Method for manufacturing complex thin-walled metal components by using local additive manufacturing for blank making and hot gas bulging compounding

Abstract

The present invention belongs to the technical field of forming and manufacturing of thin-walled metal components, and discloses a method for manufacturing complex thin-walled metal components by combining local additive manufacturing of blanks and hot gas bulging. The steps are as follows: determining the overall forming scheme; pre-deforming the original blank; cutting local areas of the pre-deformed blank; 3D printing supplementary sections; finally, bulging and forming the prefabricated blank; and post-processing the bulged complex thin-walled metal component. The present invention not only avoids the problems such as long processing cycle, high material cost, and relatively high usage cost existing in 3D printing of blanks. Moreover, it is possible to prepare blanks with sufficient dimensions / width-thickness by 3D printing. When forming complex thin-walled metal components with large dimensions, the problem that the external dimensions of the required original blank exceed the existing blank preparation capacity can be solved. In addition, the present invention can also produce heterogeneous blanks with different thicknesses, and precisely control the wall thickness of each part of the component. Under the requirement of ensuring the service performance of the thin-walled metal component, the lightweight level of the component is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of forming and manufacturing of complex thin-walled metal components, and particularly relates to a method for manufacturing complex thin-walled metal components by local additive manufacturing of billets and hot gas expansion composite manufacturing. Background Art

[0002] Complex thin-walled metal components are a very common type of structural components in the fields of aerospace, as well as in transportation equipment such as automobiles and high-speed rails. According to the service requirements of complex thin-walled metal components, such as tensile strength, shape and size, corrosion resistance, etc., it is first necessary to select the material of the component and optimize the design of the shape and size. Then, a suitable metal billet is selected, and a suitable forming method is used to manufacture the required complex thin-walled metal component. The formed complex thin-walled metal component must meet the design requirements in terms of shape and size, wall thickness distribution, mechanical properties, etc. At the same time, it is also necessary to consider comprehensively from the perspectives of the difficulty of the forming process during manufacturing, material utilization rate, production efficiency, manufacturing cost, etc.

[0003] Currently, the thin-walled billets used to manufacture complex thin-walled metal components are mainly thin-walled plate billets and thin-walled tube billets. When manufacturing complex thin-walled metal components using traditional processes (such as machining or plastic forming), the following problems exist: (1) When forming complex thin-walled components, it is necessary to undergo very complex deformations, and problems such as wrinkling, cracking, and uneven wall thickness are likely to occur. (2) It is often difficult to prepare billets with sufficient dimensions / width-thickness for high-performance materials. For example: for aluminum alloy plate billets with a thickness less than 5 mm, the maximum width of the billets that can be prepared by existing rolling equipment is approximately 2.5 m. (3) For materials with poor forming performance, such as magnesium alloys, cracking and other problems are extremely likely to occur in local large deformation or complex deformation regions during forming. To solve the above problems, the existing processes for manufacturing complex thin-walled metal components mainly include two types: (1) The process of stamping and forming in blocks first and then welding: that is, large parts are divided into small individual components and stamped and formed separately, and complex-shaped thin-walled components are prepared by subsequent welding and shaping. (2) The process of welding blank preparation + hot gas expansion forming: that is, under the requirement of ensuring the service performance of complex thin-walled metal components, the lightweight level of metal components can be increased as much as possible. The blank with different thicknesses, different properties and different materials can be obtained by welding, and then the complex shape can be obtained by the large deformation of the original blank. The former is often difficult to control the springback during stamping and forming, and welding deformation and coarse grain structure are likely to occur during the subsequent welding process, reducing its reliability and accuracy. The latter is prone to defects such as wrinkling, cracking or uneven wall thickness in local areas during hot gas pressure forming due to the large difference between the shape of the preformed blank and the shape of the final component. In addition, after welding, due to the different structures and mechanical properties of the weld zone and the base metal, the interaction of each region during deformation makes it difficult to coordinate the deformation of the weld and the base metal.

