7-series aluminum alloy plate as well as preparation method and application thereof

Abstract

The invention provides a 7-series aluminum alloy plate as well as a preparation method and application thereof. The preparation method comprises the steps that raw materials of the 7-series aluminum alloy plate are sequentially subjected to smelting, casting treatment, homogenization treatment and hot rolling treatment, and a first plate is obtained; the first plate is subjected to solid solution heat treatment including a solid solution heating stage and a solid solution heat preservation stage, and a second plate is obtained; the second plate is subjected to aging treatment, and the 7-series aluminum alloy plate is obtained; the time used in the solid solution heating stage is equal to the product of the solid solution heating coefficient and the plate thickness, and the solid solution heating coefficient is 0.8-2.8 min / mm; the time used in the solid solution heat preservation stage is equal to the product of the solid solution heat preservation coefficient and the plate thickness, and the solid solution heat preservation coefficient is 0.5-2.5 min / mm. According to the method, various parameters of solid solution heat treatment are accurately controlled, so that the internal structure uniformity and purity of the obtained 7-series aluminum alloy thick plate are effectively ensured, and the mechanical property of the plate is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy material processing, and in particular to a 7 series aluminum alloy plate, a preparation method and application thereof. Background Art

[0002] Aviation aluminum alloys have developed rapidly in the past 20 to 30 years, and advanced new 2xxx, 7xxx (i.e. 2 series and 7 series) and aluminum-lithium alloys have been widely researched and developed. In particular, 7 series alloys, as representatives of ultra-high strength aluminum alloys, have long occupied a very important position in the aerospace field.

[0003] For 7xxx alloys with high component contents such as 7050, during the casting and solidification process, the various alloy elements in its components are unevenly distributed due to component segregation, forming a large number of multi-type non-equilibrium crystalline phases, which have a certain "genetic" effect on the subsequent organization of the alloy. Especially for aluminum alloy plates, after homogenization and hot rolling, there are still some residual S phases after equalization, as well as second phases such as MgZn2 and T phases that precipitate and coarsen during the subsequent processing, which are not conducive to the aging precipitation strengthening effect of the later plate; and because these phases are too large in size, they are not conducive to the performance of the later finished plate, so it is necessary to eliminate the phases in the plate through another high-temperature heat treatment, that is, solid solution treatment, so as to fully dissolve the solute atoms back into the aluminum alloy matrix.

[0004] However, the solution time for 7xxx thick plate products can only be determined based on experience. At the same time, due to the lack of understanding of the solid solution evolution effect of the actual product structure, the solid solution time is often higher than the actual plate demand, resulting in energy waste and limited production, and at the same time it is not conducive to the plate structure performance. The short-time solid solution and two-stage solid solution process schemes used in existing reports are all for small-size samples or thin plate products for rapid solid solution, which is difficult to match in the actual large-size thick plate production, and is not applicable to the solid solution treatment of thick plates and ultra-thick plates. In general, there is no reasonable method to determine the solid solution heat treatment time in combination with the thickness segment for large-size 7 series aluminum alloy thick plates. Therefore, it is necessary to combine the organizational characteristics and temperature field evolution laws of large-size industrial thick plates to formulate a more scientific and reasonable solid solution process system, correspond the process to the plate thickness specifications, and more effectively realize process control, so as to achieve full solid solution of the plate in a targeted manner in a shorter time, and at the same time make the final performance of the obtained plate not lower than the existing process, thereby improving production efficiency and obtaining an aged alloy thick plate with excellent performance.

[0005] Based on this, how to optimize the preparation method of 7 series aluminum alloy plates to significantly reduce the proportion of the second phase in their internal metallographic structure, and then comprehensively improve their mechanical strength and plasticity, is one of the important technical problems that need to be solved in this field. Summary of the invention

[0006] The main purpose of the present invention is to provide a 7 series aluminum alloy plate, a preparation method and application thereof, so as to solve the problem that the solid solution system of the 7 series aluminum alloy plate in the prior art is unreasonable and it is difficult to obtain excellent mechanical properties in a shorter solid solution heat treatment time.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides a method for preparing a 7 series aluminum alloy plate, comprising: step S1, smelting and casting the raw material of the 7 series aluminum alloy plate to obtain an ingot; step S2, homogenizing the ingot to obtain a homogenized ingot, and hot rolling the homogenized ingot to obtain a first plate with a plate thickness of 25 mm to 200 mm; step S3, performing a solution heat treatment including a solution heating stage and a solution heat preservation stage on the first plate to obtain a second plate; step S4, performing an aging treatment on the second plate to obtain a 7 series aluminum alloy plate; the temperature of the solution heating stage is 460°C to 490°C, and the time used in the solution heating stage is recorded as T 升 , then T 升 =solid solution heating coefficient × plate thickness, solid solution heating coefficient is 0.8min / mm~2.8min / mm; the time used in the solid solution insulation stage is recorded as T 保 , then T 保 =solid solution thermal insulation coefficient×plate thickness, the solid solution thermal insulation coefficient is 0.5min / mm~2.5min / mm.

[0008] Furthermore, the solid solution heating coefficient is 1.0 min / mm to 2.5 min / mm, and the solid solution insulation coefficient is 0.5 min / mm to 1.9 min / mm; preferably, the temperature in the solid solution heating stage is 475°C to 480°C.

