JP2016049568A - Rail cooling method and heat treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To homogenize the cooling rates at the head vertex central portion and the head vertex end portions of a rail while suppressing an investment cost and a running cost.SOLUTION: When a rail 1 is forcibly cooled by injecting a cooling medium to at least the head portion 11 of either a rail 1 hot-rolled to an austenite region temperature or higher, or a head 1 of the rail heated to the austenite region temperature or higher, the injection rate of the cooling medium is distributed in a direction perpendicular to the longitudinal direction of the rail 1 as to at least one of the head vertex surface or the head side surface. In the case where the injection quantity is distributed all over the head vertex surface, the injection rate is so distributed that it may be higher at the widthwise central portion than the widthwise end portions. In the case where the injection rate is distributed as to the head side surface, the cooling medium is so injected onto the widthwise end portion of the head vertex surface and the head side surface as that the injection rate of the lower portion of the head side surface may be larger than that of the higher portion.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rail cooling method and a heat treatment apparatus for manufacturing a high-hardness rail by forcibly cooling a rail that is hot-rolled or higher than an austenite temperature or a rail that is heated to a temperature higher than an austenite temperature.

As a rail excellent in wear resistance and toughness, a high-hardness rail having a pearlite structure with a fine head is known. Such a high-hardness rail is generally manufactured by the following manufacturing method.
First, a rail that has been hot-rolled at an austenite region temperature or higher, or a rail that has been heated to an austenite region temperature or higher is carried into a heat treatment apparatus in an upright state. The upright state means a state in which the head of the rail is upward and the sole is downward. At this time, the rail is in a state where the rolling length is, for example, about 100 m, or in a state where the length per rail is, for example, about 25 m (hereinafter also referred to as “saw cutting”). It is conveyed to the heat treatment apparatus. When the rail is sawed and then transferred to the heat treatment apparatus, the heat treatment apparatus may be divided into a plurality of zones having lengths corresponding to the sawed rail.

  Next, in the heat treatment apparatus, the toe portion of the rail is restrained by a clamp, and the top portion of the rail, the head side portion, the sole portion, and if necessary, the abdomen is forcibly cooled by the cooling medium. Air, water, mist or the like is used as the cooling medium. In such a rail manufacturing method, by controlling the temperature history during forced cooling, the entire head including the inside of the rail can be made into a fine pearlite structure. Here, the heat treatment apparatus is provided with a single header or a plurality of headers, and the rail is forcibly cooled by a cooling medium sprayed from the header. At this time, the upper end (hereinafter also referred to as “head top surface”) end of the rail head is a curved surface, and the cooling medium is ejected from many directions. For this reason, since the flow of the cooling medium at the end of the top surface becomes complicated, it becomes difficult to control the cooling at the end of the top surface. Further, since the end portion of the parietal surface is cooled from many directions, the cooling rate is generally higher than that of the central portion and the side surface of the parietal surface.

  Generally, increasing the cooling rate of the rail during heat treatment increases the hardness, but depending on the steel type, excessively increasing the cooling rate results in a structure with significantly low toughness other than pearlite such as martensite and bainite (hereinafter referred to as `` It is also referred to as “abnormal tissue”). As the quality of the rail, since it is necessary to be excellent in hardness and toughness, it is required to improve both of these characteristics. For this reason, it is necessary to control a high cooling rate with high precision in the heat treatment in the rail. However, when cooling the head of the rail, the cooling rate is difficult to be uniform at the end of the parietal surface and the central part of the parietal surface, and thus there may be variations in hardness and toughness in the width direction of the parietal surface. . For this reason, a technique for cooling the top surface of the rail in the width direction at a uniform cooling rate is required.

For example, Patent Document 1 discloses a method of performing a heat treatment with a cooling medium while heating an end of the top surface of the rail with an induction heating device as a method of uniformly cooling the top surface of the rail in the width direction.
Further, Patent Document 2 discloses that a gauge corner is used to cool a rail by a head surface cooling header and a head side surface cooling header for the purpose of preventing overcooling of the gauge corner portion (end portion of the top surface) of the rail. A method is disclosed in which no cooling medium is applied to the part.
Further, Patent Document 3 discloses a method in which the center of the top and the gauge corner can be set to a desired hardness by controlling the distance from the rails of the head surface cooling header and the head side surface cooling header.

JP-A-57-137425 Japanese Patent Laid-Open No. 02-007371 Japanese Patent Laid-Open No. 64-087719

However, the method described in Patent Document 1 is not preferable because it requires a large amount of capital investment for providing the equipment and the running cost becomes very high.
In addition, in the method described in Patent Document 2, when heat-treating shapes having different head widths of the rail, in order to prevent the cooling medium from being directly applied to the gauge corner portion, the top plate is replaced in accordance with the head width. In the case where the top plate is welded to the header, it is not preferable because the header needs to be replaced and the work efficiency is lowered.
Furthermore, the method described in Patent Document 3 is not preferable because uniformity in the width direction of the parietal surface is maintained, but cooling of the head side surface is weakened, so that internal cooling is weakened and hardness is lowered.

  Therefore, the present invention has been made paying attention to the above-mentioned problems, and it is possible to make the cooling rate uniform between the central portion of the top surface of the rail and the end portion of the top surface while suppressing the investment cost and the running cost. An object of the present invention is to provide a rail cooling method and a heat treatment apparatus that can be used.

  In order to achieve the above object, a rail cooling method according to an aspect of the present invention includes a hot-rolled rail having a temperature higher than an austenite region temperature, or a cooling medium on at least a head of a rail heated to a temperature higher than an austenite region. When the rail is forcibly cooled, the injection amount of the cooling medium is distributed in a direction perpendicular to the longitudinal direction of the rail on at least one of the top surface and the side surface of the rail, and the injection amount is set on the top surface. In the case of distribution, in the case where the cooling medium is sprayed over the entire parietal surface by distributing so that the spray amount in the center in the width direction is larger than the end portion in the width direction of the parietal surface, and the spray amount is distributed over the head side surface. Is characterized in that the cooling medium is sprayed to the width direction end of the top surface and the head side surface in such a manner that the spray amount in the lower portion is larger than that in the upper portion of the head side surface.

  In addition, the rail heat treatment apparatus according to one aspect of the present invention is a rail by injecting a cooling medium onto at least a head of a rail that has been hot-rolled to an austenite region temperature or higher, or a rail that has been heated to an austenite region temperature or higher. Cooling means for forcibly cooling the cooling medium, and the cooling means distributes the injection amount of the cooling medium in a direction perpendicular to the longitudinal direction of the rail and at least one of the top surface and the side surface of the rail. In the case where the cooling medium is sprayed over the entire parietal surface by distributing so that the spray amount in the center in the width direction is larger than the end in the width direction of the parietal surface, Further, the cooling medium is sprayed to the widthwise end portion and the head side surface of the top surface in a distributed manner so that the injection amount of the lower portion is larger than the upper portion of the head side surface.

  According to the rail cooling method and heat treatment apparatus of the present invention, it is possible to make the cooling rate uniform between the central portion of the top surface of the rail and the end portion of the top surface while suppressing the investment cost and the running cost.

