Aluminum alloy thin plate and manufacturing method therefor

Abstract

Disclosed in the present invention is an aluminum alloy thin plate, comprising Al and unavoidable impurity elements, and further comprising the following chemical elements in percentage by mass: Mg: 2.45-2.70%, Cu: 1.40-1.60%, Mn≤0.1%, Cr: 0.185-0.2%, Zn: 5.70-5.90%, and Ti: 0.03-0.035%. Also disclosed in the present invention is a method for manufacturing the aluminum alloy thin plate, comprising the steps of: smelting and casting to obtain an ingot; soaking; heating; hot rolling; cold rolling; solution quenching treatment: the solution temperature being 475-485°C, and the quenching means being water quenching; and aging treatment: the aging treatment temperature being 140-150°C, and the aging treatment time being 5-8 h.

Description

Aluminum alloy sheet and method for manufacturing the same TECHNICAL FIELD

[0001] The present application relates to an aluminum alloy and a method for manufacturing the same, in particular to an aluminum alloy sheet and a method for manufacturing the same. BACKGROUND

[0002] 7-series aluminum alloy (Al-Zn-Mg-Cu) is a kind of high-strength aluminum alloy, usually containing aluminum and zinc as main alloying elements, and other elements such as copper, magnesium and zirconium. This kind of alloy can reach very high strength level after proper heat treatment, so it is widely used in aerospace, automobile manufacturing and military fields which require lightweight and high strength.

[0003] 7-series aluminum alloy sheet with thickness of 0.8-1.2mm can be used to manufacture relevant structural parts in the aviation industry, and the traditional typical production process is: melting and casting → soaking → preheating → rolling → uncoiling → charging → solid solution in salt bath tank → quenching → first straightening → artificial aging → second straightening → sawing → packaging → warehousing → delivery. As can be seen, the traditional production process is complex, and when the salt bath tank is used as the solid solution treatment equipment, the transfer time from solid solution to quenching is difficult to control, resulting in insufficient solid solution or poor solid solution and quenching stability.

[0004] The Chinese patent document with publication number CN106967936A and publication date of July 21, 2017, entitled "Preparation method of aviation cargo ultra-wide aluminum alloy sheet" discloses a preparation method of aviation cargo ultra-wide aluminum alloy sheet. The above patent document uses an air cushion type continuous heat treatment unit for solid solution and quenching treatment, which improves the solid solution and quenching stability. However, the coiled material of the above patent application needs to be sawn into sheets for artificial aging after solid solution and quenching heat treatment, which greatly reduces the production efficiency. SUMMARY

[0005] One of the purposes of the present application is to provide an aluminum alloy sheet with good mechanical properties.

[0006] In order to achieve the above purpose, the present application provides an aluminum alloy sheet containing Al and inevitable impurity elements, which further contains the following chemical elements with mass percentage as follows:

[0007] Mg: 2.45-2.70%, Cu: 1.40-1.60%, Mn≤0.10%, Cr: 0.185-0.200%, Zn: 5.70-5.90%, Ti: 0.030-0.035%.

[0008] Further, in the aluminum alloy sheet according to the present application, the mass percentage of each chemical element is as follows:

[0009] Mg: 2.45-2.70%, Cu: 1.40-1.60%, Mn≤0.10%, Cr: 0.185-0.200%, Zn: 5.70-5.90%, Ti: 0.030-0.035%; the balance being Al and unavoidable impurity elements.

[0010] The design principles of the chemical components of the aluminum alloy sheet according to the present application are as follows:

[0011] Mg and Zn: In the aluminum alloy sheet according to the present application, Mg and Zn are the elements with the highest content in the 7-series aluminum alloy except for Al. The MgZn2 strengthening phase formed by these two elements is the key phase for strengthening the 7-series aluminum alloy, greatly improving the mechanical properties of the 7-series aluminum alloy after heat treatment. However, excessive addition of Mg and Zn will reduce the corrosion resistance of the alloy. Therefore, in the aluminum alloy sheet according to the present application, the mass percentage content of Mg is controlled to be between 2.45-2.70%, and can be further controlled to be between 2.50-2.65%, and the mass percentage content of Zn is controlled to be between 5.70-5.90%, and can be further controlled to be between 5.75-5.90%.

