High-cold-resistant steel for railway bogie and production method of high-cold-resistant steel

Abstract

The invention discloses high cold-resistant steel for a railway bogie, which is characterized by comprising the following components in percentage by mass: 0.05 to 0.09 percent of C, 0.15 to 0.35 percent of Si, 1.15 to 1.30 percent of Mn, less than or equal to 0.012 percent of P, less than or equal to 0.003 percent of S, 0.025 to 0.045 percent of Alt, 0.015 to 0.030 percent of Nb, 0.15 to 0.30 percent of Ni, 0.45 to 0.55 percent of Cr, 0.3 to 0.35 percent of Cu, less than or equal to 50ppm of N, less than or equal to 2ppm of H and the balance of Fe and inevitable impurities. The purity and the structure uniformity of molten steel are improved through the smelting process and the rolling process, the low-temperature toughness and the fatigue resistance are stably improved, and the requirements for high cold resistance and fatigue resistance of the steel for the bogie are met.

Description

Technical Field

[0001] The invention relates to a highly cold-resistant steel for railway bogies and a production method thereof. Background Art

[0002] Railway bogie steel is a key, foundational steel material for rail transit manufacturing and a crucial component for the safety, comfort, and reliability of rail transit products. It bears the majority of the vehicle's dynamic loads, determining both operational safety and economic efficiency. Due to its unique service environment, the product has stringent requirements for low-temperature toughness, controlled molten steel purity, internal quality control, weather resistance, and fatigue performance. The product is primarily used in subway, intercity, and locomotive projects.

[0003] Due to the complex service environment requirements, rail transit has put forward technical requirements for bogie steel, such as high cold resistance, high fatigue resistance, and excellent weldability. However, existing technologies basically limit the low-temperature toughness of materials to -40°C and -50°C. In Northern Europe and extremely cold regions, materials are required to have lower service temperatures. Some vehicle manufacturers have proposed that railway bogie steel should have both -40°C and -55°C service temperatures. Therefore, the development of highly cold-resistant railway bogie steel to meet the technical requirements of lower service environment temperatures and provide strong technical support for bogie steel is of great significance to the rail transit industry. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a highly cold-resistant railway bogie steel and a production method thereof in view of the shortcomings of the above-mentioned existing technologies, thereby improving the purity and structural uniformity of molten steel through smelting and rolling processes, achieving a steady improvement in low-temperature toughness and fatigue resistance, and meeting the high cold resistance and fatigue performance requirements of bogie steel.

[0005] The technical solution of the present invention to solve the above technical problems is: a highly cold-resistant steel for railway bogies, comprising the following components, by mass percentage: C: 0.05-0.09%, Si: 0.15-0.35%, Mn: 1.15-1.30%, P≤0.012%, S≤0.003%, Alt: 0.025-0.045%, Nb: 0.015-0.030%, Ni: 0.15-0.30%, Cr: 0.45-0.55%, Cu: 0.3-0.35%, N≤50ppm, H≤2ppm, and the rest being Fe and unavoidable impurities.

[0006] The present invention further defines the scheme: Preferably, the thickness of the high cold-resistant railway bogie steel is 6-50 mm.

[0007] Preferably, the mechanical properties of the high cold-resistant railway bogie steel meet the following requirements: ReH ≥ 355 MPa; Rm: 490-630 MPa, A ≥ 22%, lateral impact value at -40°C and -55°C ≥ 60 J, the proportion of dispersed inclusions ≤ 5 μm in steel plate is more than 95%, the grade of various inclusions is ≤ 4.0, the grade of banded structure is ≤ 3.0, and the fatigue performance meets the requirement of 1×10 7 The first service requirement is that the fatigue limit strength is above 280MPa and the corrosion resistance rate is 50% of that of ordinary Q235B.

