Post weld heat treatment apparatus

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

Post-heat treatment equipment

[0001] The present invention relates to a post-heat treatment device for welded rails.

[0002] It is known that after welding a rail joint, a post-heat treatment is carried out for the purpose of reducing residual stress present in the rail, for example.

[0003] An example of a document that describes the above-described post-heat treatment is Patent Document 1. Patent Document 1 describes a post-heat treatment device that includes an induction heating coil that is arranged at a distance of 20 mm to 300 mm from the welding center of the rail in the longitudinal direction and heats at least the column portion of the rail.

[0004] Another related technique is, for example, Patent Document 2. Patent Document 2 describes a post-heat treatment device that detects the welded portion of rails joined by welding and reheats it to remove residual stress from the welded portion.

[0005] Patent No. 5477452 International Publication No. 2018 / 020872

[0006] However, using either of the techniques disclosed in Patent Document 1 or Patent Document 2, it was difficult to obtain a rail that satisfied the required characteristics such as wear resistance and breakage resistance.

[0007] Therefore, an object of the present invention is to obtain a rail that satisfies the various required characteristics such as the above-mentioned wear resistance and breakage resistance.

[0008] In considering the above problem, the inventors discovered that it is possible to manufacture rails with high levels of properties such as abrasion resistance and breakage resistance by distributing the required properties to each part of the rail. Specifically, for example, abrasion resistance is imparted to the head portion. Breakage resistance is imparted to the pillar portion. Breakage resistance is imparted to the base portion. For example, by imparting at least some of the properties described above to each part, it is possible to realize rails with more appropriate properties.

[0009] However, it is difficult to impart the above-mentioned characteristics to each part using known techniques. As a result of investigation, the inventors discovered that it is possible to impart appropriate characteristics to each part by appropriately heating each part using the following configuration.

[0010] Specifically, a post-heat treatment device according to one embodiment of the present invention is a post-heat treatment device that performs heat treatment on a welded rail, and is configured to include an induction heating coil that covers the entire circumference of the rail, and a magnetic body that is arranged to cover the inner surface of the induction heating coil in a portion of the rail that corresponds to a heat suppression location where heating needs to be suppressed.

[0011] By being configured as described above, the present invention can appropriately heat the rail after welding, and appropriately impart the required properties to the rail.

[0012] FIG. 1 is a diagram illustrating a configuration example of a post-heat treatment device in a first embodiment of the present disclosure; FIG. 2 is a diagram illustrating an example of a portion constituting a rail; FIG. 3 is a diagram illustrating an example of a head; FIG. 4 is a diagram illustrating an example of a distance; FIG. 5 is a diagram illustrating an example of a configuration of a post-heat treatment device; FIG. 6 is a diagram illustrating an example of a graph summarizing the experimental example shown in FIG. 6; FIG. 7 is a diagram illustrating an example of a graph summarizing the experimental example shown in FIG. 8; FIG. 8 is a diagram illustrating an experimental example; FIG. 9 is a diagram illustrating a comparative example.

[0013] <Embodiment 1> In a first embodiment of the present invention, as illustrated in Fig. 1, a post-heat treatment device 100 will be described that performs heat treatment on a welded rail 200 to reduce residual stress present in the welded portion and the periphery of the welded portion of the rail 200. As illustrated in Fig. 1, the post-heat treatment device 100 has an induction heating coil 110 that covers the entire circumference of the rail 200. Furthermore, magnetic materials for shielding magnetic flux and magnetic materials for concentrating magnetic flux are arranged at predetermined locations on the induction heating coil 110.

[0014] As illustrated in Figure 2, rail 200 is composed of a head portion 210 located at the top and coming into contact with wheels and the like when rail 200 is installed, a foot portion located at the bottom and coming into contact with sleepers and the like, and a post portion 220 connecting head portion 210 and foot portion. The foot portion is composed of a sole portion 230, a toe portion 240, and a toe portion 250. As illustrated in Figure 3, head portion 210 can be further divided into a top portion 211 which is the uppermost and flat part, head side portions 212 and 213 located on the sides, and corner portions 214 and 215 which connect top portion 211 and head side portions 212 and 213.

