An aluminum alloy profile for large-scale transportation and a method for manufacturing the same

Abstract

This invention discloses an ultra-large aluminum alloy profile for transportation and its preparation method, belonging to the field of aluminum alloy preparation. This application optimizes the composition of the aluminum alloy profile, significantly refining the grains, inhibiting the recrystallization process, and increasing the recrystallization temperature. This results in dispersion precipitation strengthening and substructure strengthening of the alloy, as well as improved ductility and toughness and reduced stress corrosion cracking susceptibility. By combining composition and processing, an ultra-large aluminum alloy profile for transportation with excellent hardness, tensile strength, yield strength, and elongation can be obtained, meeting market demands.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy preparation, and more specifically, to an ultra-large aluminum alloy profile for transportation and its preparation method. Background Technology

[0002] In recent years, low-carbon, environmentally friendly, green, and energy-saving technologies have become the main directions for global industrial development. Energy conservation and emission reduction in the transportation sector have also received increasing attention from countries worldwide. Lightweighting of transportation vehicles is one of the major measures to achieve energy conservation in transportation. Besides adopting new technologies in the design of structures and engines, selecting lighter and lower-density materials is the most effective way to achieve these goals. Aluminum alloys, with their low density, high specific strength and stiffness, excellent machinability, heat dissipation, casting performance, dimensional stability, and ease of recycling, are widely used in aerospace, large buses, high-speed buses, light rail trains, rail transit, urban transportation, and marine transportation, and are currently one of the lightest metal structural materials used on a large scale. However, the application of aluminum alloy profiles in the transportation sector currently faces several challenges, primarily including: First, the application of aluminum alloys in various transportation vehicle components requires high comprehensive performance in terms of strength, corrosion resistance, pressure resistance, and weldability, necessitating a coordinated match among these properties to meet application requirements. Second, transportation-grade aluminum alloy profiles often feature large dimensions, thin walls, numerous cavities, and high width-to-thickness ratios. Ensuring extrudability, ease of forming, and uniform microstructure and properties after extrusion places high demands on the extrusion process. Third, ultra-large, complex-section transportation-grade aluminum alloy profiles present significant deformation challenges, requiring sophisticated mold design. Inadequate mold design often leads to difficulties in extrusion forming, mold breakage, and substandard product quality. In summary, current technologies cannot fully meet the production requirements of ultra-large, complex-section transportation-grade aluminum alloy profiles. Summary of the Invention

[0003] Based on this, in order to solve the problem that the performance of existing ultra-large aluminum alloys used in transportation cannot meet the requirements, this invention provides an ultra-large aluminum alloy profile for transportation and its preparation method, the specific technical solution of which is as follows:

[0004] An extra-large aluminum alloy profile for transportation applications, the aluminum alloy profile comprising the following components by weight percentage:

[0005] Mg 0.62%–0.70%, Si 0.75%–0.85%, Mn 0.25%–0.30%, Cu 0.15%–0.20%, Ti 0.02%–0.03%, Y+Zr 0.06%–0.16%, Fe ≤0.15%, the total amount of trace Mn+Y+Zr is controlled at 0.4%–0.7%, and the balance is Al; the content of a single impurity element is ≤0.05%, and the total content of impurity elements is ≤0.15%.

[0006] This invention also provides a method for preparing ultra-large aluminum alloy profiles for transportation, the method comprising the following steps:

[0007] Aluminum ingots are added to the melting furnace, followed by intermediate alloys and then magnesium ingots. The melting temperature is controlled. Once all the furnace charge has melted, the electromagnetic stirring device is activated to stir the melt and obtain a uniform melt.

[0008] Pre-refining is carried out in a melting furnace, followed by refining in a holding furnace. During the refining process in the holding furnace, the oxidation and slag formation of the melt and the gas absorption should be controlled to a minimum to obtain an alloy liquid.

[0009] After refining in the holding furnace is completed, titanium agent is added to the alloy liquid, stirred and slag is removed, and the melt is covered with sodium-free and calcium-free covering agent. After standing for 20 to 30 minutes, it is released for casting. During the release casting, the alloy liquid flows from the outlet of the holding furnace through the online degassing and slag removal device for online refining, degassing and slag removal. Then it enters the diversion plate for semi-continuous same-level hot top casting to obtain aluminum rods.

[0010] The aluminum rod is subjected to quality analysis. When it meets the requirements of the extrusion process, it is homogenized, then heat-treated, and then hot-extruded and quenched online to obtain the extruded profile.

[0011] Extruded profiles are aged to obtain extra-large aluminum alloy profiles for transportation.

[0012] Furthermore, the master alloy includes Al-20 Si master alloy, Al-50 Cu master alloy, Al-10 Mn master alloy, Al-10 Y master alloy, and Al-4 Zr master alloy.

[0013] Furthermore, the smelting temperature is 730℃~760℃.

[0014] Furthermore, the pre-refining temperature in the melting furnace is 730℃~750℃, and high-purity argon is used as a carrier to introduce the refining agent into the melt to remove most of the oxide inclusions and dissolved hydrogen in the melt.

[0015] Furthermore, the refining process in the holding furnace involves: introducing the pre-refined melt from the smelting furnace into the holding furnace; and, at a temperature of 720℃~730℃, performing spray refining in the holding furnace, using high-purity argon gas as a carrier to introduce the refining agent into the melt. The refining tube is moved back and forth at different parts and depths in the melt, and the immersion depth of the refining tube in the melt is controlled by adjusting the argon gas pressure to ensure that the melt turbulence height is less than 50mm.

[0016] Furthermore, the online refining process is as follows: in front of the melt inlet of the online degassing device, a wire feeder is used to add Al-5Ti-1B rod-shaped grain refiner with a diameter of 9.5 mm into the flow channel to refine the alloy melt online. The addition speed is controlled at 1800 mm / min to 2100 mm / min.

