A printing method for improving surface quality of electron beam additive manufacturing

Abstract

The application discloses a printing method for improving the surface quality of electron beam additive manufacturing, and the method comprises the following steps: slice parameter optimization, design of a contour dotted line scanning strategy, and perimeter change and contour parameter adjustment. The method of the application realizes the flattening and homogenization of electron beam scanning traces by in-situ remelting of an electron beam, and improves the surface quality of the vertical workpiece side surface by optimizing the slices, and finely controlling the size and appearance of the contour melt channel. The application belongs to the field of additive manufacturing of alloy structural parts.

Description

Technical Field

[0001] The present invention belongs to the field of additive manufacturing of alloy structural parts, and in particular relates to a printing method for improving the surface quality of electron beam additive manufacturing. Background Art

[0002] Electron beam powder bed fusion (EB-PBF) uses an electron beam as a high-energy heat source, offering advantages such as high energy efficiency, no reflection, high power density, high vacuum and no pollution, high powder bed preheating temperature, and low residual stress. Although EB-PBF has been proven suitable for the preparation of a variety of high-performance alloys, the surface quality of EB-PBF-formed parts is generally low, and surface quality optimization is challenging. During the EB-PBF forming process, the same part will have planes with significantly different surface qualities. The top and bottom surfaces are defined as surfaces strictly parallel to the build platform, while the planes along the forming direction are defined as side surfaces. The forming conditions for the two are completely different. The side surfaces are primarily formed by stacking multiple layers, which is prone to step effects. Edge buildup marks and adsorbed, adhered semi-molten particles are also major factors affecting the side surface quality. The top surface, on the other hand, consists primarily of a single plane, which is flattened by overlapping melt tracks left by the electron beam scanning path. Top surface flattening is primarily controlled by infill parameters such as scan current, scan speed, scan line spacing, and print layer thickness. Choosing the appropriate scan line spacing based on the specific device's electron beam spot size, and selecting the appropriate scan speed and current based on layer thickness ensures the densification of the infilled structure alloy. Scan line lengths vary depending on cross-sectional area. Overall, top surface quality is closely related to its infill parameters.

[0003] The surface quality of the vertical workpiece side surface is mainly formed by melt accumulation, and its surface quality is related to factors such as layer thickness, powder particle size distribution, sphericity, powder flowability, beam spot quality, and melt edge stability. Fluctuations in the scanning melt, edge accumulation marks, and edge adsorption and adhesion of powder will all have a significant impact on its surface quality. During the printing process, it is common to increase the workpiece allowance, and then use grinding, shot peening, abrasive flow, polishing and other methods to remove the surface allowance to obtain ideal surface quality and dimensional accuracy. However, for thin-walled workpieces with complex structures and high room temperature brittleness, there are often problems such as high processing difficulty, uncontrollable dimensional accuracy, and high cost.

[0004] In general, existing processes for optimizing the surface quality of EB-PBF-formed parts are immature, with issues such as poor side surface quality and difficult, time-consuming, and costly post-processing. Therefore, improving the surface quality of EB-PBF-manufactured parts is crucial for reducing production costs and processing time, expanding EB-PBF toward more refined and complex processes, and promoting the industrialization and application of additive manufacturing technology. Summary of the Invention

[0005] In order to solve the technical problems of poor side surface forming quality of workpieces formed by existing EB-PBF technology, high difficulty, long time and high cost in post-processing, the present invention proposes a printing method for improving the surface quality of electron beam additive manufacturing. This method uses electron beam in-situ remelting to achieve flattening and uniformity of electron beam scanning marks, and improves the surface quality of the vertical side surface of the workpiece through slicing optimization and refined control of the contour melt channel size-morphology.

