Method for reducing residual stress of quenched aluminum alloy plate
By cold rolling and stretching the quenched aluminum alloy sheet, the problem of residual stress in the quenched aluminum alloy sheet was solved, and stress reduction and performance improvement of the sheet were achieved.
Patent Information
- Application Number
- CN202511155917.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-18
- Publication Date
- 2025-11-21
AI Technical Summary
Existing technologies cannot effectively eliminate residual stress in quenched aluminum alloy sheets, leading to problems such as deformation, dimensional instability, and decreased weldability during processing and use.
The aluminum alloy sheet is subjected to cold rolling and stretching treatments after quenching. The specific steps are as follows: the cold rolling amount is 0.2% to 1.0%, which is carried out within 12 hours after quenching; the stretching amount is 1.0% to 3.0%, which is carried out within 24 hours after quenching.
It significantly reduces the residual stress in quenched aluminum alloy sheets, improves the dimensional stability and mechanical properties of the sheets, and ensures the smooth progress of subsequent processing.
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Figure CN120989538A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of aluminum alloy sheet technology, and more specifically, to a method for reducing residual stress in quenched aluminum alloy sheets. Background Technology
[0002] To improve the performance of aluminum alloy sheets, quenching is often used in the manufacturing process. Rapid cooling locks alloying elements in a high-temperature solid solution state within the aluminum matrix, forming a supersaturated solid solution that provides a foundation for subsequent age hardening. However, the quenching process cools the surface material before the core, resulting in residual tensile stress in the core and residual compressive stress on the surface. High residual stress can cause deformation of the sheet in its free state, such as warping and twisting, which severely affects the sheet's geometric dimensions and shape accuracy, making subsequent processing (such as cutting, stamping, and welding) difficult. During machining operations such as drilling and milling, high-stress sheets may experience accelerated tool wear, increased cutting forces, and decreased surface finish. The presence of residual stress also reduces the dimensional stability of the sheet; its dimensions may change with temperature, humidity, or prolonged storage, which is unacceptable for applications requiring high dimensional stability (such as precision instruments and electronic equipment). Residual stress also affects the weldability of the sheet; high-stress areas near the weld may lead to cracking, affecting the strength and reliability of the weld joint.
[0003] Therefore, controlling and eliminating residual stress in aluminum alloy sheets is crucial to ensure dimensional stability, mechanical properties, and corrosion resistance during processing and use. However, traditional techniques are not very effective at eliminating internal stress in quenched aluminum alloy sheets, which still significantly impacts the sheet's machinability. Summary of the Invention
[0004] The main objective of this application is to provide a method for reducing residual stress in quenched aluminum alloy sheets, thereby solving the problem in the prior art that the stress in quenched aluminum alloy sheets cannot be effectively eliminated, thus affecting the shape and processing performance of the sheet.
[0005] To achieve the above objectives, according to one aspect of this application, a method for reducing residual stress in quenched aluminum alloy sheets is provided, comprising the following steps:
[0006] Step S1: The quenched aluminum alloy sheet is cold rolled to obtain a cold-rolled sheet; wherein, the cold rolling is carried out within 12 hours after the aluminum alloy sheet is quenched, and the cold rolling amount is 0.2% to 1.0%.
[0007] Step S2: The cold-rolled sheet is subjected to stretching treatment to obtain aluminum alloy sheet with reduced residual stress; wherein, the stretching treatment is carried out within 24 hours after the aluminum alloy sheet is quenched, and the stretching amount is 1.0% to 3.0%.
[0008] Furthermore, in step S1, the cold rolling amount is 0.5% to 1.0%.
[0009] Furthermore, in step S1, the cold rolling amount is 0.75 to 1.0%.
[0010] Furthermore, in step S2, the stretching amount is 1.0% to 2.0%.
[0011] Furthermore, in step S1, the cold rolling process is carried out within 6 hours after the aluminum alloy sheet is quenched.
[0012] Furthermore, in step S2, the stretching treatment is performed within 12 hours after the aluminum alloy sheet has been quenched.