[0004] To reduce the above-mentioned defects, the invention patent (Patent No.: 201911365925.5) proposes a method for manufacturing complex thin-walled metal components using 3D printing and hot gas pressure bulging, that is, first preparing a preform close to the shape of the final component by 3D printing, and then obtaining the required dimensional accuracy and structural properties of the component through hot gas pressure forming. However, although complex thin-walled metal components with complex shapes can be prepared in principle using this process, for large-sized complex thin-walled metal components, when using 3D printing to make the preform, there are problems such as long processing cycles, relatively high material costs, the need for a dedicated processing environment, and relatively high usage costs. In addition, when printing components with extremely thin walls of large sizes, due to the inherent large temperature gradient and high cooling rate of additive manufacturing technology, the residual stress inside the printing material is increased, and thus the deformation tendency is increased. When the deformation amount reaches a certain level, it is easy to cause the laser beam to be unable to act on the cross-section of the formed component, making it difficult for the blank to continue to be formed.

[0005] To solve the problems existing in the existing 3D printing method when preparing large-sized thin-walled blanks, such as long processing cycles, high manufacturing costs, and the difficulty in continuously forming the blank due to large residual stress deformation caused by complex thermal conditions during the printing process, a new forming method for complex thin-walled metal components needs to be developed. Summary of the Invention

[0006] The object of the present invention is to provide a method for manufacturing complex thin-walled metal components using local additive manufacturing of the preform and hot gas inflation composite, which can solve the problems existing in the existing 3D printing method when preparing large-sized thin-walled blanks, such as long processing cycles, high manufacturing costs, and the difficulty in continuously forming the blank due to large residual stress deformation caused by complex thermal conditions during the printing process.

[0007] Technical Solution of the Present Invention:

[0008] A method for manufacturing complex thin-walled metal components using local additive manufacturing of the preform and hot gas inflation composite comprises the following steps:

[0009] Step 1. Determination of the overall forming scheme: Analyze the characteristics of the complex thin-walled metal component to be prepared to obtain the geometric characteristics of the local complex area and the geometric shape of the external overall contour of the complex thin-walled metal component; the preform is prepared by pre-deforming the original blank and local additive manufacturing. The local complex area of the complex thin-walled metal component is approximately formed by 3D printing, and the geometric shape of the external overall contour of the complex thin-walled metal component is integrally gas-expanded by a hot gas pressure forming process.

[0010] Step 2. Pre - deformation of the original blank: According to the analysis results of the geometric shape of the external overall contour of the complex thin - walled metal component in Step 1, determine the pre - deformation process of the original blank. For a pre - formed tube blank with a planar two - dimensional axis, perform one - time pre - bending and one - time flattening forming preparation; for a pre - formed tube blank with a spatial three - dimensional axis, perform multiple pre - bending and multiple flattening forming preparations. During the pre - forming process, a pressure medium is evenly distributed inside the original tube blank to prevent wrinkling and cracking during the deformation process; for a pre - formed plate blank with a simple shape and a half - cone angle < 40°, perform single - pass pre - deformation; for a pre - formed plate blank with a complex shape and a half - cone angle ≥ 40°, use more than two - pass pre - deformation.

[0011] Step 3. Cutting of local areas of the pre - deformed blank: According to the analysis results of the geometric features of the local complex areas of the complex thin - walled metal component in Step 1, determine the cutting areas required for the pre - deformed blank and use numerical control machining methods or laser cutting, etc. to perform cutting processing on the areas to be cut of the pre - deformed blank; cut the required areas on the pre - deformed blank, and then perform grinding and cleaning on the cutting areas to achieve good metallurgical bonding with the subsequent 3D printing and the pre - deformed blank.

[0012] Step 4. 3D printing of the supplementary section: Adjust the position and angle of the cut pre - deformed blank obtained in Step 3 according to the design requirements and fix it on the workbench. According to the analysis results of the geometric features of the local complex areas of the thin - walled metal component in Step 1, determine the material and contour shape of the 3D - printed supplementary section. The material for 3D printing uses a material with properties similar to the original blank or higher strength and stiffness than the original blank according to the service performance of the local area of the complex thin - walled metal component. Then, use 3D printing technology to perform local additive manufacturing on the cutting area of the pre - deformed blank to achieve approximate forming of the local complex area, thereby obtaining the final pre - formed blank.

