Laser selective melting additive manufacturing parameter matching and forming method based on molten pool energy coupling

Abstract

The application discloses a laser selective melting additive manufacturing parameter matching and forming method based on a molten pool energy coupling. Through fusing material melting thermodynamics, molten pool heat diffusion dynamics and adjacent scanning path energy superposition coupling mechanism, inherent thermal physical indexes of the material, laser optical hardware parameters and three types of core process parameters, i.e., laser power, scanning speed and path spacing, are quantitatively constrained and associated. Without carrying out a large number of pre-experiments, a stable and effective process window can be drawn before metal component forming, the process development cycle under the scene of new materials and different printing layer thicknesses is greatly shortened, and the generation probability of metallurgical defects such as un-melting, over-melting, spoon hole and splashing is reduced.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing technology, and more specifically to a laser selective melting additive manufacturing parameter matching and forming method based on molten pool energy coupling. Background Technology

[0002] Selective laser melting (SLM) is a typical metal additive manufacturing technology that uses a laser beam to melt metal powder layer by layer along a preset scanning path, and then stacks these layers to obtain metal parts. The main process parameters in SLM include laser power, scanning speed, interlayer spacing, layer thickness, scanning strategy, spot size, and preheating temperature. Among these, laser power, scanning speed, and interlayer spacing directly affect the heat input per unit time and unit volume, thus influencing the molten pool depth, molten pool width, interlayer metallurgical bonding, porosity defects, surface quality, and final mechanical properties.

[0003] Currently, the most common parameter design methods in the development of laser selective melting processes mainly include the following categories:

[0004] The first type is the empirical parameter transfer method. This involves directly transferring mature parameters from existing materials, equipment, or similar parts to new materials, layer thicknesses, or parts, and then adjusting them through a small number of experiments. This method is simple to operate, but it is highly dependent on engineering experience. When the thermal properties of the material, powder state, equipment spot size, absorptivity, or layer thickness change, the original parameters are often difficult to apply directly.

[0005] The second type is the volume energy density method. This method typically uses the volume energy density formula: E = P / vht (where P is the laser power, v is the scanning speed, h is the channel spacing, and t is the layer thickness). It combines power, speed, channel spacing, and layer thickness into a single energy density index, used only for a rough assessment of the overall energy input level. This index only reflects the average total energy received per unit volume of powder and cannot reflect the transient thermal behavior during laser treatment. Even if two sets of process parameters yield the same volume energy density, the corresponding molten pool evolution behavior will differ significantly. For example, when the volume energy densities of two sets of parameters are equal, the molten pool stability, spatter tendency, keyhole formation risk, molten pool cooling rate, and molten pool aspect ratio differ significantly between high-power, high-speed processes and low-power, low-speed processes. Relying solely on the volume energy density index cannot accurately predict various metallurgical defects during the forming process, such as incomplete fusion, over-melting, spheroidization, spatter, and keyholes. Therefore, this method only has the advantages of convenient calculation and comparison. It is essentially an empirical evaluation method and cannot quantitatively characterize the actual depth of the molten pool, the width of the molten pool, the internal thermal diffusion law of the powder, and the molten pool overlap coupling relationship between adjacent scanning channels.

[0006] The third category is the experimental screening method, such as single-pass experiments, single-layer experiments, orthogonal experiments, density experiments, and mechanical property verification experiments. This method gradually determines the appropriate combination of power, speed, and channel spacing through a large number of experiments, and can obtain a relatively reliable process window. However, the experimental cycle is long, the material consumption is large, and the testing cost is high. Especially when developing new materials, new layer thicknesses, or new equipment parameters, repeated trial and error are required.

[0007] Furthermore, the pass spacing in existing methods is usually selected based on experience, such as by giving a fixed overlap ratio according to the spot diameter or the width of the molten pool, but it does not fully consider whether the energy superposition in the middle area of ​​two adjacent scan passes is sufficient to achieve the melting conditions. When the pass spacing is too large, incomplete fusion defects are easily generated between adjacent molten passes; when the pass spacing is too small, it will cause excessive repeated melting, excessive heat input, reduced forming efficiency, and increased residual stress.

[0008] The aforementioned problems arise because laser selective melting is a complex transient process involving laser absorption, powder melting, heat conduction, molten pool flow, interlayer remelting, and rapid solidification. The material's melting point, density, specific heat, latent heat of fusion, thermal conductivity, laser absorptivity, spot radius, and layer thickness all influence the molten pool formation process. Without a thermodynamic and kinetic-based computational model, it is difficult to accurately determine during the parameter design phase how much energy is needed for melting, whether heat can be transferred to the target depth within the laser's action time, and whether adjacent scanning channels can achieve sufficient overlap.

[0009] In summary, existing laser selective melting parameter design methods mainly rely on empirical transfer, volume energy density estimation, and experimental trial and error. They lack a parameter calculation method based on material thermodynamic melting conditions, target melting depth, thermal diffusion process, and the energy superposition relationship between adjacent melting channels. This results in long development cycles, high experimental costs, poor parameter transferability, and difficulty in effectively avoiding defects such as incomplete fusion, over-melting, spatter, and keyholes before experiments. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of existing laser selective melting process parameters that rely on trial and error and the inability of the volume energy density method to characterize the evolution of the molten pool. It provides a laser selective melting additive manufacturing parameter matching and forming method based on molten pool energy coupling. Based on the material melting thermodynamics, molten pool thermal diffusion kinetics, and adjacent channel energy superposition mechanism, it establishes a quantitative constraint relationship between parameters such as material melting point, metal material density, solid-phase heat capacity, latent heat of melting, preset single-layer printing thickness, laser spot radius, and laser absorptivity and laser power, scanning speed, and channel spacing. This enables rapid locking of the effective process window before forming and shortens the process development cycle for new materials and new layer thicknesses.

[0011] According to a first aspect of the present invention, a laser selective melting additive manufacturing parameter matching method based on molten pool energy coupling is provided. During the implementation process, a complete set of basic input parameters are first collected. The parameter categories are divided into three types: thermal property parameters corresponding to the metal material to be formed, optical parameters of the laser forming equipment, and the pre-set single-layer printing thickness.

[0012] For the melting process of metal powder, based on the thermodynamic law of the material being heated from the preheating temperature of the substrate at room temperature to the melting critical point and completing the solid-liquid phase transition, the minimum energy threshold required for the complete melting of a unit volume of powder is derived, namely the enthalpy of melting. This enthalpy of melting is the underlying benchmark for all subsequent process parameters, and is uniquely determined by the inherent properties of the metal material such as density, solid-phase heat capacity, melting point, and latent heat of melting.

[0013] To eliminate interlayer non-fusion defects, a remelting coefficient is introduced based on the preset single-layer printing thickness to calculate the target melting depth, so that the actual melting depth is greater than the single-layer thickness of the powder, ensuring that a stable metallurgical bond is formed between adjacent printing layers.

[0014] Based on the actual spot type of the laser equipment, a corresponding energy analysis model is selected to describe the transverse energy distribution of the laser. On this basis, a comprehensive heat loss correction coefficient is introduced to uniformly compensate for various energy losses caused by heat conduction, powder porosity, laser reflection, and multiple repeated remelting. A centerline melting criterion is constructed to limit the matching boundary between laser power and scanning speed, avoiding incomplete fusion due to insufficient energy or overmelting and spattering caused by excessive energy.