[0015] In considering the above-mentioned problems, the inventors discovered that it is possible to manufacture a rail 200 with high levels of properties such as abrasion resistance and breakage resistance by distributing the required properties to each part of the rail 200. Specifically, for example, abrasion resistance is imparted to the head part 210. Breakage resistance is imparted to the pillar part 220. Breakage resistance is imparted to the foot parts such as the sole part 230 and the toe parts 240 and 250. For example, by imparting at least some of the properties described above to each part, it is possible to realize a rail 200 with more appropriate properties.

[0016] Furthermore, after further investigation, the inventors discovered that by heating each part under conditions appropriate for that part, it is possible to impart the appropriate characteristics to each part as described above. Specifically, for example, for the base part 220, in order to impart breakage resistance, it is necessary to ensure the effect of reducing residual stress while preventing excessive softening. Therefore, it is desirable to heat to around 600 to 700°C. Furthermore, for the head part 210, it is desirable to heat to around 250 to 600°C in order to ensure a minimum effect of reducing residual stress while also ensuring wear resistance. Furthermore, for the foot parts such as the sole part 230 and the toe parts 240 and 250, it is necessary to ensure a minimum effect of reducing residual stress while preventing a decrease in hardness in order to impart breakage resistance and suppress plastic deformation due to the load received from the wheel. Therefore, it is desirable to heat to around 250 to 650°C. For example, as described above, by heating each part at an appropriate temperature, it is possible to impart appropriate characteristics to each part. According to the above-mentioned conditions, it is clear that it is desirable to suppress heating of the head 210 and foot portion more than heating of the column portion 220. In other words, it is desirable that the head 210 and foot portion are not excessively heated when heating the column portion 220 to the target temperature of 600 to 700°C. Therefore, in relation to the required characteristics, it can be said that the column portion 220 of the rail 200 is the portion that needs to be heated, and the head 210 and foot portion are the portions where heating is suppressed.

[0017] An example of the configuration of the post-heating treatment apparatus 100 having a configuration for achieving the above-described heating conditions will be described in more detail below. In the following, as illustrated in FIG. 4 , the distance h, which is the shortest distance between the corner portion 214 of the head portion 210 and the induction heating coil 110, is used as a representative distance between the head portion 210 and the induction heating coil 110. Furthermore, the distance f, which is the shortest distance between the toe portion 240 and the induction heating coil 110, is used as a representative distance between the foot portion and the induction heating coil 110. Experiments conducted by the present inventors have shown that when heating is performed using an existing coil without using a magnetic material, the corner portions 214 and 215 of the head portion 210 and the toe portions 240 and 250 are most likely to be heated. Therefore, in order to more appropriately manage the heating conditions, the above-described distances h and f are used as representative distances between the head portion 210 and the induction heating coil 110 and the toe portion and the induction heating coil 110. Furthermore, the distance n, which is the shortest distance between the narrowest part of the column 220 and the induction heating coil 110, is used as a representative distance between the column 220 and the induction heating coil 110. Experiments conducted by the inventors have confirmed that, when a magnetic material for magnetic flux shielding is not used, even if the distance between the foot and the coil, such as distance f, is more than twice the distance in existing post-heat treatment devices 100, it is difficult to maintain the temperature of the toe portions 240, 250 at a temperature corresponding to the required characteristics when the column 220 is heated to the required temperature. Furthermore, the above distances are merely examples, and the distance may be determined at a location other than those exemplified above.

[0018] FIG. 1 is a front view showing an example configuration of a post-heat treatment device 100. As shown in FIG. 1, the post-heat treatment device 100 has an induction heating coil 110 that covers the entire circumference of a rail 200. Also, as shown in FIG. 1, first magnetic bodies 120 and 130, which are magnetic bodies for shielding magnetic flux, are arranged at predetermined locations of the induction heating coil 110 facing a head portion 210, which is a heating-suppressed area. For example, in the example shown in FIG. 1, the first magnetic body 120 is arranged at a location facing a corner portion 214 of the head portion 210, and the first magnetic body 130 is arranged at a location facing a corner portion 215. Also, second magnetic bodies 140 and 150, which are magnetic bodies for shielding magnetic flux, are arranged at predetermined locations of the induction heating coil 110 facing a foot portion, which is a heating-suppressed area. 1, for example, second magnetic body 140 is arranged at a location of the foot that faces toe portion 240, and second magnetic body 150 is arranged at a location that faces toe portion 250. Furthermore, third magnetic bodies 160 and 170, which are magnetic bodies for concentrating magnetic flux, are arranged at predetermined locations of induction heating coil 110 that face column portion 220, which is the location that needs to be heated.

