Medium carbon steel train axle and production method thereof

Abstract

The invention discloses a medium carbon steel train axle and a production method thereof, and belongs to the technical field of train axles, and the production method comprises the following steps: uniformly heating a continuous casting billet to a temperature above a plastic deformation temperature, and carrying out heat preservation; carrying out rough rolling and finish rolling on the heated continuous casting billet, and then sequentially carrying out water cooling and air cooling to obtain a rolled billet; the rolled blank is machined, and the axle is obtained; carrying out induction quenching heat treatment on the axle neck part of the axle; tempering the axle subjected to induction quenching heat treatment; the tempered axle is subjected to shot peening strengthening treatment; the weight percentage of the carbon element in the medium carbon steel train axle is 0.28-0.60%; compared with a traditional production process, the production method provided by the invention has the advantages that an axle forging forming procedure is omitted, a high-quality axle product is obtained by directly machining and forming round billet continuous casting, round billet rolling and machining in combination with a tempering heat treatment and surface strengthening process, the production cost is reduced, and the manufacturing efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of train axle technology, specifically relating to a medium carbon steel train axle and its manufacturing method. Background Technology

[0002] As a core load-bearing component in rail transit, the manufacturing process of train axles has long relied on forging and rolling technologies. Forged axles mainly employ free forging or die forging processes, improving the mechanical properties of materials through high-temperature plastic deformation. Rolling, on the other hand, involves continuously deforming heated steel billets through a series of rolls to gradually form a billet resembling the shape of an axle, which is then machined to obtain the finished product. While these traditional processes are mature and reliable, they have significant limitations in terms of energy consumption, material utilization, production efficiency, and manufacturing costs.

[0003] Forging and rolling processes rely on high-temperature heating above 1000°C, and the repeated heating processes result in huge energy consumption and high CO2 emissions. Traditional axle manufacturing involves multiple processes with interdependencies, leading to long production cycles. Especially in multi-variety, small-size, and small-batch production, equipment replacement and adjustment further reduce production efficiency. Forged and rolled blanks often have significant dimensional fluctuations and may have surface defects such as cracks or oxide scale, requiring additional allowances in subsequent machining to improve yield. This situation leads to accelerated tool wear during machining, affecting machining accuracy and surface quality, and increasing the difficulty of quality control.

[0004] The shortcomings of traditional forging and rolling axle processes in terms of production efficiency, energy consumption, cost, and quality control have prompted companies to explore more efficient and greener alternative technologies. Modern rail transit and heavy-duty transportation place higher demands on the strength and fatigue resistance of axles. Although traditional forging processes improve material properties through plastic deformation, they are lengthy and energy-intensive. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a medium-carbon steel train axle and its production method. This method eliminates the axle forging process, directly forming the axle using continuously cast round billets, rolled round billets, and machining. It also combines tempering heat treatment and surface strengthening processes to obtain high-quality axle products. This method can meet the production needs of axles with multiple varieties, small specifications, and small batches, reducing production costs, improving manufacturing efficiency and flexibility, reducing energy consumption, and promoting green development.

[0006] This invention provides a method for producing medium carbon steel train axles, the method comprising the following steps:

[0007] S1. Heat the continuously cast billet uniformly to above the plastic deformation temperature and hold it at that temperature.

[0008] S2. The heated continuous casting billet is subjected to rough rolling and finish rolling, and then water cooling and air cooling are performed in sequence to obtain the rolled billet.

[0009] S3. The rolled billet is machined to obtain the axle;

[0010] S4. Perform induction hardening heat treatment on the journal section of the axle.

[0011] S5. Temper the axle after induction hardening heat treatment.

[0012] S6. Shot peening is performed on the tempered axle.

[0013] The carbon content in the medium carbon steel train axle is 0.28-0.60% by weight.

[0014] Electromagnetic stirring (EMS) technology is used in the process of obtaining the continuous casting billet to reduce the phenomenon of component segregation; the continuous casting billet is a continuous casting round billet.

