Production method for improving segregation of bainite steel rail alloy

Abstract

The invention discloses a production method for improving bainite steel rail alloy segregation, which comprises the following steps: 1) a smelting process: carrying out molten iron pretreatment, converter top and bottom combined blowing smelting, LF furnace external refining, vacuum treatment VD or RH-square billet continuous casting and casting billet slow cooling on a steel rail meeting component requirements to obtain a 280 * 380mm square billet; and (2) the obtained 280 * 380 mm continuous casting square billet enters a steel rail rolling procedure, and the finished steel rail is obtained through stepping heating, high-pressure water descaling, BD1 rough rolling cogging, casting blank slow cooling, square billet reheating, high-pressure water descaling, BD1 rough rolling, BD2 rough rolling mill rolling, CCS finishing mill rolling, cooling bed cooling, straightening, flaw detection and tempering. According to the production method for improving the bainite steel rail alloy segregation, the steel rail narrow component control technology and the homogenization technology are combined, and the bainite steel rail alloy element segregation condition can be effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical materials technology, and in particular relates to a production method for improving the segregation of bainitic rail alloys. Background Technology

[0002] Due to the complexity and diversity of the service environment of rails, railway operation requires rails to possess comprehensive properties such as good strength-toughness matching, wear resistance, and fatigue resistance. With the rapid development of my country's railways towards high speed and heavy load, the operational practice of existing pearlitic rails on railway lines shows that wear and rolling contact fatigue (RCF) damage to rails (including turnouts) are becoming increasingly prominent, leading to a higher failure frequency, significantly shortening the service life of rails and turnouts, and even jeopardizing traffic safety. Compared to pearlitic rails, bainitic rails have higher resistance to rolling contact fatigue and higher impact toughness and fracture toughness. Domestic heavy rail steel manufacturers have conducted relevant research and trial application work. Due to the excellent combination of high strength, good wear resistance, and toughness, bainitic steel has been widely used in turnout manufacturing in the railway industry both domestically and internationally, and has very high research value.

[0003] Segregation of alloying elements reduces the mechanical properties of rails, particularly their toughness, plasticity, and corrosion resistance. Segregation leads to uneven strength and toughness across different parts of the rail, reducing the load-bearing capacity of heavy rails and increasing the risk of serious accidents such as rail breakage. It also causes inconsistent wear resistance on the rail surface, resulting in problems like corrugation, shortening the service life of heavy rails and increasing the frequency of maintenance and replacement. Furthermore, the abnormal chemical composition of segregated areas may make them more susceptible to corrosion, thus affecting the overall quality and performance of the heavy rail. As user requirements for rail quality become increasingly stringent, it is no longer sufficient to meet the demand for homogeneous steel. Therefore, controlling elemental segregation in continuously cast billets has become a key focus in the production of heavy rail steel.

[0004] Bainitic rails developed and applied both domestically and internationally generally use low-carbon or medium-low-carbon series with a carbon content of 0.15-0.40%, mainly composed of an alloy strengthening system of Mn-Si-Cr, supplemented by micro-alloying elements such as Mo, V, Nb, Ni, B, and Al, to achieve an excellent match of strength, hardness, and toughness in bainitic rails. The tensile strength of the rails is generally between 1200-1500MPa, the hardness is ≥350HB, and the impact strength is ≥40J. Because bainitic rails are primarily strengthened by alloying, their alloy element content is significantly higher than that of pearlitic rails. Bainitic rails can contain over 5% alloy elements, while pearlitic rails typically contain between 1.2% and 2.3%. This increase in alloy elements inevitably leads to segregation of alloy elements within the cast billet and finished rail. Furthermore, bainitic rails are affected by existing production processes, resulting in a longer cooling and solidification time for the continuously cast billet, making it more difficult to control segregation. This negatively impacts the quality of the billet and rail, and also seriously affects the later service life of the track. Severe segregation in bainitic rails can cause railhead damage and spalling, seriously affecting the safety and service life of the track.

