A hole shaft connecting fitting processing technology and structure

Abstract

The application discloses a hole shaft connecting hardware processing technology and structure, and relates to the technical field of metal processing, which comprises the following steps: expanding the inner hole of the connecting hardware to a preset size range; installing a bushing in the expanded inner hole, wherein the inner wall of the bushing is provided with a reinforcing layer; and forming a wear-resistant layer on the outer surface of a matched bolt by using a thermal spraying process, so that the outer surface of the bolt and the inner wall of the bushing form a matched pair of grinding parts. The bushing with the reinforcing layer is inlaid in the inner hole of the connecting hardware, and the bolt with the wear-resistant layer formed by the thermal spraying process is matched, so that the bolt and the inner wall of the bushing form a matched pair of grinding parts, the hole shaft interface can be replaced and the coating thickness can be adjusted, the overall service life of the connecting hardware is prolonged, and the maintenance cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of metal processing technology, and in particular to a processing technology and structure for hole-shaft connection fittings. Background Technology

[0002] Hole-shaft connections are a key structural form in power fittings, mechanical transmissions, and power transmission line devices. They typically achieve positioning and load transfer by passing bolts or pins through holes in the fitting body. During long-term service, these connections are subjected to alternating loads, impacts, and fretting wear. Especially in outdoor environments with high humidity, high salt spray, and severe temperature differences, problems such as hole wall wear, bolt seizing, increased clearance, and connection instability are prone to occur.

[0003] Existing hardware commonly uses 35CrMo, Q235, and Q355 metal materials to machine holes. The hole walls are in direct contact with bolts or pins. Due to the small clearance, under eccentric stress or wind-induced vibration, fretting wear-corrosion coupling occurs: the hole walls gradually wear due to repeated micro-displacements, and metal debris undergoes electrochemical corrosion in humid media, accelerating hole enlargement and loosening of connections. In severe cases, this can lead to hardware failure or fastener breakage. To improve wear resistance, existing technologies typically employ thermal spraying, welding, or hardening treatments on the hole wall area, but these methods present challenges such as difficulties in machining internal holes and controlling thickness. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a processing technology and structure for hole-shaft connection fittings. By embedding a bushing with a reinforcing layer inside the inner hole of the connection fitting, and cooperating with a bolt that has been thermally sprayed to form a wear-resistant layer, the bolt and the inner wall of the bushing form a matching wear pair. This enables the hole-shaft interface to be replaceable and the coating thickness to be adjustable, thereby extending the overall service life of the connection fitting and reducing maintenance costs.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, embodiments of the present invention provide a machining process for hole-shaft connection fittings, including: Enlarge the inner hole of the connecting hardware to a preset size range; A bushing is installed inside the enlarged inner bore, wherein the inner wall of the bushing has a reinforcing layer; A wear-resistant layer is formed on the outer surface of the matching bolts by thermal spraying, so that the outer surface of the bolts and the inner wall of the bushing form a matching wear pair. By enlarging the inner hole of the connecting hardware and inserting a reinforced bushing, the problem of reinforcing the inner hole, which was originally difficult to process directly, is transformed into a problem of externally controllable processing of the bushing, which effectively improves the feasibility of the process and the stability of the reinforcement layer quality.

[0006] As a further implementation, the inner hole of the bushing is divided into a wear zone and a non-wear zone, the inner wall of the wear zone is elliptical arc, and the inner wall of the non-wear zone is circular arc; The reinforcing layer is located in the wear area.

[0007] The above setup allows for the use of the elliptical structure in the wear zone to reserve the thickness of the reinforcing layer, enabling quantitative and uniform sintering of the wear-resistant coating. This effectively avoids process defects such as coating cracking and porosity. Meanwhile, the arc-shaped reference structure in the non-wear zone ensures assembly coaxiality and avoids problems such as bolt eccentric wear and local stress concentration.

