Cold heading forming method of titanium alloy high-pressure oil pipe joint

Abstract

This invention relates to the field of titanium forging manufacturing technology, and more particularly to a cold heading method for titanium alloy high-pressure oil pipe joints. The invention involves determining the rounded corner forming restriction area of ​​the wire to be formed, coating this area with a fluorescent material; obtaining a cluster distribution map of the grayscale changes of the coated rounded corner forming restriction area before and after forming to identify several types of grayscale change labels; determining the cold heading stability of the rounded corner forming restriction area based on the distribution fluctuations of the sub-regions corresponding to each type of grayscale change label; and determining the optimized forming parameters for pulse forging of the rounded corner forming restriction area of ​​the wire by analyzing the curve trends of the distribution characterization curves of the sub-regions corresponding to each type of grayscale change label. Furthermore, a quantitative evaluation system and adaptive control method for the rounded corner forming process of the oil pipe joint are established, achieving quality improvement and efficient production of high-quality hydraulic connection components.

Description

Technical Field

[0001] This invention relates to the field of titanium forging manufacturing technology, and in particular to a cold heading method for titanium alloy high-pressure oil pipe joints. Background Technology

[0002] In the fields of aerospace and high-end hydraulic equipment, titanium alloy high-pressure oil pipe joints, as core components for fluid transmission and sealing connections, are generally formed using cold heading technology to ensure continuous metal flow lines and that structural strength and fatigue performance meet stringent service requirements. Titanium alloys have become the mainstream material for aerospace forgings, but these materials have poor plasticity, weak fluidity, and significant springback effects. During the cold heading process, the head edges and sealing edges are prone to uncontrollable natural rounded corners (R) due to the free flow and springback of the material, making it difficult to directly form the sharp or right-angled structures required by the design.

[0003] In the current manufacturing of high-quality forgings and aerospace titanium forgings, it is common to rely on subsequent cutting, trimming, grinding and other processes to remove free-formed rounded corners. This not only destroys the continuous metal flow lines formed by cold heading, reducing the reliability of high-pressure sealing and structural mechanical properties of the joint, but also has problems such as complicated processes, high processing costs and poor batch consistency. Conventional visual inspection can only achieve dimensional measurement and cannot accurately characterize the extension differences and rounded corner forming freedom in small areas. It is difficult to predict free R-corner defects in advance and cannot meet the manufacturing requirements of aerospace titanium alloy high-pressure oil pipe joints for the head without free-formed rounded corners, high precision and high consistency.

[0004] Existing technologies do not consider the weak fluidity and significant springback effect of titanium alloys as materials for high-pressure oil pipe joints during forging, which leads to the formation of uncontrollable natural fillet radius R. Existing technologies lack evaluation methods and adaptive control methods for the fillet radius formation process of oil pipe joints, which affects the quality improvement and efficient production of high-quality hydraulic connection components. Summary of the Invention

[0005] Therefore, this invention provides a cold heading method for titanium alloy high-pressure oil pipe joints to overcome the problem that the existing technology lacks evaluation and adaptive control methods for the rounded corner forming process of oil pipe joints, which affects the quality improvement and efficient production of high-quality hydraulic connection components.

[0006] To achieve the above objectives, the present invention provides a cold heading method for titanium alloy high-pressure oil pipe joints, comprising: Based on the forging template of the titanium alloy high-pressure oil pipe joint, the wire is mapped to a region to determine the rounded corner forming restriction area of ​​the wire to be formed, and a fluorescent material is coated in the rounded corner forming restriction area. The grayscale information of several detection points within the rounded corner molding restriction area coated with fluorescent material is obtained. The grayscale information is clustered to obtain a grayscale change cluster distribution map, and several grayscale change labels are determined according to the grayscale rule interval. The distribution of sub-regions corresponding to various grayscale change labels is statistically analyzed. Based on the distribution fluctuation of sub-regions corresponding to various grayscale change labels in the continuously acquired grayscale change cluster distribution map, it is determined whether the cold heading stability of the rounded corner forming restriction area is qualified. In response to the unsatisfactory stability of cold heading, pulse forging pressure with increasing frequency is applied to the rounded corner forming restriction area of ​​the wire. The optimized forming parameters for pulse forging of the rounded corner forming restriction area of ​​the wire are determined based on the curve trend of the distribution characterization curve of the sub-region corresponding to various gray scale change labels.

[0007] Furthermore, the process of determining the corner rounding restriction area of ​​the wire to be formed includes: The forging template of the titanium alloy high-pressure oil pipe joint is divided at equal intervals along the axial direction to obtain several continuous forming surfaces. Extract the contour coordinates of all fillet features in each forming surface and map them to the axial surface of the wire to be processed based on the axial ratio between the wire and the forging. The axial surface of the wire to be processed with rounded corner features on its upper contour coordinates is defined as the rounded corner forming restriction area.

