Material hardness matching method and system for avoiding manufacturing defects of rotary swaging shaft

Abstract

The invention provides a material hardness matching method and system for avoiding manufacturing defects of a variable-cross-section variable-wall-thickness rotary swaging shaft, and the method comprises the following steps: S1, matching the hardness range of a material, and recording the hardness range of a blank; s2, the hardness range after rotary forging is determined; s3, according to the hardness range of the spline section, the axial force range needed by rotary swaging shaft pushing spline forming of the material within the hardness range of the blank is calculated; s4, the critical axial force range of axial buckling is calculated, S5, whether the axial force range of the cold-pushing spline is within the critical axial force range of axial buckling or not is compared, and if yes, the blank hardness range serves as a material hardness matching result; and if not, the hardness range of the blank is reduced according to the preset step length and serves as the updated hardness range of the blank, and then the steps S2-S5 are repeated till the comparison result is yes. According to the method, the rotary swaging process and the spline pushing process are coupled, the proper rotary swaging material blank hardness range is screened out, and machining defects in the rotary swaging shaft machining and manufacturing process are avoided.

Description

Technical Field

[0001] The present invention relates to the field of mechanical manufacturing, and particularly to a material hardness matching method and system for avoiding manufacturing defects of swaged shafts. Background Art

[0002] A swaged shaft is a shaft part mainly formed by swaging. Swaging can form hollow shaft parts and is widely used in the production of shafts for various machines such as automobiles, tractors, machine tools, and locomotives. Its processing process mainly includes cold swaging forming of blanks and cold push forming of splines. Swaging forming is further divided into two processes: forming with a mandrel and forming without a mandrel; the subsequent manufacturing process of swaging forming is cold push spline machining. During the manufacturing process of swaged shafts, if the material strength matching is too high, swaging manufacturing defects such as folding, surface cracks, and layered fractures during swaging without a mandrel will occur; if the material strength matching is too low, although it is easier to swage and form, defects such as axial buckling deformation and axial instability during the cold push spline forming process will occur. Therefore, the matching of the minimum strength and the maximum strength of the blank material is the key to avoiding manufacturing defects of swaged shafts. Summary of the Invention

[0003] The present invention is made to solve the above problems, and aims to provide a material hardness matching method and system for avoiding manufacturing defects of swaged shafts.

[0004] The present invention provides a material hardness matching method for avoiding manufacturing defects of swaged shafts. The swaged shaft is obtained by swaging and spline forming a blank. Swaging includes swaging forming without a mandrel and swaging forming with a mandrel. It has the following characteristics. The material hardness matching method includes the following steps: Step S1, aiming at avoiding swaging defects, combining material characteristics, matching the hardness range of the material, denoted as the blank hardness range; Step S2, according to the work hardening characteristics of the material and the swaging strain distribution, calculating the hardness hardening range of the material after swaging within the blank hardness range; and Step S3, according to the push spline manufacturing process and the hardness range of the spline section within the hardness hardening range after swaging, calculating the axial force range required for push spline forming of the swaged shaft for the material within the blank hardness range, denoted as the cold push spline axial force range; Step S4, according to the hardness hardening range after swaging, calculating the critical axial force range of axial buckling during swaging of the material within the blank hardness range; Step S5, comparing whether the cold push spline axial force range is within the axial buckling critical axial force range. If so, then enter Step S6. If not, then enter Step S7; Step S6, taking the blank hardness range as the material hardness matching result; Step S7, reducing the blank hardness range by a predetermined step length and taking it as the updated blank hardness range, and then repeating Steps S2 - S5 until the comparison result is yes.

[0005] In the method for matching material hardness to avoid manufacturing defects of swaged shafts provided by the present invention, it may also have the following characteristics: Among them, in step S1, the lowest hardness in the blank hardness range is affected by the blank manufacturing cost and cannot be too low, and the highest hardness in the blank hardness range is the highest strength at which defect-free non-core-rod swaging forming occurs.

