Method for coating a railway track, use of a laser cladding machine, use of a coating, railway track and railway vehicle

Abstract

Method for coating a railway rail (12) by means of laser cladding, wherein the method comprises: providing a railway rail (12) having a rail head (18); and coating at least one area (56) of the rail head (18) with a material (30) by laser cladding, wherein a laser beam (26) is directed at the rail head (18) during the laser cladding process.

Description

[0001] The invention relates to a method for coating a railway track, the use of a laser cladding machine, the use of a coating, a railway track and a railway vehicle.

[0002] Rail vehicles, such as trains, typically travel along a track consisting of two parallel rails. Each rail vehicle can have multiple wheels that contact the rails. The wheels are designed to be guided by the two rails. Each wheel has a tread for contacting the rail and a flange to prevent lateral slippage.

[0003] Railway tracks are typically made of high-strength steel, preferably carbon steel or alloy steel. The steel used in railway tracks can have a high carbon content and may contain other alloying elements such as chromium, manganese, or vanadium to optimize its mechanical properties, particularly wear resistance and toughness. For example, steels of grades R260 or R350HT can be used to manufacture railway tracks, which exhibit high tensile strength and are resistant to mechanical stress and weathering.

[0004] Railway wheels are typically made of high-strength steel, which is hardened by forging and subsequent heat treatment. The steel used in railway wheels is designed to withstand the high compressive and tensile forces that occur, in particular, when traveling along railway tracks.

[0005] Due to contact between railway wheels and rails, as well as high mechanical stresses, wear and tear occurs on both the wheels and rails, necessitating their regular replacement. While railway wheels can be replaced easily and largely without disrupting rail operations, replacing rails is usually complex and often leads to disruptions.

[0006] The object of the present invention is to reduce disturbances during the operation of a railway transport system.

[0007] The invention solves this problem by providing a method with the features of claim 1, a use with the features of claim 8, a use with the features of claim 9, a railway track with the features of claim 10 and a railway vehicle with the features of claim 11.

[0008] A method according to the invention serves to coat a railway rail by means of laser cladding. The method comprises: providing a railway rail having a rail head; and coating at least one area of ​​the rail head, in particular at least one section of a running surface and / or a section of a guide surface of the rail head, with a material by laser cladding. During laser cladding, a laser beam is used to coat the area of ​​the rail head with the material.

[0009] Advantageously, laser cladding allows the railhead area to be coated with a material that can withstand the high compressive and tensile forces encountered when a rail vehicle, such as a train, tram, or other vehicle, passes over the track. This increases the wear resistance of the rail, resulting in a longer service life. Consequently, the extended service life of the rail reduces disruptions to rail operations, such as those caused by track replacement work.

[0010] The railway track can be referred to as a rail. Coating can be understood as the application of a coating. The coating can be made of a specific material. The coating can have a surface roughness of 10 µm (micrometers) to 20 µm. Coating can be carried out for the purpose of reducing wear on the rail head.

[0011] The material can be in powder form. It can be harder than the material used to form the rail head. The material can contain a nickel-based, iron-based, or cobalt-based alloy; in particular, it can have a nickel, iron, or cobalt content of at least 50%, and in particular 60%. Preferably, the material can contain a nickel-chromium alloy; in particular, it can contain at least 50%, and in particular 60%, of the nickel-chromium alloy. The material can also contain, for example, a carbide, in particular tungsten carbide, or zirconium oxide.

[0012] Laser cladding involves welding material onto the surface using a laser beam. In other words, laser cladding creates a weld between the material and the rail head. During laser cladding, the material can be blown from a nozzle using a carrier gas, so that the laser beam welds the material onto the rail head.

[0013] Laser cladding can be a high-speed laser cladding process. In particular, high-speed laser cladding can reduce the heat-affected zone.

[0014] Laser cladding can be performed with a deposition rate of up to 1200 cm³. 2 / min (square centimeters per minute).

