Production process for improving anodic oxidation of 7075 aluminum alloy thick plate

Abstract

The invention provides a production process for improving anodic oxidation of a 7075 aluminum alloy thick plate. The production process comprises the following steps: S1) heating a 7075 aluminum alloy cast ingot; the heating temperature is 350 to 390 DEG C; s2) carrying out hot rolling on the heated aluminum alloy cast ingot; the single-pass rolling reduction of hot rolling is smaller than or equal to 20 mm, and meanwhile the finish rolling temperature after rolling is completed is controlled to be 350 DEG C or below; and (S3) the hot-rolled thick aluminum alloy plate is subjected to solid solution quenching and aging treatment, and the 7075 thick aluminum alloy plate is obtained. According to the method, low-temperature heating at the temperature of 350-390 DEG C is adopted before rolling, low-temperature rolling is achieved, meanwhile, the rolling deformation is adjusted to be small-deformation rolling, more deformation stored energy is stored in the rolling process, hot rolling recrystallization structures are reduced as much as possible, and therefore the structure obtained after rolling is improved, and the color difference problem obtained after anodic oxidation is solved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloys, and in particular to a production process for improving anodization of 7075 aluminum alloy thick plates. Background Art

[0002] 7075 aluminum alloy Al-Zn-Mg-Cu series high-strength aluminum alloy, with high specific strength, low density, large elastic modulus and good processing performance and other outstanding excellent characteristics, is widely used in the production of various high-load parts and components. In order to achieve certain mechanical properties, the addition of Zn, Mg and Cu and other alloying elements in the aluminum alloy will significantly reduce the corrosion performance of the alloy, and corrosion resistance is one of the important performance indicators for measuring aluminum alloys. Therefore, it is very important to improve the corrosion resistance of aluminum alloys so that they can be more widely used. Anodizing is an effective method to improve the corrosion resistance and wear resistance of aluminum alloys. By changing the type, concentration and other process conditions of the electrolyte, an anodized film that meets different performance requirements can be obtained. For aluminum alloy materials with high-quality surfaces, the surface quality after anodizing is particularly important. After anodizing, aluminum and aluminum alloys may have certain appearance defects, such as blackening, yellowing, uneven coloring and other color difference defects, which will affect the normal use of the alloy.

[0003] A large number of technical studies have shown that the factors currently known to affect the color difference of aluminum alloy after anodizing are mainly aluminum alloy material factors, such as regional segregation, second phase distribution, texture distribution, etc. The conventional 7075 thick plate production process mainly uses hot rolling to roll the area with the best shaping with a certain amount of deformation, and then solution quenching and aging to achieve various performance indicators that meet the requirements. At present, the main processes used in the 7075 thick plate processing section are ingot heating, rolling, solution quenching, aging, sawing, performance testing and packaging. The main technical disadvantages of the above processes are as follows:

[0004] 1) The macro segregation of the main alloy elements (high at the edge of the thickness section and low at the center) caused by the 7075 alloy ingot during the casting process will affect the difference in the content of the precipitated phases at the edge and center of the thick plate after quenching and aging, thereby causing color difference defects at the edge and center of the thickness section after anodizing;

[0005] 2) After quenching, a large amount of nanoscale η phase precipitates in the grains and at the grain boundaries, forming more ZnSO 4 and Zn(OH) 2 The corrosion products cannot be dissolved and discharged in time and are deposited at the aluminum interface, causing the plate to appear bright in the center of the thickness and white at both ends.

[0006] In view of the above problems, it is of great significance to provide a process for improving the anodizing of 7075 aluminum alloy to solve the problem of anodizing color difference. Summary of the invention

[0007] The technical problem solved by the present invention is to provide a production process for anodizing a 7050 aluminum alloy thick plate. The production process provided by the present application can improve the structure after rolling and improve the color difference problem after anodizing.

[0008] In view of this, the present application provides a production process for improving anodizing of 7075 aluminum alloy thick plates, comprising the following steps:

[0009] S1) heating a 7075 aluminum alloy ingot; the heating temperature is 350-390° C.;

[0010] S2) hot rolling the heated aluminum alloy ingot; the single-pass reduction of the hot rolling is ≤20 mm, and the final rolling temperature after rolling is controlled to be below 350° C.;

[0011] S3) subjecting the hot-rolled aluminum alloy thick plate to solid solution quenching and aging treatment to obtain a 7075 aluminum alloy thick plate.

