A method of forging a 7xxx-series aluminium alloy billet and a panel for an aircraft structure

Abstract

The present application relates to the field of alloy forging, in particular to a kind of 7XXX series aluminum alloy blank forging method and plate for aircraft structure.The method provided by the present application comprises the following steps: 7XXX series aluminum alloy ingot is subjected to 1 wide upsetting deformation and 7-12 passes of thick drawing, to obtain blank;The reduction of the ingot subjected to wide upsetting deformation is 20%-40%, and the reduction speed is not more than 4mm / s;The thickness of the ingot is reduced by 10%-15% after each pass of thick drawing, and the reduction speed is not more than 4mm / s;The drawing feed of the ingot subjected to thick drawing is 10%-20% of the initial total length of feed.The method of the present application distributes each parameter of the forging process, transmits strain from the core of the ingot to the surface through the drawing deformation of multiple passes, and realizes uniform distribution in the thickness direction of the ingot, finally ensures that the surface of the plate has consistent grain structure and uniform mechanical properties with the core.

Description

Technical Field

[0001] This invention relates to the field of alloy forging, specifically a forging method for 7XXX series aluminum alloy billets and sheet metal for aircraft structures. Background Technology

[0002] Large aluminum alloy sheets are raw materials used in the aerospace industry to manufacture large parts. With the development of integrated part design, the demand for large sheets is increasing, and the performance requirements are also becoming more stringent. Large sheets are typically manufactured using ingot rolling. However, for thicker sheets, limitations in ingot thickness and equipment capacity mean that existing ingot rolling methods cannot introduce sufficient strain at the center of the sheet thickness, resulting in poor uniformity of the grain structure. The fundamental reasons are: firstly, under insufficient strain conditions, dislocation multiplication is limited, making it difficult to form a micro-subcrystalline structure. This fails to achieve grain refinement, resulting in coarse grains at the center of the sheet thickness and fine grains on the surface, ultimately leading to uneven mechanical properties; secondly, the lower strain at the center of the thickness makes it difficult to break down and refine the coarse phases, which severely impact the fatigue performance of the finished sheet.

[0003] In summary, the microstructure differences caused by the rolling process lead to uneven performance of sheet metal parts. Areas with lower mechanical properties become the weak points of the sheet metal, seriously affecting its use in high-end equipment. For example, the low microstructure uniformity and mechanical properties of large 7XXX series aluminum alloy sheet metal parts used in aircraft frame beams urgently need to be addressed. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a forging method for 7XXX series aluminum alloy billets and plate parts for aircraft structures. The method provided by the present invention can prepare 7XXX series aluminum alloy billet plate parts with mechanical properties that meet the requirements, and can ensure that the surface layer of the plate part has the same grain structure and uniform mechanical properties as the core of the plate part.

[0005] This invention provides a forging method for 7XXX series aluminum alloy billets, comprising the following steps:

[0006] The 7XXX series aluminum alloy ingot is subjected to one wide-axis upsetting deformation and 7 to 12 thick-axis drawing processes to obtain 7XXX series aluminum alloy billet.

[0007] The reduction amount of the ingot undergoing wide-axis upsetting deformation is 20% to 40%, and the reduction speed does not exceed 4 mm / s;

[0008] The thickness of the ingot decreases by 10% to 15% with each pass of thickness drawing, and the pressing speed of the thickness drawing does not exceed 4 mm / s.

[0009] The thickness-lengthening feed of the ingot is 10% to 20% of the initial total feed length.

[0010] This invention first involves subjecting a 7XXX series aluminum alloy ingot to a single wide-axis upsetting deformation. The reduction amount during this deformation is 20%–40%, and the reduction speed does not exceed 4 mm / s. In some embodiments of this invention, the aluminum alloy ingot has a width of 1290 mm, which is then subjected to a single wide-axis upsetting deformation to a width of 774 mm–1032 mm.