[0015] In step S1, to facilitate rolling deformation, ensure plasticity, prevent coarse grains or overheating, and improve the solid solution strengthening effect, the continuously cast round billet is heated to T±20℃, T=0.7×(1687-65C-30Si-25Mn-20Cr-15Ni) and held at that temperature for t0 min. D0 is the diameter of the continuously cast billet, in mm; δ is the thermal diffusivity, with a value of 0.01~0.02 mm. 2 / min; the unit of T is ℃, and in the formula for calculating T, the value of each component is its content in steel × 100.

[0016] In step S2, the final rolling temperature of the finishing mill is controlled at T2±20℃, where T2=879-40C+20Cr. Carbon is controlled by non-recrystallization rolling, and chromium is refined by inhibiting grain growth to improve the strength and toughness of the steel. In the calculation formula of T2, the value of each component is its content in the steel × 100. The unit of T2 is ℃.

[0017] In step S2, the water is sprayed to cool the temperature to 600°C and then air-cooled to room temperature.

[0018] In step S2, after final rolling, the compression ratio of the rolled billet is ≥6, and the single-pass reduction in roughing rolling is ≤0.3×(d0-d f The deformation after rough rolling is (0.6~0.7)×(d0-d). f The single-pass reduction in finishing milling is controlled within (0.07~0.15)×(d0-d). f ), where d0 is the diameter of the continuously cast billet in mm, and df is the diameter of the rolled billet in mm.

[0019] In step S2, the rolled billet is a rolled round billet.

[0020] In step S3, the diameter d of the rolled billet f With the maximum diameter D of the axle wheel seat f The difference d f -D f ≥ 5mm to remove surface oxide scale and other defects. To ensure uniform heat treatment, guarantee surface strengthening effect, and avoid stress concentration, the surface roughness Ra of the machined axle journal should be ≤ 3.2μm, and the surface roughness Ra of the axle body should be 3.2~6.3μm.

[0021] In step S4, to obtain a good hardened layer depth, hardness, and microstructure on the axle surface while reducing the risk of deformation and cracking, the induction hardening heat treatment process is as follows: induction heating to A c3 +80~130℃, then cool to room temperature using an 8~10wt% polyalkylene glycol aqueous solution.

[0022] A c3 =910-203sqr(C)+44.7Si-15.2Ni+31.5Mo+104V, where each component is represented by its content in the steel × 100. A c3 The unit is ℃.

[0023] In step S5, the tempering conditions are: tempering temperature 150~250℃, holding time 3~5h, in order to remove residual stress.

[0024] In step S6, the shot peening intensity is 0.35~0.50 mmA.

[0025] The diameter D of the medium carbon steel train axle is ≤260mm; the medium carbon steel train axle comprises the following chemical composition by weight percentage: C: 0.28~0.60%, Si: ≤0.35%, Mn≤1.5%, P≤0.03%, S≤0.08%, Cr≤1.5%, Mo≤0.3%, V≤0.20%, [N]≤0.03%, Ca≤0.008%, with the remainder being Fe and other unavoidable impurities.

[0026] Carbon (C) is the core element for stabilizing austenite (γ-Fe), and its content significantly affects the phase transformation critical point (A2) of steel. c1 and A c3During rolling, carbon, through solid solution strengthening and the formation of pearlite, is the most important element for improving the strength and hardness of steel. The carbon content determines the phase transformation products of controlled cooling after rolling, which is fundamental to obtaining the target microstructure (such as ferrite-pearlite, bainite). Si has a significant solid solution strengthening effect in ferrite, making it an effective element for improving steel strength while having relatively little impact on toughness. It can inhibit cementite formation and promote ferrite transformation. Cr is a carbide-forming element that significantly improves the hardenability of steel. Ni mainly exists in steel in a solid solution state, significantly improving toughness while increasing strength. During the heating and rolling process of continuously cast round billets, these elements work synergistically to achieve the excellent comprehensive performance of axle steel.

[0027] The present invention also provides a medium carbon steel train axle produced by the aforementioned production method, the metallographic structure of which is pearlite and ferrite, the grain size grade is 7.5 or higher; the tensile strength is ≥650MPa, the yield strength is ≥369MPa, the elongation is ≥23%, Z is ≥46%, the longitudinal KU2 is ≥35J, and the transverse KU2 is ≥25J.