[0015] The centerline position of adjacent scanning channels is selected as the energy verification area. The total input energy of the two beams in the verification area is superimposed to construct the inter-channel melt pool superposition melting criterion that satisfies the complete fusion between channels. The maximum allowable value of the channel spacing is obtained to avoid the inter-channel porosity caused by excessive channel spacing, while preventing the severe heat accumulation and reduced forming efficiency caused by excessively small channel spacing.

[0016] As an optional implementation, the thermal properties of the metallic material include material density ρ and solid-phase heat capacity C. p,s Material melting point T m Latent heat of fusion L m The initial preheating temperature of the substrate is T0; the inherent parameters of the laser equipment include the laser spot radius and the laser absorptivity η.

[0017] As an optional implementation, the relationship of the enthalpy of melting of material per unit volume is shown in equation (1):

[0018] (1)

[0019] In the formula, H m ρ is the enthalpy of fusion of the material per unit volume; C is the density of the metallic material; p,s The solid phase heat capacity; Tm T0 is the melting point of the material; T0 is the initial preheating temperature of the substrate; L m This is the latent heat of fusion.

[0020] As an optional implementation, the target melt depth satisfies the relationship (2):

[0021] (2)

[0022] In the formula, D is the target melting depth; λ is the remelting coefficient, with a value range of 1.6 to 2.2; and t is the preset single-layer printing thickness.

[0023] As an optional implementation, the laser spot includes a Gaussian distributed spot, a flat-top distributed spot, or an annular spot, and a centerline energy distribution and adjacent melt channel superimposed energy model are constructed using the corresponding spot energy analysis model.

[0024] As an optional implementation method, the energy input level at the scanning center is first characterized by the energy distribution of the centerline, and then the constraint formula for the matching relationship between the laser power and the scanning speed is obtained by combining the centerline melting criterion formula.

[0025] Wherein, when the laser spot is a Gaussian distribution spot, the centerline energy distribution is as shown in equation (3-1); when the laser spot is a flat-top distribution spot, the centerline energy distribution is as shown in equation (3-2); when the laser spot is an annular spot, the centerline energy distribution is as shown in equation (3-3).

[0026]

[0027] In the formula, F0 is the energy absorbed per unit area at the laser centerline; P is the laser power; v is the scanning speed; r is the Gaussian spot radius; r f r is the radius of the flat-top light spot. o r is the outer radius of the annular light spot; i η is the inner radius of the annular laser spot; η is the laser absorptivity.

[0028] The centerline melting criterion is shown in equation (4):

[0029] (4)

[0030] In the formula, F0 is the energy absorbed per unit area at the laser centerline; χ is the heat loss correction coefficient; D is the target melting depth; and Hm is the enthalpy of fusion per unit volume.

[0031] When the laser spot is a Gaussian distribution, the constraint formula for the matching relationship between laser power and scanning speed is shown in equation (5-1); when the laser spot is a flat-top distribution, the constraint formula for the matching relationship between laser power and scanning speed is shown in equation (5-2); when the laser spot is an annular spot, the constraint formula for the matching relationship between laser power and scanning speed is shown in equation (5-3).

[0032]

[0033] In the formula, P is the laser power; v is the scanning speed; r is the Gaussian spot radius; r f r is the radius of the flat-top light spot. o r is the outer radius of the annular light spot; i η is the inner radius of the annular laser spot; χ is the laser absorptivity; D is the heat loss correction factor; H is the target melting depth. m It is the enthalpy of fusion per unit volume.

[0034] As an optional implementation method, the total input energy of the two lasers in the verification area is calculated by superimposing the energy of adjacent melting channels, and then combined with the inter-channel fusion criterion formula to derive the upper limit constraint formula for channel spacing.

[0035] When the laser spot is a Gaussian distribution spot, the superimposed energy formula of the adjacent melting channels is as shown in formula (6-1); when the laser spot is a flat-top distribution spot, the superimposed energy formula of the adjacent melting channels is as shown in formula (6-2); when the laser spot is an annular spot, the superimposed energy formula of the adjacent melting channels is as shown in formula (6-3).

[0036]

[0037] In the formula, F total The total input energy of the interaction between two adjacent melting channels; η is the laser absorptivity; P is the laser power; v is the scanning speed; r is the Gaussian spot radius; r f r is the radius of the flat-top light spot. o r is the outer radius of the annular light spot; i h is the inner radius of the annular light spot; h is the channel spacing.

[0038] The inter-channel fusion criterion is shown in equation (7):

[0039] (7)

[0040] In the formula, F total χ is the total input energy of the interaction between two adjacent melting channels; D is the heat loss correction factor; h H represents the minimum melting depth in the inter-channel region. m Enthalpy of fusion per unit volume;

[0041] When the laser spot is a Gaussian distribution, the upper limit constraint of the channel spacing is as shown in equation (8-1); when the laser spot is a flat-top distribution, the upper limit constraint of the channel spacing is as shown in equation (8-2); when the laser spot is an annular spot, the upper limit constraint of the channel spacing is as shown in equation (8-3).

[0042]

[0043] In the formula, h is the channel spacing; r is the Gaussian spot radius; r f r is the radius of the flat-top light spot. o r is the outer radius of the annular light spot; i η is the inner radius of the annular spot; P is the laser absorptivity; v is the laser power; χ is the scanning speed; D is the heat loss correction factor. h H represents the minimum melting depth in the inter-channel region. m It is the enthalpy of fusion per unit volume.

[0044] As an optional implementation, the heat loss correction coefficient χ is taken as 1.0~3.5 to uniformly compensate for heat conduction loss, powder porosity loss, laser reflection loss and energy loss caused by repeated remelting of multiple layers.

[0045] As an optional implementation, the minimum melting depth D in the interpass region h The value ranges from 1.0t to 1.5t, where t is the preset single-layer printing thickness, ensuring that there are no unfused defects between adjacent scanning tracks.

[0046] According to a second aspect of the present invention, a metal additive manufacturing method is provided, wherein the laser selective melting process parameters are determined by using the aforementioned laser selective melting additive manufacturing parameter matching method based on molten pool energy coupling, and powder spreading, laser scanning melting, and layer-by-layer stacking forming processes are performed based on the determined laser selective melting process parameters to prepare the required metal component. The final metal component has no obvious metallurgical defects and stable mechanical properties.

[0047] As can be seen from the above technical solutions of the present invention, the laser selective melting additive manufacturing parameter matching method based on molten pool energy coupling proposed in this invention has the following significant advantages compared with the existing laser selective melting process parameter development mode that relies on experience transfer, single-body energy density estimation, and a large number of trial and error experiments:

[0048] (1) The present invention can directly obtain the process parameter range with actual formability by calculation before formal forming, without the need to carry out single-pass, single-layer, orthogonal multi-group trial and error experiments. Only the thermal properties of the material and the optical parameters of the equipment are input to obtain the effective process range of laser power, scanning speed and track spacing before printing. This transforms the traditional development method of extensive experimentation and parameter screening into a development method of determining candidate ranges through physical models and then conducting a small number of verifications, thereby reducing invalid test combinations and corresponding powder, substrate and testing consumption.