[0019] FIG. 5 also shows an example of the post-heat treatment device 100 as viewed from the side. Referring to FIG. 5, the post-heat treatment device 100 has induction heating coils 110 configured as described above, with one turn on each side sandwiching the rail weld. In other words, the post-heat treatment device 100 described in this embodiment has one turn of the induction heating coil 110 on each side of the rail weld. For example, in the example shown in FIG. 5, the post-heat treatment device 100 has one turn of the induction heating coil 110-1 on the left side of the rail weld and one turn of the induction heating coil 110-2 on the right side of the rail weld. For example, the induction heating coil 110-1 is positioned so that the distance between the center of the rail weld and the induction heating coil 110-1 is 50 mm, and the induction heating coil 110-2 is positioned so that the distance between the center of the rail weld and the induction heating coil 110-2 is 50 mm. The post-heat treatment device 100 may have multiple turns of the induction heating coil 110 on each side sandwiching the rail weld. Furthermore, the distance between the center of the rail weld and induction heating coil 110-1, induction heating coil 110-2, etc. may be other than that exemplified above.

[0020] The induction heating coils 110-1 and 110-2 are arranged, for example, so that the current flows in opposite directions. The induction heating coils 110-1 and 110-2 may also be arranged so that the current flows in the same direction. Each configuration will be described in more detail below.

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

[0022] As described above, the induction heating coil 110 covers the entire circumference of the rail 200 when viewed from the front. For example, as shown in Patent Document 2, the induction heating coil 110 can be divided into two or more coil members, and the divided coil members can be joined together to cover the entire circumference of the rail 200. The induction heating coil 110 may also cover the entire circumference of the rail 200 by methods other than those exemplified above.

[0023] Furthermore, the induction heating coil 110 can cover the entire circumference of the rail 200 so that the relationship between the distance between the column portion 220 and the induction heating coil 110 and the distance between the head portion 210 and the induction heating coil 110 falls within a predetermined range. Specifically, the induction heating coil 110 can cover the entire circumference of the rail 200 so that the value of (distance n) / (distance h) is 0.2 or more and 1.5 or less. As will be described later, by adjusting the distance n and the distance h to the above values, each part can be heated in a more desirable state. In other words, by adjusting the distances n and h to fall within the above range, each part can be heated more appropriately according to its characteristics.

[0024] Furthermore, experiments by the present inventors have shown that heating can be performed more efficiently as the distance between the induction heating coil 110 and the rail 200 becomes shorter. Therefore, by covering the entire circumference of the rail 200 so that the distance between the column portion 220 and the induction heating coil 110 is shorter than the distance between the head portion 210 and the induction heating coil 110, more efficient heating of the column portion 220 can be achieved. Specifically, from the perspective of more efficient heating of the column portion 220, it can be said that it is more desirable for the value of (distance n) / (distance h) to be equal to or greater than 0.2 and less than 1.

[0025] Furthermore, the induction heating coil 110 can cover the entire circumference of the rail 200 so that the relationship between the distance between the column portion 220 and the induction heating coil 110 and the distance between the foot portion and the induction heating coil 110 falls within a predetermined range. Specifically, the induction heating coil 110 can cover the entire circumference of the rail 200 so that the value of (distance n) / (distance f) is 0.2 or more and 2.0 or less. As will be described later, by adjusting the distance n and the distance f to achieve the above values, each part can be heated in a more desirable state. In other words, by adjusting the distances n and f to fall within the above range, heating can be performed more appropriately according to the characteristics of each part.