[0013] Furthermore, the cold rolling process is carried out within 3 hours after the aluminum alloy sheet is quenched.
[0014] Furthermore, the stretching treatment is carried out within 6 hours after the aluminum alloy sheet is quenched.
[0015] Furthermore, in step S1, the aluminum alloy sheet is a 2-series aluminum alloy sheet, a 7-series aluminum alloy sheet, or an aluminum-lithium alloy sheet.
[0016] Furthermore, in step S1, the thickness of the aluminum alloy sheet is 6.67mm to 200mm.
[0017] Furthermore, the grade of the aluminum alloy sheet is 7050.
[0018] Furthermore, the finished product preparation process of aluminum alloy sheet includes, in sequence: melting and casting, homogenization, solution heat preservation, quenching, cold rolling, stretching, and artificial aging; wherein, the quenched aluminum alloy sheet is the sheet after quenching of the solution heat preservation aluminum alloy sheet.
[0019] Further, in step S1, the equipment for cold rolling is a reversible rolling mill with a rolling pressure of 30,000 to 100,000 kN; in step S2, the equipment for stretching is a stretching straightener with a stretching force of 60,000 to 200,000 kN.
[0020] Compared with the prior art, this application has the following beneficial effects:
[0021] The method for reducing residual stress in quenched aluminum alloy sheets provided in this application involves first performing a specific amount of cold rolling on the quenched aluminum alloy sheet to reduce some of the surface compressive stress and core tensile stress without changing the residual stress distribution. Then, the cold-rolled sheet is subjected to a specific amount of stretching to further reduce the surface residual compressive stress and core tensile stress without changing the residual stress distribution. The synergistic effect of these two operations significantly reduces the residual stress in the quenched aluminum alloy sheet, providing a good sheet matrix for subsequent processing and improving the dimensional stability and mechanical properties of the processed products. Attached Figure Description
[0022] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:
[0023] Figure 1 A schematic diagram illustrating the principle of cold rolling + stretching to reduce residual stress in quenched aluminum alloy sheets according to an embodiment of this application;
[0024] Figure 2 A distribution diagram of residual stress on the thickness of the sheet under insufficient cold rolling conditions provided in this application embodiment;
[0025] Figure 3 The residual stress distribution diagram on the thickness of the sheet under excessive cold rolling conditions is provided for the embodiments of this application;
[0026] Figure 4 The residual stress distribution curve in the thickness direction of the quenched plate before cold rolling is provided in Embodiment 1 of this application.
[0027] Figure 5 The residual stress distribution curve in the thickness direction of the plate after quenching and cold rolling by 1.0% is provided for Embodiment 1 of this application;
[0028] Figure 6 The residual stress distribution curve in the thickness direction of the plate after quenching and cold rolling by 0.75% is provided for Comparative Example 1 of this application.
[0029] Figure 7 The residual stress distribution curve in the thickness direction of the plate after quenching and cold rolling for 1.0% is provided for Comparative Example 2 of this application.
[0030] Figure 8 The residual stress distribution curve in the thickness direction of the plate after quenching and cold rolling for 1.25% is provided for Comparative Example 3 of this application.
[0031] Figure 9The residual stress distribution curve in the thickness direction of the plate after quenching and cold rolling for 1.50% is provided for Comparative Example 4 of this application. Detailed Implementation
[0032] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.
[0033] Residual compressive stress is generated on the surface of quenched aluminum alloy sheets. High residual stress can cause deformation of the sheet in its free state, such as warping and twisting, which can seriously affect the geometric dimensions and shape accuracy of the sheet, making subsequent processing (such as cutting, stamping, welding, etc.) difficult, and reducing the dimensional stability of the sheet. To solve this problem, the art often uses tensile straightening of aluminum alloy sheets. By applying a certain amount of tensile plastic deformation, the difference in deformation strain between the surface and the core of the sheet is reduced, thereby reducing the residual stress. However, this method can only reduce the peak value of the residual stress and is difficult to change the distribution trend of the residual stress across the thickness. For high precision requirements of machined parts, further reduction of the residual stress in the sheet is needed.
