JPH1017995A - Rail with high strength and damage resistance, having hardness distribution excellent in damage resistance in railhead vertex part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a high-strength and damage-resisting rail free from the occurrence of local concentration of accumulation of fatigue in a railhead vertex part and excellent in contact fatigue damage resistance by providing the railhead vertex part with proper hardness distrubution. SOLUTION: The rail is produced by hot rolling by using, as a stock, a steel slab which has a composition containing, by weight, 0.60-0.85% C, 0.1-1.0% Si, 0.5-1.5% Mn, <0.035% P, <0.04% S, and <0.05% Al and further containing specific small amounts of at least one element among Cr, Mo, V, Ni, and Nb. The rail with a temp. not lower than the Ar1 point is cooled by an air header and formed into fine pearlitic structure, and further, by means of regulation of cooling, the hardness of the rail, in a corner part 2 and a railhead side part 3, is regulated to 341-405 Brinell hardness HB, and, as to the hardness of a railhead vertex part 1, hardness is gradually increased with the approach from the central part to a position at a distance of 20mm in a width direction and the hardness in this position is regulated to 341-405 Brinell hardness HB and the hardness in the central part is regulated to a value lower than the hardness in the above position by 10-50 Brinell hdrdness HB.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength, damage-resistant rail for abrasion resistance used on a sharp curve of a high axle heavy railway.
In particular, it relates to a high-strength, damage-resistant rail with improved damage resistance at the crown.

[0002]

2. Description of the Related Art The head of a rail generally has a crown, a corner, a head side, and a jaw. And, in the track using wooden sleepers in the sharply curved part of the high axle heavy railway, the conventionally used high-strength rail for wear resistance has a hardness between the corner part and the head side part, and the top part. It is formed by heat treatment so as to be equal. Therefore, from the viewpoint of the material, the wear resistance characteristics of the rail corner portion and the rail top portion are equal.

[0003] However, the contact between the wheel and the rail is complicated, and the contact environment differs depending on the position of the rail head. In the sharply curved section of the high axle heavy railway, the slip acting on the rail gauge corner (inner corner) and the rail head side surface is large, while the contact pressure is large at the rail head and the rail gauge corner. As a result, in the conventional high-strength rail for wear resistance, the wear of the rail gauge corner portion and the rail head side portion is promoted more than the rail top portion. Therefore, the rail top always wears more slowly than the rail gauge corners, and the contact pressure from the wheels is greatest at the center of the rail top where wear is slower.

[0004] Such a conventional high-strength rail for wear resistance, in which the wear characteristics of the rail head are uniform, comes into contact with the wheel as described above. It is slow in adaptation, has a long local excessive contact stress, and is liable to cause fatigue defects. In addition, the maximum contact pressure acts on the center of the top of the rail even after the rail and the wheel are fitted. In the case of tracks using wooden sleepers, there are few problems in such a state, but in the case of high rigidity tracks using concrete sleepers,
The problem that the damage called a head check occurs at the center of the top of the rail has become evident because the maximum contact pressure that has a shock increases as the railway vehicle passes.

Conventionally, in order to prevent such a head check, a method has been adopted in which the surface of the rail head is ground before fatigue accumulates on the rail. Also, it is difficult to determine the optimum cutting time.

On the other hand, JP-A-6-17193 discloses that
A rail that can prevent such a head check occurring at the center of the crown is shown. This rail has a high hardness at the corners and the head side, and a hardness at the top of the head is set to 0.9 or less of the hardness at the corners and the head side, and thus the hardness of the top is reduced. Thus, the wear rate of the portion is increased, the contact force at the top of the head is dispersed, the maximum contact stress is reduced, and damage to the top of the head is reduced.

However, the occurrence of damage to the crown is governed by the contact stress, and the contact stress and its distribution are governed by the distribution of the wear rate of the crown, that is, the distribution of the crown in the rail width direction. Even when the hardness range of the corner portion and the head side portion and the hardness range of the top portion are specified, the damage reduction effect may not be obtained, and the life of the rail may not always be long.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an appropriate hardness distribution at the top of the rail so that local concentration of fatigue accumulation does not occur at the top of the rail, and the resistance to the top is reduced. It is an object of the present invention to provide a high-strength, damage-resistant rail which has excellent contact fatigue damage, can reduce track maintenance costs as a result, and has a long service life.

