A cold heading process for connecting a backrest welding nut blank

Abstract

The application provides a backrest connecting welding nut blank cold heading forming process, and relates to the field of cold heading forming, and sequentially comprises the following steps: step 1, blanking; step 2, shaping: extruding a bottom round corner and a top about 3° conical surface of a cylindrical blank through a first station cold heading die; step 3, turning over the blank by 180° and placing it into a second station cold heading die, extruding a pull hole positioning hole at the end of the bottom about 3° conical surface and upsetting the top round corner end into a preformed step; step 4, upsetting flange and preforming pull hole positioning hole: translating the blank and placing it into a third station cold heading die for upsetting, upsetting and flattening the end face of the bottom pull hole positioning hole, and upsetting and forming the flange. Step 5, reverse extruding inner hole; step 6, extruding through hole. Step 7, stamping and cutting the flange shape feature. The application meets the strength of the welding nut, locally increases the step special-shaped structure, and adapts to the assembly requirements of different hole diameter connecting pieces.

Description

Technical Field

[0001] This invention relates to the field of cold heading forming technology, specifically to a cold heading forming process for a back-to-back welding nut blank. Background Technology

[0002] In the manufacturing of automotive backrest connectors, cold heading has become the mainstream processing method for welded nut parts due to its high efficiency, high material utilization, and good mechanical properties. However, existing cold-headed welded nuts still face the following technical bottlenecks: Currently, cold heading mainly produces standard welded nuts with a simple structure, making it difficult to meet modern demands for irregularly shaped connectors. Summary of the Invention

[0003] This invention provides a cold heading process for backrest connection welding nut blanks to solve the technical problems mentioned in the background art.

[0004] To solve the above-mentioned technical problems, the present invention discloses a cold heading forming process for a backrest connection welding nut blank, comprising:

[0005] Step 1: Make a cylindrical blank;

[0006] Step 2: The cylindrical blank is extruded through the cold heading die at the first station to form the bottom rounded corners and the top conical surface;

[0007] Step 3: Flip the blank obtained in Step 2 180° and place it into the cold heading mold at the second station. Extrude the bottom conical end to form the drawing hole positioning hole and the top rounded end to form the pre-formed step.

[0008] Step 4: Transfer the blank obtained in Step 3 into the cold heading mold at the third station for upsetting. Upset and flatten the bottom hole positioning hole end face, and then upset to form the flange.

[0009] Step 5: Transfer the blank obtained in Step 4 into the cold heading mold at the fourth station for reverse extrusion, and extrude the inner hole on the end face of the bottom hole positioning hole.

[0010] Step 6: Transfer the blank obtained in Step 5 into the cold heading mold at the fifth station for piercing, and punch through the entire workpiece. After the through part becomes punching waste and is discharged, a circular through hole is obtained.

[0011] Step 7: The blank obtained in Step 6 is transferred into the cold heading mold at the sixth station. The punching rod forces the round flange into the main mold cavity of the irregular size. The excess flange material is cut off on the end face of the main mold to obtain the structural features of the irregular flange.

[0012] Preferably, in step 1, the cold heading disc is cut into individual cylindrical blanks by the cutting station of the cold heading machine.

[0013] Preferably, in the step 2, the angle between the generatrix of the top conical surface and the cone bottom of the conical surface is 3±A°, A is 0.1-0.3.

[0014] Preferably, the step 2 is performed between the step 1 and the step 2, and the step 2 includes:

[0015] Step 21: detecting the hardness and surface roughness of the batch blank to be upset, and determining the corresponding cold upsetting hardening coefficient of the batch blank to be upset based on the material type of the batch blank to be upset and the material type-blank hardness range-cold upsetting hardening coefficient mapping table of the blank;

[0016] Step 22: obtaining the cavity structure parameters and cavity surface roughness of the current mold, and determining the filling state coefficient of the batch blank to be upset based on the cavity structure parameters of the current mold, the cavity surface roughness of the current mold, the yield strength of the batch blank to be upset and the surface roughness of the batch blank to be upset;

[0017] Step 23: determining the initial cold upsetting parameter interval of the batch blank to be upset based on the corresponding cold upsetting hardening coefficient of the batch blank to be upset and the filling state coefficient of the batch blank to be upset;

[0018] Step 24: determining the cold upsetting parameter during the cold upsetting measurement based on the initial cold upsetting parameter, and performing the cold upsetting measurement process on the batch blank to be upset based on the cold upsetting parameter during the cold upsetting measurement, to determine the final cold upsetting parameter of the batch blank to be upset.

[0019] Preferably, the step 24 includes:

[0020] Step 241: performing the cold upsetting measurement process on the batch blank to be upset with the initial cold upsetting parameter interval, detecting the temperature of the surface temperature measurement area of the blank before and after the cold upsetting measurement, and timing the contact time between the cold upsetting upper die and the batch blank to be upset during the cold upsetting measurement process;

[0021] Step 242: determining the blank temperature characteristic parameter and the blank deformation zone thermal stress concentration coefficient based on the detection results of the cold upsetting measurement process related parameters, and determining whether the actual forming quality is qualified based on the forming quality detection after forming;

[0022] Step 243: when the reference qualified condition is met, the initial cold upsetting parameter interval is determined as the final cold upsetting parameter; the reference qualified condition is that the blank temperature characteristic parameter and the blank deformation zone thermal stress concentration coefficient both meet the corresponding preset allowable range and the actual forming quality is qualified;

[0023] Step 244: including:

[0024] Step 2441: fixing the cold upsetting speed and the pressure maintaining time, and determining the adjusted cold upsetting pressure based on the hot stress concentration coefficient of the blank deformation zone and the blank temperature characteristic parameter, and repeating steps 241-243 based on the adjusted cold upsetting pressure and other cold upsetting parameters unchanged;

[0025] Step 2442: when the final cold upsetting parameters cannot be determined based on step 2441, the adjusted cold upsetting speed is determined based on the cold upsetting parameters in step 2441, and steps 241-243 are repeated based on the adjusted cold upsetting speed and other cold upsetting parameters unchanged.

[0026] Preferably, step 242 specifically comprises:

[0027] Based on the determination of the blank temperature gradient and the blank temperature characteristic parameter in step 241, the hot stress concentration coefficient of the blank deformation zone is determined based on the blank temperature gradient and the key size of the blank.