[0006] The present invention provides a printing method for improving the surface quality of electron beam additive manufacturing, the method comprising: slicing parameter optimization, design of contour dotted line scanning strategy, and perimeter variation and contour parameter adjustment;

[0007] The slicing parameter optimization includes: establishing a three-dimensional model of a pre-printed vertical workpiece, slicing the three-dimensional model to obtain layered scanning data, slicing the contour scanning path according to the contour melt width, defining a proportional relationship between the distance between the filling scanning path and the contour scanning path and the actual melt width of the contour melt and the filling melt; sequentially performing a powder bed preheating scan, a contour scanning path scan, and a filling scanning path scan to obtain a printed entity;

[0008] The design of the outline dotted line scanning strategy includes: the powder bed preheating scan, outline scanning path scan and filling scanning path scan adopt a beam scanning method, and the outline dotted line scanning strategy is designed as follows: the overlapping method between the beams is designed to achieve in-situ remelting of the continuous melt path by controlling the length of a single melt pool and the overlapping distance and overlapping method between the melt pools, and the melt path is flattened and homogenized; the outline scanning adopts the melt path after the flattening treatment;

[0009] The circumference change and profile parameter adjustment include: according to the change in the circumference of the workpiece contour, limiting the proportional relationship between the number of beams, the beam overlap distance, the dwell time of each beam, and the length of the beam micro-melting channel in the dotted line scanning, so as to achieve consistent control of the workpiece surface quality during the forming process, and obtain a surface roughness Ra of the vertical workpiece less than 12.6μm.

[0010] As an embodiment of the present invention, the slicing optimization of the contour scanning path according to the contour melt width includes: limiting the interval between the contour scanning path and the actual contour of the workpiece

[0011] L 补偿 =a×d 轮廓 , where d 轮廓 is the width of the profile melt channel, which is 0.3-1.4 mm; a is the proportional coefficient, which is 0.2-0.8;

[0012] The relationship between the distance between the filling scanning path and the contour scanning path and the actual width of the contour melt channel and the filling melt channel is defined as follows: 搭接 =(1-β)×(r 填充 +r 轮廓 ), where β is the contour filling overlap coefficient, which is 0.6-1;

[0013] r 填充 The radius of the molten pool is 0.2-1 mm, r 轮廓 The radius of the contour molten pool is 0.15-0.7mm.

[0014] As an embodiment of the present invention, the filling scanning path is a serpentine scan, with a starting angle of 90° and a rotation of 90° layer by layer.

[0015] As an embodiment of the present invention, the method further includes: performing a powder spreading process before the slicing parameter optimization, wherein the powder spreading layer thickness of the powder spreading process does not exceed 100 μm, the powder particle size is 45-150 μm, and the powder composition is Ti6Al4V (TC4) and Ti 48 Al2Cr2Nb(TiAl 4822 ), the vacuum pressure of the molding chamber is 2-3×10 -3 mbar, the vacuum pressure of the electron gun is not less than 5×10 -5 mbar;

[0016] In the powder bed preheating scan, the TC4 powder bed preheating temperature is 550-750°C, the TiAl powder bed preheating temperature is 900-1050°C, the preheating method is grid preheating, the scanning direction is unidirectional scanning, the preheating beam current is 25-40mA, the scanning speed is 10-25m / s, the number of scans is 1-10 times, and the preheating time is 10-40min.

[0017] As an embodiment of the present invention, the parameters of the beam splitting scanning method include: scanning speed v is 300-12000mm / s, beam current I is 2-20mA; contour beam splitting length L 分束 =L 轮廓周长 / N 分束数量 , the value is 1-100mm; the dwell time t of each beam is 0-5ms, the beam overlap distance x is 0-20mm, and the number of scans n is 1-5 times.

[0018] As an embodiment of the present invention, the distance traveled by the electron beam in a single beam-down process during the beam splitting scanning is: L 熔池 =v×t+x;

[0019] Among them, L 熔池The micro-melt length of the split beam, v is the scanning speed, t is the residence time of each beam, x is the split beam overlap distance; the end of the electron beam walking distance is the start of the lower beam of the adjacent molten pool;

[0020] The split beam overlap distance x is the actual overlap distance of the adjacent molten pool in space, and the distance is the in-situ remelt distance of the melt channel, and the ratio of x and vt is limited as follows: x = m x v x t; wherein m is a positive integer, and is 1-5.

[0021] As an embodiment of the present application, in the split beam scanning, the micro-melt length L of the split beam is limited as follows: 熔池 The ratio of the profile melt channel width d 轮廓 is as follows:

[0022] L 熔池 = s x d 轮廓 ; wherein the ratio coefficient s is 1-6, d 轮廓 is 0.3-1.4mm.

