JPH06279928A - High strength rail excellent in toughness and ductility and its production - Google Patents

Abstract

PURPOSE:To obtain a rail steel excellent in toughness and ductility by subjecting a heated steel bloom, which has a composition containing specific amounts of C, Si, Mn, S, Cr, etc., and to which deoxidizing treatment is applied, to cooling under prescribed conditions and forming pearlite where V nitride precipitated on MnS is used as a nucleus. CONSTITUTION:A steel, which has a composition consisting of, by weight, 0.55-0.85% C, 0.2-1.2% Si, 0.5-1.5% Mn, 0.006-0.035% S, 0.1-1% Cr, 0.01-1% V, 0.0005-0.03% N, and the balance Fe and is deoxidized by the addition of Mn and/or Si, is refined. At the time of applying cooling, from an austenite region temp., to the head or further bottom part of a rail prepared by subjecting a bloom of this steel to hot rolling, etc., cooling is done through the temp. region between 700 and 500 deg.C at (1 to 5) deg.C/sec cooling rate. By the above procedure, pearlite where V nitride precipitated on MnS in an austenite grain is used as a nucleus can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength rail in which the pearlite structure of rail steel is refined to improve toughness and ductility, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, railway transportation has been aimed at higher loads and higher speeds, and the characteristics required for rails have become increasingly severe. For heavy-duty railways, measures against wear on sharp curves and internal fatigue damage to rail heads are required. On high-speed railways, surface damage mainly on straight sections is cited as an issue. In addition to these, it is recognized that rail rupture tends to occur intensively in winter in cold regions, and improving the toughness of rail materials in cold region railways is a characteristic that is essential for safe rail transportation. ing.

Further, in order to improve the efficiency of rail transportation, speeding up and heavy loading of cargo have been promoted, but along with this, wear and fatigue damage of rail heads are rapidly increasing. In order to cope with such harsh environment of use of rail materials, especially increase in wear, technological development for strengthening rail steel has been accelerated, and rail materials in curved sections are mostly used in Japan and abroad. All of the high-strength rails now dominate.

On the other hand, on the other hand, as the wear resistance of the rail steel is improved, a fatigue damage layer that should be scraped off due to wear remains on the rail head surface, especially on the gauge corner (GC) surface where the wheel flange root is pressed, A tendency to produce surface damage has become apparent. Further, the improvement of the wear resistance of the rail steel means that the stress concentration inside the rail GC due to the wheel load is fixed at one point, and the fatigue damage from the inside of the rail head rapidly increases. In order to improve such rail head surface damage and resistance to internal fatigue damage, it is important to improve the toughness and ductility of the rail material.

The following methods are conceivable as methods for improving the toughness and ductility of high-strength rails. (1) A method in which a rail head that has been once cooled to room temperature after normal rolling is reheated at a low temperature and then accelerated cooling is performed. (2) A method of accelerating and cooling the rail head after refining austenite grains by controlled rolling. (3) A method in which after controlled rolling, it is reheated to a low temperature before pearlite transformation and then accelerated cooling is performed. As a toughness evaluation method for rail steel, there is impact absorption energy at + 20 ° C in the 2mm U-notch Charpy test defined by the Russian GOST standard. According to this standard, the impact absorption energy at + 20 ° C of the high-strength heat-treated rail is 0.25 MJ / m ² or more is required. Also,
The ductility of the rail affects the generation of fatigue damage to the rail head, and the ductility requirement of the high-strength rail in China is that the diameter of the parallel part is 6 mm from the depth of 10 mm inside the rail head GC.
It is said that an elongation value of 12% or more is required in a tensile test with a parallel length of 30 mm.

[0006]

In the above method (1), in order to improve the toughness and ductility to a great extent, JP-A-55-12 is used.
Reheating to a low temperature of 850 ° C. or lower, which is lower than the normal heating temperature as described in Japanese Patent No. 5231, attempts to improve toughness and ductility by making the austenite grain size fine. When heating and deepening the heating to the inside of the rail head, it is necessary to lower the amount of heat input and heat for a long time. Therefore, there is a problem that heat treatment productivity is significantly impaired and manufacturing cost is increased. Also,
As described in JP-A-52-138427 and JP-A-52-138428, the method (2) is toughness due to austenite grain refinement during rolling.
In order to improve the ductility, a large reduction at high temperature is required, which causes a problem from the viewpoint of rail rolling mill capacity or rail shape control. Furthermore, the method (3) is described in Japanese Patent Publication No.
After rolling 5% or more at 0 ° C. or less, 750 to 750 again
This is a method in which the austenite grains are made fine by heating at 900 ° C. Since a heating furnace for low-temperature reheating after rolling is required, there are many problems from the viewpoint of workability, productivity, and manufacturing cost.