[0009]

In order to solve the above-mentioned problems, the present invention firstly provides C: 0.60-0.
85%, Si: 0.1-1.0%, Mn: 0.5-1.
5%, P: 0.035% or less, S: 0.040% or less,
Al: is 0.05% or less, the balance being Fe and unavoidable impurities, the hardness of the corner and head side portions are H _B three hundred and forty-one to four hundred and five in Brinell hardness in the width direction from the top center of the top portion The hardness at a position 20 mm apart is H _B 341 to 405, and the hardness at the center of the crown is
The Brinell hardness is 10 to 50 lower than the hardness at a position 20 mm in the width direction from the center of the crown, and the hardness between the center of the crown and the position 20 mm in the width direction from the center of the crown is the width from the center of the crown. Monotonically increasing outward in the direction
The actual hardness of the portion in between, the hardness at the center of the crown of the portion in between and the width of 20 mm from the center of the crown in the width direction.
Provided is a high-strength, damage-resistant rail in which the difference from the hardness obtained by interpolating the hardness at a distant position with a straight line is within 10 in Brinell hardness.

Second, C: 0.60 to 0.8 by weight%
5%, Si: 0.1 to 1.0%, Mn: 0.5 to 1.5
%, P: 0.035% or less, S: 0.040% or less, A
l: 0.05% or less, and Cr: 0.05 to
1.5%, Mo: 0.01 to 0.20%, V: 0.01
-0.10%, Ni: 0.1-1.0%, Nb: 0.0
Containing one or more of 05 to 0.15%, the balance being Fe and unavoidable impurities, the hardness of the corner portion and head side portions are H _B three hundred and forty-one to four hundred and five in Brinell hardness, its head 20 mm in width direction from the center of the top at the top
The hardness at the distant position is H _B 341 to 405, and the hardness at the center of the crown is 10 to 50 Brinell hardness lower than the hardness at a position 20 mm in the width direction from the center of the crown, and the center of the crown and the head are The hardness between the top center and the position 20 mm apart in the width direction monotonically increases from the center of the top toward the outside in the width direction, and the actual hardness of the portion between the top and the center of the top is And a hardness obtained by interpolating the hardness at a position 20 mm apart from the center of the crown in the width direction with a straight line and having a Brinell hardness of 10 or less.

The occurrence of damage to the top of the rail is governed by the contact stress, and the contact stress and its distribution change with the progress of the wear-in. The change process is the distribution of the wear rate, that is, the hardness distribution in the rail width direction. Is governed by

According to the study of the present inventors, if this hardness distribution is appropriate, the technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. HEI 6-17193 can greatly reduce the damage. It has been found that local contact stress may be concentrated in accordance with the progress of wear-in and the damage reduction effect may be lost.

That is, in the above-mentioned Japanese Patent Laid-Open No. 6-17193, only the hardness range of the corner portion and the head side portion and the hardness range of the top portion are described, and nothing is described about the hardness distribution in the rail width direction. Therefore, there is a possibility that the contact stress and the hardness distribution that makes the distribution appropriate are not obtained at the top of the head.

Further, in the above-mentioned Japanese Patent Application Laid-Open No. 6-17193, the hardness at the top of the head is specified to be 0.9 or less of the hardness at the corners and the side of the head, which surely increases the contact stress at the top of the head. Decrease.

However, as a result of research conducted by the present inventors,
When the difference in hardness between the crown and the corners increases in this way, the contact stress at the center of the contact portion is greatly reduced. It was found that damage could progress at that location. Therefore, the life of the entire rail may not be extended.

Therefore, in the present invention, as described above, by controlling the hardness distribution in the width direction of the top of the rail to control the process of changing the contact stress due to the progress of adaptation,
To prevent the local concentration of fatigue accumulation on the rail top, and to improve the contact fatigue damage resistance of the rail top in a high-rigidity track use environment.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

FIG. 1 is a sectional view showing the head of the high-strength and damage-resistant rail according to the present invention. The rail head has a top part 1, a corner part 2, a head side part 3, and a jaw part 4.
One of the corners 2 is a gauge corner that comes into contact with the wheel during use.

