Full-pearlite steel rail and production method and application thereof

Abstract

The invention provides a full-pearlite steel rail and a production method and application thereof. According to the invention, by controlling the content of elements in the steel rail, especially the C, Mn and Cr elements and the content ratio thereof, and optimizing the online heat treatment process of the steel rail, the steel rail with a full pearlitic structure is obtained under the condition that other production processes of the steel rail are not limited, and the tensile strength of the steel rail is greater than or equal to 1100MPa, the percentage elongation after fracture is greater than or equal to 10%, and the surface hardness is greater than or equal to 330HB. Meanwhile, the production method of the all-pearlite steel rail is simple and easy to operate, and large-scale application and popularization of the all-pearlite steel rail in lines such as high-speed railways and passenger and freight mixed transportation railways are facilitated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of rail production, and particularly relates to a full pearlite rail and a production method and application thereof. BACKGROUND

[0002] With the rapid development of domestic high-speed railway and mixed passenger and freight railway, higher requirements are put forward for the physical quality of rails. At present, in addition to the increasingly strict requirements for the size precision, surface quality of rails, the judgment standard and range of the internal quality of rails are gradually developing in the direction of more accuracy and larger range. Among these strict provisions, the microstructure requirement of in-line heat-treated rails cannot be ignored.

[0003] In recent years, domestic and foreign rail production enterprises have conducted a large number of researches to reduce the probability of occurrence of abnormal organizations such as martensite in rails, and the related patent technologies involved are as follows:

[0004] Patent CN 200510022444.6 discloses a pearlite heat-treated rail and a production method thereof. The chemical composition includes, by weight percentage, C: 0.70-0.95%, Si: 0.20-1.10%, Mn: 0.50-1.50%, V: 0.01-0.20%, Cr: 0.15-1.20%, P: ≤0.035%, S: ≤0.035%, and Al: ≤0.00%. The method includes the following steps: 1) smelting, 2) casting and rolling, 3) cooling from 650-880℃ to 400-500℃ at a cooling rate of 1-10℃ / s, or heating the steel rail cooled to room temperature to 850-1100℃, and then naturally cooling to 650-880℃, and cooling to 400-500℃ at a cooling rate of 1-10℃ / s, stopping cooling, and 4) naturally placing. It is tested that the rail produced by the patent is full pearlite organization and has good wear resistance. However, the patent does not consider the influence law of the proportion of each element content in the steel on the microstructure of the rail, and the production method includes multiple heating procedures, which is complex in technology, high in cost, and cannot be widely applied.

[0005] 400-500℃, stopping cooling, and 4) naturally placing. It is tested that the rail produced by the patent is full pearlite organization and has good wear resistance. However, the patent does not consider the influence law of the proportion of each element content in the steel on the microstructure of the rail, and the production method includes multiple heating procedures, which is complex in technology, high in cost, and cannot be widely applied.

[0006] Patent CN 201710394383.3 discloses a strong and tough pearlite rail and a manufacturing method thereof. The manufacturing method includes the following steps: a, hot rolling the steel billet into a rail, and the final rolling temperature is 900-1000℃; b, when the center temperature of the top surface of the rail is air-cooled to 850℃, cooling medium is sprayed to the rail head top surface, both sides of the rail head and the lower jaw of both sides of the rail head, and the center temperature of the top surface is cooled to 630-650℃; c, continue to spray the cooling medium, and after the surface layer temperature of the rail head is cooled to 480-500℃, air-cool to room temperature. The method prepares a rail with better strength and toughness by controlling the steel composition and two-stage accelerated cooling, and is suitable for heavy load and mixed passenger and freight railway applications. However, the rail described in the patent needs to add alloy elements such as V, NB and Ti, resulting in high production cost of the rail, and the interaction of elements such as Mn and Cr which can cause martensite abnormal organization is not considered, and the rail organization optimization is only carried out from the subsequent heat treatment process, which cannot fundamentally control the generation of abnormal organization of the rail.

