Additive manufacturing method for pre-buried defective metal structure

Abstract

The invention discloses an additive manufacturing method for a pre-embedded defective metal structure, which comprises the following steps: through spatial partition parameter regulation and control of an LPBF (Liquid Crystal Partition Fiber) process, constructing a gradient structure of a matrix region-functional region in a structural part, realizing control on a three-dimensional crack path, and breaking through the limitation that a traditional plane grooving is only suitable for a two-dimensional structure; precise regulation and control can be realized through parameter scaling from a micro structural member to a large structural member; the performance is stable, accurate and controllable; and position precision: three-dimensional precise positioning of the functional area is realized through digitized model partitioning and high-precision scanning forming of LPBF equipment, the strength weakening amplitude of the functional area can be continuously regulated and controlled through parameters such as energy density, a scanning strategy and a microstructure, and different crack control requirements are met.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology, and specifically relates to an additive manufacturing method for a pre-embedded defect metal structure. Background Technology

[0002] Laser powder bed melting (LPBF) technology, as one of the mainstream processes in metal additive manufacturing, leverages its near-net-shape forming advantages of "layer-by-layer melting and stacking" to manufacture components with complex internal cavities and topology optimizations that are difficult to process using traditional cutting processes. It has become a core technology for the rapid R&D and small-batch production of high-end metal components. Its process principle involves selectively melting metal powder layers using a high-energy laser beam along a preset path. After cooling and solidification, a single layer is formed. This process is repeated until the entire component is manufactured. Traditional methods of pre-embedding defects have significant drawbacks.

[0003] Mechanical grooving (such as wire cutting and electrical discharge machining) has low precision and is prone to introducing additional defects (such as microcracks and surface oxide layers) beyond stress concentration at the groove edges. Stress concentration design (such as sharp corners and thin-walled structures) is only suitable for simple two-dimensional structures and cannot be adapted to complex three-dimensional components. Moreover, the direction of crack propagation is easily affected by the overall stress field of the component, resulting in poor controllability. The core objective of traditional laser powder bed melting (LPBF) process is to pursue the uniformity of the density (usually ≥99.5%) and mechanical properties (strength, plasticity, fatigue life, etc.) of the entire component area. This objective contradicts the need to "precisely construct local weakened areas" in special scenarios. Summary of the Invention

[0004] The purpose of this invention is to provide an additive manufacturing method for pre-embedded defect metal structures to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an additive manufacturing method for a pre-embedded defect metal structure, the specific steps of which are as follows:

[0006] S1. Partitioning: Based on the geometric requirements of the target crack path, the precise division of the "functional area" and "matrix area" is completed in the three-dimensional digital model;

[0007] S2, parameter adjustment;

[0008] (1) Parameter settings for the matrix region: The parameters of the material are combined with the standard parameters for laser powder bed melting of the material to ensure high density and excellent mechanical properties in the matrix region. The laser power is optimized according to the powder melting efficiency, specifically according to the following formula:

[0009] E = P / V * D * t;

[0010] Where E is energy density, P is power, V is scanning speed, D is layer thickness, and t is scanning interval. The printing parameters are balanced and optimized according to the calculation formula.

[0011] The scanning spacing ensures the overlap between adjacent scanning trajectories and avoids gaps where the fusion is incomplete. The scanning spacing is related to the overlap amount, i.e., the amount of overlap between adjacent scanning trajectories, and is used to determine the scanning spacing.

[0012] Layer thickness: Appropriate to powder particle size to ensure sufficient melting of a single layer;

[0013] Scanning strategy: Suppress interlayer stress accumulation by rotating the angle to reduce the generation of primary cracks in the matrix region;

[0014] (2) Functional area parameter settings: Through the single or combined application of three methods, namely "energy density regulation, scanning strategy regulation, and micro-organization regulation", the intensity of the functional area can be precisely weakened.

[0015] S3. Post-processing: Based on material properties and actual application requirements, the following targeted post-processing processes can be selected to further enhance the performance gradient between the matrix region and the functional region.