[0019] Damage to the rails, especially head checking of the crown 1, occurs in a short period of time as the contact stress applied to the rail head increases. This will be described with reference to FIGS. FIG. 2 shows that the radius of curvature of the tread is 1
5mm rail specimen with a maximum diameter of 30mm and 30mm diameter
FIG. 4 is a schematic diagram showing a two-cylinder contact rolling fatigue test method using a wheel test piece having a flat peripheral surface. When the relationship between the vertical load and the damage life is obtained by this test, the result shown in FIG. 3 is obtained. That is, it can be confirmed that when the vertical load is high, that is, when the contact stress is high, damage occurs in a short period (that is, the damage life is short).

On the other hand, in the initial stage of using a new or modified high-strength rail, if the familiarity with the wheels is not good,
Concentrated vertical load acts on the rail, which easily causes damage. In addition, when the shape of the portion of the rail that contacts the wheel conforms to the wheel due to the wear of the rail, vertical stress selectively acts on the portion where the wear rate is low. From these facts, it can be said that in order to extend the service life of the rail, it is effective to disperse the maximum normal stress that has been severely acting due to the low wear rate on the top surface of the conventional rail.

As described above, in order to prevent the head from being checked at the crown 1, a method of controlling the contact state so that the contact pressure from the wheels is not locally concentrated can be considered.

In the present invention, the rail composition is adjusted while maintaining the strength and abrasion resistance for supporting the train and reducing the maximum contact stress at the top of the rail. And than the head side,
By making the hardness of the crown lower, the difference between the hardness at the center of the crown and the hardness at a position 20 mm in the width direction therefrom, and by optimizing the hardness distribution therebetween, The contact stress did not locally have a large peak in the course of running-in due to wear, and the contact stress was appropriately dispersed to prevent the local accumulation of fatigue accumulation.

Next, the component composition of the rail according to the present invention will be described.

First, C is 0.60 to 0.85% by weight. When the content is 0.6% or more, good strength and wear resistance can be expected, while when it exceeds 0.85%, toughness is reduced due to precipitation of proeutectoid cementite.

[0025] Si is 0.1 to 1.0% by weight. 0.1% or more is required to secure the rail strength.
%, The toughness and weldability deteriorate.

Mn is 0.5 to 1.5% by weight. 0.5% or more is required to secure the rail strength.
%, The toughness and weldability are adversely affected.

P and S are used to avoid ductility deterioration.
P: 0.035% by weight or less, S: 0.040% by weight or less.

Since Al is a component that deteriorates fatigue performance, the upper limit is 0.05%.

Particularly with respect to rails used in places where contact conditions between the wheels and the rails are severe, in order to further improve the abrasion resistance and strength of the rail gauge corners, C is used.
One or more of r, Mo, V, Ni and Nb are added in a low alloy.

Cr is 0.05-1.50%. 0.
If it is at least 05%, the pearlite lamella spacing will be reduced to make the pearlite finer and improve the strength, abrasion resistance and damage resistance, but if it exceeds 1.50%, the weldability will be adversely affected.

Mo is 0.01 to 0.2% by weight. M
o is an element that increases the strength similarly to Cr, and its effect appears at 0.01% or more. In contrast, 0.2%
If it exceeds, weldability will deteriorate.

Nb and V are precipitation strengthening elements, and are 0.005 to 0.15% by weight and 0.01 to 0.10% by weight, respectively. In order for these to obtain the effect as a precipitation strengthening element, it is necessary to add 0.005% or more of Nb and 0.01% or more of V. On the other hand, if Nb exceeds 0.15% or V exceeds 0.10%, coarse carbonitrides of Nb or V precipitate and deteriorate the toughness of the rail.

Ni is an element effective for improving strength and toughness, and is 0.1 to 1.0% by weight. If the amount is less than 0.1%, the effect does not appear, and the effect is saturated at 1.0%.

The rail according to the present invention has such a component composition and has a fine pearlite structure. And
In the present invention, as described above, in controlling the wear characteristics of each part of the rail by adjusting the hardness distribution of the rail head, in particular, adjusting the hardness distribution at the top of the head to reduce the wear resistance of that part. By controlling and appropriately controlling the change in contact stress caused by wear-in progress due to wear, fatigue accumulation is dispersed, and head check damage at the top of the rail due to generation of high contact pressure in a highly rigid track is suppressed. A preferred hardness distribution is achieved, for example, by adjusting the heat treatment in each part.

