Continuous heat treatment method of Al-Cu-Li aluminum lithium alloy

Abstract

The invention relates to the field of alloy heat treatment, in particular to a continuous heat treatment method of an Al-Cu-Li system aluminum lithium alloy. According to the continuous heat treatment method of the aluminum-lithium alloy, the speed of the thin plate coiled material passing through the air cushion furnace is controlled, so that the solid solution treatment and quenching time of the plate is controlled, the aluminum-lithium alloy thin plate roll type continuous solid solution treatment process is achieved, the original effect of solid solution heat treatment is achieved, and meanwhile solid solution heat treatment can be conducted on the whole roll of plate; the time of multi-heat heating and heat preservation in a traditional mode is omitted, the heat treatment efficiency is greatly improved, the solid solution heat treatment mode is heat treatment in the same furnace and the same batch, and the plate performance inevitably has large uniformity and stability. Besides, due to the characteristic that the surface of the aluminum-lithium alloy is easy to oxidize and damage, a slicing and stacking mode is replaced by a mode of controlling the passing speed, uncoiling and applying certain tension, and scratches caused by surface oxidation and free deformation between plates can be reduced.

Description

Technical Field

[0001] The invention relates to the field of alloy heat treatment, in particular to a continuous heat treatment method for an Al-Cu-Li series aluminum-lithium alloy. Background Art

[0002] Industrial heat treatment of aluminum-lithium alloy sheets has always been a difficult problem due to their easy oxidation and high performance and surface requirements. Industrial heat treatment is solution heat treatment, which refers to a heat treatment process in which the alloy is heated to a high-temperature single-phase region and maintained for a certain period of time to allow the excess phase to fully dissolve into the matrix, and then cooled at a certain rate to obtain a supersaturated solid solution. The traditional solution heat treatment method is coil slitting-stacking-heating-solution insulation-quenching. The equipment used for solution treatment is a box-type air furnace or salt bath furnace with a water tank. Aluminum-lithium alloy stacks are easily oxidized during solution treatment. The longer the time in the furnace, the more seriously the surface quality is affected. In addition, the air furnace heats up slowly and the temperature control accuracy is poor, resulting in poor stability between batches of sheet-type solution-treated plates. In addition, although the use of a salt bath tank isolates the air and reduces surface oxidation, the plate has a large free deformation in the salt bath tank, and the plate shape is poor after quenching; and the high-temperature melting reaction of the aluminum-lithium alloy will explode, posing a huge safety hazard. At present, the salt bath tank solution heat treatment process of aluminum-lithium alloy has been cancelled in China; moreover, the above two solution heat treatment methods can only be loaded into the furnace in sheet form, and the number of plates treated at a single time is limited. Multiple loading, heating, and insulation are required, and the heat treatment efficiency is very low. At present, there is no relevant aluminum-lithium alloy thin plate solution treatment implementation plan in China that can avoid these defects. Summary of the invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a continuous heat treatment method for Al-Cu-Li aluminum-lithium alloy. The method provided by the present invention replaces the traditional salt bath solution heat treatment process, which can not only greatly improve the production efficiency, but also reduce the surface quality damage of the plate and improve the batch uniformity and stability of the plate performance.

[0004] The present invention provides a continuous heat treatment method for an Al-Cu-Li aluminum-lithium alloy, comprising the following steps:

[0005] The Al-Cu-Li aluminum-lithium alloy is continuously passed through a solid solution zone and a quenching zone for heat treatment;

[0006] The temperature of the solid solution zone is 460°C to 530°C;

[0007] The Al-Cu-Li aluminum-lithium alloy continuously passes through the solid solution zone at a speed of 10 to 15 minutes.

