Aging treatment process of high-strength and high-toughness aluminum profile for rail transit

Abstract

The application discloses an aging treatment process of high-strength and high-toughness aluminum profile for rail transit and belongs to the technical field of aluminum profiles. The aging treatment process is innovative in adopting stepwise heating and divided-speed cooling. The stepwise heating is specifically shown as follows: the temperature of a first constant-temperature sub-stage is 160 DEG C, and the time is 1.5 h; the temperature of a second constant-temperature sub-stage is 180 DEG C, and the time is 1 h; the temperature of a third constant-temperature sub-stage is 190 DEG C, and the time is 0.5 h; and the total temperature rising range is 30 DEG C. The divided-speed cooling is first carried out at a speed of 15-20 DEG C / min to 150-170 DEG C, then carried out at a speed of 10-12 DEG C / min to 50 DEG C, and finally naturally cooled to room temperature. The aging treatment process realizes the uniform distribution of precipitated phases, the elimination of residual stress and the optimization of mechanical properties through stepwise heating and divided-speed cooling, maximally retains strength and toughness, and obtains the balance of high-strength and high-toughness of the aluminum profile.

Description

Technical Field

[0001] This invention belongs to the field of aluminum profile technology, specifically relating to an aging treatment process for high-strength and tough aluminum profiles used in rail transit. Background Technology

[0002] Lightweighting of rail transit equipment is a key technological direction for improving operational efficiency and reducing energy consumption. High-strength and high-toughness aluminum alloy profiles, due to their excellent specific strength, good formability, and corrosion resistance, have become an ideal choice for vehicle body structural components. However, while pursuing ultra-high strength, alloys often face challenges such as insufficient toughness, high stress corrosion sensitivity, and poor microstructural stability, which severely restricts their application in critical load-bearing components of rail transit systems with extremely high safety requirements. Aging treatment is a process step that effectively controls the final properties of aluminum alloys. Although traditional single-stage or simple multi-stage aging processes can achieve high strength, they often fail to achieve the optimal balance between strength and toughness.

[0003] Therefore, developing a refined, multi-stage, synergistically controlled aging treatment process for high-strength and tough aluminum profiles used in rail transit, to achieve precise control over the morphology, size, and distribution of precipitated phases, significantly improve toughness and microstructure stability while maximizing strength retention, and effectively suppress residual stress and over-aging risks, has become an urgent technical requirement to meet the stringent service requirements of rail transit. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an innovative aging treatment process.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] An aging treatment process for high-strength and tough aluminum profiles used in rail transit includes the following steps:

[0007] (1) After the aluminum profile is quenched, it is placed in an aging furnace for aging treatment. The aging furnace is heated to 100-130℃ at a heating rate of 60℃ / h and held for 1-2h.

[0008] (2) Stepwise heating: Heat to 160-190℃ at a rate of 8℃ / min and keep warm for a total of 3 hours;

[0009] (3) High temperature for short time: raise the temperature to 200-220℃ and keep it for 10-30 minutes;

[0010] (4) Partial-rate cooling: Cool to room temperature at partial rates;

[0011] The stepped heating stage consists of two step phases and three isothermal sub-phases, with a total heating range of 30°C.

[0012] The temperature of the first isothermal phase is 160℃ and the time is 1.5h; the temperature of the second isothermal phase is 180℃ and the time is 1h; the temperature of the third isothermal phase is 190℃ and the time is 0.5h.

[0013] The aluminum profile comprises the following components by weight percentage: Zn: 5.8-6.8%, Mg: 2.0-2.6%, Cu: 1.0-1.6%, Zr: 0.08-0.16%, Sc: 0.08-0.20%, Mn: 0.03-0.05%, Cr: 0.02-0.04%, Ti: 0.02-0.03%, with the balance being Al.