[0023] As an embodiment of the present application, in the split beam scanning, the micro-melt length L of the split beam is limited as follows:

[0024] t 间隔 = (L 熔池 / v) x (N-1), L 间隔 = L 周长 / N,

[0025] Wherein, N is the number of split beams, L 熔池 is the micro-melt length of the split beam, v is the scanning speed, t 间隔 is the residence time of each beam, x is the split beam overlap distance, L 间隔 is the interval distance of the adjacent points in time in the molten pool, L 周长 is 0-800mm, L 间隔 > 2 x L 熔池 , t 间隔 ≥ 3ms.

[0026] The above technical solutions provided by the present application at least bring the following beneficial effects:

[0027] The scanning strategy and process method provided by the present invention first optimize the slicing process, optimize the design of the filling-contour scanning path, and optimize the overlap distance and overlap method between the melt paths in the same layer, thereby ensuring the density of the workpiece forming, the top surface flatness and the workpiece dimensional accuracy; then, utilizing the scanning characteristics of the high-frequency beam jump of the electron beam, a beam scanning strategy is adopted to design and control the size of the micro-melting pool of the contour scanning, control the overlap between the micro-melting pools, and realize the in-situ remelting of the contour melt path; by controlling the number of scanning times and the number of in-situ remelting times, the contour melt path is flattened and homogenized.

[0028] By controlling the duration of a single beam drop and the overlap distance between split beams, and limiting the ratio between the actual distance traveled by a single beam drop and the width of the melt channel, the melt channel is built without collapse, minimal powder absorption, and minimal accumulation. By limiting the ratio between the contour perimeter and the number of split beams, the interaction between spatially and temporally adjacent melt pools is controlled, improving the problem of poor side surface consistency caused by perimeter variations during printing.

[0029] This invention optimizes the slicing process by controlling the micro-melt pool morphology and size, as well as the contoured melt path morphology and size, to achieve optimized surface quality on the side surfaces of thin-walled alloy workpieces. This method optimizes the side surface quality of TC4 alloy to within Ra12.6μm, and that of TiAl alloy to within Ra15μm. This method requires no modification to existing equipment, with virtually no increase in printing costs, and provides an effective solution for reducing side surface roughness during EB-PBF forming. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 A schematic diagram of a single-layer slicing, scanning strategy, and scanning path in one embodiment of the present invention;

[0032] Figure 2 Schematic diagram of a single beam-down model and an isolated molten pool overlap model in a split beam scanning embodiment of the present invention;

[0033] Figure 3 This is a white light interferometry 3D topography image of a single melt track without in-situ remelting and flattening treatment in one embodiment of the present invention;

[0034] Figure 4This is a white light interferometry 3D topography image of a single melt track that has undergone in-situ remelting and flattening treatment in one embodiment of the present invention;

[0035] Figure 5 A top view of a single melt channel at different beam splitting interval lengths in one embodiment of the present invention;

[0036] Figure 6 This is a white light interferometry 3D topography image of the vertical side surface quality of TC4 in Example 1 of the present invention;

[0037] Figure 7 This is an SEM image of the vertical side surface of TC4 in Example 1 of the present invention.

[0038] Reference numerals

[0039] 1-actual contour line, 2-contour scanning lower beam line, 3-filling scanning lower beam path, 4-beam scanning single beam travel distance, 5-beam jump, 6-contour scanning path and the actual contour of the workpiece L 补偿 , 7- Minimum distance L between the filling scanning path and the contour scanning path 搭接 ,8-actual width of filling channel d 填充 , 9- actual width of the contour melt d 轮廓 , 10-single lower beam walking distance L 熔池 , 11-Overlapping method between molten pools, 12-Five overlapping models of point molten pools in contour dotted line scanning strategy DETAILED DESCRIPTION

[0040] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0041] The printing method for improving the surface quality of electron beam additive manufacturing of the present invention includes slicing parameter optimization, design of contour dotted line scanning strategy, and perimeter change and contour parameter adjustment; wherein,

