Intermittent scanning type selective laser melting forming method for porous metal part

Abstract

The invention belongs to the technical field of laser additive manufacturing, and discloses an intermittent scanning type selective laser melting forming method for a porous metal part, which comprises the following steps: layering and slicing a three-dimensional digital-analog of the porous metal part to be formed according to a preset layer thickness; each layer of slice is sequentially filled with intermittent laser scanning tracks, laser intermittent scanning track filling data are obtained, and the intermittent laser scanning tracks are arranged in the mode that the intermittent laser scanning tracks in the same layer of slice are parallel to one another, and a preset included angle is formed between the intermittent laser scanning tracks in the odd-numbered layer of slice and the intermittent laser scanning tracks in the even-numbered layer of slice; the laser scanning track is composed of solid line scanning tracks and interval tracks, and the solid line scanning tracks and the interval tracks are alternately and linearly arranged; and selective laser melting forming is carried out based on the preset layer thickness and the laser intermittent scanning track filling data, so that the porous metal part is obtained. According to the preparation method, the preparation process of the porous metal part is simplified, and the metal part with high porosity, pore uniformity and pore connectivity can be prepared.

Description

Technical Field

[0001] The present application belongs to the field of laser additive manufacturing technology, and more specifically, relates to an intermittent scanning laser selective melting forming method for porous metal parts. Background Art

[0002] Porous metal parts have the advantages of low density and large specific surface area. They are usually widely used as functional metal parts in aerospace, automobile manufacturing, energy, biomedicine, construction, electronics and other fields. Although traditional preparation methods of porous metal parts, such as sintering and foaming, can meet the production needs of porous metal parts to a certain extent, it is difficult to achieve high-performance and high-efficiency manufacturing of porous metal parts. Selective laser melting (SLM) is one of the laser additive manufacturing technologies that is developing very rapidly at this stage. This technology has the advantages of wide material adaptability, short manufacturing cycle, and strong performance. It provides a new solution for the customization and structural function integration production needs of complex porous metal parts. For example, a laser selective melting forming method for a multi-level interconnected microporous metal sweating structure is disclosed in a Chinese patent application with announcement number CN112935277B. This method obtains the first-level micropores by performing simple digital-analog Boolean operations on the original digital model of the part, sets the spacing of the laser scanning trajectory line to be greater than the cladding line width to obtain the second-level micropores, and increases the laser energy input to generate pores at the bottom of the melt to obtain the third-level micropores. Through multi-level micropore design, the spatial interconnectivity and uniformity of the pores are enhanced, which solves the problems of single pore direction and anisotropic pore structure to a certain extent. However, this method still relies on the preprocessing of the part model, which not only increases the manufacturing cost but also reduces the production efficiency.

[0003] In summary, the existing SLM forming methods of porous metal parts are difficult to meet the requirements of high-efficiency and high-performance forming of porous metal parts with controllable pore structure, interconnected pores and isotropic pores without changing the original digital model of the metal parts. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of the present invention is to provide an intermittent scanning laser selective melting forming method for porous metal parts, aiming to solve the problem that the existing SLM forming method of porous metal parts cannot meet the manufacturing needs of porous metal parts with simplified model design, reduced model data volume, adjustable pore structure, uniform pore distribution and interconnected pores.

[0005] To achieve the above-mentioned purpose, the present application proposes an intermittent scanning laser selective melting forming method for porous metal parts, the forming method comprising: S1 slices the three-dimensional digital model of the porous metal part to be formed into layers according to a preset layer thickness to obtain multi-layer slices; S2 uses an intermittent laser scanning trajectory to fill each slice layer in sequence, and obtains laser intermittent scanning trajectory filling data, wherein the intermittent laser scanning trajectory is set as follows: the intermittent laser scanning trajectories in the same slice layer are parallel to each other, and the intermittent laser scanning trajectories in the odd-numbered slice layer and the intermittent laser scanning trajectories in the even-numbered slice layer form a preset angle; the laser scanning trajectory is composed of a solid line scanning trajectory and an interval trajectory, and the solid line scanning trajectory and the interval trajectory are arranged alternately and in a straight line; S3 performs laser selective melting based on the preset layer thickness and the laser intermittent scanning track filling data. During the forming process, laser melting is performed on the solid line scanning track and laser melting is stopped at the interval track to obtain a porous metal part.