[0034] According to one aspect of this application, a method for reducing residual stress in quenched aluminum alloy sheets is provided, the method comprising the following steps:
[0035] Step S1: The quenched aluminum alloy sheet is cold rolled to obtain a cold-rolled sheet; wherein, the cold rolling is carried out within 12 hours after the quenching process of the aluminum alloy sheet is completed, and the cold rolling amount is 0.2% to 1.0%.
[0036] Step S2: The cold-rolled sheet is subjected to stretching treatment to obtain aluminum alloy sheet with reduced residual stress; wherein, the stretching treatment is carried out within 24 hours after the quenching process of the aluminum alloy sheet is completed, and the stretching amount is 1.0% to 3.0%.
[0037] The principle of residual stress elimination in this application for quenched aluminum alloy sheets (or quenched aluminum alloy sheets) is as follows: Figure 1 As shown; specifically as follows:
[0038] (1) Residual stress distribution in quenched sheet metal: A schematic diagram of the residual stress distribution in the thickness of quenched sheet metal is shown below. Figure 1 As shown in Figure A, the X-axis represents the residual stress under tensile and compressive conditions; positive values represent tensile stress, and negative values represent compressive stress; the red solid line represents the residual stress distribution in the quenched state, and the residual stress distribution of the quenched plate satisfies the distribution law of surface compressive stress and core tensile stress; the Y-axis represents the plate thickness, and the coordinate center is located in the core of the plate; the surface compressive stress is -σ1, and the core tensile stress is σ1.
[0039] (2) The effect of cold rolling on the residual stress of sheet metal without residual stress: When the sheet metal has no initial residual stress, the rolls plastically compress and deform the sheet metal. The surface material extends in the rolling direction and is restricted by the materials in front and behind, generating compressive stress. The core material generates tensile stress and reaches mechanical equilibrium. The cold rolling stress is distributed along the thickness as follows: Figure 1 As shown in B; the blue solid line represents the effect of residual stress on the sheet metal without residual stress during cold rolling; when the material undergoes plastic deformation, the surface compressive stress reaches the compressive yield strength -σ. s The tensile stress in the core reaches σ. s .
[0040] (3) The effect of cold rolling on the residual stress of quenched sheet metal - Before stress superposition: When the rolls roll the quenched sheet metal, the rolling compressive stress on the surface of the sheet metal is superimposed with the residual compressive stress of quenching, and the rolling tensile stress in the core of the sheet metal is superimposed with the residual tensile stress of quenching. Before stress superposition, as shown... Figure 1 The yellow dashed line indicates the C.
[0041] (4) The effect of cold rolling on the residual stress of quenched sheet metal - After stress superposition: The rolling compressive stress on the surface of the sheet metal is superimposed with the quenching residual compressive stress, and the rolling tensile stress in the core of the sheet metal is superimposed with the quenching residual tensile stress. After stress superposition, the results are as follows: Figure 1 The yellow solid line D indicates that, since the rolling stress has reached the yield strength, the superimposed material undergoes some plastic deformation, and the stress distribution is slightly higher than the yield strength.
[0042] (5) Residual stress of the sheet after cold rolling: When the cold rolling amount is between 0.2% and 1%, for example, any value or a range between 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, and 1%; the residual stress of the sheet after roll removal is as follows: Figure 1 The red solid line E indicates that the surface compressive stress is -σ², the core tensile stress is σ², and the residual stress distribution still satisfies the surface compressive stress and core tensile stress state; similar to the residual stress of the quenched plate. Figure 1 Compared to A), the residual stress is significantly reduced.
[0043] (6) In order to prevent the aluminum alloy from undergoing natural aging after quenching, which would increase the strength of the material and reduce the residual stress reduction effect of cold rolling, cold rolling is required to be carried out within 12 hours after quenching.
[0044] (7) Further effects of stretching on residual stress in sheet metal - Before stress superposition: The cold-rolled sheet metal is subjected to a stretching treatment of 1% to 3%, and the stretching plastic deformation causes σ to be generated between the surface and the core of the sheet metal. s Stress. This stress, before being superimposed with the residual stress of the plate, is as follows: Figure 1 As shown in F.