[0017] The degassing process is as follows: the alloy melt is degassed online using a fluted double graphite rotor online degassing device, wherein the degassing medium is high-purity argon gas with a purity of 99.99%, the rotor speed is controlled at 200 r / min to 280 r / min, and the compressed gas flow rate is controlled at 4 m3 / h to 4.5 m3 / h.

[0018] The slag removal process involves using 40ppi and 50ppi ceramic foam filter plates to perform two-stage online filtration of the melt.

[0019] Furthermore, the semi-continuous same-level hot top casting is as follows: the melt enters the crystallizer through the guide plate, and the descent speed of the lifting platform is controlled according to the flow rate of the melt and the cooling water. During the descent, an aluminum rod is gradually formed. The temperature of the semi-continuous same-level hot top casting is 710℃~720℃, the speed is 20mm / min~30mm / min, and the cooling water pressure is 0.1MPa~0.2MPa.

[0020] Furthermore, the conditions for the hot extrusion treatment are as follows: aluminum rod temperature is 480℃~520℃, die temperature is 440℃~460℃, extrusion cylinder temperature is 400℃~450℃, extrusion speed is 1.0mm / s~3.0mm / s, extrusion outlet temperature is 510℃~540℃, and online quenching reduces the temperature to below 50℃ within 5 minutes.

[0021] Furthermore, the aging treatment involves the extruded profile being held at 545℃~550℃ for 50min~60min, then rapidly water-quenched, followed by aging at 170℃~175℃ for 0.5h~1h, left to stand for 40h~48h, and then undergoing extended aging at 170℃~175℃ for 6h~8h.

[0022] The above scheme optimizes the composition of the aluminum alloy profile, specifically controlling the Mg2Si content and excess silicon content. The main strengthening phases of the alloy are Mg2Si, excess silicon, and Al3Zr / Al3(Y,Zr). The tensile strength of the alloy increases with the increase of Mg2Si and excess silicon content. The average content of the strengthening phase Mg2Si in the alloy is controlled below 1.0%, while the average content of excess silicon is controlled not to exceed 0.35%. The alloy contains Fe and Mn. During the actual casting and crystallization process, Si in the alloy will preferentially form β-AlFeSi or α-Al with Fe or Mn. 12 The (FeMn)3Si intermetallic compound consumes some Si. Therefore, the internal control standard maintains the magnesium content in the alloy at 0.62%–0.70% to ensure the tensile strength of the aluminum alloy profile. Adding small amounts of microalloying elements Mn, Y, and Zr can form MnAl6 and Al3Zr / Al3(Y,Zr) phases, significantly refining the grains, inhibiting recrystallization, increasing the recrystallization temperature, and providing some dispersion precipitation strengthening and substructure strengthening effects. It also improves the alloy's ductility and toughness and reduces stress corrosion cracking susceptibility. Adding Cu provides some solid solution, reducing the corrosion resistance of the aluminum alloy profile. Online addition of Al-5Ti-1B can achieve a good grain refinement effect.

[0023] This application optimizes the process to ensure the uniformity of the alloy liquid and the quality of casting. The combination of composition and process can produce ultra-large aluminum alloy profiles for transportation with excellent hardness, tensile strength, yield strength and elongation, thus meeting market demand. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] An embodiment of the present invention provides an extra-large aluminum alloy profile for transportation, wherein the aluminum alloy profile comprises the following components by weight percentage:

[0027] Mg 0.62%–0.70%, Si 0.75%–0.85%, Mn 0.25%–0.30%, Cu 0.15%–0.20%, Ti 0.02%–0.03%, Y+Zr 0.06%–0.16%, Fe ≤0.15%, the total amount of trace Mn+Y+Zr is controlled at 0.4%–0.7%, and the balance is Al; the content of individual impurity elements is ≤0.05%, and the total content of impurity elements is ≤0.15%.

[0028] In this application, to ensure the strength of the aluminum alloy profiles, the content of Mg2Si and excess silicon is controlled. The main strengthening phases of the aluminum alloy profiles are Mg2Si, excess silicon, and Al3Zr / Al3(Y,Zr). The tensile strength of the alloy increases with the increase of Mg2Si and excess silicon content, but at the same time, its quenching sensitivity also increases, and its elongation and extrudability decrease, thus increasing the difficulty of the extrusion production process. Therefore, the average content of the strengthening phase Mg2Si in the aluminum alloy profiles is controlled below 1.0%, while the average content of excess silicon is controlled not to exceed 0.35%. The aluminum alloy profiles contain Fe and Mn. In the actual casting and crystallization process, Si in the aluminum alloy profiles will preferentially form β-AlFeSi or α-Al with Fe or Mn. 12 (FeMn)3Si intermetallic compounds consume some Si. Therefore, the internal control standards control the magnesium content in aluminum alloy profiles to 0.62%–0.70% and the silicon content to 0.75%–0.85%.

[0029] This application aims to improve the corrosion resistance and weldability of aluminum alloy profiles, especially the strength of argon arc welded joints. It requires the addition of small amounts of microalloying elements Mn, Y, and Zr, which can form MnAl6 and Al3Zr / Al3(Y,Zr) phases, significantly refining the grain size, inhibiting the recrystallization process, and increasing the recrystallization temperature. This provides some dispersion precipitation strengthening and substructure strengthening to the aluminum alloy profiles, and also improves the alloy's ductility and toughness and reduces stress corrosion cracking susceptibility. However, high levels of these trace alloying elements can lead to the formation of coarse, brittle, and hard aluminides; therefore, the total amount of microalloying elements added to the alloy must be controlled between 0.4% and 0.7%.

