Method for hot necking spinning of 34crmo4 steel cylindrical part based on finite element simulation

Abstract

The application discloses a 34CrMo4 steel cylindrical part hot necking spinning method based on finite element simulation and belongs to the technical field of metal plastic forming.The method comprises the following steps: 1, establishing a spinning three-dimensional model; 2, establishing a constitutive model, inputting a constitutive equation into finite element software, inputting material parameters, and performing contact setting on the three-dimensional model; 3, obtaining an arc line spinning track, adding the arc line spinning track to the motion track of a spinning wheel, adding boundary conditions on a pipe blank, using quality scaling, and performing mesh division on the pipe blank; and 4, performing finite element simulation on the spinning three-dimensional model to obtain a final spinning simulation result.The application can save a large amount of simulation time by performing finite element simulation, adopting a spinning wheel revolution model and using quality scaling technology; the hot necking spinning simulation of the cylindrical part can be performed through the arc line spinning track in different passes, the material flow can be slowed down, the thickness of the necking spinning part can be more uniformly distributed, and the forming quality of the necking spinning part of the gas cylinder head can be improved.

Description

Technical Field

[0001] This invention belongs to the field of metal plastic forming technology, specifically relating to a hot-dip spinning method for 34CrMo4 steel cylindrical parts based on finite element simulation. Background Technology

[0002] 34CrMo4 steel has high endurance strength and creep strength at high temperatures, good impact toughness at low temperatures, good hardenability, no tendency to overheat, small quenching deformation, and good plasticity when cold-formed. It is used as an important structural component working under high loads and is widely used in aerospace, military, automotive and other fields.

[0003] Spin forming is a continuous, localized forming method that integrates the characteristics of traditional metal pressure processing. It features high material utilization and low processing costs. The spin forming process for high-pressure gas cylinder heads involves radial compression, which causes the diameter of the tube blank to continuously decrease. This results in poor forming effect at the forming end, severe wrinkling, and instability at the free end of the forming end.

[0004] Current research indicates that a significant factor contributing to variations in the quality of spun forming at the necking point is the trajectory of the spinning wheel, as different spinning trajectories result in varying stress levels. Furthermore, the spun forming simulation is a moldless spun forming process. Without a mandrel for support, this method can lead to uneven wall thickness distribution at the necking point, causing stress concentration and instability, ultimately resulting in spun forming defects.

[0005] Traditional verification spinning methods involve numerous spinning tests on blanks. When spinning defects are found, the process is repeatedly modified and repeated tests are conducted. This not only consumes a lot of manpower, material resources, and financial resources, but also leads to an indefinite extension of the production time to obtain qualified products. Summary of the Invention

[0006] In view of the above-mentioned problems in the existing technology, the purpose of this invention is to provide a hot-closing spinning method for 34CrMo4 steel cylindrical parts based on finite element simulation. By analyzing the spinning quality through simulation results, the spinning process parameters are adjusted to ensure the reliability and stability of the spun parts.

[0007] This invention provides the following technical solution:

[0008] The hot-dip spinning method for 34CrMo4 steel cylindrical parts based on finite element simulation includes the following steps:

[0009] S1. Based on the hot-closing spinning process of 34CrMo4 steel cylindrical parts, a simplified finite element model is established to create a three-dimensional spinning model of the spinning wheel, fixture, and tube blank to be processed.

[0010] S2. A constitutive model of 34CrMo4 steel is established through hot compression tests. The constitutive equations in the model are input into the finite element software, along with the material parameters of 34CrMo4 steel. Contact settings are then applied to the three-dimensional model. The contact settings employ a rotary revolution model.

[0011] S3. Determine the arc-shaped spinning trajectory based on the outer contour line of the final spun part, and add the obtained arc-shaped spinning trajectory to the motion trajectory of the spinning wheel; at the same time, add boundary conditions on the tube blank, use mass scaling, and mesh the tube blank.

[0012] S4. Perform a multi-pass arc-shaped spinning trajectory hot-closing spinning finite element simulation on the three-dimensional spinning model. After the last spinning pass is completed, the final spinning simulation result is obtained.

[0013] Furthermore, in the spinning 3D model, the fixture and spinning wheel are set as rigid bodies, and the tube blank is set as a deformable solid.

[0014] Furthermore, in the constitutive model, the expression for the constitutive equation is as follows:

[0015]

[0016] Where A is the initial yield strength, B is the hardening parameter, n is the hardening exponent, m is the thermal softening parameter, and T is the initial yield strength. melt T0 is the melting temperature, and T0 is the reference temperature; ε P For equivalent plastic strain, This is the equivalent plastic strain rate; is the reference strain rate of the material; T is the temperature.

[0017] Furthermore, the quality scaling involves adjusting the density of some elements, thereby amplifying the time increment to improve computational efficiency; this is used for Dynamic Explicit problems.

