CN113967668B - Processing method for improving forming precision of 7A85 alloy extruded sheet large-size cylindrical part - Google Patents

Processing method for improving forming precision of 7A85 alloy extruded sheet large-size cylindrical part Download PDF

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CN113967668B
CN113967668B CN202111104503.XA CN202111104503A CN113967668B CN 113967668 B CN113967668 B CN 113967668B CN 202111104503 A CN202111104503 A CN 202111104503A CN 113967668 B CN113967668 B CN 113967668B
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ultrasonic vibration
extruded sheet
aging
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CN113967668A (en
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毛郭灵
朱聪聪
刘东洋
童广泽
高文理
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Hunan University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C23/00—Extruding metal; Impact extrusion
    • B21C23/02—Making uncoated products
    • B21C23/04—Making uncoated products by direct extrusion
    • B21C23/06—Making sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C31/00—Control devices, e.g. for regulating the pressing speed or temperature of metal; Measuring devices, e.g. for temperature of metal, combined with or specially adapted for use in connection with extrusion presses
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D5/00—Bending sheet metal along straight lines, e.g. to form simple curves
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/10—Alloys based on aluminium with zinc as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/053—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with zinc as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F3/00—Changing the physical structure of non-ferrous metals or alloys by special physical methods, e.g. treatment with neutrons

Abstract

The invention discloses a processing method for improving the forming precision of a large-size cylindrical part of a 7A85 alloy extruded sheet. The method comprises the following steps: extruding and forming to obtain a 7A85 alloy sheet with the thickness of 3-8 mm; annealing treatment; solution treatment; spray quenching, wherein the water spray pressure is 190-205 KPa, and the water flow density is 45-60 L.m‑2·S‑1The duration is 8-17 s; roll bending; the thin plate is placed into a part die, ultrasonic vibration is introduced in the process of creep aging, the frequency of the ultrasonic vibration is 1.8-2.0 Khz, the amplitude is 18-25 mu m, the time is 13-20 min, the temperature of the creep aging is 145-160 ℃, and the time is 20-30 h. The invention ensures the mechanical property and reliability of the 7A85 alloy sheet part, reduces the residual stress of the part to be less than 48MPa, and has the rebound of less than or equal to 10 mm.

Description

Processing method for improving forming precision of 7A85 alloy extruded sheet large-size cylindrical part
Technical Field
The invention relates to a treatment method for improving the forming precision of a large-size cylindrical part of a 7A85 alloy extruded sheet, belongs to the technical field of wrought aluminum alloy industrialization, and particularly relates to a treatment method for improving the forming precision of the large-size cylindrical part of the 7A85 alloy extruded sheet by combining spray quenching, creep aging and ultrasonic vibration.
Background
The Al-Zn-Mg-Cu alloy (7XXX series aluminum alloy) has good processing performance, small density and high specific strength, is the alloy with the highest strength in aluminum alloys, and is widely applied to the field of aerospace, for example, the 7075 alloy is applied to a B-29 type bomber, and the 7085 alloy is applied to a main beam of a wing, an upper wing skin and the like. The 7A85 alloy is an Al-Zn-Mg-Cu alloy which is independently researched and developed in China and widely applied to stressed structural members in aviation and aerospace. In recent years, the development trend of lightweight and high-reliability manufacturing of aerospace equipment puts higher requirements on the processing performance of the 7A85 alloy, and the forming precision of the alloy, especially the 7A85 alloy plate, needs to be improved, and the mechanical property of the alloy plate is ensured. The plastic working process of the 7a85 alloy plate comprises extrusion and rolling, the heat treatment process comprises annealing, solution treatment, quenching, aging and the like, and during the plastic working and heat treatment process (such as extrusion, rolling and quenching) of the 7a85 alloy plate, large residual stress can be generated, and the residual stress is harmful, can cause the part to generate warping or distortion deformation, even cracking and the like, and has great influence on the forming precision and reliability of the 7a85 alloy plate part. The residual stress in the method is measured by an X-ray method, the grain spacing and the crystal face direction are changed due to the residual stress, the X-ray of the sample can be shifted, and the size of the residual stress can be calculated through the shift amount.