[0006] In the method for matching material hardness to avoid manufacturing defects of swaged shafts provided by the present invention, it may also have the following characteristics: Among them, the material is 25CrMo4 material, and the blank hardness range is 150 - 170 HB or 150 - HV190.

[0007] In the method for matching material hardness to avoid manufacturing defects of swaged shafts provided by the present invention, it may also have the following characteristics: Among them, in step S2, the work-hardening characteristic of the material is obtained by fitting the stress-strain curve obtained from the material tensile test, and the work-hardening formula is as shown in Equation 1.

[0008] σ = 728(ε + ε 0 ) 0.175 (1)

[0009] In the formula, σ is the true stress, ε is the true strain, ε 0 is the pre-strain value. The swaging strain distribution includes multiple potential positions. The multiple potential positions include the spline forming position, the position with the minimum radial dimension, and the transition section position. The true strain of each potential position is calculated respectively. For non-core-rod swaging forming, the true strain ε is calculated according to Equation 2 below.

[0010]

[0011] In the formula, t 0 is the wall thickness of the blank before non-core-rod swaging; t is the wall thickness of the blank after non-core-rod swaging; r m0 is the initial equivalent radius of the blank r m0 = r 0 - t 0 / 2; r m is the equivalent radius after swaging r m = r - t / 2; r 0 is the radius of the blank before swaging; r is the radius of the blank after swaging.

[0012] For core-rod swaging forming, the true strain ε is calculated according to Equation 3 below.

[0013]

[0014] In the formula, t 0Let \(t_0\) be the wall thickness of the blank before core rod rotary forging; \(t\) be the wall thickness of the blank after core rod rotary forging. Substitute the true strains at each calculated potential position into Formula 1 respectively to obtain the true stresses at each potential position under the minimum hardness and the maximum hardness within the blank hardness range. Take the minimum value and the maximum value of the true stress under the minimum hardness of the blank hardness range as the minimum hardness value and the maximum hardness value of the material after rotary forging at this minimum hardness respectively. Take the minimum value and the maximum value of the true stress under the maximum hardness of the blank hardness range as the minimum hardness value and the maximum hardness value of the material after rotary forging at this maximum hardness respectively.

[0015] In the material hardness matching method for avoiding manufacturing defects of rotary forging shafts provided by the present invention, it may further have the following characteristics:

[0016] Among them, in step S3, according to the push spline manufacturing process and the hardness range of the spline section, the axial force required for the formation of the push spline of the rotary forging shaft is calculated according to the empirical formula (Formula 4).

[0017]

[0018] In the formula, \(A\) is the area of the front rod part of the push spline, \(\mu\) is the friction coefficient; \(\alpha\) is the semi-angle of the die entrance; \(d_1\) 0 and \(d_2\) 1 are the diameters before and after cold extrusion of the spline; \(HB\) is the hardness after rotary forging of the spline section, and \(t\) is the strength-hardness conversion coefficient.

[0019] In the material hardness matching method for avoiding manufacturing defects of rotary forging shafts provided by the present invention, it may further have the following characteristics: Among them, when the blank hardness is 150 HB, the minimum value of the hardness \(HB\) after rotary forging of the spline section is 187 HB; when the blank hardness is 170 HB, the maximum value of the hardness \(HB\) after rotary forging of the spline section is 196 HB.

[0020] In the material hardness matching method for avoiding manufacturing defects of rotary forging shafts provided by the present invention, it may further have the following characteristics: Among them, in step S4, for the hardness hardening range after rotary forging, through the buckling simulation analysis of the simulation software, the relationship between the buckling critical point, the critical axial force at this position and the hardness of the material after rotary forging can be obtained, and then the critical axial force range of axial buckling during rotary forging of the material within the blank hardness range can be obtained.

[0021] In the material hardness matching method for avoiding manufacturing defects of rotary forging shafts provided by the present invention, it may further have the following characteristics: Among them, in step S7, the predetermined step size is 1 HB.