[0008] The present invention provides a production method for high cold-resistant railway bogie steel, which specifically includes a smelting process, a heating process and a rolling process, wherein: Smelting process: Top and bottom combined blowing converter + LF refining + RH vacuum + continuous casting process is adopted. The oxygen content of the converter steel is controlled to ≤500ppm. The LF refining furnace produces white slag and controls the calcium-aluminum ratio to 1.6-1.8. The RH refining furnace vacuum time is 15 minutes, the static stirring time is 12-20 minutes, and magnesium-calcium wire is added after breaking the vacuum. Continuous casting uses 220mm billets, and the cooling system adopts a strong cooling system. The dynamic reduction is controlled at 3-5mm. Heating process: The billet cooling time is ≥48 hours, and continuous furnace is used for staged heating. The total heating time is 9-15min / cm, the soaking section is kept warm for 30-40min, and the soaking temperature is 1180-1200℃. Rolling process: 5-7 rough rolling passes, the total reduction rate of the last three rough rolling passes is ≥35%; 3-5 finishing rolling passes, the reduction rate of the first finishing pass is ≥10%, the starting rolling temperature is 830-970℃, and the final cooling temperature is 650-690℃.

[0009] Preferably, during the static stirring time, the first two-thirds are stirred with a large flow rate, and the remaining time is stirred with a small flow rate.

[0010] The beneficial effects of the present invention are: the present invention adopts a low-carbon + nickel-chromium-copper combination component design, and utilizes a strong controlled rolling process to solve the technical problem of poor low-temperature toughness of weathering steel. The product has an impact energy of ≥200J at -55°C, and a ductile-brittle transition temperature of -60°C. The product has excellent low-temperature toughness, excellent weather resistance and fatigue properties, and the product can meet the technical requirements for bogie steel in special, low-temperature and complex service environments. DETAILED DESCRIPTION Example

[0011] This embodiment provides a highly cold-resistant railway bogie steel, using 12 mm thick S355J2W bogie steel, which includes the following components, by mass percentage: C: 0.072%, Si: 0.26%, Mn: 1.24%, P: 0.010%, S: 0.002%, Alt: 0.034%, Nb: 0.021%, Ni: 0.25%, Cr: 0.48%, Cu: 0.31%, N: 0.0040%, H: 0.00015%, and the remainder is Fe and unavoidable impurities.

[0012] This embodiment provides a method for producing high cold-resistant railway bogie steel, which specifically includes a smelting process, a heating process, and a rolling process, wherein: Smelting process: Top and bottom combined blowing converter + LF refining + RH vacuum + continuous casting process; converter tapping oxygen 480ppm, LF refining furnace produces white slag, and the calcium-aluminum ratio is controlled at 1.7; continuous casting uses 220mm billets and adopts a forced cooling secondary cooling system to improve center segregation; Heating process: The billet cooling time is ≥48 hours, and continuous furnace is used for staged heating. The total heating time is 13 min / cm, the soaking section is kept warm for 35 min, and the soaking temperature is 1180°C. Rolling process: rolled steel plate thickness 120mm, width 2000mm, rough rolling 7 passes, intermediate billet thickness 40mm, total reduction rate of the last three rough rolling passes 33%; finishing rolling 5 passes, reduction rate of the first finishing pass 10%, starting rolling temperature 960℃, final cooling temperature 720℃.

[0013] In this embodiment, the 12 mm thick S355J2W bogie steel has a steel plate with a dispersed inclusion ratio of 96% with a size of ≤5 μm, various inclusion levels of ≤1.0, a banded structure of 2.0, a fatigue limit strength of 285 MPa, and a corrosion resistance rate of 50% of that of ordinary Q235B. Example

[0014] A highly cold-resistant railway bogie steel is provided, which uses 50 mm thick S355J2W bogie steel and comprises the following components, by mass percentage: C: 0.068%, Si: 0.25%, Mn: 1.25%, P: 0.010%, S: 0.001%, Alt: 0.032%, Nb: 0.023%, Ni: 0.26%, Cr: 0.49%, Cu: 0.32%, N: 0.0039%, H: 0.00010%, and the remainder is Fe and unavoidable impurities.

