Rolling contact damage resistant nano ceramic particle reinforced train wheel steel and preparation method thereof

Abstract

The invention provides rolling contact damage resistant nano ceramic particle reinforced train wheel steel and a preparation method thereof, and belongs to the technical field of preparation of train wheel steel. According to the steel for the wheel, Al powder, Ti powder and multi-walled carbon nanotubes are mixed to obtain mixed powder, and TiC / Al intermediate alloy is prepared through ball milling, cold press molding and hot press sintering; the TiC / Al intermediate alloy is crushed into alloy chippings, the alloy chippings are placed at the bottom of a steel ladle, molten steel of the wheel steel is tapped to the steel ladle, and the wheel steel is obtained after vacuum degassing refining, continuous casting, forging and heat treatment. The introduction method of the TiC / Al intermediate alloy carrier is adopted, the problems of particle aggregation, segregation, floating or sedimentation and the like caused by poor wettability and density difference when nanoparticles are directly added are effectively avoided, and the rolling contact damage resistance of the wheel steel is improved by introduction of the TiC / Al intermediate alloy carrier; and the high-performance requirements of modern rail transit on the steel for the wheels are met.

Description

Technical Field

[0001] This invention belongs to the field of steel preparation technology for train wheels, and particularly relates to a steel for train wheels reinforced with nano-ceramic particles that is resistant to rolling contact damage and its preparation method. Background Technology

[0002] As rail transit continues to develop towards high speed and heavy load, key load-bearing components such as train wheels are facing unprecedented challenges. Currently, the development of most high-performance train wheel steels still follows the traditional approach of strengthening and toughening metallic materials, such as composition design, microalloying, and microstructure control. However, significant breakthroughs have not been achieved in performance optimization, which undoubtedly indicates that traditional composition optimization and microstructure control methods have reached a significant bottleneck in improving the performance of wheel materials.

[0003] To address the aforementioned bottlenecks in strengthening wheel materials, a metal material strengthening and toughening technology based on nano-ceramic particles has attracted significant attention. Unlike traditional composition control techniques, this technology is characterized by introducing nano-ceramic particles during the smelting process. It utilizes a heterogeneous nucleation mechanism to regulate the as-cast microstructure, and in subsequent microstructure control stages, these particles act as pinning and nucleation sites, ultimately achieving a refined and uniform microstructure. While appropriate amounts of nanoparticles can effectively improve the overall material performance, direct addition still has significant limitations: the wettability between nano-ceramic particles and molten steel is poor, and the density difference between the two makes it difficult to achieve uniform distribution of nano-ceramic particles in the molten steel. Therefore, overcoming the technical limitations of existing addition methods and fundamentally improving the wettability and dispersion stability of nano-ceramic particles in the melt to achieve a uniform and dispersed distribution in the wheel steel matrix has become a key bottleneck driving this technology towards large-scale engineering applications.

[0004] Based on this, the present invention aims to provide a method that can effectively solve the above problems, so as to achieve the efficient and uniform introduction of nano-ceramic particles into the steel matrix for wheels, thereby giving full play to their strengthening effect and meeting the stringent requirements of high-end wheels for comprehensive performance. Summary of the Invention

[0005] Aiming to solve the core problem of poor wettability and easy agglomeration of nano-ceramic reinforcing phases in existing technologies, which makes it difficult to uniformly disperse in the steel matrix, this invention proposes a rolling contact damage resistant nano-ceramic particle reinforced steel for train wheels and its preparation method. This invention adopts a composite process of "in-situ synthesis + metal carrier transition". By pre-preparing TiC / Al intermediate alloy fragments containing nano-ceramic particles and introducing them into molten steel, the Al matrix is ​​melted in the molten steel by the up-and-down turbulence and convection of the molten steel. The Al matrix reacts with oxygen in the molten steel to generate steel slag that floats on the surface of the molten steel. The released TiC particles are uniformly dispersed in the steel matrix, achieving efficient and uniform introduction of the reinforcing phase, thereby significantly improving the rolling contact damage resistance of the wheel steel.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing steel for train wheels reinforced with nano-ceramic particles resistant to rolling contact damage, comprising the following steps: (1) Al powder, Ti powder and multi-walled carbon nanotubes are mixed to obtain a mixed powder, which is then ball-milled, cold-pressed and hot-pressed to obtain a TiC / Al master alloy; (2) The TiC / Al intermediate alloy obtained in step (1) is crushed into alloy fragments and placed at the bottom of the ladle. The molten steel for wheels is then poured into the ladle and subjected to primary refining, vacuum degassing refining, continuous casting, forging and heat treatment to obtain the steel for wheels.