[0006] The above forming method provided by the present application realizes that the porous metal parts are completely connected layer by layer and by channel during the laser selective melting forming process, and the porosity, pore distribution uniformity and pore connectivity of the metal parts are greatly improved, and its anisotropy is effectively improved. At the same time, it also shortens the manufacturing cycle of porous metal parts, simplifies the production process, and greatly reduces the production cost of porous metal parts.

[0007] Furthermore, in step S2, the length of the solid line scanning track is 0.1 mm to 5 mm, and the length of the interval track is 0.05 mm to 2.5 mm.

[0008] Furthermore, the ratio of the length of the interval track to the length of the solid line scanning track is between 0.1 and 0.5.

[0009] Furthermore, in step S2, the laser moving speed at the interval track is greater than the laser scanning speed at the solid line scanning track.

[0010] Furthermore, the laser moving speed at the interval track is in the range of 1000mm / s~6000mm / s; the laser scanning speed at the solid line scanning track is in the range of 300mm / s~2000mm / s.

[0011] Furthermore, in step S2, within the same slice layer, the spacing between adjacent intermittent laser scanning tracks is greater than the width of the laser melt track formed by the laser scanning tracks; and / or, the spacing between adjacent intermittent laser scanning tracks is 1 to 5 times the width of the laser melt track.

[0012] Furthermore, in step S3, when printing layer by layer, the laser galvanometer motor is used to rotate and control the laser scanning tracks in the odd-numbered slices and the even-numbered slices to form an angle, and the angle satisfies: 0°<ω<180°.

[0013] Furthermore, the angle between the laser scanning tracks between the odd-numbered layers and the even-numbered layers can be divided by 180°.

[0014] Furthermore, in step S1, the preset layer thickness is 0.02 mm to 0.4 mm.

[0015] Furthermore, in step S1, when the porosity requirements of different segments on the porous metal part to be formed are different, the porous metal part segments are sliced ​​into segments according to different porosities; in the corresponding step S2, in different segments, the solid line scanning track length and / or the interval track length of the intermittent laser scanning track in each layer of the slice are different.

[0016] In general, the above technical solutions conceived by this application have the following technical advantages compared with the prior art: 1. The intermittent scanning laser selective melting forming method for porous metal parts provided in this application does not require additional processing of the original three-dimensional digital model of the metal parts, that is, the three-dimensional digital model of the porous metal parts can be designed according to the physical shape, and there is no need to design the pore structure, which greatly reduces the design difficulty of the three-dimensional digital model of the porous metal parts and significantly reduces the amount of data of the three-dimensional digital model. The manufacturing of porous metal parts can be achieved through the intermittent scanning laser selective melting forming method, which greatly simplifies the preparation process flow, and the preparation process flow meets the requirements of high-efficiency and high-quality forming of porous metal parts.

[0017] 2. The intermittent scanning laser selective melting forming method provided in the present application designs an intermittent scanning laser trajectory line, in which the solid line scanning trajectory and the interval trajectory are alternately arranged in a straight line. When the porous metal parts are actually prepared, laser scanning and melting are performed at the solid line scanning trajectory, and the laser scanning is stopped at the interval trajectory. A metal structure with pores in each layer can be obtained, and the pores are completely connected layer by layer and track by track during the preparation of the porous metal parts. The porosity, pore distribution uniformity and pore connectivity are greatly improved, and the anisotropy is effectively improved.

[0018] 3. The intermittent scanning laser selective melting forming method provided in the present application not only shortens the manufacturing cycle of porous metal parts, simplifies the production process, but also greatly reduces the production cost of porous metal parts.

[0019] 4. The intermittent scanning laser selective melting forming method provided in the present application can adjust the porosity and pore structure of porous metal parts by only changing the length of the solid line scanning track and the interval track in the laser trajectory line intermittent parameters, and is easy to operate.

