A method for controlling the thickness uniformity of aluminum alloy thin-walled integral heads

Abstract

The present invention relates to a method for controlling the wall thickness uniformity of an aluminum alloy thin-walled integral head, comprising: performing unequal-thickness thinning according to the size of the head component to be formed and according to the thickness variation law, and then applying the thickness compensation to the blank; preheating the thinned blank; placing the preheated blank in a preforming die for low-temperature preforming, and reinforcing the blank with a material storage and cooling unit with a rounded corner structure of the die to obtain a preformed component; placing the preformed component in a final forming die for final forming, and reinforcing the blank with rounded corners of the die and cooling of the punch to obtain a final formed component. This method for controlling the wall thickness uniformity of an aluminum alloy thin-walled integral head aims to address the problems of long cycle times, high costs, uneven wall thickness, and poor integrity associated with traditional manufacturing processes.

Description

Technical Field

[0001] The present invention relates to the technical field of metal forming, and in particular to a method for controlling the thickness uniformity of an aluminum alloy thin-walled integral head. Background Art

[0002] There are two main methods for manufacturing large-size head skins:

[0003] 1. Split welding method

[0004] In the aerospace industry, the traditional manufacturing process for large tank bottoms and aluminum alloy head skin components, such as those used in large aerospace aluminum alloy tanks, is split-flap welding. For example, a φ3350mm aerospace head consists of a top cover and eight melon-shaped skin segments. The top cover is formed by stamping or drawing, while the melon-shaped skin segments are stretched using a Ramon stretch forming machine. The top and melon-shaped skin segments are then assembled and welded using complex welding tooling. This manufacturing method is inefficient, costly, and exhibits poor overall performance. The greater the number of skin segments, the more welds there are, and the greater the number of melon-shaped skin segments that need to be formed. This results in long welding and forming cycles, typically nearly a month per head. This requires extensive forming and welding tooling, with the melon-shaped segment welding tooling being particularly complex and expensive, typically costing millions of dollars. High weld quality and airtightness requirements are crucial, necessitating lengthy X-ray and helium mass spectrometry inspection cycles. The weld strength is typically only about 80% of the parent material, resulting in reduced overall head strength and high weld residual stress.

[0005] 2. Integral forming method

[0006] For large, thick-walled steel heads, blanks are commercially available, and integral forming methods include spinning, stamping, and explosive forming. Spinning, a dieless process, suffers from poor precision and is therefore suitable for forming large, thick-walled steel heads. Traditional stamping and explosive forming methods have low yields, large wall thickness allowances, and require subsequent machining, resulting in high processing costs and long manufacturing cycles.

[0007] Therefore, the inventors provide a method for controlling the wall thickness uniformity of an aluminum alloy thin-walled integral head. Summary of the Invention

[0008] (1) Technical problems to be solved

[0009] The embodiment of the present invention provides a method for controlling the wall thickness uniformity of an aluminum alloy thin-walled integral head, which solves the technical problems of long manufacturing process cycle, high cost, poor wall thickness uniformity and poor integrity.

[0010] (2) Technical solution

[0011] The present invention provides a method for controlling the thickness uniformity of an aluminum alloy thin-walled integral head, comprising the following steps:

[0012] According to the size of the head part to be formed, the thickness variation law is followed by reverse compensation to the blank through unequal thickness thinning processing;

[0013] Preheating the thinned blank;

[0014] The preheated blank is placed in a preforming die for low-temperature preforming. The blank is reinforced by the material storage and cooling unit of the die radius upward structure to obtain a preformed part.

[0015] The preformed part is placed in the final forming die for final forming. The blank is reinforced by the radius of the die and the cooling of the punch to obtain the final formed part.

[0016] Furthermore, the reverse compensation is performed on the blank by unequal thickness thinning according to the size of the head part to be formed and the thickness variation law, which specifically includes the following steps:

[0017] According to the size of the head part, the size of the blank is expanded and calculated to obtain the outer dimensions of the blank;

[0018] The blank is thinned according to the outer dimensions.

[0019] Furthermore, the size of the blank is expanded and calculated based on the size of the head part to obtain the outer dimensions of the blank, which specifically includes the following steps:

[0020] Use numerical simulation methods or thickness data accumulated from actual production to determine the thickness variation law of the head stamping;

[0021] According to the thickness variation rule, the thickness of the thinned area or thickened area of the final-formed part is reversely compensated to the blank to obtain the outer dimensions of the blank.