In view of the state of the art, the present invention provides a high-strength rail having a fine pearlite structure and excellent in toughness and ductility by producing fine pearlite from inside of austenite grains, which has not been conventionally considered, and a method for producing the same. Is intended to provide.

[0008]

That is, according to the present invention, Mn and / or Si is added to a molten steel as a deoxidizing element and a deoxidizing treatment is applied to the molten steel to produce a molten steel.
0.85%, Si: 0.20 to 1.20%, Mn:
0.50 to 1.50%, S: 0.006 to 0.0
35%, Cr: 0.1 to 1.0%, V: 0.
001 to 1.00%, N: 0.0005 to 0.030
%, With the balance being iron and unavoidable impurities, a steel slab produced by the ingot-agglomeration method or the continuous casting method is hot-rolled to obtain M having a size of 0.1 to 20 μm.
The number of nS is 25 to 1100 per 1 mm ^{2 in} rail steel.
It is a high-strength rail excellent in toughness and ductility, characterized by the presence of zero, and a method for producing the same. Further, the present invention provides molten steel with one of four sets of (Zr), (Zr and Mn), (Zr and Si), (Zr, Mn and Si).
A set of deoxidizing elements was added and subjected to deoxidizing treatment to be ingot, C: 0.55 to 0.85% by weight, Si: 0.2
0 to 1.20%, Mn: 0.50 to 1.50%,
S: 0.006 to 0.035%, Cr: 0.1 to 1.
0%, V: 0.001-1.00%, N
: 0.0005 to 0.030%, Zr: 0.0005
Of 0.1 to 20 μm is obtained by hot rolling a steel slab containing 0.1 to 0.15% of steel, the balance of which is iron and unavoidable impurities, produced by an ingot-agglomeration method or a continuous casting method. The number of MnS of size is 25 per 1 mm ^{2 in} rail steel.
It is a high-strength rail excellent in toughness and ductility, characterized by the presence of ˜11,000 pieces, and a manufacturing method thereof. Further, according to the present invention, Mn and / or Si is added to the molten steel as a deoxidizing element, and the molten steel is subjected to deoxidizing treatment to be melted.
: 0.55 to 0.85%, Si: 0.20
1.20%, Mn: 0.50 to 1.50%, S
: 0.006-0.035%, Cr: 0.1-1.0
%, V: 0.001-1.00%, Ti:
0.0006-0.075%, N: 0.0005-
A steel slab containing 0.030%, the balance of which is iron and unavoidable impurities, produced by an ingot-agglomeration method or a continuous casting method is hot-rolled into a size of 0.1 to 20 μm. The number of MnS is 25 per 1 mm ^{2 in} rail steel
It is a high-strength rail excellent in toughness and ductility, characterized by the presence of ˜11,000 pieces, and a manufacturing method thereof. Furthermore, the present invention relates to molten steel (Zr), (Zr and M
n), (Zr and Si), (Zr, Mn and Si)
1 set of 4 sets of deoxidizing element was added and subjected to deoxidation treatment to be melted, and C by weight%: 0.55 to 0.85%,
Si: 0.20 to 1.20%, Mn: 0.50
1.50%, S: 0.006-0.035%,
Cr: 0.1-1.0%, V: 0.001
~ 1.00%, Ti: 0.0006-0.075%, N
: 0.0005 to 0.030%, Zr: 0.0005
Of 0.1 to 20 μm is obtained by hot rolling a steel slab containing 0.1 to 0.15% of steel, the balance of which is iron and unavoidable impurities, produced by an ingot-agglomeration method or a continuous casting method. The number of MnS of size is 25 per 1 mm ^{2 in} rail steel.
It is a high-strength rail excellent in toughness and ductility, characterized by the presence of ˜11,000 pieces, and a manufacturing method thereof.

In the present invention, the pearlite transformation, which was conventionally said to be generated only from the austenite grain boundaries,
It is characterized in that V nitrides and / or Ti carbonitrides, which become nuclei for pearlite transformation, are arranged in MnS in austenite grains to generate pearlite transformation also in austenite grains. Perlite that transforms from the grain boundary,
By controlling / promoting the nucleation of MnS in the austenite grains, the structure is remarkably refined due to the superposition effect with pearlite generated from within the grains, and as a result, the toughness and ductility can be greatly improved.