[0030] The addition of Cu to the aluminum alloy profiles in this application will have a certain solid solution strengthening effect, but it will also reduce the corrosion resistance of the alloy. Therefore, the amount of Cu added is 0.15% to 0.20%.

[0031] In this application, the Fe content of impurities is controlled below 0.15% because high Fe content has a significant impact on the corrosion resistance, fatigue performance, and extrusion performance of the alloy.

[0032] The addition of Ti in this application refines the microstructure of both the casting and weld seams, reducing the tendency for cracking. The method of adding Al-5Ti-1B online during casting achieves a good grain refinement effect. The total amount of titanium added is controlled between 0.02% and 0.03%.

[0033] This invention also provides a method for preparing ultra-large aluminum alloy profiles for transportation, the method comprising the following steps:

[0034] Aluminum ingots are added to the melting furnace, followed by intermediate alloys and then magnesium ingots. The melting temperature is controlled. Once all the furnace charge has melted, the electromagnetic stirring device is activated to stir the melt and obtain a uniform melt.

[0035] Pre-refining is carried out in a melting furnace, followed by refining in a holding furnace. During the refining process in the holding furnace, the oxidation and slag formation of the melt and the gas absorption should be controlled to a minimum to obtain an alloy liquid.

[0036] After refining in the holding furnace is completed, titanium agent is added to the alloy liquid, stirred and slag is removed, and the melt is covered with sodium-free and calcium-free covering agent. After standing for 20 to 30 minutes, it is released for casting. During the release casting, the alloy liquid flows from the outlet of the holding furnace through the online degassing and slag removal device for online refining, degassing and slag removal. Then it enters the diversion plate for semi-continuous same-level hot top casting to obtain aluminum rods.

[0037] The aluminum rod is subjected to quality analysis. When it meets the requirements of the extrusion process, it is homogenized, then heat-treated, and then hot-extruded and quenched online to obtain the extruded profile.

[0038] Extruded profiles are aged to obtain extra-large aluminum alloy profiles for transportation.

[0039] In one embodiment, the master alloy includes Al-20 Si master alloy, Al-50 Cu master alloy, Al-10 Mn master alloy, Al-10 Y master alloy, and Al-4 Zr master alloy.

[0040] In one embodiment, the melting temperature is 730°C to 760°C.

[0041] In one embodiment, the magnesium ingot is added by placing it in a high-temperature corrosion-resistant stainless steel cage and pressing it into the melt to prevent oxidation and burn-off of the magnesium ingot.

[0042] In one embodiment, the pre-refining temperature in the melting furnace is 730°C to 750°C, and high-purity argon is used as a carrier to introduce the refining agent into the melt to remove most of the oxide inclusions and dissolved hydrogen in the melt.

[0043] In one embodiment, the stirring blades of the electromagnetic stirring device are movably connected to the stirring shaft, and the stirring blades can swing up and down on the stirring shaft, thereby stirring the melt in the corner of the smelting furnace to ensure the uniformity of melt temperature and chemical composition.

[0044] In one embodiment, the refining process in the holding furnace involves: introducing the pre-refined melt from the smelting furnace into the holding furnace; and, at a temperature of 720℃~730℃, performing jet refining in the holding furnace. High-purity argon gas is used as a carrier to introduce the refining agent into the melt. A refining tube is moved back and forth within the melt at different locations and depths, and the immersion depth of the refining tube is controlled by adjusting the argon gas pressure to ensure that the melt turbulence height is less than 50mm. This back-and-forth movement of the refining tube within the melt at different locations and depths ensures the uniformity of the melt refining process.

[0045] In one embodiment, the online refining process is as follows: in front of the melt inlet of the online degassing device, a wire feeder is used to add Al-5Ti-1B rod-shaped grain refiner with a diameter of 9.5 mm into the flow channel to refine the alloy melt online. The addition speed is controlled at 1800 mm / min to 2100 mm / min.

[0046] The degassing process involves using a fluted double-graphite rotor online degassing device to degas the alloy melt online. The degassing medium is high-purity argon gas with a purity of 99.99%, the rotor speed is controlled at 200 r / min to 280 r / min, and the compressed gas flow rate is controlled at 4 m³ / min. 3 / h~4.5m 3 / h;

[0047] The slag removal process involves using 40ppi and 50ppi ceramic foam filter plates to perform two-stage online filtration of the melt.

[0048] In one embodiment, the semi-continuous same-level hot top casting involves the molten metal entering the crystallizer through an inlet plate. The descent speed of the lifting platform is controlled according to the flow rates of the molten metal and cooling water, gradually forming an aluminum rod during the descent. The semi-continuous same-level hot top casting temperature is 710℃~720℃, the speed is 20mm / min~30mm / min, and the cooling water pressure is 0.1MPa~0.2MPa. This application limits the casting temperature to ensure good fluidity of the aluminum alloy molten metal after run-casting, thereby ensuring good filling properties. Because the diameter of the cast aluminum rod in this application is relatively large, the solidification rates of the inner and outer parts of the ingot are inconsistent during casting, easily leading to porosity defects. If the casting temperature is too low, the central part of the aluminum rod cannot be effectively and timely fed, resulting in severe porosity defects, which in turn lead to extrusion cracks during subsequent extrusion, seriously affecting the extrusion quality. A graphite sleeve is embedded in the semi-continuous same-level hot top casting crystallizer, serving a cooling and lubrication function during the cooling process. Since the width of the graphite sleeve is fixed, the cooling height of the ingot is also fixed. The casting speed should be selected to ensure good formability of the alloy ingot, that is, to ensure that the alloy ingot does not crack and has good surface quality. Given the relatively large diameter of the aluminum rod, the casting speed is limited. Furthermore, the cooling intensity has a significant impact on the ingot's microstructure, properties, cracking tendency, and surface quality. The flow rate, velocity, and temperature of the cooling water, the structure of the crystallizer, and the casting temperature are the three fundamental factors determining the cooling intensity. In industrial aluminum alloy casting production, for a given alloy grade and ingot specifications, the crystallizer structure and casting temperature are basically fixed; the ingot cooling intensity can only be controlled by adjusting the flow rate and velocity of the cooling water.