[0045] (8) Further effects of tension on residual stress in sheet metal - after stress superposition: Since the tensile stress has reached the yield strength, the superimposed material yields and undergoes a certain amount of plastic deformation. The residual stress distribution is as follows: Figure 1 The purple solid line of G is shown.
[0046] (9) Further effects of tension on residual stress in sheet metal - after tension unloading: After tension unloading, the residual stress distribution along the thickness is redistributed, as shown in the figure. Figure 1 As shown in H. At this time, the surface compressive stress is -σ3, and the core tensile stress is σ3. This is compared to the residual stress of the sheet after the rolls are removed. Figure 1 The residual stress is further reduced compared to the E).
[0047] (10) In order to prevent the aluminum alloy from undergoing natural aging after quenching, which would increase the strength of the material and reduce the effect of cold rolling residual stress reduction, it is required to perform tensile treatment within 24 hours after quenching.
[0048] When the cold rolling amount is less than 0.2%, the deformation of the sheet metal during the cold rolling process is mainly elastic deformation. Cold rolling has a small effect on reducing the residual stress of the quenched sheet metal, and the residual stress distribution is as follows: Figure 2 As shown. After unloading from cold rolling, the residual stress on the surface becomes compressive stress -σ4, and the residual stress in the core becomes compressive stress σ4.
[0049] When the cold rolling amount exceeds 1.0%, excessive plastic stretching occurs on the surface of the sheet during the cold rolling process, while the stretching in the core is relatively small. This causes the residual stress on the surface to become tensile stress σ5 after unloading, and the residual stress in the core to become compressive stress -σ5. This alters the distribution pattern of residual stress across the thickness, as shown in the diagram. Figure 3 As shown, this causes problems with the deformation patterns during subsequent machining.
[0050] In this embodiment of the application, during cold rolling, the aluminum alloy sheet undergoes natural aging after quenching, resulting in changes to its internal structure, dimensions, and properties. Excessive natural aging is detrimental to subsequent cold rolling and stretching effects. Therefore, the cold rolling time must be controlled within a reasonable range. For example, cold rolling can be performed within 12 hours after the quenching process of the aluminum alloy sheet. Alternatively, cold rolling can be performed within any value or any range between 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, and 12 h after quenching, resulting in significant stress relief. To further enhance stress relief, the cold rolling process can be controlled to occur within 6 hours, 3 hours, or even within 30 minutes after quenching.
[0051] Similarly, to prevent the natural aging of quenched aluminum alloy sheets from affecting subsequent tensile properties, the timing of the tensile treatment needs to be controlled within a certain time range. Since the initial cold rolling process has already significantly eliminated the stress in the sheet, and the effect of natural aging is also weakened, the subsequent tensile treatment time can be controlled within 24 hours; for example, any value or a range between 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, and 24h. To further improve the stress reduction effect, the tensile treatment time can be controlled within 12 hours after the sheet quenching is completed, further within 6 hours, and for example, within 3 hours.
[0052] In this embodiment of the application, when cold rolling quenched aluminum alloy sheets, the amount of cold rolling needs to be controlled. As mentioned earlier, if the amount of cold rolling is too small, the stress reduction effect is small; if the amount of cold rolling is too large, the stress in the sheet will redistribute, and the stress will actually increase. Therefore, based on the aforementioned 0.2% to 1% cold rolling amount, the amount of cold rolling can be optimized to further improve the stress reduction effect. For example, controlling the amount of cold rolling at 0.5% to 1.0% results in a significant stress relief effect; further controlling the amount of cold rolling at 0.75% to 1.0% results in an even more significant stress relief effect. However, when the amount of cold rolling exceeds 1.0%, compressive stress is generated on the surface, causing the residual stress in the sheet to no longer satisfy the distribution state of surface compressive stress and core tensile stress, which will undergo a reverse change, thereby affecting the subsequent processing and deformation performance of the sheet.
