Post weld heat treatment device

Abstract

Provided is a post weld heat treatment apparatus for performing heat treatment on a welded rail, the post-heat treatment apparatus comprising: an induction heating coil that covers the entire periphery of the rail; and a magnetic body that is disposed so as to cover the inner surface of the induction heating coil at a portion of the rail corresponding to a heating suppression location where heating is required to be suppressed.

Description

TITLE OF INVENTION: POST WELD HEAT TREATMENT DEVICE TECHNICAL FIELD

[0001] The present invention relates to a post weld heat treatment device for welded rail. BACKGROUND ART

[0002] It is known to perform post weld heat treatment after welding joints of rails for the purpose of, for example, reducing residual stress in the rails.

[0003] As a document describing the post weld heat treatment as mentioned above, for example, Patent Literature 1 is known. Patent Literature 1 describes a post weld heat treatment device that is arranged at a distance of 20 mm or more and 300 mm or less from the welding center of a rail in the longitudinal direction and includes an induction heating coil heating at least the column portion of the rail.

[0004] Further, as a related technique, for example, Patent Literature 2 is known. Patent Literature 2 describes a post weld heat treatment device that detects and reheats the weld joint of rails connected by welding and removes residual stress in the weld joint. CITATION LIST PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Publication JP 5477452 Patent Literature 2: WO 2018 / 020872 SUMMARY OF INVENTION TECHNICAL PROBLEM

[0006] However, even when employing the techniques disclosed in Patent Literature 1 and Patent Literature 2, it has been difficult to obtain rails that satisfy properties such as wear resistance and fracture resistance.

[0007] Accordingly, the present invention aims to solve the task of obtaining rails that satisfy various required properties such as the aforementioned wear resistance and fracture resistance. SOLUTION TO PROBLEM

[0008] In conceiving the abovementioned task, the present inventors discovered that by distributing necessary properties to each part of a rail, it is possible to manufacture rails that maintain high levels of properties such as wear resistance and fracture resistance. Specifically, for example, wear resistance or the like is imparted to a head portion. Moreover, fracture resistance or the like is imparted to a column part. Moreover, fracture resistance or the like is imparted to a foot portion. For example, by imparting at least some of the aforementioned properties to each part, it becomes possible to enable a rail that has more suitable properties.

[0009] However, it is difficult to impart the properties as mentioned above to each part using a known technique. Accordingly, as a result of investigations, the present inventors and the like have discovered that applying appropriate heating on each part by the following configuration enables the imparting of suitable properties to each part.

[0010] To be specific, a post weld heat treatment device as an aspect of the present invention is a post weld heat treatment device performing heat treatment on a welded rail, and includes: an induction heating coil that covers an entire periphery of the rail; and a magnetic body arranged in such a manner as to cover an inner surface of the induction heating coil at a portion corresponding to a heating suppressing location of the rail, where heating suppression is required. ADVANTAGEOUS EFFECTS OF INVENTION

[0011] With the configurations as described above, the present invention can enable appropriate heating on a rail after welding and appropriate imparting required properties to the rail. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] [Fig. 1] Fig. 1 is a diagram showing an example of a configuration of a post weld heat treatment device in a first example embodiment of the present disclosure. [Fig. 2] Fig. 2 is a diagram for describing an example of parts constituting a rail. [Fig. 3] Fig. 3 is a diagram for describing an example of a head part. [Fig. 4] Fig. 4 is a diagram for describing an example of a distance. [Fig. 5] Fig. 5 is a diagram showing an example of a configuration of a post weld heat treatment device. [Fig. 6] Fig. 6 is a diagram showing an experimental example and a comparative example. [Fig. 7] Fig. 7 is a diagram showing an example of a graph summarizing the experimental example shown in Fig. 6 and so forth. [Fig. 8] Fig. 8 is a diagram showing an experimental example and a comparative example. [Fig. 9] Fig. 9 is a diagram showing an example of a graph summarizing the experimental example shown in Fig. 8 and so forth. [Fig. 10] Fig. 10 is a diagram showing an experimental example. [Fig. 11] Fig. 11 is a diagram showing a comparative example. DESCRIPTION OF EXAMPLE EMBODIMENTS

[0013] <First Example Embodiment> In a first example embodiment of the present invention, as illustrated in Fig. 1, a post weld heat treatment device 100 will be described that performs heat treatment on a welded rail 200 and thereby reduces residual stress present in a weld joint of the rail 200 and the periphery of the weld joint. As illustrated in Fig. 1, the post weld heat treatment device 100 has an induction heating coil 110 that covers the entire periphery of the rail 200. Moreover, a magnetic body for flux shielding and a magnetic body for flux concentration are arranged at predetermined locations of the induction heating coil 110.

