A method and model for predicting delamination defects in a high-temperature alloy pierce process

Abstract

The application relates to a high-temperature alloy cross-piercing process interlayer defect prediction method and model, and particularly relates to a high-temperature alloy cross-piercing process interlayer defect prediction method and model, which comprises the following steps: establishing a high-temperature alloy cross-piercing finite element model, and performing high-temperature alloy cross-piercing finite element simulation; extracting all data of equivalent strain, temperature, strain rate, maximum shear strain, stress triaxiality, maximum shear stress, equivalent stress and maximum shear strain at the moment of deformation termination in the whole deformation process; calculating integral to determine damage value, average temperature and average strain rate; and performing high-temperature alloy compression-shear deformation experiments under the average temperature and average strain rate determined in the previous step. The application can predict engineering fracture problems in an actual deformation process through simple compression-shear hot simulation deformation experiments and finite element simulation technology, reduces the trial-and-error process in the actual production process, and saves manpower, material resources and financial resources.

Description

Technical Field

[0001] This invention relates to the field of delamination defect prediction, specifically to a method and model for predicting delamination defects in the piercing process of high-temperature alloy skew rolling. Background Technology

[0002] Skew rolling piercing: Skew rolling piercing is a forming process that uses localized, continuous plastic deformation to transform solid bars into hollow seamless tubes. Due to its advantages of high material utilization, low forming load, and high production efficiency, it has been applied to the manufacture of seamless tubes from advanced materials such as alloy steel, aluminum alloys, titanium alloys, and magnesium alloys. However, because high-temperature alloys have high deformation resistance, narrow processing windows, poor deformation penetration, and their microstructure is sensitive to temperature and strain rate, the use of this technology to prepare nickel-based high-temperature alloy seamless tubes has not yet been industrialized. Delamination defects are the direct cause of this situation, essentially due to the lack of a method for predicting external delamination defects in skew rolling piercing of high-temperature alloys.

[0003] Delamination defects: Delamination defects are arc-shaped or annular cracks of a certain width parallel to the inner and outer surfaces of the pipe wall. They mainly occur in special steels and high-temperature alloys. Depending on their location, delamination defects are further divided into "external delamination defects" and "internal delamination defects." Annular cracks near the outer surface of the pipe are called external delamination defects, and annular cracks near the inner surface are called internal delamination defects. Generally speaking, external delamination defects occur in the region r / R = 0.8-0.9, and internal delamination defects occur in the region r / R = 0.1-0.2. Here, r refers to the distance from the sampling point to the center of the billet, and R refers to the radius of the billet.

[0004] Existing technologies lack a method for predicting delamination defects during the skew rolling piercing process of high-temperature alloys. Among similar technologies, patent 201910196012.9 mentions setting the mandrel extension of the push rod to 5mm-15mm, the feed angle of the two-roll skew rolling piercing mill to 8°-15°, the rolling angle to 15°, the reduction rate to 7%-17%, and the roll speed to 30r / min-40r / min to avoid external delamination defects. However, this patent only relates to process parameters that can avoid external delamination defects and does not describe a method for predicting delamination defects. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method and model for predicting delamination defects in the piercing process of high-temperature alloys through simple compression-shear-thermal simulation deformation experiments and finite element simulation technology. This method can predict engineering fracture problems in actual deformation processes, reduce trial and error in actual production, and save manpower, material resources, and financial resources.

[0006] This invention provides a method for predicting delamination defects during the piercing process of high-temperature alloy skew rolling, comprising the following steps:

[0007] (1) Establish a finite element model of skew rolling piercing of high-temperature alloy and perform finite element simulation of skew rolling piercing of high-temperature alloy to extract the equivalent strain ε, temperature T, and strain rate during the entire deformation process. Maximum shear strain Stress triaxiality Maximum shear stress Equivalent stress and the maximum shear strain at the end of deformation Substitute all the data into the following formula to calculate the integral and determine the damage value D;

[0008] ;

[0009] In the formula, Represents the positive operation, when When it is greater than zero, then equal ,when When less than or equal to zero, then The value is 0;

[0010] The average temperature is calculated using the following formula:

[0011] ;

[0012] The average strain rate is calculated using the following formula:

[0013] ;

