A manufacturing process for a diaphragm disc coupling and the diaphragm disc coupling itself.

Abstract

This invention relates to the field of rail transit transmission component manufacturing technology, and discloses a manufacturing process and method for diaphragm disc couplings. The method uses 31CrMoV9 alloy steel as the base material. After raw material composition re-testing and flaw detection, the process involves sequentially blanking, heating, free forging, three-stage forging and three-stage drawing, die forging, post-forging heat treatment, rough machining, low-temperature stress relief, precision machining, surface strengthening, and hydrogen removal treatment to obtain a diaphragm disc coupling for use in high-speed train bogie transmission systems. This invention solves the problems of insufficient strength and toughness matching, easy deformation during thin-walled structure processing, and unstable service life when using domestically produced materials to manufacture diaphragm discs. It is suitable for the mass production of high-reliability diaphragm disc couplings for high-speed trains, intercity trains, and urban rail transit transmission systems.

Description

Technical Field

[0001] This invention relates to the field of manufacturing technology for rail transit transmission components, specifically to a manufacturing process and method for a diaphragm disc coupling. Background Technology

[0002] Diaphragm couplings are a type of transmission component that relies on the elastic deformation of a thin-walled metal diaphragm to transmit torque and compensate for axial, radial, and angular misalignments. For the transmission system of high-speed train bogies, diaphragm couplings are subjected to alternating torque, impact loads, vibration loads, and corrosion from complex environments over long periods. Their material strength, impact toughness, fatigue performance, machining accuracy, and surface quality directly affect the safety of train operation and maintenance costs.

[0003] Currently, high-end diaphragm discs for high-speed trains face high procurement costs and long delivery cycles, and still suffer from insufficient lifespan and high maintenance frequency under actual domestic service conditions. Although domestic companies have attempted to manufacture diaphragm discs using alloy structural steel, maraging steel, or high-strength elastic steel, the following problems generally exist: First, the compositional fluctuations and inclusion control levels of domestically produced materials vary, making it difficult to achieve a stable strength-toughness match when directly using conventional forging and heat treatment processes; second, diaphragm discs are thin-walled disc-type parts, and during processing, residual stress release can easily lead to end-face runout, groove runout, and hole system position deviations; third, existing processes mostly focus on optimizing single stages, lacking a comprehensive collaborative control method covering the entire process from raw material re-inspection, forging, heat treatment, precision machining, surface treatment to service verification.

[0004] Therefore, it is necessary to propose a manufacturing process for diaphragm couplings made of domestically produced 31CrMoV9 alloy steel. By coordinating the control of forging deformation path, heat treatment microstructure, precision machining of thin-walled structures, and surface treatment, the mechanical properties, dimensional consistency, and service life of the diaphragm couplings can be improved. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a manufacturing process method for diaphragm disc couplings and a diaphragm disc coupling, which solves the problems of insufficient material strength and toughness matching, poor uniformity of forging structure, large performance fluctuation after heat treatment, difficulty in controlling deformation during thin-walled structure processing, and unstable service life in the existing manufacturing process of diaphragm disc couplings.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a manufacturing process for a diaphragm disc coupling, comprising the following steps: S1. Select 31CrMoV9 alloy steel as the base material for the diaphragm disc coupling. Perform chemical composition retesting, carbon and sulfur analysis and ultrasonic testing on the 31CrMoV9 alloy steel to remove raw materials that do not meet the requirements due to compositional segregation, inclusions or internal defects. S2. Cut the qualified base material obtained in step S1 into a billet, and preheat and heat the billet to make the billet reach the forging temperature. S3. The heated billet is subjected to free forging, three-stage forging and die forging in sequence to obtain a film disc forging billet; wherein, the three-stage forging is used to break the as-cast structure, refine the grains and improve the radial and axial uniformity of the billet structure; S4. Perform post-forging heat treatment on the diaphragm forging blank, the post-forging heat treatment including normalizing, quenching and tempering, so that the diaphragm forging blank forms tempered martensite or tempered sorbite structure. S5. Roughly machine the heat-treated diaphragm forging blank, retain the finishing allowance after rough machining, and perform low-temperature stress relief treatment. S6. Use a special positioning fixture to perform precision machining on the stress-relieved diaphragm disc forging blank, and machine the center hole, end face, outer circle, groove and circumferential connecting hole in sequence to obtain the diaphragm disc body; S7. Perform surface treatment and hydrogen removal treatment on the membrane disk body to obtain the membrane disk coupling.