[0053] Similarly, based on a reasonable cold rolling amount, the stress in the sheet can be further reduced by adjusting the stretching amount; for example, controlling the stretching amount to 1.0%–2.5% results in a significant stress reduction effect, and further controlling the stretching amount to 1.0%–2.0% yields an even more significant stress reduction effect. When a stretching amount of 1.0%–2.0% is used in conjunction with the aforementioned cold rolling amount of 0.5%–1.0%, the reduction effect on the compressive stress on the surface and the tensile stress in the core of the sheet is even better; the structure, dimensions, and mechanical properties of the treated aluminum alloy sheet remain stable over a long period of time.
[0054] The cold rolling and stretching process of this application embodiment has a significant stress reduction effect, especially for quenched aluminum alloy sheets with a specific thickness. For example, the thickness of the quenched aluminum alloy sheet is 6.67mm to 200mm; for example, any value or range between any two of 6.67, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, and 200mm; or, for example, 20 to 150mm. The above-mentioned cold rolling and stretching process is more suitable for quenched aluminum alloy sheets with the above-mentioned thickness range. The above-mentioned cold rolling and stretching amounts can ensure that residual stress inside the sheet is eliminated without causing surface cracks or other negative changes in mechanical properties.
[0055] The cold rolling and drawing processes and the specific cold rolling amount and specific drawing amount of the embodiments of this application are more applicable to quenched aluminum alloy sheets, especially 2-series aluminum alloy sheets, 7-series aluminum alloy sheets or aluminum-lithium alloy sheets, such as aluminum alloy sheets with grade 7050.
[0056] The finished product manufacturing process of the aforementioned aluminum alloy sheet includes: melting and casting, homogenization, solution treatment and heat preservation, quenching, cold rolling, stretching, and artificial aging. The processing target of this application embodiment is the aluminum alloy sheet after quenching, referred to as the quenched aluminum alloy sheet. Cold rolling and stretching are chosen in this state primarily because the aluminum alloy sheet in this state possesses suitable plasticity and ductility, making it easy to adjust the sheet structure by applying cold rolling and stretching forces, and also requiring control within a certain timeframe.
[0057] The equipment for cold rolling and stretching is existing technology, as long as it can achieve the aforementioned cold rolling and stretching amounts. For example, the cold rolling equipment is a reversible rolling mill with a roll pressure of 30,000 to 100,000 kN, or even 50,000 kN; the stretching equipment is a stretching straightener with a stretching force of 60,000 to 200,000 kN, or even 120,000 kN.
[0058] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.
[0059] The aluminum alloy sheet used in this application embodiment is grade 7050; the general preparation process includes melting and casting - homogenization - solution heat preservation (temperature 450℃) - quenching (water quenching to room temperature) - tensile straightening - artificial aging; the aluminum alloy sheet after the above quenching is taken as the experimental sample.
[0060] The residual stress distribution diagram of the above experimental samples was obtained by the delamination method for residual stress testing.
[0061] Example 1
[0062] Step S1: The sample was taken from the aluminum alloy sheet 0.5 hours after the above quenching process as the quenched state aluminum alloy sheet; the sheet thickness was 80mm, and the grade was 7050; the distribution of residual stress in the thickness direction of the sheet before cold rolling was as follows. Figure 4 As shown;
[0063] Step S2: The above-mentioned quenched aluminum alloy sheet is cold rolled using a reversible rolling mill with a diameter of 1m (roll pressure of 50000kN) with a cold rolling amount of 1.0% to obtain a cold-rolled sheet.
[0064] Step S3: The above cold-rolled sheet (sheet that has been cold-rolled 3 hours after quenching) is subjected to tensile treatment (tensile force of 120000kN tensile straightening machine) with a tensile amount of 2.0% to obtain the final aluminum alloy sheet with reduced residual stress.
[0065] The distribution of residual stress in the thickness direction of the final sheet was detected, and the detection data are shown in Table 1 and... Figure 5 As shown.
[0066] Example 2
[0067] The difference between Example 2 and Example 1 is that the cold rolling amount in step S1 is replaced with 0.5%; the distribution of residual stress in the thickness direction of the plate is shown in Table 1.