In each of the above-mentioned inventions, after cooling from the austenite region after hot working (hot rolling) or further heating, accelerated cooling at 700 to 500 ° C. at 1 to 5 ° C./sec is further performed. The pearlite can be miniaturized, and it is effective in improving the toughness.

[0011]

The present invention will be described in detail below. First,
The necessity of deoxidation and the reason for limiting the deoxidizing element will be described. There are two purposes of deoxidation in the present invention, one of which is to control the oxide that becomes the core of MnS, and Mn and Si are manganese silicate (MnO-SiO) effective as a generation nucleus of MnS. ₂ ) As a constituent element, it is added for the purpose of controlling the number and distribution of MnS. Further, Zr is used for the purpose of suppressing the decrease in the number of oxides floating from the molten steel by forming oxides having a large specific gravity, and by adding Zr, MnS
Adding an effective Zr oxides or purpose of further controlling the number and distribution of MnS as an element of manganese silicate (MnO-SiO ₂₎ containing Zr as nuclei for.

Another purpose of deoxidation is to reduce the amount of oxygen in molten steel as much as possible by adding Mn and / or Si as deoxidizing elements. This is to reduce the amount of oxygen in advance so that Ti is not deposited as an oxide and wasted. Further, (Zr), (Zr and Mn), (Zr and Si), (Zr, Mn and S
By adding the deoxidizing element in one of the four groups of i), the effect of reducing the oxygen amount becomes extremely large, and the oxygen amount can be further reduced. That is, M as a deoxidizing element
n and / or Si is added, and at least V and T
The amount of oxygen in molten steel is set to 20 ppm or less before the addition of i, and V and Ti are more efficiently formed to form their carbonitrides without forming oxides (Zr),
(Zr and Mn), (Zr and Si), (Zr, M
(n and Si) by adding one of four deoxidizing elements, the oxygen content in the molten steel is reduced to 10 ppm or less before addition of at least V and Ti, and V and Ti do not form an oxide. The objective is to efficiently produce those carbonitrides. Al, which is generally used as a deoxidizer, does not add Al because it forms alumina clusters that are harmful to the occurrence of fatigue damage from inside the rail.

The reason why the number of MnS of 0.1 to 20 μm after deoxidation is limited to 25 to 11,000 per mm ² will be described. Oxygen is reduced by sufficient deoxidation, as a result, a fine oxide is generated, MnS is finely dispersed in austenite with this oxide as a nucleus, and V nitrides: VN and Ti carbonitride with this MnS as a nucleus. Thing: Ti (C,
N) is generated. A pearlite transformation is generated from V precipitates and Ti precipitates having MnS as nuclei in the austenite grains. At this time, in MnS having a size of less than 0.1 μm, nuclei of V precipitates and Ti precipitates are formed. However, when MnS of more than 20 μm is generated, Mn
The absolute number of S is reduced, and as a result, the number of MnS that is a nucleus of pearlite is reduced. Therefore, the size of MnS is limited to 0.1 to 20 μm. The reason why the number of MnS is limited to 25 to 11,000 per 1 mm ² is as follows.
This is because less than 25 MnS cannot secure sufficient nucleation sites for improving the toughness and ductility.
If more than 000 MnS are produced, the rail steel itself is contaminated and the toughness and ductility are rather deteriorated. Therefore, the number of MnS per 1 mm ² is limited to 25 to 11,000.

Next, the reason why the chemical composition of the deoxidized molten steel is limited as described above will be described. C is an essential element for strengthening and generating a pearlite structure,
Further, it is an element that uniquely exerts an effect on wear resistance as well, but if it is less than 0.55%, a large amount of proeutectoid ferrite which is unfavorable for wear resistance and damage resistance is generated in the austenite grain boundary, If it exceeds 85%, not only harmful harmful pro-eutectoid cementite that embrittles the austenite grain boundaries is generated, but also martensite is generated in the heat-separated layer of the rail head and the minute segregation part of the welded portion, which significantly impairs toughness and ductility. ．
It was limited to 55 to 0.85%.

