Two-stage solution treatment method for 2xxx series aluminum alloy and aluminum alloy profile production method

Abstract

The invention relates to the technical field of aluminum alloy production, and provides a 2xxx series aluminum alloy two-stage solution treatment method which comprises a primary solution treatment stage and a stepped strengthening solution treatment stage. Specifically, in the primary solution treatment stage, the aluminum alloy is subjected to heat preservation for 4-6 h at the temperature of 495 DEG C; then carrying out primary quenching; the step type strengthening solution treatment stage comprises the step that the aluminum alloy is subjected to heat preservation for 15-30 min at the temperature of 490 DEG C; raising the temperature to 507 DEG C at a heating rate of 1-3 DEG C / h, and keeping the temperature for 6-8 hours; and secondary quenching. Therefore, a two-stage treatment mode is adopted; a uniform solid solution is formed in the primary treatment; in the step-type strengthening solid solution treatment stage, a low-speed heating mode is adopted, so that a low-melting-point eutectic compound is fully melted, and overburning is avoided; meanwhile, the heating temperature is remarkably increased, and a coarse second phase is eliminated. And the performance of the aluminum alloy is improved. The invention further provides a production method of the aluminum alloy profile.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy production, and in particular relates to a two-stage solid solution treatment method for 2xxx series aluminum alloys and an aluminum alloy profile production method. Background Art

[0002] 2xxx alloys are deformable and heat-treatable aluminum alloys with high strength, good corrosion resistance and forgeability, and are widely used in the aerospace field.

[0003] Aluminum alloy ingots usually contain coarse second phases, eutectic phases precipitated from non-equilibrium crystals and other compounds. The presence of these coarse phases greatly affects the performance of aluminum alloys. Existing heat treatment processes such as ingot homogenization, ingot deformation processing, and deformed structure solution treatment are all aimed at reducing or eliminating these coarse compound phases, thereby achieving the purpose of improving alloy performance.

[0004] However, due to the restriction of low melting point non-equilibrium eutectic phase in aluminum alloy, the homogenization temperature and solution temperature need to be much lower than the eutectic temperature to avoid eutectic remelting and overburning during heat treatment. However, the lower heat treatment temperature also makes it impossible for the coarse compound phase to be completely dissolved, which affects the heat treatment effect and hinders the improvement of alloy performance.

[0005] In summary, the prior art obviously has inconveniences and defects in practical use, so it is necessary to improve it. Summary of the invention

[0006] In view of the above-mentioned defects, the present invention mainly provides a two-stage solid solution treatment method for 2xxx series aluminum alloys to solve the technical problems that the existing heat treatment temperature is limited, which affects the heat treatment effect and hinders the improvement of alloy performance.

[0007] In order to solve the above problems, the present invention provides a two-stage solution treatment method for 2xxx series aluminum alloys, including a primary solution treatment stage and a stepped strengthening solution treatment stage; specifically:

[0008] The primary solution treatment stage includes heating the aluminum alloy at 495°C for 4-6 hours, followed by a quenching step.

[0009] The step-by-step strengthening solution treatment stage includes the following steps:

[0010] S1, keep the aluminum alloy at 490℃ for 15-30min;

[0011] S2, raise the temperature to 507°C at a heating rate of 1-3°C / h and keep it at that temperature for 6-8h;

[0012] S3, secondary quenching.

[0013] According to the two-stage solution treatment method for 2xxx series aluminum alloys of the present invention, the heating rate of step S1 is 40° C. / h.

[0014] According to the two-stage solution treatment method for 2xxx series aluminum alloys of the present invention, the cooling methods of the primary quenching and the secondary quenching are both water cooling.

[0015] According to the two-stage solution treatment method for 2xxx series aluminum alloys of the present invention, the water temperature does not exceed 25° C. before and after quenching.

[0016] According to the two-stage solid solution treatment method of 2xxx series aluminum alloy of the present invention, the composition of the aluminum alloy is Si: 0.4-0.6%; Fe: ≤0.5%; Cu: 4.4-4.8%; Mn: 0.8-1.1%; Mg: 0.45-0.7%; Cr: 0.1%; Zn: 0.2-0.25%; impurity elements <0.15%; and the rest is Al.

[0017] According to the two-stage solution treatment method for 2xxx series aluminum alloys of the present invention, the impurity elements are composed of multiple elements, wherein the content of any one element does not exceed 0.05%.