Research by Guoshigui et Al shows that spray quenching can improve the hardenability of a 7050 aluminum alloy (Al-Zn-Mg-Cu alloy) thick plate (Guoshigui. 7050 aluminum alloy material spray quenching test and simulation research [ D ]. Zhongnan university, 2010.). Studies by Argwari et al show that the spray quenching cooling intensity is high, the required time is short, and the uniformity is good for 7000 series aluminum alloy thick plates (Argwari, Zhang, Sumbexia. 7000 series aluminum alloy thick plates numerical simulation and analysis of spray quenching [ J ]. proceedings of the science and technology institute of Heilongjiang, 2010,20(2): 124-. Research by symplectic et Al shows that when the thickness of the 7075 aluminum alloy (Al-Zn-Mg-Cu alloy) is less than 30mm, the residual stress generated by spray quenching is small (symplectic 7075 aluminum alloy thick plate quenching residual stress and sensitivity analysis [ D ]. Nanchang aviation university.). Chenkanghua et al optimize the spray quenching process to reduce the residual stress of aluminum alloy (Chenkanghua, a beautiful royal, Chenshiyi, et al., a multistage spray quenching process with low residual stress for age-hardening aluminum alloy: CN104195481A [ P ]. 2016.). At present, some researches on an Al-Zn-Mg-Cu alloy spray quenching process exist, but the researches on a 7A85 alloy spray quenching process and a spray quenching process applied to improve the forming precision of a 7A85 alloy thin plate part do not exist.
Creep aging is a process for integrating the artificial aging of aluminum alloy and the forming of parts, namely, the aging treatment is carried out to enable the material to have the required performance, and meanwhile, the creep deformation of the material at the artificial aging temperature under the action of elastic stress is utilized to obtain a workpiece with a designed shape. Huanglin et al analyzed the bending creep process and spring back effect of a 7B04 aluminum alloy slab using finite element ABAQUS software (Huanglin, Wanmin, Huangshuo, et al. 7B04 aluminum alloy slab creep age forming finite element analysis [ J ] aerospace manufacturing technology, 2007.). Studies by Chen wish et al show that the tensile strength of creep aged specimens is slightly improved compared to artificial aging (Chen wish, Deng Lu, Wan Li, et al. the effect of creep aging on the structure and properties of 7050 aluminum alloy sheet [ J ] Material engineering, 2012(1): 71-76.). At present, the creep aging of the 7A85 alloy is not researched, and the creep aging is not researched for improving the forming precision of the 7A85 alloy sheet part.
The research of the wanonitis shows that the ultrasonic vibration aging can better eliminate the residual stress of the metal rod (the wanonitis, the ultrasonic vibration aging residual stress elimination mechanism analysis and the experimental research [ D ]. Tai Yuan chei university, 2014.). The research of the tensile strain shows that the ultrasonic vibration aging has obvious effect on eliminating the residual stress of the small workpiece (the tensile strain, Wanchenying, ultrasonic vibration aging feasibility analysis and experimental research [ J ] mechanical design and manufacture, 2013(07): 140-. The ultrasonic vibration during aging is beneficial to reducing the residual stress, but at present, no research is carried out on the ultrasonic vibration aging of the 7A85 alloy, and no research is carried out on the application of the ultrasonic vibration aging for improving the forming precision of a 7A85 alloy thin plate part.
So far, no report about how to improve the forming precision of parts while ensuring the mechanical property and reliability of large-size cylindrical parts made of large-size 7A85 alloy extruded sheets is available.
Disclosure of Invention
In order to improve the forming precision of the large-size cylindrical part while ensuring the mechanical property and reliability of the large-size 7A85 alloy extruded sheet, the invention provides a treatment method for improving the forming precision of the large-size cylindrical part of the 7A85 alloy extruded sheet by combining spray quenching, creep aging and ultrasonic vibration.
The invention relates to a processing method for improving the forming precision of a large-size cylindrical part of a 7A85 alloy extruded sheet; the method comprises the following steps:
step one, extrusion molding: and extruding the 7A85 alloy cast ingot to obtain A3-8 mm 7A85 alloy sheet. The method used in step one includes conventional methods.
Step two, annealing treatment: the 7a85 alloy extruded sheet was annealed. The method used in step two includes conventional methods.