[0014] Furthermore, the two steps include a low-temperature step and a high-temperature step. The low-temperature step is the entire process from the first isothermal sub-stage to the second isothermal sub-stage of the step-heating process; the high-temperature step is the entire process from the second isothermal sub-stage to the third isothermal sub-stage of the step-heating process.

[0015] Furthermore, the low-temperature step temperature difference is 20°C; the high-temperature step temperature difference is 10°C.

[0016] Furthermore, in step (4), the fractional cooling first cools to 150-170°C at a rate of 15-20°C / min, then cools to 50°C at a rate of 10-12°C / min, and finally cools naturally to room temperature.

[0017] The aging process of this invention employs a stepped heating method. Stepped heating avoids the sudden, explosive precipitation of supersaturated solid solutions and promotes multiple nucleation stages. Low-temperature steps stimulate the nucleation of new phases, increasing the density of strengthening phases, while high-temperature steps promote the coarsening of existing phases, reducing lattice distortion energy and improving toughness. During the stepped heating stage, a large number of fine, coherent strengthening phases precipitate uniformly. These precipitates effectively hinder dislocation movement, providing high strength. Precise control of the three sub-stages of stepped heating allows for more uniformly sized and rationally distributed precipitates, improving the microstructural stability of the material at service temperatures. Furthermore, the stepped heating stage reduces stress concentration, thereby improving the material's fatigue resistance and extending its service life.

[0018] The aging process of this invention employs high temperature and short time, reducing the holding time in the high-temperature section and significantly lowering power consumption. Furthermore, it promotes the coarsening of fine reinforcing phases, balancing strength and toughness.

[0019] The present invention employs fractional cooling during the aging process. In the first stage, the temperature is cooled to 150-170°C at a rate of 15-20°C / min to quickly pass through the precipitation-sensitive region, suppress GP precipitation, and avoid performance degradation. In the second stage, the temperature is cooled to 50°C at a rate of 10-12°C / min to reduce residual stress and prevent deformation. Finally, after being removed from the furnace, the temperature is allowed to cool naturally to room temperature to complete the microstructure stabilization.

[0020] Beneficial effects

[0021] This invention achieves a balance between high strength and toughness by precisely controlling the precipitated phase through stepwise heating in multiple stages.

[0022] This invention effectively suppresses the excessive growth and coarsening of precipitated phases in the sensitive temperature range through fractional cooling, locks in the microstructure optimized at high temperature for a short time, and prevents performance loss. At the same time, the second-stage cooling, which slows down the cooling rate, helps to reduce the residual stress caused by the temperature gradient generated by rapid cooling, which is beneficial to subsequent processing and stability.

[0023] The aging process of this invention achieves uniform distribution of precipitated phases, elimination of residual stress, and optimization of mechanical properties through stepped heating and fractional cooling. For high-strength and high-toughness aluminum profiles used in rail transit, this process not only meets the engineering requirements of high strength and lightweight, but also significantly improves the reliability and service life of the material by reducing the risk of over-aging and intergranular corrosion. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0025] Example 1

[0026] An aging treatment process for high-strength and tough aluminum profiles used in rail transit includes the following steps:

[0027] (1) After the aluminum profile is quenched, it is placed in an aging furnace for aging treatment. The aging furnace is heated to 100°C at a heating rate of 60°C / h and held for 1h.

[0028] (2) Stepwise heating: Heat to 160-190℃ at a rate of 8℃ / min and keep warm for a total of 3 hours;

[0029] (3) High temperature for short time: raise to 200℃ and keep warm for 10 minutes;

[0030] (4) Partial-rate cooling: Cool to room temperature at partial rates;

[0031] The stepped heating stage consists of two step phases and three isothermal sub-phases, with a total heating range of 30°C.

[0032] The temperature of the first isothermal phase is 160℃ and the time is 1.5h; the temperature of the second isothermal phase is 180℃ and the time is 1h; the temperature of the third isothermal phase is 190℃ and the time is 0.5h.

