A method for producing a high wear resistant pearlitic rail

Abstract

The application discloses a preparation method of high wear-resistant pearlite rail, comprising the following steps: controlling low sulfur and low phosphorus of molten steel during smelting; casting the molten steel into billets; performing multi-pass rolling after heating the billets; obtaining refined pearlite structure by using accelerated cooling process after rolling; forming a surface strengthening layer by using air blast cooling or induction heat treatment; wherein, the final rolling temperature is controlled in the range of 820-900 DEG C, and the cooling speed in the controlled cooling stage is 2-8 DEG C / s; the chemical composition in percentage by mass is as follows: C: 0.68%-0.82%, Mn: 0.80%-1.50%, Si: 0.15%-0.40%, Cr: 0.20%, and the rest is Fe and impurities; wherein, the rail structure is refined pearlite structure. The application aims to provide a preparation method of high wear-resistant pearlite rail, so as to solve the problems of fast abrasion and obvious crack propagation of the existing rail under rolling and sliding contact conditions.

Description

Technical Field

[0001] This invention relates to the field of rail transit materials and friction and wear technology, and in particular to a method for preparing a high wear-resistant pearlitic steel rail. Background Technology

[0002] Railway rails endure the combined effects of cyclic rolling and sliding from train wheels throughout their service life, especially on curved tracks. Due to the significant lateral forces and slip ratios between the wheel flange and the rail side, the rail surface is prone to severe wear, plastic flow, and fatigue damage. Rail side wear is a critical issue affecting track lifespan and train safety. As train speeds and axle loads increase, the contact stress in the wheel-rail contact area continues to rise. Under repeated cyclic loading, the rail surface material is susceptible to localized deformation accumulation, gradually leading to cracks, spalling, and material detachment. While pearlitic rails, widely used in railway lines, offer high strength, good machinability, and low manufacturing costs, they still suffer from insufficient wear resistance under high contact stress and slip conditions. This problem is particularly pronounced on small-radius curves, heavy-haul lines, and areas with frequent start-stop cycles in urban rail transit.

[0003] Studies have shown that rail wear behavior is closely related to the roll-slip contact state between the wheel and rail. When the wheel-rail contact is under low slip conditions, the rail surface mainly exhibits slight oxidative wear with a relatively low material loss rate. As the slip rate increases, the surface gradually shows obvious plastic flow and shear deformation, and local areas begin to form thin metal flakes. Under higher slip conditions, the wheel-rail surface contact state further deteriorates, easily leading to severe wear phenomena such as ploughing, scratching, and blocky material peeling, causing the rail wear rate to increase rapidly. In addition, under long-term cyclic stress, a work-hardened layer forms on the rail surface. Local areas are prone to microcracks due to stress concentration. As the cracks continue to expand, they will further induce surface peeling and even spalling, seriously affecting the service stability of the rail.

[0004] Currently, to improve the wear resistance of rails, existing technologies typically employ methods such as increasing rail hardness, increasing pearlite content, or heat treatment for strengthening. For example, increasing the carbon content increases the volume fraction of pearlite, or heat treatment processes increase the surface hardness of the rail, thereby reducing the material wear rate. However, research has found that simply increasing hardness, while able to slow down wear to some extent, easily leads to a decrease in material toughness, making the rail more prone to brittle cracks under complex wheel-rail loads. Simultaneously, traditional pearlitic rails still have shortcomings in terms of microstructure uniformity and lamellar refinement. When the surface layer is subjected to large shear stress, localized plastic deformation easily occurs within the microstructure, accelerating material failure. In recent years, some studies have begun to use microalloying elements such as Cr and V to strengthen pearlitic rails, improving rail performance by enhancing microstructure stability and refining grains. However, under high-slip conditions, these methods still struggle to effectively suppress severe wear formation.