The same effect can be obtained even if the wear rate is adjusted by changing the metal structure of the crown. That is, in the present invention, the hardness distribution of the rail is adjusted by appropriate treatment on the premise of the fine pearlite structure, but by changing the metal structure, the wear characteristics can be controlled regardless of the hardness. . For example, as shown in FIG. 4, for the same hardness, the fine pearlite structure has the best wear characteristics. Also, as shown in this figure,
By controlling the metal structure, it is also possible to increase the wear rate while increasing the hardness and improving the fatigue strength.

Next, the reasons for limiting the hardness of the rail having a fine pearlite structure of the present invention will be described.

The hardness of the rail corner portion and the head side portion is H _B 3
Set in the range of 41~H _B 405. This is to make the strength and wear resistance of the rails sufficient.

The hardness distribution at the top of the head is as shown below. That is, hardness H at position apart 20mm in the width direction from the top center of the top portion _B three hundred forty-one to four
The hardness at the center of the top of the head is 1 Brinell hardness compared to the hardness at a position 20 mm in the width direction from the center of the top of the head.
The hardness between the center of the crown and the position 20 mm apart from the center of the crown in the width direction monotonically increases from the center of the crown toward the outside in the width direction. The difference between the hardness at the center of the crown and the hardness obtained by interpolating the hardness at the position 20 mm apart in the width direction from the center of the crown with a straight line in the portion between them is 1 in Brinell hardness.
It is within 0.

The reason for defining the hardness distribution at the top of the head in this manner is as follows. The contact width between the wheel and the rail is the smallest when it is new or immediately after cutting (approximately 10 mm in the case of a high axle heavy railway), and gradually widens as the break-in progresses due to wear. In response, the contact force is dispersed, and the contact stress distribution changes to a flat one. The relationship between the contact stress distribution and the hardness distribution in this running-in process was investigated variously by numerical simulation.

FIG. 5 shows the distribution of the contact stress in the width direction on a rail having a uniform hardness at the top of H _B 368. In the figure, only the right half from the center of the crown is shown.

From this figure, it can be seen that a large contact stress is generated at the center of the top of the head at the time of new use or at the beginning of use immediately after cutting, and the contact stress distribution becomes flat as the break-in due to wear progresses. However, the contact stress is always highest at the center of the crown even if the adaptation proceeds. Therefore, the accumulation of fatigue is concentrated at the central portion of the crown, and damage such as a head check occurs at the central portion of the crown.

Next, the contact stress distribution was examined for a case where three types of hardness distributions (cases a, b, and c) as shown in FIG. In case a, the hardness at the center of the crown is 25 lower in Brinell hardness than at a position 20 mm in the width direction from the center of the crown, and in case b, the hardness is 4%.
0 lower, and in case c, lower by 60.

FIG. 7 shows the contact stress distribution of case a, and FIGS. 8 and 9 show the contact stress distributions of cases a to c at 10 million tons and 80 million tons, respectively.
Are shown in comparison with the uniform hardness rail shown in FIG.

By comparing FIG. 7 with FIG. 5, it can be seen that the contact stress at the center of the top of the rail of the case a decreases faster than that of the case a with uniform hardness. This is because wear progresses faster than at the periphery because the hardness at the center is low. Thereby, the accumulation of fatigue at the center of the crown can be significantly reduced.

On the other hand, as shown in FIG. 7, the contact stress at the end of the contact portion is increased by an amount corresponding to the decrease in the contact stress at the center of the head, and the peak of the contact stress is not at the center of the top of the head but at the end of the contact portion. And the fatigue accumulation at that position increases. However, as shown in FIG. 7, as the adaptation due to wear progresses, the position where the contact stress becomes maximum gradually moves in the rail width direction to the center or the end of the top of the head. In other words, the position where the fatigue accumulation is greatest moves with the progress of familiarization, and the fatigue accumulation is dispersed. Therefore, damage to the rail as a whole is reduced.