Step three, solution treatment: performing solution treatment on the sheet obtained in the second step, wherein the temperature is controlled to be 460-477 ℃ during the solution treatment, and the heat preservation time is 0.8-3 h;
step four, spray quenching: carrying out spray quenching on the thin plate obtained in the step three, wherein the water spray pressure is 190-205 KPa, and the water flow density is 45-60 L.m-2·S-1The duration is 8-17 s.
Step five, roll bending:
performing roll bending treatment on the thin plate obtained in the step four to obtain a roll-bent product;
step six, ultrasonic vibration creep aging:
placing the product subjected to roll bending in the step five into a limiting die, and then assisting with ultrasonic vibration in the creep aging process to obtain a part; the frequency of ultrasonic vibration is 1.8-2.0 Khz, the amplitude is 18-25 mu m, the time is 13-20 min, the temperature of creep aging is 145-160 ℃, and the time is 20-30 h; the node of introduction of ultrasonic vibration includes introduction of ultrasonic vibration at the time of mesophase transition.
In the first step, the contents of the elements of the 7A85 alloy are respectively as follows: 7.0 to 8.0wt% of Zn; 1.5-2.3 wt% of Mg; 1.5-2.3 wt% of Cu; 0.09-0.18 wt% of Zr; fe <0.05 wt%; ti: <0.05 wt%; si < 0.05%; the balance of Al.
In the first step, during extrusion forming, the preheating temperature of the cast ingot is 440-455 ℃, the extrusion temperature is 420-435 ℃, the extrusion ratio is 30: 1-40: 1, and the extrusion speed is 2-2.5 mm/s.
And in the second step, the annealing temperature is 340-360 ℃ during annealing treatment, and the time is 28-32 h.
The diameter of the part obtained by the invention can be 1.5-2.3 m.
The height of the part can reach 1 m-1.3 m.
As a preferred embodiment; after creep aging is carried out for 5-12 hours, ultrasonic vibration is introduced.
The frequency of the ultrasonic vibration is 1.85-2.0 Khz, the amplitude is 19-21 mu m, and the time is 15-20 min.
The invention relates to a processing method for improving the forming precision of a 7A85 alloy extruded sheet part; the tensile strength of the part obtained in the sixth step is greater than 580MPa, the elongation is greater than 10%, the residual stress is less than 48MPa, and the resilience is less than or equal to 10 mm.
According to the invention, because the 7A85 thin plate is large, the plate is easily heated unevenly, stress is generated, and the structure is uneven, so that spray quenching is used, if the treatment in one step is not good, the mechanical property of the part is not enough, namely the service life is short, even the part is cracked, and the part cannot be manufactured.
The roll bending treatment process is arranged before aging after spraying, because: the alloy after aging treatment has high strength and large roll bending difficulty; roll bending before spray quenching can cause more uneven quenching, larger residual stress and more uneven structure, only solid solution strengthening is carried out after quenching, the strength of the alloy is not very high, and roll bending has operability, so roll bending is carried out before aging after spray quenching. Meanwhile, the roll bending can generate larger residual stress in the part, so that the residual stress is greatly reduced through subsequent ultrasonic vibration and creep aging, the rebound value is reduced, and the forming precision is improved.
If the aging is carried out purely, the rebound value of the part is still larger when the part is rolled and bent, so that the part needs to be placed in a limiting die (namely a part die) for aging, namely creep aging, a part of stress is released in the aging process, but the release degree is limited, the main purpose of the aging is to increase precipitated phases in the alloy and improve the strength, and ultrasonic vibration needs to be added to further release the stress.
The ultrasonic vibration of the present invention has two purposes: one to relieve stress and one to provide energy to transform the GP zone into more efficiently strengthening precipitate phases (e.g., eta "and eta' phases).