Si not only contributes to the strengthening of the ferrite phase in the pearlite structure by solid solution hardening, but also contributes to a slight improvement in the toughness and ductility of the rail steel. Further, Si is an important element that constitutes a manganese silicate-based oxide, which becomes the core of MnS together with Mn, and its effect cannot be expected if it is less than 0.2%, and Si is 0.2% or more as a deoxidizing element. It is necessary to add it, and if it exceeds 1.2%, embrittlement is caused and weld bondability is reduced, so 0.20 to
Limited to 1.20%.

Like C, Mn is an element that lowers the pearlite transformation temperature and enhances the hardenability to contribute to higher strength. Further, like Mn, it acts as a constituent element of manganese silicate as the core of MnS and as a deoxidizer. It is indispensable as an acid element. However, if it is less than 0.5%, its effect is small, and if it exceeds 1.50%, the content is limited to 0.50 to 1.50% so that a martensite structure is easily generated in the segregated portion.

Although S is generally known as a harmful element, in the present invention, MnS is produced with an oxide such as manganese silicate in austenite grains as a nucleus, and the MnS-based precipitates: VN and Ti.
(C, N) is generated, and a pearlite structure having these precipitates as transformation nuclei is generated, which is an essential element. However, if it is less than 0.006%, M as pearlite transformation nucleus
Since the amount of nS is reduced, the pearlite intragranular transformation cannot be secured. On the other hand, if it exceeds 0.035%, a large amount of MnS is formed and the toughness and ductility are remarkably reduced, so 0.002 to 0.
Limited to 035%.

[0018] Cr contributes to higher strength by lowering the pearlite transformation, and at the same time contributes to improving wear resistance by strengthening the cementite phase in the pearlite structure. On the other hand, it lowers the impact toughness of cementite. It also has the effect of causing it. However, the cementite strengthening effect of Cr cannot be ignored, and addition of a small amount of Cr is also desirable from the viewpoint of preventing softening of the welded joint. Therefore, it is limited to 0.1 to 1.0% within a range in which a certain contribution is expected to secure the strength and the toughness and ductility are not impaired. V is an important component of the present invention, and it was found that the pearlite transformation centered on the V-nitride precipitated on MnS during cooling was found. Can be expected from within the austenite grains, and as a result, a rail steel composed of fine pearlite grains can be obtained, and the toughness can be greatly improved. However, if it is less than 0.001%, this effect is weak, and if it exceeds 1.00%, V precipitates are coarsened and become a starting point of fatigue crack initiation from inside the rail head. It was limited to the range of 0.001 to 1.00%.

Ti, like V, is an important constituent element of the present invention. The effect of the pearlite transformation centered on Ti carbonitride deposited on MnS during cooling is due to the pearlite transformation by V nitride. By superimposing them, the transformation from within the austenite grains can be expected more effectively. But 0.000
If it is less than 6%, this effect is weak, and if it exceeds 0.075%, Ti precipitates are coarsened and become the starting point of fatigue crack initiation from inside the rail head.
It was limited to the range of 006 to 0.075%.

N acts as a transformation nucleus of pearlite M
It is a constituent element of V-nitride and Ti carbonitride on nS. In order to effectively precipitate VN and TiN,
0005% or more is required, and if it exceeds 0.030%, coarse VN and TiN are generated, which becomes the starting point of fatigue cracks in the rail, so the N addition amount is 0.0005 to 0.030.
Limited to%.

Although Zr is used as a deoxidizing element, it exists mainly in the form of an oxide in steel, and if it is too small, the effect of deoxidizing is low, so its content is 0.0005%.
The above is required, and if more than 0.15% is added, Z
The Zr content is 0.0005 to 0. 0 because the R precipitates become coarse and become the starting point of fatigue crack initiation from the inside of the rail head.
The range was limited to 15%. Inevitable impurity element P
Is preferably reduced as much as possible in order to improve the toughness of the rail steel.

The rail steel having the above-mentioned composition is subjected to melting including the above-mentioned deoxidation in a commonly used melting furnace such as a converter or an electric furnace, and this molten steel is ingoted or agglomerated. Method or continuous casting method, and then hot rolling. The rail that has been hot-rolled has V-nitride and / or T precipitated on MnS in the austenite grains during cooling.
The pearlite transformation is also generated from i-carbonitride and constitutes fine pearlite grains together with pearlite generated from the austenite grain boundaries. As a result, a high-strength rail having excellent toughness can be manufactured as rolled.

