Prediction and calculation method for utilization rate of laser cladding powder

Abstract

The invention belongs to the technical field of metal additive manufacturing, and relates to a method for predicting and calculating the utilization rate of laser cladding powder, which comprises the following steps of: 1, establishing a prediction model: establishing a powder utilization rate prediction model by adopting a second-order multiple regression equation; 2, calculating the utilization rate of the powder according to the actual measurement values of the geometric dimensions of the coating under different process parameters; 3, the obtained multiple sets of process parameters and the calculated utilization rate are substituted into the established powder utilization rate prediction model, the value of each coefficient in the powder utilization rate prediction model is obtained, and finally the powder utilization rate prediction model corresponding to different laser cladding process parameters is obtained; according to the method, the optimal matching point is quickly found by predicting the powder utilization rate under different process parameters, and the optimal process parameters are selected for cladding to improve the powder utilization rate; therefore, the optimal process parameters can be calculated, and under the condition of the process parameters, the effective utilization rate of the powder can be effectively increased, and the processing cost of laser cladding can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal additive manufacturing, and relates to a prediction calculation method for the powder utilization rate of laser cladding. Background Art

[0002] Laser Cladding is an advanced surface modification technology. By using a high-energy laser beam, metal powder or wire is melted synchronously with the surface of the substrate, and a dense coating with metallurgical bonding is formed after rapid solidification. This technology can prepare high-performance alloy layers on inexpensive substrates, significantly improving wear resistance, corrosion resistance, heat resistance and other properties, while achieving precise repair and remanufacturing. Laser Cladding has many core advantages such as high bonding strength, small heat influence, flexible materials, performance customization, green and efficient. Laser Cladding is used in the energy industry, mining machinery, petrochemical industry for equipment repair and remanufacturing, in transportation and die manufacturing for surface strengthening, and in nuclear power equipment and 3D printing for the expansion of emerging fields. Therefore, laser cladding technology is widely used in a variety of industries and technical fields.

[0003] However, during the laser cladding process, a part of the powder is melted in the laser beam and metallurgically bonded with the substrate to form a coating, while another part of the powder is scattered outside the laser beam due to splashing, collision and other phenomena during the spraying process, resulting in powder loss and reducing the powder utilization efficiency. In severe cases, the powder utilization rate is even less than 50%. The process parameters used in laser cladding, such as powder feeding amount, laser power, scanning speed, etc., have a direct impact on the powder utilization rate. And the low powder utilization rate of laser cladding will cause a series of problems such as increased costs, reduced production efficiency, degraded process, and environmental impact.

[0004] Therefore, a device or method for improving the powder utilization rate of laser cladding with low cost, high precision and high efficiency is needed to solve the above technical problems. Summary of the Invention

[0005] The technical solution adopted by the present invention to solve the technical problems is: a prediction calculation method for the powder utilization rate of laser cladding, comprising the following steps: Step 1, establishing a prediction model: establishing a powder utilization rate prediction model using a second-order multiple regression equation; Step 2, calculating the measured utilization rate of the powder according to the actual measured values of the coating geometric dimensions under different process parameters; Step 3, substituting the multiple groups of process parameters and measured utilization rates obtained in Step 2 into the powder utilization rate prediction model established in Step 1 to obtain the values of the coefficients in the powder utilization rate prediction model, and finally obtaining the powder utilization rate prediction model corresponding to different laser cladding process parameters.

[0006] Preferably, in Step 1, the powder utilization rate prediction model is:

[0007] Among them, represents the predicted powder utilization rate, respectively represent the coefficients, P represents the laser power, V s represents the scanning speed, V f represents the powder feeding rate; In step 2, the process parameters include: laser power, scanning speed, and powder feeding rate.

