Composite heat treatment method for hot die and cold die of aluminum alloy sheet

Abstract

The invention relates to the technical field of non-ferrous metal processing, and particularly provides a hot-cold die composite heat treatment method for an aluminum alloy sheet. The aluminum alloy sheet hot and cold die composite heat treatment method comprises the following steps that S1, a workpiece is placed in a quenching device, an up-down split type heating die is adopted for closing and clamping the workpiece, heat preservation is conducted for 5-20 min at the temperature of 400-550 DEG C, and solution treatment is conducted; s2, transferring the workpiece subjected to the solution treatment to a cooling station, and closing and clamping the workpiece subjected to the solution treatment by adopting an up-and-down split type cooling mold for quenching treatment to obtain a finished product; wherein the temperature of the upper cooling mold and the temperature of the lower cooling mold are controlled to be 15-25 DEG C. According to the invention, a continuous treatment mode of combining an up-down split hot die and a cold die is adopted, so that the plate is effectively supported by the die in the whole solid solution and quenching process, thereby successfully overcoming the defects of the traditional air cushion furnace process in the aspects of plate shape control and performance uniformity; and therefore, the high-quality aluminum alloy thin plate which is flat in plate shape and uniform in structure can be stably prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of non-ferrous metal processing, and particularly relates to a hot and cold die combined heat treatment method for aluminum alloy sheet. BACKGROUND

[0002] In the field of aerospace vehicle manufacturing, thin-walled structures are widely used to meet the core requirements of structural strength, service life and weight control. Aluminum alloy sheets are widely used in key components such as frames, beams, webs, partitions, panels and skins. The thickness of such sheets mainly ranges from 0.6 to 2.0 mm, which maximizes the weight reduction of the aircraft structure and supports the lightweight development of aerospace technology.

[0003] In recent years, although the production capacity of aluminum alloy sheets with a thickness of 0.3 mm or more has been achieved, in the actual production process, the 0.3-0.5 mm thin sheets face serious shape deformation and surface damage problems after quenching. Even after solid solution quenching and subsequent online straightening treatment in the air cushion furnace, the sheet surface still often shows obvious intermediate waves, wrinkles and lower surface scratches, etc. defects, resulting in low overall product yield, large quality fluctuations and long delivery cycle. These problems mainly result from the insufficient adaptability of the existing air cushion furnace process to ultra-thin sheets. In terms of sheet shape control, the shape of the ultra-thin sheet during air cushion suspension is sinusoidal, the thinner the sheet, the greater the wave amplitude, and due to the weight of the sheet, the heated sheet always has a downward deformation trend, making it difficult to maintain a stable floating height, resulting in uncontrollable plastic deformation during heating and cooling. On the other hand, it is difficult to achieve uniform cooling of ultra-thin sheets during quenching. When the sheet is heated to the solid solution and then enters the cooling stage, the material is in a hot and cold alternating state, and the rheological stress changes sharply. At this time, the impact of the nozzle flow on the sheet surface is uneven, and the shrinkage of each region during cooling is inconsistent, resulting in a significant difference in local cooling rate. For ultra-thin sheets, such non-uniform cooling has a particularly significant impact, which easily leads to uneven distribution of microstructure and properties, and further causes defects such as breakage and deviation during subsequent straightening, significantly reducing the yield of 0.3-0.5 mm thick sheets.

[0004] Currently, the yield of 0.2-0.5 mm thick aluminum alloy sheets produced by aluminum alloy manufacturers is basically maintained at about 10%, and in some cases even less than 10%. The whole batch of materials is frequently scrapped during production, resulting in a significant extension of the delivery cycle and difficulties in delivery, especially for 0.3 mm thick quenched sheets, the procurement route is extremely unstable, and it is difficult to match the progress of existing and new aerospace vehicle development and production. Therefore, developing a high-precision and high-uniformity heat treatment process suitable for ultra-thin aluminum alloy sheets has important practical significance for improving sheet quality and yield. SUMMARY

[0005] In view of the above problems, the present application provides an aluminum alloy sheet hot-cold die combined heat treatment method, by adopting the continuous treatment mode of the upper and lower split hot-cold die combination, the plate is effectively supported by the die in the whole process of solid solution and quenching, and then a high-quality aluminum alloy sheet with flat shape and uniform structure is prepared.