[0012] Cu: In the aluminum alloy sheet according to the present application, Cu can effectively improve the strength of the alloy and also can improve the corrosion resistance of the alloy. Cu can also effectively improve the supersaturation of the alloy solid solution, and generate strengthening phases through solid solution strengthening to improve the strength of the alloy. At the same time, when copper dissolves into the alloy matrix, the potential difference between the grain boundaries and the grain interior changes. Due to the reduction of the potential difference, the corrosion state of the alloy is more uniform, greatly improving the corrosion resistance of the alloy. Therefore, in the aluminum alloy sheet according to the present application, the mass percentage content of Cu is controlled to be between 1.40-1.60%, and can be further controlled to be between 1.43-1.57%.

[0013] Mn: In the aluminum alloy sheet according to the present application, the trace addition of Mn can improve the corrosion resistance and tensile strength of the 7-series aluminum alloy, but excessive addition will reduce the solubility of trace elements such as Cr. Therefore, in the aluminum alloy sheet according to the present application, the mass percentage content of Mn is controlled to be≤0.10%. In some embodiments, the mass percentage content of Mn is≤0.07%.

[0014] Cr: In the aluminum alloy sheet according to the present application, Cr forms fine CrAl7, (CrFe)Al7 intermetallic compounds, which are distributed inside the grains, refining the alloy grains and improving the casting performance of the aluminum alloy sheet. Therefore, in the aluminum alloy sheet according to the present application, the mass percentage content of Cr is controlled to be between 0.185-0.200%.

[0015] Ti: In the aluminum alloy sheet described in the present application, the Ti element can refine the grain structure, but when the mass percentage content of the Ti element is too high, it will affect the ductility of the material. Therefore, in the aluminum alloy sheet described in the present application, the mass percentage content of the Ti element is controlled between 0.030-0.035%.

[0016] Further, in the aluminum alloy sheet described in the present application, the mass percentage content of the Zn element and the Mg element also satisfies Zn:Mg = 2.10-2.40. Further, the mass percentage content of the Zn element and the Mg element satisfies Zn:Mg = 2.20-2.40. Further, the mass percentage content of the Zn element and the Mg element also satisfies Zn:Mg = 2.23-2.36.

[0017] In the preferred embodiment of the present application, by optimizing the Zn:Mg ratio in the alloy to 2.1-2.4, the content and size of the MgZn2 strengthening phase can be further controlled, thereby further improving the mechanical properties of the aluminum alloy sheet.

[0018] Further, in the inevitable impurities of the aluminum alloy sheet described in the present application, Si≤0.08%, Fe≤0.18%.

[0019] In the present application, both Si and Fe elements are inevitable impurities, so it is desirable to have as low content as possible under the condition.

[0020] Further, in the aluminum alloy sheet described in the present application, the area fraction of the MgZn2 phase in the matrix is 1.0%-1.25%.

[0021] Further, in the aluminum alloy sheet described in the present application, the area fraction of the MgZn2 phase in the matrix is 1.08%-1.19%.

[0022] Further, in the aluminum alloy sheet described in the present application, the size of the MgZn2 phase in the matrix is 0.6-1.1 μm.

[0023] Further, in the aluminum alloy sheet described in the present application, the size of the MgZn2 phase in the matrix is 0.65-0.90 μm.

[0024] Further, in the aluminum alloy sheet described in the present application, the size of the MgZn2 phase in the matrix is 0.65-0.88 μm.

