JPH09168814A - Method for preventing vertical bend of rail - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rail without vertical bend after cooling down to room temp. SOLUTION: A rail 1, after hot rolling, the temp. of the head part 11 of which is higher and the temp. of the bottom part 13 is lower is made in the state where the belly part (web) 12 is horizontal by arranging a jig 51 under the head part in the state where the rail is horizontally laid and the middle part in the longitudinal direction is fixed with a stopper 4. The head part is elongated by bending the other part in a direction in which the head part becomes convex with a transfer 5, even after the high-temp. head part shrinkes greatly thermally after cooling, by making the length of the head part same as the bottom part, the rail without vertical bend is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has less bending when cooled to a higher temperature and does not require straightening thereafter.
Alternatively, the present invention relates to a rail manufacturing method that requires a small correction amount.

[0002]

2. Description of the Related Art Rails for railroads are manufactured by hot rolling, but due to their special shape, the temperature distribution that was uniform immediately after the start of rolling has a considerable difference in position in the latter half of rolling. . That is, the bottom portion 13 (hereinafter, the lower flange portion when the rail is in use is referred to as the bottom portion.
The portion in contact with the wheel is referred to as a head portion 11, and the web portion between the head portion and the bottom portion is referred to as an abdominal portion 12. ) Has a large surface area with respect to the amount of steel as compared with the head, the amount of heat transfer to the rolls and the like is larger than that on the head side, and as a result, the temperature becomes lower than the head.

For example, the temperature difference between the head portion and the bottom portion at the end of rolling reaches 200 ° C. in the example shown in FIG. If you cool the rail with this temperature difference as it is,
Naturally, the heat shrinkage of the hot head becomes larger than the heat shrinkage of the cold bottom, and after sufficient cooling, bending occurs in the direction in which the head becomes concave (the bottom becomes an outer circle). .

On the other hand, since the rail is asymmetric as described above, even if there is no temperature difference inside the rail at the start of cooling, the cooling rate during cooling differs depending on the position.
It is also known to bend up and down.

Many techniques have been studied to reduce or eliminate the bending of the rail after cooling. However, most of them are disclosed in JP-A-59-31824.
JP-A-61-60827, JP-A-63-
As disclosed in Japanese Patent No. 114923, Japanese Patent Application Laid-Open No. 6-218423, etc., it is a measure against bending that occurs during cooling of a rail once heated to a uniform temperature, and at the end of hot rolling. The technique paying attention to the bending due to such a temperature difference is only found in Japanese Patent Laid-Open No. 5-76921.

In this Japanese Patent Laid-Open No. 5-76921,
It is described that a rail with less bending can be obtained after cooling by bending the end of the rail so that the head is convex at high temperature.

[0007]

Correcting the bend generated in the rail after cooling is remarkably low in efficiency and high in cost. Further, if the amount of correction is large, there arises a problem of deterioration of internal quality such as increase in residual stress.

However, as described above, most of the techniques for the cooling method for obtaining a rail with less bending after cooling are performed on the assumption that a straight and uniform high temperature rail is first obtained. ing. Therefore, it can be said that this is not an essential solution, although it can be applied to some extent to a cooling method in which bending does not occur in a rail having a large internal temperature difference after hot rolling.

The technique described in Japanese Patent Application Laid-Open No. 5-76921 is a technique for reducing the bending of the end portion, which is difficult to straighten the roll, and is a technique with low equipment cost and high efficiency. However, the center portion of the rail in the length direction is premised on roll straightening, and it can be said that this is a rather half-finished technique aiming at a limited effect, and the number of steps may increase in some cases. In addition, it is expected that there will be a problem in terms of quality that a complicated bend will remain in the product due to the difference in width between the head and the bottom.

[0010]

DISCLOSURE OF THE INVENTION The inventors of the present invention have investigated various methods with the aim of establishing a technique for manufacturing rails with high straightness which is efficient, economical, and relatively simple equipment. Then, the invention described below was completed.

Conventionally, the bending of the rail after cooling has been attributed to the difference in temperature at the start of cooling (at the end of rolling) and the difference in cooling rate between the head and the bottom in the cooling process. The bending caused by the difference in the cooling rate between the head and bottom during the cooling process is such that when cooling a rail with a completely uniform temperature, the temperature at the bottom first drops and the head becomes convex. The part is compressed and shortened, and after the head is cooled, the head is shorter than the bottom, so that the head bends in a direction in which it becomes concave.

However, the present inventors have found that the bending caused by this cooling rate is not so large in reality when the temperature of the head is high, because the cooling rate of the head is high, and the bending that occurs after cooling is The present invention has been completed based on the finding that it is substantially determined by the temperature distribution inside the rail at the start of cooling (at the end of rolling).

