Method for producing a rail transit profile

Abstract

This invention discloses a method for preparing rail transit profiles, belonging to the field of aluminum alloy profile preparation. The method includes batching, smelting, casting, ingot homogenization, ingot extrusion, and aging treatment to obtain the rail transit profiles. By optimizing the process parameters, this invention reduces defects such as edge surface scratches, cracks, peeling, bubbles, and fissures in the integrally formed rail transit profiles. Simultaneously, it reduces wear and tear on extrusion equipment, saves on equipment maintenance costs, and yields large-format integrally formed rail transit profiles with significantly improved mechanical properties and a cross-sectional hardness of 88HBW–96HBW, meeting application requirements.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy profile preparation, and more specifically, to a method for preparing rail transit profiles. Background Technology

[0002] The development direction of rail transit profiles is towards lightweight, large-scale one-piece molding, and high strength and toughness. Due to its advantages such as light weight, good sealing, corrosion resistance, aesthetics, and comfort, aluminum alloy car bodies are gradually replacing carbon steel car bodies and stainless steel car bodies, and are used in EMU trains and urban rail transit vehicles.

[0003] The main production equipment required for manufacturing rail transit profiles in existing technologies includes: ① a casting production line, which provides qualified large-sized round ingots for extrusion production. ② an extrusion production line, which produces qualified rail transit profiles for supply to the large component workshop. ③ a large component processing production line, which performs machining and welding on the rail transit profiles. Existing technologies often use welding to widen the rail transit profiles. For example, Chinese patent application CN201911376051.3 discloses a rail transit aluminum profile with an embedded assembly mechanism, including an aluminum profile body. An L-shaped left-side adjustment port is provided on the lower end of the left outer wall of the aluminum profile body, and an L-shaped right-side adjustment port is provided on the lower end of the right outer wall of the aluminum profile body. This invention uses a limiting block to adjust the position of the fixed translation frame inside the adjustment port, thereby facilitating the fixed assembly and use of the aluminum profile. For example, Chinese patent application number CN202011206004.7 discloses a high-strength hollow aluminum profile for rail transit. This technology improves the structural strength of the aluminum alloy profile by welding multiple mounting plates, splicing components, and support plates onto the base. However, it is cumbersome to use and does not provide a solution for a transportation-type aluminum profile that can be integrally formed.

[0004] The existing technology has the following problems: Existing technologies mostly use welding to widen the profiles for rail transit, but the mechanical properties at the welded location can only reach 50%-70% of the base material, and crack initiation points are prone to form at the welded location, affecting the overall comprehensive mechanical and performance properties. Therefore, producing integrally molded rail transit profiles that meet performance requirements is of great significance. Summary of the Invention

[0005] Based on this, in order to provide rail transit profiles with excellent mechanical properties and integral molding, the present invention provides a method for preparing rail transit profiles, the specific technical solution of which is as follows:

[0006] A method for preparing rail transit profiles, the method comprising the following steps: batching, smelting, casting, ingot homogenization, ingot extrusion, and aging treatment to obtain the rail transit profiles;

[0007] The ingot extrusion process is performed using a forward extrusion press with an extrusion ratio of 28–30. The extrusion temperature is 520℃–540℃, held for 12–24 hours. The extrusion cylinder temperature is 420℃–440℃, and the die temperature is 500℃–510℃, held for 24–36 hours, with a temperature difference of ≤5℃ between the left and right sides of the die. The main cylinder speed for extruding the first ingot is 0.5 mm / s–0.8 mm / s. After normal material output is detected, the length of the ingot is adjusted to be at least twice the length of the first ingot, and the main cylinder speed is adjusted accordingly. The speed is 1.2mm / s-1.5mm / s; the extruded profiles are produced in a flat manner and are cooled by online strong air. The upper fan covers a width of 1.2m-1.8m, the lower fan covers a width of 1.2m-1.8m, and the wind speed of the upper and lower fans is 30m / s-35m / s. The left fan covers a width of 0.5m-0.8m, the right fan covers a width of 0.5m-0.8m, and the wind speed of the left and right fans is 40m / s-45m / s.

[0008] The rail transit profile comprises the following components by weight percentage:

[0009] Si 0.60%–0.70%, Fe 0–0.30%, Cu 0–0.10%, Mn 0.15%–0.20%, Cr 0–0.02%, Zn 0–0.10%, Ti 0–0.05%, individual impurity element <0.05%, total impurity element <0.15%, Al is the balance.

