Method for establishing rotating bending fatigue life prediction model of inclusion-containing workpiece

Abstract

The invention discloses a method for establishing an inclusion-containing metal rotation bending fatigue life prediction model. A certain metal is selected, a fatigue life model directly related to the actual width or diameter of the inclusion is established through metallographic sample preparation, electrolytic corrosion, SEM / EDS detection, a rotating bending fatigue test and the like, and gaps which are neglected by a traditional metallographic inclusion detection method all the time and are formed around the inclusion and are also unfavorable for the fatigue performance of the metal are considered. By adopting the model, the actual width or diameter of the inclusion obtained by a traditional metallographic inclusion detection method can be used for directly predicting the rotating bending fatigue life of the metal, so that more convenient and accurate guidance is provided for selection of a smelting process in a metal production process and control of the inclusion.

Description

Technical Field

[0001] The invention relates to the technical field of metal detection and analysis, and relates to a method for establishing a rotation bending fatigue life prediction model for a workpiece containing inclusions. Background Art

[0002] Most metals require excellent fatigue resistance and fatigue life, but internal inclusions often become the origin of fatigue cracks, causing fatigue fractures in the metal during use. The types of inclusions in metals produced by different control processes are different, and can basically be divided into two types: low-melting point plastic inclusions and high-melting point hard inclusions. Domestic and foreign studies have shown that the thermal expansion, solidification shrinkage coefficient and hardness of inclusions and metal matrix are different, resulting in the formation of voids around the inclusions during heating and cooling or during pressing, and the voids formed between the inclusions and the metal matrix have the same adverse effect on its fatigue properties as the inclusions. However, the traditional metallographic inclusion detection method cannot detect the voids formed around the inclusions, and the metal fatigue life model established for inclusions at home and abroad does not consider the influence of the voids. In addition, the final actual shapes of different types of inclusions in the metal are also different, and predecessors have not directly established a relationship between the actual width or diameter of the inclusion and the fatigue life. However, the establishment of such models has a more direct and clear guiding significance for the selection of smelting processes and the control of inclusions in the metal production process. The establishment of the model can also make it possible to accurately predict the metal rotational bending fatigue life using the actual width or diameter of the inclusions obtained through traditional metallographic inclusion detection methods. Summary of the invention

[0003] The purpose of the present invention is to provide a method for establishing a fatigue life prediction model for metal rotation bending containing inclusions, taking into account the voids formed around the inclusions that have been ignored by traditional metallographic inclusion detection methods and are also detrimental to the fatigue performance of the metal, and establishing a fatigue life model directly related to the actual width or diameter of the inclusions, so that the actual width or diameter of the inclusions obtained by the traditional metallographic inclusion detection method can be used to accurately predict the fatigue life of the metal rotation bending, which is intended to provide more convenient and accurate guidance for the selection of smelting technology and the control of inclusions in the metal production process.

[0004] The technical solution of the present invention is:

[0005] A method for establishing a fatigue life prediction model for a metal rotation bending containing inclusions is provided, comprising the following steps:

[0006] Step 1: Metallographic sample preparation

[0007] Obtaining samples from the same batch of metal products to be analyzed, and taking samples from the end and / or the middle of the metal products, grinding and polishing the longitudinal section of each sample;

[0008] Step 2: Electrolytic polishing and SEM / EDS inspection

[0009] The longitudinal section of each sample was electropolished, and the images of inclusions and voids around the inclusions on the longitudinal section were observed and collected by scanning electron microscope. The composition of the inclusions was detected by energy spectrum, and the size of the inclusions and the area of ​​the voids around the inclusions were calculated by image software. The inclusion shrinkage coefficient CC was calculated by the formula: S 空 is the void area around the inclusion, in μm 2 ; S 夹 is the inclusion area, unit: μm 2 ; The inclusion shrinkage coefficient CC is used as the inclusion evaluation parameter;

[0010] Step 3: Rotational bending fatigue test and prediction model establishment

[0011] Each sample was subjected to a rotating bending fatigue test, and the size of the inclusions at the origin of the fatigue fracture crack was observed and measured by scanning electron microscopy to obtain the rotating bending fatigue test data; the sum of the size of the inclusions and the surrounding voids was taken as the initial size of the fatigue origin crack, and a correction calculation was performed based on the grain slip energy theory and the Paris formula to form a prediction model for the rotating bending fatigue life of the metal parts containing inclusions corresponding to the sample. Prediction model for rotating bending fatigue life containing inclusions.

