Processing method of 7-series aluminum alloy

Abstract

The invention discloses a processing treatment method of 7-series aluminum alloy, which overcomes the contradiction that high strength and high corrosion resistance of the existing 7-series aluminum alloy cannot be achieved at the same time, and solves the problems that the material performance of the existing 7-series aluminum alloy aging method cannot be fully exerted or a multi-stage aging process is complicated and poor in applicability. The problems can be well solved, the novel method is easy and convenient to operate, and the prepared 7-series aluminum alloy material is higher in strength and better in corrosion resistance and meets the use requirement; in addition, by combining optimization of chemical components and adding a certain amount of Zr and Sc elements, recrystallization is synergistically inhibited, the strength of the aluminum alloy is improved, meanwhile, by combining with the Mn element, the toughness of the aluminum alloy is synergistically improved, Al3Sc nanoparticles are formed by Sc, the structure is refined, the corrosion resistance is improved, the galvanic corrosion of a grain boundary precipitated phase is further reduced by combining with a subsequent treatment process, and the corrosion resistance of the aluminum alloy is improved. And the 7-series aluminum alloy with the strength, toughness and corrosion resistance meeting the requirements is integrally obtained.

Description

Technical Field

[0001] The present invention relates to the field of material processing, and more particularly, to a processing method for 7-series aluminum alloy. Background Art

[0002] 7-series aluminum alloy is a typical medium-strength alloy in the Al-Zn-Mg system. This alloy has good plastic processing performance and moderate strength after artificial aging. 7-series aluminum alloy is a good choice for aluminum alloy poles and towers. Since the online quenching after extrusion processing of general 7-series alloy cannot achieve the ideal solution treatment effect, offline quenching is required to obtain higher strength and its mechanical properties, while offline quenching will increase the manufacturing cost. After solution quenching, aging and other process treatments, better working performance can be obtained. The heat treatment process of aluminum alloy directly affects the microstructure change, recrystallization, and solid solution degree of strengthening elements of aluminum alloy, thus affecting the final mechanical properties of the alloy. With the urgent market demand for higher-performance 7-series aluminum alloy, the conventional heat treatment currently used cannot meet the current production requirements. At present, comprehensive properties such as strength, fracture toughness, and corrosion resistance have become the main assessment indicators for high-performance aluminum alloy. There are various aging treatment systems for 7-series aluminum alloy. Among them, peak aging can make the aluminum alloy obtain higher strength, but the corrosion resistance and fracture toughness are poor; over-aging (T74) can improve the corrosion resistance and fracture toughness of the aluminum alloy, but it is at the expense of strength. This urgently requires a processing method that can simultaneously improve the strength, fracture toughness, and corrosion resistance of aluminum alloy, so that the strength, fracture toughness, and corrosion resistance can all meet the market demand.

[0003] In addition, at present, the conventional aging process of 7-series aluminum alloy is generally single-stage aging or two-stage aging with low temperature first and then high temperature. This kind of aging process generally improves the corrosion resistance by sacrificing a certain strength to achieve over-aging. Regression re-aging or three-stage aging has a short high-temperature regression treatment with high temperature and short time. Therefore, it has high requirements for equipment, poor operation convenience, and uneven performance is likely to occur in thicker materials. In the past ten years or so, some non-isothermal aging processes and processes introducing non-isothermal into regression re-aging have emerged. However, most of them use a constant heating rate, or put forward the idea of changing the heating rate but the rate design is unreasonable, the performance of the material cannot be fully exerted, and there are problems such as many operation steps, complicated process, and high requirements for equipment. Summary of the Invention

[0004] The object of the present invention is to provide an aging heat treatment method for 7xxx series aluminum alloy materials, to overcome the contradiction that the high strength, fracture toughness and corrosion resistance of existing 7xxx series aluminum alloys cannot be achieved simultaneously, and to solve the problems that the material properties of existing aging methods for 7xxx series aluminum alloys are not fully utilized or the multi-stage aging process is cumbersome and has poor applicability. The present invention can well solve the above problems. The proposed new method is easy to operate, and the prepared 7xxx series aluminum alloy material has higher strength and better corrosion resistance, meeting the use requirements. The specific technical solutions are as follows:

[0005] A processing method for 7xxx series aluminum alloy, comprising the following steps:

[0006] Prepare a 7xxx series aluminum alloy material;

[0007] Subject the 7xxx series aluminum alloy material to be processed to solution treatment or online quenching;

[0008] Then pre-stretch the 7xxx series aluminum alloy material at 0.5 - 3%;

[0009] Saw cut the stretched 7xxx series aluminum alloy material according to a set length, and then naturally park it at room temperature. The natural parking time at room temperature is: 0 < t0 ≤ 168 h;

[0010] Among them, the 7xxx series aluminum alloy material comprises the following components by mass percentage: Si: 0.2 - 0.5%, Fe: ≤0.2%, Cu: 1.2 - 2.3%, Mg: 1.3 - 2.6%, Mn: 0.1 - 0.3%, Zn: 4.1 - 6.7%, Ti: 0.05 - 0.08%, Zr: 0.01 - 0.03%, Sc: 0.03 - 0.05%, other single elements ≤0.05%, the total amount of other impurity elements ≤0.15%, and the balance is Al.

[0011] Further, the preparation method of the 7xxx series aluminum alloy material further comprises melting, refining and impurity removal, continuous casting and extrusion forming.

[0012] Further, the temperature of the melting is 745 - 760°C. After all the aluminum alloy raw materials are melted, a refining agent and a covering agent are added, the slag is skimmed, the melt composition is detected online. After the composition is qualified, the melt is statically placed for 15 - 20 min, and the gas and slag in the melt are removed again. Subsequently, continuous casting is carried out at a temperature of 700 - 720°C to obtain an ingot, and then extrusion treatment is carried out. The conditions for the extrusion treatment are: the temperature of the extrusion cylinder is 400 - 450°C, the temperature of the extrusion die is 450 - 470°C; the preheating temperature of the ingot is 460 - 480°C; the extrusion ratio is 10 - 30, and the extrusion speed is 1.0 - 3.0 mm / min.

[0013] Furthermore, in the artificial aging treatment stage: Then put the 7-series aluminum alloy material into the aging furnace, heat it from the current starting temperature to 130-150 °C in the aging furnace at the first heating rate V1, then continue to heat it to 170-220 °C at the second heating rate V2, and then cool it to 130-150 °C and the starting temperature at the second cooling rate V21 and the first cooling rate V11 respectively. Finally, heat it to 130-170 °C again at the third heating rate V3. Finally, take out the 7-series aluminum alloy material from the aging furnace and cool it to room temperature to complete the treatment of the 7-series aluminum alloy material.

[0014] Furthermore, the stretching treatment is carried out at room temperature with an elongation rate of 2%-3%.

[0015] Furthermore, the natural parking time at room temperature is: 0 < t0 ≤ 72h.

[0016] Furthermore, the first heating rate V1 is: 5 °C ≤ V1 ≤ 20 °C / h; the first cooling rate V11 is: 5 °C ≤ V11 ≤ 20 °C / h.

[0017] Furthermore, the first heating rate V1 is: 5 °C ≤ V1 ≤ 10 °C / h; the first cooling rate V11 is: 5 °C ≤ V11 ≤ 10 °C / h.

[0018] Furthermore, the second heating rate V2 is: 20 °C ≤ V2 ≤ 40 °C / h; the second cooling rate V21 is: 20 °C ≤ V21 ≤ 40 °C / h.

[0019] Furthermore, the third heating rate V3 is: 5 °C ≤ V3 ≤ 40 °C / h.

[0020] 1. The purpose of the present invention is to provide a processing method for 7-series aluminum alloy materials, which overcomes the contradiction that the strength, toughness and corrosion resistance of existing �-series aluminum alloys cannot be achieved at the same time, and the prepared 7-series aluminum alloy materials have better strength, toughness and corrosion resistance, meeting the use requirements.