[0010] Furthermore, the length of the ingot is 500mm to 1000mm.

[0011] Furthermore, the melting treatment temperature is 720℃~760℃, the composition of the rail transit profile is controlled according to the proportion, and casting is carried out under the temperature conditions of 750~760℃ for the furnace eye alloy liquid and 670~700℃ for the pan tail alloy liquid.

[0012] Furthermore, during the smelting process, argon gas is used for blowing refining at least twice, with each blowing refining session lasting 12 to 20 minutes. A dual-rotor degassing device is used to remove hydrogen online by purging argon gas, ensuring that the hydrogen content of the ingot is <0.15 mL / 100 g Al. Then, Al-5Ti-1B wire refining agent is added using a dual wire feeder to refine the grains. The online addition position of the titanium boron wire is at least 2 m in front of the filter plate to ensure that the wire feeder operates normally throughout the process. The online filtration adopts a two-stage filtration method, with the first stage using a 40-mesh foam ceramic filter plate and the second stage using a 50-mesh foam ceramic filter plate.

[0013] Furthermore, once all the raw materials have melted, ultrasonic treatment is added for 10 to 20 minutes. The ultrasonic treatment is intermittent, with 1 minute of ultrasonic treatment followed by a 5-minute pause, and then another 1 minute of treatment, and this cycle is repeated. The ultrasonic treatment conditions are 35 kHz to 50 kHz.

[0014] Furthermore, the initial casting speed is 18 mm / min to 20 mm / min, the steady-state casting speed is 24 mm / min to 26 mm / min, the water pressure is 200 kPa to 240 kPa, and the casting water flow rate is 35 m³ / min. 3 / h~55m 3 / h.

[0015] Furthermore, the temperature of the ingot homogenization treatment is 550℃~570℃, and the time is 10h~12h.

[0016] Furthermore, the aging treatment temperature is 170℃~175℃, and the holding time is 6h~8h.

[0017] Furthermore, the width of the rail transit profile is 1000mm±0.5mm, the wall thickness of the large aluminum plate is 4.0mm±0.2mm, and the wall thickness of the inner rib is 3.0mm±0.3mm; the plane gap of the large aluminum plate is <1.5mm, the curvature is <0.5mm / m, and the twist is <0.5mm / m.

[0018] The above-mentioned solution can reduce defects such as edge surface scratches, cracks, peeling, bubbles and cracks in the integrally molded rail transit profiles by optimizing the process parameters of the preparation method. At the same time, it can also obtain integrally molded rail transit profiles with significant mechanical properties and large specifications, and the cross-sectional hardness reaches 88HBW~96HBW, which meets the application requirements.

[0019] This application optimizes the composition of rail transit profiles, combining it with an optimized process to produce a significant direct weakening effect under the specified composition ratio. After extrusion, a non-basal surface texture is formed, which helps to improve plasticity and formability. Furthermore, the optimization of extrusion processing parameters can improve the tension-compression yield asymmetry, reduce wear and tear on extrusion equipment, and save on equipment maintenance costs. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the rail transit profile prepared in Embodiment 1 of the present invention.

[0021] Explanation of reference numerals in the attached figures

[0022] 1. Large aluminum sheet; 2. Internal reinforcement. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] A method for preparing a rail transit profile according to one embodiment of the present invention includes the following steps: batching, smelting, casting, ingot homogenization, ingot extrusion, and aging treatment to obtain the rail transit profile.

[0026] The ingot extrusion process is performed using a forward extrusion press with an extrusion ratio of 28–30. The extrusion temperature is 520℃–540℃, held for 12–24 hours. The extrusion cylinder temperature is 420℃–440℃, and the die temperature is 500℃–510℃, held for 24–36 hours, with a temperature difference of ≤5℃ between the left and right sides of the die. The main cylinder speed for extruding the first ingot is 0.5 mm / s–0.8 mm / s. After normal material output is detected, the length of the ingot is adjusted to be at least twice the length of the first ingot, and the main cylinder speed is adjusted accordingly. The speed is 1.2mm / s-1.5mm / s; the extruded profiles are produced in a flat manner and are cooled by online strong air. The upper fan covers a width of 1.2m-1.8m, the lower fan covers a width of 1.2m-1.8m, and the wind speed of the upper and lower fans is 30m / s-35m / s. The left fan covers a width of 0.5m-0.8m, the right fan covers a width of 0.5m-0.8m, and the wind speed of the left and right fans is 40m / s-45m / s.