According to the present invention, the head portion, which becomes shorter after cooling, is bent to be convex in a high temperature state so as to be extended, and the head portion after cooling and the bottom portion have the same length.
The invention, when cooling a high temperature rail, estimates the temperature distribution of the rail, predicts the vertical bending amount that occurs after cooling to room temperature, and bends the rail in the vertical direction in advance so that the bending amount becomes zero. This is a method to prevent the rail from bending up and down.

The second invention is a method for preventing vertical bending of a rail, which is carried out by the steps shown in the first invention. A) A step of measuring the rail temperature. (B) The step of obtaining the bending amount from the estimation result of the temperature distribution of the rail, and (c) the jig 51 which can be moved together with the rail is placed under the head in the horizontal position of the rail, and A step in which the surface connecting the bottom centers is made horizontal, and d) a step in which the rails are moved by a plurality of transfers 5 parallel to the surface connecting the center of the rail head and the center of the rail and in a direction perpendicular to the longitudinal direction of the rails, E) Put the stopper 4 on the center of the rail in the longitudinal direction,
Stopping the movement of this part, and continuously moving the other part of the rail by transfer to bend the rail so that the head becomes convex. Process.

The bending process is performed so as to form an arc having a head as an outer circle. The amount of bending is calculated from the rail dimensions, temperature distribution during processing, etc. The direction of applying the bending force needs to be substantially parallel to the plane connecting the center of the head and the center of the bottom. It need not be perpendicular to the bottom surface (the surface opposite the bottom head) or the top surface. It is sufficient that the arc connecting the center of the head of the rail after bending and the arc connecting the center of the bottom are both concentric circles and on the same plane.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, bending is performed at a high temperature in the opposite direction to the bending direction after cooling. It is of course within the scope of the present invention to repeat the experiment to determine the temperature of each part of the rail and the bending amount corresponding to the temperature difference.

For example, there is a rail manufacturing method that goes through the following steps. 1) a step of measuring the temperature of the rail, 2) a step of obtaining the temperature difference between the head and the bottom of the rail, 3) a step of obtaining the bending amount from the temperature and the temperature difference between the head and the bottom of the rail, 4) Rail bending process, and 5) Cooling process.

The temperature difference mainly corresponds to the amount of bending after cooling. Further, the temperature is related to the amount of springback during bending.

Of the above steps, 3) instead of the step of obtaining the bending amount from the temperature and temperature difference between the head and bottom of the rail, 3 ') the step of obtaining the bending amount from the estimation result of the temperature distribution inside the rail It is also possible to In addition, 3 ') the step of obtaining the bending amount from the estimation result of the temperature distribution inside the rail will be more specifically described. 3-1) From the estimation result of the temperature distribution inside the rail,
(1) using the equation, and obtaining a temperature moment _{Mθ, Mθ = αE∫ s T ·} Zds ·············· (1) where alpha: linear expansion coefficient E: Young's modulus T: Temperature S: Total of section of rail section Z: Distance from center point of section of rail toward head or bottom direction 3-2) Bending after cooling to room temperature using the temperature momen Mθ The step of obtaining the quantity hθ from the equation (2), and hθ = MθL ² / 8E ² (2) where L: rail length 3-2) In consideration of the amount of springback, the bending amount after the unloading of bending is hθ, and the step of obtaining the condition h ₀ for bending so that the directions are opposite to each other by the equation (3), h ₀ = hθ + L ² M / 8EI .............. (3) where M: bending moment (material of when given a bend h ₀ Calculating from academic theory) I:. From the center point of the cross-section of the rail, the line perpendicular to the direction connecting the head and the bottom (Y-axis) becomes about the moment of inertia.

The steps of 4) bending the rails are as follows.
The distance from the center of the direction is h₀Bend the rails to
This is the pulling process, where the center of the line connecting both ends of the rail.
Points are the corresponding positions in the widthwise cross section at both ends of the rail.
It is the center point of the line that connects the
Distance h ₀Means that between the center points before and after bending
Distance h₀To become.

When performing the bending work with the rail placed horizontally, in order to perform the bending work as described above, the bending work is carried out with the rail standing up (corresponding to the azimuth of the usage state of the rail). Unlike that, it requires special equipment.

FIG. 3 shows a state in which the rail is moving in order to perform bending with the rail placed horizontally. Reference numeral 1 is a rail in a high temperature state, 3 is a cooling floor, and 5 is a transfer for moving the rail for bending. In this case, the rail head 11 is directly on the cooling floor, and the rail is in the bottom direction (left direction).
When a part of the bottom part 13 is fixed to a stopper 4 (not shown) and then the movable transfer further moves in the direction of the arrow to bend the rail, the rail moves only up and down. Instead, it has a complicated shape that is bent in the left-right direction, and the shape after cooling is also bent.

