CN113403467B - Production method for improving wear resistance of heat-treated steel rail - Google Patents
Production method for improving wear resistance of heat-treated steel rail Download PDFInfo
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- CN113403467B CN113403467B CN202110576248.2A CN202110576248A CN113403467B CN 113403467 B CN113403467 B CN 113403467B CN 202110576248 A CN202110576248 A CN 202110576248A CN 113403467 B CN113403467 B CN 113403467B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/04—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rails
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
Abstract
The invention discloses a production method for improving the wear resistance of a heat-treated steel rail, which comprises the step of carrying out dynamic accelerated cooling heat treatment on a rail head of the steel rail after hot rolling, wherein the starting cooling temperature is controlled to be 720 plus materials, a dynamic staged cooling process is adopted, namely the whole rail head cooling process is divided into 7 stages, the cooling speed of the 1 st stage is 5-7 ℃/s, the cooling speed of the 2 nd stage is 7-8 ℃/s, the cooling speed of the 3 rd stage is 8-10 ℃/s, the cooling speed of the 4 th stage is 1-2 ℃/s, the cooling speed of the 5 th stage is 4-6 ℃/s, the cooling speed of the 6 th stage is 3-4 ℃/s, the cooling speed of the 7 th stage is 2-3 ℃/s, when the temperature of the rail head is reduced to be below 300 ℃, the accelerated cooling is stopped, and finally the rail head is naturally cooled to the room temperature. The invention improves the wear resistance of the steel rail by reasonably controlling the Rockwell hardness distribution of the cross section, ensures that the rail head of the steel rail has good toughness and improves the comprehensive use performance of the steel rail.
Description
Technical Field
The invention relates to a production method of a steel rail, in particular to a production method for improving the wear resistance of a heat-treated steel rail, and belongs to the technical field of on-line heat-treated steel rail production.
Background
The railway construction in China is rapidly developing towards the direction of passenger transport high speed and freight transport heavy loading, the running speed, the load capacity and the running density of a train are obviously increased, the use environment of a steel rail is more severe, the problems of abrasion, fatigue damage and the like of the steel rail are increasingly serious, and the service life and the driving safety of the steel rail are seriously influenced.
At present, steel rail manufacturers at home and abroad generally adopt an online heat treatment process to improve the strength and hardness of the steel rail so as to improve the service performance of the steel rail. The on-line heat treatment of the steel rail mainly utilizes the residual heat of the rolled steel rail to carry out accelerated cooling on a rail head, obtain a more refined pearlite structure and improve the strength and the hardness of the steel rail. The Rockwell hardness of the cross section is a key index related to the service performance of the heat-treated steel rail, the prior on-line heat treatment process of the steel rail in the domestic steel works generally adopts a basically constant cooling speed for the surface of a rail head, the Rockwell hardness of the cross section of the heat-treated steel rail is gradually reduced from the surface of the rail head to the inside of the steel rail, a surface layer material has good wear resistance, and meanwhile, the internal hardness is reduced, so that the material is ensured to have certain toughness. On a heavy-duty line, however, the train axle is heavy, the surface layer material is worn quickly, the wear resistance of the steel rail is obviously reduced, and the service life of the steel rail is influenced; and if the whole rail head material is completely hardened, the toughness of the steel rail is obviously reduced, and the driving safety is threatened.
In the steel rail on-line heat treatment method, the Chinese patent with the publication number of CN 1793403A discloses a pearlite heat treatment steel rail and a production method thereof, wherein the production method comprises smelting, rolling and heat treatment, the steel rail is cooled to 400-500 ℃ from 650-880 ℃ at the cooling speed of 1-10 ℃/s, and then is naturally cooled to room temperature, and the produced steel rail has good wear resistance.
Chinese patent publication No. CN1178250A provides a heat treatment method for producing a high-strength steel rail using rolling waste heat, wherein the steel rail includes 0.65-0.85 mass% of C, 0.21-1.2 mass% of Si, 0.50-1.5 mass% of Mn, and at least one of V, Cr, Ti, Mo, Cu, Ni, and rare earth elements. The rail kept in the high temperature state in the austenite region after hot rolling is continuously fed into a unit equipped with a heat treatment device, and a cooling medium is sprayed to the rail through a nozzle to uniformly accelerate cooling of the rail, thereby obtaining a fine pearlite structure with gradually reduced hardness.