[0021] 2. Through the optimization of the 7-series aluminum alloy composition in this application, a certain amount of Zr and Sc elements are added to synergistically inhibit recrystallization, which helps to improve the strength of the aluminum alloy. At the same time, combined with Mn elements, it synergistically provides the toughness of the aluminum alloy, and Sc forms Al3Sc nanometer particles, which refine the structure and improve the corrosion resistance. Combined with the subsequent treatment process, the galvanic corrosion of grain boundary precipitation phases is further reduced, and 7-series aluminum alloys with strength, toughness and corrosion resistance meeting the requirements are obtained as a whole. Specific embodiments

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with its embodiments. It should be understood that the specific implementation manners described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific implementation manners and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0024] The present invention provides a processing method for 7-series aluminum alloy, including the following steps:

[0025] Prepare 7-series aluminum alloy materials;

[0026] Subject the 7-series aluminum alloy materials to be processed to solution treatment or online quenching treatment;

[0027] Let the aluminum alloy materials after solution treatment or online quenching stand naturally at room temperature for 0 - 168 h, then heat the materials in an aging furnace from room temperature or a certain temperature T1 higher than room temperature to a certain temperature T2 between 130 - 150 °C at a first heating rate V1, then continue to heat it to a certain temperature T3 between 170 - 220 °C at a second heating rate V2, then cool it to T2 and T1 at a second cooling rate V21 and a first cooling rate V11 respectively, and finally heat it to a certain temperature T4 between 13-170 °C at a third heating rate V3 again, and finally take it out of the furnace and cool it to room temperature. After the continuous heating and continuous cooling with the two heating / cooling rates described in the present invention and then applying continuous heating treatment again, the corrosion resistance of the prepared materials is equivalent to or better than that of T73 aging, and at the same time, its strength is much higher than that of ordinary T6 aging treatment.

[0028] A processing method for 7-series aluminum alloy in an embodiment of the present invention includes the following steps:

[0029] Prepare 7-series aluminum alloy materials;

[0030] Subject the 7-series aluminum alloy materials to be processed to solution treatment or online quenching treatment;

[0031] Then pre-stretch the 7-series aluminum alloy materials by 0.5 - 3%;

[0032] Saw the stretched 7-series aluminum alloy materials to a set length, and then let them stand naturally at room temperature, and the natural standing time at room temperature is: 0 < t0 ≤ 168 h;

[0033] Artificial aging treatment stage: Then place the 7-series aluminum alloy material in an aging furnace and heat it from the current starting temperature to 130 - 150°C at the first heating rate V1 in the aging furnace. Then continue to heat it to 170 - 220°C at the second heating rate V2. Then cool it to 130 - 150°C and the starting temperature at the second cooling rate V21 and the first cooling rate V11 respectively. Finally, heat it to 130 - 170°C again at the third heating rate V3. Finally, take out the 7-series aluminum alloy material from the aging furnace and cool it to room temperature to complete the treatment of the 7-series aluminum alloy material.

[0034] In one embodiment, the 7-series aluminum alloy material comprises the following components by mass percentage: Si: 0.2 - 0.5%, Fe: ≤0.2%, Cu: 1.2 - 2.3%, Mg: 1.3 - 2.6%, Mn: 0.1 - 0.3%, Zn: 4.1 - 6.7%, Ti: 0.05 - 0.08%, Zr: 0.01 - 0.03%, Sc: 0.03 - 0.05%, other single elements ≤0.05%, total amount of other impurity elements ≤0.15%, and the balance is Al.

[0035] In one embodiment, the preparation method of the 7-series aluminum alloy material further comprises melting, refining and impurity removal, continuous casting and extrusion molding.

[0036] In one embodiment, the temperature of the melting is 745 - 760°C. After all the aluminum alloy raw materials are melted, add a refining agent and a covering agent, skim the slag, and on-line detect the melt composition. After the composition is qualified, let the melt stand for 15 - 20 min, remove the gas and slag in the melt again, and then conduct continuous casting at a temperature of 700 - 720°C to obtain an ingot, and then conduct extrusion treatment. The conditions for the extrusion treatment are: the temperature of the extrusion cylinder is 400 - 450°C, the temperature of the extrusion die is 450 - 470°C; the preheating temperature of the ingot is 460 - 480°C; the extrusion ratio is 10 - 30, and the extrusion speed is 1.0 - 3.0 mm / min.