[0007] Further, in step S1, the 31CrMoV9 alloy steel comprises, by mass percentage: C 0.27-0.34%, Si ≤ 0.40%, Mn 0.40-0.70%, Cr 2.30-2.70%, Mo 0.15-0.25%, V 0.10-0.20%, P ≤ 0.025%, S ≤ 0.025%, with the balance being Fe and unavoidable impurities.

[0008] Furthermore, in step S2, the billet is first preheated at 780-850°C, and then heated to 1050-1150°C and held at that temperature to ensure uniform temperature inside and outside the billet before entering the forging process.

[0009] Furthermore, in step S3, the three-stage upsetting and three-stage drawing process includes alternating upsetting and drawing, with a single upsetting reduction rate of 25-45%, a total forging ratio of 3.0-6.0, and a final forging temperature of not less than 850℃.

[0010] Furthermore, in step S4, the normalizing temperature is 880–930°C, followed by air cooling after holding; the quenching temperature is 850–900°C, followed by oil cooling or polymer medium cooling after holding; and the tempering temperature is 540–620°C, followed by air cooling after holding.

[0011] Furthermore, in step S5, during rough machining, a finishing allowance of 0.3 to 1.5 mm is retained at both ends of the membrane disc body, the central hole, the outer circle, and the groove, respectively. The low-temperature stress relief treatment temperature is 180 to 260°C, and the heat preservation time is 1 to 4 hours.

[0012] Furthermore, in step S6, precision machining uses the end face and center hole as a composite reference, and employs double-sided symmetry, layered cutting, and multiple passes with small depth of cut to process the thin-walled elastic zone in order to control residual stress and deformation during machining; the precision-machined diaphragm body meets the following requirements: Φ80 inner hole runout ≤0.02mm, roundness ≤0.01mm, straightness ≤0.01mm, end face runout ≤0.02mm, and groove runout ≤0.02mm.

[0013] Furthermore, in step S7, the surface treatment includes sandblasting, cleaning, and electroless nickel plating, with the electroless nickel plating layer having a thickness of 5–20 μm; the dehydrogenation treatment temperature is 180–220 °C, and the treatment time is 2–5 h.

[0014] Furthermore, the tensile strength of the resulting diaphragm disc coupling is ≥1200MPa; Yield strength ≥900MPa, elongation ≥11%, impact energy ≥40J, and no obvious cracks after 3 million cycles under simulated actual service conditions.

[0015] Furthermore, the diaphragm disc coupling includes a diaphragm disc body, which has a central connecting portion, an outer peripheral connecting portion, and a thin-walled elastic deformation zone located between the central connecting portion and the outer peripheral connecting portion; the central connecting portion is provided with a central hole, the outer peripheral connecting portion is provided with a plurality of connecting holes along the circumferential direction, and the thin-walled elastic deformation zone is provided with an annular groove for releasing stress and adjusting torsional stiffness.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention uses 31CrMoV9 alloy steel as the base material for diaphragm couplings. Before material feeding, chemical composition re-testing, carbon-sulfur analysis, and ultrasonic flaw detection are performed to eliminate substandard materials with compositional segregation, inclusions, or internal defects at the source, reducing performance instability caused by raw material fluctuations. Through a combination of free forging, three-stage forging, and die forging processes, the billet undergoes sufficient plastic deformation in both the axial and radial directions, which is beneficial for breaking down the original microstructure, refining grains, and improving metal flow line distribution. Combined with normalizing, quenching, and tempering heat treatment, the diaphragm disc forms a stable tempered martensite or tempered sorbite microstructure, thus ensuring high strength while also considering impact toughness and fatigue performance, improving the service reliability of the diaphragm coupling under alternating torque, impact loads, and vibration loads.