Chinese patent application No. CN106661651B provides a method and an apparatus for manufacturing a heat-treated steel rail having excellent hardness and toughness of the head surface layer by adding various alloying elements. The steel rail comprises 0.75-0.85 mass% of C, 0.5-1.0 mass% of Si, 0.5-1.0 mass% of Mn, 0.5-1.0 mass% of Cr, 0-0.01 mass% of V, and the balance of Fe and inevitable impurities. The steel rail head is cooled at a cooling rate of-5 ℃/s to 5 ℃/s before the completion of the phase change of the pearlite phase after the steel rail surface is forcibly cooled at a cooling rate of 10 ℃/s to 700 ℃ before the temperature of the steel rail surface is 500 ℃ to 700 ℃.
The invention patent of China with publication number CN 102220545A provides a high-carbon high-strength heat-treated steel rail with excellent wear resistance and plasticity and a production method thereof, the residual temperature of the hot steel rail after rolling is 680-one-900 ℃, the steel rail is cooled to 400-one-500 ℃ at the cooling speed of 1.5-10 ℃/s, and then is naturally cooled to room temperature, the tensile strength of the steel rail is more than or equal to 1330MPa, the elongation is more than or equal to 9%, the hardness of the rail head is more than or equal to 380HB, the structure is fine pearlite, the steel rail has excellent wear resistance and plasticity, and can meet the use requirements of heavy haul railways.
However, the above patents only focus on the steel rail heat treatment method and the improvement of tread hardness and strength, and do not relate to the problem of improving the wear resistance of the steel rail by reasonably controlling the cross section Rockwell hardness, and a production method capable of improving the wear resistance of the heat-treated steel rail is urgently needed to solve the problem of poor wear resistance of the heat-treated steel rail of the current heavy haul railway.
Disclosure of Invention
The invention aims to solve the technical problems that the surface hardened layer of the cross section of the heat-treated steel rail of the existing heavy-duty railway is shallow and the wear resistance is poor, and provides a production method for improving the wear resistance of the heat-treated steel rail, which improves the wear resistance of the steel rail by reasonably controlling the Rockwell hardness of the cross section and ensures that the rail head of the steel rail has good toughness.
The invention is realized in such a way that:
a production method for improving the wear resistance of a heat-treated steel rail mainly comprises the steps of carrying out dynamic accelerated cooling heat treatment on a rail head of the steel rail after hot rolling, wherein the starting cooling temperature is controlled to be 720-800 ℃, and a dynamic staged cooling process is adopted, namely the whole rail head cooling process is divided into 7 stages, the cooling speed of the 1 st stage is 5-7 ℃/s, the cooling speed of the 2 nd stage is 7-8 ℃/s, the cooling speed of the 3 rd stage is 8-10 ℃/s, the cooling speed of the 4 th stage is 1-2 ℃/s, the cooling speed of the 5 th stage is 4-6 ℃/s, the cooling speed of the 6 th stage is 3-4 ℃/s, the cooling speed of the 7 th stage is 2-3 ℃/s, when the temperature of the rail head is reduced to be below 300 ℃, the accelerated cooling is stopped, and finally the rail head is naturally cooled to room temperature.
The further scheme is as follows:
the cooling temperature is controlled to be 740-780 ℃, a dynamic stage cooling process is adopted, namely the whole rail head cooling process is divided into 7 stages, the cooling speed of the 1 st stage is 5.5-6.5 ℃/s, the cooling speed of the 2 nd stage is 7.2-7.8 ℃/s, the cooling speed of the 3 rd stage is 8.5-9.5 ℃/s, the cooling speed of the 4 th stage is 1.2-1.8 ℃/s, the cooling speed of the 5 th stage is 4.5-5.5 ℃/s, the cooling speed of the 6 th stage is 3.5-4 ℃/s, the cooling speed of the 7 th stage is 2.2-2.6 ℃/s, when the temperature of the rail head is reduced to be below 300 ℃, accelerated cooling is stopped, and finally the rail head is naturally cooled to the room temperature;
the further scheme is as follows:
cooling time of the 1 st stage, the 2 nd stage and the 3 rd stage is 7-10s, cooling time of the 4 th stage is 5-8s, cooling time of the 5 th stage and the 6 th stage is 15-20s respectively, and accelerated cooling is stopped when the temperature of the rail head is reduced to below 300 ℃ in the 7 th stage;
the further scheme is as follows:
the cooling speed difference between the 1 st stage and the 2 nd stage, and between the 2 nd stage and the 3 rd stage is controlled within 2 ℃/s;
the further scheme is as follows:
when the rail head is accelerated and cooled, a certain cooling speed is applied to the rail bottom, the cooling speed is controlled to be 70-80% of the cooling speed of the rail head, and when the rail head stops accelerated cooling, the rail bottom also stops cooling correspondingly;
the further scheme is as follows:
carrying out accelerated cooling heat treatment on the full length of the steel rail, wherein the rail head temperature refers to the temperature of the surface of the central part of the tread of the steel rail head;
the further scheme is as follows:
in the above production method, the chemical composition of the steel rail comprises 0.78-0.85 wt% of C, 0.60-0.80 wt% of Si, 0.75-1.10 wt% of Mn, 0.08-0.15 wt% of V, 0.10-0.15 wt% of Cr, less than or equal to 0.025 wt% of P, less than or equal to 0.025 wt% of S, and the balance of Fe and inevitable impurities, based on the total weight of the steel rail;
the further scheme is as follows:
the cooling medium is a cooling medium commonly used in the art and includes, but is not limited to, water, polymer solution, oil, compressed air, water mist, or oil mist mixture.
