A process for processing pallet nuts

Abstract

This invention discloses a processing technology for pallet nuts, belonging to the field of aerospace fastener manufacturing technology. The process includes the following steps: material preparation, CNC turning, hot upsetting, solution heat treatment, CNC turning, wire cutting, milling, fitter work, intermediate inspection, end capping, stabilization + aging heat treatment, sandblasting, local annealing, fluorescence detection, metallographic inspection, surface silver plating, performance testing, final inspection, and packaging. Through heat treatment processes such as solution heat treatment and stabilization + aging heat treatment, the strength of the pallet nut reaches 1210 MPa, and the hardness is HRC32-42. The end capping section ensures proper locking, providing anti-loosening and vibration resistance while maintaining the structural integrity of the pallet nut, further guaranteeing its structural strength, rigidity, and other mechanical properties.

Description

Technical Field

[0001] This invention relates to a process for processing pallet nuts, belonging to the field of aerospace fastener manufacturing technology. Background Technology

[0002] In the field of aerospace fasteners, fasteners used to connect critical components in high-temperature environments need to maintain good mechanical properties and anti-loosening performance at high temperatures, as well as be easy to install, fix, disassemble, and maintain. The pallet nut is a new type of fastener, integrating the functions of a rivet nut and a self-locking nut, combining riveting functionality with self-locking performance. For example... Figures 1 to 3 As shown, a D-shaped support plate 13 is provided in the middle of the support plate nut 1. The D-shaped support plate 13 can effectively prevent the nut body from rotating during bolt installation and disassembly. The threaded part of the support plate nut 1 is tightened to prevent loosening and vibration. The non-threaded end of the support plate nut 1 can be flared and riveted on one side to fix and limit its axial movement, achieving good anti-torsional and anti-loosening performance, providing a solution for fastening connections in narrow spaces where nuts cannot be fixed. When the support plate nut 1 is riveted, the flared section 12 deforms under the action of riveting force to rivet the nut onto the base 2. The flared section 12 must not produce cracks or fissures that affect the performance of the product. The strength requirement of the support plate nut 1 is 1210MPa, the hardness requirement is HRC32-42, and the material is high-temperature alloy GH738.

[0003] Chinese patent document CN105465142A discloses a high-temperature alloy inlaid self-locking nut assembly and its processing method, including the following steps: material preparation → blanking → surface treatment → hot upsetting → deplating → annealing → CNC turning → deburring → thread extrusion → CNC turning → deburring → wire cutting → finishing → aging → annealing → sandblasting → flaw detection → surface treatment → assembly → riveting → packaging and warehousing. The self-locking nut is made of high-temperature alloy material A286, and the self-locking nut obtained by this processing method has a strength greater than or equal to 1100 MPa.

[0004] Although the materials used in this self-locking nut assembly and the pallet nut are both high-temperature alloys, there are fundamental differences between GH738 and A286 in terms of physical properties and mechanical properties. Therefore, the above processing methods and parameters are not applicable to processing pallet nuts made of GH738 and ensuring that their strength reaches 1210MPa and their hardness is HRC32-42. In addition, the pallet nut includes a D-shaped pallet, which is not present in the self-locking nut assembly. This structural difference also means that the above processing methods cannot be used to process the pallet nut. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides a process for processing pallet nuts.

[0006] This invention is achieved through the following technical solution:

[0007] A process for manufacturing a support plate nut, the support plate nut comprising an internal thread section and a flared section, wherein one end of the outer circumference of the internal thread section has a tapered section after material removal, and the other end has a D-shaped support plate, and one end of the flared section is coaxially connected to the end of the internal thread section near the D-shaped support plate; the process for manufacturing the support plate nut includes the following steps:

[0008] (1) Material preparation: Prepare bar stock of GH738 material according to the external dimensions of the pallet nut;

[0009] (2) Numbering: Remove the black oxide scale from the surface of the bar stock according to the size requirements of the hot upsetting blank;

[0010] (3) Hot forging: D-shaped support plates are forged using high-frequency induction heating;

[0011] (4) Solution heat treatment: Place the upset semi-finished product in a vacuum heat treatment furnace, heat to 850℃~860℃, preheat for 30min~40min, raise the temperature to 1040℃~1080℃±10℃, hold for 60min~90min, and then air cool or oil cool.

