2.

Fig.7.1: Welding machine K-190:

1-bed; 2 - lifting rollers; 3- fixed column;

4, 7-hydraulic presses (in columns); 5 - fastening of rods; 6-rods;

8-movable column.

Fig.7.2: Self-propelled track-rail welding machine PRSM-4

Table 7.2

The continuous flash welding process occurs as follows. After the clamps of the welding machine approach the rail ends, a welding current passes through the contact points of the welded ends of the rails. Since, due to the roughness of the metal, the area of ​​point contact is very small, the ohmic resistance of the contact and the current strength are very high.

The consequence of this is the transformation of “solid” contacts due to their heating, melting and evaporation into “bridges” of liquid metal. This process is maintained by constantly bringing the clamps of the welding machine closer together and leads to uniform heating of the entire welding surface area. The closing speed of the clamps of the welding machine must correspond to the melting speed of the rail ends. When the rail ends reach the required thermal interface, the process of their continuous melting automatically proceeds to the next stage of welding - upsetting. During upsetting, the speed of approach of the rails instantly increases several times, the welding current is turned on, liquid metal is squeezed out from the melted surfaces and the actual welding of the ends of the rails, which are in a plastic state, occurs. At the welding site it forms weld, subject to further mechanical and heat treatment.

Thus, the continuous fusion welding process includes: a heating stage carried out during the continuous fusion process; the upsetting stage, as a result of which welding occurs; the stage of cooling the welded rails in air outside the machine.

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

Arc welding

It is worth noting that one of the most common methods used when welding rail strands 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 layer by layer with the necessary welding material. The latter melts due to the temperature of the arc discharge. To weld the ends of railway rails using this method, alternating current can be used coming from a transformer or D.C., obtained from a mobile welding unit.

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 fracture. In this case, the profile should have an elevation of 3 to 5 millimeters. In this position, the rails should be fixed with a gap of 14 to 16 mm.

An electrode is inserted between the ends of the railway 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 across the entire cross-section.

To prevent metal from spreading, various methods are used to close the gap between the rails. After welding, the work area is ground around the entire perimeter.

Thermite welding

The technology of this type of welding is based on 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 that is completely identical to the geometry of the rail itself.

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

Thermite technology is also called aluminothermic welding of rails, since it uses aluminum. Interestingly, the thermite reaction occurs within just 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 produce steel required quality and parameters. Interestingly, at the end of the reaction, a layer-by-layer separation occurs into liquid steel and light slag, which appears on top.

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

Gas press welding

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

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

Due to the above advantages, this type of welding is very effective in welding heavy railway rails. Before the actual welding is carried out, the ends of the railway rails are pressed tightly against each other. In this case, using a circular saw of a rail cutting machine or a mechanical hacksaw, simultaneous cutting of the ends of both rails is carried out. As a result, maximum purity of the metal is ensured, as well as high sealing density. 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 of heating the ends of the rails, for which multi-flame burners are used.

After this, the ends of the rails must be clamped using 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 vibrations is 50 vibrations per minute. At the same time, the rails are compressed with a force of 10 to 13 tons, which is determined 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 this, it is also normalized.

Results

So, there are three key technologies for welding rails. Each of them has its own “pros” and “cons”. However, it is worth noting that aluminothermic welding fully complies with all modern stringent requirements for seamless railway tracks. Therefore, its use is completely justified in the construction and repair of modern highways.

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goodsvarka.ru

Rail welding

When working with crane installations and installing railway tracks, the need arises for connecting and welding rails. In this case, a special technology is used, which ensures 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 using the following technologies:

• Termite.
• Electric arc.
• Gas press welding.

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

Electric arc welding of rail joints

Today, this technology has become most widespread, which is explained by the simplicity of the equipment, the ease of the work itself and the quality of the connection. When performing welding work, the rails are laid in the desired position, after which the space between the joints is filled layer by layer with welding material. 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 a transformer is used. It is also possible to use mobile welding machines operating on 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, they are qualitatively welded to 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 the electricity power of about 350 Amperes. The electrode quickly fills the gap between the rails being connected, 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 sand the connecting seam around the perimeter.