It is a schematic diagram which shows the heat processing apparatus which concerns on one Embodiment of this invention. It is a side view which shows a part of heat processing apparatus. It is sectional drawing which shows each site | part of a rail. It is a top view which shows a top perforated plate nozzle. It is a top view which shows a head side perforated plate nozzle. It is a top view which shows the parietal perforated plate nozzle of model A1. It is a top view which shows the parietal perforated plate nozzle of model A2. It is a top view which shows the parietal perforated plate nozzle of model A3. It is a top view which shows the parietal perforated plate nozzle of model A4. It is a top view which shows the parietal perforated plate nozzle of model A5. It is a top view which shows the head side perforated plate nozzle of model B1. It is a top view which shows the head side perforated plate nozzle of model B2. It is a top view which shows the head side perforated plate nozzle of model B3. It is a top view which shows the head side perforated plate nozzle of model B4.

DESCRIPTION OF EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.
<Configuration of heat treatment equipment>
First, with reference to FIGS. 1-5, the heat processing apparatus 2 in one Embodiment of this invention is demonstrated. The heat treatment apparatus 2 is an apparatus that forcibly cools the rail 1 that has been hot-rolled to the austenite region temperature or higher, or the rail 1 that has been heated to the austenite region temperature or higher, and heats the rail on the downstream side of the hot rolling line. It is continuously provided on the downstream side of the heating device. As shown in FIGS. 1 and 2, the rail 1 is arranged so that the longitudinal direction is parallel to the z-axis direction perpendicular to the xy plane.

  As shown in FIGS. 1 and 2, the heat treatment apparatus 2 includes a parietal header 20, head headers 21a and 21b, a foot header 22, support restraint portions 23a and 23b, a first thermometer 24a, Two thermometers 24b and a control unit 25 are provided. Here, as shown in FIG. 2 and FIG. 3, the rail 1 includes a head portion 11, an abdomen portion 12, and a foot portion 13, and the upper portion and the foot portion 13 in which the head portion 11 is on the y-axis positive direction side. It is carried into the heat treatment apparatus 2 in a state of being arranged below the y-axis negative direction side. As shown in FIG. 3, the surface of the head 11 is composed of a parietal surface central portion 11a, parietal surface end portions 11b and 11c, cranial side surfaces 11d and 11e, and lower jaw portions 11f and 11g. The foot 13 has a foot back surface 13a at the end on the y-axis negative direction side. In the following description, a region indicated by the parietal surface central portion 11a and the parietal surface end portions 11b and 11c is referred to as a parietal surface.

The heat treatment apparatus 2 is provided so as to extend in the z-axis direction. According to the length of the rail 1, at least one head header 20, head-side headers 21a and 21b, sole header 22 and support restraint portions 23a and 23b are provided. It is provided one by one. When a plurality of the parietal header 20, the head side headers 21a and 21b, the sole header 22 and the support restraint portions 23a and 23b are provided, the plurality of parietal headers 20, the head side headers 21a and 21b, the sole header 22 and the support restraint The parts 23a and 23b are provided side by side in the z-axis direction.
The parietal header 20 has a parietal perforated plate nozzle 201 and jets a cooling medium from the parietal perforated plate nozzle 201 to the entire length in the x-axis direction of the parietal surface central portion 11a and the parietal surface end portions 11b and 11c of the rail 1. It is a cooling means for forcibly cooling the portion 11. Air, spray water, mist, or the like is used as the cooling medium. Further, the parietal header 20 is arranged such that the parietal perforated plate nozzle 201 faces the central part 11 a of the parietal surface of the rail 1.

As shown in FIG. 4, the top perforated plate nozzle 201 is a rectangular member in the xz plan view, and is provided with a plurality of circular nozzle holes 202 through which a cooling medium is injected. The nozzle holes 202 form a row separated by a predetermined interval in the z-axis direction. A plurality of rows (for example, seven rows) of nozzle holes 202 are provided in the x-axis direction. Further, the nozzle holes 202 in adjacent rows are arranged so as to be shifted in the z-axis direction by a distance that is ½ of the interval at which the nozzle holes 202 are separated (staggered arrangement). The perforated perforated plate nozzle 201 of the present embodiment includes a first nozzle hole 202a provided in the center three rows in the x-axis direction and a second row provided in two rows on both ends in the x-axis direction from the first nozzle hole 202a. There are two types of nozzle holes 202, two nozzle holes 202b. Since the second nozzle hole 202b is formed to have a smaller diameter than the first nozzle hole 202a, the opening area is reduced. In the present embodiment, the diameter of the second nozzle hole 202b only needs to be smaller than the diameter of the first nozzle hole 202a, but more preferably 20% to 80% of the diameter of the first nozzle hole 202a. Is desirable. In the example shown in FIG. 4, the distance d ₁ from the row of the first nozzle holes 202a at the center in the x-axis direction to the row of the second nozzle holes 202b at the end in the x-axis direction is the distance d ₁ The length is about the length in the x-axis direction from the center to the head side surfaces 11d and 11e, for example, 45 mm.

As described above, the first nozzle hole 202a provided at the center in the x-axis direction has a larger opening area than the second nozzle hole 202b provided at the end in the x-axis direction. For this reason, the parietal header 20 injects the cooling medium onto the rail 1 with a distribution in the width direction of the top surface of the rail 1 that is the x-axis direction so that the injection amount at the center in the width direction is larger than the end in the width direction. To do.
The head-side headers 21a and 21b have head-side perforated plate nozzles 211a and 211b (211), respectively, and the head side surface 11d and 11e of the rail 1 from the head-side perforated plate nozzle 211 and the y-axis of the top surface end portions 11b and 11c. The cooling means cools the head 11 by injecting a cooling medium over the entire length in the direction. Further, the head-side headers 21a and 21b cool the both lower end surfaces 11f and 11g and the both end surfaces of the abdomen 12 in the x-axis direction as necessary. As with the top header 20, air, spray water, mist, and the like are used as the cooling medium. The head-side headers 21a and 21b are arranged such that the head-side perforated plate nozzles 211a and 211b face the head side surfaces 11d and 11e of the rail 1, respectively.

As shown in FIG. 5, the head-side perforated plate nozzle 211 is a rectangular member in the yz plan view, and is provided with a plurality of circular nozzle holes 212 through which a cooling medium is injected. The nozzle holes 212 form a row spaced apart by a predetermined interval in the z-axis direction. One or a plurality of rows (for example, 5 rows) of nozzle holes 212 are provided in the y-axis direction. Further, the nozzle holes 212 in adjacent rows are arranged so as to be shifted in the z-axis direction by a distance that is ½ of the interval at which the nozzle holes 212 are separated (staggered arrangement). The head-side perforated plate nozzle 211 of the present embodiment is a single or a plurality of (for example, three rows) first nozzle holes 212a provided on the y-axis negative direction side, and a single or a plurality of first nozzle holes 212a provided on the y-axis positive direction side. Two types of nozzle holes 212a and 212b with a plurality of rows (for example, two rows) of second nozzle holes 212b are provided. Since the second nozzle hole 212b is formed to have a smaller diameter than the first nozzle hole 212a, the opening area is reduced. In the present embodiment, the diameter of the second nozzle hole 212b may be smaller than the diameter of the first nozzle hole 212a, but more preferably 20% or more and 80% or less of the diameter of the first nozzle hole 212a. Is desirable. In the example shown in FIG. 5, the distance d ₂ from the row of the second nozzle holes 212b at the end on the y-axis positive direction side to the row of the first nozzle holes 212a at the end on the y-axis negative direction side is the top surface The length is about the length in the y-axis direction from the end portions 11b and 11c to the head side surfaces 11d and 11e, for example, 30 mm.