[0017] This invention employs a low-temperature stress-relief treatment after rough machining, and utilizes a combination of end face and center hole positioning, double-sided symmetrical machining, layered cutting, and multiple passes with small depths of cut during the precision machining stage. This reduces residual stress release and deformation accumulation in the thin-walled elastic zone during machining, improving the machining accuracy and dimensional consistency of the center hole, end face, groove, and connecting hole. Subsequent sandblasting, cleaning, electroless nickel plating, and dehydrogenation treatments enhance the corrosion resistance and environmental failure resistance of the diaphragm disc surface, while reducing the risk of hydrogen embrittlement during surface treatment. This invention forms a comprehensive collaborative manufacturing method encompassing raw material inspection, forging, microstructure control, stress relief, precision machining, and surface strengthening. It is suitable for the stable mass production of diaphragm disc couplings for high-speed trains, intercity trains, and urban rail transit transmission systems. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the manufacturing process of the diaphragm coupling of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1 This embodiment provides a manufacturing process method for a diaphragm disc coupling, including the following steps: S1. 31CrMoV9 alloy steel was selected as the base material for the diaphragm coupling. The 31CrMoV9 alloy steel, by mass percentage, comprises: C 0.27%, Si 0.20%, Mn 0.40%, Cr 2.30%, Mo 0.15%, V 0.10%, P 0.018%, S 0.010%, with the balance being Fe and unavoidable impurities. The alloy steel underwent chemical composition re-testing, carbon and sulfur analysis, and ultrasonic testing to confirm the absence of cracks, inclusions, shrinkage cavities, and significant component segregation that would affect its use.

[0021] S2. The qualified substrate obtained in step S1 is cut into a cylindrical billet. The billet is first heated to 780°C for preheating, and then heated to 1050°C for holding. After the temperature inside and outside of the billet is uniform, it enters the forging process.

[0022] S3. The heated billet is subjected to free forging, three-stage upsetting and three-stage drawing and die forging in sequence. The three-stage upsetting and three-stage drawing includes three alternating upsetting and three alternating drawing. The single upsetting reduction rate is 25%, the total forging ratio is 3.0, and the final forging temperature is not lower than 850℃ to obtain the diaphragm forging billet.

[0023] S4. Perform post-forging heat treatment on the diaphragm forging blank, specifically: normalize at 880℃, hold and then air cool; then quench at 850℃, hold and then oil cool; then temper at 540℃, hold and then air cool, so that the diaphragm forging blank forms a tempered martensite or tempered sorbite structure.

[0024] S5. Roughly machine the heat-treated diaphragm plate forging blank, leaving a finishing allowance of 0.3mm at each of the two end faces, the central hole, the outer circle, and the groove of the diaphragm plate body; after rough machining, perform low-temperature stress relief treatment at a temperature of 180℃ and a holding time of 1h.

[0025] S6. A special positioning fixture is used to precision machine the stress-relieved diaphragm disc forging blank. Using the end face and center hole as a composite datum, the center hole, end face, outer circle, groove, and circumferential connecting hole are machined sequentially. During the precision machining process, the thin-walled elastic zone is machined using double-sided symmetry, layered cutting, and multiple passes with small depth of cut to obtain the diaphragm disc body.

[0026] S7. The diaphragm disc body is subjected to sandblasting, cleaning and electroless nickel plating in sequence. The thickness of the electroless nickel plating layer is 5μm. After nickel plating, hydrogen removal treatment is performed at a temperature of 180℃ for 2 hours to obtain the diaphragm disc coupling.

