Aluminothermic welding method for rails

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The method enhances rail head strength by using a split mold and controlled air cooling to achieve uniform and durable rail connections, addressing the inconsistency in existing welding methods.

RU2865111C1Active Publication Date: 2026-06-30OBSHCHESTVO S OGRANICHENNOJ OTVETABTVENNOSTJU KOVCHEG

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Patent Information

Authority / Receiving Office: RU · RU
Patent Type: Patents
Current Assignee / Owner: OBSHCHESTVO S OGRANICHENNOJ OTVETABTVENNOSTJU KOVCHEG
Filing Date: 2025-12-18
Publication Date: 2026-06-30

AI Technical Summary

Technical Problem

Existing aluminothermic welding methods for railway rails do not achieve uniform and predictable strengthening of the weld seam and the adjacent area, leading to inconsistent rail head strength and durability.

Method used

A method involving a split mold, aluminothermic composition, and controlled air cooling using three groups of nozzles to ensure uniform and accelerated cooling of the weld seam and adjacent areas, forming a high-quality and durable rail connection.

Benefits of technology

The method achieves uniform strengthening of the rail head, ensuring a hardness of over 370 HB and long-term resistance to cyclic loads, with a durable connection capable of withstanding 1.5 million cycles without deformation.

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Abstract

FIELD: welding.SUBSTANCE: invention relates to aluminothermic welding of rails and can be used to repair railway rails without removing them from the track. The method of aluminothermic welding of rails involves the following operations: the ends of the rails are installed to form a welding gap between their ends; a split mould is placed around the ends of the rails in the area of the welding gap; the ends of the rails and the split mould are heated to a temperature in the range of 1000-1500 °C; molten metal is fed from the reaction crucible into a split mould; the temperature of the ends of the rails and the split mould is maintained at no less than 800 °C until the end of pouring; the weld after solidification and the area adjacent to it are cooled with a jet of compressed air to a temperature of 250-300 °C, then in air. The mentioned cooling is carried out by air flows supplied from three groups of air nozzles. The first group of air nozzles is directed towards the area of the casting bridge seat, and the second and third groups of air nozzles are directed towards the area of the rail head junction with the mould, on each side of the mould.EFFECT: uniform predictable strengthening of the rail head in the area of the weld and the area adjacent to it.7 cl, 4 dwg

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Description

[0001] Field of technology

[0002] The invention relates to aluminothermic welding, more specifically, to rail butt joints produced using aluminothermic welding. The invention can be used to repair railway rails without removing them from the track.

[0003] State of the art

[0004] A method for aluminothermic welding of rails is known from the prior art, described in RU 2163184 C1, 20.02.2001 or RU 2574144 C1, 10.02.2016, and providing for cooling of the weld seam and the near-weld zone first with a jet of compressed air to a temperature of 250...300°C, and then in air.

[0005] Also known from the prior art is a method for aluminothermic welding of rails, described in CN 215251068 U, 12 / 21 / 2021, and providing for cooling the rail head after aluminothermic welding of rails, by blowing air at an adjustable flow rate over the upper and side surfaces of the rail head.

[0006] Furthermore, a method for aluminothermic welding of rails is known from the prior art, described in JP 2002263866 A, 17.09.2002 (also published as JP 4351402 B2, 28.10.2009), and providing for cooling the rail head from a temperature of more than 600°C to a temperature of 400°C or lower, for example, about 350°C, by blowing air from a compressor over the upper and side surfaces of the rail head at a pressure of 0.25...4.90 kPa.

[0007] Known methods provide for accelerated cooling with an air flow, and accordingly, provide some strengthening in the area of the weld seam of the rail head; however, the known methods do not allow for uniform predictable strengthening of the rail head in the area of the weld seam and the area adjacent to it.

[0008] Disclosure of invention

[0009] Thus, the objective of the invention is to eliminate the disadvantages of the prior art, and the technical result of the invention is to create a method for aluminothermic welding of rails, which makes it possible to obtain uniform, predictable strengthening of the rail head in the area of the weld seam and the area adjacent to it, by ensuring uniform, accelerated (relative to air cooling) cooling of the said areas, as a result of which a high-quality and durable connection of the rails can be obtained.