[0008] Preferably, in the said step 2, the steps to obtain the measured powder utilization rate are: Step 2-1, process parameter setting: Set the process parameters of laser cladding according to the orthogonal test design scheme; Step 2-2, laser cladding: Clad a coating on the surface of the substrate according to the process parameters set in step 2-1; Step 2-3, coating size detection: Detect the morphology and size of the coating clad in step 2-2. The content of the morphology and size detection includes: the width of the coating and the height of the coating; Step 2-4, data recording: Record the process parameters in step 2-2 and the results of the morphology and size detection in step 2-3; Step 2-5, calculate the measured powder utilization rate of the coating powder: Calculate the measured powder utilization rate of the coating according to the actual morphology of the coating, combined with the melting height and melting width of the coating.

[0009] More preferably, in the said step 2, single-layer and single-pass laser cladding is used for actual measurement.

[0010] More preferably, when the laser beam is a circular spot in the said step 2, the measured powder utilization rate is: In the formula, represents the measured powder utilization rate, represents the density of the clad layer, S represents the travel of the laser beam, W represents the melting width of the coating, H represents the melting height of the coating, V s represents the scanning speed, V f represents the powder feeding rate.

[0011] More preferably, when laser cladding is used to strengthen the surface of non-magnetic metal parts and the material of the parts is 316L steel, the powder utilization rate prediction model is:

[0012] Wherein, represents the predicted powder utilization rate, P represents the laser power.

[0013] Preferably, the powder utilization rate prediction model in step 1 is tested; the test methods include: comparing the predicted value of the regression equation with the experimental value, significance test of the regression equation, significance test of the regression coefficient, residual analysis, and experimental verification.

[0014] Preferably, in step 2, the spot shapes of the laser beams used include: circular spot, rectangular spot, annular spot, linear spot, and composite spot.

[0015] The beneficial effects of the present invention are: 1. By establishing a prediction model between the powder utilization rate and process parameters, the present invention calculates the powder utilization rate under given laser cladding process parameters based on the powder utilization rate prediction model; by predicting the powder utilization rate under different process parameters, the best matching point can be quickly found, and the optimal process parameters are selected for cladding to improve its powder utilization rate; therefore, the present invention can calculate the optimal process parameters, under which the effective utilization rate of the powder can be effectively improved and the processing cost of laser cladding can be reduced.

[0016] 2. Predicting the powder utilization rate in advance by the present invention can also quantify the material consumption before the cladding is implemented, more accurately plan the powder amount during procurement, reduce costs, and in addition, the present invention can evaluate the powder utilization rate under the new cladding process and verify the energy-saving effect of the new process through prediction; therefore, the present invention can not only save process costs and improve production efficiency, but also guide process optimization and technological innovation. Description of the Drawings

[0017] Figure 1 is a schematic diagram for calculating the single-pass coating volume of a prediction calculation method for the powder utilization rate of laser cladding of the present invention; Figure 2 is a schematic cross-sectional view of the straight part in the middle of the coating of the present invention; Figure 3 is a schematic diagram for calculating the volume of one end of the coating of the present invention; Figure 4 is a microscopic observation diagram of the cross-section of the coating obtained by the orthogonal experiment of laser cladding of the present invention; Figure 5 is a residual normal probability distribution diagram of the powder utilization rate prediction model of the present invention; Figure 6 is a comparison diagram of the predicted value and the experimental value of the powder utilization rate prediction model of the present invention; Figure 7 is a schematic diagram of the steps of the prediction calculation method of the present invention.

[0018] In the figure, 1 is the base material; 2 is the middle part of the coating; 3 is the end part of the coating. Specific Embodiment

[0019] The following will clearly and completely describe the relevant technologies in the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0020] Reference Figures 1 to 7 As shown, the prediction calculation method for the powder utilization rate of laser cladding in this embodiment includes the following steps: S1. Process parameter setting: According to the orthogonal test design scheme, set the process parameters of laser power, scanning speed, and powder feeding rate; S2. Laser cladding: Start the laser and clad single-pass coatings with different process parameters on the surface of the base material according to the designed process parameters; S3. Coating size detection: After the cladding is completed, perform morphological size detection on the coating, including the detection of the width and height of the coating; S4. Data recording: Record the parameters during the laser cladding process and the data of the detected coating morphological size for subsequent calculation of the coating volume.