[0027] Testing revealed that the diaphragm coupling produced in this embodiment has a tensile strength of 1226 MPa, a yield strength of 922 MPa, an elongation of 11.2%, and an impact energy of 2.6 J. The Φ80 inner bore runout is 0.014 mm, roundness is 0.009 mm, straightness is 0.009 mm, end face runout is 0.016 mm, and groove runout is 0.013 mm. No obvious cracks were observed after 3 million cycles under simulated actual service conditions.

[0028] Example 2 This embodiment provides a manufacturing process method for a diaphragm disc coupling, including the following steps: S1. 31CrMoV9 alloy steel was selected as the base material for the diaphragm coupling. The 31CrMoV9 alloy steel, by mass percentage, comprises: C 0.31%, Si 0.28%, Mn 0.55%, Cr 2.50%, Mo 0.20%, V 0.15%, P 0.015%, S 0.008%, with the balance being Fe and unavoidable impurities. The alloy steel underwent chemical composition re-testing, carbon and sulfur analysis, and ultrasonic testing to confirm that the raw material meets the requirements for diaphragm coupling manufacturing.

[0029] S2. Cut the qualified base material into billets, preheat the billets to 815℃, then heat them to 1100℃ and hold them at that temperature to ensure uniform temperature inside and outside the billets before they enter the forging process.

[0030] S3. The heated billet is subjected to free forging, three-stage upsetting and three-stage drawing and die forging in sequence. The three-stage upsetting and three-stage drawing includes three alternating upsetting and three alternating drawing. The single upsetting reduction rate is 35%, the total forging ratio is 4.5, and the final forging temperature is not lower than 870℃ to obtain the diaphragm forging billet.

[0031] S4. Perform post-forging heat treatment on the diaphragm forging blank, specifically: normalize at 905℃, hold and then air cool; then quench at 875℃, hold and then cool with polymer medium; then temper at 580℃, hold and then air cool, so that the diaphragm forging blank obtains a uniform tempered structure.

[0032] S5. Roughly machine the heat-treated diaphragm plate forging blank, leaving a finishing allowance of 0.9mm at each of the two end faces, the center hole, the outer circle, and the groove of the diaphragm plate body; after rough machining, perform low-temperature stress relief treatment at a temperature of 220℃ and a holding time of 2.5h.

[0033] S6. A special positioning fixture is used to perform precision machining on the stress-relieved diaphragm plate forging blank. The end face and the center hole are used as a composite reference. The thin-walled elastic zone is machined by double-sided symmetrical machining, layered cutting and multiple passes with small depth of cut. The center hole, end face, outer circle, groove and circumferential connecting hole are machined in sequence to obtain the diaphragm plate body.

[0034] S7. The diaphragm disc body is sandblasted, cleaned, and electroless nickel plated with a thickness of 12μm. After nickel plating, it is dehydrogenated at a temperature of 200℃ for 3 hours to obtain the diaphragm disc coupling.

[0035] Testing revealed that the diaphragm coupling produced in this embodiment has a tensile strength of 1234 MPa, a yield strength of 938 MPa, an elongation of 12.3%, and an impact energy of 43.8 J. The Φ80 inner bore runout is 0.015 mm, roundness is 0.007 mm, straightness is 0.007 mm, end face runout is 0.014 mm, and groove runout is 0.014 mm. No obvious cracks were observed after 3 million cycles under simulated actual service conditions.

[0036] Example 3 This embodiment provides a manufacturing process method for a diaphragm disc coupling, including the following steps: S1. 31CrMoV9 alloy steel is selected as the base material for the diaphragm disc coupling. The 31CrMoV9 alloy steel, by mass percentage, comprises: C 0.34%, Si 0.40%, Mn 0.70%, Cr 2.70%, Mo 0.25%, V 0.20%, P 0.020%, S 0.012%, with the balance being Fe and unavoidable impurities. The alloy steel undergoes chemical composition re-testing, carbon and sulfur analysis, and ultrasonic testing to eliminate raw materials with internal defects or abnormal compositions.