[0028] Preferably, a step 7 control parameter determination process is performed between the steps 6 and 7, and the step 7 control parameter determination process comprises:

[0029] Step 71: detecting the diameter of the circular flange of the blank obtained in step 6 and the thickness of the flange face at different positions, and determining the interference coefficient based on the diameter of the circular flange of the blank obtained in step 6 and the inner diameter of the main mold cavity;

[0030] Step 72: determining the flange face thickness uniformity coefficient based on the thickness of the flange face at different positions;

[0031] Step 73: obtaining a plurality of descending sub-sections divided by the target descending section of the circular flange, and the reference descending speed range of the descending sub-section and the reference speed gradient of the adjacent descending sub-section;

[0032] Step 74: determining the target extrusion pressure based on the interference coefficient, and determining the modified speed gradient of the adjacent descending sub-section based on the target extrusion pressure;

[0033] Step 75: determining the target descending speed of each descending sub-section based on the interference coefficient, the target extrusion pressure, the flange face thickness uniformity coefficient, and the modified speed gradient of the adjacent descending sub-section;

[0034] When performing step 7 on the batch of blanks obtained in step 6 of the current batch, the actual descending speed of each descending sub-section is controlled to be the corresponding target descending speed, and the actual extrusion pressure is controlled to be the target extrusion pressure.

[0035] The application also discloses a cold upsetting forming die for a backrest connecting welding nut blank, which is applied to the cold upsetting forming process of the backrest connecting welding nut blank. The forming die comprises a first station cold upsetting die, a second station cold upsetting die, a third station cold upsetting die, a fourth station cold upsetting die, a fifth station cold upsetting die and a sixth station cold upsetting die.

[0036] The technical solutions of the present application are described in further detail below with reference to the accompanying drawings and examples.

[0037] Compared with the prior art, the present application has the following beneficial effects:

[0038] The forming process of the present application is designed using multi-station metal cold upsetting forming technology, which uses the highest forming technology in cold upsetting technology and determines a complete set of correct forming methods for metal fluid deformation of the metal part.

[0039] The completed steps can be adjusted according to the different seat skeleton hole diameters to meet the assembly requirements of the special-shaped connecting piece of the modern automobile seat system.

[0040] The backrest connecting welding nut provided by the present application realizes three technical breakthroughs through the innovative multi-station precision plastic forming process:

[0041] (1) Gradient deformation technology is adopted to realize local step special-shaped structure forming while ensuring overall strength, and material utilization rate is improved to 95%;

[0042] (2) The metal flow path is optimized to make the product metal flow line continuity reach more than 98%;

[0043] (3) The special-shaped flange structure is stamped to reduce the need for subsequent secondary processing.

[0044] The technical scheme effectively solves the problems of traditional process in structure adaptability, material performance and process economy, and provides a more optimized solution for the automobile seat connecting piece. DETAILED DESCRIPTION

[0045] The accompanying drawings are used to provide a further understanding of the present application, and constitute a part of the specification, together with the embodiments of the present application, to explain the present application, and do not constitute a limitation on the present application. In the drawings:

[0046] Figure 1 It is a process flow diagram of the present application;

[0047] Figure 2 It is a schematic diagram of the blank at each step of the present application;

[0048] Figure 3 It is a schematic diagram of the main components of the first station cold upsetting die of the present application;

[0049] Figure 4 It is a schematic diagram of the main components of the second station cold upsetting die of the present application;

[0050] Figure 5The main component schematic diagram of the third station cold heading die of the present application is shown in the figure;

[0051] Figure 6 The main component schematic diagram of the fourth station cold heading die of the present application is shown in the figure;

[0052] Figure 7 The main component schematic diagram of the fifth station cold heading die of the present application is shown in the figure;

[0053] Figure 8 The main component schematic diagram of the sixth station cold heading die of the present application is shown in the figure. DETAILED DESCRIPTION

[0054] The preferred embodiments of the present application are described below in conjunction with the accompanying drawings, and it should be understood that the preferred embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.

[0055] In addition, the description such as "first", "second" and the like in the present application is only for the purpose of description, and does not mean to particularly indicate the order or sequence, nor to limit the present application, which is merely to distinguish the components or operations described by the same technical terms, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implying the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions and technical features of various embodiments can be combined with each other, but it must be based on the realization of ordinary skilled in the art, and when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor within the protection scope required by the present application.

[0056] The present application provides the following embodiments:

[0057] Embodiment 1, the present application provides a cold heading forming process for connecting the backrest welding nut blank, as shown in Figures 1-8 , comprising:

[0058] Step 1: blanking: making cylindrical blank;

[0059] Step 2: shaping: extruding the cylindrical blank through the first station cold heading die to form the bottom round corner and the top conical surface;

[0060] Step 3: preforming and positioning hole of preforming hole: the blank obtained in step 2 is turned over 180° and put into the second station cold heading die, the bottom conical surface end is extruded to form the positioning hole of the preforming hole and the top round corner end is preformed to form the preforming step;

[0061] Step 4: roughing flange and preforming hole positioning hole: the blank obtained in step 3 is translated and placed into the third station cold heading die for roughing, the bottom hole positioning hole end face is roughened and flattened, and the flange is formed;

[0062] Step 5: extruding a through hole: the blank obtained in step 4 is translated and placed into the fourth station cold heading die for reverse extrusion, and an inner hole is extruded on the bottom hole positioning hole end face;

[0063] Step 6: the blank obtained in step 5 is translated and placed into the fifth station cold heading die for piercing, and the whole workpiece is punched through, and the through part is discharged as punching waste, and a circular through hole after punching is obtained;

[0064] Step 7: stamping and cutting flange shape features: the blank obtained in step 6 is translated and placed into the sixth station cold heading die, and the circular flange is extruded into the special-shaped size main die cavity by the punch, and the excess flange material is cut on the main die end face, and the special-shaped flange structure feature is obtained.

[0065] In the step 1, the cold heading disc is cut into a single cylindrical blank by the cold heading machine cutting station.

[0066] In the step 2, the angle between the generatrix of the top conical surface and the conical bottom of the conical surface is 3±A°, and A is 0.1-0.3.

[0067] The application further discloses a cold heading forming die for a backrest connecting welding nut blank, which is applied to the cold heading forming process of the backrest connecting welding nut blank.

[0068] The first station cold heading die comprises a first punch rod 11, a first punch sleeve 21, a first main die shell 31, a first main die core 41 and a first main die ejector pin 51.

[0069] The second station cold heading die comprises a second punch rod 12, a second punch sleeve 22, a second main die shell 32, a second main die core 42 and a second main die ejector pin 52.

[0070] The third station cold heading die comprises a third punch rod 13, a third punch sleeve 23, a third main die shell 33, a third main die core 43, a third main die ejector pin 53 and a third punch sleeve pipe 63.

[0071] The fourth station cold heading die comprises a fourth punch rod 14, a fourth punch sleeve 24, a fourth main die shell 34, a fourth main die core 44, a fourth main die ejector pin 54, a fourth punch sleeve pipe 64, a fourth back punch 74 and a fourth back punch sleeve pipe 84.

[0072] The fifth station cold heading die comprises: a fifth main die shell 35; a fifth main die core 45; a fifth main die ejector pin 55; a fifth punch sleeve 65; a fifth punch 95; a fifth back punch 75; a back punch sleeve 85; six butterfly springs; and a fifth punch rod is a three-needle punch rod;

[0073] The sixth station cold heading die comprises: a sixth punch rod 16; a sixth punch sleeve 26; a sixth main die shell 36; a sixth main die core 46; a trimming die 10; a trimming die core 101; a sixth main die ejector pin 66; and six butterfly springs;

[0074] The purpose of the present application is to provide a cold heading forming process for a backrest connecting welding nut blank.