[0022] A material hardness matching system for avoiding manufacturing defects of rotary forging shafts. The rotary forging shaft is obtained by subjecting a blank to rotary forging and spline forming. Rotary forging includes coreless rotary forging forming and core-containing rotary forging forming, and has the following characteristics: a matching module for matching the hardness range of the material, denoted as the blank hardness range, with the aim of avoiding rotary forging defects and in combination with the material properties; a hardness calculation module for calculating the hardness hardening range after rotary forging of the material within the blank hardness range according to the work hardening characteristics of the material and the rotary forging strain distribution; and a spline axial force calculation module for calculating the axial force range required for rotary forging shaft spline pushing forming of the material within the blank hardness range according to the push spline manufacturing process and the hardness range of the spline section within the hardness hardening range after rotary forging of the material, denoted as the cold push spline axial force range; a critical axial force calculation module for calculating the critical axial force range of axial buckling during rotary forging of the material within the blank hardness range according to the hardness hardening range after rotary forging; a comparison module for comparing whether the cold push spline axial force range is within the axial buckling critical axial force range. If so, then proceed to step S6. If not, then proceed to step S7; a matching confirmation module for taking the blank hardness range as the material hardness matching result; a loop module for reducing the blank hardness range by a predetermined step length and taking it as the updated blank hardness range, and then repeating steps S2 - S5 until the comparison result is yes.

[0023] Functions and effects of the invention

[0024] According to the material hardness matching method and system for avoiding manufacturing defects of rotary forging shafts involved in the present invention, because, with the aim of avoiding rotary forging defects, the hardness range of the material is matched in combination with the material properties, denoted as the blank hardness range; according to the work hardening characteristics of the material and the rotary forging strain distribution, the hardness hardening range after rotary forging of the material within the blank hardness range is calculated; and according to the push spline manufacturing process and the hardness range of the spline section within the hardness hardening range after rotary forging, the axial force range required for rotary forging shaft spline pushing forming of the material within the blank hardness range is calculated, denoted as the cold push spline axial force range; according to the hardness hardening range after rotary forging, the critical axial force range of axial buckling during rotary forging of the material within the blank hardness range is calculated, and it is compared whether the cold push spline axial force range is within the axial buckling critical axial force range. If so, the blank hardness range is taken as the material hardness matching result; if not, the blank hardness range is reduced by a predetermined step length and taken as the updated blank hardness range, and then the above steps are repeated until the comparison result is yes. Therefore, the material hardness matching method and system for avoiding manufacturing defects of rotary forging shafts of the present invention couple the rotary forging and push spline processes in the rotary forging manufacturing process, screen out the appropriate hardness range of the rotary forging material blank, and avoid processing defects during the rotary forging manufacturing process. Description of the drawings

[0025] Figure 1It is the dimensional drawing of the swaging material blank in Embodiment 1 of the present invention;

[0026] Figure 2 It is the dimensional drawing of the swaging material product structure in Embodiment 1 of the present invention;

[0027] Figure 3 It is the schematic flow diagram of the material hardness matching method for avoiding manufacturing defects of the swaging shaft in Embodiment 1 of the present invention;

[0028] Figure 4 It is the internal surface defect diagram of the swaging material in Embodiment 1 of the present invention;

[0029] Figure 5 It is the schematic diagram of the swaging cross-section segmentation in Embodiment 1 of the present invention.

[0030] Figure 6 It is the simulation diagram of the cold push spline defect of the swaging material;

[0031] Figure 7 It is the physical diagram of the cold push spline defect of the swaging material;

[0032] Figure 8 It is the module schematic diagram of the material hardness matching system for avoiding manufacturing defects of the swaging shaft in Embodiment 2 of the present invention. Detailed implementation manners

[0033] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or communication with each other; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0034] In order to make the technical means, creative features, achieved purposes, and effects achieved by the present invention easy to understand, the following embodiments will specifically describe the swaging material blank hardness screening method and system of the present invention in conjunction with the drawings.

[0035] Embodiment 1

[0036] Figure 1 It is the dimensional drawing of the swaging material blank in Embodiment 1 of the present invention.

[0037] Figure 2 It is the dimensional drawing of the swaging material product structure in Embodiment 1 of the present invention.