[0009] Further, the plate thickness is 25mm~50mm, the solid solution heating coefficient is 1.4min / mm~2.8min / mm, preferably 1.6min / mm~2.5min / mm, and the solid solution insulation coefficient is 1.1min / mm~2.4min / mm, preferably 1.1min / mm~1.9min / mm; or, the plate thickness is 51mm~75mm, the solid solution heating coefficient is 1.3min / mm~2.6min / mm, preferably 1.5min / mm~2.3min / mm, and the solid solution insulation coefficient is 1.0min / mm~2.2min n / mm, preferably 1.0min / mm~1.75min / mm; or, the plate thickness is 76mm~100mm, the solid solution heating coefficient is 1.2min / mm~2.4min / mm, preferably 1.4min / mm~2.1min / mm, and the solid solution insulation coefficient is 0.9min / mm~2.0min / mm, preferably 0.9min / mm~1.6min / mm; or, the plate thickness is 101mm~125mm, the solid solution heating coefficient is 1.1min / mm~2.2min / mm, preferably 1.3min / mm~1.9 min / mm, the solid solution heat preservation coefficient is 0.8min / mm~1.8min / mm, preferably 0.8min / mm~1.45min / mm; or, the plate thickness is 126mm~150mm, the solid solution temperature rise coefficient is 1.0min / mm~2.0min / mm, preferably 1.2min / mm~1.7min / mm, the solid solution temperature rise coefficient is 0.7min / mm~1.6min / mm, preferably 0.7min / mm~1.3min / mm; or, the plate thickness is 151mm~175mm, the solid solution temperature rise coefficient is 0.9min / mm~1.8min / mm, preferably 1.1min / mm~1.5min / mm, the solid solution thermal insulation coefficient is 0.6min / mm~1.4min / mm, preferably 0.8min / mm~1.15min / mm; or, the plate thickness is 176mm~200mm, the solid solution heating coefficient is 0.8min / mm~1.6min / mm, preferably 1.0min / mm~1.3min / mm, the solid solution thermal insulation coefficient is 0.5min / mm~1.2min / mm, preferably 0.7min / mm~1.0min / mm.

[0010] Furthermore, the metallographic structure of the second plate includes a matrix phase and a second phase, and the area of ​​the second phase accounts for 0.8% to 1.5% of the metallographic structure; preferably, the second phase is selected from one or more of a Fe-containing second phase, an S phase and a T phase.

[0011] Further, the temperature of the homogenization treatment is 460° C. to 490° C., and the time is 20 h to 50 h; preferably, the temperature of the homogenization treatment is 475° C. to 485° C., and the time is 20 h to 26 h.

[0012] Further, the hot rolling treatment is carried out at 390°C to 450°C, and the rolling ratio of the hot rolling treatment is 55% to 95%; preferably, the hot rolling treatment is carried out at 420°C to 440°C.

[0013] Further, the aging treatment is a double-stage aging treatment, which includes a first-stage aging treatment at a temperature of 118°C to 123°C for 3h to 6h and a second-stage aging treatment at a temperature of 160°C to 166°C for 14h to 24h. Preferably, the double-stage aging treatment includes a first-stage aging treatment at a temperature of 121°C to 122°C for 4h to 5h and a second-stage aging treatment at a temperature of 163°C to 165°C for 18h to 24h.

[0014] A second aspect of the present invention provides a 7 series aluminum alloy sheet material, which is prepared by the above-mentioned preparation method of the 7 series aluminum alloy sheet material.

[0015] Furthermore, the 7 series aluminum alloy sheet has a tensile strength of 500 MPa to 550 MPa, a yield strength of 440 MPa to 490 MPa, and an elongation of 11.0% to 16.0%.

[0016] A third aspect of the present invention provides an application of the above-mentioned 7 series aluminum alloy sheet as a structural material in the fields of automobiles, ships, rail transportation and aerospace.

[0017] By applying the technical solution of the present invention, the internal structure uniformity and purity of the obtained 7 series aluminum alloy thick plate are effectively ensured by precisely controlling various parameters of the solution heat treatment, thereby significantly improving the mechanical properties of the plate, including tensile strength, yield strength and elongation, so that it meets or exceeds the high standards for structural materials in the aerospace field. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 This is a scanning electron microscope photograph of the 7 series aluminum alloy plate obtained in Example 3;

[0020] Figure 2 This is a scanning electron microscope photograph of the 7 series aluminum alloy plate obtained in Example 10;

[0021] Figure 3 This is a scanning electron microscope photograph of the 7 series aluminum alloy plate obtained in Comparative Example 3;

[0022] Figure 4 This is a scanning electron microscope photograph of the 7 series aluminum alloy plate obtained in Comparative Example 6;

[0023] Figure 5 This is a metallographic photograph of the 7 series aluminum alloy plate obtained in Example 3;

[0024] Figure 6 This is a metallographic photograph of the 7 series aluminum alloy plate obtained in Comparative Example 3. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0026] As described in the background technology, the 7 series aluminum alloy sheet in the prior art has the problem that it is difficult to obtain excellent mechanical properties in a shorter solution heat treatment time due to the unreasonable solid solution system. In order to solve the above technical problems, the first aspect of the present invention provides a preparation method of a 7 series aluminum alloy sheet, including: step s1, smelting and casting the raw materials of the 7 series aluminum alloy sheet to obtain an ingot; step S2, homogenizing the ingot to obtain a homogenized ingot, hot rolling the homogenized ingot to obtain a first sheet with a thickness of 25mm to 200mm; step S3, performing a solid solution heat treatment including a solid solution heating stage and a solid solution heat preservation stage on the first sheet to obtain a second sheet; step S4, performing an aging treatment on the second sheet to obtain a 7 series aluminum alloy sheet; the temperature of the solid solution heating stage is 460℃ to 490℃, and the time used in the solid solution heating stage is recorded as T 升 , the solid solution temperature rise coefficient is recorded as X 升 , then T 升 = is X 升 × Plate thickness, solid solution temperature rise coefficient X 升 0.8min / mm~2.8min / mm; the time used in the solution and heat preservation stage is recorded as T 保 , the solid solution insulation coefficient is recorded as X 保 , then T 保 =X 保 × Plate thickness, solid solution insulation coefficient X 保 It is 0.5min / mm~2.5min / mm.