[0026] Furthermore, as in the case of the head portion 210 described above, more efficient heating of the column portion 220 can be achieved by covering the entire circumference of the rail 200 so that the distance between the column portion 220 and the induction heating coil 110 is shorter than the distance between the foot portion and the induction heating coil 110. Specifically, from the perspective of more efficient heating of the column portion 220, it can 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 embodiment, the induction heating coil 110 does not cover the rail 200 in a shape similar to the shape of the rail 200, but rather covers the head 210, column 220, and foot of the rail 200 in a generally rectangular shape. That is, the induction heating coil 110 has a shape that combines angular shapes corresponding to the head 210, column 220, and foot. In other words, the induction heating coil 110 has a shape in which a rectangular shape corresponding to the head 210 and a rectangular shape corresponding to the foot are connected by a linear shape corresponding to the column 220. Covering the rail 200 in this manner ensures a greater distance between the induction heating coil 110 and the portions of the rail 200 that correspond to the rounded portions, such as corners 214 and 215 and toes 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] 1 , the induction heating coil 110 covers the rail 200 in a portion thereof that covers the head 210 of the rail 200 and is located below the head 210, so that the closer it is to the column portion 220, the closer it is to the head 210. In other words, the rectangular shape corresponding to the head 210, the portion below the head 210, is shaped like a V in front view. By making the induction heating coil 110 shaped like a V below the head 210 in this way, it is possible to place the induction heating coil 110 as close as possible to the column portion 220 while keeping the induction heating coil 110 as far away as possible from the head side portions 212, 213 and the corner portions 214, 215. Furthermore, in the example shown in FIG. 1 , the portion of the induction heating coil 110 below the foot that faces the sole portion 230 has a shape that is convex toward the rail 200. Similarly, with the above-described shape, the induction heating coil 110 can be placed close to the sole 230 while being spaced apart from the toes 240 and 250 .

[0029] The first magnetic bodies 120 and 130 are magnetic bodies for shielding magnetic flux and are installed at predetermined locations facing the head 210. For example, the first magnetic bodies 120 and 130 are installed at predetermined locations facing the corner portions 214 and 215 of the head 210. For example, the first magnetic bodies 120 and 130 are made of a polyiron core or a silicon steel plate. The first magnetic bodies 120 and 130 may also be made of other known magnetic bodies.

[0030] In this embodiment, the first magnetic bodies 120, 130 are arranged at predetermined locations on the induction heating coil 110 so as to cover the inner surface of the induction heating coil 110. With this arrangement, the first magnetic bodies 120, 130 shield the magnetic flux at the locations where they are arranged, thereby preventing overheating of the rail 200 at those locations. In other words, the first magnetic bodies 120, 130 are arranged at predetermined locations on the induction heating coil 110 so as to cover at least the inner circumferential surface that faces the rail 200.

[0031] The first magnetic bodies 120, 130 are desirably arranged on the induction heating coil 110 so as to satisfy a predetermined inner surface coverage rate of the entire inner surface of the induction heating coil 110 facing the head 210. Specifically, the first magnetic body 120 is desirably arranged on the inner surface of the induction heating coil 110 so that a coverage rate C2, which is the ratio of the portion of the induction heating coil 110 that is covered by the first magnetic body 120 to the entire portion of the induction heating coil 110 that faces the corner portion 214, is greater than 0% and not more than 65%. By arranging the first magnetic body 120 at such a rate, the first magnetic body 120 can more appropriately suppress heating of the head 210. More preferably, the first magnetic body 120 is desirably arranged on the inner surface of the induction heating coil 110 so that the coverage rate C2 is greater than 0% and not more than 30%. By arranging the first magnetic body 120 at such a rate, the first magnetic body 120 can more appropriately suppress heating of the head 210.

[0032] Similarly, the first magnetic body 130 is desirably arranged on the inner surface of the induction heating coil 110 so that a coverage rate C2, which is the ratio of the portion of the induction heating coil 110 that is covered by the first magnetic body 130 to the entire portion of the induction heating coil 110 that faces the corner portion 215, is greater than 0% and not more than 65%. By arranging the first magnetic body 130 at such a rate, the first magnetic body 130 can more appropriately suppress heating of the head 210. More preferably, the first magnetic body 130 is desirably arranged on the inner surface of the induction heating coil 110 so that the coverage rate C2 is greater than 0% and not more than 30%. By arranging the first magnetic body 130 at the above rate, the first magnetic body 130 can more appropriately suppress heating of the head 210.

[0033] As long as the above-mentioned arrangement ratio is satisfied, the arrangement locations of the first magnetic bodies 120, 130 may be other than those illustrated in Fig. 1. For example, the arrangement locations of the first magnetic bodies 120, 130 may be shifted upward or downward from the vicinity of the center of the corner portions 214, 215 illustrated in Fig. 1, and may cover the top portion 211 or the side portions 212, 213 of the head.