[0007] This invention first prepares a TiC / Al master alloy by ball milling, cold pressing, and hot pressing sintering of Al powder, Ti powder, and multi-walled carbon nanotubes. TiC nanoparticles are then synthesized in situ using powder metallurgy and encapsulated within an Al matrix, addressing the issues of easy oxidation and poor dispersion of nanoparticles. The master alloy is then crushed and placed at the bottom of a ladle. The high temperature and convection after the molten steel is tapped allow the Al matrix to melt and react with oxygen in the molten steel, generating slag that floats to the surface. The released TiC nanoparticles are then uniformly dispersed within the steel matrix. Subsequent primary refining and vacuum degassing refining achieve homogenization and improved purity of the molten steel. Continuous casting and forging achieve billet formation and microstructural densification. Heat treatment regulates the microstructure of the steel (refining pearlite and optimizing ferrite morphology), ultimately improving the rolling contact damage resistance of wheel steel.

[0008] Furthermore, step (1) specifically includes the following steps: S1. Place Al powder, Ti powder and multi-walled carbon nanotube powder into a mixer. Set the speed of the mixer to 5-50 r / min and the mixing time to 5-20 h. After mixing evenly, a mixed powder is obtained. S2. The mixed powder obtained in S1 is loaded into a ball milling jar together with the ball milling media, wherein the mass ratio of the ball milling media to the mixed powder is 3:1. Then, under the protection of an inert atmosphere, the mixture is ball milled at a speed of 20-80 rpm for 20-40 hours. After the ball milling is completed, the mixture is dried to obtain Al, Ti and multi-walled carbon nanotube ceramic mixed particles. S3. After removing the mixed particles, wrap them with aluminum foil and press them into cold blocks using a cold press to obtain precast blocks; S4. Place the preform in a vacuum sintering furnace and perform hot pressing sintering under a protective atmosphere. After cooling to room temperature, a sintered body is obtained, which is the TiC / Al master alloy.

[0009] Furthermore, in the mixed powder, the mass fraction of Ti powder is 20-30%, the mass fraction of multi-walled carbon nanotube powder is 2-10%, and the remainder is Al powder.

[0010] Furthermore, the Al powder has a particle size of 2µm, the Ti powder has a particle size of 0-25µm, and the multi-walled carbon nanotube powder has a tube diameter of 3-15nm and a tube length of 15-30µm.

[0011] Furthermore, the hot pressing sintering is carried out under a protective atmosphere at a pressure of 10–50 MPa and a temperature of 850–950 °C.

[0012] Furthermore, step (2) specifically includes the following steps: S5. The alloy scraps are added to the bottom of the ladle. Then, the molten steel for wheels melted in the electric furnace is tapped into the ladle. The ladle then enters the LF ladle refining furnace for refining, and high-purity argon gas is blown into the molten steel simultaneously for stirring to promote further dispersion of the scraps. After that, the ladle enters the RH ladle refining furnace for vacuum degassing and refining, and then is continuously cast to obtain a continuously cast billet. S6. The continuously cast billet is forged and heat-treated to obtain the steel for wheels.

[0013] Furthermore, the TiC / Al master alloy is descaled and crushed into alloy fragments with a particle size of less than 5 mm.

