Production process of U71MnG steel rail for high-speed railway with speed of 400km per hour
By optimizing the composition and process parameters of U71MnG steel rails, the problems of toughness and straightness of steel rails in high-speed railways have been solved, realizing the production of high-performance steel rails that meet the requirements of high-speed railways with a speed of 400 km/h.
Patent Information
- Application Number
- CN202511011558.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-22
- Publication Date
- 2025-11-14
AI Technical Summary
Existing U71MnG high-speed rails face higher requirements in high-speed railways with speeds of 400km/h, such as wheel-rail friction changes and the straightness required for safe and stable operation. Therefore, it is necessary to optimize and upgrade the production process to improve toughness and straightness.
By employing optimized rail composition and customized controlled rolling and air cooling technology, controlling heating rate and temperature, adjusting cooling bed pitch, and combining high-pressure water descaling and rail pre-bending treatment, a reasonable rolling process is formulated to ensure rail quality and performance.
It improves the tensile strength, tread hardness and elongation of the rails, meets the high standards of high-speed railways, and ensures the straightness and safety of the rails.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to the field of metallurgical materials technology, and in particular to a production process for U71MnG steel rails used in high-speed railways with a speed of 400 km / h. Background Technology
[0002] Recently, the development of the CR450 high-speed train, which will increase the speed from 350 km / h to 400 km / h, has commenced, with plans to roll off the production line in 2024. According to information released by the China State Railway Group, the CR450 technological innovation project mainly includes technological innovations in the CR450 trainset and infrastructure such as 400 km / h high-speed rail lines, bridges, and tunnels. The 50 km / h speed increase signifies a significant upgrade for the entire high-speed rail industry chain, encompassing numerous technical fields including machinery, metallurgy, materials, power electronics, chemicals, information control, computers, and precision instruments. The increased speed of the CR450 trainset also drives continuous upgrading of the high-speed rail industry chain. As a crucial component and piece of equipment for high-speed rail, the quality and performance of steel rails face new breakthroughs and requirements with the increased train speed, necessitating optimization, upgrading, and innovative breakthroughs based on the current 350 km / h high-speed rail.
[0003] U71MnG high-speed rails possess high strength, toughness, and fatigue resistance, and are widely used in my country's high-speed railways. Facing the development demands of 400km / h high-speed rails, further improvements in quality and performance are needed based on the current production of 350km / h high-speed rails. While specific production methods have not yet been reported, the rails face higher requirements regarding wheel-rail friction changes, safe and stable operation, and straightness after high-speed trains increase in speed. Baogang possesses extensive experience and technology in high-speed rail production, and has previously supplied rails for key high-speed lines such as the Beijing-Shanghai and Lanzhou-Xinjiang lines. This patent, addressing the future growth rate of high-speed rail, provides a process method to improve the toughness and straightness of U71MnG rails, which has significant production and economic implications for continuously building the Baogang high-speed rail brand. Summary of the Invention
[0004] The purpose of this invention is to provide a production process for U71MnG steel rails used in high-speed railways with a speed of 400km / h. This process optimizes the steel composition and adopts a customized controlled rolling and air-cooling technology to smelt high-quality high-speed rail steel with standard strength, hardness, and good toughness, which can then be used in high-speed railways.
[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0006] This invention discloses a manufacturing process for U71MnG steel rails used in high-speed railways with a speed of 400 km / h, comprising:
[0007] The heating rate in section I should be controlled to prevent rapid temperature increases, and the heating time in section I should be guaranteed to be more than 1 hour. The temperature in the preheating section should not exceed 800℃. The billet heating temperature should be uniform, and overheating or burning of the billet is strictly prohibited. During continuous production, the heating temperature and heating time of each billet in each section of the furnace should be guaranteed. The heating process is shown in the table below:
[0008]
[0009] The surface of the steel billet must be descaled by high-pressure water.
[0010] The billet is rolled into rails by a universal rolling mill, with the initial rolling temperature controlled at 1050℃~1100℃ and the final rolling temperature ≤900℃.
[0011] The cooling bed step speed is as follows: when the step distance increases from 200mm to 600mm, the initial cooling temperature is 450±10℃ and the cooling rate is ≥0.50℃ / s; when the temperature reaches the straightening temperature from 450±10℃, the cooling rate is ≥0.2℃ / s.
[0012] Furthermore, the rail pre-bending adopts an arc shape, with a maximum pre-bending of 1.5m; the straightening temperature on the pre-bending cooling bed shall not exceed 60℃, and the straightened rail shall be straight.
[0013] Furthermore, the chemical composition of the U71MnG rail by weight percentage is as follows: C 0.65-0.80%; Si 0.17-0.58%; Mn 0.70-1.20%; P≤0.025%; S≤0.025%, with the remainder being Fe and unavoidable impurities.
[0014] Furthermore, the chemical composition of the U71MnG rail by weight percentage is: C 0.723%; Si 0.40%; Mn 0.89%; P 0.011%; S 0.005%, with the remainder being Fe and unavoidable impurities.
[0015] Furthermore, the chemical composition of the U71MnG rail by weight percentage is: C 0.737%; Si 0.37%; Mn 0.87%; P 0.015%; S 0.005%, with the remainder being Fe and unavoidable impurities.
[0016] Furthermore, the chemical composition of the U71MnG rail by weight percentage is: C 0.702%; Si 0.45%; Mn 0.89%; P 0.017%; S 0.003%, with the remainder being Fe and unavoidable impurities.