[0033] The aluminum profile comprises the following components by weight percentage: Zn: 5.8%, Mg: 2.0%, Cu: 1.0%, Zr: 0.08%, Sc: 0.08%, Mn: 0.03%, Cr: 0.02%, Ti: 0.02%, with the balance being Al.

[0034] The two steps include a low-temperature step and a high-temperature step. The low-temperature step is the entire process from the first isothermal sub-stage to the second isothermal sub-stage of the step-heating process; the high-temperature step is the entire process from the second isothermal sub-stage to the third isothermal sub-stage of the step-heating process.

[0035] The low-temperature step temperature difference is 20℃; the high-temperature step temperature difference is 10℃.

[0036] In step (4), the fractional cooling first cools to 150°C at a rate of 15°C / min, then cools to 50°C at a rate of 10°C / min, and finally cools naturally to room temperature.

[0037] Example 2

[0038] An aging treatment process for high-strength and tough aluminum profiles used in rail transit includes the following steps:

[0039] (1) After the aluminum profile is quenched, it is placed in an aging furnace for aging treatment. The aging furnace is heated to 120°C at a heating rate of 60°C / h and held for 2 hours.

[0040] (2) Stepwise heating: Heat to 160-190℃ at a rate of 8℃ / min and keep warm for a total of 3 hours;

[0041] (3) High temperature for short time: raise to 210℃ and keep warm for 20 minutes;

[0042] (4) Partial-rate cooling: Cool to room temperature at partial rates;

[0043] The stepped heating stage consists of two step phases and three isothermal sub-phases, with a total heating range of 30°C.

[0044] The temperature of the first isothermal phase is 160℃ and the time is 1.5h; the temperature of the second isothermal phase is 180℃ and the time is 1h; the temperature of the third isothermal phase is 190℃ and the time is 0.5h.

[0045] The aluminum profile comprises the following components by weight percentage: Zn: 6.2%, Mg: 2.3%, Cu: 1.3%, Zr: 0.12%, Sc: 0.08-0.20%, Mn: 0.04%, Cr: 0.03%, Ti: 0.02%, with the balance being Al.

[0046] The two steps include a low-temperature step and a high-temperature step. The low-temperature step is the entire process from the first isothermal sub-stage to the second isothermal sub-stage of the step-heating process; the high-temperature step is the entire process from the second isothermal sub-stage to the third isothermal sub-stage of the step-heating process.

[0047] The low-temperature step temperature difference is 20℃; the high-temperature step temperature difference is 10℃.

[0048] In step (4), the fractional cooling first cools to 170°C at a rate of 17°C / min, then cools to 50°C at a rate of 11°C / min, and finally cools naturally to room temperature.

[0049] Example 3

[0050] An aging treatment process for high-strength and tough aluminum profiles used in rail transit includes the following steps:

[0051] (1) After the aluminum profile is quenched, it is placed in an aging furnace for aging treatment. The aging furnace is heated to 130°C at a heating rate of 60°C / h and held for 2 hours.

[0052] (2) Stepwise heating: Heat to 160-190℃ at a rate of 8℃ / min and keep warm for a total of 3 hours;

[0053] (3) High temperature for short time: raise to 220℃ and keep warm for 30 minutes;

[0054] (4) Partial-rate cooling: Cool to room temperature at partial rates;

[0055] The stepped heating stage consists of two step phases and three isothermal sub-phases, with a total heating range of 30°C.

[0056] The temperature of the first isothermal phase is 160℃ and the time is 1.5h; the temperature of the second isothermal phase is 180℃ and the time is 1h; the temperature of the third isothermal phase is 190℃ and the time is 0.5h.

[0057] The aluminum profile comprises the following components by weight percentage: Zn: 6.8%, Mg: 2.6%, Cu: 1.6%, Zr: 0.16%, Sc: 0.20%, Mn: 0.05%, Cr: 0.04%, Ti: 0.03%, with the balance being Al.