Aluminothermic rail welding

The thermite welding method is based on the ability of aluminum oxide and iron to react with each other at high temperatures. This thermite welding is also called aluminothermic technology. To perform such welding, a high-temperature resistant form is used, which in its own way appearance identical to the geometry of the rails. This form must withstand temperatures of more than 2000 degrees, at which contact between aluminum and iron occurs.

This welding technology was discovered at the end of the 19th century. However, due to its technological complexity, it became widespread 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 maintain its geometry.

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

The thermite method of welding rails allows you to join bulk-hardened and surface-hardened materials. It must be said that with the help of such technology a strong and durable connection is ensured, therefore the thermite welding method has found application in the manufacture of jointless high-speed railways.

Gas press technology

This original rail joining technology involves the use of temperatures below the melting point, but due to high pressure, a high-quality rail connection is ensured. The advantages of this welding technology include the following:

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

This type of gas press welding is widely used when joining heavy railway rails. When performing this, special equipment is used, which allows to ensure the highest possible pressure of the connected rails. Hardware They are pressed tightly against each other, after which the ends are heated using a special clamp, and due to high pressure the rails are connected to each other. During such work, it is necessary to ensure that the elements being welded are washed with carbon trichloride. This allows for the connection of metal elements at the molecular level.

Operating temperature indicators for gas press technology are about 1200 degrees. For this type of work, multi-flame burners and powerful hydraulic presses are used. For high-quality heating of the joint, multi-flame burners are used, which carry out numerous vibrations in the area of ​​the welded joint, which allows high-quality heating of the metal. The hydraulic press used to connect the rails provides a pressure of 13 tons or more. The shrinkage of rails when connecting them using this technology is about 20 millimeters.

Conclusion

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

svarkagid.com

High-quality welding of rail joints

• 10th of November
• 88 views
• 28 rating

• Main characteristics
• Practical recommendations
• Additional points

Welding of rail joints is in great demand today. As is known, when rolling stock passes prefabricated joints, they begin to deteriorate at high speed. At the same time, the smooth running disappears, which is why the top covering of the railway track is destroyed. And this option will help correct the situation.

Butt welding diagram.

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 breaks precisely in the places where the joint is formed. Such a gap, even when installing butt plates, has a great impact on the rigidity of the structure, and subsidence begins to increase.

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

Resistance welding design diagram.

• rail track maintenance costs are reduced by almost 30%;
• Electricity is significantly saved, fuel consumption is reduced by about 10%;
• service life increases upper paths,
• rolling stock can operate much longer;
• passengers experience greater comfort when the train moves;
• The operation of automatic locking and electrical circuits becomes more reliable.

Due to such positive qualities, the seamless option has been adopted by all the main railway lines in the world.

Sometimes it's a choice certain type welding of joints depends on the cost of work and productivity. This choice entails the appearance in particularly critical structures of welding joints, the quality of which is at a very low level.

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

When the parts are made of a material that can be easily welded, 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 complex. Moreover, the execution of work requires strict adherence technological process.

Rail welding is in demand today because the rail thread breaks and the running gear of cars quickly wears out.

Rail steel contains 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 rails. They concentrate stress, which can lead to the destruction of the butt joint and the collapse of the composition.

Today there are two types of welding of rail joints:

• contact;
• aluminothermic.

Resistance welding has become widespread, but it has several serious disadvantages and limitations when carried out renovation work railway tracks:

• welding requires special rail welding machines, which are very expensive;
• the duration of equipment delivery and its subsequent evacuation;
• to carry out the work it is necessary to involve numerous teams;
• in the absence of a large amount of time, you have to constantly perform work without following 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 point.

Contact welding of joints is inferior to aluminothermic welding of rails. For this you need to have:

• complex and very expensive equipment;
• a large brigade;
• interruptions during train movement.

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

It must be said 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 the butt ends.

Three people are required to weld the joint. Their training takes place in the most short time. The weight of the equipment used reaches 350 kg. For welding work, 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 autonomously right in the floor.

Technologists were able to select a specific composition of the thermite solution and its granularity. This helped achieve a thermite reaction that does not explode, does not decay, and maintains the most optimal speed and temperature of all materials involved in the reaction.

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 for heating.