[0008] Furthermore, the process of acquiring grayscale information from several detection points includes: After the cold heading stamping stroke in the rounded corner forming restriction area ends and the mold is demolded, the rounded corner forming restriction area is illuminated by a coaxial light source. The fluorescence grayscale image of the area is acquired, and several detection points are obtained by dividing the area into equally spaced grids. The grayscale value of each detection point is extracted and calculated with the initial grayscale value to obtain a set of grayscale change information.

[0009] Furthermore, the process of determining the grayscale variation cluster distribution map and identifying several grayscale variation labels based on grayscale rule intervals includes: A clustering algorithm is used to cluster the grayscale change information set, and the three types of grayscale change values ​​obtained by clustering are respectively assigned to different degrees of extension; Assign corresponding grayscale change labels to sub-regions in different grayscale ranges to generate a grayscale change clustering distribution map with grayscale change labels; The grayscale change labels include a first grayscale change label corresponding to a first degree of extension, a second grayscale change label corresponding to a second degree of extension, and a third grayscale change label corresponding to a third degree of extension.

[0010] Furthermore, the process of statistically analyzing the distribution of sub-regions corresponding to various grayscale change labels includes: Calculate the pixel area of ​​the sub-region corresponding to the first gray-level change label, the second gray-level change label, and the third gray-level change label in the gray-level change clustering distribution map, respectively; The area ratio of the corresponding sub-region of each grayscale change label is calculated by comparing the pixel area with the total pixel area of ​​the rounded corner restriction area.

[0011] Furthermore, the process for determining whether the cold heading stability of the rounded corner forming restriction area is qualified includes: The stability characterization coefficients are compared with the preset stability reference coefficients; If the stability characterization coefficient is less than or equal to the stability reference coefficient, the cold heading stability of the rounded corner forming restriction area is deemed qualified; if the stability characterization coefficient is greater than the stability reference coefficient, the cold heading stability of the rounded corner forming restriction area is deemed unqualified.

[0012] Furthermore, the determination of the stability characterization coefficient includes: calculating the standard deviation of the sub-region area ratio of various gray-scale change labels in a continuous time series, and taking the maximum standard deviation among the standard deviations of the area ratios of the three types of gray-scale change labels as the stability characterization coefficient.

[0013] Furthermore, the process of determining the distribution characterization curves of the sub-regions corresponding to various grayscale change labels includes: According to the continuous production sequence of cold-forged parts, the area proportions corresponding to the same grayscale change label are sorted sequentially. A rectangular coordinate system is established with the production time sequence as the horizontal axis and the area ratio as the vertical axis. The continuous area ratio data in the time sequence are fitted to generate the first distribution characterization curve of the area ratio of the pixel area of ​​the sub-region corresponding to the first gray-level change label over time, the second distribution characterization curve of the area ratio of the pixel area of ​​the sub-region corresponding to the second gray-level change label over time, and the third distribution characterization curve of the area ratio of the pixel area of ​​the sub-region corresponding to the third gray-level change label over time.

[0014] Furthermore, the process of determining whether the trend of the distribution characterization curve has entered a preset state includes: Select a continuous time-series sliding window and extract the area ratio data of the first distribution characterization curve, the second distribution characterization curve, and the third distribution characterization curve within the current sliding window; Calculate the maximum fluctuation difference of the area ratio data of each distribution characterization curve within the current sliding window; Each maximum fluctuation difference is compared with a preset fluctuation difference threshold. If all maximum fluctuation differences are less than or equal to the fluctuation difference threshold, then the curve trend of the distribution characterization curve is determined to have entered a preset state.

[0015] Furthermore, the process of determining and optimizing molding parameters includes: Traverse the continuous time-series sliding window; The sliding window that first determines the curve trend of the distribution characterization curve enters the preset state is defined as the target sliding window; The starting time of the target sliding window is obtained, and the application frequency of the pulse forging pressure corresponding to the starting time is determined as the optimization forming parameter.

[0016] The beneficial effects of the technical solution shown in this application include: This invention determines the rounded corner forming restriction area of ​​the wire to be formed, and coats the rounded corner forming restriction area with fluorescent material; by obtaining the grayscale change clustering distribution map of the rounded corner forming restriction area coated with fluorescent material before and after forming, several types of grayscale change labels are determined; the cold heading forming stability of the rounded corner forming restriction area is determined based on the distribution fluctuation of the sub-regions corresponding to each type of grayscale change label; and the optimal forming parameters for pulse forging of the rounded corner forming restriction area of ​​the wire are determined by the curve trend of the distribution characterization curve of the sub-regions corresponding to each type of grayscale change label. Furthermore, a quantitative evaluation system and adaptive control method for the rounded corner forming process of oil pipe joints are established, achieving quality improvement and efficient production of high-quality hydraulic connection components.

