阅读说明：本技术 一种过共析钢轨及其制备方法 (Hypereutectoid steel rail and preparation method thereof ) 是由 袁俊 邹明 邓勇 汪渊 于 2020-11-30 设计创作，主要内容包括：本发明涉及金属材料热处理领域,公开了一种过共析钢轨及其制备方法。该方法包括：(1)采用高压水枪对钢坯进行喷射,喷射压力为20-30MPa,喷射角度为40-50°,然后将钢坯轧制成小断面钢坯,接着将小断面钢坯轧制成钢轨；(2)利用步骤(1)得到的钢轨的余热进行加速冷却,得到过共析钢轨；其中,在步骤(1)中,在小断面钢坯轧制成钢轨的过程中,每次轧制前对钢坯喷洒重油、石墨和水的混合物。该方法制备的过共析钢轨尺寸精度不超过±0.5mm,钢轨凹坑深度≤0.5mm,抗拉强度≥1400MPa,延伸率≥10％,适宜机车速度≥120km/h、年运量≥1亿吨的高速重载线路使用。(The invention relates to the field of heat treatment of metal materials, and discloses a hypereutectoid steel rail and a preparation method thereof. The method comprises the following steps: (1) spraying the steel billet by using a high-pressure water gun, wherein the spraying pressure is 20-30MPa, and the spraying angle is 40-50 degrees, rolling the steel billet into a small-section steel billet, and then rolling the small-section steel billet into a steel rail; (2) accelerated cooling is carried out by utilizing the waste heat of the steel rail obtained in the step (1) to obtain a hypereutectoid steel rail; in the step (1), in the process of rolling the small-section steel billet into the steel rail, a mixture of heavy oil, graphite and water is sprayed on the steel billet before each rolling. The hypereutectoid steel rail prepared by the method has the dimensional accuracy of not more than +/-0.5 mm, the depth of a steel rail pit is not more than 0.5mm, the tensile strength is not less than 1400MPa, the elongation is not less than 10%, and the hypereutectoid steel rail is suitable for high-speed heavy-load lines with the locomotive speed not less than 120km/h and the annual transport capacity not less than 1 hundred million tons.)

1. A preparation method of a hypereutectoid steel rail is characterized by comprising the following steps:

(1) spraying the steel billet by using a high-pressure water gun, wherein the spraying pressure is 20-30MPa, and the spraying angle is 40-50 degrees, rolling the steel billet into a small-section steel billet, and then rolling the small-section steel billet into a steel rail;

(2) accelerated cooling is carried out by utilizing the waste heat of the steel rail obtained in the step (1) to obtain a hypereutectoid steel rail;

in the step (1), in the process of rolling the small-section steel billet into the steel rail, a mixture of heavy oil, graphite and water is sprayed on the steel billet before rolling each time, and the mass ratio of the heavy oil to the graphite to the water is 1:1-3: 1-7.

2. The method for preparing hypereutectoid steel rails according to claim 1, wherein in the step (1), the preparation method of the steel billet comprises converter smelting, LF refining, RH vacuum treatment, protective casting, cooling and heating in a heating furnace.

3. The method for preparing a hypereutectoid steel rail according to claim 2, wherein in the step (1), the heating temperature of the heating furnace is 1230-.

4. The method for producing a hypereutectoid steel rail according to claim 1, wherein in the step (2), the cooling rate of the accelerated cooling is 1 to 4 ℃/s.

5. Hypereutectoid steel rail produced by the method according to any one of claims 1 to 4.

6. The hypereutectoid steel rail according to claim 5, comprising 0.8 to 1.2% by weight of C, 0.1 to 0.8% by weight of Si, 0.4 to 1.3% by weight of Mn, 0.002 to 0.02% by weight of P, 0.001 to 0.7% by weight of Cr, 0.001 to 0.12% by weight of V, 0.001 to 0.004% by weight of Al, and the balance of Fe and S and inevitable impurities, based on the total weight of the hypereutectoid steel rail.