[0027] The rail transit profile comprises the following components by weight percentage:

[0028] The alloy composition is as follows: Si 0.60%–0.70%, Fe 0–0.30%, Cu 0–0.10%, Mn 0.15%–0.20%, Cr 0–0.02%, Zn 0–0.10%, Ti 0–0.05%, individual impurity element <0.05%, total impurity element <0.15%, Al as the balance. The speed limit for aluminum alloy extrusion mainly depends on the type of extruder and the solidus temperature of the alloy itself. During low-temperature extrusion, if the load required for the material to plastically deform exceeds the maximum tonnage of the extruder, extrusion cannot proceed. During high-temperature extrusion, if the local temperature of the extrusion die exceeds the solidus temperature of the alloy, the surface of the extruded material melts, subsequently leading to cracks. The solidus temperature of the alloy depends on the selection and content of the alloying elements. Adding a large amount of Si significantly lowers the solidus temperature of Al-Si alloys; therefore, the Si content is limited to 0.60%–0.70% in this application. Cu has a certain solid solution effect, and CuAl2 has a significant age-hardening effect. Appropriate addition of Mn can increase the recrystallization temperature and significantly refine the recrystallized grains. The dispersed particles of MnAl6 compounds hinder the growth of recrystallized grains. Another function of MnAl6 is to dissolve iron impurities to form (Fe,Mn)Al6, reducing the harmful effects of iron. Zn can significantly increase tensile strength and yield strength, but it has the disadvantage of stress corrosion cracking; therefore, its addition is limited to 0–0.10%. Considering the ability of aluminum alloys to form plastic profiles at high temperatures and the room temperature plasticity of extrusion, Cr is added at 0–0.02%. During extrusion, fine second phases such as binary Mg2Si, Al2Cu, and Al3Cr precipitate, which is beneficial to achieving high plasticity at room temperature and improving subsequent forming ability.

[0029] In one embodiment, the length of the ingot is 500mm to 1000mm.

[0030] In one embodiment, the melting process is carried out at a temperature of 720°C to 760°C, the composition of the rail transit profile is controlled according to the proportion, and casting is carried out at a temperature of 750°C to 760°C for the furnace eye alloy liquid and 670°C to 700°C for the pan tail alloy liquid.

[0031] In one embodiment, during the smelting process, argon gas is used for blowing refining at least twice, with each blowing refining session lasting 12 to 20 minutes. A dual-rotor degassing device is used to remove hydrogen online by purging argon gas, ensuring that the hydrogen content of the ingot is <0.15 mL / 100 g Al. Then, Al-5Ti-1B wire refiner is added using a dual wire feeder to refine the grains. The online addition position of the titanium boron wire is at least 2 m in front of the filter plate to ensure that the wire feeder operates normally throughout the process. The online filtration adopts a two-stage filtration method, with the first stage using a 40-mesh foam ceramic filter plate and the second stage using a 50-mesh foam ceramic filter plate.

[0032] In one embodiment, after all the raw materials have melted, an ultrasonic treatment is added for 10 to 20 minutes. The ultrasonic treatment is intermittent, with a 1-minute ultrasonic treatment followed by a 5-minute pause, and then another 1-minute treatment, and this cycle is repeated. The ultrasonic treatment conditions are 35 kHz to 50 kHz.

[0033] In one embodiment, the ultrasonic treatment power is 1000W to 1200W. After ultrasonic treatment, the gas in the molten alloy is reduced, and the cavitation bubbles expand and contract, collapsing. At the same time, under the acoustic flow effect of ultrasonic treatment, the molten alloy generates convection, thereby smoothing and uniformly distributing the edges of the broken dendrites. This improves the blockage caused by the large number of dendrites in the narrow part of the mold, which is conducive to filling the mold.

[0034] In one embodiment, the initial casting speed is 18 mm / min to 20 mm / min, the steady-state casting speed is 24 mm / min to 26 mm / min, the water pressure is 200 kPa to 240 kPa, and the casting water flow rate is 35 m³ / min. 3 / h~55m 3 / h.

[0035] In one embodiment, the ingot homogenization treatment is carried out at a temperature of 550°C to 570°C for 10 to 12 hours.