[0022] Furthermore, the preheated blanks are placed in a preforming die for low-temperature preforming, and the blanks are reinforced by the die radius upward structure storage and cooling unit to obtain preformed parts, specifically:

[0023] The thinned blank is placed in the preforming die, drawn to a specified depth, and the temperature of the blank at the corner of the die is reduced by a cooling element to obtain the preformed part.

[0024] Furthermore, the preformed part is placed in a final forming die for final forming, and the blank is reinforced by the rounded corners of the die and the cooling of the punch to obtain the final formed part, which specifically includes the following steps:

[0025] heating the preformed part to a set temperature;

[0026] A coolant is placed in the cavity of the final forming die, and the heated preformed part is placed in the final forming die;

[0027] The final-shaped part is obtained by deep drawing using a punch filled with the coolant.

[0028] Furthermore, the preformed part is heated to a set temperature, specifically:

[0029] The preformed parts are heated in a heating furnace, wherein the heating temperature is 150° C. to 250° C. and the heating time is 1 to 3 hours.

[0030] Furthermore, the coolant is injected into the convex mold of the final forming mold to make the convex mold lower than room temperature or lower than 100° C. to 150° C. of the preformed part.

[0031] Furthermore, the thinned blank is preheated, specifically:

[0032] The thinned blank is preheated in a heating furnace; wherein the preheating temperature is 150° C. to 250° C., and the preheating time is 1 to 3 hours.

[0033] Furthermore, the blank is an aluminum alloy plate with a plate width of ≥3000 mm and a thickness of ≤5.5 mm.

[0034] (3) Beneficial effects

[0035] In summary, this invention achieves the desired high strength in the center of the blank and good plasticity in the areas around the flange where flow is required by controlling the radius of the punch and die to maintain low temperatures and the sheet metal to maintain high temperatures. The resulting weld-free, integral skin eliminates at least four welds compared to traditional manufacturing methods, significantly improving the product's stiffness and strength, and enhancing its service performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0037] Figure 1 This is a flow chart of a method for controlling the wall thickness uniformity of an aluminum alloy thin-walled integral head provided by an embodiment of the present invention;

[0038] Figure 2 This is a schematic structural diagram of billet thinning in a method for controlling the wall thickness uniformity of an aluminum alloy thin-walled integral head provided by an embodiment of the present invention;

[0039] Figure 3 This is a schematic structural diagram of blank thickness optimization in a method for controlling the wall thickness uniformity of an aluminum alloy thin-walled integral head provided by an embodiment of the present invention;

[0040] Figure 4 yes Figure 3 A magnified view of the structure at point A;

[0041] Figure 5 1 is a schematic structural diagram of a preforming mold provided by an embodiment of the present invention;

[0042] Figure 6 This is a schematic diagram of a first working state of a final forming die provided by an embodiment of the present invention;

[0043] Figure 7 This is a schematic diagram of a second working state of a final forming die provided by an embodiment of the present invention.

[0044] In the picture:

[0045] 101-preforming punch; 102-preforming die; 103-preforming cooling element; 104-preforming blank holder; 201-final forming punch; 202-final forming die; 203-final forming cooling element; 204-final forming blank holder; 205-coolant; 100-thinned blank; 200-preforming part; 300-final forming part; a-blank thickness; b-blank thickness after thinning; δb-blank thickness after compensation. DETAILED DESCRIPTION

[0046] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are intended to illustrate the principles of the present invention and are not intended to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments and covers any modifications, replacements, and improvements to the parts, components, and connection methods without departing from the spirit of the present invention.

[0047] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0048] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0049] It should also be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "disposed" and "installed" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0050] For thin-walled aluminum alloy head parts, the maximum width of 5mm thick plates supplied on the market does not exceed 2500mm, and globally it does not exceed 2800mm. Based on this situation, split forming followed by welding remains the primary method for manufacturing large aluminum alloy head skins. For aluminum alloy integral head skin parts with a billet width ≥3000mm and a part thickness requirement of less than 6mm, welding will not meet the requirements. If thick-walled aluminum plates are stamped or spun and then machined, the required tooling is complex (vacuum adsorption tooling), the machine tool requirements are high, the inside and outside surfaces are processed separately, and the machining cost of a single set of products is expensive.