[0075] The present application uses shaping, upsetting, deep hole drawing, extrusion piercing, stamping and trimming, and other technologies to form a complete cold heading forming process for the backrest connecting welding nut blank.

[0076] The present application provides a backrest connecting welding nut formed by multi-station precision plastic forming, which realizes the following technical breakthroughs: on the basis of meeting the strength of the welding nut, locally increasing the stepped special-shaped structure, adapting to the assembly requirements of different hole diameter connecting pieces, and realizing the design concept of meeting the strength and light weight; and the forming process provided by the present application can realize continuous metal flow lines of the welding nut, and improve the fatigue strength and dynamic bearing capacity.

[0077] The above technical scheme has the following beneficial effects:

[0078] The forming process of the present application is designed using multi-station metal cold heading forming technology, which uses the highest forming technology in cold heading technology to determine a complete and correct forming method for the deformation of the metal fluid of the metal part.

[0079] The completed step can be adjusted according to the different seat skeleton hole diameters to meet the assembly requirements of the special-shaped connecting piece of the modern automobile seat system.

[0080] The backrest connecting welding nut provided by the present application realizes three technical breakthroughs through the innovative multi-station precision plastic forming process:

[0081] (1) The gradient deformation technology is adopted to realize the forming of the local stepped special-shaped structure while ensuring the overall strength, and the material utilization rate is improved to 95%;

[0082] (2) By optimizing the metal flow path, the product metal flow line continuity reaches more than 98%;

[0083] (3) The structure of the punched special-shaped flange reduces the need for subsequent secondary processing.

[0084] The technical scheme effectively solves the problems of traditional processes in structure adaptability, material performance and process economy, and provides a more optimized solution for automobile seat connecting pieces.

[0085] In embodiment 2, on the basis of embodiment 1, a cold upsetting parameter determination process of step 2 is performed between step 1 and step 2, and the cold upsetting parameter determination process of step 2 comprises:

[0086] Step 21: detecting the hardness and surface roughness of the batch of blank to be upset (the batch of blank to be upset of step 2), and determining the cold upsetting hardening coefficient corresponding to the batch of blank to be upset based on the material type of the batch of blank to be upset and the material type-blank hardness range-cold upsetting hardening coefficient mapping table of the blank (corresponding to the process of step 2);

[0087] Cold upsetting hardening coefficient ; wherein, is the hardness of the blank before cold upsetting; is the hardness of the blank after cold upsetting; is the cold upsetting strain of the blank (the ratio of the cold upsetting deformation amount to the corresponding original size, which can be the average strain when there are multiple deformation amounts); is the natural logarithm; , It can be determined based on the experimental data and historical data of the current same kind and same size blank producing the same size product; this step is for determining the current batch of blank;

[0088] The "material type-blank hardness range-cold upsetting hardening coefficient mapping table" is a table that corresponds one-to-one the different material types, the range of blank cold upsetting pre-hardness, and the corresponding cold upsetting hardening coefficient according to experimental or production data. After detecting the material type and cold upsetting pre-hardness of the batch of blank to be upset, the corresponding cold upsetting hardening coefficient of the blank can be directly found from the table, without the need to calculate the cold upsetting pre-hardness, post-hardness, strain, etc. every time, to provide parameter basis for cold upsetting process conveniently and quickly.

[0089] Step 22: obtaining the cavity structure parameters and cavity surface roughness of the current mold, and determining the filling state coefficient of the batch of blank to be upset based on the cavity structure parameters of the current mold, the cavity surface roughness of the current mold, the yield strength of the batch of blank to be upset and the surface roughness of the batch of blank to be upset;

[0090] Step 23: determining the initial cold upsetting parameter interval of the batch of blank to be upset based on the cold upsetting hardening coefficient corresponding to the batch of blank to be upset and the filling state coefficient of the batch of blank to be upset;

[0091] In the cold upsetting process, the cold upsetting hardening coefficient (reflecting the material deformation hardening law) and the filling state coefficient (reflecting the difficulty of cavity filling) are the core quantitative indicators of "material properties" and "mold properties". Through experiments or simulations, a mapping table of "hardening coefficient-filling coefficient → cold upsetting parameter (extrusion force, speed, mold temperature, etc.) interval" can be established in advance. Subsequently, only the current blank coefficient needs to be matched, and the parameter interval can be quickly queried.

[0092] Step 24: Determine the cold upsetting measured time cold upsetting parameters based on the initial cold upsetting parameters (which can be determined based on the methods of embodiments 3 or 4; or based on existing methods), and perform a cold upsetting measurement process on the blank of the batch to be upset based on the cold upsetting measured time cold upsetting parameters to determine the final cold upsetting parameters of the blank of the batch to be upset.

[0093] ;

[0094] Wherein, Q is the filling state coefficient of the blank of the batch to be upset; K is the complexity coefficient of the cavity structure of the current mold; is the uneven deformation coefficient of the blank of the current mold (determined by the ratio of the maximum depth to the minimum width of the cavity, the larger the ratio, the larger the uneven deformation coefficient of the blank; The value range is 0.1~0.4); is the surface roughness of the cavity of the current mold; is the surface roughness of the blank of the batch to be upset; 、 、 、 、 respectively, the reference complexity coefficient of the cavity structure, the reference uneven deformation coefficient of the blank, the reference surface roughness of the cavity of the mold, the reference yield strength of the blank, and the reference surface roughness of the blank; 、 、 respectively, the cavity influence index (the value is 0.8~1.2), the yield strength influence index (the value is 1~1.5), and the roughness influence index (the value is 0.6~1); is the yield strength of the blank of the batch to be upset; 、 、 The greater the impact on the filling effect (such as filling integrity and filling speed), the greater the value; the above influence indexes are mainly obtained through theoretical analysis, experimental determination, and experience summary and optimization.

[0095] The complexity coefficient of the cavity structure of the current mold is used to measure the difficulty of the mold cavity shape to the blank filling. The more complex the cavity structure, the greater the metal flow resistance and the more irregular the path;

[0096] Simple cavity: K is [1.0, 1.2], the cavity shape is regular, the metal flow resistance is small, and the filling is easy.

[0097] Medium complex cavity: K is (1.2, 1.5], the cavity has a small amount of special-shaped structure or poor depth-width ratio (specific to each material), and the metal flow is hindered.

[0098] Complex cavity: K is (1.5, 2.0], the cavity structure is complex, with many special-shaped features or large depth-width ratio, and the metal flow is difficult.