[0036] In one embodiment, the aging treatment temperature is 170℃~175℃, and the holding time is 6h~8h.

[0037] In one embodiment, the width of the rail transit profile is 1000mm±0.5mm, the wall thickness of the large aluminum plate is 4.0mm±0.2mm, and the wall thickness of the inner rib is 3.0mm±0.3mm; the plane gap of the large aluminum plate is <1.5mm, the curvature is <0.5mm / m, and the twist is <0.5mm / m.

[0038] The above-mentioned solution can reduce defects such as edge surface scratches, cracks, peeling, bubbles and cracks in the integrally molded rail transit profiles by optimizing the process parameters of the preparation method. At the same time, it can also obtain integrally molded rail transit profiles with significant mechanical properties and large specifications, and the cross-sectional hardness reaches 88HBW~96HBW, which meets the application requirements.

[0039] This application optimizes the composition of rail transit profiles, combining it with an optimized process to produce a significant direct weakening effect under the specified composition ratio. After extrusion, a non-basal surface texture is formed, which helps to improve plasticity and formability. Furthermore, the optimization of extrusion processing parameters can improve the tension-compression yield asymmetry, reduce wear and tear on extrusion equipment, and save on equipment maintenance costs.

[0040] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0041] Example 1:

[0042] A rail transit profile comprises the following components by weight percentage:

[0043] Si 0.60%, Fe 0.30%, Cu 0.10%, Mn 0.20%, Cr 0.02%, Zn 0.10%, Ti 0.04%, individual impurity element <0.05%, total impurity element <0.15%, Al is the balance;

[0044] A method for preparing a rail transit profile, the method comprising the following steps:

[0045] The raw materials are prepared according to the composition of the rail transit profiles, and then smelted at 760℃. After all the raw materials have melted, ultrasonic treatment is added for 13 minutes. The ultrasonic treatment is intermittent, with 1 minute of ultrasonic treatment followed by a 5-minute pause, and then another 1 minute of treatment, which is repeated. The ultrasonic treatment conditions are 45KHz and 1000W. During the smelting process, argon gas is used for blowing and refining twice, with each blowing and refining lasting 20 minutes. A dual-rotor degassing device is used to remove hydrogen online by purging argon gas, so that the hydrogen content of the ingot is <0.15mL / 100gAl. Then, Al-5Ti-1B wire refiner is added to the double wire feeder for grain refinement. The online addition position of the titanium boron wire is at least 2m in front of the filter plate to ensure that the wire feeder operates normally throughout the process. The online filtration adopts a two-stage filtration. The first stage filtration uses a 40-mesh foam ceramic filter plate, and the second stage filtration uses a 50-mesh foam ceramic filter plate.

[0046] The composition of the rail transit profiles was controlled according to the proportions. Casting was carried out under the following conditions: the furnace head alloy liquid temperature was 760℃, and the tail end alloy liquid temperature was 690℃. The initial casting speed was 18 mm / min, the steady-state casting speed was 24 mm / min, the water pressure was 220 kPa, and the casting water flow rate was 50 m³ / min. 3 / h;

[0047] The ingot was homogenized at 550℃ for 12 hours.

[0048] After homogenization, the ingots are peeled and extruded using a forward extrusion press with an extrusion ratio of 30. The extrusion temperature is 540℃ for 20 hours, the extrusion cylinder temperature is 440℃, and the die temperature is 510℃ for 35 hours, with a temperature difference of ≤5℃ between the left and right sides of the die. The main cylinder speed for extruding the first ingot is 0.8 mm / s. After normal material output is detected, the length of the ingot is adjusted to at least twice the length of the first ingot, and the main cylinder speed is adjusted to 1.2 mm / s. The extruded profiles are output in a flat manner and are cooled by online strong air. The upper fan has a coverage width of 1.2m, the lower fan has a coverage width of 1.2m, and the wind speed of both the upper and lower fans is 35m / s. The left fan has a coverage width of 0.8m, the right fan has a coverage width of 0.8m, and the wind speed of both the left and right fans is 45m / s.

[0049] The extruded ingot is kept at 175℃ for 8 hours to obtain rail transit profiles.