[0049] In one embodiment, during the semi-continuous same-level hot top casting process, a hydrogen analyzer is used to measure the hydrogen content in the alloy melt in the flow channel, and the hydrogen content is measured at ingot lengths of 1m, 3m and 5m respectively.

[0050] In one embodiment, the homogenization treatment is carried out at a temperature of 540°C to 545°C for 6 to 8 hours. During the semi-continuous horizontal hot-top casting process, rapid cooling can cause inhomogeneity in the microstructure and composition of the aluminum rod, resulting in residual inhomogeneous material. Homogenization treatment promotes microstructure uniformity and reduces segregation and coarse dendrites.

[0051] In one embodiment, the heat treatment is to heat to 500°C within 3 to 5 minutes.

[0052] In one embodiment, the hot extrusion conditions are: aluminum rod temperature 480℃~520℃, die temperature 440℃~460℃, extrusion cylinder temperature 400℃~450℃, extrusion speed 1.0mm / s~3.0mm / s, extrusion outlet temperature 510℃~540℃, and online quenching reducing the temperature to below 50℃ within 5 minutes. This application limits the hot extrusion conditions to prevent tailing, bubbles, oxide scale, or impurities from being incorporated. Since aluminum alloy profiles contain trace elements such as Mn and Zr, which promote the formation of intragranular intermetallic compounds, adversely affecting quenching performance, high quenching cooling intensity, precise control of longitudinal and transverse cooling intensity, and rapid cooling speed are required. In one embodiment, infrared thermography is used to accurately and rapidly measure the extruded profile outlet temperature with a response speed of 0.3s and a measurement accuracy of ±2℃. The extrusion temperature feedback is used to control the extrusion speed through the extruder PLC system, forming an extrusion temperature-extrusion speed control feedback system to ensure stable extruded profile exit.

[0053] In one embodiment, the aging treatment involves the extruded profile being held at 545℃~550℃ for 50min~60min, then rapidly water-quenched, followed by aging at 170℃~175℃ for 0.5h~1h, left to stand for 40h~48h, and then undergoing extended aging at 170℃~175℃ for 6h~8h.

[0054] In one embodiment, the aluminum alloy profile has a width of 900mm to 1200mm, a solid height of 60mm to 80mm, a wall thickness of 3.5mm to 4.0mm, a width-to-height ratio of 15 to 17, and a width-to-thickness ratio of 285 to 290. By optimizing the composition and process of the aluminum alloy profile, the above solution can obtain ultra-large-sized aluminum alloy profiles for transportation applications with excellent hardness, tensile strength, yield strength, and elongation, thus meeting market demands. However, due to the large width-to-thickness ratio, numerous cavities, and thin walls of the aluminum alloy profile, excessive mold pressure and uneven mold stress can easily lead to bridge deformation and fracture during extrusion molding. This necessitates the design of a mold with strong pressure relief capacity, balanced flow, and uniform pressure distribution, placing stringent requirements on mold design.

[0055] In one embodiment, the die used in the hot extrusion process is a die with an outer circle, and the width of the extruded profile can account for 80% to 85% of the width of the die.

[0056] In one embodiment, during the hot extrusion process, the guide plate structure of the die is configured with a 4-inlet, 16-outlet flow guide method. The width of the extruded profile in this application has a high ratio to the width of the die, making the die prone to elastic deformation under pressure. The 4-inlet, 16-outlet flow guide scheme reduces the inlet pressure and ensures uniform flow.

[0057] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0058] Example 1:

[0059] Example 1: The aluminum alloy profile for extra-large transportation applications comprises the following components by weight percentage:

[0060] Mg 0.62%, Si 0.75%, Mn 0.30%, Cu 0.15%, Ti 0.03%, Y+Zr 0.16%, Fe≤0.15%, the total amount of trace Mn+Y+Zr is controlled at 0.7%, and the balance is Al; the content of a single impurity element is ≤0.05%, and the total content of impurity elements is ≤0.15%.

[0061] A method for manufacturing an extra-large aluminum alloy profile for transportation, the method comprising the following steps:

[0062] Aluminum ingots are added to the melting furnace, followed by Al-20 Si master alloy, Al-50 Cu master alloy, Al-10 Mn master alloy, Al-10 Y master alloy and Al-4 Zr master alloy, and then magnesium ingots. The melting temperature is controlled at 760℃. After all the furnace charge in the melting furnace has melted, the electromagnetic stirring device is started to stir the melt to obtain a uniform melt.

[0063] Pre-refining is carried out in a melting furnace at a temperature of 750℃. High-purity argon gas with a purity of 99.99% is used as a carrier to introduce the refining agent into the melt. Then, at a temperature of 730℃, in-holding furnace refining is carried out. High-purity argon gas with a purity of 99.99% is used as a carrier to introduce the refining agent into the melt. In-holding furnace refining is carried out. During the in-holding furnace refining process, it is necessary to control the oxidation and slag formation of the melt and the gas absorption to a minimum. The refining tube is moved back and forth in different parts and depths of the melt. The immersion depth of the refining tube in the melt is controlled by adjusting the argon gas pressure to ensure that the turbulence height of the melt is less than 50mm, so as to obtain an alloy liquid.