[0012] Preferably, the electrolytic polishing process in step 2 is: the sample is used as the anode and the copper sheet is used as the cathode, and the distance is 4cm to 6cm, and they are respectively connected to the positive and negative electrodes of a voltage-stabilized power supply (with a range of 0.5V to 1V); a solution of 3% to 5% benzyltriethylammonium chloride, 12% to 17% methyl isobutyl ketone and 78% to 85% anhydrous methanol is prepared, and the longitudinal section of the sample is immersed in the solution by 1mm to 3mm at a temperature of 0°C to 4°C, and the electrolytic polishing time is 10s to 20s.

[0013] Preferably, in step 1, samples are taken at one end, 1 / 4 length position, 1 / 2 length position, 3 / 4 length position and the other end of the disk, round rod and / or plate.

[0014] Preferably, the longitudinal cross-sectional area of ​​the sample is 1 cm 2 , and then ground with 60 mesh, 400 mesh, 800 mesh, 1500 mesh and 2000 mesh sandpaper in sequence, and mechanically polished with polishing paste with a particle size of 1.5μm.

[0015] Preferably, the fatigue life recorded in step 3 is equal to the internal fatigue crack initiation life + the internal fatigue crack growth life, that is: N f =N i +N p , N fis fatigue life, N i is the internal fatigue crack initiation life, N p Internal fatigue crack growth life.

[0016] Preferably, the grain slip energy theory and the Paris formula are combined for correction calculation, considering that the crack size at the junction of steady-state crack extension and non-steady-state crack extension is much larger than the initial size of fatigue origin crack; and according to the inclusion shrinkage coefficient CC and fatigue strength calculation method, for low melting point plastic inclusions, its cross section is regarded as an ellipse, S 夹 =π×a×b, a is the inclusion length, μm; b is the inclusion width, μm; for hard inclusions with high melting points, their cross sections are regarded as circular, d is the inclusion diameter, μm; fatigue test stress value Δσ, MPa; geometric constant β1, Metal elastic modulus E, GPa; metal shear modulus G, GPa; microhardness HV;

[0017] Establish the rotating bending fatigue life N of plastic inclusions f1 The prediction model is:

[0018]

[0019] Establish the rotating bending fatigue life N of hard inclusions f2 The prediction model is:

[0020]

[0021] The rotation bending fatigue test data was substituted into the above model and iterated through MATLAB software to make the function satisfy The value is the smallest, and the fatigue resistance parameter △K of the metal part is obtained th , C and n values, and the results are fed back to the established metal rotation bending fatigue life N f1 Prediction model and rotary bending fatigue life of metals containing hard inclusions f2 In the prediction model, a prediction model for the rotary bending fatigue life of metal parts containing inclusions is obtained.

[0022] Preferably, the rotary bending fatigue test data includes the rotary bending fatigue life, a is the inclusion length, b is the inclusion width, the inclusion diameter d and the diameter and the inclusion shrinkage coefficient CC value. a is the inclusion length and b is the inclusion width, and the relationship between a and the inclusion diameter d is or. That is, preferably, the rotary bending fatigue test data includes the rotary bending fatigue life, a is the inclusion length, b is the inclusion width and the diameter and the inclusion shrinkage coefficient CC value. Or preferably, the rotary bending fatigue test data includes the rotary bending fatigue life, the inclusion diameter d and the diameter and the inclusion shrinkage coefficient CC value.

[0023] Taking into account the voids formed around inclusions, which have been ignored by traditional metallographic inclusion detection methods and are also detrimental to the fatigue performance of metals, a fatigue life model directly related to the actual width or diameter of the inclusions was established. The establishment of this model makes it possible to use the actual width or diameter of the inclusions obtained by traditional metallographic inclusion detection methods to accurately predict the complete fatigue life of metal rotation, which will provide more convenient and accurate guidance for the selection of smelting processes and the control of inclusions in the metal production process.

[0024] The working principle of this method is that the thermal expansion, solidification shrinkage coefficient and hardness of the inclusions and the metal matrix are different, which causes the formation of voids of different sizes around different types of inclusions during heating and cooling or during the pressing process. The electrode decomposition potential of the matrix at the contact surface between the metal matrix and the inclusion is higher. A specific neutral non-aqueous electrolytic polishing method is used to dissolve the matrix at the contact surface between the metal and the inclusion in a short time, and the voids between the exposed inclusions and the metal matrix can be accurately measured. Then, the sum of the sizes of the inclusions and the voids around them is used as the initial size of the fatigue origin crack. According to the grain slip energy theory and the classic Paris formula, it is corrected that the crack size at the junction of the steady-state crack extension and the unsteady-state crack extension is much larger than the initial size of the fatigue origin crack. The unsteady-state expansion rate of the fatigue crack is very fast, and its life is very short, which is much smaller than the life of the steady-state crack extension. The fatigue life N is ignored. f Prediction model. The model directly links the actual width or diameter of different types of inclusions with fatigue life according to the different shapes they have after being pressed due to their different melting points.