[0014] As illustrated in Fig. 2, the rail 200 is composed of a head part 210 positioned upward and in contact with a wheel and the like when the rail 200 is installed, a foot part positioned downward and in contact with a rail tie and the like, and a column part 220 connecting the head part 210 and the foot part. Moreover, the foot part is composed of a sole part 230, a toe part 240, and a toe part 250. Moreover, as illustrated in Fig. 3, the head part 210 can be further divided into a head top part 211 that is positioned uppermost and is a flat portion, head side parts 212 and 213 positioned on the side faces, and corner parts 214 and 215 connecting the head top part 211 with the head side parts 212 and 213.

[0015] In conceiving the abovementioned task, the present inventors discovered that imparting necessary properties to the respective parts of the rail 200 in a distributed manner makes it possible to manufacture the rail 200 that has high levels of properties such as wear resistance and fracture resistance. To be specific, for example, wear resistance and so forth are imparted to the head part 210. Moreover, fracture resistance and so forth are imparted to the column part 220. Moreover, fracture resistance and so forth are imparted to the foot part including the sole part 230 and the toe parts 240 and 250. For example, by imparting at least some of the properties as described above to the respective parts, it is possible to enable the rail 200 having more appropriate properties.

[0016] Further, as a result of examination, the present inventors discovered that heating under conditions suitable for the respective parts makes it possible to impart appropriate properties to the respective parts as described above. To be specific, for example, in order to impart fracture resistance to the column part 220, it is required to secure an effect of reducing residual stress and prevent excessive softening. Therefore, at the time of heating, it is desirable to heat to around 600 to 700 °C. Moreover, in order to secure the effect of reducing residual stress at the minimum and also secure wear resistance for the head part 210, it is desirable to heat around 250 to 600 °C. Moreover, for the foot part including the sole part 230 and the toe parts 240 and 250, in order to impart residual stress and inhibit plastic deformation due to load from a wheel, it is necessary to prevent decrease in fracture resistance while securing the residual stress reduction effect at the minimum. Therefore, at the time of heating, it is desirable to heat around 250 to 650 °C. For example, as described above, heating at temperatures suitable for the respective parts makes it possible to impart appropriate properties to the respective parts. In addition, according to the conditions described above, it can be seen that heating the head part 210 and the foot part is preferably inhibited more than heating the column part 220. In other words, at the time of heating the column part 220 up to a target temperature of 600 to 700 °C, it is desirable that the head part 210 and the foot part are not excessively heated. Accordingly, from the perspective of the required properties, it can be concluded that, in the rail 200, the column part 220 is a heating requiring location, whereas the head part 210 and the foot part are heating suppressing locations.

[0017] Hereinafter, an example of a configuration of the post weld heat treatment device 100 having a configuration for enabling the abovementioned heating condition will be described in more detail. In the following description, as illustrated in Fig. 4, a distance h, which is the shortest distance between the corner part 214 of the head part 210 and the induction heating coil 110, is employed as a representative of the distance between the head part 210 and the induction heating coil 110. Further, a distance f, which is the shortest distance between the toe part 240 and the induction heating coil 110, is employed as a representative of the distance between the foot part and the induction heating coil 110. As a result of an experiment by the present inventors, it was found that when heating is performed using an existing coil without using a magnetic body, the corner parts 214 and 215 of the head part 210 and the toe parts 240 and 250 are most likely to be heated. Then, in order to more properly control the heating state, the distance h and the distance f are used as a representative of the distance between the head part 210 and the induction heating coil 110 and a representative of the distance between the foot part and the induction heating coil 110. Further, a distance n, which is the shortest distance between the most constricted location of the column part 220 and the induction heating coil 110, is employed as a representative of the distance between the column part 220 and the induction heating coil 110. It should be noted that, according to the experiment by the present inventors, it was confirmed that in a case where a magnetic body for flux shielding is not used, even if the distance between the foot part and the coil, such as the distance f, is equal to or more than two times the distance in the existing post weld heat treatment device 100, it is difficult to keep the temperature of the toe parts 240 and 250 at a temperature corresponding to the necessary property when the column part 220 is heated to the necessary temperature. In addition, the abovementioned distances are examples, and distances may be determined at locations other than those illustrated above.

[0018] Fig. 1 is a front view showing an example of a configuration of the post weld heat treatment device 100. As shown in Fig. 1, the post weld heat treatment device 100 has the induction heating coil 110 that covers the entire periphery of the rail 200. Moreover, as shown in Fig. 1, first magnetic bodies 120 and 130, which are magnetic bodies for flux shielding, are arranged at predetermined locations facing the head part 210 that is the heating suppressing location of the induction heating coil 110. For example, in the case illustrated in Fig. 1, the first magnetic body 120 is arranged at a location facing the corner part 214 of the head part 210, and the first magnetic body 130 is arranged at a location facing the corner part 215. Further, second magnetic bodies 140 and 150, which are magnetic bodies for flux shielding, are arranged at predetermined locations facing the foot part that is the heating suppressing location of the induction heating coil 110. For example, in the case illustrated in Fig. 1, the second magnetic body 140 is arranged at a location facing the toe part 240 of the foot part, and the second magnetic body 150 is arranged at a location facing the toe part 250. Further, third magnetic bodies 160 and 170, which are magnetic bodies for flux concentration, are arranged at predetermined locations facing the column part 220 that is a location that needs to be heated of the induction heating coil 110.

