Method for controlling deformation of large structural member of additive preparation frame body

Abstract

The invention discloses a method for controlling deformation of a large structural member of an additive manufacturing frame body, and belongs to the technical field of additive manufacturing. The method comprises the following steps: firstly, splitting a frame body structural member into a plurality of sub-components according to structural information, respectively adding the plurality of sub-components, then connecting the sub-components subjected to preliminary machining into the frame body structural member in an isothermal partition manner, then carrying out heat treatment, size measurement, shape correction and machining on the whole structural member, and carrying out stress detection, regulation and control on the whole process. By means of the isothermal partition connection process and real-time stress detection and regulation, deformation control over the large-scale structural member of the additive manufacturing frame body is achieved, the problem of rapid additive manufacturing of the large-scale structural member of the existing frame body is solved, the production efficiency is improved, the production cost is reduced, the mechanical property of the material is guaranteed, and the production cost is reduced. And workpiece deformation caused by integrated additive stress accumulation is effectively avoided.

Description

Technical Field

[0001] The present invention relates to a method for controlling the deformation of large-scale structural parts of an additive manufacturing frame, belonging to the technical field of additive manufacturing. Background Art

[0002] The aerospace industry is a typical representative of the country's high-end equipment manufacturing industry, and its products are characterized by complex structures, multiple processes, and small batches. With the increasing complexity of typical aerospace components such as aero-engines, large aircraft, and new-generation launch vehicles, as well as the continuous emergence of new materials, the structures of parts tend to be more complex and larger. However, the traditional manufacturing method combining casting, forging, and machining will be difficult to meet the above manufacturing requirements. Additive manufacturing technology can well solve such problems. Metal additive manufacturing is a new technology that uses laser, electron beam, or arc as the heat source to stack materials layer by layer according to three-dimensional model data, thereby directly manufacturing metal parts.

[0003] As a new manufacturing method, additive manufacturing has outstanding advantages in the manufacturing of high-performance large-scale difficult-to-machine metal components such as titanium alloys, superalloys, and ultra-high-strength steels. However, for large-scale structural parts, due to their large sizes during additive manufacturing, it is difficult for existing equipment to perform integrated forming, and large additive stresses will be generated during the integrated forming process, resulting in workpiece deformation. In addition, for workpieces with special structures, there will be problems such as difficult additive path planning and difficult machining, which limit the application of additive manufacturing in large-size and difficult-to-machine metal components.

[0004] To solve the above technical problems, domestic and foreign scholars have reported some exploratory studies. For example, model optimization, zonal printing, optimizing additive paths, etc. Although such process means have a certain effect of reducing stress and preventing deformation, they are difficult to implement for some large-scale structural parts with complex structures. Therefore, researchers have to explore some composite process methods with high costs and complex processes. The additive and subtractive hybrid manufacturing equipment provided in Patent CN 114474713 A can simultaneously achieve additive and subtractive manufacturing through the same set of motion control system, effectively reducing the errors generated during additive and subtractive manufacturing, but has high requirements for the performance of the equipment and complex operations. The deformation control scheme for additive manufacturing of large thin-walled structural parts designed in Patent CN114211001 A can correct the shape of the structural parts throughout the additive manufacturing process, avoiding irreversible deformation caused by the accumulation of internal stress and deformation. However, it is not applicable to small-batch structural parts, increasing the production cost. Summary of the Invention

[0005] The object of the present invention is to overcome the defects existing in the above-mentioned prior art, and to provide a method for controlling the deformation of large-scale structural parts of an additive manufacturing frame. Through the process of isothermal zonal connection, as well as the real-time detection and regulation of stress, the deformation of large-scale structural parts of the additive manufacturing frame is controlled, the problem of rapid additive manufacturing of large-scale structural parts of the existing frame is solved, the production efficiency is improved and the production cost is reduced. It not only ensures the mechanical properties of the material, but also effectively avoids the deformation of the workpiece caused by the accumulation of integral additive stress, providing process guidance for the additive manufacturing of large-scale structural parts of the frame.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for controlling the deformation of large-scale structural parts of an additive manufacturing frame, comprising the following steps:

[0008] S1: Frame structure processing: Based on the structural information of the components constituting the frame structure, the frame model is optimized to obtain a number of sub-component models;

[0009] S2: Additive manufacturing: Use lungoPNT software to slice the optimized sub-component models, and perform additive manufacturing with different process parameters according to the number of sliced layers to obtain a number of sub-component blanks;