[0015] The area can be a surface section of the rail head. The rail head can have a running surface and a guide surface. The area can be formed by a surface section of the running surface and / or a surface section of the guide surface of the rail head. It is also conceivable that the entire running surface and / or the entire guide surface of the rail head constitutes the area. In particular, coating the rail head can be a coating of the running surface and / or the guide surface of the rail head.

[0016] The coating process can include: generating the laser beam, in particular using a fiber laser, a disk laser, or a laser diode. In particular, the fiber laser or the laser diode can generate a laser beam that is especially suitable for laser cladding.

[0017] Another aspect of the process is that coating the rail head creates a hard and wear-resistant coating on the rail head.

[0018] Another aspect of the process is that laser cladding can create a metallurgical bond between the material and the railway track without the occurrence of cracks and pores.

[0019] In a further development of the process, laser cladding comprises: irradiating a zone of the rail head with the laser beam; heating the material with the laser beam; and introducing the heated material into the zone. Advantageously, this allows for an increase in the coating speed, particularly the feed rate. Specifically, heating the material before it is introduced into the zone accelerates the creation or formation of the weld joint between the material and the rail head. Another benefit is that this reduces the thermal stress on the rail head during the coating process.

[0020] The material can be heated before it is introduced into the zone.

[0021] The material can be heated with the laser beam in such a way that at least 50% of the laser beam's power is absorbed by the material. In other words, a significant portion of the laser beam's thermal energy can be absorbed by the material.

[0022] The railhead zone can be a section of the area. The zone can be defined by a spot created by the laser beam upon striking the railhead. This zone can be referred to as the irradiation zone.

[0023] The zone can be an area with a size in the range of 1.5 mm. 2 (square millimeters) up to 3 mm 2 The zone has a circular shape. In particular, the zone can have a diameter ranging from 1.5 mm (millimeters) to 2 mm.

[0024] In a further development of the process, the rail head is irradiated in such a way that the rail head is at least partially melted in the treated zone. Additionally or alternatively, the material is heated in such a way that it is at least partially melted. Advantageously, this allows the coating speed, particularly the feed rate, to be further increased. Another benefit is that this method can produce metallurgically bonded, homogeneous layers.

[0025] Preferably, the material is at least partially melted and the rail head is at least partially melted in the zone before the material is introduced into the zone. In other words, the material can be at least partially melted before it comes into contact with the rail head. If both the material and the rail head are in a molten state when the material comes into contact with the rail head, the weld between the material and the rail head can be formed particularly quickly.

[0026] In a further development of the process, the laser beam has a core area and a ring area. The ring area surrounds the core area, specifically circumferentially. Advantageously, this allows for a particularly stable and resilient welded connection between the material and the rail head, which is why the resulting coating can withstand the high compressive and tensile forces that occur when a rail vehicle passes over the railway track.

[0027] In particular, the ring area can be used to preheat and / or postheat the material and / or the rail head. The core area can be used to create the weld joint between the material and the rail head. Preheating and postheating ensure a particularly good bond between the material and the rail head, thereby improving the stability of the coating.

[0028] The core area can have a circular intensity profile. The ring area can have an annular intensity profile. The beam diameter of the core area can be smaller than the inner diameter of the ring area. The ring area can define an inner region, with the core area located within the inner region of the ring area. The core area can be adjacent to the ring area. Alternatively, the core area and the ring area can be spaced apart.

[0029] The power output of the core area can differ from the power output of the ring area. The power output of the core area can be adjusted independently of the power output of the ring area.

[0030] In a further development of the process, the coating is applied at a speed, in particular a feed rate, ranging from 3 m / min (meters per minute) to 800 m / min, more specifically from 50 m / min to 600 m / min, and preferably from 80 m / min to 500 m / min. This speed can be achieved by laser cladding, especially high-speed laser cladding. Advantageously, this allows the coating of railway tracks even when they are already laid as part of a track. For example, a downtime of a rail network containing the railway track may be sufficient to coat it. Preferably, this allows railway tracks already laid overnight to be subsequently coated using this process, or an existing coating to be renewed.

