Non-stub-bar cross wedge rolling composite near-net forming method for high-performance shaft

Abstract

The invention relates to the technical field of metal plastic forming, in particular to a stub-bar-free cross wedge rolling composite near-net forming method for a high-performance shaft, which comprises the following steps: heating a metal bar to a temperature interval where the metal bar is subjected to plastic deformation, and performing taper angle pre-forming treatment on the end part of the metal bar to obtain a pre-processed blank; the pre-machined blank is placed in a rolling area of a cross wedge rolling machine tool, radial rolling is conducted on the pre-machined blank through wedge-shaped molds of an upper roller and a lower roller so that the pre-machined blank can generate axial plastic extension to obtain a formed shaft part, and cooling and appearance finishing are conducted on the formed shaft part to obtain a high-performance shaft part; whether the forming stability of the high-performance shaft meets the requirement or not is determined based on the relative roundness error of the end of the high-performance shaft; determining whether to increase the relative difference rate of the upper and lower rolls; whether the relative temperature drop rate of the end in the rolling forming process is increased or not is determined; and whether the jacking force on the end part of the pre-machined blank is reduced or not is determined. The forming stability of the high-performance shaft part is improved.

Description

Technical Field

[0001] This invention relates to the field of metal plastic forming technology, and in particular to a near-net-shape forming method using headless wedge cross rolling for high-performance shaft components. Background Technology

[0002] Against the backdrop of rapid development in high-end shaft manufacturing and precision rolling technology, the headless wedge cross rolling composite near-net-shape forming method has become an important technical means to improve material utilization, reduce energy consumption, and improve machining accuracy. Because high-performance shafts typically have complex cross-sectional shapes and high-precision dimensional requirements, their forming process involves the coupling of multiple factors such as blank plastic flow, wedge extrusion, and multi-stage continuous rolling. This leads to problems such as significant material waste, accumulated dimensional deviations, and high risks of machining defects in traditional single-stage or segmented rolling methods. Existing forming methods mostly rely on empirical parameters or simple finite element simulations, which can only guarantee shape accuracy under single-stage conditions and lack the ability to comprehensively optimize overall energy consumption, material flow stability, and processing rhythm. Therefore, there is an urgent need for a headless wedge cross rolling composite near-net-shape forming method for high-performance shafts that can integrate blank plasticity analysis, boundary constraint optimization, and rolling process energy consumption control to achieve synergistic optimization of material utilization and energy efficiency.

[0003] Chinese Patent Publication No. CN104942536A discloses a highly efficient, near-net-shape precision forming method for hollow valve blanks in engines. The method includes: Step 1: Manufacturing a wedge rolling die and a forging die; Step 2: Heating the valve metal tube material to the rolling temperature; Step 3: Rolling the heated valve metal tube material to the rolling temperature using the wedge rolling die, thereby changing the outer diameter of the valve metal tube material and elongating it along its axial direction to form a symmetrical hollow valve blank; the symmetry line of the symmetrical hollow valve blank is perpendicular to its axis, and the middle part of the hollow valve blank is the rod portion. The hollow valve blank has two discs at both ends, and the connecting section between the rod and the disc is its neck; Step 4: Divide the hollow valve blank along the symmetry line to form a first hollow valve preform and a second hollow valve preform with the same structure; each hollow valve preform consists of a continuous and sequentially connected rod, neck, and disc; Step 5: Forge the first hollow valve preform or the second hollow valve preform using the forging die to form the disc of the first hollow valve preform or the disc of the second hollow valve preform into a hollow valve disc, thus realizing the manufacturing of the hollow valve. It can be seen that the aforementioned high-efficiency near-net-shape engine hollow valve blank precision forming method suffers from insufficient stability in the forming of high-performance shaft components due to forging instability caused by temperature gradients and rolling stress. Summary of the Invention

[0004] Therefore, the present invention provides a near-net-shape forming method for high-performance shaft components using a cross-rolling composite without a blanking head wedge, in order to overcome the problem of insufficient stability in the forming of high-performance shaft components caused by die forging instability due to temperature gradient and rolling stress in the prior art.

[0005] To achieve the above objectives, the present invention provides a near-net-shape forming method for high-performance shaft components using a headless wedge cross rolling process, comprising: The metal rod is heated to the temperature range in which it undergoes plastic deformation, and the end of the metal rod is pre-formed with a tapered angle to obtain a pre-processed blank. The pre-processed blank is placed in the rolling area of ​​a wedge cross rolling mill. The pre-processed blank is radially rolled by the wedge-shaped die of the upper and lower rolls to induce axial plastic elongation of the pre-processed blank to obtain a shaped shaft. The shaped shaft is then cooled and its shape is trimmed to obtain a high-performance shaft. The relative roundness error of the end of the high-performance shaft is obtained, and the stability of the forming of the high-performance shaft is determined based on the relative roundness error of the end of the high-performance shaft. If the stability of the high-performance shaft forming does not meet the requirements, the axial metal flow rate deviation rate of the pre-processed blank is obtained to determine whether the compatibility of the plastic flow of the pre-processed blank meets the requirements. If the compatibility of the plastic flow of the pre-processed blank does not meet the requirements, then determine whether to increase the relative difference rate between the upper and lower rolls. If it is not necessary to increase the relative difference rate of the upper and lower rolls, then it is determined whether to increase the relative temperature drop rate at the ends during the rolling process based on the end constraint pressure coefficient of the pre-processed blank. If it is not necessary to reduce the relative temperature drop rate at the ends during the rolling process, then it is determined whether to reduce the pushing force on the ends of the pre-processed blank based on the end constraint pressure coefficient of the pre-processed blank.