[0014] Furthermore, the amount of the alloy scraps is 0.02 to 0.20 wt.% of the mass of the molten steel for the wheel.

[0015] Furthermore, the chemical composition of the molten steel for wheels, by mass percentage, includes: C 0.65–0.72%, Si 0.80–0.90%, Mn 0.90–1.00%, P≤0.018%, S≤0.018%, Cr 0.10–0.20%, V 0.03–0.06%, Mo 0.04–0.07%, Cu 0.20–0.27%, Ti 0.01–0.10%, Ni 0.16–0.20%, and Cr+Mo+Ni≤0.50%, with the remainder being Fe and unavoidable impurities.

[0016] Furthermore, the tapping temperature is 1520–1680℃, and high-purity argon gas is blown in throughout the process; the initial refining temperature is 1500–1700℃, and the time is 50–60 min; the vacuum degassing refining temperature is 1550–1600℃, and the time is 20–30 min.

[0017] Furthermore, the heating temperature for forging is 1200–1300°C, and the forging ratio is ≥4.

[0018] Furthermore, the heat treatment involves heating to 850–890°C, holding at that temperature for 2–3 hours, quenching at 510–540°C, and then tempering at 350–500°C.

[0019] The present invention also proposes a steel for train wheels reinforced with nano-ceramic particles that is resistant to rolling contact damage, which is prepared according to the above preparation method.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects: (1) The method for preparing steel for train wheels reinforced with nano-ceramic particles that resist rolling contact damage provided by the present invention adopts a two-step method of “TiC / Al intermediate alloy preparation - carrier introduction”, which effectively avoids the problems of particle agglomeration, segregation, floating or settling caused by poor wettability and density difference when directly adding nanoparticles in the background technology.

[0021] (2) The TiC nanoparticles generated by the in-situ reaction of this invention have a clean surface and are free from oxidation pollution, which can form a high-strength metallurgical bonding interface with the steel matrix. At the same time, a pearlitic microstructure with a fine interlamellar spacing is obtained, resulting in excellent reinforcing phase performance. The introduction of TiC / Al intermediate alloy carrier effectively inhibits the agglomeration and burn-off of TiC nanoparticles in molten steel, giving full play to its strengthening effect, thereby improving the rolling contact damage resistance of wheel steel and meeting the high-performance requirements of modern rail transit for wheel steel. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The image shows the microstructure of the TiC / Al master alloy prepared in Example 1. Figure 2 The XRD pattern of the TiC / Al master alloy prepared in Example 1; Figure 3 To compare the wear of the wheel steel samples in the examples and embodiments under the same number of cycles; Figure 4 Metallographic photograph of the steel used for producing wheels, for Comparative Example 1; Figure 5 A photograph showing the microstructure of the steel used for producing wheels, as shown in Comparative Example 1. Figure 6 A metallographic photograph of the wheel steel produced in Example 1; Figure 7 A photograph of the microstructure of the wheel steel produced in Example 1; Figure 8 Photographs showing the damaged surface morphology of the wheel specimen in Comparative Example 1; Figure 9 Photographs showing the damaged surface morphology of the wheel sample from Example 1; Figure 10 The curves show the variation of the adhesion coefficient at the wheel-rail contact interface for two types of wheel steel samples, namely Comparative Example 1 and Example 1. Detailed Implementation

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0026] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0027] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0028] This invention provides a method for preparing steel for train wheels reinforced with nano-ceramic particles resistant to rolling contact damage, comprising the following steps: (1) Al powder, Ti powder and multi-walled carbon nanotubes are mixed to obtain a mixed powder, which is then ball-milled, cold-pressed and hot-pressed to obtain a TiC / Al master alloy; (2) The TiC / Al intermediate alloy obtained in step (1) is crushed into alloy fragments and placed at the bottom of the ladle. The molten steel for wheels is then poured into the ladle and subjected to primary refining, vacuum degassing refining, continuous casting, forging and heat treatment to obtain steel for wheels.

