A method and device for improving the hardness of the re-austenitization zone of a hypereutectoid rail joint

Abstract

The present invention discloses a method and device for improving the hardness of the re-austenization zone of a hypereutectoid rail joint, the method comprising: front-end processing; flash welding the hypereutectoid rail joint, the welding comprising pre-flash, flash, accelerated burning, top forging and forging stages; circumferential quenching the hypereutectoid rail joint with residual heat after welding, the circumferential quenching comprising uniformly spraying compressed air on the top, side and lower jaw of the rail head for accelerated cooling; and rear-end processing. The ratio of the hardness of the re-austenization zone of the high-strength hypereutectoid rail joint for heavy-duty railway welded by the method and device to the hardness of the rail base material is 0.95 to 1.10, which ensures the smoothness of the joint and can easily meet the technical index requirements specified in the standard. After welding is completed, the residual heat of the rail joint after welding is fully utilized to improve the hardness of the joint and effectively ensure production efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of rail welding, and in particular to a method and a device for improving the hardness of a re-austenitizing zone of a hypereutectoid rail joint. Background Art

[0002] In the field of rail production, rails with a carbon content of more than 0.90% are usually called hypereutectoid rails. Technicians increase the thickness of cementite sheets and cementite density in the matrix to improve the hardness and wear resistance of the rails, that is, increase the carbon content to obtain higher hardness. The higher the strength and hardness of the rails, the worse the welding performance of the rails. The welded joints are the weak link in the railway lines. Therefore, the optimization of the performance of heavy-load rail welded joints is also a focus of research by scholars at home and abroad.

[0003] The re-austenitizing zone of rail flash welding refers to the area in the rail joint where austenite phase transformation occurs during the welding heating process. Because the phase transformation law during heating and cooling is the same as the heat treatment normalizing process, this area is also often called the normalizing zone. Under normal circumstances, the microstructure, tensile and impact properties of the re-austenitizing zone of rail flash welding are better than those of the parent material. However, the hardness index of the re-austenitizing zone of the flash welded joint of rails with different chemical compositions and supply conditions will be different from that of the parent material. Generally speaking, the hardness of the rail is mainly determined by the cooling rate. For rail material metals with the same starting temperature, the greater the cooling rate during the cooling process, the higher the hardness. If the cooling rate of the re-austenitizing zone after welding is greater than the cooling rate of the base material, the hardness of the re-austenitizing zone will be higher than that of the base material; if the cooling rate of the re-austenitizing zone after welding is less than the cooling rate of the base material, the hardness of the re-austenitizing zone will be lower than that of the base material. Compared with the base material of the rail, the hardness of the re-austenitizing zone is too high or too low, which will affect the smoothness of the joint during service, and abnormal harmful structures such as martensite and bainite will also affect the performance of the rail joint.

[0004] Therefore, there is a need in the prior art for improving the hardness of the re-austenitized zone of a hypereutectoid rail joint. Summary of the invention

[0005] In view of this, the purpose of the embodiments of the present invention is to propose a method and device for improving the hardness of the re-austenization zone of a hypereutectoid rail joint, by controlling welding parameters and post-weld cooling treatment to improve the hardness of the re-austenization zone of a high-strength hypereutectoid rail joint for heavy-duty railways, thereby effectively ensuring the smoothness of the rail joint.

[0006] Based on the above purpose, an embodiment of the present invention provides a method for improving the hardness of a hypereutectoid rail joint re-austenization zone, the method comprising:

[0007] (1) Perform front-end processing on the hypereutectoid rail joint;

[0008] (2) flash welding the hypereutectoid rail joint, including pre-flash, flash, accelerated burning, top forging and forging stages;

[0009] (3) performing circumferential quenching treatment on the hypereutectoid rail joint with residual heat after welding, wherein the circumferential quenching treatment includes uniformly spraying compressed air on the top, side and lower jaw of the rail head to accelerate cooling;

[0010] (4) performing back-end processing on the hypereutectoid rail joint;

[0011] Among them, each processing step is connected by a conveying roller to form a production line, and the hypereutectoid rail joint is driven by the conveying roller to enter each processing step in turn. The quenching length during the circumferential quenching treatment is 10 to 50 meters.