[0049] (2) The process parameters obtained by the method of the present invention are not limited to a single process point, but can form a stable and formable process window with a certain width. Moreover, after testing and verification, multiple sets of parameter combinations have obtained samples with good fusion state, indicating that the present invention does not obtain a single parameter point that is accidentally effective, but a parameter matching range that can be used for actual process selection.

[0050] (3) The parameters determined by the method of the present invention can not only realize the forming of the sample, but also obtain stable actual mechanical properties. According to the mechanical property test of the formed sample, each sample can maintain a high and relatively stable strength level. Therefore, the parameters obtained by the method of the present invention can be further implemented from the theoretical melting conditions to the forming quality and mechanical properties of the actual component, rather than just staying at the energy input value level.

[0051] (4) The method of the present invention can be adapted to a variety of commonly used metal powders such as titanium alloy, stainless steel, and high temperature alloy, and can be adapted to multiple types of laser spots. Under different laser spots and different layer thickness conditions, only the basic input parameters or corresponding formulas need to be replaced to quickly generate a set of process parameters. The generated process parameters can be used to print the parts, and the performance of the formed parts meets the requirements. Compared with the empirical parameter migration method, the adaptability across materials, layer thicknesses and equipment is significantly improved.

[0052] (5) The present invention uses whether the middle area of ​​adjacent scanning channels can reach the specified melting depth as the basis for channel spacing design, so that channel spacing is quantitatively related to material melting enthalpy, laser power, scanning speed, spot size and laser absorption rate. In actual embodiments, after adopting the corresponding engineering channel spacing, no obvious metallurgical defects such as incomplete fusion or keyholes were observed in the metallographic cross-section of each group of samples. Therefore, compared with the method of setting a fixed overlap rate only according to the spot diameter, the present invention can determine the channel spacing based on the actual energy requirements of adjacent melting channels, and transform the channel spacing from empirical overlap ratio to quantitative design based on the energy coupling of adjacent melting channels, providing calculable parameter basis for balancing fusion quality and scanning efficiency. Attached Figure Description

[0053] Figure 1 This is a flowchart of the laser selective melting additive manufacturing parameter matching method based on molten pool energy coupling of the present invention.

[0054] Figure 2 This is a diagram showing the positional relationship of the laser traveling to point O in an example of the present invention.

[0055] Figure 3 This is a diagram showing the positional relationship between the verification areas formed by two adjacent lasers in an example of this invention.

[0056] Figure 4 This is a metallographic image of the sample in Example 1 of this invention.

[0057] Figure 5 This is a metallographic image of the sample in Example 2 of the present invention.

[0058] Figure 6 This is a metallographic image of the sample in Example 3 of the present invention.

[0059] Figure 7 This is a metallographic image of the sample in Example 4 of this invention.

[0060] Figure 8 This is a metallographic image of the sample in Example 5 of the present invention. Detailed Implementation

[0061] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0062] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, in which numerous illustrative embodiments are shown. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described below in more detail, can be implemented in any of a number of ways.

[0063] Combination Figure 1 As shown, in one embodiment of the present invention, a laser selective melting additive manufacturing parameter matching method based on molten pool energy coupling is provided, including: obtaining basic input parameters, determining the enthalpy of melting of material per unit volume Hm, determining the target melting depth D, determining the constraint formula for the matching relationship between laser power P and scanning speed v, and determining the maximum allowable value of the channel spacing h.

[0064] Get basic input parameters

[0065] During the implementation process, a complete set of basic input parameters are first collected. The parameter categories are divided into three types: the thermal properties of the metal material to be formed, the optical parameters of the laser forming equipment, and the pre-set single-layer printing thickness.

[0066] Among them, the thermophysical parameters of metallic materials include the density ρ of the metallic material and the solid-phase heat capacity C. p,s Material melting point T m Latent heat of fusion Lm The initial preheating temperature of the substrate is T0; the inherent parameters of the laser equipment include the laser spot radius and the laser absorptivity η.

[0067] Understandably, the laser spot radius corresponds to the actual spot type of the laser device; for example, r is the Gaussian spot radius, r f r is the radius of the flat-top light spot. o r is the outer radius of the annular light spot. i denoted as the inner radius of the annular light spot.

[0068] Determine the enthalpy of fusion H of a unit volume of material m

[0069] For the melting process of metal powder, based on the thermodynamic law of the material being heated from the preheating temperature of the substrate at room temperature to the melting critical point and completing the solid-liquid phase transition, the minimum energy threshold required for the complete melting of a unit volume of powder is derived, namely the melting enthalpy. This melting enthalpy is the underlying benchmark for all subsequent process parameters, and is uniquely determined by the inherent properties of the metal material such as density, solid-phase heat capacity, melting point, and latent heat of fusion.

[0070] In some examples, the relationship of the enthalpy of fusion of a unit volume of material is shown in equation (1):

[0071] (1)

[0072] In the formula, H m ρ is the enthalpy of fusion of the material per unit volume; C is the density of the metallic material; p,s The solid phase heat capacity; T m T0 is the melting point of the material; T0 is the initial preheating temperature of the substrate; L m This is the latent heat of fusion.

[0073] Determine the target melting depth D

[0074] To eliminate interlayer non-fusion defects, a remelting coefficient is introduced based on the single-layer printing thickness to calculate the target melting depth, so that the actual melting depth is greater than the single-layer thickness of the powder, ensuring that a stable metallurgical bond is formed between adjacent printing layers.

[0075] In some examples, the target melt depth satisfies relation (2):

[0076] (2)

[0077] In the formula, D is the target melting depth; λ is the remelting coefficient, with a value range of 1.6 to 2.2; and t is the preset single-layer printing thickness.

[0078] Constraints for determining the matching relationship between laser power P and scanning speed v

[0079] Based on the actual spot type of the laser equipment, the corresponding energy analysis model is selected to describe the lateral energy distribution of the laser. On this basis, a comprehensive heat loss correction coefficient is introduced to uniformly compensate for various energy losses caused by heat conduction, powder porosity, laser reflection, and multi-layer repeated remelting. A centerline melting criterion is constructed to limit the matching boundary between laser power and scanning speed, and avoid problems such as incomplete fusion caused by insufficient energy or overmelting and spatter caused by excessive energy.

[0080] Specifically, the energy input level at the scanning center is first characterized by the energy distribution of the centerline, and then the constraint formula for the matching relationship between the laser power and the scanning speed is obtained by combining the centerline melting criterion.

[0081] Among them, the energy distribution along the center line is related to the type of laser spot, which includes Gaussian distribution spots, flat-top distribution spots, or annular spots.

[0082] (1) When the laser spot is a Gaussian distributed spot

[0083] Combination Figure 2 As shown, the radius of the Gaussian spot is r, the scanning speed is v, and the absorptivity is η. With the center of the spot as the origin O, the energy absorbed per unit area of ​​the Gaussian spot at a certain longitudinal position (point A) is as shown in equation (9-1):

[0084] (9-1)

[0085] Among them, F y The energy absorbed at point A in the longitudinal direction, where P is the laser power, v is the scanning speed, and r is the spot radius. Let y be the absorption rate, and y be the longitudinal distance from point A to the scanning center O.

