Heat treatment process of 7021 aluminum alloy plate with high conductivity and high performance

Abstract

The invention discloses a heat treatment process of a 7021 aluminum alloy plate with high conductivity and high performance, and belongs to the field of aluminum alloy preparation. By optimizing the process conditions of the 7021 aluminum alloy plate, the conductivity of the 7021 aluminum alloy plate can be improved, and the mechanical property of the 7021 aluminum alloy plate can be obviously improved. And by adding the composite refining agent, the internal grain size of the 7021 aluminum alloy plate can be reduced, so that in the subsequent process, grain growth cannot be caused, and the mechanical property of the 7021 aluminum alloy plate cannot be affected. Besides, through parameter optimization of a solid solution process and a regression reaging process, the tensile strength of the 7021 aluminum alloy plate reaches 500MPa, the yield strength reaches 465MPa, the percentage elongation after fracture reaches 14.0%, and the conductivity reaches 38.9% IACS (International Annealed Copper Standard).

Description

Technical Field

[0001] The invention relates to a preparation process of an aluminum alloy, and in particular to a heat treatment process of a 7021 aluminum alloy plate with high electrical conductivity and high performance. Background Art

[0002] 7021 aluminum alloy Al-Zn-Mg series is a high-strength aluminum alloy with many advantages such as high strength, high toughness, corrosion resistance, and welding performance. It is widely used in all aspects of life. With the rapid development of the transportation industry, lightweighting of vehicle bodies has become an inevitable development trend. More and more car companies choose aluminum alloy plates instead of traditional steel plates for vehicle body production, which provides conditions for the widespread application of aluminum alloys in the transportation industry. Aluminum alloys have high specific strength. Under the same strength, aluminum alloys are lighter and can save energy. There are few cases in which automobiles do not meet the requirements due to insufficient strength in actual use. Insufficient stiffness is a common design defect. Stiffness is related to the material's own characteristics and structure. Without changing the material, simple structural optimization can greatly improve the body stiffness. Structural optimization places high demands on the deformation performance of the material. 7 series aluminum alloys are heat-treatable strengthening alloys. The internal organization can be changed through heat treatment processes to obtain aluminum alloy products with better performance.

[0003] The existing technology for the heat treatment process of 7 series aluminum alloys is mainly based on the traditional single heat treatment process, which mostly improves a certain performance of the material, but does not significantly improve the comprehensive mechanical properties of the material. The existing technology also uses the over-aging method to improve the conductivity, but the over-aging method reduces the mechanical properties of the aluminum alloy and cannot guarantee excellent conductivity and mechanical properties at the same time. Summary of the invention

[0004] Based on this, in order to solve the technical problem that the existing technology improves the electrical conductivity while reducing the mechanical properties, the present invention provides a heat treatment process for 7021 aluminum alloy plates with high electrical conductivity and high performance. The specific technical solution is as follows:

[0005] A heat treatment process for a 7021 aluminum alloy plate with high electrical conductivity and high performance, the heat treatment process comprising the following steps:

[0006] The raw materials of the 7021 aluminum alloy plate are smelted, and then a refining agent is added and argon is used for refining, and the smelting process requires uniform composition, thorough degassing and slag removal, and then a double wire feeder is used to add Al-5Ti-1B wire refiner for grain refinement, and a covering agent is used for covering, filtering, and hot top semi-continuous casting to produce a round ingot with a diameter of 178 mm;

[0007] The round ingot is subjected to extrusion treatment, and the die temperature of the extrusion treatment is 460°C to 490°C, the temperature of the extrusion barrel is 380°C to 400°C, the temperature of the round ingot is 480°C to 510°C, and the extrusion speed is 4m / min to 6m / min to obtain an extruded plate;

[0008] The extruded sheet is subjected to solution treatment, left for more than 72 hours, and then subjected to regression and aging treatment.

[0009] Furthermore, the raw materials for preparing the 7021 aluminum alloy plate include the following components in percentage by mass:

[0010] 0%~0.10% Si, 0%~0.20% Fe, 0%~0.25% Cu, 0%~0.10% Mn, 1.2%~1.6% Mg, 0~0.05% Cr, 5.5%~6.0% Zn, 0.10%~0.18% Zr, 0~0.10% Ti, single impurity element <0.05%, total <0.15%, Al is the balance.