FIG. 4 shows a state in which the jig 51 is arranged under the head so that the head does not directly contact the cooling floor and the abdomen is horizontal. This jig moves with the transfer. When the rail is bent in this way, the rail can be bent only in the vertical direction.

The force is fixed at the center of the bottom so that the head is convex (the point where the force is applied is hereinafter referred to as the force point).
Of course, even if the end of the head is moved, on the contrary, the end of the head is used as a fixed force point, and the center of the bottom may be moved, or a force may be applied so that both move.

The number of fixed and movable power points is not particularly specified.
It is sufficient that the total number is three or more and that the rails are symmetrical with respect to the central portion in the length direction of the rail. The direction of the force applied to each force point is also not specified. They may be parallel to each other, may be directed to the same point, may be diverged from the same point, and may be other than these. The amount of bending is appropriate, and the condition is that the surface connecting the center of the head and the center of the bottom after bending is on the same plane as the surface connecting the center of the head and the center of the bottom before bending.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.
The rolled high-temperature rail 1 is transferred from the upper right side of the drawing to the rail carry-in table 2 in a horizontal position by a roller (not shown). Here, the transfer 5 is located at the position indicated by the broken line, that is, on the head side of the rail on the right side of the position where the rail is loaded. Further, the jig 51 that holds the head from below and keeps the abdomen of the rail horizontally in a horizontal position is located on the rail carry-in table side at the right end of the cooling floor, which is the position indicated by the broken line.

When the rail is loaded to the left of the transfer, the transfer moves the rail to the side of the cooling floor. In FIG. 1, the number of transfers is three in order to simplify the drawing, but the larger the number, the more accurately the shape of the bending process can be controlled. The bottom of the rail rests on the cooling floor over the jig, the bottom rests on the cooling floor, and the head rests on the jig, and the plane connecting the head center and the bottom center of the rail is substantially horizontal.

In this state, while the head of the rail is supported by the jig, the rail is moved to the left by a certain distance by the transfer, and eventually the bottom center portion of the rail hits the stopper 4 protruding on the cooling floor and the center portion of the rail. Stops moving. However, since there is no stopper near the end of the rail, the end of the rail is moved further leftward by transfer, and the rail keeps the surface connecting the center of the head and the center of the bottom horizontal, It is bent so that the parts are convex.

After reaching the predetermined bending amount, the stopper dives under the cooling floor, all the transfers move to the left again and move the rail to the left, and then the transfer and the jig return to their original positions. , Wait for the next rail loading.

Since the jig for holding the position of the head does not need to keep the abdomen of the rail horizontal after the rail is restrained by the stopper and the transfer, it does not need to move together with the transfer. , You may return to the original position first.

The above embodiment will be further described with reference to FIG. The high temperature rail 1 is horizontally transferred to the rail loading table 2 as shown in (5-1). Here, the transfer 5 is waiting on the right side of the rail. Also,
The jig 51 for keeping the abdomen of the rail horizontal is located at the right end of the cooling floor 3 on the side of the rail carry-in table.

Next, the transfer moves the rail to the cooling floor side (5-2), the bottom of the rail goes over the jig and is placed on the cooling floor, the bottom is on the cooling floor, and the head is on the jig. The surface connecting the center of the head and the center of the bottom of the rail is almost horizontal. (5-3)

In this state, the head is supported by the jig and the rail is moved leftward by a certain distance by the transfer (5-3). Eventually, the center of the bottom of the rail pops out on the cooling floor. When the rail 4 hits the stopper 4, the movement of the central portion of the rail stops.

However, since the stopper 4 is not arranged near the end of the rail, the end of the rail is further moved to the left by transfer, and the rail horizontally connects the plane connecting the center of the head and the center of the bottom. While keeping it, bend it so that the head becomes convex. (5-4) In addition, 52 is a stopper that determines the movement amount of each lancer 5 for realizing the bending amount hθ determined by the equation (3), and the jig moves to the left of this stopper 52. do not do.

After the predetermined bending amount is reached, the stopper 4 dives under the cooling floor, and all the transfers move to the left again to move the rail to the left, after which the transfer and the jig are returned to their original positions. Return to and wait for the next rail to be loaded. (5-5, 5-6)

In the embodiment shown in FIG. 6, the transfer 5 with a jig and the transfer 6 without a jig are alternately arranged. The transfer 5 and the transfer 6 have a mechanism to move by different hydraulic systems.