7. The hypereutectoid steel rail according to claim 6, wherein the hypereutectoid steel rail contains 0.01 to 0.02% by weight of Mo, 0.001 to 0.02% by weight of Sn, 0.05 to 0.15% by weight of Cu, and 0.01 to 0.02% by weight of As, based on the total weight of the hypereutectoid steel rail.

8. The hypereutectoid steel rail according to claim 6 or 7, wherein the content of hydrogen in the hypereutectoid steel rail is 2ppm or less.

9. The hypereutectoid steel rail according to claim 8, wherein the hypereutectoid steel rail contains oxygen in an amount of 20ppm or less.

10. The hypereutectoid steel rail according to claim 9, wherein the content of nitrogen in the hypereutectoid steel rail is 60ppm or less.

Technical Field

The invention relates to the field of heat treatment of metal materials, in particular to a hypereutectoid steel rail and a preparation method thereof.

Background

The railway is divided into a passenger special line railway, a passenger-cargo mixed transportation mode and a heavy-load freight special line railway transportation mode according to the operation mode. The running speed of the passenger special line railway is usually more than or equal to 160km/m, and the running speed of the heavy-load freight special line railway is usually less than or equal to 80 km/m. The steel rail required by the passenger special line railway has high dimensional precision and surface quality and lower strength index. Heavy-duty freight railway rails need to have high strength and high toughness rail quality, and due to the low running speed, the requirements on the size and the surface quality are wide.

Heavy haul railways at home and abroad are gradually developing to a railway transportation mode with large axle load and high density. Internationally, when a customer of a heavy-duty line such as australia purchases a steel rail, the specified tread hardness of the purchased steel rail is over 420 HB. Along with the continuous improvement of the economy of China and the continuous improvement of the freight volume of railways, high-speed heavy haul railways with locomotive speeds of more than or equal to 120km/h and annual freight volumes of more than or equal to 1 hundred million tons get attention of users. The existing full pearlite steel rail only adopts special production processes of alloying, controlled rolling, controlled cooling and the like, and the highest tread hardness can only reach about 430 HB. Therefore, heavy-duty lines at home and abroad are focused on hypereutectoid steel rails. The hypereutectoid steel rail has the advantages that certain secondary cementite is precipitated in the structure due to the increase of the carbon content, the wear resistance of the steel rail is improved, and the hardness of the tread of the hypereutectoid steel rail reaches up to 460 HB. However, the existing hypereutectoid steel rails are rolled by adopting carbon small sections, and the toughness and the plasticity of the steel rails are reduced by secondary cementite separated out from the structure, so that the existing hypereutectoid steel rails are easy to contact, fatigue and block drop under the condition of difficult grinding, and the operating efficiency and the driving safety of a line are seriously influenced. Therefore, the existing common carbon hypereutectoid steel rail rolled with a small section is difficult to meet the development requirements of domestic and foreign heavy-load lines, and a production method of the hypereutectoid steel rail with high strength, high toughness, wear resistance, contact fatigue resistance and block dropping resistance is urgently needed.

Disclosure of Invention

The invention aims to solve the problem that hypereutectoid steel rails are easy to contact fatigue and fall blocks in the prior art, and provides the hypereutectoid steel rails and the preparation method thereof, the method adopts heavy oil graphite water mixed lubrication rolling, ensures the infiltration of the surface carbon content of the hypereutectoid steel rails, and also ensures the requirements of the hypereutectoid steel rails on high precision and high surface quality, the dimensional precision of the prepared hypereutectoid steel rails is not more than +/-0.5 mm, the pit depth of the steel rails is not more than 0.5mm, the tensile strength is not less than 1400MPa, the elongation is not less than 10 percent, and the hypereutectoid steel rails are suitable for being used in high-speed heavy-load lines with locomotive speed of not less than 120km/h and annual transport capacity of not less than 1.