[0013] Step 5. Hydro - forming of the final pre - formed blank: Heat the hydro - forming die so that the temperature of the hydro - forming die reaches the set conditions. Place the pre - formed blank after local additive manufacturing obtained in Step 4 into the hydro - forming die, close the die, and then fill the inside of the pre - formed blank with a high - pressure gas medium to cause the pre - formed blank to undergo hydro - forming deformation and conform to the cavity of the hydro - forming die to obtain the required external contour. At the same time, keep the hydro - forming die in a closed state, allow the formed complex thin - walled metal component to stay at high temperature and high pressure for a certain period of time, reduce the gas pressure inside or on the surface of the complex thin - walled metal component to the set value, and after the temperature of the hydro - forming die drops to the set value, take out the formed complex thin - walled metal component.

[0014] Step 6. Post-treatment of the hydroformed complex thin-walled metal component: Remove the process section from the hydroformed complex thin-walled metal component, and perform necessary deburring, polishing, and cleaning on the ends and surface of the complex thin-walled metal component to obtain the final required complex thin-walled metal component.

[0015] The beneficial effects of the present invention are as follows:

[0016] (1) The present invention adopts a method of fabricating complex thin-walled metal components by local additive manufacturing of blanks and hydroforming. When fabricating complex thin-walled metal components by this method, first, the original blank is plastically formed and machined to obtain a preformed blank with several shaped holes, then local additive manufacturing is carried out on the preformed blank using 3D printing technology, and finally, integral forming is carried out by hydroforming. This avoids problems such as long processing cycles, high material costs, the need for a dedicated processing environment, relatively high usage fees, and difficulty in continuously forming the blank due to large residual stress deformation caused by complex thermal conditions during the printing process.

[0017] (2) The present invention adopts a method of fabricating complex thin-walled metal components by local additive manufacturing of blanks and hydroforming. When fabricating complex thin-walled metal components by this method, blanks with sufficient dimensions / width-thickness can be prepared by 3D printing technology. When forming complex thin-walled metal components with larger dimensions, the problem that the required external dimensions of the original blank exceed the existing blank preparation capacity can be solved.

[0018] (3) The present invention adopts a method of fabricating complex thin-walled metal components by local additive manufacturing of blanks and hydroforming. When fabricating complex thin-walled metal components by this method, heterogeneous differential-thickness blanks can be made by cutting and 3D printing technology to precisely control the wall thickness of each part area of the complex thin-walled metal component. Under the condition of ensuring the service performance requirements of the thin-walled metal component, the lightweight level of the component is maximally improved. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the method for fabricating complex thin-walled metal components by local additive manufacturing of blanks and hydroforming.

[0020] Figure 2 It is a schematic diagram of an equal-diameter tube.

[0021] Figure 3 It is a schematic diagram of the tube blank after the first pre-forming and flattening of the equal-diameter tube.

[0022] Figure 4 It is a schematic diagram of the tube blank after the second pre-forming of the equal-diameter tube.

[0023] Figure 5 It is a schematic diagram of the blank obtained by locally cutting the preformed tube blank.

[0024] Figure 6 Schematic diagram of the 3D printing supplementary section for the pre-deformed tube blank after cutting.

[0025] Figure 7 Schematic diagram of the blank obtained by 3D printing the supplementary section for the pre-deformed tube blank after cutting.

[0026] Figure 8 Schematic diagram of hot gas bulging forming.

[0027] Figure 9 Schematic diagram of the component after hot gas bulging forming.