[0037] S2. Cut the qualified base material obtained in step S1 into a billet, preheat the billet to 850°C, and then heat it to 1150°C and hold it until the billet reaches the forging temperature.

[0038] S3. The heated billet is subjected to free forging, three-stage upsetting and three-stage drawing and die forging in sequence. The three-stage upsetting and three-stage drawing includes three alternating upsetting and three alternating drawing. The single upsetting reduction rate is 45%, the total forging ratio is 6.0, and the final forging temperature is not lower than 900℃ to obtain the diaphragm forging billet.

[0039] S4. Perform post-forging heat treatment on the diaphragm forging blank, specifically: normalize at 930℃, hold and then air cool; then quench at 900℃, hold and then oil cool; then temper at 620℃, hold and then air cool, so that the diaphragm forging blank forms a tempered structure with good strength and toughness.

[0040] S5. Roughly machine the heat-treated diaphragm plate forging blank, leaving a finishing allowance of 1.5mm at each of the two end faces, the central hole, the outer circle, and the groove of the diaphragm plate body; after rough machining, perform low-temperature stress relief treatment at a temperature of 260℃ for 4 hours.

[0041] S6. Use a special positioning fixture to perform precision machining on the stress-relieved diaphragm forging blank. Use the end face and center hole as a composite reference to machine the center hole, end face, outer circle, groove and circumferential connecting hole in sequence. When machining the thin-walled elastic zone, use double-sided symmetrical machining, layered cutting and multiple passes with small depth of cut to reduce residual stress and deformation during machining.

[0042] S7. The diaphragm disc body is sandblasted, cleaned, and electroless nickel plated with a thickness of 20μm. After nickel plating, it is dehydrogenated at a temperature of 220℃ for 5 hours to obtain the diaphragm disc coupling.

[0043] Testing revealed that the diaphragm coupling produced in this embodiment has a tensile strength of 1228 MPa, a yield strength of 926 MPa, an elongation of 13.5%, and an impact energy of 45.2 J. The Φ80 inner bore runout is 0.013 mm, roundness is 0.006 mm, straightness is 0.006 mm, end face runout is 0.013 mm, and groove runout is 0.012 mm. No obvious cracks were observed after 3 million cycles under simulated actual service conditions.

[0044] Comparative Example 1 The difference between this comparative example and Example 3 is that the three-stage forging and three-stage drawing process is not performed. Instead, the heated billet is subjected to ordinary free forging and die forging. All other steps and parameters are the same as in Example 3.

[0045] Comparative Example 2 The difference between this comparative example and Example 3 is that in step S5, after rough machining, low-temperature stress relief treatment is not performed, but precision machining is performed directly. The remaining steps and parameters are the same as in Example 3.

[0046] Comparative Example 3 The difference between this comparative example and Example 3 is that in step S7, the membrane disk body is not subjected to dehydrogenation treatment after chemical nickel plating, while the remaining steps and parameters are the same as in Example 3.

[0047] Performance testing 1. Raw material composition testing Samples were taken from different locations on the 31CrMoV9 alloy steel raw material for testing. A handheld spectrometer was used to quickly retest the content of alloying elements such as Cr, Mo, V, Mn, and Si. A carbon-sulfur analyzer was used to determine the C and S contents. At least three testing points were taken from each batch of raw material, and the average value of the results was used. If the content of the main alloying elements exceeded the set range, or the content of impurity elements such as P and S was too high, the batch of raw material was deemed unsuitable for the manufacture of diaphragm couplings.