[0010] The mentioned technical result is achieved by the method of aluminothermic welding of rails, which involves the following operations:

[0011] install the ends of the rails to form a welding gap between their ends,

[0012] Place a split mold around the ends of the rails in the welding gap area and seal the contact of the split mold with the ends of the rails,

[0013] install a reaction crucible filled with a dose of aluminothermic composition over the mold,

[0014] Heat the ends of the rails and the split mold to a temperature in the range of 1000…1500°C,

[0015] ignite a dose of aluminothermic composition and heat it until molten metal is formed,

[0016] The molten metal is fed from the reaction crucible into the split mold,

[0017] until the end of pouring is completed, the temperature of the rail ends and the split mold is maintained at no less than 800°C,

[0018] withstand molten metal until it solidifies and forms a weld,

[0019] After hardening, the weld seam and the area adjacent to it are cooled with a jet of compressed air to a temperature of 250…300°C, then in air,

[0020] wherein the said cooling is carried out by air flows supplied from three groups of air nozzles,

[0021] The first group of air nozzles contains two or four nozzles, the axes of which are directed towards the landing area of the casting bridge,

[0022] the second group of air nozzles contains four nozzles, the axes of two of which are directed toward the area of the junction of the upper part of the head of one rail with the mold, and the axis of each of the other two nozzles is directed toward the area of the junction of the side part of the head of one rail with the mold, respectively, one nozzle on each side of the said one rail,

[0023] The third group of air nozzles also contains four nozzles, the axes of two of which are directed toward the area of the junction of the upper part of the head of the opposite rail with the mold, and the axis of each of the other two nozzles is directed toward the area of the junction of the side part of the head of the opposite rail with the mold, respectively, one nozzle on each side of the said opposite rail.

[0024] It should be noted that the described design allows for uniform predictable strengthening of the rail head in the weld area and the area adjacent to it, by ensuring uniform accelerated (relative to air cooling) cooling of the said areas, and, accordingly, to obtain a section of the rail of equal strength (for example, in accordance with GOST R 51685-2013), ensuring long-term resistance to cyclic loads, i.e. to obtain a high-quality and durable rail connection.

[0025] In particular forms of implementation, the method of aluminothermic welding of rails provides for the following.

[0026] The distance from the edge of each nozzle of the first group to the upper plane of the casting bridge seat is from 140 to 200 mm.

[0027] The distance from the edge of each nozzle of the second and third groups to the junction of the rail head with the mold is from 190 to 280 mm.

[0028] The air flow rate of each nozzle of the first group is from 22 to 37 L / min.

[0029] The air flow rate of each nozzle of the second and third groups is from 26 to 52 L / min.

[0030] The bore diameter of each nozzle of the first group is from 3 to 5.5 mm.

[0031] The flow diameter of each nozzle of the second and third groups is from 4 to 8 mm.

[0032] It should be noted that the described design allows to obtain a hardness of the rail head rolling surface of more than 370 HB.

[0033] Brief description of the drawings

[0034] The invention is explained by the following graphic materials.

[0035] Fig. 1. Example of implementation of the method of aluminothermic welding of rails, top view (schematic).

[0036] Fig. 2. An example of the implementation of the method of aluminothermic welding of rails, view from the side of the rail (schematic).

[0037] Fig. 3. Example of implementation of the method of aluminothermic welding of rails, side view (schematic).

[0038] Fig. 4. Visualization of the interpolation of the hardness distribution along the rolling surface of the rail head after implementing the aluminothermic rail welding method.

[0039] Implementation of the invention

[0040] Before carrying out the described method of aluminothermic welding of rails, the ends of the rail (in particular, the ends) are pre-cleaned from rust, scale, paint and greasy films using a metal brush and abrasive materials or by firing with an oxygen-acetylene flame with excess oxygen.

[0041] In turn, within the framework of the implementation of the characterized method of aluminothermic welding of rails, the following operations are provided.

[0042] The rail ends (1, 2) are installed, creating a welding gap between their ends. A reasonable gap for aluminothermic welding with intermediate casting is 25±2 mm; however, the described aluminothermic welding method can also be used with a gap of 50 mm or more.