The invention also comprises other conventional methods in the steel rail production process, such as molten iron desulphurization, converter smelting, LF refining, vacuum treatment, continuous casting, casting blank heating, rolling, straightening and the like, and the steps are not particularly limited and can be carried out according to the conventional steel rail production process method. For example, the casting process should be carried out under the protection of the whole process to prevent the contact with air, the cast steel billet should be slowly cooled, a walking beam heating furnace is adopted to heat the casting blank, the heat preservation treatment is carried out, a universal rolling production line is adopted to roll, a horizontal and vertical composite straightening process is adopted, and the like;
according to the production method capable of improving the wear resistance of the heat-treated steel rail, provided by the invention, the rail head is subjected to dynamic staged accelerated cooling, the cooling speed and the cooling time of each stage are reasonably distributed, the dynamic balance of the external cooling flow field and the heat exchange of high-temperature metal is realized, the wear resistance of the steel rail is improved by reasonably controlling the Rockwell hardness distribution of the cross section, and meanwhile, the good toughness of the steel rail head is ensured, and the comprehensive use performance of the steel rail is improved.
Drawings
FIG. 1 is a schematic representation of Rockwell hardness measurement of a rail head cross section of a steel rail;
fig. 2 is a schematic diagram of a rail rolling contact wear test.
Detailed Description
The present invention will be further described with reference to the following examples.
The invention provides a production method for improving the wear resistance of a heat-treated steel rail, which mainly comprises the steps of carrying out dynamic accelerated cooling heat treatment on a rail head of the steel rail after hot rolling, wherein the starting cooling temperature is controlled to be 720-800 ℃, a dynamic stage cooling process is adopted, namely, the whole rail head cooling process is divided into 7 stages, the cooling speed of the 1 st stage is 5-7 ℃/s, the cooling speed of the 2 nd stage is 7-8 ℃/s, the cooling speed of the 3 rd stage is 8-10 ℃/s, the cooling speed of the 4 th stage is 1-2 ℃/s, the cooling speed of the 5 th stage is 4-6 ℃/s, the cooling speed of the 6 th stage is 3-4 ℃/s, the cooling speed of the 7 th stage is 2-3 ℃/s, when the temperature of the rail head is reduced to below 300 ℃, accelerated cooling is stopped, and finally, the rail head is naturally cooled to room temperature.
Preferably, the starting cooling temperature is controlled to be 740-780 ℃, a dynamic staged cooling process is adopted, namely the whole rail head cooling process is divided into 7 stages, the cooling speed of the 1 st stage is 5.5-6.5 ℃/s, the cooling speed of the 2 nd stage is 7.2-7.8 ℃/s, the cooling speed of the 3 rd stage is 8.5-9.5 ℃/s, the cooling speed of the 4 th stage is 1.2-1.8 ℃/s, the cooling speed of the 5 th stage is 4.5-5.5 ℃/s, the cooling speed of the 6 th stage is 3.5-4 ℃/s, the cooling speed of the 7 th stage is 2.2-2.6 ℃/s, when the temperature of the rail head is reduced to be lower than 300 ℃, accelerated cooling is stopped, and finally the rail head is naturally cooled to the room temperature.