[0099] For example (the specific complex coefficient determination rule for different cold heading steps can be determined according to the actual situation):

[0100] Simple case: If the mold cavity only needs to extrude a small round corner at the bottom (corner radius r = 1mm) and a shallow conical surface at the top (conical height h = 2mm, bottom diameter similar to the diameter of the blank), the cavity shape is regular, the metal flow path is clear, the resistance is small, and the filling is smooth. It belongs to a simple cavity, so K is 1.1.

[0101] Medium complex case: The mold cavity needs to extrude a larger round corner r = 3mm at the bottom, and a conical surface h = 5mm at the top, and there is a small transition step (step height 0.5mm) between the conical surface and the blank. At this time, the cavity has certain special-shaped structure, the metal flow needs to adapt to the round corner, conical surface and transition step, the resistance increases, it belongs to a medium complex cavity, and K is 1.3.

[0102] Complex case: The mold cavity not only needs to extrude a large round corner r = 4mm at the bottom and a high conical surface h = 8mm at the top, but also has 2 symmetrical small grooves (groove depth 1mm, width 2mm) on the conical surface for subsequent positioning. The cavity has multiple special-shaped features, the metal flow needs to fill the round corner, conical surface and groove, the path is complex, the resistance is large, and it belongs to a complex cavity, K is 1.6.

[0103] The beneficial effects of the above technical solutions are:

[0104] Through the "material type of blank - hardness range of blank - cold heading hardening coefficient mapping table", the cold heading hardening coefficient can be directly found, without the need to perform complex hardness and strain calculations before and after cold heading each time, greatly simplifying the preliminary work of cold heading parameter determination, and improving the convenience and efficiency of parameter acquisition.

[0105] The filling state coefficient formula comprehensively considers the mold cavity structure, the blank deformation uniformity, the blank yield strength, and roughness and other factors, can accurately evaluate the filling state of the blank to be upset, provides a reliable basis for determining the cold upsetting process parameters, helps to improve the quality of the cold upsetting product, and reduces the waste caused by filling problems.

[0106] Based on the accurate cold upsetting hardening coefficient and the filling state coefficient, the cold upsetting parameter interval is determined, and the final cold upsetting parameters are determined through actual measurement, which can optimize the cold upsetting process parameters, make the cold upsetting process more stable and efficient, and improve the overall level of cold upsetting production.

[0107] In embodiment 3, on the basis of embodiment 2, the step 24 comprises:

[0108] Step 241: cold upsetting the blank to be upset with the median value of the initial cold upsetting parameter interval, and detecting the temperature of the surface temperature measuring area of the blank before and after the cold upsetting measurement, and timing the contact time between the cold upsetting upper die and the blank to be upset during the cold upsetting measurement;

[0109] Step 242: determining the blank temperature characteristic parameter and the blank deformation zone thermal stress concentration coefficient based on the detection results of the related parameters of the cold upsetting measurement process, and determining whether the actual forming quality is qualified based on the forming quality detection after forming;

[0110] Step 243: when the reference qualified condition is reached, the median value of the initial cold upsetting parameter interval is determined as the final cold upsetting parameter; the reference qualified condition is that the blank temperature characteristic parameter and the blank deformation zone thermal stress concentration coefficient meet the corresponding preset allowable range and the actual forming quality is qualified; the above-mentioned preset allowable range is determined according to test or industry standard.

[0111] Step 244 comprises:

[0112] Step 2441: fixing the cold upsetting speed and the holding time, and determining the adjusted cold upsetting pressure based on the blank deformation zone thermal stress concentration coefficient and the blank temperature characteristic parameter, and repeating steps 241-243 based on the adjusted cold upsetting pressure and other unchanged cold upsetting parameters;

[0113] Step 2442: when the final cold upsetting parameter cannot be determined based on step 2441, the adjusted cold upsetting speed is determined based on the cold upsetting parameters in step 2441, and steps 241-243 are repeated based on the adjusted cold upsetting speed and other unchanged cold upsetting parameters.

[0114] Specifically, step 242 comprises:

[0115] The blank temperature gradient and the blank temperature characteristic parameter are determined based on step 241, and the blank deformation zone thermal stress concentration coefficient is determined based on the determined blank temperature gradient and the key size of the blank.

[0116] The blank temperature characteristic parameter Y = (the average value of the temperature of the surface temperature measurement area of the blank after cold heading - the average value of the temperature of the surface temperature measurement area of the blank before cold heading) ÷ the contact time of the upper die of cold heading with the batch of blank to be headed during the actual cold heading process;

[0117] The blank deformation zone thermal stress concentration coefficient is specifically:

[0118] ;

[0119] D is the diameter of the batch of blank to be headed before cold heading; D is the diameter of the batch of blank to be headed after cold heading; r is the fillet radius of the batch of blank to be headed after cold heading; is the cone angle of the conical surface of the batch of blank to be headed; is the optimal cone angle of the conical surface (corresponding to the type of the batch of blank to be headed); is the maximum allowable temperature gradient of the batch of blank to be headed after cold heading;

[0120] To determine the optimal cone angle of a specific type of blank, an experimental determination combined with experience summary method (or based on simulation (such as Deform software)) can be used. First, for a specific type of blank, cold heading experiments with different cone angles are carried out. In the experiment, the metal flow, stress distribution and forming quality are observed, and the cone angle that makes the cold heading process the most smooth and the forming quality the best is found. This cone angle is the optimal cone angle of the blank of this type.

[0121] The blank temperature gradient R = (the absolute difference between the average temperature of the deformation area and the average temperature of the non-deformation area in the surface temperature measurement area of the blank ÷ the first distance);

[0122] The first distance is the distance between the center of the deformation area and the center of the non-deformation area in the surface temperature measurement area of the blank;

[0123] The adjusted cold heading pressure = ;

[0124] The adjusted cold heading speed = ;

[0125] is the cold heading pressure before adjustment; is the cold heading speed before adjustment; is the median value of the preset allowable range corresponding to the blank deformation zone thermal stress concentration coefficient; is the median value of the preset allowable range corresponding to the blank temperature characteristic parameter; 、 are respectively the cold heading pressure correction coefficient corresponding to the blank deformation zone thermal stress concentration coefficient and the cold heading pressure correction coefficient corresponding to the blank temperature characteristic parameter; 、 respectively, and the cold heading speed correction coefficient corresponding to the blank temperature characteristic parameter;

[0126] , , , The value range is greater than 0 and less than 0.5, which is mainly obtained through process test and numerical simulation:

[0127] Test level: Under the working conditions of different blank deformation zone thermal stress concentration coefficients (deviation ) and different blank temperature characteristic parameters (deviation ), cold heading process test is carried out, the actual optimal adjustment amount of cold heading pressure and cold heading speed is recorded, and the , Theoretical calculation is associated to fit the approximate range of correction coefficient.

[0128] Numerical simulation level: the finite element software is used to establish the simulation model of the cold heading process, the deformation of the blank under different thermal stress concentration coefficients and temperature characteristic parameters is simulated, the theoretical correction requirement of cold heading pressure and speed is calculated, and the correction coefficient is further calibrated. Through comparison and regression analysis of test data and simulation results, the specific value of each correction coefficient is finally determined.