[0006] Furthermore, determining whether the stability of the high-performance shaft forming meets the requirements based on the relative roundness error of the ends of the high-performance shaft includes: The relative roundness error of the end of the high-performance shaft is compared with a preset relative roundness error; If the relative roundness error of the end of the high-performance shaft is less than or equal to the preset relative roundness error, then the stability of the high-performance shaft forming is determined to meet the requirements. If the relative roundness error of the end of the high-performance shaft is greater than the preset relative roundness error, then the stability of the high-performance shaft forming is determined to be unsatisfactory.

[0007] Furthermore, given that the stability of the high-performance shaft forming does not meet the requirements, the compatibility of the plastic flow of the pre-processed blank is determined based on the axial metal flow rate deviation rate of the pre-processed blank.

[0008] Furthermore, the compatibility of the plastic flow of the pre-processed blank is determined based on the axial metal flow rate deviation rate of the pre-processed blank, including: The axial metal flow rate deviation rate of the pre-processed blank is compared with the preset first deviation rate; If the axial metal flow rate deviation rate of the pre-processed blank is less than or equal to the preset first deviation rate, then the compatibility of the plastic flow of the pre-processed blank is determined to meet the requirements. If the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset first deviation rate, then it is determined that the compatibility of the plastic flow of the pre-processed blank does not meet the requirements.

[0009] Further, determine whether to increase the relative difference rate between the upper and lower rolls, including: The axial metal flow rate deviation rate of the pre-processed blank is compared with the preset first deviation rate and the preset second deviation rate, respectively; If the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset first deviation rate and less than or equal to the preset second deviation rate, then the relative difference rate between the upper and lower rolls is increased. If the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset second deviation rate, it is determined that there is no need to increase the relative difference rate between the upper and lower rolls.

[0010] Furthermore, the increase in the relative difference rate of the upper and lower rolls is determined by the difference between the axial metal flow rate deviation rate of the pre-processed blank and the preset first deviation rate.

[0011] Furthermore, based on the condition that the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset second deviation rate, it is initially determined that the constraint conditions of the rolling boundary do not meet the requirements for the plastic stable flow of the pre-processed blank, and the constraint conditions of the rolling boundary are determined according to the end constraint pressure coefficient of the pre-processed blank to determine whether they meet the requirements for the plastic stable flow of the pre-processed blank.

[0012] Furthermore, the constraint conditions of the rolling boundary based on the end constraint pressure coefficient of the pre-machined blank are determined to meet the requirements for plastic stable flow of the pre-machined blank, including: The end constraint pressure coefficient of the pre-processed blank is compared with the preset first pressure coefficient and the preset second pressure coefficient, respectively. If the end constraint pressure coefficient of the pre-processed blank is greater than the preset first pressure coefficient and less than or equal to the preset second pressure coefficient, then the constraint conditions of the rolling boundary are determined to meet the requirements for plastic stable flow of the pre-processed blank.

[0013] Furthermore, if the end constraint pressure coefficient of the pre-processed blank is less than or equal to the preset first pressure coefficient, then the reason why the constraint condition of the rolling boundary does not meet the plastic stable flow requirements of the pre-processed blank is that the end rolling boundary constraint of the pre-processed blank is insufficient, and the end relative temperature drop rate during the rolling process is increased. The increase in the relative temperature drop rate at the end during the rolling process is determined by the difference between the preset first pressure coefficient and the end constraint pressure coefficient of the pre-processed blank.

[0014] Furthermore, if the end constraint pressure coefficient of the pre-processed blank is greater than the preset second pressure coefficient, the reason why the constraint condition of the rolling boundary does not meet the plastic stable flow requirements of the pre-processed blank is that the end rolling boundary of the pre-processed blank is over-constrained, and the pushing force on the end of the pre-processed blank is reduced. The reduction in the pushing force at the end of the pre-processed blank is determined by the difference between the end constraint pressure coefficient of the pre-processed blank and the preset second pressure coefficient.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The method of the present invention determines whether the stability of the forming of high-performance shaft parts meets the requirements based on the relative roundness error of the ends of the high-performance shaft parts. During wedge rolling and die forging, the uneven local hardness and plasticity of the metal tube material, and the local stress concentration caused by the die fitting clearance, can easily lead to the end diameter being too large or too small, affecting the final forming accuracy. By determining the stability of the forming of high-performance shaft parts, the links in the forming process that are prone to dimensional deviations can be identified, providing a quantitative basis for determining the degree of impact on the processing accuracy of high-performance shaft parts and its causes. The energy consumption constraint perturbation tolerance coefficient of the energy consumption task coupling model is adjusted based on the axial metal flow rate deviation rate of the pre-processed blank. Because the axial plastic flow of the pre-processed blank is prone to non-uniform distribution, it causes the local volumetric flow rate to deviate from the ideal state during rolling, resulting in material accumulation or necking. The defects can be addressed by increasing the relative difference rate between the upper and lower rolls, which can enhance the axial tensile effect of the blank, generate an additional shear stress field in the core of the rolled piece, thereby breaking up coarse grains in the metal material and improving the strain distribution between the core and the surface, achieving uniform plastic flow. The relative temperature drop rate at the end and the thrust force at the end of the pre-processed blank during the rolling process can be adjusted according to the end constraint pressure coefficient of the pre-processed blank. Insufficient or excessive end constraint can lead to free expansion or local stagnation at the end of the blank, increasing the axial volumetric flow rate deviation and uneven strain distribution between the core and the end, thus disrupting the overall plastic flow stability. By reducing the end temperature or the end thrust force, the end constraint can be strengthened or relaxed accordingly, making the plastic flow between the end and the core of the pre-processed blank more uniform, reducing the axial flow rate deviation rate, improving the stability and uniformity of blank forming, and improving the stability of high-performance shaft forming.