The bottom of the rail 1 hits the stopper 4,
The movable transfer 5 accompanied by the jig 51 further moves a predetermined distance, bends the rail by a predetermined amount, and then returns to the original position together with the jig. After the rail reaches a predetermined curvature, the stopper hangs down on the cooling floor, and the transfer 6 moves further to return to the position after transferring the rail for a predetermined distance. Reference numeral 10 is a rail that has been cooled and straightened.

Of course, the pattern is not limited to the above pattern, and rails having substantially the same shape can be obtained by the bending method described below. 1) (Transfer 5, transfer 6, jig 5
1, the rail 1 starts moving → (the center of the bottom of the rail corresponds to the stopper 4) → (the jig stops moving again) → (the transfer 5 stops moving) →
(Transfer 6 stops due to a certain amount of bending)
→ (Stopper goes down) → (Transfer 6 restarts moving) 2) (Transfer 5, transfer 6, jig 5
1, the rail 1 starts to move) → (the center of the bottom corresponds to the stopper 4 and the jig and the transfer 5 stop moving and return) → (the predetermined amount of bending causes the transfer 6
Stop moving) → (stopper lowers) → (transfer 6 restarts moving) 3) (transfer 5, transfer 6, jig 5)
1, rail 1 starts moving → (bottom center part hits stopper 4) → (transfer 5, transfer 6, jig stops moving due to a certain amount of bending) → (stopper lowers) → (transfer 5, cure The tool returns and the transfer 6 resumes its movement).

The first rail of the 50-kg rail having a length of 25 m after the start of hot rolling had a temperature distribution as shown in FIG. Based on this temperature distribution, the bending amount calculated using the above equations (1), (2) and (3) was 900 mm. Repeating the same operation for the 10 subsequent pieces, the processing amount range is 8
Bending of 50 to 950 mm was performed.

The amount of bending of these rails after cooling is
It was within ± 10 mm (+ is a convex head) and no correction was necessary. After that, 110 rails were heated to 690 to 710 ° C, 490 to 510 ° C, and the temperature difference between the head and the bottom was 1 respectively.
Confirm that the temperature is between 90 and 210 ° C,
Bending was performed in the range of 70 to 920 mm.

As a result, there were 102 rails in which the amount of bending after cooling the rails was within ± 10 mm.
There were eight that exceeded ± 10 mm (within ± 20 mm). The amount of bending after cooling of 10 rails that were not bent by the method of the present invention was 800 to 90.
It was in the range of 0 mm and required a large correction.

[0042]

According to the method of the present invention, it is possible to efficiently and economically obtain a rail having a small bend. The method of the present invention is an innovative process that does not require straightening after cooling. It is also an excellent method that can be applied regardless of the material of steel and cooling rate, and has a low residual stress of the product.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus for implementing the present invention.

FIG. 2 is a diagram showing a temperature distribution of a rail after completion of hot rolling.

FIG. 3 is a cross-sectional view of a rail in a horizontal position.

FIG. 4 is a cross-sectional view of a state in which a jig is arranged under the head of a rail and is horizontally placed.

FIG. 5 is an explanatory diagram showing a method for carrying out the present invention.

FIG. 6 is a conceptual diagram of an example of an apparatus for carrying out the present invention.

[Explanation of symbols]

 1-High temperature rail 11-High temperature rail head 12-High-temperature rail belly 13-High-temperature rail bottom 2-Rail loading table 3・ ・ ・ Cooling floor 4 ・ ・ ・ Stopper 5 ・ ・ ・ ・ ・ Transfer (with jig) 51 ・ ・ ・ ・ Jig for maintaining the height of the head 52 ・ ・ ・Jig stopper to keep height 6 …… Transfer (without jig)

Claims (2)

[Claims] 1. When cooling a high-temperature rail, the temperature distribution of the rail is estimated, the vertical bending amount that occurs after cooling to room temperature is predicted, and the rail is bent in the vertical direction in advance so that the bending amount becomes zero. A method to prevent vertical bending of rails, which is characterized by processing. 2. The method for preventing vertical bending of a rail according to claim 1, wherein the method includes the following steps. A) A step of measuring the rail temperature. (B) The step of obtaining the bending amount from the estimation result of the temperature distribution of the rail, and (c) the jig 51 which can be moved together with the rail is placed under the head in the horizontal position of the rail, and A step in which the surface connecting the bottom centers is made horizontal, and d) a step in which the rails are moved by a plurality of transfers 5 parallel to the surface connecting the center of the rail head and the center of the rail and in a direction perpendicular to the longitudinal direction of the rails, E) Put the stopper 4 on the center of the rail in the longitudinal direction,
Stopping the movement of this part, and continuously moving the other part of the rail by transfer to bend the rail so that the head becomes convex. Process.