[0010] S3: Stress relief treatment: Perform stress relief treatment on the number of sub-component blanks obtained by additive manufacturing;

[0011] S4: Machining treatment: Roughly process the number of sub-component blanks after stress relief treatment according to the dimensional information to obtain a number of sub-components;

[0012] S5: Isothermal zonal connection of sub-components: Isothermally connect the number of sub-components after machining into frame structural parts according to the dimensional requirements;

[0013] S6: Workpiece heat treatment: Perform heat treatment on the frame structural parts after isothermal zonal connection. Heat treatment fixtures need to be installed before heat treatment;

[0014] S7: Dimensional measurement: Measure the dimensions of the frame structural parts after heat treatment according to the dimensional requirements;

[0015] S8: Straightening: Use straightening fixtures to straighten the frame structural parts that do not meet the dimensional requirements until the dimensions meet the requirements;

[0016] S9: Finish machining: Perform milling machining on the frame structural parts with qualified dimensional measurements;

[0017] S10: Stress detection and regulation: After the frame structural parts are subjected to additive manufacturing, stress relief treatment, machining treatment, and isothermal zonal connection of sub-components, stress detection needs to be performed respectively, and stress regulation is performed according to the detection results.

[0018] Further, the frame structural member is a large-sized and complex-structured member.

[0019] The large size of the frame structural member means that the overall dimensions are approximately 2.5 m in length, 1.5 m in width, and 0.5 m in height.

[0020] Complex structure means that the frame structural member includes a front frame, a rear frame, cross beams, a left side beam, and a right side beam.

[0021] Further, the structural information includes models, drawings, dimensional requirements, etc., including but not limited to. In the present invention, the structural information includes the front frame, rear frame, cross beams, left side beam, and right side beam of the frame structural member.

[0022] Further, the optimization process of the frame model includes:

[0023] S11: Based on the structural information of the frame structural member, the frame model is divided into several sub-component models;

[0024] S12: The divided sub-component models are structurally optimized according to the requirements of the additive manufacturing process, including adding allowances, corner treatment, etc.

[0025] Further, in step S2, the additive manufacturing is one of arc, electron beam, plasma, and laser additive manufacturing.

[0026] Further, the additive manufacturing is arc additive manufacturing, with an additive voltage of 15 V - 25 V, an additive current of 70 A - 100 A, a wire feeding speed of 6 m / min - 12 m / min, and a welding speed of 6 mm / s - 15 mm / s.

[0027] Further, the additive manufacturing method adjusts different process parameters according to the number of layers sliced by the software for additive manufacturing, which is specifically divided into three parts:

[0028] S21: Backing: The first layer has an additive current of 90 - 100 A, a wire feeding speed of 10 - 12 m / min, and other parameters remain unchanged;

[0029] S22: Filling: The intermediate transition layer has an additive current of 80 - 90 A, a wire feeding speed of 8 - 10 m / min, and other parameters remain unchanged;

[0030] S23; Surfacing: The last layer has an additive current of 70 - 80 A, a wire feeding speed of 6 - 8 m / min, and other parameters remain unchanged.

[0031] Further, in step S3, the stress relief treatment includes the following: subjecting the blank of the sub-component obtained by additive manufacturing to stress relief annealing, with the heat treatment parameters being: heating at a rate of 50 - 100 °C / h to 150 - 300 °C, then holding for 2 - 6 h, and cooling in air to room temperature upon furnace discharging;

[0032] Further, in step S4, the processing information refers to performing surface machining on the area to be welded in the next step using a milling machine and performing finish machining on the areas that are difficult to machine after welding according to the drawings.

[0033] Further, in step S5, the dimensional requirements include the workpiece dimensions required by documents such as drawing dimensions and technical agreements.

[0034] Further, the isothermal zone connection means heating the area of the sub-components to be connected to 150 °C - 300 °C through ceramic heating sheets, and the specific connection method is welding;

[0035] Further, the isothermal zone connection includes the following three parts:

[0036] S51: Assembling the divided sub-components according to the dimensional requirements, and welding shrinkage allowances should be left during assembly;

[0037] S52: Installing a fixing tooling for the assembled sub-components along the direction perpendicular to the welding;

[0038] S53: Heating the sub-components fixed by the tooling, and then welding them in a certain order to obtain the target structural part.