[0086] When the distance from the centerline is y=0, taking y=0 yields equation (3-1):

[0087] (3-1)

[0088] In the formula, F0 is the energy absorbed per unit area at the laser centerline; P is the laser power; v is the scanning speed; r is the Gaussian spot radius; and η is the laser absorptivity.

[0089] When the melting depth at the centerline needs to reach a position of depth D, the required energy is as shown in equation (4):

[0090] (4)

[0091] In the formula, F0 is the energy absorbed per unit area at the laser centerline; χ is the heat loss correction coefficient; D is the target melting depth; H m It is the enthalpy of fusion per unit volume.

[0092] Combining equations (3-1) and (4) yields After simplification, we obtain the constraint equation (5-1) for the matching relationship between laser power and scanning speed:

[0093] (5-1)

[0094] In the formula, P is the laser power; v is the scanning speed; r is the Gaussian spot radius; η is the laser absorptivity; χ is the heat loss correction coefficient; D is the target melting depth; H m It is the enthalpy of fusion per unit volume.

[0095] (2) When the laser spot is a flat-topped distribution spot

[0096] In the radius r of the flat-top light spot f Inside the light spot, the energy density is uniformly distributed, while outside the spot, the energy is 0. The energy density can be expressed as shown in formula (10):

[0097] (10)

[0098] Where, q f It is the energy density of the flat-top light spot. r is the laser absorption rate. f Where is the radius of the flat-top laser spot, and P is the laser power.

[0099] Combination Figure 2 As shown, the energy absorbed per unit area of ​​the flat-topped light spot at point A is as shown in equation (9-2):

[0100] (9-2)

[0101] in, ,when At that time, F y =0.

[0102] At the position where y=0 on the center line, the center line energy distribution corresponding to the flat-topped light spot is obtained (3-2):

[0103] (3-2)

[0104] Combining equations (3-2) and (4), we obtain the constraint equation (5-2) for the matching relationship between laser power and scanning speed:

[0105] (5-2)

[0106] In the formula, P is the laser power; v is the scanning speed; r f η is the radius of the flat-top laser spot; χ is the laser absorptivity; D is the heat loss correction factor; H is the target melting depth. mIt is the enthalpy of fusion per unit volume.

[0107] (3) When the laser spot is a ring-shaped distribution spot

[0108] The thermal energy distribution of the annular light spot is within the radius r of the annular light spot. i and the outer radius r of the annular light spot o Between these regions, the energy in the central and outer areas is lower and can be approximated as 0. The energy at different positions of the ring light is approximated as shown in equation (11):

[0109] (11)

[0110] Where, r o r is the outer radius of the annular light spot. i denoted as the inner radius of the annular light spot.

[0111] Combination Figure 2 As shown, the energy absorbed per unit area by the annular light spot at point A is a piecewise function. When At point A, the energy is as shown in equation (9-3):

[0112] (9-3)

[0113] when At that time, the energy at point A is as shown in equation (9-4):

[0114] (9-4)

[0115] when At that time, F y =0.

[0116] To ensure production efficiency, equation (9-4) is selected. Therefore, when the centerline y=0, the energy at the centerline is as shown in equation (3-3):

[0117] (3-3)

[0118] Combining equations (3-3) and (4), we obtain the constraint equation (5-3) for the matching relationship between laser power and scanning speed:

[0119] (5-3)

[0120] In the formula, P is the laser power; v is the scanning speed; r o r is the outer radius of the annular light spot. i η is the inner radius of the annular laser spot; χ is the laser absorptivity; D is the heat loss correction factor; H is the target melting depth. m It is the enthalpy of fusion per unit volume.

[0121] Meanwhile, the effective action time of the laser acting on a certain position of the powder is calculated by formula (12):

[0122] (12)

[0123] Where β represents the effective action coefficient (whether the laser beam landing point on the powder bed is a perfect circle; if it is, then β=2; otherwise, β<2), and r' is the corresponding laser spot radius. That is, when the laser spot is a Gaussian distribution, r' is r; when the laser spot is a flat-top distribution, r' is r. f When the laser spot is a ring-shaped distribution, r' is 2(r o -r i ) / v.

[0124] The depth of thermal diffusion penetration in the molten pool is given by equation (13):

[0125] (13)

[0126] Where α is the thermal diffusivity, which is related to the material itself, and γ is the thermal penetration coefficient, with a common value range of 1-3.

[0127] In order to obtain the target melting depth D, it is required that ,therefore, The upper limit of the scanning speed is obtained by rearranging the equations, as shown in equation (14):

[0128] (14)

[0129] Taking an ideal case where the laser quality is ideal, we take α=2 and β=2. Then the upper limit of the scanning speed can be expressed as equation (15):

[0130] (15)

[0131] Equation (15) proves that the constraint equations (5-1), (5-2) and (5-3) for the matching relationship between laser power and scanning speed are valid.

[0132] Understandably, after obtaining the matching relationship between laser power and scanning speed, one of the parameters can be determined first, such as the scanning speed. The scanning speed can be selected from the commonly used scanning speed for laser selective melting. Then, the corresponding laser power can be obtained according to equations (5-1), (5-2) and (5-3).

[0133] In one example, the scanning speed based on the optimal size of the device should be controlled between 600 mm / s and 2000 mm / s. Therefore, one or more scanning speeds can be determined within the above range. Then, the corresponding laser power can be determined according to the matching relationship between laser power and scanning speed, resulting in multiple combinations of scanning speed and laser power. One of the combination parameters can be selected as needed.

[0134] Determine the maximum allowable value of track spacing h.

[0135] The centerline position of adjacent scanning channels is selected as the energy verification area. The total input energy of the two beams in the verification area is superimposed to construct the inter-channel melt pool superposition melting criterion that satisfies the complete fusion between channels. The maximum allowable value of the channel spacing is obtained to avoid the inter-channel porosity caused by excessive channel spacing, while preventing the severe heat accumulation and reduced forming efficiency caused by excessively small channel spacing.

[0136] Specifically, the total input energy of the two lasers in the verification area is calculated by superimposing the energy of adjacent melting channels, and then combined with the inter-channel fusion criterion to derive the upper limit constraint formula for channel spacing.

[0137] Among them, the superposition of energy between adjacent melting channels is related to the type of laser spot, including Gaussian distribution spot, flat-top distribution spot or ring spot.

[0138] (1) When the laser spot is a Gaussian distributed spot

[0139] Combination Figure 3 As shown, the pass spacing h is essentially the thermodynamic superposition of the molten pool between two adjacent passes. The midpoint of two adjacent vectors is h / 2 from the centerline of each vector. The energy left at that position after the Gaussian spot scans the powder is... As shown in equation (16):

[0140] (16)

[0141] Energy of the interaction between the two melting channels As shown in equation (6-1):

[0142] (6-1)

[0143] In the formula, F total η is the total input energy of the interaction between two adjacent melting channels; P is the laser absorptivity; v is the scanning speed; r is the Gaussian spot radius; h is the channel spacing.

[0144] To avoid non-merging between stages, it is necessary to:

[0145] (7)

[0146] In the formula, F total χ is the total input energy of the interaction between two adjacent melting channels; D is the heat loss correction factor; h H represents the minimum melting depth in the inter-channel region. m It is the enthalpy of fusion per unit volume.