[0029] In a preferred embodiment of the present invention, step (1) specifically includes the following steps: S1. Put 20-30% Ti powder, 2-10% multi-walled carbon nanotube powder and the balance Al powder into a mixer. Set the speed of the mixer to 5-50 r / min and the mixing time to 5-20 h. After mixing evenly, a mixed powder is obtained. S2. The mixed powder obtained in S1 is loaded into a ball milling jar together with the ball milling media, wherein the mass ratio of the ball milling media to the mixed powder is 3:1. Then, under the protection of an inert atmosphere, the mixture is ball milled at a speed of 20-80 rpm for 20-40 hours. After the ball milling is completed, the mixture is dried to obtain Al, Ti and multi-walled carbon nanotube ceramic mixed particles. S3. After the mixed particles are taken out, they are wrapped with aluminum foil and pressed into cold blocks using a cold press to obtain preformed blocks. The pressing rate of the cold press is controlled at 10-50 MPa / min, and the final pressing pressure is 100-500 MPa, preferably 200-300 MPa. After reaching the set pressure, the pressure is held for 30-300 seconds, preferably 60-120 seconds. S4. Place the preform in a vacuum sintering furnace and hot press sinter it under a protective atmosphere at a pressure of 10-50 MPa. The sintering temperature is 850-950℃, and the holding time is 30-120 min. After cooling to room temperature, the sintered body is obtained, which is the TiC / Al master alloy.

[0030] In a preferred embodiment of the present invention, step (2) specifically includes the following steps: S5. The TiC / Al master alloy is descaled and crushed into alloy fragments with a diameter range of 1-5 mm. These fragments are added to the bottom of the ladle, with the total amount of TiC / Al master alloy fragments controlled to be 0.02-0.20 wt.% of the mass of the molten wheel steel. Immediately afterwards, the molten wheel steel (chemical composition by mass percentage: C 0.65-0.72%, Si 0.80-0.90%, Mn 0.90-1.00%, P≤0.018%, S≤0.018%, Cr 0.10-0.20%, V 0.03-0.06%, Mo 0.04-0.07%, Cu 0.20-0.27%, Ti 0.01-0.10%, Ni...) is added to the ladle. The steel (containing 0.16-0.20% Cr+Mo+Ni≤0.50%, with the remainder being Fe and unavoidable impurities) is tapped into a ladle at 1520-1680℃. The ladle then enters the LF ladle refining furnace for primary refining at 1500-1700℃ for 50-60 minutes, while high-purity argon is simultaneously blown into the molten steel for stirring to further disperse debris. Afterward, the ladle enters the RH ladle refining furnace for vacuum degassing refining at 1550-1600℃ for 20-30 minutes, followed by continuous casting to obtain a continuously cast billet. S6. The continuously cast billet is heated and deformed by forging. The heating temperature of the continuously cast billet is 1200-1300℃, and the forging ratio is ≥4 to obtain a forged billet. S7. Heat the forging billet to 850-890℃, hold for 2-3 hours, and quench at 510-540℃. Then temper at 350-500℃ to obtain wheel steel.

[0031] This invention also proposes a steel for train wheels reinforced with nano-ceramic particles that is resistant to rolling contact damage, which is prepared according to the above preparation method.

[0032] All raw materials used in the embodiments of the present invention are commercially available. The particle size of Al powder is 2µm, the particle size of Ti powder is 0-25µm, and the diameter of multi-walled carbon nanotube powder is 3-15nm and the tube length is 15-30µm.

[0033] The technical solution of the present invention will be further illustrated by the following embodiments.