In the invention, the cooling time of the 1 st stage, the 2 nd stage and the 3 rd stage is 7-10s, the cooling time of the 4 th stage is 5-8s, the cooling time of the 5 th stage and the 6 th stage is 15-20s, and the accelerated cooling is stopped when the 7 th stage is cooled until the temperature of the rail head is reduced to be below 300 ℃.
In the invention, the cooling speed difference between the 1 st stage and the 2 nd stage, and between the 2 nd stage and the 3 rd stage is controlled within 2 ℃/s.
The reasons for selecting the above process parameters are as follows: (1) the heat treatment strengthening principle of the steel rail is as follows: the rolled steel rail is still in the austenite temperature range, accelerated cooling is carried out, the pearlite transformation temperature is reduced, a refined pearlite structure is obtained, and the strength, the hardness and the wear resistance of the steel rail are improved. The initial cooling temperature is controlled to be 720-800 ℃, because the amount of metal of the rail head is large, if the rail head is directly cooled after rolling, the initial cooling temperature is too high, the surface layer begins to be cooled, but the core temperature is very high, heat conduction can be carried out outwards, the supercooling degree of pearlite phase transformation is insufficient, the final performance is affected, meanwhile, the initial cooling temperature is too high, which means that the austenitizing temperature and the final rolling temperature of the rail need to be increased, the problems of thick austenite grains, increased surface defects and the like are directly caused, the initial cooling temperature is too low, the distance from the phase transformation point of the pearlite is short, the supercooling degree is low, the phase transformation driving force is insufficient, and the risk of generating abnormal structures can be brought. The inventor finds that the opening cooling temperature of 720-800 ℃ is suitable through research. (2) The dynamic stage cooling process is adopted, namely the whole rail head cooling process is divided into 7 stages, the cooling speed of the 1 st stage is 5-7 ℃/s, the cooling speed of the 2 nd stage is 7-8 ℃/s, the cooling speed of the 3 rd stage is 8-10 ℃/s, the cooling time is 7-10s, the 1 st stage aims to quickly take away the heat of the rail head surface layer, quickly form a stable refined pearlite layer and ensure the surface tread hardness, meanwhile, a foundation is laid for the subsequent heat treatment, after the surface pearlite phase transformation is completed, the pearlite phase is changed to the secondary surface and the interior of the rail head, the heat transfer efficiency of high-temperature metal is reduced, at the moment, the cooling speed of the 2 nd stage and the cooling speed of the 3 rd stage are sequentially improved, the cooling speed is basically consistent within a certain depth of the surface layer, the pearlite phase transformation driving force is required to be consistent, and finally a hardened layer consistent with the surface hardness is obtained, the wear resistance is improved. (3) The cooling speed of the 4 th stage is 1-2 ℃/s, and the temperature stress and the phase change stress generated by accelerated cooling of the first 3 stages are mainly homogenized to prepare for cooling of the next stage. (4) The cooling speed of the 5 th stage is 4-6 ℃/s, the cooling speed of the 6 th stage is 3-4 ℃/s, the cooling speed of the 7 th stage is 2-3 ℃/s, at the moment, the rail head has enough metal quantity to generate pearlite phase change, the heat storage area of the core part can be further reduced, the internal heat is firstly conducted to the cooling pearlite layer, then the heat is dissipated to the outside through convection, and the 3 stages adopt the process of reducing the cooling speed in sequence to ensure that the actual cooling speed of the transition interface is uniformly reduced so as to ensure that the hardness is not reduced in a jumping way. When the temperature of the rail head is reduced to below 300 ℃, the pearlite transformation of the whole rail head is finished, and the accelerated cooling is not required to be carried out continuously.
In the invention, when the rail head is accelerated and cooled, a certain cooling speed is applied to the rail bottom, the cooling speed is controlled to be 70-80% of the cooling speed of the rail head, because the cooling speed of the rail head is higher, if the rail bottom is naturally cooled, the rail bottom temperature difference of the rail head is overlarge to cause the large-amplitude bending of the rail, in order to ensure the straightness of the rail in the heat treatment process, a certain cooling speed is generally applied to the rail bottom, the metal content of the rail bottom is smaller than that of the rail head, the cooling speed is generally controlled to be about 70-80% of the cooling speed of the rail head, and the temperature consistency of the rail bottom of the rail head is kept as much as possible.