[0020] 5. The intermittent scanning laser selective melting forming method provided by the present application can also realize the change of pore gradient by adjusting the length of the solid scanning track and the interval track in the laser intermittent scanning track line of different slice layers in different sections when the porosity requirements of different sections of the same part are different, so as to manufacture porous metal parts with gradient porosity changes. In short, the intermittent scanning laser selective melting forming method provided by the present application can simultaneously simplify the preparation process of gradient porous metal parts, increase the design freedom of porous metal parts, and provide a new solution for the integrated manufacturing of porous metal parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of a process flow of an intermittent scanning laser selective melting forming method for a porous metal part provided in the present application; Figure 2 It is a schematic diagram of the conventional continuous scanning laser scanning trajectory line and the corresponding melt path structure provided by the present application; Figure 3 It is a schematic diagram of the intermittent laser scanning trajectory line and the corresponding melt path structure provided by the present application; Figure 4 It is a schematic diagram of the intermittent laser scanning trajectory line and the corresponding solid line trajectory and interval trajectory length provided by the present application; Figure 5 It is a schematic diagram of the traditional continuous scanning laser scanning melt filling effect and the intermittent laser scanning melt filling effect based on a 90° interlayer angle provided by the present application; Figure 6 It is a schematic diagram of the segmented setting of the intermittent laser scanning trajectory line of the titanium alloy porous gradient metal flat plate part provided in Example 3 of the present application. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] This application proposes a discontinuous scanning laser selective melting forming method for porous metal parts, such as Figure 1 As shown, the forming method includes: S1 imports the three-dimensional digital model of the porous metal part into the laser selective melting equipment, and slices the three-dimensional digital model of the porous metal part to be formed into layers according to the preset layer thickness to obtain multi-layer slices; S2 uses an intermittent laser scanning trajectory to fill each slice layer in sequence, and obtains laser intermittent scanning trajectory filling data, wherein the intermittent laser scanning trajectory is set as follows: the intermittent laser scanning trajectories in the same slice layer are parallel to each other, and the intermittent laser scanning trajectories in the odd-numbered slice layer and the intermittent laser scanning trajectories in the even-numbered slice layer form a preset angle; the laser scanning trajectory is composed of a solid line scanning trajectory and an interval trajectory, and the solid line scanning trajectory and the interval trajectory are arranged alternately and in a straight line; S3 performs laser selective melting based on the preset layer thickness and laser intermittent scanning track filling data. During the forming process, laser melting is performed on the solid line scanning track and the laser melting is stopped at the interval track to obtain porous metal parts.

[0024] In step S1, the three-dimensional digital model of the porous metal part is first imported into the laser selective melting equipment, and the three-dimensional digital model is sliced ​​in layers according to the preset layer thickness, so as to obtain the layer-by-layer cross-sectional contour of the three-dimensional digital model from bottom to top; in the present application, the original model of the three-dimensional digital model of the porous metal part can be designed as a solid model, without the need for additional design of the pore structure, and the amount of data of the three-dimensional digital model is significantly reduced.

[0025] In step S2, each layer of slices is filled in sequence using an intermittent laser scanning trajectory, and the intermittent laser scanning trajectory is specifically set as: 1) In the same slice layer, the intermittent laser scanning tracks are parallel to each other, and the line spacing between two adjacent laser scanning tracks is greater than the width of the laser melt track formed after laser melting along any laser scanning track line, so as to ensure that adjacent laser melt tracks do not touch each other, thereby forming initial pores. The laser melt track refers to the melting track formed by the laser melting the metal powder bed along the laser scanning track line. The width of the laser melt track is related to the laser processing parameters such as the powder material, the preset layer thickness, and the laser power. The laser melt track width value can be obtained through a large amount of basic process test historical data. The line spacing of the laser scanning track refers to the distance between the center axes of two adjacent laser scanning track lines in the same slice layer.

[0026] Specifically, the line spacing of adjacent intermittent laser scanning track lines in the same layer of slices is selected within the range of 1-5 times the width of the laser melt, such as the line spacing of adjacent intermittent laser scanning track lines is 1.5 times, 2 times, 2.5 times, 3 times, 3.5 times, 4 times, 4.5 times, 5 times, etc., or any multiple between any two of the above multiples, to ensure that adjacent laser melts do not touch and can produce initial pores. The line spacing of adjacent intermittent laser scanning track lines selected according to this principle will be easier to calculate and the values ​​will be more regular, which will help improve the stability and reliability of equipment forming, and thus improve the forming quality of porous metal parts. On the premise of ensuring that adjacent melts do not touch, the multiple can be adjusted as needed. The larger the multiple, the larger the initial pore size and the larger the corresponding porosity.

