Method for optimizing coercive force of WC-Co hard alloy based on response surface method

Abstract

The invention relates to a method for optimizing the coercive force of a WC-Co hard alloy based on a response surface method. The method comprises the following steps: firstly, determining main factors influencing the coercive force of the WC-Co hard alloy in a sintering process and the value ranges of the factors; designing a response curved surface test scheme by adopting a center composite design method, and testing according to the scheme; establishing a response surface model according to test data, and analyzing a test result to obtain a binary multiple regression equation; performing variance analysis and significance analysis on the regression equation to obtain a variance analysis table and a four-in-one residual image, and judging whether the equation fits test data or not; establishing a contour map and a curved surface map according to the response surface model, and determining an optimal point position by combining the graphs; and establishing a response optimization graph, and determining an optimal sintering process condition. The influence of the highest sintering temperature and the heat preservation time at the temperature on the coercive force of the WC-Co hard alloy is comprehensively considered, the relation between the coercive force of the WC-Co hard alloy and sintering process parameters is obtained, and an optimization scheme is obtained.

Description

Technical Field

[0001] The invention relates to a method for optimizing the coercive force of WC-Co hard alloy based on response surface method, and belongs to the technical field of powder metallurgy. Background Art

[0002] At present, coercive force refers to the value of the reverse magnetic field strength required to reduce the residual magnetization intensity of cemented carbide to zero in the saturated magnetization state, and the common unit is kA / m. By measuring the coercive force, the performance and quality of cemented carbide can be evaluated to ensure that it meets specific usage requirements.

[0003] The sintering process of WC-Co cemented carbide has a significant effect on the coercive force. At present, there are many process parameters involved in the sintering process, such as the maximum sintering temperature and the holding time at this temperature. These factors are interrelated. The interaction between the parameters may have a nonlinear effect on the coercive force, and the interaction is extremely complex, making the sintering process optimization process more difficult. Existing optimization methods usually use trial and error or single-factor experiments to optimize the sintering process parameters. This method requires a large number of experiments, data collection, and demonstration analysis. It is impossible to take into account the interaction and nonlinear relationship between the parameters, consumes a lot of manpower and material resources, is too costly, and may not achieve the expected results. In addition, the existing methods may not necessarily find the global optimal solution, and the result may only have a good response within a certain range. Therefore, there is currently no suitable sintering process optimization method, and it is impossible to accurately predict and optimize the coercive force.

[0004] Therefore, it is necessary to design a method to optimize the coercive force of WC-Co cemented carbide based on response surface methodology. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology is characterized by comprising the following steps:

[0008] 1) Determine the main factors affecting the coercive force of WC-Co cemented carbide in the sintering process and their value ranges;

[0009] 2) Design a response surface experiment plan using the central composite design method and conduct the experiment according to the plan;

[0010] 3) Establish a response surface model based on the test data, analyze the test results, and obtain a binary multiple regression equation;

[0011] 4) Perform variance analysis and significance analysis on the regression equation to obtain a variance analysis table and a four-in-one residual graph to determine whether the equation fits the experimental data;

[0012] 5) Establish contour plots and surface plots based on the response surface model, and determine the optimal point position based on the plots;

[0013] 6) Establish a response optimization diagram to determine the optimal sintering process conditions.

[0014] Furthermore, in the above-mentioned method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology, in step 1), the maximum sintering temperature A and the holding time B at this temperature are selected as variables, and the coercive force Y of WC-Co cemented carbide is the model response value; the adjustment range of the maximum sintering temperature is 1380°C to 1500°C, and the adjustment range of the holding time is 30min to 210min.

[0015] Furthermore, in the above-mentioned method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology, in step 2), the experimental design is performed based on the central composite sequential design method, and a full factorial experimental design scheme with 2 factors, 5 levels and 6 center points is generated using MINITAB software;

[0016] The test method is to set the sintering program of the sintering furnace, the maximum sintering temperature and the holding time are adjustable, the pressed mixed soft billet is placed in the sintering furnace for sintering to obtain WC-Co cemented carbide, and the coercive magnetism of the batch of alloys is measured using a YSK-IV coercive magnetometer.