[0037] In one embodiment, the stretching treatment is carried out at room temperature, and the elongation is 2% - 3%.

[0038] In one embodiment, the room temperature natural parking time is: 0 < t0 ≤ 72 h.

[0039] In one embodiment, the first heating rate V1 is less than the second heating rate V2; the first cooling rate V11 is less than the second cooling rate V21.

[0040] In one embodiment, the first heating rate V1 is: 5°C ≤ V1 ≤ 20°C / h; the first cooling rate V11 is: 5°C ≤ V11 ≤ 20°C / h.

[0041] In one embodiment, the first heating rate V1 is: 5°C ≤ V1 ≤ 10°C / h; the first cooling rate V11 is: 5°C ≤ V11 ≤ 10°C / h.

[0042] In one embodiment, the second heating rate V2 is: 20°C ≤ V2 ≤ 40°C / h; the second cooling rate V21 is: 20°C ≤ V21 ≤ 40°C / h.

[0043] In one embodiment, the third heating rate V3 is: 5°C ≤ V3 ≤ 40°C / h.

[0044] In one embodiment, the starting temperature at which the 7xxx series aluminum alloy starts to be heated at the first heating rate V1 in the aging furnace is room temperature, or a certain temperature higher than room temperature and less than 100°C.

[0045] In one embodiment, the solutionizing or in-line quenching temperature is 450 - 550°C.

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0047] The implementation solutions of the present invention will be described in detail below in conjunction with specific embodiments.

[0048] Example 1:

[0049] A processing method for a 7xxx series aluminum alloy, comprising the following steps:

[0050] The 7xxx series aluminum alloy material comprises the following components by mass percentage: Si: 0.3%, Fe: 0.05%, Cu: 2.1%, Mg: 1.8%, Mn: 0., Zn: 4.1%, Ti: 0.05%, Zr: 0.03%, Sc: 0.03%, other single elements ≤ 0.05%, total amount of other impurity elements ≤ 0.15%, and the balance is Al;

[0051] According to the composition of the 7xxx series aluminum alloy material, the raw materials are melted at a temperature of 750 °C. After all the aluminum alloy raw materials are melted, a refining agent and a covering agent are added. The slag is skimmed off, and the melt composition is detected online. After the composition is qualified, the melt is allowed to stand for 20 min, and the gas and slag in the melt are removed again. Subsequently, continuous casting is carried out at a temperature of 720 °C to obtain an ingot, which is then subjected to extrusion treatment. The conditions for the extrusion treatment are as follows: the temperature of the extrusion cylinder is 420 °C, the temperature of the extrusion die is 470 °C; the preheating temperature of the ingot is 460 °C; the extrusion ratio is 30, and the extrusion speed is 2.0 mm / min.

[0052] The 7xxx series aluminum alloy material to be processed is subjected to solution or online quenching treatment at 450 °C.

[0053] Then the 7xxx series aluminum alloy material is stretched at an elongation rate of 1%.

[0054] The stretched 7xxx series aluminum alloy material is sawed to a set length and then left to stand naturally at room temperature for 168 h.

[0055] Artificial aging treatment stage: Then the 7xxx series aluminum alloy material is placed in an aging furnace and heated from the current starting temperature to 130 °C at a first heating rate V1, then continuously heated to 170 °C at a second heating rate V2. Then, it is cooled to 130 °C and the starting temperature at a second cooling rate V21 and a first cooling rate V11 respectively. Finally, it is heated to 130 °C again at a third heating rate V3. Finally, the 7xxx series aluminum alloy material is taken out of the aging furnace and cooled to room temperature to complete the treatment of the 7xxx series aluminum alloy material.

[0056] The starting temperature at which the 7xxx series aluminum alloy starts to be heated in the aging furnace at a heating rate V1 is room temperature.