The operation lasts approximately 7 minutes. Control over heating and its completion is carried out visually. It is very important here that the heating is carried out by a highly qualified welder.

Electric contact welding diagram.

Such preheating is an important component of the technological process for 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 the residual stresses of the weld seam and the heat-affected zone are noticeably reduced, and cracks do not appear.

After the rail has passed the heating stage, welding work is performed and the thermite mixture ignites. The thermite ignition reaction process begins. He is in automatic mode released into the inter-joint rail gap.

After much experimentation, it was proven that the main technological parameters, which affect the quality of the future weld, can be considered;

• preheating time;
• power of the gas flame used.

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

• reinforced rails;
• unreinforced rails;
• open hearth rails;
• Bessemer made rails.

You can weld rails of a wide variety of railway tracks in this way: station tracks, access tracks, and even turnouts.

But remember: the rails that will be welded must be of the same type and have the same suitability group.

expertsvarki.ru

Welding rails

In the railway industry and construction, equipment is used that moves along rails. As a rule, it has quite a lot of weight, and accordingly the metal faces heavy loads. In order for the products to withstand all the difficulties of operation, welding of rails must occur exactly with the prescribed technologies, since this is a complex process. On the one hand, the large diameter of the products adds problems, which does not allow them to be boiled to their full depth, which would provide more high quality. On the other hand, the welded joint will always be the weakest point of the structure and must be strengthened.

Welding rails

Welding of rail joints can take place both manually and automatically. After this, it is always necessary to carry out processing of the material to achieve a smooth surface. Thus, for a high-quality process, the following is required:

• Use professional equipment;
• It is necessary to select suitable consumables;
• Provide better conditions for welding thanks to fluxes and other means;
• Observe precise welding conditions;
• Carefully process the resulting connection so that the rails are suitable for use.

Weldability properties

People have been working on the problem posed by welding crane rails, as well as their other varieties, for quite 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 any other heat treatments. Nevertheless, modern technologies allow you to 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.

Welding crane rails

Welding of track rails is carried out in accordance with GOST 103-76. This includes several methods that differ in the principle of action, complexity, technique used and other nuances. Each of them helps in its own way to combat 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 - used for relatively short sections of track on various enterprises. These are wide-gauge options for which grades RP75, RP65 and RP50 are used.
• Narrow gauge railway - used in underground mines and narrow gauge railways. The brands used here are P24, P18, P11 and P8.
• Mine for conductors in mines - used when creating continuous and sectional broad gauge tracks. Also used for turnouts. The brands used here are P43, P38 and P33.
• Frame - used for the construction of intersections and connections along the path. Here you need the PP65 brand.
• Crane - used to create paths for construction cranes on sites. There may be brands such as KR140, KR120, KR100, KR80 and KR70.
• Pointed - used for the upper structure of the railway track. They are used to make turnouts, circular support devices, etc. The brands OR75, OR65, OR50 and OR43 are suitable here.
• Railway - standard products for creating continuous and sectional main tracks for railway transport. The grades P75, P65 and P50 are used here.
• Tramways with gutter – used to create paths for trams. The brands T62 and T58 are used here.
• Counter rails – used in the upper structures of railway tracks. These can be brands RK75, RK65 and RK50.
• Antennae - crosspieces are made from them, which have a continuous rolling surface. Brand UR65.

Rail welding methods

There are various methods of welding rails that are used in modern times. Among them it is worth highlighting the main ones:

Arc welding rails by hand - the simplest and most accessible method. It is suitable for connecting joints and lashes. The products are placed with a small gap, which is gradually filled with molten metal. Here, alternating or direct current is used.

Electric arc welding of rails manually

One of the variations of the previous option is the bath method. For this purpose, a special bath is used, which delays the flow of the molten material. The ends are pre-cut perpendicular to their axis. Installation is carried out without breaking. 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.

Bath rail welding

Thermite welding of railway rails is based on the chemical reaction of iron oxide and aluminum. Upon their contact and under the influence of temperatures of more than two thousand degrees, the steel takes on 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 press 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 strands here is achieved due to high pressure. The quality of the connection turns out to be quite high, and its structure is very homogeneous. Here it is necessary to tightly join the ends of the product. On a rail cutting machine, a hacksaw cuts the ends of two products, which helps to clean the joining surface as much as possible. Before joining, the ends are treated with carbon tetrachloride. Next comes heating and clamping of the workpieces using a hydraulic press.