[0012] Preferably, the heating temperature is 360-380°C.

[0013] Preferably, the heating temperature is 374-379°C.

[0014] Preferably, the rolling reduction of the hot rolling is as follows: the rolling reduction of a single pass is ≤ 20 mm, and the number of passes is 2 to 20.

[0015] Preferably, the hot rolling rolling reduction specifically includes rolling with different single-pass reductions performed in sequence, which are: single-pass reduction ≤20mm, 2 to 5 passes, single-pass reduction ≤15mm, 15 to 20 passes.

[0016] Preferably, the final rolling temperature of the hot rolling is less than 350°C.

[0017] Preferably, the final rolling temperature of the hot rolling is 320-340°C.

[0018] Preferably, the cooling rate of the quenching is 60-80°C / s.

[0019] Preferably, the solution quenching is specifically as follows: heating and keeping warm for a certain time according to the thickness of the hot-rolled aluminum alloy thick plate, and then rapidly cooling by spray quenching to obtain a microstructure free of recrystallized structure; the aging temperature of the aging treatment is 120°C to 130°C, and the heat preservation is 16 to 24 hours.

[0020] Preferably, the thickness of the 7075 aluminum alloy ingot is 400 mm, and the thickness of the 7075 aluminum alloy thick plate is 15 to 35 mm.

[0021] The present application provides a production process for improving anodization of 7050 aluminum alloy thick plates, which first heats a 7075 aluminum alloy ingot, then hot-rolls the heated aluminum alloy ingot, and finally performs solid solution quenching and aging treatment on the hot-rolled aluminum alloy thick plates; the present application adopts low-temperature heating of 350-390°C before rolling to achieve low-temperature rolling, and at the same time adjusts the rolling deformation to small deformation rolling, so that more deformation energy is stored during the rolling process, and the hot rolling recrystallization structure is reduced as much as possible, thereby improving the structure after rolling and improving the color difference problem after anodization; further, due to the MgZn from the edge to the core during the quenching process of the 7075 thick plate, the MgZn 2 The uneven precipitation of phases, increasing the quenching cooling rate to further reduce the influence of the quenching cooling rate on the color difference, achieving the uniformity of the quenching structure, and also improving the anodized color difference. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a real photo of the 7075 aluminum alloy thick plate of the present invention having obvious color difference at the waist after anodizing;

[0023] Figure 2 This is a real photo of the 7075 aluminum alloy thick plate of the present invention with slight color difference after anodizing;

[0024] Figure 3 This is a real photo of the 7075 aluminum alloy thick plate of the present invention after anodizing without color difference. DETAILED DESCRIPTION

[0025] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0026] Aiming at the problem of anodic oxidation color difference caused by the inability to completely eliminate the macro-segregation of alloying elements during the casting process of 7050 aluminum alloy ingots, the present application provides a production process for improving the anodic oxidation color difference of 7050 aluminum alloy thick plates, which improves the microstructure after rolling and improves the color difference after anodic oxidation by optimizing the hot rolling process of the heating section and combining the optimization of the solid solution quenching process. Specifically, the embodiment of the present invention discloses a production process for improving the anodic oxidation of 7075 aluminum alloy thick plates, comprising the following steps:

[0027] S1) heating a 7075 aluminum alloy ingot; the heating temperature is 350-390° C.;

[0028] S2) hot rolling the heated aluminum alloy ingot; the single-pass reduction of the hot rolling is ≤20 mm, and the final rolling temperature after rolling is controlled to be below 350° C.;

[0029] S3) subjecting the hot-rolled aluminum alloy thick plate to solid solution quenching and aging treatment to obtain a 7075 aluminum alloy thick plate.

[0030] For 7075 aluminum alloy, its composition by mass percentage is: Si≤0.40%, Fe≤0.50%, Cu1.2~2.0%, Mn≤0.30%, Mg 2.1~2.9%, Cr 0.18~0.28%, Zn 5.1~6.1%, Ti≤0.20%, and the balance is Al. The process route of 7050 aluminum alloy thick plate includes: ingot milling → ingot heating → hot rolling → solution quenching → aging → sawing → performance testing → packaging.