[0038] Taking a certain rotary forging shaft as the object, with the material grade of 25CrMo4, using seamless steel pipe as the blank, through rotary forging and spline forming, the blank dimensions are as Figure 1 shown, and the product structure and dimensions are as Figure 2 shown.

[0039] Among them, the involute spline parameters are respectively at the I end: number of teeth 27, module 1.0583, pressure angle 45°, pitch diameter 28.575; at the III end: number of teeth 34, module 0.79375, pressure angle 45°, pitch diameter 26.988.

[0040] The manufacturing process of a certain rotary forging shaft: seamless steel pipe blanking, non-mandrel rotary forging I, mandrel-containing rotary forging and stretching II, non-mandrel rotary forging III, cold pushing spline, heat treatment, etc. During the manufacturing process of the rotary forging shaft, if the material strength matching is too high, forging manufacturing defects such as folding, surface cracks, and layered fracture will occur during non-mandrel rotary forging; if the material strength matching is too low, although it is easier to form by rotary forging, defects such as axial buckling deformation and axial instability will occur during the cold pushing spline forming process. Therefore, the minimum and maximum strength matching of the material is the key technology to avoid forging shaft manufacturing defects.

[0041] This embodiment provides a method for matching the material hardness to avoid forging shaft manufacturing defects.

[0042] Figure 3 is a schematic flow chart of the method for matching the material hardness to avoid forging shaft manufacturing defects in Embodiment 1 of the present invention.

[0043] As Figure 3 shown, the method for matching the material hardness to avoid forging shaft manufacturing defects in this embodiment includes the following steps:

[0044] Step S1, aiming to avoid forging defects, combining with the material characteristics, match the hardness range of the material, denoted as the blank hardness range.

[0045] As Figure 1 and Figure 2 shown, the rotary forging process of the rotary forging shaft includes non-mandrel rotary forging section I, mandrel-containing rotary forging section II, and non-mandrel rotary forging section III. During non-mandrel rotary forging, there is no support on the inner wall, the inner surface is in tension, and the metal forms by natural flow. If the blank strength is too high, forging manufacturing defects such as folding, surface cracks, and layered fracture will occur. During mandrel-containing rotary forging, both the inner and outer surfaces are under pressure, and the influence of the blank strength on forging defects is not obvious. The highest strength at which no defects occur during non-mandrel rotary forging forming is used as the highest strength of the material, and the lowest strength is affected by the blank manufacturing cost and cannot be too low.

[0046] Among them, in step S1, the lowest hardness in the blank hardness range is affected by the blank manufacturing cost and cannot be too low, and the highest hardness in the blank hardness range is the highest strength at which no defects occur during non-mandrel rotary forging forming.

[0047] The material is 25CrMo4, and the hardness range of the blank is 150 - 170 HB or 150 - HV190.

[0048] Figure 4 It is the internal surface defect diagram of the swaged material in Embodiment 1 of the present invention.

[0049] As Figure 4 shown, the figure shows the defects generated on the internal surface of the non - mandrel swaging when the hardness of the blank is higher than the highest hardness HB170.

[0050] Step S2: According to the work - hardening characteristics of the material and the swaging strain distribution, calculate the hardness hardening range of the material within the blank hardness range after swaging.

[0051] Among them, in step S2, the work - hardening characteristics of the material are obtained by fitting the stress - strain curve obtained from the material tensile test. The work - hardening formula is as shown in Equation 1,

[0052] σ = 728(ε + ε 0 ) 0.175 (1)

[0053] In the formula, σ is the true stress, ε is the true strain, and ε 0 is the pre - strain value. The swaging strain distribution includes multiple potential positions. The multiple potential positions include the spline forming position, the position with the minimum radial dimension, and the transition section position. Calculate the true strain of each potential position respectively. For non - mandrel swaging forming, the true strain ε is calculated according to the following Equation 2,

[0054]