[0014] (2) Conduct high-temperature alloy compression-shear deformation experiments at the average temperature and average strain rate determined in step (1) to determine the axial compression at the moment of material fracture. Then, establish a finite element model of compression-shear deformation and perform finite element simulation of compression-shear deformation. Extract the stress triaxiality during the compression-shear process to determine the axial compression at the moment of material fracture. Maximum shear stress Equivalent stress Maximum shear strain and the maximum shear strain at the end of deformation The damage threshold of high-temperature alloys is determined by the following formula;

[0015] ;

[0016] In the formula, Represents the positive operation, when When it is greater than zero, then equal ,when When less than or equal to zero, then The value is 0;

[0017] In the formula Indicates the damage threshold;

[0018] (3) Based on the D value determined in steps (1) and (2) and The value is substituted into the following formula to solve for the damage. :

[0019] ;

[0020] according to The result determines whether a delamination defect has occurred: If If the value is greater than or equal to 1, then a delamination defect will occur during the skew rolling piercing process of this high-temperature alloy. If the value is less than 1, then no delamination defect will occur during the skew rolling piercing process of this high-temperature alloy.

[0021] Preferably, the finite element model includes a geometric model, a material model, and boundary conditions established using 3D modeling software based on the geometric parameters in the corresponding deformation process;

[0022] The material model includes thermal parameters and mechanical parameters. The thermal parameters include thermal conductivity obtained by a thermal conductivity meter and specific heat capacity measured by a specific heat capacity meter.

[0023] The mechanical parameters include Young's model and flow stress curves measured using a Gleeble thermal simulation tester;

[0024] The boundary conditions are: a friction factor of 0.85 and a heat transfer coefficient between the billet and the die of 10000 W / (m²). 2 ·K), the heat transfer coefficient between the billet and air is 50W / (m). 2 (K), the sample uses a ring grid.

[0025] A prediction model, obtained using a method for predicting delamination defects in the piercing process of high-temperature alloy skew rolling, is as follows:

[0026] ,

[0027] In the formula For damage, ε, , , , , The equivalent strain ε and maximum shear strain are obtained from the finite element simulation of the entire deformation process during the skew rolling piercing of high-temperature alloys. Stress triaxiality Maximum shear stress Equivalent stress and the maximum shear strain at the end of deformation ;

[0028] In the formula, Represents the positive operation, when When it is greater than zero, then equal ,when When less than or equal to zero, then The value is 0.

[0029] This invention can predict engineering fracture problems in actual deformation processes through simple compression-shear-thermal simulation experiments and finite element simulation technology, thereby reducing the trial-and-error process in actual production and saving human, material, and financial resources. Attached Figure Description

[0030] Figure 1 This is the front view of the geometric model of the GH4169 alloy skew rolling piercing finite element model in the embodiment.

[0031] Figure 2 for Figure 1 The left view.

[0032] Figure 3 for Figure 1 Top view.

[0033] Figure 4 This is a schematic diagram of the flow stress curve of the GH4169 alloy skew rolling piercing finite element model in the embodiment.

[0034] Figure 5 This is a front view of the GH4169 alloy compression-shear deformation test specimen in the example.

[0035] Figure 6 for Figure 5 The left view.

[0036] Figure 7 for Figure 5 AA view.

[0037] Figure 8 The image shows the compression-shear isometric view of the GH4169 alloy compression-shear deformation test specimen in the example.

[0038] Figure 9 The image shows the actual specimen of the GH4169 alloy compression-shear deformation test sample in the example, with an axial compression of 2 mm.

[0039] Figure 10 The image shows the actual specimen of the GH4169 alloy compression-shear deformation test sample in the example, with an axial compression of 3 mm.

[0040] Figure 11The image shows the actual specimen of the GH4169 alloy compression-shear deformation test sample in the example, with an axial compression of 4 mm.

[0041] Figure 12 This is the geometric model of the finite element simulation of the compression-shear deformation of the GH4169 alloy in the example.

[0042] Figure 13 This is a schematic diagram illustrating the delamination defect generated during the skew rolling piercing process of GH4169 alloy in the example.

[0043] Figure 14 This is a schematic diagram illustrating the damage evolution in the region r / R=0-1 under the critical parameter of delamination defects.

[0044] Figure 15 This is a schematic diagram illustrating the damage evolution in the region r / R=0.75-1 under the critical parameter of delamination defect.

