Composite treatment method for forming property of high-strength aluminum alloy sheet

Abstract

The invention discloses a composite treatment method for forming property of a high-strength aluminum alloy sheet. The composite treatment method comprises the steps of blanking, pressure quenching, bending and aging. An aluminum alloy blank is blanked according to the unfolding size of a part and then heated and subjected to heat preservation, then the aluminum alloy blank is rapidly transferred into a pressure quenching die to complete solid solution-quenching treatment, then bending forming is completed within 3 hours, and then heating and heat preservation are conducted to complete artificial aging. During quenching, the die is adopted for applying pressure, the aluminum alloy can be always kept in a flat plate state at the moment, the temperature is high, the rigidity is weak, but the aluminum alloy is restrained by the die, the aluminum alloy is not prone to deformation in the quenching process, the residual stress after quenching is low, abnormal deformation in the subsequent bending forming process is smaller, and the size precision is high; after the plate is quenched, residual stress is low, self-deformation is small, residual stress of room-temperature shape correction does not exist, abnormal deformation does not exist after bending forming, and therefore shape correction is not needed, and efficiency is higher. Compared with a traditional process method, the method is easy and convenient to operate, high in forming quality and efficiency and worthy of application and popularization.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment pressure quenching and forming, and in particular relates to a composite processing method for forming a high-strength aluminum alloy thin plate. Background Art

[0002] Aluminum is the most abundant metal element in the earth's crust, and its total reserves account for about 7.45% of the total earth's crust. The output of aluminum and aluminum alloys ranks second only to steel materials among metal materials, and is the most used and widely used material among non-ferrous metal materials. Aluminum alloys can be divided into heat-treatable and non-heat-treatable aluminum alloys according to whether the solute atoms have changes in solid solubility. Among the heat-treatable aluminum alloys, high-strength aluminum alloys such as Al-Mg-Si-Cu series, Al-Zn-Mg-Cu series, and Al-Cu-Mg series are widely used in the manufacture of special defense vehicles, such as Al-Cu-Mg series 2A12 aluminum alloy, Al-Mg-Si-Cu series 2A14 aluminum alloy, and Al-Zn-Mg-Cu series 7A52 aluminum alloy. Due to the performance requirements of the special defense vehicle structure, this type of aluminum alloy still needs to maintain the high performance requirements of the T6 or T7 heat treatment state after forming. Due to the large and thin size of the plate, the deformation of this type of parts is difficult to control during the heat treatment process. The production process of traditional technology is: free quenching → leveling → bending → aging. The problems of this method are: ① During the solution treatment, the thin plate is in an unconstrained state, and the parts are greatly deformed during heat treatment, which makes subsequent leveling difficult and takes a long time; ② After the solution treatment, when it is placed at room temperature, the strengthened aluminum alloy enters the natural aging process, and its hardness and strength will gradually increase. Generally, leveling and bending need to be completed within 4 hours. Due to the long leveling and bending processing time, in order to complete the leveling and bending of all parts within 4 hours, the single output is very small; ③ The leveling skills of the operator are very high; ④ The production cost is high, the production efficiency is low, and the quality consistency is poor. Summary of the invention

[0003] In order to solve the above problems existing in the prior art, the present invention provides a composite processing method for forming high-strength aluminum alloy thin plate parts. The invention has a good effect on the precise forming of high-strength aluminum alloy thin plate parts such as Al-Mg-Si-Cu series, Al-Zn-Mg-Cu series, Al-Cu-Mg series, etc. and maintains high mechanical properties, and has the characteristics of simple operation, high forming quality and efficiency.