[0017] Furthermore, by extracting the grayscale value corresponding to each detection point and calculating a unified set of grayscale change information with the initial grayscale value, this invention can transform the surface fluorescence distribution state after cold heading into a quantifiable and comparable data set. This provides a reliable and spatially unique quantitative basis for subsequent grayscale clustering analysis, forming stability determination, adaptive adjustment of stamping parameters, and identification of rounded corner over-forming defects, thereby achieving precise control over the rounded corner forming dimensional accuracy and surface forming quality during the cold heading process.

[0018] Furthermore, by having the three types of grayscale change values ​​obtained from clustering correspond to different material stretching degrees, the present invention can transform the surface stretching state, which is difficult to directly characterize during the molding process, into a quantifiable and comparable grayscale change feature, thereby achieving accurate characterization of the material stretching uniformity, stretching sufficiency, and stretching stability in the rounded corner molding restricted area.

[0019] Furthermore, the distribution characterization curves of the sub-regions corresponding to the first, second, and third grayscale change labels in this invention can intuitively and completely present the dynamic change law, fluctuation amplitude, and development trend of three different types of regions with different degrees of extension during the continuous forming process, transforming the changes in the degree of freedom of free R-angle forming, which are difficult to observe directly, into quantifiable, traceable, and comparable curve morphological features.

[0020] Furthermore, by traversing continuous time-series sliding windows and determining the sliding window where the curve trend of the first determination distribution characterization curve enters a preset state as the target sliding window, this invention can accurately capture the earliest convergence point where the cold heading forming state tends to stabilize during the pulse forging pressure control process with increasing frequency. This avoids stress overload, corner cracking, or local overpressure deformation of titanium alloy materials due to excessive increase in pulse frequency. The invention also obtains the starting time of the target sliding window and determines the pulse forging pressure application frequency corresponding to this time as the optimization forming parameter. Under the premise of meeting forming stability and sharp corner forming accuracy, the lowest effective pulse frequency can be locked as the optimal process parameter. This fully utilizes the effects of pulse forging pressure to compact internal porosity, release local stress, suppress material springback and free rounded corner formation, while preventing energy waste, increased equipment wear and product structural damage caused by excessively high pulse frequency. This achieves quality improvement and efficient production of high-quality hydraulic connection components. Attached Figure Description

[0021] Figure 1 This is a step diagram of the cold heading forming method for a titanium alloy high-pressure oil pipe joint according to an embodiment of the present invention; Figure 2 This is a step diagram illustrating the process of determining the rounded corner forming restriction area in an embodiment of the present invention; Figure 3 This is a flowchart illustrating the logic for determining whether the stability of cold heading is qualified according to an embodiment of the present invention. Figure 4 A flowchart illustrating the steps for determining and optimizing molding parameters in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0023] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] It should be noted that in the description of this invention, the terms "upper," "lower," "inner," "outer," etc., which indicate the direction or positional relationship, are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0025] It should be understood that although the terms "first," "second," etc., may be used in this invention to describe various types of information, these information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information.

[0026] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Please see Figure 1 The diagram shows the steps of a cold heading method for a titanium alloy high-pressure oil pipe joint according to an embodiment of the present invention. The cold heading method for the titanium alloy high-pressure oil pipe joint of the present invention includes: Step S100: Map the wire region according to the forging template of the titanium alloy high-pressure oil pipe joint, determine the rounded corner forming restriction area of ​​the wire to be formed, and coat the rounded corner forming restriction area with fluorescent material. For example, after determining the rounded corner forming restriction area, an ultraviolet-excited fluorescent coating is used as a marker substance, which can excite a uniform gray-scale reflection signal under ultraviolet light with a wavelength of 365nm; the coating is applied using an inkjet printing device, and the coating time is before the wire cold heading forming, with the coating thickness controlled between 5μm and 80μm.

[0028] Step S200: Obtain grayscale information of several detection points within the rounded corner forming restriction area coated with fluorescent material; perform clustering processing on the grayscale information to obtain a grayscale change clustering distribution map; and determine several grayscale change labels according to the grayscale rule intervals. Step S300: Statistically analyze the distribution of sub-regions corresponding to various grayscale change labels. Based on the distribution fluctuation of sub-regions corresponding to various grayscale change labels in the continuously acquired grayscale change clustering distribution map, determine whether the cold heading stability of the rounded corner forming restriction area is qualified. In step S400, in response to the result of unqualified cold heading stability, pulse forging pressure with increasing frequency is applied to the rounded corner forming restriction area of ​​the wire. The optimized forming parameters for pulse forging the rounded corner forming restriction area of ​​the wire are determined based on the curve trend of the distribution characterization curve of the sub-region corresponding to various gray scale change labels.