The production method can be used for online heat treatment of the steel rail with any conventional component, can effectively improve the wear resistance of the heat treatment steel rail, and meanwhile, the inventor finds that the steel rail with a specific chemical component can have a better effect compared with the steel rail with other chemical components, and can be more suitable for the production method. The steel rail with the specific chemical composition comprises 0.78-0.85 wt% of C, 0.60-0.80 wt% of Si, 0.75-1.10 wt% of Mn, 0.08-0.15 wt% of V, 0.10-0.15 wt% of Cr, less than or equal to 0.025 wt% of P, less than or equal to 0.025 wt% of S and the balance of Fe and inevitable impurities based on the total weight of the steel rail;
the production method further comprises: the processes of molten iron desulfurization, converter smelting, LF refining, vacuum treatment, continuous casting, casting blank heating, rolling, straightening and the like are not particularly limited, and the processes can be carried out according to a conventional steel rail production process method. For example, the casting process should be carried out under full protection from air contact; slowly cooling the cast steel billet; heating a casting blank by adopting a walking beam heating furnace, and carrying out heat preservation treatment; rolling by adopting a universal rolling production line; and a horizontal and vertical composite straightening process and the like are adopted.
In the present invention, the cooling medium for accelerated cooling and slow cooling is a cooling medium commonly used in the art, and includes, but is not limited to, water, polymer solution, oil, compressed air, water mist or oil mist mixture, and any substance capable of providing a uniform cooling flow field.
The room-temperature metallographic structure of the whole section of the heat-treated steel rail obtained by the method is fine lamellar pearlite and a small amount of ferrite, abnormal structures such as bainite and martensite do not appear, and the mechanical properties of the steel rail meet the requirements of relevant standards.
For a better understanding of the present invention, the following examples are included to further illustrate the present invention, but it should be understood that the examples described herein are only for the purpose of illustrating the present invention and are not to be construed as limiting the present invention.
The metallurgical chemical compositions of examples 1 to 4 of the present invention are shown in Table 1.
Table 1 example steel rail chemical composition
Examples 1 to 3
(1) The method is carried out according to the conventional steel rail smelting and casting method, and the working procedures comprise molten iron desulphurization, converter smelting, LF refining, vacuum treatment and continuous casting. Wherein, the alkalinity of the converter slag is controlled to be 2.5-3.8; when molten steel is discharged about 1/4, alloy such as silicon, manganese, vanadium and the like and carburant are added along with the steel flow, and when the molten steel is discharged to 3/4, the alloy and the carburant are all added; the treatment time of the LF furnace is more than 40 min; RH vacuum degree is less than or equal to 90Pa, pure vacuum treatment time is not less than 20min, casting process is carried out under protection of the whole process to prevent contact with air, and cast steel billet is slowly cooled.
(2) The method is carried out according to the conventional steel rail rolling method, the steel billet is sent into a walking beam heating furnace to be heated and insulated at the heating temperature of 1210-1320 ℃ for the heat preservation time of 160-240min, and rolled into the steel rail by a universal rolling mill at the initial rolling temperature of 1080-1150 ℃ and the final rolling temperature of 880-930 ℃.
(3) The steel rail is subjected to dynamic stage online heat treatment, and specific process parameters of accelerated cooling after rolling are shown in table 2.
Table 2 example accelerated cooling process parameters
The performance indexes of tensile strength, tread hardness, metallographic structure, fracture toughness, Rockwell hardness and the like of the steel rails of the examples and the comparative examples are measured by a method specified by TB/T2344-2012 standard by taking the U75V heat-treated steel rail which is the widest application range on the current national iron heavy-duty line as a comparative example, and the results are shown in tables 3 and 4. The Rockwell hardness of the cross section of the rail head of the steel rail is measured and shown in an attached figure 1. The distance between the 1 st point and the surface is 5mm, and the distances between the other points are 5 mm; D. the distance between the line E and the lower jaw is 5 mm; B. line C is the angle bisector of lines A, D and A, E.
TABLE 3 comparison of mechanical properties of examples and comparative examples
TABLE 4 comparison of Rockwell hardness in Cross-section of examples and comparative examples
TABLE 4 comparison of Rockwell hardness in Cross-section of examples and comparative examples
In order to verify the wear resistance of the steel rail obtained by the invention, an M-2000 rolling contact wear tester is adopted to carry out contact fatigue wear tests on the steel rails of the examples and the comparative examples under the same test conditions. The abrasion weight loss was measured by relative rolling of the cylindrical samples, and the schematic diagram of the test is shown in fig. 2. The upper samples were taken from 5mm depth and 15mm depth sections of the example and comparative rails respectively, and the lower samples were wheel steels with a brinell hardness of 380 HB.