[0025] Disks, rods and / or plates

[0026] The advantages of the present invention are: (1) by using this method, by controlling the neutral non-aqueous solution electrolytic polishing method, the voids of different sizes around different types of inclusions that have been ignored by traditional detection methods and are also detrimental to metal fatigue performance are completely exposed, which provides more accurate data for the establishment of fatigue life models;

[0027] (2) Using this method, the sum of the size of the inclusion and the voids around it is taken as the initial size of the fatigue origin crack, and a more accurate fatigue life N is established. f The prediction model establishes a direct relationship between fatigue life and the actual width or diameter of the inclusions that can be obtained through traditional metallographic inspection methods.

[0028] (3) This method is simple, practical and has strong applicability. It can be widely applied to the study of inclusions in metals of various types and processes. The established model has the ability to quickly predict the rotational bending fatigue life of metals containing inclusions of different types and shapes. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Fig. 1 is a typical Al2O3-SiO2-CaO and Al2O3-CaO-CaS inclusion and the morphology of the surrounding voids provided by the present invention;

[0030] Figure 2 The dimensions of the rotating bending fatigue test specimens provided in this instruction are:

[0031] FIG3 is provided in this specification for the situation of inclusions at the origin of the crack in the rotating bending fatigue fracture;

[0032] FIG. 4 is a rotational bending fatigue life prediction model provided in this specification. DETAILED DESCRIPTION

[0033] The disclosed examples will be more fully described with reference to the accompanying drawings, in which some (but not all) of the disclosed examples are shown. In fact, many different examples may be described and these examples should not be construed as limited to the examples set forth herein. Instead, these examples are described so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.

[0034] As shown in FIG1 , a method for establishing a fatigue life prediction model for a metal rotation bending containing inclusions is provided, comprising the following steps:

[0035] Step 1: Metallographic sample preparation

[0036] Obtaining samples from the same batch of metal products to be analyzed, and taking samples from the end and / or the middle of the metal products, grinding and polishing the longitudinal section of each sample;

[0037] Step 2: Electrolytic polishing and SEM / EDS inspection

[0038] The longitudinal section of each sample was electropolished, and the images of inclusions and voids around the inclusions on the longitudinal section were observed and collected by scanning electron microscope. The composition of the inclusions was detected by energy spectrum, and the size of the inclusions and the area of ​​the voids around the inclusions were calculated by image software. The inclusion shrinkage coefficient CC was calculated by the formula: S 空 is the void area around the inclusion, in μm 2 ; S 夹 is the inclusion area, unit: μm 2 ; The inclusion shrinkage coefficient CC is used as the inclusion evaluation parameter;

[0039] Step 3: Rotational bending fatigue test and prediction model establishment

[0040] Each sample was subjected to a rotating bending fatigue test. The size of the inclusions at the origin of the fatigue fracture crack was observed and measured by scanning electron microscopy. The fatigue life of the sample when it broke was recorded to obtain the rotating bending fatigue test data. The sum of the size of the inclusions and the surrounding voids was taken as the initial size of the fatigue origin crack. The calculation was corrected based on the grain slip energy theory and the Paris formula to form a prediction model for the rotating bending fatigue life of the metal parts containing inclusions corresponding to the sample. Prediction model for rotating bending fatigue life containing inclusions

[0041] The electrolytic polishing process in step 2 is: the sample is used as the anode and the copper sheet is used as the cathode, and the distance is 4cm to 6cm, respectively connected to the positive and negative electrodes of the voltage-stabilized power supply (range is 0.5V to 1V); a solution of 3% to 5% benzyltriethylammonium chloride, 12% to 17% methyl isobutyl ketone and 78% to 85% anhydrous methanol is prepared, and the longitudinal section of the sample is immersed in the solution by 1mm to 3mm at a temperature of 0℃ to 4℃, and the electrolytic polishing time is 10s to 20s.

[0042] In step 1, samples are taken from one end, 1 / 4 length position, 1 / 2 length position, 3 / 4 length position and the other end of the disk, round rod and / or plate.