[0012] (5) Machining: According to the design drawings, machine the outline of the internal thread section, the constriction section and the flaring section, and machine the thread bottom hole of the internal thread section and the inner hole of the flaring section, and then tap the thread bottom hole.

[0013] (6) Wire cutting: Cut the shape of the D-shaped tray according to the design drawings;

[0014] (7) Plain milling: Mill the small chamfers on the D-shaped support plate according to the design drawings;

[0015] (8) Fitter: Deburring, removing wire cut remelting layer, and filing the arc to ensure a smooth transition at the tangent;

[0016] (9) Mid-term inspection: Inspect all dimensions of the support plate nut according to the design drawings;

[0017] (10) Closing: The locking part of the part is closed by extrusion, and the closed section is elliptical or polygonal.

[0018] (11) Stabilization + Aging Heat Treatment: Place the closed pallet nut in a vacuum heat treatment furnace, heat to 845℃±10℃, keep warm for 3h~5h, and air cool; then heat the pallet nut to 760℃±10℃, keep warm for 16h±1h, and air cool, so that the hardness of the pallet nut reaches HRC32~42.

[0019] (12) Sandblasting: Sandblasting removes the oxide layer on the surface of the pallet nut;

[0020] (13) Local annealing: Local annealing is performed on the flared section;

[0021] (14) Fluorescence detection: Check that the surface of the tray nut must not have any abrupt changes in plane, and that the closing section must not have any cracks, folds or hairline defects.

[0022] (15) Metallographic inspection: Inspect the metal flow lines at the thread of the tray nut, the flow lines at the transition of the D-shaped tray, the grain size and oxidation depth of the tray nut, and whether there are any signs of overheating, burning, folding, or cracking.

[0023] (16) Silver plating: Silver plating is applied to the surface of the pallet nut, with a plating thickness of 5μm to 8μm;

[0024] (17) Performance tests: Locking performance test, axial load test, riveting test and ejection test are performed on the plate nut;

[0025] (18) Final inspection: Inspect all dimensions of the support plate nut according to the design drawings;

[0026] (19) Packaging and warehousing.

[0027] In step (3), when upsetting the D-shaped pallet, rough upsetting is performed first, and then fine upsetting is performed to obtain the D-shaped pallet shape.

[0028] In step (10), during the process of obtaining the closing section by extrusion, a locking performance process test is required to determine the closing size. The closing size is measured at the middle of the closing section, and the thread gauge should be able to be smoothly screwed into the closing section one and a half turns.

[0029] After the first piece of the flared section is partially annealed in step (13), a 60° conical mandrel is used to perform a riveting test on the flared section. When the flared section is flared to 1.2 times the original hole diameter, it is considered qualified if there are no cracks at the flared section.

[0030] After the first piece of flared section is partially annealed in step (13), the grain size of the flared section material is checked by metallography. The grain size is between level 2 and level 6, and it should be basically uniform, without obvious coarse and fine grain bands, and without overheating or burning. The oxidation depth is not greater than 0.01 mm. After the first piece passes inspection, the local annealing heat treatment parameters are solidified.

[0031] The step (13) involves local annealing of the flared section using high-frequency induction heating, including the following steps:

[0032] Step A: Vertically install and fix the pallet nut onto the lifting platform, ensuring that the flared section faces upwards;

[0033] Step B: Set the oscillation coefficient of the high-frequency induction heating equipment to 300-400;

[0034] Step C: Lift the pallet nut using the lifting platform until the flared section is aligned with the induction heating tube of the high-frequency induction heating equipment in terms of height;

[0035] Step D: Pass argon gas directly above the tray nut so that the tray nut is enveloped in an argon atmosphere;

[0036] Step E: Start the high-frequency induction heating equipment to heat the flared section;

[0037] Step F: Turn off the high-frequency induction heating equipment and cool the flared section to below 200°C in an argon atmosphere to complete the annealing treatment of the flared section.

[0038] The high-frequency induction heating equipment and the lifting platform are both mounted on the workbench;

[0039] The high-frequency induction heating equipment includes a high-frequency induction generator and an induction heating tube. Both ends of the induction heating tube are connected to the high-frequency induction generator. The middle part of the induction heating tube gradually spirals from the outside to the inside, and the center line of the middle part of the induction heating tube is on the same horizontal plane.