[0051] For aluminum alloy integral head skin parts with a blank width of ≥3000mm and a thickness of 5.5mm or less, the shortcomings of the existing technology are:

[0052] The split welding method has high manufacturing costs, lengthy processes, long manufacturing cycles, difficulty in controlling welding deformation, large welding residual stress, and lower weld strength than the parent material, resulting in poor overall performance.

[0053] Thick-walled plate forming machine processing method, the machining tooling is complex and expensive, the processing cycle is long, the machine tool requirements are high, the manufacturing efficiency is low, and the processing residual stress causes serious deformation of the thin-walled skin;

[0054] The liquid filling forming method of tailor-welded blanks requires special equipment and a pressure-assisted system, has poor promotional potential, and is expensive per product.

[0055] Figure 1 The figure is a flow chart of a method for controlling the wall thickness uniformity of an aluminum alloy thin-walled integral head provided by an embodiment of the present invention. The method may include the following steps:

[0056] S100, according to the size of the head part to be formed, and according to the thickness variation law, reverse compensation is made to the blank through unequal thickness thinning processing;

[0057] S200, preheating the blank after thinning;

[0058] S300, placing the preheated blank in a preforming die for low-temperature preforming, and reinforcing the blank through a material storage structure with rounded corners of the die and a cooling unit to obtain a preformed part;

[0059] S400, placing the preformed part in the final forming die for final forming processing, reinforcing the blank through the rounding of the die and cooling of the punch to obtain the final formed part.

[0060] In the above embodiment, the head forming is divided into two stages: preforming and final forming. Figure 5 In the structural form shown, the preforming die 101 is designed to be upward-tilted and cooperates with the preforming blank holder 104 to maximize the storage of materials in the preforming stage to meet the requirements of smooth forming and wall thickness distribution of the final forming. Due to the optimization of the thickness of the blank, a preforming cooling element 103 is set at the fillet of the preforming die 101. The inner diameter of the preforming die must be smaller than the inner diameter of the final forming die. The interior of the final forming die is hollow (the actual state of the casting die), and a coolant 205 is built into the final forming die to make the liquid level lower than the fillet lower tangent point of the final forming die 201 ( Figure 7 As shown), so that the top is in a low temperature state.

[0061] As a preferred embodiment, in step S100, according to the size of the head part to be formed and the thickness variation law, the reverse compensation is applied to the blank through unequal thickness thinning processing, which specifically includes the following steps:

[0062] S101. Based on the size of the head part, the size of the blank is expanded and calculated to obtain the outer dimensions of the blank;

[0063] S102, performing thinning processing on the blank according to the outer dimensions.

[0064] As a preferred embodiment, in step S101, the size of the blank is expanded and calculated based on the size of the head part to obtain the outer dimensions of the blank, which specifically includes the following steps:

[0065] S1011. Determine the thickness variation pattern of the stamped head by using numerical simulation methods or thickness data accumulated from actual production;

[0066] S1012. According to the thickness variation rule, the thickness of the thinned area or thickened area of the final formed part is reversely compensated to the blank to obtain the outer dimensions of the blank.

[0067] Specifically, numerical simulation methods or thickness data accumulated from actual production are used to obtain the variation law of the thickness of the plate during head stamping. Taking thinning and thickening factors into consideration, the target thickness of the blank before head forming is determined. The minimum thickness ultra-wide integral plate (plate width ≥ 3000mm) close to the target thickness is selected. Under this plate width requirement, the thickness a of the blank supplied on the market must be greater than the target thickness b of the blank (e.g. Figure 2As shown), according to the thickness variation law, the thickness of the thinning or thickening area is reversely compensated to the head blank. The thickness value of the maximum thickness position of the compensated blank is δb, so the compensation value is δb-b (as shown Figure 3 、 4 shown).

[0068] As a preferred embodiment, in step S300, the preheated blank is placed in a preforming die for low-temperature preforming, and the blank is reinforced by the die radius upward structure storage and cooling unit to obtain a preformed part, specifically:

[0069] The thinned blank is placed in the preforming die, drawn to a specified depth, and the temperature of the blank at the corner of the die is reduced by a cooling element to obtain a preformed part.