[0029] Specifically, please refer to Figure 2The diagram illustrates the steps for determining the rounded corner forming restriction area in an embodiment of the present invention. The process for determining the rounded corner forming restriction area of ​​the wire to be formed includes: Step S101: Divide the forging template of the titanium alloy high-pressure oil pipe joint into equal intervals along the axial direction to obtain several continuous forming surfaces. Step S102: Extract the contour coordinates of all fillet features in each forming surface and map them to the axial surface of the wire to be processed based on the axial ratio between the wire and the forging. Step S103: The axial surface of the wire to be processed with rounded corner features on the upper contour coordinates is defined as the rounded corner forming restriction area.

[0030] Those skilled in the art will understand that the rounded corner feature in this invention refers to the structural transition region where, during the cold forging process of titanium alloy high-pressure oil pipe joints, the design requires a sharp corner, right angle, or small radius of curvature. However, due to the poor plasticity, weak fluidity, and significant springback effect of titanium alloys, uncontrollable natural free R-angles are easily formed due to the free flow of metal. This can be identified by importing the three-dimensional model of the titanium alloy high-pressure oil pipe joint forging into the three-dimensional modeling software SolidWorks, establishing a global reference coordinate system with the center of the joint head end face as the origin, and identifying the region with a radius of curvature R < 0.1 mm as the required sharp or right angle region, which is the core region most prone to forming free R-angles during the cold forging process. The 3D modeling software performs a full-surface curvature scan on each formed surface, extracts all contour lines that meet the curvature radius threshold, and records the starting point coordinates, ending point coordinates, curvature center coordinates, curvature radius, and the position of the formed surface to which each contour line belongs. All extracted contour lines are filtered, and adjacent rounded corner contour lines with a spacing of less than 0.5mm are merged to form a continuous rounded corner feature area. It is known to those skilled in the art that the sharp corner transition of the sealing edge of the joint head of the titanium alloy high-pressure oil pipe joint, the transition between the joint surface and the cylindrical surface, the small curvature radius rounded corner at the root of the joint thread, and the transition between the inner hole and the end face of the joint are structural transition areas that are prone to forming uncontrollable natural free R-angles.

[0031] In this invention, the forging template of the titanium alloy high-pressure oil pipe joint is divided at equal intervals, with a division step size of 10mm, decomposing the template into several continuous and equally wide annular surfaces. Three-dimensional modeling software is used to extract the contour coordinate point set of all rounded corner features within each forming surface. The coordinate point set includes the contour start point, end point, curvature center, and curvature radius parameters. Based on the ratio of the axial length of the wire blank to the axial length of the finished forging, an axial mapping ratio coefficient is determined. A linear mapping algorithm is then used to convert the contour coordinates of the rounded corner features of the forging into the axial surface coordinates of the wire to be processed.

[0032] This invention extracts the contour coordinates of all fillet features within each forming surface, enabling precise location of areas on the forging that are prone to forming natural fillet radius (R) due to the free flow of cold-heading metal and material springback. By mapping the contour coordinates of the fillet features of the forging to the corresponding axial surface of the wire to be processed through the axial proportional relationship between the forging and the wire, the geometric correspondence between the area to be formed on the wire and the final forming position of the forging is maintained. This ensures that fluorescent coating, grayscale detection, and pulse forging control all act on areas prone to generating free R-angles.

[0033] Specifically, the process of obtaining grayscale information from several detection points includes: After the cold heading stamping stroke in the rounded corner forming restriction area ends and the mold is demolded, the rounded corner forming restriction area is illuminated by a coaxial light source. The fluorescence grayscale image of the area is acquired, and several detection points are obtained by dividing the area into equally spaced grids. The grayscale value of each detection point is extracted and calculated with the initial grayscale value to obtain a set of grayscale change information.

[0034] In this invention, after the cold heading stamping stroke is completed in the area to be rounded and the mold is completely demolded, a 365nm coaxial ultraviolet light source is used to vertically irradiate the area. The coaxial light source can eliminate the shadows and reflection distortions caused by tilted irradiation, ensuring the uniformity of fluorescence signal acquisition. An industrial camera is used to acquire fluorescence grayscale images. The acquired fluorescence grayscale images are divided into equally spaced grids with a grid side length of 2mm. The grayscale value of the center point of each grid is extracted, with a grayscale value range of 0-255. The grayscale values ​​of all detection points are arranged in the order of grid coordinates. In this invention, the grayscale change value of each detection point in the grayscale change information set = grayscale value of the detection point after cold heading - initial grayscale value. For the UV-365 type industrial ultraviolet excitation fluorescent coating used in this embodiment, the initial grayscale value is 220. The grayscale change values ​​of each detection point constitute the grayscale change information set.