[0042] Slicing parameter optimization: Create a vertical workpiece 3D model and slice the 3D model to obtain layered scanning data, such as Figure 1 As shown in the figure, the contour scanning path is designed according to the actual melt channel width of the contour, and the workpiece precision size requirements and the contour melt channel width d are calculated. 轮廓 Determine the distance L between the contour scanning path and the actual contour line 补偿 =a×d 轮廓 ; where a is 0.2-0.8, d 轮廓 Take 0.3-1.4mm to define the proportional relationship between the distance between the filling scanning path and the contour scanning path and the contour and filling melt widths, and determine the distance L from the filling scanning path to the contour scanning path based on the filling melt width and the contour melt width. 搭接=(1-β)×(r 填充 +r 轮廓 ), where β = 0.6-1, r 填充 =0.2-1mm, r 轮廓 =0.15-0.7mm; perform powder bed preheating scan, contour scanning path scan and filling scanning path scan in sequence to obtain a printed entity.

[0043] The location of the scan path for filling the outline is crucial in this step. Whether the outline scanning path matches the outline melt width determines whether the workpiece dimensional accuracy can be achieved. The fill scan path must match the fill and outline melt widths. If the distance between the two is too large, the fill will not be filled and the outline will easily separate. If the distance is too close, the larger fill melt will completely cover or even extend beyond the outline melt, further deteriorating the surface quality.

[0044] Design of contour dotted line scanning strategy: The contour scanning in the slice parameter optimization adopts the beam scanning method, such as Figure 1 As shown, the perimeter is evenly divided into several parts. After the electron beam enters the contour scanning line, it travels a single beam down distance L 熔池 After that, it jumps to the starting point of the next partition at a jump speed of 2000-5000m / s and continues scanning. After the first round of all partition scanning is completed, it jumps to the first partition at a distance of v×t from the starting point and continues scanning until the contour is completely scanned. Figure 2 As shown. The outline dotted line scanning strategy is: design the overlap mode between beams, and by controlling the length of a single molten pool and the overlap distance and overlap mode between molten pools, the overlap between adjacent molten pools is divided into five types, namely, type A, when x=0, there is no overlap between micro-molten pools; type B, x<v×t, taking x=1 / 2v×t as an example, the dotted line scanning melt channel formed at this time is remelted 1 / 2v×t every v×t interval; type C, x=v×t, at this time, the dotted line scanning melt channel is remelted once in situ; type D, x>v×t, when x is a non-integer multiple of vt, taking x=1.5v×t as an example, the melt channel is remelted once and twice alternately; type E, x>v×t, when x is an integer multiple of v×t, taking x=4v×t as an example, the entire melt channel is remelted 5 times. At the same time, limit L 熔池 with d 轮廓 The proportional relationship L 熔池 =(1~6)×d 轮廓 The melt path is flattened and homogenized through in-situ remelting. This scanning strategy is used for all contour scanning in this method. In this step, the best results are achieved when the relationship between x and v × t is an integer multiple, but the maximum value of x should not exceed 5 times v × t.

[0045] The ratio of x to vt in this step and L 熔池 with d 轮廓 The ratio relationship is crucial. Figure 3 、 4 As shown in the figure, the upper surface of the unsmoothed melt channel exhibits significant undulations, hindering subsequent powder spreading and accumulation. After remelting and leveling, the melt channel exhibits high edge stability, minimal powder absorption, and a uniformly distributed upper surface height. This morphology provides a favorable foundation for uniform powder spreading and stable accumulation of the next layer. The micro-melt pool formed by the electron beam's single downward travel distance is affected by factors such as the bank effect and gravity while molten. Stable solidification within this ratio of melt pool width to melt pool length is essential to ensure that melt circulation during accumulation does not damage the melt pool walls and overflow to form a melt nodule.

[0046] Step (3) Perimeter change and contour parameter adjustment.