[0004] The technical solution adopted by the present invention is as follows: A composite processing method for forming a high-strength aluminum alloy sheet, comprising blanking → press quenching → bending → aging, Cutting process: The aluminum alloy sheet has been processed to the right shape and size or nearly to the right shape before heat treatment; Press quenching process: Place a material rack at the bottom of the box furnace, and place the aluminum alloy sheet flat on the material rack for heating. Set the hydraulic press pressure to the minimum. After the parts are heated and kept warm (such as heating to 500-550℃ and keeping warm for 2-4 hours), use tongs to take the parts out of the box furnace, transfer them to the lower die of the press quenching mold within 20 seconds, and then start the hydraulic press. When the upper die of the press quenching mold contacts the parts, stop applying pressure immediately, and then spray water for 2-3 minutes until the parts cool down. Bending process: Use a bending machine to bend the aluminum alloy sheet parts that have been press-quenched to the size of the drawing. The interval between press-quenching and bending should be controlled within 3 hours; Aging process: Aluminum alloy thin plates are neatly placed in a box furnace or a trolley furnace, and parameters are selected according to the material type for aging treatment (such as heating and insulation at 160℃~180℃ for 4~10h).

[0005] Furthermore, in the press quenching process, the rack is a SUS304 steel rack with a height of 40 to 60 mm.

[0006] Furthermore, in the press quenching process, when multiple layers of aluminum alloy thin plate parts are placed on the rack, the upper layer parts extend out toward the furnace door by a distance of ≥30 mm, preferably 30-80 mm, compared with the lower layer parts.

[0007] Furthermore, in the press quenching process, the press quenching die is composed of an upper press die, an upper water spray system, a lower press die, a lower water spray system, a U-bolt kit and connecting bolts. The upper press die is composed of an L-shaped press column, a flat plate, a transition plate, a connecting plate and a fixed ear plate; the upper water spray system and the lower water spray system are welded by a main water pipe and a water distribution pipe. The main water pipe is connected to the circulating water, and small holes are drilled on the water distribution pipe for spraying; the lower press die is composed of an L-shaped press column, a flat plate, a transition plate, a connecting plate, a positioning block and a fixed ear plate. The upper press die and the lower press die are fixed by a U-bolt kit and connecting bolts; the press quenching die has a limit and water spray function. During the solution treatment, the die will accurately limit the part and spray water to cool it, while ensuring the flatness of the part (or other fixed shapes) to obtain an oversaturated and unstable solid solution structure. Due to the good flatness of the part, it can be transferred to the bending process without leveling, and the plate can be bent to the required size within 3 hours using a bending machine.

[0008] Furthermore, the main water pipe and the branch water pipe are made of No. 20 steel seamless steel pipe and are surface oxidized.

[0009] Furthermore, the main water pipe has a diameter of φ75 mm and is connected to water, and the water inlet connection port is arranged in the middle of the main water pipe.

[0010] Furthermore, the interval between the water distribution pipes is 70mm, the diameter of a single water distribution pipe is φ30mm, and a water spray port with a diameter of φ2mm is drilled every 20mm. The water spray ports are arranged in a cycle of center, 5mm to the right, 5mm to the left, center, etc.

[0011] Furthermore, the L-shaped pressure column is made of Q235 steel, which is surface oxidized and evenly distributed on the flat plate together with the water distribution pipe, with a spacing of 70 mm.

[0012] Furthermore, after the upper pressure mold and the lower pressure mold are connected to the hydraulic press and the platform, the L-shaped pressure column and the water distribution pipe are both distributed vertically.

[0013] Compared with the prior art, the beneficial effects of the present invention are: (1) The entire manufacturing process of parts is short, the production process is less dependent on skills such as calibration, and the production cost is low; (2) The press quenching die has good versatility. In addition to strengthening aluminum alloys, it can also be used for press quenching of low-alloy steel plates; (3) During quenching, the mold is used to apply pressure. At this time, the temperature of the aluminum alloy is high and the rigidity is weak, but it can always maintain a flat state due to the constraint of the mold. It is not easy to deform during the quenching process, and the residual stress after quenching is low. The abnormal deformation in the subsequent bending process is also smaller, and the dimensional accuracy is high; (4) The residual stress of the plate after quenching is low, the deformation itself is small, and there is no residual stress of room temperature correction. There is no abnormal deformation after bending, so there is no need for correction, which is more efficient. Compared with traditional process methods, this method is easy to operate, has high forming quality and efficiency, and is worthy of promotion and application.

[0014] (5) The main water pipe, water distribution pipe, L-shaped pressure column, etc. have been surface oxidized and have good anti-rust performance.