[0028] In the figure: 1 equal-diameter tube, 2 tube blank after the first pre-forming flattening, 3 tube blank after the second pre-forming flattening, 4 blank obtained by locally cutting the pre-deformed tube blank, 5 powder feeder, 6 laser head, 7 workbench, 8 blank fixing die, 9 blank obtained after local cutting of the tube blank and additive manufacturing, 10 gas source control switch, 11 high-pressure gas source, 12 left punch, 13 water-cooling plate, 14 heat insulation plate, 15 upper die, 16 right punch, 17 lower die, 18 part after hot gas bulging forming. Specific implementation manners

[0029] The following further illustrates the specific implementation manners of the present invention in combination with the attached drawings and technical solutions.

[0030] Example 1: In combination with Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 It is described that the method for manufacturing complex thin-walled metal components by combining local additive manufacturing of blanks and hot gas bulging is carried out according to the following steps:

[0031] A method for manufacturing complex thin-walled metal components by combining local additive manufacturing of blanks and hot gas bulging, the steps are as follows:

[0032] Step 1. Determination of the overall forming scheme: Analyze the characteristics of the complex thin-walled metal component to be prepared to obtain the geometric characteristics of the local complex area and the geometric shape of the external overall contour of the complex thin-walled metal component; The preform is prepared by pre-deforming the original blank and local additive manufacturing. The local complex area of the complex thin-walled metal component is approximately formed by the 3D printing method, and the geometric shape of the external overall contour of the complex thin-walled metal component is integrally gas-expanded formed by the hot gas pressure forming process;

[0033] Step 2. Pre-deform the original blank: According to the analysis results of the geometric shape of the external overall contour of the complex thin-walled metal component in Step 1, determine the pre-deformation process of the original blank. For the prefabricated pipe blank with a planar two-dimensional axis, perform one-time pre-bending and one-time flattening forming preparation; for the prefabricated pipe blank with a spatial three-dimensional axis, perform multiple pre-bending and multiple flattening forming preparations. During the pre-forming process, a pressure medium is evenly distributed inside the original pipe blank to prevent wrinkling and cracking during the deformation process; for the prefabricated plate blank with a simple shape and a half cone angle < 40°, perform single-pass pre-deformation; for the prefabricated plate blank with a complex shape and a half cone angle ≥ 40°, use more than two passes of pre-deformation;

[0034] Step 3. Cut the local area of the pre-deformed blank: According to the analysis results of the geometric features of the local complex area of the complex thin-walled metal component in Step 1, determine the cutting area required for the pre-deformed blank and use numerical control machining methods or laser cutting, etc. to perform cutting processing on the cutting area of the pre-deformed blank; cut the required area on the pre-deformed blank, and then perform grinding and cleaning on the cutting area to achieve good metallurgical bonding with the pre-deformed blank for subsequent 3D printing;

[0035] Step 4. 3D print the supplementary section: Adjust the position and angle of the pre-deformed blank with several special-shaped holes obtained in Step 3 according to the design requirements and fix it on the workbench. According to the analysis results of the geometric features of the local complex area of the thin-walled metal component in Step 1, determine the material and contour shape of the 3D printed supplementary section. The material for 3D printing uses a material with properties similar to those of the original blank or with higher strength and stiffness than the original blank according to the service performance of the local area of the complex thin-walled metal component. Then use 3D printing technology to perform local additive manufacturing on the cutting area of the pre-deformed blank to achieve approximate forming of the local complex area, thereby obtaining the final prefabricated blank;

[0036] Step 5. Expand and form the final prefabricated blank: Heat the hot gas expansion forming die to make the temperature of the expansion forming die reach the set conditions. Place the prefabricated blank after local additive manufacturing obtained in Step 4 in the expansion forming die, close the die, and then fill the prefabricated blank with a high-pressure gas medium to make the prefabricated blank undergo expansion deformation and conform to the cavity of the expansion forming die to obtain the required external contour. At the same time, keep the expansion forming die in a closed state, make the formed complex thin-walled metal component stay at high temperature and high pressure for a certain period of time, reduce the gas pressure inside or on the surface of the complex thin-walled metal component to the set value, and after the temperature of the expansion forming die drops to the set value, take out the formed complex thin-walled metal component;

[0037] Step 6. Post-treatment of the hydroformed complex thin-walled metal component: Remove the process section from the complex thin-walled metal component after hydro-pneumatic forming, and perform necessary deburring, polishing and cleaning on the ends and surfaces of the complex thin-walled metal component to obtain the final required complex thin-walled metal component.

