Aluminum alloy sheet and manufacturing method thereof

Abstract

The invention discloses an aluminum alloy sheet, which contains Al and inevitable impurity elements, and further contains the following chemical elements in percentage by mass: 2.45 to 2.70 percent of Mg, 1.40 to 1.60 percent of Cu, less than or equal to 0.1 percent of Mn, 0.185 to 0.2 percent of Cr, 5.70 to 5.90 percent of Zn and 0.03 to 0.035 percent of Ti. The invention further discloses a manufacturing method of the aluminum alloy sheet, which comprises the following steps: smelting and casting to obtain a cast ingot; soaking; heating is performed; hot rolling; cold rolling; solid solution quenching treatment: the solid solution temperature is 475-485 DEG C, and the quenching mode is water quenching; and aging treatment: the aging treatment temperature is 140-150 DEG C, and the aging treatment time is 5-8 hours.

Description

TECHNICAL FIELD

[0001] The present application relates to an aluminum alloy and a manufacturing method thereof, in particular to an aluminum alloy sheet and a manufacturing method thereof. 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 the field of aerospace, automobile manufacturing and military which needs 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 its traditional typical production process flow 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 flow 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. In the prior art:

[0004] The Chinese patent document with publication number CN106967936A, publication date of July 21, 2017, and name of "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 above patent roll material 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≤0.1%, Cr: 0.185-0.2%, Zn: 5.70-5.90%, Ti: 0.03-0.035%.

[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≤0.1%, Cr: 0.185-0.2%, Zn: 5.70-5.90%, Ti: 0.03-0.035%; the balance being Al and inevitable impurity elements.

[0010] The design principle of each chemical component of the aluminum alloy sheet is as follows:

[0011] Mg and Zn: In the aluminum alloy sheet, Mg and Zn are the elements with the highest content in the 7-series aluminum alloy except Al. The MgZn2 strengthening phase formed by the two elements is the key phase for strengthening the 7-series aluminum alloy, which greatly improves 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, the mass percentage content of Mg is controlled to be between 2.45-2.70%, and can be further controlled to be between 2.5-2.65%, 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, 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 a strengthening phase 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 boundary and the grain interior changes, and due to the reduction of the potential difference, the corrosion state of the alloy is more uniform, which greatly improves the corrosion resistance of the alloy. Therefore, in the aluminum alloy sheet, 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, a small amount 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, the mass percentage content of Mn is controlled to be ≤0.1%.

[0014] Cr: In the aluminum alloy sheet, 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, the mass percentage content of Cr is controlled to be between 0.185-0.2%.

[0015] Ti: In the aluminum alloy sheet of the present invention, Ti can refine the grain structure, but when the mass percentage content of Ti is too high, it will affect the ductility of the material. Therefore, in the aluminum alloy sheet of the present invention, the mass percentage content of Ti is controlled between 0.03% and 0.035%.

[0016] Furthermore, in the aluminum alloy sheet described in this invention, the mass percentage content of each element also satisfies Zn:Mg = 2.1 to 2.4.

[0017] Furthermore, the mass percentage of each element also satisfies Zn:Mg = 2.23 to 2.36.

[0018] In a preferred embodiment of the present invention, by optimizing the Zn:Mg ratio in the alloy to 2.1 to 2.4, the content and size of the reinforcing phase of MgZn2 can be further controlled, thereby further improving the mechanical properties of the aluminum alloy sheet.

[0019] Furthermore, in the unavoidable impurities of the aluminum alloy sheet described in this invention, Si ≤ 0.08% and Fe ≤ 0.18%.

[0020] In this invention, both Si and Fe are unavoidable impurities, so their content is preferred to be as low as possible when conditions permit.

[0021] Furthermore, in the aluminum alloy sheet of the present invention, the area fraction of the MgZn2 phase in its matrix is ​​1.0% to 1.25%.

[0022] Furthermore, in the aluminum alloy sheet of the present invention, the area fraction of the MgZn2 phase in its matrix is ​​1.08% to 1.19%.

[0023] Furthermore, in the aluminum alloy sheet of the present invention, the size of the MgZn2 phase in its matrix is ​​0.6 to 1.1 μm.

[0024] Furthermore, in the aluminum alloy sheet of the present invention, the size of the MgZn2 phase in its matrix is ​​0.65 to 0.88 μm.

[0025] Furthermore, the aluminum alloy sheet of the present invention has a yield strength ≥500MPa, a tensile strength ≥570MPa, and an elongation ≥11.8%.

[0026] Furthermore, the thickness of the aluminum alloy sheet described in this invention is 0.8 to 1.2 mm.

[0027] Another objective of this invention is to provide a method for manufacturing aluminum alloy sheets, which has high production efficiency and can achieve cost reduction and efficiency improvement while ensuring quality.