[0027] 2) Make the projections of the intermittent laser scanning trajectories in the odd-numbered and even-numbered slices on the XY horizontal plane intersect, that is, the intermittent laser scanning trajectory lines between adjacent layers are at a preset angle. The preset angle, that is, the angle between adjacent layers, is greater than 0° and less than 180°, because in some laser selective melting equipment, the adjustment of the angle between adjacent layers is achieved by the rotation angle of the laser galvanometer motor. Within this rotation angle range, the laser galvanometer motor can drive the laser emission end to rotate so that the intermittent laser scanning trajectory can cover the entire contour area of ​​the porous metal part, thereby achieving uniform melting and accumulation of the metal powder. If the angle between adjacent layers exceeds this range, it may increase the complexity of the software control motor, and may also affect the stability and reliability of the laser selective melting equipment, resulting in duplication or omission of the laser scanning trajectory line.

[0028] In a more preferred embodiment, the angle between the laser scanning tracks between the odd-numbered layers and the even-numbered layers can divide 180°, such as 30°, 45°, 60°, 90°, etc. During the laser selective melting process, due to rapid heating and cooling, residual stress will be generated inside the metal parts. The angle between adjacent layers is selected to be an angle value that can divide 180°, which can make the rotation angle of the motor easier to control and make the distribution of the laser scanning track line between different layers more uniform, which helps to reduce the accumulation of residual stress and improve the forming quality of porous metal parts.

[0029] 3) If Figure 2 As shown in FIG. 1 , the conventional continuous laser scanning track A and its corresponding melting track B are both a whole straight line segment. Figure 3 As shown, the intermittent laser scanning trajectory provided by this application a The solid line scanning trajectory a1 and the interval track between two adjacent solid line scanning tracks a2 Alternating composition and solid line scanning trajectory a1 and interval trajectory a2 The length of the laser is adjustable; the laser scans the track only in the solid line a1 Scanning molten metal powder while spacing the track a2 The scanning is stopped within the melting work, so that the interval track a2 Finally, the interconnected channels of the initial pores are formed, and the corresponding melt channels b Also intermittent, including solid melt path b1 and interval melt channel b2 .

[0030] Specifically, Figure 4 As shown, the solid line scanning track length m refers to the line segment length of a single laser action track line, and the interval track length n refers to the line segment length of a single laser non-action track line. a1The length m is 0.1mm~5mm, the interval track a2 The length n is 0.05mm~2.5mm, and the interval track a2 The length n and the solid line scanning trajectory a1 The ratio of the length m is between 0.1 and 0.5. When the ratio n / m is less than 0.10, the laser interval track length is too short to form a stable interconnected channel; when the ratio n / m is greater than 0.50, the laser interval track length n will be greater than the solid line scanning track length m, and at this time, the solid line melt path b1 will not be sufficient to maintain the stable forming of porous metal parts.

[0031] In step S2, the laser speeds at the solid line scanning track and the interval track are also set so that the laser moving speed at the interval track is greater than the laser scanning speed at the solid line scanning track. The purpose is to reduce the time without laser action in the interval track, thereby improving production efficiency and reducing costs.

[0032] Specifically, the scanning speed at the solid line scanning trajectory refers to the actual scanning speed when the laser scans the solid line scanning trajectory, and the laser movement speed at the interval trajectory refers to the speed at which the laser moves from the end of the previous solid line scanning trajectory through the interval trajectory to the initial end of the next solid line scanning trajectory. More specifically, the laser movement speed at the interval track is set to be in the range of 1000mm / s~6000mm / s, such as 1000mm / s, 2000mm / s, 3000mm / s, 4000mm / s, 5000mm / s, 6000mm / s, or any speed value between any two of the above speed values; the laser scanning speed at the solid line scanning track is in the range of 300mm / s~2000mm / s, such as 300mm / s, 500mm / s, 700mm / s, 900mm / s, 1000mm / s, 1300mm / s, 1500mm / s, 1800mm / s, 2000mm / s, or any speed value between any two of the above speed values.

[0033] In step S3, the thickness of the single-layer powder bed for laser selective melting is set to a preset layer thickness, and the preset layer thickness is 0.02mm-0.4mm, such as 0.02mm, 0.05mm, 0.08mm, 0.1mm, 0.13mm, 0.15mm, 0.18mm, 0.2mm, 0.23mm, 0.25mm, 0.28mm, 0.3mm, 0.35mm, 0.4mm, etc., or any value between any two of the above values. If the thickness of the single-layer powder bed is less than 0.02mm, the forming efficiency is too low; if the thickness of the single-layer powder bed is greater than 0.40mm, the forming accuracy is too low.