[0012] In some embodiments, the welding process of step (2) includes:

[0013] The high-voltage time in the pre-flash stage is 45s to 65s, and the flash speed is 0.1mm / s to 0.6mm / s;

[0014] The low pressure time in the flash stage is 80s to 140s, and the flash speed is 0.1mm / s to 0.6mm / s;

[0015] The flash acceleration speed in the accelerated burning stage is 0.5 mm / s to 2.0 mm / s;

[0016] The live forging time in the forging stage is 0.1s to 2.0s, and the forging timing is 1.0s to 3.0s;

[0017] The rail consumption in the forging stage is 2.0mm~4.0mm, the forging time is 1.5s~3.0s, and the average speed is 0.60mm / s~2.60mm / s.

[0018] In some embodiments, compressed air with a pressure value of 50 kPa to 300 kPa is uniformly sprayed on the top, sides and lower jaw of the rail head.

[0019] In some embodiments, the conveying speed of the conveying roller is set to 0.2 m / s to 2.5 m / s.

[0020] In some embodiments, the main chemical composition of the hypereutectoid rail includes:

[0021] The mass fraction of carbon is between 0.90% and 1.20%, the mass fraction of silicon is between 0.10% and 1.00%, the mass fraction of manganese is between 0.60% and 1.50%, the mass fractions of phosphorus and sulfur do not exceed 0.020%, the mass fraction of chromium does not exceed 0.3%, and the mass fraction of vanadium does not exceed 0.01%.

[0022] In some embodiments, the minimum tensile strength of the hypereutectoid rail is 1200 MPa, and the minimum hardness of the hypereutectoid rail head is 400 HB.

[0023] Another aspect of the present invention is to provide a device for improving the hardness of the re-austenitization zone of a hypereutectoid rail joint, the device being used for circumferential quenching treatment, and comprising:

[0024] Conveyor rollers;

[0025] A plurality of quenching units are arranged in sequence along the conveying roller direction, each quenching unit comprises a rail head air box, a first air duct symmetrically distributed on the side of the rail head, and a second air duct symmetrically distributed on the lower jaw of the rail head. The longitudinal lengths of the air box and the air duct are consistent, and the distances from the adjacent rail surfaces are the same. A plurality of air outlets are evenly distributed on the air box and the air duct to spray compressed air to the rail joints.

[0026] In some embodiments, each quenching unit includes a rail head air box, two first air ducts symmetrically distributed on the side of the rail head, and two second air ducts symmetrically distributed on the lower jaw of the rail head. Each quenching unit independently controls the compressed air pressure value.

[0027] In some embodiments, the pressure of the compressed air before entering the quenching device is 50 kPa to 300 kPa.

[0028] In some embodiments, the total length of the quenching device composed of multiple quenching units is 10m to 50m, the width of the wind box is ≥70mm, the length of the wind box and the air duct is ≥150mm, the diameter of the air duct is Φ25mm to Φ30mm, the distance between the wind box and the air duct and the surface of the adjacent rail is 20mm to 40mm, the diameter of the air outlet is Φ1mm to Φ3mm, and the spacing between the air outlets is 5mm to 15mm.

[0029] The present invention has at least the following beneficial technical effects:

[0030] The method of the present invention is implemented by a mobile rail flash welding machine. The welding process mainly includes five main stages: pre-flash, flash, accelerated burning, top forging and forging. After the flash welding process is completed, a special fixed online quenching device is used to perform circumferential air quenching treatment on the joint. The ratio of the hardness of the high-strength hypereutectoid rail joint for heavy-duty railway welded by this method and device in the austenite zone to the hardness of the rail base material is 0.95-1.10, which ensures the smoothness of the joint and can easily meet the technical indicators specified in the standard. After the welding is completed, the residual heat of the rail joint after welding is fully utilized to improve the hardness of the joint and effectively ensure the production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A flow chart of an embodiment of a method for improving the hardness of the re-austenitizing zone of a hypereutectoid rail joint provided by the present invention;

[0033] Figure 2 A schematic diagram of an embodiment of a quenching unit provided by the present invention;