[0058] The two steps include a low-temperature step and a high-temperature step. The low-temperature step is the entire process from the first isothermal sub-stage to the second isothermal sub-stage of the step-heating process; the high-temperature step is the entire process from the second isothermal sub-stage to the third isothermal sub-stage of the step-heating process.

[0059] The low-temperature step temperature difference is 20℃; the high-temperature step temperature difference is 10℃.

[0060] In step (4), the fractional cooling first cools to 150°C at a rate of 20°C / min, then cools to 50°C at a rate of 12°C / min, and finally cools naturally to room temperature.

[0061] Comparative Example 1

[0062] An aging treatment process for high-strength and tough aluminum profiles used in rail transit includes the following steps:

[0063] (1) After the aluminum profile is quenched, it is placed in an aging furnace for aging treatment. The aging furnace is heated to 130°C at a heating rate of 60°C / h and held for 2 hours.

[0064] (2) Heating: Heat to 160℃ at a rate of 8℃ / min and keep warm for 3 hours;

[0065] (3) High temperature for short time: raise to 220℃ and keep warm for 30 minutes;

[0066] (4) Partial-rate cooling: Cool to room temperature at partial rates;

[0067] The aluminum profile comprises the following components by weight percentage: Zn: 6.8%, Mg: 2.6%, Cu: 1.6%, Zr: 0.16%, Sc: 0.20%, Mn: 0.05%, Cr: 0.04%, Ti: 0.03%, with the balance being Al.

[0068] In step (4), the fractional cooling first cools to 150°C at a rate of 20°C / min, then cools to 50°C at a rate of 12°C / min, and finally cools naturally to room temperature.

[0069] Compared with Example 3, this comparative example is identical to Example 3 except that the stepped heating is not used and the temperature is raised to 160°C and held for 3 hours.

[0070] Comparative Example 2

[0071] An aging treatment process for high-strength and tough aluminum profiles used in rail transit includes the following steps:

[0072] (1) After the aluminum profile is quenched, it is placed in an aging furnace for aging treatment. The aging furnace is heated to 130°C at a heating rate of 60°C / h and held for 2 hours.

[0073] (2) Heating: Heating to 180℃ at a rate of 8℃ / min and holding for a total of 3 hours;

[0074] (3) High temperature for short time: raise to 220℃ and keep warm for 30 minutes;

[0075] (4) Partial-rate cooling: Cool to room temperature at partial rates;

[0076] The aluminum profile comprises the following components by weight percentage: Zn: 6.8%, Mg: 2.6%, Cu: 1.6%, Zr: 0.16%, Sc: 0.20%, Mn: 0.05%, Cr: 0.04%, Ti: 0.03%, with the balance being Al.

[0077] In step (4), the fractional cooling first cools to 150°C at a rate of 20°C / min, then cools to 50°C at a rate of 12°C / min, and finally cools naturally to room temperature.

[0078] Compared with Example 3, this comparative example is identical to Example 3 except that the stepped heating is not used and the temperature is raised to 180°C and held for 3 hours.

[0079] Comparative Example 3

[0080] An aging treatment process for high-strength and tough aluminum profiles used in rail transit includes the following steps:

[0081] (1) After the aluminum profile is quenched, it is placed in an aging furnace for aging treatment. The aging furnace is heated to 130°C at a heating rate of 60°C / h and held for 2 hours.

[0082] (2) Stepwise heating: Heat to 160-190℃ at a rate of 8℃ / min and keep warm for a total of 3 hours;

[0083] (3) High temperature for short time: raise to 220℃ and keep warm for 30 minutes;

[0084] (4) Cooling: Cool to room temperature;

[0085] The stepped heating stage consists of two step phases and three isothermal sub-phases, with a total heating range of 30°C.