[0006] In the first aspect, the present application provides an aluminum alloy sheet hot-cold die combined heat treatment method, comprising the following steps: S1. The workpiece is placed in the quenching device, the upper and lower split heating die is closed to clamp the workpiece, and the solid solution treatment is carried out at 400-550℃ for 5-20min. S2. The workpiece after solid solution treatment is transferred to the cooling station, the upper and lower split cooling die is closed to clamp the workpiece after solid solution treatment for quenching treatment, and the finished product is obtained; wherein the temperature of the upper and lower cooling die is controlled at 15-25℃.

[0007] The present application adopts the upper and lower split heating die and the upper and lower split cooling die to realize the continuous solid solution and quenching treatment of the plate, the die provides effective support for the plate in the whole process of solid solution and quenching, and its shape is accurately controlled until it is cooled to room temperature (15-25℃), thereby effectively inhibiting the sagging deformation of the ultra-thin plate due to its own weight, avoiding the shape out-of-control problems such as sinusoidal wave formed by the plate floating in the traditional air cushion furnace and wrinkles caused by cooling shrinkage, and stabilizing the straightness of the finished aluminum alloy sheet within 0.1mm / m, thereby solving the problem of shape control of ultra-thin aluminum alloy sheet.

[0008] The present application relies on the rigid structure of the upper and lower split mold and the mold closing pressure to form a full and close contact between the mold surface and the plate surface, and to establish a uniform heat conduction interface. During the solid solution stage, the heating mold ensures accurate temperature control of the plate within the range of 450-550℃, realizes overall synchronous heating and uniform heating, and prevents overburning while ensuring sufficient dissolution of solute atoms; during the quenching stage, the cooling mold realizes rapid and uniform cooling at a stable low temperature, ensures that the cooling starting temperature is higher than the quenching sensitive temperature and reaches the required cooling speed, and prevents the precipitation of coarse equilibrium phases. In addition, due to the large thermal conductivity coefficient of aluminum alloy and the rapid heat dissipation of thin plates, the plate after solid solution must be transferred to the cooling station within a few seconds, otherwise the temperature will drop rapidly and affect the solid solution effect. However, the existing mold pressing and quenching technology cannot realize the rapid transfer and accurate positioning of large length coiled materials (single length more than 5m), resulting in premature temperature drop of the thin plate and causing adverse phase change. The present application successfully realizes the rapid roller conveying of the plate after solid solution and the accurate positioning in the cooling mold through the segmented hot and cold mold combination equipment, breaks through the technical bottleneck of difficult continuous partition quenching of large size thin plates, and finally obtains large length aluminum alloy thin plates with sufficient solid solution and excellent microstructure and performance, the surface roughness of the finished plate is ≤10μm, the microstructure and performance are highly consistent, the production risks such as belt breakage and deviation caused by uneven performance are greatly reduced, and the high-quality continuous production of large length size aluminum alloy thin plates is successfully realized.

[0009] Preferably, in step S1, the workpiece is a rolled aluminum alloy plate with a thickness of 0.2-2mm.

[0010] Preferably, the aluminum alloy plate is selected from 2xxx series aluminum alloy, such as 2A12 aluminum alloy, 2A14 aluminum alloy, 2024 aluminum alloy, etc.

[0011] Preferably, in step S1, the opening and closing speed of the upper and lower split heating mold is 40-60mm / min.

[0012] Preferably, in step S2, the workpiece is transferred to the cooling station within 5s after solid solution treatment.

[0013] Preferably, in step S2, the opening and closing speed of the upper and lower split cooling mold is 40-60mm / min.

[0014] Preferably, in step S2, the quenching time is 5-20min. Further preferably, the quenching time is the same as the solid solution time, which ensures that the heat in the center of the plate is fully discharged, thereby realizing uniform cooling and phase change of the whole cross section of the plate, effectively avoiding performance degradation in the center due to insufficient cooling, and obtaining a finished product with more consistent microstructure and performance; at the same time, the solid solution and quenching can be started and completed simultaneously in time, which can realize continuous production and greatly improve the production efficiency.

[0015] Preferably, after the quenching treatment in step S2, the method further comprises winding and slitting treatment.

[0016] In a second aspect, the present application also provides an aluminum alloy sheet prepared by the aluminum alloy sheet hot-cold die combined heat treatment method.

[0017] Preferably, the aluminum alloy sheet is selected from 2xxx series aluminum alloy, such as 2A12 aluminum alloy, 2A14 aluminum alloy, 2024 aluminum alloy, etc.