As described above, the first nozzle hole 212a provided on the negative y-axis side has a larger opening area than the second nozzle hole 212b provided on the positive y-axis side. For this reason, the head-side header 21 injects the cooling medium onto the rail 1 with a distribution such that the injection amount of the lower part becomes larger with respect to the vertical direction of the head 11 of the rail 1 that is the y-axis direction.
The sole header 22 has a sole perforated plate nozzle 221, and is a cooling means that cools the foot portion 13 by spraying a cooling medium from the sole perforated plate nozzle 221 to the entire length of the bottom surface 13 a of the rail 1. As with the top header 20, air, spray water, mist, and the like are used as the cooling medium. The sole header 22 is disposed such that the sole porous plate nozzle 221 faces the sole surface 13 a of the rail 1.

The sole perforated plate nozzle 221 is a member provided with a plurality of nozzle holes for injecting a cooling medium. Unlike the top perforated plate nozzle 201 and the head side perforated plate nozzle 211, the sole perforated plate nozzle 221 is provided with circular nozzle holes having the same diameter at substantially equal positions in the xz plane.
Moreover, the parietal header 20, the head side headers 21a and 21b, and the sole header 22 are connected to a cooling medium supply device via a conveyance pipe (not shown) provided with a flow control valve. The injection amount of the cooling medium is adjusted by adjusting the flow control valve based on an instruction from the control unit 26 described later.

The support restraint portions 23a and 23b are devices that support and restrain the rail 1 by sandwiching both end portions of the foot portion 13 in the x-axis direction. A plurality of support restraint portions 23 a and 23 b are provided, for example, separated by several meters over the entire length of the rail 1 in the longitudinal direction.
The first thermometer 24a is a non-contact type thermometer such as a radiation thermometer, and measures the surface temperature of at least one portion of the top surface central portion 11a. The first thermometer 24 a transmits the measurement result of the surface temperature of the top surface central portion 11 a to the control unit 25.

The second thermometer 24b is a non-contact type thermometer like the first thermometer 24a, and measures the surface temperature of at least one of the top surface end portions 11b and 11c. The second thermometer 24 b transmits the measurement result of the surface temperature of the top surface end portions 11 b and 11 c to the control unit 25.
Based on the measurement results of the first thermometer 24a and the second thermometer 24b, the control unit 25 controls the flow of the transport pipes connected to the parietal header 20, the head side headers 21a and 21b, and the sole header 22, respectively. And the cooling rate of the rail 1 is adjusted by adjusting the injection amount of the cooling medium.

  The heat treatment apparatus 2 has an oscillation mechanism (not shown). The oscillation mechanism is provided in the support restraint portions 23 a and 23 b and causes the support restraint portions 23 a and 23 b to oscillate (reciprocate) in the longitudinal direction of the rail 1. For this reason, the rail 1 reciprocates with respect to the parietal header 20, the head side headers 21a, 21b, and the foot header 22 by operating the oscillation mechanism in a state where the rail 1 is constrained by the support restraint portions 23a, 23b. Moving.

<Rail cooling method>
Next, the manufacturing method of the rail 1 using the cooling method of the rail 1 which concerns on one Embodiment of this invention is demonstrated. In the method for manufacturing the rail 1 according to the embodiment of the present invention, first, the hot-rolled rail 1 or the heated rail 1 is conveyed to the heat treatment apparatus 2. When the hot-rolled rail 1 is used, the steel material is heated to a predetermined temperature in a heating furnace in advance and then hot-rolled to be rolled into the shape of the rail 1. On the other hand, when the heated rail 1 is used, the rail 1 is heated to a predetermined temperature in advance using a heating furnace, a heating device, or the like. In any case, the predetermined temperature is a temperature at which the surface temperature of the head 11 becomes equal to or higher than the austenite region temperature at the start of forced cooling by the heat treatment apparatus 22.

After the rail 1 is transported to the heat treatment apparatus 2, the rail 1 is supported and restrained by the heat treatment apparatus 2 by the foot 13 being sandwiched between the support restraint portions 23 a and 23 b.
Next, forced cooling is started by injecting a cooling medium from the parietal header 20, the head side headers 21 a and 21 b, and the sole header 22. The surface temperature of the head 11 of the rail 1 at the start of forced cooling is equal to or higher than the austenite region temperature.

  Further, the rail 1 is forcibly cooled with a temperature history in which at least the surface layer structure of the top surface becomes a pearlite structure. At this time, the control unit 25 controls the flow control valve so that at least the surface layer structure of the head 11 becomes a pearlite structure, and adjusts the cooling history and the forced cooling time of the rail 1 to adjust the temperature history. Specifically, the control unit 25 causes the cooling medium to be injected from the head-side headers 21a and 21b with a preset injection amount, and further from the measurement results of the first thermometer 24a and the second thermometer 24b, The cooling rate of the part 11a and the top surface end parts 11b and 11c is calculated. Next, the injection amount of the cooling medium injected from the top header 20 is adjusted so that the cooling speed of the top surface end portions 11b and 11c becomes the target cooling speed. In addition, the injection amount of the cooling medium injected from the head-side headers 21a and 21b is set based on the cooling rate at which the hardness inside the head 11 is required. In addition, as an example of the temperature history which becomes a pearlite structure, for example, the top surface end portions 11b and 11c of the rail 1 have an average of 3 ° C./second when the surface temperature of the top surface at the start of forced cooling is 900 ° C. The forced cooling is performed at the cooling rate for 180 seconds.

The control unit 25 is connected to the sole header 22 so that the injection conditions such as the injection amount of the cooling medium and the injection pressure in the sole header 22 are the same as the injection conditions of the head headers 21a and 21b. Control the flow control valve. Further, the spray distance of the sole header 22 may be the same as the spray distance of the head headers 21a and 21b, or may be changed according to the target cooling rate.
After the rail 1 is forcibly cooled, the rail 1 is released from the restraint of the foot 13 by the support restraint portions 23a and 23b, and is transported to the cooling floor as the next step.
Next, the rail 1 is cooled to 200 ° C. or less, preferably 150 ° C. or less in an upright state or an inverted state by natural cooling or cooling by a fan on the cooling floor.

  Here, the cooling medium sprayed from the parietal header 20 and the head side headers 21a and 21b directly hits the parietal surface end portions 11b and 11c. For this reason, when injecting the cooling medium with a uniform injection amount without having distribution to the parietal surface and the cranial surfaces 11d and 11e, the cooling of the parietal surface end portions 11b and 11c as compared with the parietal surface central portion 11a. Increases speed. However, in the present embodiment, with respect to the top of the parietal header 20 and the top of the head side surfaces 11d and 11e that are distributed so that the injection amount of the parietal surface central portion 11a is larger than the parietal end portions 11b and 11c. By using the head-side headers 21a and 21b having a distribution so that the injection amount in the lower part is increased, the top surface can be cooled at a uniform cooling rate in the x-axis direction.

