Method for manufacturing a steel tube cold-drawing die

Abstract

The application discloses a manufacturing method of a steel pipe cold-drawing die. The manufacturing method of the steel pipe cold-drawing die comprises the following steps: collecting process parameters of a reference steel pipe in an actual cold-drawing manufacturing process; establishing a reference die simulation model based on parameters of the reference die and a reference steel pipe simulation model based on parameters of the reference steel pipe before cold-drawing, performing mesh division on the reference steel pipe simulation model, and performing a steel pipe cold-drawing finite element analysis to obtain a finite element basic model; and substituting initial parameters of a target die and initial parameters of a target steel pipe into the finite element basic model, performing a cold-drawing finite element analysis, and improving the initial parameters of the target die with a product quality parameter as an optimization target to obtain optimized parameters of the target die, and then obtaining a simulation model of the target die. Compared with a large number of trial dies in the prior art, the manufacturing method of the steel pipe cold-drawing die can reduce production cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel pipe cold drawing, and particularly relates to a manufacturing method of a steel pipe cold drawing die. BACKGROUND

[0002] Drawing is a kind of processing technology of materials, and can be classified into cold drawing and hot drawing according to processing temperature. Cold drawing refers to drawing of materials at normal temperature, and cold drawing products have advantages of high size precision and good surface smoothness compared with hot drawing products. Cold drawing technology has been widely applied in production of various steel pipes.

[0003] Cold drawn steel pipes have advantages of smooth surface, good straightness, correct roundness and high strength, and are generally suitable for precision seamless steel pipes with high requirements on size precision and surface smoothness in mechanical structures and hydraulic equipment. At present, the steel pipes are drawn by using a drawing method of nesting of inner and outer dies. There are many factors affecting cold drawing quality in cold drawing production, and product quality control is relatively difficult. The die shape plays a crucial role in product quality. How to design the die shape, for example, how to determine the parameters of the entry slope of the inner and outer dies, the length of the sizing zone and the length of the die, directly affects the quality of the cold drawn products.

[0004] The design method of the traditional die mainly comes from actual production experience. In actual production process, a die design scheme with relatively good product quality can be obtained by repeatedly modifying the die, repeatedly drawing the steel pipe, and classifying, summarizing, comparing and analyzing the product quality. This experience-based design method needs a large number of trial die processes, and has problems of large material waste, high labor cost, long time consumption, and inability to observe the forming process of the product in real time, and difficulty in knowing the essence and rules of the product quality change. Especially when the material types of the cold drawn pipes are various and the sizes of the cold drawn pipes are numerous, it is a huge and headless work to design the die by using the traditional method. SUMMARY

[0005] The present application provides a manufacturing method of a steel pipe cold drawing die to improve the design efficiency of the die.

[0006] The present application provides a manufacturing method of a steel pipe cold drawing die, comprising the following steps:

[0007] Collecting process parameters of a reference steel pipe in actual cold drawing manufacturing process, the process parameters including parameters of a reference die, parameters of the reference steel pipe before cold drawing and parameters of the reference steel pipe after cold drawing;

[0008] A simulation model of the reference mold is established based on its parameters, and a simulation model of the reference steel pipe is established based on its parameters before cold drawing. The simulation model of the reference steel pipe is meshed, and a finite element analysis (FEM) of the cold drawing of the steel pipe is performed. During the FEM simulation, the friction coefficient between the steel pipe and the mold is adjusted to ensure that the product quality parameters obtained from the FEM are consistent with the parameters of the reference steel pipe after cold drawing, thus obtaining the basic finite element model.

[0009] The initial parameters of the target mold and the target steel pipe are substituted into the finite element basic model and cold drawing finite element analysis is performed. The initial parameters of the target mold are improved with the product quality parameters as the optimization target to obtain the optimized parameters of the target mold, and then the simulation model of the target mold is obtained.

[0010] In some embodiments, adjusting the friction coefficient during the finite element analysis of cold-drawn steel pipes includes using a back-calculation algorithm to adjust the friction coefficient during the finite element analysis of cold-drawn steel pipes.

[0011] In some embodiments, a conventional friction coefficient is first used to perform finite element simulation analysis and calculate the simulated pull-out force. The simulated pull-out force is then compared with the actual pull-out force. If there is a difference between the simulated pull-out force and the actual pull-out force, the friction coefficient is modified according to the difference, and the finite element simulation analysis is performed again. The above steps are repeated cyclically. When the simulated pull-out force and the actual pull-out force are consistent, the friction coefficient is the ideal friction coefficient.