According to the study of the present inventors, the phenomenon that the contact stress at the center of the crown decreases and the peak position of the contact stress shifts is almost governed by the hardness distribution from the center of the crown to a position 20 mm in the width direction. Was found. When the hardness in this range increases monotonically and almost linearly from the center of the crown toward the outside in the width direction, the above phenomenon occurs smoothly. However, for example, if there is a portion where the hardness changes from an increase to a decrease in this range, the contact stress at that position becomes abnormally large, causing damage.

Therefore, according to the present invention, "the hardness between the center of the crown and the position 20 mm apart from the center of the crown in the width direction monotonically increases from the center of the crown toward the outside in the width direction. Between the actual hardness of the portion and the hardness at the center of the top of the portion and the width
The difference from the hardness obtained by interpolating the hardness at a position distant by mm with a straight line is within 10 in Brinell hardness. "

As is clear from the comparison of cases a to c in FIGS. 8 and 9, when the difference between the hardness at the center of the head and the hardness at the position 20 mm apart from the center of the head in the width direction increases, The peak of the contact stress generated at the end of the part increases. In case c in which the hardness difference is Brinell hardness of 60, as shown in these figures, the peak value of the contact stress becomes very large, which causes damage. Therefore,
In the present invention, the upper limit of the difference between the hardness at the center of the crown and the hardness at a position 20 mm apart from the center of the crown in the width direction is defined as Brinell hardness of 50.

Conversely, if the difference between the hardness at the center of the crown and the hardness at a position 20 mm in the width direction therefrom is smaller than 10 in Brinell hardness, the contact stress distribution for reducing the damage described above appears sufficiently. Therefore, the lower limit of the hardness difference was set to 10 in Brinell hardness. The preferred range of the difference between the hardness at the center of the crown and the hardness at a position 20 mm in the width direction from the center is 15 to 4 in Brinell hardness.
0.

The hardness at a position 20 mm in the width direction from the center of the top of the head is defined in the range of H _B 341 to H _B 405 for the same reason as setting the hardness of the corner and the head side. Although the hardness between the corner and the position 20 mm apart from the center of the crown in the width direction does not significantly affect the contact stress, the hardness does not fluctuate greatly and the hardness changes almost uniformly or smoothly and monotonously. It is desirable to go.

Even when the hardness distribution is asymmetrical with respect to the center of the crown, it is necessary for each side to satisfy the above-mentioned hardness condition.

In addition, since it is inevitable that the hardness slightly varies in production, a portion where the hardness does not monotonically increase in the width direction locally or microscopically may appear.
In the present invention, it is only necessary that the hardness monotonically increase macroscopically.

Regarding the hardness in the depth direction, it is preferable that the above hardness condition of the present invention is satisfied in a horizontal section at least at a depth of at least 10 mm, preferably 23 mm from the top face. As a result, even when the rail wear has significantly progressed, damage can be reduced.

[0054] Incidentally, slow in the environment in contact conditions between the vehicle and the rail is not very strict as the curve, head side portions, the hardness range in the corner and a position away 20mm from the top center in the width direction H _B 320 it is also possible to lower the to H _B 380.

In the rail according to the present invention, the hardness in the range from the position 20 mm away from the center of the head side, the corner and the top of the head to the corner from the center in the width direction is sufficiently increased to improve the strength and wear resistance of the rail. In the crown, the hardness at the center is made lower than the hardness at a position 20 mm apart from the center in the width direction, and the hardness at the intermediate position is adjusted so as to change almost linearly, thereby causing wear. As the break-in progresses, the contact stress at the central part of the crown, where the wear rate is large, decreases, and damage to that part is suppressed, and the wear rate at the crown is appropriately controlled in the width direction. Since the peak value of the generated contact stress does not become excessive and the peak position moves, as a result, the accumulation of fatigue is not concentrated but dispersed on the top surface of the head. Therefore, the occurrence of fatigue damage is suppressed, the number of times of cutting can be reduced, and as a result, the maintenance cost of the track can be reduced, and the life of the rail can be extended.

[0056]

Embodiments of the present invention will be described below.

The steel having the composition shown in Table 1 within the range of the rail composition according to the present invention was used as the rail material.