[0008] As a further implementation, the short axis of the wear zone is consistent with the inner diameter of the inner hole of the connecting hardware before enlargement, which can be precisely connected with the arc-shaped reference structure of the non-wear zone to ensure that the reference size of the inner hole of the bushing base remains unchanged. The long half-axis of the wear zone is larger than the set value of the short half-axis. The incremental dimension of the long half-axis relative to the short half-axis can accurately reserve the uniform forming thickness of the reinforcing layer, providing a regular forming space for the sintering and forming of the powder metallurgy wear-resistant coating.

[0009] As a further implementation, the method for providing a reinforcing layer in the wear zone includes: The mixed powder is filled into the wear area of ​​the bushing, and the mixed powder is pressed under cold pressing conditions so that the wear area has an arc-shaped outer contour after pressing. The pressed bushing is sent into a vacuum sintering furnace for dewaxing and metallurgical sintering to form a reinforcing layer in the wear zone.

[0010] By employing a preparation process that combines directional powder filling in the wear zone, cold pressing and shaping with vacuum dewaxing and metallurgical sintering, wear-resistant reinforcing materials can be precisely placed in the friction area. Cold pressing allows the powder to be compacted and shaped into a regular arc contour, ensuring uniform thickness and consistent performance of the reinforcing layer. Vacuum segmented dewaxing avoids forming defects such as porosity, blistering, and cracking. High-temperature metallurgical sintering then achieves diffusion and fusion of the composite powder and a high-strength metallurgical bond with the bushing substrate, effectively improving the density, bonding strength, and structural stability of the reinforcing layer.

[0011] As a further implementation, the dewaxing process is divided into two stages, wherein the first stage sintering temperature is 250~300℃ and the sintering time is 1~1.5 hours; the second stage sintering temperature is 400~450℃ and the sintering time is 1~1.5 hours. The metallurgical sintering temperature is 1050~1070℃, and the holding time is 20~30 minutes.

[0012] The low-temperature and high-temperature dual-stage gradient dewaxing method can achieve complete removal of paraffin additives. The low-temperature stage slowly volatilizes the surface additives, avoiding defects such as pores and bubbling caused by excessively rapid dewaxing at one time. The high-temperature stage thoroughly removes residual additives, preventing cracking and porosity caused by rapid volatilization of paraffin during subsequent sintering, and effectively ensuring the integrity of the sintered green body structure and the uniformity of the microstructure.

[0013] As a further implementation, the method for preparing the mixed powder includes: Ni60 powder, TiC powder, and carbon black powder are mixed according to a set mass percentage; paraffin wax of a set mass fraction is added to the mixed powder and mixed evenly; this allows the Ni60 matrix phase, TiC hard phase, and carbon black lubricating phase to be uniformly compounded, ensuring the synergistic matching of matrix toughness, wear resistance, and lubrication performance, while the appropriate amount of paraffin wax enhances the molding plasticity and bonding stability of the mixed powder.

[0014] As a further implementation, the method of installing the bushing into the inner hole includes: Press the bushing into the inner hole; The bushing and connecting hardware are preheated before being welded together. The assembly and fixing method of pressing the bushing first and then preheating and welding it ensures that the bushing and connecting hardware are evenly and firmly combined, effectively improving the axial and circumferential fixing reliability of the bushing.

[0015] As a further implementation, the process of forming the wear-resistant layer includes: Using Ni60 and WC reinforcing phase powder as thermal spraying powder, a wear-resistant layer of a set thickness is deposited on the bolt shank through thermal spraying process; a dense and firm wear-resistant coating can be formed on the bolt shank, which can form a wear pair with the bushing reinforcement layer with matching performance, effectively reducing bolt wear and ensuring stable hole-shaft fit accuracy.

[0016] As a further implementation method, the bolts after the thermal spraying process are remelted to form a metallurgically bonded reinforced surface layer; this can enable the sprayed layer to form a dense metallurgical bond with the bolt substrate, thereby improving the bonding strength of the wear-resistant layer.

[0017] Secondly, embodiments of the present invention also provide a hole-shaft connection hardware structure, which is manufactured using the aforementioned hole-shaft connection hardware processing technology.