[0011] This invention involves subjecting a 7XXX series aluminum alloy ingot to one broad-axis upsetting deformation, followed by 7 to 12 passes of thick-axis drawing to obtain a 7XXX series aluminum alloy billet. Specifically, this invention involves sequentially subjecting the aluminum alloy ingot to 2 to 3 passes of first thick-axis drawing, 2 to 4 passes of second thick-axis drawing, and 3 to 5 passes of third thick-axis drawing.

[0012] The thickness of the aluminum alloy ingot described in this invention decreases by 10-15% with each pass of the thick-thickness drawing process. Specifically, the thickness reduction of the aluminum alloy ingot with each pass of the thick-thickness drawing process is 10-15% of the thickness of the aluminum alloy ingot after the previous pass of the thick-thickness drawing process. The pressing speed of the thick-thickness drawing process described in this invention does not exceed 4 mm / s.

[0013] The aluminum alloy ingot of this invention is drawn according to the reduction amount and the number of passes in the thickness-to-thickness drawing process. The thickness-to-thickness drawing feed amount of the aluminum alloy ingot of this invention is 10% to 20% of the initial total feed length. Specifically, the thickness-to-thickness drawing feed amount of the aluminum alloy ingot of this invention is 10% to 20% of the initial total feed length. More specifically, the first thickness-to-thickness drawing feed amount of the aluminum alloy ingot of this invention is 15% to 20% of the initial total feed length; the second thickness-to-thickness drawing feed amount is 13% to 18% of the initial total feed length; and the third thickness-to-thickness drawing feed amount is 11% to 16% of the initial total feed length.

[0014] In some embodiments of the present invention, the first thickness-length drawing feed of the aluminum alloy ingot is 15.5% to 19.38% of the initial total feed length; the second thickness-length drawing feed of the aluminum alloy ingot is 13.95% to 17.06% of the initial total feed length; and the third thickness-length drawing feed of the aluminum alloy ingot is 11.62% to 15.51% of the initial total feed length. In some embodiments of the present invention, the initial total length of the aluminum alloy ingot is 1290 mm, and the thickness-length drawing feed of the aluminum alloy ingot is 150 mm to 250 mm; specifically, the first thickness-length drawing feed of the aluminum alloy ingot is 200 mm to 250 mm; the second thickness-length drawing feed of the aluminum alloy ingot is 180 mm to 220 mm; and the third thickness-length drawing feed of the aluminum alloy ingot is 150 mm to 200 mm.

[0015] Before undergoing a single wide-direction upsetting deformation, the aluminum alloy ingot of this invention further includes heating it to 400–430°C, preferably 420°C, and holding it at that temperature for at least 350 minutes. Specifically, the mold used in the subsequent forging process of the aluminum alloy ingot also needs to be heated to 400°C–430°C and held for 350–380 minutes.

[0016] The aluminum alloy ingot of the present invention, after being drawn thickly, further includes sequentially undergoing solution quenching and artificial aging. In some embodiments of the present invention, the solution quenching temperature is 470℃~480℃, and the time is 3h~6h. In some embodiments of the present invention, the artificial aging specifically involves: holding the solution-quenched aluminum alloy billet at a temperature of 115℃~123℃ for 4h~8h, and then raising the temperature to 155℃~160℃ and holding it for 10h~16h. The heating medium for the artificial aging in the present invention is air, and the billet is air-cooled after the holding period. In some embodiments of the present invention, the solution-quenched aluminum alloy billet is held at a temperature of 120℃ for 4h, and then raised to 160℃ and held for 10h.

