Aluminum-lithium alloy profile with high batch stability and preparation method thereof

Abstract

The preparation method of the aluminum-lithium alloy profile with the high batch stability comprises the following steps that forging is conducted, specifically, an aluminum-lithium alloy cast ingot is heated and then forged, and the single-pass upsetting deformation of upsetting and drawing during forging is 60-75%; extrusion: heating the forged blank, the extrusion container and the die, and then carrying out extrusion treatment; solid solution quenching: carrying out solid solution quenching treatment on the blank subjected to extrusion treatment to obtain a profile; low-temperature heat preservation is conducted, specifically, the profile obtained after solution quenching treatment is subjected to low-temperature heat preservation treatment, the temperature ranges from 0 DEG C to 5 DEG C, and the heat preservation time is not shorter than 30 min; and carrying out pre-stretching and aging treatment on the profile subjected to low-temperature heat preservation treatment. According to the invention, the production efficiency can be improved, and the aluminum-lithium alloy material with high batch stability and excellent performance can be prepared, so that the requirements of a new generation of airplanes on the profile can be better met.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of aluminum-lithium alloy profiles, and particularly relates to an aluminum-lithium alloy profile with high batch stability and a preparation method thereof. Background Art

[0002] Compared with conventional high-strength 7-series aluminum alloys, aluminum-lithium alloys not only have the advantages of low density, high strength, and high stiffness, but also have good damage resistance and welding performance, and thus are widely used in the field of aircraft. However, due to problems such as performance uniformity and batch stability of domestic aluminum-lithium alloy profiles, they cannot fully meet the requirements of new-generation aircraft. At present, most of the aluminum-lithium alloy profiles used in aviation are still mainly imported. The conventional preparation methods of existing aluminum-lithium alloy profiles include processes such as ingot casting, extrusion, solution quenching, pre-stretching, and aging. Among them, ingot casting is generally prepared by semi-continuous casting technology, so there are differences in the core and surface structures, which in turn lead to fluctuations in the properties of the profiles; pre-stretching can effectively improve the properties of aluminum-lithium alloy profiles and reduce residual stress. However, due to the natural aging effect, the strength of aluminum-lithium alloys continuously increases when staying at room temperature and above after quenching, resulting in inconsistent properties of profiles pre-stretched at different times after quenching. If the processing time is long, the tensile force will increase sharply, and it is easy to occur phenomena such as being unable to pull and cracking. In the prior art, the material loading amount in the furnace is usually controlled within a small range to ensure that pre-stretching is completed within 3 hours, thereby avoiding the occurrence of phenomena such as being unable to pull and cracking. Therefore, the prior art has an adverse impact on both the production efficiency and performance stability of the profiles.

[0003] In order to solve the above problems, researchers have carried out extensive research in aspects such as composition optimization, ingot structure optimization, homogenization annealing, and extrusion parameter control. However, at present, the requirement of good batch stability still cannot be fully achieved. Therefore, the present invention aims to propose a preparation method of an aluminum-lithium alloy profile with high batch stability, solve the problems of large performance fluctuations, insufficient batch stability, low efficiency, etc. existing in the existing manufacturing methods, so as to better meet the actual production and processing needs. Summary of the Invention

[0004] The technical problem solved by the present invention is a preparation method of an aluminum-lithium alloy profile with high batch stability, which solves the problems of large performance fluctuations, insufficient batch stability, low efficiency, etc. existing in the existing manufacturing methods, so as to better meet the actual production and processing needs.

[0005] The technical problem solved by the present invention is also to obtain an aluminum-lithium alloy profile with high batch stability.