[0018] Furthermore, the process of obtaining the arc-shaped spinning trajectory is as follows:

[0019] Based on the initial tube blank diameter and the final taper diameter, the outer contour line of the head of the formed part is drawn using Origin software. Several points are taken on this curve and input into the finite element software as the spinning trajectory of the spinning wheel.

[0020] Furthermore, the boundary conditions include a temperature field, which is added to the tube blank based on the actual spinning temperature, and the temperature field is divided into dynamic meshes; the dynamic meshes are divided using hexahedral elements.

[0021] Furthermore, the spinning process in the spinning finite element simulation includes multiple passes. Each pass's spinning wheel includes axial and radial feeds. The spinning wheel performs converging spinning along the arc direction. After the last pass is completed, the final spun part is obtained.

[0022] Furthermore, the feed rate for each pass in multi-pass spinning is defined using amplitude curves in finite element software.

[0023] Furthermore, in the multi-pass spinning simulation, when each pass is completed and the next pass is entered, the simulation results of the previous pass need to be added to the billet model of the next pass.

[0024] By employing the above-described technology, the beneficial effects of the present invention compared to the prior art are as follows:

[0025] This invention proposes to use a rotary wheel revolution model instead of the traditional fixture-driven billet rotation model through finite element simulation, and to save a significant amount of simulation time by using mass scaling technology. By simulating the hot-dip spinning of 34CrMo4 steel cylindrical parts through a multi-pass arc-shaped spinning trajectory, the material flow can be slowed down, resulting in a more uniform thickness distribution in the spun-dip section and improving the forming quality of the gas cylinder end cap spinning part. Compared to traditional spinning tests, the analysis of the hot spinning process using finite element simulation in this invention saves time, manpower, and financial resources. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the multi-pass hot-sealing spinning path of a cylindrical part in an example of the present invention, where O1 represents the first pass spinning of the bottle neck, O2 represents the second pass spinning of the bottle neck, and O3 represents the third pass spinning of the bottle neck.

[0027] Figure 2 This is a schematic diagram of the self-rotating model of the hot-dip spinning wheel for multi-pass 34CrMo4 steel cylindrical parts in an example of the present invention;

[0028] Figure 3 This is a finite element simulation result of the first pass of hot-dip spinning of a multi-pass 34CrMo4 steel cylindrical part in an example of the present invention.

[0029] Figure 4 This is a finite element simulation result of the second pass of hot-dip spinning of a multi-pass 34CrMo4 steel cylindrical part in an example of the present invention.

[0030] Figure 5 The figure shows the finite element simulation results of the third pass of hot-dip spinning of a multi-pass 34CrMo4 steel cylindrical part in an example of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] Conversely, this invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the invention as defined in the claims. Furthermore, to provide a better understanding of the invention, certain specific details are described in detail below. However, those skilled in the art will fully understand the invention even without these detailed descriptions.

[0033] Please see Figures 1-5 This example provides a method for hot-dip spinning of 34CrMo4 steel cylindrical parts based on finite element simulation, which includes the following steps:

[0034] Step 1: Based on the actual hot-drying and spinning process of 34CrMo4 steel cylindrical parts, after reasonably simplifying the finite element model, establish a three-dimensional model of the spinning wheel, fixture, and tube blank to be processed. Figure 2 Assembly drawing of a three-dimensional model for multi-pass hot-dip spinning;

[0035] In this step, since the tube blank is heated to a high temperature during spinning, the rigidity of the spinning wheel and the fixture is much greater than that of the tube blank. Therefore, in the three-dimensional model, the spinning wheel and the fixture are set as rigid bodies, and the tube blank is set as a deformable solid.

[0036] Step 2: Input the constitutive model of 34CrMo4 established through hot compression test into the finite element model, add relevant material properties, and then assign the material property Tube blank to the tube blank geometry;

[0037] In this step, the constitutive equation of the constitutive model of 34CrMo4 is expressed as follows:

[0038]

[0039] Where A is the initial yield strength, B is the hardening parameter, n is the hardening exponent, m is the thermal softening parameter, and T is the initial yield strength. melt T0 is the melting temperature, and T0 is the reference temperature; ε P For equivalent plastic strain, This is the equivalent plastic strain rate; The reference strain rate of the material is T; T is the temperature.

[0040] According to the experimental results, in the constitutive equation of 34CrMo4, the initial yield strength A is 842.6 MPa, the hardening parameter B is 564.5 MPa, the hardening index n is 0.7, the thermal softening parameter m is 1.6, the melting temperature is 1515℃, and the reference temperature is 25℃.

[0041] Step 3: When setting up the contact action in the finite element model, map the wheel reference point onto the axis of the tube blank to obtain the projection point of the wheel reference point. Connect the reference point and the projection point to create a line feature. This line feature can be defined as the revolution radius line of the wheel.