[0064] After refining in the holding furnace is completed, titanium agent is added to the alloy melt, and the mixture is stirred and slag is removed. The melt is then covered with a sodium-free and calcium-free covering agent. After standing for 30 minutes, the melt is released for casting. During release casting, the alloy melt flows from the holding furnace outlet through an online degassing and slag removal device for online refining, degassing, and slag removal. The online refining process involves adding 9.5mm diameter Al-5Ti-1B rod-shaped grain refiner to the flow channel using a wire feeder before the melt inlet of the online degassing device, refining the alloy melt online at a rate controlled at 2100mm / min. The degassing process involves using a flow channel type dual-graphite rotor online degassing device to degas the alloy melt online. The degassing medium is 99.99% high-purity argon gas, the rotor speed is controlled at 280r / min, and the compressed gas flow rate is controlled at 4m³ / min. 3 / h; The slag removal process is as follows: the melt is subjected to two-stage online filtration using 40ppi and 50ppi ceramic foam filter plates.

[0065] The melt enters the crystallizer through the inlet plate. The descent speed of the lifting platform is controlled according to the flow rate of the melt and cooling water. During the descent, aluminum rods are gradually formed. The temperature of the semi-continuous horizontal hot top casting is 710℃, the speed is 20mm / min, and the cooling water pressure is 0.2MPa to obtain aluminum rods.

[0066] The aluminum rod is subjected to quality analysis. When it meets the requirements of the extrusion process, it is homogenized at 545°C for 6 hours, and then heat-treated by heating to 500°C within 3 minutes. The aluminum rod temperature is then set to 520°C, the die temperature to 440°C, the extrusion cylinder temperature to 450°C, the extrusion speed to 1.0 mm / s, and the extrusion outlet temperature to 510°C. The rod is then quenched online to reduce the temperature to below 50°C within 5 minutes to obtain the extruded profile.

[0067] The extruded profiles are subjected to aging treatment under the following conditions: the extruded profiles are kept at 550℃ for 50 minutes, then rapidly quenched in water, then aged at 170℃ for 0.5 hours, left to stand for 40 hours, and then subjected to extended aging treatment at 170℃ for 8 hours to obtain extra-large aluminum alloy profiles for transportation.

[0068] Example 2:

[0069] Example 2: The extra-large aluminum alloy profiles for transportation applications comprise the following components by weight percentage:

[0070] Mg 0.65%, Si 0.85%, Mn 0.30%, Cu 0.20%, Ti 0.025%, Y+Zr 0.06%, Fe≤0.15%, the total amount of trace Mn+Y+Zr is controlled at 0.5%, and the balance is Al; the content of individual impurity elements is ≤0.05%, and the total content of impurity elements is ≤0.15%.

[0071] A method for manufacturing an extra-large aluminum alloy profile for transportation, the method comprising the following steps:

[0072] Aluminum ingots are added to the melting furnace, followed by Al-20 Si master alloy, Al-50 Cu master alloy, Al-10 Mn master alloy, Al-10 Y master alloy and Al-4 Zr master alloy, and then magnesium ingots. The melting temperature is controlled at 760℃. After all the furnace charge in the melting furnace has melted, the electromagnetic stirring device is started to stir the melt to obtain a uniform melt.

[0073] Pre-refining is carried out in a melting furnace at a temperature of 740℃. High-purity argon gas with a purity of 99.99% is used as a carrier to introduce the refining agent into the melt. Then, at a temperature of 725℃, in-holding furnace refining is carried out. High-purity argon gas with a purity of 99.99% is used as a carrier to introduce the refining agent into the melt. In-holding furnace refining is carried out. During the in-holding furnace refining process, it is necessary to control the oxidation and slag formation of the melt and the gas absorption to a minimum. The refining tube is moved back and forth in different parts and depths of the melt. The immersion depth of the refining tube in the melt is controlled by adjusting the argon gas pressure to ensure that the turbulence height of the melt is less than 50mm, so as to obtain an alloy liquid.

[0074] After refining in the holding furnace is completed, titanium agent is added to the alloy melt, and the mixture is stirred and slag is removed. The melt is then covered with a sodium-free and calcium-free covering agent. After standing for 30 minutes, the melt is released for casting. During release casting, the alloy melt flows from the holding furnace outlet through an online degassing and slag removal device for online refining, degassing, and slag removal. The online refining process involves adding 9.5mm diameter Al-5Ti-1B rod-shaped grain refiner to the flow channel using a wire feeder before the melt inlet of the online degassing device, refining the alloy melt online at a rate controlled at 2100mm / min. The degassing process involves using a flow channel type dual-graphite rotor online degassing device to degas the alloy melt online. The degassing medium is 99.99% high-purity argon gas, the rotor speed is controlled at 280r / min, and the compressed gas flow rate is controlled at 4m³ / min. 3 / h; The slag removal process is as follows: the melt is subjected to two-stage online filtration using 40ppi and 50ppi ceramic foam filter plates.

[0075] The melt enters the crystallizer through the inlet plate. The descent speed of the lifting platform is controlled according to the flow rate of the melt and cooling water. During the descent, aluminum rods are gradually formed. The temperature of the semi-continuous horizontal hot top casting is 720℃, the speed is 30mm / min, and the cooling water pressure is 0.2MPa to obtain aluminum rods.

[0076] The aluminum rod is subjected to quality analysis. When it meets the requirements of the extrusion process, it is homogenized at 545°C for 8 hours, and then heat-treated by heating to 500°C within 5 minutes. The aluminum rod temperature is then set to 480°C, the die temperature to 450°C, the extrusion cylinder temperature to 450°C, the extrusion speed to 2.0 mm / s, and the extrusion outlet temperature to 520°C. The rod is then quenched online to reduce the temperature to below 50°C within 5 minutes to obtain the extruded profile.