[0039] Specifically, subjecting the frame structural parts after isothermal zone connection to heat treatment, with the solution treatment system being: heating at a rate of 100 - 200 °C / h to 400 - 800 °C, holding for 6 - 10 h, and then water cooling; the aging treatment system being: heating at a rate of 50 - 100 °C / h to 150 - 300 °C, then holding for 2 - 6 h, and cooling in air to room temperature upon furnace discharging. Heat treatment tooling needs to be installed before workpiece heat treatment, and the tooling structure includes: internal square tubes to prevent the side beams from shrinking inward, long plates to prevent the side beams from twisting up and down, square tubes connecting each area, and external square tubes to prevent the side beams from deforming outward. The square tubes are hollow steel tubes with a wall thickness of 10 mm, and the areas where the internal square tubes are connected to the workpiece need to be isolated with aluminum blocks.

[0040] Further, in step S7, the method of dimension measurement is three-dimensional scanning, specifically including:

[0041] S71: Obtaining the scanning information of the frame structural parts that have completed heat treatment, including the external contour and three-dimensional dimensions;

[0042] S72: Determine the dimensional information of the frame structural members that have completed heat treatment currently, including length, width, height, angle, surface concavity and convexity, etc.;

[0043] S73: Determine that the dimensional information of the frame structural members that have completed heat treatment currently matches the corresponding model information.

[0044] Further, in step S8, the straightening is one of mechanical straightening or thermal straightening.

[0045] Further, in step S10, the method for stress detection is the electrochemical blind hole detection method, and the method for controlling stress is stress relief heat treatment.

[0046] Further, the control of stress according to the detection results is divided into the following five parts:

[0047] S101: Select the area to be measured and the punching points on the frame structural members, install strain gauges and strain meters, and use a punching instrument to punch holes in the area to be measured;

[0048] S102: After the value on the strain meter tends to be stable, substitute the strain value measured by the strain gauge into the formula:

[0049]

[0050] The magnitude of the principal stress of the frame structural member can be calculated, where σ max , σ min are two principal stresses in the frame structural member; σ max is the maximum principal stress, σ min is the minimum principal stress; the included angle of the 3 strain gauges is 120°; A and B are the release coefficients of the strain gauges, and their values are obtained through experimental calibration, respectively reflecting the energy ratio released by the material when experiencing a strain and a stress; the release strains measured by the three sensitive grids in the strain gauge are ε 0 , ε 120 , ε 240 .

[0051] S103: Then, perform stress detection on the additively manufactured frame structural member (i.e., the frame structural member before stress relief treatment) and the frame structural member after stress relief treatment respectively, and obtain the maximum principal stresses of the two as σ 1 and σ 2 , and then obtain the stress change rate during stress relief treatment as δ 1 according to the formula. The formula is as follows:

[0052]

[0053] S104: Perform detection on the (n - 1)th and nth steps that need to be subjected to stress detection subsequently, and obtain σn-1 and σ n , and then according to the formula, the stress change rate δ at the nth step can be obtained n , and the formula is as follows:

[0054]

[0055] S105: Compare the stress change rate δ at the nth step n with the stress change rate δ after stress relief treatment 1 . If δ n ≥δ 1 , stress relief heat treatment is required, otherwise it is not required.

[0056] Advantages of the present invention:

[0057] The present invention takes into account the problem that stress accumulation caused by the integration of the frame structure parts during additive manufacturing will lead to workpiece deformation. Through the process of isothermal zonal connection and real-time detection and regulation of stress, the control of the deformation of the large frame structure parts prepared by additive manufacturing is realized, solving the problem of rapid additive manufacturing of existing large frame structure parts. At the same time, the production efficiency is improved and the production cost is reduced; the subsequent heat treatment not only releases the stress in the workpiece but also ensures the mechanical properties of the material; the stress measurement and control at each stage can provide real-time stress data and perform stress relief treatment to prevent the accumulation of residual stress in the workpiece. The additive manufacturing method for large frame structure parts provided by this invention patent can be applied to additive manufacturing such as arc, electron beam, plasma, laser, etc.