[0086] The temperature of the first isothermal phase is 160℃ and the time is 1.5h; the temperature of the second isothermal phase is 180℃ and the time is 1h; the temperature of the third isothermal phase is 190℃ and the time is 0.5h.

[0087] The aluminum profile comprises the following components by weight percentage: Zn: 6.8%, Mg: 2.6%, Cu: 1.6%, Zr: 0.16%, Sc: 0.20%, Mn: 0.05%, Cr: 0.04%, Ti: 0.03%, with the balance being Al.

[0088] The two steps include a low-temperature step and a high-temperature step. The low-temperature step is the entire process from the first isothermal sub-stage to the second isothermal sub-stage of the step-heating process; the high-temperature step is the entire process from the second isothermal sub-stage to the third isothermal sub-stage of the step-heating process.

[0089] The low-temperature step temperature difference is 20℃; the high-temperature step temperature difference is 10℃.

[0090] In step (4), the temperature is cooled to 50°C at a rate of 20°C / min, and finally cooled naturally to room temperature.

[0091] Compared with Example 3, this comparative example is identical to Example 3 except that it does not use fractional cooling and is cooled at a rate of 20°C / min.

[0092] Comparative Example 4

[0093] An aging treatment process for high-strength and tough aluminum profiles used in rail transit includes the following steps:

[0094] (1) After the aluminum profile is quenched, it is placed in an aging furnace for aging treatment. The aging furnace is heated to 130°C at a heating rate of 60°C / h and held for 2 hours.

[0095] (2) Stepwise heating: Heat to 160-190℃ at a rate of 8℃ / min and keep warm for a total of 3 hours;

[0096] (3) High temperature for short time: raise to 220℃ and keep warm for 30 minutes;

[0097] (4) Cooling: Cool to room temperature;

[0098] The stepped heating stage consists of two step phases and three isothermal sub-phases, with a total heating range of 30°C.

[0099] The temperature of the first isothermal phase is 160℃ and the time is 1.5h; the temperature of the second isothermal phase is 180℃ and the time is 1h; the temperature of the third isothermal phase is 190℃ and the time is 0.5h.

[0100] The aluminum profile comprises the following components by weight percentage: Zn: 6.8%, Mg: 2.6%, Cu: 1.6%, Zr: 0.16%, Sc: 0.20%, Mn: 0.05%, Cr: 0.04%, Ti: 0.03%, with the balance being Al.

[0101] The two steps include a low-temperature step and a high-temperature step. The low-temperature step is the entire process from the first isothermal sub-stage to the second isothermal sub-stage of the step-heating process; the high-temperature step is the entire process from the second isothermal sub-stage to the third isothermal sub-stage of the step-heating process.

[0102] The low-temperature step temperature difference is 20℃; the high-temperature step temperature difference is 10℃.

[0103] In step (4), the temperature is cooled to 50°C at a rate of 12°C / min, and finally cooled naturally to room temperature.

[0104] Compared with Example 3, this comparative example is identical to Example 3 except that it does not use fractional cooling and is cooled at a rate of 12°C / min.

[0105] Comparative Example 5

[0106] An aging treatment process for high-strength and tough aluminum profiles used in rail transit includes the following steps:

[0107] (1) After the aluminum profile is quenched, it is placed in an aging furnace for aging treatment. The aging furnace is heated to 130°C at a heating rate of 60°C / h and held for 2 hours.

[0108] (2) Heating: Heat to 180℃ at a rate of 8℃ / min and keep warm for 3 hours;

[0109] (3) High temperature for short time: raise to 220℃ and keep warm for 30 minutes;

[0110] (4) Cooling: Cool to room temperature;

[0111] The aluminum profile comprises the following components by weight percentage: Zn: 6.8%, Mg: 2.6%, Cu: 1.6%, Zr: 0.16%, Sc: 0.20%, Mn: 0.05%, Cr: 0.04%, Ti: 0.03%, with the balance being Al.