[0018] In a third aspect, the present application also provides a quenching device for the aluminum alloy sheet hot-cold die combined heat treatment method, comprising: a traction structure comprising a feed roller and a take-up roller, the traction structure being used to drive the workpiece to move; a heating station provided with an upper and lower split heating die, the upper and lower split heating die comprising an upper heating die and a lower heating die capable of moving towards or away from each other, the upper heating die and the lower heating die being provided with an electric heating element; a cooling station provided with an upper and lower split cooling die, the upper and lower split cooling die comprising an upper cooling die and a lower cooling die capable of moving towards or away from each other, the upper cooling die and the lower cooling die being provided with a water cooling element.

[0019] Preferably, the upper heating die and the lower heating die further comprise a temperature controller for detecting temperature and controlling the temperature of the upper and lower split heating die, ensuring accurate and stable solid solution temperature, preventing incomplete solid solution caused by insufficient temperature, and avoiding overburning defects caused by excessive temperature.

[0020] Preferably, the upper and lower cooling die further comprises a temperature controller for detecting temperature and controlling the temperature of the upper and lower split cooling die, ensuring stable low temperature state in continuous production process, and realizing effective quenching.

[0021] Preferably, the traction speed of the traction structure is 0.5-5 m / s.

[0022] Preferably, the die material of the upper and lower split heating die and the upper and lower split cooling die is selected from die steel.

[0023] The aluminum alloy sheet hot-cold die combined heat treatment method provided by the present application has the following beneficial effects compared with the prior art: The present application successfully overcomes the shortcomings of the traditional air cushion furnace process in plate shape control and performance uniformity by adopting the continuous treatment mode of the upper and lower split hot and cold dies, so that the plate is effectively supported by the die throughout the solid solution and quenching process, thereby being able to stably prepare high-quality aluminum alloy thin plates with flat plate shape and uniform structure. The method has the characteristics of continuous process and high degree of automation, and has good industrial application prospect. At the same time, the present application realizes rapid transfer and accurate laying within 5 seconds after solid solution through the segmented hot and cold die equipment, overcomes the problem of decreased solid solution effect caused by the rapid heat conduction of aluminum alloy and rapid temperature drop of thin plate in the traditional die quenching, and finally makes the surface roughness of the finished plate ≤10 μm, the structure and performance are highly consistent, and realizes the high-quality continuous production of large-length-size aluminum alloy thin plates. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A process principle diagram of the aluminum alloy thin plate hot and cold die composite heat treatment method provided for embodiment 1 of the present application is shown in the figure. Figure 2 A macroscopic morphology diagram of the finished aluminum alloy thin plate prepared in embodiment 1 of the present application is shown in the figure. Figure 3 A microscopic morphology diagram of the finished aluminum alloy thin plate prepared in embodiment 1 of the present application is shown in the figure. DETAILED DESCRIPTION

[0025] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the specific embodiments will be briefly introduced below. Obviously, the embodiments described below are some embodiments of the present application, and other embodiments can also be obtained by those skilled in the art without creative labor on the basis of these embodiments.

[0026] The specific experimental steps or conditions not mentioned in the embodiments can be carried out according to the conventional experimental steps or conditions described in the literature in the art. The raw materials or instruments used are conventional products that can be obtained by purchase, including but not limited to the raw materials or instruments used in the embodiments of the present application.

[0027] Embodiment 1 The present embodiment provides a 2024 aluminum alloy thin plate hot and cold die composite heat treatment method, and a process principle diagram is shown in the figure. Figure 1 The present embodiment provides a 2024 aluminum alloy thin plate hot and cold die composite heat treatment method, and a process principle diagram is shown in the figure. (1) The 0.3mm thick 2024 aluminum alloy sheet in roll 2024 is installed on the feed roller and pulled to the take-up roller, and the conveying speed is set to 2.5m / s; when the sheet enters the heating station, the feed roller and the take-up roller stop moving, the upper heating die and the lower heating die are closed at a speed of 50mm / min to make the die fully contact with the sheet, the sheet is heated to 495℃ by the heating die for 5.5min for solid solution treatment, and the heating area is 1.5m*5m; (2) After completing the solid solution treatment, the upper heating die and the lower heating die are opened at a speed of 50mm / min, the feed roller and the take-up roller are restarted, and the sheet after solid solution treatment is transferred to the cooling station within 3s; after the sheet enters the cooling station, the feed roller and the take-up roller are stopped again, the upper cooling die and the lower cooling die are closed at a speed of 50mm / min, and the upper and lower cooling dies are used to realize rapid cooling of the sheet to complete quenching treatment; wherein the temperature of the upper cooling die and the lower cooling die is set to 25℃, the holding time is 5.5min, and the heating area is 1.5m*5m; (3) The upper cooling die and the lower cooling die are opened at a speed of 50mm / min, and the feed roller and the take-up roller are started to collect the sheet after quenching within 3s; after the whole roll treatment is completed, the roll is unfolded, the area after the hot and cold die composite heat treatment is cut according to the required size for standby, and the junction area of the sheet without hot and cold die composite heat treatment is cut off to ensure uniform organization and performance, and the finished 2024 aluminum alloy sheet is obtained.