[0017] The aluminum alloy ingot of the present invention has a thickness of 450mm to 550mm. The aluminum alloy ingot of the present invention is composed of 7XXX series aluminum alloy. Specifically, the aluminum alloy ingot of the present invention is composed of Al-Zn-Mg-Cu series aluminum alloy, preferably AA7085 aluminum alloy. In some embodiments of the present invention, the aluminum alloy ingot of the present invention comprises the following components: 1.6wt.% to 1.75wt.% Cu, 1.45wt.% to 1.6wt.% Mg, 7.3wt.% to 7.8wt.% Zn, 0.09wt.% to 0.11wt.% Zr, not more than 0.05wt.% Mn, not more than 0.05wt.% Cr, not more than 0.05wt.% Fe, not more than 0.05wt.% Si, other impurity elements totaling not more than 0.15wt.%, and the balance Al. To meet the requirements of uniform grain structure and high mechanical properties for large 7XXX series aluminum alloy forgings used in aircraft structural components, this invention adopts a novel forging process of ingot upsetting and direct thickness drawing to replace rolled plates, thereby obtaining a uniform grain structure and improving the mechanical properties of large plates.

[0018] The present invention also provides a sheet metal for aircraft structures, which is processed from a blank obtained by the forging method described above. Specifically, the sheet metal for aircraft structures is an Al-Zn-Mg-Cu series aluminum alloy sheet metal for aircraft structures, preferably an AA7085 aluminum alloy sheet metal for aircraft structures.

[0019] This invention provides a forging method for 7XXX series aluminum alloy billets, comprising the following steps: subjecting a 7XXX series aluminum alloy ingot to one pass of wide-direction upsetting and 7-12 passes of thick-direction drawing to obtain a 7XXX series aluminum alloy billet; the reduction amount of the wide-direction upsetting deformation of the ingot is 20%-40%, and the reduction speed does not exceed 4 mm / s; the thickness of the ingot decreases by 10%-15% for each pass of thick-direction drawing, and the reduction speed of the thick-direction drawing does not exceed 4 mm / s; the thick-direction drawing feed amount of the ingot is 10%-20% of the initial total feed length. This invention, based on the characteristics of large 7XXX series aluminum alloy plates used in aircraft structural components, and taking into account the different strain distribution characteristics during forging deformation compared to rolling deformation, innovatively allocates parameters such as elongation reduction, elongation feed, and reduction speed to transfer strain from the ingot core to the ingot surface layer, achieving uniform distribution along the ingot thickness direction. This ultimately ensures that the plate surface layer has the same grain structure and uniform mechanical properties as the plate core. Experiments show that the forgings obtained by the forging method described in this invention have a uniform grain structure from the core to the surface layer, and their mechanical properties are higher than those of conventional plate materials. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the forging process in Embodiment 1 of the present invention;

[0021] Figure 2 This is a grain structure diagram of the surface layer of a conventionally rolled sheet.

[0022] Figure 3 This is a grain structure diagram of the center of a conventionally rolled sheet.

[0023] Figure 4 This is a grain structure diagram of the surface layer of the forged plate of the present invention;

[0024] Figure 5 This is a grain structure diagram of the center of the forged plate of the present invention. Detailed Implementation

[0025] This invention discloses a forging method for 7XXX series aluminum alloy billets and sheet metal for aircraft structures. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art will clearly be able to modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0026] The present invention will be further described below with reference to the embodiments:

[0027] Example 1

[0028] This invention describes the forging and testing of 7085 aluminum alloy ingots according to the following process: ingot sawing → ingot and mold heating → forging → solution quenching → artificial aging → testing.

[0029] The composition of the AA7085 aluminum alloy ingot used in this embodiment is as follows: 1.7wt% Cu, 1.55wt% Mg, 7.4wt% Zn, 0.1wt% Zr, not more than 0.05wt% Mn, not more than 0.05wt% Cr, not more than 0.05wt% Fe, not more than 0.05wt% Si, other impurity elements not more than 0.15wt% in total, and the balance Al.

[0030] The specific forging process of the aluminum alloy ingot of this invention is as follows:

[0031] (1) Ingot sawing: Cut ingots with a length of 1900mm × width of 1290mm × thickness of 470mm;

[0032] (2) Heating of ingots and molds: The ingots are heated to 410℃ and held for 360 minutes. The molds are heated to 400℃ and held for 360 minutes.