[0031] In a further development of the process, the coating is applied such that the material thickness in the area of ​​the rail head after coating is in the range of 5 µm to 150 µm, particularly 10 µm to 100 µm. Advantageously, such thicknesses can significantly reduce wear on the railway track while simultaneously producing a coating that withstands the high compressive and tensile forces that occur when a rail vehicle passes over the track.

[0032] The thickness of the material after coating can be the thickness of a coating produced by the coating process.

[0033] In a further development of the process, the coating is carried out by a laser cladding machine. The laser cladding machine is moved relative to the railway track during the coating process, or the railway track is moved relative to the laser cladding machine during the coating process.

[0034] The laser cladding machine can be moved relative to the railway track during the coating process, even if the track has already been laid. This allows for the coating of an already laid railway track. Specifically, the laser cladding machine can be moved along the railway track during the coating process.

[0035] The railway track can be moved relative to the laser cladding machine during the coating process if the railway track is coated after the railway track has been manufactured and before the railway track has been laid.

[0036] One use of a laser cladding machine according to the invention relates to using the laser cladding machine for coating a railway track. The preceding description of the method can also apply to identical or functionally equivalent features of the use of the laser cladding machine.

[0037] One use according to the invention of a coating produced by laser cladding relates to the use of the coating to reduce wear on a railway track. The preceding description of the method can also apply to identical or functionally equivalent features of the use of the coating.

[0038] A railway rail according to the invention is suitable for forming a track, in particular a track, for a rail vehicle. The railway rail has a rail head with a coating, at least in certain areas, for contacting a railway wheel and for reducing wear on the railway rail. Advantageously, the coating can increase the wear resistance of the railway rail. The preceding description of the method can also apply to railway rails with identical or functionally equivalent features.

[0039] The coating can be produced by laser cladding. A welded joint can be formed between the coating material and the rail head material. This welded joint can be produced by at least partially melting the rail head and at least partially melting the coating material. Preferably, the rail head material and the coating material can be at least partially melted before the two materials come into contact.

[0040] The rail vehicle can be designed as a train, a railway, or a railway vehicle.

[0041] The coating can be produced using laser cladding. Laser cladding, in particular, allows the coating material to be welded to the railhead, preventing damage to the coating from the high compressive and tensile forces that occur when a rail vehicle passes over the track.

[0042] A rail vehicle according to the invention, in particular a train, railway, or railway vehicle, comprises a plurality of railway wheels for moving the rail vehicle along a track and a laser cladding machine. The track has a first railway rail and a second railway rail. The first railway rail and the second railway rail run parallel to each other. The laser cladding machine is configured to coat at least a portion of a rail head of the first railway rail and / or a rail head of the second railway rail with a material by laser cladding while the rail vehicle is moving along the track. Advantageously, already laid railway rails can be coated using the rail vehicle.

[0043] The rail vehicle may be designed to travel along the track. The rail vehicle may have a drive system, in particular an electric motor and / or a diesel engine, for moving the rail vehicle, especially for driving, along the track.

[0044] The previously given description of the procedure can also apply to identical or functionally equivalent features of the rail vehicle.

[0045] Further advantages and advantageous embodiments of the invention can be seen from the figures, their description, and the claims. All features disclosed in the figures, their description, and the claims can be essential to the invention, both individually and in any combination. The figures show: Fig. 1 A schematic representation of a laser cladding machine during the coating of a railway track, Fig. 2 a schematic representation of a cross-section of the railway track of Fig. 1 before coating, Fig. 3 A schematic representation of a cross-section of a laser beam of the laser cladding machine of Fig. 1, Fig. 4 a schematic representation of a cross-section of the railway track of Fig. 1 after coating, Fig. 5 a schematic representation of a rail vehicle during the coating of a railway track, and Fig. 6 A schematic representation of a cross-section of a track on which the rail vehicle of Fig. It is placed in 5th position.