[0129] The beneficial effects of the above technical solutions are:

[0130] By accurately calculating the key indicators such as blank deformation zone thermal stress concentration coefficient and temperature characteristic parameter, the cold heading pressure and speed are dynamically adjusted. When the blank thermal stress concentration is more serious or the temperature deviates from the reasonable range, the cold heading pressure and speed are timely reduced, effectively avoiding defects such as cracks and size out-of-tolerance of cold heading parts, and greatly improving the forming precision and surface quality of cold heading parts.

[0131] Based on the scientific parameter calculation and correction mechanism, the process parameters in the cold heading process can be adjusted in real time according to the actual state of the blank, reducing the process fluctuations caused by parameter mismatch, making the cold heading production process more stable, reducing the scrap rate, and ensuring the continuity and stability of production.

[0132] Full consideration is given to the differences in blank types, geometric parameters (such as diameter, fillet radius, taper angle, etc.), and the optimal taper angle of different blank types is determined to flexibly adapt to the cold heading production needs of various blanks, expand the application scenarios of cold heading process, and improve the universality of the process.

[0133] Compared with the traditional method of adjusting process parameters depending on experience, the method realizes rapid and accurate adjustment of parameters by means of quantitative calculation, reduces the time cost of parameter debugging, improves the efficiency of cold heading production, and reduces the dependence on the experience of operators, facilitating the standardization and popularization of the process.

[0134] In embodiment 4, on the basis of embodiment 2 or 3, step 2 further comprises a detection alarm process, and the detection alarm process comprises:

[0135] Step 201: Collecting cold heading defect-free historical data, and dividing the data into first-level data and second-level data according to matching degrees; constructing a two-dimensional table with cold heading hardening coefficients as rows and blank filling state coefficients as columns; and preferentially filling the cold heading force and cold heading speed of the first-level data into the header intersection cells, and filling the cold heading force and cold heading speed of the second-level data into the header intersection cells and marking as reference if the first-level data is missing.

[0136] When there are multiple groups of data in the same cell, the parameter fluctuation range is calculated, and the current parameter fluctuation value formula is: (the maximum value of the current parameter-the minimum value of the current parameter) / the average value of the current parameter; if the fluctuation range is less than or equal to 5%, the average value ± the fluctuation range (the average value ± the fluctuation range correspond to the cold heading force and the cold heading speed) is stored; if the fluctuation range is greater than 5%, the abnormal value is removed, and the latest m (such as 10) group average values are stored; if there is no data in the cell, the data of adjacent groups is retrieved and interpolated to complete the data;

[0137] The first-level data is of the same material and has the same cold heading hardening coefficient and blank filling state coefficient; and the second-level data is of the same material, has different cold heading hardening coefficients and blank filling state coefficients, but meets the requirements and is marked as a reference level.

[0138] Step 202: Associating the mold cavity temperature gradient (which can also be in the form of average value ± fluctuation range) with the two-dimensional table cell data and filling it into the corresponding intersection cell;

[0139] The calculation formula of the mold cavity temperature gradient is: (the highest temperature of the mold cavity key temperature detection area-the lowest temperature of the mold cavity key temperature detection area) ÷ the distance between the place where the highest temperature of the mold cavity key temperature detection area is located and the place where the lowest temperature of the mold cavity key temperature detection area is located.

[0140] Step 203: During the production of the current batch of blanks, the actual mold cavity temperature gradient is periodically detected, and when the absolute difference between the actual mold cavity temperature gradient and the mold cavity temperature gradient associated with the two-dimensional table is greater than a preset value, an alarm is given.

[0141] Step 204: Determine the maximum allowable pressure fluctuation value corresponding to the current batch of blank based on the cold heading force, cold heading speed, and mold cavity temperature gradient in the two-dimensional table corresponding to the current batch of blank; when the actual pressure fluctuation value is greater than the maximum allowable pressure fluctuation value during the production of the current batch of blank, an alarm is given.

[0142] Interpolation is a method of estimating unknown values between known data points, such as linear interpolation. By using the cold heading hardening coefficient, blank filling state coefficient, and corresponding cold heading force and cold heading speed of adjacent effective cells (filled with cold heading force and cold heading speed data), the cold heading force and cold heading speed completion values of the current blank cell are calculated to achieve reasonable data filling and ensure the integrity of the two-dimensional table, providing a data basis for subsequent operations related to mold cavity temperature gradient, etc.

[0143] When there is no data in the cross cell, the completion value is calculated by the following steps:

[0144] Determine the known conditions:

[0145] The cold heading hardening coefficient of the blank cell is "target hardening coefficient", and the blank filling state coefficient is "target filling coefficient";

[0146] The coefficients of adjacent cell 1 are "known hardening coefficient 1" and "known filling coefficient 1", and the corresponding cold heading force is "known force 1" and the cold heading speed is "known speed 1";

[0147] The coefficients of adjacent cell 2 are "known hardening coefficient 2" and "known filling coefficient 2", and the corresponding cold heading force is "known force 2" and the cold heading speed is "known speed 2".

[0148] Cold heading force completion value calculation: blank cell cold heading force completion value = known force 1 + [(target hardening coefficient - known hardening coefficient 1) ÷ (known hardening coefficient 2 - known hardening coefficient 1)] × (known force 2 - known force 1)

[0149] Cold heading speed completion value calculation: blank cell cold heading speed completion value = known speed 1 + [(target filling coefficient - known filling coefficient 1) ÷ (known filling coefficient 2 - known filling coefficient 1)] × (known speed 2 - known speed 1);

[0150] Maximum allowable pressure fluctuation value = reference coefficient × cross cell cold heading force representative value × reference temperature gradient ÷ associated temperature gradient characteristic value;

[0151] Wherein:

[0152] Cross cell cold heading force representative value: refers to the cold heading force characteristic value (such as mean value) stored in the two-dimensional table corresponding to the current batch of blank;

[0153] When the associated temperature gradient is a fixed value, the associated temperature gradient characteristic value is the value; when the associated temperature gradient is a range, the associated temperature gradient characteristic value is the mean value of the range.

[0154] The reference coefficient is generally a coefficient fitted based on a large amount of historical defect-free production data, and the value range is generally between 0.05 and 0.2, which is used for proportional scaling of the cold heading force representative value and other parameters to obtain a reasonable maximum allowable pressure fluctuation value range.

[0155] The reference temperature gradient is a mold cavity temperature gradient reference value determined by statistics based on long-term defect-free production data of the same material and the same type of product in the cold heading process. It reflects the typical level of the temperature change rate of the key area of the mold cavity in the stable state of the process (i.e. the temperature difference per unit distance).