[0011] Furthermore, the temperature of the smelting treatment is 720°C to 750°C.

[0012] Furthermore, the refining temperature is 690°C to 710°C, and the refining time is 30min to 40min.

[0013] Furthermore, the static treatment time is 15 minutes to 20 minutes.

[0014] Furthermore, the filtration adopts double-stage filtration, the first stage filtration adopts a 40-mesh foam ceramic filter plate, and the second stage filtration adopts a 50-mesh foam ceramic filter plate.

[0015] Furthermore, the temperature of the hot top semi-continuous casting is 720° C. to 740° C., the speed is 95 mm / min to 105 mm / min, and the water pressure is 260 KPa to 300 KPa.

[0016] Furthermore, the temperature of the solution treatment is 490°C to 500°C, the holding time is 2h to 3h, and water quenching is performed.

[0017] Furthermore, the process of the regression and aging treatment is: keeping warm at 120℃~125℃ for 24h~28h, keeping warm at 165℃~175℃ for 1h~2h, and keeping warm at 120℃~125℃ for 24h~28h.

[0018] Furthermore, the 7021 aluminum alloy plate has a tensile strength of 500 MPa, a yield strength of 465 MPa, an elongation after fracture of 14.0%, and an electrical conductivity of 38.9% IACS.

[0019] In the above scheme, by optimizing the process conditions of 7021 aluminum alloy sheet, not only the conductivity of 7021 aluminum alloy sheet can be improved, but also its mechanical properties can be significantly improved. By adding a composite refining agent, the internal grain size of 7021 aluminum alloy sheet can be reduced, so that in the subsequent process, it will not cause grain growth and affect the mechanical properties of 7021 aluminum alloy sheet. In addition, by optimizing the parameters of the solid solution process and the regression and aging process, the tensile strength of 7021 aluminum alloy sheet reaches 500MPa, the yield strength reaches 465MPa, the elongation after fracture reaches 14.0%, and the conductivity reaches 38.9%IACS. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with its embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0022] A heat treatment process for a 7021 aluminum alloy plate with high electrical conductivity and high performance in one embodiment of the present invention comprises the following steps:

[0023] The raw materials of the 7021 aluminum alloy plate are smelted, and then a refining agent is added and argon is used for refining, and the smelting process requires uniform composition, thorough degassing and slag removal, and then a double wire feeder is used to add Al-5Ti-1B wire refiner for grain refinement, and a covering agent is used for covering, filtering, and hot top semi-continuous casting to produce a round ingot with a diameter of 178 mm;

[0024] The round ingot is subjected to extrusion treatment, and the die temperature of the extrusion treatment is 460°C to 490°C, the temperature of the extrusion barrel is 380°C to 400°C, the temperature of the round ingot is 480°C to 510°C, and the extrusion speed is 4m / min to 6m / min to obtain an extruded plate;

[0025] The extruded sheet is subjected to solution treatment, left for more than 72 hours, and then subjected to regression and aging treatment.

[0026] In one embodiment, the raw material for preparing the 7021 aluminum alloy plate includes the following components in percentage by mass:

[0027] 0%~0.10% Si, 0%~0.20% Fe, 0%~0.25% Cu, 0%~0.10% Mn, 1.2%~1.6% Mg, 0~0.05% Cr, 5.5%~6.0% Zn, 0.10%~0.18% Zr, 0~0.10% Ti, single impurity element <0.05%, total <0.15%, Al is the balance.

[0028] In one embodiment, the temperature of the smelting process is 720°C to 750°C.

[0029] In one embodiment, the refining temperature is 690° C. to 710° C., and the refining time is 30 min to 40 min.

[0030] In one embodiment, the refining agent is prepared from sodium nitrate, zinc chloride and magnesium chloride in a mass ratio of (1-5): (1-3): (1-7).

[0031] In one embodiment, the preparation method of the refining agent is: adding sodium nitrate, zinc chloride and magnesium chloride into a ball mill, heating to 120°C to 200°C, treating at a speed of 50r / min to 100r / min for 30min to 60min, cooling, then ball milling, sieving, and obtaining a refining agent with a particle size of ≤100mm.

[0032] In one embodiment, the static treatment time is 15 minutes to 20 minutes.

[0033] In one embodiment, the filtration is carried out by double-stage filtration, the first stage filtration uses a 40-mesh foam ceramic filter plate, and the second stage filtration uses a 50-mesh foam ceramic filter plate.