[0034] Example 1 S1. Put 24% Ti powder, 6% multi-walled carbon nanotube powder and 70% Al powder into a mixer. Set the speed of the mixer to 50 r / min and the mixing time to 5 h. After mixing evenly, a mixed powder is obtained. S2. The mixed powder obtained in S1 is loaded into a ball milling jar together with the ball milling media, wherein the mass ratio of the ball milling media to the mixed powder is 3:1. Then, under the protection of an inert atmosphere, it is ball milled at a speed of 50 rpm for 30 h. After the ball milling is completed, it is dried to obtain Al, Ti and multi-walled carbon nanotube ceramic mixed particles. S3. After the mixed particles are taken out, they are wrapped with aluminum foil and pressed into cold blocks using a cold press to obtain preforms. The pressing rate of the cold press is controlled at 30MPa / min, and the final pressing pressure is 300MPa. After reaching the set pressure, the pressure is held for 60s. S4. Place the preform in a vacuum sintering furnace and hot press sinter at a pressure of 50 MPa under a protective atmosphere. The sintering temperature is 900℃, and the holding time is 60 min. After cooling to room temperature, the sintered body is obtained, which is the TiC / Al master alloy. S5. The TiC / Al master alloy is descaled and crushed into alloy fragments with a diameter range of 1-5 mm. These fragments are added to the bottom of the ladle, with the total amount of TiC / Al master alloy fragments controlled to be 0.067 wt.% of the mass of the molten wheel steel. Immediately afterwards, the molten wheel steel (chemical composition by mass percentage: C 0.72%, Si 0.90%, Mn 1.00%, P 0.014%, S 0.015%, Cr 0.19%, V 0.06%, Mo 0.07%, Cu 0.25%, Ti 0.06%, Ni...) is added to the ladle. (0.18%, Cr+Mo+Ni=0.44%, the remainder being Fe and unavoidable impurities) The steel is tapped to a ladle at 1620℃, and then the ladle enters the LF ladle refining furnace for primary refining at 1600℃ for 60 minutes, while high-purity argon gas is blown into the molten steel simultaneously for stirring to promote further dispersion of debris; after that, the ladle enters the RH ladle refining furnace for vacuum degassing refining at 1580℃ for 30 minutes, and then continuously cast to obtain a continuously cast billet; S6. The continuously cast billet is heated and deformed by forging. The heating temperature of the continuously cast billet is 1250℃ and the forging ratio is 4.5 to obtain a forged billet. S7. The forging billet is heated to 870℃, held for 2.8h, and then quenched at 530℃, followed by tempering at 450℃ to obtain wheel steel.

[0035] Comparative Example 1 The molten steel for wheels (chemical composition by mass percentage: C 0.72%, Si 0.90%, Mn 1.00%, P 0.014%, S 0.015%, Cr 0.19%, V 0.06%, Mo 0.07%, Cu 0.25%, Ti 0.06%, Ni 0.18%, Cr+Mo+Ni=0.44%, the remainder being Fe and unavoidable impurities) smelted in an electric arc furnace is tapped into a ladle at 1620°C. The ladle then enters an LF ladle refining furnace for primary refining at 1600°C for 60 minutes. Afterward, the ladle enters an RH ladle refining furnace for vacuum degassing refining at 1580°C for 30 minutes. Finally, it is continuously cast to obtain a continuously cast billet. The continuously cast billet is heated and deformed by forging. The heating temperature of the continuously cast billet is 1250℃ and the forging ratio is 4.5 to obtain the forged billet. The forged billet was heated to 870℃, held for 2.8 hours, quenched at 530℃, and then tempered at 450℃ to obtain wheel steel.

[0036] Comparative Example 2 Same as Example 1, except that the preparation of TiC / Al master alloy is omitted and alloy debris is replaced with TiC nanoparticles of equal mass, while the rest of the preparation steps are the same.

[0037] Comparative Example 3 Same as Example 1, except that the TiC / Al master alloy is replaced with a TiC / Cu master alloy, that is, in the preparation process of the TiC / Al master alloy, Al powder is replaced with an equal mass of Cu powder.

[0038] Comparative Example 4 Same as Example 1, except that the particle size of the alloy fragments is 10-15 mm.