[0007] Patent CN 202310775798.6 discloses a super-fine pearlite rail for heavy load railway and a production method thereof. The chemical composition of the steel is as follows: C 0.84-0.94%, Si 0.50-0.70%, Mn 0.75-0.90%, Cr 0.3≤Cr / C≤0.5, V 0.07-0.10%, Nb 0.01-0.03%, P≤0.015%, S≤0.010%, and the balance is Fe and inevitable impurities. The method is mainly applied to heavy load railway small radius line (curve line with a radius less than 300m), and through alloy composition design, controlled rolling and controlled cooling technology, the strength and hardness of the rail are improved while maintaining good toughness, and the contact fatigue resistance of the rail is improved. However, the rail uses a high content of alloy elements, has a narrow application range, and is difficult to be widely applied, and the control of the full pearlite structure of the rail is not fundamentally strengthened. SUMMARY

[0008] Therefore, the purpose of the present application is to provide a full pearlite rail and a production method and application thereof. The full pearlite rail has a long service life, is simple and easy to operate, and is beneficial to its large-scale popularization and application in high-speed railway and mixed passenger and freight railway lines.

[0009] To achieve this purpose, the present application adopts the following technical solutions:

[0010] In a first aspect, the present application provides a full pearlite rail, which has the following chemical components in terms of mass fraction: C: 0.60-0.85%, Si: 0.40-0.70%, Mn: 0.70-1.20%, Cr: 0.01-0.20%, V: 0.001-0.020%, P: 0.005-0.015%, S: 0.008-0.015%, and the balance of Fe and inevitable impurities.

[0011] C+Mn=1.5-1.8%, C / Mn≤0.95, Mn+Cr=0.90-1.05%, and Mn / Cr=5.5-7.0.

[0012] Preferably, the full pearlite rail has the following chemical components in terms of mass fraction:

[0013] C: 0.77%, Si: 0.55%, Mn: 0.90%, Cr: 0.15%, V: 0.002%, P: 0.007%, S: 0.009%, and the balance of Fe and inevitable impurities;

[0014] or

[0015] C: 0.73%, Si: 0.49%, Mn: 0.79%, Cr: 0.12%, V: 0.006%, P: 0.010%, S: 0.011%, and the balance of Fe and inevitable impurities;

[0016] or

[0017] C: 0.80%, Si: 0.61%, Mn: 0.85%, Cr: 0.14%, V: 0.004%, P: 0.012%, S: 0.014%, and the balance of Fe and inevitable impurities.

[0018] Preferably, the full pearlite rail has a full cross-section microstructure of pearlite.

[0019] Preferably, the full pearlite rail has a tensile strength ≥1100 MPa, an elongation after fracture ≥10%, and a surface hardness ≥330 HB.

[0020] In a second aspect, the present application provides a production method of the full pearlite rail, which comprises the following steps:

[0021] The furnace charge is subjected to converter smelting, LF furnace refining, RH vacuum treatment, and continuous casting to obtain a billet, which is subjected to rolling, on-line heat treatment, and processing, and thus the full pearlite rail is obtained.

[0022] The on-line heat treatment comprises accelerated cooling and air cooling in sequence.

[0023] The accelerated cooling is that after the rolling of the billet, the rail top surface and the rail head sides are accelerated cooled when the rail top surface temperature is 750-810 DEG C, and the cooling speed is 1.0-2.5 DEG C / s.

[0024] The air cooling is that the accelerated cooling is stopped when the accelerated cooling is to 490-550 DEG C, and the rail is air cooled to room temperature.

[0025] Preferably, the accelerated cooling is that after the rolling of the billet, the rail top surface and the rail head sides are accelerated cooled when the rail top surface temperature is 775-810 DEG C, and the cooling speed is 1.9-2.5 DEG C / s.

[0026] Preferably, the air cooling is that the accelerated cooling is stopped when the accelerated cooling is to 490-525 DEG C, and the rail is air cooled to room temperature.

[0027] Preferably, the cooling medium used in the on-line heat treatment is compressed air and / or water mist.

[0028] Preferably, the air cooling is carried out on a cooling bed.

[0029] Preferably, the billet obtained after continuous casting has a cross-sectional size of 250mm*250mm to 320mm*410mm and a length of 5000mm-7000mm.