When high strength and high toughness are required, a temperature between 700 and 500 ° C. during the cooling process from the end of rolling or from the reheated austenite region temperature once for the purpose of heat treatment after cooling to room temperature is 1 ~ 5 ℃ / sec
With rail steel that has been accelerated and cooled by, even higher toughness can be obtained. That is, as a characteristic of pearlite structure steel, pearlite transformation is caused at low temperature by accelerated cooling,
This is because the rate of generation of pearlite transformation nuclei is improved, and as a result, pearlite grains can be made fine. Therefore, the pearlite structure (transformation within austenite grains) centered on V-nitrides and / or Ti carbonitrides precipitated on MnS and the pearlite transformation from the austenite grain boundaries due to accelerated cooling are superposed to form a further rail steel. It is possible to achieve improvement in toughness. At this time, the cooling medium is
It is desirable to use a gas-liquid mixture such as air or mist and to set the strength of the rail head or bottom to 1100 MPa or more.

[0024]

EXAMPLES Next, examples of production of high strength rails having high toughness produced according to the present invention will be described. Table 1 shows Zr,
The chemical composition of the sample steel when one or more kinds of Mn and Si are deoxidized is shown. For comparison, Table 1 also shows the chemical composition of the sample steel when deoxidation control was not performed and when V and / or Ti was not deoxidation controlled. In addition, the measurement results of the number of MnS of 0.1 to 20 μm existing in the microstructures of these test steels after cooling, and whether the microstructure after cooling contains pearlite intragranular transformation having MnS as a nucleus. Table 2 shows the results of observation
Shown in. In the steel of the present invention and the comparative steel that were appropriately deoxidized, it was confirmed that a predetermined amount of fine MnS was formed, and in the steel of the present invention in which V was added, the V nitriding centered on MnS from within the austenite grains was clearly observed. It was confirmed that the pearlite structure originated from the substance and / or Ti carbonitride as a starting point.

Table 3 shows the as-rolled state and 700 to 700 for each chemical component from the austenite range temperature in order to keep the strength constant.
Tensile strength, elongation, and 2 of the rail steel after accelerated cooling in which the cooling rate was changed in the range of 1 to 5 ° C / sec.
The measurement result of the impact absorption energy in +20 degreeC in mmU notch Charpy test is shown. Tensile test for rail head G
A test piece having a parallel part diameter of 6 mm and a parallel part length of 30 mm was sampled from a depth position of 10 mm inside C. As a result, the steel of the present invention is
A sufficient improvement in ductility as an effect of the pearlite microstructure was observed as compared with the comparative steel. Impact test piece is rail head 1
It was collected from the bottom of mm. This test condition is based on the Russian GOST standard that regulates the toughness of heat treated rails. According to this standard, the impact absorption energy at + 20 ° C of high strength heat treated rails must be 0.25 MJ / m ² or more. Therefore, the fine pearlite structure steels in which the pearlite transformation is generated even in the austenite grains by performing the appropriate deoxidation according to the present invention all sufficiently satisfy the Charpy absorbed energy specified in the GOST standard.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

[0031]

[Table 6]

[0032]

[Table 7]

[0033]

INDUSTRIAL APPLICABILITY The rail steel of the present invention is controlled by M
By controlling the number of nS to utilize V nitride and / or Ti carbonitride precipitated in MnS in austenite grains as pearlite transformation nuclei,
The pearlite grains become finer, and impact absorption energy of 0.25 MJ / m ² or more can be obtained. Furthermore, the ductility of the rail steel as well as the toughness can be greatly improved by the generation of the fine pearlite structure.

Front Page Continuation (72) Inventor Masamitsu Wakao 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Co., Ltd.Technology Development Division (72) Inventor Fusao Ishikawa 20-1 Shintomi, Futtsu, Chiba Nippon Steel Co., Ltd. Company Technology Development Division

Claims (6)