[0058]

[Table 1]

A conventional hard-head rail in which a conventional head slack quench heat treatment was applied to a 60 kg rail material formed of steel A in Table 1 and a special head in which cooling at the top of the head was weakened for the same material. A head slack quench and a rail according to the present invention were prepared.

The rail according to the present invention was manufactured as follows. That is, after forming the rail material by hot rolling, the rail material head in Ar ₁ or more, air header air header 5 and the head side portions cooling for arranged parietal cooling as shown in FIG. 10 Air was blown from a plurality of nozzles provided in 6 to cool the rail material head.
FIG. 11A is a view showing the nozzle arrangement of the head cooling air header 5 used here, and as shown in this figure, the number of nozzle holes is reduced at the center thereof. That is, in the conventional header for cooling the top, the nozzle holes are uniformly arranged as shown in FIG. 11B, but here, the number of nozzle holes in the center of the header is reduced, and the header is blown to the top of the rail. The amount of air was reduced. Also, the pressure of the air in the header was controlled so that the air pressure jetted to the top of the head was lower than the air pressure jetted to the side of the head.

FIG. 12 shows the hardness distribution of a portion 1 mm below the top surface of these rails. In FIG. 12, reference symbol A indicates the hardness distribution of the conventional rail, and reference symbols B and C indicate the hardness distribution of the rail of the present invention. In addition, FIG.
The width of the portion where the number of the nozzle holes of the head cooling nozzle header 5 of 1 (a) is reduced is narrower than that of the nozzle header used in manufacturing the rail C.

As is clear from this figure, the reference A of the conventional rail has a substantially uniform hardness distribution from the corner to the center of the crown, whereas the reference B and C of the rail of the present invention.
Had a hardness distribution as shown below.
In other words, the hardness at the center of the crown is 20 m in the width direction from there.
With respect to the hardness at a position apart by m, the code B has 23 (Brinell hardness, the same applies hereinafter) on the left and 21 lower on the right, and the code C has 11 lower on the left and 13 lower on the right. The hardness of both B and C monotonically increases from the center of the head to the position 20 mm away from the center of the head, and the actual hardness of the portion between them and the hardness at the center of the head and in the width direction from the center of the head. The difference from the hardness obtained by interpolating the hardness at the position separated by 20 mm with a straight line was within 6 for code B and within 4 for code C.

Next, the rail material shown in Table 1 was used for a width of 50 mm.
A cylindrical test piece having a hardness distribution in the width direction of the disc by processing the discs, heating them, and then cooling the center of the disc side surface from the corners in the same manner as the above-described rail cooling method. It was created. Table 2 shows the hardness distribution of these test pieces. Here, various hardness distributions are formed in the width direction by adjusting the cooling method, and those having a hardness distribution within the scope of the present invention (examples of the present invention) and those having a hardness distribution outside the scope of the present invention (comparative) Example) was created. In addition, steel type A
Has produced a conventional rail having a uniform hardness without performing such controlled cooling (conventional example).

Using these test pieces, a damage life test was performed using a two-cylinder rolling tester. The hardness of the wheel test piece was about H _B 331. Table 2 shows the test results. In Table 2, the damage life of each test piece is shown as a ratio to the damage life of a test piece corresponding to a conventional rail having a uniform hardness.

[0065]

[Table 2]

As shown in Table 2, in the example of the present invention, it was confirmed that the damage life was improved by 1.3 times or more as compared with the conventional example, and at the maximum was 1.9 times.

From these test results, in order to extend the damage life, it is possible to reduce the contact stress at the center of the crown and to suppress the peak value of the contact stress generated at the end of the contact portion. It has been confirmed that the head hardness distribution of the present invention, which can disperse fatigue accumulation by moving the peak generation position from the center of the head to the outside in the width direction, is effective.

[0068]

As described above, according to the present invention, it is possible to suppress damage to the top of the head caused by an excessive contact pressure such as a head check, and to extend the life of the rail. Therefore, it is possible to solve a problem in introducing a high rigidity track using a concrete sleeper or the like in a sharp curve of a high axle heavy railway, and to reduce track maintenance costs. As described above, the rails of the present invention, which are excellent in wear resistance and damage resistance, are expected to be used with the spread of highly rigid tracks in the future.
It is expected to be effective for reducing railway maintenance costs, and has extremely high economic value.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a head of a rail according to the present invention.