[0008] The continuous heat treatment method provided by the present invention is a continuous heat treatment method for aluminum-lithium alloy, that is, for aluminum alloy containing Li element, specifically for Al-Cu-Li aluminum-lithium alloy, and the continuous heat treatment method provided by the present invention is for Al-Cu-Li aluminum-lithium alloy thin plate with a thickness of 0.1 mm to 4 mm. The Al-Cu-Li aluminum-lithium alloy of the present invention includes: Si: 0 to 0.15 wt%; Fe: 0 to 0.20 wt%; Cu: 2.0 to 3.5 wt%; Mn: 0 to 0.80 wt%; Mg: 0.20 to 0.9 wt%; Cr: 0 to 0.08 wt%; Zn: 0 to 0.40 wt%; Ti: 0 to 0.20 wt%; Zr: 0.02 to 0.28 wt%; Ag: 0.10 to 0.60 wt%; Li: 0.5 to 1.5 wt%; the balance is Al. Preferably, the Al-Cu-Li aluminum-lithium alloy comprises: Si: 0~0.08 wt%; Fe: 0~0.10 wt%; Cu: 2.5~3.0 wt%; Mn: 0~0.50 wt%; Mg: 0.25~0.8 wt%; Cr: 0~0.05wt%; Zn: 0~0.35 wt%; Ti: 0~0.10 wt%; Zr: 0.04~0.18 wt%; Ag: 0.10~0.50 wt%; Li: 0.8~1.1wt%; the balance is Al. In certain embodiments of the present invention, the Al-Cu-Li aluminum-lithium alloy is 2198 aluminum-lithium alloy. The present invention adopts a coil-type continuous heat treatment method for aluminum-lithium alloy thin plates, which greatly improves production efficiency, reduces surface quality damage of the plate, and improves batch uniformity and stability of plate performance.

[0009] The present invention continuously passes the Al-Cu-Li aluminum-lithium alloy through the solid solution zone and the quenching zone for heat treatment. Specifically, the Al-Cu-Li aluminum-lithium alloy continuously passes through the solid solution zone to experience heating and heating, and then continuously passes through the quenching zone for quenching. In certain embodiments of the present invention, the present invention assembles, unwinds, and fixes the Al-Cu-Li aluminum-lithium alloy coil as a whole roll, controls the unwinding aluminum-lithium alloy to be transported at a certain speed through the furnace body heating zone and the heating zone in turn for solid solution treatment, and then the aluminum-lithium alloy after solid solution treatment continues to pass through the quenching zone at the same speed for quenching treatment.

[0010] The present invention controls the Al-Cu-Li aluminum-lithium alloy to pass through the solid solution zone and the quenching zone at a certain speed. The speeds of passing through the solid solution zone and the quenching zone are the same, and both pass through the heating zone for 10 to 15 minutes, that is, the passing speed is determined by the distance of the Al-Cu-Li aluminum-lithium alloy passing through the solid solution zone / passing speed = 10 to 15 minutes. For example, when the distance of the aluminum-lithium alloy passing through the solid solution zone is 30 meters, the passing speed is 30 meters / (10 to 15 meters / min) = 2 to 3 meters / min. The temperature of the solid solution zone of the present invention is 460°C to 530°C. The quenching zone of the present invention quenches the aluminum-lithium alloy passing through with water, and the water volume of the quenching zone is 0.1 to 0.4 bar.

[0011] In the whole process of continuously passing the Al-Cu-Li aluminum-lithium alloy through the solid solution zone and the quenching zone for heat treatment, the head and tail ends of the aluminum-lithium alloy are stretched by 0.4% to 0.6%, preferably 0.5%. The stretching applied to the head and tail ends of the aluminum-lithium alloy further reduces the surface quality damage of the plate.

[0012] After the heat treatment, the present invention also includes cold deformation. Through the continuous heat treatment method provided by the present invention, the deformation amount of the Al-Cu-Li aluminum-lithium alloy during cold deformation is reduced, and a relatively uniform surface can be obtained without large deformation amount cold deformation. In some embodiments of the present invention, the deformation amount of the cold deformation is 1.5~3.5%.