[0058] The present invention discloses a method for controlling the deformation of large frame structure parts prepared by additive manufacturing. First, the frame structure parts are split into several sub-parts according to the structural information, and several sub-parts are additively manufactured respectively. Then, the preliminarily machined sub-parts are connected in an isothermal zone to form a frame structure part. Next, the overall structure part is subjected to heat treatment, dimensional measurement, straightening, machining, and the stress during the whole process is detected and regulated. The present invention realizes the control of the deformation of large frame structure parts prepared by additive manufacturing through the process of isothermal zonal connection and real-time detection and regulation of stress, solves the problem of rapid additive manufacturing of existing large frame structure parts, improves the production efficiency and reduces the production cost, not only ensures the mechanical properties of the material but also effectively avoids the deformation of the workpiece caused by the accumulation of integrated additive stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 is a flowchart of the additive manufacturing method for the large frame structure parts of the present invention;

[0060] Figure 2 is a structural schematic diagram of the example frame structure part of the present invention;

[0061] Figure 3Sub-component model of the frame structure member in the embodiment of the present invention:

[0062] 1 - Left beam, 2 - Right beam, 3 - Front frame, 4 - Rear frame, 5 - Cross beam, a - Stress detection area;

[0063] Figure 4 Schematic diagram of the heat treatment tooling for the frame structure member in the embodiment of the present invention:

[0064] 11 - Inner square tube, 12 - Long plate, 13 - Square tube, 14 - Outer square tube;

[0065] Figure 5 Schematic diagram of the straightening tooling for the frame structure member in the embodiment of the present invention:

[0066] 101 - Frame structure member, 102 - Ceramic heating sheet, 103 - Support steel plate, 104 - Jack, 105 - Aluminum block, 106 - Bolt. Specific implementation manners

[0067] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0068] Embodiment 1

[0069] As Figures 1 to 5 shown, the method for controlling the deformation of the large-scale frame structure member prepared by additive manufacturing provided in the embodiment of the present invention solves the problem of rapid additive manufacturing of the existing large-scale frame structure member, and includes the following steps:

[0070] First is the three-dimensional model of the frame structure member. As Figure 2 shown, the structure of this frame structure member is complex and difficult to process and manufacture by traditional methods. The overall dimensions are approximately 2.5 m in length, 1.5 m in width, and 0.5 m in height. The relatively large size leads to large stress generated during integrated additive manufacturing, resulting in workpiece deformation, and the integrated additive manufacturing cycle is relatively long. Therefore, the process of isothermal zone connection is adopted, and real-time detection and regulation of stress are carried out to control the deformation of the workpiece. Figure 1 Flow chart of the additive manufacturing method for the large-scale frame structure member of the present invention, and the specific method is as follows:

[0071] S1: Frame structure processing: Based on the structural information of the frame structure member, the frame model is optimized to obtain several sub-component models;

[0072] The specific steps are:

[0073] S11: Based on the structural information of the components that make up the frame structure, the frame model can be divided into five parts, namely the front frame 3, the rear frame 4, the cross beam 5, the left side beam 1, and the right side beam 2;

[0074] S12: Optimize the structure of the segmented sub-component models according to the requirements of the additive manufacturing process. For example, change the straight corners to 45-degree rounded corners, which can not only avoid stress concentration but also optimize the additive path; based on the segmented model, add a 4-mm margin inside and a 7-mm margin outside; fill the holes that need to be machined later to generate the optimized sub-component models, as Figure 3 shown.

[0075] S2: Additive manufacturing: Use software to slice the optimized sub-component models, and adjust different process parameters according to the number of sliced layers for additive manufacturing to obtain several sub-component blanks. The additive material selected is 2319 aluminum alloy wire with a diameter of 1.2 mm, the substrate is 2319 plate with a thickness of 30 mm, the shielding gas is argon with a purity of 99.999%, the gas flow rate is 25 L / min, the additive voltage is 20 V, and the welding speed is 10 mm / s.

[0076] The additive manufacturing method performs additive manufacturing by adjusting different process parameters according to the number of layers sliced by the software, which is specifically divided into three parts:

[0077] S21: Backing: The additive current for the first layer is 95 A, the wire feeding speed is 10 m / min, and other parameters remain unchanged;

[0078] S22: Filling: The additive current for the intermediate transition layer is 85 A, the wire feeding speed is 8 m / min, and other parameters remain unchanged;

[0079] S23; Surfacing: The additive current for the last layer is 75 A, the wire feeding speed is 6 m / min, and other parameters remain unchanged.