[0043] The longitudinal cross-sectional area of ​​the sample is 1 cm 2 , and then ground with 60 mesh, 400 mesh, 800 mesh, 1500 mesh and 2000 mesh sandpaper in sequence, and mechanically polished with polishing paste with a particle size of 1.5μm.

[0044] The fatigue life recorded in step 3 is equal to the internal fatigue crack initiation life + internal fatigue crack growth life, that is: N f =N i +N p , N f is fatigue life, N i is the internal fatigue crack initiation life, N p Internal fatigue crack growth life.

[0045] Preferably, the grain slip energy theory and the Paris formula are combined for correction calculation, considering that the crack size at the junction of steady-state crack extension and non-steady-state crack extension is much larger than the initial size of fatigue origin crack; and according to the inclusion shrinkage coefficient CC and fatigue strength calculation method, for low melting point plastic inclusions, its cross section is regarded as an ellipse, S 夹 =π×a×b, a is the inclusion length, μm; b is the inclusion width, μm; for hard inclusions with high melting points, their cross sections are regarded as circular, d is the inclusion diameter, μm; fatigue test stress value Δσ, MPa; geometric constant β1, Metal elastic modulus E, GPa; metal shear modulus G, GPa; microhardness HV;

[0046] Establish the rotating bending fatigue life N of plastic inclusions f1 The prediction model is:

[0047]

[0048] Establish the rotating bending fatigue life N of hard inclusions f2 The prediction model is:

[0049]

[0050] The rotation bending fatigue test data was substituted into the above model and iterated through MATLAB software to make the function satisfy The value is the smallest, and the fatigue resistance parameter △K of the metal part is obtained th , C and n values, and the results are fed back to the established metal rotation bending fatigue life N f1 Prediction model and rotary bending fatigue life of metals containing hard inclusions f2 In the prediction model, a prediction model for the rotary bending fatigue life of metal parts containing inclusions is obtained.

[0051] The rotating bending fatigue test data include rotating bending fatigue life, a is the inclusion length, b is the inclusion width, inclusion diameter d and diameter and inclusion shrinkage coefficient CC value.

[0052] Electrolytic polishing and SEM / EDS detection: The longitudinal section of each sample was electrolytically polished under specific conditions: the sample was used as the anode and the copper sheet was used as the cathode, and the distance was 4 cm to 6 cm, respectively connected to the positive and negative electrodes of a voltage-stabilized power supply (range 0.5 V to 1 V). A solution of 3% to 5% benzyltriethylammonium chloride, 12% to 17% methyl isobutyl ketone and 78% to 85% anhydrous methanol was prepared, and the longitudinal section of the sample was immersed in the solution at a temperature of 0°C to 4°C for 1 mm to 3 mm, and electrolytically polished for 10s to 20s.

[0053] Embodiment 1:

[0054] A method for predicting the fatigue life of rotating bending of metals containing inclusions. A steel plant produces spring steel through the silicon deoxidation inclusion plasticization control process, and the wire rod composition is: C: 0.57, Si: 1.53, Mn: 0.71; Cr: 0.67; Als: 0.0003; Ca: 0.0001, S: 0.005; T. [O]: 0.0012. In the same furnace of spring steel, 5 semi-cylindrical specimens were taken from the head, 1 / 4 length, 1 / 2 length, 3 / 4 length and tail of the Φ10mm wire rod of the third roll. The length of the specimen was 10mm. The longitudinal sections of the 25 specimens were polished in sequence with 60 mesh, 400 mesh, 800 mesh, 1500 mesh and 2000 mesh sandpaper, and mechanically polished with a polishing paste with a particle size of 1.5μm. Then, the longitudinal sections of each sample were electropolished: the sample was used as the anode and the copper sheet was used as the cathode, and the distance was 4 cm, respectively connected to the positive and negative electrodes of the voltage-stabilized power supply (range was 1 V). A solution of 3% benzyltriethylammonium chloride, 15% methyl isobutyl ketone and 82% anhydrous methanol was prepared, and the longitudinal section of the sample was immersed in the solution for 2 mm at a temperature of 0°C, and electropolished for 15 seconds. Then, a scanning electron microscope was used to observe and collect images of inclusions and the voids around them on the cross section, and the energy spectrum was used to detect the composition of the inclusions, as shown in Figure 1(a). The size of the inclusions and the area of ​​the voids around them were calculated by image software, and the inclusion shrinkage coefficient CC was introduced as the inclusion evaluation parameter: The calculated CC value is 7.9%.