[0013] The present invention provides a continuous heat treatment method for Al-Cu-Li aluminum-lithium alloy. The continuous heat treatment method provided by the present invention realizes the process of continuous solid solution treatment of aluminum-lithium alloy thin plates by controlling the speed of thin plate coils passing through an air cushion furnace, thereby controlling the time of solid solution treatment and quenching of the plate, achieving the original effect of solid solution heat treatment, and can simultaneously solid solution heat treat the entire coil of plate, eliminating the time of heating and heat preservation of multiple furnaces in the traditional method, greatly improving the heat treatment efficiency, and such solid solution heat treatment method is the same furnace and the same batch of heat treatment, and the plate performance must have greater uniformity and stability. In addition, due to the characteristics of easy oxidation and damage of the surface of aluminum-lithium alloy, the present invention replaces the slicing and stacking method by controlling the passing speed and unwinding, and applying a certain tension, which can reduce the scratches caused by surface oxidation and free deformation between the plates. Therefore, the continuous heat treatment method of aluminum-lithium alloy plate coil provided by the present invention solves the problems of low temperature control accuracy, low efficiency and poor effect of traditional solid solution heat treatment methods of Al-Cu-Li aluminum-lithium alloy thin plate coils, and achieves better technical effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1It is a process flow chart of the coil-type continuous heat treatment method of the Al-Cu-Li series aluminum-lithium alloy sheet of the present invention;

[0015] Figure 2 This is a flowchart of the traditional solution heat treatment process;

[0016] Figure 3 This is a surface photo of the plate after solution heat treatment in Example 1 of the present invention;

[0017] Figure 4 This is a photo of the surface of the plate after solution treatment in Comparative Example 2 of the present invention;

[0018] Figure 5 This is a process diagram of the continuous heat treatment of the present invention in Example 1 of the present invention;

[0019] Figure 6 This is a process diagram of the solution heat treatment process of Comparative Example 1 of the present invention;

[0020] Figure 7 This is a process diagram of the solution heat treatment process of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0021] The present invention discloses a continuous heat treatment method for Al-Cu-Li aluminum-lithium alloy. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the method and application of this article without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0022] like Figure 1 As shown, Figure 1 The process flow chart of the Al-Cu-Li aluminum-lithium alloy sheet coil continuous heat treatment method of the present invention is as follows: Figure 1 It can be seen that the coil-type continuous heat treatment method of the Al-Cu-Li aluminum-lithium alloy sheet of the present invention specifically includes: ① uncoiling and threading the aluminum-lithium alloy sheet coil. ② controlling the sheet to be conveyed through the furnace body heating zone and heating zone at a certain speed: ③ controlling the sheet to pass through the quenching zone. ④ after the solution treatment is completed, transfer to the next process.

[0023] like Figure 2 As shown, Figure 2 This is the process flow diagram of traditional solution heat treatment. Figure 2 It can be seen that the traditional solution heat treatment process includes air furnace solution treatment and salt bath solution treatment, which specifically includes: ① aluminum coil. ② slicing and stacking. ③ solution treatment and quenching in air furnace / salt bath. ④ plate after heat treatment.

[0024] The chemical composition of the 2198 alloy used in the specific implementation of the present invention is shown in Table 1:

[0025] Table 1

[0026]

[0027] Note: - indicates that the element is not dosed.

[0028] The chemical composition of the 5A90 alloy used in the specific implementation of the present invention is shown in Table 2:

[0029] Table 2

[0030]

[0031] Note: - indicates that the element is not dosed.

[0032] The present invention will be further described below in conjunction with embodiments:

[0033] Example 1

[0034] ① Assemble, unwind, thread and fix the cold-rolled 2198 aluminum-lithium alloy sheet coil (batches Q20Y516-1 and Q20Y516-2) with a thickness of 2.0 mm and a width of 1200 mm;

[0035] ② Apply 0.5% stretching at both ends of the coil, and control the plate to be conveyed through the heating zone and heating zone of the furnace at a certain speed. 2.0mm thick, 1200mm wide 2198 alloy solution process parameters: set the solution temperature to 505℃, the heating zone + heating zone length to 22.5m, the plate conveying speed to 3m / min, that is, the solution time is 22.5 / 3=7.5min. The total length of the coil is about 220m, and the solution treatment time of the whole coil is (220+22.5) / 3=81min.

[0036] ③Control the plate to pass through the quenching zone, and the water volume in the quenching zone is 0.3 bar.

[0037] ④ After the solution treatment is completed, the next process is carried out for cold deformation of 1.5% (combined with the 0.5% stretching applied in the whole process, which is equivalent to adding 2% tension) to obtain the heat-treated plate.