[0028] This invention targets small-sized axles. By controlling the metallurgical and rolling processes, axle blank raw materials with dense internal structure and good isotropic quality are obtained. High-performance axle products are then obtained through machining, heat treatment, and surface strengthening treatment.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] Compared to traditional production processes, the production method provided by this invention eliminates the forging process for axles. It utilizes continuously cast round billets, rolled round billets, and machining for direct forming, combined with tempering heat treatment and surface strengthening processes to obtain high-quality axle products. In terms of material utilization, through optimized processing paths, a material utilization rate of nearly 60-70% can be achieved, a significant improvement compared to traditional processes. This method enables flexible production of axles of different specifications, making it particularly suitable for customized needs involving multiple varieties, small specifications, and small batches. This method omits multiple forging or rolling processes, greatly shortening the production cycle, significantly reducing energy consumption and CO2 emissions, significantly lowering production costs, improving manufacturing efficiency and flexibility, and aligning with the concept of green development. Attached Figure Description

[0031] Figure 1 The low-magnification microstructure of the axle in Example 1;

[0032] Figure 2 The low-magnification microstructure of the axle in Comparative Example 1;

[0033] Figure 3 The microstructure of the near-surface of the axle in Comparative Example 1;

[0034] Figure 4 The microstructure of the axle near the surface in Example 1. Detailed Implementation

[0035] The present invention provides a medium carbon steel train axle, comprising the following chemical composition by weight percentage: C: 0.28~0.60%, Si: ≤0.35%, Mn≤1.5%, P≤0.03%, S≤0.08%, Cr≤1.5%, Mo≤0.3%, V≤0.20%, [N]≤0.03%, Ca≤0.008%, with the remainder being Fe and other unavoidable impurities.

[0036] The method for producing medium carbon steel train axles includes the following steps:

[0037] S1. The process involves smelting in an electric arc furnace, refining in an LF furnace, degassing under RH or VD vacuum conditions, and continuous casting to obtain a continuously cast round billet. The billet is then uniformly heated to T ± 20℃, where T = 0.7 × (1687 - 65C - 30Si - 25Mn - 20Cr - 15Ni), and held at that temperature for t0 min. D0 is the diameter of the continuously cast billet, in mm; δ is the thermal diffusivity, with a value of 0.01~0.02 mm. 2 / min; The unit of T is ℃. In the formula for calculating T, the value of each component is its content in steel × 100.

[0038] S2. The heated continuous casting billet is subjected to rough rolling and finish rolling, then water spray cooling to 600℃ and then air cooling to room temperature to obtain rolled round billet;

[0039] S3. The rolled billet is machined to obtain the axle;

[0040] S4. Perform induction hardening heat treatment on the journal section of the axle.

[0041] S5. Temper the axle after induction hardening heat treatment.

[0042] S6. Shot peening is performed on the tempered axle.

[0043] In step S2, the final rolling temperature of the finishing mill is controlled at T2±20℃, where T2=879-40C+20Cr. In the calculation formula of T2, the value of each component is its content in the steel ×100; the unit of T2 is ℃.

[0044] In step S2, after final rolling, the compression ratio of the rolled billet is ≥6, and the single-pass reduction in roughing rolling is ≤0.3×(d0-d f The deformation after rough rolling is (0.6~0.7)×(d0-d). f The single-pass reduction in finishing milling is controlled within (0.07~0.15)×(d0-d).f ), where d0 is the diameter of the continuously cast billet and df is the diameter of the rolled billet.

[0045] In step S3, the diameter d of the rolled billet f With the maximum diameter D of the axle wheel seat f The difference d f -D f For axle journals with a diameter of ≥ 5mm, the surface roughness Ra of the machined axle journals is ≤ 3.2μm, and the surface roughness Ra of the axle body is 3.2~6.3μm.