[0027] The above preparation method strictly sets the temperature of the solution treatment, refines the solution treatment into the solution heating stage and the solution insulation stage, and further accurately controls the temperature coefficients involved in the two stages, thereby obtaining a solution heat treatment mechanism that can be well adapted to the 7 series aluminum alloy plate. Relying on this solution heat treatment mechanism, the internal structure of the 7 series aluminum alloy plate is more uniform, the impurity second phase content is lower and more evenly distributed, and there are fewer defects, that is, the microscopic morphology is more superior, and thus it shows significantly enhanced mechanical properties, including tensile strength, yield strength and elongation, which can well meet the application needs of various fields.

[0028] In particular, the preparation method provided by the present invention is more suitable for the actual production of large-size industrial thick plates, especially in the range of 25 mm to 200 mm. Different plate thickness specifications and their initial organizational characteristics can be more effectively combined with the solid solution mechanism provided by the present invention, and the full solid solution of the plate can be achieved in a more targeted manner within a more suitable time. The process is simple and controllable, which can effectively improve production efficiency and ultimately obtain aged alloy thick plates with excellent mechanical properties.

[0029] In application, in order to adapt to the actual production needs, the specifications of the ingots obtained by casting are generally (400mm~550mm)×(1300mm~2000mm) (thickness×width).

[0030] Furthermore, based on the above-mentioned solution heat treatment mechanism, the inventors have further optimized the solution heating coefficient to be 1.0min / mm~2.5min / mm and the solution insulation coefficient to be 0.5min / mm~1.9min / mm through a large number of experiments. The temperature coefficient ranges involved in these two solution heat treatment processes can better adapt to the composition of the 7 series aluminum alloy and the plate thickness range of 25mm~200mm, thereby more effectively optimizing the solution process of the aluminum alloy plate, and ultimately more significantly enhancing the various mechanical properties of the resulting plate.

[0031] At the same time, it is more preferred that the temperature of the solution heating stage is 475°C to 480°C, so as to better adapt to the composition of the 7 series aluminum alloy and the previous homogenization and hot rolling processes to obtain a plate with better comprehensive mechanical properties.

[0032] In several typical implementations:

[0033] The plate thickness is 25 mm to 50 mm, the solid solution heating coefficient is 1.4 min / mm to 2.8 min / mm, preferably 1.6 min / mm to 2.5 min / mm, and the solid solution thermal insulation coefficient is 1.1 min / mm to 2.4 min / mm, preferably 1.1 min / mm to 1.9 min / mm; or,

[0034] The plate thickness is 51 mm to 75 mm, the solid solution heating coefficient is 1.3 min / mm to 2.6 min / mm, preferably 1.5 min / mm to 2.3 min / mm, and the solid solution thermal insulation coefficient is 1.0 min / mm to 2.2 min / mm, preferably 1.0 min / mm to 1.75 min / mm; or,

[0035] The plate thickness is 76 mm to 100 mm, the solid solution heating coefficient is 1.2 min / mm to 2.4 min / mm, preferably 1.4 min / mm to 2.1 min / mm, and the solid solution thermal insulation coefficient is 0.9 min / mm to 2.0 min / mm, preferably 0.9 min / mm to 1.6 min / mm; or,

[0036] The plate thickness is 101 mm to 125 mm, the solid solution heating coefficient is 1.1 min / mm to 2.2 min / mm, preferably 1.3 min / mm to 1.9 min / mm, and the solid solution thermal insulation coefficient is 0.8 min / mm to 1.8 min / mm, preferably 0.8 min / mm to 1.45 min / mm; or,

[0037] The plate thickness is 126 mm to 150 mm, the solid solution heating coefficient is 1.0 min / mm to 2.0 min / mm, preferably 1.2 min / mm to 1.7 min / mm, and the solid solution thermal insulation coefficient is 0.7 min / mm to 1.6 min / mm, preferably 0.7 min / mm to 1.3 min / mm; or,

[0038] The plate thickness is 151 mm to 175 mm, the solid solution heating coefficient is 0.9 min / mm to 1.8 min / mm, preferably 1.1 min / mm to 1.5 min / mm, and the solid solution thermal insulation coefficient is 0.6 min / mm to 1.4 min / mm, preferably 0.8 min / mm to 1.15 min / mm; or,

[0039] The plate thickness is 176 mm to 200 mm, the solid solution heating coefficient is 0.8 min / mm to 1.6 min / mm, preferably 1.0 min / mm to 1.3 min / mm, and the solid solution thermal insulation coefficient is 0.5 min / mm to 1.2 min / mm, preferably 0.7 min / mm to 1.0 min / mm.

[0040] For the larger plate thickness range of 25mm to 200mm, the inventors further refined and classified the plate thickness range through a large number of experiments, and optimized the solid solution heating coefficient and solid solution insulation coefficient accordingly for different plate thickness parameters, and obtained the above-mentioned more accurate solid solution heat treatment mechanisms. The above-mentioned solid solution heat treatment mechanism for plate thickness can more effectively combine the plate thickness specifications and its initial organizational characteristics with the parameter settings of the two stages of solid solution, enhance the uniformity of solid solution heat treatment, promote the uniform distribution of alloying elements in 7 series aluminum alloy plates, and the re-dissolution of the second phases such as η phase (MgZn2), T phase (AlZnMg(Cu)), S phase (Al2MgCu) generated in the previous steps, optimize the distribution of the second phase and grain boundary parameters, so that the microstructure of the obtained 7 series aluminum alloy plate is better and the mechanical properties are also better.

[0041] And, in several more typical embodiments, the metallographic structure of the second plate obtained by the above-mentioned solution heat treatment includes a matrix phase and a second phase, and the area of ​​the second phase accounts for 0.8% to 1.5% of the metallographic structure. That is, the second phase content in the obtained second plate is lower, and the corresponding 7 series aluminum alloy plate also exhibits higher mechanical properties.