[0030] In a third aspect, the present application provides an application of the full pearlite rail in high-speed railway or mixed passenger and freight railway.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] The present application provides a full pearlite rail, by controlling the element content in the rail steel, especially the C, Mn and Cr elements and the content ratio thereof, and by optimizing the on-line heat treatment process of the rail, a rail with full pearlite structure is obtained without limiting other production processes of the rail, the tensile strength of which is greater than or equal to 1100MPa, the elongation after fracture is greater than or equal to 10%, and the surface hardness is greater than or equal to 330HB. Thus, the full pearlite rail provided by the present application can effectively reduce the occurrence probability of rail damage caused by internal abnormal structure during service, prolong the service life of the rail, and improve the railway operation efficiency and safety. At the same time, the production method of the full pearlite rail provided by the present application is simple and easy to operate, which is beneficial to its large-scale popularization and application in high-speed railway and mixed passenger and freight railway. DETAILED DESCRIPTION

[0033] The technical solutions of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of the present application.

[0034] At present, the related technologies for controlling the microstructure of the steel rail to be full pearlite mostly control the microstructure of the steel rail by modifying some parameters in the production process of the steel rail, but generally do not involve the control of the content and proportion of the elements that are prone to cause the generation of abnormal structures such as martensite in the steel rail, and cannot realize the comprehensive regulation and control of the mechanical properties and the microstructure in the on-line heat-treated steel rail. In the exploration of the method for realizing the microstructure of the steel rail to be full pearlite, there are still obvious deficiencies. Based on this, the present application provides a full pearlite steel rail, the chemical composition of which consists of the following components in terms of mass fraction: C: 0.60-0.85%, Si: 0.40-0.70%, Mn: 0.70-1.20%, Cr: 0.01-0.20%, V: 0.001-0.020%, P: 0.005-0.015%, S: 0.008-0.015%, and the balance being Fe and unavoidable impurities.

[0035] Among them, C+Mn=1.5-1.8%, which can be 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75% or 1.8%; C / Mn≤0.95; Mn+Cr=0.90-1.05%, which can be 0.90%, 0.95%, 1.00% or 1.05%, etc.; Mn / Cr=5.5-7.0, which can be 5.5, 6.0, 6.5 or 7.0, etc.

[0036] In the present application, the above-mentioned C: 0.60-0.85% can be 0.60%, 0.65%, 0.70%, 0.75%, 0.80% or 0.85%, etc.

[0037] The above-mentioned Si: 0.40-0.70% can be 0.40%, 0.45%, 0.50%, 0.55%, 0.60%, 0.65% or 0.70%, etc.

[0038] The above-mentioned Mn: 0.70-1.20% can be 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.05, 1.11, 1.15 or 1.20, etc.

[0039] The above-mentioned Cr: 0.01-0.20% can be 0.01%, 0.05%, 0.1%, 0.15% or 0.20%, etc.

[0040] The V is 0.001-0.020%, which can be 0.001%, 0.005%, 0.01%, 0.015%, 0.02% and the like.

[0041] The P is 0.005-0.015%, which can be 0.005%, 0.008%, 0.010%, 0.012% or 0.015% and the like.

[0042] The S is 0.008-0.015%, which can be 0.008%, 0.009%, 0.010%, 0.012% or 0.015% and the like.

[0043] In some embodiments of the present application, the chemical composition of the full pearlite rail consists of the following components by mass fraction:

[0044] C: 0.77%, Si: 0.55%, Mn: 0.90%, Cr: 0.15%, V: 0.002%, P: 0.007%, S: 0.009%, the balance being Fe and inevitable impurities;

[0045] Or

[0046] C: 0.73%, Si: 0.49%, Mn: 0.79%, Cr: 0.12%, V: 0.006%, P: 0.010%, S: 0.011%, the balance being Fe and inevitable impurities;

[0047] Or

[0048] C: 0.80%, Si: 0.61%, Mn: 0.85%, Cr: 0.14%, V: 0.004%, P: 0.012%, S: 0.014%, the balance being Fe and inevitable impurities.

