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

Abstract

The method for producing aluminum-lithium alloy profiles with high batch stability disclosed herein comprises the following steps: forging: heating an aluminum-lithium alloy ingot and then forging it, with the single-pass upsetting deformation during forging being 60-75%; extrusion: heating the forged billet, extrusion barrel, and die and then extruding it; solution quenching: subjecting the extruded billet to a solution quenching treatment to produce a profile; low-temperature holding: subjecting the solution quenched profile to a low-temperature holding treatment at a temperature of 0-5°C for at least 30 minutes; and pre-stretching and aging the low-temperature holding treated profile. The method improves production efficiency and facilitates the production of aluminum-lithium alloy profiles with high batch stability and excellent performance, thereby better meeting the profile requirements of next-generation aircraft.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum-lithium alloy profile preparation, and in particular 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 properties, and are therefore widely used in the field of aviation aircraft.

[0003] The conventional preparation method of existing aluminum-lithium alloy profiles includes ingot casting, extrusion, solution quenching, pre-stretching, aging and other processes. Among them, the ingot is generally prepared by a semi-continuous casting process, so there are differences in the core and surface tissues, which in turn leads to fluctuations in profile performance; pre-stretching can effectively improve the performance of aluminum-lithium alloy profiles and reduce residual stress, but due to the natural aging effect, the aluminum-lithium alloy stays at room temperature or above after quenching, causing the strength to continue to increase, resulting in inconsistent performance of profiles pre-stretched at different times after quenching. If the processing time is long, the tensile force will increase sharply, and phenomena such as inability to pull and cracking are prone to occur. In the existing technology, the material loading amount is usually controlled to a small range to ensure that the pre-stretching is completed within 3 hours, thereby avoiding the occurrence of inability to pull and cracking. Therefore, the existing technology has an adverse effect on the production efficiency and performance stability of the profile.

[0004] To address these issues, researchers have conducted extensive research in areas such as composition optimization, ingot structure optimization, homogenization annealing, and extrusion parameter control. However, achieving full batch stability remains elusive. Therefore, the present invention aims to provide a method for preparing aluminum-lithium alloy profiles with high batch stability. This method addresses the significant performance fluctuations, insufficient batch stability, and low efficiency inherent in existing manufacturing methods, thereby better meeting the needs of actual production and processing. Summary of the Invention

[0005] The technical problem solved by the present invention is a method for preparing aluminum-lithium alloy profiles with high batch stability, which solves the problems of large performance fluctuations, insufficient batch stability, low efficiency, etc. in existing manufacturing methods, so as to better meet actual production and processing needs.

[0006] The technical problem solved by the present invention is also to obtain an aluminum-lithium alloy profile with high batch stability.

[0007] The technical problem solved by the present invention is achieved by adopting the following technical solutions:

[0008] A method for preparing aluminum-lithium alloy profiles with high batch stability comprises the following steps:

[0009] Forging: The aluminum-lithium alloy ingot is heated and then forged. The single-pass upsetting deformation of the forging process is 60-75%.

[0010] Extrusion: The forged billet, extrusion cylinder and die are heated and then extruded;

[0011] Solution quenching: The extruded billet is subjected to solution quenching to obtain a profile;

[0012] Low temperature insulation: The profiles after solution quenching treatment are subjected to low temperature insulation treatment at a temperature of 0 to 5°C, and the insulation time is not less than 30 minutes; the profiles after low temperature insulation treatment are pre-stretched and aged.

[0013] Furthermore, in the forging step, the aluminum-lithium alloy ingot is heated to 440° C. to 490° C., kept warm for 6 to 12 hours, and then forged.

[0014] Furthermore, during the forging step, upsetting is performed 2 to 4 times.

[0015] Furthermore, in the extrusion step, before extrusion, the billet is heated to 430° C. to 480° C. and kept warm for 0.5 to 1 hour; the mold is heated to 410° C. to 460° C. and kept warm for 8 to 15 hours.

[0016] Furthermore, 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.