[0012] In some embodiments, meshing the reference steel pipe simulation model includes setting at least sixteen mesh layers in the thickness direction of the reference steel pipe simulation model, setting the aspect ratio of the mesh element to a range of 1.5 to 1, and setting the element type to a high-order fully integral element.

[0013] In some embodiments, the reference mold simulation model is set as an elastic body, and the meshing of the reference mold simulation model includes: in the thickness direction of the reference mold simulation model, from the side where the reference mold simulation model contacts the reference steel pipe simulation model to the side away from the reference steel pipe simulation model, the mesh size of the reference mold simulation model gradually increases.

[0014] In some embodiments, the reference mold simulation model is set as a rigid body, and the establishment of the reference mold simulation model based on the parameters of the reference mold includes: modeling the part of the reference mold that contacts the reference steel pipe.

[0015] In some embodiments, establishing a simulation model of the reference mold based on the parameters of the reference mold and establishing a simulation model of the reference steel pipe based on the parameters of the reference steel pipe before cold drawing includes establishing an axisymmetric model of the reference mold based on the parameters of the reference mold, establishing an axisymmetric model of the reference steel pipe based on the parameters of the reference steel pipe before cold drawing, and performing finite element analysis of cold drawing of the steel pipe using the axisymmetric model of the reference mold and the axisymmetric model of the reference steel pipe.

[0016] In some embodiments, the length of the reference steel pipe simulation model is a portion of the actual length of the reference steel pipe.

[0017] In some embodiments, a static implicit algorithm is used for finite element analysis of cold-drawn steel pipes.

[0018] In some embodiments, displacement loading is applied to a reference steel pipe simulation model to perform finite element analysis of cold drawing of the steel pipe.

[0019] In some embodiments, collecting process parameters of the reference steel pipe in the actual cold drawing process includes sampling the material of the reference steel pipe before and after drawing and obtaining the force-displacement curve of the reference steel pipe before drawing and the force-displacement curve of the reference steel pipe after drawing through billet tensile test, and converting the force-displacement curve into an engineering stress-strain curve according to the size characteristics of the tensile specimen, and then converting the engineering stress-strain curve into a true stress-strain curve.

[0020] In some embodiments, the manufacturing method further includes producing and manufacturing the target mold using a simulation model of the target mold.

[0021] Based on the manufacturing method of cold-drawing die for steel pipes provided by this invention, a mature cold-drawing process for steel pipes is used as a reference. A simulation model is established based on the process parameters of the reference steel pipe in the actual cold-drawing manufacturing process to perform finite element analysis of cold-drawing of steel pipes to restore the actual cold-drawing process. During the finite element analysis, the friction coefficient is adjusted so that the product size, shape, stress and other parameters obtained by the finite element analysis are consistent with the actual cold-drawn steel pipe products. At this time, the finite element model can truly reflect the forming process of the actual product, and the friction coefficient at this time is the ideal friction coefficient. Thus, a basic finite element model is obtained. Then, the parameters of the target die are analyzed, designed and optimized using this basic finite element model, and a die simulation model with ideal product quality can be obtained. Compared with the existing technology that requires a large number of trial molds, the production cost can be reduced.

[0022] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0024] Figure 1 This is a schematic diagram illustrating the principle steps of a cold-drawing die for steel pipes according to an embodiment of the present invention.

[0025] Figure 2 This is a longitudinal cross-sectional view of one embodiment of the cold drawing die for steel pipes according to the present invention.

[0026] Figure 3 This represents the axial stress distribution along the wall thickness of the steel pipe under ideal drawing conditions.

[0027] Figure 4 A schematic diagram showing the setting of discrete elements and nodes on the stress distribution line.

[0028] Figure 5 The mesh on the wall thickness of the steel pipe simulation model before performing finite element analysis of the cold-drawn steel pipe.

[0029] Figure 6 Deformation of the grid lines of the steel pipe before mold optimization.

[0030] Figure 7 Deformation of the grid lines in the steel pipe after mold optimization. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, and the spatial relative descriptions used herein will be interpreted accordingly.