[0005] Patent application number 201510764544.X discloses "A method for controlling center segregation of large-section heavy rail steel billets". This method uses a casting temperature with a superheat of 25-35℃, a casting speed of 0.65-0.75m / min, and a 10-14mm reduction at the end. At the same time, the heavy rail steel obtained by electromagnetic stirring in the crystallizer is tested. A total of 16 points are tested, and the carbon segregation of the billet is controlled between 0.95-1.08. The segregation control effect is not ideal. This method is for high carbon heavy rail steels such as U71Mn, U75V, and U78CrV, and does not perform segregation detection and analysis on alloy strengthening elements such as Si and Mn.

[0006] Patent application number 202111349469.2 discloses "A method for controlling carbon segregation in the center of hypereutectoid steel produced from small square billets." This method employs an end-stage electromagnetic stirring current of 260A and a frequency of 7Hz; a casting speed controlled at 1.9m / min; a crystallizer water flow rate of 120m³ / h; and a secondary cooling water flow rate of 0.70L / Kg. The produced billet has a small square cross-section of 150×150mm, with a central carbon segregation index between 0.94 and 1.05. This method is for the production of high-carbon, low-alloy SWRH82B hypereutectoid steel wire. The steel grade has low Si, Mn, and Cr content, making alloy element segregation less likely. However, this patent does not address the segregation control, detection, or explanation of alloy strengthening elements.

[0007] Patent application number 201711079587.X discloses a smelting method for improving the quality of bainitic rail billets. This method controls the billet drawing speed at 0.3-0.5 m / min, the crystallizer water flow rate at 2600-2800 L / min, the crystallizer liquid level at 18.50-19.57 m, and the crystallizer protective slag thickness at 4.1-4.7 mm, reducing the rejection rate by 5%. However, this method results in excessively low drawing speeds for heavy rails, reducing billet output, increasing energy consumption and production costs, and causing prolonged residence time of molten steel in the crystallizer, potentially leading to excessive columnar crystal growth and increasing the risk of defects such as central porosity and central segregation. Furthermore, this method does not compare the degree of segregation in the cast billet or finished rail. Since many factors influence the rejection rate of cast billets, the method provided in this patent does not necessarily represent a reduction in cast billet segregation and surface defects. Summary of the Invention

[0008] The purpose of this invention is to provide a production method for improving the segregation of bainitic rail alloys. By combining narrow composition control technology and homogenization technology, the segregation of alloy elements in bainitic rails can be effectively improved.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] This invention discloses a production method for improving bainitic rail alloy segregation, comprising:

[0011] 1) Smelting process: Steel rails meeting the composition requirements undergo molten iron pretreatment, converter top and bottom blowing smelting, LF ladle refining, vacuum treatment (VD or RH), billet continuous casting, and slow cooling of the billet to obtain 280×380mm square billets; the specific production method for improving the segregation of alloying elements in bainitic steel rails during the smelting process is as follows:

[0012] ① Iron pretreatment: The sulfur content in the molten iron after pretreatment is ≤0.005%;

[0013] ② Converter smelting: The final carbon content at the converter end point is ≥0.06%, and the tapping temperature is ≥1580℃;

[0014] ③ LF Furnace Refining: A dual LF furnace refining process is used to complete deoxidation, desulfurization, alloying, and heating. In the first stage of LF refining, deoxidizing alloys are added and the main alloying elements in the steel are added. The total calcium and barium content in the deoxidizing alloy reaches more than 28%, achieving rapid deoxidation and assisted desulfurization. The first stage of LF refining achieves an active oxygen content of ≤10ppm and a sulfur content of ≤0.003% in the steel, reducing element segregation in the continuously cast billet. In the second stage of LF refining, the alloy composition and temperature in the steel are finely adjusted to ensure that the alloy composition deviation does not exceed 0.05%.