[0050] The rail transit profile prepared in Example 1 has a width of 1000mm ± 0.5mm, a large aluminum plate wall thickness of 4.0mm ± 0.2mm, and an inner rib wall thickness of 3.0mm ± 0.3mm; the plane gap of the large aluminum plate is < 1.5mm, the curvature is < 0.5mm / m, and the twist is < 0.5mm / m.

[0051] After testing, the rail transit profile prepared in Example 1, as examined under low magnification, showed no cracks on the surface, bright grains, and no non-metallic inclusions. The grain size met the Class II requirements of GB / T 3246.2—2012, with a coarse grain ring <0.1mm, and the extrusion weld was a continuous dark fine line. The rail transit profile prepared in Example 1, as examined under high magnification, showed no overheating, and the grain size index was not lower than Class II requirements of GB / T 3246.1—2012. Hardness testing was conducted at intervals <50mm, with a hardness range of 91HBW to 95HBW. Tensile strength testing showed a tensile strength of 270MPa, a yield strength of 235MPa, and an elongation after fracture of 9%. Overall, large-section rail transit profiles with large dimensions, hardness, appearance, and mechanical properties all meeting the requirements for use were obtained.

[0052] Example 2:

[0053] A rail transit profile comprises the following components by weight percentage:

[0054] Si 0.60%, Fe 0.2%, Cu 0.10%, Mn 0.15%, Cr 0.01%, Zn 0.10%, Ti 0.03%, individual impurity element <0.05%, total impurity element <0.15%, Al is the balance;

[0055] A method for preparing a rail transit profile, the method comprising the following steps:

[0056] The raw materials are prepared according to the composition of rail transit profiles, and then smelted at 740℃. After all raw materials have melted, ultrasonic treatment is added for 18 minutes. The ultrasonic treatment is intermittent, with 1 minute of ultrasonic treatment followed by a 5-minute pause, and then another 1 minute of treatment, which is repeated. The ultrasonic treatment conditions are 40KHz and 1200W. During the smelting process, argon gas is used for blowing and refining twice, with each blowing and refining session lasting 15 minutes. A dual-rotor degassing device is used to remove hydrogen online by purging argon gas, ensuring that the hydrogen content of the ingot is <0.15mL / 100gAl. Then, Al-5Ti-1B wire refiner is added to the double wire feeder for grain refinement. The online addition position of the titanium boron wire is at least 2m in front of the filter plate to ensure that the wire feeder operates normally throughout the process. The online filtration adopts a two-stage filtration method, with the first stage using a 40-mesh foam ceramic filter plate and the second stage using a 50-mesh foam ceramic filter plate.

[0057] The composition of the rail transit profiles was controlled according to the proportions. Casting was carried out at a furnace head alloy melt temperature of 750℃ and a tail end alloy melt temperature of 670℃. The initial casting speed was 18 mm / min, the steady-state casting speed was 24 mm / min, the water pressure was 200 kPa, and the casting water flow rate was 35 m³ / min. 3 / h;

[0058] The ingot was homogenized at 550℃ for 10 hours.

[0059] After homogenization, the ingots are peeled and extruded using a forward extrusion press with an extrusion ratio of 30. The extrusion temperature is 520℃ for 12 hours, the extrusion cylinder temperature is 420℃, and the die temperature is 500℃ for 36 hours, with a temperature difference of ≤5℃ between the left and right sides of the die. The main cylinder speed for extruding the first ingot is 0.8 mm / s. After normal material output is detected, the length of the ingot is adjusted to at least twice the length of the first ingot, and the main cylinder speed is adjusted to 1.5 mm / s. The extruded profiles are output in a flat manner and are cooled by online strong air. The upper fan has a coverage width of 1.2m, the lower fan has a coverage width of 1.2m, and the wind speed of both the upper and lower fans is 30m / s. The left fan has a coverage width of 0.8m, the right fan has a coverage width of 0.8m, and the wind speed of both the left and right fans is 45m / s.

[0060] The extruded ingot is kept at 175℃ for 8 hours to obtain rail transit profiles.

[0061] The rail transit profile prepared in Example 2 has a width of 1000mm ± 0.5mm, a large aluminum plate wall thickness of 4.0mm ± 0.2mm, and an inner rib wall thickness of 3.0mm ± 0.3mm; the plane gap of the large aluminum plate is < 1.5mm, the curvature is < 0.5mm / m, and the twist is < 0.5mm / m.

