An eccentric thin-walled structural component, a molded cavity assembly structure, and a preparation method thereof.

Abstract

This invention relates to the field of aluminum-based composite materials technology, specifically to an eccentric thin-walled structural component, a molded cavity assembly structure, and a preparation method thereof. The structural component is prepared using this method. The preparation method includes assembling the molded cavity assembly structure; spraying a release agent onto the inner wall surface of the molded cavity; filling the molded cavity in batches with aluminum alloy powder of a target composition ratio, and obtaining a blank through multiple cold pressing passes; wherein the aluminum alloy powder includes a reinforcing phase with a mass percentage of 40%-70%; obtaining a pre-finished product through hot pressing sintering; disassembling the molded cavity, removing the pre-finished product, and obtaining the eccentric thin-walled structural component through post-processing. This invention not only yields eccentric thin-walled structural components with high tensile strength but also significantly improves material utilization, significantly reduces processing time and costs, solves the problem of stress concentration leading to cracks or even breakage during blank demolding, and addresses the issues of large processing allowances and high processing difficulty.

Description

Technical Field

[0001] This invention relates to the field of aluminum-based composite materials technology, specifically to an eccentric thin-walled structural component, a molded cavity assembly structure, and a preparation method thereof. Background Technology

[0002] Aluminum matrix composites have been widely used in aerospace, automotive manufacturing, and engineering structures due to their high specific strength, high specific stiffness, and excellent corrosion resistance. However, traditional methods for preparing aluminum matrix composites face many challenges in achieving high-content reinforcing phase aluminum matrix composites, especially for the preparation of eccentric thin-walled structural components, which suffers from high fabrication difficulty and processing costs.

[0003] Currently, traditional methods for preparing aluminum matrix composites generally include stir casting, powder metallurgy, and methods involving the preparation of ingots followed by machining. Among these, stir casting suffers from the problem of reinforcing phase sedimentation, especially when preparing aluminum matrix composites with high volume fraction of reinforcing phase. The reinforcing phase is difficult to distribute uniformly within the matrix, leading to unstable material properties and even affecting the service life and reliability of the final product. Compared to stir casting, powder metallurgy can achieve a uniform distribution of 70% reinforcing phase in aluminum matrix composites, effectively improving the material's mechanical properties, wear resistance, and high-temperature performance. However, for eccentric thin-walled structural parts (height 150-300mm, wall thickness 3-10mm, inner diameter of the hollow section 100-200mm, length and width of the eccentric part 100-160mm), powder metallurgy, due to the high height and thin wall of the cold-pressed billet, is prone to stress concentration during demolding, leading to cracks or even breakage. The method of first preparing the ingot and then machining it has problems such as large machining allowance and high machining difficulty. Especially for eccentric thin-walled structural parts with high ceramic content, the machining allowance and machining difficulty increase many times, which greatly increases the processing cost.

[0004] In summary, there is a need to develop an eccentric thin-walled structural component, a molded cavity assembly structure, and a preparation method to solve the problems existing in the current powder metallurgy method and the method of preparing ingots first and then machining them. Summary of the Invention

[0005] The purpose of this invention is to provide an eccentric thin-walled structural component, a molded cavity assembly structure, and a manufacturing method thereof. The specific technical solution is as follows:

[0006] In a first aspect, the present invention provides a molding cavity assembly structure for an eccentric thin-walled structural component, comprising an upper mold detachably disposed at the upper end of a female mold, and a lower mold detachably disposed at the lower end of the female mold; a heating element circumferentially disposed on the outer side of the female mold; a core column coaxially disposed within the female mold, with a circumferential pre-reserved gap between them; a plurality of detachable reinforcing rib mold blocks circumferentially spaced within the circumferential pre-reserved gap, and each of the detachable reinforcing rib mold blocks being disposed on the inner wall of the female mold; both ends of the core column being interference-fitted with the upper mold and the lower mold respectively; and a molding cavity being formed by the female mold, the upper mold, the lower mold, the core column, and all the detachable reinforcing rib mold blocks.