[0049] Herein, the design idea of the chemical composition of the full pearlite rail in the present application is explained:

[0050] C is a key element for pearlite formation, which directly determines the interlamellar spacing of pearlite and the thickness of cementite by forming a lamellar structure of cementite (Fe3C) and ferrite, thereby affecting the strength and hardness. When the C content is <0.60%, the proportion of pearlite structure of the rail is insufficient, resulting in low strength and hardness, which affects the wear resistance. When the C content is >0.85%, the cementite lamella thickens, the pearlite becomes brittle, the elongation after fracture decreases, the risk of rail fracture increases, which affects the fatigue performance and safety of the rail. Therefore, the C content in the present application is limited to 0.60-0.85%.

[0051] Si as a solid solution strengthening element, can improve the strength of ferrite matrix, and reduce the oxide inclusions in steel, optimize the pearlite structure. When Si content < 0.40%, its solid solution strengthening effect is insufficient; when Si content > 0.70%, the C activity is increased, VC is precipitated too early, the effect of subsequent heat treatment is affected, and the weldability is reduced. Therefore, the Si content in the application is limited to 0.40-0.70%.

[0052] Mn can significantly improve the hardenability of steel by reducing the austenite transformation temperature and increasing the supercooling degree, and can refine the pearlite lamellar spacing and improve the mechanical properties of the rail. When Mn content < 0.70%, the pearlite is not refined enough, the hardenability is reduced, which will lead to insufficient strength and hardness of the steel; when Mn content > 1.20%, the risk of grain coarsening increases, which may reduce the toughness and plasticity of the rail, and form bainite or martensite in the Mn segregation area, affecting the welding performance. Therefore, the Mn content in the application is limited to 0.70-1.20%.

[0053] Cr as a carbide forming element, can form various carbides with carbon in steel, and can improve the hardenability, strength and wear resistance of the rail. When Cr content < 0.01%, the hardenability is insufficient, and the strengthening effect is not obvious; when Cr content > 0.20%, σ phase may be formed, which will sharply reduce the impact toughness and affect the safe use of the rail. Therefore, the Cr content in the application is limited to 0.01-0.20%.

[0054] V can significantly improve the strength and toughness of the rail by forming carbonitride to inhibit the growth of austenite grains and refine the pearlite lamellar spacing. When V content < 0.001%, the grain refinement effect is insufficient, the pearlite lamellar spacing is large, and the strength and wear resistance of the rail are reduced; when V content > 0.020%, excessive carbonitride is precipitated, which may reduce the plasticity and toughness, and affect the processing performance of the rail. Therefore, the V content in the application is limited to 0.001-0.020%.

[0055] P as a harmful element in steel that is difficult to completely remove, is easy to segregate at the grain boundary, which will reduce the toughness of the rail. Therefore, the P content in the application should be strictly controlled below 0.015% to ensure the impact toughness of the rail.

[0056] S in steel is easy to form MnS inclusions, which will affect the fatigue performance and wear resistance of the rail. Therefore, the S content in the application should be controlled below 0.015% to reduce the size and number of sulfide inclusions.

[0057] In the present application, the C+Mn is limited in the range of 1.5-1.8%, which can ensure sufficient total amount of carbon and manganese to form high-strength pearlite, while avoiding the decrease of plasticity and toughness, and can combine with the online heat treatment process design to optimize the pearlite structure by controlling the austenite decomposition temperature; the C / Mn is limited to be ≤0.95, which can ensure that the solid solution strengthening effect of Mn is not weakened by excessive carbon, while avoiding the increase of brittleness caused by excessive carbon; the Mn+Cr is limited in the range of 0.90-1.05%, which can ensure that the two together optimize the pearlite structure and avoid the negative effects caused by the increase of Mn or Cr; the Mn / Cr is limited in the range of 5.5-7.0, which can avoid the risk of temper brittleness or σ phase precipitation caused by excessive Cr, while controlling the content of Mn element to avoid insufficient hardenability.