[0062] After testing, the low-magnification inspection of the rail transit profile prepared in Example 2 revealed no cracks on the surface, bright grains, and no non-metallic inclusions. The grain size met the Class II requirements of GB / T 3246.2—2012, with a coarse grain ring <0.1mm, and the extrusion weld was a continuous dark fine line. The high-magnification inspection of the rail transit profile prepared in Example 2 showed no overheating, and the grain size index was not lower than Class II requirements of GB / T 3246.1—2012. Hardness testing was conducted at intervals <50mm, with a hardness range of 89HBW to 95HBW. Tensile strength testing showed a tensile strength of 272MPa, a yield strength of 235MPa, and an elongation after fracture of 9%. Overall, large-section rail transit profiles with large dimensions, hardness, appearance, and mechanical properties all meeting the requirements for use were obtained.

[0063] Example 3:

[0064] A rail transit profile comprises the following components by weight percentage:

[0065] Si 0.70%, Fe 0.20%, Cu 0.10%, Mn 0.15%, Cr 0.01%, Zn 0.10%, Ti 0.03%, individual impurity element <0.05%, total impurity element <0.15%, Al is the balance;

[0066] A method for preparing a rail transit profile, the method comprising the following steps:

[0067] The raw materials are prepared according to the composition of the rail transit profiles, and then smelted at 760℃. After all the raw materials have melted, ultrasonic treatment is added for 15 minutes. The ultrasonic treatment is intermittent, with 1 minute of ultrasonic treatment followed by a 5-minute pause, and then another 1 minute of treatment, which is repeated. The ultrasonic treatment conditions are 35KHz and 1000W. During the smelting process, argon gas is used for blowing and refining twice, with each blowing and refining session lasting 12 minutes. A dual-rotor degassing device is used to remove hydrogen online by purging argon gas, so that the hydrogen content of the ingot is <0.15mL / 100gAl. Then, Al-5Ti-1B wire refiner is added to the double wire feeder for grain refinement. The online addition position of the titanium boron wire is at least 2m in front of the filter plate to ensure that the wire feeder operates normally throughout the process. The online filtration adopts a two-stage filtration. The first stage filtration uses a 40-mesh foam ceramic filter plate, and the second stage filtration uses a 50-mesh foam ceramic filter plate.

[0068] The composition of the rail transit profiles was controlled according to the proportions. Casting was carried out at a furnace head alloy melt temperature of 760℃ and a tail end alloy melt temperature of 700℃. The initial casting speed was 18 mm / min, the steady-state casting speed was 24 mm / min, the water pressure was 200 kPa, and the casting water flow rate was 50 m³ / min. 3 / h;

[0069] The ingot was homogenized at 550℃ for 10 hours.

[0070] After homogenization, the ingots are peeled and extruded using a forward extrusion press with an extrusion ratio of 30. The extrusion temperature is 520℃ for 12 hours, the extrusion cylinder temperature is 420℃, and the die temperature is 500℃ for 30 hours, with a temperature difference of ≤5℃ between the left and right sides of the die. The main cylinder speed for extruding the first ingot is 0.5 mm / s. After normal material output is detected, the length of the ingot is adjusted to at least twice the length of the first ingot, and the main cylinder speed is adjusted to 1.2 mm / s. The extruded profiles are output in a flat manner and are cooled by online strong airflow. The upper fan has a coverage width of 1.2m, the lower fan has a coverage width of 1.2m, and the wind speed of both the upper and lower fans is 30m / s. The left fan has a coverage width of 0.8m, the right fan has a coverage width of 0.8m, and the wind speed of both the left and right fans is 45m / s.

[0071] The extruded ingot is kept at 175℃ for 8 hours to obtain rail transit profiles.

[0072] The width of the rail transit profile prepared in Example 3 is 1000mm±0.5mm, the wall thickness of the large aluminum plate is 4.0mm±0.2mm, and the wall thickness of the inner rib is 3.0mm±0.3mm; the plane gap of the large aluminum plate is <1.5mm, the curvature is <0.5mm / m, and the twist is <0.5mm / m.