[0035] For example, in this embodiment of the invention, the K-means clustering algorithm is used to cluster the grayscale change information set, and the number of clusters can be 3. The three grayscale change values ​​obtained by clustering correspond to the three material extensibility levels according to their numerical values. The higher the grayscale change value, the greater the surface extensibility. The high grayscale change value corresponds to the first extensibility level, the medium grayscale change value corresponds to the second extensibility level, and the low grayscale change value corresponds to the third extensibility level.

[0036] Specifically, the process of determining the grayscale variation cluster distribution map and identifying several grayscale variation labels based on grayscale rule intervals includes: A clustering algorithm is used to cluster the grayscale change information set, and the three types of grayscale change values ​​obtained by clustering are respectively assigned to different degrees of extension; Assign corresponding grayscale change labels to sub-regions in different grayscale ranges to generate a grayscale change clustering distribution map with grayscale change labels; The grayscale change labels include a first grayscale change label corresponding to a first degree of extension, a second grayscale change label corresponding to a second degree of extension, and a third grayscale change label corresponding to a third degree of extension.

[0037] For example, in this invention, grayscale change values ​​within the same grayscale rule interval are classified into the same type of extension state; a first grayscale change label, a second grayscale change label, and a third grayscale change label are assigned to the sub-regions of each grayscale rule interval, generating a grayscale change clustering distribution map with grayscale change labels, thereby realizing a visual and quantitative characterization of the material extension state.

[0038] In this invention, the grayscale change value ranges and material extension correspondences for the three types of grayscale change labels can be set as follows: First grayscale change label: Grayscale change value ≥25, which is the core stress deformation zone of R-corner forming, where the material undergoes severe plastic deformation and the surface fluorescent coating is stretched significantly with the substrate; Second grayscale change label: Grayscale change value is 10-25, indicating that the material has undergone moderate plastic deformation; Third grayscale change label: grayscale change value ≤ 9.

[0039] It is understood that by using the three types of grayscale change values ​​obtained from clustering to correspond to different material stretching degrees, this invention can transform the surface stretching state, which is difficult to directly characterize during the forming process, into a quantifiable and comparable grayscale change feature. This enables precise characterization of the material stretching uniformity, stretching sufficiency, and stretching stability in the rounded corner forming restricted area. The generated grayscale change clustering distribution map with grayscale change labels can transform the discrete grayscale value set into a visual distribution map with spatial location attributes, thereby providing a quantifiable basis for the adaptive adjustment of subsequent cold heading forming parameters, accurate identification of forming defects, and closed-loop control of forming stability.

[0040] Specifically, the process of statistically analyzing the distribution of sub-regions corresponding to various grayscale change labels includes: Calculate the pixel area of ​​the sub-region corresponding to the first gray-level change label, the second gray-level change label, and the third gray-level change label in the gray-level change clustering distribution map, respectively; The area ratio of the corresponding sub-region of each grayscale change label is calculated by comparing the pixel area with the total pixel area of ​​the rounded corner restriction area.

[0041] In this invention, the pixel area of ​​the sub-regions corresponding to the first grayscale change label, the second grayscale change label, and the third grayscale change label is calculated by pixel statistics. The pixel area is the number of effective pixels of the corresponding label. The total pixel area of ​​the rounded corner restriction area is calculated. The calculation formula is used: Area ratio = (Pixel area of ​​a certain grayscale change label sub-region / Total pixel area of ​​the rounded corner restriction area) × 100%. The area ratios corresponding to the three types of grayscale change labels are calculated respectively.

[0042] Specifically, please refer to Figure 3 As shown, this is a flowchart illustrating the logic of determining whether the cold heading stability is qualified according to an embodiment of the present invention. The process of determining whether the cold heading stability of the rounded corner forming restriction area is qualified includes: The stability characterization coefficients are compared with the preset stability reference coefficients; If the stability characterization coefficient is less than or equal to the stability reference coefficient, the cold heading stability of the rounded corner forming restriction area is deemed qualified; if the stability characterization coefficient is greater than the stability reference coefficient, the cold heading stability of the rounded corner forming restriction area is deemed unqualified.

[0043] Specifically, the determination of the stability characterization coefficient includes: calculating the standard deviation of the sub-region area ratio of various gray-scale change labels in a continuous time series, and taking the maximum standard deviation among the standard deviations of the area ratios of the three types of gray-scale change labels as the stability characterization coefficient.