[0034] refer to Figure 1 In some embodiments, the manufacturing method of the cold drawing die for steel pipes of the present invention includes the following steps:

[0035] S10, Collect the process parameters of the reference steel pipe in the actual cold drawing process. The process parameters include the parameters of the reference mold, the parameters of the reference steel pipe before cold drawing, and the parameters of the reference steel pipe after cold drawing.

[0036] S20. A simulation model of the reference mold is established based on the parameters of the reference mold, and a simulation model of the reference steel pipe is established based on the parameters of the reference steel pipe before cold drawing. Mesh the simulation models of the reference mold and the reference steel pipe, and perform finite element analysis of the cold drawing of the steel pipe. The reference steel pipe and the reference mold are in contact. During the finite element simulation analysis of the cold drawing of the steel pipe, the friction coefficient between the reference steel pipe and the reference mold is adjusted to ensure that the product quality parameters obtained from the finite element simulation analysis of the cold drawing of the steel pipe are consistent with the parameters of the reference steel pipe after cold drawing, thus obtaining the basic finite element model; and

[0037] S30: Substitute the initial parameters of the target mold and the initial parameters of the target steel pipe into the finite element basic model and perform finite element analysis of cold drawing of the steel pipe. Then, use the product quality parameters of the target steel pipe obtained through the finite element analysis of cold drawing of the steel pipe as the target to improve the initial parameters of the target mold to obtain the optimized parameters of the target mold, and thus obtain the simulation model of the target mold.

[0038] The manufacturing method of the cold-drawing die for steel pipes in this invention uses a mature cold-drawing process for steel pipes as a reference. A simulation model is established based on the process parameters of the reference steel pipe in the actual cold-drawing manufacturing process to perform finite element analysis of the cold-drawing process, thus recreating the actual cold-drawing process. During the finite element analysis, the friction coefficient is adjusted so that the product dimensions, shape, and stress parameters obtained from the finite element analysis are consistent with the actual cold-drawn steel pipe product. At this point, the finite element model can accurately reflect the forming process of the actual product, and the friction coefficient at this point is the ideal friction coefficient. This yields a basic finite element model, which is then used to analyze, design, and optimize the parameters of the target die, resulting in a die simulation model with relatively ideal product quality. Compared with the prior art, which requires a large number of trial molds, this method can reduce production costs.

[0039] Among them, product quality parameters include residual stress on the product surface, roundness and straightness of the steel pipe, and deformation shape of the pipe tail.

[0040] The friction coefficient between the steel pipe and the die is one of the important input parameters for ensuring calculation accuracy. In actual drawing processes, the friction coefficient is actually a relatively stable parameter, but its determination is difficult due to the lack of sufficient measurement methods. To obtain the friction coefficient, in some embodiments, adjustments are made to the friction coefficient during the finite element analysis of the cold-drawn steel pipe, including using a back-calculation algorithm.

[0041] Specifically, the simulated pull-out force is first calculated using a conventional friction coefficient through finite element simulation. The simulated pull-out force is then compared with the actual pull-out force. If there is a difference between the simulated and actual pull-out forces, the friction coefficient is modified according to the difference, and the finite element simulation is performed again. This process is repeated until the simulated and actual pull-out forces are consistent. In this case, the friction coefficient is the ideal friction coefficient.

[0042] The process parameters used in the actual cold drawing manufacturing of steel pipes include the actual drawing force. Specifically, during the actual drawing process, the drawing force curve of the drawing machine is output.

[0043] Once the friction coefficient is determined, the basic finite element model is also determined.

[0044] In some embodiments, meshing the reference steel pipe simulation model includes setting at least sixteen mesh layers in the thickness direction of the simulation model, with the aspect ratio of the mesh elements ranging from 1.5 to 1, and setting the element type to high-order fully integral elements. Setting at least sixteen mesh layers in the thickness direction of the reference steel pipe simulation model ensures better computational accuracy. It should be noted that the aspect ratio of the mesh elements here refers to the ratio between the length and width of the mesh element. For example, an aspect ratio of 1.5 means the ratio of the length to the width of the mesh element is 1.5:1, and an aspect ratio of 1 means the ratio of the length to the width of the mesh element is 1:1.