[0046] Fig. Figure 1 shows a laser cladding machine 10 during the coating of a railway track 12. A cross-section of the railway track 12 before coating is shown in Figure 1. Fig. 2 shown.

[0047] Railway rail 12 is made of steel. Railway rail 12 serves to form a track for a rail vehicle. For this purpose, railway rail 12 and another railway rail, which is identical in construction to railway rail 12, are arranged parallel to each other at a defined distance and fastened to several railway sleepers.

[0048] The railway track 12 has a rail foot 14, a rail web 16 and a rail head 18. The rail foot 14 serves to fasten the railway track 12 to the railway sleepers.

[0049] The railhead 18 has a running surface 20 and a guide surface 22. The running surface 20 of the railhead 18 serves to contact a running surface of the railway wheel, and the guide surface 22 serves to contact a flange of the railway wheel to prevent the railway wheel from slipping laterally. This allows a rail vehicle, which has the railway wheel, to travel safely along the track, in particular the railway rail 12.

[0050] When rail vehicles frequently travel along railway track 12, wear occurs on the railway track 12. To reduce the wear of the railway track 12, the railway track 12 is coated using the laser cladding machine 10 after its manufacture and before it is fastened to the railway sleepers, see [reference]. Fig. 1.

[0051] The laser cladding machine 10 has a laser beam source 24 for generating a laser beam 26. The laser beam source 24 is designed as a fiber laser. However, it is also conceivable that the laser beam source 26 is designed as a disk laser or as a laser diode.

[0052] The laser cladding machine 10 has a protective enclosure 29 that prevents unwanted escape of laser radiation from the laser beam source 24 out of the laser cladding machine 10.

[0053] The laser cladding machine 10 has a material container 28 for storing material 30. Material 30 is a powdered material. Material 30 contains a nickel-chromium alloy. Material 30 is harder than the steel of the railway track 12.

[0054] The material 30 and the laser beam 26 are simultaneously fed to a processing head 32 of the laser cladding machine 10. The feeding of the material 30 and the laser beam 26 is in Fig. 1 symbolized by arrows.

[0055] The powdered material 30 is transported to the processing head 32 by means of compressed air. Alternatively, a protective gas could be used for transporting the material 30 instead of compressed air. The material 30 is guided via channels 34 of the processing head 32 to an exit side 36 of the processing head 32. At the exit side 36, the material 30 and the laser beam 26 exit the processing head 32. The material 30 and the laser beam 26 exit the processing head 32 at different locations.

[0056] The laser beam 26 exits the processing head 32 in such a way that it is directed towards the railway track 12. The laser beam 26 strikes the railway track 12. This causes a zone 38 of the track head 18 to be irradiated with the laser beam 26. Zone 38 is defined by a spot that the laser beam 26 creates on the track head 18.

[0057] Fig. Figure 3 shows a cross-section of the laser beam 26 after it exits the processing head 32. The laser beam 26 has a core region 40 and an annular region 42. The annular region 42 completely surrounds the core region 40. The annular region 42 borders the core region 40. The core region 40 has a circular intensity profile, and the annular region 42 has an annular intensity profile. The power of the laser beam 26 in the core region 40 differs from the power of the laser beam 26 in the annular region 42. In the illustrated embodiment, the power in the core region 40 is greater than the power in the annular region 42. It is also conceivable that the power in the core region is less than the power in the annular region 42. The laser beam source 24 is designed to adjust the power in the core region 40 and the power in the annular region 42, in particular independently of each other.

[0058] The material 30 is guided to the exit side 36 via the channels 34 in such a way that, after exiting the processing head 32, it crosses the path of the laser beam 26. This causes the material 30 to first enter the ring region 42 and then the core region 40 of the laser beam. As a result, the material 30 is irradiated by the laser beam 26. In other words, the material 30 is heated by the laser beam 26. The material 30 is partially melted by the laser beam 26. At least 50% of the power of the laser beam 26 can be absorbed by the material 30.