[0017] Furthermore, in the solution quenching step, the solution temperature is 510-530° C., the holding time is 2-4 hours, and the quenching transfer time is 6-10 seconds.

[0018] Furthermore, in the pre-stretching step, the stretching is performed with a stretching amount of 2 to 4%.

[0019] Furthermore, in the aging treatment step, the aging temperature is 140-160° C. and the temperature is kept at 140-38 hours.

[0020] Furthermore, the aluminum-lithium alloy ingot is a 2195 aluminum-lithium alloy ingot, and the mass percentage of the chemical composition in 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: 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.

[0021] An aluminum-lithium alloy profile with high batch stability is prepared by the method described above. The aluminum-lithium alloy profile has a tensile strength greater than 600 MPa, a yield strength greater than 550 MPa, an elongation greater than 13%, and a tensile strength CV value less than 2.5%.

[0022] Beneficial effects: The method for preparing aluminum-lithium alloy profiles with high batch stability described in the present invention adopts a method of upsetting and drawing during forging to combine multi-directional forging and extrusion to replace the original ingot casting and extrusion method, so as to improve the uniformity of the core and surface tissues of the ingot and solve the problem of large differences in the core and surface tissues of the ingot; during the extrusion process, the method of keeping the billet warm in the extrusion barrel for 10 to 15 minutes is adopted to keep the states of different billets basically consistent before extrusion, thereby reducing the influence of temperature fluctuations caused by the contact between the surface of the billet and the extrusion barrel and the mold; and combined with subsequent low-temperature constant temperature methods and other processes to suppress the natural aging effect of the aluminum-lithium alloy, the consistency of the state of the profile before pre-stretching is maintained, the performance fluctuation is greatly reduced, and the production efficiency is improved at the same time; in addition, the present invention realizes the efficient preparation and production of aluminum-lithium alloy profiles with high batch stability and a tensile strength CV value of ≤3% through the coordinated control of various processes and parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the metallographic structure diagram of the edge of the aluminum-lithium alloy ingot in Example 1.

[0024] Figure 2 This is the metallographic structure diagram of the core of the aluminum-lithium alloy ingot in Example 2.

[0025] Figure 3 This is the metallographic structure diagram of the edge of the aluminum-lithium alloy ingot in Example 1 after forging and blanking using the method of the present invention.

[0026] Figure 4 This is the metallographic structure diagram of the core of the aluminum-lithium alloy ingot in Example 1 after forging and blanking using the method of the present invention. DETAILED DESCRIPTION

[0027] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below with reference to specific embodiments.

[0028] Example 1

[0029] The method for preparing an aluminum-lithium alloy profile with high batch stability described in this embodiment is a 2195 aluminum-lithium alloy profile. The chemical composition of the 2195 aluminum-lithium alloy ingot is 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 comprises the following steps:

[0030] Forging: The aluminum-lithium alloy ingot is heated to 460°C and kept at this temperature for 8 hours before forging. The three-upsetting and three-drawing process is used during forging, and the deformation of a single upsetting pass is 65%;

[0031] Extrusion: Heat the forged billet to 450°C and keep it warm for 0.7h; heat the die to 440°C and keep it warm for 10h. After the temperature of the extrusion barrel is controlled at 440°C, transfer the billet to the extrusion barrel and keep it warm for 12min before extrusion. During extrusion, the extrusion rod speed is 0.6mm / s, and the outlet temperature of the extruded profile is controlled at 450°C.

[0032] Solution quenching: The extruded billet is subjected to solution quenching to obtain a profile; during the solution quenching treatment, the solution temperature is 515°C, the holding time is 2.5h, and the quenching transfer time is controlled within 8s;

[0033] Low temperature insulation: transfer the profiles after solution quenching treatment to a low temperature box for low temperature insulation treatment, control the temperature at 2°C, and the insulation time is 50 minutes;

[0034] The low-temperature heat-insulating profile is pre-stretched with a stretching amount of 2.5%;

[0035] Then carry out aging treatment at a temperature of 150°C for 32 hours.