[0015] (6) The materials used for the molds are all ordinary steel, and the manufacturing process only involves welding, assembly and other methods. It is easy to manufacture and has low cost.

[0016] (7) SUS304 steel racks are kept warm at aluminum alloy quenching temperature (about 500°C) for long-term use and are not easily deformed. Parts can be placed and heated on the racks to ensure good flatness.

[0017] (8) The upper and lower water spray design and the staggered and evenly distributed water channels ensure that there are no dead angles in the spraying and no quenching "soft spots" will be produced.

[0018] (9) The cooling rate of circulating water spray is much greater than that of tank water. Aluminum alloy parts can obtain very good solid solubility in this state, and the parts can obtain very good mechanical properties after aging treatment.

[0019] (10) The cross-shaped L-shaped pressure column layout of the upper and lower pressure dies can correct the deformation caused by heating of the parts and control the quenching deformation. The parts after press quenching can be transferred to the bending process without leveling, which has high production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the press quenching die structure; Figure 2 Schematic diagram of the upper die structure; Figure 3 Schematic diagram of the lower die structure; Figure 4 It is a schematic diagram of the water spray system structure; Figure 5 This is a physical picture of the press quenching die assembled on the hydraulic press; Figure 6 This is the main view of the aluminum alloy sheet before bending; Figure 7 This is a physical picture of the aluminum alloy sheet after press quenching; Figure 8 It is the finished product of aluminum alloy thin plate after bending and aging treatment; Figure 1 Middle: 1. L-shaped pressure column; 2. U-shaped bolt kit; 3. Connecting bolt; 4. Connecting plate; 5. Fixing ear plate; 6. Main water pipe; 7. Positioning block; 8. Water distribution pipe; 9. Flat plate; 10. Transition plate. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0022] like Figures 1 to 4 As shown, the specific structure of the press quenching die used in the present invention is: it is composed of an upper pressure die, an upper water spray system, a lower pressure die, a lower water spray system, a U-shaped bolt kit and connecting bolts. The upper pressure die is composed of an L-shaped pressure column 1, a flat plate 9, a transition plate 10, a connecting plate 4 and a fixed ear plate 5. The upper water spray system and the lower water spray system are welded by a main water pipe 6 and a water branch pipe 8. The main water pipe 6 is connected to the circulating water, and a small hole is drilled on the water branch pipe 8 for spraying. The lower pressure die is composed of an L-shaped pressure column, a flat plate, a transition plate, a connecting plate, a positioning block and a fixed ear plate. The upper pressure die and the lower pressure die are fixed by a U-shaped bolt kit 2 and a connecting bolt 3. Before the quenching treatment of the aluminum alloy thin plate, the upper pressure die is connected to the upper platform of the hydraulic press, the lower pressure die is connected to the working platform of the hydraulic press, and the water is connected to the water inlet with a matching water pipe. The pressure of the hydraulic press is set to the minimum, and it is confirmed that all equipment can work normally. Example 1

[0023] by Figure 6 Taking the 2A14 aluminum alloy sheet shown above as an example, the production steps are as follows: (1) Cutting: Use laser cutting or other methods to cut the plane size and shape of the aluminum plate to the size required by the process.

[0024] (2) Furnace loading: Place a SUS304 steel rack with a height of about 50 mm in the box-type furnace, and place the aluminum alloy thin plate parts flat on the rack for heating. When placing multiple layers, the upper layer parts should extend ≥30 mm toward the furnace door compared to the lower layer parts.

[0025] (3) Heating: Heat the 2A14 aluminum plate in a box-type resistance furnace, raise the temperature to 500°C at a rate of 3-5°C / min, and then keep it warm for 3 hours.

[0026] (4) Quenching: Open the furnace door, take out the aluminum plate with tongs, close the furnace door, and transfer the aluminum plate to the lower pressure mold within 20 seconds. When the upper pressure mold fits the aluminum plate, stop applying pressure immediately, start the water pump, and then spray water for 1 to 2 minutes until the part cools down to complete the quenching process; then repeat the cycle until the quenching of the aluminum plate in the furnace is completed.