[0007] Optionally, the spacing between any two adjacent removable reinforcing rib mold blocks is 3-10 mm.

[0008] Optionally, the upper mold includes a main body, a first eccentric side plate, and a second eccentric side plate; the main body includes an integrally formed first arc segment and a second arc segment, which are symmetrically curved towards each other; the first eccentric side plate and the second eccentric side plate are respectively disposed on both sides of the main body, and both are connected to the main body by an arc; each corner of the first eccentric side plate on the side away from the main body is chamfered, and each corner of the second eccentric side plate on the side away from the main body is chamfered, and the radius of each chamfer is R7-R15.

[0009] Optionally, the height of the female mold is 300-500mm.

[0010] In a second aspect, the present invention provides a method for manufacturing an eccentric thin-walled structural component, comprising:

[0011] Step S1: Assemble the molding cavity assembly structure of the eccentric thin-walled structural component to form the molding cavity;

[0012] Step S2: Spray a release agent onto the inner wall surface of the molding cavity;

[0013] Step S3: After the release agent dries, aluminum alloy powder with the target composition ratio is filled into the molding cavity in batches, and a blank is obtained by cold pressing in multiple passes; wherein, the aluminum alloy powder includes a reinforcing phase with a mass percentage of 40%-70%;

[0014] Step S4: The preform in the molding cavity is subjected to hot pressing and sintering treatment to obtain a pre-finished product;

[0015] Step S5: Disassemble the molding cavity, remove the pre-finished product, and obtain the molded eccentric thin-walled structural component through post-processing.

[0016] Optionally, the aluminum alloy powder may further include the following components in weight percentage: 25%-55% aluminum powder, 2%-4% copper powder, 1%-2% magnesium powder and 0.2%-1% zinc powder; the aluminum powder has a particle size of 10-120 μm, and the reinforcing phase has a particle size of 10-120 μm; the reinforcing phase includes at least one of silicon carbide, titanium carbide and zirconium oxide.

[0017] Optionally, the final pressure used in the multi-pass cold pressing is 100-200MPa, and the holding time is 10-20s; the cold pressing pressure of each pass before the final pressure in the multi-pass cold pressing is 50-100MPa.

[0018] Optionally, the hot pressing sintering process uses a hot pressing pressure of 100-150 MPa, a sintering temperature of 560-600℃, and a sintering time of 0.5-1 h; the hot pressing pressure is maintained during the sintering stage until the sintering is completed; the hot pressing sintering process is completed under an inert atmosphere.

[0019] Optionally, the post-processing includes machining; or, the post-processing includes machining and multiple heating and cooling processes.

[0020] In a third aspect, the present invention provides an eccentric thin-walled structural component, which is prepared by the aforementioned method for preparing eccentric thin-walled structural components.

[0021] The application of the technical solution of the present invention has at least the following beneficial effects:

[0022] (1) The present invention provides a molding cavity combination structure for an eccentric thin-walled structural component, which can form a molding cavity for the eccentric thin-walled structural component, and solves the problems of large processing allowance and high processing difficulty in the prior art method of preparing round ingots first and then machining.

[0023] (2) The method for preparing an eccentric thin-walled structural component provided by the present invention employs a specific molding cavity combination structure in step S1 to form a detachable molding cavity, thereby avoiding stress concentration and cracking or even breakage during demolding of the blank; the method employs a release agent sprayed in step S2 to prevent the aluminum alloy powder from reacting with the inner wall of the molding cavity during hot pressing and sintering, and to facilitate demolding of the pre-finished product; the method employs step S3 to limit the aluminum alloy powder to contain 40%-70% by mass of reinforcing phase, thereby preparing an eccentric thin-walled component with a high content of reinforcing phase. The method of preparing eccentric thin-walled structural components results in high tensile strength. The batch filling and multi-pass cold pressing operation allows for the selection of a suitable die for the height of the billet, eliminating the need for excessively tall dies and reducing die usage costs. The hot pressing sintering treatment in step S4 accelerates the diffusion rate of low-melting-point alloying elements in the billet, achieving metallurgical bonding at the interface of the billet pressed during the multi-pass cold pressing stage. Step S5 involves disassembling the forming cavity and subsequent post-processing to obtain the formed eccentric thin-walled structural component. This invention not only yields eccentric thin-walled structural components with high tensile strength but also significantly improves material utilization and reduces processing time and costs.