[0036] In this embodiment, the edge and core structures of the aluminum-lithium alloy ingot are as follows: Figure 1 and Figure 2 As shown, the aluminum-lithium alloy ingot is forged and the edge and core structures are as follows: Figure 3 and Figure 4 As shown in the figure, the surface and core structures of aluminum-lithium alloy ingots differ significantly. However, the differences between the surface and core structures of the ingots forged using the method of the present invention are greatly reduced. The uniform ingot structure is achieved through heat preservation in the extrusion barrel, low-temperature constant temperature treatment before pre-deformation, and the coordinated coordination of other processes and parameters, which facilitates the production of profiles with high batch stability.

[0037] Example 2

[0038] The method for preparing an aluminum-lithium alloy profile with high batch stability described in this embodiment is a 2195 aluminum-lithium alloy profile. The chemical composition of the 2195 aluminum-lithium alloy ingot is 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 comprises the following steps:

[0039] Forging: Heat the aluminum-lithium alloy ingot to 460°C and keep it warm for 8 hours before forging. The four-upsetting and four-drawing process is used for forging. The single-pass upsetting deformation during upsetting and drawing is 60%;

[0040] Extrusion: Heat the forged billet to 450°C and keep it warm for 0.7h; heat the die to 440°C and keep it warm for 10h. After the temperature of the extrusion barrel is controlled at 440°C, transfer the billet to the extrusion barrel and keep it warm for 15min before extrusion. During extrusion, the extrusion rod speed is 0.8mm / s, and the outlet temperature of the extruded profile is controlled at 450°C.

[0041] Solution quenching: The extruded billet is subjected to solution quenching to obtain a profile; during the solution quenching treatment, the solution temperature is 515°C, the holding time is 2.5h, and the quenching transfer time is controlled within 8s;

[0042] Low temperature insulation: transfer the profiles after solution quenching treatment to a low temperature box for low temperature insulation treatment, control the temperature at 1°C, and the insulation time is 42 minutes;

[0043] The low-temperature heat-insulating profile is pre-stretched with a stretching amount of 2.5%;

[0044] Then carry out aging treatment at a temperature of 150°C for 32 hours.

[0045] Example 3

[0046] The method for preparing an aluminum-lithium alloy profile with high batch stability described in this embodiment is a 2195 aluminum-lithium alloy profile. The chemical composition of the 2195 aluminum-lithium alloy ingot is 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 comprises the following steps:

[0047] Forging: Heat the aluminum-lithium alloy ingot to 480°C, keep it warm for 12 hours, and then forge it. The three-upsetting and three-drawing process is used for forging. The single-pass upsetting deformation during upsetting and drawing is 75%;

[0048] Extrusion: Heat the forged billet to 480°C and keep it warm for 0.5h; heat the die to 460°C and keep it warm for 9h. After the temperature of the extrusion barrel is controlled at 420°C, transfer the billet to the extrusion barrel and keep it warm for 10min before extrusion. During extrusion, the extrusion rod speed is 0.8mm / s, and the outlet temperature of the extruded profile is controlled at 430°C.

[0049] Solution quenching: The extruded billet is subjected to solution quenching to obtain a profile; during the solution quenching treatment, the solution temperature is 530°C, the holding time is 2 hours, and the quenching transfer time is controlled within 10 seconds;

[0050] Low temperature insulation: transfer the profiles after solution quenching treatment to a low temperature box for low temperature insulation treatment, control the temperature at 4°C, and the insulation time is 45 minutes;

[0051] The profile after low temperature insulation treatment is pre-stretched with a stretching amount of 4%;

[0052] Then carry out aging treatment at a temperature of 140°C for 38 hours.