[0017] Furthermore, in the above-mentioned method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology, in step 3), the measured coercive force data is substituted into MINITAB software to fit a binary multiple regression equation:

[0018] Y=-1354+2.124A+1.689B-0.000781A 2 -0.000099B 2 -0.001209AB

[0019] Wherein, Y represents the coercive force of WC-Co cemented carbide, A represents the maximum sintering temperature, and B represents the holding time at temperature A.

[0020] Furthermore, the above-mentioned method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology, wherein, in step 4), variance analysis is performed according to the response surface model, and the total effect main effect and the 2-factor interaction effect term of the response surface model are significant, and the correlation parameter P value of the model is 0.000, which is less than 0.05, indicating that the experimental data has no loss of fit and the model fitting is significant; residual diagnosis is performed on the response surface model to generate a residual graph; the normal probability graph and histogram in the residual graph indicate that the residual obeys a normal distribution; for the residual scatter plot with the order of observation values ​​as the horizontal axis, each point randomly fluctuates irregularly up and down the horizontal axis, indicating that the model has a high degree of fit with the actual experimental results.

[0021] Furthermore, in the above-mentioned method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology, in step 5), a surface diagram and a contour diagram are respectively established according to the response surface model; the maximum sintering temperature range value and the holding time range value are obtained, and there is an optimal point.

[0022] Furthermore, the above-mentioned method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology, wherein, in step 6), the response optimization diagram, the second-order response surface model is solved using MINITAB software, and it is obtained that when the maximum sintering temperature is 1380°C and the holding time is 103min, the designed coercive force target value of 91Oe is achieved; 10 samples of the same batch are sintered in the same furnace at the same temperature and holding time, and the coercive force test is carried out. The average of the measured results is 90Oe, which is not much different from the predicted value, proving that the response surface model well predicts the coercive force of WC-Co cemented carbide, and the optimized process conditions and parameters are reasonable.

[0023] Compared with the prior art, the present invention has significant advantages and beneficial effects, which are specifically embodied in the following aspects:

[0024] ① The present invention is a method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology. The response surface methodology is used to optimize the coercive force of cemented carbide, a series of experiments and statistical analyses are designed, a binary multiple regression model equation of the coercive force of WC-Co cemented carbide with respect to the highest sintering temperature in the sintering process and the holding time at the temperature is established, variance analysis and significance analysis are performed on the model equation, the fitting effect of the regression equation is judged, parameters are optimized through the model equation, and finally the influence of the change of the sintering process parameters of WC-Co cemented carbide on its coercive force is accurately predicted, so as to obtain the optimal sintering process conditions;

[0025] ② The present invention comprehensively considers the influence of the maximum sintering temperature and the holding time at this temperature on the coercive force of WC-Co cemented carbide, obtains the relationship between the coercive force of WC-Co cemented carbide and the sintering process parameters based on the response surface method, and then obtains the optimization scheme of the coercive force of WC-Co cemented carbide;

[0026] ③ The response surface method of the present invention reduces the workload while fully considering the interaction between parameters, greatly improving the accuracy and credibility of the optimization results, saving process development optimization time, reducing workload, reducing optimization costs, and improving work efficiency.

[0027] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or be understood by practicing the specific embodiments of the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 : Four-in-one residual diagram of the coercive force of WC-Co cemented carbide according to an embodiment of the present invention;

[0030] Figure 2 : Response model variance and significance analysis diagram of the embodiment of the present invention;

[0031] Figure 3 : Surface diagram of coercive force of WC-Co cemented carbide according to the embodiment of the present invention, maximum sintering temperature and holding time;

[0032] Figure 4 : Contour diagram of the coercive force of WC-Co cemented carbide according to the embodiment of the present invention, the maximum sintering temperature and the holding time;

[0033] Figure 5 : Response model optimization diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the 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. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0035] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, in the description of the present invention, directional terms and order terms are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0036] The invention discloses a method for optimizing the coercive force of WC-Co cemented carbide based on the response surface method, and determines the optimal sintering process conditions when the optimal coercive force is obtained by the response surface method.