[0068] Example 3
[0069] The difference between Example 3 and Example 1 is that the cold rolling amount in step S1 is replaced with 0.75%; the distribution of residual stress in the thickness direction of the plate is shown in Table 1.
[0070] Example 4
[0071] The difference between Example 4 and Example 1 is that the stretching amount in step S2 is replaced with 1.0%; the distribution of residual stress in the thickness direction of the plate is shown in Table 1.
[0072] Example 5
[0073] The difference between Example 5 and Example 1 is that the thickness of the quenched aluminum alloy sheet in step S1 is replaced with 20mm.
[0074] Example 6
[0075] The difference between Example 6 and Example 1 is that the thickness of the quenched aluminum alloy sheet in step S1 is replaced with 150 mm.
[0076] Comparative Example 1
[0077] The difference between Comparative Example 1 and Example 1 is that the cold rolling amount in step S1 was replaced with 0.75% and no stretching treatment was performed; the distribution of residual stress in the thickness direction of the sheet is shown in Table 1 and... Figure 6 As shown.
[0078] Comparative Example 2
[0079] The difference between Comparative Example 2 and Example 1 is that the cold rolling amount in step S1 was replaced with 1.0% and no stretching treatment was performed; the distribution of residual stress in the thickness direction of the sheet is shown in Table 1 and... Figure 7 As shown.
[0080] Comparative Example 3
[0081] The difference between Comparative Example 3 and Example 1 is that the cold rolling amount in step S1 was replaced with 1.25% and no stretching treatment was performed; the distribution of residual stress in the thickness direction of the sheet is shown in Table 1 and... Figure 8 As shown.
[0082] Comparative Example 4
[0083] The difference between Comparative Example 4 and Example 1 is that the cold rolling amount in step S1 was replaced with 1.5% and no stretching treatment was performed; the distribution of residual stress in the thickness direction of the sheet is shown in Table 1 and... Figure 9 As shown.
[0084] Application examples
[0085] Residual stress: The residual stress of aluminum alloy sheet specimens with reduced residual stress in each embodiment and comparative example was tested and analyzed using the peeling method; the test results are shown in Table 1.
[0086] Table 1.
[0087]
[0088]
[0089] Note: In Table 1, a "-" before the number indicates a negative value, which is compressive stress; no "-" before the number indicates a positive value, which is tensile stress.
[0090] Examples 1-6 of this application employ a synergistic treatment process of 0.5%-1.0% cold rolling and 1.0%-2.0% stretching. The distribution trend of residual stress in the thickness direction of the final sheet is shown in Table 1. The test data shows that the residual stress of the treated sheet is very low, and the reduction effect is very significant. This indicates that by optimizing the synergistic effect of cold rolling and specific stretching, the surface stress and core tensile stress of quenched aluminum alloy sheets can be significantly reduced. Among them, Examples 1 and 5, employing a synergistic treatment process of 1.0% cold rolling and 2.0% stretching, show the lowest residual stress in the treated sheet. The results of Example 1 are as follows... Figure 5 As shown.
[0091] Compared to Example 3, Comparative Example 1 used the same cold rolling process (0.75%), but did not subject the cold-rolled sheet to tensile treatment. Table 1 shows that the residual stress in the sheet after treatment in Comparative Example 1 was still relatively high, and its distribution trend in the thickness direction is as follows: Figure 6 As shown.
[0092] Compared to Example 1, Comparative Example 2 used the same cold rolling process (1.0%), but did not subject the cold-rolled sheet to tensile treatment. Table 1 shows that the residual stress in the sheet after treatment in Comparative Example 2 was still relatively high, and its distribution trend in the thickness direction is as follows: Figure 7 As shown.
[0093] Comparative Examples 3 and 4 used unreasonable cold rolling amounts of 1.25% and 1.50% respectively, and no tensile treatment was performed on the cold-rolled sheets. Table 1 shows that compared to the original sheets without quenching, the distribution trends of compressive and tensile stresses showed a significant reverse change. This indicates that unreasonable control of the cold rolling amount not only fails to reduce stress but also has the opposite effect, increasing stress or causing stress redistribution in the sheet. Figure 8 and Figure 9 As shown.