[0073] After testing, the low-magnification inspection of the rail transit profile prepared in Example 3 showed no cracks on the surface, bright grains, and no non-metallic inclusions. The grain size met the Class II requirements of GB / T 3246.2—2012, with a coarse grain ring <0.1mm, and the extrusion weld was a continuous dark fine line. The high-magnification inspection of the rail transit profile prepared in Example 3 showed no overheating, and the grain size index was not lower than Class II requirements of GB / T 3246.1—2012. Hardness testing was conducted at intervals <50mm, with a hardness range of 90HBW to 96HBW. Tensile strength testing showed a tensile strength of 271MPa, a yield strength of 237MPa, and an elongation after fracture of 10%. Overall, large-section rail transit profiles with large dimensions, hardness, appearance, and mechanical properties all meeting the requirements for use were obtained.

[0074] Comparative Example 1:

[0075] The difference between Comparative Example 1 and Example 3 is that no ingot homogenization treatment was performed in Comparative Example 1, the length of the first ingot extruded during the extrusion process was 1000 mm, the speed of the main cylinder was 1.5 mm / s, the mold temperature was 490°C, and the temperature difference between the two sides of the mold was 15°C. Everything else was the same as in Example 3.

[0076] After testing, under the process conditions in Comparative Example 1, no complete profile was extruded after the die was plugged.

[0077] Comparative Example 2:

[0078] The difference between Comparative Example 2 and Example 3 is that, in Comparative Example 2, after the first ingot is normally extruded, the second ingot is extruded at a main cylinder speed of 0.5 mm / s, and the extruded profile is kept at 175°C for 8 hours. Everything else is the same as in Example 3.

[0079] After testing, the cross-sectional hardness of the rail transit profile obtained under the process conditions of Comparative Example 2 was 54HBW~60HBW, which is lower than the requirements of the national standard GB / T 26494-2016. The mechanical properties are unqualified and do not meet the requirements for use.

[0080] Comparative Example 3:

[0081] The difference between Comparative Example 3 and Example 3 is that in Comparative Example 3, after the first ingot is extruded, the main cylinder speed for subsequent ingots is 2.5 mm / s. Everything else is the same as in Example 3.

[0082] After testing, the rail transit profile obtained under the process conditions of Comparative Example 3 showed surface scratches on the edges and cracks on the inner diameter, making it a substandard product.

[0083] Comparative Example 4:

[0084] The difference between Comparative Example 4 and Example 3 is that Comparative Example 4 uses spray + strong wind cooling quenching, while the rest is the same as Example 3.

[0085] After testing, the rail transit profiles obtained under the process conditions of Comparative Example 3 had a plane gap > 3.0, a curvature > 2 mm / m, and a twist > 2 mm / m, making them unqualified products.

[0086] Comparative Example 5:

[0087] The difference between Comparative Example 5 and Example 3 is that in Comparative Example 5, the ingot temperature is 480°C, the extrusion cylinder temperature is 380°C, the mold temperature is 470°C, and after the first ingot is normally extruded and formed, the speed of the main cylinder of the ingots after the second ingot is 1.2 mm / s, and the extruded profile is aged at 175°C for 8 hours.

[0088] After testing, the cross-sectional hardness of the rail transit profile obtained under the process conditions of Comparative Example 5 was 75HBW-83HBW, which is lower than the requirements of the national standard GB / T 26494-2016. The mechanical properties are unqualified and do not meet the requirements for use.

[0089] Comparative Example 6:

[0090] The difference between Comparative Example 6 and Example 3 is that the mass percentage composition of the rail transit profile in Comparative Example 6 is as follows:

[0091] Si 0.70%, Fe 0.20%, Cu 0.10%, Mn 0.25%, Cr 0.15%, Zn 0.10%, Ti 0.03%, individual impurity element <0.05%, total impurity element <0.15%, Al is the balance;

[0092] The difference in the preparation method of the rail transit profile in Comparative Example 6 is that after the first ingot is extruded normally, the speed of the main cylinder for subsequent ingots is 1.5 mm / s. Everything else is the same as in Example 3.

[0093] After testing, it was found that under the conditions of Comparative Example 6, the extrusion pressure reached the limit of the equipment and could not extrude qualified products.

[0094] Comparative Example 7:

[0095] The difference between Comparative Example 7 and Example 3 is that in Comparative Example 7, the smelting process uses a dual-rotor degassing device to remove hydrogen online with nitrogen, and the online filtration uses a 50-mesh foam ceramic filter plate for single-stage filtration. The ingot is directly extruded without peeling. Everything else is the same as in Example 3.