[0040] The induction heating tube is made of a copper tube with a diameter of 3mm, and a 1mm wide copper sheet is provided on the lower part of the inner wall of the middle part of the induction heating tube.

[0041] In step D, the argon flow rate is 4 L / min to 6 L / min; in step E, the heating time of the flared section is 5 s to 8 s, and the heating temperature is 800 ℃ to 900 ℃.

[0042] In step (16), after the tray nut is silver-plated, the tray nut is kept at 650°C for 4 hours. Then, compressed air of 0.3MPa to 0.4MPa is sprayed from a nozzle with a diameter of 1.5mm and blown onto the surface of the tray nut to cool it quickly. The silver layer should not have any protrusions or peeling.

[0043] In step (19), after the capacitor paper is used to package the pallet nut, the whole thing is placed in a vacuum packaging bag for vacuum packaging.

[0044] The beneficial effects of this invention are as follows:

[0045] 1. Through heat treatment processes such as solution heat treatment, stabilization and aging heat treatment, the strength of the pallet nut is ensured to reach 1210MPa and the hardness is HRC32-42.

[0046] 2. The closing section ensures proper closing and locking, playing a role in preventing loosening and resisting vibration, while also guaranteeing the integrity of the pallet nut structure, further ensuring the structural strength, rigidity, and other mechanical properties of the pallet nut.

[0047] 3. After installing and fixing the pallet nut onto the lifting platform, use the lifting platform to accurately lift the pallet nut to the heating position to ensure the stability of the heating position.

[0048] 4. The middle part of the induction heating tube is improved, with the middle part gradually spiraling from the outside to the inside, which enables the flared section to heat up quickly and improves the local annealing efficiency of the flared section; the center line of the middle part of the induction heating tube is on the same horizontal plane, and the induction area of ​​the induction heating tube is further reduced by copper sheet, so that the induction heating range is narrowed, so as to heat the flared section and avoid the heating affecting the material properties of the internal thread section, thus achieving the purpose of local annealing treatment of the support plate nut.

[0049] 5. Silver plating on the surface of the pallet nut utilizes the excellent lubricity of the silver plating layer to greatly reduce the torque and resistance when bolts are tightened with the pallet nut, significantly reducing the heat and pressure generated during tightening, and minimizing the damage to the internal threads of the pallet nut caused by heat and pressure. The good heat dissipation properties of the silver plating layer prevent localized high temperatures from causing thread seizing. The silver plating layer, as a softer medium, reduces wear and hard friction on the threads, thus protecting the internal threads from damage to a greater extent. It can be repeatedly disassembled and reused, reducing the difficulty of pallet nut installation, ensuring maintenance and replacement, and significantly reducing labor and material costs. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the structure of the support plate nut of the present invention;

[0051] Figure 2 for Figure 1 A schematic diagram of the left-side view structure;

[0052] Figure 3 This is a schematic diagram of the structure of the bracket nut flared section of the present invention after flaring and riveting, and then installed on the base body.

[0053] Figure 4 This is a schematic diagram of the structure of the high-frequency induction heating device of the present invention when it is used in conjunction with a lifting platform to perform partial annealing on the flared section of the pallet nut.

[0054] Figure 5 This is a schematic diagram of the structure of the induction heating tube of the present invention.

[0055] In the diagram: 1-Panel nut, 10-Constriction section, 11-Internal thread section, 12-Flanged section, 13-D-shaped tray, 2-Base, 3-Workbench, 4-High-frequency induction heating equipment, 40-High-frequency induction generator, 41-Induction heating tube, 5-Lifting platform, 6-Argon nozzle. Detailed Implementation

[0056] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0057] like Figures 1 to 5 As shown, the present invention discloses a processing method for a pallet nut. The pallet nut 1 includes an internal thread section 11 and a flared section 12. One end of the outer surface of the internal thread section 11 has a tapered section 10 after material removal, and the other end has a D-shaped pallet 13. One end of the flared section 12 is coaxially connected to the end of the internal thread section 11 near the D-shaped pallet 13. The processing method of the pallet nut 1 includes the following steps:

[0058] (1) Material preparation: Prepare bar stock of GH738 material according to the external dimensions of the pallet nut 1.

[0059] (2) Numbering: Remove the black oxide scale from the surface of the bar stock according to the required dimensions of the hot upsetting blank. Removing the black oxide scale from the surface of the bar stock prevents folding during upsetting.