[0094] The above comparison shows that this application uses a method of cold rolling followed by stretching to reduce stress in quenched aluminum alloy sheets. The cold rolling amount needs to be controlled between 0.2% and 1%. Insufficient cold rolling has a small effect on reducing residual stress; excessive cold rolling will change the distribution of residual stress in the thickness direction, resulting in even greater residual stress. Therefore, the cold rolling amount in the first step of this application must be controlled within a suitable range to provide a better foundation for the second step of stretching. Controlling the stretching amount between 1% and 3% can further reduce the stress in the sheet. The cold rolling amount and the stretching amount have a good synergistic effect in reducing stress in quenched aluminum alloy sheets, jointly promoting the stress relief effect.
[0095] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.
[0096] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for reducing residual stress in quenched aluminum alloy sheets, characterized in that, The method includes the following steps: Step S1: The quenched aluminum alloy sheet is cold-rolled to obtain a cold-rolled sheet; wherein the cold rolling process is carried out within 12 hours after the quenching of the aluminum alloy sheet, and the cold rolling amount is 0.2% to 1.0%. Step S2: The cold-rolled sheet is subjected to a stretching treatment to obtain an aluminum alloy sheet with reduced residual stress; wherein the stretching treatment is carried out within 24 hours after the aluminum alloy sheet is quenched, and the stretching amount is 1.0% to 3.0%.
2. The method for reducing residual stress in quenched aluminum alloy sheets according to claim 1, characterized in that, In step S1, the cold rolling amount is 0.5% to 1.0%.
3. The method for reducing residual stress in quenched aluminum alloy sheets according to claim 1, characterized in that, In step S1, the cold rolling amount is 0.75 to 1.0%.
4. The method for reducing residual stress in quenched aluminum alloy sheets according to any one of claims 1 to 3, characterized in that, In step S2, the stretching amount is 1.0% to 2.0%.
5. The method for reducing residual stress in quenched aluminum alloy sheets according to any one of claims 1 to 4, characterized in that, In step S1, the cold rolling process is carried out within 6 hours after the aluminum alloy sheet is quenched. And / or, in step S2, the stretching process is performed within 12 hours after the aluminum alloy sheet has been quenched.
6. The method for reducing residual stress in quenched aluminum alloy sheets according to any one of claims 1 to 4, characterized in that, The cold rolling process is carried out within 3 hours after the aluminum alloy sheet is quenched. And / or, the stretching treatment is performed within 6 hours after the aluminum alloy sheet has been quenched.
7. The method for reducing residual stress in quenched aluminum alloy sheets according to any one of claims 1 to 6, characterized in that, In step S1, the aluminum alloy sheet is a 2-series aluminum alloy sheet, a 7-series aluminum alloy sheet, or an aluminum-lithium alloy sheet.
8. The method for reducing residual stress in quenched aluminum alloy sheets according to any one of claims 1 to 7, characterized in that, In step S1, the thickness of the aluminum alloy sheet is 6.67mm to 200mm; And / or, the grade of the aluminum alloy sheet is 7050.
9. The method for reducing residual stress in quenched aluminum alloy sheets according to any one of claims 1 to 8, characterized in that, The finished product preparation process of the aluminum alloy sheet includes, in sequence: melting and casting, homogenization, solution heat preservation, quenching, cold rolling, stretching, and artificial aging; wherein, the quenched aluminum alloy sheet is the sheet after quenching of the solution heat preservation aluminum alloy sheet.
10. The method for reducing residual stress in quenched aluminum alloy sheets according to any one of claims 1 to 9, characterized in that, In step S1, the equipment for cold rolling is a reversible rolling mill with a rolling pressure of 30,000 to 100,000 kN. And / or, in step S2, the equipment for the stretching treatment is a stretching straightening machine with a stretching force of 60,000 to 200,000 kN.