[0046] In step S4, the induction hardening heat treatment process is as follows: induction heating to A c3 +80~130℃, then cooled to room temperature using an 8~10wt% polyalkylene glycol aqueous solution. Wherein, A c3 =910-203sqr(C)+44.7Si-15.2Ni+31.5Mo+104V, where each component is represented by its content in the steel × 100. A c3 The unit is ℃.

[0047] In step S5, the tempering conditions are: tempering temperature 150~250℃, holding time 3~5h, in order to remove residual stress.

[0048] The present invention will now be described in detail with reference to the embodiments.

[0049] Example 1

[0050] Example 1: The axle diameter is φ200mm, made of medium carbon steel with a carbon content of 0.4%, and its chemical composition is shown in Table 1. Molten steel undergoes electric arc furnace smelting + LF refining + VD treatment + continuous casting. The continuous casting process for the billet uses electromagnetic stirring (EMS) technology, ultimately yielding a φ600mm billet. The billet is heated to 1150℃ and held for 3 hours before rough rolling. The single-pass reduction in rough rolling is 65mm, followed by four passes and then finish rolling. The single-pass reduction in finish rolling is 30mm, with the final pass reduction ≤30mm. After multiple finish rolling passes, a φ205mm axle billet is obtained. The final rolling temperature is controlled at 855℃, and the axle billet compression ratio is 8.6. It is then cooled to 600℃ by water spraying and air-cooled. The billet length is cut according to the finished axle dimensions. Before heat treatment, it is machined according to the finished axle dimensions, thoroughly removing surface oxide scale and other defects. The surface roughness Ra of the machined axle journal is 3.2 μm, and the surface roughness Ra of the axle body is 3.2 μm. The machined axle journal and arc transition area are subjected to induction hardening heat treatment, induction heating to 880℃, electrical input power of 150kW, frequency of 9 kHz, and scanning speed of 7 mm / s. After heating, it is simultaneously cooled to room temperature using a 10wt% PAG aqueous solution. The induction hardened axle is then transferred to a furnace for low-temperature tempering at 180℃ for 4 hours to fully remove residual stress. After removing the axle from the furnace, it is air-cooled. After air cooling, the axle body is shot-peened with a shot peening intensity of 0.40 mmA.

[0051] Comparative Example 1

[0052] Comparative Example 1 uses an axle with a diameter of φ200mm, made of medium carbon steel with a carbon content of 0.4%, and its chemical composition is shown in Table 1. It is made of the same material as Example 1. The production process follows the traditional procedure: electric arc furnace or converter smelting → LF furnace refining → RH or VD vacuum degassing → continuous casting → billet heating → axle billet rolling → axle blank forging → rough turning of the axle blank → axle end face machining → normalizing + normalizing + tempering → axle machining → flaw detection. A φ600mm steel billet is obtained through continuous casting, and then a 260mm square billet is obtained through rolling. After forging, a φ220mm axle billet is obtained, which is then rough-machined and subjected to normalizing + normalizing + tempering heat treatment in a heating furnace. The axle is first normalized to 860±10℃ and held for 4~5 hours. After cooling, it is reheated to 810±10℃ and held for 4~5 hours. Then it is cooled to below 250℃ and held at 540℃ for 6 hours before being air-cooled.

[0053] Tensile tests were performed on the axle according to GB 228. The specimens were taken from any position halfway from the axle centerline to the surface, parallel to the axle axis. The results are shown in Table 2. Example 1 is comparable to Comparative Example 1. Specimens were cut from a cross-section perpendicular to the axis at the undeformed large end of the tensile specimen. The grain size of the axle was inspected according to YB / T 5148. The results are shown in Table 3. The low-magnification microstructure of the axle is shown in... Figure 1 , Figure 2 The microstructure consists entirely of ferrite and pearlite, such as Figure 3 , Figure 4 As shown, the grain size test results are comparable. Therefore, Example 1 can obtain microstructure and properties comparable to Comparative Example 1. Compared with Comparative Example 1, Example 1 has a simpler process, a 40% reduction in process time, a 35% reduction in equipment energy consumption, and an improved production efficiency.