[0006] The technical problem solved by the present invention is achieved by adopting the following technical solutions: A preparation method of an aluminum-lithium alloy profile with high batch stability includes the following steps: Forging: The aluminum-lithium alloy ingot is heated and then forged. During forging, the upsetting deformation amount in a single upsetting-drawing pass is 60 - 75%. Extrusion: The forged blank, the extrusion cylinder and the die are heated and then extrusion treatment is carried out. Solution quenching: The blank after extrusion treatment is subjected to solution quenching treatment to obtain profiles. Low-temperature heat preservation: The profiles after solution quenching treatment are subjected to low-temperature heat preservation treatment at a temperature of 0 - 5°C for a heat preservation time of not less than 30 min. The profiles after low-temperature heat preservation treatment are subjected to pre-stretching and aging treatment.

[0007] Furthermore, in the forging step, the aluminum-lithium alloy ingot is heated to 440°C - 490°C, held for 6 - 12 h, and then forging treatment is carried out.

[0008] Furthermore, in the forging step, upsetting-drawing is carried out 2 - 4 times.

[0009] Furthermore, in the extrusion step, before extrusion, the blank is heated to 430°C - 480°C and held for 0.5 - 1 h; the die is heated to 410°C - 460°C and held for 8 - 15 h.

[0010] Furthermore, in the extrusion step, after the blank is transferred to the extrusion cylinder, it is held in the extrusion cylinder for 10 - 15 min before extrusion; the speed of the extrusion rod is 0.3 - 0.8 mm / s; the temperature of the extrusion cylinder is 410 - 460°C, and the temperature at the exit of the extruded profile is 430 - 480°C.

[0011] Furthermore, in the solution quenching step, the solution temperature is 510 - 530°C, the holding time is 2 - 4 h, and the quenching transfer time is 6 - 10 s.

[0012] Furthermore, in the pre-stretching step, stretching is carried out with a stretching amount of 2 - 4%.

[0013] Furthermore, in the aging treatment step, the aging temperature is 140 - 160°C and the holding time is 24 - 38 h.

[0014] Furthermore, the aluminum-lithium alloy ingot is a 2195 aluminum-lithium alloy ingot. The mass percentages of chemical components in the 2195 aluminum-lithium alloy ingot are: 3.7 - 4.3% of Cu, 0.8 - 1.2% of Li, 0.25 - 0.8% of Mg, 0.08 - 0.16% of Zr, 0.25 - 0.6% of Ag, and the balance is Al and impurities: 3.7 - 4.3% of Cu, 0.8 - 1.2% of Li, 0.25 - 0.8% of Mg, 0.08 - 0.16% of Zr, 0.25 - 0.6% of Ag, and the balance is Al and impurities.

[0015] An aluminum-lithium alloy profile with high batch stability, which is prepared by the method described above. The tensile strength of the aluminum-lithium alloy profile is >600 MPa, the yield strength is >550 MPa, and the elongation is >13%; the CV value of the tensile strength is <2.5%.

[0016] Beneficial effects: The preparation method of the aluminum-lithium alloy profile with high batch stability according to the present invention uses the method of upsetting and drawing in forging to combine multi-directional forging and billet opening with extrusion to replace the original method of ingot casting and extrusion, so as to improve the uniformity of the core and surface structures of the ingot and solve the problem of large differences in the core and surface structures of the ingot; in the extrusion process, the method of keeping the billet in the extrusion cylinder at a constant temperature for 10-15 minutes is used to keep the states of different billets basically the same before extrusion and reduce the influence of temperature fluctuations at the contact between the billet surface and the extrusion cylinder and the die; and combined with subsequent processes such as low-temperature constant-temperature methods to inhibit the natural aging effect of the aluminum-lithium alloy, maintain the consistency of the profile before pre-stretching, greatly reduce performance fluctuations, and improve production efficiency at the same time; in addition, through the coordinated control of each process and parameters, the present invention realizes the high-efficiency preparation and production of aluminum-lithium alloy profiles with high batch stability and a CV value of the tensile strength ≤3%. Description of the Drawings

[0017] Figure 1 It is the edge metallographic structure diagram of the aluminum-lithium alloy ingot in Example 1.

[0018] Figure 2 It is the core metallographic structure diagram of the aluminum-lithium alloy ingot in Example 2.