[0077] The extruded profiles are subjected to aging treatment under the following conditions: the extruded profiles are kept at 545℃ for 50 minutes, then rapidly water-quenched, then aged at 175℃ for 0.5 hours, left to stand for 48 hours, and then subjected to extended aging treatment at 175℃ for 8 hours to obtain extra-large aluminum alloy profiles for transportation.

[0078] Example 3:

[0079] Example 3: The aluminum alloy profiles for extra-large transportation applications comprise the following components by weight percentage:

[0080] Mg 0.66%, Si 0.80%, Mn 0.30%, Cu 0.16%, Ti 0.03%, Y+Zr 0.12%, Fe≤0.15%, the total amount of trace Mn+Y+Zr is controlled at 0.6%, and the balance is Al; the content of individual impurity elements is ≤0.05%, and the total content of impurity elements is ≤0.15%.

[0081] A method for manufacturing an extra-large aluminum alloy profile for transportation, the method comprising the following steps:

[0082] Aluminum ingots are added to the melting furnace, followed by Al-20 Si master alloy, Al-50 Cu master alloy, Al-10 Mn master alloy, Al-10 Y master alloy and Al-4 Zr master alloy, and then magnesium ingots. The melting temperature is controlled at 740℃. After all the furnace charge in the melting furnace has melted, the electromagnetic stirring device is started to stir the melt to obtain a uniform melt.

[0083] Pre-refining is carried out in a melting furnace at a temperature of 745℃. High-purity argon gas with a purity of 99.99% is used as a carrier to introduce the refining agent into the melt. Then, at a temperature of 730℃, in-holding furnace refining is carried out. High-purity argon gas with a purity of 99.99% is used as a carrier to introduce the refining agent into the melt. In-holding furnace refining is carried out. During the in-holding furnace refining process, it is necessary to control the oxidation and slag formation of the melt and the gas absorption to a minimum. The refining tube is moved back and forth in different parts and depths of the melt. The immersion depth of the refining tube into the melt is controlled by adjusting the argon gas pressure to ensure that the turbulence height of the melt is less than 50mm, so as to obtain an alloy liquid.

[0084] After refining in the holding furnace is completed, titanium agent is added to the alloy melt, and the mixture is stirred and slag is removed. The melt is then covered with a sodium- and calcium-free covering agent. After standing for 25 minutes, it is released for casting. During release casting, the alloy melt flows from the holding furnace outlet through an online degassing and slag removal device for online refining, degassing, and slag removal. The online refining process involves adding 9.5mm diameter Al-5Ti-1B rod-shaped grain refiner to the flow channel using a wire feeder before the melt inlet of the online degassing device, refining the alloy melt online at a rate controlled at 2000mm / min. The degassing process involves using a flow channel type dual-graphite rotor online degassing device to degas the alloy melt online. The degassing medium is 99.99% high-purity argon gas, with the rotor speed controlled at 250r / min and the compressed gas flow rate controlled at 4.2m³ / min. 3 / h; The slag removal process is as follows: the melt is subjected to two-stage online filtration using 40ppi and 50ppi ceramic foam filter plates.

[0085] The melt enters the crystallizer through the inlet plate. The descent speed of the lifting platform is controlled according to the flow rate of the melt and cooling water. During the descent, aluminum rods are gradually formed. The temperature of the semi-continuous horizontal hot top casting is 720℃, the speed is 25mm / min, and the cooling water pressure is 0.2MPa to obtain aluminum rods.

[0086] The aluminum rod is subjected to quality analysis. When it meets the requirements of the extrusion process, it is homogenized at 545°C for 8 hours, and then heat-treated by heating to 500°C within 5 minutes. The aluminum rod temperature is 500°C, the die temperature is 450°C, the extrusion cylinder temperature is 450°C, the extrusion speed is 2.0 mm / s, the extrusion outlet temperature is 520°C, and then online quenching is performed to reduce the temperature to below 50°C within 5 minutes to obtain the extruded profile.

[0087] The extruded profiles are subjected to aging treatment under the following conditions: the extruded profiles are kept at 545℃ for 50 minutes, then rapidly water-quenched, then aged at 175℃ for 0.5 hours, left to stand for 48 hours, and then subjected to extended aging treatment at 175℃ for 8 hours to obtain extra-large aluminum alloy profiles for transportation.

[0088] The aluminum rods from Examples 1-3 were analyzed and tested. The results of visual inspection and low-magnification analysis are as follows: grain size grade 1-1.5 (grade 1.5 only in the center of the aluminum rod); porosity less than grade 1; no inclusions or cracks were found in the low-magnification microstructure, nor were bright crystals or feather-like grain structures observed; no inclusions, obvious scratches, or cold shuts were found on the appearance of the aluminum rods; no internal cracks were found after ultrasonic testing; the hydrogen content was 0.13-0.14 ml / 100gAl. The analysis results show that the 670mm diameter aluminum rods prepared according to the above process parameters fully meet the requirements of subsequent extrusion processes and can guarantee the effectiveness of subsequent extrusion treatment.

[0089] It should be noted that the aluminum alloy profiles prepared in Examples 1 to 3 have a width of 1000 mm, a product height of 60 mm, a product wall thickness of 4.0 mm, a width-to-height ratio of 16.6, and a maximum width-to-thickness ratio of 286.

[0090] Comparative Example 1:

[0091] The difference between Comparative Example 1 and Example 3 lies in the composition of the aluminum alloy profile; otherwise, they are the same as in Example 3. The aluminum alloy profile in Comparative Example 1 comprises the following components by mass percentage:

[0092] Mg 0.66%, Si 0.80%, Mn 0.52%, Cu 0.56%, Ti 0.03%, Y 0.11%, Zr 0.06%, Fe ≤0.15%, balance Al; individual impurity element content ≤0.05%, total impurity element content ≤0.15%.