[0021] S5. Establishment of the predicted coating model: Use a second-order multiple regression equation to establish a coating morphology prediction model, and test the regression model, including the comparison of the predicted values and experimental values of the regression equation, the significance test of the regression equation, the significance test of the regression coefficients, residual analysis, and experimental verification.

[0022] S6. Calculate the powder utilization rate of the coating: According to the actual morphology of the coating, establish a calculation model for the molten mass of the single-pass cladding layer powder, and calculate the powder utilization rate of the single-pass coating in combination with the melting height and melting width of the coating.

[0023] In step S6, laser heating and melting is a very complex physical process. In order to establish a calculation model for the molten mass of the single-pass cladding layer powder, the following assumptions are made: (1) The cross-sectional profile of the single-pass coating is regarded as a part of a circle, as Figure 2 shown. (2) The end profile of the single-pass coating is regarded as a part of a sphere, as Figure 2 shown. (3) The physical properties of the powder and the substrate material are constant.

[0024] The measured utilization rate of the powder is expressed as:

[0025] Wherein, mis the coating quality, M is the powder mass output by the powder feeder within the time of a single laser cladding layer.

[0026] When preparing a single laser cladding layer by laser cladding, let the action time of the laser be t , the time t The expression of is:

[0027] Among them, S is the travel distance of the laser beam, V S is the laser scanning speed.

[0028] The powder mass output by the powder feeder within the time of a single laser cladding layer M , can be represented by the product of the powder feeding rate V f and the laser action time t :

[0029] The coating quality m is expressed as:

[0030] In the formula, is the coating density, V is the coating volume.

[0031] Since the laser beam used in this embodiment is a circular spot, the actual morphology of the coating is as shown in the schematic Figure 1 . Then the volume V of the coating is expressed as:

[0032] Among them, V 2 is Figure 1 the volume of the middle straight part of the coating in, V 3 is Figure 1 the volume of one end part of the coating in.

[0033] The cross-sectional schematic diagram of the middle straight part of the coating is as shown in Figure 2 . Among them, the cross-section of the middle part 2 of the coating on the substrate 1 is a missing circle, and the radius of the missing circle is R , the central angle corresponding to the arc of the missing circle is θ , W is the melting width, H is the melting height.

[0034] The length L of the middle straight part of the coating is the travel distance SSubtracting the lengths of the two end portions in the direction of the laser beam movement, the length of the straight portion in the middle of the coating 2 can be expressed as:

[0035] Then the volume of the straight portion in the middle of the coating 2 V 2 can be expressed as:

[0036] The coating end 3 is as Figure 3 shown, where, in the coating end 3, W is the melt width, H is the melt height.

[0037] Then the volume of one coating end 3 V 3 is expressed as:

[0038] The volume of the coating V is expressed as:

[0039] Among them, the angle of the complete sector occupied by the missing circle part θ can be further expressed as:

[0040] The missing circle radius R can be further expressed as:

[0041] The actual powder utilization rate is:

[0042] In step S5, the establishment of the predicted coating model includes establishing and predicting the powder utilization rate of the coating through a second-order multiple regression equation. During the laser cladding process, the form of the multiple regression model of the coating powder utilization rate is:

[0043] Among them, is the regression equation, n represents the number of input values, represents the i th input value, are the regression coefficients of each item, e is the residual term.

[0044] Set the height of the laser cladding coating to be H , and the width of the cladding to be W , with the laser power P, scanning speed V s and powder feeding rate V f as input factors, and the powder utilization rate of laser cladding as the output response, to establish a powder utilization rate prediction model:

[0045] Among them, represents each coefficient, represents the predicted value of the powder utilization rate.

[0046] Example

[0047] In this example, the surface of a non-magnetic metal part is strengthened, and the material of this part is 316L steel.