[0025] Further, the aluminum alloy sheet according to the present application has a yield strength of ≥ 500 MPa, a tensile strength of ≥ 570 MPa, and an elongation of ≥ 11.8%. In some embodiments, the aluminum alloy sheet according to the present application has a yield strength of 500-520 MPa. In some embodiments, the aluminum alloy sheet according to the present application has a tensile strength of 570-580 MPa. In some embodiments, the aluminum alloy sheet according to the present application has an elongation of 11.8-15.0%.

[0026] Further, the aluminum alloy sheet according to the present application has a thickness of 0.8-1.2 mm.

[0027] Further, the aluminum alloy sheet according to the present application has a flatness of ≤ 3.5 mm / m. In some embodiments, the aluminum alloy sheet according to the present application has a flatness of ≤ 3.0 mm / m. In some embodiments, the aluminum alloy sheet according to the present application has a flatness of ≤ 2.5 mm / m. In some embodiments, the aluminum alloy sheet according to the present application has a flatness of ≤ 2.0 mm / m.

[0028] Another object of the present application is to provide a manufacturing method of an aluminum alloy sheet, which has high production efficiency and can achieve the purpose of cost reduction and efficiency increase under the premise of ensuring quality.

[0029] To achieve the above object, the present application provides a manufacturing method of an aluminum alloy sheet, comprising the steps of:

[0030] melting and casting to obtain an ingot;

[0031] soaking;

[0032] heating;

[0033] hot rolling;

[0034] cold rolling;

[0035] solution quenching treatment: the solution temperature is 475-485 ℃, and the quenching method is water quenching;

[0036] aging treatment: the aluminum alloy material after the solution quenching treatment is transferred to an aging unit within 8 h for aging treatment, the aging treatment temperature is 140-150 ℃, and the aging treatment time is 5-8 h.

[0037] On the basis of the component design, the present application improves the aging treatment temperature and shortens the aging treatment time, optimizes the artificial aging heat treatment system, and realizes energy saving under the premise of ensuring the mechanical properties.

[0038] In addition, by optimizing the residence time between quenching and aging treatment, the present application can reduce the non-uniformity of the strength increase in the natural aging process of the coiled material, and thus improve the sheet shape.

[0039] Further, the method further comprises sawing and milling the obtained ingot, wherein the ingot gate is not sawed, the ingot sprue head is sawed to a length of ≥200mm, the ingot large face is milled to a quantity of ≥15mm, and the ingot side vertical face is milled to a quantity of ≥14mm.

[0040] Further, in the soaking step of the manufacturing method, the soaking temperature is 470-480℃, and the soaking time is 36-48h.

[0041] Further, in the heating step of the manufacturing method, the heating temperature is 420-450℃, and the temperature is maintained for 3-24h after heating.

[0042] Further, in the hot rolling step of the manufacturing method, the maximum pass reduction rate is controlled to be ≥40%, and the hot rolling final rolling temperature is controlled to be 310-330℃. In some embodiments, the maximum pass reduction rate is controlled to be between 40-45%.

[0043] Further, the thickness of the hot-rolled plate obtained by hot rolling is 3.0-4.0mm.

[0044] Further, in the cold rolling step of the manufacturing method, the aluminum alloy material temperature at the cold rolling outlet is 80-120℃.

[0045] Further, the thickness of the cold-rolled plate obtained by cold rolling is 0.8-1.2mm.

[0046] Further, in the solid solution treatment step of the manufacturing method, a continuous heat treatment unit is used for solid solution quenching treatment and stretch straightening, the speed of the solid solution quenching process section is 12-15m / min, and the stretch straightening deformation amount is 0.5%-1.5%.

[0047] Further, in the manufacturing method, the aluminum alloy material after solid solution quenching treatment is transferred to an aging unit within 8h for aging treatment.

[0048] The aluminum alloy thin plate and the manufacturing method thereof have the following characteristics and beneficial effects:

[0049] The aluminum alloy thin plate has good mechanical properties, and in some embodiments, the yield strength is ≥500MPa, the tensile strength is ≥570MPa, and the elongation is ≥11.8%.