[0016] Furthermore, this invention determines whether the stability of high-performance shaft forming meets the requirements by setting a preset relative roundness error. During the wedge rolling and die forging processes, the local hardness and plasticity of the metal tube material are uneven, and the mold fitting clearance causes local stress concentration, which can easily lead to the end diameter being too large or too small, affecting the final forming accuracy. By determining the stability of high-performance shaft forming, the links in the forming process that are prone to dimensional deviations can be identified, providing a quantitative basis for determining the degree of impact on the processing accuracy of high-performance shafts and the reasons for such deviations, thereby further improving the stability of high-performance shaft forming.

[0017] Furthermore, by setting a preset first deviation rate and a preset second deviation rate, the present invention adjusts the energy consumption constraint disturbance tolerance coefficient of the energy consumption task coupling model. Since the axial plastic flow of the pre-processed blank is prone to non-uniform distribution, it causes the local volumetric flow rate to deviate from the ideal state during the rolling process, resulting in material accumulation or necking defects. By increasing the relative difference rate between the upper and lower rolls, the axial tensile effect of the blank can be enhanced, and an additional shear stress field can be generated in the core of the rolled piece, thereby breaking the coarse grains in the metal material and improving the strain distribution in the core and surface layers, realizing the homogenization of plastic flow, and further improving the stability of high-performance shaft forming.

[0018] Furthermore, by setting a preset first pressure coefficient and a preset second pressure coefficient, the present invention adjusts the relative temperature drop rate at the ends during the rolling process. Due to insufficient end constraint, the blank ends expand freely, which increases the axial volumetric flow rate deviation and causes uneven strain distribution between the core and the ends, thereby destroying the overall plastic flow stability. By reducing the end temperature, the end constraint can be enhanced, making the plastic flow of the pre-processed blank ends and core more uniform, reducing the axial flow rate deviation rate, improving the stability and uniformity of blank forming, and further improving the stability of high-performance shaft forming.

[0019] Furthermore, the present invention adjusts the jacking force at the end of the pre-processed blank by setting a preset first pressure coefficient and a preset second pressure coefficient. Due to excessive constraint, the blank is locally stagnant, which increases the axial volumetric flow rate deviation and causes uneven strain distribution between the core and the end, thereby destroying the overall plastic flow stability. By reducing the end jacking force, the end constraint can be relaxed accordingly, making the plastic flow between the end and the core of the pre-processed blank more uniform, reducing the axial flow rate deviation rate, improving the stability and uniformity of blank forming, and further improving the stability of high-performance shaft forming. Attached Figure Description

[0020] Figure 1 This is an overall flowchart of the near-net-shape forming method of headless wedge cross rolling for high-performance shaft components according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating the process of determining the stability of high-performance shaft forming using a near-net-shape cross rolling composite method without a material head wedge for high-performance shafts, as described in an embodiment of the present invention. Figure 3 This is a flowchart illustrating the process of determining whether to increase the relative difference rate between the upper and lower rolls in a near-net-shape forming method using a headless wedge cross rolling process for high-performance shaft components, as described in an embodiment of the present invention. Figure 4 This is a flowchart illustrating the logic of determining whether to increase the relative temperature drop rate at the end during the rolling process in a near-net-shape composite cross-rolling method for high-performance shaft components without a material head wedge, as described in this embodiment of the invention. Detailed Implementation

[0021] 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.

[0022] 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.

[0023] Please see Figure 1 As shown, it is an overall flowchart of the near-net-shape forming method of headless wedge cross rolling for high-performance shaft components according to an embodiment of the present invention.

[0024] This invention discloses a near-net-shape forming method for high-performance shaft components using headless wedge cross rolling, comprising: Step S1: Heat the metal rod to the temperature range where it undergoes plastic deformation, and perform a tapered pre-forming process on the end of the metal rod to obtain a pre-processed blank. Step S2: Place the pre-processed blank in the rolling area of ​​a wedge cross rolling mill, and radially roll the pre-processed blank using the wedge-shaped die of the upper and lower rolls to induce axial plastic extension of the pre-processed blank to obtain a shaped shaft. Cool and shape the shaped shaft to obtain a high-performance shaft. Step S3: Obtain the relative roundness error of the end of the high-performance shaft, and determine whether the stability of the high-performance shaft forming meets the requirements based on the relative roundness error of the end of the high-performance shaft. Step S4: If the stability of the high-performance shaft forming does not meet the requirements, the axial metal flow rate deviation rate of the pre-processed blank is obtained to determine whether the compatibility of the plastic flow of the pre-processed blank meets the requirements. Step S5: If the compatibility of the plastic flow of the pre-processed blank does not meet the requirements, determine whether to increase the relative difference rate of the upper and lower rolls based on the axial metal flow rate deviation rate of the pre-processed blank. Step S6: If it is not necessary to increase the relative difference rate of the upper and lower rolls, then determine whether to increase the relative temperature drop rate at the ends during the rolling process based on the end constraint pressure coefficient of the pre-processed blank. Step S7: If it is not necessary to reduce the relative temperature drop rate at the end during the rolling process, determine whether to reduce the pushing force on the end of the pre-processed blank based on the end constraint pressure coefficient of the pre-processed blank.