[0053] Comparative Example 1

[0054] In this comparative example, the aluminum-lithium alloy profile is a 2195 aluminum-lithium alloy profile. The chemical composition of the 2195 aluminum-lithium alloy ingot is as follows: 4.2% Cu, 1.1% Li, 0.56% Mg, 0.12% Zr, 0.4% Ag by weight, with the remainder being Al and impurities. The preparation method adopts a conventional process, comprising the following steps:

[0055] (1) Heat the aluminum-lithium alloy ingot to 450°C and keep it warm for 0.7h; heat the mold to 440°C and keep it warm for 10h; the extrusion barrel temperature is 440°C; extrude the heated ingot with an extrusion rod speed of 0.3-0.8mm / s and control the outlet temperature of the extruded profile to 450°C

[0056] (2) The extruded profile is solution quenched at a solution temperature of 515°C, a holding time of 2.5 h, and a quenching transfer time of 8 s;

[0057] (3) After quenching, pre-stretching treatment is performed with a stretching amount of 2.5%;

[0058] (4) The pre-stretched profile is aged at a temperature of 150°C for 32 hours.

[0059] Comparative Example 2

[0060] In this comparative example, the aluminum-lithium alloy profile is a 2195 aluminum-lithium alloy profile. The chemical composition of the 2195 aluminum-lithium alloy ingot is as follows: 4.2% Cu, 1.1% Li, 0.56% Mg, 0.12% Zr, 0.4% Ag by weight, with the remainder being Al and impurities. The preparation method comprises the following steps:

[0061] (1) Heat the aluminum-lithium alloy ingot to 450°C and keep it warm for 0.7h; heat the mold to 440°C and keep it warm for 10h; and heat the extrusion barrel to 440°C;

[0062] (2) Extruding the heated ingot; the extrusion rod speed is 0.6 mm / s, and the outlet temperature of the extruded profile is controlled at 450°C;

[0063] (3) The extruded profile is solution quenched at a solution temperature of 515°C, a holding time of 2.5 h, and a quenching transfer time of 8 s;

[0064] (4) Transfer the profile after solution quenching treatment to a low-temperature box for low-temperature insulation treatment, control the temperature to 2°C, and the insulation time is 50 minutes;

[0065] The low-temperature heat-insulating profile is pre-stretched with a stretching amount of 2.5%;

[0066] Then carry out aging treatment at a temperature of 150°C for 32 hours.

[0067] Comparative Example 3

[0068] In this comparative example, the aluminum-lithium alloy profile is a 2195 aluminum-lithium alloy profile. The chemical composition of the 2195 aluminum-lithium alloy ingot is as follows: 4.2% Cu, 1.1% Li, 0.56% Mg, 0.12% Zr, 0.4% Ag by weight, with the remainder being Al and impurities. Low-temperature heat preservation treatment is not used during preparation. The preparation method comprises the following steps:

[0069] (1) The aluminum-lithium alloy ingot is heated to 460°C and kept at this temperature for 8 hours before forging. The three-upsetting and three-drawing process is adopted during forging, wherein the single-pass upsetting deformation is 65%;

[0070] (2) The forged billet is heated to 450°C and kept warm for 0.7h; the die is heated to 440°C and kept warm for 10h. After the temperature of the extrusion barrel is controlled at 440°C, the billet is transferred to the extrusion barrel and kept warm in the extrusion barrel for 12min before extrusion. During extrusion, the extrusion rod speed is 0.6mm / s, and the outlet temperature of the extruded profile is controlled at 450°C.

[0071] (3) The extruded billet is subjected to solution quenching treatment to obtain a profile; during the solution quenching treatment, the solution temperature is 515°C, the holding time is 2.5h, and the quenching transfer time is controlled within 8s;

[0072] (4) The quenched profile is pre-stretched with a stretching amount of 2.5%;

[0073] Then carry out aging treatment at a temperature of 150°C for 32 hours.