[0024] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0026] Figure 1 This is a schematic diagram of the axial cross-sectional structure of the molding cavity assembly structure of an eccentric thin-walled structural component in Example 1.

[0027] Figure 2 This is a schematic cross-sectional view of the molded cavity assembly structure of an eccentric thin-walled structural component in Example 1.

[0028] Figure 3 yes Figure 1 Schematic diagram of the upper and middle mold;

[0029] Figure 4 yes Figure 1 Schematic diagram of the middle and lower mold structure;

[0030] Figure 5 yes Figure 1 Schematic diagram of the detachable reinforcing rib mold block;

[0031] Among them, 1. Female mold, 2. Upper mold, 2.1. Main body, 2.2. First eccentric side plate, 2.3. Second eccentric side plate, 3. Lower mold, 4. Core column, 5. Detachable reinforcing rib mold block, 5.1. First arc block, 5.2. Second arc block. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0033] Example 1:

[0034] See Figures 1-5 A molding cavity assembly structure for an eccentric thin-walled structural component includes an upper mold 2 (made of H13 steel) detachably mounted on the upper end of a female mold 1 (the height of the female mold 1 is 300-500mm, specifically 500mm; the material of the female mold 1 is H13 steel); a lower mold 3 (the lower mold 3 is annular, with a thickness of 10-20mm; the material of the lower mold 3 is H13 steel) detachably mounted on the lower end of the female mold 1; and a circumferentially arranged... Heating elements (specifically electric heating rods), numbering 8-12, each with the same height as the female mold 1, are arranged sequentially and circumferentially on the outer side of the female mold 1 and connected to a power source; a core pillar 4 (made of H13 steel) is coaxially arranged inside the female mold 1, with a circumferential pre-reserved gap between them, the width of which is 15-30mm; multiple detachable reinforcing rib mold blocks 5 (detachable) are arranged circumferentially at intervals within the circumferential pre-reserved gap. The reinforcing rib mold is made of H13 steel or 45# steel, and each of the detachable reinforcing rib mold blocks 5 is provided on the inner wall of the female mold 1 (specifically, blind holes (diameter 5-10mm, depth 6-10mm) are provided on each of the detachable reinforcing rib mold blocks 5, and through holes adapted to the blind holes are provided on the female mold 1. The same internal thread structure is provided on the inner wall surface of the blind holes and the through holes. H13 steel rods with external thread structures adapted to the internal thread structure are inserted and locked in the blind holes and the through holes, so that each of the detachable reinforcing rib mold blocks 5 can be detachably fitted onto the inner wall of the female mold 1); the two ends of the core column 4 are respectively interference-fitted with the upper mold 2 and the lower mold 3 (specifically, mounting through holes adapted to the core column 4 are provided on the upper mold 2 and the lower mold 3); the female mold 1, the upper mold 2, the lower mold 3, the core column 4 and all the detachable reinforcing rib mold blocks 5 form a molding cavity.

[0035] See Figure 5The spacing between any two adjacent detachable reinforcing rib mold blocks 5 is 10mm. Each detachable reinforcing rib mold block 5 comprises an integrally formed first arc-shaped block 5.1 and a second arc-shaped block 5.2, which are arranged sequentially along a direction away from the inner wall of the female mold 1. The size of the second arc-shaped block 5.2 is smaller than the size of the first arc-shaped block 5.1. The number, shape, and arrangement of the detachable reinforcing rib mold blocks 5 are determined according to the structural condition of the eccentric thin-walled structural component. Generally, the number of detachable reinforcing rib mold blocks 5 is 5-12.