[0034] Figure 3 A schematic diagram of the re-austenitization zone of the rail joint provided by the present invention. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0036] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions; the terms "first", "second", etc. in the specification and claims of the present invention or the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0037] In addition, reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0038] like Figure 1 The flowchart of an embodiment of the method for improving the hardness of the re-austenitization zone of a hypereutectoid rail joint provided by the present invention is shown, and the method comprises:

[0039] (1) Perform front-end processing on the hypereutectoid rail joint;

[0040] (2) flash welding the hypereutectoid rail joint, including pre-flash, flash, accelerated burning, top forging and forging stages;

[0041] (3) performing circumferential quenching treatment on the hypereutectoid rail joint with residual heat after welding, wherein the circumferential quenching treatment includes uniformly spraying compressed air on the top, side and lower jaw of the rail head to accelerate cooling;

[0042] (4) performing back-end processing on the hypereutectoid rail joint;

[0043] Among them, each processing step is connected by a conveying roller to form a production line, and the hypereutectoid rail joint is driven by the conveying roller to enter each processing step in turn. The quenching length during the circumferential quenching treatment is 10 to 50 meters.

[0044] Furthermore, the above-mentioned high-strength hypereutectoid rail for heavy-duty railway is characterized in that the mass fraction of carbon in the main chemical composition of the rail is 0.90% to 1.20%, the mass fraction of silicon is 0.10% to 1.00%, the mass fraction of manganese is 0.60% to 1.50%, the mass fraction of phosphorus and sulfur does not exceed 0.020%, the mass fraction of chromium does not exceed 0.3%, and the mass fraction of vanadium does not exceed 0.01%. The minimum tensile strength of the rail is 1200MPa, and the minimum hardness of the rail head is 400HB.

[0045] Furthermore, the front-end process and the back-end process in the method of the present invention are conventional processes for rail joint welding, and therefore, the present invention will not be further explained. For the continuous flash welding in step (2), the flash process is mainly achieved by pre-flash, flash, and accelerated sintering, and the flash process is smooth, continuous and uninterrupted. In order to achieve the purpose of improving the hardness of the hypereutectoid rail joint in the austenite zone, the heat input of the welding process and the cooling rate of the joint cooling process need to be strictly controlled. And after the welding is completed, the joint is subjected to the circumferential quenching treatment of step (3).

[0046] Furthermore, the basic function of the above-mentioned pre-flash stage is to make the section of the rail to be welded flat and clean through flash blasting, providing relatively uniform and flat favorable conditions and basic heat for the subsequent flash. In order to achieve the purpose of controlling heat input, it is mainly necessary to control the high-voltage time and flash speed in this stage. The high-voltage time in the pre-flash stage is 45s to 65s, and the flash speed is 0.1mm / s to 0.6mm / s.

[0047] Furthermore, the main function of the above-mentioned flash stage is to make the section of the rail to be welded flat and clean through flash blasting, providing relatively uniform and flat favorable conditions and basic heat for the subsequent flash. In order to achieve the purpose of controlling heat input, it is mainly necessary to control the low pressure time and flash speed of this stage. The low pressure time of the flash stage is 80s to 140s, and the flash speed is 0.1mm / s to 0.6mm / s.

[0048] Furthermore, the main function of the above-mentioned accelerated burning stage is to form a protective atmosphere in the entire welding area to prevent end face oxidation, and finally form a suitable temperature field distribution to provide conditions for upsetting. In order to achieve the purpose of controlling heat input, it is mainly necessary to control the flash acceleration speed in this stage. The flash acceleration speed in the accelerated burning stage is 0.5mm / s to 2.0mm / s.

[0049] Furthermore, the main function of the above-mentioned upset forging stage is to make the steel rail to be welded in a high-temperature plastic state produce atomic bonding. In order to achieve the purpose of controlling heat input, it is mainly necessary to control the charged upset forging time and upset forging timing in this stage. The charged upset forging time is 0.1s to 2.0s, and the upset forging timing is 1.0s to 3.0s.

[0050] Furthermore, the forging stage is mainly used to continuously apply load to the rail joint during the metal crystallization process of the joint after the rail top forging. The rail consumption in the forging stage is 2.0 mm to 4.0 mm, the forging time is 1.5 s to 3.0 s, and the average speed is 0.60 mm / s to 2.60 mm / s.