[0037] The specific steps are as follows:

[0038] Step 1: Determine the main factors affecting the coercive force of WC-Co cemented carbide during the sintering process and the range of the factors.

[0039] The maximum sintering temperature A and the holding time B at this temperature are selected as variables, and the coercive force Y is the model response value; the adjustment range of the maximum sintering temperature is 1380℃~1500℃, and the adjustment range of the holding time is 30min~210min;

[0040] Step 2: Design a response surface experiment plan using the central composite design method and complete the experiment according to the plan.

[0041] The experimental design was carried out based on the central composite sequential design method (the setting results are shown in Table 1), and the MINITAB software was used to generate a full factorial experimental design scheme with 2 factors, 5 levels and 6 center points (the experimental scheme and results are shown in Table 2), without randomizing the experimental order.

[0042] Table 1 Experimental factors and level settings

[0043]

[0044] The specific test method is: set the sintering program of the sintering furnace, the maximum sintering temperature and the holding time are adjustable, put the pressed mixed material soft billet into the sintering furnace for sintering to obtain WC-Co hard alloy, and use the YSK-IV coercive magnetometer to measure the coercive force of the batch of alloys; the experimental results of WC-Co hard alloy with a cobalt content of 16% are shown in Table 2:

[0045] Table 2 Central composite sequential experimental design and results

[0046]

[0047] Step 3: Establish a response surface model based on the experimental data, analyze the experimental results, and obtain the binary multiple regression equation.

[0048] Substitute the coercive force data measured above into the MINITAB software to fit the binary multiple regression equation:

[0049] Y=-1354+2.124A+1.689B-0.000781A 2 -0.000099B 2 -0.001209AB

[0050] Wherein, Y represents the coercive force of WC-Co cemented carbide, A represents the maximum sintering temperature, and B represents the holding time at temperature A;

[0051] Step 4: Perform variance analysis and significance analysis on the regression equation to obtain the variance analysis table and four-in-one residual graph to determine whether the equation fits the experimental data.

[0052] According to the response surface model, variance analysis was performed. Figure 2 It can be seen that the total effect main effect and the two-factor interaction effect of the response surface model are significant, and the correlation parameter P value of the model is 0.000, which is less than 0.05, indicating that the test data has no lack of fit and the model fit is significant. The response surface model is diagnosed with residuals and a residual plot is generated. Figure 1 It can be seen that the normal probability diagram and histogram in the residual diagram show that the residuals obey the normal distribution; for the scatter plot of the residuals with the order of observation values ​​as the horizontal axis, each point fluctuates randomly up and down the horizontal axis without any regularity, indicating that the model has a high degree of fit with the actual experimental results.

[0053] Step 5: Create contour plots and surface plots based on the response surface model, and determine the optimal point location based on the graphs.

[0054] According to the response surface model, we establish Figure 3 and Figure 4 The surface and contour plots shown. Figure 4It can be seen that the highest sintering temperature is between 1380℃ and 1390℃, and the holding time is between 30min and 200min, and there is an optimal point.

[0055] Step 6: Establish a response optimization diagram to determine the optimal sintering process conditions.

[0056] Response optimization diagram Figure 5 As shown in the figure, the second-order response surface model was solved by MINITAB software, and it was found that when the maximum sintering temperature was 1380℃ and the holding time was 103min, the designed coercive force target value of 91Oe could be achieved. Ten samples of the same batch were sintered in the same furnace at the same temperature and holding time, and the coercive force test was carried out. The average value of the measured results was 90Oe, which was not much different from the predicted value, proving that the response surface model well predicted the coercive force of WC-Co cemented carbide, and the optimized process condition parameters were reasonable.