[0036] See Figure 3 The upper mold 2 includes a main body 2.1, a first eccentric side plate 2.2, and a second eccentric side plate 2.3. The main body 2.1 includes an integrally formed first arc segment and a second arc segment, which are symmetrically curved towards each other. The first eccentric side plate 2.2 and the second eccentric side plate 2.3 are respectively disposed on both sides of the main body 2.1 and are both connected to the main body 2.1 by an arc. Each corner of the first eccentric side plate 2.2 on the side away from the main body 2.1 is chamfered, and each corner of the second eccentric side plate 2.3 on the side away from the main body 2.1 is chamfered. The radius of each chamfer is R7-R15 (radius unit is mm). The use of arc connection and chamfer structure with specific radius facilitates demolding of the pre-finished product.

[0037] A method for fabricating an eccentric thin-walled structural component, comprising:

[0038] Step S1: Assemble the molding cavity assembly structure of the eccentric thin-walled structural component to form the molding cavity;

[0039] Step S2: Spray a release agent (specifically graphite) onto the inner wall of the molding cavity. The spray thickness is 1-3mm. This is to prevent the aluminum alloy powder from reacting with the inner wall of the molding cavity during hot pressing and sintering, and to facilitate the demolding of the pre-finished product.

[0040] Step S3: After the release agent dries, aluminum alloy powder with the target composition ratio is filled into the molding cavity in batches, and a blank is obtained by cold pressing in multiple passes. The operation method of batch filling and cold pressing in multiple passes makes it easier to select a female mold 1 that matches the height of the blank when making a blank of a certain height, without having to select an excessively tall female mold 1, thereby reducing the cost of using female mold 1; wherein, the aluminum alloy powder includes a reinforcing phase with a mass percentage of 48%;

[0041] Step S4: The preform in the molding cavity is subjected to hot pressing and sintering treatment to obtain a pre-finished product;

[0042] Step S5: Disassemble the molding cavity, remove the pre-finished product, and obtain the molded eccentric thin-walled structural component through post-processing.

[0043] The aluminum alloy powder also includes the following components by mass percentage: 45% aluminum powder, 4% copper powder, 2% magnesium powder, and 1% zinc powder; the aluminum powder has a particle size of 10-120 μm (the D50 particle size of the aluminum powder is 30 μm), and the reinforcing phase has a particle size of 10-120 μm (the D50 particle size of the reinforcing phase is 70 μm); the reinforcing phase is silicon carbide and titanium carbide, and the mass ratio of silicon carbide to titanium carbide is 5:1. The aluminum alloy powder with this specific component ratio facilitates the fabrication of eccentric thin-walled structural parts with a dense structure.

[0044] In the multi-pass cold pressing (a total of 4 passes), the final pressure is 200 MPa, and the holding time is 20 seconds. Each pass before the final pressure in the multi-pass cold pressing process has a pressure of 50 MPa and requires no holding time. By using multi-pass cold pressing, the relatively low pressure in the passes before the final pressure results in a relatively low density of the green body. Under the high pressure of the final pressure, the powder at the green body interface can flow between each other, forming a complete green body without obvious interfaces.

[0045] The hot-pressing sintering process employs a hot-pressing pressure of 100 MPa, a sintering temperature of 560℃, and a sintering time of 1 hour. The hot-pressing pressure is maintained during the sintering stage until completion. The hot-pressing sintering process is completed under an inert atmosphere. Specifically, before the hot-pressing sintering process, a high-temperature, airtight sleeve is used to enclose the forming cavity assembly structure and the pressure head required for hot pressing, for heat preservation and the introduction of inert gas. The forming cavity and the high-temperature sleeve are connected, and the inert atmosphere is a nitrogen atmosphere. Nitrogen gas is introduced into the forming cavity and the high-temperature sleeve until the dew point reaches -40℃ to ensure the high purity of the inert atmosphere, thereby preventing the billet from being oxidized during the hot-pressing sintering process and improving the sintering quality of the billet. The hot-pressing sintering process accelerates the diffusion rate of low-melting-point alloying elements in the billet, enabling metallurgical bonding at the interface of the billet pressed in the multiple cold pressing stages.