[0156] The beneficial effects of the above technical solutions are:

[0157] By collecting defect-free historical data (first-level and second-level data) in stages and preferentially using high-matching-degree data, the basic reliability of core parameters such as cold heading force and cold heading speed in the two-dimensional table is ensured. For blank cells, a linear interpolation completion method is used to calculate reasonable values based on the coefficient difference of adjacent effective data and the parameter association relationship, avoiding process parameter discontinuity caused by data loss. This data processing method not only retains the core value of historical successful experience, but also fills in the data blanks through scientific interpolation methods, providing complete and continuous data basis for subsequent process monitoring and early warning, and reducing the decision bias caused by incomplete data.

[0158] The scheme binds and stores the cold heading force, cold heading speed and mold cavity temperature gradient range in the two-dimensional table, establishing a direct mapping relationship between "process parameters-temperature characteristics". This association is not simply a data superposition, but based on historical defect-free production records, the reasonable fluctuation interval of the mold temperature field under specific process parameters is refined, so that temperature monitoring is upgraded from "isolated detection" to "targeted monitoring matching process parameters".

[0159] The calculation model of the maximum allowable pressure fluctuation value combines the cold heading force representative value and the mold temperature gradient characteristics, breaking through the limitations of the traditional "fixed threshold".

[0160] Standardized process parameter management reduces the dependence on human experience The construction of the two-dimensional table and the calculation logic of the data completion rule and the early warning threshold are all based on clear quantitative standards (such as data grading rules, interpolation formulas, and temperature and pressure alarm conditions), so that the selection, monitoring and adjustment of cold heading process parameters are changed from "depending on operator experience judgment" to "standardized decision based on data model".

[0161] Through multi-layer monitoring such as temperature gradient deviation early warning and pressure fluctuation overrun early warning, the transformation from "defect detection after the fact" to "risk early warning in the process" is realized. For example, when the mold temperature gradient exceeds the relevant range, the system gives an early warning, which can stop the machine for inspection of the mold cooling system or the billet preheating state in time to avoid batch defects caused by continuous production; pressure fluctuation overrun early warning can quickly identify equipment abnormalities (such as hydraulic system failure), reducing the cost of mold repair or billet waste caused by the expansion of equipment problems.

[0162] In the embodiment 5, on the basis of any one of the embodiments 1-4, a step 7 control parameter determination process is performed between the step 6 and the step 7, and the step 7 control parameter determination process comprises:

[0163] Step 71: detecting the diameter of the circular flange of the billet obtained in the step 6 and the thickness of the flange face at different positions, and determining an interference coefficient based on the diameter of the circular flange of the billet obtained in the step 6 and the inner diameter of the main mold cavity;

[0164] Step 72: determining a flange face thickness uniformity coefficient based on the thickness of the flange face at different positions;

[0165] Flange face thickness uniformity coefficient = 1 - (standard deviation of the thickness of the flange face at different positions ÷ average value of the thickness of the flange face at different positions);

[0166] Step 73: obtaining a plurality of descending sub-sections divided by the target descending section of the circular flange, and a reference descending speed range of the descending sub-section and a reference speed gradient of adjacent descending sub-sections;

[0167] Step 74: determining a target extrusion pressure based on the interference coefficient, and determining a corrected speed gradient of adjacent descending sub-sections based on the target extrusion pressure;

[0168] Step 75: determining a target descending speed of each descending sub-section based on the interference coefficient, the target extrusion pressure, the flange face thickness uniformity coefficient, and the corrected speed gradient of adjacent descending sub-sections;

[0169] When performing the step 7 on the batch of billets obtained in the step 6 of the current batch, the actual descending speed of each descending sub-section is controlled to be the corresponding target descending speed, and the actual extrusion pressure is controlled to be the target extrusion pressure.

[0170] ;

[0171] is the reference speed gradient of the i-th group of adjacent descending sub-sections (the first group of adjacent descending sub-sections is the first descending sub-section and the second descending sub-section); is the corrected speed gradient of the i-th group of adjacent descending sub-sections (the difference between the speed of the latter descending sub-section and the speed of the former descending sub-section); is the target extrusion pressure; reference extrusion force; is the correction coefficient of the extrusion force-velocity gradient corresponding to the i-th group of adjacent descending sub-sections (the value is greater than or equal to -0.5 and less than or equal to 0.5);

[0172] The correction coefficient is obtained through experiments: during extrusion forming, for the i-th group of adjacent descending sub-sections, different target extrusion forces are set, the qualified descending velocity gradient (the forming process of the flange from one sub-section to the next sub-section is smooth, and no forming defects or mold damage caused by sudden change of velocity) and the reference velocity gradient of the adjacent descending sub-sections under the corresponding conditions are measured, and then the correction coefficient is obtained through data analysis and fitting combined with the reference extrusion force and other data.

[0173] ;

[0174] is the interference coefficient; is the reference interference coefficient;

[0175] The interference coefficient is the ratio of the diameter of the circular flange of the blank obtained in step 6 to the reference inner diameter of the main mold cavity for cooperating with the circular flange to realize the forming of the special-shaped flange body; is the target descending velocity of the j-th descending sub-section; is the reference descending velocity of the j-th descending sub-section; is the correction velocity gradient of the j-th descending sub-section and its previous descending sub-section; is the reference velocity gradient of the j-th descending sub-section and its previous descending sub-section; 、 、 are the descending velocity correction indexes corresponding to the extrusion force, the descending velocity correction indexes corresponding to the interference coefficient, and the descending velocity correction indexes corresponding to the velocity gradient, respectively;

[0176] 、 all take values greater than or equal to 0.2 and less than or equal to 0.8; takes a value greater than or equal to -0.5 and less than or equal to 0.5;

[0177] Correction index acquisition: process test level: under different extrusion forces, interference coefficients, and velocity gradients, cold heading tests are performed on the blank, and the optimal descending velocity for the best forming quality of the cold heading part under each working condition is recorded. The optimal descending velocity obtained by the test is compared with the reference descending velocity, and the change amount of the extrusion force, the interference coefficient, and the velocity gradient is combined to fit the approximate range of the correction index. For example, by fixing the interference coefficient and the velocity gradient, changing the extrusion force, and observing the relationship between the optimal adjustment proportion of the descending velocity and the change proportion of the extrusion force, the correction index is determined. The possible value range of the correction index. Numerical simulation level: a simulation model of the cold heading process is established by using finite element software to simulate the deformation process of the blank under different extrusion forces, interference coefficients, and velocity gradients, analyze the relationship between the forming quality (such as metal flow uniformity, stress distribution, etc.) and the falling speed, calculate the theoretically optimal falling speed correction law, and then calibrate the correction index to make it more consistent with the actual process requirements. Through comparison and regression analysis of a large amount of experimental data and simulation results, the specific value of each correction index is finally determined.

[0178] A preset blank material type-flange cutting thickness range-interference coefficient range-target extrusion force mapping table is provided.