<Modification>
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

For example, in the said embodiment, although the heat processing apparatus 2 was continuously provided in the downstream of the hot rolling line, or the downstream of the heating apparatus which heats a rail, this invention is not limited to this example. The heat treatment apparatus 2 may be provided independently from the hot rolling line or the heating apparatus.
Moreover, in the said embodiment, the heat processing apparatus 2 may have the abdominal-part header for cooling the abdominal part 12 of the rail 1. FIG. The abdomen header is provided with a perforated plate nozzle at one end in the same manner as the parietal header 20, the head side headers 21a and 21b and the sole header 22, and cools the abdomen 12 by injecting a cooling medium from the perforated plate nozzle. The abdomen header is arranged so that the perforated plate nozzle faces the abdomen 12 of the rail 1.

  Further, in the above embodiment, the heat treatment apparatus 2 has the parietal header 20 and the head-side headers 21a and 21b as cooling means for cooling the head 11 of the rail 1, but the present invention is limited to this example. Not. For example, the heat treatment apparatus 2 is a head header formed so as to cover the head 11 in the xy plane view perpendicular to the longitudinal direction of the rail 1 as a cooling means replacing the parietal header 20 and the head-side headers 21a and 21b. You may have. The head header has a substantially arc-shaped perforated plate nozzle that covers the head 11 in the xy plan view, and cools the head 11 by ejecting a cooling medium from the perforated plate nozzle. The perforated plate nozzle of the head header has a plurality of nozzle holes through which a cooling medium is jetted onto the top surface and the side surface of the head. The plurality of nozzle holes are holes having a plurality of diameters, and the amount of the cooling medium sprayed is distributed with respect to the top surface or the head side surfaces 11d and 11e like the top perforated plate nozzle 201 or the head side perforated plate nozzle 211. Arranged.

Further, in the above-described embodiment, the heat treatment apparatus 2 includes the nozzle hole 202 so that the parietal perforated plate nozzle 201 and the head perforated plate nozzle 211 have a distribution in the injection amount of the cooling medium with respect to the parietal surface or the head side surfaces 11d and 11e. , 212 are formed, but the present invention is not limited to this example. For example, the nozzle holes 202 and 212 are formed so that only one of the head-perforated plate nozzle 201 and the head-side perforated plate nozzle 211 has a distribution in the injection amount of the cooling medium with respect to the top surface or the head side surfaces 11d and 11e. May be.
Further, in the above embodiment, the rows of nozzle holes 202 and 212 adjacent in the x-axis direction or the y-axis direction are shifted in the z-axis direction and arranged in a staggered arrangement, but the present invention is in such an example. It is not limited. For example, the nozzle holes 202 and 212 adjacent to each other in the x-axis direction or the y-axis direction may be arranged such that the nozzle holes 202 and 212 in the adjacent rows are aligned in the x-axis direction or the y-axis direction.

  Furthermore, in the said embodiment, the top perforated plate nozzle 201 has the 1st nozzle hole 202a in the center side of a x-axis direction, and the 2nd nozzle hole 202b whose diameter is smaller than the 1st nozzle hole 202a in the end side of a x-axis direction. However, the present invention is not limited to such an example. The top perforated plate nozzle 201 only needs to have a smaller amount of coolant injection on the end side than the central portion in the x-axis direction. For example, the perforated plate nozzle 201 may have nozzle holes 202 having three or more types of diameters. Further, the perforated perforated plate nozzle 201 may be provided with nozzle holes 202 having one type or a plurality of types of diameters so that the number of nozzle holes 202 on the central side is larger than the end side in the x-axis direction. .

Furthermore, in the above embodiment, the head-side perforated plate nozzle 211 has the first nozzle hole 212a on the y-axis negative direction side and the second nozzle hole having a smaller diameter than the first nozzle hole 212a on the end side in the y-axis positive direction. However, the present invention is not limited to this example. The head-side perforated plate nozzle 211 only needs to have a smaller amount of coolant injected on the y-axis positive direction side than on the y-axis negative direction side. For example, the head-side perforated plate nozzle 211 may have nozzle holes 212 having three or more types of diameters. Further, the head-side perforated plate nozzle 211 is provided with nozzle holes 212 having one or more types of diameters so that the number of nozzle holes 212 on the y-axis negative direction side is larger than that on the y-axis positive direction side. May be.
Furthermore, in the above embodiment, the nozzle holes 202 and 212 have a circular shape, but the present invention is not limited to such an example. For example, the nozzle holes 202 and 212 may have a shape such as an ellipse or a polygon. In addition, by making the shape of the nozzle holes 202 and 212 circular, processing becomes easier than other shapes.

Furthermore, in the said embodiment, although the control part 25 controlled the cooling rate based on the temperature measurement result of the 1st thermometer 24a and the 2nd thermometer 24b, this invention is not limited to this example. For example, the control unit 25 may adjust the injection amount of the cooling medium so as to achieve the target cooling speed based on the results of the injection amount and the cooling speed of the cooling medium obtained in advance. At this time, the first thermometer 24a and the second thermometer 24b may not be provided in the heat treatment apparatus 2.
Furthermore, in the said embodiment, although the control part 25 adjusted the cooling rate by adjusting the flow control valve of a conveyance pipe, this invention is not limited to this example. For example, the control unit 25 may adjust the cooling rate by controlling the cooling medium supply device and adjusting the jetting pressure of the cooling medium, the water content of the cooling medium, and the like.

Furthermore, in the above embodiment, the distance d ₂ of the head-side perforated plate nozzle 211, top surface end 11b, the head sides 11d from 11c, the y-axis direction to 11e was to be formed into substantially a same length as, the The invention is not limited to such examples. For example, the distance d ₂ is top surface short portion 11b, may be formed into substantially a same length as that of to the bottom of the abdomen 12 from 11c. At this time, in the rail 1, the lower jaw portions 11 f and 11 g and the abdomen 12 are cooled in addition to the head side surfaces 11 d and 11 e by the cooling medium ejected from the head-side perforated plate nozzle 211. In addition, it is not necessary to give distribution in particular about the injection quantity of the cooling medium with respect to chin lower part 11f, 11g, and the abdominal part 12. FIG. For example, the head-side perforated plate nozzle 211, the distance _{d 2} may be 160 mm.

  Furthermore, in the said embodiment, although the oscillation mechanism was provided in the support restraint parts 23a and 23b, this invention is not limited to this example. For the oscillation mechanism, it is only necessary that the injection position of the cooling medium relative to the rail 1 is moved. For example, the oscillation mechanism is provided in the cooling means including the parietal header 20, the head side headers 21a and 21b, and the sole header 22. May be. Thus, by providing an oscillation mechanism in the heat treatment apparatus 2, the rail 1 can be uniformly cooled in the longitudinal direction. However, if the rail 1 can be cooled sufficiently uniformly in the longitudinal direction from the arrangement of the nozzle holes 202 and 212, the oscillation mechanism may not be provided.

<Effect of embodiment>
(1) In the rail cooling method according to the embodiment of the present invention, the cooling medium is sprayed onto the rail 1 that has been hot-rolled over the austenite region temperature or at least the head 11 of the rail 1 that has been heated over the austenite region temperature. Thus, when the rail 1 is forcibly cooled, the injection amount of the cooling medium is distributed in a direction perpendicular to the longitudinal direction of the rail 1 on at least one of the top surface and the head side surfaces 11d and 11e of the rail 1, and the top surface When the injection amount is distributed, the cooling medium is injected over the entire parietal surface by distributing the injection amount so that the injection amount of the width direction central portion 11a is larger than the width direction end portions 11b and 11c of the parietal surface. When the injection amount is distributed with respect to 11d and 11e, the cooling medium is distributed so that the lower injection amount is larger than the upper portion of the head side surfaces 11d and 11e, and the width of the top surface is reduced. Kotan portion (top surface ends 11b, 11c) and the head side 11d, is injected into 11e.