[0034] When the laser selective melting process is used for actual layer-by-layer manufacturing, the metal powder materials selected include commonly used metal additive manufacturing materials such as nickel-based high-temperature alloys, titanium alloys, aluminum alloys, cobalt-based alloys, and tungsten-based alloys. During the preparation process, the laser galvanometer motor is used to rotate to control the laser scanning trajectory in the odd-numbered layer slices and the laser scanning trajectory in the even-numbered layer slices to form an angle, and the angle satisfies: 0°<ω<180°.

[0035] In other preferred embodiments, in step S1, when the porosity requirements of different segments on the porous metal part to be formed are different, the porous metal part segments are sliced ​​into segments according to different porosities; in the corresponding step S2, in different segments, the solid line scanning trajectory length and / or the interval trajectory length of the intermittent laser scanning trajectory in each layer of the slice are different.

[0036] The specific implementation methods of different porosities are: ① Overall pore control method for porous metal parts: set the same solid line scanning track length and interval track length for all slice layers. By adjusting the solid line scanning track length and interval track length, the overall control of the internal pore characteristics of porous metal parts can be achieved; ②Porosity gradient control method for porous metal parts: According to the actual pore requirements, the slice layers of the three-dimensional model of the porous metal parts are segmented, and different solid line scanning track lengths and interval track lengths are set for slice layers of different segments, or different solid line scanning track lengths and the same interval track lengths are set for slice layers of different segments, or the same solid line scanning track lengths and different interval track lengths are set for slice layers of different segments, so that the gradient setting of the pore characteristics of the porous metal parts is achieved through the combination of solid line scanning tracks and interval tracks of various lengths.

[0037] The intermittent scanning laser selective melting forming method of the porous metal parts provided above is described below through multiple embodiments.

[0038] Example 1 This embodiment takes the porous test block of GH4169 nickel-based high-temperature alloy as an example, and its size is 10mm×10mm×10mm. The specific steps of the forming method of the porous test block of GH4169 nickel-based high-temperature alloy are as follows: (1) The three-dimensional digital model of the porous nickel-based high-temperature alloy test block (hereinafter referred to as the three-dimensional digital model) is imported into the laser selective melting equipment; the three-dimensional digital model is sliced ​​in layers according to the preset layer thickness of 0.05 mm to obtain the layer-by-layer cross-sectional profile of the three-dimensional digital model from bottom to top, and the layer-by-layer cross-sectional profile is square and has a size of 10 mm × 10 mm. The three-dimensional digital model of the porous nickel-based high-temperature alloy test block only contains the outer dimensions of the physical test block, and no design is made on its internal pore structure.

[0039] (2) An intermittent laser scanning trajectory is used to fill the multi-layer slice section layer by layer. The relevant parameters of the intermittent laser scanning trajectory are set as: ① In the same layer section, the intermittent laser scanning trajectory lines are set to be parallel to each other; according to the basic process test, it is confirmed that the laser melt width of the GH4169 nickel-based high-temperature alloy under the condition of laser power of 300W is 100μm; accordingly, the spacing between adjacent laser scanning trajectory lines is set to 1.5 times the melt width, that is, the spacing between adjacent laser scanning trajectory lines is 150μm, to ensure that adjacent laser melts do not touch, thereby forming initial pores.

[0040] ② The intermittent laser scanning trajectory is composed of a solid line scanning trajectory and an interval trajectory arranged alternately to form a linear trajectory; specifically, the solid line scanning trajectory length m=1.00mm, the interval trajectory length n=0.20mm, the ratio of the interval trajectory length to the solid line trajectory length is 0.2, the laser scanning speed of the solid line scanning trajectory segment is set to 1000mm / s, and the moving speed of the laser skipping the interval trajectory segment is set to 3000mm / s; the laser only works in the solid line scanning trajectory segment, and does not work in the interval trajectory segment, so that there is no melt path in the interval trajectory segment, thereby forming an interconnected channel of the initial pores; ③ The included angle of the intermittent laser scanning trajectory between two adjacent layers (i.e. the angle between adjacent layers) is selected to be 90°.