[0042] Furthermore, for the 7 series aluminum alloy plate provided by the present invention, in the second plate obtained by solution heat treatment, the second phase is selected from one or more of the Fe-containing second phase (Al7Cu2Fe), S phase (Al2MgCu) and T phase (AlZnMg(Cu)).

[0043] At the same time, in order to more effectively eliminate the component segregation produced during the casting process and improve the uniformity and stability of the ingot before hot rolling, the preferred homogenization treatment temperature is 460°C to 490°C and the time is 20h to 50h, and the more preferred temperature is 475°C to 485°C and the time is 20h to 26h, so as to obtain 7 series aluminum alloy plates with higher comprehensive mechanical properties.

[0044] As for the hot rolling forming process, the inventors have conducted a large number of experiments and based on the homogenization treatment conditions, it is preferred that the hot rolling treatment be carried out at 390°C to 450°C, more preferably at 420°C to 440°C, and the rolling rate of the hot rolling treatment be 55% to 95%. The first plate formed by the hot rolling treatment has a better internal structure, better mechanical properties and processing properties, which can provide better prerequisites for subsequent solution heat treatment, thereby more significantly improving the mechanical properties of the obtained 7 series aluminum alloy plate.

[0045] Furthermore, in practical applications, in order to obtain an aluminum alloy plate whose thickness and other specification parameters better meet the application requirements, the obtained second plate may be pre-stretched and stretched.

[0046] In several typical embodiments, the aging treatment is a two-stage aging treatment, which includes a first-stage aging treatment at a temperature of 118°C to 123°C and a time of 3h to 6h and a second-stage aging treatment at a temperature of 160°C to 166°C and a time of 14h to 24h. More preferably, the temperature of the first-stage aging treatment is 121°C to 122°C and the time is 4h to 5h, and the temperature of the second-stage aging treatment is 163°C to 165°C and the time is 18h to 24h. The above-mentioned more preferred two-stage aging treatment can be better prepared with the organizational structure of the second plate obtained by the above-mentioned solid solution heat treatment provided by the present invention, and its strength and toughness are improved.

[0047] A second aspect of the present invention provides a 7 series aluminum alloy sheet material, which is prepared by the above-mentioned preparation method of the 7 series aluminum alloy sheet material.

[0048] Furthermore, the tensile strength of the 7 series aluminum alloy sheet is 500MPa-550MPa, the yield strength is 440MPa-490MPa, and the elongation is 11.0%-16.0%. The high-performance 7 series aluminum alloy sheet prepared by the above method has excellent comprehensive mechanical properties, higher safety and reliability, and can be well adapted to the application requirements of various fields.

[0049] The third aspect of the present invention provides an application of the above-mentioned 7 series aluminum alloy sheet as a structural material in the fields of automobiles, ships, rail transit and aerospace. The 7 series aluminum alloy sheet provided by the present invention has excellent comprehensive mechanical properties, especially tensile strength, yield strength and elongation, that is, it can take into account the requirements of high strength and high toughness, and can be used as a key structural material in the fields of automobiles, ships, rail transit and aerospace. In particular, in practical applications, with respect to aerospace materials, by adopting the 7 series aluminum alloy sheet of the present application, aerospace vehicles can achieve lighter weight, higher structural strength and better environmental resistance, thereby improving flight efficiency, extending service life, reducing maintenance costs, and contributing to the continuous progress of the aerospace industry.

[0050] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0051] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0052] Example 1

[0053] A preparation method of 7050 aluminum alloy plate:

[0054] Take 7050 aluminum alloy as an example, whose chemical composition is: 0.12% Si, 0.15% Fe, 2.3% Cu, 0.1% Mn, 2.2% Mg, 0.04% Cr, 6.2% Zn, 0.1% Zr, 0.06% Ti, and the remainder is Al.

[0055] (1) casting to obtain an ingot;

[0056] (2) Homogenization and hot rolling: Under the condition of slow temperature increase, the above ingot is subjected to homogenization treatment at a temperature of 480° C. for 20 h, and then air-cooled to obtain a homogenized ingot; then the obtained homogenized ingot is hot-rolled at a temperature of 440° C. with a total rolling rate of 90% to obtain a first plate with a thickness of 35 mm;

[0057] (3) Solution heat treatment: The alloy was placed in the furnace with the maximum loading amount and the furnace temperature was set to 477°C. During the implementation, a thermocouple was used to measure the temperature of the metal. The first step of the metal solution heating stage took 84 min (i.e., the solution heating coefficient X 升 =2.4), and during this time, the furnace temperature reaches the set 477°C; then the second step of solid solution insulation stage is carried out, and the insulation time is set to 53min (i.e., solid solution insulation coefficient X 保 =1.5); the total time of the solution heat treatment is 137 min. The heat-treated plate, i.e., the second plate, is obtained;

[0058] (4) Aging: The second plate is subjected to a double-stage aging treatment, wherein the first stage aging treatment is performed at 120° C. for 5 h, and the second stage aging treatment is performed at 163° C. for 22 h, so that its final state is T7451 state, and a 7050 aluminum alloy plate is obtained.

[0059] Example 2

[0060] A preparation method of 7050 aluminum alloy plate:

[0061] (1) casting to obtain an ingot;

[0062] (2) Homogenization and hot rolling: Under the condition of slow heating, the above ingot is subjected to homogenization treatment at a temperature of 478° C. for 24 h, and then air-cooled to obtain a homogenized ingot; then the obtained homogenized ingot is hot-rolled at a temperature of 440° C. with a total rolling rate of 85% to obtain a first plate with a thickness of 65 mm;

[0063] (3) Solution heat treatment: The alloy was placed in the furnace with the maximum loading amount and the furnace temperature was set to 477°C. During the implementation process, a thermocouple was used to measure the temperature of the metal. The first step of the metal solution heating stage took 137 min (i.e., the solution heating coefficient X 升=2.1), and during this time, the furnace temperature reaches the set 477°C; then the second step of solid solution insulation stage is carried out, and the insulation time is set to 85min (i.e., solid solution insulation coefficient X 保 =1.3); the total time of the solution heat treatment is 222min. The heat-treated plate, i.e., the second plate, is obtained;

[0064] (4) Aging: The second plate is subjected to a double-stage aging treatment, wherein the first stage aging treatment is performed at 121° C. for 4.5 h, and the second stage aging treatment is performed at 163° C. for 22 h, so that its final state is T7451 state, and a 7050 aluminum alloy plate is obtained.