[0059] The portion of the laser beam 26 not absorbed by the material 30 strikes the rail head 18, forming zone 38. The rail head 18 is melted in zone 38 by the laser beam 26. As a result, the partially melted material 30 comes into contact with the locally melted rail head 18. A weld is formed between the rail head 18 and the material 30. In other words, the material 30 is selectively welded onto the rail head 18 by means of the laser cladding machine 10. Therefore, the coating of the rail head 18 is a laser cladding process.

[0060] The laser cladding machine 10 has a transport device 44 that moves the railway rail 12 in a direction of movement 46 during the coating of the rail head 18. The rail head 18 is guided past the processing head 32. The transport device 44 moves the railway rail 12 past the processing head 32 at a speed of 100 m / min.

[0061] The transport device 44 has a plurality of driven rollers 48. However, it is also conceivable that the transport device 44 has an alternative means of transport to the rollers 48 for moving the railway track 12 past the processing head 32.

[0062] Consequently, the railway rail 12 is coated with material 30 using the laser cladding machine 10, forming a coating 52. In other words, the material 30 welded onto the rail head 18 forms a coating 52. The coating 52 has a thickness 54 of 80 µm.

[0063] Fig. Figure 4 shows a cross-section of the railway track 12 after coating with the material 30. Fig. Figure 4 shows that the rail head 18 is coated in an area 56. Area 56 is a surface section of the rail head 18. Area 56 comprises part of the running surface 20 and part of the guide surface 22 of the rail head 18. In other words, the running surface 20 and the guide surface 22 of the rail head 18 are partially coated with the coating 52. It is also conceivable that the entire running surface 20 and / or the entire guide surface 22 of the rail head 18 are coated.

[0064] Additionally, for better understanding in Fig. Figure 4 shows a railway wheel 58 in section. The railway wheel 58 has a tread 60 for contacting the railway rail 12 and a flange 62 for securing the railway wheel 58 against lateral slippage. When the railway wheel 58 rolls along the railway rail 12, the tread 60 of the railway wheel 58 contacts the coating 52, and if there is a risk of the railway wheel 58 slipping laterally off the railway rail 12, the flange 62 additionally contacts the coating 52 and prevents lateral slippage. The coating 52 prevents direct contact between the steel of the railway rail 12 and the railway wheel 58, thus reducing wear on the railway rail 12 caused by the coating 52.

[0065] In Fig. Figure 5 shows a further embodiment of a laser cladding machine 10, wherein identical and functionally equivalent elements are represented by the same reference numerals, and in this respect reference is made to the above descriptions of the embodiment of the Fig. 1 can be referenced, so that essentially only the existing differences will be addressed.

[0066] The laser cladding machine 10 of the Fig. 5 is integrated into a rail vehicle 64. In other words, the rail vehicle 64 has the laser cladding machine 10. The rail vehicle 64 can use the laser cladding machine 10 to coat already laid railway tracks 12 by laser cladding.

[0067] The rail vehicle 64 is a railway wagon and has a plurality of railway wheels 58. In the illustrated embodiment, the rail vehicle 64 has four railway wheels 58. In the side view of the Fig. However, due to the perspective, only two of the four railway wheels 58 are visible.

[0068] The railway wheels 58 are identical in construction. Each railway wheel 58 is corresponding to the one in Fig. The railway wheels 58 shown in Figure 4 are designed to move the rail vehicle 64 along a track 66.

[0069] Fig. Figure 6 shows a cross-section of track 66 and, for better understanding, two of the railway wheels 58 of the rail vehicle 64. Track 66 has a first railway rail 68 and a second railway rail 70. The first railway rail 68 and the second railway rail 70 run parallel to each other. The guide surface 22 of the first railway rail 68 and the guide surface 22 of the second railway rail 70 face each other. The two railway rails 68, 70 are fastened to a plurality of railway sleepers 72.