[0045] Since the mold is always within the elastic deformation range during cold drawing, the reference mold simulation model can be set as an elastic body or a rigid body. In some embodiments, the reference mold simulation model is set as an elastic body. To ensure calculation accuracy, the meshing of the reference mold simulation model includes gradually increasing the mesh size from the side where the reference mold simulation model contacts the reference steel pipe simulation model towards the side away from the reference steel pipe simulation model. This way, the farther away from the contact point between the steel pipe and the mold, the larger the mesh size, significantly reducing the number of mold meshes and saving computation time. In other embodiments, the reference mold simulation model is set as a rigid body. In this case, only the part where the reference mold simulation model contacts the reference steel pipe simulation model needs to be modeled; other parts may not be represented in the simulation model. Figure 6 and Figure 7 In the illustrated embodiment, the reference mold simulation model is set as a rigid body. As shown in the figure, the reference mold simulation model only needs to establish the part that is in contact with the steel pipe. The reference mold simulation model seen in the figure is just two strips, and the part with the grid in the middle is the reference steel pipe simulation model.

[0046] Based on finite element analysis theory, when the geometric model, material characteristics, and loading method are all axisymmetric, the results calculated using the axisymmetric model are consistent with those calculated using the three-dimensional model. The cold drawing process of steel pipes exhibits good axisymmetry. To save computation time, in some embodiments, an axisymmetric model is used instead of a three-dimensional solid model. Specifically, establishing a reference mold simulation model based on the parameters of the reference mold and establishing a reference steel pipe simulation model based on the parameters of the reference steel pipe before cold drawing includes establishing an axisymmetric model based on the parameters of the reference mold and establishing an axisymmetric model based on the parameters of the reference steel pipe before cold drawing.

[0047] Because cold-drawn steel pipes are relatively long, the cold-drawing process is actually a smooth and uniform motion. The material deformation characteristics of a small pipe segment can usually encompass the deformation characteristics of the entire pipe segment. To save computation time, only a small segment of the pipe length needs to be analyzed. In some embodiments, the length of the reference steel pipe simulation model is a portion of the actual length of the reference steel pipe.

[0048] Furthermore, actual cold drawing is a stable and slow motion process, which can be regarded as a quasi-static process. Therefore, static implicit algorithms can be used for finite element analysis of cold drawing of steel pipes to effectively eliminate the influence of dynamic inertia on the calculation accuracy.

[0049] In some embodiments, the manufacturing method further includes producing and manufacturing the target mold using a simulation model of the target mold. After obtaining the simulation model of the target mold, it is still necessary to manufacture the target mold based on the simulation model, and then use the target mold to draw the steel pipe. Finally, the mold is modified and confirmed based on the quality of the drawn product.

[0050] The following is a detailed description of the specific steps involved in manufacturing a cold-drawing die for steel pipes, using a specific embodiment as an example.

[0051] This invention uses a mature steel pipe cold drawing process as a reference, designs a cold drawing simulation calculation model using finite element simulation technology, and uses this cold drawing simulation calculation model to guide the design of cold drawing dies.

[0052] like Figure 2 As shown, the die used for drawing steel pipe 1 includes an inner die 2 and an outer die 3. The inner die 2 includes an outer bevel angle N1, an inner bevel angle N2, a slope length N3 for the inner bevel angle, a sizing band length N4, a transition fillet N5 between the inner bevel angle and the sizing band, and a transition fillet N6 between the outer bevel angle and the inner bevel angle. The outer die 3 includes an outer bevel angle W1, an inner bevel angle W2, a slope length W3 for the inner bevel angle, a sizing band length W4, a transition fillet W5 between the inner bevel angle and the sizing band, and a transition fillet W6 between the outer bevel angle and the inner bevel angle. The longitudinal indentation of the inner die 2 relative to the outer die 3 is A. Figure 2 The middle arrow indicates the pulling direction. Steel pipe 1 enters from the right side between inner mold 2 and outer mold 3 and exits from the left side.

[0053] This invention uses a mature cold drawing process for steel pipes as a reference. Therefore, the actual production data of the mature cold drawing process for steel pipes must first be collected. In the following description, the steel pipe used in the mature cold drawing process for steel pipes is referred to as the reference steel pipe, and the mold used in the mature cold drawing process for steel pipes is referred to as the reference mold.