[0019] Further, Fig. 5 shows an example of the post weld heat treatment device 100 viewed from the side direction. Referring to Fig. 5, the post weld heat treatment device 100 has, for example, one for each, the induction heating coil 110 having the configuration as described above, located to sandwich the weld joint of the rail. In other words, the post weld heat treatment device 100 described in this example embodiment has one induction heating coil 110 on each side of the rail weld joint. For example, in the case illustrated in Fig. 5, the post weld heat treatment device 100 has one induction heating coil 110-1 located on the left side of the rail weld joint, and one induction heating coil 110-2 located on the right side of the rail weld joint. For example, the induction heating coil 110-1 is arranged in such a manner that the distance between the center of the rail weld joint and the induction heating coil 110-1 is 50 mm, and the induction heating coil 110-2 is arranged in such a manner that the distance between the center of the rail weld joint and the induction heating coil 110-2 is 50 mm. In addition, the post weld heat treatment device 100 may have a plurality of induction heating coils 110 so as to sandwich the weld joint of the rail. Moreover, the distance between the center of the rail weld joint and the induction heating coil 110-1, the induction heating coil 110-2 and so forth may be other than that illustrated above.

[0020] In addition, the induction heating coil 110-1 and the induction heating coil 1102 are arranged in such a manner that, for example, the flowing currents are oppositely directed. The induction heating coil 110-1 and the induction heating coil 110-2 may be arranged in such a manner that the flowing currents are in the same direction. The respective components will be described in more detail below.

[0021] The induction heating coil 110 is a coil heating the rail 200. For example, the induction heating coil 110 is connected to a high-frequency power supply or the like that supplies high-frequency current, and heats the rail 200 by receiving supply of high-frequency current from the high-frequency power supply or the like. For example, the induction heating coil 110 can be supplied with electric current having a frequency ranging from 1 kHz to 20 kHz from the high-frequency power supply or the like. The electric current flowing through the induction heating coil 110 may be other than the example illustrated above.

[0022] As described above, the induction heating coil 110 covers the entire periphery of the rail 200 when viewed from the front. For example, the induction heating coil 110 can be divided into two or more coil members as shown in Patent Literature 2, and it is possible to cover the entire periphery of the rail 200 by joining the divided coil members. The induction heating coil 110 may cover the entire periphery of the rail 200 by a method other than that illustrated above.

[0023] Further, the induction heating coil 110 can cover the entire periphery of the rail 200 in such a manner that the relation between the distance between the column part 220 and the induction heating coil 110 and the distance between the head part 210 and the induction heating coil 110 is within a predetermined range. To be specific, the induction heating coil 110 can cover the entire periphery of the rail 200 in such a manner that the value of (distance n) / (distance h) is 0.2 or more and 1.5 or less. As will be described later, it is possible by adjusting the distance n and the distance h in such a manner as to achieve the abovementioned value to heat each part in a more desirable state. That is to say, by adjusting to the above range, it is possible to heat more appropriately in accordance with the property of each part.

[0024] Further, as a result of an experiment conducted by the present inventors, it was confirmed that heating can be performed more efficiently as the distance between the induction heating coil 110 and the rail 200 is shorter. Therefore, by covering the entire periphery of the rail 200 in such a manner that the distance between the column part 220 and the induction heating coil 110 is shorter than the distance between the head part 210 and the induction heating coil 110, it is possible to achieve more efficient heating of the column part 220. To be specific, from the viewpoint of more efficient heating of the column part 220, it can also be said that it is more desirable for the value of (distance n) / (distance h) to be 0.2 or more and less than 1.

[0025] Further, the induction heating coil 110 can cover the entire periphery of the rail 200 in such a manner that the relation between the distance between the column part 220 and the induction heating coil 110 and the distance between the foot part and the induction heating coil 110 is within a predetermined range. To be specific, the induction heating coil 110 can cover the entire periphery of the rail 200 in such a manner that the value of (distance n) / (distance f) ranges from 0.2 to 2.0. As will be described later, it is possible by adjusting the distance n and the distance f to achieve the abovementioned value to heat each part in a more desirable state. That is to say, by adjusting to the above range, it is possible to heat more appropriately in accordance with the property of each part.

[0026] Further, as in the case of the head part 210 described above, by covering the entire periphery of the rail 200 in such a manner that the distance between the column part 220 and the induction heating coil 110 is shorter than the distance between the foot part and the induction heating coil 110, it is possible to achieve more efficient heating of the column part 220. To be specific, from the viewpoint of more efficient heating of the column part 220, it can also be said that it is more desirable for the value of (distance n) / (distance f) to be 0.2 or more and less than 1.