[0038] Comparative Example 1

[0039] In this comparative example 1, a cold-rolled 5A90 aluminum-lithium alloy sheet (batch P20A205) with a thickness of 2.0 mm and a width of 1200 mm is subjected to solution heat treatment according to a salt bath solution treatment process, specifically comprising the following steps:

[0040] The cold-rolled plates are sliced ​​and stacked, and then the stacked plates are placed in a 460±5℃ salt bath for solution insulation for 30 minutes. After the insulation, they are transferred to a water tank for quenching. After quenching, they are straightened and deformed by 2% to obtain plates.

[0041] Comparative Example 2

[0042] In this comparative example 2, a cold-rolled 5A90 aluminum-lithium alloy sheet (batch Q20AB08) with a thickness of 2.0 mm and a width of 1200 mm is subjected to a solution heat treatment according to an air furnace solution treatment process, specifically comprising the following steps:

[0043] The cold-rolled plates are sliced ​​and stacked, and then the stacked plates are placed in an air furnace with the furnace gas set to 460±5℃. After the metal thermocouple reaches 455℃, the temperature is kept for 40 minutes. After the insulation is completed, water is sprayed for quenching. After quenching, 2% straightening deformation is performed to obtain the plates.

[0044] Plate surface quality comparison:

[0045] Compared with the comparative example using the conventional solution heat treatment process, the surface quality of the heat-treated plate obtained by the embodiment using the solution heat treatment process of the present invention is also better.

[0046] like Figure 3 As shown, Figure 3 This is a photograph of the surface of the plate after solution heat treatment in Example 1 of the present invention. Since the plate is conveyed through the high-temperature zone, the upper and lower surfaces do not contact other plates, which will not cause surface color difference and the qualified rate of the plate surface quality is significantly improved.

[0047] like Figure 4 As shown, Figure 4 This is a photograph of the surface of the plate after solution treatment in Comparative Example 2 of the present invention. The plate obtained in Comparative Example 2 after heat treatment will produce large free deformation under high temperature. The contact between the surfaces of the plates will produce large-area color difference that is difficult to eliminate, and the surface quality is unqualified.

[0048] Plate uniformity comparison:

[0049] like Figure 5 As shown, Figure 5 This is a process diagram of the continuous heat treatment of the present invention in Example 1 of the present invention. Figure 5 It can be seen that the present invention adopts the method of conveying solid solution treatment of the entire aluminum coil ( Figure 5 -②), the whole roll is processed at the same time, all are from the same batch, the plates of different lengths are of the same thickness (accuracy ±0.2 mm), the plates are heated very evenly; after superimposed tension, the plates are less deformed and more consistent ( Figure 5-④), only a small amount of correction is required at the back end to meet the product standards, so the uniformity between batches of plates is better. Figure 5 A comparison is also given of Example 1 of the present invention in which no cold deformation is performed after the solution treatment process (the plate is deformed only by the tensile stress when the plate is moved by the belt, i.e., the stretching amount applied in ② is 0.5%).

[0050] like Figure 6 and Figure 7 As shown, Figure 6 This is a process diagram of the solution heat treatment process of Comparative Example 1 of the present invention, Figure 7 FIG. 2 is a process diagram of the solution heat treatment process of Comparative Example 2 of the present invention. Figure 6 It can be seen that the traditional air furnace and salt bath solution treatment requires the aluminum coil / aluminum plate to be cut and stacked in each pile ( Figure 6 -②), the air heat transfer rate of different thicknesses of the stack is quite different, each sheet takes different time to reach temperature, and the sheets are heated unevenly; after solution quenching, the free deformation of the whole stack of sheets is very large ( Figure 6 -④), the correction amount of each plate at the back end is large and inconsistent, resulting in poor uniformity between batches of plates. Figure 7 It can be seen that the situation is the same and I will not repeat it.

[0051] Comparison of room temperature tensile properties of plates:

[0052] The CV value is the coefficient of variation, which characterizes the volatility of the data. The smaller the CV value, the smaller the volatility of the data and the higher the stability. As shown in Tables 3, 4 and 5 below, the tensile performance data of the plates produced by the solution heat treatment of the present invention are more uniform. The CV values ​​of the measured data in Table 3 (solution treatment of the aluminum-lithium alloy plate of the present invention) are much smaller than those in Table 4 (solution heat treatment of the aluminum-lithium alloy plate in a salt bath) and Table 5 (solution heat treatment of the aluminum-lithium alloy plate in an air furnace), indicating that the solution heat treatment of the present invention can improve the stability of the performance of the plate batches.