[0054] Table 1 Chemical composition of axle steel (wt.%)

[0055]

[0056] Table 2 Tensile mechanical properties of axles

[0057]

[0058] Table 3. Grain size test results of axle microstructure

[0059]

[0060] Example 2

[0061] Example 2: The axle diameter is φ200mm, made of medium carbon steel with a carbon content of 0.30%, and its chemical composition is shown in Table 1. The molten steel undergoes electric arc furnace smelting + LF refining + VD treatment + continuous casting. Electromagnetic stirring (EMS) technology is used in the continuous casting process to obtain a φ600mm billet. The billet is heated to 1130℃ and held for 3 hours before rough rolling. The single-pass reduction in rough rolling is 85mm. After 3 passes, finish rolling is performed, with a single-pass reduction of 50mm and a final pass reduction ≤50mm. After multiple finish rolling passes, a φ205mm axle billet is obtained. The final rolling temperature is controlled at 870℃, and the axle billet compression ratio is 8.6. It is then cooled to 600℃ by water spraying and followed by air cooling.

[0062] The steel billet was cut to the length required for the finished axle dimensions and machined before heat treatment, adhering to the dimensions of the finished axle to thoroughly remove surface oxide scale and other defects. The surface roughness of the machined axle journal was Ra=3.2μm, and the surface roughness of the axle body was Ra=3.2μm. The machined axle journal and the arc transition area were then subjected to induction hardening heat treatment. Induction heating was performed to 895℃, with an electrical input power of 150kW, a frequency of 9 kHz, and a scanning speed of 7mm / s. After heating, the axle was simultaneously cooled to room temperature using a 10wt% PAG aqueous solution. The induction-hardened axle was then transferred to a furnace for low-temperature tempering at 180℃ for 4 hours to thoroughly remove residual stress. After removing the axle from the furnace, it was air-cooled. Following air cooling, the axle body underwent shot peening with an intensity of 0.40mmA.

[0063] Comparative Example 2

[0064] Comparative Example 2: The axle diameter is φ200mm, made of medium carbon steel with a carbon content of 0.30%, and its chemical composition is shown in Table 1. The molten steel undergoes electric arc furnace smelting + LF refining + VD treatment + continuous casting. Electromagnetic stirring (EMS) technology is used in the continuous casting process to obtain a φ480mm billet. The billet is heated to 1130℃ and held for 3 hours before rough rolling. The single-pass reduction in rough rolling is 60mm. After 3 passes, finish rolling is performed, with a single-pass reduction of 25mm and a final pass reduction ≤25mm. After multiple finish rolling passes, a φ205mm axle billet is obtained. The final rolling temperature is controlled at 860℃, and the axle billet compression ratio is 5.5. It is then cooled to 600℃ by water spraying and followed by air cooling.

[0065] The steel billet was cut to the length required for the finished axle dimensions and machined before heat treatment, adhering to the dimensions of the finished axle to thoroughly remove surface oxide scale and other defects. The surface roughness of both the journal and body of the machined axle was Ra=3.2μm. The journal and arc transition areas of the machined axle were then subjected to induction hardening heat treatment. Induction heating was performed to 895℃, with an electrical input power of 150kW, a frequency of 9 kHz, and a scanning speed of 7mm / s. Simultaneously, a 10wt% PAG aqueous solution was used for cooling after heating. The induction-hardened axle was then transferred to a furnace for low-temperature tempering at 180℃ for 4 hours to fully remove residual stress. After removing the axle from the furnace, it was air-cooled. Following air cooling, the axle body underwent shot peening with an intensity of 0.40mmA.

[0066] Tensile tests were conducted on the axle body according to GB 228 "Metallic Materials - Tensile Testing Method". The specimens were taken from any position halfway from the axle centerline to the surface, parallel to the axle axis. The results are shown in Table 4. The surface hardness and tensile strength at the surface position of Comparative Example 2 were lower than those of Example 2. This is because the steel billet used in Comparative Example 2 had a compression ratio <6 after rolling, preventing the coarse cast structure in the core from being fully broken down and recrystallized, resulting in coarse and uneven grains, and a decrease in tensile strength and yield strength. The microstructures of Example 2 and Comparative Example 2 were both ferrite and pearlite, with a significant difference in grain size.