[0044] It is understood that the stability characterization coefficient of the present invention reflects the dynamic fluctuation of material extension, topological distribution and forming quality during cold heading. The smaller the fluctuation, the more stable the cold heading process is and the more consistent the area ratio distribution is. When the stability characterization coefficient is less than or equal to the preset stability reference coefficient, it indicates that the area ratio fluctuation of the sub-regions corresponding to various grayscale change labels is small and the forming process is highly consistent during multiple rounds of forming, that is, the cold heading stability is qualified. When the stability characterization coefficient is greater than the preset stability reference coefficient, it indicates that the area ratio fluctuation is large and the forming process has obvious dispersion during multiple rounds of forming, that is, the cold heading stability is unqualified.

[0045] For example, 30 consecutive forgings are selected as time-series samples, and the standard deviation δ of the area ratio of various gray-scale change label sub-regions in the continuous time series is calculated. The formula for calculating the standard deviation is: ; Where, x i x represents the area percentage of a certain type of grayscale variation label sub-region. av The average area percentage is denoted by n, and the number of forgings is denoted by n. The maximum value among the standard deviations of the area percentages of the three types of grayscale variation labels is determined as the stability characterization coefficient.

[0046] In this invention, the stability reference coefficient is set by those skilled in the art according to the product accuracy requirements. Optionally, the stability reference coefficient can be set to 3%.

[0047] Specifically, the process of determining the distribution characterization curves of the sub-regions corresponding to various grayscale change labels includes: According to the continuous production sequence of cold-forged parts, the area proportions corresponding to the same grayscale change label are sorted sequentially. A rectangular coordinate system is established with the production time sequence as the horizontal axis and the area ratio as the vertical axis. The continuous area ratio data in the time sequence are fitted to generate the first distribution characterization curve of the area ratio of the pixel area of ​​the sub-region corresponding to the first gray-level change label over time, the second distribution characterization curve of the area ratio of the pixel area of ​​the sub-region corresponding to the second gray-level change label over time, and the third distribution characterization curve of the area ratio of the pixel area of ​​the sub-region corresponding to the third gray-level change label over time.

[0048] In practice, the area percentage data corresponding to the same grayscale change label is sorted chronologically according to the production sequence of cold-forged parts. A two-dimensional rectangular coordinate system is constructed with production time as the horizontal axis and area percentage as the vertical axis. The least squares method is used to fit the temporally continuous area percentage data to generate the first distribution characterization curve of the sub-region corresponding to the first grayscale change label, the second distribution characterization curve of the sub-region corresponding to the second grayscale change label, and the third distribution characterization curve of the sub-region corresponding to the third grayscale change label. The three curves can intuitively reflect the dynamic change trend and fluctuation amplitude of the three types of extended regions in the continuous forming process.

[0049] It is understood that the distribution characterization curves of the sub-regions corresponding to the first, second, and third grayscale change labels in this invention can intuitively and completely present the dynamic change patterns, fluctuation amplitudes, and development trends of three types of regions with different degrees of extension during the continuous forming process.

[0050] Specifically, the process of determining whether the trend of the distribution characterization curve has entered a preset state includes: Select a continuous time-series sliding window and extract the area ratio data of the first distribution characterization curve, the second distribution characterization curve, and the third distribution characterization curve within the current sliding window; Calculate the maximum fluctuation difference of the area ratio data of each distribution characterization curve within the current sliding window; Each maximum fluctuation difference is compared with a preset fluctuation difference threshold. If all maximum fluctuation differences are less than or equal to the fluctuation difference threshold, the curve trend of the distribution characterization curve is determined to have entered a preset state; if there is a maximum fluctuation difference greater than the fluctuation difference threshold, the curve trend of the distribution characterization curve is determined not to have entered the preset state.

[0051] For example, a continuous time-series sliding window is selected, with a window length of 5 forging products and a sliding step of 2 forging products; all area percentage data of the first, second, and third distribution characterization curves within the current sliding window are extracted, and the maximum fluctuation difference of each curve within the window is calculated respectively. The maximum fluctuation difference = the maximum area percentage within the window - the minimum area percentage within the window; the fluctuation difference threshold is preset according to the product forming accuracy, and optionally, the fluctuation difference threshold is set to 1%.

[0052] Understandably, by selecting a continuous time-series sliding window and simultaneously extracting the area proportion data of the three types of distribution characterization curves within the current window, the distribution changes during the continuous forming process can be dynamically monitored. The maximum fluctuation difference of the area proportion data of each distribution characterization curve within the sliding window can be calculated separately, which can accurately quantify the real-time fluctuation amplitude of each type of extension region in continuous production, and objectively reflect the stability of material extension and rounded corner forming during cold heading. By comparing each maximum fluctuation difference with the preset fluctuation difference threshold one by one, and using the simultaneous satisfaction of the threshold requirements by all curves as the judgment condition, it can be ensured that the high, medium and low extension regions all reach a stable state.