[0005] Further research revealed that the pearlite lamellar spacing, microstructure uniformity, and surface deformation capacity significantly influence the wear resistance of rails. The finer the pearlite lamellae, the stronger the material's resistance to plastic flow and shear deformation, effectively reducing surface stress concentration and slowing crack formation and propagation. Therefore, obtaining a refined and stable pearlite microstructure through rational control of chemical composition and controlled rolling and cooling processes is crucial for improving the wear resistance of rails under rolling-sliding combined contact conditions. Existing rail materials still suffer from high wear rates, limited service life, and high maintenance costs during long-term service on curved tracks. Therefore, it is necessary to develop a high-wear-resistant pearlite rail with higher microstructure stability and stronger resistance to rolling-sliding wear, along with its preparation method, to meet the demands of modern railways for long-life, high-reliability rail materials. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing high wear-resistant pearlitic steel rails, so as to solve the problems of rapid wear and obvious crack propagation of existing steel rails under rolling contact conditions.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] This invention discloses a method for preparing high wear-resistant pearlitic steel rails, comprising: controlling the molten steel to be low in sulfur and phosphorus during smelting; casting the molten steel to form a steel billet; heating the steel billet and then rolling it in multiple passes; obtaining a refined pearlitic microstructure by an accelerated cooling process after rolling; and forming a surface strengthening layer by using air jet cooling or induction heat treatment; characterized in that: the final rolling temperature is controlled at 820~900℃, and the cooling rate during the controlled cooling stage is 2~8℃ / s; wherein the air jet cooling... The process is as follows: after final rolling, the temperature is first rapidly cooled to 570-600℃ at 4-8℃ / s, then slowly cooled to 500℃ at 1.5-3.5℃ / s, followed by air cooling. The air pressure is 0.25-0.27MPa, and the nozzle is 15-18mm away from the rail surface, blowing air symmetrically onto the rail head and both sides. The induction heat treatment process is as follows: the rail head is heated to 800-1000℃ using a 1-10kHz medium frequency and held for 15-25 seconds, followed by cooling with air spray at 2-8℃ / s.

[0009] Its chemical composition by mass percentage is as follows: C: 0.68%~0.82%, Mn: 0.80%~1.50%, Si: 0.15%~0.40%, Cr: 0.20%~1.20%, V: 0.01%~0.06%, with the remainder being Fe and impurities; the microstructure of the rail is a refined pearlite microstructure.

[0010] Furthermore, the steel billet is heated to 1180°C.

[0011] Furthermore, the final rolling temperature is controlled at 860℃.

[0012] Furthermore, after rolling, air jet cooling is used for accelerated cooling, with the cooling rate controlled at 5℃ / s.

[0013] Furthermore, the pearlite lamellar spacing is 70~130nm.

[0014] Furthermore, the surface hardness of the rail is 360~430HB.

[0015] Furthermore, a reinforcing layer with a thickness of 0.2~0.8mm is formed on the surface of the rail.

[0016] Furthermore, its chemical composition by mass percentage is as follows: C: 0.76%, Mn: 1.200%, Si: 0.32%, Cr: 0.85%, V: 0.03%, with the remainder being Fe and impurities; the rail microstructure is a refined pearlitic microstructure.

[0017] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0018] By controlling the content of C, Mn, Cr, and V elements, and combining this with controlled rolling and cooling processes, a refined pearlitic microstructure is obtained, improving the resistance to plastic deformation and wear resistance of the rail surface layer. Specifically: C is used to increase the pearlitic volume fraction; Mn is used to improve hardenability; Cr is used to improve wear resistance; and V is used to refine the grains and improve microstructure stability. By controlling the cooling rate, the pearlitic lamellars are refined, thereby reducing localized plastic flow of the surface material under rolling-slip contact conditions.

[0019] The rail of this invention maintains a relatively stable surface structure even under high slip conditions, slowing down crack formation and propagation. Therefore, the rail of this invention has good wear resistance and service stability. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings.

[0021] Figure 1 Diagram of pearlitic microstructure of steel rail;

[0022] Figure 2 A comparison of the wear rates of two types of rails under different slip ratios;

[0023] Figure 3 This study compares the crack propagation depth of two types of rails under different cycles. Detailed Implementation

[0024] The present invention will be further described below with reference to embodiments.

[0025] The steel billet is heated to 1180℃. A multi-pass controlled rolling process is employed, with the final rolling temperature controlled at 860℃. After rolling, accelerated cooling is achieved using a jet cooling method, with a cooling rate controlled at 5℃ / s. The surface of the rail undergoes enhanced cooling treatment. Once the rail has air-cooled to 850~870℃, it enters the heat treatment unit. A symmetrical jet cooling system is used to cool the top and sides of the rail head using air cooling, controlling the air pressure at 0.25~0.27MPa, the nozzle distance from the rail surface at 16~18mm, and the initial air velocity at 4.5~4.8m / s. Forced cooling is stopped once the rail head temperature drops to 635~645℃, and the rail is allowed to air-cool naturally to room temperature. The chemical composition of the rail is shown in Table 1.