In order to achieve the above object, an aspect of the present invention provides a method for preparing a hypereutectoid steel rail, the method comprising the steps of:

(1) spraying the steel billet by using a high-pressure water gun, wherein the spraying pressure is 20-30MPa, and the spraying angle is 40-50 degrees, rolling the steel billet into a small-section steel billet, and then rolling the small-section steel billet into a steel rail;

(2) accelerated cooling is carried out by utilizing the waste heat of the steel rail obtained in the step (1) to obtain a hypereutectoid steel rail;

in the step (1), in the process of rolling the small-section steel billet into the steel rail, a mixture of heavy oil, graphite and water is sprayed on the steel billet before rolling each time, and the mass ratio of the heavy oil to the graphite to the water is 1:1-3: 1-7.

Preferably, in the step (1), the preparation method of the steel billet comprises converter smelting, LF refining, RH vacuum treatment, protective casting, cooling and heating in a heating furnace.

Preferably, in the step (1), the heating temperature of the heating furnace is 1230-.

Preferably, in the step (2), the cooling speed of the accelerated cooling is 1-4 ℃/s.

In a second aspect, the invention provides a hypereutectoid steel rail prepared by the above method.

Preferably, the hypereutectoid steel rail contains 0.8 to 1.2% by weight of C, 0.1 to 0.8% by weight of Si, 0.4 to 1.3% by weight of Mn, 0.002 to 0.02% by weight of P, 0.001 to 0.7% by weight of Cr, 0.001 to 0.12% by weight of V, 0.001 to 0.004% by weight of Al, and the balance of Fe and S and inevitable impurities, based on the total weight of the hypereutectoid steel rail.

Preferably, the hypereutectoid steel rail contains 0.01 to 0.02 wt% of Mo, 0.001 to 0.02 wt% of Sn, 0.05 to 0.15 wt% of Cu, and 0.01 to 0.02 wt% of As, based on the total weight of the hypereutectoid steel rail.

Preferably, the content of hydrogen in the hypereutectoid steel rail is less than or equal to 2 ppm.

Preferably, the content of oxygen in the hypereutectoid steel rail is less than or equal to 20 ppm.

Preferably, the content of nitrogen in the hypereutectoid steel rail is less than or equal to 60 ppm.

The preparation method of the hypereutectoid steel rail adopts the mixed lubrication rolling of heavy oil graphite water, ensures the infiltration of the surface carbon content of the hypereutectoid steel rail, also ensures the requirements of the hypereutectoid steel rail on high precision and high surface quality, ensures that the dimensional precision of the prepared hypereutectoid steel rail is not more than +/-0.5 mm, the depth of a steel rail pit is not more than 0.5mm, the tensile strength is not less than 1400MPa, the elongation is not less than 10 percent, and is suitable for being used by a high-speed heavy-load line with the locomotive speed of not less than 120km/h and the annual transport capacity of not less than 1 hundred million tons.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, one or more new ranges of values may be obtained from combinations of values between the endpoints of each range, the endpoints of each range and the individual values, and the individual values of the points, and these ranges of values should be considered as specifically disclosed herein.

The invention provides a preparation method of a hypereutectoid steel rail on the one hand, which comprises the following steps:

(1) spraying the steel billet by using a high-pressure water gun, wherein the spraying pressure is 20-30MPa, and the spraying angle is 40-50 degrees, rolling the steel billet into a small-section steel billet, and then rolling the small-section steel billet into a steel rail;

(2) accelerated cooling is carried out by utilizing the waste heat of the steel rail obtained in the step (1) to obtain a hypereutectoid steel rail;

in the step (1), in the process of rolling the small-section steel billet into the steel rail, a mixture of heavy oil, graphite and water is sprayed on the steel billet before rolling each time, and the mass ratio of the heavy oil to the graphite to the water is 1:1-3: 1-7.

In the present invention, in step (1), the preparation method of the steel billet may be a conventional method in the art. Preferably, the preparation method of the steel billet comprises converter smelting, LF refining, RH vacuum treatment, protective casting, cooling and heating by a heating furnace.