[0057] In summary, the present invention is based on the method for optimizing the coercive force of WC-Co cemented carbide based on the response surface method, adopts the response surface method to optimize the coercive force of cemented carbide, designs a series of experiments and statistical analysis, establishes a binary multiple regression model equation of the coercive force of WC-Co cemented carbide with respect to the highest sintering temperature in the sintering process and the holding time at the temperature, performs variance analysis and significance analysis on the model equation, judges the fitting effect of the regression equation, optimizes the parameters through the model equation, and finally accurately predicts the influence of the change of the sintering process parameters of WC-Co cemented carbide on its coercive force, so as to obtain the optimal sintering process conditions. The influence of the highest sintering temperature and the holding time at the temperature on the coercive force of WC-Co cemented carbide is comprehensively considered, and the relationship between the coercive force of WC-Co cemented carbide and the sintering process parameters is obtained based on the response surface method, thereby obtaining the optimization scheme of the coercive force of WC-Co cemented carbide. Compared with the existing methods, the response surface method of the present invention reduces the workload while fully considering the interaction between parameters, greatly improving the accuracy and credibility of the optimization results, saving process development optimization time, reducing the workload, reducing the optimization cost, and improving work efficiency.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention. It should be noted that similar numbers and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0059] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0060] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

Claims

1. A method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology, characterized in that: The steps include: 1) Determine the main factors affecting the coercive force of WC-Co cemented carbide in the sintering process and their value ranges; 2) Design a response surface experiment plan using the central composite design method and conduct the experiment according to the plan; 3) Establish a response surface model based on the test data, analyze the test results, and obtain a binary multiple regression equation; 4) Perform variance analysis and significance analysis on the regression equation to obtain a variance analysis table and a four-in-one residual graph to determine whether the equation fits the experimental data; 5) Establish contour plots and surface plots based on the response surface model, and determine the optimal point position based on the plots; 6) Establish a response optimization diagram to determine the optimal sintering process conditions.

2. The method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology according to claim 1, characterized in that: In the step 1), the maximum sintering temperature A and the holding time B at the temperature are selected as variables, and the coercive force Y of WC-Co cemented carbide is selected as the model response value; the adjustment range of the maximum sintering temperature is 1380°C to 1500°C, and the adjustment range of the holding time is 30min to 210min.

3. The method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology according to claim 1, characterized in that: In step 2), the experimental design is performed based on the central composite sequential design method, and a full factorial experimental design scheme with 2 factors, 5 levels and 6 center points is generated using MINITAB software; The test method is to set the sintering program of the sintering furnace, the maximum sintering temperature and the holding time are adjustable, the pressed mixed soft billet is placed in the sintering furnace for sintering to obtain WC-Co cemented carbide, and the coercive magnetism of the batch of alloys is measured using a YSK-IV coercive magnetometer.

4. The method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology according to claim 1, characterized in that: In step 3), the measured coercive force data is substituted into MINITAB software to obtain a binary multiple regression equation: Y=-1354+2.124A+1.689B-0.000781A 2 -0.000099B 2 -0.001209AB Wherein, Y represents the coercive force of WC-Co cemented carbide, A represents the maximum sintering temperature, and B represents the holding time at temperature A.

5. The method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology according to claim 1, characterized in that: In the step 4), variance analysis is performed according to the response surface model. The total effect, main effect and 2-factor interaction effect items of the response surface model are significant. The correlation parameter P value of the model is 0.000, which is less than 0.05, indicating that the test data has no loss of fit and the model fitting is significant. The response surface model is diagnosed with residuals to generate a residual graph. The normal probability graph and histogram in the residual graph indicate that the residuals obey a normal distribution. For the scatter plot with the order of observations as the horizontal axis, the points fluctuate randomly on the horizontal axis without regularity, indicating that the model has a high degree of fit with the actual experimental results.

6. The method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology according to claim 1, characterized in that: In the step 5), a surface map and a contour map are respectively established according to the response surface model; the maximum sintering temperature range value and the holding time range value are obtained, and there is an optimal point.

7. The method for optimizing the coercive force of WC-Co cemented carbide based on response surface methodology according to claim 1, characterized in that: In the step 6), the response optimization diagram is solved by using MINITAB software to solve the second-order response surface model, and it is found that when the maximum sintering temperature is 1380°C and the holding time is 103min, the designed coercive force target value of 91Oe is achieved; 10 samples of the same batch are sintered in the same furnace at the same temperature and holding time, and the coercive force test is carried out. The average of the measured results is 90Oe, which is not much different from the predicted value, proving that the response surface model well predicts the coercive force of WC-Co cemented carbide, and the optimized process condition parameters are reasonable.

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