[0015] ④ Vacuum treatment (VD or RH): The deep vacuum degassing time is ≥ 20 min, the soft blowing time after vacuum degassing is ≥ 20 min, the deep vacuum degree is ≤ 0.10 kPa, and the molten steel shall not be exposed during soft blowing;

[0016] ⑤ Bloom continuous casting: The tundish heating technology is adopted, and the automatic temperature control mode is used. The heating temperature is controlled between 1500 - 1600 °C, the molten steel temperature is controlled within the range of the target temperature ± 2 - 3 °C, and the superheat degree is stably controlled at 20 - 25 °C; In the secondary cooling section, weak cooling water distribution is adopted, the secondary cooling water ratio used is 0.50 - 2.00 L / kg, and the cooling water pressure is between 0.2 - 0.6 MPa; The current of the final electromagnetic stirring is controlled between 300 - 500 A, and the frequency is controlled between 3 - 7 Hz; The dynamic soft reduction parameter range is 0.4 < fs < 0.8, the total reduction amount is controlled at 3 - 8 mm, and the reduction rate is between 1.0 - 2.0 mm / m; The continuous casting machine uses constant casting speed pouring, the casting speed is controlled at 0.60 - 0.65 ± 0.02 m / min, and the protective casting measures are adopted to prevent secondary oxidation of the molten steel. Through the above production, a 280×380 mm bloom is obtained;

[0017] ⑥ Slab slow cooling: The 280×380 mm slabs produced are further improved in slab segregation by adopting the temperature-controlled slow cooling method. The slabs enter the temperature-controlled cooling furnace for heat preservation treatment, where the heat preservation temperature is ≥ 700 °C, the heat preservation time is ≥ 100 h, the slabs are cooled with the furnace, and the cooling speed is ≤ 4 °C / h;

[0018] 2) The 280×380 mm continuous casting blooms obtained in the above ⑥ enter the rail rolling process, and after walking beam heating - high-pressure water descaling - BD1 rough rolling and blooming - slab slow cooling - bloom reheating - high-pressure water descaling - BD1 rough rolling - BD2 rough rolling - CCS finishing rolling - cooling bed cooling - straightening - flaw detection - tempering, the finished rails are obtained; In the rail rolling process, the specific production method for improving the segregation of alloying elements in bainitic rails is as follows:

[0019] ① Heating of 280×380 mm blooms: The soaking temperature is between 1180 - 1280 °C, and the total heating time is ≥ 3 h;

[0020] ② BD1 rough rolling and blooming: The rolling start temperature is controlled between 1120 - 1140 °C, the final rolling temperature is controlled between 1080 - 110 °C, and the blooming rolling passes are ≥ 2 times, thus obtaining 270×300 mm blooms;

[0021] ③ Slab slow cooling: The 270×300 mm slabs produced by BD1 rough rolling are further improved in slab segregation by adopting heat preservation slow cooling. The slabs enter the heat preservation furnace and are cooled with the furnace. The cooling speed of slab slow cooling is ≤ 10 °C / h, and the slabs can be air-cooled when the temperature is below 200 °C;

[0022] ④ Reheating of 270×300mm billet: The 270×300mm billet is reheated at a temperature between 1180-1280℃ for a total heating time of ≥3h.

[0023] ⑤ BD1, BD2, CCS rail rolling: the initial rolling temperature is controlled between 1080-1150℃, the final rolling temperature is ≤930℃, and the rolling compression ratio is ≥9:1;

[0024] ⑥ Cooling on the cooling bed: The rails are cooled at 280mm / steps on the cooling bed, with one push per step; this ensures the effect of slow cooling of the closely packed rails.

[0025] ⑦ Rail tempering: The rail tempering temperature is controlled between 300-400℃, and the holding time is ≥20h.

[0026] Furthermore, the chemical composition of the rail, by mass percentage, includes: C: 0.18-0.25%, Si: 0.80-1.30%, Mn: 1.60-2.50%, Cr: 0.80-1.20%, Ni: 0.30-0.70%, Mo: 0.20-0.60%, V: ≤0.10%, Nb: ≤0.10%, P ≤0.015%, S ≤0.015%, Al ≤0.010%, with the remainder being Fe and unavoidable impurities; wherein, the total content of alloying elements in the rail material is ≥5.5%.