[0028] The macroscopic morphology of the finished 2024 aluminum alloy sheet prepared in this embodiment is shown in Figure 2 , and the microscopic morphology is shown in Figure 3 , which is taken by a FEI-Apero type scanning electron microscope in a secondary electron mode, and the scale is 100μm.

[0029] The finished 2024 aluminum alloy sheet prepared in this embodiment is detected by a three-coordinate measuring machine and a surface roughness measuring instrument, the straightness is 0.1mm / m, the surface roughness is 9.5μm, the sheet shape is good, and the performance is uniform.

[0030] The embodiment provides a quenching device for the hot and cold die composite heat treatment method of the aluminum alloy sheet. The traction structure includes a feed roller and a take-up roller for driving the workpiece to move; The heating station is provided with an upper and lower split heating die, the upper and lower split heating die includes an upper heating die and a lower heating die capable of moving towards or away from each other, the upper heating die and the lower heating die are provided with an electric heating element; the upper heating die and the lower heating die further include a temperature controller for detecting temperature and controlling the temperature of the upper and lower split heating die to ensure accurate setting of the temperature to prevent incomplete solid solution caused by too low temperature or overburning caused by too high temperature, and the die material is selected from die steel; The cooling station is provided with an upper and lower split cooling die, the upper and lower split cooling die includes an upper cooling die and a lower cooling die capable of moving towards or away from each other, the upper cooling die and the lower cooling die are provided with a water cooling element; the upper and lower cooling die further include a temperature controller for detecting temperature and controlling the temperature of the upper and lower split cooling die to prevent the die temperature from rising too high to effectively quench during batch production, and the die material is selected from die steel.

[0031] Embodiment 2 The embodiment provides a 2024 aluminum alloy sheet hot and cold die combined heat treatment method, including the steps of: (1) The thickness of the 0.5mm coiled 2024 aluminum alloy plate is installed on the feeding roller, and is pulled to the collecting roller, and the conveying speed is set to 3m / s; when the plate enters the heating station, the feeding roller and the collecting roller stop moving, the upper heating die and the lower heating die close at a speed of 50mm / min, so that the die and the plate are in full contact, the plate is heated to 505℃ by the heating die for 9min for solid solution treatment, and the heating area is 1.5m*5m; (2) After completing the solid solution treatment, the upper heating die and the lower heating die open at a speed of 50mm / min, the feeding roller and the collecting roller are restarted, and the plate treated by the solid solution is transferred to the cooling station within 3s; after the plate enters the cooling station, the feeding roller and the collecting roller are stopped again, the upper cooling die and the lower cooling die close at a speed of 50mm / min, and the upper and lower cooling dies are used to realize rapid cooling of the plate to complete quenching treatment; wherein the temperature of the upper cooling die and the lower cooling die is set to 25℃, the holding time is 9min, and the heating area is 1.5m*5m; (3) The upper cooling die and the lower cooling die are opened at a speed of 50mm / min, and the feeding roller and the collecting roller are started, and the plate treated by quenching is collected on the collecting roller within 3s; after the whole roll treatment is completed, the roll is unfolded, the area treated by the hot and cold die combined heat treatment is cut according to the required size for standby, and the junction area of the sheet not treated by the hot and cold die combined heat treatment is cut off to ensure uniform organization and performance, and the finished 2024 aluminum alloy sheet is obtained.

[0032] The finished 2024 aluminum alloy sheet prepared in the embodiment is detected by using a three-coordinate measuring machine and a surface roughness measuring instrument, the straightness is 0.09mm / m, the surface roughness is 9.3μm, the plate shape is good, and the performance is uniform.

[0033] The quenching device used in this embodiment refers to that in Embodiment 1.