[0017] Furthermore, the chemical composition of the U71MnG rail by weight percentage is: C 0.710%; Si 0.35%; Mn 0.92%; P 0.012%; S 0.004%, with the remainder being Fe and unavoidable impurities.
[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows:
[0019] This invention improves rail performance by optimizing rail composition, reducing rolling temperature, and increasing cooling bed pitch. It also develops a reasonable rolling process, which improves the quality of rail steel. The rolled rails produced using this process have excellent tensile strength, tread hardness, and elongation. Detailed Implementation
[0020] A manufacturing process for U71MnG steel rails used in high-speed railways with a speed of 400km / h:
[0021] The heating rate in section I should be controlled to prevent rapid temperature increases, and the heating time in section I should be guaranteed to be at least 1 hour. The temperature in the preheating section should not exceed 800℃. The billet heating temperature should be uniform, and overheating or burning of the billet is strictly prohibited. During continuous production, the heating temperature and heating time of each billet in each section of the furnace should be guaranteed. The heating process is as follows, see Table 1:
[0022] Table 1 Heating process of U71MnG steel billet
[0023]
[0024]
[0025] The surface of the steel billet must be descaled by high-pressure water.
[0026] The billet is rolled into rails by a universal rolling mill. The initial rolling temperature is controlled at 1050℃~1100℃, and the final rolling temperature is ≤900℃.
[0027] Cooling bed step speed: when the step distance increases from 200mm to 600mm, the cooling rate is ≥0.50℃ / s from the initial cooling temperature to 450℃, and ≥0.2℃ / s from 450℃ to the straightening temperature.
[0028] The rails are pre-bent in an arc shape, with a maximum pre-bending length of 1.5m. The straightening temperature on the pre-bending cooling bed must not exceed 60℃, and the straightened rails should be straight.
[0029] This invention improves rail performance by optimizing rail composition, reducing rolling temperature, and increasing cooling bed pitch. It also develops a reasonable rolling process, which improves the quality of rail steel. The rolled rails produced using this process have excellent tensile strength, tread hardness, and elongation.
[0030] The present invention will be further described below with reference to specific embodiments.
[0031] The chemical composition of each embodiment is shown in Table 1:
[0032] Table 1. Components of each embodiment (mass percentage / %)
[0033]
[0034] The smelted continuous casting billet is rolled by a universal rolling mill, and the rolling process is shown in Table 2.
[0035] Table 2 Rolling process of each embodiment
[0036]
[0037] The rolled rails were subjected to performance and straightness measurements according to the TB / T2344.1-2020 standard.
[0038] Table 2 Mechanical properties of each embodiment
[0039]
[0040] It can be seen that this method produces U71MnG rails with an elongation of over 12% and excellent toughness. The rail straightness and other properties strictly meet the standard requirements.
[0041] 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 manufacturing process for U71MnG steel rails used in high-speed railways with a speed of 400 km / h, characterized in that: include: The heating rate of the first heating stage should be controlled to prevent rapid heating and ensure that the heating time of the first stage is more than 1 hour. The preheating temperature must not exceed 800℃; the billet heating temperature must be uniform, and overheating or burning of the billet is strictly prohibited; during continuous production, the heating temperature and heating time of each billet in each section of the furnace should be guaranteed, and the heating process is as follows: The surface of the steel billet must be descaled by high-pressure water. The billet is rolled into rails by a universal rolling mill, with the initial rolling temperature controlled at 1050℃~1100℃ and the final rolling temperature ≤900℃. The cooling bed step speed is as follows: when the step distance increases from 200mm to 600mm, the initial cooling temperature is 450±10℃ and the cooling rate is ≥0.50℃ / s; when the temperature reaches the straightening temperature from 450±10℃, the cooling rate is ≥0.2℃ / s.
2. The manufacturing process for U71MnG steel rails for 400km / h high-speed railways according to claim 1, characterized in that: The rails are pre-bent in an arc shape, with a maximum pre-bending length of 1.5m. The straightening temperature on the pre-bending cooling bed must not exceed 60℃, and the straightened rails should be flat.
3. The manufacturing process for U71MnG steel rails for 400km / h high-speed railways according to claim 1, characterized in that: The chemical composition of the U71MnG rail by weight percentage is as follows: C 0.65-0.80%; Si 0.17-0.58%; Mn 0.70-1.20%; P≤0.025%; S≤0.025%, with the remainder being Fe and unavoidable impurities.
4. The manufacturing process for U71MnG steel rails for 400km / h high-speed railways according to claim 3, characterized in that: The chemical composition of the U71MnG steel rail by weight percentage is: C 0.723%; Si 0.40%; Mn 0.89%; P 0.011%. S 0.005%, the remainder being Fe and unavoidable impurities.
5. The manufacturing process for U71MnG steel rails for 400km / h high-speed railways according to claim 3, characterized in that: The chemical composition of the U71MnG rail by weight percentage is: C 0.737%; Si 0.37%; Mn 0.87%; P 0.015%; S 0.005%, with the remainder being Fe and unavoidable impurities.
6. The manufacturing process for U71MnG steel rails for 400km / h high-speed railways according to claim 3, characterized in that: The chemical composition of the U71MnG rail by weight percentage is: C 0.702%; Si 0.45%; Mn 0.89%; P 0.017%; S 0.003%, with the remainder being Fe and unavoidable impurities.
7. The manufacturing process for U71MnG steel rails for 400km / h high-speed railways according to claim 3, characterized in that: The chemical composition of the U71MnG rail by weight percentage is: C 0.710%; Si 0.35%; Mn 0.92%; P 0.012%; S 0.004%, with the remainder being Fe and unavoidable impurities.