[0112] In step (4), the temperature is cooled to 50°C at a rate of 20°C / min, and finally cooled naturally to room temperature.

[0113] Compared with Example 3, this comparative example does not use stepped heating or fractional cooling, but the other raw materials and steps are the same as in Example 3.

[0114] Performance testing

[0115] The manufacturing process of high-strength and tough aluminum profiles for rail transit includes melting and casting the raw materials, followed by homogenization, rolling, solution treatment, quenching, and aging. The melting and casting temperature is 700℃; the homogenization process is carried out at 460℃ for 8-12 hours; the rolling temperature is 420℃; the solution treatment temperature is 465℃ for 1-2 hours; and the quenching process uses air, water mist, or water to cool the aluminum profiles at a rate of 5-8℃ / s.

[0116] The aluminum profiles obtained by the aging treatment methods in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests. The mechanical properties were tested in accordance with GB / T228.1-2021 Metallic Materials - Tensile Testing - Part 1 - Room Temperature Test Method. The Vickers hardness value was calculated by pressing a diamond pyramid indenter into the material surface under a specific load and measuring the diagonal of the indentation. The test data are shown in Table 1.

[0117] Table 1 Performance test results of aluminum profiles in each treatment group

[0118]

[0119] As shown in Table 1, the yield strength of the aluminum profiles treated with the aging method of this invention is above 330 MPa, the tensile strength is above 360 ​​MPa, and the elongation after fracture is above 17%. The test results from the examples demonstrate that the aluminum profiles obtained through the aging treatment of this invention retain strength and toughness to the maximum extent. In contrast, comparisons that remove the stepped heating or fractional cooling process during aging treatment fail to leverage the synergistic effect of both methods, resulting in an imbalance between high strength and toughness and a significant decrease in various properties.

[0120] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. An aging treatment process for high-strength and tough aluminum profiles used in rail transit, characterized in that, Includes the following steps: (1) After the aluminum profile is quenched, it is placed in an aging furnace for aging treatment. The aging furnace is heated to 100-130℃ at a heating rate of 60℃ / h and held for 1-2h. (2) Stepwise heating: Heat to 160-190℃ at a rate of 8℃ / min and keep warm for a total of 3 hours; (3) High temperature for short time: raise the temperature to 200-220℃ and keep it for 10-30 minutes; (4) Partial-rate cooling: Cool to room temperature at partial rates; The stepped heating stage consists of two step phases and three isothermal sub-phases, with a total heating range of 30°C. The temperature of the first isothermal stage is 160℃, and the holding time is 1.5h; the temperature of the second isothermal stage is 180℃, and the holding time is 1h; the temperature of the third isothermal stage is 190℃, and the holding time is 0.5h. The aluminum profile comprises the following components by weight percentage: Zn: 5.8-6.8%, Mg: 2.0-2.6%, Cu: 1.0-1.6%, Zr: 0.08-0.16%, Sc: 0.08-0.20%, Mn: 0.03-0.05%, Cr: 0.02-0.04%, Ti: 0.02-0.03%, with the balance being Al.

2. The aging treatment process for high-strength and high-toughness aluminum profiles for rail transit according to claim 1, characterized in that, The two steps include a low-temperature step and a high-temperature step; the low-temperature step is the entire process from the first isothermal sub-stage to the second isothermal sub-stage of the step-heating process, and the high-temperature step is the entire process from the second isothermal sub-stage to the third isothermal sub-stage of the step-heating process.

3. The aging treatment process for high-strength and high-toughness aluminum profiles for rail transit according to claim 2, characterized in that, The low-temperature step temperature difference is 20℃; the high-temperature step temperature difference is 10℃.

4. The aging treatment process for high-strength and tough aluminum profiles for rail transit according to claim 1, characterized in that, In step (4), the partial cooling rate is first 15-20℃ / min to 150-170℃, then 10-12℃ / min to 50℃, and finally naturally cooled to room temperature.

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