[0027] As illustrated in Fig. 1, in this example embodiment, the induction heating coil 110 does not cover the rail 200 in a shape similar to the shape of the rail 200, but covers the head part 210, the column part 220 and the foot part of the rail 200 in a substantially rectangular shape, respectively. That is to say, the induction heating coil 110 has a shape combining polygonal forms corresponding to the head part 210, the column part 220 and the foot part, respectively. In other words, the induction heating coil 110 has a shape in which a rectangular shape corresponding to the head part 210 and a rectangular shape corresponding to the foot part are connected by a linear shape corresponding to the column part 220. By covering the rail 200 in this manner, it is possible to further ensure the distances between the induction heating coil 110 and portions corresponding to R parts of the rail 200, such as the corner parts 214 and 215 and the toe parts 240 and 250. However, the induction heating coil 110 may cover the rail 200 in a shape similar to the shape of the rail 200.

[0028] Further, in the case illustrated in Fig. 1, the induction heating coil 110 covers the rail 200 in such a manner that, of a portion covering the head part 210 of the rail 200, a portion located below the head part 210 becomes more proximity to the head part 210 as it becomes more proximity to the column part 220. That is to say, the shape of the portion below the head part 210 of the rectangular shape corresponding to the head part 210 is an inverted V-shape when seen from the front. By thus forming the induction heating coil 110 below the head part 210 in an inverted V-shape, it is possible to separate the induction heating coil 110 from the head side parts 212 and 213, the corner parts 214 and 215 and so forth as much as possible while bringing the induction heating coil 110 closer to the column part 220 as much as possible. Further, in the case illustrated in Fig. 1, the induction heating coil 110 is formed in such a manner that a portion facing the sole part 230 is protruded toward the rail 200 below the foot part. Likewise, according to the shape described above, it is possible to separate the induction heating coil 110 from the toe parts 240 and 250 while bringing the induction heating coil 110 closer to the sole part 230.

[0029] The first magnetic bodies 120 and 130 are magnetic bodies for flux shielding, installed at predetermined locations facing the head part 210. For example, the first magnetic bodies 120 and 130 are arranged at predetermined locations facing the corner parts 214 and 215 of the head part 210. For example, the first magnetic bodies 120 and 130 are poly-iron cores, silicon metal plates or the like. The first magnetic bodies 120 and 130 may be other known magnetic bodies.

[0030] In this example embodiment, the first magnetic bodies 120 and 130 are arranged at predetermined locations of the induction heating coil 110 in such a manner as to cover the inner surface of the induction heating coil 110. According to such arrangement, the first magnetic bodies 120 and 130 shield magnetic flux at arrangement locations, thereby suppressing overheating of the rail 200 at the locations. In other words, the first magnetic bodies 120 and 130 are arranged at predetermined locations of the induction heating coil 110 in such a manner as to cover at least the inner periphery facing the rail 200.

[0031] It is desirable that the first magnetic bodies 120 and 130 are arranged on the induction heating coil 110 in such a manner as to satisfy a predetermined inner surface coverage rate of the entire inner surface of the induction heating coil 110 facing the head part 210. To be specific, it is desirable that the first magnetic body 120 is arranged on the inner surface of the induction heating coil 110 in such a manner that a coverage rate C2, which is the rate of a portion covered by the first magnetic body 120 to the entire portion facing the corner part 214 of the induction heating coil 110, is more than 0% and equal to or less than 65%. By arrangement at such a rate, the first magnetic body 120 can suppress heating of the head part 210 more appropriately. Further, it is more preferable that the first magnetic body 120 is arranged on the inner surface of the induction heating coil 110 in such a manner that the coverage rate C2 is more than 0% and equal to or less than 30%. By arrangement at such a rate, the first magnetic body 120 can suppress heating of the head part 210 further appropriately.

[0032] Likewise, it is desirable that the first magnetic body 130 is arranged on the inner surface of the induction heating coil 110 in such a manner that the coverage rate C2 that is the rate of a portion covered by the first magnetic body 130 to the entire portion facing the corner part 215 of the induction heating coil 110 is more than 0% and equal to or less than 65%. By arrangement at such a rate, the first magnetic body 130 can suppress heating of the head part 210 more appropriately. Further, it is more preferable that it is arranged on the inner surface of the induction heating coil 110 in such a manner that the coverage rate C2 is more than 0% and equal to or less than 30%. By arrangement at such a rate, the first magnetic body 130 can suppress heating of the head part 210 still more appropriately.

[0033] As long as the arrangement rate is satisfied, the arrangement places of the first magnetic bodies 120 and 130 may be other than those illustrated in Fig. 1. For example, the arrangement places of the first magnetic bodies 120 and 130 may be shifted upward or downward relative to the centers of the corner parts 214 and 215 illustrated in Fig. 1, and may cover the head top part 211 and the head side parts 212 and 213.