[0034] In one of the embodiments, the temperature of the hot top semi-continuous casting is 720° C. to 740° C., the speed is 95 mm / min to 105 mm / min, and the water pressure is 260 KPa to 300 KPa.

[0035] In one embodiment, the solution treatment temperature is 490°C to 500°C, the holding time is 2h to 3h, and water quenching is performed.

[0036] In one embodiment, the process of the regression and aging treatment is: keeping warm at 120℃~125℃ for 24h~28h, keeping warm at 165℃~175℃ for 1h~2h, and keeping warm at 120℃~125℃ for 24h~28h.

[0037] In one embodiment, the 7021 aluminum alloy plate has a tensile strength of 500 MPa, a yield strength of 465 MPa, an elongation after fracture of 14.0%, and an electrical conductivity of 38.9% IACS.

[0038] The embodiments of the present invention will be described in detail below with reference to specific examples.

[0039] Embodiment 1:

[0040] A raw material for preparing a 7021 aluminum alloy plate includes the following components in percentage by mass:

[0041] 0.10% Si, 0.20% Fe, 0.12% Cu, 0.10% Mn, 1.2% Mg, 0.02% Cr, 5.5% Zn, 0.10% Zr, 0.03% Ti, individual impurity elements <0.05%, total <0.15%, Al is the balance;

[0042] A heat treatment process for a high conductivity and high performance 7021 aluminum alloy plate comprises the following steps:

[0043] Sodium nitrate, zinc chloride and magnesium chloride in a mass ratio of 3:2:5 are added to a ball mill, heated to 120°C, processed at a speed of 50 r / min for 40 minutes, cooled, ball-milled again, and sieved to obtain a refining agent with a particle size of ≤100 mm;

[0044] The raw materials of the 7021 aluminum alloy plate are melted at 720°C, and then a refining agent is added and argon is used to refine at 690°C for 30 minutes, and the smelting process requires uniform composition and thorough degassing and slag removal. Then, a double wire feeder is used to add Al-5Ti-1B wire refiner for grain refinement, and a covering agent is used for covering. Two-stage filtration is used, a 40-mesh foam ceramic filter plate is used for the first stage filtration, and a 50-mesh foam ceramic filter plate is used for the second stage filtration. A round ingot with a diameter of 178 mm is cast by hot top semi-continuous casting at a temperature of 720°C, a speed of 95 mm / min, and a water pressure of 260 KPa.

[0045] The round ingot is subjected to extrusion treatment, and the die temperature of the extrusion treatment is 460° C., the temperature of the extrusion barrel is 380° C., the round ingot temperature is 480° C., and the extrusion speed is 4 m / min to obtain an extruded plate;

[0046] The extruded sheet is solution treated at 490° C. for 2 hours, water quenched, and parked for 80 hours, and then subjected to regression and aging treatment. The process of the regression and aging treatment is: keeping at 120° C. for 24 hours, keeping at 175° C. for 2 hours, and keeping at 120° C. for 24 hours.

[0047] Embodiment 2:

[0048] A raw material for preparing a 7021 aluminum alloy plate includes the following components in percentage by mass:

[0049] 0.05% Si, 0.20% Fe, 0.22% Cu, 0.10% Mn, 1.5% Mg, 0.04% Cr, 5.6% Zn, 0.15% Zr, 0.10% Ti, individual impurity elements <0.05%, total <0.15%, Al is the balance;

[0050] A heat treatment process for a high conductivity and high performance 7021 aluminum alloy plate comprises the following steps:

[0051] Sodium nitrate, zinc chloride and magnesium chloride in a mass ratio of 5:1:4 are added to a ball mill, heated to 150°C, processed at a speed of 50 r / min for 40 minutes, cooled, ball-milled again, and sieved to obtain a refining agent with a particle size of ≤100 mm;

[0052] The raw materials of the 7021 aluminum alloy plate are melted at 750°C, and then a refining agent is added and argon is used to refine at 700°C for 40 minutes, and the smelting process requires uniform composition and thorough degassing and slag removal. Then, a double wire feeder is used to add Al-5Ti-1B wire refiner for grain refinement, and a covering agent is used for covering. Two-stage filtration is used, a 40-mesh foam ceramic filter plate is used for the first stage filtration, and a 50-mesh foam ceramic filter plate is used for the second stage filtration. A round ingot with a diameter of 178 mm is cast by hot top semi-continuous casting at a temperature of 730°C, a speed of 105 mm / min, and a water pressure of 280 KPa.