[0019] Figure 3 It is the edge metallographic structure diagram of the aluminum-lithium alloy ingot in Example 1 after forging and billet opening by the method of the present invention.

[0020] Figure 4 It is the core metallographic structure diagram of the aluminum-lithium alloy ingot in Example 1 after forging and billet opening by the method of the present invention. Detailed Embodiments

[0021] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0022] Example 1

[0023] The preparation method of the aluminum-lithium alloy profile with high batch stability described in this example. The aluminum-lithium alloy profile is a 2195 aluminum-lithium alloy profile. The mass percentages of chemical components in the 2195 aluminum-lithium alloy ingot are: 4.2% of Cu, 1.1% of Li, 0.56% of Mg, 0.12% of Zr, 0.4% of Ag, and the balance is Al and impurities. Its preparation method includes the following steps: Forging: Heat the aluminum-lithium alloy ingot to 460 °C, hold for 8 h and then forge. When forging, use the three-upsetting and three-drawing process, and the upsetting deformation per single pass is 65%; Extrusion: Heat the forged blank to 450 °C and hold for 0.7 h; heat the die to 440 °C and hold for 10 h. After controlling the temperature of the extrusion cylinder to 440 °C, transfer the blank to the extrusion cylinder, hold for 12 min in the extrusion cylinder and then extrude. When extruding, the speed of the extrusion rod is 0.6 mm / s, and control the outlet temperature of the extruded profile to 450 °C; Solution quenching: Perform solution quenching treatment on the extruded blank to obtain the profile; when performing solution quenching treatment, the solution temperature is 515 °C, the holding time is 2.5 h, and the quenching transfer time is controlled within 8 s; Low-temperature holding: Transfer the profile after solution quenching treatment to a low-temperature box for low-temperature holding treatment, control the temperature at 2 °C, and the holding time is 50 min; Pre-tension the profile after low-temperature holding treatment with a 2.5% tensile amount; Then perform aging treatment, the aging temperature is 150 °C, and hold for 32 h.

[0024] In this embodiment, the edge and core structures of the aluminum-lithium alloy ingot are respectively as Figure 1 and Figure 2 shown. After forging and blooming the aluminum-lithium alloy ingot, the edge and core structures are respectively as Figure 3 and Figure 4 shown. It can be seen that there are significant differences in the surface and core structures of the aluminum-lithium alloy ingot, while after forging and blooming using the method of the present invention, the differences in the surface and core structures of the blank are greatly reduced. And for the uniform blank structure, through heat preservation in the extrusion cylinder, low-temperature constant-temperature treatment before pre-deformation, combined with the synergistic cooperation of other processes and parameters, it is beneficial to obtain profiles with high batch stability.

[0025] Example 2

[0026] For the method for preparing an aluminum-lithium alloy profile with high batch stability described in this embodiment, the aluminum-lithium alloy profile is a 2195 aluminum-lithium alloy profile. The mass percentages of chemical components in the 2195 aluminum-lithium alloy ingot are: 4.2% Cu, 1.1% Li, 0.56% Mg, 0.12% Zr, 0.4% Ag, and the balance is Al and impurities. Its preparation method includes the following steps: Forging: Heat the aluminum-lithium alloy ingot to 460 °C, hold for 8 h and then forge. When forging, use the four-upsetting and four-drawing process, and the upsetting deformation per single pass during upsetting and drawing is 60%; Extrusion: Heat the forged blank to 450 °C and hold for 0.7 h; heat the die to 440 °C and hold for 10 h. After controlling the temperature of the extrusion cylinder at 440 °C, transfer the blank to the extrusion cylinder, hold for 15 min in the extrusion cylinder and then perform extrusion. During extrusion, the speed of the extrusion rod is 0.8 mm / s, and control the outlet temperature of the extruded profile at 450 °C; Solution quenching: Perform solution quenching treatment on the extruded blank to obtain the profile; during the solution quenching treatment, the solution temperature is 515 °C, the holding time is 2.5 h, and the quenching transfer time is controlled within 8 s; Low-temperature holding: Transfer the profile after solution quenching to a low-temperature box for low-temperature holding treatment, control the temperature at 1 °C, and the holding time is 42 min; Pre-tension the profile after low-temperature holding treatment with a 2.5% tensile amount; Then perform aging treatment, the aging temperature is 150 °C, and hold for 32 h.