[0034] The second magnetic bodies 140 and 150 are magnetic bodies for flux shielding, installed at predetermined locations facing the foot part. For example, the second magnetic bodies 140 and 150 are installed at predetermined locations facing the toe parts 240 and 250 of the foot part. For example, as well as the first magnetic bodies 120 and 130, the second magnetic bodies 140 and 150 are poly-iron cores, silicon metal plates or the like. The second magnetic bodies 140 and 150 may be other known magnetic bodies.

[0035] In this example embodiment, in the same manner as the first magnetic bodies 120 and 130, the second magnetic bodies 140 and 150 are arranged at predetermined locations of the induction heating coil 110 in such a manner as to cover the inner surface of the induction heating coil 110. According to such arrangement, the second magnetic bodies 140 and 150 shield magnetic flux at the arrangement locations, thereby suppressing overheating of the rail 200 at the locations. In other words, the second magnetic bodies 140 and 150 are arranged at predetermined locations of the induction heating coil 110 in such a manner as to cover at least the inner circumferential surface facing the rail 200.

[0036] Similarly to the first magnetic bodies 120 and 130, it is desirable that the second magnetic bodies 140 and 150 are arranged on the induction heating coil 110 in such a manner as to satisfy a predetermined inner surface coverage rate of the entire inner surface of the induction heating coil 110 facing the foot part. To be specific, it is desirable that the second magnetic body 140 is arranged on the inner surface of the induction heating coil 110 in such a manner that a coverage rate C1, which is the rate of a portion covered by the second magnetic body 140 to the entire portion facing the toe part 240 of the induction heating coil 110, is 5% or more and equal to or less than 95%. By arrangement at such a rate, the second magnetic body 140 can suppress heating of the toe part 240 more appropriately. Further, more preferably, it is desirable that it is arranged on the inner surface of the induction heating coil 110 in such a manner that the coverage rate C1 is 8% or more and 60% or less, and it is more desirable that it is arranged on the inner surface of the induction heating coil 110 in such a manner that the coverage rate C1 is 10% or more and 30% or less. By arrangement at the above rate, the second magnetic body 140 can suppress heating of the toe part 240 still further appropriately.

[0037] Likewise, it is desirable that the second magnetic body 150 is arranged on the inner surface of the induction heating coil 110 in such a manner that the coverage rate C1 that is the rate of a portion covered by the second magnetic body 150 to the entire portion facing the toe part 250 of the induction heating coil 110 is 5% or more and less than 95%. By arrangement at such a rate, the second magnetic body 150 can suppress heating of the toe part 250 more appropriately. More preferably, it is desirable that it is arranged on the inner surface of the induction heating coil 110 in such a manner that the coverage rate C1 is 8% or more and less than 60%, and it is more desirable that it is arranged on the inner surface of the induction heating coil 110 in such a manner that the coverage rate C1 is 10% or more and less than 30%. By arrangement at the above rate, the second magnetic body 150 can suppress heating of the toe part 250 still more appropriately.

[0038] As long as the arrangement rate is satisfied, the arrangement places of the second magnetic bodies 140 and 150 may be other than those illustrated in Fig. 1. For example, the arrangement places of the second magnetic bodies 140 and 150 may be upward or downward of the toe parts 240 and 250.

[0039] The third magnetic bodies 160 and 170 are magnetic bodies for flux concentration, installed at predetermined locations facing the column part 220. For example, in the same manner as the first magnetic bodies 120 and 130 and the second magnetic bodies 140 and 150, the third magnetic bodies 160 and 170 are poly-iron cores, silicon metal plates, or the like. The third magnetic bodies 160 and 170 may be other known magnetic bodies.

[0040] In this example embodiment, the third magnetic bodies 160 and 170 are arranged at predetermined locations of the induction heating coil 110 in such a manner as to cover the outer surface of the induction heating coil 110. According to such arrangement, the third magnetic bodies 160 and 170 concentrate magnetic flux at the arrangement locations and heat the rail 200 at the corresponding locations more efficiently. In other words, the third magnetic bodies 160 and 170 are arranged at predetermined locations of the induction heating coil 110 in such a manner as to cover the outer periphery excluding the inner circumference surface facing the rail 200.

[0041] Referring to Fig. 1, the third magnetic bodies 160 and 170 are arranged at one side facing the column part 220 and the other side facing the column part 220 in such a manner as to sandwich the column part 220 of the rail 200. The rate of portions covered by the third magnetic bodies 160 and 170 to the entire portion facing the column part 220 of the induction heating coil 110 may be any rate such as 5% or more and 100% or less.