[0058] The present application also provides a production method of the full pearlite rail, comprising the following steps:

[0059] The furnace charge is subjected to converter smelting, LF furnace refining, RH vacuum treatment and continuous casting to obtain a billet, and the billet is subjected to rolling, online heat treatment and processing, and the full pearlite rail is obtained.

[0060] The converter smelting, LF furnace refining, RH vacuum treatment and continuous casting to obtain a billet, and the rolling and processing of the billet can be carried out according to the means well known to those skilled in the art, and will not be described here. The billet obtained after continuous casting has a cross-sectional size of 250mm×250mm to 320mm×410mm, such as 250mm×250mm, 300mm×250mm, 320mm×250mm, 250mm×300mm, 250mm×350mm, 250mm×410mm or 320mm×410mm, etc., and a length of 5000mm-7000mm, such as 5000mm, 5500mm, 6500mm or 7000mm, etc.

[0061] In the present application, the online heat treatment is a key process, and the accelerated cooling and air cooling are preferred.

[0062] The accelerated cooling is that, after the rolling of the billet is completed, the rail top surface and both sides of the rail head are subjected to accelerated cooling when the temperature of the rail top surface is 750-810℃, and the cooling speed is 1.0-2.5℃ / s.

[0063] The air cooling is that, when the accelerated cooling is stopped at 490-550℃, the rail is air cooled to room temperature.

[0064] In the present application, the above-mentioned 750-810℃ can be 750℃, 755℃, 760℃, 765℃, 770℃, 775℃, 780℃, 785℃, 790℃, 795℃, 800℃, 805℃ or 810℃, etc. The above-mentioned 1.0-2.5℃ / s can be 1.0℃ / s, 1.1℃ / s, 1.2℃ / s, 1.3℃ / s, 1.4℃ / s, 1.5℃ / s, 1.6℃ / s, 1.7℃ / s, 1.8℃ / s, 1.9℃ / s, 2.0℃ / s, 2.1℃ / s, 2.2℃ / s, 2.3℃ / s, 2.4℃ / s or 2.5℃ / s, etc.

[0065] The above-mentioned 490-550℃ can be 490℃, 495℃, 500℃, 505℃, 510℃, 515℃, 520℃, 525℃, 530℃, 540℃, 545℃ or 550℃, etc.

[0066] In some specific embodiments of the present application, the online heat treatment comprises accelerated cooling and air cooling, the accelerated cooling is that after the rolling of the billet is finished, the rail top surface and both sides of the rail head are subjected to accelerated cooling when the rail top surface temperature is 775℃, and the cooling speed is 1.9℃ / s; the air cooling is that when the accelerated cooling is stopped at 525℃, the rail is air cooled to room temperature.

[0067] In some embodiments of the present application, the cooling medium used in the online heat treatment is compressed air and / or water mist.

[0068] It is explained that the process parameters of the above-mentioned online heat treatment are obtained through a large number of experimental explorations, and the specific findings are as follows:

[0069] (1) Only when the starting speed of the accelerated cooling of the rail (i.e. the rail top surface temperature after the rolling of the rail is finished) is controlled in the range of 750-810℃ and the cooling speed is controlled in the range of 1.0-2.5℃ / s, can the internal heat redistribution of the rail during the accelerated cooling process be ensured under the condition that the accelerated cooling medium is applied to the surface, the microstructure of the whole cross section of the rail is pearlite, and good mechanical properties are obtained;

[0070] (2) When the rail is cooled to 490-550℃, the internal pearlite transformation of the rail head is completed, and the performance of the surface layer of the rail cannot be improved by continuing the accelerated cooling, but the possibility of abnormal microstructure such as martensite in the rail will greatly increase, therefore the accelerated cooling is stopped in this temperature range;

[0071] (3) After the accelerated cooling of the rail is stopped, in order to supplement the temperature of the rail waist and rail bottom to the rail head and reduce the residual stress of the rail, the air cooling of the cooling bed is used to continue to cool the rail to room temperature without other heat preservation actions.