[0051] Furthermore, the above-mentioned circumferential quenching treatment is a process in which the rail passes through a special quenching device along the longitudinal direction of the rail at a certain running speed, and the rail welded joint with residual heat from welding is accelerated to cool under the action of compressed air with a specific pressure. Specifically, the conveying speed of the conveying roller is set to 0.2m / s to 2.5m / s, and the quenching device is used to evenly spray compressed air with a pressure value of 50kPa to 300kPa on the top, side and lower jaw of the rail head.

[0052] Another aspect of the present invention provides a device for improving the hardness of the re-austenitization zone of the hypereutectoid rail joint used in the above method, the device is a fixed online quenching device, used for circumferential quenching treatment, and is tightly connected to the outlet end of the welding machine, and the device comprises:

[0053] Conveyor rollers;

[0054] A plurality of quenching units are arranged in sequence along the conveying roller direction, each quenching unit comprises a rail head air box, a first air duct symmetrically distributed on the side of the rail head, and a second air duct symmetrically distributed on the lower jaw of the rail head. The longitudinal lengths of the air box and the air duct are consistent, and the distances from the adjacent rail surfaces are the same. A plurality of air outlets are evenly distributed on the air box and the air duct to spray compressed air to the rail joints.

[0055] In some embodiments, each quenching unit includes a rail head air box, two first air ducts symmetrically distributed on the side of the rail head, and two second air ducts symmetrically distributed on the lower jaw of the rail head, and each quenching unit independently adjusts the compressed air pressure value. Further, the pressure value of the compressed air before entering the quenching device is 50kPa to 300kPa.

[0056] In some embodiments, the total length of the quenching device composed of multiple quenching units is 10m to 50m, the width of the wind box is ≥70mm, the length of the wind box and the air duct is ≥150mm, the diameter of the air duct is Φ25mm to Φ30mm, the distance between the wind box and the air duct and the adjacent rail surface is 20mm to 40mm, the diameter of the air outlet is Φ1mm to Φ3mm, and the spacing between the air outlets is 5mm to 15mm.

[0057] The device of the present invention is mainly used in the quenching process in the above method. The welded rail joint is conveyed to a fixed quenching device via a conveying roller, and is driven by the conveying roller to pass through multiple quenching units in sequence for continuous quenching treatment. On the one hand, the cooling effect of the rail joint is better, and on the other hand, the working efficiency of the entire welding production line is higher.

[0058] The specific implementation manner of the present invention is further described below based on specific examples.

[0059] Example 1

[0060] In this embodiment, the mass fraction of carbon in the test rail material is 0.91%, the mass fraction of silicon is 0.46%, the mass fraction of manganese is 0.81%, the tensile strength of the rail is 1200MPa-1300MPa, and the rail head hardness is 405HB-415HB. The high pressure time in the pre-flash stage of continuous flash welding is 45s, and the flash speed is 0.1mm / s; the low pressure time in the flash stage is 80s, and the flash speed is 0.1mm / s; the flash acceleration speed in the accelerated burning stage is 0.5mm / s; the charged upsetting time in the upsetting stage is 0.1s, and the upsetting timing is 1.0s; the rail consumption in the forging stage is 2.0mm, the forging time is 1.5s, and the average speed is 0.60mm / s. After welding, the rail passes through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a specific pressure, the rail welded joint with residual heat from welding is accelerated to cool. The running speed of the rail is 0.2m / s; the total effective quenching length of the residual heat quenching device at the rear end of the welding process is 40m; the length of the independent quenching unit wind box and the air duct is 160mm, the width of the wind box on the top of the rail is 72mm, the internal diameter of the air duct is Φ30mm, the distance between the wind box and the air duct on the side adjacent to the rail surface is 20mm, and a number of air outlets are evenly distributed, the diameter of the air outlet is Φ3mm, and the spacing between the air outlets is 8mm; the pressure value of the compressed air before entering the quenching device is 300kPa. After inspection, the ratio of the hardness of the austenitized zone of the rail joint to the hardness of the rail base material in this embodiment is 0.95, which effectively ensures the smoothness of the joint, and the technical indicators meet the standard requirements. At the same time, the microstructure of the standard inspection part of the joint is pearlite, without abnormal structures such as martensite or bainite. The joint and its performance meet the standard technical requirements.