[0054] Specifically, the collection of actual production data includes material property collection, dimensional collection of the reference steel pipe before and after drawing, dimensional collection of the reference die, and drawing force collection. Material property collection includes the collection of basic mechanical properties of the material. Specifically, samples are taken from the material before and after drawing the reference steel pipe, and the "force-displacement curve" of the material is measured through tensile testing. This is then converted into an "engineering stress-strain curve" based on the dimensional characteristics of the tensile specimens. Finally, the "engineering stress-strain curve" is converted into a "true stress-strain curve," which is then used in subsequent modeling processes. Dimensional collection of the reference steel pipe before and after drawing requires multi-point measurement of various dimensional characteristics and averaging. Considering the actual modeling difficulty and computer computing power limitations, the finite element model needs to simplify the dimensional values ​​of the reference steel pipe to a certain extent, for example, using the length of a pipe segment to replace the entire pipe length, and using a single diameter to replace the average diameter of the pipe. The collection of reference die dimensions includes measuring the reference die, especially confirming the dimensions of its main features, including the outer bevel angle, inner bevel angle, sizing band length, transition radius between the sizing band and the inner bevel angle, and the relative longitudinal positions of the inner and outer dies during the drawing process. Additionally, the collection of actual production data includes gathering information on the stress, basic dimensions, and characteristic dimensions of the reference steel pipe after drawing, including measuring residual stress on the product surface, measuring the pipe diameter, observing abnormal features on the pipe surface, and the deformation shape and pattern of the pipe tail. During the actual drawing process, the drawing force curve of the drawing machine is output.

[0055] After collecting actual production data of the mature cold drawing process of steel pipes, it is also necessary to establish a finite element basic model based on the collected data of reference steel pipes and reference molds.

[0056] Specifically, a corresponding simulation model is built on a computer using the collected data of the reference steel pipe and the reference mold. A corresponding 3D CAD model is built based on the collected dimensions of the reference steel pipe before cold drawing and the dimensions of the reference mold.

[0057] After establishing the 3D CAD model, it is also necessary to mesh the reference mold and reference steel pipe. Figure 3 This refers to the axial stress distribution along the wall thickness of the steel pipe under ideal cold-drawn conditions, specifically the axial stress distribution from the inner wall 11 to the outer wall 12. To ensure that the finite element analysis results of this embodiment accurately reflect... Figure 3 The sinusoidal stress characteristics shown necessitate a sufficient number of elements or nodes along the thickness of the steel pipe. Figure 4It is known that a complete stress distribution curve can be approximately divided into four arc segments of different shapes. For each arc segment, at least three finite element meshes are needed to basically depict its shape. Thus, at least twelve elements are needed for the four arc segments. Since large-diameter steel pipes are quite thick, actual analysis has shown that the stress distribution in the thickness direction is much more complex than the ideal sinusoidal stress distribution curve. Therefore, arranging twelve layers of elements in the pipe thickness direction is far from sufficient. Furthermore, since the steel pipe undergoes bending deformation in both the longitudinal and transverse directions during cold drawing, based on finite element analysis theory, the aspect ratio of the elements should not be too large. After multiple calculations, analyses, and comparisons, and considering the computing power of the computer, this embodiment sets at least sixteen mesh layers in the thickness direction of the reference steel pipe, and the element type is set to high-order fully integral elements, such as... Figure 5 As shown, the aspect ratio of the element before deformation is 1:1, which ensures better computational accuracy in the finite element mesh model.

[0058] Furthermore, since cold-drawn steel pipes are relatively long, the cold-drawing process is a smooth and uniform motion. The material deformation characteristics of a small pipe segment can typically encompass the deformation characteristics of the entire pipe segment. To save computation time, only a small segment of the pipe length is analyzed in the finite element simulation. Moreover, based on finite element analysis theory, when the geometric model, material characteristics, and loading method are all axisymmetric, the results obtained using an axisymmetric model are essentially consistent with those obtained using a three-dimensional model. The cold-drawing process of steel pipes exhibits significant axisymmetry. To save computation time, this embodiment uses an axisymmetric model instead of a three-dimensional solid model, which greatly reduces computation time.

[0059] After meshing the reference steel pipe simulation model, it is also necessary to mesh the reference mold simulation model. Since the mold is always within the elastic deformation range during cold drawing, the mold simulation model can be set as an elastic body or a rigid body. When the mold simulation model is an elastic body, to ensure calculation accuracy, the finite element mesh size of the mold simulation model can be designed with a gradient variation. That is, the mesh size at the location in contact with the steel pipe is designed to be the same as that of the steel pipe, and the mesh size is set larger the farther away from the contact location, thus significantly reducing the number of meshes in the mold simulation model and saving calculation time. Figure 6 and Figure 7 As shown, when the mold simulation model is a rigid body, only the part of the mold that contacts the steel pipe needs to be modeled. Therefore, the mold seen in the two figures is just two strips. The part with the grid in the middle is the steel pipe, which enters the mold from right to left.