[0053] The round ingot is subjected to extrusion treatment, and the die temperature of the extrusion treatment is 480° C., the temperature of the extrusion barrel is 400° C., the temperature of the round ingot is 500° C., and the extrusion speed is 5 m / min to obtain an extruded plate;

[0054] The extruded sheet is solution treated at 495° C. for 2 hours, water quenched, and parked for 80 hours, and then subjected to regression and aging treatment. The process of the regression and aging treatment is: insulation at 125° C. for 24 hours, insulation at 170° C. for 2 hours, and insulation at 120° C. for 28 hours.

[0055] Embodiment 3:

[0056] A raw material for preparing a 7021 aluminum alloy plate includes the following components in percentage by mass:

[0057] 0.10% Si, 0.20% Fe, 0.22% Cu, 0.10% Mn, 1.6% Mg, 0.03% Cr, 5.8% Zn, 0.18% Zr, 0.10% Ti, individual impurity elements <0.05%, total <0.15%, Al is the balance;

[0058] A heat treatment process for a high conductivity and high performance 7021 aluminum alloy plate comprises the following steps:

[0059] Sodium nitrate, zinc chloride and magnesium chloride in a mass ratio of 3:2:5 are added to a ball mill, heated to 150°C, processed at a speed of 50 r / min for 45 minutes, cooled, ball-milled again, and sieved to obtain a refining agent with a particle size of ≤100 mm;

[0060] The raw materials of the 7021 aluminum alloy plate are melted at 750°C, and then a refining agent is added and argon is used to refine at 710°C for 40 minutes, and the smelting process requires uniform composition and thorough degassing and slag removal. Then, a double wire feeder is used to add Al-5Ti-1B wire refiner for grain refinement, and a covering agent is used for covering. Two-stage filtration is used, and a 40-mesh foam ceramic filter plate is used for the first stage filtration, and a 50-mesh foam ceramic filter plate is used for the second stage filtration. A round ingot with a diameter of 178 mm is cast by hot top semi-continuous casting at a temperature of 740°C, a speed of 105 mm / min, and a water pressure of 300 KPa.

[0061] The round ingot is subjected to extrusion treatment, and the die temperature of the extrusion treatment is 490° C., the temperature of the extrusion barrel is 400° C., the temperature of the round ingot is 510° C., and the extrusion speed is 6 m / min to obtain an extruded plate;

[0062] The extruded sheet is solution treated at 500° C. for 2 hours, water quenched, and parked for 80 hours, and then subjected to regression and aging treatment. The process of the regression and aging treatment is: keeping at 125° C. for 24 hours, keeping at 170° C. for 1 hour, and keeping at 120° C. for 24 hours.

[0063] Comparative Example 1:

[0064] The difference between Comparative Example 1 and Example 3 is that in Comparative Example 1, only sodium nitrate is used as the refining agent, and the rest is the same as Example 3.

[0065] Comparative Example 2:

[0066] The difference between Comparative Example 2 and Example 3 is that in Comparative Example 2, only sodium chloride is used as the refining agent, and the rest is the same as Example 3.

[0067] Comparative Example 3:

[0068] The difference between Comparative Example 3 and Example 3 is that in Comparative Example 3, only magnesium chloride is used as the refining agent, and the rest is the same as Example 3.

[0069] Comparative Example 4:

[0070] The difference between Comparative Example 4 and Example 3 is that the refining agent in Comparative Example 4 is obtained by mixing sodium nitrate, zinc chloride and calcium chloride in a mass ratio of 1:7:2.

[0071] Comparative Example 5:

[0072] The difference between Comparative Example 5 and Example 3 is that the temperature of the solution treatment in Comparative Example 5 is 430°C, and the T6 aging is performed at 120°C for 24 hours. The rest is the same as Example 3.

[0073] Comparative Example 6:

[0074] The difference between Comparative Example 6 and Example 3 is that the temperature of the solution treatment in Comparative Example 6 is 550°C, and the T6 aging is performed at 120°C for 24 hours. The rest is the same as Example 3.