[0016] Heat treatment: For metallic materials, the difference in hardness, strength or plasticity between the functional area and the matrix area can be increased by adjusting the heat treatment process parameters, including heat treatment temperature, holding time and cooling method, thereby enhancing the crack guiding effect.

[0017] Surface finishing: White corundum sandblasting is used to remove adhering powder and spheroidized particles from the surface of structural components, ensuring that the surface roughness of both the functional area and the substrate area is controlled within the required range.

[0018] Preferably, the geometric requirements for the target crack path in S1 specifically include straight lines, broken lines, and curves.

[0019] Preferably, the division principle in S1 is as follows: Matrix region: Based on the mechanical analysis of the structural component, the matrix region, as the main load-bearing area of ​​the structural component, must meet the overall strength and stiffness requirements of the structure, with a density control standard of relative density ≥99.5%, and mechanical properties must meet the industrial application standards of the corresponding material; Functional region: Must be continuously distributed along the target path, i.e., the target crack path, and key printing parameters can be adjusted as needed.

[0020] Width: Typical value 0.1-2mm;

[0021] Position accuracy: Precise positioning is achieved through 3D modeling software to ensure that the position does not deviate from the target path.

[0022] Preferably, the substrate region parameter settings in S2 also include scanning spacing: to ensure the overlap rate of adjacent scanning trajectories and avoid gaps where no molten metal is formed; the scanning spacing is related to the overlap amount, and the two are negatively correlated. The calculation formula is: overlap amount = molten pool width - scanning spacing. The overlap amount is the amount of overlap between adjacent scanning trajectories. The scanning spacing is determined in this way to ensure printing quality.

[0023] Preferably, the energy density regulation in S2 specifically involves reducing the volume energy density of the functional region.

[0024] The calculation formula is:

[0025] ED = P / (v × h × t);

[0026] Where P is the laser power, v is the scanning speed, h is the scanning spacing, and t is the layer thickness.

[0027] Typical regulatory methods include:

[0028] Power reduction: Keep the scanning speed, spacing, and layer thickness unchanged, but reduce the laser power;

[0029] Speed ​​increase: Keep the laser power, spacing, and layer thickness unchanged, and increase the scanning speed.

[0030] Preferably, the scanning strategy control in S2 specifically utilizes the stress concentration effect and thermal accumulation difference of the scanning strategy to reduce crack resistance and guide crack propagation along the functional zone.

[0031] Preferably, the microstructure control in S2 specifically targets phase change sensitive materials by adjusting the cooling method, such as water cooling, air cooling, or air cooling, to control the cooling rate, thereby forming a coarse grain structure in the functional area and further widening the strength difference between the functional area and the matrix area.

[0032] The technical effects and advantages of this invention are: precise controllability; positional accuracy: through digital model partitioning and high-precision scanning forming with LPBF equipment, three-dimensional precise positioning of functional areas is achieved, with a positional error ≤ ±0.05mm, far exceeding the ±0.1mm error of mechanical grooving; strength control precision: the degree of strength weakening of functional areas can be continuously controlled by parameters such as energy density, scanning strategy, and microstructure to meet different crack control requirements; structural compatibility and adaptation to complex three-dimensional structures: functional areas can be preset inside three-dimensional components (such as internal cavities and curved surfaces) to achieve control of three-dimensional crack paths, breaking through the limitation of traditional planar grooving being only applicable to two-dimensional structures; adaptation to structural components of different sizes: from micro-structural components to large components, precise control can be achieved through parameter scaling; performance stability (high reliability).

[0033] Stable performance in the matrix region: Utilizing high-density parameter design, the mechanical property fluctuation in the matrix region is ≤±5%, ensuring the overall load-bearing capacity of the structural components remains stable; Consistent performance in functional regions: Through standardized parameter control schemes (such as fixed combinations of energy density and scanning strategies), the microstructure (such as porosity and lack of fusion) of functional regions exhibits high consistency; Material universality: It can be adapted to various commonly used metal materials in LPBF, and by adjusting parameters specifically to suit the physical and metallurgical properties of different materials, there is no need to develop entirely new equipment or processes for different materials, reducing the cost of technology promotion. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the printing partition of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] This invention provides, for example Figure 1 The figure shows an additive manufacturing method for a pre-embedded defect metal structure, with gray representing the matrix area and red representing the functional area.