[0060] After establishing and meshing the above-mentioned mold simulation model and steel pipe simulation model, finite element analysis of the cold drawing process needs to be performed using these models. Since actual cold drawing is a stable and slow process, it can be considered a quasi-static problem, making a static implicit algorithm more suitable for analysis. This effectively eliminates the influence of dynamic inertia on calculation accuracy. Therefore, in this embodiment, the actual cold drawing process is reconstructed based on the above-mentioned mold simulation model and steel pipe simulation model using a static implicit algorithm, also known as the benchmarking process. Furthermore, based on the collected material data and actual loading method, material properties and boundary conditions are assigned to the simulation model. During the simulation analysis, some parameters with uncertain values, such as the friction coefficient, are adjusted to ensure that the product dimensions, shape, and stress parameters obtained through finite element simulation are comparable to the actually measured data. At this point, the finite element model can realistically reflect the actual product forming process, and the various analysis parameters are relatively ideal calculation parameters. The calculation method and model at this point can serve as the basic finite element model for designing other similar molds.

[0061] The friction coefficient between the steel pipe and the mold is one of the important input parameters for ensuring calculation accuracy. Since measuring the friction coefficient is difficult, this embodiment uses a reverse estimation algorithm to estimate its magnitude. First, a conventional friction coefficient value is used for simulation analysis of the drawing process. The calculated drawing force is then compared with the actual drawing force. If there is a difference between the two forces, the friction coefficient is adjusted according to the magnitude of the difference, and the calculation is repeated. Through this iterative process of adjusting the friction coefficient value and recalculating, the calculated drawing force is eventually made consistent with the actual drawing force in production. This final friction coefficient value is the ideal friction coefficient value. Once the friction coefficient value is determined, the basic finite element model is also determined.

[0062] Based on the established finite element model, the initial dimensional parameters of the target mold to be optimized are substituted into the calculation model, and the cold drawing process is simulated. The changes in various quality indicators of the product before and after cold drawing are analyzed, and the factors and causes affecting product quality are compared and analyzed. Schemes and methods for optimizing the dimensional parameters of the target mold are proposed. A new finite element model is established for the optimized target mold, and the mold is calculated, compared, analyzed and optimized again. Through this repeated calculation and optimization process, a mold size with relatively ideal product quality can finally be obtained, thus completing the mold optimization process.

[0063] like Figure 6 and Figure 7As shown, before the steel pipe enters the mold, its grid lines are parallel, and the grid consists of small squares with an aspect ratio of approximately 1:1. When the steel pipe comes into contact with the mold, it is squeezed by the mold, causing the steel pipe to deform, becoming longer and thinner. Different molds will result in different deformation states of the steel pipe, that is, different deformation shapes of the grid lines. Figure 6 The image shows the deformation grid lines of the steel pipe before the mold was optimized. Figure 7 The image shows the deformation grid lines of the steel pipe after the mold has been optimized, and... Figure 6 In comparison, Figure 7 In the process, the overall grid lines remain parallel, indicating that the material deformation on the same cross section of the steel pipe is relatively uniform, resulting in better product quality, such as good roundness and straightness of the steel pipe, flat pipe tail shape, uniform distribution of internal material structure, and low residual stress.

[0064] Based on the optimal mold design scheme obtained from finite element calculations, the mold is produced and manufactured. Through actual production, the product quality is observed, and the reliability of the optimized mold is judged.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for manufacturing a cold-drawing die for steel pipes, characterized in that, Includes the following steps: Collect the process parameters of the reference steel pipe in the actual cold drawing manufacturing process. The process parameters include the parameters of the reference mold, the parameters of the reference steel pipe before cold drawing, and the parameters of the reference steel pipe after cold drawing. A simulation model of the reference mold is established based on the parameters of the reference mold, and a simulation model of the reference steel pipe is established based on the parameters of the reference steel pipe before cold drawing. The simulation model of the reference steel pipe is meshed and a finite element analysis of cold drawing of the steel pipe is performed. During the finite element simulation analysis of cold drawing of the steel pipe, the friction coefficient between the steel pipe and the mold is adjusted so that the product quality parameters obtained by the finite element simulation analysis of cold drawing of the steel pipe are consistent with the parameters of the reference steel pipe after cold drawing, so as to obtain the finite element basic model. The product quality parameters include the residual stress on the product surface, the roundness, straightness and deformation shape of the pipe tail. as well as The initial parameters of the target mold and the target steel pipe are substituted into the finite element basic model and cold drawing finite element analysis is performed. The initial parameters of the target mold are improved with product quality parameters as the optimization target to obtain the optimized parameters of the target mold, and then the simulation model of the target mold is obtained.