[0033] (3) Forging: The ingot is forged using a 10,000-ton press. Figure 1 for Figure 1 This is a schematic diagram of the forging process in Embodiment 1 of the present invention. The specific steps used are as follows:

[0034] ① Wide-direction upsetting: The ingot is subjected to one wide-direction upsetting deformation, with a deformation amount of 30%. After deformation, the width of the ingot is 1290mm × 70% = 903mm.

[0035] ②Thickness elongation: Perform thickness elongation on the ingot after width deformation according to the following steps S1 to S4;

[0036] S1: The ingot is pressed down in 3 passes to elongate it along the width direction; the elongation feed is 200mm and the pressing down per pass is 15% of the current ingot thickness;

[0037] S2: The ingot is pressed down in 3 passes to elongate it along the width direction; the elongation feed is 180mm and the pressing down per pass is 13% of the current ingot thickness;

[0038] S3: The ingot is pressed down in 3 passes to elongate it along the width direction; the elongation feed is 150mm, and each pass reduces the thickness of the ingot by 11%.

[0039] S4: The large blank plate obtained after the thickness drawing is flattened and the edges are cut to obtain a large blank plate with a length of about 3000mm × width of about 2000mm × thickness of about 180mm.

[0040] (4) Heat treatment: The above-mentioned large billet plates are subjected to solution quenching and artificial aging heat treatment. The solution quenching temperature is 475℃ and the time is 4h. The artificial aging adopts two-stage aging. The first stage aging temperature is 120℃ and the metal is held for 4 hours. The second stage is 155℃ and the metal is held for 12 hours. The heating medium is air. After the holding is completed, the metal is removed from the furnace and air-cooled.

[0041] (5) Testing: The grain structure, room temperature tensile properties and fracture toughness of the test plate in the longitudinal, transverse and high directions.

[0042] Comparative Example 1

[0043] (1) Ingot sawing: Cut ingots with a length of 1900mm × width of 1290mm × thickness of 470mm;

[0044] (2) Heating of ingots and molds: The ingots are heated to 450℃ and held for 360 minutes. The molds are heated to 400℃ and held for 360 minutes.

[0045] (3) Forging: The ingot is forged using a 10,000-ton press. The specific steps are as follows:

[0046] ① Wide-direction upsetting: The ingot is subjected to one wide-direction upsetting deformation, with a deformation amount of 60%. After deformation, the width of the ingot is 1290mm × 40% = 516mm.

[0047] ②Thickness elongation: Perform thickness elongation on the ingot after width deformation according to the following steps S1 to S4;

[0048] S1: The ingot is pressed down in 3 passes to elongate it along the width direction; the elongation feed is 200mm and the pressing down per pass is 30% of the current ingot thickness;

[0049] S2: The ingot is pressed down in 3 passes to elongate it along the width direction; the elongation feed is 180mm and the pressing down per pass is 30% of the current ingot thickness;

[0050] S3: The ingot is pressed down in 3 passes to elongate it along the width direction; the elongation feed is 150mm, and each pass reduces the thickness of the current ingot by 30%.

[0051] S4: The large blank plate obtained after the thickness drawing is flattened and the edges are cut to obtain a large blank plate with a length of about 3000mm × width of about 2000mm × thickness of about 180mm.

[0052] (4) Heat treatment: The above-mentioned large billet plates are subjected to solution quenching and artificial aging heat treatment. The solution quenching temperature is 475℃ and the time is 4h. The artificial aging adopts two-stage aging. The first stage aging temperature is 120℃ and the metal is held for 4 hours. The second stage is 160℃ and the metal is held for 10 hours. The heating medium is air. After the holding is completed, the metal is removed from the furnace and air-cooled.

[0053] (5) Testing: The grain structure, room temperature tensile properties and fracture toughness of the test plate in the longitudinal, transverse and high directions.