[0037] 1. Structural component digital model partitioning design:

[0038] Based on the geometric requirements of the target crack path (such as straight lines, polylines, and curves), the precise division of the "functional area" and "matrix area" is completed in the 3D digital model (modeled using CAD software, in STL or STEP format). The division principles are as follows:

[0039] Matrix region: Based on the structure of the structural component, mechanical analysis is performed to determine the matrix region and functional region. As the main load-bearing area of ​​the structural component, the matrix region must meet the overall strength and stiffness requirements of the structure. The density control standard is relative density ≥99.5%, and the mechanical properties must meet the industrial application standards of the corresponding materials.

[0040] Functional area: As a preset crack initiation and propagation channel, it needs to be continuously distributed along the target path, i.e., the target crack path. Key printing parameters can be adjusted as needed.

[0041] Width: Typical value 0.1-2mm (set according to the size of the structural component and the crack propagation accuracy requirements, such as 0.1-0.5mm for micro structural components and 1-2mm for large components).

[0042] Position accuracy: Precise positioning using CAD software ensures accurate deviation from the target path. The deviation range varies depending on the simulation scenario. For example, in finite element crack analysis of structural components, for high-precision simulations (such as precision parts or aerospace components), the deviation needs to be controlled within ±0.1~0.5mm, matching the accuracy of the simulation mesh (such as element size). For engineering-level simulations (such as overall fracture analysis of structural components), the deviation can be relaxed to ±0.5~2mm, focusing on reflecting the crack propagation trend and key turning points (such as turning at stress concentration points).

[0043] 2. Laser powder bed melting zone parameter control (core process control)

[0044] Layered manufacturing is performed using industrial-grade LPBF equipment. The equipment control system enables the application of differentiated process parameters to different areas within the same layer. The specific parameter settings are as follows:

[0045] (1) Matrix region parameter settings (normal densification parameters)

[0046] Taking Ti6Al4V alloy (powder particle size 15-45μm) as an example, the parameters are combined with the standard parameters for laser powder bed melting of this material to ensure high density and excellent mechanical properties in the matrix region:

[0047] Laser power: Optimized based on powder melting efficiency to avoid incomplete fusion due to low energy density or spatter due to high energy density; E=P / V*D*t, optimized according to the calculation formula, where E is energy density, P is power, V is scanning speed, D is layer thickness, and t is scanning interval. The printing parameters are balanced and adjusted according to the calculation formula to optimize printing parameters.

[0048] Scanning speed: Balancing forming efficiency and density, excessive speed can lead to splattering, while insufficient speed can result in inadequate density. There is no fixed value for scanning speed; it must be comprehensively weighed in conjunction with printing technology, material properties, and model requirements. The core principle is "maximizing efficiency while ensuring print quality."

[0049] Scan spacing: Ensures the overlap between adjacent scan tracks to avoid gaps where the scan tracks are not fully melted; the scan spacing is related to the overlap amount, i.e., the amount of overlap between adjacent scan tracks, and is used to determine the scan spacing to ensure print quality.

[0050] Layer thickness: Appropriate to powder particle size to ensure sufficient melting of a single layer;

[0051] Scanning strategy: By rotating the angle, interlayer stress accumulation is suppressed, reducing the generation of primary cracks in the matrix region. The interlayer rotation angle is generally set at 67°. The principle for selecting the interlayer rotation angle is to minimize the overlap of printed layers in the direction to reduce stress accumulation.

[0052] This parameter combination can achieve a relative density of ≥99.5% in the matrix region, mechanical properties that meet the performance indicators of relevant material standards, and fully meet the structural load-bearing requirements.