[0038] When preparing a complex thin-walled metal component by the method of the present invention, first perform plastic forming and machining on the original blank to obtain a preformed blank, then perform local additive manufacturing on the preformed blank by 3D printing technology, and finally perform local or overall forming by hydro-pneumatic forming. This method can avoid problems such as long processing cycle, high material cost, need for a special processing environment, relatively high usage cost, and difficulty in continuous forming of the blank due to large residual stress deformation caused by complex thermal conditions during the printing process when manufacturing the blank by 3D printing. Moreover, when preparing a complex thin-walled metal component by this method, a blank with sufficient size / width-thickness can be prepared by 3D printing technology. When forming a complex thin-walled metal component with a large size, the problem that the external dimension of the required original blank exceeds the existing blank preparation capacity can be solved. In addition, this method can also be made into a heterogeneous differential thickness blank by cutting and 3D printing technology to accurately control the wall thickness of each part area of the complex thin-walled metal component. Under the requirement of ensuring the service performance of the thin-walled metal component, the lightweight level of the component is improved to the greatest extent.

[0039] Example 2: Combine Figure 2 , Figure 3 , Figure 4 It is described that in Step 2, after necessary cutting and grinding of the equal-diameter tube, fill it with a solid medium; then place it in a preforming die, close the die, form the equal-diameter tube into the required preformed blank, keep the hydroforming die in a closed state for a certain period of time, then take out the preformed blank, and take out the solid medium to obtain the blank after the first preforming press bending. Repeat the above steps to obtain the blank after the nth preforming press bending / flattening. Other steps are the same as those in Example 1.

[0040] Obtaining a relatively complex preformed blank through preforming not only reduces the deformation amount during subsequent hydro-pneumatic forming, avoids defects such as local bulging and thinning cracks, edge biting at the parting line during the die closing process, and wrinkling due to uneven material distribution in each cross-section; but also avoids problems such as long 3D printing processing cycle and high manufacturing cost when using 3D printing to complete the blank manufacturing.

[0041] Example 3: Combine Figure 5 , Figure 6 , Figure 7It is noted that in Step 4, a CAD geometric model of the supplementary section is established according to the three-dimensional shape and dimensional requirements of the 3D printed supplementary section, and the STL model of the supplementary section is extracted. Then, the STL model is processed by a layer slicing software. Then, taking aluminum alloy, superalloy, magnesium alloy, titanium alloy powder or wire as raw materials, local additive manufacturing is carried out by using 3D printing technology (such as laser metal deposition technology). Other steps are the same as those in Embodiment 1.

[0042] By means of the shape of the 3D printed supplementary section, not only can a blank with sufficient size / width-thickness be prepared, but also the wall thickness of each part of the complex thin-walled metal component can be accurately controlled, improving the service performance of the component. At the same time, for materials with poor formability, problems such as wrinkling, cracking, and uneven wall thickness in local areas during the hot gas bulging forming of complex thin-walled metal components can be avoided.

[0043] Embodiment 4: Combining Figure 7 , Figure 8 , Figure 9 It is noted that in Step 5, a high-frequency induction heating device is used to heat the bulging forming die. When the blank is made of aluminum alloy, the die is heated to 350°C - 450°C; when the blank is made of superalloy, the die is heated to 850°C - 950°C; when the blank is made of magnesium alloy, the die is heated to 150°C - 400°C; when the blank is made of titanium alloy, the die is heated to 650°C - 850°C. Nitrogen with a pressure of 3 - 6.5 Mpa is introduced into the interior or surface of the blank for hot gas bulging forming, causing the blank to bulge and conform to the die cavity within a time period of 10 - 50 s to obtain the required external contour. Other steps are the same as those in Embodiment 1.