[0054] The mechanical properties of the forgings of this invention are shown in Table 1. After multiple tests, the measured properties of the plate obtained in Example 1 of this invention are higher than those of the plate and Comparative Example 1 in terms of tensile strength, elongation, and fracture toughness. Moreover, Example 1 shows a better combination of mechanical properties.

[0055] Figure 2 This is a grain structure diagram of the surface layer of a conventionally rolled sheet. Figure 3 This is a grain structure diagram of the center of a conventionally rolled sheet. Figure 2 and Figure 3 It can be seen that the surface grains of conventionally rolled sheets are fine, while the grains in the center of the sheet are coarse. This leads to a significant difference in performance between the center and the surface of the sheet, with the coarse grain structure in the center of the sheet resulting in a decrease in the tensile properties measured at the center of the sheet thickness.

[0056] Figure 4 This is a grain structure diagram of the surface layer of the forged plate of the present invention. Figure 5 This is a grain structure diagram of the center of the forged plate of the present invention. (From...) Figure 4 and Figure 5 It can be seen that the surface and center grain structure of the forged plate of the present invention are uniform and consistent. More importantly, the forging structure of the present invention introduces a large amount of uniform deformation, and there are a large number of uniform subgrains in the thickness direction. In contrast, Comparative Example 1 uses a larger upsetting deformation in the first step, which causes uneven grain flow. At the same time, a larger feed rate is used in the subsequent drawing process, which causes longitudinal fluctuations in the metal flow. Significant differences in the structure between the large strain region and the small strain region are generated, resulting in areas with poor mechanical properties and a decrease in the average performance.

[0057] Table 1 shows a comparison of the mechanical properties of Example 1, Comparative Example 1, and conventional sheet materials.

[0058] Table 1

[0059]

[0060] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A forging method for 7XXX series aluminum alloy billets, characterized in that, Includes the following steps: The 7XXX series aluminum alloy ingot is subjected to one wide-axis upsetting deformation, followed by 2-3 passes of first thick-axis drawing, 2-4 passes of second thick-axis drawing, and 3-5 passes of third thick-axis drawing to obtain the 7XXX series aluminum alloy billet. The reduction of the ingot in the wide-direction upsetting deformation is 20%~40%, and the reduction speed does not exceed 4 mm / s; The thickness of the ingot decreases by 10% to 15% with each pass of thickness drawing, and the pressing speed of the thickness drawing does not exceed 4 mm / s. The thickness-lengthening feed of the ingot is 10% to 20% of the initial total feed length.

2. The forging method according to claim 1, characterized in that, The first thickness elongation feed of the aluminum alloy ingot is 15% to 20% of the initial total feed length; the second thickness elongation feed of the aluminum alloy ingot is 13% to 18% of the initial total feed length; and the third thickness elongation feed of the aluminum alloy ingot is 11% to 16% of the initial total feed length.

3. The forging method according to claim 1, characterized in that, Before undergoing one wide-direction upsetting deformation, the aluminum alloy ingot is further subjected to heating to 400℃~430℃ and held at that temperature for no less than 350 minutes.

4. The forging method according to claim 1, characterized in that, After the aluminum alloy ingot is drawn out to the thickness, the forged plate is also subjected to solution quenching and artificial aging in sequence. The artificial aging process specifically involves: holding the solution-quenched aluminum alloy plate at a temperature of 115ºC~123ºC for 4 h~8 h, and then raising the temperature to 155ºC~160ºC and holding it for 10 h~16 h.

5. The forging method according to claim 4, characterized in that, The solution quenching temperature is 470°C to 480°C; the solution quenching time is 3 h to 6 h.

6. The forging method according to claim 1, characterized in that, The thickness of the aluminum alloy ingot is 450 mm to 550 mm.

7. The forging method according to claim 1, characterized in that, The aluminum alloy ingot is composed of an Al-Zn-Mg-Cu series aluminum alloy.

8. A sheet metal component for aircraft structure, characterized in that, It is obtained by processing a billet obtained by any of the forging methods described in claims 1 to 7.

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