[0027] Furthermore, the produced bainitic rail sections include at least 43-75 kg / m, 50AT1 rail, and 60AT1 rail.

[0028] Furthermore, the final rolling temperature for the finished product is 930℃.

[0029] Furthermore, the rolling pitch is controlled at 280mm.

[0030] Furthermore, the tempering temperature of the rails is 350℃.

[0031] Furthermore, the segregation indices of Si, Mn, and Cr were all controlled between 0.99 and 1.01.

[0032] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0033] This invention provides a production method for improving alloy segregation in finished bainitic steel rails. In the smelting stage: This invention optimizes the deoxidation and alloying processes to reduce fluctuations in molten steel composition, lower the content of harmful gases and inclusions in the steel, and reduce segregation caused by inclusion aggregation. It employs tundish induction heating technology, electromagnetic stirring, low superheat casting, and light reduction techniques to promote molten steel convection and solute atom diffusion, effectively reducing central and dendritic segregation, resulting in a significant improvement in the internal quality of the continuously cast billet. In the rolling stage: This invention controls the heating, rolling, and cooling processes, utilizing high temperatures to promote alloy element diffusion and reduce as-cast segregation. It employs secondary heating rolling and high compression ratio rolling to further break up dendritic segregation bands and central segregation zones in the cast billet, resulting in a more uniform composition and microstructure. This achieves the control of the segregation index of alloying elements such as Si, Mn, and Cr in the finished bainitic rails between 0.99 and 1.01, effectively improving the segregation of alloying elements in bainitic rails, ensuring uniform microstructure and mechanical properties of the rails, and further improving the service performance of bainitic rails. Attached Figure Description

[0034] The present invention will be further described below with reference to the accompanying drawings.

[0035] Figure 1 This is a schematic diagram showing the sampling locations for rail components. Detailed Implementation

[0036] The specific implementation of this invention is as follows:

[0037] 1) Bainitic steel rails are processed through molten iron—molten iron pretreatment—converter top and bottom re-blowing smelting—LF ladle refining—vacuum treatment (VD or RH)—square billet continuous casting—slow cooling of billet, thus obtaining 280×380mm square billets.

[0038] 2) Iron pretreatment: The sulfur content in the molten iron after pretreatment is ≤0.005%.

[0039] 3) Converter smelting: The C content at the converter endpoint is ≥0.06%, and the tapping temperature is ≥1580℃.

[0040] 4) LF Furnace Refining: Double LF furnaces are used for refining to complete deoxidation, desulfurization, alloying, and temperature raising. In the first stage of LF refining, deoxidizing alloys are added and main alloying elements in the steel are added proportionally. The total content of calcium and barium in the deoxidizing alloy reaches over 28%, which can rapidly deoxidize and assist in desulfurization. In the first stage of LF refining: All alloys such as Si, Mn, Cr, and Mo in the steel are supplemented. The in-position temperature of the molten steel is ≥1580°C, the out-of-position temperature is ≥1630°C, the heating time is ≥40 min, a white slag is formed, the slag basicity R≥1.5. In the first stage of refining, the active oxygen content in the steel can be ≤10 ppm, the sulfur content in the steel is ≤0.003%, reducing the segregation of elements in the continuous casting billet. In the second stage of LF refining: The in-position temperature of the molten steel is ≥1620°C, the out-of-position temperature is ≥1650°C, the heating time is ≥30 min, and the soft blowing time is ≥30 min; refining is to finely adjust the alloy composition and temperature in the steel to ensure that the deviation of the alloy composition does not exceed 0.05%.

[0041] 5) Vacuum Treatment (VD or RH): The deep vacuum degassing time is ≥20 min, the soft blowing time after vacuum degassing is ≥20 min, the deep vacuum degree is ≤0.10 kPa, and the molten steel shall not be exposed during soft blowing.