[0041] The intermittent laser scanning trajectory set in step (2) is used to fill all slice cross-sectional contours layer by layer from bottom to top, so as to generate a laser intermittent scanning filling file that can be recognized by the laser selective melting device. Specifically, after merging the laser scanning filling files of each layer, a complete laser intermittent scanning filling data containing the laser scanning filling information of all slice layers is obtained.

[0042] (3) The dried GH4169 nickel-based high-temperature alloy metal powder is loaded into the laser selective melting equipment, and the laser selective melting forming of the high-temperature alloy porous test block is completed layer by layer from bottom to top according to the preset layer thickness of 0.05 mm in step (1) and the complete laser intermittent scanning filling file obtained in step (2); during the forming process, the laser melts the metal powder in the solid line scanning track of the intermittent laser scanning track to form a dense pore wall, and the laser is turned off in the interval track to form an interconnected channel between the initial pores. According to the layer-by-layer intermittent scanning laser selective melting forming method, a nickel-based high-temperature alloy porous test block with uniform pore distribution and interconnected pores is prepared, and its internal pore structure is as follows: Figure 5 As shown in the middle right figure, compared with the same conditions, the laser selective melting process prepared by continuous laser scanning trajectory Figure 5 The internal pore structure of the metal plate shown in the middle left figure clearly shows that the metal in this embodiment has a larger internal porosity, better pore distribution uniformity, and stronger pore connectivity.

[0043] Example 2 This embodiment takes the AlSi10Mg aluminum alloy porous metal flat plate as an example, whose size is 100mm×80mm×10mm. The specific steps of the forming method of the AlSi10Mg aluminum alloy porous metal flat plate are as follows: (1) The three-dimensional digital model of the AlSi10Mg aluminum alloy porous metal flat plate metal part (with a size of 100 mm × 80 mm × 10 mm, hereinafter referred to as the three-dimensional digital model) is imported into the laser selective melting equipment; the three-dimensional digital model is sliced ​​according to the preset layer thickness of 0.02 mm, and the layer-by-layer cross-sectional profile of the three-dimensional digital model is obtained from bottom to top. The layer-by-layer cross-sectional profile is a rectangle with a size of 80 mm × 10 mm; the three-dimensional digital model of the aluminum alloy porous metal flat plate is designed according to the outer dimensions of the solid plate, and there is no need to additionally design the pore structure.

[0044] (2) The preset intermittent laser scanning trajectory is used to fill the multi-layer slice section layer by layer. The relevant parameters of the intermittent laser scanning trajectory are set as: ① In the same layer section, the intermittent laser scanning trajectory lines are set to be parallel to each other; according to the basic process test, it is confirmed that the width of the AlSi10Mg aluminum alloy laser melt channel under the condition of laser power of 400W is 150μm; accordingly, the spacing between adjacent intermittent laser scanning trajectory lines is set to 2.0 times the melt channel width, that is, the spacing between adjacent intermittent laser scanning trajectory lines is 300μm, to ensure that adjacent melt channels do not touch, thereby forming initial pores; ② The intermittent laser scanning trajectory is composed of a solid line scanning trajectory and an interval trajectory arranged alternately to form a linear trajectory; specifically, the length of the solid line scanning trajectory is m=2.00mm, the length of the interval trajectory is n=0.50mm, the ratio of the interval trajectory length to the solid line trajectory length is 0.25, the laser scanning speed of the solid line scanning trajectory segment is set to 1400mm / s, and the moving speed of the laser skipping the interval trajectory segment is set to 4000mm / s; the laser only works in the solid line scanning trajectory segment, and does not work in the interval trajectory segment, so that there is no melt path in the interval trajectory segment, thereby forming an interconnected channel of the initial pores; ③ The included angle of the intermittent laser scanning trajectory between two adjacent layers (i.e., the angle between adjacent layers) is selected to be 60°.

[0045] The intermittent laser scanning trajectory set in step (2) is used to fill all slice cross-sectional contours layer by layer from bottom to top, so as to generate a laser intermittent scanning filling file that can be recognized by the laser selective melting device. Specifically, after merging the laser scanning filling files of each layer, a complete laser intermittent scanning filling data containing the laser scanning filling information of all slice layers is obtained.