[0018] The beneficial effects of this invention are as follows: This invention enlarges the inner bore of the connecting hardware and inserts a bushing within it, creating a uniform and controllable thickness reinforcing layer on the inner wall of the bushing. Simultaneously, a wear-resistant layer is formed on the outer surface of the matching bolts using thermal spraying, creating a matching wear pair between the bolts and the inner wall of the bushing. Without directly altering the overall structure and installation method of the connecting hardware, this invention achieves controllable reinforcement of the critical wear area of ​​the inner bore. It reduces the wear rate of the connecting hardware's inner bore, suppresses the expansion of the hole-groove gap and localized failure, and improves the overall matching and durability of the friction pair between the connecting hardware and the bolts. This enhances the service reliability of overhead transmission line connecting hardware under conditions of strong winds, sandstorms, heavy corrosion, and long-term vibration. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a process flow diagram of the connecting hardware processing according to one or more embodiments of the present invention; Figure 2 This is a cross-sectional view of the bushing according to one or more embodiments of the present invention; Figure 3 This is a front view of the bushing and pressing mold assembly according to one or more embodiments of the present invention; Figure 4 This is a side view of the bushing and pressing mold according to one or more embodiments of the present invention; Figure 5 This is a top view of the bushing and pressing mold according to one or more embodiments of the present invention; Figure 6 This is a schematic diagram of the wear condition of the reinforcing holes and reinforcing bolts of the ZBD hanging plate made of 35CrMo steel in Embodiment 3 of the present invention after a wear test; Figure 7 This is a schematic diagram of the wear condition of the ZBD hanging plate reinforced holes and reinforced bolts made of 35CrMo steel in Embodiment 4 of the present invention after a wear test; Figure 8 This is a schematic diagram showing the wear condition of ZBD mounting plate holes and unreinforced bolts made of ordinary Q355 steel after a wear test; Figure 9 This shows the wear condition of the ZBD mounting plate holes and unreinforced bolts made of 35CrMo steel after a wear test.

[0021] Among them, 1. Bushing, 2. Wear area, 3. Non-wear area, 4. Reinforcing layer, 5. Mold body, 6. Mold shaft. Detailed Implementation

[0022] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] Terminology Explanation: ZBD mounting plates are a type of connecting hardware in electrical fittings, also known as three-legged right-angle mounting plates. They are a type of steering connecting hardware that changes the direction of connection.

[0024] Example 1: Hole-shaft connections are a typical structural form in power fittings, mechanical transmissions, and power line suspension devices. They typically use bolts or pins inserted into holes in the fitting body for positioning and force transmission. Under long-term alternating loads, impacts, and fretting wear, coupled with outdoor high humidity, high salt spray, and drastic temperature changes, this type of connection is prone to problems such as hole wall wear, bolt seizing, increased clearance, and connection instability.

[0025] Existing hardware holes are mostly machined directly from metal materials, with the hole wall in direct contact with the fastener. Due to the small clearance, under eccentric stress or wind-induced vibration, reciprocating micro-slippage occurs between the hole wall and the shaft surface, inducing a fretting wear-corrosion coupling effect: the hole wall material gradually peels off due to cyclic shearing, and the wear debris undergoes electrochemical corrosion in the humid medium, further accelerating the hole diameter expansion and connection loosening, ultimately leading to a decrease in load-bearing capacity or even hardware failure.

[0026] To improve the wear resistance of connecting fittings, existing technologies typically involve thermal spraying, welding, or hardening treatment on the hole wall area. However, due to the small size of the inner hole of the connecting fitting, surface reinforcement methods such as laser cladding, thermal spraying, and spin coating sintering are difficult to directly modify and strengthen it. Furthermore, the complex size and shape of the connecting fitting makes clamping difficult. The inner hole of the connecting fitting is used in conjunction with the bolt, and the wear resistance of the bolt needs to be improved simultaneously. The surface reinforcement effects of the two need to be precisely matched, as excessive reinforcement of one will lead to rapid wear and failure of the other.