[0039] Comparative Example 5 Same as Example 1, except that the amount of alloy scrap added is 0.01 wt. of the mass of the molten steel for wheels.

[0040] Performance testing The microstructure of the TiC / Al master alloy prepared in Example 1 is shown in the photograph. Figure 1 XRD pattern can be found Figure 2 .according to Figure 1 It can be seen that the TiC nanoparticles have an approximately spherical morphology. Based on particle size statistics, most of the synthesized nanoparticles are between 60-120 nm, with an average diameter of 82.5 nm. Figure 2 It can be seen that the diffraction peaks correspond to the standard peaks of α-Al and TiC, and no other impurity peaks were found, which indicates that the synthesis reaction was completed and no intermediate phase was generated.

[0041] To compare the surface crack initiation resistance and wear resistance of the steel used in the production of wheels in Example 1 and Comparative Example 1, the wheel performance was tested according to standard YB / T5345 "Test Method for Rolling Contact Fatigue of Metallic Materials". This test was conducted on a wheel-rail rolling contact fatigue test bench using a dual-sample grinding test. The specific procedure was as follows: Before the test, the samples were ultrasonically cleaned and weighed. Each group of samples was measured six times, and the arithmetic mean was taken as the initial mass. The selected friction pair was U75V steel rail material. The test parameters were set as follows: maximum Hertzian contact stress 630.5 MPa, spindle speed 500 r / min, slip ratio 3%, and total test duration 10 hours. The test was conducted in stages. First, a 6000s rolling contact damage test was performed. Immediately after completion, the test conditions were switched to a wet rolling contact fatigue test using distilled water as the lubricating medium. After the test, the samples were ultrasonically cleaned and dried again, then weighed. The same method was repeated six times, and the arithmetic mean was taken for subsequent wear calculation. The wear amount of the steel wheel specimens in the comparative examples and embodiments under the same number of cycles is as follows: Figure 3 As shown in the figure, the wheel exhibits the worst wear resistance without any alloy scraps, with a wear amount of 0.2624g. While the wear resistance of the other comparative examples shows some improvement, it is still inferior to that of Example 1, which demonstrates the best wear resistance. A metallographic photograph of the steel used for the wheels produced in Comparative Example 1 is shown below. Figure 4 See microscopic tissue photos Figure 5 The metallographic photograph of the wheel steel produced in Example 1 is shown below. Figure 6 See microscopic tissue photos Figure 7 It can be seen that the ferrite in the wheel of Example 1 is in the form of fine strips / granules, which are more numerous and densely distributed. At the same time, the spacing between the pearlite lamellars is refined. In contrast, the microstructure of Comparative Example 1 contains proeutectoid ferrite, and the pearlite lamellars are larger and the uniformity is generally poor.

[0042] The damaged surface morphology photograph of the wheel specimen in Comparative Example 1 is shown below. Figure 8 The damaged surface morphology photograph of the wheel specimen in Example 1 is shown below. Figure 9 As can be seen, compared with the example sample, the comparative sample has more prominent flaking damage characteristics, obvious peeling pits are formed on the surface, and the surface roughness is high.

[0043] Figure 10 The curves showing the adhesion coefficient variation at the wheel-rail contact interface for the two wheel steel samples from Comparative Example 1 and Example 1 reveal that the adhesion coefficient of the comparative example sample fluctuates significantly with increasing cycle number. This is attributed to the unevenness of the wheel-rail contact interface during the wear process. The surface morphology characteristics, adhesion coefficient variation patterns, and wear test results corroborate each other, indicating that under the same experimental conditions, the wheel sample from Example 1 exhibits superior wear resistance.

[0044] The experimental results from the above comparative examples and embodiments demonstrate that adding a certain amount of TiC nanoparticles can effectively strengthen wheel steel.