[0057] The first heating rate V1 is 5 °C / h; the first cooling rate V11 is 5 °C / h.

[0058] The second heating rate V2 is 20 °C / h; the second cooling rate V21 is 20 °C / h.

[0059] The third heating rate V3 is 5 °C / h.

[0060] Example No.: 2

[0061] A processing method for a 7xxx series aluminum alloy, comprising the following steps:

[0062] The 7xxx series aluminum alloy material comprises the following components by mass percentage: Si: 0.3%, Fe: 0.05%, Cu: 1.2%, Mg: 1.8%, Mn: 0.2%, Zn: 4.2%, Ti: 0.06%, Zr: 0.02%, Sc: 0.03%, other single elements ≤ 0.05%, total amount of other impurity elements ≤ 0.15%, and the balance is Al;

[0063] According to the components of the 7xxx series aluminum alloy material, the raw materials are melted at a temperature of 750 °C. After all the aluminum alloy raw materials are melted, a refining agent and a covering agent are added, the slag is skimmed off, and the melt composition is detected online. After the composition is qualified, the melt is allowed to stand for 20 min, and the gas and slag in the melt are removed again. Subsequently, continuous casting is carried out at a temperature of 720 °C to obtain an ingot, which is then subjected to extrusion treatment. The conditions for the extrusion treatment are as follows: the temperature of the extrusion cylinder is 420 °C, the temperature of the extrusion die is 470 °C; the preheating temperature of the ingot is 460 °C; the extrusion ratio is 30, and the extrusion speed is 2.0 mm / min;

[0064] The 7xxx series aluminum alloy material to be processed is subjected to solution treatment or online quenching treatment at 550 °C;

[0065] Then the 7xxx series aluminum alloy material is stretched at an elongation rate of 3%;

[0066] The stretched 7xxx series aluminum alloy material is sawed into a set length, and then left to stand naturally at room temperature. The duration of natural standing at room temperature is 168 h;

[0067] Artificial aging treatment stage: Then the 7xxx series aluminum alloy material is put into an aging furnace and heated from the current starting temperature to 150 °C at a first heating rate V1, then continuously heated to 220 °C at a second heating rate V2, and then cooled to 150 °C and the starting temperature at a second cooling rate V21 and a first cooling rate V11 respectively. Finally, it is heated to 170 °C again at a third heating rate V3. Finally, the 7xxx series aluminum alloy material is taken out of the aging furnace and cooled to room temperature to complete the treatment of the 7xxx series aluminum alloy material.

[0068] The starting temperature at which the 7xxx series aluminum alloy starts to be heated in the aging furnace at a heating rate V1 is room temperature.

[0069] The first heating rate V1 is 20 °C / h; the first cooling rate V11 is 20 °C / h.

[0070] The second heating rate V2 is 40 °C / h; the second cooling rate V21 is 40 °C / h.

[0071] The third heating rate V3 is 40 °C / h.

[0072] Example 3:

[0073] A processing method for 7-series aluminum alloy, comprising the following steps:

[0074] The 7-series aluminum alloy material comprises the following components by mass percentage: Si: 0.4%, Fe: 0.06%, Cu: 2.3%, Mg: 2.0%, Mn: 0.3%, Zn: 4.5%, Ti: 0.06%, Zr: 0.03%, Sc: 0.04%, other single elements ≤ 0.05%, total amount of other impurity elements ≤ 0.15%, and the balance is Al;

[0075] According to the components of the 7-series aluminum alloy material, the raw materials are melted at a temperature of 760 °C. After all the aluminum alloy raw materials are melted, a refining agent and a covering agent are added, the slag is skimmed off, and the melt composition is detected online. After the composition is qualified, the melt is allowed to stand for 20 min, and the gas and slag in the melt are removed again. Subsequently, continuous casting is carried out at a temperature of 720 °C to obtain an ingot, and then extrusion treatment is carried out. The conditions for the extrusion treatment are: the temperature of the extrusion cylinder is 450 °C, the temperature of the extrusion die is 470 °C; the preheating temperature of the ingot is 450 °C; the extrusion ratio is 30, and the extrusion speed is 2.0 mm / min;