[0027] Based on this, this embodiment provides a hole-shaft connection hardware processing technology, which enlarges the inner hole of the connection hardware to a preset size range; a bushing 1 is installed in the enlarged inner hole, wherein the inner wall of the bushing 1 has a reinforcing layer 4; a wear-resistant layer is formed on the outer surface of the matching bolt by thermal spraying welding, so that the outer surface of the bolt and the inner wall of the bushing 1 form a matching wear pair.

[0028] In this embodiment, surface reinforcement is performed on the inner hole of bushing 1 using metallurgical technology, which enables mass production. At the same time, bushing 1 is reinforced using powder metallurgy, and bolts are reinforced using thermal spraying. The two have overlap in the selection of powders, which facilitates the matching of the hardness of the friction pair.

[0029] like Figure 1As shown, the processing technology in this embodiment mainly includes the following steps: The fittings are expanded, the bushing 1 with the reinforcing layer 4 is machined, and the bolts with the wear-resistant layer are manufactured.

[0030] Specifically, the hole enlargement steps are as follows: Mechanical boring is used to enlarge the inner diameter of the connecting hardware by 10% to 15% based on the original inner diameter. This enlargement range can ensure the bolt assembly while preventing the bushing 1 from deforming due to sintering.

[0031] The processing of bushing 1 with reinforcing layer 4 includes: (1) Prepare the mixed powder: First, Ni60 powder with a particle size of 60μm~80μm, TiC powder with a particle size of 15μm~20μm, and carbon black with a particle size of 15μm~20μm were selected.

[0032] Using Ni60 powder as the matrix phase, excessively large powder size will lead to excessive porosity and affect corrosion resistance; TiC powder is a hard phase that needs to be dispersed and its size needs to be smaller than that of Ni60 powder. Selecting 15μm~20μm can maximize the packing density and improve the compactness of the reinforcing layer 4; Carbon black powder is a lubricating phase, and the size selection criteria are the same as those for TiC powder.

[0033] Then, Ni60 powder, TiC powder, and carbon black powder are mixed according to a certain mass percentage.

[0034] In this embodiment, the mass percentage of Ni60 powder is 60%–70%, the mass percentage of TiC powder is 30%–40%, and the mass percentage of carbon black powder is 5%–10%. Ni60 powder dominates the mixed powder composition, ensuring sufficient continuity and toughness of the metal matrix. The 30%–40% mass percentage of TiC powder prevents excessive ceramic phase content from causing coating embrittlement, cracking, or decreased bonding performance. The carbon black powder content is controlled at 5%–10%, providing lubrication and friction reduction; too low a content results in insignificant lubrication, while too high a content affects the continuity of the metal matrix and the density of the coating.

[0035] Finally, a certain mass fraction of paraffin is added to the mixed powder, and a powder mixer is used to thoroughly mix the powder.

[0036] In this embodiment, the paraffin wax content is 2.5% to 4% by mass, which ensures sufficient bonding strength and workability of the powder while avoiding excessive organic components. If the paraffin wax content is too low, the powder is difficult to form stably, and powdering, cracking, or localized loosening may occur after coating. If the paraffin wax content is too high, more volatilized residues and pores are likely to be generated during subsequent heating or sintering, affecting the density, bonding strength, and wear and corrosion resistance of the reinforcing layer 4.

[0037] (2) Machining bushing 1: like Figure 2 As shown, bushing 1 is cylindrical in shape, and its outer diameter is consistent with the inner diameter of the connecting hardware after the hole is enlarged. Its inner hole is divided into two parts: wear zone 2 and non-wear zone 3. The inner wall of wear zone 2 is elliptical arc.

[0038] In this embodiment, the long half-axis of the wear zone 2 is 10% to 12.5% ​​longer than the short half-axis. This is because the difference between the long and short half-axis is the thickness of the reinforcing layer 4. If the thickness is too small, the wear resistance will be insufficient. If the thickness is too large, on the one hand, the inner wall of the bushing 1 will be too thin and easily deformed. On the other hand, it will cause defects such as cracking during the sintering process of the reinforcing layer 4.