In the creep aging process of the invention, the change of the precipitated phase is approximately two stages, the first stage forms GP zone, which is easy to realize, the GP zone can be obtained even if the alloy is placed at room temperature for a period of time, the second stage is that the GP zone is converted into the precipitated phase with higher strengthening efficiency, which is generated only under the condition of high-temperature artificial aging and is relatively difficult to convert, and then the precipitated phase grows up and is relatively stable in size, thus achieving the maximum strengthening efficiency. Therefore, the vibration is not added in the early aging period of the method when the GP zone is formed at the beginning of aging, namely the early aging period, but the vibration is added in the middle aging period of the method when the GP zone is transformed to a precipitated phase with higher strengthening efficiency, namely the middle aging period of the method, one effect is that basically the same stress releasing effect can be achieved, the other effect is that partial energy can be provided for phase transformation to promote the precipitated phase transformation, and if the vibration is added in the growth process of the precipitated phase, namely the later aging period of the method, the effect of promoting the precipitated phase transformation is not good enough. However, if the vibration time is too long, the damage to the part mold is large, the service life is greatly shortened, and therefore the time is not suitable to be too long.
The invention has the following advantages:
(1) the forming precision of the large-size 7A85 alloy extruded sheet part is improved, and the mechanical property and reliability of the large-size 7A85 alloy extruded sheet part are not influenced.
(2) After spray quenching, creep aging and ultrasonic vibration treatment, the tensile strength of a 7A85 alloy extruded large-size sheet (3-8 mm) part is greater than 580MPa, the elongation is greater than 10%, the residual stress is reduced to be less than 48MPa (can be less than 40MPa after optimization), the forming precision is greatly improved, and the resilience is reduced to be less than 10mm (can be less than 6mm after optimization).
Drawings
FIG. 1 shows the springback value representation method;
FIG. 2 tensile specimen dimensions;
FIG. 3 is a schematic view of a mold.
The forming accuracy in the present invention is represented by the springback value, and as shown in fig. 1, the larger the springback value is, the worse the forming accuracy is, and the smaller the springback value is, the better the forming accuracy is.
The mechanical properties of the invention are measured by a room temperature tensile test, and the dimensions of the tensile test sample are shown in figure 2.
Detailed Description
In the examples and comparative examples exemplified in the present invention, the annealing conditions were: the temperature is 345 ℃ and the time is 29 h.
The first embodiment is as follows:
(1) step one, extrusion forming: extruding the 7A85 alloy cast ingot by a conventional method to obtain a 5mm 7A85 alloy sheet;
(2) step two, annealing treatment: annealing the 7A85 alloy extruded sheet according to a conventional method;
(3) step three, solution treatment: carrying out solution treatment on the sheet obtained in the step two, wherein the temperature is controlled to be 475 ℃ during the solution treatment, and the heat preservation time is 1 h;
(4) step four, spray quenching: spraying and quenching the thin plate obtained in the third step, wherein the water spraying pressure is 200KPa, and the water flow density is 50 L.m-2·S-1Duration of 12 s;
(5) step five, roll bending;
(6) step six, ultrasonic vibration creep aging:
and (3) placing the part obtained in the step five into a part die (namely a limiting die) for creep aging at the temperature of 155 ℃ for 28h, and carrying out ultrasonic vibration at the frequency of 1.85Khz and the amplitude of 20 mu m for 15min when the creep aging is carried out for 5 h.
After the above treatment, the tensile strength of the 7A85 alloy extruded sheet part was 580MPa, the elongation was 13%, the residual stress was 48MPa, and the spring back value was 10 mm. The diameter of the part is 2m and the height is 1.1 m.
Example two:
(1) step one, extrusion molding: extruding the 7A85 alloy cast ingot by a conventional method to obtain a 5mm 7A85 alloy sheet;
(2) step two, annealing treatment: annealing the 7A85 alloy extruded sheet according to a conventional method;
(3) step three, solution treatment: carrying out solution treatment on the sheet obtained in the step two, wherein the temperature is controlled to be 475 ℃ during the solution treatment, and the heat preservation time is 1 h;
(4) step four, spray quenching: spraying and quenching the thin plate obtained in the third step, wherein the water spraying pressure is 200KPa, and the water flow density is 50 L.m-2·S-1Duration of 12 s;
(5) step five, roll bending;
(6) step six, ultrasonic vibration creep aging: and putting the part obtained in the step five into a part die for creep aging at the temperature of 155 ℃ for 28h, and carrying out ultrasonic vibration at the frequency of 1.95Khz and the amplitude of 20 mu m for 15min when the creep aging is carried out for 5 h.