[0065] Example 3

[0066] A preparation method of 7050 aluminum alloy plate:

[0067] (1) casting to obtain an ingot;

[0068] (2) Homogenization and hot rolling: Under the condition of slow heating, the above ingot is subjected to homogenization treatment at a temperature of 478° C. for 26 h, and then air-cooled to obtain a homogenized ingot; then the obtained homogenized ingot is hot-rolled at a temperature of 430° C. with a total rolling rate of 75% to obtain a first plate with a thickness of 100 mm;

[0069] (3) Solution heat treatment: The alloy was placed in the furnace with the maximum loading amount and the furnace temperature was set to 478°C. During the implementation, a thermocouple was used to measure the temperature of the metal. The first step of the metal solution heating stage took 160 min (i.e., the solution heating coefficient X 升 =1.6), and during this time, the furnace temperature reaches the set 485°C; then the second step of solid solution insulation stage is carried out, and the insulation time is set to 110min (i.e., solid solution insulation coefficient X 保 =1.1); the total time of the solution heat treatment is 270 min. The heat-treated plate, i.e., the second plate, is obtained;

[0070] (4) Aging: The second plate is subjected to a double-stage aging treatment, wherein the first stage aging treatment is performed at 120° C. for 4.5 h, and the second stage aging treatment is performed at 163° C. for 24 h, so that its final state is T7451 state, and a 7050 aluminum alloy plate is obtained.

[0071] The scanning electron microscope photos of the obtained 7050 aluminum alloy sheet are shown in Figure 1 , metallographic photos see Figure 5 .

[0072] Example 4

[0073] A preparation method of 7050 aluminum alloy plate:

[0074] (1) casting to obtain an ingot;

[0075] (2) Homogenization and hot rolling: Under the condition of slow heating, the above ingot is subjected to homogenization treatment at a temperature of 480° C. for 24 h, and then air-cooled to obtain a homogenized ingot; then the obtained homogenized ingot is hot-rolled at a temperature of 420° C. with a total rolling rate of 65% to obtain a first plate with a thickness of 150 mm;

[0076] (3) Solution heat treatment: The alloy was placed in the furnace with the maximum loading amount and the furnace temperature was set to 479°C. During the implementation, a thermocouple was used to measure the temperature of the metal. The first step of the metal solution heating stage took 210 min (i.e., the solution heating coefficient X 升 =1.4), and during this time, the furnace temperature reaches the set 487°C; then the second step of solid solution insulation stage is carried out, and the insulation time is set to 150min (i.e., solid solution insulation coefficient X 保 =1.0); the total time of the solution heat treatment is 360 min. A heat-treated plate, i.e., the second plate, is obtained;

[0077] (4) Aging: The second plate is subjected to a double-stage aging treatment, wherein the first stage aging treatment is performed at 121° C. for 5 h, and the second stage aging treatment is performed at 164° C. for 20 h, so that its final state is T7451 state, and a 7050 aluminum alloy plate is obtained.

[0078] Example 5

[0079] A preparation method of 7050 aluminum alloy plate:

[0080] (1) casting to obtain an ingot;

[0081] (2) Homogenization and hot rolling: Under the condition of slow heating, the above ingot is subjected to homogenization treatment at a temperature of 482° C. for 20 h, and then air-cooled to obtain a homogenized ingot; then the obtained homogenized ingot is hot-rolled at a temperature of 420° C. with a total rolling rate of 55% to obtain a first plate with a thickness of 190 mm;

[0082] (3) Solution heat treatment: The alloy was placed in the furnace with the maximum loading amount and the furnace temperature was set to 479°C. During the implementation, a thermocouple was used to measure the temperature of the metal. The first step of the metal solution heating stage took 228 min (i.e., the solution heating coefficient X 升 =1.2), and during this time, the furnace temperature reaches the set 490°C; then the second step of solid solution insulation stage is carried out, and the insulation time is set to 171min (i.e., solid solution insulation coefficient X 保 =0.9); the total time of the solution heat treatment is 399 min. The heat-treated plate, i.e., the second plate, is obtained;

[0083] (4) Aging: The second plate is subjected to a double-stage aging treatment, wherein the first stage aging treatment is performed at 121° C. for 4 h, and the second stage aging treatment is performed at 165° C. for 18 h, so that its final state is T7451 state, and a 7050 aluminum alloy plate is obtained.

[0084] Example 6

[0085] A preparation method of 7050 aluminum alloy plate:

[0086] The difference between this embodiment and embodiment 1 is that the hot rolling reduction rate is changed so that the thickness of the first plate is changed to 120 mm, and the solution temperature rise coefficient X is set during the solution heat treatment. 升 =2.0, solution heat preservation coefficient Xba =1.2, the total time for solution heat treatment is 240+144=384min.

[0087] Example 7

[0088] A preparation method of 7050 aluminum alloy plate:

[0089] The difference between this embodiment and embodiment 1 is that the hot rolling reduction rate is changed so that the thickness of the first plate is changed to 170 mm, and the solution temperature rise coefficient X is set during the solution heat treatment. 升 =1.5, solid solution insulation coefficient X 保 =1.0, the total time consumed for solution heat treatment is 255+170=425min.