[0070] Among them, Figure 5 As shown, the thinned blank 100 is placed on the preforming die and drawn to a specified depth; the size of the preforming part 200 is set to achieve the effect of material storage; due to the large size and heat capacity of the blank, the mold in contact with it heats up severely, and the preforming cooling element 103 is used to reduce the temperature of the blank at the rounded corners of the preforming die 101, thereby improving the strength of the rounded corner area; at the same time, the wall thickness is compensated here during the blank machining stage.

[0071] As a preferred embodiment, in step S400, the preformed part is placed in a final forming die for final forming, and the blank is reinforced by the rounded corners of the die and the cooling of the punch to obtain the final formed part, which specifically includes the following steps:

[0072] S401, heating the preformed part to a set temperature;

[0073] S402, placing a coolant in the cavity of the final forming mold and placing the heated preformed part in the final forming mold;

[0074] S403, deep drawing is performed using a punch filled with coolant to obtain a final formed part.

[0075] Specifically, if Figure 6-7 As shown, a coolant 205 is placed in the cavity of the final forming mold, and the preformed part is placed on the final forming mold. The final forming cooling element 203 is used to reduce the temperature at the fillet of the final forming die 201, thereby improving the joint strength and preventing excessive thinning of the material at this location.

[0076] Due to the coolant 203 within the final forming punch 202, the temperature of the preformed part 200 in contact with the final forming punch 202 drops, resulting in a lower temperature than the rest of the blank. The material in this deformed area, particularly the filleted area, bears significant loads during force transmission, and cooling can improve its resistance. The cantilevered area is a thinned region, and this thinning is compensated for by thickening the blank during machining. Rapid forming driven by the final forming punch 202 results in increased strength at the filleted corners of the final forming die 201. The cantilevered and top areas complete the deep drawing of the preformed part during the blank's temperature drop, resulting in the final formed part 300.

[0077] As a preferred embodiment, in step S401, the preformed part is heated to a set temperature, specifically:

[0078] The preformed parts are heated in a heating furnace, wherein the heating temperature is 150° C. to 250° C. and the heating time is 1 to 3 hours.

[0079] As a preferred embodiment, in step S402, a coolant is injected into the punch of the final forming mold to make the punch below room temperature or 100°C to 150°C lower than the preformed part.

[0080] Specifically, coolant is injected into the male mold cavity to enhance the strength of the sheet material that is in contact with the male mold and cooled, especially the support wall force transmission area under the radius of the female mold, so as to better bear the load in subsequent deep drawing and effectively control thinning.

[0081] As a preferred embodiment, in step S400, the preformed part is placed in a final forming mold for low temperature final forming treatment. After the final formed part is obtained, the following steps are further included:

[0082] Step S500: grinding the final formed part.

[0083] As a preferred embodiment, in step S200, the thinned blank is preheated, specifically:

[0084] The thinned blank is preheated in a heating furnace; wherein the preheating temperature is 150° C. to 250° C., and the preheating time is 1 to 3 hours.

[0085] As a preferred embodiment, the blank is an aluminum alloy sheet with a width of 3000 mm or greater and a thickness of 5.5 mm or less. Specifically, for head components with a blank size of 3000 mm or greater and a thickness of 4 to 5 mm, this method can produce head components with no welds, no residual stress from welding or machining, uniform thickness distribution, and good integrity. The required equipment and mold structures are simple, easy to operate, have a short processing cycle, and are highly scalable.

[0086] Example

[0087] Taking the φ2450x5.5mm aluminum alloy skin as an example, the head is a standard head with a long-short axis ratio of 2:1, a long axis of 1225mm, and a short axis of 612.5mm. The specific forming process is as follows:

[0088] 1. Calculate the unfolded blank based on the actual part size. The unfolded blank size can be obtained by theoretical calculation or numerical simulation, such as φ3200x5.5mm;

[0089] 2. Use numerical simulation to simulate the head forming process and obtain the wall thickness distribution law after forming; the head wall thickness is thinned in the cantilever area, with a thickness of 0.5 to 1.0 mm; the thinned thickness is compensated to the corresponding position of the blank, with a compensation thickness of 0.4 to 0.8 mm, and the wall thickness compensation area of this part is appropriately increased;