[0034] The second magnetic bodies 140, 150 are magnetic bodies for shielding magnetic flux and are installed at predetermined locations facing the foot portions. For example, the second magnetic bodies 140, 150 are installed at predetermined locations of the foot portions facing the toe portions 240, 250. For example, the second magnetic bodies 140, 150 are made of a polyiron core or a silicon steel plate, similar to the first magnetic bodies 120, 130. The second magnetic bodies 140, 150 may also be made of other known magnetic bodies.

[0035] In this embodiment, the second magnetic bodies 140, 150, like the first magnetic bodies 120, 130, are arranged at predetermined locations on the induction heating coil 110 so as to cover the inner surface of the induction heating coil 110. By arranging them in this manner, the second magnetic bodies 140, 150 shield the magnetic flux at the locations where they are arranged, thereby suppressing overheating of the rail 200 at those locations. In other words, the second magnetic bodies 140, 150 are arranged at predetermined locations on the induction heating coil 110 so as to cover at least the inner circumferential surface that faces the rail 200.

[0036] Like the first magnetic bodies 120 and 130, the second magnetic bodies 140 and 150 are preferably arranged on the induction heating coil 110 so as to satisfy a predetermined inner surface coverage rate of the entire inner surface of the induction heating coil 110 facing the toes 240. Specifically, the second magnetic body 140 is preferably arranged on the inner surface of the induction heating coil 110 so that a coverage rate C1, which is the proportion of the portion of the induction heating coil 110 that is covered by the second magnetic body 140 to the entire portion of the induction heating coil 110 facing the toes 240, is 5% to 95%. By arranging the second magnetic body 140 at such a rate, the second magnetic body 140 can more appropriately suppress heating of the toes 240. More preferably, the second magnetic body 140 is arranged on the inner surface of the induction heating coil 110 so that the coverage rate C1 is 8% to 60%, and even more preferably, the second magnetic body 140 is arranged on the inner surface of the induction heating coil 110 so that the coverage rate C1 is 10% to 30%. By arranging the second magnetic body 140 in the above proportions, the second magnetic body 140 can more appropriately suppress heating of the toe portion 240 .

[0037] Similarly, the second magnetic body 150 is desirably arranged on the inner surface of the induction heating coil 110 so that a coverage rate C1, which is the ratio of the portion of the induction heating coil 110 that is covered by the second magnetic body 150 to the entire portion of the induction heating coil 110 that faces the toe portion 250, is 5% or more and less than 95%. By arranging the second magnetic body 150 at such a rate, the second magnetic body 150 can more appropriately suppress heating of the toe portion 250. More preferably, the second magnetic body 150 is arranged on the inner surface of the induction heating coil 110 so that the coverage rate C1 is 8% or more and less than 60%, and even more preferably, the second magnetic body 150 is arranged on the inner surface of the induction heating coil 110 so that the coverage rate C1 is 10% or more and less than 30%. By arranging the second magnetic body 150 at each of the above rates, the second magnetic body 150 can more appropriately suppress heating of the toe portion 250.

[0038] As long as the above-mentioned placement ratio is satisfied, the placement locations of the second magnetic bodies 140, 150 may be other than those illustrated in Fig. 1. For example, the placement locations of the second magnetic bodies 140, 150 may be above or below the toe portions 240, 250.

[0039] The third magnetic bodies 160 and 170 are magnetic bodies for concentrating magnetic flux, and are installed at predetermined locations facing the column portion 220. For example, the third magnetic bodies 160 and 170 are made of a polyiron core or a silicon steel plate, similar to the first magnetic bodies 120 and 130 and the second magnetic bodies 140 and 150. The third magnetic bodies 160 and 170 may also be made of other known magnetic bodies.

[0040] In this embodiment, the third magnetic bodies 160, 170 are arranged at predetermined locations on the induction heating coil 110 so as to cover the outer surface of the induction heating coil 110. By arranging them in this manner, the third magnetic bodies 160, 170 concentrate the magnetic flux at the locations where they are arranged, and more efficiently heat the rail 200 at those locations. In other words, the third magnetic bodies 160, 170 are arranged at predetermined locations on the induction heating coil 110 so as to cover the outer periphery excluding the inner periphery that faces the rail 200.

[0041] 1 , the third magnetic bodies 160, 170 are arranged on one side facing the pillar portion 220 of the rail 200 so as to sandwich the pillar portion 220. The proportion of the portion of the induction heating coil 110 that is covered with the third magnetic bodies 160, 170 relative to the entire portion that faces the pillar portion 220 may be any proportion, such as 5% or more and 100% or less.