[0080] S3: Stress relief treatment: Perform stress relief annealing on the five sub-component blanks obtained by additive manufacturing. The heat treatment parameters are: at a heating rate of 100 °C / h, raise the temperature to 175 °C, then hold for 6 h, and furnace cool to room temperature;

[0081] S4: Machining treatment: Rough machine the five sub-component blanks after stress relief treatment according to the machining information to obtain five sub-components. The positions that need to be machined are mainly the positions where the side beams, cross beams are welded to the front and rear frames, and the positions that are not easy to machine on the front and rear frames after welding.

[0082] S5: Isothermal zone connection of sub-components: Isothermally connect the five sub-components after machining into frame structure parts according to the size requirements. The isothermal zone connection includes the following three parts:

[0083] S51: Assemble the five divided sub-components according to the dimensional requirements, leaving a margin of 3 mm during assembly to prevent shrinkage of the weld seam during welding.

[0084] S52: Install the fixing tooling for the assembled sub-components along the direction perpendicular to welding. The tooling uses flexible steel rods, and three flexible steel rods need to be installed on both sides of the left and right side beams. This can not only prevent the inward shrinkage of the side beams during welding but also prevent the deformation of the workpiece caused by the accumulation of welding residual stress.

[0085] S53: Heat the sub-components fixed by the tooling to 200 °C using ceramics, and then perform welding according to diagonal symmetry. First, perform spot welding, then fillet welding, and finally full welding to obtain the frame structure member.

[0086] S6: Workpiece heat treatment: Heat-treat the frame structure member after isothermal zone connection. Solution treatment system: With a heating rate of 100 °C / h, raise the temperature to 535 °C, hold for 8 h, and then water-cool. Aging treatment system: With a heating rate of 100 °C / h, raise the temperature to 175 °C, then hold for 4 h, and take it out of the furnace and air-cool to room temperature. Before workpiece heat treatment, heat treatment tooling needs to be installed. The schematic diagram of the tooling is as Figure 4 , and its structure includes: an internal square tube 11 to prevent the inward shrinkage of the side beam, a long plate 12 to prevent the up-and-down distortion of the side beam, a square tube 13 connecting each area, and an external square tube 14 to prevent the outward deformation of the side beam. The square tube 13 is a hollow steel tube with a wall thickness of 10 mm, and the area where the internal square tube 11 is connected to the workpiece needs to be isolated with aluminum blocks.

[0087] S7: Dimensional measurement: Perform three-dimensional scanning on the heat-treated frame structure member according to the dimensional requirements, specifically including:

[0088] S71: Obtain the scanning information of the heat-treated frame structure member that has been completed.

[0089] S72: Determine the dimensional information of the heat-treated frame structure member based on the scanning information of the heat-treated frame structure member that has been completed.

[0090] S73: Determine that the dimensional information of the heat-treated frame structure member matches the corresponding model information. According to the matching information, it is found that the left side beam part has a bending deformation upward and needs to be straightened.

[0091] S8: Straightening: Straighten the left side beam using the straightening tooling. The straightening method is to use ceramics for heating and design the tooling to apply pressure with a jack for straightening. The specific straightening tooling is as Figure 5, where 101 is the frame structural member, 102 is the ceramic heating sheet, 103 is the support steel plate, 104 is the jack, 105 is the aluminum block, and 106 is the bolt. First, use the ceramic heating sheet 102 to heat the left beam 1 to 250 °C, and then use the jack 104 to apply downward pressure, so that the workpiece moves downward by 2 mm every half hour until the size meets the requirements. Then turn off the heating, turn on the heating again for one hour after cooling, repeat 3 times, and finally stop the heating. Remove the straightening tooling after 8 hours and measure the size again. At this time, the frame size meets the requirements.

[0092] S9: Finish machining: Finish machine the frame structural members with qualified measured dimensions according to the 3D digital model.

[0093] S10: Stress detection and regulation: Stress detection is required after the structural members are subjected to additive manufacturing, stress relief treatment, machining treatment, and isothermal zone connection of sub-components. Stress control is carried out according to the detection results. The method of stress detection is the electrochemical blind hole detection method, and the method of controlling stress is stress relief heat treatment. The detection position is Figure 3 in area a of

[0094] S101: Select the area to be measured and the drilling points on the frame structural member, install strain gauges and strain meters, and use a drilling instrument to drill holes in the area to be measured;

[0095] S102: After the values on the strain meter tend to be stable, substitute the strain values measured by the strain gauges into the formula:

[0096]

[0097] The principal stress of the frame structural member can be calculated. Among them, σ max , σ min are the two principal stresses in the frame structural member; σ max is the maximum principal stress, and σ min is the minimum principal stress; the included angle of the 3 strain gauges is 120°; A and B are the release coefficients of the strain gauges, and their values are obtained through experimental calibration, respectively reflecting the energy release ratio of the material when experiencing one strain and stress; the release strains measured by the three sensitive grids in the strain gauge are ε 0 , ε 120 , ε 240 .