[0060] (3) Hot upsetting: D-shaped support plate 13 is upsetting by high frequency induction heating.

[0061] (4) Solution heat treatment: The upsetting semi-finished product is placed in a vacuum heat treatment furnace, heated to 850℃~860℃, preheated for 30min~40min, heated to 1040℃~1080℃±10℃, held for 60min~90min, and then air-cooled or oil-cooled. Solution heat treatment changes the crystal structure and mechanical properties of the alloy to achieve the expected strength, toughness, corrosion resistance, etc. In contrast, the annealing heat treatment in the existing technology controls the temperature and time of the metal material to cause the grains to recrystallize or grow, thereby improving the plasticity and toughness of the material and reducing residual stress and structural defects. It can be seen that there is an essential difference between solution heat treatment and annealing heat treatment.

[0062] (5) Machining: According to the design drawings, machine the outer shape of the internal thread section 11, the constriction section 10 and the flaring section 12, and machine the threaded bottom hole of the internal thread section 11 and the inner hole of the flaring section 12, and then tap the threaded bottom hole.

[0063] (6) Wire cutting: According to the design drawings, wire cut the shape of the D-shaped support plate 13;

[0064] (7) Milling: Mill the small chamfer 130 on the D-shaped support plate (13) according to the design drawings;

[0065] (8) Fitter: Deburring, removing wire cut remelting layer, and filing the arc to ensure a smooth transition at the tangent;

[0066] (9) Mid-term inspection: Inspect the dimensions of the support plate nut 1 according to the design drawings;

[0067] (10) Closing: The locking part of the part is closed by extrusion, and the closed section 10 after closing is elliptical or polygonal.

[0068] (11) Stabilization + aging heat treatment: Place the closed pallet nut 1 in a vacuum heat treatment furnace, heat it to 845℃±10℃, keep it at the temperature for 3h~5h, and then air cool it; then heat the pallet nut 1 to 760℃±10℃, keep it at the temperature for 16h±1h, and then air cool it, so that the hardness of the pallet nut 1 reaches HRC32~42.

[0069] (12) Sandblasting: Sandblasting removes the oxide layer on the surface of the pallet nut 1;

[0070] (13) Local annealing: Local annealing is performed on the flared section 12;

[0071] (14) Fluorescence detection: Check that the surface of the tray nut 1 must not have any abrupt changes in plane, and that the constriction section 10 must not have any cracks, folds or hairline defects.

[0072] (15) Metallographic inspection: Inspect the metal flow lines at the thread of the support plate nut 1, the flow lines at the transition of the D-shaped support plate 13, the grain size and oxidation depth of the support plate nut 1, and whether there are any overheating, burning, folding, or cracking phenomena.

[0073] (16) Silver plating: Silver plating is applied to the surface of the tray nut 1, with a silver plating thickness of 5μm to 8μm;

[0074] (17) Performance tests: Locking performance test, axial load test, riveting test and ejection test are performed on the pallet nut 1;

[0075] (18) Final inspection: Inspect all dimensions of the support plate nut 1 according to the design drawings;

[0076] (19) Packaging and warehousing.

[0077] In step (3), when upsetting the D-shaped pallet 13, rough upsetting is performed first, and then fine upsetting is performed to obtain the shape of the D-shaped pallet 13.

[0078] In step (10), during the process of obtaining the constriction section 10 by extrusion, a locking performance process test is required to determine the constriction size. The constriction size is measured at the middle of the constriction section 10, and the thread gauge should be able to smoothly screw into the constriction section 10 one and a half turns. Compared with the existing technology of using wire cutting to cut six grooves for constriction, the constriction section 10 of this application, while ensuring normal constriction and locking, playing a role in preventing loosening and vibration, also ensures the integrity of the support plate nut 1 structure, further ensuring the structural strength and rigidity of the support plate nut 1 and other mechanical properties.

[0079] After the first flared section 12 is partially annealed in step (13), a 60° conical mandrel is used to perform a flaring test on the flared section 12. When the flaring is flared to 1.2 times the original hole diameter, the absence of cracks at the flared section indicates that it is qualified.

[0080] After the first piece of the flared section 12 is partially annealed in step (13), the grain size of the material of the flared section 12 is checked by metallography. The grain size is between level 2 and level 6, and it should be basically uniform, without obvious coarse and fine grain bands, and without overheating or burning. The oxidation depth is not greater than 0.01 mm. After the first piece passes the inspection, the local annealing heat treatment parameters are solidified.