[0050] In some embodiments, the application controls the content and size of the MgZn2 strengthening phase by optimizing the Zn:Mg ratio in the alloy, so that the area fraction of the MgZn2 phase in the matrix is 1.08% to 1.19%, and the size is 0.65 to 0.88 microns, thereby further improving the strength of the material, with a yield strength of 506 MPa or more, a tensile strength of 576 MPa or more, and an elongation of 14.6%.

[0051] On the basis of the component design, the application improves the aging treatment temperature and shortens the aging treatment time, realizes the optimization of the artificial aging heat treatment system, and realizes energy saving under the premise of ensuring the mechanical properties.

[0052] The application controls the residence time between quenching and artificial aging, avoids the adverse effects of strength improvement after natural aging on the plate shape, and realizes the improvement of the plate shape. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 shows the effect of natural aging time on the yield strength of aluminum alloy sheet. DETAILED DESCRIPTION

[0054] The aluminum alloy sheet and the manufacturing method thereof described in the application will be further explained and described below in conjunction with the drawings and specific examples in the specification, but the explanation and description do not constitute undue limitations on the technical solutions of the application.

[0055] Examples 1-6 and Comparative Examples 1-8

[0056] The aluminum alloy sheet of Examples 1-6 of the application is prepared by the following steps:

[0057] (1) Melting and casting to obtain an ingot, and sawing and milling the obtained ingot, wherein the ingot sprue is not sawn, the sawn length of the ingot tail is greater than or equal to 200 mm, the milling amount of the large face of the ingot is greater than or equal to 15 mm, and the milling amount of the side vertical face of the ingot is greater than or equal to 14 mm;

[0058] (2) Soaking: the soaking temperature is 470 to 480 DEG C, and the soaking time is 36 to 48 hours;

[0059] (3) Heating: the heating temperature is 420 to 450 DEG C, and the time after reaching the temperature is 3 to 24 hours;

[0060] (4) Hot rolling: the maximum pass reduction rate is controlled to be greater than or equal to 40%, and the hot rolling final rolling temperature is controlled to be 310 to 330 DEG C;

[0061] (5) Cold rolling: the aluminum alloy material temperature at the cold rolling outlet is 80 to 120 DEG C;

[0062] (6) Solution treatment: the solution temperature is 475-485℃, and the quenching method is water quenching; the solution quenching treatment and the tension straightening are carried out by using a gas cushion type continuous heat treatment unit, the speed of the solution quenching process section is 12-15m / min, and the deformation of the tension straightening is 0.5%-1.5%;

[0063] (7) Aging treatment: the aluminum alloy material after the solution quenching treatment is transferred to an aging unit in a box-type furnace within 8h to carry out aging treatment, the aging treatment temperature is 140-150℃, and the aging treatment time is 5-8h.

[0064] It should be noted that the comparative examples 1-8 are prepared by using the above-mentioned step process, but the process parameters do not meet the requirements of the present application.

[0065] Table 1 lists the mass percentage content ratios of various chemical elements of the aluminum alloy sheets of the examples 1-6 and the comparative aluminum alloy sheets of the comparative examples 1-8.

[0066] Table 1. (wt%, the balance is Al and other unavoidable impurities except Si and Fe)

[0067] Tables 2-1, 2-2 and 2-3 list the specific process parameters of the aluminum alloy sheets of the examples 1-6 and the comparative aluminum alloy sheets of the comparative examples 1-6.

[0068] Table 2-1.

[0069] Table 2-2.

[0070] Table 2-3.

[0071] The microstructure of the prepared aluminum alloy sheets of the examples 1-6 and the comparative aluminum alloy sheets of the comparative examples 1-8 is detected, and the detection results are recorded in Table 3. Among them:

[0072] Microstructure detection method: to obtain the area fraction and size of the MgZn2 phase of the aged aluminum alloy sheet in the examples and the comparative examples, a scanning electron microscope is used to observe the microstructure of the aluminum alloy sheet after aging treatment, and Image Pro Plus commercial software is used to count the area fraction and phase size of the MgZn2 phase.