[0055] In the formula, t 0 is the wall thickness of the blank before non - mandrel swaging; t is the wall thickness of the blank after non - mandrel swaging; r m0 is the initial equivalent radius of the blank r m0 = r 0 - t 0 / 2; r m is the equivalent radius after swaging r m = r - t / 2; r 0 is the radius of the blank before swaging; r is the radius of the blank after swaging,

[0056] For mandrel - assisted swaging forming, the true strain ε is calculated according to the following Equation 3,

[0057]

[0058] In the formula, t 0Let \(t_0\) be the wall thickness of the blank before core rod rotary forging; \(t\) be the wall thickness of the blank after core rod rotary forging. Substitute the true strains at each calculated potential position into Formula 1 respectively to obtain the true stresses at each potential position under the minimum hardness and the maximum hardness of the blank hardness range. Take the minimum value and the maximum value of the true stress under the minimum hardness of the blank hardness range as the minimum hardness and the maximum hardness of the material after rotary forging at this minimum hardness respectively. Take the minimum value and the maximum value of the true stress under the maximum hardness of the blank hardness range as the minimum hardness and the maximum hardness of the material after rotary forging at this maximum hardness respectively.

[0059] Figure 5 It is a schematic diagram of the sectional segmentation of the rotary forging in Embodiment 1 of the present invention.

[0060] As Figure 5 shown, taking 25CrMo4 material as an example, different sectional categories of the rotary forging material are analyzed. A is the spline forming position, B is the position with the minimum radial dimension, and C is the transition section position. Among them, sections A, B, and C are all rotary forging without a core rod. According to the preset parameters and using the above equivalent strain calculation formula, the equivalent strains corresponding to sections A, B, and C of 25CrMo4 material are calculated to be 0.45, 0.72, and 0.32 respectively.

[0061] When the blank hardness is 150 HB, according to the work hardening formula, the maximum value of the hardness change of the rotary forging shaft after rotary forging forming is in section B, which is 203 HB, and the minimum value is in section C, which is 176 HB;

[0062] When the blank hardness is 170 HB, according to the work hardening formula, the maximum value of the hardness change of the rotary forging shaft after rotary forging forming is in section B, which is 210 HB, and the minimum value is in section C, which is 189 HB.

[0063] Step S3: According to the push spline manufacturing process and the hardness range of the spline section in the hardness hardening range of the material after rotary forging, calculate the axial force range required for the push spline forming of the rotary forging shaft from the material in the blank hardness range, denoted as the cold push spline axial force range.

[0064] Among them, in step S3, according to the push spline manufacturing process and the hardness range of the spline section, the axial force required for the push spline forming of the rotary forging shaft is calculated according to the empirical formula (4),

[0065]

[0066] In the formula, \(A\) is the cross-sectional area of the rod part before push spline, \(\mu\) is the friction coefficient; \(\alpha\) is the half angle of the die entrance; \(d\) 0 and \(d\) 1 are the diameters before and after cold extrusion of the spline; HB is the hardness of the spline section after rotary forging, and \(t\) is the strength hardness conversion coefficient.

[0067] Taking the above 25CrMo4 material as an example, the equivalent strain of the spline section is 0.45. According to the work-hardening formula, the true stress of the spline section is obtained, which is also the hardness of the spline section after rotary swaging hardening.

[0068] When the blank hardness is 150 HB, the hardness HB of the spline section after rotary swaging is the minimum value of 187 HB. Substituting it into the cold-pushing spline axial force calculation formula 4, the minimum cold-pushing spline axial force is 140 KN.

[0069] When the blank hardness is 170 HB, the maximum hardness HB of the spline section after rotary swaging is 196 HB. Substituting it into the cold-pushing spline axial force calculation formula 4, the maximum cold-pushing spline axial force is 147 KN.

[0070] Step S4: Calculate the critical axial force range of axial buckling during rotary swaging for materials within the blank hardness range according to the hardness hardening range after rotary swaging.

[0071] Among them, in step S4, according to the hardness hardening range after rotary swaging, through the buckling simulation analysis of the simulation software, the relationship between the critical axial force at the buckling critical point and the position and the hardness of the material after rotary swaging can be obtained, and then the critical axial force range of axial buckling during rotary swaging for materials within the blank hardness range can be obtained.