[0081] The step (13) involves local annealing of the flared section 12 using high-frequency induction heating, including the following steps:

[0082] Step A: Vertically install and fix the pallet nut 1 onto the lifting platform 5, ensuring that the flared section 12 faces upwards;

[0083] Step B: Set the oscillation coefficient of the high-frequency induction heating device 4 to 300-400;

[0084] Step C: Lift the pallet nut 1 using the lifting platform 5 until the flared section 12 is aligned with the induction heating tube 41 of the high-frequency induction heating device 4 in height;

[0085] Step D: Pass argon gas directly above the support plate nut 1 so that the support plate nut 1 is enveloped in an argon atmosphere;

[0086] Step E: Start the high-frequency induction heating device 4 to heat the flared section 12;

[0087] Step F: Turn off the high-frequency induction heating device 4 and allow the flared section 12 to cool to below 200°C in an argon atmosphere, completing the annealing treatment of the flared section 12. Based on the structural characteristics of the pallet nut 1, the flared section 12 is very thin (only 0.55mm) and short (only 3.9mm), and the annealing process must not affect the material properties of the internal thread section 11. Due to the thinness of the flared section 12, a high-frequency electromagnetic induction heating method is suitable to prevent overheating of the pallet nut 1. The lifting platform 5 achieves its lifting function through a servo motor-driven worm gear screw mechanism, with a lifting stroke error within ±0.2mm. After the pallet nut 1 is installed and fixed on the lifting platform 5, the lifting platform 5 accurately lifts the pallet nut 1 to the heating position, ensuring a stable heating position.

[0088] The high-frequency induction heating device 4 and the lifting platform 5 are both mounted on the workbench 3;

[0089] The high-frequency induction heating device 4 includes a high-frequency induction generator 40 and an induction heating tube 41. Both ends of the induction heating tube 41 are connected to the high-frequency induction generator 40. The middle part of the induction heating tube 41 gradually spirals from the outside to the inside, and the center line of the middle part of the induction heating tube 41 is on the same horizontal plane. In use, the high-frequency induction heating device 4 is model WH-V1-26, with an input power of 26KVA and an induction heating frequency of 35KHZ~50KHZ. The flared section 12 is relatively short, only 3.9mm long. However, commonly used induction heating tubes are generally cylindrical spiral tubes with a large heating area. During heating, the entire support plate nut 1 is within the heating range, which cannot achieve the purpose of local annealing. Therefore, the middle part of the induction heating tube 41 is improved so that it gradually spirals from the outside to the inside, which can make the flared section 12 heat up quickly and improve the local annealing efficiency of the flared section 12. The center line of the middle part of the induction heating tube 41 is on the same horizontal plane, which reduces the induction area and narrows the induction heating range, so as to heat the flared section 12 and achieve the purpose of local annealing treatment of the support plate nut 1.

[0090] The induction heating tube 41 is made of copper tube with a diameter of 3mm, and a 1mm wide copper sheet is provided on the lower part of the inner wall of the middle section of the induction heating tube 41. The copper sheet further reduces the induction area of ​​the induction heating tube 41, making the induction heating range narrower, so as to heat the flared section 12 and avoid the heating affecting the material properties of the internal thread section 11, thereby achieving the purpose of local annealing treatment of the support plate nut 1.

[0091] In step D, the argon flow rate is 4 L / min to 6 L / min; in step E, the heating time of the flared section 12 is 5 s to 8 s, and the heating temperature is 800℃ to 900℃. During use, an argon nozzle 6 is installed directly above the middle of the support nut 1 and the induction heating tube 41. The argon nozzle is connected to a gas cylinder via a gas pipe. The gas cylinder contains sufficient industrial-grade 99.99% argon gas, and a pressure reducing valve and flow meter are installed at the cylinder outlet. The argon gas is then supplied by turning on the argon gas switch, and the argon flow rate is controlled at 4 L / min to 6 L / min, so that the argon gas surrounds the support nut 1, isolating it from air and reducing oxidation of the heating section of the support nut 1, which appears a bright red color.

[0092] In step (16), after the surface of the pallet nut 1 is silver-plated, the pallet nut 1 is kept at 650°C for 4 hours. Then, compressed air of 0.3MPa to 0.4MPa is sprayed from a nozzle with a diameter of 1.5mm and blown onto the surface of the pallet nut 1 to cool it quickly. The silver layer should not have any protrusions or peeling.