[0039] The inner wall of the non-wear zone 3 is arc-shaped, and its diameter is consistent with the inner diameter of the connecting hardware before the hole is enlarged. The axial length of the bushing 1 is greater than the thickness of the connecting hardware. This embodiment can utilize the elliptical structure of the wear zone 2 to reserve the forming thickness of the reinforcing layer 4, thereby achieving quantitative and uniform sintering of the wear-resistant coating, effectively avoiding process defects such as coating cracking and porosity. At the same time, the arc-shaped reference structure of the non-wear zone 3 can ensure assembly coaxiality and avoid bolt eccentric wear and local stress concentration problems.

[0040] In addition, the inner and outer surfaces of bushing 1 need to be sandblasted before use to keep the surface roughness at Ra6.3μm~12.5μm.

[0041] (3) Mixed powder loading and sintering: Under cold pressing conditions, the mixed powder is pressed into the wear area 2 of the bushing 1 by a pressing mold, so that the shape of the wear area 2 changes from an elliptical arc to a circular arc, forming a complete circle with the non-wear area 3.

[0042] In this embodiment, the filling and pressing of powder onto bushing 1 is accomplished using a pressing die. For example... Figure 3 - Figure 5 As shown, the pressing mold includes a mold body 5 and a mold shaft 6. The mold body 5 is used to support the bushing 1 and limit the axial displacement of the powder. The mold shaft 6 passes through the inner hole of the bushing 1 and is used to press the powder.

[0043] The mold body 5 is provided with a support groove, which is adapted to the shape of the bushing 1. The bushing 1 is placed horizontally in the support groove with its axis in place, so that the two ends of the mold body 5 form a shield corresponding to the wear area 2 of the bushing, which is used to accommodate the mixed powder to be pressed and limit the overflow of the mixed powder during the pressing process.

[0044] In this embodiment, the mold shaft 6 is cylindrical, and its outer diameter is smaller than the inner diameter of the bushing 1. Preferably, the outer diameter of the mold shaft 6 is 4mm to 8mm smaller than the inner diameter of the bushing 1, so that the mold shaft 6 can smoothly extend into the inner hole of the bushing 1 and roll and press along the corresponding position of the wear area 2 in the inner hole of the bushing 1.

[0045] The specific suppression process is as follows: First, place the bushing 1 in the mold body 5, so that the bushing wear area 2 is directly opposite the support groove of the mold body 5, and the wear area 2 and the support groove together form a powder receiving space.

[0046] Then, mixed powder is fed into the bushing 1 at the position corresponding to the wear area 2. The amount of powder fed should be such that the mixed powder can cover the wear area 2 and is slightly higher than the target forming contour. Preferably, the thickness of the powder fed in a single feeding is 0.2 mm to 1.0 mm higher than the target arc contour, so as to leave room for the compaction and shrinkage of the powder in the subsequent pressing process.

[0047] After powder feeding, the mold shaft 6 is inserted into the inner hole of the bushing 1, so that the outer surface of the mold shaft 6 contacts the mixed powder, and the mixed powder is rolled and pressed. The pressure applied to the mold shaft 6 is preferably 50MPa to 300MPa, the single rolling pressing speed is preferably 1mm / s to 20mm / s, and the number of round-trip pressings is preferably 3 to 20. Through rolling pressing, the mixed powder gradually fills the wear area 2 and is compacted and shaped under the constraint of the support groove of the mold body 5, reducing the problems of local powder accumulation, displacement, or uneven compaction.

[0048] After rolling and pressing back and forth several times, remove the mold shaft 6 and observe the formation of the powder layer in the wear area 2. If the powder layer has local depressions, insufficient thickness, or does not completely cover the wear area 2, continue to add mixed powder to the corresponding position and repeat the rolling and pressing process; if the powder layer has local bulges or edge powder overflow, remove the excess powder and continue pressing to make the powder layer surface gradually become flat, continuous and dense.

[0049] Repeat the powder feeding, rolling pressing and observation and repair steps until the powder layer fully fills the wear area 2 and its surface is continuous and dense, without obvious cracks, obvious holes and obvious powder fall-off.