[0048] 2. Ultrasonic flaw detection Ultrasonic testing is performed on the billet or diaphragm forging before and after forging. The testing area includes the central area, the outer circumference area, the corresponding area of ​​the thin-walled elastic zone, and the area where the connecting holes are located. During testing, the probe is scanned radially, axially, and circumferentially to observe for cracks, shrinkage cavities, inclusion concentrations, delamination, or other internal discontinuous defects. Ultrasonic testing of steel forgings can be performed according to the current GB / T6402-2024 standard; this standard has replaced GB / T6402-2008 and is the current ultrasonic testing method for steel forgings.

[0049] 3. Tensile property test Tensile specimens are taken from the heat-treated diaphragm disc forging blank or from the furnace-fed specimens heat-treated in the same furnace as the diaphragm disc. The sampling direction is preferably aligned with the main stress direction of the diaphragm disc. After machining the specimens into standard tensile specimens, room temperature tensile tests are performed on a universal testing machine to measure tensile strength, yield strength, and elongation after fracture. Room temperature tensile property testing of metallic materials can be performed according to GB / T228.1-2021, which is a current recommended national standard.

[0050] Each group of samples shall contain no fewer than 3 pieces, and the average value of the test results shall be taken. The qualification criteria for the diaphragm disc coupling are: tensile strength ≥1200MPa, yield strength ≥900MPa, and elongation ≥11%. These criteria are consistent with the mechanical performance requirements for 31CrMoV9 diaphragm discs set in the project objectives.

[0051] 4. Impact performance test Impact test specimens were cut from heat-treated diaphragm forgings of the same batch and machined into V-notch impact specimens. Before testing, the notch size and the machining quality at the notch root were checked to confirm that the specimens were free of burrs, cracks, and obvious machining defects. Subsequently, an impact test was conducted using a pendulum impact testing machine, and the impact absorbed energy was recorded. Charpy pendulum impact testing of metallic materials can be performed according to GB / T229-2020, which is a current recommended national standard.

[0052] Each group should contain no fewer than three samples, and the average value of the test results should be taken. The acceptable impact energy for diaphragm couplings is ≥40J. If the impact energy of a single sample is significantly lower than expected, further analysis should be conducted, taking into account the fracture morphology and metallographic structure, to determine if there are inclusions, microstructure segregation, or abnormal heat treatment.

[0053] 5. Metallographic structure testing Metallographic samples were taken from corresponding positions in the thin-walled elastic zone, central connecting part, and outer peripheral connecting part of the film disk. After mounting, polishing, and etching, the microstructure was observed under an optical microscope or scanning electron microscope. The focus of observation was on the degree of grain refinement, banded structure, inclusion distribution, decarburized layer, uniformity of tempered structure, and the presence of overheating, burning, or quenching cracks.

[0054] The example samples should primarily exhibit a uniform tempered martensite or tempered sorbite microstructure with a relatively uniform grain distribution. Continuous network defects, obvious banded segregation, or penetrating microcracks should not appear in the thin-walled elastic region. Comparative sample samples, if not subjected to the triple-hardening and triple-drawing process, often show localized deterioration in microstructure uniformity or increased banded microstructure.

[0055] 6. Dimensional accuracy inspection The dimensions of the precision-machined diaphragm disc body are inspected using a coordinate measuring machine, roundness tester, dial indicator, or high-precision gauge. Inspection items include Φ80 inner hole runout, roundness, straightness, end face runout, groove runout, connecting hole position accuracy, and total diaphragm disc thickness.

[0056] During testing, the diaphragm disc's center hole and reference end face are used as positioning references. The diaphragm disc is fixed on the testing fixture, and the runout values ​​at the center hole, end face, and groove are measured respectively. At least three circumferential positions are tested for each sample, and the maximum value is taken as the test result for that sample. The acceptance criteria are: Φ80 inner hole runout ≤ 0.02mm, roundness ≤ 0.01mm, straightness ≤ 0.01mm, end face runout ≤ 0.02mm, and groove runout ≤ 0.02mm. These accuracy indicators are the key processing indicators for the diaphragm disc coupling in this case.