[0045] Figure 16 To verify the damage in the embodiments Actual product image.

[0046] Figure 17 To verify the damage in the embodiments Actual product image.

[0047] Figure 18 To verify the damage in the embodiments Actual product image. Detailed Implementation

[0048] This invention provides a method for predicting delamination defects during the piercing process of high-temperature alloy skew rolling, comprising the following steps:

[0049] (1) Establish a finite element model of skew rolling piercing of high-temperature alloy and perform finite element simulation of skew rolling piercing of high-temperature alloy to extract the equivalent strain ε, temperature T, and strain rate during the entire deformation process. Maximum shear strain Stress triaxiality Maximum shear stress Equivalent stress and the maximum shear strain at the end of deformation Substitute all the data into the following formula to calculate the integral and determine the damage value D;

[0050] ;

[0051] In the formula, Represents the positive operation, when When it is greater than zero, then equal ,when When less than or equal to zero, then The value is 0;

[0052] The average temperature is calculated using the following formula:

[0053] ;

[0054] The average strain rate is calculated using the following formula:

[0055] ;

[0056] (2) Conduct high-temperature alloy compression-shear deformation experiments at the average temperature and average strain rate determined in step (1) to determine the axial compression at the moment of material fracture. Then, establish a finite element model of compression-shear deformation and perform finite element simulation of compression-shear deformation. Extract the stress triaxiality during the compression-shear process to determine the axial compression at the moment of material fracture. Maximum shear stress Equivalent stress Maximum shear strain and the maximum shear strain at the end of deformation The damage threshold of high-temperature alloys is determined by the following formula;

[0057]

[0058] In the formula, Represents the positive operation, when When it is greater than zero, then equal ,when When less than or equal to zero, then The value is 0;

[0059] In the formula Indicates the damage threshold;

[0060] (3) Based on the D value determined in steps (1) and (2) and The value is substituted into the following formula to solve for the damage. :

[0061] ;

[0062] according to The result determines whether a delamination defect has occurred: If If the value is greater than or equal to 1, then a delamination defect will occur during the skew rolling piercing process of this high-temperature alloy. If the value is less than 1, then no delamination defect will occur during the skew rolling piercing process of this high-temperature alloy.

[0063] The finite element model includes the geometric model, material model, and boundary conditions established using 3D modeling software based on the geometric parameters in the corresponding deformation process;

[0064] The material model includes thermal parameters and mechanical parameters. The thermal parameters include thermal conductivity obtained by a thermal conductivity meter and specific heat capacity measured by a specific heat capacity meter.

[0065] The mechanical parameters include Young's model and flow stress curves measured using a Gleeble thermal simulation tester;

[0066] The boundary conditions are: a friction factor of 0.85 and a heat transfer coefficient between the billet and the die of 10000 W / (m²). 2 ·K), the heat transfer coefficient between the billet and air is 50W / (m). 2 ·K).

[0067] A prediction model, obtained using a method for predicting delamination defects in the piercing process of high-temperature alloy skew rolling, is as follows:

[0068] ,

[0069] In the formula For damage, ε, , , , , The equivalent strain ε and maximum shear strain are obtained from the finite element simulation of the entire deformation process during the skew rolling piercing of high-temperature alloys. Stress triaxiality Maximum shear stress Equivalent stress and the maximum shear strain at the end of deformation ;

[0070] In the formula, Represents the positive operation, when When it is greater than zero, then equal ,when When less than or equal to zero, then The value is 0.

[0071] Example 1

[0072] The locations of external delamination defects are all within the range of r / R = 0.8-0.9, where r refers to the distance from the sampling point to the center of the billet, and R refers to the radius of the billet. Taking the data extracted at r / R = 0.85 as an example:

[0073] (1) Establish the finite element model of GH4169 alloy skew rolling piercing: including material model, geometric model and boundary conditions.

[0074] Based on the geometric parameters of the rolls, guide plates, mandrels, and pushers in the skew rolling piercing process, a 3D model of the deformation tool is drawn using 3D modeling software and its assembly is completed. This model is then imported into finite element simulation software to construct a geometric model, such as... Figure 1-3 As shown, the billet is located between two rolls and a guide plate, and the skew rolling piercing deformation is achieved by using a mandrel and a pusher block;

[0075] The material model includes: thermal parameters and mechanical parameters.