[0073] Table 3 lists the microstructure observation results of the aluminum alloy sheets of the examples 1-6 and the comparative aluminum alloy sheets of the comparative examples 1-8.

[0074] Table 3.

[0075] As can be seen from Table 3 above, the area fraction of MgZn2 phase in the matrix of the aluminum alloy thin plates of Examples 1-6 prepared by the manufacturing method of the present application is between 1.08% and 1.19%, and the size of the MgZn2 phase in the matrix is between 0.65 and 0.88 μm.

[0076] In addition, the mechanical properties and flatness of the prepared aluminum alloy thin plates of Examples 1-6 and the comparative aluminum alloy thin plates of Comparative Examples 1-8 were tested, and the test results are recorded in Table 4. Among them:

[0077] Tensile test: in order to obtain the mechanical properties of the aged finished aluminum alloy thin plates in the examples and comparative examples, the GB / T 16865-2013 tensile test sample and method were used to test the room temperature tensile mechanical properties of the aged finished aluminum alloy thin plates.

[0078] Flatness test: after the finished product is unwound, it is placed on a horizontal platform, and a ruler and a plug gauge are used to measure the plate shape to confirm the flatness.

[0079] Table 4 lists the mechanical properties and plate flatness test results of the aluminum alloy thin plates of Examples 1-6 and the comparative aluminum alloy thin plates of Comparative Examples 1-8 of the present application.

[0080] Table 4.

[0081] As can be seen from Table 4 above, the aluminum alloy thin plates of Examples 1-6 prepared by the manufacturing method of the present application have good mechanical properties, the yield strength is all higher than 500 MPa, the tensile strength is all higher than 570 MPa, the elongation is ≥11.8%, and the plate shape is good.

[0082] The MgZn2 size of Comparative Example 1 is coarse, and the strengthening effect is poor.

[0083] The time from the solid solution quenching treatment to the aging treatment of Comparative Example 2 is 24 h, and the plate shape performance of the finished product coiled material is poor when it is unwound, which adversely affects the use of the user.

[0084] The time from the solid solution quenching treatment to the aging treatment of Comparative Example 3 is 48 h, and the plate shape performance of the finished product coiled material is poor when it is unwound, which adversely affects the use of the user.

[0085] Although the mechanical properties and plate shape of Comparative Example 4 are good, the artificial aging time needs 24 h, which greatly reduces the industrial production efficiency.

[0086] Although the mechanical properties and plate shape of Comparative Example 5 are good, the artificial aging time needs 12 h, which greatly reduces the industrial production efficiency.

[0087] The comparative example 6 does not satisfy the requirement of the application in the Zn / Mg ratio, and further leads to a small amount of MgZn2 and poor strengthening effect, and the strength does not satisfy the requirement of the application; and the artificial aging time thereof needs 24 h, which greatly reduces the industrial production efficiency.

[0088] The comparative example 7 and the comparative example 8 have a low aging temperature and a short aging time, and further lead to a small amount of MgZn2 and poor strengthening effect, and the strength does not satisfy the requirement of the application.

[0089] Fig. 1 shows the effect of natural aging time on the yield strength of the aluminum alloy sheet.

[0090] As shown in Fig. 1, after the solution quenching of the aluminum alloy coil, the yield strength of the alloy continuously increases in a range with the extension of the parking time. Therefore, with the increase of the parking time between the quenching and the artificial aging, the uneven increase of the strength of the aluminum alloy coil will lead to the continuous deterioration of the alloy sheet shape, and therefore the application reduces the parking time and obtains a good sheet shape.

[0091] It should be noted that the combination manner of the technical features in the application is not limited to the combination manner described in the claims of the application or the combination manner described in the specific embodiments, and all the technical features described in the application can be freely combined or combined in any manner, unless contradictory to each other.

