JPH07216454A - Heat treatment of rail - Google Patents

Abstract

PURPOSE:To make uniform the hardness of rail in its longitudinal direction by mounting partition plates on a cooling header to cool the specific range from the end part of rail and separating the space in between both surfaces of the cooling header and the rail head part in the rail longitudinal direction. CONSTITUTION:The header part of a hot rolled rail 11 is directly heat-treated by a cooling device 10 which is provided with cooling headers 12-14 and by which approximate all length of the rail head part is encircled with a cooling medium of air. In this method, among all cooling headers 12-14, one or more pieces of partition plates 15 are mounted respectively to the cooling headers 12-14 for cooling the range of approximate <=3m from the end part of rail. The space in between surfaces of the cooling header part and the rail head part is separated in the rail longitudinal direction. By this method, since the air blown from the cooling headers 12-14 can not be blown in the rail longitudinal direction, the rail end part is heat-treated in the same condition as the center part of rail 11 and the hardness of the rail head part is made uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rail heat treatment method, and more particularly to a heat treatment method for obtaining uniform hardness in the rail length direction.

[0002]

2. Description of the Related Art As a heat treatment method for hot-rolled rails, Japanese Patent Publication No. 2-6810 and Japanese Patent Publication No. 2-73.
Japanese Patent No. 71 discloses a method of heat-treating a rail head located above a heated austenite region by blowing air from a cooling header arranged so as to surround the head to cool the rail head. In order to obtain a desired hardness, the above-mentioned publication uses a cooling header having a crown portion and both head side portions to improve cooling efficiency, and injects air toward the rail crown surface, the head side surface, and the jaw lower surface. The necessary cooling conditions of are shown.

[0003]

However, in the rail heat treatment method described in the above publication, as shown in FIG. 6, the hardness of the top of the rail in the vicinity of the end of the rail slightly rises relative to that in the center of the rail. There is a tendency. In other words, heat treated rails are mainly used for railroad tracks that are frequently passed by trains and have a large freight car weight, and their wear resistance is higher than that of non-heat treated rails. On the contrary, it is expensive. Therefore, the increase in hardness near the end of the rail means that the progress of wear during use of the rail differs between the center and the end, and the flatness of the rail head is impaired. This induces the vertical acceleration when the train is running, and gives an abnormal impact force to the rail head. Therefore, if the rail head is left unattended, the rail may be damaged. From this, now
There is a problem that rail heads are regularly trimmed by customers, but this causes an increase in track maintenance costs.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a rail heat treatment method for uniformizing the hardness in the length direction when heat treating the rail.

[0005]

A method according to the above-mentioned object.
The rail heat treatment method described above is a rail heat treatment method in which a hot-rolled rail is directly heat-treated by a cooling device that includes a cooling header and surrounds substantially the entire length of the rail head with air as a cooling medium. In the cooling header, at least one partition plate is attached to the cooling header that cools a range within about 3 m from the end of the rail, and between the surface of the cooling header and the surface of the rail head. The space formed is separated in the rail length direction. Here, the cooling header that cools a range within about 3 m from the end of the rail may be composed of one or a plurality of cooling headers, and is also used as a cooling header that cools the center side of the rail. It may be Further, the partition plate is preferably provided in a direction orthogonal to the length direction of the rail,
It may be arranged diagonally in the length direction of the rail to divide the space formed between the surface of the cooling header and the surface of the rail head in the rail length direction.

[0006]

In order to solve the above problems, the inventor has
The air flow during cooling was investigated to find the cause of the increase in hardness near the rail ends. As a result, even though the direction of air discharged from each part of the cooling header is perpendicular to the rail surface, air flow occurs in the rail length direction on the rail surface near the rail end. I found out that Moreover, the range is within 3 m from the rail end, and this air flow in the rail length direction increases the cooling efficiency of the rail surface near the rail end with respect to that at the center of the rail. It was estimated that the hardness near the rail ends increased compared to that at the center.

Therefore, the present inventor has invented a technique for making the substantial cooling efficiency of the rail surface near the rail end portion during cooling equal to that at the rail central portion by blocking the air flow in the rail length direction. . As a specific method, as described above, one or more partition plates that restrict the air flow so that the cooling air flow near the rail end is perpendicular to the rail surface are provided within 3 m from the rail end. It has been found that it is suitable to arrange the rails so that the flow in the direction toward the end of the rail is blocked and the hardness of the top of the rail is made uniform as shown in an example in FIG.

When the partition plate is installed at a position closer to the center than the end of the rail by 3 m and the partition plate is not arranged on the end side of the rail, cooling air rails are again installed on the end side of the partition plate. A flow in the lengthwise direction occurs and
It has also been found that the above problem cannot be solved by causing an increase in hardness in the vicinity of the end portion as shown in Example 1. Moreover, after arranging the partition plate within 3 m from the rail end part, further installing a plurality of partition plates toward the central part,
Although the effect did not decrease, the effect did not increase with the addition of the partition plate.