[0072] Specifically, the complete manufacturing process of the full pearlite steel rail according to the present application can be as follows: using low-sulfur vanadium-containing molten steel, smelting by a converter (or an electric furnace), LF refining, RH vacuum treatment, obtaining a billet by protective continuous casting of a large billet, heating the billet in a billet heating furnace, high-pressure water descaling before rolling of the billet, rolling the billet by a universal rolling mill, on-line heat treatment of the steel rail (the specific process and parameters are as described above), air cooling at room temperature in a step-by-step cooling bed chamber, flat-stand combined straightening, steel rail specification inspection, processing line treatment, surface inspection and warehousing.

[0073] Tests show that the full-section microstructure of the steel rail obtained according to the component design and the above process is pearlite, and the steel rail has excellent mechanical properties, with a tensile strength of ≥1100 MPa, an elongation after fracture of ≥10% and a surface hardness of ≥330 HB.

[0074] Based on this, the present application further provides an application of the above full-pearlite steel rail in high-speed railways or mixed passenger and freight railways.

[0075] In order to further illustrate the present application, the following examples are used for illustration.

[0076] The chemical components of the steel rails involved in Examples 1-3 and Comparative Examples 1-4 are shown in Table 1 (the balance is Fe and unavoidable impurities), and the calculation results of C+Mn, C / Mn, Mn+Cr and Mn / Cr of each example are shown in Table 2.

[0077] Table 1

[0078]

[0079]

[0080] Table 2

[0081] No. C + Mn (wt. %) C / Mn Mn + Cr (wt. %) Mn / Cr Example 1 1.67 0.86 1.05 6.00 Example 2 1.52 0.92 0.91 6.58 Example 3 1.65 0.94 0.99 6.07 Comparative Example 1 1.76 0.81 1.17 4.85 Comparative Example 2 1.74 0.66 1.18 8.08 Comparative Example 3 1.70 1.00 0.99 6.07 Comparative Example 4 1.67 0.86 1.05 6.00

[0082] The production method of the pearlite steel rail adopted in Examples 1-3 and Comparative Examples 1-3 comprises, in sequence: using low-sulfur vanadium-containing molten steel, smelting by a converter, LF refining, RH vacuum treatment, obtaining a billet by protective continuous casting of a large billet, heating the billet in a billet heating furnace, high-pressure water descaling before rolling of the billet, rolling the billet by a universal rolling mill, on-line heat treatment of the steel rail, air cooling at room temperature in a step-by-step cooling bed chamber, flat-stand combined straightening, steel rail specification inspection, processing line treatment, surface inspection and warehousing.

[0083] Among them, Examples 1-3 and Comparative Examples 1-3 adopt the same on-line heat treatment production process (processes 1#, 2# and 3#), and Comparative Example 4 adopts a comparative on-line heat treatment production process (process 4#), and the detailed processes are shown in Table 3, and the differences between the remaining processes of the examples and the comparative examples can be ignored.

[0084] Table 3

[0085] No. Accelerated cooling start temperature (°C) Accelerated cooling rate (°C / s) Accelerated cooling end temperature (°C) Process 1 775 1.9 525 Process 2 801 2.4 550 Process 3 759 1.2 505 Process 4 720 2.5 450

[0086] According to the above chemical composition and production process, the tensile properties, surface hardness and microstructure of the steel rails obtained in Examples 1-3 and Comparative Examples 1-4 are shown in Tables 4-6. Specifically, the tensile strength and elongation after fracture of the steel rails are measured according to GB / T 228.1 "Metallic Materials - Tensile Testing - Part 1: Method of Test at Room Temperature"; the surface hardness of the steel rails is measured by Brinell hardness measurement method according to the provisions in GB / T 231.1 "Metallic Materials - Brinell Hardness Test - Part 1: Test Method"; and the microstructure of the steel rails is determined according to TB / T2344.1-2020 "Steel Rails - Part 1: Rails of 43 kg / m to 75 kg / m" and the provisions in GB / T 13298-2015 "Metallic Materials - Microstructure Examination Methods".