[0074] Comparative Example 4

[0075] In this comparative example, the aluminum-lithium alloy profile is a 2195 aluminum-lithium alloy profile. The chemical composition of the 2195 aluminum-lithium alloy ingot is as follows: 4.2% Cu, 1.1% Li, 0.56% Mg, 0.12% Zr, 0.4% Ag by weight, with the remainder being Al and impurities. The preparation method comprises the following steps:

[0076] (1) The aluminum-lithium alloy ingot is heated to 460°C and kept at this temperature for 8 hours before forging. The forging is performed using a one-upsetting-one-drawing process, wherein the single-pass upsetting deformation is 20%;

[0077] (2) The forged billet is heated to 450°C and kept warm for 0.7h; the die is heated to 440°C and kept warm for 10h. After the temperature of the extrusion barrel is controlled at 440°C, the billet is transferred to the extrusion barrel and kept warm in the extrusion barrel for 5min for extrusion treatment; the extrusion rod speed during extrusion is 0.6mm / s, and the outlet temperature of the extruded profile is controlled at 450°C;

[0078] (3) The extruded billet is subjected to solution quenching treatment to obtain a profile; during the solution quenching treatment, the solution temperature is 515°C, the holding time is 2.5h, and the quenching transfer time is controlled within 8s;

[0079] (4) Transfer the profile after solution quenching treatment to a low-temperature box for low-temperature insulation treatment, control the temperature to 10°C, and the insulation time is 25 minutes;

[0080] (5) Pre-stretching the low-temperature heat-insulating profile with a stretching amount of 2.5%;

[0081] (6) Then carry out aging treatment at a temperature of 150°C for 32 hours.

[0082] The performance of the profiles obtained in each embodiment and control example was tested, wherein the tensile strength, yield strength and elongation were tested according to the method specified in GB / T228.1.

[0083] In the present invention, tensile strength stability is reflected by the tensile strength CV value. The smaller the CV value, the better the stability. The tensile strength CV value is tested in accordance with the relevant requirements for aviation profile standardization. The tensile strength CV value is calculated as follows: CV = (standard deviation / average value) × 100%.

[0084] Table 1 Comparison of performance of profile products in various embodiments and comparative examples

[0085]

[0086] In the present invention, a method of combining upsetting and multi-directional forging to open the blank and extrusion during forging is adopted to improve the uniformity of the core and surface tissues of the ingot, solve the problem of large differences in the core and surface tissues of the ingot, adopt a method of heat preservation in the extrusion barrel to reduce the temperature fluctuation of the blank, and combine with subsequent low-temperature constant temperature methods and other processes to suppress the natural aging effect of the aluminum-lithium alloy, maintain the consistency of the state of the profile before pre-stretching, greatly reduce performance fluctuations, and improve production efficiency at the same time. The performance of the prepared product is far superior to that of the product prepared by the traditional process, and the furnace loading does not need to be controlled, and the production efficiency is greatly improved. In addition, the present invention can achieve high-efficiency preparation and production of high-batch stability aluminum-lithium alloy profiles with a tensile strength CV value of ≤3% through the coordinated control of each process and parameters. It can be seen from the control example that in the present invention, the synergistic effect of process conditions and parameter control is extremely critical.

[0087] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in 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 pass is 60~75%; Extrusion: The forged billet, extrusion barrel, and die are heated before extrusion. Before extrusion, the billet is heated to 430-480°C and kept warm for 0.5-1 hour. The die is heated to 410-460°C and kept warm for 8-15 hours. After the billet is transferred to the extrusion barrel, it is kept warm in the barrel for 10-15 minutes before extrusion. The extrusion rod speed is 0.3-0.8 mm / s. The extrusion barrel temperature is 410-460°C, and the outlet temperature of the extruded profile is 430-480°C. 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 solution quenching step, the solution temperature is 510~530℃, the holding time is 2~4h, and the quenching transfer time is 6~10s.

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

4. 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 at 24~38h.

5. 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 chemical composition of the 2195 aluminum-lithium alloy ingot is as follows: 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 remainder is Al and impurities.

6. 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 5, wherein the aluminum-lithium alloy profile has a tensile strength greater than 600 MPa, a yield strength greater than 550 MPa, an elongation greater than 13%; and a tensile strength CV value ≤ 3%.

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