[0044] Hot gas bulging forming can achieve high shape and dimensional accuracy. At the same time, after obtaining the required shape by hot gas bulging forming, maintaining it under high temperature and high pressure for a period of time can eliminate the micro holes existing during 3D printing, improve the density and uniformity of the tissue performance of the material, and also cause the micro powder particles existing on the outer surface of the 3D printed blank to be extruded and filled into adjacent micro pits, which can improve the flatness and smoothness of the outer surface of the component and improve the forming quality of large-size complex thin-walled metal components.

Claims

1. A method for manufacturing complex thin-walled metal components by combining local additive manufacturing and hot air expansion, characterized in that: Here are the steps: Step 1: Determine the overall forming plan: Perform feature analysis on the complex thin-walled metal component to be prepared to obtain the geometric features of the local complex area and the geometric shape of the external overall contour of the complex thin-walled metal component; the preform is prepared by pre-deformation of the original billet and local additive manufacturing, and the local complex area of the complex thin-walled metal component is approximated by 3D printing method to achieve the approximate forming of the local complex area. The geometric shape of the external overall contour of the complex thin-walled metal component is achieved by hot gas pressure forming process to achieve overall gas expansion forming; Step 2: Pre-deform the original blank: Based on the analysis results of the geometric shape of the external overall contour of the complex thin-walled metal component in step 1, the pre-deformation process of the original blank is determined. For prefabricated tube blanks with a two-dimensional plane axis, one pre-bending and one flattening forming process are performed; for prefabricated tube blanks with a three-dimensional space axis, multiple pre-bending and multiple flattening forming processes are performed. During the pre-forming process, the pressure medium is evenly distributed inside the original tube blank to prevent wrinkling and cracking during the deformation process; for prefabricated slabs with a simple shape and a semi-cone angle of less than 40°, a single pre-deformation process is performed; for prefabricated slabs with a complex shape and a semi-cone angle of ≥40°, two or more pre-deformations are used; Step 3: Cutting the local area of the pre-deformed blank: Based on the analysis results of the geometric characteristics of the local complex area of the complex thin-walled metal component in step 1, determine the required cutting area of the pre-deformed blank and perform cutting processing on the area to be cut of the pre-deformed blank; Cut the required area on the pre-deformed blank, then grind and clean the cut area to ensure good metallurgical bonding between the subsequent 3D printing and the pre-deformed blank; Step 4, 3D printing supplementary section: The position and angle of the pre-deformed blank obtained after cutting in step 3 are adjusted according to the design requirements and fixed on the workbench. Based on the analysis results of the geometric characteristics of the local complex area of the thin-walled metal component in step 1, the material and contour shape of the 3D printed supplementary section are determined. The 3D printed material is a material with similar performance to or higher strength and stiffness than the original blank based on the service performance of the local area of the complex thin-walled metal component. Then, 3D printing technology is used to perform local additive manufacturing on the cut area of the pre-deformed blank to achieve approximate forming of the local complex area, thereby obtaining the final prefabricated blank; Step 5, final prefabricated blank expansion forming: heating the hot air expansion forming mold to make the expansion forming mold temperature reach the set conditions, placing the prefabricated blank obtained in step 4 after partial additive manufacturing in the expansion forming mold, closing the mold, and then filling the interior of the prefabricated blank with a high-pressure gas medium to cause the prefabricated blank to undergo expansion deformation and abut against the expansion forming mold cavity to obtain the required shape contour, while keeping the expansion forming mold in a closed state, so that the formed complex thin-walled metal component stays at high temperature and high pressure for a certain period of time, reducing the gas pressure inside or on the surface of the complex thin-walled metal component to a set value, and after the expansion forming mold temperature is reduced to a set value, the formed complex thin-walled metal component is taken out; Step 6. Post-processing of bulged complex thin-walled metal components: remove the process section of the complex thin-walled metal components after hot air bulging, and perform necessary deburring, polishing and cleaning on the ends and surfaces of the complex thin-walled metal components to obtain the final required complex thin-walled metal components.

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