[0087] Table 4 (Process 1#, Comparative Example 4 is 4#)

[0088]

[0089] Table 5 (Process 2#)

[0090]

[0091] Table 6 (Process 3#)

[0092]

[0093] By comparing the examples and comparative examples, it can be seen that under the same process conditions, the different element contents and proportions of the steel rails of the examples of the present application have a significant influence on the final microstructure and properties of the steel rails, and the final microstructure and properties of the steel rails obtained under different process conditions also have great differences. At the same time, from Tables 4-6, it can be seen that the steel rails obtained by the method of the present application have more stable full pearlite microstructure and better mechanical properties than Comparative Examples 1-4, with a tensile strength of ≥1100 MPa, an elongation after fracture of ≥10%, and a surface hardness of ≥330 HB.

[0094] The above description of the disclosed examples enables one of ordinary skill in the art to make or use the application. Various modifications to these examples will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other examples without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the examples shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A fully pearlitic steel rail, characterized in that, Its chemical composition, by mass fraction, consists of the following components: C: 0.60–0.85%, Si: 0.40–0.70%, Mn: 0.70–1.20%, Cr: 0.01–0.20%, V: 0.001–0.020%, P: 0.005–0.015%, S: 0.008–0.015%, with the balance being Fe and unavoidable impurities; C+Mn=1.5~1.8%, C / Mn≤0.95, Mn+Cr=0.90~1.05%, Mn / Cr=5.5~7.

0.

2. The all-pearlitic steel rail according to claim 1, characterized in that, The chemical composition of the fully pearlitic steel rail, by mass fraction, consists of the following components: composition: C: 0.77%, Si: 0.55%, Mn: 0.90%, Cr: 0.15%, V: 0.002%, P: 0.007%, S: 0.009%, balance Fe and unavoidable impurities; or C: 0.73%, Si: 0.49%, Mn: 0.79%, Cr: 0.12%, V: 0.006%, P: 0.010%, S: 0.011%, balance Fe and unavoidable impurities; or C: 0.80%, Si: 0.61%, Mn: 0.85%, Cr: 0.14%, V: 0.004%, P: 0.012%, S: 0.014%, balance Fe and unavoidable impurities.

3. The all-pearlitic steel rail according to claim 1, characterized in that, The entire cross-section of the rail is composed of pearlite microstructure.

4. The all-pearlitic steel rail according to any one of claims 1 to 3, characterized in that, The rail has a tensile strength ≥1100MPa, elongation after fracture ≥10%, and surface hardness ≥330HB.

5. A method for producing a fully pearlitic steel rail as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The furnace charge is sequentially smelted in a converter, refined in an LF furnace, vacuum treated in an RH furnace, and continuously cast to obtain a steel billet. The steel billet is then rolled, heat-treated online, and processed to obtain the final product. The online heat treatment includes sequential accelerated cooling and air cooling; The accelerated cooling is as follows: after the billet rolling is completed, when the temperature of the top surface of the rail is 750-810℃, the top surface of the rail and both sides of the rail head are accelerated cooled at a rate of 1.0-2.5℃ / s. The air cooling process involves accelerating the cooling process to 490–550°C, then stopping the accelerated cooling and allowing the rails to air-cool to room temperature.

6. The production method according to claim 5, characterized in that, The accelerated cooling is as follows: after the billet rolling is completed, when the temperature of the rail top surface is 775-810℃, the rail top surface and both sides of the rail head are accelerated cooled at a rate of 1.9-2.5℃ / s. The air cooling process involves accelerating the cooling to 490–525°C, then stopping the accelerated cooling and allowing the rail to air cool to room temperature.

7. The production method according to claim 5 or 6, characterized in that, The cooling medium used in the online heat treatment is compressed air and / or water mist.

8. The production method according to any one of claims 5 to 7, characterized in that, The air cooling is performed on a cooling bed.

9. The production method according to any one of claims 5 to 8, characterized in that, The steel billet obtained after continuous casting has a cross-sectional size of 250mm×250mm to 320mm×410mm and a length of 5000mm to 7000mm.

10. The application of the all-pearlite rail according to any one of claims 1 to 4 or the all-pearlite rail obtained by the production method according to any one of claims 5 to 8 in high-speed railways or passenger and freight railways.

Images