[0076] The thermal parameters include thermal conductivity and specific heat capacity, which are measured using a thermal conductivity meter and a specific heat capacity meter.

[0077] The mechanical parameters, including Young's model and flow stress curves, were determined using a Gleeble thermal simulation testing machine. The determined data are as follows:

[0078] physical quantity numerical values Young's modulus (GPa) 208.46–0.094× Thermal conductivity (W / (m·°C)) 12.58+0.016× Specific heat capacity (J / (kg·°C)) 361.21+0.326×

[0079] Flow stress curve as shown Figure 4 As shown;

[0080] The boundary conditions are: a friction factor of 0.85 and a heat transfer coefficient between the billet and the die of 10000 W / (m²). 2 K), the heat transfer coefficient between the billet and air is 50 W / (m²). 2 (K), the sample uses a ring grid.

[0081] Then, finite element numerical simulation is performed to extract the equivalent strain ε, temperature T, and strain rate throughout the deformation process. Maximum shear strain Stress triaxiality Maximum shear stress Equivalent stress and the maximum shear strain at the end of deformation Substitute all the data into the following formula to calculate the integral and determine the damage value D;

[0082] ;

[0083] In the formula, Represents the positive operation, when When it is greater than zero, then equal ,when When less than or equal to zero, then The value is 0;

[0084] The average temperature is calculated using the following formula:

[0085] ;

[0086] The average strain rate is calculated using the following formula:

[0087] ;

[0088] The calculated average temperature is 1150℃, the average strain rate is 10 / s, and the calculated D value is 0.3.

[0089] (2) Based on the average temperature and average strain rate determined in step (1), a high-temperature alloy compression-shear deformation experiment with the same temperature and strain rate is conducted to determine the compression amount corresponding to the material fracture time.

[0090] A schematic diagram of the compression-shear deformation test specimen of GH4169 alloy, as shown below. Figure 5-8 As shown, the compression-shear deformation test of GH4169 alloy was completed on a Gleeble 3500 thermal simulation testing machine. The compression at the fracture point was determined by gradually increasing the deformation amount. The critical compression determined by the experiment was 3 mm. Figures 9-11 This is a photograph of the actual specimen of GH4169 alloy subjected to compression-shear deformation test.

[0091] Then, a finite element model of the compression-shear deformation of GH4169 alloy was established, and the compression-shear deformation finite element simulation was performed. The geometric model is as follows: Figure 12 As shown, the sample is located between the top mold and the bottom mold;

[0092] The material model includes: thermal parameters and mechanical parameters.

[0093] The thermal parameters include thermal conductivity and specific heat capacity, which are measured using a thermal conductivity meter and a specific heat capacity meter.

[0094] The mechanical parameters, including Young's model and flow stress curves, were determined using a Gleeble thermal simulation testing machine.

[0095] The confirmed data is as follows:

[0096] physical quantity numerical values Young's modulus (GPa) 208.46–0.094× Thermal conductivity (W / (m·°C)) 12.58+0.016× Specific heat capacity (J / (kg·°C)) 361.21+0.326×

[0097] Boundary conditions for finite element simulation of compression-shear deformation: The lower die remains stationary while the upper die moves downward to compress the specimen to achieve the compression-shear deformation process. The compression-shear specimen uses a tetrahedral mesh.

[0098] Finite element numerical simulation was performed at a temperature of 1150℃, a strain rate of 10 / s, and an axial compression of 3 mm. The stress triaxiality during this process was extracted. Maximum shear stress Equivalent stress Maximum shear strain and the maximum shear strain at the end of deformation The damage threshold of GH4169 alloy is determined to be 0.29 using the following formula:

[0099] ;

[0100] (3) Based on the D value determined in steps (1) and (2) and The value is substituted into the following formula to solve for the damage. :

[0101] ;

[0102] get .because Therefore, the skew rolling piercing process produced delamination defects, as shown in the following figure. Figure 13 As shown.