[0147] Substituting equation (6-1) into equation (7) and rearranging, we obtain equation (8-1) for the upper limit constraint of track spacing:

[0148] (8-1)

[0149] In the formula, h is the channel spacing; r is the Gaussian spot radius; η is the laser absorptivity; P is the laser power; v is the scanning speed; χ is the heat loss correction coefficient; D h H represents the minimum melting depth in the inter-channel region. m It is the enthalpy of fusion per unit volume.

[0150] (2) When the laser spot is a flat-topped distribution spot

[0151] Energy of the interaction between the two melting channels As shown in equation (6-2):

[0152] (6-2)

[0153] In the formula, F total The total input energy is the energy of the interaction between two adjacent melting channels; η is the laser absorptivity; P is the laser power; v is the scanning speed; r f is the radius of the flat-top light spot; h is the channel spacing.

[0154] Substituting equation (6-2) into equation (7) and rearranging, we obtain equation (8-2) for the upper limit constraint of track spacing.

[0155] (8-2)

[0156] In the formula, h is the track spacing; r f η is the radius of the flat-top laser spot; η is the laser absorptivity; P is the laser power; v is the scanning speed; χ is the heat loss correction factor; D h H represents the minimum melting depth in the inter-channel region. m It is the enthalpy of fusion per unit volume.

[0157] (3) When the laser spot is a ring-shaped distribution spot

[0158] To ensure production efficiency, equation (9-4) is selected. Therefore, the energy of the interaction between the two melting channels... As shown in equation (6-3):

[0159] (6-3)

[0160] In the formula, F total The total input energy is the energy of the interaction between two adjacent melting channels; η is the laser absorptivity; P is the laser power; v is the scanning speed; r o r is the outer radius of the annular light spot; i is the inner radius of the annular light spot; h is the channel spacing.

[0161] Substituting equation (6-3) into equation (7) and rearranging, we obtain equation (8-3) for the upper limit constraint of track spacing.

[0162] (8-3)

[0163] In the formula, h is the track spacing; r o r is the outer radius of the annular light spot; i η is the inner radius of the annular spot; P is the laser absorptivity; v is the laser power; χ is the scanning speed; D is the heat loss correction factor. h H represents the minimum melting depth in the inter-channel region. m It is the enthalpy of fusion per unit volume.

[0164] In some examples, the heat loss correction factor χ is set to 1.0 to 3.5 to uniformly compensate for heat conduction loss, powder porosity loss, laser reflection loss, and energy loss caused by repeated remelting of multiple layers.

[0165] In some examples, the minimum melting depth D in the inter-channel region h The value ranges from 1.0t to 1.5t, where t is the preset single-layer printing thickness, ensuring that there are no unfused defects between adjacent scanning tracks.

[0166] Finally, based on the type of laser used, the three core process parameters of laser power, scanning speed and channel spacing can be determined by combining equations (1), (2), (5-1) and (8-1), or equations (1), (2), (5-2) and (8-2), or equations (1), (2), (5-3) and (8-3) on the basis of the basic input parameters.

[0167] It is understood that the method of the present invention can also be adapted to other laser spot types. It is only necessary to construct the corresponding centerline energy distribution and adjacent melt channel superposition energy formula using the corresponding spot energy analysis model, and then obtain the required parameters according to the above method.

[0168] In another embodiment of the present invention, a metal additive manufacturing method is also provided. The laser selective melting (SDM) process parameters are determined using the aforementioned laser selective melting parameter matching method based on molten pool energy coupling. Based on the determined SDM process parameters, powder spreading, laser scanning melting, and layer-by-layer stacking are directly executed to prepare the desired metal component. The metal component prepared by this method effectively avoids various metallurgical defects such as incomplete fusion, over-melting, spatter, and keyholes. The component has high overall density and small fluctuations in mechanical properties. At the same time, it overcomes the pain points of traditional process development models, such as lengthy development cycles for new materials / layer thicknesses, high costs of experimental materials, and poor adaptability of process parameters across operating conditions.

[0169] To facilitate better understanding, the present invention will be further illustrated below with several specific examples, but the preparation process is not limited to these examples, and the content of the present invention is not limited to these examples.

[0170] Unless otherwise specified, the following embodiments are all conventional methods.

[0171] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0172] Example 1

[0173] Print TC4 components using a Gaussian distribution light spot. The basic input parameters are shown in Table 1.

[0174] Table 1

[0175] parameter Value Material TC4 / Ti-6Al-4V Preset single-layer printing thickness t 0.04 mm <![CDATA[Material melting point T m > 1660 ℃ <![CDATA[Initial preheating temperature T0 of the substrate]]> 25 ℃ Density ρ of metallic materials <![CDATA[4.43 g / cm 3 = 0.00443 g / mm 3 ]]> <![CDATA[Solid phase specific heat capacity C p,s > 0.56 J / g·K thermal conductivity k 7.1 W / m·K <![CDATA[Latent heat of fusion L m > 365 J / g Laser absorption rate η 0.27 Gaussian spot radius r 0.05 mm remelting coefficient λ 2.0 Heat loss correction factor χ 2.5

[0176] (1) The amount of H required for a unit volume of material to melt from room temperature and then heated to its melting point. m for:

[0177]

[0178] That is, theoretically, 1 mm can be melted 3 TC4 requires 5.67 J / mm 3 Energy.

[0179] (2) With a layer thickness of t=0.04 mm, during the LPBF process, it is not possible to melt only the current powder layer; the previous layer must also be melted. Otherwise, the interlayer bonding will be insufficient. Taking the remelting coefficient as λ=2.0, the target melting depth D is:

[0180] D = λt = 2.0 × 0.04 = 0.08 mm

[0181] (3) According to equation (5-1), substituting the above parameters, we get P / v≥0.263 W / mm·s -1 Let P = 0.263v.

[0182] Based on P=0.263v, the power-speed table can be obtained, as shown in Table 2:

[0183] Table 2

[0184] serial number Scan speed v Corresponding power P 1-1 600 mm / s 158 W 1-2 700 mm / s 184 W 1-3 800 mm / s 210 W 1-4 900 mm / s 237 W 1-5 1000 mm / s 263 W 1-6 1100 mm / s 289 W

[0185] (4) Assuming that the melting in the middle region of the channel spacing needs to reach D h =1.2t=1.2×0.04=0.048 mm. According to formula (8-1) and P=0.263v, we get h≤0.0776 mm. The engineering value of h is 0.075-0.08 mm.

[0186] With h = 0.08 mm, and scanning speed and power as shown in Table 2, six parameter combinations were obtained. Cubes measuring 10 mm × 10 mm × 10 mm were then prepared for observation. Figure 4 As shown, no obvious metallurgical defects were found in any of the samples obtained under the 6 sets of combined data (samples 1-1 to 1-6 correspond to numbers 1-1 to 1-6 in Table 2 respectively).

[0187] Mechanical properties were tested on 6 groups of samples, and the results are shown in Table 3.