[Claims] 1. A rail produced by deoxidizing molten steel into a steel slab, which is manufactured by a process including hot working, wherein C: 0.55 to 0.85% Si: 0.20 by weight%. 1.20% Mn: 0.50 to 1.50% S: 0.006 to 0.035% Cr: 0.1 to 1.0% V: 0.001 to 1.00% N: 0.0005 to 0.030%, the balance consisting of iron and inevitable impurities, M
A high-strength rail with excellent toughness and ductility, characterized in that nS has a size of 0.1 to 20 μm in steel, and the number thereof is 25 to 11,000 per 1 mm ² . 2. A rail produced by deoxidizing molten steel to obtain a steel slab, which is manufactured by a process including hot working, and has a weight percentage of C: 0.55 to 0.85% Si: 0.20. 1.20% Mn: 0.50 to 1.50% S: 0.006 to 0.035% Cr: 0.1 to 1.0% V: 0.001 to 1.00% N: 0.0005 to 0.030% and Ti: 0.0006 to 0.075%, Zr: 0.0005 to 0.15%, one or two kinds, and the balance consisting of iron and inevitable impurities.
A high-strength rail with excellent toughness and ductility, characterized in that nS has a size of 0.1 to 20 μm in steel, and the number thereof is 25 to 11,000 per 1 mm ² . 3. Mn and / or Si as a deoxidizing element is added to molten steel and subjected to a deoxidizing treatment to be melted. C: 0.55 to 0.85% by weight% Si: 0.20 to 1. 20% Mn: 0.50 to 1.50% S: 0.006 to 0.035% Cr: 0.1 to 1.0% V: 0.001 to 1.00% N: 0.0005 to 0. Molten steel containing 030% and the balance of iron and unavoidable impurities was manufactured by the ingot-agglomeration method or the continuous casting method. A steel piece was heated to a high temperature after the hot rolling or for the purpose of heat treatment. After that, when cooling the head or the bottom of the rail from the austenite region temperature, accelerated cooling is carried out at a temperature of 700 to 500 ° C. at 1 to 5 ° C./sec.
A method for producing a high-strength rail having excellent toughness and ductility, which is characterized in that pearlite having V nitrides deposited on nS as nuclei is generated. 4. A molten steel containing (Zr), (Zr and Mn),
(Zr and Si), (Zr, Mn and Si), one set of four sets of deoxidizing elements was added and subjected to deoxidizing treatment to be melted, and C: 0.55 to 0.85 by weight%. % Si: 0.20 to 1.20% Mn: 0.50 to 1.50% S: 0.006 to 0.035% Cr: 0.1 to 1.0% V: 0.001 to 1.00 Molten steel containing% N: 0.0005 to 0.030% Zr: 0.0005 to 0.15% and the balance being iron and unavoidable impurities was manufactured by an ingot-casting method or a continuous casting method. After the steel strip is hot-rolled or heated to a high temperature for the purpose of heat treatment, the rail head or bottom is cooled from austenite temperature to 700-500 ° C for 1-5 ° C / sec. Accelerated cooling with, M in austenite grains
A method for producing a high-strength rail having excellent toughness and ductility, which is characterized in that pearlite having V nitrides deposited on nS as nuclei is generated. 5. Mn and / or Si as a deoxidizing element is added to molten steel and subjected to deoxidation treatment to produce molten steel, and C: 0.55 to 0.85% by weight% Si: 0.20 to 1. 20% Mn: 0.50 to 1.50% S: 0.006 to 0.035% Cr: 0.1 to 1.0% V: 0.001 to 1.00% Ti: 0.0006 to 0. 075% N: 0.0005 to 0.030% of molten steel consisting of iron and unavoidable impurities with the balance being produced by the ingot-agglomeration method or the continuous casting method. Or, after heating to a high temperature for the purpose of heat treatment, when cooling the head or the bottom of the rail from the austenite region temperature, accelerated cooling at 700 to 500 ° C. at 1 to 5 ° C./sec, M
A method for producing a high-strength rail having excellent toughness and ductility, which comprises producing pearlite with V nitride and / or Ti carbonitride as nuclei precipitated on nS. 6. A molten steel containing (Zr), (Zr and Mn),
(Zr and Si), (Zr, Mn and Si), one set of four sets of deoxidizing elements was added and subjected to deoxidizing treatment to be melted, and C: 0.55 to 0.85 by weight%. % Si: 0.20 to 1.20% Mn: 0.50 to 1.50% S: 0.006 to 0.035% Cr: 0.1 to 1.0% V: 0.001 to 1.00 % Ti: 0.0006 to 0.075% N: 0.0005 to 0.030% Zr: 0.0005 to 0.15% with the balance being iron and inevitable impurities. A steel piece produced by the ingot method or the continuous casting method is heated to a high temperature for the purpose of heat rolling after completion of hot rolling, or after the head or the bottom of the rail is cooled from the austenite range temperature to 700 to Accelerated cooling at a temperature of 1 to 5 ° C / sec between 500 ° C and M in austenite grains
A method for producing a high-strength rail having excellent toughness and ductility, which comprises producing pearlite with V nitride and / or Ti carbonitride as nuclei precipitated on nS.