[0025] Specifically, the metal bars include 45 steel bars, ductile iron bars, and carburized steel bars, all of which are solid at room temperature.

[0026] Specifically, the pre-processed blank is a solid bar in a high-temperature plastic state.

[0027] Specifically, a formed shaft is a preformed part that has the basic geometric characteristics of a finished shaft after rolling deformation.

[0028] Specifically, high-performance shaft components are finished shaft parts that have undergone cooling and dimensional adjustments.

[0029] Specifically, the temperature ranges for plastic deformation of 45 steel bars, ductile iron bars, and carburized steel bars are 450℃~850℃, 750℃~800℃, and 900℃~1100℃, respectively.

[0030] Specifically, the ends are the head regions at both ends in the axial direction of the metal bar, and their length corresponds to the length of the wedge entry section of the wedge cross rolling die.

[0031] Specifically, the process of radially rolling the pre-processed blank using wedge dies of upper and lower rolls involves feeding a bar heated to a high-temperature plastic state and pre-forming the end with a tapered angle into the space between upper and lower wedge dies that rotate in the same direction. The wedge surface of the die first bites into and crushes the blank, and through radial compression, forces the solid metal to flow mainly along the axial direction to fill the die cavity, thereby rolling the blank into a shaft.

[0032] Specifically, the compatibility of plastic flow in pre-processed blanks refers to the degree to which the velocity field, strain rate field, and stress field of the internal metal particles of the pre-processed blank satisfy the conservation of mass, conservation of momentum, and constitutive relations after the end of the pre-processed blank is matched with the wedge mold.

[0033] Specifically, the relative speed difference between the upper and lower rolls is the ratio of the absolute value of the difference between the rotational speeds of the upper and lower rolls to the average rotational speed of the upper and lower rolls.

[0034] Specifically, the relative temperature drop rate at the end during the rolling process is the ratio of the difference between the initial average metal temperature of the end face and the average metal temperature of the adjusted end face during the rolling process to the initial average metal temperature of the end face.

[0035] Specifically, the pushing force at the end of the pre-machined blank is an active constraint force on the end of the pre-machined blank along the axial direction.

[0036] In practice, the method of this invention determines whether the stability of high-performance shaft forming meets the requirements based on the relative roundness error of the end of the high-performance shaft. During wedge rolling and die forging, the uneven local hardness and plasticity of the metal tube material, coupled with the die fitting clearance leading to local stress concentration, can easily cause the end diameter to be too large or too small, affecting the final forming accuracy. By determining the stability of high-performance shaft forming, the links in the forming process that are prone to dimensional deviations can be identified, providing a quantitative basis for determining the degree and cause of the impact on the processing accuracy of high-performance shafts. The energy consumption constraint perturbation tolerance coefficient of the energy consumption task coupling model is adjusted based on the axial metal flow rate deviation rate of the pre-processed blank. Because the axial plastic flow of the pre-processed blank is prone to non-uniform distribution, it causes the local volumetric flow rate to deviate from the ideal state during rolling, resulting in material accumulation or necking defects. By increasing... The relative speed difference between the upper and lower rolls can enhance the axial tensile effect of the blank, generating an additional shear stress field in the core of the rolled piece. This breaks up coarse grains within the metal material and improves the strain distribution between the core and surface, achieving uniform plastic flow. The relative temperature drop rate at the ends and the thrust force at the ends of the pre-processed blank during the rolling process are adjusted according to the end constraint pressure coefficient of the pre-processed blank. Insufficient or excessive end constraint can lead to free expansion or localized stagnation at the blank ends, increasing the axial volumetric flow rate deviation and causing uneven strain distribution between the core and ends, thus disrupting the overall plastic flow stability. By reducing the end temperature or the end thrust force, the end constraint can be strengthened or relaxed accordingly, making the plastic flow between the ends and core of the pre-processed blank more uniform, reducing the axial flow rate deviation rate, improving the stability and uniformity of blank forming, and enhancing the stability of high-performance shaft forming.

[0037] Please continue reading. Figure 2 As shown, it is a logic flowchart of the process for determining the stability of high-performance shaft forming using a near-net-shape cross rolling composite method for high-performance shafts according to an embodiment of the present invention.

[0038] Specifically, determining whether the stability of the high-performance shaft forming meets the requirements based on the relative roundness error of the ends of the high-performance shaft includes: The relative roundness error of the end of the high-performance shaft is compared with a preset relative roundness error; If the relative roundness error of the end of the high-performance shaft is less than or equal to the preset relative roundness error, then the stability of the high-performance shaft forming is determined to meet the requirements. If the relative roundness error of the end of the high-performance shaft is greater than the preset relative roundness error, then the stability of the high-performance shaft forming is determined to be unsatisfactory.