[0093] After packaging the pallet nut 1 with capacitor paper in step (19), the whole thing is placed in a vacuum packaging bag for vacuum packaging. There is a very significant problem in the assembly process between the internal thread on the pallet nut 1 and the external thread on the bolt, etc., that is, the internal and external threads are prone to seizing (also known as "engagement" or "meshing"), which makes it impossible to install or remove the pallet nut 1 or the installation and removal torque is extremely large. The reason for this phenomenon is that when the internal and external threads are tightened, the threads will generate a lot of heat and pressure, which will damage the passivation layer or oxide layer between the internal and external threads, causing the internal and external threads to shear and block, and then engage (stick), making it impossible to install or remove the pallet nut 1. After silver plating the surface of the pallet nut 1, the silver layer not only beautifies its appearance but also serves the following purposes: First, the silver plating on the threads of the pallet nut 1 provides excellent lubricity, significantly reducing the torque and resistance when bolts are tightened onto the pallet nut 1, and substantially reducing the heat and pressure generated during tightening, minimizing the damage to the internal threads caused by heat and pressure. Second, the heat dissipation performance of the silver plating is far superior to that of GH738. The silver plating quickly transfers heat to the entire pallet nut 1 and the bolts connected to it, thus preventing localized high temperatures from causing thread seizing. Third, as a softer medium, the silver plating reduces wear and friction on the threads, thus protecting the internal and external threads from damage to a greater extent. It allows for repeated disassembly and reuse, reducing the installation difficulty of the pallet nut 1, ensuring easy maintenance and replacement, and significantly reducing labor and material costs. After packaging the pallet nut 1 in capacitor paper, it is placed in a vacuum-sealed bag to prevent oxidation, corrosion, and rust.

Claims

1. A process for processing pallet nuts, characterized in that: The support plate nut (1) includes an internal thread section (11) and a flared section (12). One end of the outer circular surface of the internal thread section (11) has a tapered section (10) after material removal, and the other end has a D-shaped support plate (13). One end of the flared section (12) is coaxially connected to the end of the internal thread section (11) near the D-shaped support plate (13). The processing technology of the support plate nut (1) includes the following steps: (1) Material preparation: Prepare bar stock of material GH738 according to the external dimensions of the pallet nut (1); (2) Numbering: Remove the black oxide scale from the surface of the bar stock according to the size requirements of the hot upsetting blank; (3) Hot forging: D-shaped pallets are forged using high-frequency induction heating (13); (4) Solution heat treatment: Place the upset semi-finished product in a vacuum heat treatment furnace, heat to 850℃~860℃, preheat for 30min~40min, raise the temperature to 1040℃~1080℃±10℃, hold for 60min~90min, and then air cool or oil cool. (5) Machining: According to the design drawings, machine the outline of the internal thread section (11), the constriction section (10) and the flared section (12), and machine the thread bottom hole of the internal thread section (11) and the inner hole of the flared section (12), and then tap the thread bottom hole. (6) Wire cutting: According to the design drawings, wire cut the shape of the D-shaped tray (13); (7) Milling: Mill the small chamfer (130) on the D-shaped support plate (13) according to the design drawings; (8) Fitter: Deburring, removing wire cut remelting layer, and filing the arc to ensure a smooth transition at the tangent; (9) Inspection: Inspect the dimensions of the pallet nut (1) according to the design drawings; (10) Closing: The locking part of the part is closed by extrusion. The closed section (10) after closing is elliptical or polygonal. (11) Stabilization + aging heat treatment: Place the closed pallet nut (1) in a vacuum heat treatment furnace, heat to 845℃±10℃, keep warm for 3h~5h, and air cool; then heat the pallet nut (1) to 760℃±10℃, keep warm for 16h±1h, and air cool, so that the hardness of the pallet nut (1) reaches HRC32~42. (12) Sandblasting: Sandblasting removes the oxide layer on the surface of the pallet nut (1); (13) Local annealing: Local annealing is performed on the flared section (12); (14) Fluorescence detection: Check that the surface of the tray nut (1) is free from any abrupt changes in plane, and that the constriction section (10) is free from cracks, folds or hairline defects; (15) Metallographic inspection: inspect the metal flow lines at the thread of the tray nut (1), the flow lines at the transition of the D-shaped tray (13), the grain size and oxidation depth of the tray nut (1), and whether there are overheating, burning, folding, or cracking phenomena. (16) Silver plating: Silver plating is applied to the surface of the tray nut (1), with a plating thickness of 5μm to 8μm; (17) Performance test: The locking performance test, axial load test, riveting test and ejection test are carried out on the plate nut (1); (18) Final inspection: Inspect each dimension of the support plate nut (1) according to the design drawings; (19) Packaging and warehousing.