[0018] A method for producing an aluminum alloy profile comprises the following steps:

[0019] Z1, cast aluminum ingot;

[0020] Z2, homogenization treatment;

[0021] Z3, sawing treatment;

[0022] Z4, extrusion molding, extruding aluminum ingots into profiles;

[0023] Z5, solution treatment;

[0024] The profile is subjected to a solution treatment using the two-stage solution treatment method for 2xxx series aluminum alloys;

[0025] Z6, tensile straightening;

[0026] Z7, aging treatment.

[0027] According to the aluminum alloy profile production method of the present invention, the stretching rate in the stretching and straightening step does not exceed 2%.

[0028] According to the aluminum alloy profile production method of the present invention, the aging treatment is a peak aging treatment.

[0029] According to the aluminum alloy profile production method of the present invention, the peak aging is: keeping warm at 175° C. for 12 hours.

[0030] In summary, the two-stage solution treatment method of the 2xxx series aluminum alloy of the present invention adopts a two-stage treatment method; a uniform solid solution is formed in the primary treatment; in the step-type strengthening solution treatment stage, a slow heating method is adopted to fully melt the low-melting point eutectic compound to avoid overburning; at the same time, the heating temperature is significantly increased to eliminate the coarse second phase. The performance of the aluminum alloy is improved. The present invention also provides a method for producing aluminum alloy profiles, which can significantly improve the overall performance of the profile products by using the two-stage solution treatment method. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram of an embodiment of a two-stage solution treatment of the present invention; DETAILED DESCRIPTION

[0032] See also Figure 1 The present invention provides a two-stage solution treatment method for 2xxx series aluminum alloys, including a primary solution treatment stage and a stepped strengthening solution treatment stage; specifically:

[0033] The primary solution treatment stage includes heating the aluminum alloy at 495°C for 4-6 hours, followed by a quenching step.

[0034] In the primary solution treatment stage, the solution temperature is low to avoid overburning; the holding time is long to form a uniform solid solution; it is beneficial to the homogenization of the aluminum alloy composition and improve performance.

[0035] The step-by-step strengthening solution treatment stage includes the following steps:

[0036] S1, keep the aluminum alloy at 490℃ for 15-30min;

[0037] Optionally, the heating rate of step S1 is a free heating rate, such as 40°C / h; heating at a faster rate can not only allow most alloy elements to be fully melted again to form a uniform solid solution, but also prevent abnormal grain growth. At the same time, it can also increase production speed.

[0038] S2, raise the temperature to 507°C at a heating rate of 1-3°C / h and keep it at that temperature for 6-8h;

[0039] When aluminum alloy solidifies in non-equilibrium, the following eutectic reaction will occur:

[0040]

[0041] The present invention adopts a slower heating rate, so that the aluminum alloy can fully absorb heat for a longer time, and the temperature will not rise too quickly. In the process of absorbing heat, the low melting point eutectic compound phase (such as Al2Cu, Al2CuMg, Mg 2Si, etc.) are fully decomposed, thereby avoiding the remelting of the low-melting point eutectic phase and causing overburning.

[0042] Since these low-melting-point eutectic phases have decomposed and disappeared before reaching the melting point, as the temperature slowly increases, when the heating temperature exceeds the melting point of the low-melting-point compound, overburning will not occur.

[0043] Compared with the existing solution treatment process, the present invention adopts a slow heating method to avoid overburning, so that the heating temperature is significantly increased, so that the coarse compound phase can be completely dissolved, thereby achieving the purpose of reducing the size and amount of the coarse second phase, and ultimately improving the mechanical properties of the aluminum alloy.

[0044] S3, secondary quenching;

[0045] Furthermore, the cooling methods for the primary quenching and the secondary quenching are both water cooling; more preferably, the water temperature does not exceed 25°C before and after quenching.

[0046] The aluminum alloy of the present invention is an Al-Cu alloy, and its components are Si: 0.4-0.6%, Fe: ≤0.5%, Cu: 4.4-4.8%, Mn: 0.8-1.1%, Mg: 0.45-0.7%, Cr: 0.1%, Zn: 0.2-0.25%, impurity elements <0.15%, and the rest is Al.