[0046] The post-processing includes machining; or, the post-processing includes machining and multiple heating and cooling processes. Specifically, a CNC lathe is used to machine a width of 2-5mm on the interface where the detachable reinforcing rib mold block 5 is joined to the pre-finished product. The detachable reinforcing rib mold block 5 is then removed by tapping. If tapping is insufficient to remove the detachable reinforcing rib mold block 5, the pre-finished product embedded with the detachable reinforcing rib mold block 5 is subjected to multiple heating processes (using a heating temperature of 200-400℃, specifically 300℃) and cooling. Utilizing the difference in thermal expansion coefficients between the aluminum-based composite material and steel, the detachable reinforcing rib mold block 5 is loosened and then removed.

[0047] Comparative Example 1 (preparing round ingots first and then machining them into shape):

[0048] Unlike Example 1, in step S1, the forming cavity is a cylindrical cavity, and the inner diameter of the cylinder is the same as the outer diameter of the upper mold 2. After demolding in step S5, a cylindrical blank is obtained, which is then machined to obtain an eccentric thin-walled structural part with the same shape as in Example 1.

[0049] Comparative Example 2:

[0050] Unlike Comparative Example 1, the sintering temperature was 600℃ and the sintering time was 3h.

[0051] Table 1 shows the statistical data on processing time, processing cost, material utilization rate, and tensile strength of the eccentric thin-walled structural parts with the same shape prepared in Examples 1 and Comparative Examples 1-2. The tensile strength data was obtained according to GB_T228.1-2021 Metallic materials, tensile testing—Part 1: Test methods at room temperature. Regarding processing time and processing cost data, the data from Comparative Example 1 is used as the baseline, while the data from Examples 1 and Comparative Examples 2 are percentage data compared to Comparative Example 1.

[0052] Table 1. Processing time, processing cost, material utilization rate, and tensile strength data.

[0053]

[0054] As shown in Table 1, compared with Comparative Examples 1-2, the eccentric thin-walled structural component prepared by Example 1 of this invention not only has high tensile strength, but also significantly improves material utilization and significantly reduces processing time and processing cost.

[0055] In Comparative Example 1, the cylindrical blank was directly machined into an eccentric thin-walled structural component. This resulted in a large machining allowance, very low material utilization, long machining time, and high machining costs, which is not conducive to industrial production. Furthermore, compared to Example 1, the eccentric thin-walled structural component prepared in Comparative Example 1 had lower tensile strength. This is mainly because the cylindrical blank was heated by heat transfer from the mold, resulting in lower temperatures closer to the center of the blank. Additionally, due to the short holding time, the closer the cylindrical blank was to the center, the more difficult it was to reach the sintering temperature, hindering the achievement of sufficient metallurgical bonding at the blank interface, thus leading to even lower tensile strength.