[0047] According to the change of the workpiece contour circumference, the proportional relationship between the number of beams, the beam overlap distance, the dwell time of each beam, and the length of the beam micro-melting channel is limited in the dotted line scanning to achieve consistent control of the workpiece surface quality during the forming process. The relationship between the number of beams and the contour circumference should follow:

[0048] t 间隔 =(L 熔池 / v)×(N-1), L 间隔 =L 周长 / N, where N is the number of beams, L 熔池 is the length of the micro-melting channel, v is the scanning speed, and the dwell time of each beam is t 间隔 is the interval time between adjacent molten pools in space, and the beam overlap distance L 间隔 is the distance between adjacent points in time in the molten pool, L 周长 Take 0-800mm, L 间隔 >2×L 熔池 , t 间隔 ≥3ms.

[0049] In this step, t 间隔 and L 间隔 The choice of t is crucial. 间隔 When it is shorter, the preceding molten pool is not completely cooled, e.g. Figure 5 As shown in the figure, with the same perimeter, when N = 2, the melt pool morphology becomes shuttle-shaped, with the front and rear melt pools interfering with each other, preventing complete flattening. When N is too large, the distance between the melt pools becomes too small, resulting in a morphology similar to that of a continuous, unbundled melt path. By limiting the melt pool length and interval time, the size and morphology of the micro-melt pools can be controlled. Within this limited range, the mutual influence between the melt pools is minimized, minimizing the impact on the remelting and flattening effect.

[0050] The present invention adopts a beam splitting scanning strategy to achieve in-situ remelting and flattening of the contour melt path, thus optimizing the side surface quality of vertical metal parts. This is a brand-new technology. The main technical bottlenecks are the following two: (1) There are many methods for optimizing the side surface quality of EB-PBF, but there are few reports on optimizing the surface quality by optimizing the printing process through scanning strategies alone; (2) In EB-PBF printing, the control and flattening of the micro-melt pool and the size and morphology of the contour melt path is a difficult point. This application obtains a stable, highly flat contour melt path with low edge powder absorption through slicing parameter optimization, scanning strategy design, micro-melt pool, and melt path size-morphology control. The contour melt path is obtained by using these contour parameters. The surface quality of the printed side of TC4 vertical workpieces is improved from Ra (20-35) μm to Ra12.6 μm, and the surface quality of the printed side of TiAl vertical workpieces is improved from Ra (25-50) μm to Ra15 μm.

[0051] Example 1

[0052] A printing method for improving surface quality of electron beam additive manufacturing comprises the following steps:

[0053] Take 40kg of TC4 pre-alloyed powder with a particle size distribution of 45-150μm and put it into the powder bin of the EB-PBF equipment. Set the powder feeding method to single-side powder feeding to effectively avoid powder adhesion caused by powder splashing during the printing process.

[0054] Select a 210mm x 210mm build plate, mark the center, and level it. The build plate should be 210mm x 210mm and made of stainless steel. Stainless steel conducts heat quickly and will not deform during the build process at temperatures below 800 degrees Celsius.

[0055] The forming chamber and high-voltage electron gun are in high vacuum state to effectively prevent material oxidation. The vacuum pressure of the forming chamber is 2-3×10 -3 mbar, the vacuum pressure of the electron gun is not less than 5×10 -5 mbar; after reaching the vacuum degree, the high-voltage electron beam is calibrated, calibrated and centered.

[0056] Import the printed STL model into Magics for slicing optimization to ensure the density of the fill and contour overlap. The contour melt width d is selected. 熔道 =0.5mm, L 补偿 =0.2mm; Filling channel width d 填充 =1mm, β overlap coefficient is selected as 0.8, L 搭接 =0.15mm.

[0057] The TC4 pre-alloyed powder corresponding to the equipment process parameters is selected. The specific parameters are as follows: layer thickness is 50μm, base plate preheating temperature: 700-750℃, powder bed preheating temperature: 550-650℃, scanning speed (v) is 300-12000mm / s, beam current (I) is 2-20mA. Contour beam length (L 分束 =L 轮廓周长 / N 分束数量 ):1-100mm; each beam dwell time: t(ms)=0.2-1, beam overlap distance: x(mm)=vt, number of scans: n:1-5, L 熔池 =s×d 轮廓 , S is 1-6, L 间隔 >2×L 熔池 , t 间隔 ≥3ms. The flattened profile melt path obtained by this method is less affected by electron beam fluctuations during long-distance profile scanning, has high melt path flatness, and has small side accumulation marks after accumulation, resulting in high accumulation stability.