[0072] Figure 6 It is the simulation diagram of the cold-pushing spline defects of the rotary swaged material.

[0073] Figure 7 It is the physical diagram of the cold-pushing spline defects of the rotary swaged material.

[0074] As Figure 6 and Figure 7 shown, for the above 25CrMo4 material, it can be obtained from the simulation and the combined analysis of the defective rotary swaged shaft that the critical point of the cold-pushing spline is at section C.

[0075] When the blank hardness is 150 HB, according to formula 1, the maximum hardness change of the rotary swaged shaft after rotary swaging forming is at position B, which is 203 HB, and the minimum is at position C, which is 176 HB. At this time, the minimum critical axial force of axial buckling is 139 KN.

[0076] When the blank hardness is 170 HB, according to formula 1, the maximum hardness change of the rotary swaged shaft is 210 HB, and the minimum is 189 HB. At this time, the maximum critical axial force of axial buckling is 149 KN.

[0077] Step S5: Compare whether the cold-pushing spline axial force range is within the axial buckling critical axial force range. If it is, then enter step S6; if not, then enter step S7.

[0078] Step S6, take the blank hardness range as the material hardness matching result; Step S7, narrow down the blank hardness range by a predetermined step size and take it as the updated blank hardness range, then repeat Steps S2 - S5 until the comparison result is yes. The predetermined step size is 1 HB.

[0079] When the blank hardness is 170 HB, the hardness of the dangerous point swaged shaft is 189 HB, the axial force of the cold - pushed spline 147 KN is less than the critical axial buckling force 149 KN, and the axial force range of the cold - pushed spline is within the axial buckling critical axial force range, meeting the requirements;

[0080] When the blank hardness is 150 HB, the hardness of the dangerous point swaged shaft is 176 HB, the axial force of the cold - pushed spline 140 KN is greater than or equal to the critical axial force 139 KN at which buckling occurs, and the axial force range of the cold - pushed spline is not within the axial buckling critical axial force range, not meeting the requirements. It is necessary to increase the end value of the blank hardness range of 150 HB by a predetermined step size to narrow down the blank hardness range. In this example, for the 25CrMo4 material, increase the end value of the blank hardness range of 150 HB with a step size of 1 HB, thereby narrowing down the blank hardness range. Then, compare the relationship between the axial force range of the cold - pushed spline and the axial buckling critical axial force range under the narrowed - down blank hardness range until the requirements are met. The specific calculation results are shown in Table 1.

[0081] Table 1 Hardness and Axial Force after Blank Hardness Adjustment

[0082]

[0083] It can be seen from Table 1 that when the blank hardness range is 153 HB - 170 HB, after swaging, the cold - pushed spline force 141 KN is less than the critical axial buckling force 142 KN, and the axial force range of the cold - pushed spline is within the axial buckling critical axial force range, meeting the requirements.

[0084] According to the above results, the updated blank hardness range should be 153 HB ~ 170 HB.

[0085] Embodiment 2

[0086] Figure 8 It is a schematic diagram of the module of the material hardness matching system for avoiding manufacturing defects of the swaged shaft in Embodiment 2 of the present invention.

[0087] As Figure 8As shown in the figure, this embodiment provides a material hardness matching system 80 for avoiding manufacturing defects of swaged shafts, which uses the material hardness matching method for avoiding manufacturing defects of swaged shafts in Embodiment 1 for matching. The material hardness matching system 80 for avoiding manufacturing defects of swaged shafts includes the following modules: a matching module 801, a hardness calculation module 802, a spline axial force calculation module 803, a critical axial force calculation module 804, a comparison module 805, a matching confirmation module 806, and a loop module 807.

[0088] Among them, the matching module 801 is used to adopt the above-mentioned step S1, aiming to avoid swaging defects, and in combination with material characteristics, match the hardness range of the material, denoted as the blank hardness range.