[0103] Verification comparison example:

[0104] Based on the established delamination defect prediction model, the damage evolution law of the skew rolling process under the critical process parameters of delamination defects is analyzed, and the results are as follows: Figure 14-15 As shown in the figure, the damage on the outer surface exhibits a "step-like" variation pattern due to the cyclic rolling characteristics, while the damage in the core shows a steady-state variation. Radially, the damage initially increases and then decreases from the core towards the surface, with a maximum damage of 0.98, close to the cracking critical value of 1. Therefore, the established ductile fracture model can accurately predict the cracking conditions of delamination defects during the skew rolling piercing process of GH4169 alloy.

[0105] Based on the established delamination defect prediction model, the perforation results under different parameters were compared to verify the accuracy of the established model. The results are as follows: Figure 16-18 As shown in the figure, the damage of the delamination defect prediction model can be obtained. At that time, the outer surface of the obtained pipe was severely cracked, and the surface metal was peeled off, such as Figure 16 As shown.

[0106] When injury At this point, the pipe is at the critical cracking value. While no cracking occurs on the outer surface of the pipe, cross-sectional views indicate the formation of annular cracks near the surface, a delamination defect. Figure 17 As shown.

[0107] When injury At that time, the surface quality of the obtained pipe was good, and no cracks were found in the longitudinal section. Figure 18 As shown, the results further confirm the accuracy of the established delamination defect prediction model and prediction window.

Claims

1. A method for predicting delamination defects during the piercing process of high-temperature alloy skew rolling, characterized in that, Includes the following steps: (1) Establish a finite element model of skew rolling piercing of high-temperature alloy and perform finite element simulation of skew rolling piercing of high-temperature alloy to extract the equivalent strain ε, temperature T, and strain rate during the entire deformation process. Maximum shear strain Stress triaxiality Maximum shear stress Equivalent stress and the maximum shear strain at the end of deformation Substitute all the data into the following formula to calculate the integral and determine the damage value D; ； In the formula, <> represents the positive operation, when When it is greater than zero, then equal ,when When less than or equal to zero, then The value is 0; The average temperature is calculated using the following formula: ； The average strain rate is calculated using the following formula: ； (2) Conduct high-temperature alloy compression-shear deformation experiments at the average temperature and average strain rate determined in step (1) to determine the axial compression at the time of material fracture. Then, establish a finite element model of compression-shear deformation and perform finite element simulation of compression-shear deformation. Extract the axial compression at the time of fracture and the stress triaxiality during this process. Maximum shear stress Equivalent stress Maximum shear strain and the maximum shear strain at the end of deformation The damage threshold of high-temperature alloys is determined by the following formula; ； In the formula, <> represents the positive operation, when When it is greater than zero, then equal ,when When less than or equal to zero, then The value is 0; In the formula Indicates the damage threshold; (3) Based on the D value determined in steps (1) and (2) and The value is substituted into the following formula to solve for the damage. : ； according to The result determines whether a delamination defect has occurred: If If the value is greater than or equal to 1, then a delamination defect will occur during the skew rolling piercing process of this high-temperature alloy. If the value is less than 1, then no delamination defect will occur during the skew rolling piercing process of this high-temperature alloy.

2. The method for predicting delamination defects in the piercing process of high-temperature alloy skew rolling as described in claim 1, characterized in that, The finite element model includes a geometric model, a material model, and boundary conditions established using 3D modeling software based on the geometric parameters in the corresponding deformation process. The material model includes thermal parameters and mechanical parameters. The thermal parameters include thermal conductivity obtained by a thermal conductivity meter and specific heat capacity measured by a specific heat capacity meter. The mechanical parameters include Young's modulus and flow stress curves measured using a Gleeble thermal simulation tester; The boundary conditions are: a friction factor of 0.85 and a heat transfer coefficient between the billet and the die of 10000 W / (m²). 2 ·K), the heat transfer coefficient between the billet and air is 50W / (m). 2 ·K).

3. A prediction model, characterized in that, The prediction model obtained using the prediction method for delamination defects in the piercing process of high-temperature alloys as described in claim 1 is as follows: ， In the formula For damage, ε, , , , , The equivalent strain ε and maximum shear strain are obtained from the finite element simulation of the entire deformation process during the skew rolling piercing of high-temperature alloys. Stress triaxiality Maximum shear stress Equivalent stress and the maximum shear strain at the end of deformation ; In the formula, <> represents the positive operation, when When it is greater than zero, then equal ,when When less than or equal to zero, then The value is 0.

Images