2. The manufacturing method of the cold drawing die for steel pipes according to claim 1, characterized in that, Adjusting the friction coefficient during the cold-drawing finite element analysis of the steel pipe includes using a back-calculation algorithm to adjust the friction coefficient during the cold-drawing finite element analysis of the steel pipe.

3. The method for manufacturing a cold-drawing die for steel pipes according to claim 2, characterized in that, First, a finite element simulation analysis is performed using the conventional friction coefficient to calculate the simulated pull-out force. The simulated pull-out force is then compared with the actual pull-out force. If there is a difference between the simulated pull-out force and the actual pull-out force, the friction coefficient is modified according to the difference, and the finite element simulation analysis is performed again. The above steps are repeated cyclically. When the simulated pull-out force and the actual pull-out force are consistent, the friction coefficient is the ideal friction coefficient.

4. The manufacturing method of the cold drawing die for steel pipes according to claim 1, characterized in that, Meshing the reference steel pipe simulation model involves setting at least sixteen mesh layers in the thickness direction of the reference steel pipe simulation model, setting the aspect ratio of the mesh cells to a range of 1.5 to 1, and setting the cell type to a high-order fully integral cell.

5. The method for manufacturing a cold-drawing die for steel pipes according to claim 4, characterized in that, The reference mold simulation model is set as an elastic body. The mesh division of the reference mold simulation model includes: in the thickness direction of the reference mold simulation model, from the side of the reference mold simulation model that contacts the reference steel pipe simulation model to the side that moves away from the reference steel pipe simulation model, the mesh size of the reference mold simulation model gradually increases.

6. The method for manufacturing a cold-drawing die for steel pipes according to claim 1, characterized in that, Setting the reference mold simulation model as a rigid body and establishing the reference mold simulation model based on the parameters of the reference mold includes: modeling the part of the reference mold that contacts the reference steel pipe.

7. The method for manufacturing a cold-drawing die for steel pipes according to claim 1, characterized in that, The establishment of a simulation model of the reference mold based on the parameters of the reference mold and the establishment of a simulation model of the reference steel pipe based on the parameters of the reference steel pipe before cold drawing include establishing an axisymmetric model of the reference mold based on the parameters of the reference mold and establishing an axisymmetric model of the reference steel pipe based on the parameters of the reference steel pipe before cold drawing, and performing finite element analysis of cold drawing of the steel pipe using the axisymmetric model of the reference mold and the axisymmetric model of the reference steel pipe.

8. The method for manufacturing a cold-drawing die for steel pipes according to claim 1, characterized in that, The length of the reference steel pipe simulation model is a portion of the actual length of the reference steel pipe.

9. The method for manufacturing a cold-drawing die for steel pipes according to claim 1, characterized in that, Finite element analysis of cold-drawn steel pipes was performed using a static implicit algorithm.

10. The method for manufacturing a cold-drawing die for steel pipes according to claim 1, characterized in that, Displacement loading was applied to the reference steel pipe simulation model to perform finite element analysis of the cold drawing of the steel pipe.

11. The method for manufacturing a cold-drawing die for steel pipes according to claim 1, characterized in that, The process parameters for collecting reference steel pipes during actual cold drawing manufacturing include sampling the material of the reference steel pipes before and after drawing, obtaining the force-displacement curves of the reference steel pipes before and after drawing through billet tensile tests, converting the force-displacement curves into engineering stress-strain curves based on the dimensional characteristics of the tensile specimens, and then converting the engineering stress-strain curves into true stress-strain curves.

12. The method for manufacturing a cold-drawing die for steel pipes according to any one of claims 1 to 11, characterized in that, The manufacturing method also includes producing and manufacturing the target mold using a simulation model of the target mold.

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