[0090] 3. Select a blank that can meet the 3200mm plate width and has a thickness close to 5.5mm. For example, use a 3200x3200x12mm plate and use machining to thin the 12mm thick plate to 6.0mm to obtain a φ3200x6mm blank;

[0091] 4. Preheat the φ3200x6mm billet in a heating furnace at a temperature of 150℃~250℃ for 1~3 hours;

[0092] 5. Prefabricate the preform mold with outer diameter of φ2200mm, as shown in the attached Figure 5 As shown in the figure, the die radius is made to protrude toward the blank holder to achieve the function of material storage; the preheated blank is placed on the preforming die, the blank is pressed by the blank holder, and the die radius cooling element is activated to ensure the strength of the die radius deformation area;

[0093] 6. Complete preforming to obtain the preformed head intermediate part; use a heating furnace to heat the preformed part at a temperature of 150°C to 250°C for 1 to 3 hours;

[0094] 7. Inject coolant into the final forming die to make the punch lower than room temperature or 100℃~150℃ lower than the blank. Place the preformed intermediate part on the final forming die. Figure 6 As shown; start the die radius cooling element to ensure the strength of the die radius deformation area;

[0095] 8. Complete the parts manufacturing, and the thickness distribution of the parts is between 4.9 and 5.6 mm. The accumulated thickness distribution law is the manufacturing requirement to optimize the blank thickness compensation and start the manufacturing of the second head.

[0096] It should be noted that the various embodiments in this specification are described in a progressive manner. References to the same or similar parts between the various embodiments are sufficient. Each embodiment focuses on the differences from the other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and technologies are omitted here.

[0097] The above are merely embodiments of the present application and are not intended to limit the present application. Various modifications and variations are possible for those skilled in the art without departing from the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for controlling the thickness uniformity of an aluminum alloy thin-walled integral head, characterized in that: The method comprises the following steps: According to the size of the head part to be formed, the thickness variation law is followed by reverse compensation to the blank through unequal thickness thinning processing; Preheating the thinned blank; Placing the thinned blank in the preforming die, drawing it to a specified depth, and lowering the temperature of the blank at the corner of the die through a cooling element to obtain the preformed part; heating the preformed part to a set temperature; A coolant is placed in the cavity of the final forming die, and the heated preformed part is placed in the final forming die; The final-shaped part is obtained by deep drawing using a punch filled with the coolant.

2. The method for controlling the thickness uniformity of an aluminum alloy thin-walled integral head according to claim 1, characterized in that: The method of reversely compensating the blank by unequal thickness thinning according to the size of the head part to be formed and the thickness variation law is specifically comprised of the following steps: According to the size of the head part, the size of the blank is expanded and calculated to obtain the outer dimensions of the blank; The blank is thinned according to the outer dimensions.

3. The method for controlling the thickness uniformity of an aluminum alloy thin-walled integral head according to claim 2, characterized in that: The method of expanding and calculating the size of the blank according to the size of the head part to obtain the outer dimensions of the blank specifically includes the following steps: Use numerical simulation methods or thickness data accumulated from actual production to determine the thickness variation law of the head stamping; According to the thickness variation rule, the thickness of the thinned area or thickened area of the final-formed part is reversely compensated to the blank to obtain the outer dimensions of the blank.

4. The method for controlling the thickness uniformity of an aluminum alloy thin-walled integral head according to claim 1, characterized in that: The step of heating the preformed part to a set temperature is specifically as follows: The preformed parts are heated in a heating furnace, wherein the heating temperature is 150° C. to 250° C. and the heating time is 1 to 3 hours.

5. The method for controlling the thickness uniformity of an aluminum alloy thin-walled integral head according to claim 1, characterized in that: The coolant is injected into the convex mold of the final forming mold to make the convex mold lower than room temperature or lower than 100° C. to 150° C. of the preformed part.

6. The method for controlling the thickness uniformity of an aluminum alloy thin-walled integral head according to claim 1, characterized in that: The thinned blank is preheated, specifically: The thinned blank is preheated in a heating furnace; wherein the preheating temperature is 150° C. to 250° C., and the preheating time is 1 to 3 hours.

7. The method for controlling the wall thickness uniformity of an aluminum alloy thin-walled integral head according to any one of claims 1 to 6, characterized in that: The blank is an aluminum alloy plate with a plate width of ≥3000 mm and a thickness of ≤5.5 mm.

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