After the above treatment, the tensile strength of the 7A85 alloy extruded sheet part was 590MPa, the elongation was 11%, the residual stress was 40MPa, and the spring back value was 7 mm. The diameter of the part is 2m and the height is 1.1 m.
Example three:
(1) step one, extrusion molding: extruding the 7A85 alloy cast ingot by a conventional method to obtain a 5mm 7A85 alloy sheet;
(2) step two, annealing treatment: annealing the 7A85 alloy extruded sheet according to a conventional method;
(3) step three, solution treatment: carrying out solution treatment on the sheet obtained in the step two, wherein the temperature is controlled to be 475 ℃ during the solution treatment, and the heat preservation time is 1 h;
(4) step four, spray quenching: spraying and quenching the thin plate obtained in the third step, wherein the water spraying pressure is 200KPa, and the water flow density is 50 L.m-2·S-1Duration of 12 s;
(5) step five, roll bending;
(6) step six, ultrasonic vibration creep aging: and (5) placing the part obtained in the step five into a part die for creep aging at 165 ℃ for 28h, and performing ultrasonic vibration at the frequency of 1.85Khz and the amplitude of 20 mu m for 15min when the creep aging is performed for 5 h.
After the above treatment, the tensile strength of the 7A85 alloy extruded sheet part was 595MPa, the elongation 10.5%, the residual stress 45MPa, and the spring back value 9 mm. The diameter of the part is 2m and the height is 1.1 m. Example four:
(1) step one, extrusion forming: extruding the 7A85 alloy cast ingot by a conventional method to obtain a 5mm 7A85 alloy sheet;
(2) step two, annealing treatment: annealing the 7A85 alloy extruded sheet according to a conventional method;
(3) step three, solution treatment: carrying out solution treatment on the sheet obtained in the second step, wherein the temperature is controlled to be 475 ℃ during the solution treatment, and the heat preservation time is 1 h;
(4) step four, spray quenching: spraying and quenching the thin plate obtained in the third step, wherein the water spraying pressure is 200KPa, and the water flow density is 50 L.m-2·S-1Duration of 12 s;
(5) step five, roll bending;
(6) step six, ultrasonic vibration creep aging: and putting the part obtained in the step five into a part die for creep aging at the temperature of 155 ℃ for 30 hours, and carrying out ultrasonic vibration at the frequency of 1.85Khz and the amplitude of 20 mu m for 15min when the creep aging is carried out for 5 hours.
After the above treatment, the tensile strength of the 7A85 alloy extruded sheet part was 585MPa, the elongation was 11.9%, the residual stress was 47MPa, and the spring back value was 10 mm. The diameter of the part is 2m, and the height is 1.1 m.
Example five:
other conditions are consistent with the examples, except that: step six, ultrasonic vibration creep aging: and putting the part obtained in the step five into a part die for creep aging at the temperature of 155 ℃ for 28h, and carrying out ultrasonic vibration at the frequency of 1.85Khz and the amplitude of 20 mu m for 20min when the creep aging is carried out for 5 h.
After the above treatment, the tensile strength of the 7A85 alloy extruded sheet part was 588MPa, the elongation was 11.5%, the residual stress was 40MPa, and the springback value was 7.2 mm. The diameter of the part is 2m, and the height is 1.1 m.
Example six:
other conditions were as in the examples, except that: step six, ultrasonic vibration creep aging: and putting the part obtained in the step five into a part die for creep aging at the temperature of 155 ℃ for 28h, and carrying out ultrasonic vibration at the frequency of 1.85Khz and the amplitude of 20 mu m for 20min when the creep aging is carried out for 10 h.
After the above treatment, the tensile strength of the 7A85 alloy extruded sheet part was 584MPa, the elongation was 12%, the residual stress was 40MPa, and the springback value was 7.5 mm. The diameter of the part is 2m and the height is 1.1 m. Example seven:
(1) step one, extrusion molding: extruding the 7A85 alloy cast ingot by a conventional method to obtain a 5mm 7A85 alloy sheet;
(2) step two, annealing treatment: annealing the 7A85 alloy extruded sheet according to a conventional method;
(3) step three, solution treatment: carrying out solution treatment on the sheet obtained in the second step, wherein the temperature is controlled to be 475 ℃ during the solution treatment, and the heat preservation time is 1 h;
(4) step four, spray quenching: spraying and quenching the thin plate obtained in the third step, wherein the water spraying pressure is 200KPa, and the water flow density is 50 L.m-2·S-1Duration 17 s;
(5) step five, roll bending;
(6) step six, ultrasonic vibration creep aging:
and (3) placing the part obtained in the step five into a part die (namely a limiting die) for creep aging at the temperature of 155 ℃ for 28h, and carrying out ultrasonic vibration at the frequency of 2.0Khz and the amplitude of 20 mu m for 20min when the creep aging is carried out for 6 h.