[0027] Example 3

[0028] For the method for preparing an aluminum-lithium alloy profile with high batch stability described in this example, the aluminum-lithium alloy profile is a 2195 aluminum-lithium alloy profile. The mass percentages of chemical components in the 2195 aluminum-lithium alloy ingot are as follows: 4.2% Cu, 1.1% Li, 0.56% Mg, 0.12% Zr, 0.4% Ag, and the balance is Al and impurities. Its preparation method includes the following steps: Forging: Heat the aluminum-lithium alloy ingot to 480 °C, hold for 12 h and then perform forging. During forging, use the three-upsetting and three-drawing process for forging, and the single-pass upsetting deformation amount during upsetting and drawing is 75%; Extrusion: Heat the forged blank to 480 °C and hold for 0.5 h; heat the die to 460 °C and hold for 9 h. After controlling the temperature of the extrusion cylinder at 420 °C, transfer the blank to the extrusion cylinder, hold for 10 min in the extrusion cylinder and then perform extrusion. During extrusion, the speed of the extrusion rod is 0.8 mm / s, and control the outlet temperature of the extruded profile at 430 °C; Solution quenching: Perform solution quenching treatment on the extruded blank to obtain the profile; during the solution quenching treatment, the solution temperature is 530 °C, the holding time is 2 h, and the quenching transfer time is controlled within 10 s; Low-temperature holding: Transfer the profile after solution quenching to a low-temperature box for low-temperature holding treatment, control the temperature at 4 °C, and the holding time is 45 min; Pre-tension the profile after low-temperature holding treatment with a 4% tensile amount; Then perform aging treatment, the aging temperature is 140 °C, and hold for 38 h.

[0029] Control Example 1 In this comparative example, the aluminum-lithium alloy profile is a 2195 aluminum-lithium alloy profile. The mass percentages of chemical components in the 2195 aluminum-lithium alloy ingot are as follows: 4.2% Cu, 1.1% Li, 0.56% Mg, 0.12% Zr, 0.4% Ag, and the balance is Al and impurities. The preparation method is prepared by a conventional process, including the following steps: (1) Heat the aluminum-lithium alloy ingot to 450 °C and hold for 0.7 h; heat the die to 440 °C and hold for 10 h; the temperature of the extrusion cylinder is 440 °C; extrude the heated ingot, the speed of the extrusion rod is 0.3 - 0.8 mm / s, and control the extrusion profile outlet temperature at 450 °C (2) Solutionize and quench the extruded profile, the solutionizing temperature is 515 °C, the holding time is 2.5 h, and the quenching transfer time is controlled within 8 s; (3) After quenching, perform pre-stretching treatment with a 2.5% tensile amount; (4) Age the pre-stretched profile, the aging temperature is 150 °C, and hold for 32 h.

[0030] Comparative Example 2 In this comparative example, the aluminum-lithium alloy profile is a 2195 aluminum-lithium alloy profile. The mass percentages of chemical components in the 2195 aluminum-lithium alloy ingot are as follows: 4.2% Cu, 1.1% Li, 0.56% Mg, 0.12% Zr, 0.4% Ag, and the balance is Al and impurities. The preparation method includes the following steps: (1) Heat the aluminum-lithium alloy ingot to 450 °C and hold for 0.7 h; heat the die to 440 °C and hold for 10 h; the temperature of the extrusion cylinder is 440 °C; (2) Extrude the heated ingot; the speed of the extrusion rod is 0.6 mm / s, and control the extrusion profile outlet temperature at 450 °C; (3) Solutionize and quench the extruded profile, the solutionizing temperature is 515 °C, the holding time is 2.5 h, and the quenching transfer time is controlled within 8 s; (4) Transfer the solutionized and quenched profile to a low-temperature box for low-temperature holding treatment, control the temperature at 2 °C, and the holding time is 50 min; Perform pre-stretching treatment on the profile after low-temperature holding treatment with a 2.5% tensile amount; Then perform aging treatment, the aging temperature is 150 °C, and hold for 32 h.