[0075] Comparative Example 7:

[0076] The difference between Comparative Example 7 and Example 3 is that Comparative Example 7 adopts double-stage aging T7: 120°C insulation for 6h and 160°C insulation for 20h, and the rest is the same as Example 3.

[0077] Comparative Example 8:

[0078] The difference between Comparative Example 8 and Example 3 is that the regression re-aging treatment process in Comparative Example 8 is: keeping at 120° C. for 24 hours, keeping at 200° C. for 1 hour, and keeping at 120° C. for 24 hours, and the rest is the same as Example 3.

[0079] Comparative Example 9:

[0080] The difference between Comparative Example 9 and Example 3 is that the regression and re-aging treatment process in Comparative Example 9 is: keeping at 120° C. for 24 hours, keeping at 170° C. for 3 hours, and keeping at 120° C. for 24 hours, and the rest is the same as Example 3.

[0081] The performance of the 7021 aluminum alloy plates treated in Examples 1 to 3 and the 7021 aluminum alloy plates treated in Comparative Examples 1 to 9 were tested, and the results are shown in Table 1 below.

[0082] Table 1: Performance test results

[0083]

[0084] From the data analysis of Table 1, it can be seen that the refining agent prepared by compounding the components in the present invention is helpful to improve the mechanical properties of the 7021 aluminum alloy plate, and after the process parameters are optimized, the mechanical properties and electrical conductivity can be met to meet the market demand.

[0085] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A heat treatment process for 7021 aluminum alloy sheet with high electrical conductivity and high performance, characterized in that: The heat treatment process comprises the following steps: The raw materials of the 7021 aluminum alloy plate are smelted, and then a refining agent is added and argon is used for refining, and the smelting process requires uniform composition, thorough degassing and slag removal, and then a double wire feeder is used to add Al-5Ti-1B wire refiner for grain refinement, and a covering agent is used for covering, filtering, and hot top semi-continuous casting to produce a round ingot with a diameter of 178 mm; The round ingot is subjected to extrusion treatment, and the die temperature of the extrusion treatment is 460°C to 490°C, the temperature of the extrusion barrel is 380°C to 400°C, the temperature of the round ingot is 480°C to 510°C, and the extrusion speed is 4m / min to 6m / min to obtain an extruded plate; The extruded sheet is subjected to solution treatment, left for more than 72 hours, and then subjected to regression and aging treatment.

2. The heat treatment process according to claim 1, characterized in that: The raw materials for preparing the 7021 aluminum alloy plate include the following components in percentage by mass: 0%~0.10% Si, 0%~0.20% Fe, 0%~0.25% Cu, 0%~0.10% Mn, 1.2%~1.6% Mg, 0~0.05% Cr, 5.5%~6.0% Zn, 0.10%~0.18% Zr, 0~0.10% Ti, single impurity element <0.05%, total <0.15%, Al is the balance.

3. The heat treatment process according to claim 1, characterized in that: The temperature of the smelting treatment is 720°C to 750°C.

4. The heat treatment process according to claim 1, characterized in that: The refining temperature is 690° C. to 710° C., and the refining time is 30 min to 40 min.

5. The heat treatment process according to claim 1, characterized in that: The standing treatment time is 15 min to 20 min.

6. The heat treatment process according to claim 1, characterized in that: The filtration adopts double-stage filtration, the first stage filtration adopts 40 mesh foam ceramic filter plate, and the second stage filtration adopts 50 mesh foam ceramic filter plate.

7. The heat treatment process according to claim 1, characterized in that: The temperature of the hot top semi-continuous casting is 720° C. to 740° C., the speed is 95 mm / min to 105 mm / min, and the water pressure is 260 KPa to 300 KPa.

8. The heat treatment process according to claim 1, characterized in that: The temperature of the solution treatment is 490° C. to 500° C., the holding time is 2 h to 3 h, and the solution treatment is water quenched.

9. The heat treatment process according to claim 1, characterized in that: The process of the regression and aging treatment is: keeping warm at 120°C-125°C for 24h-28h, keeping warm at 165°C-175°C for 1h-2h, and keeping warm at 120°C-125°C for 24h-28h.

10. The heat treatment process according to claim 1, characterized in that: The 7021 aluminum alloy plate has a tensile strength of 500 MPa, a yield strength of 465 MPa, an elongation after fracture of 14.0%, and an electrical conductivity of 38.9% IACS.

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