[0028] To achieve the above objectives, the present invention provides a method for manufacturing aluminum alloy thin sheets, comprising the following steps:

[0029] Smelting and casting to obtain ingots;

[0030] Heat evenly;

[0031] heating;

[0032] Hot-rolled;

[0033] Cold rolling;

[0034] Solution quenching treatment: The solution temperature is 475~485℃, and the quenching method is water quenching;

[0035] Aging treatment: The aluminum alloy material after solution quenching is transferred to the aging unit for aging treatment within 8 hours. The aging treatment temperature is 140-150℃ and the aging treatment time is 5-8 hours.

[0036] Based on the composition design, this invention increases the temperature of the aging treatment and shortens the aging treatment time, thereby optimizing the artificial aging heat treatment process and achieving energy saving while ensuring mechanical properties.

[0037] Furthermore, by optimizing the dwell time between quenching and aging treatment, this invention can reduce the unevenness of strength improvement during the natural aging process of the coil material, thereby improving the sheet shape.

[0038] Furthermore, in the homogenization step of the manufacturing method described in this invention, the homogenization temperature is 470–480°C, and the homogenization time is 36–48 h.

[0039] Furthermore, in the heating step of the manufacturing method described in this invention, the heating temperature is 420-450°C, and the temperature is maintained for 3-24 hours after reaching the set temperature.

[0040] Furthermore, in the hot rolling step of the manufacturing method described in this invention, the maximum pass reduction rate is controlled at 40% or more, and the hot rolling final temperature is controlled at 310-330°C.

[0041] Furthermore, in the cold rolling step of the manufacturing method described in this invention, the aluminum alloy material temperature at the cold rolling exit is 80–120°C.

[0042] Furthermore, in the solution treatment step of the manufacturing method described in this invention, a continuous heat treatment unit is used for solution quenching and tensile straightening. The speed of the solution quenching process section is 12-15 m / min, and the deformation amount of the tensile straightening is 0.5%-1.5%.

[0043] Furthermore, in the manufacturing method described in this invention, the aluminum alloy material after solution quenching is transferred to an aging unit for aging treatment within 8 hours.

[0044] The aluminum alloy sheet and its manufacturing method described in this invention have the following characteristics and beneficial effects:

[0045] The aluminum alloy sheet of the present invention has good mechanical properties. In some embodiments, its yield strength is ≥500MPa, tensile strength is ≥570MPa, and elongation is ≥11.8%.

[0046] In some embodiments, the present invention optimizes the Zn:Mg ratio in the alloy and controls the content and size of the reinforcing phase MgZn2, thereby making the area fraction of the MgZn2 phase in the matrix 1.08% to 1.19% and the size 0.65 to 0.88 μm, thereby further improving the strength of the material, with a yield strength of over 506 MPa, a tensile strength of over 576 MPa, and an elongation of up to 14.6%.

[0047] Based on the composition design, this invention increases the temperature of the aging treatment and shortens the aging treatment time, thereby optimizing the artificial aging heat treatment process and achieving energy saving while ensuring mechanical properties.

[0048] This invention improves the plate shape by controlling the dwell time between quenching and artificial aging, thus avoiding the adverse effects of strength improvement after natural aging on the plate shape. Attached Figure Description

[0049] Figure 1 The effect of natural aging time on the yield strength of aluminum alloy sheets is shown. Detailed Implementation

[0050] The aluminum alloy sheet and its manufacturing method described in this invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. However, this explanation and description do not constitute an undue limitation on the technical solution of this invention.

[0051] Examples 1-6 and Comparative Examples 1-6

[0052] The aluminum alloy sheets in Examples 1-6 of this invention are obtained by the following steps:

[0053] (1) Smelting and casting to obtain ingots, and milling the obtained ingots, wherein the ingot gate is not cut, the sawing length of the ingot dummy head is ≥200mm, the milling amount of the large surface of the ingot is ≥15mm, and the milling amount of the side vertical surface of the ingot is ≥14mm.

[0054] (2) Heat equalization: The heat equalization temperature is 470-480℃ and the heat equalization time is 36-48h;

[0055] (3) Heating: The heating temperature is 420-450℃, and the heating time is 3-24 hours after reaching the temperature;

[0056] (4) Hot rolling: The maximum reduction rate per pass is controlled at more than 40%, and the final hot rolling temperature is controlled at 310-330℃;

[0057] (5) Cold rolling: The aluminum alloy material temperature at the cold rolling outlet is 80-120℃;

[0058] (6) Solution quenching: The solution temperature is 475-485℃, and the quenching method is water quenching; the solution quenching and tensile straightening are carried out by an air cushion continuous heat treatment unit. The speed of the solution quenching process section is 12-15m / min, and the tensile straightening deformation is 0.5%-1.5%.