[0093] Comparative Example 2:

[0094] The difference between Comparative Example 2 and Example 3 lies in the composition of the aluminum alloy profile; otherwise, they are the same as in Example 3. The aluminum alloy profile in Comparative Example 2 comprises the following components by mass percentage:

[0095] Mg 0.21%, Si 0.80%, Mn 0.70%, Cu 0.16%, Ti 0.03%, Y+Zr 0.23%, Fe≤0.15%, balance Al; individual impurity element content ≤0.05%, total impurity element content ≤0.15%.

[0096] Comparative Example 3:

[0097] The difference between Comparative Example 3 and Example 3 lies in the composition of the aluminum alloy profile; otherwise, they are the same as in Example 3. The aluminum alloy profile in Comparative Example 3 comprises the following components by mass percentage:

[0098] Mg 0.52%, Si 0.51%, Mn 0.01%, Cu 0.16%, Ti 0.03%, Y 0.01%, Zr 0.01%, Fe ≤0.15%, balance Al; individual impurity element content ≤0.05%, total impurity element content ≤0.15%.

[0099] Comparative Example 4:

[0100] The difference between Comparative Example 4 and Example 3 is that the semi-continuous same-level hot top casting process parameters are different. Otherwise, they are the same as Example 3. The temperature of the semi-continuous same-level hot top casting in Comparative Example 4 is 650°C, the speed is 35 mm / min, and the cooling water pressure is 0.5 MPa.

[0101] Comparative Example 5:

[0102] The difference between Comparative Example 5 and Example 3 is that the extrusion processing conditions are different, while the other conditions are the same as those in Example 3. The extrusion processing conditions in Comparative Example 5 are as follows: aluminum rod temperature is 450°C, die temperature is 400°C, extrusion cylinder temperature is 500°C, extrusion speed is 5 mm / s, extrusion outlet temperature is 550°C, and online quenching reduces the temperature to below 50°C within 20 minutes.

[0103] Comparative Example 6:

[0104] The difference between Comparative Example 6 and Example 3 is that the aging treatment conditions are different. Otherwise, they are the same as Example 3. The aging treatment conditions in Comparative Example 6 are: the extruded profile is kept at 500°C for 10 hours.

[0105] Comparative Example 7:

[0106] The difference between Comparative Example 7 and Example 3 is that Comparative Example 7 was not heat-treated before extrusion, but otherwise it was the same as Example 3.

[0107] The aluminum alloy profiles prepared in Examples 1-3 were subjected to performance tests. According to GB / T12444-2006, a sliding wear test was conducted using bearing steel as the grinding ring to test the wear resistance of the aluminum alloy profiles. The rotational speed was 50 r / min, the load was 50 N, and the time was 20 min. The coefficient of friction was also measured. The aluminum alloy profiles were immersed in a 3 wt% NaCl aqueous solution for 20 days to test their corrosion resistance. The data obtained are shown in Table 1 below.

[0108] Table 1:

[0109]

[0110] As can be seen from the data analysis in Table 1, the aluminum alloy profiles prepared in this application have a smooth surface and excellent corrosion resistance.

[0111] Table 2:

[0112]

[0113] Analysis of the data in Table 2 shows that the difference between Comparative Examples 1-3 and Example 3 lies in the composition and component ratio. However, the resulting aluminum alloy profiles exhibit significant differences in mechanical properties, indicating that optimizing the composition and component ratio of the aluminum alloy profiles in this application helps improve their overall mechanical properties. The difference between Comparative Examples 4-7 and Example 3 lies in the process and process parameters. It is evident that changing the process parameters alters the mechanical properties of the resulting aluminum alloy profiles, making them inferior to those in Example 3. This demonstrates that by optimizing the process and process parameters, this application can still obtain aluminum alloy profiles with excellent tensile strength, yield strength, and elongation after fracture, even with a width of 1000 mm, a solid height of 60 mm, a wall thickness of 3.5 mm to 4.0 mm, a width-to-height ratio of 16.6, and a maximum width-to-thickness ratio of 286, thus meeting market demands.

[0114] 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.

[0115] 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. An extra-large aluminum alloy profile for transportation, characterized in that, The aluminum alloy profile comprises the following components by weight percentage: Mg 0.62%~0.70%, Si 0.75%~0.85%, Mn 0.25%~0.30%, Cu 0.15%~0.20%, Ti 0.02%-0.03%, Y+Zr 0.06%~0.16%, Fe≤0.15%, with the total amount of trace Mn+Y+Zr controlled at 0.4%~0.46%, and the balance being Al; the content of a single impurity element ≤0.05%, and the total content of impurity elements ≤0.15%; The aluminum alloy profile has a width of 900mm~1200mm, a wall thickness of 3.5mm~4.0mm, and a width-to-thickness ratio of 285~290. The method for preparing the ultra-large aluminum alloy profile for transportation includes the following steps: Aluminum ingots are added to the melting furnace, followed by intermediate alloys and then magnesium ingots. The melting temperature is controlled. Once all the furnace charge has melted, the electromagnetic stirring device is activated to stir the melt and obtain a uniform melt. Pre-refining is carried out in a melting furnace, followed by refining in a holding furnace. During the refining process in the holding furnace, the oxidation and slag formation of the melt and the gas absorption should be controlled to a minimum to obtain an alloy liquid. After refining in the holding furnace is completed, titanium agent is added to the alloy liquid, and the mixture is stirred and slag is removed. The melt is then covered with a sodium-free and calcium-free covering agent. After standing for 20 to 30 minutes, the melt is released for casting. During the release casting, the alloy liquid flows from the outlet of the holding furnace through an online degassing and slag removal device for online refining, degassing, and slag removal. It then enters the distribution plate for semi-continuous same-level hot top casting. The semi-continuous same-level hot top casting is as follows: the melt enters the crystallizer through the guide plate, and the descent speed of the lifting platform is controlled according to the flow rate of the melt and cooling water. During the descent, aluminum rods are gradually formed. The temperature of the semi-continuous same-level hot top casting is 710℃ to 720℃, the speed is 20 mm / min to 30 mm / min, and the cooling water pressure is 0.1 MPa to 0.2 MPa to obtain aluminum rods. The aluminum rod is subjected to quality analysis. Once it meets the requirements of the extrusion process, it is homogenized, then heat-treated, and then hot-extruded. The hot-extruded conditions are as follows: aluminum rod temperature 480℃~520℃, die temperature 440℃~460℃, extrusion cylinder temperature 400℃~450℃, extrusion speed 1.0mm / s~3.0mm / s, extrusion outlet temperature 510℃~540℃, and online quenching to reduce the temperature to below 50℃ within 5 minutes, followed by online quenching to obtain the extruded profile. The extruded profiles are subjected to aging treatment, which involves holding the extruded profiles at 545℃~550℃ for 50min~60min, followed by rapid water quenching, then aging at 170℃~175℃ for 0.5h~1h, resting for 40h~48h, and then undergoing extended aging at 170℃~175℃ for 6h~8h to obtain extra-large aluminum alloy profiles for transportation.