[0056] Compared to Comparative Example 1, Comparative Example 2 increased the sintering temperature and extended the sintering time. Although this improved the sintering quality and increased the tensile strength of the eccentric thin-walled structure, the tensile strength data still differed significantly from that of the eccentric thin-walled structure prepared in Example 1. This is mainly because the blank in Example 1 was almost a near-net-shape blank, with relatively thin sections. After hot pressing and sintering and demolding, the blank cooled rapidly in the air, resulting in more precipitated strengthening phases. This solid solution strengthening effect significantly improved the tensile strength.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A molding cavity assembly structure for an eccentric thin-walled structural component, characterized in that, The system includes a detachable upper mold (2) at the upper end of a female mold (1) and a detachable lower mold (3) at the lower end of the female mold (1); a heating element is circumferentially arranged on the outer side of the female mold (1); a core column (4) is coaxially arranged inside the female mold (1) with a circumferential pre-reserved gap between them; multiple detachable reinforcing rib mold blocks (5) are circumferentially spaced in the circumferential pre-reserved gap, and each of the detachable reinforcing rib mold blocks (5) is arranged on the inner wall of the female mold (1); the two ends of the core column (4) are respectively press-fitted with the upper mold (2) and the lower mold (3); and a molding cavity is formed by the female mold (1), the upper mold (2), the lower mold (3), the core column (4), and all the detachable reinforcing rib mold blocks (5). The upper mold (2) includes a main body (2.1), a first eccentric side plate (2.2), and a second eccentric side plate (2.3). The main body (2.1) includes an integrally formed first arc segment and a second arc segment, which are symmetrically bent towards each other. The first eccentric side plate (2.2) and the second eccentric side plate (2.3) are respectively disposed on both sides of the main body (2.1) and are both connected to the main body (2.1) by an arc. Each corner of the first eccentric side plate (2.2) on the side away from the main body (2.1) is chamfered, and each corner of the second eccentric side plate (2.3) on the side away from the main body (2.1) is chamfered. The radius of each chamfer is R7-R15.

2. The molding cavity assembly structure of the eccentric thin-walled structural component according to claim 1, characterized in that, The spacing between any two adjacent removable reinforcing rib mold blocks (5) is 3-10 mm.

3. The molding cavity assembly structure of the eccentric thin-walled structural component according to claim 1, characterized in that, The height of the female mold (1) is 300-500mm.

4. A method for preparing an eccentric thin-walled structural component, characterized in that, include: Step S1: Assemble the molding cavity assembly structure of the eccentric thin-walled structural member as described in any one of claims 1-3, for forming the molding cavity; Step S2: Spray a release agent onto the inner wall surface of the molding cavity; Step S3: After the release agent dries, aluminum alloy powder with the target composition ratio is filled into the molding cavity in batches, and a blank is obtained by cold pressing in multiple passes; wherein, the aluminum alloy powder includes a reinforcing phase with a mass percentage of 40%-70%; Step S4: The preform in the molding cavity is subjected to hot pressing and sintering treatment to obtain a pre-finished product; Step S5: Disassemble the molding cavity, remove the pre-finished product, and obtain the molded eccentric thin-walled structural part through post-processing; The hot pressing sintering process uses a hot pressing pressure of 100-150 MPa, a sintering temperature of 560-600℃, and a sintering time of 0.5-1 h; the hot pressing pressure is maintained during the sintering stage until the sintering is completed; the hot pressing sintering process is completed under an inert atmosphere.

5. The method for preparing an eccentric thin-walled structural component according to claim 4, characterized in that, The aluminum alloy powder also includes the following components in weight percentage: 25%-55% aluminum powder, 2%-4% copper powder, 1%-2% magnesium powder and 0.2%-1% zinc powder; the particle size of the aluminum powder is 10-120 μm, and the particle size of the reinforcing phase is 10-120 μm; the reinforcing phase includes at least one of silicon carbide, titanium carbide and zirconium oxide.

6. The method for preparing an eccentric thin-walled structural component according to claim 4, characterized in that, The final pressure used in the multi-pass cold pressing is 100-200MPa, and the holding time is 10-20s; the cold pressing pressure of each pass before the final pressure in the multi-pass cold pressing is 50-100MPa.

7. The method for preparing an eccentric thin-walled structural component according to claim 4, characterized in that, The post-processing includes machining; or, the post-processing includes machining and multiple heating and cooling processes.

8. An eccentric thin-walled structural component, characterized in that, It is prepared using the preparation method of the eccentric thin-walled structural component as described in claim 4.

Images