[0059] (7) Aging treatment: The aluminum alloy material after solution quenching is transferred to the aging unit within 8 hours for aging treatment in a box furnace. The aging treatment temperature is 140-150℃ and the aging treatment time is 5-8 hours.

[0060] It should be noted that Comparative Examples 1-6 were prepared using the above-described steps and procedures, but their process parameters do not meet the requirements of this invention.

[0061] Table 1 lists the mass percentage of each chemical element in the aluminum alloy sheets of Examples 1-6 and the comparative aluminum alloy sheets of Comparative Examples 1-6 of the present invention.

[0062] Table 1. (wt%, balance Al and other unavoidable impurities besides Si and Fe)

[0063] No. Mg Cu Mn Cr Zn Ti Si Fe Zn / Mg Example 1 2.56 1.45 0.03 0.185 5.85 0.03 0.06 0.14 2.29 Example 2 2.5 1.43 0.03 0.2 5.9 0.032 0.05 0.15 2.36 Example 3 2.56 1.55 0.05 0.195 5.75 0.034 0.07 0.13 2.25 Example 4 2.65 1.57 0 0.188 5.9 0.033 0.06 0.16 2.23 Example 5 2.54 1.51 0.06 0.198 5.87 0.031 0.05 0.15 2.31 Example 6 2.57 1.49 0.07 0.19 5.83 0.033 0.07 0.16 2.27 Comparative Example 1 2.43 1.48 0.06 0.19 5.95 0.032 0.06 0.15 2.45 Comparative Example 2 2.58 1.47 0.08 0.2 5.85 0.032 0.05 0.15 2.27 Comparative Example 3 2.53 1.45 0.08 0.19 5.83 0.032 0.07 0.16 2.30 Comparative Example 4 2.59 1.49 0.06 0.2 5.84 0.031 0.06 0.17 2.25 Comparative Example 5 2.63 1.52 0.09 0.19 5.88 0.034 0.08 0.14 2.24 Comparative Example 6 2.73 1.55 0.07 0.19 5.63 0.033 0.06 0.15 2.06

[0064] Tables 2-1, 2-2, and 2-3 list the specific process parameters of the aluminum alloy sheets of Examples 1-6 and the comparative aluminum alloy sheets of Comparative Examples 1-6 of the present invention.

[0065] Table 2-1.

[0066]

[0067] Table 2-2.

[0068]

[0069]

[0070] Table 2-3.

[0071]

[0072] The microstructure of the aluminum alloy sheets prepared in Examples 1-6 and the comparative aluminum alloy sheets prepared in Comparative Examples 1-6 was analyzed, and the results are recorded in Table 3. Wherein:

[0073] Microstructure detection method: In order to obtain the area fraction and size of the MnZn2 phase in the aged aluminum alloy thin plates in the examples and comparative examples, the microstructure of the aged aluminum alloy thin plates was observed by scanning electron microscopy, and the area fraction and size of the MgZn2 phase were statistically analyzed by Image Pro Plus commercial software.

[0074] Table 3 lists the microstructure observation results of the aluminum alloy sheets of Examples 1-6 and the comparative aluminum alloy sheets of Comparative Examples 1-6 of the present invention.

[0075] Table 3.

[0076]

[0077]

[0078] 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 described in this invention is between 1.08% and 1.19%, and the size of MgZn2 phase in the matrix is ​​between 0.65 and 0.88 μm.

[0079] Furthermore, the mechanical properties of the aluminum alloy sheets prepared in Examples 1-6 and the comparative aluminum alloy sheets prepared in Comparative Examples 1-6 were tested, and the results are recorded in Table 4. Wherein:

[0080] Tensile test: In order to obtain the mechanical properties of the finished aluminum alloy sheets after aging in the examples and comparative examples, the finished aluminum alloy sheets after aging were tested for room temperature tensile mechanical properties in accordance with GB / T 16865-2013 Tensile Test Specimens and Methods.

[0081] Table 4 lists the mechanical property test results of the aluminum alloy sheets of Examples 1-6 and the comparative aluminum alloy sheets of Comparative Examples 1-6 of the present invention.

[0082] Table 4.

[0083] No. Yield Strength (MPa) Tensile Strength (MPa) Elongation (%) Example 1 512 578 13.2 Example 2 506 576 14.6 Example 3 519 580 11.8 Example 4 515 579 14.2 Example 5 517 576 13.8 Example 6 518 577 12.9 Comparative Example 1 476 555 15.5 Comparative Example 2 508 576 14.3 Comparative Example 3 511 578 13.6 Comparative Example 4 502 589 15.1 Comparative Example 5 515 573 12.9 Comparative Example 6 477 559 16.2

[0084] As can be seen from Table 4 above, the aluminum alloy sheets of Examples 1-6 prepared by the manufacturing method described in this invention have good mechanical properties, with yield strengths all above 500 MPa, tensile strengths all above 570 MPa, elongation ≥11.8%, and good plate shape performance.