[0061] Example 2

[0062] In this embodiment, the mass fraction of carbon in the test rail material is 1.18%, the mass fraction of silicon is 0.56%, the mass fraction of manganese is 0.78%, the tensile strength of the rail is 1380MPa-1480MPa, and the rail head hardness is 425HB-450HB. The high pressure time of the pre-flash stage of continuous flash welding is 65s, and the flash speed is 0.6mm / s; the low pressure time of the flash stage is 140s, and the flash speed is 0.6mm / s; the flash acceleration speed of the accelerated burning stage is 2.0mm / s; the charged upsetting time of the upsetting stage is 2.0s, and the upsetting timing is 3.0s; the rail consumption in the forging stage is 4.0mm, the forging time is 3.0s, and the average speed is 2.60mm / s. After welding, the rail passes through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a specific pressure, the rail welded joint with residual heat from welding is accelerated to cool. The running speed of the rail is 2.0m / s; the total effective quenching length of the residual heat quenching device at the rear end of the welding process is 20m; the length of the independent quenching unit wind box and the air duct is 150mm, the width of the wind box on the top of the rail is 70mm, the inner diameter of the air duct is Φ25mm, the distance between the wind box and the air duct on the side adjacent to the rail surface is 30mm, and a number of air outlets are evenly distributed, the diameter of the air outlet is Φ2mm, and the spacing between the air outlets is 10mm; the pressure value of the compressed air before entering the quenching device is 100kPa. After inspection, the ratio of the hardness of the austenitized zone of the rail joint to the hardness of the rail base material in this embodiment is 1.02, which effectively ensures the smoothness of the joint, and the technical indicators meet the standard requirements. At the same time, the microstructure of the standard inspection part of the joint is pearlite, without abnormal structures such as martensite or bainite. The joint and its performance meet the standard technical requirements.

[0063] Example 3

[0064] In this embodiment, the mass fraction of carbon in the test rail material is 1.10%, the mass fraction of silicon is 0.73%, the mass fraction of manganese is 1.10%, the tensile strength of the rail is 1300MPa-1420MPa, and the rail head hardness is 415HB-440HB. The high pressure time in the pre-flash stage of continuous flash welding is 50s, and the flash speed is 0.4mm / s; the low pressure time in the flash stage is 100s, and the flash speed is 0.5mm / s; the flash acceleration speed in the accelerated burning stage is 1.7mm / s; the charged upsetting time in the upsetting stage is 1.2s, and the upsetting timing is 1.1s; the rail consumption in the forging stage is 2.4mm, the forging time is 2.0s, and the average speed is 1.2mm / s. After welding, the rail passes through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a specific pressure, the rail welded joint with residual heat from welding is accelerated to cool. The running speed of the rail is 1.0m / s; the total effective quenching length of the residual heat quenching device at the rear end of the welding process is 35m; the length of the independent quenching unit wind box and the air duct is 155mm, the width of the wind box on the top of the rail is 72mm, the inner diameter of the air duct is Φ25mm, the distance between the wind box and the air duct on the side adjacent to the rail surface is 30mm, and a number of air outlets are evenly distributed, the diameter of the air outlet is Φ2mm, and the spacing between the air outlets is 10mm; the pressure value of the compressed air before entering the quenching device is 200kPa. After inspection, the ratio of the hardness of the austenitized zone of the rail joint to the hardness of the rail base material in this embodiment is 0.98, which effectively ensures the smoothness of the joint, and the technical indicators meet the standard requirements. At the same time, the microstructure of the standard inspection part of the joint is pearlite, without abnormal structures such as martensite or bainite. The joint and its performance meet the standard technical requirements.