[0042] 6) The chemical composition measured before continuous casting of the rail is: C: 0.18 - 0.25%, Si: 0.80 - 1.30%, Mn: 1.60 - 2.50%, Cr: 0.80 - 1.20%, Ni: 0.30 - 0.70%, Mo: 0.20 - 0.60%, V: ≤0.10%, Nb: ≤0.10%, P≤0.015%, S≤0.015%, Al≤0.010%, and the rest is Fe and inevitable impurities. Among them, the total content of alloying elements in the rail material is ≥5.5%.

[0043] 7) Bloom Continuous Casting: The tundish heating technology is adopted, and the automatic temperature control mode is used. The heating temperature is controlled between 1500 - 1600°C, and the molten steel temperature is controlled within the range of the target temperature ±2 - 3°C, stably controlling the superheat degree at 20 - 25°C; in the secondary cooling section, weak cooling water distribution is adopted, and the secondary cooling water ratio used is 0.50 - 2.00 L / kg, and the cooling water pressure is between 0.2 - 0.6 MPa; the current of the final electromagnetic stirring is controlled between 300 - 500 A, and the frequency is controlled between 3 - 7 Hz; the dynamic soft reduction parameter range is 0.4 < fs < 0.8, the total reduction amount is controlled at 3 - 8 mm, and the reduction rate is between 1.0 - 2.0 mm / m; the continuous casting machine uses constant casting speed pouring, the casting speed is controlled at 0.60 - 0.65 ±0.02 m / min, and protective casting measures are adopted to prevent secondary oxidation of the molten steel. Through the above production, 280×380 mm blooms are obtained.

[0044] 8) Slow cooling of billet: The 280×380mm billet produced is subjected to slow cooling with temperature control to further improve the segregation of the billet. The billet enters the temperature-controlled cooling furnace for heat preservation treatment, wherein the heat preservation temperature is ≥700℃ and the heat preservation time is ≥100h. The billet is cooled with the furnace, and the cooling rate is ≤4℃ / h.

[0045] 9) The 280×380mm continuously cast square billet obtained above is subjected to step heating—high pressure water descaling—BD1 rough rolling—slow cooling of the billet—reheating of the square billet—high pressure water descaling—BD1 rough rolling—BD2 rough rolling—CCS finishing rolling—cooling on a cooling bed—straightening—flaw detection—tempering, thereby obtaining the finished steel rail.

[0046] 10) Heating of 280×380mm square billet: The uniform heating temperature is between 1180-1280℃, and the total heating time is ≥3h.

[0047] 11) BD1 rough rolling: The initial rolling temperature is controlled between 1120-1140℃, and the final rolling temperature is controlled between 1080-1100℃. The billet is rolled ≥2 times to obtain a 270×300mm billet.

[0048] 12) Slow cooling of billet: The 270×300mm billet produced by BD1 roughing mill adopts a slow cooling method to further improve the segregation of the billet. The billet enters the holding furnace for cooling with the furnace. The slow cooling rate of the billet is ≤10℃ / h. The billet temperature can be air-cooled when it is below 200℃.

[0049] 13) Reheating of 270×300mm billet: The 270×300mm billet is reheated at a temperature between 1180-1280℃ for a total heating time of ≥3h.

[0050] 14) Rolling of BD1, BD2, and CCS rails: The initial rolling temperature is controlled between 1080-1150℃, the final rolling temperature is ≤930℃, and the rolling compression ratio is ≥9:1.

[0051] 15) Cooling on the cooling bed: The rails are cooled on the cooling bed at a rate of 280mm / step, with one push per step. This ensures the effect of slow cooling of the closely packed rails.

[0052] 16) Rail Tempering: The tempering temperature of the rails is controlled between 300-400℃, and the holding time is ≥20h. Tempering promotes atomic diffusion and microstructure adjustment, thereby improving the adverse effects of microstructure and microsegregation.