[0031] Comparative Example 3 In this comparative example, the aluminum-lithium alloy profile is a 2195 aluminum-lithium alloy profile. The mass percentages of chemical components in the 2195 aluminum-lithium alloy ingot are as follows: 4.2% Cu, 1.1% Li, 0.56% Mg, 0.12% Zr, 0.4% Ag, and the balance is Al and impurities. Low-temperature heat preservation treatment is not adopted during preparation. The preparation method includes the following steps: (1) Heat the aluminum-lithium alloy ingot to 460 °C, and after holding for 8 h, perform forging. The three-upsetting and three-drawing process is adopted for forging, and the upsetting deformation amount per single pass is 65%; (2) Heat the forged blank to 450 °C and hold for 0.7 h; heat the die to 440 °C and hold for 10 h. After controlling the extrusion cylinder temperature to 440 °C, transfer the blank to the extrusion cylinder, hold for 12 min in the extrusion cylinder and then perform extrusion; during extrusion, the speed of the extrusion rod is 0.6 mm / s, and control the outlet temperature of the extruded profile to 450 °C; (3) Perform solution quenching treatment on the extruded blank to obtain the profile; during the solution quenching treatment, the solution temperature is 515 °C, the holding time is 2.5 h, and the quenching transfer time is controlled within 8 s; (4) Perform pre-tensioning treatment on the profile after quenching with a tensile amount of 2.5%; Then perform aging treatment at an aging temperature of 150 °C and hold for 32 h.

[0032] Comparative Example 4 In this comparative example, the aluminum-lithium alloy profile is a 2195 aluminum-lithium alloy profile. The mass percentages of chemical components in the 2195 aluminum-lithium alloy ingot are as follows: 4.2% Cu, 1.1% Li, 0.56% Mg, 0.12% Zr, 0.4% Ag, and the balance is Al and impurities. The preparation method includes the following steps: (1) Heat the aluminum-lithium alloy ingot to 460 °C, and after holding for 8 h, perform forging. The one-upsetting and one-drawing process is adopted for forging, and the upsetting deformation amount per single pass is 20%; (2) Heat the forged blank to 450 °C and hold for 0.7 h; heat the die to 440 °C and hold for 10 h. After controlling the extrusion cylinder temperature to 440 °C, transfer the blank to the extrusion cylinder and perform extrusion treatment after holding for 5 min in the extrusion cylinder; during extrusion, the speed of the extrusion rod is 0.6 mm / s, and control the outlet temperature of the extruded profile to 450 °C; (3) Perform solution quenching treatment on the extruded blank to obtain the profile; during the solution quenching treatment, the solution temperature is 515 °C, the holding time is 2.5 h, and the quenching transfer time is controlled within 8 s; (4) Transfer the profile after solution quenching treatment to a low-temperature box for low-temperature heat preservation treatment, control the temperature to 10 °C, and the holding time is 25 min; (5) The profiled materials after low-temperature heat preservation treatment are subjected to pre-tensile treatment with a tensile amount of 2.5%. (6) Then aging treatment is carried out, and the aging temperature is 150 °C, and heat preservation for 32 h is sufficient.

[0033] The properties of the profiled materials obtained in each example and the control example are detected. Among them, the tensile strength, yield strength, and elongation are detected according to the method specified in GB / T228.1.

[0034] In the present invention, the stability of the tensile strength is reflected by the CV value of the tensile strength. The smaller the CV value, the better the stability. According to the relevant requirements for the shaping of aviation profiled materials, the tensile strength CV value is detected for 10 batches of profiled materials in 3 furnaces. The calculation formula for the tensile strength CV value is: CV = (standard deviation / average value) × 100%.