[0089] The hardness calculation module 802 is used to adopt the above-mentioned step S2, and calculate the hardness hardening range of the material after swaging of the material within the blank hardness range according to the work hardening characteristics of the material and the swaging strain distribution.

[0090] The spline axial force calculation module 803 is used to adopt the above-mentioned step S3, and calculate the axial force range required for the swaged shaft push spline forming of the material within the blank hardness range according to the push spline manufacturing process and the hardness range of the spline section in the hardness hardening range of the material after swaging, denoted as the cold push spline axial force range.

[0091] The critical axial force calculation module 804 is used to adopt the above-mentioned step S4, and calculate the critical axial force range of axial buckling during swaging of the material within the blank hardness range according to the hardness hardening range after swaging.

[0092] The comparison module 805 is used to adopt the above-mentioned step S5, and compare whether the cold push spline axial force range is within the axial buckling critical axial force range. If so, then enter step S6; if not, then enter step S7.

[0093] The matching confirmation module 806 is used to adopt the above-mentioned step S6, and take the blank hardness range as the material hardness matching result.

[0094] The loop module 807 is used to adopt the above-mentioned step S7, reduce the blank hardness range according to a predetermined step size and take it as the updated blank hardness range, and then repeat steps S2 - S5 until the comparison result is yes, and determine the updated blank hardness range.

[0095] Those skilled in the art of this industry should understand that the present invention is not limited by the above-mentioned embodiments. What is described in the above-mentioned embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A material hardness matching method for avoiding manufacturing defects of a rotary swaged shaft, wherein the rotary swaged shaft is obtained by rotary swaging and spline forming a blank, wherein the rotary swaging includes rotary swaging without a mandrel and rotary swaging with a mandrel, and wherein: The material hardness matching method comprises the following steps: Step S1, with the goal of avoiding rotary forging defects, matching the hardness range of the material in combination with the material properties, recorded as the blank hardness range; Step S2, calculating the hardening range of the material after rotary forging within the hardness range of the blank according to the work hardening characteristics and rotary forging strain distribution of the material; and Step S3, according to the manufacturing process of the push spline and the hardness range of the spline segment in the hardening range after rotary forging, the axial force range required for rotary forging the push spline of the material in the hardness range of the blank is calculated, and recorded as the cold push spline axial force range; Step S4, calculating the critical axial force range of the material in the hardness range of the blank forging for axial buckling according to the hardening range after rotary forging, Step S5, comparing whether the cold-pushing spline axial force range is within the axial buckling critical axial force range, if so, then proceeding to step S6, if not, then proceeding to step S7; Step S6, taking the blank hardness range as the material hardness matching result; Step S7, narrowing the blank hardness range according to a predetermined step length and using it as the updated blank hardness range, and then repeating steps S2-S5 until the comparison result is yes.

2. The material hardness matching method for avoiding manufacturing defects of rotary swaging shafts according to claim 1, characterized in that: in, In step S1, the lowest hardness in the blank hardness range is affected by the blank manufacturing cost and cannot be too low. The highest hardness in the blank hardness range is the highest strength at which the coreless rotary forging can be performed without causing defects.

3. The material hardness matching method for avoiding manufacturing defects of rotary swaging shafts according to claim 2, characterized in that: in, The material is 25CrMo4 material, and the hardness range of the blank is 150-170HB or 150-HV190.