Gas press welding of rails

Modes

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

Quality checking

Regardless of whether the procedure was carried out by a rail welding machine or a person, quality control is required. The initial control method is measuring instruments. Then the condition of the seam surface is checked, as it should be as even and smooth as possible. Then a series 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 protection, check the grounding and serviceability of the equipment. You should not be close to molten metal unless necessary. When using different machines, you should check them for proper operation before use. If any equipment has breakdowns or consumables are defective, then such things should not be used in the process.

When working with crane installations and installing railway tracks, the need arises for connecting and welding rails. In this case, a special technology is used, which ensures 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 using the following technologies:

• Termite.
• Electric arc.
• Gas press welding.

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

Electric arc welding of rail joints

Today, this technology has become most widespread, which is explained by the simplicity of the equipment, the ease of the work itself and the quality of the connection. When performing welding work, the rails are laid in the desired position, after which the space between the joints is filled layer by layer with welding material. 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 a transformer is used. It is also possible to use mobile welding machines operating on 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, they are qualitatively welded to 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 rails being connected, 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 sand the connecting seam around the perimeter.

Aluminothermic rail welding

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

This welding technology was discovered at the end of the 19th century. However, due to its technological complexity, it became widespread 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 maintain its geometry.

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

The thermite method of welding rails allows you to join bulk-hardened and surface-hardened materials. It must be said that with the help of such technology a strong and durable connection is ensured, therefore the thermite welding method has found application in the manufacture of jointless high-speed railways.

Gas press technology

This original rail joining technology involves the use of temperatures below the melting point, but due to high pressure, a high-quality rail connection is ensured. The advantages of this welding technology include the following:

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

This type of gas press welding is widely used when joining heavy railway rails. When performing this, special equipment is used, which allows to ensure the highest possible pressure of the connected rails. The metal products are pressed tightly against each other, after which the ends are heated using a special clamp, and due to high pressure the rails are connected to each other. During such work, it is necessary to ensure that the elements being welded are washed with carbon trichloride. This allows for the connection of metal elements at the molecular level.

Operating temperature indicators for gas press technology are about 1200 degrees. For this type of work, multi-flame burners and powerful hydraulic presses are used. For high-quality heating of the joint, multi-flame burners are used, which carry out numerous vibrations in the area of ​​the welded joint, which allows high-quality heating of the metal. The hydraulic press used to connect the rails provides a pressure of 13 tons or more. The shrinkage of rails when connecting them using this technology is about 20 millimeters.

Conclusion

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

Welding rails using the second method - flashing with preliminary intermittent heating - consists of an intermittent heating stage, a continuous melting stage; stages of upsetting and welding, stages of cooling of welded joints. In this method, unlike the first method, the metal of the rails is heated by repeated cyclic closing and opening of the rail ends. Electric contact 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, it is paramount to strictly ensure the welding regimes approved by the Main Track Directorate of the Ministry of Railways.

7.3. Arc welding

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

Electric arc welding of joints does not require the application of sediment 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 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 cross-section of the rail.

To prevent the molten metal of the electrode from spreading, inventory copper molds are used to close the gap from the bottom and sides. The welded joints are ground along 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 the main and receiving and departure tracks.

7.4. Gas press welding

Gas press welding ensures metal connection at a temperature

below the melting point by applying pressure.

The main advantage of gas press welding of rails is the high quality of the connection and obtaining a homogeneous metal structure in the joint area, therefore this type welding is particularly advantageous when applied to heavier types of rails.

Before welding, the ends of the two rails are placed tightly against 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 using a mechanical hacksaw, which ensures a tight fit of the ends and cleanliness of the metal. Immediately before welding, the ends of the rails should be thoroughly washed with carbon tetrachloride or dichloroethane. Preparation before welding consists of preheating the ends of the rails.