2. The processing technology for the pallet nut as described in claim 1, characterized in that: In step (3), when upsetting the D-shaped pallet (13), rough upsetting is performed first, and then fine upsetting is performed to obtain the shape of the D-shaped pallet (13).

3. The processing technology for the pallet nut as described in claim 1, characterized in that: In step (10), during the process of obtaining the closing section (10) by extrusion, a locking performance process test is required to determine the closing size. The closing size is measured in the middle of the closing section (10), and the thread gauge should be able to be smoothly screwed into the closing section (10) one and a half turns.

4. The processing technology for the pallet nut as described in claim 1, characterized in that: After the first flared section (12) is partially annealed in step (13), a 60° conical mandrel is used to conduct a flaring test on the flared section (12). When the flaring is flared to 1.2 times the original hole diameter, the absence of cracks at the flared section indicates that it is qualified.

5. The processing technology for the pallet nut as described in claim 1, characterized in that: After the first piece of the flared section (12) is partially annealed in step (13), the grain size of the flared section (12) material is checked by metallography. The grain size is between level 2 and level 6, and it should be basically uniform, without obvious coarse and fine grain bands, and without overheating or burning. The oxidation depth is not greater than 0.01 mm. After the first piece passes the inspection, the local annealing heat treatment parameters are solidified.

6. The processing technology for the pallet nut as described in claim 1, characterized in that: In step (13), the flared section (12) is locally annealed using high-frequency induction heating, including the following steps: Step A: Vertically install and fix the pallet nut (1) onto the lifting platform (5), and ensure that the flared section (12) faces upward; Step B: Set the oscillation coefficient of the high-frequency induction heating device (4) to 300-400; Step C: Lift the pallet nut (1) using the lifting platform (5) until the flared section (12) is aligned with the induction heating tube (41) of the high-frequency induction heating device (4) in height; Step D: Pass argon gas directly above the plate nut (1) so that the plate nut (1) is enveloped in an argon atmosphere; Step E: Start the high-frequency induction heating device (4) to heat the flared section (12); Step F: Turn off the high-frequency induction heating device (4) and cool the flared section (12) to below 200°C in an argon atmosphere to complete the annealing treatment of the flared section (12).

7. The processing technology for the pallet nut as described in claim 6, characterized in that: The high-frequency induction heating device (4) and the lifting platform (5) are both located on the workbench (3); The high-frequency induction heating device (4) includes a high-frequency induction generator (40) and an induction heating tube (41). Both ends of the induction heating tube (41) are connected to the high-frequency induction generator (40). The middle part of the induction heating tube (41) gradually spirals from the outside to the inside, and the center line of the middle part of the induction heating tube (41) is on the same horizontal plane.

8. The processing technology for the pallet nut as described in claim 7, characterized in that: The induction heating tube (41) is made of a copper tube with a diameter of 3 mm, and a 1 mm wide copper sheet is provided on the lower part of the inner wall of the middle part of the induction heating tube (41).

9. The processing technology for the pallet nut as described in claim 6, characterized in that: In step D, the flow rate of argon gas is 4L / min to 6L / min; in step E, the heating time of the flared section (12) is 5S to 8S, and the heating temperature is 800℃ to 900℃.

10. The processing technology for the pallet nut as described in claim 1, characterized in that: In step (16), after the surface of the pallet nut (1) is silver-plated, the pallet nut (1) is kept at 650°C for 4 hours. Then, compressed air of 0.3MPa to 0.4MPa is sprayed from a nozzle with a diameter of 1.5mm and blown onto the surface of the pallet nut (1) to cool it quickly. The silver layer should not have any protrusions or peeling. In step (19), after the capacitor paper packaging pallet nut (1) is used, the whole thing is placed in a vacuum packaging bag for vacuum packaging.

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