[0045] Compared to existing technologies, this invention does not simply add nano-TiC particles directly to molten steel. Instead, it first synthesizes nano-TiC particles in situ under controlled conditions using powder metallurgy, and then uniformly encapsulates them in a metal carrier to form a TiC / Al master alloy. This TiC / Al master alloy serves as a transport carrier for the nano-reinforcing phase. During its introduction into the molten steel, the excellent wettability and compatibility between the metal carrier and the molten steel effectively prevents the nanoparticles from floating or sinking due to density differences, or from agglomerating due to interfacial non-wetting. As the metal carrier gradually melts and diffuses in the molten steel, the encapsulated nano-TiC particles are gradually and uniformly released and dispersed throughout the steel matrix. This ensures a high yield and uniform and dispersed spatial distribution of the nanoparticles, comprehensively improving the rolling contact damage resistance and service safety of wheel steel.

[0046] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing steel for train wheels reinforced with nano-ceramic particles resistant to rolling contact damage, characterized in that, Includes the following steps: (1) Al powder, Ti powder and multi-walled carbon nanotubes are mixed to obtain a mixed powder, which is then ball-milled, cold-pressed and hot-pressed to obtain a TiC / Al master alloy; (2) The TiC / Al intermediate alloy obtained in step (1) is crushed into alloy fragments and placed at the bottom of the ladle. The molten steel for wheels is then poured into the ladle and subjected to primary refining, vacuum degassing refining, continuous casting, forging and heat treatment to obtain the steel for wheels.

2. The method for preparing rolling contact damage resistant nano-ceramic particle-reinforced train wheel steel according to claim 1, characterized in that, In the mixed powder, the mass fraction of Ti powder is 20-30%, the mass fraction of multi-walled carbon nanotube powder is 2-10%, and the remainder is Al powder.

3. The method for preparing rolling contact damage resistant nano-ceramic particle-reinforced train wheel steel according to claim 1, characterized in that, The hot pressing sintering is carried out under a protective atmosphere at a pressure of 10–50 MPa and a temperature of 850–950 °C.

4. The method for preparing rolling contact damage resistant nano-ceramic particle-reinforced train wheel steel according to claim 1, characterized in that, The particle size of the alloy fragments is less than 5 mm.

5. The method for preparing rolling contact damage resistant nano-ceramic particle-reinforced train wheel steel according to claim 1, characterized in that, The amount of the alloy scrap is 0.02 to 0.20 wt. of the mass of the molten steel for wheels.

6. The method for preparing rolling contact damage resistant nano-ceramic particle-reinforced train wheel steel according to claim 1, characterized in that, The chemical composition of the molten steel for wheels, by mass percentage, includes: C 0.65–0.72%, Si 0.80–0.90%, Mn 0.90–1.00%, P≤0.018%, S≤0.018%, Cr 0.10–0.20%, V 0.03–0.06%, Mo 0.04–0.07%, Cu 0.20–0.27%, Ti 0.01–0.10%, Ni 0.16–0.20%, and Cr+Mo+Ni≤0.50%, with the remainder being Fe and unavoidable impurities.

7. The method for preparing rolling contact damage resistant nano-ceramic particle-reinforced train wheel steel according to claim 1, characterized in that, The tapping temperature is 1520–1680℃, the initial smelting temperature is 1500–1700℃, and the time is 50–60 min; the vacuum degassing refining temperature is 1550–1600℃, and the time is 20–30 min.

8. The method for preparing rolling contact damage resistant nano-ceramic particle-reinforced train wheel steel according to claim 1, characterized in that, The forging heating temperature is 1200-1300℃, and the forging ratio is ≥4.

9. The method for preparing rolling contact damage resistant nano-ceramic particle-reinforced train wheel steel according to claim 1, characterized in that, The heat treatment involves heating to 850–890°C, holding at that temperature for 2–3 hours, quenching at 510–540°C, and then tempering at 350–500°C.

10. A type of steel for train wheels reinforced with nano-ceramic particles to resist rolling contact damage, characterized in that, It is prepared according to any one of claims 1 to 9.

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