In the invention, the heating temperature of the heating furnace is 1230-1280 ℃. Specifically, the heating temperature of the heating furnace may be 1230 ℃, 1240 ℃, 1250 ℃, 1260 ℃, 1270 ℃ or 1280 ℃.

In the invention, the heating time of the heating furnace is 150-240 min. Specifically, the heating time of the heating furnace can be 150min, 160min, 170min, 180min, 190min, 200min, 210min, 220min, 230min or 240 min.

In the present invention, in step (1), the side surface of the billet is sprayed with a high-pressure water gun in order to remove scale (phosphate scale) on the surface of the billet.

In the present invention, the side surface of the billet is an outer surface of the billet except for a cross section.

In the method of the present invention, in the step (1), the injection pressure is 20 to 30 MPa. Specifically, the injection pressure may be 20MPa, 21MPa, 22MPa, 23MPa, 24MPa, 25MPa, 26MPa, 27MPa, 28MPa, 29MPa, or 30 MPa.

In the present invention, the pressure is an absolute pressure.

In the present invention, in the step (1), the injection angle is 40 to 50 °. In particular, the injection angle may be 40 °, 41 °, 42 °, 43 °, 44 °, 45 °, 46 °, 47 °, 48 °, 49 °, or 50 °.

In the present invention, when the billet is rolled into a small-section billet in step (1), there is no particular requirement for the rolling equipment, and it can be selected conventionally in the art.

In the present invention, the small cross-section billet is a billet having a cross-sectional dimension of 150mm × 150mm to 200mm × 200 mm.

In the present invention, when the small-section billet is rolled into a steel rail in step (1), there is no particular requirement for the rolling equipment, and the equipment can be selected conventionally in the art.

In the invention, in the step (1), in the process of rolling the small-section billet into the steel rail, multiple rolling passes are carried out, the rolling passes have no special requirements, the small-section billet can be rolled into the steel rail by the conventional selection in the field, and the mixture of heavy oil, graphite and water is sprayed on the side surface of the billet (except the side surface of the billet contacted with a roller way) before each rolling.

In the invention, in the step (1), the mass ratio of the heavy oil, the graphite and the water is 1:1-3: 1-7. Specifically, the mass ratio of the heavy oil, graphite and water may be 1:1:1, 1:1:3, 1:1:5, 1:1:7, 1:2:1, 1:2:3, 1:2:5, 1:2:7, 1:3:1, 1:3:3, 1:3:5 or 1:3: 7.

In the invention, after 20 steel rails are rolled, the rolling parameters and the grinding roller way are adjusted.

In the invention, in the step (2), after rolling is finished, the waste heat of the steel rail obtained in the step (1) is utilized to carry out accelerated cooling, and the cooling speed of the accelerated cooling is 1-4 ℃/s. Specifically, the cooling rate of the accelerated cooling may be 1 ℃/s, 1.5 ℃/s, 2 ℃/s, 2.5 ℃/s, 3 ℃/s, 3.5 ℃/s, or 4 ℃/s.

In a second aspect, the invention provides a hypereutectoid steel rail prepared by the above method.

In the present invention, the hypereutectoid steel rail contains 0.8 to 1.2% by weight of C, 0.1 to 0.8% by weight of Si, 0.4 to 1.3% by weight of Mn, 0.002 to 0.02% by weight of P, 0.001 to 0.7% by weight of Cr, 0.001 to 0.12% by weight of V, 0.001 to 0.004% by weight of Al, and the balance of Fe and S and inevitable impurities, based on the total weight of the hypereutectoid steel rail.

In particular embodiments, the content of C in the hypereutectoid steel rail may be 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, or 1.2 wt%.

In particular embodiments, the hypereutectoid steel rail may have a Si content of 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, or 0.8 wt%.

In particular embodiments, the hypereutectoid steel rail may have a Mn content of 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1 wt.%, 1.1 wt.%, 1.2 wt.%, or 1.3 wt.%.