[0090] Example 8

[0091] A preparation method of 7050 aluminum alloy plate:

[0092] The difference between this embodiment and embodiment 1 is that the solid solution temperature rise coefficient X is changed. 升 is 2.8, the solid solution insulation coefficient X 保 It is 2.4, that is, the total time consumed for the solution heat treatment is 98+84=182min.

[0093] Example 9

[0094] A preparation method of 7050 aluminum alloy plate:

[0095] The difference between this embodiment and embodiment 2 is that the solid solution temperature rise coefficient X is changed. 升 is 2.5, the solid solution insulation coefficient X 保 is 1.8, that is, the total time consumed for the solution heat treatment is 163+117=280min.

[0096] Example 10

[0097] A preparation method of 7050 aluminum alloy plate:

[0098] The difference between this embodiment and embodiment 3 is that the solid solution temperature rise coefficient X is changed. 升 is 1.3, the solid solution insulation coefficient X 保 It is 0.85, that is, the total time consumed for the solution heat treatment is 130+85=215min.

[0099] The scanning electron microscope photos of the obtained 7050 aluminum alloy sheet are shown in Figure 2 .

[0100] Embodiment 11

[0101] A preparation method of 7050 aluminum alloy plate:

[0102] The difference between this embodiment and embodiment 4 is that the solid solution temperature rise coefficient X is changed. 升 is 1.1, the solid solution insulation coefficient X 保 is 0.7, that is, the total time consumed for the solution heat treatment is 165+105=270.

[0103] Example 12

[0104] A preparation method of 7050 aluminum alloy plate:

[0105] The difference between this embodiment and embodiment 5 is that the solid solution temperature rise coefficient X is changed. 升 is 0.9, the solid solution insulation coefficient X 保 It is 0.6, that is, the total time consumed for the solution heat treatment is 171+114=285min.

[0106] Embodiment 13

[0107] A preparation method of 7050 aluminum alloy plate:

[0108] The difference between this embodiment and embodiment 1 is only in step (2), specifically: under the condition of slow heating, the above-mentioned ingot is subjected to homogenization treatment at a temperature of 470°C and a time of 55 hours, and after completion, it is air-cooled to obtain a homogenized ingot; thereafter, the obtained homogenized ingot is hot rolled at a temperature of 400°C and a total rolling rate of 85% to obtain a first plate, and its plate thickness is consistent with that of embodiment 1, which is still 35 mm.

[0109] Embodiment 14

[0110] A preparation method of 7050 aluminum alloy plate:

[0111] The difference between this embodiment and embodiment 1 is only in step (2), specifically: under the condition of slow heating, the above-mentioned ingot is subjected to homogenization treatment at a temperature of 482°C and a time of 18 hours, and after completion, it is air-cooled to obtain a homogenized ingot; then the obtained homogenized ingot is hot rolled at a temperature of 450°C and a total rolling rate of 95% to obtain a first plate, and its plate thickness is consistent with that of embodiment 1, which is still 35 mm.

[0112] Embodiment 15

[0113] A preparation method of 7050 aluminum alloy plate:

[0114] The difference between this embodiment and embodiment 1 is only in step (4), specifically: the second plate is subjected to a double-stage aging treatment, the conditions of the first stage aging treatment are 119° C. and 7 h, and the conditions of the second stage aging treatment are 166° C. and 14 h, to obtain a 7050 aluminum alloy plate.

[0115] Example 16

[0116] A preparation method of 7050 aluminum alloy plate:

[0117] The difference between this embodiment and embodiment 1 is only in step (4), specifically: the second plate is subjected to a double-stage aging treatment, the conditions of the first stage aging treatment are 123° C. and 2 h, and the conditions of the second stage aging treatment are 160° C. and 28 h, to obtain a 7050 aluminum alloy plate.

[0118] Comparative Example 1

[0119] A preparation method of 7050 aluminum alloy plate:

[0120] The difference between this embodiment and embodiment 1 is that the solid solution temperature rise coefficient X is changed. 升 is 0.6, the solid solution insulation coefficient X 保 It is 4.0, that is, the total time consumed for the solution heat treatment is 21+140=161min.

[0121] Comparative Example 2

[0122] A preparation method of 7050 aluminum alloy plate:

[0123] The difference between this embodiment and embodiment 2 is that the solid solution temperature rise coefficient X is changed. 升 is 0.5, the solid solution insulation coefficient X 保 It is 3.5, that is, the total time consumed for the solution heat treatment is 33+228=261min.

[0124] Comparative Example 3

[0125] A preparation method of 7050 aluminum alloy plate:

[0126] The difference between this embodiment and embodiment 3 is that the solid solution temperature rise coefficient X is changed. 升 is 0.3, the solid solution insulation coefficient X 保 It is 3.0, that is, the total time consumed for the solution heat treatment is 30+300=330min.

[0127] The scanning electron microscope photos of the obtained 7050 aluminum alloy sheet are shown in Figure 3 , metallographic photos see Figure 6 .

[0128] Comparative Example 4

[0129] A preparation method of 7050 aluminum alloy plate:

[0130] The difference between this embodiment and embodiment 4 is that the solid solution temperature rise coefficient X is changed. 升 is 2.9, the solid solution insulation coefficient X 保 is 0.1, that is, the total time consumed for the solution heat treatment is 435+15=450min.

[0131] Comparative Example 5

[0132] A preparation method of 7050 aluminum alloy plate:

[0133] The difference between this embodiment and embodiment 5 is that the solid solution temperature rise coefficient X is changed. 升 is 3.0, the solid solution insulation coefficient X 保 is 0.05, that is, the total time consumed for the solution heat treatment is 570+10=580min.

[0134] Comparative Example 6

[0135] A preparation method of 7050 aluminum alloy plate:

[0136] The only difference between this embodiment and embodiment 3 is that in the solution heat treatment, no heating stage is set, but the first plate with a thickness of 100 mm is directly placed in the furnace that has completed heating for 110 minutes for insulation to obtain a heat-treated plate, i.e., the second plate.