[0053] (2) Function area parameter settings (intensity weakening parameters)

[0054] By applying one or a combination of three methods—energy density regulation, scanning strategy regulation, and micro-organism regulation—the intensity of functional regions can be precisely weakened. The specific regulation scheme is as follows:

[0055] Energy density modulation: Reducing the volume energy density (ED, calculated as ED=P / (v×h×t), where P is laser power, v is scanning speed, h is scanning interval, and t is slice thickness) in functional regions. Typical modulation methods include:

[0056] Power reduction: Keep the scanning speed, spacing, and layer thickness unchanged, but reduce the laser power;

[0057] Speed ​​increase: Keep the laser power, spacing, and layer thickness unchanged, and increase the scanning speed.

[0058] A decrease in energy density can introduce trace amounts of spherical pores and fine unmelted particles into the functional area, thereby reducing the tensile strength and elongation of the functional area.

[0059] Scanning strategy control: Utilizing the stress concentration effect and thermal accumulation difference of the scanning strategy, crack resistance is reduced, and crack propagation is guided along functional zones. The selection of the interlaminar rotation angle affects the overlap between material layers, thereby generating stress concentration and leading to thermal accumulation differences.

[0060] Microstructure control: Phase change sensitive materials refer to a class of functional materials that can undergo phase transitions (such as solid-liquid or solid-solid transitions) at specific temperatures, absorbing or releasing a large amount of heat (latent heat) during the phase transition process while maintaining a relatively constant internal temperature. For phase change sensitive materials, the cooling rate can be controlled by adjusting the cooling method, such as water cooling, air cooling, or general cooling, thereby enabling the functional regions to form coarse-grained structures and further increasing the strength difference between the functional regions and the matrix region.

[0061] 3. Post-processing techniques

[0062] Based on material properties and actual application requirements, the following targeted post-processing techniques can be selected to further enhance the performance gradient between the matrix region and the functional region:

[0063] Heat treatment: For metallic materials, the difference in hardness, strength or plasticity between the functional area and the matrix area can be increased by adjusting the heat treatment process parameters, including heat treatment temperature, holding time and cooling method, thereby enhancing the crack guiding effect.

[0064] Surface finishing: White corundum sandblasting is used to remove adhering powder and spheroidized particles from the surface of structural components, ensuring that the surface roughness (Ra) of both the functional area and the substrate area is controlled within the required range, and avoiding interference from surface defects (such as burrs and powder adhesion) on the crack initiation location.

[0065] In summary, the main technical effects and advantages of this invention are: 1. Precise controllability; Positional accuracy: Through digital model partitioning and high-precision scanning forming with LPBF equipment, three-dimensional precise positioning of functional areas is achieved, with a positional error ≤ ±0.05mm, far exceeding the ±0.1mm error of mechanical grooving; Strength control precision: The degree of strength weakening of functional areas can be continuously adjusted through parameters such as energy density, scanning strategy, and microstructure to meet different crack control requirements; Structural compatibility, adaptable to complex three-dimensional structures: Functional areas can be preset inside three-dimensional components (such as internal cavities and curved surfaces) to achieve control of three-dimensional crack paths, breaking through the limitation of traditional planar grooving being only applicable to two-dimensional structures; Adaptability to structural components of different sizes: From micro-structural components to large components, precise control can be achieved through parameter scaling; Performance stability (high reliability)

[0066] Stable performance in the matrix region: Utilizing high-density parameter design, the mechanical property fluctuation in the matrix region is ≤±5%, ensuring the overall load-bearing capacity of the structural components remains stable; Consistent performance in functional regions: Through standardized parameter control schemes (such as fixed combinations of energy density and scanning strategies), the microstructure (such as porosity and lack of fusion) of functional regions exhibits high consistency; Material universality: It can be adapted to various commonly used metal materials in LPBF, and by adjusting parameters specifically to suit the physical and metallurgical properties of different materials, there is no need to develop entirely new equipment or processes for different materials, reducing the cost of technology promotion.