[0039] Understandably, in the near-net-shape forming method of headless wedge cross rolling for high-performance shafts, the preset relative roundness error is used to characterize the stability of high-performance shaft forming. The core logic is to convert the stability of high-performance shaft forming into a quantifiable end diameter fluctuation range. By comparing this with the preset relative roundness error, the stability of the rolling process and the end dimensional accuracy are determined. The preset relative roundness error serves as the dividing line for distinguishing whether the forming stability meets the requirements. The preset relative roundness error can be set according to actual working conditions. The setting of the preset relative roundness error aims to ensure the stability and practicality of high-performance shaft forming. Optionally, the preset relative roundness error is determined through a limited number of tests by evaluating the effect of different end diameter fluctuation ranges on the forming of high-performance shafts. The determined preset relative roundness error should be neither too small nor cause excessive interference to the forming process of high-performance shafts. For example, the preset relative roundness error is generally selected in the range of [0.7%, 0.9%].

[0040] Preferably, the preset relative roundness error is 0.8% in the preferred embodiment.

[0041] Specifically, the relative roundness error of the end of a high-performance shaft is the ratio of the difference between the maximum and minimum diameters of the end of the high-performance shaft after forming to the target designed end diameter.

[0042] In practice, this invention uses a preset relative roundness error to determine whether the stability of high-performance shaft forming meets the requirements. During wedge rolling and die forging, the local hardness and plasticity of the metal tube material are uneven, and the mold fitting clearance causes local stress concentration, which can easily lead to the end diameter being too large or too small, affecting the final forming accuracy. By determining the stability of high-performance shaft forming, the links in the forming process that are prone to dimensional deviations can be identified, providing a quantitative basis for determining the degree of impact on the processing accuracy of high-performance shafts and the reasons for such deviations, thereby further improving the stability of high-performance shaft forming.

[0043] Please continue reading. Figure 3 As shown, it is a logic flowchart of the process of determining whether to increase the relative difference rate of the upper and lower rolls in the near-net-shape forming method of cross rolling without material head wedge for high-performance shaft parts according to an embodiment of the present invention.

[0044] Specifically, given that the stability of the high-performance shaft forming does not meet the requirements, the compatibility of the plastic flow of the pre-processed blank is determined based on the axial metal flow rate deviation rate of the pre-processed blank.

[0045] Specifically, the compatibility of the plastic flow of the pre-processed blank is determined based on the axial metal flow rate deviation rate, including: The axial metal flow rate deviation rate of the pre-processed blank is compared with the preset first deviation rate; If the axial metal flow rate deviation rate of the pre-processed blank is less than or equal to the preset first deviation rate, then the compatibility of the plastic flow of the pre-processed blank is determined to meet the requirements. If the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset first deviation rate, then it is determined that the compatibility of the plastic flow of the pre-processed blank does not meet the requirements.

[0046] Specifically, determining whether to increase the relative difference rate between the upper and lower rolls includes: The axial metal flow rate deviation rate of the pre-processed blank is compared with the preset first deviation rate and the preset second deviation rate, respectively; If the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset first deviation rate and less than or equal to the preset second deviation rate, then the relative difference rate between the upper and lower rolls is increased. If the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset second deviation rate, it is determined that there is no need to increase the relative difference rate between the upper and lower rolls.

[0047] It is understandable that the preset first deviation rate is less than the preset second deviation rate. The three intervals divided by the preset first deviation rate and the preset second deviation rate correspond to three different situations: The first interval is when the axial metal flow rate deviation rate of the pre-processed blank is less than or equal to the preset first deviation rate, which corresponds to the condition that the compatibility of the plastic flow of the pre-processed blank meets the requirements. The second interval is when the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset first deviation rate and less than or equal to the preset second deviation rate. The corresponding situation is: because the axial plastic flow of the pre-processed blank is more likely to be non-uniformly distributed, the local volumetric flow rate deviates from the ideal state during the rolling process, resulting in material accumulation or necking defects. The third interval is when the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset second deviation rate. The corresponding situation is that insufficient or excessive end constraint will lead to free expansion or local stagnation at the end of the blank, which will increase the axial volume flow rate deviation and result in uneven strain distribution between the core and the end, thereby destroying the overall plastic flow stability.

[0048] Understandably, in the near-net-shape forming method of headless wedge cross rolling for high-performance shaft components, the use of preset first and second deviation rates to characterize the compatibility of the plastic flow of the pre-processed blank is based on the correlation between the axial volumetric flow rate deviation rate and the compatibility of the blank's plastic flow. This transforms the abstract compatibility judgment into a quantifiable axial volumetric flow rate deviation rate range judgment. The preset first deviation rate serves as the boundary line for meeting stability requirements, and the preset second deviation rate serves as the dividing line for the causes of instability failure, thus providing a basis for subsequent stability improvement adjustments. The preset first and second deviation rates can be set according to actual working conditions. The setting of the preset first and second deviation rates aims to ensure the stability and practicality of high-performance shaft component forming. Optionally, the preset first and second deviation rates are determined through a limited number of experiments by evaluating the forming effect of different axial volumetric flow rate deviation rates on high-performance shaft components. The determined preset first and second deviation rates should be neither too small nor cause excessive interference to the forming process of high-performance shaft components. For example, the preset first deviation rate is generally selected in the range of [1.5%, 2.5%], and the preset second deviation rate is generally selected in the range of [3.5%, 4.5%].