[0065] Comparative Example 1

[0066] In this comparative example, the mass fraction of carbon in the test rail material is 1.10%, the mass fraction of silicon is 0.73%, the mass fraction of manganese is 1.10%, the tensile strength of the rail is 1300MPa~1420MPa, and the rail head hardness is 415HB~440HB. The high pressure time in the pre-flash stage of continuous flash welding is 50s, and the flash speed is 0.4mm / s; the low pressure time in the flash stage is 100s, and the flash speed is 0.5mm / s; the flash acceleration speed in the accelerated burning stage is 1.7mm / s; the charged upsetting time in the upsetting stage is 1.2s, and the upsetting timing is 1.1s; the rail consumption in the forging stage is 2.4mm, the forging time is 2.0s, and the average speed is 1.2mm / s. After welding, the rail passes through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a specific pressure, the rail welded joint with residual heat from welding is accelerated to cool. The running speed of the rail is 3.0m / s; the total effective quenching length of the residual heat quenching device at the rear end of the welding process is 8m; the length of the independent quenching unit wind box and the air duct is 150mm, the width of the rail top wind box is 70mm, the internal diameter of the air duct is Φ25mm, the distance between the wind box and the air duct on the side adjacent to the rail surface is 30mm, and a number of air outlets are evenly distributed, the diameter of the air outlet is Φ2mm, and the spacing between the air outlets is 20mm; the pressure value of the compressed air before entering the quenching device is 40kPa. After inspection, the ratio of the hardness of the re-austenitizing zone of the rail joint to the hardness of the rail parent material in this comparative example is 0.75, which cannot meet the standard requirements. The main difference between this comparative example and Example 3 lies in the post-weld quenching device and the quenching method. After welding is completed, the rail passes through the quenching device at a running speed exceeding the claims of this patent, and the quenching device is short in length and the compressed air pressure is low, resulting in the rail joint cooling speed being too slow, and the hardness of the joint re-austenitizing zone cannot be improved. That is, when the rail material and welding method are the same, the comparative method cannot achieve the expected effect.

[0067] Comparative Example 2

[0068] In this comparative example, the mass fraction of carbon in the test rail material is 1.10%, the mass fraction of silicon is 0.73%, the mass fraction of manganese is 1.10%, the tensile strength of the rail is 1300MPa~1420MPa, and the rail head hardness is 415HB~440HB. The high pressure time in the pre-flash stage of continuous flash welding is 50s, and the flash speed is 0.4mm / s; the low pressure time in the flash stage is 100s, and the flash speed is 0.5mm / s; the flash acceleration speed in the accelerated burning stage is 1.7mm / s; the charged upsetting time in the upsetting stage is 1.2s, and the upsetting timing is 1.1s; the rail consumption in the forging stage is 2.4mm, the forging time is 2.0s, and the average speed is 1.2mm / s. After welding, the rail passes through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a specific pressure, the rail welded joint with residual heat from welding is accelerated to cool. The running speed of the rail is 1.0m / s; the total effective quenching length of the residual heat quenching device at the rear end of the welding process is 60m; the length of the independent quenching unit wind box and the air duct is 150mm, the width of the wind box on the top of the rail is 70mm, the inner diameter of the air duct is Φ30mm, the distance between the wind box and the air duct on the side adjacent to the rail surface is 30mm, and a number of air outlets are evenly distributed, the diameter of the air outlet is Φ2mm, and the distance between the air outlets is 15mm; the pressure value of the compressed air before entering the quenching device is 350kPa. After inspection, the ratio of the hardness of the re-austenitized zone of the rail joint to the hardness of the rail base material in this comparative example is 1.3, the local hardness of the joint is too high, the smoothness of the joint cannot be guaranteed, and the technical indicators do not meet the standard requirements. At the same time, abnormal martensitic structure was detected in the standard inspection part of the joint. The main difference between this comparative example and Example 3 lies in the post-weld quenching device and quenching method. After welding, the rail passes through the quenching device at a certain speed. The quenching device is long and the compressed air pressure is high, which causes the rail joint to cool too fast, causing the hardness of the joint austenitization zone to increase beyond the standard requirement range, and the microstructure is also abnormal. That is, under the same rail material and welding method, the comparative method cannot achieve the expected effect.