[0009]

Embodiments of the present invention will now be described with reference to the accompanying drawings to provide an understanding of the present invention. Here, FIG. 1 is a sectional view of a cooling device to which an embodiment of the present invention is applied, FIG. 2 is a partial side view of the cooling device (note that the rail length direction is shown in a reduced scale), and FIG. FIG. 4 is a bottom view of the nozzle plate, and FIG. 4 is a graph showing the hardness of the rail top from the rail end.

As shown in FIGS. 1 and 2, a cooling device 10 to which a rail heat treatment method according to an embodiment of the present invention is applied.
Has a cooling header 12 on the top of the rail 11, cooling headers 13 and 14 on the head side of the rail 11, and a partition plate 15 arranged between the cooling headers 12 to 14.

As shown in FIG. 3, each of the cooling headers 12 to 14 has a nozzle plate 16 having a large number of blowing holes 16a formed on the surface thereof, and the cooling headers 12 to 14 are divided into a plurality of stages in the rail length direction, each of which is provided with an air supply pipe 17. The air sent from ~ 19 is blown out substantially uniformly. Although a gap is provided between the adjacent cooling headers 12 and 13 and the cooling headers 12 and 14 in this embodiment,
Adjacent cooling headers 12 and 13 and cooling header 1
It is also possible to close the gap between 2 and 14 with a blind plate, which can prevent the airflow from being blown out obliquely from above. Further, the cooling device 10 includes an elevating device (not shown) that simultaneously elevates and lowers the cooling headers 12 to 14, and descends and covers the rail 11 only when the heat treatment of the rail 11 is performed.

The partition plate 15 is, as shown in FIG.
In this embodiment, five partition plates 15A to 15E are arranged within 3 m from the end of the cooling header 12 so as to be substantially perpendicular to the rail traveling direction. It should be noted that the partition plate 15A arranged at the most end portion is arranged at a position deviated from the rail end portion and seems to be wasteful.
This is because they are arranged in consideration of a positioning error when they are carried into the cooling device 10, and it is possible to provide a larger number in order to further reduce the influence of the positioning error of the rail end portion. .

The gap between the partition plate 15 and the rail 11 is about 2 mm, but it is desirable to make this gap as small as possible within a range that does not hinder the vertical movement of the cooling header. Further, in this embodiment, the partition plate 15 has a U-shaped inner portion that covers the rail 11, but the partition plate 15 can be formed in a similar shape to the head cross-sectional shape of the rail 11 to reduce the gap. In FIG. 2, reference numeral 20 denotes a chain conveyor that conveys the rail 11.

By thus providing the partition plate 15, the air blown out from the cooling headers 12 to 14 does not flow in the longitudinal direction of the rail 11, so that the rail 1
Heat treatment can be performed under the same conditions as in the central portion of No. 1, so that the hardness of the top portion of the rail becomes uniform. FIG. 4 is a hardness distribution in the length direction of the rail top portion thus obtained. Compared to the hardness distribution of the rail according to the conventional heat treatment method shown in FIG. 6 and the hardness distribution of the rail heat treated by placing one partition plate 5 m from the end of the cooling header shown in FIG. It can be seen that a significant reduction effect of fluctuations is obtained.

In the above embodiment, since the distance between the rail end and the cooling header end is small, the partition plate 15
The mounting position of was set within 3 m from the end of the cooling header, but if the distance between the rail end and the cooling header end is large, the partition plate will be installed within 3 m from the rail end. .

[0016]

According to the rail heat treatment method of the present invention, at least one partition plate is attached to a cooling header that cools a range within about 3 m from the end of the rail, and the surface of the cooling header is Since the space formed between the surface of the rail head and the rail head is separated in the rail length direction, air movement in the rail length direction is almost eliminated, and the rail is uniformly heat-treated. The hardness of the top becomes uniform. As a result, the wear caused by the use of rails was evened out, train travel was smooth, and track maintenance costs were reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a cooling device to which an embodiment of the present invention is applied.

FIG. 2 is a partial side view of the cooling device.

FIG. 3 is a bottom view of the nozzle plate.

FIG. 4 is a graph showing the hardness of the rail top portion from the rail end portion when one embodiment of the present invention is applied.

FIG. 5 is a graph showing the hardness of the rail top from the rail end when a partition plate is provided 5 m from the rail end.

FIG. 6 is a graph showing the hardness of the rail top from the rail end when heat treatment is performed according to the conventional example.

[Explanation of symbols]

 10 Cooling device 11 Rail 12 Cooling header 13 Cooling header 14 Cooling header 15 Partition plate 15A Partition plate 15B Partition plate 15C Partition plate 15D Partition plate 15E Partition plate 16 Nozzle plate 16a Blowout hole 17 Air supply pipe 18 Air supply pipe 19 Air supply pipe 20 chain conveyor

Claims (1)

[Claims] 1. A heat treatment method for a rail, wherein a hot-rolled rail is directly heat-treated by a cooling device having a cooling header and surrounding substantially the entire length of the rail head with air as a cooling medium. At least one partition plate is attached to a cooling header that cools a range within about 3 m from the end of the rail in the cooling header, and is formed between the surface of the cooling header and the surface of the rail head. A rail heat treatment method characterized in that a space is separated in the rail length direction.