In particular embodiments, the P content in the hypereutectoid steel rail may be 0.002 wt%, 0.005 wt%, 0.007 wt%, 0.01 wt%, 0.013 wt%, 0.015 wt%, 0.017 wt%, or 0.02 wt%.

In particular embodiments, the hypereutectoid steel rail may have a Cr content of 0.001 wt%, 0.005 wt%, 0.007 wt%, 0.01 wt%, 0.05 wt%, 0.07 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, or 0.7 wt%.

In particular embodiments, the content of V in the hypereutectoid steel rail may be 0.001 wt%, 0.003 wt%, 0.005 wt%, 0.007 wt%, 0.009 wt%, 0.01 wt%, 0.05 wt%, 0.07 wt%, 0.1 wt%, or 0.12 wt%.

In particular embodiments, the content of Al in the hypereutectoid steel rail may be 0.001 wt%, 0.002 wt%, 0.003 wt%, or 0.004 wt%.

In the present invention, the hypereutectoid steel rail contains residual elements such As Mo, Sn, Cu, and As, and it is necessary to control the content of these residual elements within an appropriate range in order to improve the overall performance of the rail.

In the present invention, the hypereutectoid steel rail contains 0.01 to 0.02% by weight of Mo, 0.001 to 0.02% by weight of Sn, 0.05 to 0.15% by weight of Cu, and 0.01 to 0.02% by weight of As, based on the total weight of the hypereutectoid steel rail.

In particular embodiments, the hypereutectoid steel rail may have a Mo content of 0.01 wt%, 0.011 wt%, 0.012 wt%, 0.013 wt%, 0.014 wt%, 0.015 wt%, 0.016 wt%, 0.017 wt%, 0.018 wt%, 0.019 wt%, or 0.02 wt%.

In particular embodiments, the content of Sn in the hypereutectoid steel rail may be 0.001 wt%, 0.003 wt%, 0.005 wt%, 0.007 wt%, 0.009 wt%, 0.01 wt%, 0.013 wt%, 0.015 wt%, 0.017 wt%, 0.019 wt%, or 0.02 wt%.

In specific embodiments, the content of Cu in the hypereutectoid steel rail may be 0.05 wt%, 0.07 wt%, 0.09 wt%, 0.1 wt%, 0.12 wt%, 0.13 wt%, or 0.15 wt%.

In particular embodiments, the As content in the hypereutectoid steel rail may be 0.01 wt%, 0.013 wt%, 0.015 wt%, 0.017 wt%, 0.019 wt%, or 0.02 wt%.

The hypereutectoid steel rail also contains gas components such as hydrogen, oxygen, nitrogen and the like, and the content of the chemical components needs to be controlled within a small range in order to improve the comprehensive performance of the steel rail.

In the invention, the content of hydrogen in the hypereutectoid steel rail is less than or equal to 2 ppm.

In the invention, the content of oxygen in the hypereutectoid steel rail is less than or equal to 20 ppm.

In the invention, the nitrogen content in the hypereutectoid steel rail is less than or equal to 60 ppm.

The preparation method of the hypereutectoid steel rail adopts the mixed lubrication rolling of heavy oil graphite water, ensures the infiltration of the surface carbon content of the hypereutectoid steel rail, ensures the requirements of the hypereutectoid steel rail on high precision and high surface quality, prolongs the service life of the steel rail, ensures that the size precision of the prepared hypereutectoid steel rail does not exceed +/-0.5 mm, the depth of a steel rail pit is less than or equal to 0.5mm, the tensile strength is more than or equal to 1400MPa, the elongation is more than or equal to 10 percent, improves the toughness of the steel rail while ensuring the strength of the hypereutectoid steel rail, and has excellent wear resistance and contact fatigue resistance. Is particularly suitable for high-speed heavy-load lines with locomotive speed more than or equal to 120km/h and annual traffic volume more than or equal to 1 hundred million tons.