FIG. 2 is a diagram for explaining a two-cylinder contact rolling test for grasping a relationship between a vertical load acting on a rail and a damage life.

FIG. 3 is a diagram showing a relationship between vertical load and damage life in the test shown in FIG. 2;

FIG. 4 is a diagram showing a relationship between hardness and a wear rate and a relationship between a structure and a wear rate in a two-cylinder contact rotating wear test.

FIG. 5 is a diagram showing a change in contact stress distribution with progress of running-in due to wear in a uniform hardness rail.

FIG. 6 is a diagram showing three types of crown hardness distributions obtained by examining changes in contact stress distribution.

FIG. 7 is a view showing a contact stress distribution accompanying the progress of running-in due to wear of the rail according to the present invention.

FIG. 8 is a diagram showing a contact stress distribution at the top of a rail according to the present invention, a rail according to a comparative example, and a rail having a uniform hardness distribution at a top of 10 million passage tons.

FIG. 9 is a diagram showing the contact stress distribution at the top of the rail according to the present invention, the rail according to the comparative example, and the rail having a uniform hardness distribution at the top of the rail at 80 million passage tons.

FIG. 10 is a diagram for explaining a method of cooling a rail material.

FIG. 11 is a diagram showing an arrangement of nozzle holes in a header for cooling the top of the rail used when performing the rail cooling method according to the present invention and the conventional cooling method.

FIG. 12 is a diagram showing an example of hardness distribution of a rail according to the present invention (reference symbols B and C) and a hardness distribution of a conventional rail (reference symbol A).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Top part 2 ... Corner part 3 ... Head side part 4 ... Jaw part 5 ... Head top cooling air header 6 ... Head side cooling air header

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kozo Fukuda 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Hideyuki Yamanaka 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor Kazuki Kobayashi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan In-tube (72) Inventor Shinichi Nagahashi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Date Honko Co., Ltd.

Claims (2)

[Claims] C. 0.60 to 0.85% by weight,
Si: 0.1 to 1.0%, Mn: 0.5 to 1.5%,
P: 0.035% or less, S: 0.040% or less, Al:
And 0.05% or less, and the balance of Fe and unavoidable impurities, the hardness of the corner and head side portions are H _B three hundred and forty-one to four hundred and five in Brinell hardness, 20 mm from the top center of the head top portion in the width direction Hardness at distant position is H _B
341 to 405, and the hardness at the center of the crown is 10 to 50 lower in Brinell hardness than the hardness at a position 20 mm in the width direction from the center of the crown, and the hardness is 20 mm in the width direction from the center of the crown and the center of the crown. The hardness between the center and the center increases monotonously outward from the center of the crown in the width direction.The actual hardness of the part in between and the hardness in the middle of the head in the middle and the width in the width direction from the center of the crown A high-strength, damage-resistant rail having a Brinell hardness of 10 or less from the hardness obtained by interpolating the hardness at a position separated by 20 mm with a straight line. 2. C: 0.60 to 0.85% by weight,
Si: 0.1 to 1.0%, Mn: 0.5 to 1.5%,
P: 0.035% or less, S: 0.040% or less, Al:
0.05% or less, and Cr: 0.05 to 1.5
%, Mo: 0.01-0.20%, V: 0.01-0.
10%, Ni: 0.1 to 1.0%, Nb: 0.005 to
0.15% contains one or more kinds, and the balance is F
consists e and unavoidable impurities, co - a H _B three hundred forty-one to four hundred and five hardness of Na portion and head side portions are in Brinell hardness, hardness at a position apart 20mm in the width direction from the top center of the top portion is H _B 341 to 405, and the hardness at the center of the crown is 10 to 50 lower in Brinell hardness than the hardness at a position 20 mm in the width direction from the center of the crown, and the hardness is 20 mm in the width direction from the center of the crown and the center of the crown. The hardness between the center and the center increases monotonously outward from the center of the crown in the width direction.The actual hardness of the part in between and the hardness in the middle of the head in the middle and the width in the width direction from the center of the crown A high-strength, damage-resistant rail having a Brinell hardness of 10 or less from the hardness obtained by interpolating the hardness at a position separated by 20 mm with a straight line.