[0053] 17) The bainitic rail sections produced above include 43-75kg / m, 50AT1 rail, 60AT1 rail, etc.

[0054] Implementation process comparison

[0055] The sampling locations for alloying elements in bainitic rails involved in this invention are as follows: Figure 1 As shown.

[0056] Samples were taken from rails produced using different processes during implementation, and according to... Figure 1 As shown, 23 points were sampled on average from the rail head to the rail bottom for alloy element testing. Depending on the specifications and height of the rail, the rail height can be divided into 23 points on average.

[0057] During the implementation process, a comparative analysis was conducted on different smelting processes, rolling processes, and tempering processes, as shown in Tables 2 and 3.

[0058] Table 2 shows different production processes in the embodiments.

[0059]

[0060] Table 3 shows different production processes in the embodiments.

[0061]

[0062] A comparative analysis of alloy elements in finished steel rails was conducted for different production methods during implementation. Sampling methods included... Figure 1 As shown, the focus is on a comparative analysis of the segregation indices of Si, Mn, and Cr in finished steel rails.

[0063] Table 3 Comparison of alloy element segregation index of finished steel rails from different embodiments

[0064]

[0065]

[0066] As shown in Table 3, in Example 1, the segregation index of Si was between 0.96 and 1.04, the segregation index of Mn was between 0.95 and 1.05, and the segregation index of Cr was between 0.97 and 1.03; in Example 2, the segregation index of Si was between 0.97 and 1.03, the segregation index of Mn was between 0.96 and 1.04, and the segregation index of Cr was between 0.97 and 1.03; in Example 3, the segregation indices of Si, Mn, and Cr were all controlled between 0.99 and 1.01. Example 3 has a better segregation index, and the segregation of alloy elements in the finished rail is significantly improved.