[0026] Table 1. Chemical composition of steel rails (wt%)

[0027] C Mn Si Cr V S P 0.76 1.20 0.32 0.85 0.03 0.009 0.012

[0028] Metallographic analysis results show that the rail microstructure is mainly composed of refined pearlite, with uniform pearlite lamellae and no obvious coarse carbides. The pearlite lamellar spacing is approximately 85 nm. Figure 1 .

[0029] The rolling-sliding wear tester was used for testing. The contact pressure was 1200 MPa, the slip ratio was 3%–30%, and the rotational speed was 400 r / min. Data comparisons are shown below. Figure 2 , Figure 3 Table 2.

[0030] Table 2. Effect of pearlite lamellar spacing on wear rate

[0031] Interlayer spacing (nm) Wear rate (mg / m) 160 2.84 130 2.16 110 1.74 85 1.37 70 1.22

[0032] Experimental results show that as the interlamellar spacing of pearlite decreases, the wear rate of the rail significantly decreases. This is because refining the pearlite improves the material's resistance to plastic deformation and reduces local stress concentration in the surface material under rolling-slip contact conditions. Simultaneously, the rail of this invention maintains a relatively stable surface structure even under high-slip conditions, slowing down crack formation and propagation. Therefore, the rail of this invention exhibits good wear resistance and service stability.

[0033] This invention optimizes the chemical composition and controlled rolling and cooling processes to obtain a refined pearlitic microstructure, thereby improving the wear resistance of the rail under rolling-slip contact conditions. Compared with traditional rails, the rails of this invention have a lower wear rate, higher surface hardness, and better microstructural stability, making them suitable for heavy-haul railways and curved tracks.

[0034] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a high wear-resistant pearlitic steel rail, comprising: During smelting, the molten steel is controlled to have low sulfur and low phosphorus content; Molten steel is poured into steel billets; The steel billet is heated and then rolled in multiple passes; The rolled material is subjected to an accelerated cooling process to obtain a refined pearlitic microstructure; a surface strengthening layer is formed by air jet cooling or induction heat treatment; the characteristics are: the final rolling temperature is controlled at 820~900℃, and the cooling rate during the controlled cooling stage is 2~8℃ / s; wherein the air jet cooling process is: after final rolling, it is first rapidly cooled to 570~600℃ at 4~8℃ / s, then slowly cooled to 500℃ at 1.5~3.5℃ / s and then air cooled, with an air pressure of 0.25~0.27MPa, the nozzle is 15~18mm away from the rail surface, and air is blown symmetrically on the rail head and both sides; the induction heat treatment process is: the rail head is heated to 800~1000℃ with a medium frequency of 1~10kHz and held for 15~25 seconds, and then cooled by air jet at 2~8℃ / s. Its chemical composition by mass percentage is as follows: C: 0.68%~0.82%, Mn: 0.80%~1.50%, Si: 0.15%~0.40%, Cr: 0.20%~1.20%, V: 0.01%~0.06%, with the remainder being Fe and impurities; the microstructure of the rail is a refined pearlite microstructure.

2. The method for preparing high wear-resistant pearlitic steel rails according to claim 1, characterized in that: The steel billet is heated to 1180℃.

3. The method for preparing high wear-resistant pearlitic steel rails according to claim 1, characterized in that: The final rolling temperature is controlled at 860℃.

4. The method for preparing high wear-resistant pearlitic steel rails according to claim 1, characterized in that: After rolling, the material is cooled by air jet cooling, with the cooling rate controlled at 5℃ / s.

5. The method for preparing high wear-resistant pearlitic steel rails according to claim 1, characterized in that: The pearlite lamellar spacing is 70~130nm.

6. The method for preparing high wear-resistant pearlitic steel rails according to claim 1, characterized in that: The surface hardness of the rail is 360~430HB.

7. The method for preparing high wear-resistant pearlitic steel rails according to claim 1, characterized in that: The surface of the rail is reinforced with a thickness of 0.2~0.8mm.

8. The method for preparing high wear-resistant pearlitic steel rails according to claim 1, characterized in that: Its chemical composition by mass percentage is: C: 0.76%, Mn: 1.200%, Si: 0.32%, Cr: 0.85%, V: 0.03%, with the remainder being Fe and impurities; the rail structure is a refined pearlitic structure.

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