[0096] After testing, the extruded profile in Comparative Example 7 had many burrs on its surface, and low-magnification inspection revealed non-metallic inclusions. The grain size did not meet the secondary requirements of GB / T 3246.2—2012.

[0097] Comparative Example 8:

[0098] The difference between Comparative Example 8 and Example 3 is that no ultrasonic treatment was performed in Comparative Example 8, but otherwise it is the same as Example 3.

[0099] Testing revealed that the grain size of the profile in Comparative Example 8 did not meet the secondary requirements of GB / T 3246.2—2012 after low-magnification inspection.

[0100] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0101] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing rail transit profiles, characterized in that: The preparation method includes the following steps: batching, smelting, casting, ingot homogenization, ingot extrusion and aging treatment to obtain rail transit profiles. The homogenization treatment of the ingot is carried out at a temperature of 550℃~570℃ for 10h~12h. The ingot extrusion process is performed using a forward extrusion press with an extrusion ratio of 28-30. The extrusion temperature is 520℃-540℃, held for 12-24 hours. The extrusion cylinder temperature is 420℃-440℃, and the die temperature is 500℃-510℃, held for 24-36 hours, with a temperature difference of ≤5℃ between the left and right sides of the die. The main cylinder speed for extruding the first ingot is 0.5mm / s-0.8mm / s. After normal material output is detected, the length of the ingot is adjusted to at least twice the length of the first ingot, and the main cylinder speed is adjusted to 1.2 mm / s. -1.5mm / s; Extruded profiles are produced in a flat manner and are cooled by online strong airflow. The upper fan covers a width of 1.2m~1.8m, the lower fan covers a width of 1.2m~1.8m, and the wind speed of the upper and lower fans is 30m / s~35m / s. The left fan covers a width of 0.5m~0.8m, the right fan covers a width of 0.5m~0.8m, and the wind speed of the left and right fans is 40m / s~45m / s. The rail transit profile comprises the following components by weight percentage: Si 0.60%~0.70%, Fe 0~0.30%, Cu 0~0.10%, Mn 0.15%~0.20%, Cr 0~0.02%, Zn 0~0.10%, Ti 0~0.05%, individual impurity element <0.05%, total impurity element <0.15%, Al is the balance; The length of the ingot is 500mm~1000mm; the width of the rail transit profile is 1000mm±0.5mm, the wall thickness of the large aluminum plate is 4.0mm±0.2mm, and the wall thickness of the inner rib is 3.0mm±0.3mm; the plane gap of the large aluminum plate is <1.5mm, the curvature is <0.5mm / m, and the twist is <0.5mm / m.

2. The preparation method according to claim 1, characterized in that, The melting process is carried out at a temperature of 720℃~760℃. The composition of the rail transit profile is controlled according to the proportion. Casting is carried out at a temperature of 750~760℃ for the furnace eye alloy liquid and 670~700℃ for the pan tail alloy liquid.

3. The preparation method according to claim 2, characterized in that, During the smelting process, argon gas is used for blowing refining at least twice, with each blowing refining session lasting 12 to 20 minutes. A dual-rotor degassing device is used to remove hydrogen online by blowing argon gas, ensuring that the hydrogen content of the ingot is <0.15 mL / 100 g Al. Then, Al-5Ti-1B wire refiner is added to the double wire feeder for grain refinement. The titanium boron wire is added online at a position more than 2 m in front of the filter plate to ensure that the wire feeder operates normally throughout the process. The online filtration adopts a two-stage filtration method, with the first stage using a 40-mesh foam ceramic filter plate and the second stage using a 50-mesh foam ceramic filter plate.

4. The preparation method according to claim 3, characterized in that, Once all raw materials have melted, add ultrasonic treatment for 10 to 20 minutes. The ultrasonic treatment is intermittent, with 1 minute of ultrasonic treatment followed by a 5-minute break, and then another 1 minute of treatment. This cycle is repeated, and the ultrasonic treatment conditions are 35 kHz to 50 kHz.

5. The preparation method according to claim 4, characterized in that, The initial casting velocity is 18 mm / min~20 mm / min, the steady-state casting velocity is 24 mm / min~26 mm / min, the water pressure is 200 kPa~240 kPa, and the casting water flow rate is 35 m³ / min. 3 / h~55m 3 / h.

6. The preparation method according to claim 1, characterized in that, The aging treatment temperature is 170℃~175℃, and the holding time is 6h~8h.

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