[0042] For example, the post-heat treatment device 100 has the configuration as described above. Note that the configuration of the post-heat treatment device 100 may be other than that exemplified above. For example, the post-heat treatment device 100 may have only one of the first magnetic bodies 120, 130 and the second magnetic bodies 140, 150. Furthermore, the post-heat treatment device 100 may have only one of the first magnetic bodies 120 and the first magnetic body 130, or only one of the second magnetic bodies 140 and the second magnetic body 150. Furthermore, the post-heat treatment device 100 may not have the third magnetic bodies 160, 170. Furthermore, the post-heat treatment device 100 may have only one of the third magnetic bodies 160 and 170.

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

[0044] As described above, the post-heat treatment device 100 includes the induction heating coil 110 and magnetic materials for shielding magnetic flux in the areas corresponding to the areas where heating is suppressed. With this configuration, the post-heat treatment device 100 can suppress heating of the areas corresponding to the areas where heating is suppressed while ensuring heating of the column sections 220, which are the areas of the rail 200 that require heating. As a result, it is possible to impart appropriate characteristics to each section, and it is possible to appropriately impart the characteristics required for the rail 200. Furthermore, as described above, the post-heat treatment device 100 can more appropriately ensure heating conditions according to the required characteristics by adjusting the arrangement ratio of each magnetic material within an appropriate range.

[0045] Furthermore, the induction heating coil 110 of the post-heat treatment device 100 covers the entire circumference of the rail 200 after adjusting the distance between the area to be heated and the rail 200 and the distance between the area to be restricted from heating and the rail 200 according to the need for heating, etc. This allows heating under more appropriate heating conditions, and more appropriate characteristics can be imparted.

[0046] Furthermore, the post-heat treatment device 100 has a magnetic material for concentrating magnetic flux at a location corresponding to the column portion 220, which is a heating-requiring location on the rail 200. With this configuration, the post-heat treatment device 100 can more appropriately heat the column portion 220, which is a heating-requiring location on the rail 200 that needs to be heated.

[0047] Next, the present invention will be described with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0048] First, the inventors compared the temperature of each part of the rail after heating, which was obtained using an actual coil that was actually created, with the temperature of each part of the rail after heating, which was obtained by simulation using general-purpose electromagnetic field analysis software (JMAG (registered trademark) manufactured by JSOL Corporation). The simulation was performed with a current value of 1000A, a frequency of 18kHz, and a rail magnetic permeability of 1.3 x 10 ―４ H / m, magnetic permeability of magnetic material 5.0 x 10 ―３ H / m, thermal conductivity of rail 47.2 W / mK, specific heat of rail 474 J / kgK, electrical resistance of rail 2.1 x 10 ―７ The test was performed with a Ω·m (all physical properties at 25°C) so that the temperature of the column section was 600°C or higher and the heating rate was 2.8°C / sec. As shown in Table 1 below, when the actual measurements and simulations were compared at two levels, the difference between the heating temperatures of each part of the rail calculated by the simulation and the actual measurements was kept within 10% of the actual measurements. This shows that the heating rate of each part of the rail due to the coil can be predicted by simulation. Note that the clearance in Table 1 below refers to the distance between each part and the coil.

[0049] Next, the inventors used the above-mentioned simulation to examine the appropriate range of each parameter while changing the coverage C1, coverage C2, (distance n) / (distance f), and (distance n) / (distance h) described in the embodiment.

[0050] Example 1 First, a simulation was carried out while fixing the conditions for the head and varying the conditions for the foot. This allowed us to consider the ranges that would satisfy the required characteristics for both the rail column and the rail base. The criteria for judgment in the examples and comparative examples are as follows: When the temperature of the column was raised to a standard temperature (600-700°C), Double circle: The temperature of the foot or head was within the standard temperature range and had the best heating efficiency Circle: The temperature of the foot or head was within the standard temperature range and also had good heating efficiency Triangle: The temperature of the foot or head was near the upper or lower limit of the standard temperature range, resulting in a decrease in heating efficiency Cross: The temperature of the foot or head was above the upper or lower limit of the standard temperature range

[0051] FIG. 6 shows an example of an example and a comparative example. The example and comparative example of FIG. 6 are summarized in a graph as shown in FIG. 7. Referring to FIGS. 6 and 7, it can be seen that when the coverage 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, the evaluation criteria determine a double circle or a circle. In other words, according to the above examples and comparative examples, it can be seen that a coverage C1 of 5% or more and 95% or less is a desirable range. Furthermore, according to the above examples and comparative examples, it can be seen that a value of (distance n) / (distance f) of 0.2 or more and 1 or less is a desirable range. Furthermore, it can be seen that a range of (distance n) / (distance f) greater than 1 and less than 2 is also acceptable, even if the heating efficiency is reduced, such as a slower temperature rise rate, and the range does not exceed the allowable range of the heating temperature of the foot (the range indicated by a triangle in the evaluation criteria).