  Here, when improving the hardness of the rail 1, it is preferable to transform the surface structure of the rail 1 to 100% pearlite. However, depending on the components contained in the rail 1, there is an element that has an effect of slowing the start and progress of the pearlite transformation. Further, depending on the component, there is an element that exerts an effect of slowing the start and progress of the bainite transformation. For this reason, even under the same cooling conditions, depending on the component system, bainite transformation is likely to occur, and the hardness of the rail 1 may decrease. For example, in the case of the rail 1 having a high Mn (manganese) content, the bainite transformation start temperature becomes high, so that bainite transformation is easily performed. Furthermore, for example, the post-transformation structure may change depending on the production conditions such as rolling reduction and rolling temperature, regardless of the influence of components. For this reason, depending on the component system and production conditions, when the cooling rate is excessively high, the bainite transformation or the martensitic transformation start temperature may be lowered before completion of the pearlite transformation including before the transformation start. A bainite structure and a martensite structure are inferior in hardness or toughness as compared with a pearlite structure.

  According to the configuration of (1) of the present invention, the cooling rate of the parietal surface central portion 11a and the parietal surface end portions 11b and 11c can be made uniform in the width direction of the parietal surface. For this reason, the surface layer structure of the parietal surface can be a uniform 100% pearlite structure regardless of the component system and manufacturing conditions, and the hardness and toughness in the width direction of the parietal surface can be made uniform. In addition, according to the above configuration, since the cooling rate can be made uniform only by distributing the injection amount of the cooling medium, for example, compared with Patent Document 1, it is not necessary to provide a facility such as a heating device. The investment cost and running cost for 2 can be suppressed.

  Further, according to the configuration of (1) above, when the injection amount is distributed on the top surface, the cooling medium may be sprayed with a distribution over the entire top surface. For this reason, even when manufacturing a plurality of types of rails 1 having different widths, the width of the top 20 is set in accordance with the maximum width, and the nozzle holes 202 are provided so that there is a distribution in each width. This can correspond to the rail 1 having a width. For this reason, compared to the cooling method in which the cooling medium is not applied to the end of the top surface as in Patent Document 2, the replacement frequency of the header and the top plate is reduced, so that work efficiency and productivity can be improved. it can.

  Furthermore, in Patent Document 3, it is necessary to reduce the cooling rate of the head side surfaces 11d and 11e in order to make the cooling rate of the central portion 11a of the parietal surface and the head side surfaces 11b and 11c uniform, and the internal hardness decreases. Was a problem. On the other hand, according to the configuration of the above (1), the cooling rate of the head side surfaces 11d and 11e can be adjusted while uniforming the cooling rate of the parietal surface central portion 11a and the parietal surface end portions 11b and 11c. For this reason, the hardness and toughness in the width direction of the crown surface can be made uniform without reducing the internal hardness.

(2) When the rail 1 is forcibly cooled, a cooling medium is sprayed from a plurality of nozzle holes 202 provided in the parietal header 20 arranged to face the parietal surface, and the plurality of nozzle holes 202 of the parietal header 20 are The area of the central portion in the width direction is larger than the end portion in the width direction of the top surface.
(3) The plurality of nozzle holes 202 of the parietal header 20 are circular, and the diameter of the nozzle hole 202 at the end in the width direction is 20% to 80% of the diameter of the nozzle hole 202 at the center in the width direction. It is.

(4) When the rail 1 is forcibly cooled, the cooling medium is ejected from the plurality of nozzle holes 212 provided in the head side headers 21a and 21b arranged to face the head side surfaces 11d and 11e, and the head side header 21a , 21b are formed so that the area of the lower portion is larger than the upper portion of the top surface.
(5) The plurality of nozzle holes 212 of the head-side headers 21a and 21b are circular, and the diameter of the uppermost nozzle hole 212 is not less than 20% and not more than 80% of the diameter of the lowermost nozzle hole 212. .

According to the above configurations (2) and (4), for example, it is also applied to an existing heat treatment apparatus having the parietal header 20 and the head-side headers 21a and 21b only by changing the shape and arrangement of the nozzle holes 202 and 212. can do. For this reason, the investment cost for making the cooling rate of the top surface of the rail 1 uniform can be suppressed.
Further, according to the configurations of (3) and (5) above, the processing becomes easier as compared with the case where the nozzle holes 202 and 212 are formed in a shape other than a circle.

(6) Cooling means 20 for forcibly cooling the rail 1 by injecting a cooling medium onto at least the head 11 of the rail 1 heated above the austenite zone temperature or the rail 1 heated above the austenite zone temperature, 21a, 21b, and the cooling means 20, 21a, 21b have a coolant injection amount distributed in a direction perpendicular to the longitudinal direction of the rail 1 with respect to at least one of the top surface and the head side surfaces 11d, 11e of the rail 1, When the injection amount is distributed with respect to the parietal surface, the cooling medium is injected over the entire parietal surface by distributing the injection amount in the central portion in the width direction compared to the width direction end of the parietal surface, and the side surface 11d, When the injection amount is distributed with respect to 11e, the cooling medium is distributed so that the lower injection amount is larger than the upper portions of the head side surfaces 11d and 11e, and the cooling medium is disposed at the end in the width direction of the top surface. Top surface ends 11b, 11c) and the head side 11d, is injected into 11e.
According to the said structure, the effect similar to (1) can be acquired.

Next, Example 1 performed by the present inventors will be described.
In Example 1, first, the rail 1 having a length of 50 m that had been hot-rolled at 900 ° C. was carried into the heat treatment apparatus 2 shown in FIGS. 1 and 2. In Example 1, the component of the rail 1 was the component A shown in Table 1.

Next, the foot 13 of the rail 1 was restrained by the support restraint portions 23a and 23b.
Then, the cooling medium was sprayed from the top header 20, the head side header 21, and the sole header 22, and the rail 1 was forcibly cooled. In Example 1, as the parietal perforated plate nozzle 201, any one of the five types of parietal perforated plate nozzles 201A to 201E of models A1 to A5 shown in FIGS. 6 to 10 was used. Moreover, as the head side perforated plate nozzle 211, any one of four types of head side perforated plate nozzles 211C to 211F of models B1 to B4 shown in FIGS. 11 to 14 was used.

  The parietal perforated plate nozzles 201A to 201E of the models A1 to A5 shown in FIGS. 6 to 10 are provided with a plurality of rows of nozzle holes 202 arranged in the z-axis direction and arranged in the x-axis direction. The nozzle hole 202 has a circular shape. Further, adjacent rows are provided with the positions in the z-axis direction of the nozzle holes 202 of each row shifted by a distance Z1 [mm]. The distance Z1 [mm] is a distance that is ½ of the separation distance of the nozzle holes 202 in each row.