[0053] The performance test of the heat-treated plate of Example 1 of the present invention was carried out, and the results are shown in Table 3:

[0054] Table 3

[0055]

[0056] The performance test of the heat-treated plate of Comparative Example 1 of the present invention was carried out, and the results are shown in Table 4:

[0057] Table 4

[0058]

[0059] The performance test of the heat-treated plate of Comparative Example 2 of the present invention was carried out, and the results are shown in Table 5:

[0060] Table 5

[0061]

[0062] In summary, the embodiment of the solid solution heat treatment process of the present invention, compared with the comparative example using the traditional solid solution heat treatment process, the process of the present invention eliminates the steps of slicing and stacking of aluminum coils, the possible increase in the number of furnaces due to the limitation of a single furnace loading, and the long-term heating of the air furnace. The process flow is significantly simplified, the efficiency and effectiveness are greatly improved, and the uniformity and stability of the plate batches are improved.

[0063] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A continuous heat treatment method for Al-Cu-Li aluminum-lithium alloy, characterized in that: The following steps are involved: The Al-Cu-Li aluminum-lithium alloy is continuously passed through a solid solution zone and a quenching zone for heat treatment; The temperature of the solid solution zone is 460°C to 530°C; The Al-Cu-Li aluminum-lithium alloy continuously passes through the solid solution zone at a speed of 10 to 15 minutes.

2. The continuous heat treatment method of Al-Cu-Li aluminum-lithium alloy according to claim 1, characterized in that: During the heat treatment, a stretching amount of 0.4% to 0.6% is applied to the head and tail ends of the Al-Cu-Li aluminum-lithium alloy.

3. The continuous heat treatment method of Al-Cu-Li aluminum-lithium alloy according to claim 1, characterized in that: After heat treatment, cold deformation is also included.

4. The continuous heat treatment method of the Al-Cu-Li aluminum-lithium alloy according to claim 3, wherein the deformation amount of the cold deformation is 1.5~3.5%.

5. The continuous heat treatment method of Al-Cu-Li aluminum-lithium alloy according to claim 1, characterized in that: The Al-Cu-Li aluminum-lithium alloy comprises: Si: 0~0.15 wt%; Fe: 0~0.20 wt%; Cu: 2.0~3.5 wt%; Mn: 0~0.80 wt%; Mg: 0.20~0.9 wt%; Cr: 0~0.08 wt%; Zn: 0~0.40 wt%; Ti: 0~0.20 wt%; Zr: 0.02~0.28 wt%; Ag: 0.10~0.60 wt%; Li: 0.5~1.5 wt%; The balance is Al.

6. The continuous heat treatment method of Al-Cu-Li aluminum-lithium alloy according to claim 5, characterized in that: The Al-Cu-Li aluminum-lithium alloy comprises: Si: 0~0.08 wt%; Fe: 0~0.10 wt%; Cu: 2.5~3.0 wt%; Mn: 0~0.50 wt%; Mg: 0.25~0.8 wt%; Cr: 0~0.05 wt%; Zn: 0~0.35 wt%; Ti: 0~0.10 wt%; Zr: 0.04~0.18 wt%; Ag: 0.10~0.50 wt%; Li: 0.8~1.1 wt%; The balance is Al.

7. The continuous heat treatment method of Al-Cu-Li aluminum-lithium alloy according to claim 6, characterized in that: The Al-Cu-Li aluminum-lithium alloy is 2198 aluminum-lithium alloy.

8. The continuous heat treatment method of the Al-Cu-Li aluminum-lithium alloy according to any one of claims 1 to 7, characterized in that: The Al-Cu-Li aluminum-lithium alloy is an Al-Cu-Li aluminum-lithium alloy thin plate with a thickness of 0.1 mm to 4 mm.

9. The continuous heat treatment method of the Al-Cu-Li aluminum-lithium alloy according to any one of claims 1 to 7, characterized in that: The water volume in the quenching zone is 0.1~0.4 bar.

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