[0052] Example 2 Next, a simulation was conducted while varying the conditions for the head portion. This allowed us to determine the range that would satisfy the required characteristics for both the rail web portion and the rail head portion. The evaluation criteria for the example and comparative example were the same as those for Example 1.

[0053] FIG. 8 shows an example of an example and a comparative example. The example and comparative example of FIG. 8 are summarized in a graph as shown in FIG. 9. Referring to FIGS. 8 and 9, it can be seen that a circle is determined based on the criteria when the coverage 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. In other words, according to the above example and comparative example, it can be seen that a desirable range for coverage C2 is 0% or more and 60% or less. Furthermore, according to the above example and comparative example, it can be seen that a desirable range for the value of (distance n) / (distance h) is 0.2 or more and 1 or less. Thus, it can be seen that it is desirable for no magnetic material to be placed on the head, or, if a magnetic material is placed, for coverage C2 to be 60% or less. Furthermore, although the heating efficiency decreases, such as the rate of temperature rise decreasing, if the range that does not exceed the allowable range of the heating temperature of the foot (the range that forms a triangle in the judgment criteria) is included, it can be seen that a range in which the coverage rate C2 is more than 60% and not more than 65%, and a range in which the value of (distance n) / (distance f) is more than 1 and not more than 1.5 are also acceptable.

[0054] Example 3 Next, a range for performing a more preferable heat treatment that satisfies all the required characteristics of the base, foot, and head was examined. The criteria for the examples and comparative examples were the same as those for Example 1. In Example 3, a simulation was performed assuming that the magnetic material arranged in the foot and the magnetic material arranged in the head do not affect each other, and that the size of the clearance between the foot and the head does not affect each other.

[0055] 10 and 11 show examples of an example and a comparative example. Referring to Fig. 10 and Fig. 11, it can be seen that preferable heating is achieved when the above-mentioned ranges are satisfied, and that appropriate heating of each part becomes difficult when the ranges are not satisfied.

[0056] <Supplementary Notes> Part or all of the above-described embodiments can also be described as follows: The post-heat treatment device and the like of the present invention will be outlined below. However, the present invention is not limited to the following configuration.

[0057] (Supplementary Note 1) A post-heat treatment device for performing heat treatment on a welded rail, comprising: an induction heating coil covering the entire circumference of the rail; and a magnetic body arranged to cover the inner surface of the induction heating coil in a portion of the rail corresponding to a heat-suppressed portion where heating needs to be suppressed. (Supplementary Note 2) A post-heat treatment device according to Supplementary Note 1, wherein the magnetic body is a first magnetic body arranged in a portion of the rail corresponding to a head portion, which is a heat-suppressed portion where heating needs to be suppressed, and the first magnetic body is arranged on the inner surface of the induction heating coil so that a coverage rate, which is the proportion of the portion of the induction heating coil that is covered by the first magnetic body to the entire portion of the induction heating coil facing the head, is greater than 0% and less than or equal to 65%. (Supplementary Note 3) A post-heat treatment device according to Supplementary Note 1 or Supplementary Note 2, wherein the induction heating coil covers the entire circumference of the rail so that the value of n / h is greater than or equal to 0.2 and less than or equal to 1.5, where n is the distance between the induction heating coil and a base portion of the rail and h is the distance between the induction heating coil and a head portion of the rail. (Supplementary Note 4) The post-heat treatment device according to any one of Supplementary Notes 1 to 3, wherein the induction heating coil covers the entire circumference of the rail such that the distance between the induction heating coil and a column portion of the rail is shorter than the distance between the induction heating coil and a head portion of the rail. (Supplementary Note 5) The post-heat treatment device according to any one of Supplementary Notes 1 to 4, wherein the magnetic body is a second magnetic body arranged in a portion of the rail corresponding to a toe portion that is a heat suppression portion that needs to be suppressed from heating, and the second magnetic body is arranged on an inner surface of the induction heating coil such that a coverage rate, which is the ratio of the portion of the induction heating coil that is covered by the second magnetic body to the entire portion of the induction heating coil that faces the toe portion, is 5% to 95%.(Supplementary Note 6) The post-heat treatment device according to any one of Supplementary Notes 1 to 5, wherein the induction heating coil covers the entire circumference of the rail such that the value of n / f is 0.2 or more and 2.0 or less, where n is the distance between the induction heating coil and a pillar portion of the rail and f is the distance between the induction heating coil and a foot portion of the rail. (Supplementary Note 7) The post-heat treatment device according to any one of Supplementary Notes 1 to 6, wherein the induction heating coil covers the entire circumference of the rail 200 such that the distance between the induction heating coil and the pillar portion of the rail is shorter than the distance between the induction heating coil and the foot portion of the rail. (Supplementary Note 8) The post-heat treatment device according to any one of Supplementary Notes 1 to 7, comprising a third magnetic body arranged to cover the outer surface of the induction heating coil in a portion of the rail corresponding to a pillar portion that is a heating-required portion of the rail.