  Among these, the top perforated plate nozzles 201A, 201C, and 201E shown in FIGS. 6, 8, and 10 are provided with nine rows of a plurality of nozzle holes 202 arranged in the z-axis direction and arranged in the x-axis direction. The distance in the x-axis direction in each column is a distance X1 [mm] from the fifth column to the third and seventh columns counting from the x-axis positive direction side serving as the center column, Each of up to the ninth column is formed so as to have a distance X2 [mm]. The second, fourth, sixth and eighth columns from the x-axis positive direction side are the middle of the first to third rows, the middle of the third to fifth rows, and the fifth to seventh rows. Are formed so as to be located in the middle of the first row and in the middle of the seventh to ninth rows.

  In the top perforated plate nozzles 201B and 201D shown in FIG. 7 and FIG. 9, five rows of nozzle holes 202 arranged in the z-axis direction are provided in the x-axis direction. The distance in the x-axis direction in each column is formed so that the distance from the third column to the first and fifth columns is a distance X2 [mm] from the x-axis positive direction side that is the central column. . The second and fourth columns from the x-axis positive direction side are formed so as to be located in the middle of the first to third columns and in the middle of the third to fifth columns, respectively.

Further, in the top perforated plate nozzles 201A and 201B shown in FIGS. 6 and 7, all the first nozzle holes 202a in each row are formed to have the same diameter R1 [mm].
The top perforated plate nozzle 201C shown in FIG. 8 has five rows in the center in the x-axis direction, and the first nozzle holes 202a in the third to seventh rows counted from the x-axis positive direction side have a diameter R1 [mm]. Each size is formed. Further, the top perforated plate nozzle 201C has a diameter R2 [mm] in which the second nozzle holes 202b in the first, second, eighth, and ninth rows counted from the x-axis positive direction side are smaller than the diameter R1 [mm]. ] Respectively. As with the top perforated plate nozzle 201C, the top perforated plate nozzle 201D shown in FIG. 9 has the first nozzle holes 202a in the second to fourth rows counted from the x-axis positive direction side having a diameter R1 [mm], first. The second nozzle holes 202b in the fifth row are formed to have a diameter R2 [mm], respectively.

  In the perforated perforated plate nozzle 201E shown in FIG. 10, the first nozzle holes 202a in the fifth row counted from the x-axis positive direction side, which is the center row in the x-axis direction, are formed with a diameter R1 [mm]. Is done. The top perforated plate nozzle 201E has a diameter R2 [mm] in which the second nozzle holes 202b in the third, fourth, sixth and seventh rows from the x-axis positive direction side are smaller than the diameter R1 [mm]. ] Respectively. Further, in the top perforated plate nozzle 201E, the third nozzle holes 202c in the first row, the second row, the eighth row, and the ninth row from the x-axis positive direction side have a diameter R3 [smaller than the diameter R2 [mm]. mm].

  The head side perforated plate nozzles 211C and 211D shown in FIG. 11 and FIG. 12 are provided with five rows of a plurality of nozzle holes 212 arranged in the z-axis direction. The nozzle hole 212 has a circular shape like the top perforated plate nozzle 201. Further, adjacent rows of nozzle holes 212 are provided such that the positions in the z-axis direction of the nozzle holes 212 of each row are shifted by a distance Z2 [mm]. The distance Z2 [mm] is a distance that is ½ of the separation distance of the nozzle holes 212 in each row. Furthermore, the distance parallel to the y-axis in each column is the distance Y1 [mm] from the first column from the y-axis positive direction side that is the top to the fifth column from the y-axis negative direction side that is the bottom. Formed to be.

The head side porous plate nozzles 211C to 211F of the models B1 to B4 shown in FIGS. 11 to 14 are provided with a plurality of rows of nozzle holes 212 arranged in the z-axis direction. The nozzle hole 202 has a circular shape. Further, adjacent rows are provided with the positions in the z-axis direction of the nozzle holes 212 of each row shifted by a distance Z2 [mm]. The distance Z2 [mm] is a distance that is ½ of the separation distance of the nozzle holes 212 in each row.
In the head-side perforated plate nozzle 211C shown in FIG. 11, five rows of nozzle holes 212 arranged in the z-axis direction are arranged in the y-axis direction. The distance in the y-axis direction in each column is a distance Y1 [mm] from the first column to the fifth column counted from the y-axis direction side. Further, the first column to the second column, the fourth column to the fifth column are formed at a distance Y2 [mm], respectively. The third column from the y-axis direction side, which is the central portion, is arranged between the first column and the fifth column. Furthermore, the first nozzle hole 212a in each row of the head side porous plate nozzle 211C is formed to have the same diameter R4.

  The head-side perforated plate nozzle 211D shown in FIG. 12 has three rows of nozzle holes 212 arranged in the z-axis direction and arranged in the y-axis direction. The distance in the y-axis direction in each column is formed with a distance Y1 [mm] from the first column to the third column counted from the y-axis direction side. Further, the first column to the second column are formed at a distance Y2 [mm]. Further, in the head side porous plate nozzle 211D, the first nozzle holes 212a in each row are all formed to have the same diameter R4, similarly to the head side porous plate nozzle 211C.

  The head side perforated plate nozzle 211E shown in FIG. 13 is provided with four rows of nozzle holes 212 arranged in the z-axis direction and arranged in the y-axis direction. The distance in the y-axis direction in each column is formed with a distance Y1 [mm] from the first column to the fourth column counted from the y-axis direction side. Further, the first column to the second column, the third column to the fourth column are formed at a distance Y2 [mm], respectively. Further, the head-side perforated plate nozzle 211E has a diameter R4 [mm] of the third and fourth rows of first nozzle holes 212a from the positive side in the y-axis direction, and a second nozzle hole 212b of the first and second rows. Each is formed in a size of a diameter R5 [mm] smaller than the diameter R4 [mm].

  The head-side perforated plate nozzle 211F shown in FIG. 14 has three rows of nozzle holes 212 arranged in the z-axis direction and arranged in the y-axis direction. The distance in the y-axis direction in each column is formed with a distance Y1 [mm] from the first column to the third column counted from the y-axis direction side. Further, the first column to the second column are formed at a distance Y2 [mm]. Further, in the head-side perforated plate nozzle 211F, the first nozzle holes 212a in the third row from the positive side in the y-axis have a diameter R4 [mm], and the second nozzle holes 212b in the first and second rows have a diameter R4 [ [mm] and a diameter R5 [mm] different from each other.

  In the top perforated plate nozzle 201 and the head side perforated plate nozzle 211 shown in FIGS. 6 to 14, the distance between the rows in the x-axis direction or the y-axis direction is a straight line passing through the centers of the nozzle holes 202 and 212 in each row. The distance for each direction is shown. The distance between the nozzle holes 202 and 212 adjacent in the z-axis direction indicates the distance between the centers of the nozzle holes 202 and 212. Moreover, the number of nozzle holes 202 and 212 provided in each row of the parietal perforated plate nozzle 201 and the head side perforated plate nozzle 211 shown in FIGS. 6 to 14 is an example. The side perforated plate nozzle 211 is appropriately provided according to the size of the distance Y1 [mm] with respect to the length in the x-axis direction and the y-axis direction.