[0058] Start preheating and printing. After printing is completed, take out the titanium alloy workpiece and test its surface roughness.

[0059] The workpiece obtained through the above steps is tested by white light interferometry experiment. The upper surface quality Ra = 6.03μm, and the side surface quality is better than Ra12.6μm. Figure 6 As shown in the figure, the surface undulation is small in the 5mm×1.8m area. Through SEM analysis of its surface quality, it can be found that Figure 7 As shown in the figure, the situation of powder adhesion on the side surface of the formed workpiece has been significantly improved, and only a small amount of powder adhesion exists at the interlayer fusion line, which has a positive significance for the optimization of surface quality.

[0060] Example 2

[0061] A printing method for improving surface quality of electron beam additive manufacturing comprises the following steps:

[0062] Take 40kg TiAl with a particle size distribution of 45-105μm 4822 The pre-alloyed powder is placed in the powder bin of the EB-PBF equipment, and the powder feeding mode is set to single-side powder feeding to effectively avoid powder adhesion caused by powder splashing during the printing process.

[0063] Select a molybdenum alloy base plate with a size of 100mm×100mm, mark the center position, and level it;

[0064] The forming chamber and high-voltage electron gun are in high vacuum state to effectively prevent material oxidation. The vacuum pressure of the forming chamber is 2-3×10 -3 mbar, the vacuum pressure of the electron gun is not less than 5×10-5 mbar; after reaching the vacuum degree, the high-voltage electron beam is calibrated, calibrated and centered.

[0065] Import the printed STL model into Magics for slicing optimization to ensure the density of the fill and contour overlap. The contour melt width d is selected. 熔道 =0.45mm, L 补偿 =0.2mm. Filling channel width d 填充 =0.8mm, L 搭接 =0.1mm.

[0066] Select TiAl corresponding to the equipment process parameters 4822 The specific parameters of the pre-alloyed powder are as follows: layer thickness of 50 μm, base plate preheating temperature of 1000-1050°C, powder bed preheating temperature of 900-950°C, scanning speed (v) of 300-12000 mm / s, and beam current (I) of 2-20 mA. Profile beam length (L beam = L profile circumference / N number of beams): 1-100 mm; dwell time per beam: t (ms) = 0.2-1, beam overlap distance: x (mm) = vt, number of scan passes: n: 1-3, L melt pool = s × d profile, S is 2-4, L interval > 2 × L melt pool, t interval ≥ 3 ms. The smoothed profile melt path obtained by this method is less affected by electron beam fluctuations during long-distance profile scanning, has high melt path flatness, and has small side stacking marks after stacking, and has high stacking stability.

[0067] Start preheating and printing. After printing is completed, take out the titanium alloy workpiece and test its surface roughness.

[0068] The above-mentioned forming temperature control effectively ensures powder bed stability. During pre-sintering, powder adhesion due to contour rolling is significantly reduced, and at this preheating temperature, light element loss is minimal. The workpieces obtained through the above steps have been tested in white light interferometry experiments, with top surface quality Ra below 6μm and side surface quality better than Ra15μm.