[0053] Specifically, please refer to Figure 4 The diagram illustrates the steps for determining and optimizing molding parameters according to an embodiment of the present invention. The process for determining and optimizing molding parameters includes: Step S401: Traverse the continuous time-series sliding window; Step S402: The sliding window in which the curve trend of the distribution characterization curve enters the preset state for the first time is determined as the target sliding window; Step S403: Obtain the start time of the target sliding window, and determine the application frequency of the pulse forging pressure corresponding to the start time as the optimization forming parameter.

[0054] During implementation, all consecutive time-series sliding windows are traversed sequentially according to the production timeline. The sliding window where the distribution characterization curve first enters the preset stable state is determined as the target sliding window. The pulse forging pressure is applied starting from an initial frequency of 5Hz and gradually increasing by a fixed step size of 2Hz. The starting time of the target sliding window is obtained, and the pulse forging pressure application frequency corresponding to that time is extracted. This frequency is determined as the pulse forging pressure optimization forming parameter for the rounded corner forming restriction area. This parameter is the minimum effective pulse frequency that meets the forming stability requirements. It can avoid stress overload and corner cracking of titanium alloy materials caused by excessively high pulse frequencies, while achieving the forming effect of compacting internal porosity, releasing stress, and suppressing free R-angles.

[0055] For example, if the initial frequency of the pulse forging pressure is 5Hz, the pulse frequency increment step is 2Hz, the window length is 5 consecutive production batches, and the sliding step is 2 forging products; When the maximum fluctuation difference of the first, second, and third distribution characterization curves within the same sliding window is ≤0.01, the curve is determined to enter a preset stable state. All consecutive time-series sliding windows are traversed sequentially according to the production time sequence. If the sliding window corresponding to the 15th to 19th forging products is the first window that simultaneously satisfies the maximum fluctuation difference of the three distribution characterization curves being ≤0.01, it is determined as the target sliding window. The starting time of this target sliding window corresponds to the application frequency of the pulse forging pressure of 11Hz. Therefore, 11Hz is determined as the pulse forging optimization forming parameter of the rounded corner forming restriction area of ​​the titanium alloy high-pressure oil pipe joint in this embodiment.

[0056] This invention, by traversing continuous time-series sliding windows and determining the sliding window where the curve trend of the initial determination distribution characterization curve enters a preset state as the target sliding window, can accurately capture the earliest convergence point where the cold heading forming state tends to stabilize during the pulse forging pressure control process with increasing frequency. This avoids stress overload, corner cracking, or local overpressure deformation of titanium alloy materials due to excessive increase in pulse frequency. The invention obtains the starting time of the target sliding window and determines the pulse forging pressure application frequency corresponding to this time as the optimized forming parameter. Under the premise of meeting forming stability and sharp corner forming accuracy, the lowest effective pulse frequency can be locked as the optimal process parameter. This can fully utilize the role of pulse forging in compacting internal porosity, releasing local stress, suppressing material springback and free rounding, while preventing energy waste, increased equipment wear and product structural damage caused by excessively high pulse frequency. Thus, it achieves the optimal, safest, and most economical adaptive optimization of pulse forging parameters.

[0057] This embodiment also provides a computer-readable storage medium storing computer program code. When the computer program code is run on a computer, the computer executes the above-described related method steps to realize the cold heading method for titanium alloy high-pressure oil pipe joints provided in the above embodiment.

[0058] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cold heading forming method for a titanium alloy high-pressure oil pipe joint, characterized in that, include: Based on the forging template of the titanium alloy high-pressure oil pipe joint, the wire is mapped to a region to determine the rounded corner forming restriction area of ​​the wire to be formed, and a fluorescent material is coated in the rounded corner forming restriction area. The grayscale information of several detection points within the rounded corner molding restriction area coated with fluorescent material is obtained. The grayscale information is clustered to obtain a grayscale change cluster distribution map, and several grayscale change labels are determined according to the grayscale rule interval. The distribution of sub-regions corresponding to various grayscale change labels is statistically analyzed. Based on the distribution fluctuation of sub-regions corresponding to various grayscale change labels in the continuously acquired grayscale change cluster distribution map, it is determined whether the cold heading stability of the rounded corner forming restriction area is qualified. In response to the unsatisfactory stability of cold heading, pulse forging pressure with increasing frequency is applied to the rounded corner forming restriction area of ​​the wire. The optimized forming parameters for pulse forging of the rounded corner forming restriction area of ​​the wire are determined based on the curve trend of the distribution characterization curve of the sub-region corresponding to various gray scale change labels.

2. The cold heading forming method for titanium alloy high-pressure oil pipe joints according to claim 1, characterized in that, The process of determining the fillet forming constraint area of ​​the wire to be formed includes: The forging template of the titanium alloy high-pressure oil pipe joint is divided at equal intervals along the axial direction to obtain several continuous forming surfaces. Extract the contour coordinates of all fillet features in each forming surface and map them to the axial surface of the wire to be processed based on the axial ratio between the wire and the forging. The axial surface of the wire to be processed with rounded corner features on its upper contour coordinates is defined as the rounded corner forming restriction area.