[0179] The main cavity is used to cooperate with the circular flange to realize the forming of the special-shaped flange body, and can be understood as the core inner diameter in the special-shaped main cavity which is matched with the special-shaped flange body part formed after extrusion with the circular flange, and is usually the characteristic inner diameter of the flange body forming area of the special-shaped main cavity, such as the equivalent reference circle inner diameter of the special-shaped cavity.

[0180] The approach contact sub-section (absolute distance range: the vertical distance between the lower end surface of the flange and the entrance end surface of the main cavity is 0.5mm-5mm): in the stage when the flange is about to contact the main cavity but has not yet started to extrude into the main cavity, it is divided into a falling sub-section. In this stage, the flange is in a free falling or low speed approaching state, which mainly prepares for the subsequent extrusion forming, and the speed control is relatively flat, the purpose is to ensure that the flange can smoothly and accurately reach the entrance position of the main cavity, avoid damage or position deviation caused by too fast speed of the flange and the main cavity, and lay a good foundation for the subsequent extrusion forming.

[0181] The initial extrusion sub-section: when the flange starts to extrude into the main cavity, it is divided into a falling sub-section. In this stage, the flange is extruded by the main cavity, and the deformation is large, and the material flow and plastic deformation are relatively violent. In order to control the deformation process and make the flange smoothly and uniformly extrude into the cavity, the falling speed needs to be strictly controlled, and a relatively moderate speed is usually used to balance the extrusion force and the deformation degree, prevent the extrusion force from increasing suddenly due to too fast speed, damage the mold or make the flange forming uneven, and also avoid too slow speed affecting the production efficiency.

[0182] The stable forming sub-section: when the deformation of the flange gradually stabilizes and approaches the final forming state, it is divided into another falling sub-section. In this stage, most of the plastic deformation of the flange has been completed, and the main purpose is to fine-tune and consolidate the forming shape. At this time, the falling speed can be adjusted adaptively according to the forming situation of the flange to ensure the size accuracy, thickness uniformity and other quality indicators of the flange, so that the flange can accurately reach the designed shape and size.

[0183] The reference descending speed range and the reference speed gradient of the adjacent descending sub-section are obtained based on experiments on the same material or based on historical data;

[0184] First, the same kind of blank material as used in production is selected, and a plurality of tests (corresponding to the reference interference coefficient) are performed on the cold heading equipment. In the test process, the target descending section of the circular flange is divided into different descending sub-sections, and then for each descending sub-section, different descending speeds are tried, and the corresponding cold heading effects, such as the forming quality of the flange, the stress condition of the die, etc., are recorded. By analyzing a plurality of test data, the speed interval in each descending sub-section that can make the flange forming quality optimal and the die stress reasonable is found out, thereby determining the reference descending speed range of the descending sub-section.

[0185] For the reference speed gradient of the adjacent descending sub-section, based on the above-mentioned tests on the same material (corresponding to the reference interference coefficient), the forming transition of the flange when the speed between adjacent sub-sections changes is observed. When the speed change rate (i.e. the speed gradient) between adjacent sub-sections is within a certain appropriate range, the forming process of the flange from one sub-section to the next sub-section is smooth, and there will be no forming defects or die damage caused by sudden speed change. By statistical analysis of these test data, a reasonable reference speed gradient between adjacent descending sub-sections is determined.

[0186] The preset "blank material type-flange cutting thickness range-interference coefficient range-target extrusion force mapping table" is established by experiments and theoretical analysis. Different blank materials (such as low carbon steel, stainless steel, etc.) have different physical properties (such as strength, plasticity, etc.); the flange cutting thickness also affects the stress condition in the forming process. The mapping table integrates these factors, and when the blank material type, flange cutting thickness range, and interference coefficient range are determined, the corresponding target extrusion force can be directly queried from the mapping table, without the need for complex calculations each time, improving the efficiency and accuracy of parameter determination in the production process.

[0187] The reference interference coefficient is a coefficient that is preset in the extrusion forming process and the like, and is used to represent the interference fit degree between the diameter of the blank circular flange and the reference inner diameter of the main die for realizing the forming of the special-shaped flange body in the reference state (such as standard process conditions, typical blank and die cooperation state (such as initially used die)).

[0188] The beneficial effects of the above technical solutions are:

[0189] The target extrusion force and the target descending speed of each descending sub-section are accurately determined by comprehensively considering the basic data such as the diameter of the circular flange of the blank, the thickness of the flange face at different positions, the interference coefficient and the thickness uniformity coefficient of the flange face. During the extrusion molding, the blank and the main mold can maintain good adaptability, the flange smoothly approaches from the approaching sub-section to the initial extrusion sub-section, and then is precisely adjusted in the stable molding sub-section. The speed and the extrusion force are accurately controlled in the whole process, the molding defects (such as uneven metal flow and unreasonable stress distribution) caused by improper speed or extrusion force are effectively avoided, the thickness of the flange face is uniform, the molding shape is accurate, the dimensional accuracy is high, and the overall molding quality of the special-shaped flange is improved.

[0190] By pre-determining the target descending speed and the target extrusion force of each descending sub-section, the optimized parameters can be directly controlled during batch production, and complex parameter adjustment is not needed each time of production. Meanwhile, reasonable speed and extrusion force control can make the blank deform efficiently and smoothly in each stage, reduce the production stagnation or rework caused by improper parameters, and improve the continuity and efficiency of production.

[0191] The application of the accurate speed gradient correction coefficient and each correction index, and the strict control of the descending speed and the extrusion force can make the force on the mold more reasonable during the molding process of the flange, avoid damage to the mold (such as mold wear and cracking) caused by sudden change of speed or sudden increase of extrusion force, prolong the service life of the mold, and reduce the cost of mold replacement and maintenance.

[0192] The "blank material type-flange cutting thickness range-interference coefficient range-target extrusion force mapping table" established based on experiments and theoretical analysis, and the reasonable acquisition and application of each parameter (such as the reference interference coefficient, the correction coefficient and the correction index) can make the whole extrusion molding process maintain stable parameter determination and control under different blanks and different flange cutting thicknesses, enhance the adaptability and stability of the process, and be beneficial to realize standardized and large-scale production.