[0058] Although the present invention has been described above with reference to the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0059] REFERENCE SIGNS LIST 100 Post-heat treatment device 110 Induction heating coil 120 First magnetic body 130 First magnetic body 140 Second magnetic body 150 Second magnetic body 160 Third magnetic body 170 Third magnetic body 200 Rail 210 Head portion 211 Top portion 212 Head side portion 213 Head side portion 214 Corner portion 215 Corner portion 220 Pillar portion 230 Sole portion 240 Toe portion 250 Toe portion

Claims

1. A post-heat treatment device for performing heat treatment on a welded rail, an induction heating coil covering the entire periphery of the rail; a magnetic body arranged to cover an inner surface of the induction heating coil in a portion of the rail corresponding to a heat suppression portion where heat suppression is required; Equipped with Post-heat treatment equipment.

2. The post-heat treatment device according to claim 1, the magnetic body is a first magnetic body arranged in a portion of the rail corresponding to a head portion, which is a heat suppression portion that needs to be suppressed from heating, The first magnetic body is arranged on the inner surface of the induction heating coil so that a coverage ratio, which is a ratio of a portion of the induction heating coil that is covered with the first magnetic body to the entire portion of the induction heating coil that faces the head, is greater than 0% and not more than 65%. Post-heat treatment equipment.

3. The post-heat treatment device according to claim 1 or 2, The induction heating coil covers the entire circumference of the rail so that the value of n / h is 0.2 or more and 1.5 or less, where n is the distance between the induction heating coil and the rail column and h is the distance between the induction heating coil and the rail head. Post-heat treatment equipment.

4. The post-heat treatment device according to claim 1 or 2, The induction heating coil covers the entire circumference of the rail so that the distance between the induction heating coil and the rail post is shorter than the distance between the induction heating coil and the rail head. Post-heat treatment equipment.

5. The post-heat treatment device according to claim 1 or 2, the magnetic body is a second magnetic body arranged in a portion of the rail corresponding to a toe portion, which is a heat suppression portion that needs to be suppressed from heating, The second magnetic body is arranged on the inner surface of the induction heating coil so that a coverage ratio, which is a ratio of a portion of the induction heating coil that is covered with the second magnetic body to the entire portion of the induction heating coil that faces the toe portion, is 5% to 95%. Post-heat treatment equipment.

6. The post-heat treatment device according to claim 1 or 2, The induction heating coil covers the entire circumference of the rail so that the value of n / f is 0.2 or more and 2.0 or less, where n is the distance between the induction heating coil and the pillar portion of the rail and f is the distance between the induction heating coil and the toe portion of the rail. Post-heat treatment equipment.

7. The post-heat treatment device according to claim 1 or 2, The induction heating coil covers the entire circumference of the rail 200 so that the distance between the induction heating coil and the pillar portion of the rail is shorter than the distance between the induction heating coil and the foot portion of the rail. Post-heat treatment equipment.

8. The post-heat treatment device according to claim 1 or 2, A third magnetic body is provided in a portion of the rail corresponding to a column portion that is a heating-required portion, and the third magnetic body is arranged to cover the outer surface of the induction heating coil. Post-heat treatment equipment.