The test conditions were as follows:
sample size: the thickness is 8mm, the inner diameter is 10mm, and the outer diameter is 20 mm;
test load: 750N;
and (3) test environment: room temperature environment;
rotating speed: the upper sample is 180r/min, and the lower sample is 200 r/min;
slip ratio: 10 percent;
total number of revolutions of the counter mill: 3X 105 times.
The contact fatigue wear test results are shown in table 5.
TABLE 5 contact fatigue wear test results of examples and comparative examples
It can be seen that the steel rails of examples 1 to 3 have good mechanical properties and metallographic structures, meet the requirements of relevant standards, and have Rockwell hardness of the cross section substantially consistent within the range from the surface layer to the depth of 15mm, while the Rockwell hardness of the cross section of the heat-treated steel rail of comparative example U75V gradually decreases with the increase of the depth. From the results of the contact wear test, the weight loss on wear of the example rail at the 15mm depth was much lower than that of the U75V heat treated rail. In contrast, the method can effectively improve the wear resistance on the premise of ensuring the structure and the mechanical property of the heat-treated steel rail.
Although the present invention has been described herein with reference to the illustrated embodiments thereof, which are intended to be preferred embodiments of the present invention, it is to be understood that the invention is not limited thereto, and that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure.
Claims (6)
1. A production method for improving the wear resistance of heat-treated steel rails is characterized by comprising the following steps:
the method comprises the steps of carrying out dynamic accelerated cooling heat treatment on the rail head of the hot rolled steel rail, wherein the starting cooling temperature is controlled to be 720-;
cooling time of the 1 st stage, the 2 nd stage and the 3 rd stage is 7-10s, cooling time of the 4 th stage is 5-8s, cooling time of the 5 th stage and the 6 th stage is 15-20s respectively, and accelerated cooling is stopped when the temperature of the rail head is reduced to below 300 ℃ in the 7 th stage; the cooling speed difference between the 1 st stage and the 2 nd stage, and between the 2 nd stage and the 3 rd stage should be controlled within 2 ℃/s.
2. The production method for improving the wear resistance of the heat-treated steel rail according to claim 1, wherein:
the cooling temperature is controlled to be 740-780 ℃, a dynamic stage cooling process is adopted, namely the whole rail head cooling process is divided into 7 stages, the cooling speed of the 1 st stage is 5.5-6.5 ℃/s, the cooling speed of the 2 nd stage is 7.2-7.8 ℃/s, the cooling speed of the 3 rd stage is 8.5-9.5 ℃/s, the cooling speed of the 4 th stage is 1.2-1.8 ℃/s, the cooling speed of the 5 th stage is 4.5-5.5 ℃/s, the cooling speed of the 6 th stage is 3.5-4 ℃/s, the cooling speed of the 7 th stage is 2.2-2.6 ℃/s, when the temperature of the rail head is reduced to be below 300 ℃, accelerated cooling is stopped, and finally the rail head is naturally cooled to the room temperature.
3. The production method for improving the wear resistance of a heat-treated steel rail according to claim 1 or 2, wherein:
when the rail head is accelerated to cool, a certain cooling speed is applied to the rail bottom, the cooling speed is controlled to be 70-80% of the cooling speed of the rail head, and when the rail head stops accelerated cooling, the rail bottom stops cooling correspondingly.
4. The production method for improving the wear resistance of a heat-treated steel rail according to claim 1 or 2, wherein:
and carrying out accelerated cooling heat treatment on the full length of the steel rail, wherein the rail head temperature refers to the temperature of the surface of the central part of the tread of the rail head of the steel rail.
5. The production method for improving the wear resistance of a heat-treated steel rail according to claim 1 or 2, wherein:
the chemical components of the steel rail comprise 0.78-0.85 wt% of C, 0.60-0.80 wt% of Si, 0.75-1.10 wt% of Mn, 0.08-0.15 wt% of V, 0.10-0.15 wt% of Cr, less than or equal to 0.025 wt% of P, less than or equal to 0.025 wt% of S and the balance of Fe and inevitable impurities based on the total weight of the steel rail.
6. The production method for improving the wear resistance of a heat-treated steel rail according to claim 1 or 2, wherein:
the cooling medium is water, polymer solution, oil, compressed air, water mist or oil mist mixture.
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