[0098] S103: Then, stress detection is carried out on the frame structural member before stress relief treatment (i.e., after additive manufacturing) and the frame structural member after stress relief treatment, and the maximum principal stresses of the two are obtained as σ 1 and σ 2 respectively. Then, according to the formula, the stress change rate during stress relief treatment is obtained as δ 1 , and the formula is as follows:

[0099]

[0100] S104: Detect the (n - 1)-th step and the n-th step that need to be stress-tested subsequently, and obtain σ n-1 and σ n respectively. Then, according to the formula, the stress change rate δ n of the n-th step can be obtained. The formula is as follows:

[0101]

[0102] S105: Compare the stress change rate δ n of the n-th step with the stress change rate δ 1 after stress relief treatment. If δ n ≥δ 1 , stress relief heat treatment is required; otherwise, it is not required.

[0103] Table 1 Stress detection data of the workpiece at each stage

[0104]

[0105] The obtained data are statistically analyzed, and the data are shown in Table 1 below. It can be seen from the table that after stress relief treatment after additive manufacturing, the residual stress generated by additive manufacturing of the workpiece can be significantly reduced, preventing the deformation of the workpiece caused by the accumulation of additive stress. The stress change rate in the workpiece after isothermal zonal connection is greater than the stress change rate after stress relief treatment. Therefore, stress relief heat treatment is carried out after isothermal zonal connection, and it can be seen that the stress change rate after stress relief heat treatment decreases significantly, reducing the stress accumulation in the workpiece. Compared with the traditional manufacturing method and the preparation method of integrated additive manufacturing, the isothermal zonal connection process is adopted, and stress detection and regulation are carried out during the process. It can not only step by step eliminate the residual stress in the material through stress relief treatment to prevent the deformation of the workpiece caused by the accumulation of residual stress, but also improve the production efficiency.

[0106] The additive region and the welding region of the additive parts obtained in the examples are subjected to tensile tests, and the tensile properties of the additive region and the welding region of the examples are obtained respectively. The tensile properties of the castings and forgings obtained by the examples and the conventional method are compared, as shown in Table 2, and the experimental temperature is 23°C. The results show that the tensile properties of the additive region and the welding region of the additive parts obtained in the examples are better than those of the castings. The tensile strength is slightly lower than that of the forgings, but the elongation is higher than that of the forgings. It can be seen that the combined process of additive manufacturing and welding, and stress detection and regulation are carried out, which not only improves the production efficiency, but also ensures the mechanical properties of the material, solving the problem of rapid additive manufacturing of large frame structural parts.

[0107] Table 2 Tensile properties of heat-treated 2319 under different preparation methods

[0108]

[0109]

[0110] Example 2

[0111] The difference between this example and Example 1 is only that:

[0112] In step S2, the additive voltage is 15V, the welding speed is 6mm / s, and the wire diameter is 0.8mm.

[0113] S21: Backing: For the first layer of additive, the current is 90A, the wire feeding speed is 11m / min, and other parameters remain unchanged;

[0114] S22: Filling: For the intermediate transition layer of additive, the current is 80A, the wire feeding speed is 9m / min, and other parameters remain unchanged;

[0115] S23; Surfacing: For the last layer of additive, the current is 70A, the wire feeding speed is 7m / min, and other parameters remain unchanged.

[0116] In step S3, the stress relief treatment includes the following: The blank of the sub-component obtained by additive manufacturing is subjected to stress relief annealing. The heat treatment parameters are: at a heating rate of 50°C / h, raise the temperature to 150°C, then hold for 2h, and then air cool to room temperature after taking out of the furnace;

[0117] In step S5, isothermal zone connection means heating the area of the sub-components to be connected to 150°C through a ceramic heating sheet, and the specific connection method is welding;

[0118] The frame structure after isothermal zone connection is heat treated. Solution treatment system: at a heating rate of 200°C / h, raise the temperature to 800°C, hold for 6h, and then water cool; Aging system: at a heating rate of 50°C / h, raise the temperature to 150°C, then hold for 2h, and then air cool to room temperature after taking out of the furnace.