[0043] As illustrated in Figures 1-3, a split mold (3, 4) is placed around the ends of the rails (1, 2) in the welding gap area and the contact of the split mold (3, 4) with the ends of the rails (1, 2) is sealed. The contact area of the mold with the rail is sealed with a molding material, which can be used, for example, a material based on kaolin and asbestos wool, while the use of other molding materials is not excluded.

[0044] A reaction crucible (not shown) filled with a dose of aluminothermic composition is installed above the mold, for example on a rotating bracket.

[0045] Heat the rail ends (1, 2) and the split mold (3, 4) to a temperature in the range of 1000…1500°C. For this purpose, use a gas torch with a normally adjusted flame, which is moved to the welding zone for the aforementioned heating. In 7…12 minutes, the rail ends (1, 2) and the casting mold (3, 4) are heated to a temperature of 1000…1500°C. It should be noted that heating above 1500°C is impractical, since partial melting of the rail metal may occur. At the same time, heating below 1000°C does not prevent rapid cooling (during pouring) of the molten metal poured into the split mold, thereby ensuring the release of slag and gases from it.

[0046] The aluminothermite composition dose is ignited (a lit thermite match is inserted into the center of the aluminothermite composition dose) and heated until molten metal is formed. The molten metal is fed from a reaction crucible (not shown) into a split mold (3, 4). After ignition of the aluminothermite composition dose, alloying, refining, and deoxidizing reactions occur, resulting in its heating until molten weld metal is formed. After 20-28 seconds, the molten weld metal is automatically released from the crucible (not shown) into a split mold (3, 4), where it fills the weld gap from the bottom up.

[0047] Until the end of pouring, maintain the temperature of the rail ends (1, 2) and the split mold (3, 4) at least 800°C to prevent rapid cooling (during pouring) of the molten metal being poured into the split mold, thereby ensuring the release of slag and gases. For this purpose, for example, provide protection from precipitation (if present) and provide additional external heating of the mold and rail ends (if necessary).

[0048] Hold molten metal until it solidifies and forms a weld (about 2 min).

[0049] After solidification, the weld seam and the area adjacent to it are cooled with a stream of compressed air to a temperature of 250...300°C, then in air, while, as illustrated in Figures 1-3, the said cooling is carried out by air streams supplied from three groups of air nozzles.

[0050] The first group of air nozzles contains two or four nozzles (5), the axes of which are directed toward the casting bridge seat area (6). The choice of the number of nozzles (5) is determined by the width of the weld seam and the need for surfacing in the rail head area.

[0051] The second group of air nozzles contains four nozzles (7, 8), the axes of two of which (7) are directed toward the area of the joint of the upper part of the head of one rail (1) with the mold (3, 4), and the axis of each of the other two nozzles (8) is directed toward the area of the joint of the side part of the head of one rail (1) with the mold (3, 4), respectively, one nozzle (8) on each side of the said one rail (1).

[0052] The third group of air nozzles also contains four nozzles (9, 10), the axes of two of which (9) are directed toward the area of the junction of the upper part of the head of the opposite rail (2) with the mold (3, 4), and the axis of each of the other two nozzles (10) is directed toward the area of the junction of the side part of the head of the opposite rail (2) with the mold (3, 4), respectively, one nozzle (10) on each side of the said opposite rail (2).

[0053] It should be noted that such a number and arrangement of nozzles allows for uniform, predictable strengthening of the rail head in the weld area and the area adjacent to it, by ensuring uniform, accelerated (relative to air cooling) cooling of the mentioned areas, and, as a result, obtaining a high-quality and durable rail connection, i.e., capable of long-term resistance to cyclic loads.

[0054] After performing the aluminothermic rail welding method described above, the riser is removed from the welded rail head using a trimming device, and the remaining weld is cleaned of any mold material residue. The weld surface on the rail head is then ground to a height of 1–1.5 mm above the top of the rail head. After the weld has completely cooled (to ambient temperature in approximately 15–20 minutes), the entire weld on the rail head is ground to the rail head size with a tolerance of 0.3 mm.

[0055] After cooling and cleaning, the rail section is secured. Ultrasonic non-destructive testing is then performed.