[0076] The 7-series aluminum alloy material to be processed is subjected to solution or online quenching treatment at 500 °C;

[0077] Then the 7-series aluminum alloy material is stretched at an elongation rate of 2%;

[0078] The stretched 7-series aluminum alloy material is sawed to a set length, and then naturally parked at room temperature. The natural parking time at room temperature is 100 h;

[0079] Artificial aging treatment stage: Then the 7-series aluminum alloy material is put into an aging furnace and heated from the current starting temperature to 140 °C at a first heating rate V1 in the aging furnace, then continuously heated to 200 °C at a second heating rate V2, and then cooled to 140 °C and the starting temperature at a second cooling rate V21 and a first cooling rate V11 respectively. Finally, it is heated to 140 °C again at a third heating rate V3. Finally, the 7-series aluminum alloy material is taken out of the aging furnace and cooled to room temperature to complete the treatment of the 7-series aluminum alloy material.

[0080] The starting temperature at which the 7-series aluminum alloy starts to be heated at a heating rate V1 in the aging furnace is 90 °C.

[0081] The first heating rate V1 is 10 °C / h; the first cooling rate V11 is 10 °C / h.

[0082] The second heating rate V2 is 30 °C / h; the second cooling rate V21 is 30 °C / h.

[0083] The third heating rate V3 is 30 °C / h.

[0084] Example 4:

[0085] A processing method for 7xxx series aluminum alloy, comprising the following steps:

[0086] The 7xxx series aluminum alloy material comprises the following components by mass percentage: Si: 0.5%, Fe: 0.05%, Cu: 2.3%, Mg: 2.2%, Mn: 0.3%, Zn: 4.2%, Ti: 0.06%, Zr: 0.03%, Sc: 0.05%, other single elements ≤ 0.05%, total amount of other impurity elements ≤ 0.15%, and the balance is Al;

[0087] According to the components of the 7xxx series aluminum alloy material, the raw materials are melted at a temperature of 760 °C. After all the aluminum alloy raw materials are melted, a refining agent and a covering agent are added, the slag is skimmed off, and the melt composition is detected online. After the composition is qualified, the melt is allowed to stand for 20 min, and the gas and slag in the melt are removed again. Subsequently, continuous casting is carried out at a temperature of 720 °C to obtain an ingot, and then extrusion treatment is carried out. The conditions for the extrusion treatment are: the temperature of the extrusion cylinder is 450 °C, the temperature of the extrusion die is 470 °C; the preheating temperature of the ingot is 460; the extrusion ratio is 30, and the extrusion speed is 2.0 mm / min;

[0088] The 7xxx series aluminum alloy material to be processed is subjected to solution or online quenching treatment at 480 °C.

[0089] Then the 7xxx series aluminum alloy material is stretched at an elongation rate of 2%.

[0090] The stretched 7xxx series aluminum alloy material is sawed into a set length, and then left to stand naturally at room temperature. The duration of natural standing at room temperature is 72 h;

[0091] Artificial aging treatment stage: Then the 7xxx series aluminum alloy material is put into an aging furnace and heated from the current starting temperature to 135 °C at a first heating rate V1 in the aging furnace, then continued to be heated to 180 °C at a second heating rate V2, and then cooled to 135 °C and the starting temperature at a second cooling rate V21 and a first cooling rate V11 respectively. Finally, it is heated to 135 °C again at a third heating rate V3. Finally, the 7xxx series aluminum alloy material is taken out of the aging furnace and cooled to room temperature to complete the treatment of the 7xxx series aluminum alloy material.

[0092] The starting temperature at which the 7xxx series aluminum alloy starts to be heated at a heating rate V1 in the aging furnace is 50 °C.

[0093] The first heating rate V1 is 15 °C / h; the first cooling rate V11 is 15 °C / h.

[0094] The second heating rate V2 is 25 °C / h; the second cooling rate V21 is 25 °C / h.

[0095] The third heating rate V3 is 25 °C / h.