[0046] (3) The dried AlSi10Mg aluminum alloy metal powder is loaded into the laser selective melting equipment, and the laser selective melting forming of the aluminum alloy porous metal plate is completed layer by layer from bottom to top according to the preset layer thickness of 0.02 mm in step (1) and the complete laser intermittent scanning filling file generated in step (2); during the forming process, the laser melted metal powder in the solid line scanning track of the intermittent laser scanning track forms a dense pore wall, and the laser is turned off in the interval track to form an interconnected channel between the initial pores. According to the layer-by-layer intermittent scanning laser selective melting forming method, a nickel-based high-temperature alloy porous test block with uniform pore distribution and interconnected pores is prepared.

[0047] Example 3 This embodiment takes a Ti6Al4V titanium alloy porous gradient metal flat plate part as an example, and its size is 150mm×70mm×10mm. The titanium alloy porous gradient metal flat plate part requires that the porosity is set at a porosity value every 50mm along the height direction (total height 150mm), and a total of three sections of porous flat plate areas with different porosities are set, and the porosity values ​​of the three sections are increased. The specific steps are: (1) The three-dimensional digital model of the Ti6Al4V titanium alloy porous gradient metal plate part (size 150mm×70mm×10mm) is imported into the laser selective melting equipment; the three-dimensional digital model is sliced ​​in layers according to the preset layer thickness of 0.04mm, so as to obtain the layer-by-layer cross-sectional profile of the three-dimensional digital model from bottom to top, and the layer-by-layer cross-sectional profile is a rectangle (size 70mm×10mm). According to the porosity requirements of the titanium alloy porous gradient metal plate, the sliced ​​layers of the porous gradient plate are divided into three sections from bottom to top according to the height range of 0-150mm, that is, corresponding to the layer number range of 1-3750, such as Figure 6 As shown: The first stage: height range 0-50mm, number of layers range 1-1250 layers; The second stage: height range 50-100mm, number of layers range 1251-2500; The third section: 100-150mm, the number of layers ranges from 2501-3750 layers; The original model of the three-dimensional digital model of the Ti6Al4V titanium alloy porous gradient metal plate is designed based on the shape information of the solid plate, without additionally designing a pore structure inside it.

[0048] (2) An intermittent laser scanning trajectory is used to fill the multi-layer slice section layer by layer. The relevant parameters of the intermittent laser scanning trajectory are set as: ① In the same layer section, the intermittent laser scanning trajectory lines are set to be parallel to each other; according to the basic process test, it is confirmed that the laser melt width of Ti6Al4V titanium alloy under the condition of laser power of 280W is 110μm; accordingly, the spacing between adjacent intermittent laser scanning trajectory lines is set to 2.5 times the melt width, that is, the spacing between the intermittent laser scanning trajectory lines is 275μm, to ensure that adjacent melts do not touch, thereby forming initial pores; ② The intermittent laser scanning trajectory is composed of a solid line scanning trajectory and an interval trajectory arranged alternately to form a linear trajectory; specifically, the laser only works in the solid line scanning trajectory segment and does not work in the interval trajectory segment, so that there will be no melt path in the interval trajectory segment, thereby forming an interconnected channel of the initial pores.

[0049] ③The angle between adjacent layers is selected as 60°.

[0050] ④ Since the titanium alloy porous gradient plate requires the porosity to be distributed in an equidistant gradient along the length direction, the solid line scanning track length and the interval track length are set in a gradient manner within the three-segment slice layering range of the porous gradient plate. Figure 6 The specific settings are as follows: The first section: 0-50mm, the number of layers ranges from 1 to 1250 layers, the solid line scanning track length m1=2.00mm, the interval track length n1=0.30mm, under this parameter, the ratio of the interval track length to the solid line scanning track length is 0.15; The second section: 50-100mm, the number of layers ranges from 1251-2500 layers, the solid line scanning track length m2=2.00mm, the interval track length n2=0.40mm, under this parameter, the ratio of the interval track length to the solid line scanning track length is 0.20; The third section: 100–150 mm, the number of layers ranges from 2501 to 3750 layers, the solid line scanning track length m3 = 2.00 mm, the interval track length n3 = 0.50 mm, under this parameter, the ratio of the interval track length to the solid line scanning track length is 0.25; The solid line scanning track length and the interval track length gradient within the above three sections of slicing layering range meet the stable forming requirements of Ti6Al4V titanium alloy porous gradient flat plate metal parts. From bottom to top, the ratios of the interval track length to the solid line scanning track length in the three sections of porous flat plate areas are 0.15, 0.20, and 0.25, respectively, and the porosity gradient increases.