[0056] In particular, to obtain the hardness of the rail head rolling surface of more than 370 HB, the following parameter value ranges should be followed:

[0057] - the distance from the edge of each nozzle (5) of the first group to the upper plane of the seat of the casting bridge (6) is from 140 to 200 mm;

[0058] - the distance from the edge of each nozzle (7, 8, 9, 10) of the second and third groups to the joint of the rail head (1, 2) with the mold (3, 4) is from 190 to 280 mm;

[0059] - the air flow rate of each nozzle (5) of the first group is from 22 to 37 l / min;

[0060] - the air flow rate of each nozzle (7, 8, 9, 10) of the second and third groups is from 26 to 52 l / min;

[0061] - the flow diameter of each nozzle (5) of the first group is from 3 to 5.5 mm;

[0062] - the flow diameter of each nozzle (7, 8, 9, 10) of the second and third groups is from 4 to 8 mm.

[0063] The above ranges of parameter values were obtained by conducting test welds and measuring the hardness of the rail head rolling surface, i.e. they were obtained experimentally and are valid for rails, in particular, OT370IK and DT370IK.

[0064] Figure 4 illustrates the results of interpolation of hardness measurements - the distribution of hardness over the rolling surface of the rail head after implementing the aluminothermic welding method for OT370IK and DT370IK rails - the rolling surface of the rail head has a hardness of 380 to 405 HB.

[0065] In addition, it should be noted that the resource tests currently underway show that the deformation of the rail at the site of the welded joint performed by the aluminothermic rail welding method is within the normal range after 1.5 million cycles.

[0066] It should be noted separately that the permitted conditions (in particular, environmental parameters, including air temperature and humidity, the presence of precipitation, etc.) for carrying out aluminothermic welding of rails depend on the materials used, including the aluminothermic composition used, however, the aforementioned permitted conditions vary slightly, as a rule, this is an ambient air temperature above 10°C and the absence of or protection from precipitation.

[0067] Thus, it can be stated that the above ranges of parameter values are valid for the absolute majority of rails present on the market, both the aforementioned hardened OT370IK and DT370IK, and non-hardened ones, for example, OT350, OT350NN, OT350SS, DT350, DT350NN, DT350SS, DT350VS, etc.

Claims

1. The method of aluminothermic welding of rails involves the following operations: the ends of the rails are installed to form a welding gap between their ends, place a split mold around the ends of the rails in the welding gap area and seal the contact of the split mold with the ends of the rails, a reaction crucible filled with a dose of aluminothermic composition is placed over the mold, heat the ends of the rails and the split mold to a temperature in the range of 1000-1500°C, ignite a dose of aluminothermic composition and heat it until molten metal is formed, molten metal is fed from the reaction crucible into a split mold, until the end of pouring, maintain the temperature of the ends of the rails and the split mold at no less than 800°C, hold the molten metal until it solidifies and a weld is formed, the weld seam after hardening and the area adjacent to it are cooled with a stream of compressed air to a temperature of 250-300°C, then in air, wherein the said cooling is carried out by air flows supplied from three groups of air nozzles, the first group of air nozzles contains two or four nozzles, the axes of which are directed towards the area of the casting bridge seat, the second group of air nozzles contains four nozzles, the axes of two of which are directed towards the area of the junction of the upper part of the head of one rail with the mold, and the axis of each of the other two nozzles is directed towards the area of the junction of the side part of the head of one rail with the mold, respectively, one nozzle on each side of the said one rail, The third group of air nozzles also contains four nozzles, the axes of two of which are directed towards the area of the junction of the upper part of the head of the opposite rail with the mold, and the axis of each of the other two nozzles is directed towards the area of the junction of the side part of the head of the opposite rail with the mold, respectively, one nozzle on each side of the said opposite rail.

2. The method according to paragraph 1, in which the distance from the edge of each nozzle of the first group to the upper plane of the seat of the casting bridge is from 140 to 200 mm.

3. The method according to paragraph 1, in which the distance from the edge of each nozzle of the second and third groups to the joint of the rail head with the mold is from 190 to 280 mm.

4. The method according to claim 1, wherein the air flow rate of each nozzle of the first group is from 22 to 37 l / min.

5. The method according to claim 1, wherein the air flow rate of each nozzle of the second and third groups is from 26 to 52 l / min.

6. The method according to claim 1, wherein the flow diameter of each nozzle of the first group is from 3 to 5.5 mm.

7. The method according to claim 1, wherein the flow diameter of each nozzle of the second and third groups is from 4 to 8 mm.