[0069] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A printing method for improving the surface quality of electron beam additive manufacturing, characterized in that: The method includes: slicing parameter optimization, design of contour dashed line scanning strategy, and perimeter change and contour parameter adjustment; The slicing parameter optimization includes: establishing a three-dimensional model of a pre-printed vertical workpiece, slicing the three-dimensional model to obtain layered scanning data, slicing the contour scanning path according to the contour melt width, defining a proportional relationship between the distance between the filling scanning path and the contour scanning path and the actual melt width of the contour melt and the filling melt; sequentially performing a powder bed preheating scan, a contour scanning path scan, and a filling scanning path scan to obtain a printed entity; The design of the outline dotted line scanning strategy includes: the powder bed preheating scan, outline scanning path scan and filling scanning path scan adopt a beam scanning method, and the outline dotted line scanning strategy is designed as follows: the overlapping method between the beams is designed to achieve in-situ remelting of the continuous melt path by controlling the length of a single melt pool and the overlapping distance and overlapping method between the melt pools, and the melt path is flattened and homogenized; the outline scanning adopts the melt path after the flattening treatment; The slicing optimization of the contour scanning path according to the contour melt width includes: limiting the interval L between the contour scanning path and the actual contour of the workpiece 补偿 =a×d 轮廓 , where d 轮廓 is the width of the profile melt channel, which is 0.3-1.4 mm; a is the proportional coefficient, which is 0.2-0.8; The relationship between the distance between the filling scanning path and the contour scanning path and the actual width of the contour melt channel and the filling melt channel is defined as follows: 搭接 =(1-β)×(r 填充 +r 轮廓 ), where β is the contour filling overlap coefficient, which is 0.6-1; r 填充 The radius of the molten pool is 0.2-1 mm, r 轮廓 The radius of the contour molten pool is 0.15-0.7 mm; The circumference change and profile parameter adjustment include: according to the change in the circumference of the workpiece contour, limiting the proportional relationship between the number of beams, the beam overlap distance, the dwell time of each beam, and the length of the beam micro-melting channel in the dotted line scanning, so as to achieve consistent control of the workpiece surface quality during the forming process, and obtain a surface roughness Ra of the vertical workpiece less than 12.6μm.

2. The method according to claim 1, characterized in that The filling scanning path is a serpentine scanning, starting at an angle of 90° and rotating 90° layer by layer.

3. The method according to claim 1, characterized in that The method further comprises: performing a powder spreading process before optimizing the slice parameters, wherein the powder spreading layer thickness of the powder spreading process does not exceed 100 μm, the powder particle size is 45-150 μm, and the powder composition is Ti6Al4V (TC4) and Ti 48 Al2Cr2Nb(TiAl 4822 ), the vacuum pressure of the molding chamber is 2-3×10 -3 mbar, the vacuum pressure of the electron gun is not less than 5×10 -5 mbar; In the powder bed preheating scan, the TC4 powder bed preheating temperature is 550-750°C, the TiAl powder bed preheating temperature is 900-1050°C, the preheating method is grid preheating, the scanning direction is unidirectional scanning, the preheating beam current is 25-40mA, the scanning speed is 10-25m / s, the number of scans is 1-10 times, and the preheating time is 10-40min.

4. The method according to claim 1, wherein The parameters of the beam splitting scanning method include: scanning speed v is 300-12000mm / s, beam current I is 2-20mA; contour beam length L 分束 =L 轮廓周长 / N 分束数量 , the value is 1-100mm; the dwell time t of each beam is 0-5ms, the beam overlap distance x is 0-20mm, and the number of scans n is 1-5 times.

5. The method according to claim 1, wherein The distance traveled by the electron beam in a single beam scan is: L 熔池 =v×t+x; Among them, L 熔池 is the length of the beam micro-melting path, v is the scanning speed, t is the dwell time of each beam, and x is the beam overlap distance; the end point of the electron beam travel distance is the starting point of the electron beam under the adjacent molten pool; The beam overlap distance x is the actual overlap distance of adjacent molten pools in space. Under this distance, the melt path realizes in-situ remelting. The ratio of x to vt is defined as: x=m×v×t; where m is a positive integer, ranging from 1 to 5.

6. The method according to claim 1, characterized in that In the beam splitting scanning, the length L of the beam splitting micro-melting channel is limited. 熔池 and the contour melt width d 轮廓 The proportional relationship is: L 熔池 =s×d 轮廓 ; The proportional coefficient s is 1-6, d 轮廓 Take 0.3-1.4mm.

7. The method according to claim 1, characterized in that In the defined dashed line scanning, the proportional relationship among the number of beams, the beam overlap distance, the dwell time of each beam, and the length of the beam micro-melting channel includes: Define t 间隔 = (L 熔池 / v) × (N - 1), L 间隔 = L 周长 / N, Where N is the number of beams, L 熔池 is the length of the beam micro-melting channel, v is the scanning speed, and the dwell time of each beam is t 间隔 is the interval time between adjacent molten pools in space, and the beam overlap distance L 间隔 is the distance between adjacent points in time in the molten pool, L 周长 Take 0-800mm, L 间隔 >2×L 熔池 , t 间隔 ≥3ms.

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