[0049] Preferably, the first deviation rate is 2% in a preferred embodiment, and the second deviation rate is 4% in a preferred embodiment.

[0050] Specifically, the deviation rate of axial metal flow rate of pre-processed blank is the ratio of the absolute value of the difference between the actual axial metal flow rate at the exit section of the pre-processed blank rolling deformation zone and the target axial metal flow rate calculated based on the blank volume conservation to the target axial metal flow rate.

[0051] Specifically, the target axial metal flow rate is calculated based on the conservation of blank volume: ; Where Q is the target axial volumetric flow rate; d1 is the target outer diameter of the formed shaft after rolling; d2 is the target inner diameter of the formed shaft after rolling; v represents the instantaneous axial movement velocity of the workpiece at the current cross-section.

[0052] Specifically, the increase in the relative difference rate of the upper and lower rolls is determined by the difference between the axial metal flow rate deviation rate of the pre-processed blank and the preset first deviation rate.

[0053] Specifically, when the difference between the axial metal flow rate deviation rate of the pre-processed blank and the preset first deviation rate is within 1%, the relative difference rate of the upper and lower rolls increases to 0.2%. When the difference between the axial metal flow rate deviation rate of the pre-processed blank and the preset first deviation rate exceeds 1%, the relative difference rate of the upper and lower rolls increases by 0.05% for every 0.5% increase beyond the initial 0.2%. For example, when the difference between the axial metal flow rate deviation rate of the pre-processed blank and the preset first deviation rate is 2%, the current relative difference rate of the upper and lower rolls is 0, and the increased relative difference rate of the upper and lower rolls is 0.2 + 0.05 × 2 = 0.3%.

[0054] In practice, this invention adjusts the energy consumption constraint disturbance tolerance coefficient of the energy consumption task coupling model by setting a preset first deviation rate and a preset second deviation rate. Since the axial plastic flow of the pre-processed blank is prone to non-uniform distribution, the local volumetric flow rate deviates from the ideal state during rolling, resulting in material accumulation or necking defects. By increasing the relative difference rate between the upper and lower rolls, the axial tensile effect of the blank can be enhanced, and an additional shear stress field can be generated in the core of the rolled piece, thereby breaking the coarse grains in the metal material and improving the strain distribution in the core and surface layers, achieving uniform plastic flow, and further improving the stability of high-performance shaft forming.

[0055] Please continue reading. Figure 4 As shown, it is a flowchart illustrating the process of determining whether to increase the relative temperature drop rate at the end during the rolling process in the near-net-shape forming method of cross rolling without material head wedge for high-performance shaft components according to an embodiment of the present invention.

[0056] Specifically, based on the condition that the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset second deviation rate, it is initially determined that the constraint conditions of the rolling boundary do not meet the requirements for the plastic stable flow of the pre-processed blank, and the constraint conditions of the rolling boundary are determined according to the end constraint pressure coefficient of the pre-processed blank to determine whether they meet the requirements for the plastic stable flow of the pre-processed blank.

[0057] Specifically, the determination is based on whether the constraint conditions of the rolling boundary on the end constraint pressure coefficient of the pre-machined blank meet the requirements for plastic stable flow of the pre-machined blank, including: The end constraint pressure coefficient of the pre-processed blank is compared with the preset first pressure coefficient and the preset second pressure coefficient, respectively. If the end constraint pressure coefficient of the pre-processed blank is greater than the preset first pressure coefficient and less than or equal to the preset second pressure coefficient, then the constraint conditions of the rolling boundary are determined to meet the requirements for plastic stable flow of the pre-processed blank.

[0058] It is understandable that the preset first pressure coefficient is less than the preset second pressure coefficient. The three intervals divided by the preset first pressure coefficient and the preset second pressure coefficient correspond to three different situations: The first interval is when the end constraint pressure coefficient of the pre-processed blank is less than or equal to the preset first pressure coefficient. The corresponding situation is: due to insufficient end constraint, the blank end expands freely, which increases the axial volume flow rate deviation and causes uneven strain distribution between the core and the end, thereby destroying the overall plastic flow stability. The second interval is when the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset first deviation rate and less than or equal to the preset second deviation rate. The corresponding situation is that the compatibility of the plastic flow of the pre-processed blank meets the requirements. The third interval is when the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset second deviation rate. The corresponding situation is that excessive end constraint will cause local plastic stagnation at the end of the blank, which will increase the axial volume flow rate deviation and cause uneven strain distribution between the core and the end, thereby destroying the overall plastic flow stability.

[0059] Understandably, in the near-net-shape forming method of headless wedge cross rolling for high-performance shaft components, the core logic of using preset first pressure coefficient and preset second pressure coefficient to characterize whether the constraint conditions of the rolling boundary meet the plastic stability flow requirements of the pre-processed blank is to transform the abstract rationality of the constraint conditions into a quantifiable pressure coefficient range judgment. By comparing the end constraint pressure coefficient of the actual pre-processed blank with the preset threshold, the rationality of the rolling boundary constraint is improved. The setting of the preset first pressure coefficient and preset second pressure coefficient aims to ensure the stability and practicality of the high-performance shaft component forming. Optionally, the preset first pressure coefficient and preset second pressure coefficient are determined through a limited number of experiments by evaluating the forming effect of different pressure coefficients on the high-performance shaft component. The determined preset first pressure coefficient and preset second pressure coefficient should satisfy the condition that they are neither too small nor cause excessive interference to the forming process of the high-performance shaft component. For example, the preset first pressure coefficient is generally selected in the range of [0.18, 0.22], and the preset second pressure coefficient is generally selected in the range of [0.38, 0.42].