[0193] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A cold-upsetting forming process for connecting a backrest welding nut blank, characterized in that: Comprise: Step 1: making cylindrical blank; Step 2: extruding the bottom round corner and the top conical surface of the cylindrical blank through the first station cold heading die; Step 3: placing the blank obtained in step 2 into the second station cold heading die by turning 180°, extruding the pull hole positioning hole at the bottom conical surface end and roughening the top round corner end into a preformed step; Step 4: placing the blank obtained in step 3 into the third station cold heading die by translation, roughening, and forming a flange on the bottom pull hole positioning hole end surface; Step 5: placing the blank obtained in step 4 into the fourth station cold heading die by translation, and inversely extruding an inner hole on the bottom pull hole positioning hole end surface; Step 6: placing the blank obtained in step 5 into the fifth station cold heading die by translation, and punching through the entire workpiece, until the through part becomes punch waste and is discharged, obtaining a circular through hole after punching; Step 7: placing the blank obtained in step 6 into the sixth station cold heading die by translation, and extruding the circular flange into the main die cavity of the special-shaped size by the punch rod, and the excess flange material is cut on the main die end surface, obtaining the special-shaped flange structure feature; The cold heading parameter determination process of step 2 is carried out between step 1 and step 2, and the cold heading parameter determination process of step 2 comprises: Step 21: detecting the hardness and surface roughness of the batch blank to be headed, and determining the cold heading hardening coefficient corresponding to the batch blank to be headed based on the material type of the batch blank to be headed and the material type-blank hardness range-cold heading hardening coefficient mapping table of the blank; Step 22: obtaining the cavity structure parameters and cavity surface roughness of the current die, and determining the filling state coefficient of the batch blank to be headed based on the cavity structure parameters of the current die and the cavity surface roughness of the current die, the yield strength of the batch blank to be headed and the surface roughness of the batch blank to be headed; Step 23: determining the initial cold heading parameter interval of the batch blank to be headed based on the cold heading hardening coefficient corresponding to the batch blank to be headed and the filling state coefficient of the batch blank to be headed; Step 24: determining the cold heading real-time parameter based on the initial cold heading parameter, and carrying out the cold heading real-time process on the batch blank to be headed based on the cold heading real-time parameter, to determine the final cold heading parameter of the batch blank to be headed.

2. A cold upset forming process for connecting backrest welding nut blanks according to claim 1, characterized in that: In step 1, the cold heading disc is cut into a single cylindrical blank by the cutting station of the cold heading machine.

3. A cold upset forming process for connecting backrest welding nut blanks as claimed in claim 1, characterized in that: In step 2, the angle between the generatrix of the top conical surface and the conical bottom of the conical surface is 3±A°, A is 0.1-0.

3.

4. A cold upset forming process for connecting backrest welding nut blanks according to claim 1, characterized in that: Step 24 comprises: Step 241: carrying out the cold heading real-time process on the batch blank to be headed with the initial cold heading parameter interval, detecting the surface temperature of the blank before and after the cold heading real-time process, and timing the contact time between the cold heading upper die and the batch blank to be headed during the cold heading real-time process; Step 242: determining the blank temperature characteristic parameter and the blank deformation zone thermal stress concentration coefficient based on the detection results of the cold heading real-time process related parameters, and determining whether the actual forming quality is qualified based on the forming quality detection after forming. Step 243: when the reference qualified condition is reached, the initial cold heading parameter interval value is determined as the final cold heading parameter; the reference qualified condition is that the blank temperature characteristic parameter and the blank deformation zone thermal stress concentration coefficient both satisfy the corresponding preset allowable range and the actual forming quality is qualified; Step 244 includes: Step 2441: fixing the cold heading speed and the holding time, and determining the adjusted cold heading pressure based on the blank deformation zone thermal stress concentration coefficient and the blank temperature characteristic parameter; repeating steps 241-243 based on the adjusted cold heading pressure and other cold heading parameters unchanged; Step 2442: when the final cold heading parameter cannot be determined based on step 2441, the adjusted cold heading speed is determined based on the cold heading parameters in step 2441, and steps 241-243 are repeated based on the adjusted cold heading speed and other cold heading parameters unchanged.

5. A cold upset forming process for connecting a backrest welding nut blank as claimed in claim 4, characterized in that: Step 242 specifically includes: Based on the blank temperature gradient and the blank temperature characteristic parameter determined in step 241, the blank deformation zone thermal stress concentration coefficient is determined based on the blank temperature gradient and the blank key size.

6. A cold upset forming process for connecting backrest welding nut blanks according to claim 1, characterized in that: The step 7 control parameter determination process is performed between the steps 6 and 7, and the step 7 control parameter determination process includes: Step 71: detecting the diameter of the circular flange of the blank obtained in step 6 and the thickness of the flange face at different positions, and determining the interference coefficient based on the diameter of the circular flange of the blank obtained in step 6 and the inner diameter of the main mold cavity; Step 72: determining the flange face thickness uniformity coefficient based on the thickness of the flange face at different positions; Step 73: obtaining a plurality of descending sub-sections divided by the target descending section of the circular flange, and the reference descending speed range of the descending sub-sections and the reference speed gradient of adjacent descending sub-sections; Step 74: determining the target extrusion pressure based on the interference coefficient, and determining the modified speed gradient of adjacent descending sub-sections based on the target extrusion pressure; Step 75: determining the target descending speed of each descending sub-section based on the interference coefficient, the target extrusion pressure, the flange face thickness uniformity coefficient, and the modified speed gradient of adjacent descending sub-sections; When performing step 7 on the current batch of blanks obtained in step 6, the actual descending speed of each descending sub-section is controlled to be the corresponding target descending speed, and the actual extrusion pressure is controlled to be the target extrusion pressure.

7. A cold upset forming process for connecting backrest welding nut blanks as claimed in claim 1, characterized in that: Step 2 further includes a detection alarm process, and the detection alarm process includes: Step 201: collecting cold heading defect-free historical data, which is divided into first-level data and second-level data according to matching degree; a two-dimensional table is constructed with cold heading hardening coefficient as row and blank filling state coefficient as column, and the first-level data of cold heading force and cold heading speed is preferentially filled in the header intersection cell, and if the first-level data is missing, the cold heading force and cold heading speed of the second-level data is filled in and marked as reference; When there are multiple sets of data in the same cell, the parameter fluctuation range is calculated; if the fluctuation range is ≤5%, the "cold heading force mean ± cold heading force fluctuation range and cold heading speed mean ± cold heading speed fluctuation range" is stored; if the fluctuation range is >5%, the abnormal value is removed, and the latest 10 sets of mean values are stored; if there is no data in the cell, the data of adjacent combinations is retrieved and interpolated to complete; Step 202: associating the mold cavity temperature gradient with the two-dimensional table cell data and filling the corresponding intersection cell. Step 203: periodically detecting the actual mold cavity temperature gradient during the production of the current batch of blank, and when the absolute difference between the actual mold cavity temperature gradient and the mold cavity temperature gradient associated with the two-dimensional table is greater than a preset value, an alarm is given; Step 204: determining the maximum allowable pressure fluctuation value corresponding to the current batch of blank based on the cold heading force, cold heading speed and mold cavity temperature gradient in the two-dimensional table corresponding to the current batch of blank; when the actual pressure fluctuation value is greater than the maximum allowable pressure fluctuation value during the production of the current batch of blank, an alarm is given.

8. A cold upset forming process for connecting a backrest welding nut blank according to claim 7, characterized in that: The first level data is of the same material and consistent cold heading hardening coefficient and blank filling state coefficient; the second level data is of the same material, with differences in cold heading hardening coefficient and blank filling state coefficient but meeting the requirements, and is marked as reference level.

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