[0042] The setting of line features in this step can define the revolution and rotation of the wheel around which it revolves, thus obtaining the wheel's revolution model;

[0043] Step 4: When setting the load in the finite element model, assign an arc-shaped spinning trajectory to the spinning wheel according to the actual spinning process; Figure 1 A schematic diagram of the hot-dip spinning path for multi-pass cylindrical parts;

[0044] In this step, the arc spinning trajectory is based on the initial tube blank diameter and the final spun part diameter. The outer contour line of the head of the formed part is drawn using Origin software, and several points are taken on this curve and input into the finite element software as the spinning trajectory of the spinning wheel.

[0045] Step 5: When setting the load in the finite element model, add the actual temperature field to the billet according to the actual spinning process, and define the spinneret feed amount for each pass through the amplitude curve in the finite element software.

[0046] In this step, the amplitude curve is defined based on several points taken when drawing the outer contour line of the head and input into the finite element software. The feed amount for each pass is allocated according to the amplitude curve when setting the load.

[0047] Step 6: Perform dynamic mesh generation on the 3D model of the tube blank;

[0048] In this step, the dynamic mesh of the tube blank is generated using hexahedral elements, with the element type selected as C3D8R, and adaptive mesh generation is used.

[0049] Step 7: Perform finite element simulation of hot-closing spinning with multiple passes of arc-shaped spinning trajectory on the three-dimensional spinning model, and obtain the final spinning simulation results; Figures 3-5 The figures show the finite element simulation results for the first, second, and third passes of hot-dip spinning.

[0050] In this step, during the multi-pass spinning simulation, when each pass is completed and the next pass is started, the simulation results of the previous pass need to be added to the billet model of the next pass. Each pass of the spinning wheel includes axial feed and radial feed. Macroscopically, the spinning wheel performs converging spinning along the arc direction. After the last pass is completed, the final spun part is obtained.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hot-dip spinning method for 34CrMo4 steel cylindrical parts based on finite element simulation, characterized in that, Includes the following steps: S1. Based on the hot-closing spinning process of 34CrMo4 steel cylindrical parts, a simplified finite element model is established to create a three-dimensional spinning model of the spinning wheel, fixture, and tube blank to be processed. S2. A constitutive model of 34CrMo4 steel is established through hot compression tests. The constitutive equations in the model are input into the finite element software, along with the material parameters of 34CrMo4 steel. Contact settings are then applied to the three-dimensional model. The contact settings employ a rotary revolution model. S3. Determine the arc-shaped spinning trajectory based on the outer contour line of the final spun part, and add the obtained arc-shaped spinning trajectory to the motion trajectory of the spinning wheel; at the same time, add boundary conditions on the tube blank, use mass scaling, and mesh the tube blank. S4. Perform a multi-pass arc-shaped spinning trajectory hot-closing spinning finite element simulation on the three-dimensional spinning model. After the last spinning pass is completed, the final spinning simulation result is obtained. In the constitutive model, the constitutive equation is expressed as follows: ； in The initial yield strength, These are hardening parameters. The hardening index, For thermal softening parameters, The melting temperature. For reference temperature; For equivalent plastic strain, This is the equivalent plastic strain rate; The reference strain rate for the material; For temperature; The spinning process in the finite element simulation includes multiple passes. Each pass has a spinning wheel with both axial and radial feeds. The spinning wheel performs converging spinning along an arc direction. After the last pass is completed, the final spun part is obtained.

2. The hot-dip spinning method for 34CrMo4 steel cylindrical parts based on finite element simulation according to claim 1, characterized in that... In the spinning 3D model, the fixture and spinning wheel are set as rigid bodies, and the tube blank is set as a deformable solid.

3. The hot-dip spinning method for 34CrMo4 steel cylindrical parts based on finite element simulation according to claim 1, characterized in that... The mass scaling is used to adjust the density of some elements, thereby amplifying the time increment to improve computational efficiency; it is used for Dynamic Explicit problems.

4. The hot-dip spinning method for 34CrMo4 steel cylindrical parts based on finite element simulation according to claim 1, characterized in that... The process of obtaining the arc-shaped spinning trajectory is as follows: Based on the initial tube blank diameter and the final closing diameter, the outer contour line of the head of the formed part is drawn using Origin software. Several points are taken on this curve and input into the finite element software as the spinning trajectory of the spinning wheel.

5. The hot-dip spinning method for 34CrMo4 steel cylindrical parts based on finite element simulation according to claim 1, characterized in that... The boundary conditions include a temperature field, which is added to the tube blank based on the actual spinning temperature. The temperature field is divided into dynamic meshes, which are divided using hexahedral elements.

6. The hot-dip spinning method for 34CrMo4 steel cylindrical parts based on finite element simulation according to claim 1, characterized in that... In multi-pass spinning, the feed rate for each pass is defined using amplitude curves in finite element software.

7. The hot-dip spinning method for 34CrMo4 steel cylindrical parts based on finite element simulation according to claim 1, characterized in that... In multi-pass spinning simulation, when each pass is completed and the next pass is started, the simulation results of the previous pass need to be added to the billet model of the next pass.

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