[0069] Comparative Example 3

[0070] In this comparative example, the mass fraction of carbon in the test rail material is 1.10%, the mass fraction of silicon is 0.73%, the mass fraction of manganese is 1.10%, the tensile strength of the rail is 1300MPa~1420MPa, and the rail head hardness is 415HB~440HB. The high pressure time in the pre-flash stage of continuous flash welding is 70s, and the flash speed is 0.1mm / s; the low pressure time in the flash stage is 160s, and the flash speed is 0.1mm / s; the flash acceleration speed in the accelerated burning stage is 0.5mm / s; the charged upsetting time in the upsetting stage is 0.1s, and the upsetting timing is 1.0s; the rail consumption in the forging stage is 1.0mm, the forging time is 1.2s, and the average speed is 0.40mm / s. After welding, the rail passes through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a specific pressure, the rail welded joint with welding residual heat is accelerated to cool. The running speed of the rail is 1.0m / s; the total effective quenching length of the residual heat quenching device at the rear end of the welding process is 35m; the length of the independent quenching unit wind box and the air duct is 155mm, the width of the wind box on the top of the rail is 72mm, the inner diameter of the air duct is Φ25mm, the distance between the wind box and the air duct on the side adjacent to the rail surface is 30mm, and a number of air outlets are evenly distributed, the diameter of the air outlet is Φ2mm, and the spacing between the air outlets is 10mm; the pressure value of the compressed air before entering the quenching device is 200kPa. After inspection, the ratio of the hardness of the austenitized zone of the rail joint to the hardness of the rail base material in this comparative example is 1.25, the local hardness of the joint is too high, the smoothness of the joint cannot be guaranteed, and the technical indicators do not meet the standard requirements. At the same time, abnormal martensitic structure was detected in the standard inspection part of the joint. The main difference between this comparative example and Example 3 lies in the welding method. The comparative example adopts a higher high pressure time and low pressure time than the claims of this patent, resulting in a large welding heat input; adopts a lower flash speed at each stage than the claims of this patent, resulting in a reduced rail consumption and less heat loss; adopts a lower top forging and forging rail consumption than the claims of this patent, resulting in a reduced rail consumption and less heat loss. In the subsequent air quenching process, the cooling rate is too fast, and the ratio of the hardness of the joint re-austenitization zone to the hardness of the rail base material does not meet the standard technical requirements. In the case of the same rail material, the comparative example method cannot achieve the expected effect.

[0071] Comparative Example 4

[0072] In this comparative example, the mass fraction of carbon in the test rail material is 1.10%, the mass fraction of silicon is 0.73%, the mass fraction of manganese is 1.10%, the tensile strength of the rail is 1300MPa~1420MPa, and the rail head hardness is 415HB~440HB. The high pressure time of the pre-flash stage of continuous flash welding is 40s, and the flash speed is 0.8mm / s; the low pressure time of the flash stage is 50s, and the flash speed is 1.0mm / s; the flash acceleration speed of the accelerated burning stage is 2.1mm / s; the charged upsetting time of the upsetting stage is 0.1s, and the upsetting timing is 1.0s; the rail consumption in the forging stage is 5.0mm, the forging time is 1.0s, and the average speed is 0.60mm / s. After welding, the rail passes through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a specific pressure, the rail welded joint with residual heat from welding is accelerated to cool. The running speed of the rail is 1.0m / s; the total effective quenching length of the residual heat quenching device at the rear end of the welding process is 35m; the length of the independent quenching unit wind box and the air duct is 155mm, the width of the wind box on the top of the rail is 72mm, the inner diameter of the air duct is Φ25mm, the distance between the wind box and the air duct on the side adjacent to the rail surface is 30mm, and there are several air outlets evenly distributed, the diameter of the air outlet is Φ2mm, and the distance between the air outlets is 10mm; the pressure value of the compressed air before entering the quenching device is 200kPa. After inspection, the ratio of the hardness of the re-austenitized zone of the rail joint to the hardness of the rail base material in this comparative example is 0.78, which effectively ensures the smoothness of the joint, and the technical indicators meet the standard requirements. At the same time, the microstructure of the standard inspection part in the joint is pearlite, without abnormal structures such as martensite or bainite. The comparative example adopts a lower high pressure time and low pressure time than the claims of this patent, resulting in a small welding heat input; adopts a higher flash speed at each stage than the claims of this patent, resulting in an increased rail consumption and a large heat loss; adopts a higher top forging and forging rail consumption than the claims of this patent, resulting in an increased rail consumption and a large heat loss. In the subsequent air quenching process, the cooling rate is too slow, and the ratio of the hardness of the joint re-austenitization zone to the hardness of the rail base material does not meet the standard technical requirements. In the case of the same rail material, the comparative example method cannot achieve the expected effect.