[0042] For example, the post weld heat treatment device 100 has the configuration as described above. The configuration of the post weld heat treatment device 100 may be other than that illustrated above. For example, the post weld heat treatment device 100 may have either the first magnetic body 120 and 130 or the second magnetic body 140 and 150. Further, the post weld heat treatment device 100 may have only one of the first magnetic bodies 120 and 130, and may have only one of the second magnetic bodies 140 and 150. Moreover, the post weld heat treatment device 100 may not have the third magnetic bodies160 and 170. Moreover, the post weld heat treatment device 100 may have one of the second magnetic bodies 160 and 170.

[0043] As shown in Fig. 5, the rail 200 is welded in advance to the other rail 200. The rail 200 may be welded to the other rail 200 at only one end, or may be welded to the other rail 200 at both ends. For example, the rail 200 may be welded by any means such as flash butt welding or thermit welding.

[0044] Thus, the post weld heat treatment device 100 has the induction heating coil 110, and also has the magnetic body for flux shielding at a portion corresponding to the heating suppressing location. According to such a configuration, the post weld heat treatment device 100 can suppress heating on the heating suppressing location, while securing heating of the column part 220 that is the heating requiring location of the rail 200. As a result, it is possible to impart appropriate properties to the respective parts, and it is possible to appropriately impart required properties to the rail 200. Further, as described above, the post weld heat treatment device 100 can secure the heating conditions responsive to the required properties more appropriately by adjusting the arrangement rate of each magnetic body to an appropriate range.

[0045] Further, the induction heating coil 110 of the post weld heat treatment device 100 covers the entire periphery of the rail 200 after adjusting the distance between the heating requiring location and the rail 200 and the distance between the heating suppressing location and the rail 200 in accordance with the necessity of heating and so forth. Consequently, it is possible to heat under more appropriate heating conditions, so that it is possible to enable imparting of more appropriate properties.

[0046] Further, the post weld heat treatment device 100 has the magnetic body for flux concentration at a location corresponding to the column part 220 that is the heating requiring location of the rail 200. According to such a configuration, the post weld heat treatment device 100 can heat more appropriately the column part 220 that is the heating requiring location that needs to be heated of the rail 200. [Implementation Example]

[0047] Next, an implementation example of the present invention and a comparative example will be provided to describe the content of the present invention. It should be noted that the content of the present invention is not limited to the implementation example.

[0048] First, the present inventor compared the temperature of each part of the rail after temperature increase acquired with an actual coil actually created, with the temperature of each part of the rail after temperature increase acquired by simulation performed using a general-purpose electromagnetic field analysis software (JMAG® by JSOL Corporation). The simulation was conducted under the following conditions: a current value of 1000 A, a frequency of 18 kHz, a rail magnetic permeability of 1.3^10-4 H / m, a magnetic body magnetic permeability of 5.0X10' H / m, a rail thermal conductivity of 47.2 W / mK, a rail specific heat of 474 J / kgK, and a rail electrical resistivity of 2.1^10-7 Q^m (all physical properties are values at 25°C), and the simulation was conducted so that the temperature at the column part was 600°C or higher and the rate of temperature increase was 2.8°C / sec. As shown in Table 1 below, a comparison was made between actually measured values and simulation at two levels, and it was found that the difference between the heating temperatures of the respective parts of the rail calculated by simulation and the actually measured values were kept within 10% of the actually measured values. As a result, it was found that the rate of temperature increase at each part of the rail caused by the coil can be predicted through simulation. It should be noted that clearances listed in Table 1 below refer to the distances between the respective parts and the coil. [Table 1] Table: Maximum attained temperature of each part of rail by coil / °C position coil 1 actual measurement coil 1 simulation coil 2 actual measurement coil 2 simulation @ head top 215 219 330 318 @ head part corner 226 218 354 334 ® column 629 624 600 605 @ toe 226 249 384 380 coil 1: clearance (Head:15mm. Foot:15mm. Column:10mm (n / f: 0.7. n / h: 0.7) ) coverage rate (Head C2: 43%. Foot Cl: 59%. Column:59% ) coil 2: clearance (Head: 15mm. Foot: 15mm. Column: 10mm (n / f: 0.7. n / h: 0.7) ) coverage rate (Head C2: 0%. Foot C1: 16%. Column:59% )

[0049] Subsequently, using the above simulation, the present inventor examined an appropriate range of each parameter while changing the coverage rate C1, the coverage rate C2, (distance n) / (distance f), and (distance n) / (distance h) described in this example embodiment.

[0050] <Implementation Example 1> First, simulation was conducted by changing a condition for the foot part with a condition for the head part fixed. Thus, a range satisfying both the required properties of the rail column part and the rail foot part was examined. It should be noted that determination criteria for the implementation example and the comparison example are as shown below. When the temperature of the column part is raised to a reference temperature (600 to 700°C): double circle: the temperature of the foot part or the head part is within the reference temperature range, and heating efficiency is optimal; circle: the temperature of the foot part or the head part is within the reference temperature range, and heating efficiency is favorable; triangle: the temperature of the foot part or the head part is close to the upper limit or the lower limit of the reference temperature range, and heating efficiency is low; and cross: the temperature of the foot part or the head part is equal to or more than the upper limit of the reference temperature range, or equal to or less than the lower limit.