[0060] Preferably, the first pressure coefficient is 0.2 in a preferred embodiment, and the second pressure coefficient is 0.4 in a preferred embodiment.

[0061] Specifically, the end constraint pressure coefficient of the pre-processed blank is the ratio of the average end constraint stress to the average rolling contact pressure.

[0062] Specifically, if the end constraint pressure coefficient of the pre-processed blank is less than or equal to the preset first pressure coefficient, the reason why the constraint condition of the rolling boundary does not meet the plastic stable flow requirements of the pre-processed blank is that the end rolling boundary constraint of the pre-processed blank is insufficient and the end relative temperature drop rate during the rolling process is increased. The increase in the relative temperature drop rate at the end during the rolling process is determined by the difference between the preset first pressure coefficient and the end constraint pressure coefficient of the pre-processed blank.

[0063] Specifically, when the difference between the preset first pressure coefficient and the end constraint pressure coefficient of the pre-processed blank is within 0.03, the relative temperature drop rate at the end during the rolling process increases to 1.2 times the original value. When the difference between the preset first pressure coefficient and the end constraint pressure coefficient of the pre-processed blank exceeds 0.03, in addition to increasing to 1.2 times the original value, for every 0.01 increase, the relative temperature drop rate at the end during the rolling process increases by 0.3%. For example, when the difference between the preset first pressure coefficient and the end constraint pressure coefficient of the pre-processed blank is 0.05, the current relative temperature drop rate at the end during the rolling process is 4%, and the increased relative temperature drop rate at the end during the rolling process is 4×1.2+0.3×2=5.4%.

[0064] In practice, this invention adjusts the relative temperature drop rate at the ends during the rolling process by setting a preset first pressure coefficient and a preset second pressure coefficient. Due to insufficient end constraint, the blank ends expand freely, which increases the axial volumetric flow rate deviation and causes uneven strain distribution between the core and the ends, thereby destroying the overall plastic flow stability. By reducing the end temperature, the end constraint can be enhanced, making the plastic flow of the pre-processed blank ends and core more uniform, reducing the axial flow rate deviation rate, improving the stability and uniformity of blank forming, and further improving the stability of high-performance shaft forming.

[0065] Specifically, if the end constraint pressure coefficient of the pre-processed blank is greater than the preset second pressure coefficient, the reason why the constraint condition of the rolling boundary does not meet the plastic stable flow requirements of the pre-processed blank is that the end rolling boundary of the pre-processed blank is over-constrained, and the pushing force on the end of the pre-processed blank is reduced. The reduction in the pushing force at the end of the pre-processed blank is determined by the difference between the end constraint pressure coefficient of the pre-processed blank and the preset second pressure coefficient.

[0066] Specifically, when the difference between the end constraint pressure coefficient of the pre-machined blank and the preset second pressure coefficient is within 0.05, the jacking force on the end of the pre-machined blank is reduced to 0.95 times the original value. When the difference between the end constraint pressure coefficient of the pre-machined blank and the preset second pressure coefficient exceeds 0.05, the jacking force on the end of the pre-machined blank is reduced by 1 kN for every 0.02 difference beyond the original value, in addition to the reduction to 0.95 times the original value. For example, if the diameter range of the current target high-performance shaft is [30 mm, 80 mm], and the difference between the end constraint pressure coefficient of the pre-machined blank and the preset second pressure coefficient is 0.07, the current jacking force on the end of the pre-machined blank is 30 kN, and the reduced jacking force on the end of the pre-machined blank is 30 × 0.95 - 1 × 2 = 26.5 kN.

[0067] In practice, this invention adjusts the jacking force at the end of the pre-processed blank by setting a preset first pressure coefficient and a preset second pressure coefficient. Excessive constraint causes local plastic stagnation in the blank, which increases the axial volumetric flow rate deviation and results in uneven strain distribution between the core and the end, thereby disrupting the overall plastic flow stability. By reducing the end jacking force, the end constraint can be relaxed accordingly, making the plastic flow between the end and the core of the pre-processed blank more uniform, reducing the axial flow rate deviation rate, improving the stability and uniformity of blank forming, and further improving the stability of high-performance shaft forming.

[0068] 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.

Claims

1. A near-net-shape forming method using headless wedge cross rolling for high-performance shaft components, characterized in that, include: The metal rod is heated to the temperature range in which it undergoes plastic deformation, and the end of the metal rod is pre-formed with a tapered angle to obtain a pre-processed blank. The pre-processed blank is placed in the rolling area of ​​a wedge cross rolling mill. The pre-processed blank is radially rolled by the wedge-shaped die of the upper and lower rolls to induce axial plastic elongation of the pre-processed blank to obtain a shaped shaft. The shaped shaft is then cooled and its shape is trimmed to obtain a high-performance shaft. The relative roundness error of the end of the high-performance shaft is obtained, and the stability of the forming of the high-performance shaft is determined based on the relative roundness error of the end of the high-performance shaft. If the stability of the high-performance shaft forming does not meet the requirements, the axial metal flow rate deviation rate of the pre-processed blank is obtained to determine whether the compatibility of the plastic flow of the pre-processed blank meets the requirements. If the compatibility of the plastic flow of the pre-processed blank does not meet the requirements, then determine whether to increase the relative difference rate between the upper and lower rolls. If it is not necessary to increase the relative difference rate of the upper and lower rolls, then it is determined whether to increase the relative temperature drop rate at the ends during the rolling process based on the end constraint pressure coefficient of the pre-processed blank. If it is not necessary to reduce the relative temperature drop rate at the ends during the rolling process, then it is determined whether to reduce the pushing force on the ends of the pre-processed blank based on the end constraint pressure coefficient of the pre-processed blank.