3. The cold heading forming method for titanium alloy high-pressure oil pipe joints according to claim 2, characterized in that, The process of obtaining grayscale information from several detection points includes: After the cold heading stamping stroke in the rounded corner forming restriction area ends and the mold is demolded, the rounded corner forming restriction area is illuminated by a coaxial light source. The fluorescence grayscale image of the area is acquired, and several detection points are obtained by dividing the area into equally spaced grids. The grayscale value of each detection point is extracted and calculated with the initial grayscale value to obtain a set of grayscale change information.

4. The cold heading forming method for titanium alloy high-pressure oil pipe joints according to claim 3, characterized in that, The process of determining the grayscale variation cluster distribution map and identifying several grayscale variation labels based on grayscale rule intervals includes: A clustering algorithm is used to cluster the grayscale change information set, and the three types of grayscale change values ​​obtained by clustering are respectively assigned to different degrees of extension; Assign corresponding grayscale change labels to sub-regions in different grayscale ranges to generate a grayscale change clustering distribution map with grayscale change labels; The grayscale change labels include a first grayscale change label corresponding to a first degree of extension, a second grayscale change label corresponding to a second degree of extension, and a third grayscale change label corresponding to a third degree of extension.

5. The cold heading forming method for titanium alloy high-pressure oil pipe joints according to claim 4, characterized in that, The process of statistically analyzing the distribution of sub-regions corresponding to various grayscale change labels includes: Calculate the pixel area of ​​the sub-region corresponding to the first gray-level change label, the second gray-level change label, and the third gray-level change label in the gray-level change clustering distribution map, respectively; The area ratio of the corresponding sub-region of each grayscale change label is calculated by comparing the pixel area with the total pixel area of ​​the rounded corner restriction area.

6. The cold heading forming method for titanium alloy high-pressure oil pipe joints according to claim 5, characterized in that, The process for determining whether the cold heading stability of the rounded corner forming restriction area is qualified includes: The stability characterization coefficients are compared with the preset stability reference coefficients; If the stability characterization coefficient is less than or equal to the stability reference coefficient, the cold heading stability of the rounded corner forming restriction area is deemed qualified; if the stability characterization coefficient is greater than the stability reference coefficient, the cold heading stability of the rounded corner forming restriction area is deemed unqualified.

7. The cold heading forming method for titanium alloy high-pressure oil pipe joints according to claim 6, characterized in that, The determination of the stability characterization coefficient includes: calculating the standard deviation of the sub-region area ratio of various gray-scale change labels in a continuous time series, and taking the maximum standard deviation among the standard deviations of the area ratios of the three types of gray-scale change labels as the stability characterization coefficient.

8. The cold heading forming method for titanium alloy high-pressure oil pipe joints according to claim 5, characterized in that, The process of determining the distribution characterization curves of the sub-regions corresponding to various grayscale change labels includes: According to the continuous production sequence of cold-forged parts, the area proportions corresponding to the same grayscale change label are sorted sequentially. A rectangular coordinate system is established with production time sequence as the horizontal axis and area proportion as the vertical axis. The continuous area proportion data in the time sequence are fitted to generate the first distribution characterization curve of the area proportion of the pixel area of ​​the sub-region corresponding to the first gray-level change label over time, the second distribution characterization curve of the area proportion of the pixel area of ​​the sub-region corresponding to the second gray-level change label over time, and the third distribution characterization curve of the area proportion of the pixel area of ​​the sub-region corresponding to the third gray-level change label over time.

9. The cold heading forming method for titanium alloy high-pressure oil pipe joints according to claim 8, characterized in that, The process of determining whether the trend of the distribution characterization curve has entered a preset state includes: Select a continuous time-series sliding window and extract the area ratio data of the first distribution characterization curve, the second distribution characterization curve, and the third distribution characterization curve within the current sliding window; Calculate the maximum fluctuation difference of the area ratio data of each distribution characterization curve within the current sliding window; Each maximum fluctuation difference is compared with a preset fluctuation difference threshold. If all maximum fluctuation differences are less than or equal to the fluctuation difference threshold, then the trend of the distribution characterization curve is determined to have entered a preset state.

10. The cold heading forming method for titanium alloy high-pressure oil pipe joints according to claim 9, characterized in that, The process of determining and optimizing molding parameters includes: Traverse the continuous time-series sliding window; The sliding window that first determines the curve trend of the distribution characterization curve enters the preset state is defined as the target sliding window; The starting time of the target sliding window is obtained, and the application frequency of the pulse forging pressure corresponding to the starting time is determined as the optimization forming parameter.

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