[0034] Embodiment 3 The embodiment provides a hot-cold die combined heat treatment method for 2A12 aluminum alloy sheet, comprising the following steps: (1) The 2A12 aluminum alloy sheet with a thickness of 0.2 mm is installed on a feeding roller and is pulled to a collecting roller, and the conveying speed is set to 1 m / s; when the sheet enters a heating station, the feeding roller and the collecting roller stop moving, the upper heating die and the lower heating die are closed at a speed of 50 mm / min, the sheet is fully contacted with the dies, the sheet is heated to 485 DEG C by the heating die for 3 min for solid solution treatment, and the heating area is 1.5 m*5 m; (2) After the solid solution treatment is completed, the upper heating die and the lower heating die are opened at a speed of 50 mm / min, and the feeding roller and the collecting roller are restarted, and the sheet after the solid solution treatment is transferred to a cooling station within 3 s; after the sheet enters the cooling station, the feeding roller and the collecting roller are stopped again, the upper cooling die and the lower cooling die are closed at a speed of 50 mm / min, the sheet is rapidly cooled by the upper and lower cooling dies, and the quenching treatment is completed; wherein the temperature of the upper cooling die and the lower cooling die is set to 25 DEG C, the holding time is 3 min, and the heating area is 1.5 m*5 m; (3) The upper cooling die and the lower cooling die are opened at a speed of 50 mm / min, and the feeding roller and the collecting roller are started, and the sheet after the quenching treatment is collected on the collecting roller within 3 s; after the whole treatment is completed, the roll is unfolded, the region after the hot-cold die combined heat treatment is cut according to the required size for standby, and the junction region of the sheet without the hot-cold die combined heat treatment is cut off, so that the structure and performance are uniform, and the finished 2A12 aluminum alloy sheet is obtained.

[0035] The finished 2A12 aluminum alloy sheet prepared in the embodiment is detected by using a three-coordinate measuring machine and a surface roughness measuring instrument, the straightness is 0.08 mm / m, the surface roughness is 9.7 μm, the sheet shape is good, and the performance is uniform.

[0036] The quenching device used in this embodiment refers to that in Embodiment 1.

[0037] Obviously, the above embodiments are only examples for clearly illustrating the present application, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments cannot be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for combined hot and cold mold heat treatment of aluminum alloy thin plates, characterized in that, Includes the following steps: S1. Place the workpiece in a quenching device, use an upper and lower split heating mold to close and clamp the workpiece, and keep it at 400-550℃ for 5-20 minutes for solution treatment. S2. The solution-treated workpiece is transferred to the cooling station, and the solution-treated workpiece is clamped in a closed cooling mold to perform quenching treatment to obtain the finished product; wherein the temperature of the upper and lower cooling molds is controlled at 15-25℃.

2. The hot and cold mold composite heat treatment method for aluminum alloy thin plates as described in claim 1, characterized in that, In step S1, the workpiece is a rolled aluminum alloy sheet with a thickness of 0.2-2mm.

3. The hot and cold mold composite heat treatment method for aluminum alloy thin plates as described in claim 1, characterized in that, In step S1, the opening and closing speed of the upper and lower split heating mold is 40-60 mm / min.

4. The hot and cold mold composite heat treatment method for aluminum alloy thin plates as described in claim 1, characterized in that, In step S2, the time for the workpiece to be transferred to the cooling station after solution treatment does not exceed 5 seconds.

5. The hot and cold mold composite heat treatment method for aluminum alloy thin plates as described in claim 1, characterized in that, In step S2, the opening and closing speed of the upper and lower split cooling mold is 40-60 mm / min.

6. The hot and cold mold composite heat treatment method for aluminum alloy thin plates as described in claim 1, characterized in that, In step S2, the quenching process takes 5-20 minutes.

7. An aluminum alloy sheet, characterized in that, It is prepared by the hot and cold mold composite heat treatment method of aluminum alloy sheet according to any one of claims 1-6.

8. A quenching apparatus for the hot-cold mold combined heat treatment method for aluminum alloy thin plates according to any one of claims 1-6, comprising: A traction structure, comprising a feeding roller and a receiving roller, is used to drive the workpiece to move. The heating station is equipped with an upper and lower split heating mold, which includes an upper heating mold and a lower heating mold that can move towards or away from each other. The upper heating mold and the lower heating mold are equipped with electric heating elements. The cooling station is equipped with an upper and lower split cooling mold, which includes an upper cooling mold and a lower cooling mold that can move towards or away from each other. The upper and lower cooling molds are equipped with water-cooling elements.

9. The quenching apparatus as described in claim 8, characterized in that, The upper heating mold and the lower heating mold also include a temperature controller, which is used to detect the temperature and control the temperature of the upper and lower split heating molds.

10. The quenching apparatus as described in claim 8, characterized in that, The traction speed of the traction structure is 0.5-5 m / s.

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