  Among the parietal perforated plate nozzle 201 and the head side perforated plate nozzle 211 shown in FIGS. 6 to 14, the top perforated plate nozzles 201 </ b> C to 201 </ b> E of models A <b> 3 to A <b> 5 shown in FIGS. 8 to 10 and FIGS. 13 and 14, respectively. The head side perforated plate nozzles 211E and 211F of the models B3 and B4 shown can distribute and inject the cooling medium injection amount in either the x-axis direction or the y-axis direction. In the first embodiment, since the cooling medium is sprayed by distributing the injection amount in at least one of the x-axis direction and the y-axis direction, the top perforated plate nozzle 201 and the head side perforated plate nozzle 211 are used as the top perforated plate nozzles 201C to 201E. And at least one of the head-side perforated plate nozzles 211E and 211F was used.

When performing forced cooling, air, mist, or spray water was used as the cooling medium. Furthermore, the control part 25 adjusted the injection quantity of the cooling medium injected from the parietal header 20 so that the cooling rate of the parietal surface edge part 11c might be 3.0 degree-C / sec. At this time, the conditions for spraying the cooling medium sprayed from the sole header 22 were the same as those for the head header. In Example 1, the forced cooling of the rail 1 by spraying the cooling medium was performed for 180 seconds.
After forced cooling, injection of the cooling medium from the parietal header 20, the head side headers 21a and 21b and the sole header 22 was stopped, and the restraint of the rail 1 by the support restraint portions 23a and 23b was released. Thereafter, the rail 1 was transported to the cooling floor, and the rail 1 was naturally allowed to cool on the cooling floor until it reached room temperature.

Further, a hardness test sample was cut and collected from the rail 1 every 2 m in the longitudinal direction, the sample was polished, and the hardness was measured by the Vickers hardness test. In Example 1, the hardness was measured at a total of three locations, that is, the position of the center of the parietal surface, the position of the end of the parietal surface, and the position of the head 25 mm depth. The central position of the parietal surface is a position that is 1 mm deep from the parietal surface at the center in the width direction of the parietal surface. The position of the end of the parietal surface is a position that is 32.5 mm away from the center in the width direction of the parietal surface to the end and has a depth of 1 mm from the parietal surface. The head 25 mm depth is a position at a depth of 25 mm from the center top surface in the width direction of the top surface.
Further, as a comparison with Example 1, the top perforated plate nozzle 201 is one of models A1 and A2 of the top perforated plate nozzles 201A and 201B, and the top side perforated plate nozzle 211 is used as the head side perforated plate of models B1 and B2. Rail 1 was forcibly cooled under conditions using either nozzle 211C or 211D (Comparative Example 1). For Comparative Example 1, a sample was taken in the same manner as in Example 1, and the hardness was measured.

  Table 2 shows the type of the cooling medium, the presence or absence of oscillation, the type of the top perforated plate nozzle 201 and the head side perforated plate nozzle 211, the results of the cooling rate, and the hardness measurement results in Example 1 and Comparative Example 1, respectively. In Example 1, 19 conditions shown in Examples 1-1 to 1-19 as conditions for applying the cooling method according to the present invention, and Comparative Examples 1-1 to 1-11 as conditions for not applying the cooling method according to the present invention. 11 conditions were confirmed. Moreover, the value of hardness in Table 2 indicates an average value of samples taken every 2 m.

In Comparative Example 1-1, the injection amount of the cooling medium injected from the head-side headers 21a and 21b so that the cooling rate of the parietal surface center portion 11a and the parietal surface end portions 11b and 11c is 3.0 ° C./sec. Was reduced as compared with Comparative Examples 1-2 to 1-11 and Examples 1-1 to 1-19. Moreover, in Comparative Example 1-2, according to the method of Patent Document 3, the head-side headers 21a and 21b are set so that the cooling rate of the parietal surface central portion 11a and the parietal surface end portions 11b and 11c is 3.0 ° C./sec. The distance between the rails 1 and the rails 1 was adjusted, and the distance between the rails 1 and 1 and the rails 1 was adjusted as compared with those of the comparative examples 1-1, 1-3, and 1-11.
Conditions other than the above in Comparative Examples 1-1 to 1-11 were the same as those in the example.

  As shown in Table 2, in Comparative Examples 1-3 to 1-11, the cooling rate of the parietal surface end portion 11c is 3.0 ° C./sec, whereas the cooling rate of the parietal surface central portion 11a is 1. The cooling rate difference was 1.2 ° C./second or more on the top surface. On the other hand, in Examples 1-1 to 1-19, the difference in the cooling rate of the parietal surface central portion 11a with respect to the parietal surface end portion 11c is 1.0 second or less, and the parietal surface as compared with Comparative Examples 1-3 to 1-11. It was confirmed that can be cooled uniformly in the width direction.

  Moreover, in Comparative Examples 1-3 to 1-11, since the cooling rate on the parietal surface is non-uniform, a difference of HV20 to HV27 occurs in the hardness at the parietal surface center position and the parietal surface end position, The hardness in the width direction at the surface layer position on the top surface was uneven. On the other hand, in Examples 1-1 to 1-19, the difference in hardness between the center position of the parietal surface and the end position of the parietal surface is HV16 or less, and the hardness at the surface layer position is higher than that of Comparative Examples 1-2 to 1-11. It was confirmed to be uniform. In Examples 1-1 to 1-19, the above-described effects are obtained in all conditions regardless of the type of cooling medium, the presence or absence of oscillation, and the application conditions of the top perforated plate nozzle 201 and the head side perforated plate nozzle 211. Obtained.

  Furthermore, in Comparative Examples 1-1 and 1-2 in which the cooling rate in the width direction of the parietal surface is made uniform, the difference in hardness between the central position of the parietal surface and the end portion of the parietal surface can be made uniform with HV1. It was. However, the hardness at the head 25 mm depth position was the lowest at HV362, and the head 11 as a whole could not obtain a sufficient hardness. On the other hand, in Examples 1-1 to 1-19, the internal hardness of the head 11 is improved as compared with the case where the injection amount on the side of the head side surfaces 11d and 11e is reduced to make the cooling speed of the top surface uniform. It was confirmed.

Next, Example 2 performed by the present inventors will be described.
In Example 2, in order to investigate the influence of the components of the rail 1, rolling and cooling were performed under the same conditions as in Example 1 for the plurality of rails 1 having changed components. In Example 2, as in Example 1, a sample was cut and collected from the rail 1 manufactured under each condition, and the hardness was measured. The sample collection method and hardness measurement position / measurement method are the same as in Example 1. Furthermore, in Example 2, the surface texture of the parietal surface end 11c was observed.

  Table 3 shows the component conditions, cooling rate, hardness measurement results, and surface texture observation results in Example 2. The value of hardness in Table 3 shows the average value of samples collected every 2 m, as in Table 2. In Examples 2-1 to 2-3, the components of the rail 1 were set to the conditions A to C shown in Table 1, and the rail 1 was manufactured under the same conditions as in the example 1-18 in the example 1. As shown in Table 1, in condition B, the Mn content was increased with respect to condition A. In condition C, the C (carbon) content was increased relative to condition B.