The present invention will be described in detail by way of examples, but the scope of the present invention is not limited thereto.

The steel billets according to examples 1 to 5 and comparative examples 1 to 7 were prepared in the same manner by sequentially performing converter smelting, LF refining, RH vacuum treatment, protective casting, cooling and furnace heating of raw materials containing the corresponding chemical components.

Example 1

(1) Spraying the side surface of the steel billet heated by the heating furnace by using a high-pressure water gun (the heating temperature of the heating furnace is 1230 ℃, the heating time of the heating furnace is 240min), the spraying pressure is 20MPa, the spraying angle is 45 degrees, then rolling the steel billet into a small-section steel billet, then rolling the small-section steel billet into a steel rail by using a U1E1, U2E2 and UF rolling mill, and spraying a mixture of heavy oil, graphite and water to the side surface of the steel billet (except the side surface of the steel billet in contact with a roller way) before each rolling in the process of rolling the small-section steel billet into the steel rail, wherein the mass ratio of the heavy oil, the graphite and the water is 1:2: 5;

(2) carrying out accelerated cooling by utilizing the waste heat of the steel rail obtained in the step (1), wherein the cooling speed of the accelerated cooling is 1 ℃/s, and obtaining a hypereutectoid steel rail A1;

wherein the hypereutectoid steel rail contains 0.9 wt% of C, 0.45 wt% of Si, 0.95 wt% of Mn, 0.01 wt% of P, 0.2 wt% of Cr, 0.06 wt% of V, 0.002 wt% of Al, 0.01 wt% of Mo, 0.002 wt% of Sn, 0.05 wt% of Cu, 0.012 wt% of As, 0.8ppm of hydrogen, 5ppm of oxygen and 45ppm of nitrogen, and the balance of Fe and S and inevitable impurities, based on the total weight of the hypereutectoid steel rail.

Example 2

(1) Spraying the side surface of the steel billet heated by the heating furnace by using a high-pressure water gun (the heating temperature of the heating furnace is 1280 ℃, the heating time of the heating furnace is 150min), the spraying pressure is 20MPa, the spraying angle is 40 degrees, then rolling the steel billet into a small-section steel billet, then rolling the small-section steel billet into a steel rail by using a U1E1, U2E2 and UF rolling mill, and spraying a mixture of heavy oil, graphite and water to the side surface of the steel billet (except the side surface of the steel billet in contact with a roller way) before each rolling in the process of rolling the small-section steel billet into the steel rail, wherein the mass ratio of the heavy oil, the graphite and the water is 1:1: 1;

(2) carrying out accelerated cooling by utilizing the waste heat of the steel rail obtained in the step (1), wherein the cooling speed of the accelerated cooling is 4 ℃/s, and obtaining a hypereutectoid steel rail A2;

wherein the hypereutectoid steel rail contains 0.8 wt% of C, 0.1 wt% of Si, 0.4 wt% of Mn, 0.002 wt% of P, 0.7 wt% of Cr, 0.12 wt% of V, 0.004 wt% of Al, 0.015 wt% of Mo, 0.001 wt% of Sn, 0.1 wt% of Cu, 0.01 wt% of As, 2ppm of hydrogen, 20ppm of oxygen and 60ppm of nitrogen, the balance being Fe and S and unavoidable impurities, based on the total weight of the hypereutectoid steel rail.

Example 3

(1) Spraying the side surface of the steel billet heated by the heating furnace by using a high-pressure water gun (the heating temperature of the heating furnace is 1255 ℃, the heating time of the heating furnace is 195min), the spraying pressure is 30MPa, the spraying angle is 50 degrees, then rolling the steel billet into a small-section steel billet, then rolling the small-section steel billet into a steel rail by using a U1E1, a U2E2 and a UF rolling mill, and spraying a mixture of heavy oil, graphite and water to the side surface of the steel billet (except the side surface of the steel billet in contact with a roller way) before each rolling in the process of rolling the small-section steel billet into the steel rail, wherein the mass ratio of the heavy oil, the graphite and the water is 1: 3;