[0070] The rail vehicle 64 has a drive 74, see Fig. 5. The drive 74 is an electric motor that drives at least one of the railway wheels 58 and thereby moves the rail vehicle 64 in a direction of movement 76 along the track 66. In other words, the rail vehicle 64 travels along the track 66. The speed of the rail vehicle 64 is 500 m / min.

[0071] The laser cladding machine 10 has two processing heads 32. In the side view of the Fig.However, due to the perspective, only one of the two processing heads 32 is visible in Figure 5. Each processing head 32 is arranged between two railway wheels 58. It is also conceivable, however, that the two processing heads 32 are arranged in the direction of movement 76 behind the railway wheels 58 of the rail vehicle 64, so that the produced coating 52 is not immediately run over by a railway wheel 58 of the rail vehicle 64 after the coating 52 has been produced. One processing head is directed towards the first railway rail 68 and the other processing head is directed towards the second railway rail 70.

[0072] While the rail vehicle 64 travels along track 66, the laser cladding machine 10 coats the rail head 18 of the first railway rail 68 and the rail head 18 of the second railway rail 70 in sections with the material 30. This makes the rail vehicle 64 suitable for coating the railway rails 68, 70 of the already laid track 66 with the material 30.

Claims

[1] Method for coating a railway track (12) by laser cladding, the method comprising: - Providing a railway track (12) having a railhead (18), and - Coating at least one area (56) of the rail head (18) with a material (30) by laser cladding, - wherein during laser cladding a laser beam (26) is used to coat the area (56) of the rail head (18). [2] Method according to claim 1, - which includes laser cladding: - Irradiating a zone (38) of the rail head (18) with the laser beam (26), - Heating the material (30) with the laser beam (26), and - Introducing the heated material (30) into the zone (38). [3] Method according to claim 2, - wherein the irradiation of the rail head (18) is carried out in such a way that the rail head (18) is at least partially melted in the zone (38), and / or - wherein the heating of the material (30) is carried out in such a way that the material (30) is at least partially melted. [4] Method according to any of the preceding claims, - wherein the laser beam (26) has a core region (40) and a ring region (42), - wherein the ring region (42) surrounds the core region (40), in particular circumferentially. [5] Method according to any of the preceding claims, - wherein the coating is carried out at a speed, in particular a feed rate, which has a value in the range of 3 m / min to 800 m / min, in particular 50 m / min to 600 m / min, preferably 80 m / min to 500 m / min. [6] Method according to any of the preceding claims, - wherein the coating is carried out in such a way that the thickness (54) of the material (30) in the area (56) of the rail head (18) after coating has a value in the range of 5 µm to 150 µm, in particular 10 µm to 100 µm. [7] Method according to any of the preceding claims, - wherein the coating is carried out by a laser cladding machine (10), - wherein the laser cladding machine (10) is moved relative to the railway track (12) during the coating process or the railway track (12) is moved relative to the laser cladding machine (10) during the coating process. [8] Use of a laser cladding machine (10) for coating a railway track (12). [9] Use of a coating (52) produced by laser cladding for reducing wear of a railway track (12). [10] Railway track (12) for forming a track for a rail vehicle (64), comprising: - a rail head (18) which has at least in some areas a coating (52) for contacting a railway wheel (58) and for reducing wear of the railway rail (12). [11] Railway vehicle (64), comprising: - a plurality of railway wheels (58) for moving the rail vehicle (64) along a track (66), and - a laser cladding machine (10), - wherein the track (66) has a first railway rail (68) and a second railway rail (70), - wherein the first railway track (68) and the second railway track (70) run parallel to each other, - wherein the laser cladding machine (10) is designed to coat at least partially with a material (30) by laser cladding a rail head (18) of the first railway rail (68) and / or a rail head (18) of the second railway rail (70) while the rail vehicle (64) is moving along the track (66).

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