[0137] The scanning electron microscope photos of the obtained 7050 aluminum alloy sheet are shown in Figure 4 .

[0138] Comparative Example 7

[0139] A preparation method of 7050 aluminum alloy plate:

[0140] The only difference between this embodiment and embodiment 5 is that in the solution heat treatment, no heating stage is set, but the first plate with a thickness of 190 mm is directly placed in the furnace that has completed heating for 171 minutes for insulation to obtain a heat-treated plate, i.e., the second plate.

[0141] Comparative Example 8

[0142] A preparation method of 7050 aluminum alloy plate:

[0143] The difference between this embodiment and embodiment 5 is that only the thickness of the first plate obtained by hot rolling is changed to 250 mm, while the solid solution temperature rise coefficient X is maintained. 升 =1.2, solid solution insulation coefficient X 保 =0.9, the total time consumed for solution heat treatment is 300+225=525min.

[0144] Comparative Example 9

[0145] A preparation method of 7050 aluminum alloy plate:

[0146] The difference between this embodiment and embodiment 1 is that only the furnace temperature of the solution heat treatment is changed to 450°C.

[0147] Comparative Example 10

[0148] A preparation method of 7050 aluminum alloy plate:

[0149] The only difference between this embodiment and embodiment 1 is that only the furnace temperature of the solution heat treatment is changed to 500°C.

[0150] Test Method

[0151] The second phase content in the metallographic structure of the homogenized ingot and the second plate was tested using a scanning electron microscope. For evaluation and calculation, 10 different areas were collected for each sample, and two magnifications of 200x and 500x were selected. The Image-Pro Plus software was used to perform statistics on the second phase area fraction and the average value was calculated.

[0152] Tensile strength, yield strength and elongation: According to GB / T 228.1-2010 “Tensile test of metallic materials Part 1: Room temperature test method”, the mechanical properties of the aluminum alloy plates obtained in each embodiment and comparative example in the length direction were tested.

[0153] The test results are shown in Table 1.

[0154] Table 1

[0155]

[0156]

[0157] From the above description, it can be seen that the above-mentioned embodiment of the present invention realizes the preparation of 7 series aluminum alloy plates with purer metallographic structure and better comprehensive mechanical properties through a more suitable solution heat treatment mechanism.

[0158] Specifically, Examples 1 to 7 respectively carry out industrial solid solution treatment in combination with different plate thickness specifications, while Comparative Examples 1 to 5 are treatments carried out under corresponding specifications by changing the solid solution heat treatment parameters with reference to the existing factory process. The results show that the aluminum alloy obtained in the examples has achieved full solid solution, and the residual second phase content and mechanical properties are higher, and the solid solution efficiency is also higher, that is, the staged solid solution mechanism provided by the present invention has excellent effect, high efficiency and feasibility. And:

[0159] For the plates with a specification of 25mm to 50mm, namely, Example 1, Example 8, Examples 13 to 16 and Comparative Examples 1, 9 and 10, Example 1 adopts the most preferred solid solution mechanism and has the best performance; Example 8 is slightly worse due to the change in the solid solution mechanism; Examples 13 and 14 have lower performance due to different homogenization treatments; Examples 15 and 16 have a decrease in final performance due to changes in aging treatment parameters; Comparative Example 9 has more second phases and low performance due to too low temperature; Comparative Example 10 is over-burned due to too high temperature, and although there are fewer second phases, the performance is low.

[0160] For plates with specifications of 51mm to 75mm, namely Example 2, Example 9 and Comparative Example 2, Example 2 adopts the most preferred solid solution mechanism and has the best performance; Example 8 is slightly worse due to changes in the solid solution mechanism; Comparative Example 2 has the worst performance due to excessive changes in the solid solution mechanism.

[0161] For plates with specifications of 76mm to 100mm, namely, Example 3, Example 10, Comparative Example 3 and Comparative Example 6, Example 3 adopts the most preferred solid solution mechanism and has the best performance; Example 10 does not fully optimize the solid solution parameter range, the matrix uniformity and the degree of re-dissolution of coarse phases are slightly reduced, and the performance is slightly worse than that; the solid solution mechanism of Comparative Example 3 changes too much, and the performance further decreases; Comparative Example 6 does not consider the refinement stage of heating and insulation, and directly performs solid solution insulation timing on thick plates. However, in actual industrial production, it takes a certain amount of time to heat up the plate, resulting in insufficient effective insulation time for this comparative example, and the full solid solution is not fully achieved, and the final performance is significantly lower than that of the embodiment.

[0162] For plates with specifications of 126mm to 150mm, namely Example 4, Example 11 and Comparative Example 4, Example 4 adopts the most preferred solid solution mechanism and has the best performance; Example 11 is slightly worse due to changes in the solid solution mechanism; Comparative Example 4 has the worst performance due to excessive changes in the solid solution mechanism.

[0163] For plates with specifications of 176mm to 200mm, namely Example 5, Example 12, Comparative Example 5 and Comparative Example 7, similarly, Example 5 adopts the most preferred solid solution mechanism and has the best performance; Example 12 does not fully optimize the solid solution parameter range, so the matrix uniformity and the degree of re-dissolution of coarse phases are slightly reduced, and the performance is slightly worse; the solid solution mechanism of Comparative Example 5 changes too much, and the performance further decreases; Comparative Example 7 is similar to Comparative Example 6, only the insulation stage is retained and the time is short, the resulting second phase is large, and the performance is the worst.

[0164] The plates with specifications of 101mm~125mm and 151mm~175mm show similar change patterns as the plates with other specifications mentioned above.