[0073] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope disclosed in the embodiments of the present invention as defined in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0074] It should be understood that, as used herein, the singular forms "a", "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" refers to any and all possible combinations including one or more of the associated listed items.

[0075] The serial numbers of the embodiments disclosed in the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0076] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A method for improving the hardness of the reaustenitized zone of a hypereutectoid rail joint, characterized in that: include: (1) Perform front-end processing on the hypereutectoid rail joint; (2) Flash welding the hypereutectoid rail joints, including pre-flash, flash, accelerated burning, top forging and forging stages; (3) performing circumferential quenching treatment on the hypereutectoid rail joint having residual heat after welding, wherein the circumferential quenching treatment comprises uniformly spraying compressed air on the top of the rail head, the side of the rail head and the lower jaw of the rail head to accelerate cooling; (4) Performing back-end processing on the hypereutectoid rail joints; Wherein, each processing step is connected by a conveying roller to form a production line, the hypereutectoid rail joint is driven by the conveying roller to enter each processing step in sequence, the quenching length during the circumferential quenching treatment is 10-50m, and the conveying speed of the conveying roller is set to 0.2m / s-2.5m / s; The welding process of step (2) includes: The high-voltage time of the pre-flash stage is 45s to 65s, and the flash speed is 0.1mm / s to 0.6mm / s; The low pressure time of the flashing stage is 80s to 140s, and the flashing speed is 0.1mm / s to 0.6mm / s; The flash acceleration speed in the accelerated burning stage is 0.5 mm / s to 2.0 mm / s; The charged upsetting time in the upsetting stage is 0.1s to 2.0s, and the upsetting timing is 1.0s to 3.0s; The rail consumption in the forging stage is 2.0 mm to 4.0 mm, the forging time is 1.5 s to 3.0 s, and the average speed is 0.60 mm / s to 2.60 mm / s; In step (3), the compressed air having a pressure value of 50 kPa to 300 kPa is uniformly sprayed on the top of the rail head, the side of the rail head and the lower jaw of the rail head; The main chemical components of hypereutectoid rails include: The mass fraction of carbon is between 0.90% and 1.20%, the mass fraction of silicon is between 0.10% and 1.00%, the mass fraction of manganese is between 0.60% and 1.50%, the mass fractions of phosphorus and sulfur do not exceed 0.020%, the mass fraction of chromium does not exceed 0.3%, and the mass fraction of vanadium does not exceed 0.01%.

2. The method for improving the hardness of the re-austenitized zone of a hypereutectoid rail joint according to claim 1, characterized in that: The minimum tensile strength of the hypereutectoid rail is 1200 MPa, and the minimum hardness of the hypereutectoid rail head is 400 HB.

3. A device for increasing the hardness of the re-austenitized zone of a hypereutectoid rail joint as used in the method according to any one of the preceding claims, the device being used for circumferential quenching treatment, characterized in that: include: Conveyor rollers; A plurality of quenching units are arranged in sequence along the conveying roller direction, each of the quenching units comprises a rail head wind box, a first wind duct symmetrically distributed on the side of the rail head, and a second wind duct symmetrically distributed on the lower jaw of the rail head, the wind box and the wind duct have the same longitudinal length and the same distance from the surface of the adjacent rail, and a plurality of air outlets are evenly distributed on the wind box and the wind duct to spray compressed air to the rail joint; The total length of the quenching device composed of the multiple quenching units is 10m~50m, the width of the wind box is ≥70mm, the length of the wind box and the wind duct is ≥150mm, the diameter of the wind duct is Φ25mm~Φ30mm, the distance between the wind box and the wind duct and the adjacent rail surface is 20mm~40mm, the diameter of the air outlet is Φ1mm~Φ3mm, and the spacing between the air outlets is 5mm~15mm; Each of the quenching units includes a rail head air box, two of the first air ducts symmetrically distributed on the side of the rail head, and two of the second air ducts symmetrically distributed on the lower jaw of the rail head. Each of the quenching units independently controls the compressed air pressure value.

4. The device for improving the hardness of the re-austenitization zone of a hypereutectoid rail joint according to claim 3, characterized in that: The pressure value of the compressed air before entering the quenching device is 50 kPa to 300 kPa.

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