[0119] In step S8, first use the ceramic heating sheet 102 to heat part of the left beam 1 to 350°C, then use the jack 104 to apply a downward pressure, so that the workpiece moves downward by 2mm every half hour until the size meets the requirements, then turn off the heating, turn on the heating again for one hour after cooling, repeat 5 times, finally stop the heating, remove the straightening tooling after 8 hours, and measure the size again. At this time, the size of the frame meets the requirements.

[0120] Example 3

[0121] The difference between this example and Example 1 is only that:

[0122] In step S2, the additive voltage is 25V, the welding speed is 15mm / s, and the wire diameter is 1.0mm.

[0123] S21: Backing: The additive current of the first layer is 100 A, the wire feeding speed is 12 m / min, and other parameters remain unchanged.

[0124] S22: Filling: The additive current of the intermediate transition layer is 90 A, the wire feeding speed is 10 m / min, and other parameters remain unchanged.

[0125] S23: Surfacing: The additive current of the last layer is 80 A, the wire feeding speed is 8 m / min, and other parameters remain unchanged.

[0126] In step S3, the stress relief treatment includes the following: performing stress relief annealing on the blank of the sub-component obtained by additive manufacturing, and the heat treatment parameters are: heating up to 300 °C at a heating rate of 80 °C / h, then holding for 4 h, and then air cooling to room temperature after taking out of the furnace.

[0127] In step S5, isothermal zone connection means heating the area of the sub-components to be connected to 300 °C through a ceramic heating sheet, and the specific connection method is welding.

[0128] The frame structure member after isothermal zone connection is heat treated. The solution treatment system is: heating up to 400 °C at a heating rate of 150 °C / h, holding for 10 h, and then water cooling; the aging treatment system is: heating up to 300 °C at a heating rate of 75 °C / h, then holding for 6 h, and then air cooling to room temperature after taking out of the furnace.

[0129] It should be understood that, in order to streamline the present disclosure and help understand one or more of the various inventive aspects, in the above description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the disclosed method should not be construed as reflecting the intention that the claimed invention requires more features than those expressly recited in each claim. Rather, as reflected in the claims, the inventive aspects lie in less than all the features of the previously disclosed embodiments. Therefore, the claims following the detailed description are hereby expressly incorporated into the detailed description, where each claim itself serves as a separate embodiment of the present invention.

[0130] Although the present invention has been described based on a limited number of embodiments, those skilled in the art in this technical field will understand, based on the above description, that other embodiments can be envisioned within the scope of the present invention thus described. In addition, it should be noted that the language used in this specification is mainly selected for the purpose of readability and teaching, rather than for the purpose of explaining or limiting the subject matter of the present invention. Therefore, many modifications and variations will be obvious to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. For the scope of the present invention, the disclosure of the present invention is illustrative rather than restrictive, and the scope of the present invention is defined by the appended claims.

[0131] The above are only the preferred embodiments of the present invention, and it should be pointed out that: for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for controlling deformation of a large structural part of an additively manufactured frame, characterized in that: The following steps are involved: S1: Frame structure processing: Optimize the frame model based on the structural information of the frame structure components to obtain several sub-component models; S2: Additive manufacturing: Use lungoPNT software to slice the optimized sub-component model, and use different process parameters for additive manufacturing according to the number of slice layers to obtain several sub-component blanks; S3: stress relief treatment: performing stress relief treatment on several sub-component blanks obtained by additive manufacturing; S4: machining: performing preliminary machining on the several sub-component blanks after stress relief treatment according to the size information to obtain several sub-components; S5: Isothermal zone connection of sub-components: several sub-components after machining are isothermally zone connected into frame structural parts at 150℃-300℃ according to size requirements; S6: Workpiece heat treatment: heat treat the frame structure parts connected by isothermal partitions, and install heat treatment tooling before heat treatment; S7: Dimension measurement: Measure the dimensions of the frame structure after heat treatment according to the dimensional requirements; S8: Orthopedic: Use orthopedic tooling to correct the frame structure parts that do not meet the size requirements until the size meets the requirements; S9: Finishing: Process the frame structural parts with qualified size measurement by milling machine; S10: Stress detection and regulation: After the frame structure undergoes additive manufacturing, stress relief treatment, machining treatment, and isothermal zone connection of sub-components, stress detection is required and stress regulation is performed based on the detection results.