[0031] In the above preparation process, according to a large number of studies, it is found that the best hot rolling plastic deformation zone of the alloy is 400-460°C. The rolling shaping is good in this temperature range, the number of hot rolling passes is small, the production efficiency is high, and there is no obvious cracking after rolling. However, due to the use of higher temperature rolling, the deformation of the surface and core in the thickness direction during the rolling process is uneven, the starting and ending temperatures of the rolling are both high, and there is rolling deformation heat during the rolling process. The rolling termination temperature is generally still above 380°C, which is above the recrystallization temperature of the 7075 aluminum alloy, and recrystallization will occur. However, due to the temperature difference and cooling difference between the surface and the core, there are also differences in the degree of recrystallization in the thickness direction. In the process after solution quenching, there are also differences in the cooling rates of the surface and the core. The organizational differences are further inherited, resulting in uneven recrystallization and color difference after oxidation.

[0032] In view of this, the present application adjusts the rolling temperature. First, the 7050 aluminum alloy ingot is heated. The preparation method of the 7050 aluminum alloy ingot is carried out according to a method well known to those skilled in the art, and no special restrictions are imposed on this. The heating is the start rolling temperature of the rolling, and the heating temperature is 350-390°C, specifically, the heating temperature is 360-380°C, and more specifically, the heating temperature is 374-379°C. The present application controls the hot rolling structure by controlling the heating temperature, and adjusts the conventional ingot heating temperature of 400-440°C to 360-380°C by low-temperature heating of the ingot to achieve low-temperature start rolling.

[0033] In the specific rolling process, the present application optimizes the distribution of rolling passes, changing from conventional large deformation rolling (20mm~40mm) to small deformation rolling (single-pass rolling amount ≤20mm). Specifically, the rolling reduction amount of the rolling is ≤20mm, 2~20 passes. More specifically, the rolling reduction amount of the hot rolling specifically includes rolling with different single-pass reduction amounts in sequence, respectively: single-pass reduction amount ≤20mm, 2~5 passes, single-pass reduction amount ≤15mm, 15~20 passes. In the hot rolling process, the final rolling temperature is further controlled from the normal >370℃ to <350℃. Furthermore, the final rolling temperature of the final rolling is 320~340℃, so that more deformation energy is stored during the rolling process, and the hot rolling recrystallization structure is reduced as much as possible. In the above hot rolling, the low temperature and small deformation rolling method is used to roll to the target thickness, and finally the uniformity and consistency of the hot rolling structure are achieved.

[0034] The present application then performs solution quenching and aging treatment on the aluminum alloy thick plate rolled to the target thickness; specifically, the process of the solution quenching is as follows: heating and heat preservation for a certain time according to the thickness of the aluminum alloy thick plate, and then rapid cooling by spray quenching to obtain a microstructure without recrystallization structure, the aging temperature of the aging treatment is 120℃~130℃, and the heat preservation is 16~24h; A large number of studies have shown that during the quenching process of the 7075 thick plate, the MgZn 2 The uneven precipitation of phases. When the sensitive range of quenching cooling rate is 10-40℃ / s, the quenching cooling rate has a greater impact on the color difference. When the quenching cooling rate is 60-80℃ / min, and further reaches 70℃ / s, the quenching cooling rate is further increased, and the effect on the color difference is not obvious. Therefore, for the quenching process, increasing the quenching flow rate and achieving uniformity of the quenching structure can effectively improve the oxidation color difference.

[0035] In the present application, the thickness of the 7050 aluminum alloy ingot is 400 mm, and the thickness of the 7075 aluminum alloy thick plate is 15 to 35 mm.

[0036] The improved production process for anodizing of 7050 aluminum alloy thick plates provided in the present application mainly includes two aspects of improvement: on the one hand, the organization is improved during hot rolling, local recrystallization during hot rolling is reduced, and organization uniformity on the thickness section is achieved; on the other hand, uniform quenching cooling is achieved by optimizing the quenching flow rate during solution quenching, and organization color difference is further eliminated; thereby solving the problem of anodizing color difference after rolling caused by the inevitable macroscopic component segregation during ingot casting, improving the organization uniformity of the aluminum alloy material, achieving basically consistent color difference after anodizing, and improving the appearance quality.