[0047] The impurity elements of the present invention may be a mixture of multiple elements, wherein the content of any one element does not exceed 0.05%.

[0048] The content of Cu element in the present invention is high, and more beneficial phases (such as Al 2 Cu), strengthens the mechanical properties of aluminum alloy.

[0049] The two-stage solid solution treatment method for 2xxx series aluminum alloys of the present invention adopts a two-stage treatment mode; a uniform solid solution is formed in the primary treatment; in the step-type strengthening solid solution treatment stage, a slow heating mode is adopted to fully melt the low-melting-point eutectic compound to avoid overburning; at the same time, the heating temperature is significantly increased, the coarse second phase is eliminated, and the performance of the aluminum alloy is improved.

[0050] The two-stage solution treatment method for 2xxx series aluminum alloys of the present invention can be used to treat a variety of aluminum alloy products, including but not limited to: aluminum alloy plates, aluminum alloy profiles, aluminum alloy workpieces, etc.

[0051] The present invention also provides a method for producing an aluminum alloy profile, comprising the following steps:

[0052] Z1, cast aluminum ingot;

[0053] Z2, homogenization treatment: make the components in the aluminum ingot more uniform, eliminate micro segregation structure, improve the processing deformation ability of the aluminum ingot, improve the mechanical properties, plasticity, etc.

[0054] Z3, sawing treatment: removing the macro component segregation part on the surface of the aluminum ingot.

[0055] Z4, extrusion molding, extruding aluminum ingots into profiles;

[0056] Z5, solution treatment;

[0057] Using the two-stage solution treatment method, the profile is subjected to solution treatment;

[0058] Z6, tensile straightening; eliminate internal stress.

[0059] Optionally, the stretching rate in the stretch-straightening step does not exceed 2%;

[0060] Z7, aging treatment;

[0061] The profile after stretching and straightening is subjected to artificial aging or natural aging treatment, and technical personnel in this field can make adaptive settings according to the requirements of product performance indicators.

[0062] As an embodiment, the aging treatment of the present invention is a peak aging treatment;

[0063] Optionally, the peak aging of the present invention is: keeping warm at 175°C for 12 hours;

[0064] The inventors used the profile production method of the present invention to manufacture multiple test bars of the embodiment; at the same time, the profile production method of the present invention was used to replace the two-stage solid solution treatment method with the existing solid solution treatment process to manufacture comparative example test bars. The composition of the embodiment and the comparative example is shown in Table 1, and the mechanical property test results are shown in Table 2.

[0065] The production process parameters of each embodiment and comparative example are as follows. The steps and parameters not described are as mentioned above, and each embodiment and comparative example are the same.

[0066] Embodiment 1;

[0067] Initial solution stage: 495℃ for 4 hours;

[0068] Step-by-step strengthening solution treatment stage:

[0069] S1, heating rate of 40°C / min, at 490°C, keep warm for 18 min;

[0070] S2, heating rate of 2°C / h, at 507°C, keep warm for 7h;

[0071] Both the primary quenching and the secondary quenching are water quenching, and the water temperature does not exceed 25°C before and after quenching.

[0072] Elongation: 1.8%;

[0073] Peak aging treatment: 175℃, keep warm for 12h;

[0074] Embodiment 2;

[0075] Initial solution stage: 495℃ for 5 hours;

[0076] Step-by-step strengthening solution treatment stage:

[0077] S1, heating rate of 40°C / min, at 490°C, hold for 27 min;

[0078] S2, heating rate of 1°C / h, at 507°C, keep warm for 6h;

[0079] Both the primary quenching and the secondary quenching are water quenching, and the water temperature does not exceed 25°C before and after quenching.

[0080] Elongation: 1.8%;

[0081] Peak aging treatment: 175℃, keep warm for 12h;

[0082] Embodiment 3;

[0083] Initial solution stage: 495℃ for 4 hours;

[0084] Step-by-step strengthening solution treatment stage:

[0085] S1, heating rate of 40°C / min, at 490°C, hold for 17 min;

[0086] S2, heating rate of 2°C / h, at 507°C, keep warm for 8h;

[0087] Both the primary quenching and the secondary quenching are water quenching, and the water temperature does not exceed 25°C before and after quenching.