2. A method for preparing an extra-large aluminum alloy profile for transportation, characterized in that, The preparation method is used to prepare the ultra-large aluminum alloy profile for transportation as described in claim 1, and the preparation method includes the following steps: Aluminum ingots are added to the melting furnace, followed by intermediate alloys and then magnesium ingots. The melting temperature is controlled. Once all the furnace charge has melted, the electromagnetic stirring device is activated to stir the melt and obtain a uniform melt. Pre-refining is carried out in a melting furnace, followed by refining in a holding furnace. During the refining process in the holding furnace, the oxidation and slag formation of the melt and the gas absorption should be controlled to a minimum to obtain an alloy liquid. After refining in the holding furnace is completed, titanium agent is added to the alloy liquid, and the mixture is stirred and slag is removed. The melt is then covered with a sodium-free and calcium-free covering agent. After standing for 20 to 30 minutes, the melt is released for casting. During the release casting, the alloy liquid flows from the outlet of the holding furnace through an online degassing and slag removal device for online refining, degassing, and slag removal. It then enters the distribution plate for semi-continuous same-level hot top casting. The semi-continuous same-level hot top casting is as follows: the melt enters the crystallizer through the guide plate, and the descent speed of the lifting platform is controlled according to the flow rate of the melt and cooling water. During the descent, aluminum rods are gradually formed. The temperature of the semi-continuous same-level hot top casting is 710℃ to 720℃, the speed is 20 mm / min to 30 mm / min, and the cooling water pressure is 0.1 MPa to 0.2 MPa to obtain aluminum rods. The aluminum rod is subjected to quality analysis. Once it meets the requirements of the extrusion process, it is homogenized, then heat-treated, and then hot-extruded. The hot-extruded conditions are as follows: aluminum rod temperature 480℃~520℃, die temperature 440℃~460℃, extrusion cylinder temperature 400℃~450℃, extrusion speed 1.0mm / s~3.0mm / s, extrusion outlet temperature 510℃~540℃, and online quenching to reduce the temperature to below 50℃ within 5 minutes, followed by online quenching to obtain the extruded profile. The extruded profiles are subjected to aging treatment, which involves holding the extruded profiles at 545℃~550℃ for 50min~60min, followed by rapid water quenching, then aging at 170℃~175℃ for 0.5h~1h, resting for 40h~48h, and then undergoing extended aging at 170℃~175℃ for 6h~8h to obtain extra-large aluminum alloy profiles for transportation.

3. The preparation method according to claim 2, characterized in that, The master alloys include Al-20 Si master alloy, Al-50 Cu master alloy, Al-10 Mn master alloy, Al-10 Y master alloy, and Al-4 Zr master alloy.

4. The preparation method according to claim 2, characterized in that, The smelting temperature is 730℃~760℃.

5. The preparation method according to claim 2, characterized in that, The pre-refining temperature in the smelting furnace is 730℃~750℃. High-purity argon gas is used as a carrier to introduce the refining agent into the melt to remove most of the oxide inclusions and dissolved hydrogen in the melt.

6. The preparation method according to claim 5, characterized in that, The refining process in the holding furnace involves: introducing the pre-refined melt from the smelting furnace into the holding furnace; spraying refining at a temperature of 720℃~730℃; using high-purity argon as a carrier to introduce the refining agent into the melt; and using a refining tube to move back and forth at different parts and depths in the melt, while adjusting the argon pressure to control the depth of the refining tube's immersion in the melt, ensuring that the melt turbulence height is less than 50mm.

7. The preparation method according to claim 2, characterized in that, The online refining process is as follows: in front of the melt inlet of the online degassing device, a wire feeder is used to add Al-5Ti-1B rod-shaped grain refiner with a diameter of 9.5 mm into the flow channel to refine the alloy melt online. The addition speed is controlled at 1800 mm / min ~ 2100 mm / min. The degassing treatment is that the alloy melt is degassed on line by using a flow channel type double graphite rotor on-line degassing device, wherein the degassing medium is high-purity argon with a purity of 99.99%, the rotor rotating speed is controlled at 200 r / min ~280 r / min, and the gas flow rate is controlled at 4 m 3 / h ~4.5m 3 / h. The slag removal process involves using 40ppi and 50ppi ceramic foam filter plates to perform two-stage online filtration of the melt.

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