[0027] (5) Bending: When the cumulative number of quenched pieces is ≥ 10, switch to the bending process and use a bending machine to bend the aluminum plate to the drawing size. The interval between press quenching and bending is controlled within 3 hours; accumulate cycles until the bending of the aluminum plate in this furnace is completed.

[0028] (6) Aging: After bending, the parts are uniformly subjected to aging treatment at a temperature of 180°C × 7h. The completion of this process means that all processing of the workpiece is completed (or all processes are completed after local finishing).

[0029] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. The above is only a preferred implementation method of the present invention. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements, modifications or changes can be made, and the above technical features can be combined in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the protection scope of the present invention.

Claims

1. A composite processing method for forming a high-strength aluminum alloy sheet, characterized in that: Including cutting → press quenching → bending → aging; Cutting process: The aluminum alloy sheet parts are processed into the right shape and size or nearly processed into the right shape and size before heat treatment; Press quenching process: Place a material rack at the bottom of the box furnace, and place the aluminum alloy sheet flat on the material rack for heating. Set the hydraulic press pressure to the minimum. After the parts are heated and kept warm, use tongs to take the parts out of the box furnace and transfer them to the lower die of the press quenching mold within 20 seconds. Then start the hydraulic press. When the upper die of the press quenching mold contacts the parts, stop applying pressure immediately, and then spray water for 2 to 3 minutes until the parts cool down. Bending process: Use a bending machine to bend the aluminum alloy sheet parts that have been press-quenched to the size of the drawing. The interval between press-quenching and bending should be controlled within 3 hours; Aging process: Aluminum alloy thin plates are placed in a box furnace or a trolley furnace, and parameters are selected according to the material type for aging treatment.

2. The composite processing method for forming a high-strength aluminum alloy sheet according to claim 1, characterized in that: In the press quenching process, the rack is a SUS304 steel rack with a height of 40-60 mm.

3. The composite processing method for forming a high-strength aluminum alloy sheet according to claim 1, characterized in that: During the press quenching process, when multiple layers of aluminum alloy thin plates are placed on the rack, the upper parts extend out toward the furnace door by ≥30mm compared to the lower parts.

4. The composite processing method for forming a high-strength aluminum alloy sheet according to claim 1, characterized in that: In the press quenching process, the press quenching mold is composed of an upper press mold, an upper water spray system, a lower press mold, a lower water spray system, a U-shaped bolt kit and connecting bolts. The upper press mold is composed of an L-shaped press column, a flat plate, a transition plate, a connecting plate and a fixed ear plate; the upper water spray system and the lower water spray system are both welded by a main water pipe and a water branch pipe. The main water pipe is connected to the circulating water, and small holes are drilled on the water branch pipe for spraying; the lower press mold is composed of an L-shaped press column, a flat plate, a transition plate, a connecting plate, a positioning block and a fixed ear plate, and the upper press mold and the lower press mold are fixed by a U-shaped bolt kit and connecting bolts.

5. The composite processing method for forming a high-strength aluminum alloy sheet according to claim 4, characterized in that: The main water pipe and the branch water pipe are made of No. 20 steel seamless steel pipe and are surface oxidized.

6. The composite processing method for forming a high-strength aluminum alloy sheet according to claim 4, characterized in that: The main water pipe has a diameter of φ75mm and is connected to water, and the water inlet connection port is arranged in the middle of the main water pipe.

7. The composite processing method for forming a high-strength aluminum alloy sheet according to claim 4, characterized in that: The interval between the water distribution pipes is 70 mm, the diameter of a single water distribution pipe is φ30 mm, and a water spraying port with a diameter of φ2 mm is drilled every 20 mm.

8. The composite processing method for forming a high-strength aluminum alloy sheet according to claim 1, characterized in that: The L-shaped pressure column is made of Q235 steel, which is surface oxidized and evenly distributed on the flat plate together with the water distribution pipe, with a spacing of 70 mm.

9. The composite processing method for forming a high-strength aluminum alloy sheet according to claim 1, characterized in that: After the upper pressure mold and the lower pressure mold are connected to the hydraulic press and the platform, the L-shaped pressure column and the water distribution pipe are both distributed vertically.

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