[0096] Comparative Example 1:

[0097] Compared with Example 1, the composition of the 7xxx series aluminum alloy in Comparative Example 1 does not include the Mn element, and the others are the same as in Example 1.

[0098] Comparative Example 2:

[0099] Compared with Example 1, the composition of the 7xxx series aluminum alloy in Comparative Example 2 does not include the Zr element, and the others are the same as in Example 1.

[0100] Comparative Example 3:

[0101] Compared with Example 1, the composition of the 7xxx series aluminum alloy in Comparative Example 3 does not include the Sc element, and the others are the same as in Example 1.

[0102] Comparative Example 4:

[0103] Compared with Example 1, the process conditions in Comparative Example 4 are as follows, and the others are the same as in Example 1;

[0104] The starting temperature at which the 7xxx series aluminum alloy starts to be heated in the aging furnace at the heating rate V1 is room temperature.

[0105] The first heating rate V1 is 20 °C / h; the first cooling rate V11 is 20 °C / h.

[0106] The second heating rate V2 is 5 °C / h; the second cooling rate V21 is  5 °C / h.

[0107] The third heating rate V3 is 15 °C / h.

[0108] Comparative Example 5:

[0109] Compared with Example 1, the process conditions in Comparative Example 5 are as follows, and the others are the same as in Example 1;

[0110] The starting temperature at which the 7xxx series aluminum alloy starts to be heated in the aging furnace at the heating rate V1 is room temperature.

[0111] The first heating rate V1 is 20 °C / h; the first cooling rate V11 is 5 °C / h.

[0112] The second heating rate V2 is 10 °C / h; the second cooling rate V21 is 10 °C / h.

[0113] The third heating rate V3 is 3 °C / h.

[0114] The relevant performance of the samples of the 7-series aluminum alloy materials in Examples 1-4 and the comparative samples of the 7-series aluminum alloy materials in Comparative Examples 1-5 was detected, and the results are shown in Table 1 below.

[0115] Table 1:

[0116]

[0117]

[0118] The present invention provides an aging heat treatment method applicable to 7-series aluminum alloys, including the following steps: The aluminum alloy material after solution treatment or online quenching is parked at room temperature for 0-168 h naturally, and then the material is heated in an aging furnace from room temperature or a certain temperature T1 higher than room temperature to a certain temperature T2 between 130-150 °C at a first heating rate V1, then it is continuously heated to a certain temperature T3 between 170-220 °C at a second heating rate V2, then it is cooled to T2 and T1 at a second cooling rate V21 and a first cooling rate V11 respectively, and finally it is heated to a certain temperature T4 between 130-170 °C again at a third heating rate V3, and finally taken out of the furnace and cooled to room temperature. After the continuous heating and continuous cooling with the two heating / cooling rates described in the present invention and then applying continuous heating again, the corrosion resistance of the prepared material is equivalent to or better than that of T73 aging. At the same time, its strength is much higher than that of ordinary T6 aging treatment. In addition, from the data analysis in Comparative Examples 1-3, it can be seen that by optimizing the chemical composition, the present application also helps to improve the strength, toughness and corrosion resistance of 7-series aluminum alloys, and overall obtains 7-series aluminum alloys with strength, toughness and corrosion resistance meeting the requirements.

[0119] The purpose of the present invention is to provide an aging heat treatment method for 7-series aluminum alloy materials, to overcome the contradiction that high strength and high corrosion resistance cannot be achieved simultaneously in existing 7-series aluminum alloys, and to solve the problems that the material properties of existing 7-series aluminum alloy aging methods are not fully utilized or the multi-stage aging process is cumbersome and the applicability is poor. The present invention can well solve the above problems. The proposed new method is simple to operate, and the prepared 7-series aluminum alloy material has higher strength and better corrosion resistance, meeting the use requirements.

[0120] After simple adjustment by those skilled in the art, the present invention can also be applied to the aging heat treatment of other series of aluminum alloys such as 6-series and 2-series.

[0121] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brief description, not all possible combinations of the technical features in the above embodiments are described. However, as long as these technical feature combinations do not conflict, they should be considered as the scope described in this specification.