[0048] Process parameter setting: The protective gas and the powder feeding gas are both high-purity argon. The flow rate of the protective gas is 20 L / min, the flow rate of the powder feeding gas is 6 L / min, and the spot diameter is fixed at 3 mm.

[0049] Laser cladding: The substrate is 316L stainless steel, with dimensions of 200 mm × 100 mm × 10 mm. Before the test, the surface of the substrate is polished sufficiently with 60-mesh sandpaper to remove the surface oxides, making the surface of the substrate flat and smooth. Then, the surface of the substrate is cleaned to remove defects such as oil stains and impurity particles on the surface of the substrate. The cladding powder is nickel-based superalloy hard alloy powder. Use the orthogonal test table to design the test plan and obtain 16 groups of test parameters. Start the laser and deposit 16 coatings with different process parameters on the surface of the substrate according to the designed process parameters.

[0050] Coating size detection: After the cladding is completed, use a wire electrical discharge machine to cut the prepared coating, and polish the cross-section of the coating until the surface is flat and smooth. Use an optical and electron microscope to measure the width and height of the coating, as Figure 4 shown.

[0051] Data recording: Record the data of each group of laser cladding process parameters and the corresponding coating morphology size.

[0052] Calculate the measured powder utilization rate of the coating: According to the actual morphology size of the coating, calculate the measured powder utilization rate of each coating: The sizes of the 16 coatings under different laser cladding process parameters obtained by the orthogonal test and the calculated measured powder utilization rates are shown in Table 1.

[0053] Table 1

[0054] In Table 1, P is the laser power (W),V s is the scanning speed (mm / s), V f is the powder feeding rate (r / min), H is the melting height (mm), W is the melting width (mm), is the measured utilization rate of the powder.

[0055] Establishment of the powder utilization rate prediction model: Substitute the test data in Table 1 into the coating powder utilization rate prediction model formula, and calculate the equation coefficients through calculation. The results are as follows:

[0056] Test the regression model, including the significance test of the regression coefficient of the regression equation, goodness-of-fit test, residual analysis, and comparison of predicted values with experimental values, and conduct experimental verification. The significance test of the prediction model obtains a P value of 0.0032, which is much smaller than 0.05, indicating that the model is significant. The regression determination coefficient value is 0.9784, close to 1, indicating that the goodness-of-fit of the prediction model is good.

[0057] Figure 5 is the residual normal probability distribution diagram of the powder utilization rate prediction model. It can be seen that the residual normal probabilities are randomly distributed near the straight line, indicating that the equation fits the random error well and has good adaptability. Figure 6 is the comparison diagram of the powder utilization rate predicted values obtained by using the prediction model and the experimental values. Each point in the figure is distributed near the straight line, indicating that the results predicted by the model are in good agreement with the experimental results and have good consistency.

[0058] To further verify the accuracy of the powder utilization rate prediction model, arbitrarily select three groups of laser power, scanning speed, and powder feeding rate different from those in Table 1 as the laser cladding process parameters. First, use the powder utilization rate prediction model to make predictions and obtain the powder utilization rate predicted values under the three groups of process parameters. Then, conduct single-layer single-pass laser cladding experiments for actual measurement to obtain the experimental values of the powder utilization rate under the three groups of process parameters. Finally, calculate the relative error between the predicted values and the experimental values. The prediction and experimental data are shown in Table 2.

[0059] Table 2

[0060] In Table 2, P is the laser power (W), V s is the scanning speed (mm / s), V f is the powder feeding rate (r / min).

[0061] As can be seen from Table 2, the maximum relative error in the prediction of powder utilization rate among the three groups of data is 5.3%, and the minimum relative error is 4.0%, which proves the accuracy of the prediction model.

[0062] Therefore, based on the prediction of powder utilization rate, in this embodiment, when selecting laser cladding process parameters, the consideration of powder utilization rate can be added, and the process parameters with higher utilization rate can be selected for implementation, reducing the waste of laser cladding cost, thereby controlling production costs, improving production efficiency, and ensuring production processes.