[0188] Table 3

[0189] serial number Yield strength MPa Tensile strength (MPa) Elongation after fracture % Sample 1-1 1108 1336 9 Sample 1-2 1093 1281 11 Samples 1-3 1112 1294 10 Samples 1-4 1151 1347 13 Samples 1-5 1163 1352 13 Samples 1-6 1181 1328 12

[0190] Mechanical performance tests show that the yield strength is stable at around 1100 MPa, the tensile strength is around 1300 MPa, and the elongation is around 10%, which is significantly higher than the mechanical performance of traditional processing methods and can meet the requirements of normal parts use.

[0191] Example 2

[0192] Print the CX component using a Gaussian distribution light spot. The basic input parameters are shown in Table 4.

[0193] Table 4

[0194] parameter Value Material CX Preset single-layer printing thickness t 0.03 mm <![CDATA[Material melting point T m > 1450 ℃ <![CDATA[Initial preheating temperature T0 of the substrate]]> 25 ℃ Density ρ of metallic materials <![CDATA[7.69 g / cm 3 = 0.00769 g / mm 3 ]]> <![CDATA[Solid phase specific heat capacity C p,s > 0.47 J / g·K <![CDATA[Latent heat of fusion L m > 280 J / g Laser absorption rate η 0.35 Gaussian spot radius r 0.04 mm remelting coefficient λ 2.0 Heat loss correction factor χ 2.5

[0195] (1) The amount of H required for a unit volume of material to melt from room temperature and then heated to its melting point. m for:

[0196]

[0197] That is, theoretically, 1 mm can be melted 3 CX requires 7.3 J / mm 3 Energy.

[0198] (2) With a layer thickness of t=0.03 mm, during the LPBF process, it is not possible to melt only the current powder layer; the previous layer must also be melted. Otherwise, the interlayer bonding will be insufficient. Taking the remelting coefficient as λ=2.0, the target melting depth D is:

[0199] D = λt = 2.0 × 0.03 = 0.06 mm

[0200] (3) According to equation (5-1), substituting the above parameters, we get P / v≥0.157 W / mm·s -1 Let P = 0.157v.

[0201] Based on P=0.157v, the power-speed table can be obtained, as shown in Table 5:

[0202] Table 5

[0203] serial number Scan speed v Corresponding power P 2-1 800 mm / s 126 W 2-2 1000 mm / s 157 W 2-3 1200 mm / s 188 W 2-4 1400 mm / s 220 W 2-5 1600 mm / s 251 W 2-6 1700 mm / s 267 W

[0204] (4) Assuming that the melting in the middle region of the channel spacing needs to reach D h =1.2t=1.2×0.03=0.036 mm. According to formula (8-1) and P=0.157v, we get h≤0.0621 mm. The engineering value of h is 0.06-0.065 mm.

[0205] With h = 0.065 mm, and scanning speed and power as shown in Table 5, six parameter combinations were obtained. Cubes measuring 10 mm × 10 mm × 10 mm were then prepared for observation. Figure 5 As shown, no obvious metallurgical defects were found in any of the samples obtained under the 6 sets of combined data (samples 2-1 to 2-6 correspond to numbers 2-1 to 2-6 in Table 5, respectively).

[0206] Mechanical properties were tested on 6 groups of samples, and the results are shown in Table 6.

[0207] Table 6

[0208] serial number Yield strength MPa Tensile strength (MPa) Elongation after fracture % Sample 2-1 1579 1655 9 Sample 2-2 1481 1556 8 Sample 2-3 1470 1703 12 Samples 2-4 1503 1583 6 Samples 2-5 1530 1677 14 Samples 2-6 1543 1616 8

[0209] Mechanical performance tests show that the yield strength is stable at around 1500 MPa, the tensile strength is above 1550 MPa, and the elongation is around 10%, which is significantly higher than the mechanical performance of traditional processing methods and can meet the requirements of normal parts use.

[0210] Example 3

[0211] Print 316L components using a Gaussian distribution light spot. The basic input parameters are shown in Table 7.

[0212] Table 7

[0213] parameter Value Material 316L stainless steel Preset single-layer printing thickness t 0.03 mm <![CDATA[Material melting point T m > 1400 ℃ <![CDATA[Initial preheating temperature T0 of substrate]]> 25 ℃ Density ρ of metallic materials <![CDATA[7.95 g / cm 3 = 0.00795 g / mm 3 ]]> <![CDATA[Solid phase specific heat capacity C p,s > 0.50 J / g·K thermal conductivity k 16 W / m·K <![CDATA[Latent heat of fusion L m > 270 J / g Laser absorption rate η 0.35 Gaussian spot radius r 0.04 mm remelting coefficient λ 2.0 Heat loss correction factor χ 2.5

[0214] (1) The amount of H required for a unit volume of material to melt from room temperature and then heated to its melting point. m for:

[0215]

[0216] That is, theoretically, 1 mm can be melted 3 316L requires 7.61 J / mm 3 Energy.

[0217] (2) With a layer thickness of t=0.03 mm, during the LPBF process, it is not possible to melt only the current powder layer; the previous layer must also be melted. Otherwise, the interlayer bonding will be insufficient. Taking the remelting coefficient as λ=2.0, the target melting depth D is:

[0218] D = λt = 2.0 × 0.03 = 0.06 mm

[0219] (3) According to equation (5-1), substituting the above parameters, we get P / v≥0.164 W / mm·s -1 Let P = 0.164v.

[0220] Based on P=0.164v, the power-speed table can be obtained, as shown in Table 8:

[0221] Table 8

[0222] serial number Scan speed v Corresponding power P 3-1 800 mm / s 131 W 3-2 1000 mm / s 164 W 3-3 1200 mm / s 197 W 3-4 1400 mm / s 230 W 3-5 1600 mm / s 262 W 3-6 1800 mm / s 295 W

[0223] (4) Assuming that the melting in the middle region of the channel spacing needs to reach D h =1.2t=1.2×0.03=0.036 mm. According to formula (8-1) and P=0.164v, we get h≤0.062 mm. The engineering value of h is 0.06-0.065 mm.

[0224] With h = 0.065 mm, and scanning speed and power as shown in Table 8, six parameter combinations were obtained. Cubes measuring 10 mm × 10 mm × 10 mm were then prepared for observation. Figure 6 As shown, no obvious metallurgical defects were found in any of the samples obtained under the 6 sets of combined data (samples 3-1 to 3-6 correspond to numbers 3-1 to 3-6 in Table 8, respectively).

[0225] Mechanical properties were tested on 6 groups of samples, and the results are shown in Table 9.

[0226] Table 9

[0227] serial number Yield strength MPa Tensile strength (MPa) Elongation after fracture % Sample 3-1 482 530 41 Sample 3-2 498 541 44 Sample 3-3 513 562 52 Sample 3-4 509 559 49 Samples 3-5 532 573 57 Samples 3-6 508 560 51

[0228] Mechanical property tests show that the yield strength of each sample is stable at around 500 MPa, the tensile strength at around 560 MPa, and the elongation at around 50%, which is significantly better than the mechanical properties of traditional processing methods and can meet the requirements for normal parts use.

[0229] Example 4

[0230] Print TC4 components using a flat-top distributed light spot. The basic input parameters are shown in Table 10.