[0037] In order to further understand the present invention, the production process for improving anodizing of 7075 aluminum alloy thick plates provided by the present invention is described in detail below in conjunction with embodiments, and the protection scope of the present invention is not limited by the following embodiments.

[0038] Example

[0039] S1) heating a 400 mm 7075 aluminum alloy ingot; the composition of the aluminum alloy ingot is shown in Table 1, and the heating temperature is the rolling start temperature, which is specifically shown in Table 2;

[0040] S2) hot rolling the heated aluminum alloy ingot to obtain an aluminum alloy thick plate of 26 mm; the final rolling temperature of the hot rolling and the distribution of the reduction amount during the hot rolling process are shown in Table 2;

[0041] S3) performing solid solution quenching and aging on the hot rolled aluminum alloy thick plate to obtain a 7075 aluminum alloy thick plate; the heating temperature for solid solution quenching is 475° C., the holding time is 60 to 120 min, and then spray cooling; the heating temperature for aging is 120° C., and the holding time is 24 h;

[0042] The 7050 aluminum alloy thick plate produced above was anodized, and the results are shown in Table 2;

[0043] Table 1 Chemical composition data of 7075 aluminum alloy ingot in the embodiment

[0044]

[0045] Table 2 Parameters in the hot rolling process and anodizing data in the embodiment

[0046]

[0047]

[0048] In the table above, the waist of the 7050 aluminum alloy thick plate has obvious color difference in the rear end of the oxidation process. Figure 1 As shown, there is a slight color difference. Figure 2 As shown, there is no color difference. Figure 3 As shown in Table 2 and Figures 1 to 3 It can be seen that the high-temperature rolling method used in the hot rolling process has a great influence on the anodized color difference of the 7050 aluminum alloy thick plate, and obvious color difference will appear in the waist. In the low-temperature rolling scheme, large deformation or high final rolling temperature during the rolling process will also affect the anodized color difference.

[0049] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0050] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A production process for improving anodization of 7075 aluminum alloy thick plates, comprising the following steps: S1) heating a 7075 aluminum alloy ingot; the heating temperature is 350-390° C.; S2) hot rolling the heated aluminum alloy ingot; the single-pass reduction of the hot rolling is ≤20 mm, and the final rolling temperature after rolling is controlled to be below 350° C.; S3) subjecting the hot-rolled aluminum alloy thick plate to solid solution quenching and aging treatment to obtain a 7075 aluminum alloy thick plate.

2. The production process according to claim 1, characterized in that: The heating temperature is 360-380°C.

3. The production process according to claim 1, characterized in that: The heating temperature is 374-379°C.

4. The production process according to claim 1, characterized in that: The rolling reduction of the hot rolling is specifically: the rolling reduction of a single pass is ≤20 mm, and the number of passes is 2 to 20.

5. The production process according to claim 1, characterized in that: The hot rolling rolling reduction specifically includes rolling with different single-pass reductions in sequence, which are: single-pass reduction ≤20mm, 2 to 5 passes, single-pass reduction ≤15mm, 15 to 20 passes.

6. The production process according to claim 1, characterized in that: The final rolling temperature of the hot rolling is less than 350°C.

7. The production process according to claim 1, characterized in that: The final rolling temperature of the hot rolling is 320-340°C.

8. The production process according to claim 1, characterized in that: The cooling rate of the quenching is 60-80°C / s.

9. The production process according to claim 1, characterized in that: The solution quenching is specifically as follows: heating and keeping the aluminum alloy thick plate for a certain time according to the thickness of the hot-rolled aluminum alloy thick plate, and then rapidly cooling by spray quenching to obtain a microstructure without recrystallization structure; the aging temperature of the aging treatment is 120°C to 130°C, and the temperature is kept for 16 to 24 hours.

10. The production process according to any one of claims 1 to 9, characterized in that: The thickness of the 7075 aluminum alloy ingot is 400 mm, and the thickness of the 7075 aluminum alloy thick plate is 15 to 35 mm.

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