[0051] Fig. 6 shows an example of the implementation example and the comparative example. Further, when the implementation example and the comparative example of Fig. 6 are summarized in a graph, it is illustrated as shown in Fig. 7. Referring to Figs. 6 and 7, it can be understood that when the coverage rate C1 is 5% or more and 95% or less and the value of (distance n) / (distance f) is 0.2 or more and 1 or less, it is determined as double circle or circle according to the determination criteria. That is to say, according to the above implementation example and comparative example, it can be seen that the coverage rate C1 is preferably in the range of 5% or more and 95% or less. Further, according to the above implementation example and comparative example, it can be understood that the value of (distance n) / (distance f) of 0.2 or more and 1 or less is a desirable range. Further, although the heating efficiency lowers, for example, in terms of reduced rate of temperature increase, it is understood that if the permissible range does not exceed the allowable heating temperature of the foot part (the range that may be considered permissible under the criteria where a triangular judgment is applied), then the value of (distance n) / (distance f) is also allowable in the range greater than 1 up to and including 2.

[0052] <Implementation Example 2> Subsequently, simulation was performed by changing a condition for the head part. With this, an examination was conducted of a range that satisfies both the required properties of the rail column part and the rail head part. It should be noted that the determination criteria for the implementation example and the comparative example are the same as in the implementation example 1.

[0053] Fig. 8 shows an example of the implementation example and the comparative example. Further, when the implementation example and the comparative example of Fig. 8 are summarized in a graph, it is illustrated in Fig. 9. Referring to Figs. 8 and 9, it can be understood that when the coverage rate C2 is 0% or more and 60% or less and the value of (distance n) / (distance h) is 0.2 or more and 1 or less, it is determined as circle according to the determination criteria. That is to say, according to the above implementation example and comparative example, it can be understood that the coverage rate C2 is preferably 0% or more and 60% or less. Further, according to the above implementation example and comparative example, it can be seen that it is desirable for the value of (distance n) / (distance h) to be 0.2 or more and 1 or less. Thus, it can be understood that it is desirable that a magnetic body is not arranged at the head part or, when a magnetic body is arranged, the coverage rate C2 is 60% or less. Furthermore, although the heating efficiency lowers, such as reduced rate of temperature increase, when including the range that does not exceed the allowable heating temperature of the foot (the range of triangle based on the determination criteria), it is understood that the coverage rate C2 between over 60% and up to 65%, as well as the value of (distance n) / (distance f) exceeding 1 and up to 1.5, are also permissible.

[0054] <Implementation Example 3> Subsequently, an examination was conducted of a range for more desirable heat treatment satisfying all the required properties of the column part, foot part, and head part. It should be noted that the determination criteria for the implementation example and the comparative example are the same as in the implementation example 1. Further, in the implementation example 3, simulation was performed assuming that a magnetic body arranged on the foot part and a magnetic body arranged on the head part do not affect each other, and that the magnitude of the clearance between the foot part and the head part does not affect each other.

[0055] Figs. 10 and 11 show an example of the implementation example and the comparative example. Referring to Figs. 10 and 11, it can be seen that preferable heating is enabled when the abovementioned ranges are satisfied and appropriate heating of each part becomes difficult when the ranges are exceeded.

[0056] <Supplementary Note> The whole or part of the example embodiments disclosed above can be described as the following supplementary notes. The overview of a post weld heat treatment device and so forth according to the present invention will be described below. However, the present invention is not limited to the following configurations.