[0085] In contrast, the MgZn2 in Comparative Example 1 was large in size and had a poor strengthening effect.

[0086] Comparative Example 2: When the finished coil was uncoiled, the sheet shape after quenching and aging for 24 hours was observed. The poor sheet shape performance will have an adverse impact on the user's use.

[0087] Comparative Example 3: When the finished coil was uncoiled, the sheet shape after quenching and aging for 48 hours was observed. The sheet shape was poor, which will have an adverse effect on the user.

[0088] Although Comparative Example 4 has good mechanical properties and plate shape, the artificial aging time requires 24 hours, which greatly reduces the efficiency of industrial production.

[0089] Although Comparative Example 5 has good mechanical properties and plate shape, the artificial aging time is 12 hours, which greatly reduces the efficiency of industrial production.

[0090] The amount of MgZn2 in Comparative Example 6 was small, resulting in a poor strengthening effect. In addition, its artificial aging time required 24 hours, which greatly reduced the efficiency of industrial production.

[0091] Figure 1 The effect of natural aging time on the yield strength of aluminum alloy sheets is shown.

[0092] like Figure 1 As shown, in this invention, after solution quenching, the yield strength of the aluminum alloy coil continuously increases within a certain range as the dwell time increases. Therefore, with the increase of the dwell time between quenching and artificial aging, the uneven increase in the strength of the aluminum alloy coil will lead to a continuous deterioration in the alloy sheet shape. Therefore, this invention reduces the dwell time.

[0093] It should be noted that the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0094] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. An aluminum alloy sheet containing Al and unavoidable impurity elements, characterized in that, It also contains the following chemical elements in the following mass percentages: Mg: 2.45~2.70%, Cu: 1.40~1.60%, Mn≤0.1%, Cr: 0.185~0.2%, Zn: 5.70~5.90%, Ti: 0.03~0.035%.

2. The aluminum alloy sheet as described in claim 1, characterized in that, Its mass percentage content of each chemical element is as follows: Mg: 2.45~2.70%, Cu: 1.40~1.60%, Mn≤0.1%, Cr: 0.185~0.2%, Zn: 5.70–5.90%, Ti: 0.03–0.035%; balance is Al and unavoidable impurity elements.

3. The aluminum alloy sheet as described in claim 1 or 2, characterized in that, The mass percentage of each element also satisfies Zn:Mg = 2.1 to 2.

4.

4. The aluminum alloy sheet as described in claim 1 or 2, characterized in that, In the unavoidable impurities, Si ≤ 0.08% and Fe ≤ 0.18%.

5. The aluminum alloy sheet as described in claim 1 or 2, characterized in that, The area fraction of the MgZn2 phase in its matrix is ​​1.0% to 1.25%.

6. The aluminum alloy sheet as described in claim 1 or 2, characterized in that, The size of the MgZn2 phase in its matrix is ​​0.6–1.1 μm.

7. The aluminum alloy sheet as described in claim 1 or 2, characterized in that, Its yield strength is ≥500MPa, tensile strength is ≥570MPa, and elongation is ≥11.8%.

8. The aluminum alloy sheet as described in claim 1 or 2, characterized in that, Its thickness is 0.8 to 1.2 mm.

9. The method for manufacturing aluminum alloy sheet according to any one of claims 1-8, characterized in that, Including the following steps: Smelting and casting to obtain ingots; Heat evenly; heating; Hot-rolled; Cold rolling; Solution quenching treatment: The solution temperature is 475~485℃, and the quenching method is water quenching; Aging treatment: The aluminum alloy material after solution quenching is transferred to the aging unit for aging treatment within 8 hours. The aging treatment temperature is 140-150℃ and the aging treatment time is 5-8 hours.

10. The manufacturing method as described in claim 9, characterized in that, In the heat homogenization step, the heat homogenization temperature is 470–480℃ and the heat homogenization time is 36–48h.

11. The manufacturing method as described in claim 9, characterized in that, In the heating step, the heating temperature is 420-450℃, and the temperature is maintained for 3-24 hours after reaching the set temperature.

12. The manufacturing method as described in claim 9, characterized in that, During the hot rolling process, the maximum reduction rate per pass is controlled at over 40%, and the final hot rolling temperature is controlled at 310–330℃.

13. The manufacturing method as described in claim 9, characterized in that, In the cold rolling process, the temperature of the aluminum alloy material at the cold rolling exit is 80-120℃.

14. The manufacturing method as described in claim 9, characterized in that, In the solution treatment step, a continuous heat treatment unit is used for solution quenching and tensile straightening. The speed of the solution quenching process section is 12-15 m / min, and the deformation of the tensile straightening is 0.5%-1.5%.

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