[0063] In summary, the present invention establishes a prediction model between powder utilization rate and process parameters, calculates the measured powder utilization rate under given laser cladding process parameters based on the powder utilization rate prediction model; by predicting the measured powder utilization rate under different process parameters, quickly finds the best matching point, selects the optimal process parameters for cladding to improve its powder utilization rate; therefore, the present invention can calculate the optimal process parameters, under which the effective utilization rate of powder can be effectively improved and the processing cost of laser cladding can be reduced.

[0064] It should be emphasized that the above are only preferred embodiments of the present invention, and there is no limitation in any form to the present invention. Any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for predicting and calculating the utilization rate of laser cladding powder, characterized in that: The following steps are involved: Step 1: Establishment of prediction model: Use second-order multiple regression equation to establish powder utilization prediction model; Step 2, calculating the actual utilization rate of the powder according to the actual measured values ​​of the coating geometric dimensions under different process parameters; Step 3: Substitute the multiple sets of process parameters and measured utilization rates obtained in step 2 into the powder utilization prediction model established in step 1 to obtain the values ​​of each coefficient in the powder utilization prediction model, and finally obtain the powder utilization prediction model corresponding to different laser cladding process parameters.

2. The method for predicting and calculating the utilization rate of laser cladding powder according to claim 1, characterized in that: In step 1, the powder utilization prediction model is: ； in, represents the predicted powder utilization, Represent the coefficients respectively, P represents the laser power, V s Indicates the scanning speed, V f Indicates the powder feeding rate; In step 2, the process parameters include: laser power, scanning speed, and powder feeding rate.

3. The method for predicting and calculating the utilization rate of laser cladding powder according to claim 1, characterized in that: In step 2, the step of obtaining the actual measured utilization rate of the powder is: Step 2-1, process parameter setting: according to the orthogonal experimental design scheme, set the process parameters of laser cladding; Step 2-2, laser cladding: cladding a coating on the surface of the substrate according to the process parameters set in step 2-1; Step 2-3, coating size detection: performing shape and size detection on the coating clad in step 2-2, wherein the shape and size detection includes: the width and height of the coating; Step 2-4, data recording: recording the process parameters in step 2-2 and the results of the shape and size detection in step 2-3; Step 2-5, calculate the actual utilization rate of the coating powder: calculate the actual utilization rate of the coating powder based on the actual morphology of the coating and the melt height and melt width of the coating.

4. The method for predicting and calculating the utilization rate of laser cladding powder according to claim 3, characterized in that: In the step 2, single-layer single-pass laser cladding is used for actual measurement.

5. The method for predicting and calculating the utilization rate of laser cladding powder according to claim 3, characterized in that: In step 2, when the laser beam is a circular spot, the formula for calculating the actual utilization rate of the powder is: In the formula, Indicates the actual utilization rate of powder, represents the density of the cladding layer, S represents the travel distance of the laser beam, W Indicates the coating's melt width, H Indicates the melting point of the coating. V s Indicates the scanning speed, V f Indicates the powder feeding rate.

6. The method for predicting and calculating the utilization rate of laser cladding powder according to claim 5, characterized in that: When laser cladding is used to strengthen the surface of non-magnetic metal parts and the part material is 316L steel, the powder utilization prediction model is: ； In the formula, represents the predicted powder utilization, P Indicates the laser power.

7. The method for predicting and calculating the utilization rate of laser cladding powder according to claim 1, characterized in that: The powder utilization prediction model in step 1 is tested; the testing methods include: comparison of the predicted value of the regression equation with the experimental value, regression equation significance test, regression coefficient significance test, residual analysis, and experimental verification.

8. The method for predicting and calculating the utilization rate of laser cladding powder according to claim 1, characterized in that: In the step 2, the spot shapes of the laser beam used include: circular spot, rectangular spot, annular spot, linear spot, and composite spot.

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