[0067] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An additive manufacturing method for a pre-embedded defect metal structure, characterized in that: The specific steps are as follows: S1. Partitioning: Based on the geometric requirements of the target crack path, the "functional area" and "matrix area" are precisely divided in the three-dimensional digital model. S2, parameter control; (1) Parameter settings for the matrix region: The parameters of the material are combined with the standard parameters for laser powder bed melting of the material to ensure high density and excellent mechanical properties in the matrix region. The laser power is optimized according to the powder melting efficiency, specifically according to the following formula: E = P / V * D * t; Where E is energy density, P is power, V is scanning speed, D is layer thickness, and t is scanning interval. The printing parameters are balanced and optimized according to the calculation formula. The scanning spacing ensures the overlap between adjacent scanning trajectories and avoids gaps where the fusion is incomplete. The scanning spacing is related to the overlap amount, i.e., the amount of overlap between adjacent scanning trajectories, and is used to determine the scanning spacing. Layer thickness: Appropriate to powder particle size to ensure sufficient melting of a single layer; Scanning strategy: Suppress interlayer stress accumulation by rotating the angle to reduce the generation of primary cracks in the matrix region; (2) Functional area parameter settings: Through the single or combined application of three methods, namely "energy density regulation, scanning strategy regulation and micro-organization regulation", the intensity of functional areas can be precisely weakened. S3. Post-processing: Based on material properties and actual application requirements, select the following targeted post-processing processes to further enhance the performance gradient of the "matrix region - functional region". Heat treatment: For metallic materials, by adjusting the heat treatment process parameters, including heat treatment temperature, holding time and cooling method, the difference in hardness, strength or plasticity between the functional area and the matrix area can be increased, thereby enhancing the crack guiding effect. Surface finishing: White corundum sandblasting is used to remove adhering powder and spheroidized particles from the surface of structural components, ensuring that the surface roughness of both the functional area and the substrate area is controlled within the required range.

2. The additive manufacturing method for a pre-embedded defect metal structure according to claim 1, characterized in that: The geometric requirements for the target crack path in S1 specifically include straight lines, broken lines, and curves.

3. The additive manufacturing method for a pre-embedded defect metal structure according to claim 1, characterized in that: The division principle in S1 is as follows: Matrix region: Based on the structural structure and mechanical analysis, the matrix region, as the main load-bearing area of ​​the structural component, must meet the overall strength and stiffness requirements of the structure. The density control standard is a relative density ≥ 99.5%, and the mechanical properties must meet the industrial application standards of the corresponding materials; Functional region: It needs to be continuously distributed along the target path, i.e., the target crack path. Key printing parameters are adjusted as needed. Width: Typical value 0.1-2mm; Position accuracy: Precise positioning is achieved through 3D modeling software to ensure that the position does not deviate from the target path.

4. The additive manufacturing method for a pre-embedded defect metal structure according to claim 1, characterized in that: The substrate region parameter settings in S2 also include scanning spacing: ensuring the overlap rate of adjacent scanning trajectories and avoiding gaps where no molten metal is formed; the scanning spacing is related to the overlap amount, and the two are negatively correlated. The calculation formula is: overlap amount = molten pool width - scanning spacing. The overlap amount is the amount of overlap between adjacent scanning trajectories, which is used to determine the scanning spacing, thereby ensuring printing quality.

5. The additive manufacturing method for a pre-embedded defect metal structure according to claim 1, characterized in that: The energy density regulation in S2 specifically involves reducing the volume energy density of the functional region. The calculation formula is: ED = P / (v × h × t); Where P is the laser power, v is the scanning speed, h is the scanning spacing, and t is the layer thickness. Typical regulatory methods include: Power reduction: Keep the scanning speed, spacing, and layer thickness unchanged, but reduce the laser power; Speed ​​increase: Keep the laser power, spacing, and layer thickness unchanged, and increase the scanning speed.

6. The additive manufacturing method for a pre-embedded defect metal structure according to claim 1, characterized in that: The scanning strategy control in S2 specifically utilizes the stress concentration effect and thermal accumulation difference of the scanning strategy to reduce crack resistance and guide crack propagation along the functional zone.

7. The additive manufacturing method for a pre-embedded defect metal structure according to claim 1, characterized in that: The microstructure control in S2 specifically targets phase change sensitive materials by adjusting the cooling method, such as water cooling, air cooling, or air cooling, to control the cooling rate, thereby forming coarse grain structures in the functional areas and further widening the strength difference between the functional areas and the matrix areas.

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