[0035]

[0036] In the present invention, the method of upsetting and drawing during forging to combine multi-directional forging and billet opening with extrusion is adopted to improve the uniformity of the core and surface structures of the ingot, solve the problem of large differences in the core and surface structures of the ingot, adopt the method of heat preservation in the extrusion cylinder to reduce the temperature fluctuation of the billet, and combine subsequent low-temperature constant-temperature methods and other processes to inhibit the natural aging effect of the aluminum-lithium alloy, maintain the consistency of the profiled materials in the state before pre-tensile, greatly reduce the performance fluctuation, and at the same time improve the production efficiency. The performance of the prepared product is far superior to that of the product prepared by the traditional process, and the loading amount in the furnace does not need to be controlled, and the production efficiency is greatly improved. In addition, through the coordinated control of each process and parameters in the present invention, the high-efficiency preparation and production of aluminum-lithium alloy profiled materials with high batch stability with a tensile strength CV value ≤ 3% can be realized. It can be seen from the control example that in the present invention, the synergistic effect of process conditions and parameter control is extremely crucial.

[0037] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing aluminum-lithium alloy profiles with high batch stability, characterized in that: The steps include: Forging: Heat the aluminum-lithium alloy ingot to 440°C~490°C, keep it warm for 6~12 hours, and then forge it. During forging, upsetting is performed 2~4 times, and the upsetting deformation of a single upsetting is 60~75%; Extrusion: The forged billet, extrusion barrel and die are heated and then extruded; Solution quenching: The extruded billet is subjected to solution quenching to obtain a profile; Low temperature insulation: The profiles after solution quenching treatment are subjected to low temperature insulation treatment at a temperature of 0~5℃, and the insulation time is not less than 30min; The profiles after low-temperature insulation treatment can be pre-stretched and aged.

2. The method for preparing aluminum-lithium alloy profiles with high batch stability according to claim 1, characterized in that: In the extrusion step, before extrusion, the billet is heated to 430°C~480°C and kept warm for 0.5~1h; the mold is heated to 410°C~460°C and kept warm for 8~15h.

3. The method for preparing aluminum-lithium alloy profiles with high batch stability according to claim 1, characterized in that: In the extrusion step, after the billet is transferred to the extrusion barrel, it is kept warm in the extrusion barrel for 10 to 15 minutes before extrusion; the extrusion rod speed is 0.3 to 0.8 mm / s; the extrusion barrel temperature is 410 to 460°C, and the outlet temperature of the extruded profile is 430 to 480°C.

4. The method for preparing aluminum-lithium alloy profiles with high batch stability according to claim 1, characterized in that: In the solution quenching step, the solution temperature is 510~530℃, the holding time is 2~4h, and the quenching transfer time is 6~10s.

5. The method for preparing aluminum-lithium alloy profiles with high batch stability according to claim 1, characterized in that: In the pre-stretching step, the stretching is performed with a stretching amount of 2 to 4%.

6. The method for preparing aluminum-lithium alloy profiles with high batch stability according to claim 1, characterized in that: In the aging treatment step, the aging temperature is 140~160℃, and the temperature is kept for 24~38h.

7. The method for preparing aluminum-lithium alloy profiles with high batch stability according to claim 1, characterized in that: The aluminum-lithium alloy ingot is a 2195 aluminum-lithium alloy ingot, and the mass percentage of the chemical composition of the 2195 aluminum-lithium alloy ingot is: 3.7-4.3% Cu, 0.8-1.2% Li, 0.25-0.8% Mg, 0.08-0.16% Zr, 0.25-0.6% Ag, and the balance is Al and impurities.

8. An aluminum-lithium alloy profile with high batch stability, characterized in that: The aluminum-lithium alloy profile is prepared by the method according to any one of claims 1 to 7, wherein the aluminum-lithium alloy profile has a tensile strength greater than 600 MPa, a yield strength greater than 550 MPa, and an elongation greater than 13%; and a tensile strength CV value ≤ 3%.

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