[0057] (Supplementary Note 1) A post weld heat treatment device that performs heat treatment on a welded rail, the post weld heat treatment device comprising: an induction heating coil that covers an entire periphery of the rail; and a magnetic body arranged in such a manner as to cover an inner surface of the induction heating coil at a portion corresponding to a heating suppressing location of the rail, where heating suppression is required. (Supplementary Note 2) The post weld heat treatment device according to supplementary note 1, wherein: the magnetic body is a first magnetic body arranged at a portion corresponding to a head part that is the heating suppressing location of the rail, where heating suppression is required; and the first magnetic body is arranged on the inner surface of the induction heating coil in such a manner that a coverage rate, which is a rate of a portion covered by the first magnetic body to an entire portion facing the head part of the induction heating coil, is more than 0% and equal to or less than 65%. (Supplementary Note 3) The post weld heat treatment device according to supplementary note 1 or 2, wherein the induction heating coil covers the entire periphery of the rail in such a manner that when a distance between the induction heating coil and a column part of the rail is n and a distance between the induction heating coil and a head part of the rail is h, a value of n / h is 0.2 or more and 1.5 or less. (Supplementary Note 4) The post weld heat treatment device according to any one of supplementary notes 1 to 3, wherein the induction heating coil covers the entire periphery of the rail in such a manner that a distance between the induction heating coil and a column part of the rail is shorter than a distance between the induction heating coil and a head part of the rail. (Supplementary Note 5) The post weld heat treatment device according to any one of supplementary notes 1 to 4, wherein: the magnetic body is a second magnetic body arranged at a portion corresponding to a toe part that is the heating suppressing portion of the rail, where heating suppression is required; and the second magnetic body is arranged on the inner surface of the induction heating coil in such a manner that a coverage rate, which is a rate of a portion covered by the second magnetic body to an entire portion facing the toe part of the induction heating coil, is 5% or more and 95% or less. (Supplementary Note 6) The post weld heat treatment device according to any one of supplementary notes 1 to 5, wherein the induction heating coil covers the entire periphery of the rail in such a manner that when a distance between the induction heating coil and a column part of the rail is n and a distance between the induction heating coil and a toe part of the rail is f, a value of n / f is 0.2 or more and 2.0 or less . (Supplementary Note 7) The post weld heat treatment device according to any one of supplementary notes 1 to 6, wherein the induction heating coil covers the entire periphery of the rail in such a manner that a distance between the induction heating coil and a column part of the rail is shorter than a distance between the induction heating coil and a toe part of the rail. (Supplementary Note 8) The post weld heat treatment device according to any one of supplementary notes 1 to 7, the post weld heat treatment device comprising 2023443064  05 Sep 2025 a third magnetic body arranged in such a manner as to cover an outer surface of the induction heating coil at a portion corresponding to a column part that is a heating requiring portion of the rail, where heating is required.

[0058] Although the present invention has been described above with reference to the above example embodiments, the present invention is not limited to the example embodiments described above. The configuration and details of the present invention can be changed in various manners that can be understood by those skilled in the art within the scope of the present invention.

[0059] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0060] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge in Australia. REFERENCE SIGNS LIST

[0061] 100 post weld heat treatment device 110 induction heating coil 120 first magnetic body 130 first magnetic body 2023443064  05 Sep 2025 140 second magnetic body 150 second magnetic body 160 third magnetic body 170 third magnetic body 200 rail 210 head part 211 head top part 212 head side part 213 head side part 214 corner part 215 corner part 220 column part 230 sole part 240 toe part 250 toe part

Claims

1. A post weld heat treatment device that performs heat treatment on a welded rail, the post weld heat treatment device comprising:an induction heating coil that covers an entire periphery of the rail; anda magnetic body arranged in such a manner as to cover an inner surface of the induction heating coil at a portion corresponding to a heating suppressing location of the rail, where heating suppression is required.

2. The post weld heat treatment device according to claim 1, wherein:the magnetic body is a first magnetic body arranged at a portion corresponding to a head part that is the heating suppressing location of the rail, where heating suppression is required; andthe first magnetic body is arranged on the inner surface of the induction heating coil in such a manner that a coverage rate, which is a rate of a portion covered by the first magnetic body to an entire portion facing the head part of the induction heating coil, is more than 0% and equal to or less than 65%.

3. The post weld heat treatment device according to claim 1 or 2, whereinthe induction heating coil covers the entire periphery of the rail in such a manner that when a distance between the induction heating coil and a column part of the rail is n and a distance between the induction heating coil and a head part of the rail is h, a value of n / h is 0.2 or more and 1.5 or less.

4. The post weld heat treatment device according to any one of claims 1 to 3, whereinthe induction heating coil covers the entire periphery of the rail in such a manner that a distance between the induction heating coil and a column part of the rail is shorter than a distance between the induction heating coil and a head part of the rail.

5. The post weld heat treatment device according to any one of claims 1 to 4, wherein:the magnetic body is a second magnetic body arranged at a portion corresponding to a toe part that is the heating suppressing portion of the rail, where heating suppression is required; andthe second magnetic body is arranged on the inner surface of the induction heating coil in such a manner that a coverage rate, which is a rate of a portion covered by the second magnetic body to an entire portion facing the toe part of the induction heating coil, is 5% or more and 95% or less.

6. The post weld heat treatment device according to any one of claims 1 to 5, whereinthe induction heating coil covers the entire periphery of the rail in such a manner that when a distance between the induction heating coil and a column part of the rail is n and a distance between the induction heating coil and a toe part of the rail is f, a value of n / f is 0.2 or more and 2.0 or less .

7. The post weld heat treatment device according to any one of claims 1 to 6, whereinthe induction heating coil covers the entire periphery of the rail in such a manner that a distance between the induction heating coil and a column part of the rail is shorter than a distance between the induction heating coil and a toe part of the rail.

8. The post weld heat treatment device according to any one of claims 1 to 7, the post weld heat treatment device comprisinga third magnetic body arranged in such a manner as to cover an outer surface of the induction heating coil at a portion corresponding to a column part that is a heating requiring portion of the rail, where heating is required.

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