[0231] Table 10

[0232] parameter Value Material TC4 / Ti-6Al-4V Preset single-layer printing thickness t 0.05 mm <![CDATA[Material melting point T m > 1660 ℃ <![CDATA[Initial preheating temperature T0 of the substrate]]> 25 ℃ Density ρ of metallic materials <![CDATA[4.43 g / cm 3 = 0.00443 g / mm 3 ]]> <![CDATA[Solid specific heat capacity C p,s > 0.56 J / g·K thermal conductivity k 7.1 W / m·K <![CDATA[Latent heat of fusion L m > 365 J / g Laser absorption rate η 0.27 <![CDATA[Flat-top spot radius r f > 0.04 mm remelting coefficient λ 2.0 Heat loss correction factor χ 2.5

[0233] (1) The amount of H required for a unit volume of material to melt from room temperature and then heated to its melting point. m for:

[0234]

[0235] That is, theoretically, 1 mm can be melted 3 TC4 requires 5.67 J / mm 3 Energy.

[0236] (2) With a layer thickness of t=0.05 mm, during the LPBF process, it is not possible to melt only the current powder layer; the previous layer must also be melted. Otherwise, the interlayer bonding will be insufficient. Taking the remelting coefficient as λ=2.0, the target melting depth D is:

[0237] D = λt = 2.0 × 0.05 = 0.1 mm

[0238] (3) According to equation (5-2), substituting the above parameters, we get P / v≥0.330 W / mm·s -1 Let P = 0.330V.

[0239] Based on P=0.330v, the power-speed table can be obtained, as shown in Table 11:

[0240] Table 11

[0241] serial number Scan speed v Corresponding power P 4-1 700 mm / s 231 W 4-2 800 mm / s 264 W 4-3 900 mm / s 297 W 4-4 1000 mm / s 330 W 4-5 1100 mm / s 363 W

[0242] (4) Assuming that the melting in the middle region of the channel spacing needs to reach D h =1.2t=1.2×0.05=0.06 mm. According to equation (8-2) and P=0.330v, we get h≤0.076 mm, so we take h=0.07 mm.

[0243] With h = 0.07 mm, and scanning speed and power as shown in Table 11, five sets of parameter combinations were obtained. Cubes measuring 10 mm × 10 mm × 10 mm were then prepared for observation. Figure 7 As shown, no obvious metallurgical defects were found in any of the samples obtained under the 5 sets of combined data (samples 4-1 to 4-5 correspond to numbers 4-1 to 4-5 in Table 11, respectively).

[0244] Mechanical properties were tested on 5 groups of samples, and the results are shown in Table 12.

[0245] Table 12

[0246] serial number Yield strength MPa Tensile strength (MPa) Elongation after fracture % Sample 4-1 1052 1125 7 Sample 4-2 1075 1119 5 Sample 4-3 1045 1247 11 Sample 4-4 987 1108 10 Sample 4-5 991 1163 11

[0247] Mechanical performance tests show that the yield strength is stable at around 1000 MPa, the tensile strength is around 1100 MPa, and the elongation is around 10%, which is significantly higher than the mechanical performance of traditional processing methods and can meet the requirements of normal parts use.

[0248] Example 5

[0249] Print TC4 components using a ring-shaped light spot distribution. The basic input parameters are shown in Table 13.

[0250] Table 13

[0251] parameter Value Material TC4 / Ti-6Al-4V Preset single-layer printing thickness t 0.04 mm <![CDATA[Material melting point T m > 1660 ℃ <![CDATA[Initial preheating temperature T0 of the substrate]]> 25 ℃ Density ρ of metallic materials <![CDATA[4.43 g / cm 3 = 0.00443 g / mm 3 ]]> <![CDATA[Solid phase specific heat capacity C p,s > 0.56 J / g·K thermal conductivity k 7.1 W / m·K <![CDATA[Latent heat of fusion L m > 365 J / g Laser absorption rate η 0.27 <![CDATA[Outer radius r of annular light spot o > 0.1 mm <![CDATA[Inner radius r of annular light spot i > 0.05 mm remelting coefficient λ 2.0 Heat loss correction factor χ 2.5

[0252] (1) The amount of H required for a unit volume of material to melt from room temperature and then heated to its melting point. m for:

[0253]

[0254] That is, theoretically, 1 mm can be melted 3 TC4 requires 5.67 J / mm 3 Energy.

[0255] (2) With a layer thickness of t=0.04 mm, during the LPBF process, it is not possible to melt only the current powder layer; the previous layer must also be melted. Otherwise, the interlayer bonding will be insufficient. Taking the remelting coefficient as λ=2.0, the target melting depth D is:

[0256] D = λt = 2.0 × 0.04 = 0.08 mm

[0257] (3) According to equation (5-3), substituting the above parameters, we get P / v≥0.495 W / mm·s -1 Let P = 0.495v.

[0258] Based on P=0.495v, the power-speed table can be obtained, as shown in Table 14:

[0259] Table 14

[0260] serial number Scan speed v Corresponding power P 5-1 600 mm / s 297 W 5-2 700 mm / s 347 W 5-3 750 mm / s 371 W 5-4 800 mm / s 396 W 5-5 810 mm / s 401 W

[0261] (4) Assuming that the melting in the middle region of the channel spacing needs to reach D h =1.2t=1.2×0.04=0.048 mm. According to equation (8-3) and P=0.495v, we get h≤0.099 mm. So we take h=0.09 mm.

[0262] With h = 0.09 mm, and scanning speed and power as shown in Table 14, five sets of parameter combinations were obtained. Cubes measuring 10 mm × 10 mm × 10 mm were then prepared for observation. Figure 8 As shown, no obvious metallurgical defects were found in any of the samples obtained under the 5 sets of combined data (samples 5-1 to 5-5 correspond to numbers 5-1 to 5-5 in Table 14 respectively).

[0263] Mechanical properties were tested on 5 groups of samples, and the results are shown in Table 15.

[0264] Table 15

[0265] serial number Yield strength MPa Tensile strength (MPa) Elongation after fracture % Sample 5-1 1137 1294 10 Sample 5-2 1075 1119 5 Sample 5-3 1131 1318 12 Sample 5-4 965 1023 5 Sample 5-5 991 1139 9

[0266] Mechanical performance tests show that the yield strength is stable at around 1000 MPa, the tensile strength is around 1150 MPa, and the elongation is around 10%, which is significantly higher than the mechanical performance of traditional processing methods and can meet the requirements of normal parts use.

[0267] As can be seen from the above, the parameter matching method based on molten pool energy coupling of this invention is used to quantitatively solve the complete set of laser selective melting process parameters. Based on the calculated parameters, standard cubic specimens are prepared. Through metallographic microscopy, no metallurgical defects such as incomplete fusion, overmelting, splashing, and keyholes are observed in the cross-sectional field of the specimens, and the internal fusion of the components is dense. At the same time, mechanical property tests are carried out on the specimens, and the key mechanical indicators such as tensile strength and elongation of the specimens all meet the industrial use standards of the corresponding metal components.

[0268] This confirms that the present invention’s method of quantitatively matching process parameters through material thermodynamics and the superposition law of molten pool energy is reliable and feasible. It can quickly obtain a stable process window that is suitable for different metal materials and different layer thicknesses without the need for a large number of pre-experimental trials and errors, effectively solving the industry pain points of long development cycle, high test cost and difficulty in predicting forming defects in traditional processes.