[0067] Table 4 Tensile mechanical properties of axles

[0068]

[0069] Table 5. Grain size test results of axle microstructure

[0070]

[0071] Example 3

[0072] Example 3: The axle diameter is φ210mm, made of medium carbon steel with a carbon content of 0.45%, and its chemical composition is shown in Table 1. The molten steel undergoes electric arc furnace smelting + LF refining + VD treatment + continuous casting. Electromagnetic stirring (EMS) technology is used in the continuous casting process to obtain a φ550mm billet. The billet is heated to 1150℃ and held for 3 hours before rough rolling. The single-pass reduction in rough rolling is 70mm. After three passes, finish rolling is performed, with a single-pass reduction of 30mm and a final pass reduction ≤30mm. After multiple finish rolling passes, a φ215mm axle billet is obtained. The final rolling temperature is controlled at 860℃, and the axle billet compression ratio is 6.5. It is then cooled to 600℃ by water spraying and followed by air cooling.

[0073] The steel billet was cut to the length required for the finished axle dimensions and machined before heat treatment, adhering to the dimensions of the finished axle to thoroughly remove surface oxide scale and other defects. The surface roughness of the machined axle journal was Ra=3.2μm, and the surface roughness of the axle body was Ra=3.2μm. The machined axle journal and the arc transition area were then subjected to induction hardening heat treatment. Induction heating was performed to 880℃, with an electrical input power of 160kW, a frequency of 10 kHz, and a scanning speed of 8mm / s. Simultaneously, a 10wt% PAG aqueous solution was used for cooling after heating. The induction-hardened axle was then transferred to a furnace for low-temperature tempering at 180℃ for 4 hours to fully remove residual stress. After removing the axle from the furnace, it was air-cooled. Following air cooling, the axle body underwent shot peening with a shot peening intensity of 0.45mmA.

[0074] Comparative Example 3

[0075] Example 3: The axle diameter specification of Example 2 is φ210mm, the material is high carbon steel with a carbon content of 0.62%, and the chemical composition is shown in Table 1. Molten steel is smelted in an electric furnace + LF refining + VD treatment + continuous casting. The continuous casting process of the billet adopts electromagnetic stirring (EMS) technology, and finally obtains a billet of φ550mm. The billet is heated to 1150℃ and held for 3 hours before rough rolling. The single-pass reduction in rough rolling is 70mm. After 3 passes, it is finished rolled. The single-pass reduction in finish rolling is 30mm, and the reduction in the last pass is ≤30mm. After multiple passes of finish rolling, a φ215mm axle billet is finally obtained. The final rolling temperature is controlled at 860℃, and the axle billet compression ratio is 6.5. Then, it is cooled to 600℃ by water spraying and air cooling.

[0076] The steel billet was cut to the length required for the finished axle dimensions and machined before heat treatment, adhering to the dimensions of the finished axle to thoroughly remove surface oxide scale and other defects. The surface roughness of the machined axle journal was Ra=3.2μm, and the surface roughness of the axle body was Ra=3.2μm. The machined axle journal and the arc transition area were then subjected to induction hardening heat treatment. Induction heating was performed to 880℃, with an electrical input power of 160kW, a frequency of 10 kHz, and a scanning speed of 8mm / s. Simultaneously, a 10wt% PAG aqueous solution was used for cooling after heating. The induction-hardened axle was then transferred to a furnace for low-temperature tempering at 180℃ for 4 hours to fully remove residual stress. After removing the axle from the furnace, it was air-cooled. Following air cooling, the axle body underwent shot peening with a shot peening intensity of 0.45mmA.

[0077] Tensile tests were conducted on the axle according to GB 228 "Metallic Materials - Tensile Testing Method". The specimen was taken from any position at half the distance from the center line of the axle to the surface and parallel to the axle axis. The results are shown in Table 6. The tensile strength of Comparative Example 3 was higher than that of Example 3, which was due to the significant effect of carbon. However, under induction hardening, obvious cracks appeared on the surface of the axle of Comparative Example 3.