After the above treatment, the tensile strength of the 7A85 alloy extruded sheet part was 590MPa, the elongation was 12.5%, the residual stress was 36MPa, and the springback value was 5 mm. The diameter of the part is 2m and the height is 1.1 m. Comparative example one:
(1) step one, extrusion molding: extruding the 7A85 alloy cast ingot by a conventional method to obtain a 5mm 7A85 alloy sheet;
(2) step two, annealing treatment: annealing the 7A85 alloy extruded sheet according to a conventional method;
(3) step three, solution treatment: carrying out solution treatment on the sheet obtained in the step two, wherein the temperature is controlled to be 475 ℃ during the solution treatment, and the heat preservation time is 1 h;
(4) step four, quenching: carrying out conventional quenching on the thin plate obtained in the step three, wherein a quenching medium is room temperature water;
(5) step five, roll bending;
(6) step six, ultrasonic vibration creep aging: and putting the part obtained in the step five into a part die for creep aging at the temperature of 155 ℃ for 28h, and carrying out ultrasonic vibration at the frequency of 1.85Khz and the amplitude of 20 mu m for 15min when the creep aging is carried out for 5 h.
After the above treatment, the tensile strength of the 7A85 alloy extruded sheet part was 580MPa, the elongation was 12.5%, the residual stress was 95MPa, and the springback value was 22 mm. The diameter of the part is 2m and the height is 1.1 m.
Comparative example two:
(1) step one, extrusion molding: extruding the 7A85 alloy cast ingot by a conventional method to obtain a 5mm 7A85 alloy sheet;
(2) step two, annealing treatment: annealing the 7A85 alloy extruded sheet according to a conventional method;
(3) step three, solution treatment: carrying out solution treatment on the sheet obtained in the step two, wherein the temperature is controlled to be 475 ℃ during the solution treatment, and the heat preservation time is 1 h;
(4) step four, spray quenching: spraying and quenching the thin plate obtained in the third step, wherein the water spraying pressure is 200KPa, and the water flow density is 50 L.m-2·S-1Duration of 12 s;
(5) step five, roll bending;
(6) step six creep aging: and putting the part obtained in the step five into a part die for creep aging, wherein the temperature of the creep aging is 155 ℃, and the time is 28 hours.
After the above treatment, the tensile strength of the 7A85 alloy extruded sheet part was 565MPa, the elongation was 14.5%, the residual stress was 75MPa, and the spring back value was 18 mm. The diameter of the part is 2m and the height is 1.1 m.
Comparative example three:
other conditions were as in the examples, except that: step six, ultrasonic vibration creep aging: and putting the part obtained in the step five into a part die for creep aging, wherein the temperature of the creep aging is 155 ℃, the time is 28 hours, and the part is ultrasonically vibrated at the beginning of the creep aging, the frequency of the ultrasonic vibration is 1.85Khz, the amplitude is 20 mu m, and the time is 15 min.
After the above treatment, the tensile strength of the 7A85 alloy extruded sheet part was 570MPa, the elongation was 14%, the residual stress was 44MPa, and the spring back value was 9.8 mm. The diameter of the part is 2m and the height is 1.1 m.
Comparative example four:
other conditions were as in the examples, except that: step six, ultrasonic vibration creep aging: and (5) placing the part obtained in the step five into a part die for creep aging at the temperature of 155 ℃ for 28 hours, and ultrasonically vibrating at the frequency of 1.85Khz and the amplitude of 20 mu m for 15min until 24 hours.