[0165] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0166] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a 7 series aluminum alloy sheet, characterized in that: include: Step S1, smelting and casting the raw material of the 7 series aluminum alloy plate to obtain an ingot; Step S2, performing homogenization treatment on the ingot to obtain a homogenized ingot, and performing hot rolling treatment on the homogenized ingot to obtain a first plate with a thickness of 25 mm to 200 mm; Step S3, performing a solution heat treatment including a solution heating stage and a solution heat holding stage on the first plate to obtain a second plate; Step S4, performing aging treatment on the second plate to obtain the 7 series aluminum alloy plate; The temperature of the solid solution heating stage is 460°C to 490°C, and the time used in the solid solution heating stage is recorded as T 升 , then T 升 =solid solution temperature rise coefficient×the plate thickness, the solid solution temperature rise coefficient is 0.8min / mm~2.8min / mm; The time used in the solution holding stage is recorded as T 保 , then T 保 =solid solution thermal insulation coefficient×the plate thickness, the solid solution thermal insulation coefficient is 0.5min / mm~2.5min / mm.

2. The method for preparing the 7 series aluminum alloy sheet according to claim 1, characterized in that: The solid solution temperature rise coefficient is 1.0min / mm to 2.5min / mm, and the solid solution thermal insulation coefficient is 0.5min / mm to 1.9min / mm; Preferably, the temperature in the solution heating stage is 475°C to 480°C.

3. The method for preparing the 7 series aluminum alloy sheet according to claim 1, characterized in that: The plate thickness is 25 mm to 50 mm, the solid solution heating coefficient is 1.4 min / mm to 2.8 min / mm, preferably 1.6 min / mm to 2.5 min / mm, and the solid solution thermal insulation coefficient is 1.1 min / mm to 2.4 min / mm, preferably 1.1 min / mm to 1.9 min / mm; or, The plate thickness is 51 mm to 75 mm, the solid solution heating coefficient is 1.3 min / mm to 2.6 min / mm, preferably 1.5 min / mm to 2.3 min / mm, and the solid solution thermal insulation coefficient is 1.0 min / mm to 2.2 min / mm, preferably 1.0 min / mm to 1.75 min / mm; or, The plate thickness is 76 mm to 100 mm, the solid solution heating coefficient is 1.2 min / mm to 2.4 min / mm, preferably 1.4 min / mm to 2.1 min / mm, and the solid solution thermal insulation coefficient is 0.9 min / mm to 2.0 min / mm, preferably 0.9 min / mm to 1.6 min / mm; or, The plate thickness is 101 mm to 125 mm, the solid solution heating coefficient is 1.1 min / mm to 2.2 min / mm, preferably 1.3 min / mm to 1.9 min / mm, and the solid solution thermal insulation coefficient is 0.8 min / mm to 1.8 min / mm, preferably 0.8 min / mm to 1.45 min / mm; or, The plate thickness is 126 mm to 150 mm, the solid solution heating coefficient is 1.0 min / mm to 2.0 min / mm, preferably 1.2 min / mm to 1.7 min / mm, and the solid solution thermal insulation coefficient is 0.7 min / mm to 1.6 min / mm, preferably 0.7 min / mm to 1.3 min / mm; or, The plate thickness is 151 mm to 175 mm, the solid solution heating coefficient is 0.9 min / mm to 1.8 min / mm, preferably 1.1 min / mm to 1.5 min / mm, and the solid solution thermal insulation coefficient is 0.6 min / mm to 1.4 min / mm, preferably 0.8 min / mm to 1.15 min / mm; or, The plate thickness is 176 mm to 200 mm, the solid solution heating coefficient is 0.8 min / mm to 1.6 min / mm, preferably 1.0 min / mm to 1.3 min / mm, and the solid solution thermal insulation coefficient is 0.5 min / mm to 1.2 min / mm, preferably 0.7 min / mm to 1.0 min / mm.

4. The method for preparing a 7 series aluminum alloy sheet according to any one of claims 1 to 3, characterized in that: The metallographic structure of the second plate includes a matrix phase and a second phase, and the area of ​​the second phase accounts for 0.8% to 1.5% of the metallographic structure; Preferably, the second phase is selected from one or more of a Fe-containing second phase, an S phase and a T phase.

5. The method for preparing a 7 series aluminum alloy sheet according to any one of claims 1 to 4, characterized in that: The homogenization treatment is performed at a temperature of 460°C to 490°C and for a time of 20h to 50h; Preferably, the homogenization treatment is carried out at a temperature of 475° C. to 485° C. and for a time of 20 h to 26 h.

6. The method for preparing a 7 series aluminum alloy sheet according to any one of claims 1 to 5, characterized in that: The hot rolling process is carried out at 390°C to 450°C, and the rolling rate of the hot rolling process is 55% to 95%; Preferably, the hot rolling treatment is performed at 420°C to 440°C.

7. The method for preparing a 7 series aluminum alloy sheet according to any one of claims 1 to 6, characterized in that: The aging treatment is a two-stage aging treatment, which includes a first-stage aging treatment at a temperature of 118°C to 123°C for a time of 3h to 6h and a second-stage aging treatment at a temperature of 160°C to 166°C for a time of 14h to 24h. Preferably, the double-stage aging treatment includes the first-stage aging treatment at a temperature of 121°C to 122°C for 4h to 5h and the second-stage aging treatment at a temperature of 163°C to 165°C for 18h to 24h.

8. A 7 series aluminum alloy sheet, characterized in that: The 7 series aluminum alloy sheet is prepared by the preparation method of the 7 series aluminum alloy sheet according to any one of claims 1 to 7.

9. The 7 series aluminum alloy sheet according to claim 8, characterized in that: The 7 series aluminum alloy plate has a tensile strength of 500MPa to 550MPa, a yield strength of 440MPa to 490MPa, and an elongation of 11.0% to 16.0%.

10. Use of the 7 series aluminum alloy sheet according to claim 8 or 9 as a structural material in the fields of automobiles, ships, rail transportation and aerospace.

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