[0088] Elongation: 1.8%;

[0089] Peak aging treatment: 175℃, keep warm for 12h;

[0090] Comparative Example 1;

[0091] Solution heat treatment process: 500℃, keep warm for 10h;

[0092] Water quenching treatment: the water temperature shall not exceed 25℃ before and after quenching.

[0093] Elongation: 1.8%;

[0094] Peak aging treatment: 175℃, keep warm for 12h;

[0095] Comparative Example 2;

[0096] Solution heat treatment process: 500℃, keep warm for 14h;

[0097] Water quenching treatment: the water temperature shall not exceed 25℃ before and after quenching.

[0098] Elongation: 1.8%;

[0099] Peak aging treatment: 175℃, keep warm for 12h;

[0100] By comparison, it can be seen that the aluminum alloy product produced by the two-stage solution treatment method of the present invention has significantly improved mechanical properties, while the plasticity has not significantly decreased, thereby improving the overall performance of the product.

[0101] Table 1: Alloy composition of each embodiment and comparative example

[0102]

[0103]

[0104] Table 2: Mechanical properties test results of various embodiments and comparative examples

[0105] Test rod Tensile strength / MPa Yield strength / MPa Elongation / % Example 1 540 475 11.0 Example 2 562 485 10.5 Example 3 550 450 12 Comparative Example 1 483 414 13 Comparative Example 2 501 464 10.5

[0106] In summary, the present invention provides a two-stage solution treatment method for 2xxx series aluminum alloys, which uses a two-stage treatment method; a uniform solid solution is formed in the primary treatment; in the step-type strengthening solution treatment stage, a slow heating method is used to fully melt the low-melting point eutectic compound to avoid overburning; at the same time, the heating temperature is significantly increased to eliminate the coarse second phase. The performance of the aluminum alloy is improved. The present invention also provides a method for producing aluminum alloy profiles, which can significantly improve the overall performance of the profile products by using a two-stage solution treatment method.

[0107] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A two-stage solution treatment method for 2xxx series aluminum alloys, characterized in that: It includes the primary solution treatment stage and the step-by-step strengthening solution treatment stage; specifically: The primary solution treatment stage includes heating the aluminum alloy at 495°C for 4-6 hours, followed by a quenching step. The step-by-step strengthening solution treatment stage includes the following steps: S1, keep the aluminum alloy at 490℃ for 15-30min; S2, raise the temperature to 507°C at a heating rate of 1-3°C / h and keep it at that temperature for 6-8h; S3, secondary quenching.

2. The two-stage solution treatment method for 2xxx series aluminum alloy according to claim 1, characterized in that: The heating rate of step S1 is 40°C / h.

3. The two-stage solution treatment method for 2xxx series aluminum alloy according to claim 1, characterized in that: The cooling methods of the primary quenching and the secondary quenching are both water cooling.

4. The two-stage solution treatment method for 2xxx series aluminum alloy according to claim 3, characterized in that: Before and after quenching, the water temperature shall not exceed 25°C.

5. The two-stage solution treatment method for 2xxx series aluminum alloys according to claim 1, characterized in that: The aluminum alloy has the following components: Si: 0.4-0.6%, Fe: ≤0.5%, Cu: 4.4-4.8%, Mn: 0.8-1.1%, Mg: 0.45-0.7%, Cr: 0.1%, Zn: 0.2-0.25%, impurity elements <0.15%, and the rest is Al.

6. The two-stage solution treatment method for 2xxx series aluminum alloy according to claim 5, characterized in that: The impurity elements are composed of multiple elements, and the content of any one of the elements does not exceed 0.05%.

7. A method for producing an aluminum alloy profile, characterized in that: The steps include: Z1, cast aluminum ingot; Z2, homogenization treatment; Z3, sawing treatment; Z4, extrusion molding, extruding aluminum ingots into profiles; Z5, solution treatment; Solution treating the profile using the two-stage solution treatment method for 2xxx series aluminum alloys as described in any one of claims 1 to 6; Z6, tensile straightening; Z7, aging treatment.

8. The method for producing an aluminum alloy profile according to claim 7, characterized in that: The stretching ratio in the stretching and straightening step does not exceed 2%.

9. The method for producing an aluminum alloy profile according to claim 7, characterized in that: The aging treatment is a peak aging treatment.

10. The method for producing an aluminum alloy profile according to claim 9, characterized in that: The peak aging is: keeping warm at 175°C for 12 hours.

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