[0078] Table 6 Tensile Mechanical Properties of Axles

[0079]

[0080] The chemical composition, processing steps, heat treatment, and surface strengthening processes in Examples 1-3 are well matched, resulting in good axle microstructure and properties. Comparative Example 1 uses a traditional process to achieve good axle microstructure and properties, but the process is more complex, energy-intensive, and less efficient than the examples. The difference in process parameters between Comparative Example 2 and Example 2 leads to a reduction in the toughness and strength of the material, which is detrimental to the safe operation of the axle. Comparative Example 3 uses the same process as Example 3, but with different compositions, indicating that this method is not suitable for the compositions of Comparative Example 3.

[0081] The above detailed description of a medium carbon steel train axle and its production method, with reference to the embodiments, is illustrative rather than limiting. Several embodiments may be listed within the defined scope. Therefore, variations and modifications that do not depart from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. A method for producing medium carbon steel train axles, characterized in that, The production method includes the following steps: S1. Heat the continuously cast billet uniformly to above the plastic deformation temperature and hold it at that temperature. S2. The heated continuous casting billet is subjected to rough rolling and finish rolling, and then water cooling and air cooling are performed in sequence to obtain the rolled billet. S3. The rolled billet is machined to obtain the axle; S4. Perform induction hardening heat treatment on the journal section of the axle. S5. Temper the axle after induction hardening heat treatment. S6. Shot peening is performed on the tempered axle. The carbon content in the medium carbon steel train axle is 0.28-0.60% by weight.

2. The production method according to claim 1, characterized in that, In step S1, the continuously cast round billet is heated to T±20℃, T=0.7×(1687-65C-30Si-25Mn-20Cr-15Ni) and held at that temperature for t0 min. D0 is the diameter of the continuously cast billet, in mm; δ is the thermal diffusivity, with a value of 0.01~0.02 mm. 2 / min; the unit of T is ℃, and in the formula for calculating T, the value of each component is its content in steel × 100.

3. The production method according to claim 1, characterized in that, In step S2, the final rolling temperature of the finishing mill is controlled at T2±20℃, where T2=879-40C+20Cr. In the calculation formula of T2, the value of each component is its content in the steel ×100; the unit of T2 is ℃.

4. The production method according to claim 1, characterized in that, In step S2, the water is sprayed to cool the temperature to 600°C and then air-cooled to room temperature.

5. The production method according to any one of claims 1-3, characterized in that, In step S2, after final rolling, the compression ratio of the rolled billet is ≥6, and the single-pass reduction in roughing rolling is ≤0.3×(d0-d f The deformation after rough rolling is (0.6~0.7)×(d0-d). f The single-pass reduction in finishing milling is controlled within (0.07~0.15)×(d0-d). f ), where d0 is the diameter of the continuously cast billet and df is the diameter of the rolled billet.

6. The production method according to any one of claims 1-3, characterized in that, In step S3, the diameter d of the rolled billet f With the maximum diameter D of the axle wheel seat f The difference d f -D f ≥ 5mm; the surface roughness Ra of the machined axle journal is ≤ 3.2μm, and the surface roughness Ra of the axle body is 3.2~6.3μm.

7. The production method according to any one of claims 1-3, characterized in that, In step S4, the induction hardening heat treatment process is as follows: induction heating to A c3 +80~130℃, then cool to room temperature using an 8~10wt% polyalkylene glycol aqueous solution.

8. The production method according to any one of claims 1-3, characterized in that, In step S5, the tempering conditions are: tempering temperature 150~250℃, holding time 3~5h.

9. The production method according to any one of claims 1-3, characterized in that, The diameter D of the medium carbon steel train axle is ≤260mm; the medium carbon steel train axle comprises the following chemical composition by weight percentage: C: 0.28~0.60%, Si: ≤0.35%, Mn≤1.5%, P≤0.03%, S≤0.08%, Cr≤1.5%, Mo≤0.3%, V≤0.20%, [N]≤0.03%, Ca≤0.008%, with the remainder being Fe and other unavoidable impurities.

10. Medium carbon steel train axles produced by the production method according to any one of claims 1-9.

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