[0057] 7. Surface coating inspection The appearance, thickness, and bonding status of the electroless nickel-plated film disc body are inspected. Visual inspection or magnification is used; the plating surface should be continuous and uniform, without peeling, blistering, pinholes, incomplete plating, or significant color differences. Plating thickness can be measured using a coating thickness gauge or cross-sectional microscopy. For each sample, at least three points should be selected from the central connection area, the thin-walled elastic zone, and the outer peripheral connection area, and the average value should be taken.

[0058] The coating thickness should be controlled within the range of 5–20 μm. After nickel plating, a dehydrogenation treatment should be performed, followed by a visual inspection and necessary fatigue tests to confirm that no microcracks have formed on the surface due to hydrogen embrittlement.

[0059] 8. Fatigue service simulation test The fabricated diaphragm coupling was installed on a dedicated fatigue testing rig, and alternating torque, axial compensation displacement, and vibration loads were set according to the actual service conditions of the high-speed train bogie transmission system. During the test, the number of cycles, load changes, temperature rise, and abnormal vibrations were recorded.

[0060] At regular intervals, the machine should be stopped to inspect the surface condition of the diaphragm disc, with a focus on the thin-walled elastic zone, the root of the annular groove, the transition fillet of the central connection, and the periphery of the circumferential connection holes for cracks. Visual inspection, magnetic particle testing, penetrant testing, or microscopic observation can be used to confirm the presence of cracks. The pass / fail criterion is: after 3 million cycles under simulated actual service conditions, the diaphragm disc body should show no obvious cracks, the periphery of the connection holes should show no expanding cracks, and the critical dimensions should not exhibit deformation that affects assembly and transmission performance. This cycle life requirement is consistent with the project objective of "3 million cycles without obvious cracks."

[0061] Table 1: Performance Tests of Comparative Examples 1-3

[0062] As shown in Table 1, and in Comparative Example 1, without the three-stage forging process and using only ordinary free forging and die forging, the tensile strength, yield strength, elongation after fracture, and impact energy of the diaphragm coupling all decreased significantly, and microcracks appeared after 1.8 million cycles of alternating load. This indicates that the three-stage forging process is not a simple conventional forging step, but a key process in this invention to achieve microstructure refinement, breakage and segregation, and improved radial and axial microstructure uniformity. Without this step, the internal microstructure uniformity of the billet is insufficient, and the thin-walled elastic zone is more prone to crack initiation under alternating load, leading to a reduction in fatigue life.

[0063] As can be seen from Comparative Example 2, without low-temperature stress relief treatment after rough machining, the tensile strength, yield strength, elongation, and impact energy of the diaphragm disk material itself remain at a good level. However, the runout of the Φ80 inner hole, the end face runout, and the groove runout all significantly exceed the levels of the previous example, exhibiting obvious dimensional deformation. This indicates that low-temperature stress relief treatment has a limited effect on improving material strength, but plays a crucial role in the dimensional stability of thin-walled diaphragm disk parts. Because the diaphragm disk body has a thin-walled elastic deformation zone and annular groove structure, if the residual stress is not fully released after rough machining, springback deformation is likely to occur during subsequent finishing and placement, thus affecting assembly accuracy and transmission stability.

[0064] Comparative Example 3 shows that without dehydrogenation treatment after electroless nickel plating, the dimensional accuracy of the diaphragm coupling basically meets the requirements, and the tensile strength and yield strength are not significantly reduced. However, the impact energy decreases, and surface microcracks appear after 2.2 million cycles. This result indicates that for 31CrMoV9 high-strength alloy steel diaphragm discs, dehydrogenation treatment after electroless nickel plating can reduce the risk of hydrogen embrittlement caused by hydrogen entering the substrate during the plating process, reduce the tendency for crack initiation at the plating-substrate interface, and thus improve the reliability of the diaphragm disc under alternating loads and complex service environments.