2. The near-net-shape forming method for high-performance shaft components using headless wedge cross rolling according to claim 1, characterized in that, Determining whether the stability of the high-performance shaft forming meets the requirements based on the relative roundness error of the ends of the high-performance shaft includes: The relative roundness error of the end of the high-performance shaft is compared with a preset relative roundness error; If the relative roundness error of the end of the high-performance shaft is less than or equal to the preset relative roundness error, then the stability of the high-performance shaft forming is determined to meet the requirements. If the relative roundness error of the end of the high-performance shaft is greater than the preset relative roundness error, then the stability of the high-performance shaft forming is determined to be unsatisfactory.

3. The near-net-shape forming method for high-performance shaft components using headless wedge cross rolling according to claim 2, characterized in that, Under the condition that the stability of the high-performance shaft forming does not meet the requirements, the compatibility of the plastic flow of the pre-processed blank is determined according to the axial metal flow rate deviation rate of the pre-processed blank.

4. The near-net-shape forming method for high-performance shaft components using headless wedge cross rolling according to claim 3, characterized in that, The compatibility of the plastic flow of the pre-machined blank is determined based on the axial metal flow rate deviation rate, including: The axial metal flow rate deviation rate of the pre-processed blank is compared with the preset first deviation rate; If the axial metal flow rate deviation rate of the pre-processed blank is less than or equal to the preset first deviation rate, then the compatibility of the plastic flow of the pre-processed blank is determined to meet the requirements. If the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset first deviation rate, then it is determined that the compatibility of the plastic flow of the pre-processed blank does not meet the requirements.

5. The near-net-shape forming method for high-performance shaft components using headless wedge cross rolling according to claim 4, characterized in that, Determine whether to increase the relative speed difference between the upper and lower rolls, including: The axial metal flow rate deviation rate of the pre-processed blank is compared with the preset first deviation rate and the preset second deviation rate, respectively; If the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset first deviation rate and less than or equal to the preset second deviation rate, then the relative difference rate between the upper and lower rolls is increased. If the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset second deviation rate, it is determined that there is no need to increase the relative difference rate between the upper and lower rolls.

6. The near-net-shape forming method for high-performance shaft components using headless wedge cross rolling according to claim 5, characterized in that, The increase in the relative difference rate of the upper and lower rolls is determined by the difference between the axial metal flow rate deviation rate of the pre-processed blank and the preset first deviation rate.

7. The near-net-shape forming method for high-performance shaft components using headless wedge cross rolling according to claim 6, characterized in that, Based on the condition that the axial metal flow rate deviation rate of the pre-processed blank is greater than the preset second deviation rate, it is initially determined that the constraint conditions of the rolling boundary do not meet the requirements for the plastic stable flow of the pre-processed blank, and the constraint conditions of the rolling boundary are determined according to the end constraint pressure coefficient of the pre-processed blank to determine whether they meet the requirements for the plastic stable flow of the pre-processed blank.

8. The near-net-shape forming method for high-performance shaft components using headless wedge cross rolling according to claim 7, characterized in that, The determination of whether the constraint conditions of the rolling boundary meet the requirements of the plastic stable flow of the pre-machined blank is based on the end constraint pressure coefficient of the pre-machined blank, including: The end constraint pressure coefficient of the pre-processed blank is compared with the preset first pressure coefficient and the preset second pressure coefficient, respectively. If the end constraint pressure coefficient of the pre-processed blank is greater than the preset first pressure coefficient and less than or equal to the preset second pressure coefficient, then the constraint conditions of the rolling boundary are determined to meet the requirements for plastic stable flow of the pre-processed blank.

9. The near-net-shape forming method for high-performance shaft components using headless wedge cross rolling according to claim 8, characterized in that, If the end constraint pressure coefficient of the pre-processed blank is less than or equal to the preset first pressure coefficient, then the reason why the constraint condition of the rolling boundary does not meet the plastic stable flow requirements of the pre-processed blank is that the end rolling boundary constraint of the pre-processed blank is insufficient, and the end relative temperature drop rate during the rolling process is increased. The increase in the relative temperature drop rate at the end during the rolling process is determined by the difference between the preset first pressure coefficient and the end constraint pressure coefficient of the pre-processed blank.

10. The near-net-shape forming method for high-performance shaft components using headless wedge cross rolling according to claim 9, characterized in that, If the end constraint pressure coefficient of the pre-processed blank is greater than the preset second pressure coefficient, then the reason why the constraint condition of the rolling boundary does not meet the plastic stable flow requirements of the pre-processed blank is that the end rolling boundary of the pre-processed blank is over-constrained, and the pushing force on the end of the pre-processed blank is reduced. The reduction in the pushing force at the end of the pre-processed blank is determined by the difference between the end constraint pressure coefficient of the pre-processed blank and the preset second pressure coefficient.

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