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

MG – 65R, MG – 75R. A multi-flame burner type MG - P65 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 – lower part of the burner; 4 – gas pipeline; 5 and 9 – pipelines for running water; 6 – gas clamp 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 1200 0 C with a system of multi-flame burners that perform oscillatory movements along the joint (50 oscillations per minute). At the same time, the rails are compressed with a force established by calculation (10 - 13 tons) until a settlement of a given value is obtained (about 20 mm).

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

After welding, the joint is processed and then normalized.

7.5. Aluminothermic welding

The creation of high-speed lines and seamless tracks sets high quality standards for rails, especially at the points of their connection. Aluminothermic rail welding fully meets these standards.

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

Welding of joints of rail strands and joints (except for insulating ones) of turnouts laid on wooden or reinforced concrete sleepers and beams can be carried out on the main, receiving and departure, station and hump tracks of the railways of the Russian Federation, on access roads 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 of the reduction of pure iron from its oxide with the help of aluminum, releasing a large amount of heat:

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

The thermite reaction occurs in the crucible within a few seconds after ignition of the thermite portion, consisting of a mixture of powdered aluminum, iron oxide, steel particles that dampen the reaction, and alloying additives necessary to obtain steel of the required quality. The reaction takes place at temperatures above 2000 o C with a 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-Termit (Germany), Reltech (Czech Republic and France), perform work related to thermite welding of rail elements in the area of ​​connecting tracks. When laying a continuous track, the thermite method of welding rails (Fig. 1.4.) plays a leading role. Currently, in the turnout area, it is the main method of connecting rails. It is a cost-effective technology with great flexibility of application. In most cases, welding can be carried out without closing the stage. The technology of the Elektro-Termite company, having become most widespread compared to other companies, represents two main methods of electro-thermit welding on the Russian market, namely the so-called SoWoS method and the SkFau method (SkV) (Fig. 1.5) .

This welding method, due to its relatively low strength characteristics It is rarely used in tram facilities and on railway station tracks. The advantage of the electric arc welding method is that it can weld rails on the road.

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

Bath way ‘

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

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

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

The applied current is 300-350 a. For welding, use electrodes of the UONI-IZ/55A grade with a temporary resistance to the metal of 55 kg/mm2.

Currently, in connection with the emergence of new grades of rail steel with increased strength data, it is recommended to use UONI-13/85u electrodes with a temporary resistance of the deposited metal of 85 kg/mm2-

As a rule, the assembly of joints for welding is carried out on the joint - iakh. The ends of the rails are cut using a square using 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 linear line. m.

The amount of joint lift is adjusted using wooden wedges, and checking is done with a special steel meter ruler with length-adjustable pins at the ends.

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

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

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

Several variants of such plates are used:

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

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

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

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

The base 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.

When using the hot welding method, it is important to retain liquid deposited metal and slag in the inter-joint gap. For this purpose, special reusable copper molds are used: the bottom ones for welding the sole and the side ones for welding the neck and head.

On the outside, the shapes have a rectangular shape. Their internal contour corresponds to the shape of the section of the rail with which they mate. There is a recess along the axis of the mold, which during welding is filled with liquid deposited metal to form a joint reinforcement.

When installing the forms, their axis is aligned with the joint gap, and the side forms are also secured with a clamp.

The gap at the junction of the forms with the surface of the rails should not exceed 1 mm. Otherwise, the edges of the molds must be coated with fireproof 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 performing the following passes, you need to carefully monitor that the liquid bath of molten metal is located along the entire length of the sole.

During the welding process, oscillatory movements of the electrode must be performed quickly. The welding of the sole should be completed 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 -

At the bottom of the joint, the weld seam should have a reinforcement of 2-3 mm, and the edges of the sole should be overlapped with a smooth seam.

After welding the sole, the surface of the seam must be cleaned of slag.

After installing the side forms, subsequent welding should begin immediately 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 conducted, continuously filling the entire gap with deposited metal.

When finishing welding the joint, it is necessary to deposit a profitable part 4-5 mm thick on the rolling surface, which compensates for shrinkage during crystallization of the joint.

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

The disadvantages of the hot welding method are hot cracks and lack of penetration. Hot cracks sometimes appear when welding rails made of Bessemer steel, which contains an increased amount of harmful impurities such as sulfur, phosphorus, and nitrogen. The same defects can occur when the welding processes of heavy types of rails are accelerated.

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

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