After the above treatment, the tensile strength of the 7A85 alloy extruded sheet part was 568MPa, the elongation was 14.1%, the residual stress was 43MPa, and the spring back value was 9.7 mm. The diameter of the part is 2m and the height is 1.1 m.

Claims (5)

1. A processing method for improving the forming precision of a large-size cylindrical part of a 7A85 alloy extruded sheet; the method is characterized in that: the method comprises the following steps:
step one, extrusion molding:
extruding the 7A85 alloy cast ingot to obtain A3-8 mm 7A85 alloy sheet;
step two, annealing treatment:
annealing the obtained 7A85 alloy extruded sheet;
step three, solution treatment:
carrying out solution treatment on the sheet obtained in the step two, wherein the temperature is controlled to be 460-477 ℃ during the solution treatment, and the heat preservation time is 0.8-3 h;
step four, spray quenching:
carrying out spray quenching on the thin plate obtained in the step three, wherein the water spray pressure is 190-205 KPa, and the water flow density is 45-60 L.m-2•S-1The duration is 8-17 s;
step five, roll bending;
performing roll bending treatment on the sheet obtained in the step four to obtain a roll-bent product;
step six, ultrasonic vibration creep aging:
placing the product subjected to roll bending in the step five into a limiting die, and then assisting with ultrasonic vibration in the creep aging process to obtain a part; the frequency of ultrasonic vibration is 1.8-2.0 Khz, the amplitude is 18-25 mu m, the time is 13-20 min, the temperature of creep aging is 145-160 ℃, and the time is 20-30 h; introducing ultrasonic vibration after creep aging for 5-12 h; the diameter of the part is 1.5 m-2.3 m, and the height of the part is 1 m-1.3 m.
2. The processing method for improving the forming precision of the 7A85 alloy extruded sheet large-size cylindrical part according to claim 1; the method is characterized in that: in the first step, the contents of the elements of the 7A85 alloy are respectively as follows: 7.0 to 8.0wt% of Zn; 1.5-2.3 wt% of Mg; 1.5-2.3 wt% of Cu; 0.09-0.18 wt% of Zr; fe <0.05 wt%; ti: <0.05 wt%; si <0.05 wt%; the balance of Al.
3. The processing method for improving the forming precision of the 7A85 alloy extruded sheet large-size cylindrical part according to claim 1; the method is characterized in that: in the first step, during extrusion forming, the preheating temperature of the cast ingot is 440-455 ℃, the extrusion temperature is 420-435 ℃, the extrusion ratio is 30: 1-40: 1, and the extrusion speed is 2-2.5 mm/s.
4. The processing method for improving the forming precision of the 7A85 alloy extruded sheet large-size cylindrical part according to claim 1; the method is characterized in that: in the second step, the annealing temperature is 340-360 ℃ and the time is 28-32 h during the annealing treatment.
5. The processing method for improving the forming precision of the 7A85 alloy extruded sheet large-size cylindrical part according to claim 1; the method is characterized in that: the tensile strength of the part obtained in the sixth step is greater than 580MPa, the elongation is greater than 10%, the residual stress is less than 48MPa, and the resilience is less than or equal to 10 mm.
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CN102978544A (en) * 2012-11-21 2013-03-20 中南大学 Method for multilevel creep age forming of Al-Zn-Mg-Cu series aluminium alloy plate
CN104404326A (en) * 2014-12-12 2015-03-11 西南铝业（集团）有限责任公司 7A85 aluminium alloy hot-top casting process and 7A85 aluminium alloy ingot
CN104451292A (en) * 2014-12-12 2015-03-25 西南铝业（集团）有限责任公司 7A85 aluminum alloy

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101050512A (en) * 2006-04-03 2007-10-10 郑州大学 High effective heat treatment method for wheel hub founded at low pressure from high performance A356 alloy
CN102978544A (en) * 2012-11-21 2013-03-20 中南大学 Method for multilevel creep age forming of Al-Zn-Mg-Cu series aluminium alloy plate
CN104404326A (en) * 2014-12-12 2015-03-11 西南铝业（集团）有限责任公司 7A85 aluminium alloy hot-top casting process and 7A85 aluminium alloy ingot
CN104451292A (en) * 2014-12-12 2015-03-25 西南铝业（集团）有限责任公司 7A85 aluminum alloy

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