2. The method according to claim 1, characterized in that In S1, the structural information includes the front frame, rear frame, cross beam, left beam and right beam of the frame structure.

3. The method according to claim 1, characterized in that In S1, the optimization process of the frame model includes: S11: dividing the frame model into a plurality of sub-component models based on the structural information of the frame structure components; S12: Structural optimization of the segmented sub-component model according to the additive manufacturing process requirements, including addition of excess and corner processing.

4. The method according to claim 1, characterized in that: In S2, the additive manufacturing is arc additive manufacturing; The additive manufacturing method adjusts different process parameters according to the number of layers of software slices to perform additive manufacturing, which is specifically divided into three parts: S21: Primer: The first layer additive current is 90-100A, wire feeding speed is 10-12m / min, additive voltage is 15V-25V, welding speed is 6mm / s-15mm / s; S22: Filling: intermediate transition layer additive current 80-90A, wire feeding speed 8-10m / min, additive voltage 15V-25V, welding speed 6mm / s-15mm / s; S23； Covering: The last layer of additive current is 70-80A, wire feeding speed is 6-8m / min, additive voltage is 15V-25V, and welding speed is 6mm / s-15mm / s.

5. The method according to claim 1, characterized in that In S3, the stress relief treatment includes the following: the sub-component blank obtained by additive manufacturing is subjected to stress relief annealing, and the heat treatment parameters are: heating to 150-300°C at a heating rate of 50-100°C / h, then keeping warm for 2-6h, and air cooling to room temperature after being taken out of the furnace.

6. The method according to claim 1, characterized in that In S6, the frame structure parts connected by isothermal partitions are heat treated. The solution treatment system is as follows: the temperature is increased to 400-800℃ at a heating rate of 100-200℃ / h, kept at this temperature for 6-10h, and then water-cooled. The aging system is as follows: the temperature is increased to 150-300℃ at a heating rate of 50-100℃ / h, and then kept at this temperature for 2-6h, and then air-cooled to room temperature after being taken out of the furnace.

7. The method according to claim 1, characterized in that In S7, the dimension measurement method is three-dimensional scanning, which specifically includes: S71: Obtain scanning information of the frame structure that has completed the heat treatment, including the external contour and three-dimensional size; S72: Determine the size information of the frame structure component that has completed the heat treatment according to the scanning information of the frame structure component that has completed the heat treatment, including the length, width, height, angle, and surface roughness; S73: Determine whether the size information of the frame structure component that has completed the heat treatment matches the corresponding model information.

8. The method according to claim 1, characterized in that In S10, the stress detection method is an electrochemical blind hole detection method, and the stress regulation method is a stress relief heat treatment.

9. The method according to claim 1, characterized in that: In S10, the stress regulation according to the detection results is divided into the following five parts: S101: Select the area to be tested and the punching point on the frame structure, install the strain gauge and the strain meter, and use the punching instrument to punch holes in the area to be tested; S102: After the value on the strain gauge becomes stable, substitute the strain value measured by the strain gauge into the formula: The principal stress of the frame structure can be calculated, where σ max , σ min are the two principal stresses in the frame structure; max is the maximum principal stress, σ min is the minimum principal stress; the angle between the three strain gauges is 120°; A and B are the release coefficients of the strain gauges, whose values ​​are obtained based on experimental calibration, and they respectively reflect the energy ratio released by the material after experiencing a strain and stress; the release strains measured by the three sensitive grids in the strain gauge are ε0, ε 120 , ε 240 . S103: Then, stress detection is performed on the frame structure after additive manufacturing and stress relief treatment, and the maximum principal stresses of the two are obtained as σ1 and σ2, respectively. Then, the stress change rate during stress relief treatment is obtained according to the formula, which is as follows: S104: Perform stress testing on the n-1th step and the nth step, and obtain σ n-1 and σ n , and then the stress change rate δ of the nth step can be obtained according to the formula n , the formula is as follows: S105: The stress change rate δ of step n n Compared with the stress change rate δ1 after stress relief treatment, if δ n ≥δ1, stress relief heat treatment is required, otherwise not.

10. The method according to claim 1, characterized in that The frame structural members are large-sized and complex-structured structural members; the large-sized frame structural members refer to the overall dimensions, which are ≥2.5m in length, ≥1.5m in width, and ≥0.5m in height; the complex structure means that the frame structural members include the front frame, rear frame, cross beam, left beam, and right beam.

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