[0055] Set 800MPa, 775MPa and 750MPa as the maximum stress, and perform 12 rotation bending fatigue tests according to HB5152-96. The sample size is as follows: Figure 2 , the size of inclusions at the origin of fatigue fracture cracks was observed and measured by scanning electron microscopy, as shown in Figure 3(a). The sum of the size of the inclusions and the voids around them was taken as the initial size of the fatigue origin crack, and the calculation was corrected by combining the grain slip energy theory and the classical Paris formula. Considering that the crack size at the junction of steady-state crack extension and non-steady-state crack extension is much larger than the initial size of the fatigue origin crack, the cross section of the Al2O3-SiO2-CaO low-melting plastic inclusion is regarded as an ellipse with an aspect ratio of 10.2, that is, S 夹 =10.2×π×b 2 , the fatigue life of 12 rotational bending, the diameter of inclusions at the origin of fatigue fracture crack and the CC value of inclusions are brought in. The elastic modulus E of the spring steel is 210GPa, the metal shear modulus G is 80GPa, and the metal microhardness HV is 508. Through iterative calculation of MATLAB software, the prediction model of the rotational bending fatigue test is obtained as follows:

[0056]

[0057] The errors between the 12 sets of experimental data and the model calculation are all within 5.3%, as shown in Figure (4a), proving that the model has a high prediction accuracy.

[0058] Embodiment 2:

[0059] The longitudinal section of each sample was electropolished: the sample was used as the anode and the copper sheet was used as the cathode, and the distance was 4 cm, respectively connected to the positive and negative electrodes of the voltage-stabilized power supply (range was 1 V). A solution of 3% benzyltriethylammonium chloride, 15% methyl isobutyl ketone and 82% anhydrous methanol was prepared, and the longitudinal section of the sample was immersed in the solution for 2 mm at a temperature of 0°C and electropolished for 15 seconds. Then, a scanning electron microscope was used to observe and collect images of inclusions and the voids around them on the cross section, and the energy spectrum was used to detect the composition of the inclusions, as shown in Figure 1(b). The size of the inclusions and the area of ​​the voids around them were calculated by image software, and the inclusion shrinkage coefficient CC was introduced as an inclusion evaluation parameter: The calculated CC value was 23.5%.

[0060] Set 800MPa, 775MPa and 750MPa as the maximum stress, and perform 12 rotation bending fatigue tests according to HB5152-96. The sample size is as follows: Figure 2 , the size of inclusions at the origin of fatigue fracture cracks was observed and measured by scanning electron microscopy, as shown in Figure 3(b). The sum of the size of the inclusions and the voids around them was taken as the initial size of the fatigue origin crack, and the calculation was corrected by combining the grain slip energy theory and the classic Paris formula, and considering that the crack size at the junction of the steady-state crack extension and the unsteady-state crack extension is much larger than the initial size of the fatigue origin crack, the cross section of the Al2O3-CaO-CaS type high melting point hard inclusions is considered to be circular, that is, By bringing in the 12 times rotational bending fatigue life, the diameter of inclusions at the origin of fatigue fracture cracks and the CC value of the inclusions, the elastic modulus E of the spring steel is 210 GPa, the metal shear modulus G is 80 GPa, and the metal microhardness HV is 508, and through iterative calculations using MATLAB software, the prediction model for the rotational bending fatigue test is obtained as follows:

[0061]

[0062] The errors between the 12 sets of experimental data and the model calculation are all within 4.8%, as shown in Figure (4b), proving that the model has a high prediction accuracy.

[0063] The description of different advantageous arrangements has been presented for purposes of illustration and description, but the description is not intended to be exclusive or limited to examples of the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art. Additionally, different advantageous examples may describe different advantages over other advantageous examples. The selected example or examples are chosen and described in order to best illustrate the principles of the examples, the practical application, and to enable those of ordinary skill in the art to understand the disclosure with various examples with various modifications suitable for the particular use contemplated.