[0067] 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 production method for improving the segregation of bainitic rail alloys, characterized in that: Including: 1) Smelting process: Rails meeting the composition requirements undergo the processes of hot metal - hot metal pretreatment - combined blowing top and bottom converter smelting - LF ladle furnace refining - vacuum treatment VD or RH - billet continuous casting - slow cooling of the cast billet, thus obtaining a 280×380mm billet; in the said smelting process, the specific production method for improving the segregation of alloy elements in bainite rails is as follows: ① Hot metal pretreatment: After hot metal pretreatment, the sulfur content in the hot metal ≤ 0.005%; ② Converter smelting: The C content at the end of the converter ≥ 0.06%, and the tapping temperature ≥ 1580°C; ③ LF ladle furnace refining: Double LF ladle furnace refining is adopted to complete deoxidation, desulfurization, alloying, and temperature raising. In the first-stage LF refining, deoxidizing alloys are added and the main alloy elements in the steel are added. The total content of calcium and barium in the deoxidizing alloy reaches more than 28% for rapid deoxidation and auxiliary desulfurization. In the first stage of LF refining, the active oxygen content in the steel ≤ 10 ppm, and the sulfur content in the steel ≤ 0.003% to reduce the segregation of elements in the continuous casting billet; in the second stage of LF refining, the alloy composition and temperature in the steel are finely adjusted to ensure that the deviation of the alloy composition does not exceed 0.05%; ④ Vacuum treatment (VD or RH): The deep vacuum degassing time ≥ 20 min, the soft blowing time after vacuum degassing ≥ 20 min, the deep vacuum degree ≤ 0.10 kPa, and the molten steel shall not be exposed during soft blowing; ⑤ Billet continuous casting: The tundish heating technology is adopted, and the automatic temperature control mode is used. The heating temperature is controlled between 1500 - 1600°C, the molten steel temperature is controlled within the range of the target temperature ±2 - 3°C, and the superheat is stably controlled at 20 - 25°C; in the secondary cooling section, weak cooling water distribution is adopted, and the secondary cooling water ratio used is 0.50 - 2.00 L / kg, and the cooling water pressure is between 0.2 - 0.6 MPa; the current of the final electromagnetic stirring is controlled between 300 - 500 A, and the frequency is controlled between 3 - 7 Hz; the dynamic soft reduction parameter range is 0.4 < fs < 0.8, the total reduction amount is controlled at 3 - 8 mm, and the reduction rate is between 1.0 - 2.0 mm / m; the continuous casting machine uses constant casting speed pouring, the casting speed is controlled at 0.60 - 0.65 ± 0.02 m / min, and protective casting measures are adopted to prevent secondary oxidation of the molten steel. Through the above production, a 280×380mm billet is obtained; ⑥ Slow cooling of the cast billet: The 280×380mm cast billet produced is further improved in segregation by the temperature-controlled slow cooling method. The cast billet enters the temperature-controlled cooling furnace for heat preservation treatment, where the heat preservation temperature ≥ 700°C, the heat preservation time ≥ 100 h, the cast billet cools with the furnace, and the cooling rate ≤ 4°C / h; 2) The 280×380mm continuous casting billet obtained in the above ⑥ enters the rail rolling process, and after walking beam heating - high-pressure water descaling - BD1 rough rolling and blooming - slow cooling of the cast billet - reheating of the billet - high-pressure water descaling - BD1 rough rolling - BD2 rough rolling mill rolling - CCS finishing mill rolling - cooling bed cooling - straightening - flaw detection - tempering, the finished rails are obtained; in the said rail rolling process, the specific production method for improving the segregation of alloy elements in bainite rails is as follows: ① Heating of the 280×380mm billet: The soaking temperature is between 1180 - 1280°C, and the total heating time ≥ 3 h; ②BD1 rough rolling: The initial rolling temperature is controlled between 1120-1140℃, and the final rolling temperature is controlled between 1080-1100℃. The billet is rolled ≥2 times to obtain a 270×300mm billet. ③ Slow cooling of billet: The 270×300mm billet produced by BD1 rough rolling adopts a heat preservation and slow cooling method to further improve the segregation of the billet. The billet enters the heat preservation furnace and is cooled with the furnace. The slow cooling rate of the billet is ≤10℃ / h. The billet temperature can be air-cooled when it is below 200℃. ④ Reheating of 270×300mm billet: The 270×300mm billet is reheated at a temperature between 1180-1280℃ for a total heating time of ≥3h. ⑤ BD1, BD2, CCS rail rolling: the initial rolling temperature is controlled between 1080-1150℃, the final rolling temperature is ≤930℃, and the rolling compression ratio is ≥9:1; ⑥ Cooling on the cooling bed: The rails are cooled at 280mm / steps on the cooling bed, with one push per step; this ensures the effect of slow cooling of the closely packed rails. ⑦ Rail tempering: The rail tempering temperature is controlled between 300-400℃, and the holding time is ≥20h.

2. The production method for improving bainitic rail alloy segregation according to claim 1, characterized in that: The chemical composition of the rail by weight percentage Includes: C: 0.18-0.25%, Si: 0.80-1.30%, Mn: 1.60-2.50%, Cr: 0.80-1.20%, Ni: 0.30-0.70%, Mo: 0.20-0.60%, V: ≤0.10%, Nb: ≤0.10%, P ≤0.015%, S ≤0.015%, Al ≤0.010%, with the remainder being Fe and unavoidable impurities.

3. The production method for improving bainitic rail alloy segregation according to claim 1, characterized in that: The produced bainitic rail sections include at least 43-75 kg / m, 50AT1 rail, and 60AT1 rail.

4. The production method for improving bainitic rail alloy segregation according to claim 1, characterized in that: The final rolling temperature for the finished product is 930℃.

5. The production method for improving bainitic rail alloy segregation according to claim 1, characterized in that: The rolling pitch is controlled at 280mm.

6. The production method for improving bainitic rail alloy segregation according to claim 1, characterized in that: The tempering temperature of the rail is 350℃.

7. The production method for improving bainitic rail alloy segregation according to claim 1, characterized in that: The segregation indices of Si, Mn, and Cr were all controlled between 0.99 and 1.01.

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