[0051] After the corresponding slice section contour is completely filled according to the intermittent laser scanning trajectory set above, the laser scanning filling files generated layer by layer are merged to obtain a complete laser intermittent scanning filling file containing the laser scanning filling file information of all slice layers.

[0052] (3) The dried Ti6Al4V titanium alloy metal powder is loaded into the laser selective melting equipment, and the laser selective melting forming of the Ti6Al4V titanium alloy gradient porous metal flat plate metal part is completed layer by layer and track by track from bottom to top according to the preset layer thickness of 0.04 mm in step (1) and the complete laser intermittent scanning filling file obtained in step (2); during the forming process, in the laser intermittent scanning track, the laser melts the metal powder in the solid line scanning track to form a dense pore wall, and the laser is turned off in the interval track, thereby forming an interconnected channel between the initial pores. After layer-by-layer intermittent scanning laser selective melting forming, a Ti6Al4V titanium alloy gradient porous metal flat plate metal part with uniform pore gradient distribution and interconnected pores is obtained.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for forming porous metal parts by intermittent scanning laser selective melting, characterized in that: The forming method comprises: S1 slices the three-dimensional digital model of the porous metal part to be formed into layers according to a preset layer thickness to obtain multi-layer slices; S2 uses an intermittent laser scanning trajectory to fill each slice layer in sequence, and obtains laser intermittent scanning trajectory filling data, wherein the intermittent laser scanning trajectory is set as follows: the intermittent laser scanning trajectories in the same slice layer are parallel to each other, and the intermittent laser scanning trajectories in the odd-numbered slice layer and the intermittent laser scanning trajectories in the even-numbered slice layer form a preset angle; the laser scanning trajectory is composed of a solid line scanning trajectory and an interval trajectory, and the solid line scanning trajectory and the interval trajectory are arranged alternately and in a straight line; S3 performs laser selective melting based on the preset layer thickness and the laser intermittent scanning track filling data. During the forming process, laser melting is performed on the solid line scanning track and laser melting is stopped at the interval track to obtain a porous metal part.

2. The intermittent scanning laser selective melting forming method of a porous metal part according to claim 1, characterized in that: In step S2, the length of the solid line scanning track is 0.1 mm to 5 mm, and the length of the interval track is 0.05 mm to 2.5 mm.

3. The intermittent scanning laser selective melting forming method of a porous metal part according to claim 2, characterized in that: The ratio of the length of the interval track to the length of the solid line scanning track is between 0.1 and 0.

5.

4. The intermittent scanning laser selective melting forming method for porous metal parts according to claim 1, characterized in that: In step S2, the laser moving speed at the interval track is greater than the laser scanning speed at the solid line scanning track.

5. The intermittent scanning laser selective melting forming method of a porous metal part as claimed in claim 4, characterized in that: The laser moving speed at the interval track is in the range of 1000mm / s~6000mm / s; the laser scanning speed at the solid line scanning track is in the range of 300mm / s~2000mm / s.

6. The intermittent scanning laser selective melting forming method of a porous metal part according to claim 1, characterized in that: In step S2, within the same slice layer, the spacing between adjacent intermittent laser scanning tracks is greater than the width of the laser melt track formed by the laser scanning tracks; and / or, the spacing between adjacent intermittent laser scanning tracks is 1 to 5 times the width of the laser melt track.

7. The intermittent scanning laser selective melting forming method for porous metal parts according to claim 1, characterized in that: In step S3, when printing layer by layer, the laser galvanometer motor is used to rotate and control the laser scanning tracks in the odd-numbered slices and the even-numbered slices to form an angle, and the angle satisfies: 0°<ω<180°.

8. The intermittent scanning laser selective melting forming method of a porous metal part according to claim 7, characterized in that: The angle between the laser scanning tracks between the odd-numbered layers and the even-numbered layers can divide 180°.

9. The intermittent scanning laser selective melting forming method for porous metal parts according to claim 1, characterized in that: In step S1, the preset layer thickness is 0.02 mm to 0.4 mm.

10. The intermittent scanning laser selective melting forming method for porous metal parts according to claim 1, characterized in that: In step S1, when the porosity requirements of different segments on the porous metal part to be formed are different, the porous metal part segments are sliced ​​into segments according to different porosities; in the corresponding step S2, in different segments, the solid line scanning track length and / or the interval track length of the intermittent laser scanning track in each layer of the slice are different.

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