Claims

1. A method for establishing a rotational bending fatigue life prediction model for a part containing inclusions, characterized in that: The following steps are involved: Step 1, obtaining samples from the metal parts of the same batch to be analyzed, and taking samples from the ends and / or the middle of the metal parts, and grinding and polishing the longitudinal section of each sample; Step 2: Electrolytically polish the longitudinal section of each sample, observe and collect pictures of inclusions and voids around the inclusions on the longitudinal section through a scanning electron microscope, detect the composition of the inclusions using an energy spectrum, calculate the size of the inclusions and the area of ​​the voids around the inclusions through an image software, and calculate the inclusion shrinkage coefficient CC, the formula is: S 空 is the void area around the inclusion, in μm 2 ; S 夹 is the inclusion area, unit: μm 2 ; The inclusion shrinkage coefficient CC is used as the inclusion evaluation parameter; Step 3: Perform a rotating bending fatigue test on each sample, observe and measure the size of inclusions at the origin of fatigue fracture cracks through a scanning electron microscope, and obtain rotating bending fatigue test data; take the sum of the size of the inclusions and the surrounding voids as the initial size of the fatigue origin crack, and perform a correction calculation based on the grain slip energy theory and the Paris formula to form a prediction model for the rotating bending fatigue life of the metal parts containing inclusions corresponding to the sample. Prediction model for rotating bending fatigue life containing inclusions.

2. The method for establishing a rotary bending fatigue life prediction model for a workpiece containing inclusions according to claim 1, characterized in that: The electrolytic polishing process in step 2 is: the sample is used as the anode and the copper sheet is used as the cathode, and the distance is 4cm to 6cm, respectively connected to the positive and negative electrodes of the voltage-stabilized power supply (range is 0.5V to 1V); a solution of 3% to 5% benzyltriethylammonium chloride, 12% to 17% methyl isobutyl ketone and 78% to 85% anhydrous methanol is prepared, and the longitudinal section of the sample is immersed in the solution by 1mm to 3mm at a temperature of 0℃ to 4℃, and the electrolytic polishing time is 10s to 20s.

3. The method for establishing a rotary bending fatigue life prediction model for a workpiece containing inclusions according to claim 1, characterized in that: In step 1, samples are taken from one end, 1 / 4 length position, 1 / 2 length position, 3 / 4 length position and the other end of the disk, round rod and / or plate.

4. The method for establishing a rotary bending fatigue life prediction model for a workpiece containing inclusions according to claim 1, characterized in that: The longitudinal cross-sectional area of ​​the sample is 1 cm 2 , and then ground with 60 mesh, 400 mesh, 800 mesh, 1500 mesh and 2000 mesh sandpaper in sequence, and mechanically polished with polishing paste with a particle size of 1.5μm.

5. The method for establishing a rotary bending fatigue life prediction model for a workpiece containing inclusions according to claim 1, characterized in that: The fatigue life recorded in step 3 is equal to the internal fatigue crack initiation life + internal fatigue crack growth life, that is: N f =N i +N p , N f is fatigue life, N i is the internal fatigue crack initiation life, N p Internal fatigue crack growth life.

6. The method for establishing a rotary bending fatigue life prediction model for a workpiece containing inclusions according to claim 1, characterized in that: The grain slip energy theory and Paris formula are combined to make a modified calculation, considering that the crack size at the junction of steady-state crack extension and unsteady-state crack extension is much larger than the initial size of fatigue origin crack; According to the inclusion shrinkage coefficient CC and fatigue strength calculation method, for low melting point plastic inclusions, its cross section is regarded as an ellipse, S 夹 =π×a×b, a is the inclusion length, μm; b is the inclusion width, μm; for hard inclusions with high melting points, their cross sections are regarded as circular, d is the inclusion diameter, μm; fatigue test stress value Δσ, MPa; geometric constant β1, Metal elastic modulus E, GPa; metal shear modulus G, GPa; microhardness HV; Establish the rotating bending fatigue life N of plastic inclusions f1 The prediction model is: Establish the rotating bending fatigue life N of hard inclusions f2 The prediction model is: The rotation bending fatigue test data was substituted into the above model and iterated through MATLAB software to make the function satisfy △K th , C and n values, and the results are fed back to the established metal rotation bending fatigue life N f1 Prediction model and rotary bending fatigue life of metals containing hard inclusions f2 In the prediction model, a prediction model for the rotary bending fatigue life of metal parts containing inclusions is obtained.

7. The method for establishing a rotary bending fatigue life prediction model for a workpiece containing inclusions according to claim 1, characterized in that: The rotating bending fatigue test data include the rotating bending fatigue life, a is the inclusion length, b is the inclusion width and diameter, and the inclusion shrinkage coefficient CC value.

8. The method for establishing a rotary bending fatigue life prediction model for a workpiece containing inclusions according to claim 1, characterized in that: The rotating bending fatigue test data include the rotating bending fatigue life, the inclusion diameter d and the diameter and inclusion shrinkage coefficient CC value.

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