[0015] This embodiment provides a method for producing high cold-resistant railway bogie steel, which specifically includes a smelting process, a heating process, and a rolling process, wherein: Smelting process: Top and bottom combined blowing converter + LF refining + RH vacuum + continuous casting process; converter tapping oxygen 485ppm, LF refining furnace produces white slag, and the calcium-aluminum ratio is controlled at 1.65; continuous casting uses 220mm billets, adopts a forced cooling secondary cooling system, and dynamic reduction to improve center segregation; Heating process: Billet cooling time ≥ 48 hours, total heating time 13min / cm, soaking section holding time 32min, soaking temperature 1185℃; Rolling process: rolled steel plate thickness 50mm, width 2000mm, rough rolling 6 passes, intermediate billet thickness 92mm, total reduction rate of the last three rough rolling passes 30%; finishing rolling 5 passes, reduction rate of the first finishing pass 11%, starting rolling temperature 845℃, final cooling temperature 640℃.

[0016] In this embodiment, the 50mm thick S355J2W steel plate has a dispersed inclusion ratio of 95% with a size of ≤5μm, various inclusion levels ≤1.0, banded structure level 2.5, fatigue strength of 290MPa, and corrosion resistance rate of 50% of ordinary Q235B.

[0017] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the scope of protection required by the present invention.

Claims

1. A highly cold-resistant steel for railway bogies, characterized by: The steel comprises the following components by mass percentage: C: 0.05-0.09%, Si: 0.15-0.35%, Mn: 1.15-1.30%, P≤0.012%, S≤0.003%, Alt: 0.025-0.045%, Nb: 0.015-0.030%, Ni: 0.15-0.30%, Cr: 0.45-0.55%, Cu: 0.3-0.35%, N≤50ppm, H≤2ppm, and the rest are Fe and unavoidable impurities.

2. The highly cold-resistant railway bogie steel according to claim 1, characterized in that: The thickness of the high cold-resistant railway bogie steel is 6-50 mm.

3. The highly cold-resistant railway bogie steel according to claim 1, characterized in that: The mechanical properties of the high cold-resistant railway bogie steel meet the following requirements: ReH ≥ 355 MPa; Rm: 490-630 MPa, A ≥ 22%, lateral impact value at -40°C and -55°C ≥ 60 J, the proportion of dispersed inclusions ≤ 5 μm in the steel plate is more than 95%, the grade of various inclusions is ≤ 4.0, the grade of banded structure is ≤ 3.0, and the fatigue performance meets 1×10 7 The first service requirement is that the fatigue limit strength is above 280MPa and the corrosion resistance rate is 50% of that of ordinary Q235B.

4. The method for producing high cold-resistant railway bogie steel according to any one of claims 1 to 3, characterized in that: Specifically, it includes smelting process, heating process and rolling process, among which: Smelting process: Top and bottom combined blowing converter + LF refining + RH vacuum + continuous casting process is adopted. The oxygen content of the converter steel is controlled to ≤500ppm. The LF refining furnace produces white slag and controls the calcium-aluminum ratio to 1.6-1.

8. The RH refining furnace vacuum time is 15 minutes, the static stirring time is 12-20 minutes, and magnesium-calcium wire is added after breaking the vacuum. Continuous casting uses 220mm billets, and the cooling system adopts a strong cooling system. The dynamic reduction is controlled at 3-5mm. Heating process: The billet cooling time is ≥48 hours, and continuous furnace is used for staged heating. The total heating time is 9-15min / cm, the soaking section is kept warm for 30-40min, and the soaking temperature is 1180-1200℃. Rolling process: 5-7 rough rolling passes, the total reduction rate of the last three rough rolling passes is ≥35%; 3-5 finishing rolling passes, the reduction rate of the first finishing pass is ≥10%, the starting rolling temperature is 830-970℃, and the final cooling temperature is 650-690℃.

5. The method for producing high cold-resistant railway bogie steel according to claim 4, characterized in that: During the static stirring time, the first two-thirds are stirred with a large flow rate, and the remaining time is stirred with a small flow rate.