[0092] It should be further noted that the above-mentioned embodiments are only specific embodiments of the application. Obviously, the application is not limited to the above-mentioned embodiments, and similar changes or modifications made on the basis of the disclosure of the application are directly derived or easily thought by those skilled in the art, and should all belong to the protection scope of the application.

Claims

1. An aluminum alloy sheet containing Al and inevitable impurity elements, characterized by, It also contains the following chemical elements with the following mass percentages: Mg: 2.45-2.70%, Cu: 1.40-1.60%, Mn≤0.10%, Cr: 0.185-0.200%, Zn: 5.70-5.90%, Ti: 0.030-0.035%.

2. The aluminum alloy sheet of claim 1, wherein, The mass percentages of the chemical elements are as follows: Mg: 2.45-2.70%, Cu: 1.40-1.60%, Mn≤0.10%, Cr: 0.185-0.200%, Zn: 5.70-5.90%, Ti: 0.030-0.035%; the balance being Al and unavoidable impurities.

3. The aluminum alloy sheet of claim 1 or 2, wherein, The mass percentages of the Zn and Mg elements also satisfy Zn:Mg=2.1-2.4; preferably, the mass percentages of the Zn and Mg elements satisfy Zn:Mg=2.2-2.4; more preferably, the mass percentages of the Zn and Mg elements also satisfy Zn:Mg=2.23-2.

36.

4. The aluminum alloy sheet of claim 1 or 2, wherein, Among the unavoidable impurities, Si≤0.08%, Fe≤0.18%.

5. The aluminum alloy sheet of claim 1 or 2, wherein, The area fraction of the MgZn2 phase in the matrix is 1.0%-1.25%, preferably 1.08%-1.19%.

6. The aluminum alloy sheet of claim 1 or 2, wherein, The size of the MgZn2 phase in the matrix is 0.6-1.1 μm, preferably 0.65-0.90 μm, more preferably 0.65-0.88 μm.

7. The aluminum alloy sheet of claim 1 or 2, wherein The yield strength is ≥500 MPa, the tensile strength is ≥570 MPa, and the elongation is ≥11.8%; and / or the flatness is ≤3.5 mm / m, preferably ≤3.0 mm / m.

8. The aluminum alloy sheet of claim 1 or 2, wherein, The thickness is 0.8-1.2 mm.

9. The method of producing an aluminum alloy sheet according to any one of claims 1 to 8, characterized in that, The method comprises the steps of: melting and casting to obtain an ingot; soaking; heating; hot rolling; cold rolling; solution quenching treatment: the solution temperature is 475-485°C, and the quenching method is water quenching; aging treatment: the aluminum alloy material after the solution quenching treatment is transferred to an aging machine within 8 h for aging treatment, the aging treatment temperature is 140-150°C, and the aging treatment time is 5-8 h.

10. The production method according to claim 9, wherein In the soaking step, the soaking temperature is 470-480°C, and the soaking time is 36-48 h.

11. The production method according to claim 9, wherein In the heating step, the heating temperature is 420-450°C, and the temperature is maintained for 3-24 h after heating.

12. The production method according to claim 9, wherein In the hot rolling step, the maximum pass reduction rate is controlled to be greater than 40%, and the hot rolling final rolling temperature is controlled to be 310-330°C.

13. The production method according to claim 9, wherein In the cold rolling step, the aluminum alloy material temperature at the cold rolling outlet is 80-120°C.

14. The production method according to claim 9, wherein In the solution treatment step, a continuous heat treatment unit is used for solution quenching treatment and stretch straightening, the solution quenching process section speed is 12-15 m / min, and the stretch straightening deformation amount is 0.5%-1.5%.

15. The production method according to claim 9, wherein The melting and casting also comprises sawing and milling the ingot, wherein the ingot casting gate is not sawn, the sawn length of the ingot casting head is ≥200 mm, the ingot casting large face milling amount is ≥15 mm, and the ingot casting side vertical face milling amount is ≥14 mm.

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