[0122] The embodiments described above only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A processing method for 7-series aluminum alloy, characterized in that, It includes the following steps: Prepare a 7xxx series aluminum alloy material; Subject the 7xxx series aluminum alloy material to be processed to solution treatment or online quenching; Then pre-stretch the 7xxx series aluminum alloy material at 0.5 - 3%; Saw cut the stretched 7xxx series aluminum alloy material to a set length, and then let it stand naturally at room temperature, where the natural standing time at room temperature is: 0 < t0 ≤ 168 h; Among them, the 7xxx series aluminum alloy material includes the following components by mass percentage: Si: 0.2 - 0.5%, Fe: ≤0.2%, Cu: 1.2 - 2.3%, Mg: 1.3 - 2.6%, Mn: 0.1 - 0.3%, Zn: 4.1 - 6.7%, Ti: 0.05 - 0.08%, Zr: 0.01 - 0.03%, Sc: 0.03 - 0.05%, other single elements ≤0.05%, the total amount of other impurity elements ≤0.15%, and the balance is Al.

2. The processing method of the 7-series aluminum alloy according to claim 1, characterized in that, The preparation method of the 7xxx series aluminum alloy material also includes melting, refining and impurity removal, continuous casting, and extrusion molding.

3. The processing method of the 7-series aluminum alloy according to claim 2, characterized in that, The temperature of the melting is 745 - 760 °C. After all the aluminum alloy raw materials are melted, a refining agent and a covering agent are added, the slag is skimmed off, and the melt composition is detected online. After the composition is qualified, the melt is allowed to stand for 15 - 20 min, and the gas and slag in the melt are removed again. Subsequently, continuous casting is carried out at a temperature of 700 - 720 °C to obtain an ingot, and then extrusion treatment is performed. The conditions for the extrusion treatment are: the temperature of the extrusion cylinder is 400 - 450 °C, the temperature of the extrusion die is 450 - 470 °C; the preheating temperature of the ingot is 460 - 480 °C; the extrusion ratio is 10 - 30, and the extrusion speed is 1.0 - 3.0 mm / min.

4. The processing method of the 7-series aluminum alloy according to claim 1, wherein, Artificial aging treatment stage: Then put the 7xxx series aluminum alloy material into an aging furnace, heat it from the current starting temperature to 130 - 150 °C at the first heating rate V1 in the aging furnace, then continue to heat it to 170 - 220 °C at the second heating rate V2, then cool it to 130 - 150 °C and the starting temperature at the second cooling rate V21 and the first cooling rate V11 respectively, and finally heat it to 130 - 170 °C again at the third heating rate V3. Finally, take out the 7xxx series aluminum alloy material from the aging furnace and cool it to room temperature to complete the treatment of the 7xxx series aluminum alloy material.

5. The processing method of the 7-series aluminum alloy according to claim 1, characterized in that, The stretching treatment is carried out at room temperature, and the elongation is 2% - 3%.

6. The processing method of the 7-series aluminum alloy according to claim 1, wherein The natural standing time at room temperature is: 0 < t0 ≤ 72 h.

7. The processing method of 7-series aluminum alloy according to claim 1, characterized in that, The first heating rate V1 is: 5 °C ≤ V1 ≤ 20 °C / h; the first cooling rate V11 is: 5 °C ≤ V11 ≤ 20 °C / h.

8. The processing method of the 7-series aluminum alloy according to claim 1, characterized in that, The first heating rate V1 is: 5 °C ≤ V1 ≤ 10 °C / h; the first cooling rate V11 is: 5 °C ≤ V11 ≤ 10 °C / h.

9. The processing method of the 7-series aluminum alloy according to claim 1, characterized in that, The second heating rate V2 is: 20 °C ≤ V2 ≤ 40 °C / h; the second cooling rate V21 is: 20 °C ≤ V21 ≤ 40 °C / h.

10. The processing method of the 7-series aluminum alloy according to claim 1, wherein, The third heating rate V3 is: 5 °C ≤ V3 ≤ 40 °C / h.

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