4. The material hardness matching method for avoiding manufacturing defects of a rotary swaging shaft according to claim 2 or 3, characterized in that: in, In step S2, the work hardening characteristics of the material are obtained by fitting the stress-strain curve obtained by the material tensile test. The work hardening formula is shown in Formula 1: σ=728(ε+ε0) 0.175 (1) In the formula, σ is the true stress, ε is the true strain, ε0 is the prestrain value, The rotary forging strain distribution includes multiple potential positions, including a spline forming position, a radial minimum size position, and a transition section position, and the true strain of each of the potential positions is calculated respectively. For the coreless rotary forging, the true strain ε is calculated according to the following formula 2: Where t0 is the wall thickness of the blank before spin forging without mandrel; t is the wall thickness of the blank after spin forging without mandrel; r m0 is the initial equivalent radius r of the blank m0 =r0-t0 / 2; r m is the equivalent radius r after rotary forging m =rt / 2; r0 is the radius of the blank before rotary forging; r is the radius of the blank after rotary forging, For the core-containing rotary forging, the true strain ε is calculated according to the following formula 3: Where t0 is the wall thickness of the blank before rotary forging with the mandrel; t is the wall thickness of the blank after rotary forging with the mandrel. Substitute the calculated true strains of each potential position into Formula 1 to obtain the true stress of each potential position at the lowest hardness and the highest hardness of the blank hardness range. The minimum and maximum values ​​of the true stress at the lowest hardness in the hardness range of the blank are respectively taken as the minimum and maximum values ​​of the hardness of the material after rotary forging at the lowest hardness. The minimum and maximum values ​​of the true stress at the highest hardness in the hardness range of the blank are respectively taken as the minimum and maximum values ​​of the hardness of the material after rotary forging at the highest hardness.

5. The material hardness matching method for avoiding manufacturing defects of a rotary swaging shaft according to any one of claims 1 to 3, characterized in that: in, In step S3, according to the manufacturing process of the push spline and the hardness range of the spline segment, the axial force required for the push spline of the rotary forging shaft is calculated according to the empirical formula 4: Where A is the front rod area of ​​the push spline, μ is the friction coefficient; α is the semi-angle of the die entrance; d0 and d1 are the front and rear diameters of the cold extruded spline; HB is the hardness of the spline segment after rotary forging, and t is the strength-hardness conversion coefficient.

6. The material hardness matching method for avoiding manufacturing defects of rotary swaging shafts according to claim 5, characterized in that: in, When the blank hardness is 150HB, the minimum hardness HB of the spline segment after rotary forging is 187HB; When the blank hardness is 170HB, the maximum hardness HB of the spline segment after rotary forging is 196HB.

7. The material hardness matching method for avoiding manufacturing defects of rotary swaging shafts according to claim 4, characterized in that: in, In step S4, according to the hardening range of the hardness after rotary forging, the buckling simulation analysis of the simulation software is used to obtain the relationship between the buckling danger point and the critical axial force at this position and the hardness of the material after rotary forging, and then the critical axial force range of the rotary forging of the material in the hardness range of the blank is obtained.

8. The material hardness matching method for avoiding manufacturing defects of rotary swaging shafts according to claim 1, characterized in that: in, In step S7, the predetermined step length is 1HB.

9. A material hardness matching system for avoiding manufacturing defects of a rotary swaged shaft, wherein the variable cross-section and variable wall thickness rotary swaged shaft is obtained by rotary swaging and spline forming of a blank, wherein the rotary swaging includes rotary swaging without a mandrel and rotary swaging with a mandrel, characterized in that include: A matching module is used to match the hardness range of the material in combination with the material properties in order to avoid the occurrence of rotary forging defects, which is recorded as the blank hardness range; A hardness calculation module, used for calculating the hardness hardening range of the material after rotary forging within the hardness range of the blank according to the work hardening characteristics and rotary forging strain distribution of the material; as well as A spline axial force calculation module is used to calculate the axial force range required for rotary forging of the axial push spline of the material in the hardness range of the blank according to the push spline manufacturing process and the hardness range of the spline segment in the hardening range of the material after rotary forging, which is recorded as the cold push spline axial force range; The critical axial force calculation module is used to calculate the critical axial force range of the axial buckling of the material in the hardness range of the blank according to the hardening range after rotary forging. A comparison module, used for comparing whether the cold-pushing spline axial force range is within the axial buckling critical axial force range, if so, then proceeding to step S6, if not, then proceeding to step S7; A matching confirmation module, used for taking the blank hardness range as a material hardness matching result; A loop module is used to reduce the blank hardness range according to a predetermined step size and use it as an updated blank hardness range, and then repeat steps S2-S5 until the comparison result is yes.

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