[0065] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A manufacturing process for a diaphragm disc coupling, characterized in that, Includes the following steps: S1. Select 31CrMoV9 alloy steel as the base material for the diaphragm disc coupling. Perform chemical composition retesting, carbon and sulfur analysis and ultrasonic testing on the 31CrMoV9 alloy steel to remove raw materials that do not meet the requirements due to compositional segregation, inclusions or internal defects. S2. Cut the qualified base material obtained in step S1 into a billet, and preheat and heat the billet to make the billet reach the forging temperature. S3. The heated billet is subjected to free forging, three-stage forging and die forging in sequence to obtain a film disc forging billet; wherein, the three-stage forging is used to break the as-cast structure, refine the grains and improve the radial and axial uniformity of the billet structure; S4. Perform post-forging heat treatment on the diaphragm forging blank, the post-forging heat treatment including normalizing, quenching and tempering, so that the diaphragm forging blank forms tempered martensite or tempered sorbite structure. S5. Roughly machine the heat-treated diaphragm forging blank, retain the finishing allowance after rough machining, and perform low-temperature stress relief treatment. S6. Use a special positioning fixture to perform precision machining on the stress-relieved diaphragm disc forging blank, and machine the center hole, end face, outer circle, groove and circumferential connecting hole in sequence to obtain the diaphragm disc body; S7. Perform surface treatment and hydrogen removal treatment on the membrane disk body to obtain the membrane disk coupling.

2. The manufacturing process of the diaphragm disc coupling according to claim 1, characterized in that, In step S1, the 31CrMoV9 alloy steel comprises, by mass percentage: C 0.27-0.34%, Si ≤0.40%, Mn 0.40-0.70%, Cr 2.30-2.70%, Mo 0.15-0.25%, V 0.10-0.20%, P ≤0.025%, S ≤0.025%, with the balance being Fe and unavoidable impurities.

3. The manufacturing process of the diaphragm disc coupling according to claim 1, characterized in that, In step S2, the billet is first preheated at 780-850°C, and then heated to 1050-1150°C and held at that temperature to ensure uniform temperature inside and outside the billet before it enters the forging process.

4. The manufacturing process of the diaphragm disc coupling according to claim 1, characterized in that, In step S3, the three-stage upsetting and three-stage drawing process includes alternating upsetting and drawing, with a single upsetting reduction rate of 25-45%, a total forging ratio of 3.0-6.0, and a final forging temperature of not less than 850℃.

5. The manufacturing process of the diaphragm disc coupling according to claim 1, characterized in that, In step S4, the normalizing temperature is 880–930°C, followed by air cooling after holding; the quenching temperature is 850–900°C, followed by oil cooling or polymer medium cooling after holding; and the tempering temperature is 540–620°C, followed by air cooling after holding.

6. The manufacturing process of the diaphragm disc coupling according to claim 1, characterized in that, In step S5, during rough machining, a finishing allowance of 0.3 to 1.5 mm is retained at both ends of the membrane disc body, the central hole, the outer circle, and the groove. The low-temperature stress relief treatment temperature is 180 to 260°C, and the heat preservation time is 1 to 4 hours.

7. The manufacturing process of the diaphragm disc coupling according to claim 1, characterized in that, In step S6, precision machining uses the end face and center hole as a composite reference, and employs double-sided symmetry, layered cutting, and multiple passes with small depth of cut to process the thin-walled elastic zone in order to control residual stress and deformation during machining.

8. The manufacturing process of the diaphragm disc coupling according to claim 1, characterized in that, In step S7, the surface treatment includes sandblasting, cleaning, and electroless nickel plating, with the electroless nickel plating layer having a thickness of 5–20 μm.

9. The manufacturing process of the diaphragm disc coupling according to claim 1, characterized in that, In step S7, the dehydrogenation treatment temperature is 180–220°C, and the treatment time is 2–5 hours.

10. A diaphragm disc coupling, characterized in that, It is prepared using the manufacturing process described in any one of claims 1 to 9.

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