(2) carrying out accelerated cooling by utilizing the waste heat of the steel rail obtained in the step (1), wherein the cooling speed of the accelerated cooling is 2.5 ℃/s, so as to obtain a hypereutectoid steel rail A3;

wherein the hypereutectoid steel rail contains 1.2% by weight of C, 0.8% by weight of Si, 1.3% by weight of Mn, 0.02% by weight of P, 0.001% by weight of Cr, 0.001% by weight of V, 0.001% by weight of Al, 0.02% by weight of Mo, 0.02% by weight of Sn, 0.15% by weight of Cu, 0.02% by weight of As, 1ppm of hydrogen, 10ppm of oxygen and 35ppm of nitrogen, the balance being Fe and S and unavoidable impurities, based on the total weight of the hypereutectoid steel rail.

Example 4

The procedure of example 1 was followed, except that, in the step (1), the injection pressure was 25MPa, to obtain hypereutectoid steel rail A4.

Example 5

The procedure of example 1 was followed, except that, in the step (1), the injection pressure was 30MPa, to obtain hypereutectoid steel rail A5.

Comparative example 1

The process of example 1 was followed, except that, in step (1), the spraying angle was 60 ° and the mixture of heavy oil, graphite and water was not sprayed, to obtain hypereutectoid steel rail D1.

Comparative example 2

The process of example 1 was carried out, except that, in step (1), the injection pressure was 18MPa, the injection angle was 35 ℃ and the mixture of heavy oil, graphite and water was not sprayed, to obtain hypereutectoid steel rail D2.

Comparative example 3

The process was carried out as described in example 2, except that in step (1), the injection pressure was 15MPa, and hypereutectoid steel rail D3 was obtained.

Comparative example 4

The process was carried out as described in example 2, except that in step (1), the injection angle was 20 °, and hypereutectoid steel rail D4 was obtained.

Comparative example 5

The process was carried out as described in example 2, except that in step (1), the spray angle was 70 °, and hypereutectoid steel rail D5 was obtained.

Comparative example 6

The process was carried out as described in example 3, except that in step (1), the mixture of heavy oil, graphite and water was not sprayed, to obtain hypereutectoid steel rail D6.

Comparative example 7

The process was carried out as described in example 3, except that in step (1), the mass ratio of heavy oil, graphite and water was 1:4:8, to obtain hypereutectoid steel rail D7.

Test example 1

The finished steel rails obtained in the examples and comparative examples were subjected to tensile sample sampling, and the dimensional accuracy, rail pit depth, tensile strength, and elongation of the steel rail were tested. The size precision, the depth of the steel rail pits, the tensile strength and the elongation percentage of the steel rail are detected by adopting the standard of TB/T2344-. The test results are shown in table 1.

TABLE 1

Numbering	Dimensional accuracy/mm	Depth of rail pit/mm	Tensile strength/MPa	Elongation/percent
					A1	0.5	0.5	1405	10
A2	0.3	0.4	1468	12
					A3	0.3	0.4	1453	11
A4	0.4	0.3	1423	11
					A5	0.4	0.3	1426	10
D1	0.9	0.8	1422	11
					D2	1.2	1.5	1423	10
D3	1.1	1.2	1427	11
					D4	0.9	0.6	1429	10
D5	0.6	1.0	1451	10
					D6	0.8	0.9	1435	10
D7	0.5	1.1	1426	10

The results in Table 1 show that the hypereutectoid steel rail prepared by the method has the dimensional accuracy of not more than +/-0.5 mm, the depth of a steel rail pit is not more than 0.5mm, the tensile strength is not less than 1400MPa, and the elongation is not less than 10%. Therefore, the hypereutectoid steel rail prepared by the method has higher dimensional accuracy and surface quality, and is particularly suitable for high-speed heavy-load lines with locomotive speed of more than or equal to 120km/h and annual transport capacity of more than or equal to 1 hundred million tons.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.