  Moreover, in Example 2, the rail 1 was manufactured on the conditions of Comparative Examples 2-1 to 2-9 as comparative conditions for Examples 2-1 to 2-3, the hardness was measured, and the surface texture was observed. In Comparative Examples 2-1 to 2-3, the components of the rail 1 were set to the conditions A to C shown in Table 1, and the rail 1 was manufactured under the same conditions as the comparative example 1-1 in the example 1. In Comparative Examples 2-4, 2-6, and 2-8, the components of the rail 1 were set to Condition A to Condition C shown in Table 1, and the top perforated plate nozzle 201 and the head used in Comparative Example 1-1 in Example 1 were used. The other perforated plate nozzle 211 was used and the other conditions were the same as those of Comparative Example 1-3. In Comparative Examples 2-5, 2-7, and 2-9, the components of the rail 1 were set to Condition A to Condition C shown in Table 1, and the top perforated plate nozzle 201 and the head used in Comparative Example 1-1 in Example 1 were used. A side perforated plate nozzle 211 was used. Further, in Comparative Examples 2-5, 2-7, and 2-9, when the cooling rate is controlled, it is ejected from the parietal header 20a so that the cooling rate of the parietal surface central portion 11a is 3.0 ° C./sec. The cooling medium injection amount was controlled, and other conditions were the same as those in Comparative Example 1-3.

  In Examples 2-1 to 2-3, the difference in hardness between the center position of the parietal surface and the end position of the parietal surface is HV0 to HV2, and the hardness in the width direction of the parietal surface is uniform under any of the component conditions. It was confirmed. Moreover, in Examples 2-1 to 2-3, it was confirmed that the surface texture of the parietal surface end portion 11c was a 100% pearlite structure under any of the component conditions. Furthermore, in Examples 2-1 to 2-3, as the contents of C and Mn were increased, the hardness at the center of the parietal surface, the end of the parietal surface, and the 25 mm depth position of the head gradually increased. .

  In Comparative Examples 2-1 to 2-3 in which the cooling rate in the width direction of the parietal surface was made uniform, the difference in hardness between the parietal surface center portion and the parietal surface end portion was HV1 to HV3. Also, the hardness in the width direction of the parietal surface became uniform. In Comparative Examples 2-1 to 2-3, the surface texture was 100% pearlite under any of the component conditions. However, in Comparative Examples 2-1 to 2-3, when compared with the same component conditions of Examples 2-1 to 2-3, the hardness at the head 25 mm depth position is low under any condition. The difference with the same component conditions of 2-1 to 2-3 became HV19-22.

  In Comparative Examples 2-4, 2-6, and 2-8, a difference in cooling rate of 1.2 ° C./second occurs between the parietal surface central portion 11a and the parietal surface end portion 11c, and the parietal surface central portion position and the parietal surface The difference in hardness from the end position was HV22 to HV36. Further, in Comparative Examples 2-4, 2-6, and 2-8, the surface texture was 100% pearlite in any of the component conditions, but compared to Examples 2-1 to 2-3, The hardness in the width direction became non-uniform.

  In Comparative Examples 2-5, 2-7, and 2-9, the amount of cooling medium sprayed was controlled so that the cooling rate of the central surface 11a of the parietal surface was 3.0 ° C./second, and thus the parietal surface end portion 11c. The cooling rate was 5.0 ° C./second. Further, in Comparative Example 2-5, the difference in hardness between the position at the center of the parietal surface and the position at the end of the parietal surface was HV31, and the hardness in the width direction of the parietal surface was not uniform. In Comparative Examples 2-7 and 2-9, unlike the other Comparative Examples and Examples, the hardness at the end of the top surface is lower than the hardness at the center of the top surface, and the difference in hardness is HV28 to HV86. It was confirmed. Moreover, the surface structure of the parietal end 11c of Comparative Example 2-5 is 100% pearlite, and the surface structure of the parietal end 11c of Comparative Examples 2-7 and 2-9 is a composite structure of bainite and pearlite. It was.

  From the above results, according to the rail cooling method and the heat treatment apparatus according to the present invention, the cooling of the top surface center portion 11a and the top surface end portions 11b and 11c of the rail 1 is achieved while suppressing the investment cost and the running cost. It was confirmed that the speed could be made uniform.

1: Rail 11: Head 11a: Center part of parietal surface 11b, 11c: End part of parietal surface 11d, 11e: Side face 11f, 11g: Lower jaw 12: Abdomen 13: Foot part 13a: Back surface 2: Heat treatment device 20: Head header 201: Head perforated plate nozzle 202: Nozzle hole 202a: First nozzle hole 202b: Second nozzle hole 21a, 21b: Head side header 211, 211a, 211b: Head side perforated plate nozzle 212: Nozzle hole 212a: First Nozzle hole 212b: Second nozzle hole 22: Foot header 221: Foot perforated plate nozzles 23a, 23b: Support restraint portion 24a: First thermometer 24b: Second thermometer 25: Control unit

Claims (6)

When the rail is forcibly cooled by injecting a cooling medium onto at least the head of the rail that has been hot-rolled over the austenite region temperature or the rail that has been heated to over the austenite region temperature,
For at least one of the top surface and the head side surface of the rail, distribute the injection amount of the cooling medium in a direction perpendicular to the longitudinal direction of the rail,
In the case of distributing the injection amount with respect to the parietal surface, the cooling medium is injected over the entire parietal surface by distributing the injection amount so that the injection amount in the central portion in the width direction is larger than the end portion in the width direction of the parietal surface. And
When the injection amount is distributed with respect to the head side surface, the cooling medium is distributed so that the lower injection amount is larger than the upper portion of the head side surface, and the cooling medium is distributed in the width direction end of the top surface and the head side surface. A rail cooling method characterized by spraying on the rail. When forcibly cooling the rail,
Injecting the cooling medium from a plurality of nozzle holes provided in the top header arranged to face the top surface,
The rail cooling method according to claim 1, wherein the plurality of nozzle holes of the parietal header are formed so that an area of a central portion in the width direction is larger than an end portion in the width direction of the parietal surface.   The plurality of nozzle holes of the top header are circular, and the diameter of the nozzle hole at the end in the width direction is 20% to 80% of the diameter of the nozzle hole at the center in the width direction. The rail cooling method according to claim 2. When forcibly cooling the rail,
Injecting the cooling medium from a plurality of nozzle holes provided in a head-side header arranged to face the head side surface,
The cooling of the rail according to any one of claims 1 to 3, wherein the plurality of nozzle holes of the head-side header are formed so that a lower area is larger than an upper part of the top surface. Method.   The plurality of nozzle holes of the head-side header are circular, and the diameter of the uppermost nozzle hole is 20% to 80% of the diameter of the lowermost nozzle hole. The rail cooling method according to claim 4. A cooling means for forcibly cooling the rail by injecting a cooling medium onto at least the head of the rail that has been hot-rolled over the austenite region temperature or the rail that has been heated to the austenite region temperature or more,
The cooling means is
With respect to at least one of the top surface and the head side surface of the rail, the injection amount of the cooling medium is distributed in a direction perpendicular to the longitudinal direction of the rail,
When the injection amount is distributed with respect to the parietal surface, the cooling medium is injected over the entire parietal surface by distributing the injection amount so that the injection amount at the central portion in the width direction is larger than the end portion in the width direction of the parietal surface. And
When the injection amount is distributed with respect to the head side surface, the cooling medium is distributed such that the lower injection amount is larger than the upper portion of the head side surface, and the cooling medium is distributed in the widthwise end of the top surface and the head side surface. A rail heat treatment apparatus characterized by being sprayed onto the rail.

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