[0269] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for matching parameters in laser selective melting additive manufacturing based on molten pool energy coupling, characterized in that, Includes the following steps: Obtain basic input parameters, which include the thermophysical properties of the metal material to be formed, the inherent parameters of the laser equipment, and the preset single-layer printing thickness; Based on the thermodynamic conditions for a metallic material to be heated from its initial temperature to its melting point and complete a phase transformation and melting, determine the enthalpy of fusion required for a unit volume of metallic material to completely melt. The target melting depth is obtained by combining the preset single-layer printing thickness, so that the target melting depth is greater than the single-layer printing thickness, ensuring the interlayer metallurgical remelting bond; Based on the energy distribution characteristics of the laser spot, a comprehensive heat loss correction coefficient is introduced to construct a centerline melting criterion that ensures the energy at the laser scanning centerline meets the condition for complete melting of the metallic material, thus obtaining the matching constraint relationship between laser power and scanning speed; and Using the centerline of two adjacent scanning tracks as the energy verification area, the input energy of the two lasers in the verification area is superimposed to obtain the total energy of the melt track superposition. The inter-track melt pool superposition melting criterion that satisfies the complete fusion between tracks is constructed, and the maximum allowable value of the track spacing is obtained.

2. The parameter matching method for laser selective melting additive manufacturing based on molten pool energy coupling according to claim 1, characterized in that, The thermophysical parameters of the metallic material include the metallic material density ρ and the solid-phase heat capacity C. p,s Material melting point T m Latent heat of fusion L m The initial preheating temperature of the substrate is T0; the inherent parameters of the laser equipment include the laser spot radius and the laser absorptivity η.

3. The parameter matching method for laser selective melting additive manufacturing based on molten pool energy coupling according to claim 1, characterized in that, The relationship between the enthalpy of fusion of a unit volume of material is shown in equation (1): （1） In the formula, H m ρ is the enthalpy of fusion of the material per unit volume; C is the density of the metallic material; p,s T represents the solid phase heat capacity; m T0 is the melting point of the material; T0 is the initial preheating temperature of the substrate; L m This is the latent heat of fusion.

4. The laser selective melting additive manufacturing parameter matching method based on molten pool energy coupling according to claim 1, characterized in that, The target melting depth satisfies the relationship (2): （2） In the formula, D is the target melting depth; λ is the remelting coefficient, with a value range of 1.6 to 2.2; and t is the preset single-layer printing thickness.

5. The laser selective melting additive manufacturing parameter matching method based on molten pool energy coupling according to claim 1, characterized in that, The laser spot includes a Gaussian distribution spot, a flat-top distribution spot, or an annular spot. The energy distribution of the center line and the superposition of adjacent melting channels are constructed using the corresponding spot energy analysis model.

6. The laser selective melting additive manufacturing parameter matching method based on molten pool energy coupling according to claim 1, characterized in that, First, the energy input level at the scanning center is characterized by the energy distribution of the centerline. Then, by combining the centerline melting criterion, the constraint formula for the matching relationship between laser power and scanning speed is obtained. Wherein, when the laser spot is a Gaussian distribution spot, the centerline energy distribution is as shown in equation (3-1); when the laser spot is a flat-top distribution spot, the centerline energy distribution is as shown in equation (3-2); when the laser spot is an annular spot, the centerline energy distribution is as shown in equation (3-3). In the formula, F0 is the energy absorbed per unit area at the laser centerline; P is the laser power; v is the scanning speed; r is the Gaussian spot radius; r f r is the radius of the flat-top light spot. o r is the outer radius of the annular light spot; i η is the inner radius of the annular laser spot; η is the laser absorptivity. The centerline melting criterion is shown in equation (4): （4） In the formula, F0 is the energy absorbed per unit area at the laser centerline; χ is the heat loss correction coefficient; D is the target melting depth; and Hm is the enthalpy of fusion per unit volume. When the laser spot is a Gaussian distribution, the constraint formula for the matching relationship between laser power and scanning speed is shown in equation (5-1); when the laser spot is a flat-top distribution, the constraint formula for the matching relationship between laser power and scanning speed is shown in equation (5-2); when the laser spot is an annular spot, the constraint formula for the matching relationship between laser power and scanning speed is shown in equation (5-3). In the formula, P is the laser power; v is the scanning speed; r is the Gaussian spot radius; r f r is the radius of the flat-top light spot. o r is the outer radius of the annular light spot; i η is the inner radius of the annular laser spot; χ is the laser absorptivity; D is the heat loss correction factor; H is the target melting depth. m It is the enthalpy of fusion per unit volume.

7. The laser selective melting additive manufacturing parameter matching method based on molten pool energy coupling according to claim 1, characterized in that, The total input energy of the two lasers in the verification area is calculated by superimposing the energy of adjacent melting channels. Then, the upper limit constraint formula for the inter-channel fusion criterion is derived by combining the formulas. When the laser spot is a Gaussian distribution spot, the superimposed energy formula of the adjacent melting channels is as shown in formula (6-1); when the laser spot is a flat-top distribution spot, the superimposed energy formula of the adjacent melting channels is as shown in formula (6-2); when the laser spot is an annular spot, the superimposed energy formula of the adjacent melting channels is as shown in formula (6-3). In the formula, F total The total input energy of the interaction between two adjacent melting channels; η is the laser absorptivity; P is the laser power; v is the scanning speed; r is the Gaussian spot radius; r f r is the radius of the flat-top light spot. o r is the outer radius of the annular light spot; i h is the inner radius of the annular light spot; h is the channel spacing. The inter-channel fusion criterion is shown in equation (7): （7） In the formula, F total χ is the total input energy of the interaction between two adjacent melting channels; D is the heat loss correction factor; h H represents the minimum melting depth in the inter-channel region. m Enthalpy of fusion per unit volume; When the laser spot is a Gaussian distribution, the upper limit constraint of the channel spacing is as shown in equation (8-1); when the laser spot is a flat-top distribution, the upper limit constraint of the channel spacing is as shown in equation (8-2); when the laser spot is an annular spot, the upper limit constraint of the channel spacing is as shown in equation (8-3). In the formula, h is the channel spacing; r is the Gaussian spot radius; r f r is the radius of the flat-top light spot. o r is the outer radius of the annular light spot; i η is the inner radius of the annular spot; P is the laser absorptivity; v is the laser power; χ is the scanning speed; D is the heat loss correction factor. h H represents the minimum melting depth in the inter-channel region. m It is the enthalpy of fusion per unit volume.

8. The laser selective melting additive manufacturing parameter matching method based on molten pool energy coupling according to claim 6 or 7, characterized in that, The heat loss correction factor χ is set to a value of 1.0 to 3.

5.

9. The parameter matching method for laser selective melting additive manufacturing based on molten pool energy coupling according to claim 7, characterized in that, Minimum melting depth D in the inter-channel region h The value range is 1.0t to 1.5t, where t is the preset single-layer printing thickness.

10. A method for metal additive manufacturing, characterized in that, The laser selective melting additive manufacturing parameter matching method based on molten pool energy coupling as described in any one of claims 1-9 is used to determine the laser selective melting process parameters. Based on the determined laser selective melting process parameters, powder spreading, laser scanning melting, and layer-by-layer stacking forming processes are performed to prepare the required metal components.

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