[0050] The sintering process is as follows: The pressed bushing 1 is placed on a support fixture and fed into a vacuum sintering furnace. The vacuum sintering furnace is evacuated to a vacuum level of -1 bar to provide an oxygen-free or weakly oxidizing environment for dewaxing and sintering. It should be noted that the support fixture used here is an existing fixture, and its structure will not be described in detail.

[0051] Dewaxing and metallurgical sintering are carried out in a vacuum sintering furnace.

[0052] The dewaxing stage is divided into two stages: the first stage sintering temperature is 250℃~300℃ and the sintering time is 1 hour~1.5 hours; the second stage sintering temperature is 400℃~450℃ and the sintering time is 1 hour~1.5 hours; during the process of raising the temperature from room temperature to the two stage temperatures, the heating rate is controlled at 3℃ / min.

[0053] Dewaxing requires two stages. If the low-temperature stage is missing, the high-temperature stage will dewax too quickly, resulting in defects such as pores and bubbling. Conversely, if the high-temperature stage is missing, dewaxing will be insufficient, causing the paraffin wax to volatilize rapidly during the sintering process, leading to defects such as bubbling and cracking. Furthermore, paraffin wax begins to decompose at around 220℃~250℃ and decomposes rapidly at around 350℃. The dewaxing temperature must be higher than these two temperatures. To ensure thorough dewaxing, each dewaxing stage needs to be maintained for 1 to 1.5 hours.

[0054] After dewaxing and sintering, metallurgical sintering is performed without opening the furnace. The temperature is continued to rise to 1050℃~1070℃, held for 20min~30min, and then cooled to 150℃ in the furnace before being removed. Within the temperature range of 1050℃~1070℃, the Ni60 alloy can form a continuous metal matrix, enhancing the density and interfacial bonding strength of the composite reinforcing layer 4.

[0055] Meanwhile, TiC, as a high-melting-point hard reinforcing phase, can maintain a stable distribution in the metal matrix and play a wear-resistant supporting role. Controlling the holding time to 20-30 minutes can ensure that the composite powder is fully sintered and the interface diffuses, while avoiding coarsening of the microstructure, segregation of the reinforcing phase, or excessive oxidation of the matrix caused by prolonged high temperature.

[0056] (4) Install bushing 1 onto the connecting hardware.

[0057] The bushing 1 is pressed into the inner hole. The outer diameter of the bushing 1 and the inner hole are fitted with an interference fit or a slight interference fit to ensure the radial stability of the bushing 1 during assembly. After the bushing 1 is assembled, its two axial end faces are respectively higher than the edge of the hole by a certain length, forming an annular protrusion structure at the hole.

[0058] Before welding, the connecting hardware and the assembled bushing 1 are preheated to 200℃. Welding is then performed using gas-shielded arc welding. During welding, either continuous circumferential welding or symmetrical segmented welding is employed to ensure even heat distribution in the circumferential direction and prevent localized overheating. After welding, the components are cooled in air.

[0059] Furthermore, the manufacturing process of bolts with a wear-resistant layer includes: Bolts of a certain strength grade are selected as the hole-shaft connectors, and the bolt shanks are sandblasted to remove the hot-dip galvanized layer, so that the surface roughness is maintained at Ra6.3μm~12.5μm.

[0060] Ni60 powder with a particle size of 60μm~80μm and WC (tungsten carbide) powder with a particle size of 40μm~60μm are used as thermal spray welding powders. The mass fraction of Ni60 powder is 70%~80% and the mass fraction of WC powder is 20%~30%. A wear-resistant layer with a thickness of 10%~12.5% ​​of the diameter of the bolt is deposited on the bolt shank through thermal spray welding process.

[0061] Thermal spraying differs from powder metallurgy. Hard phases with too low powder diameter and density can clog the spray gun and cause uneven powder spraying. Therefore, WC powder with larger particle size and higher density is selected as the reinforcing phase.

[0062] To ensure that the wear-resistant layer of the bolt and the inner hole reinforcing layer 4 of the bushing 1 have similar wear resistance, the amount of WC powder added needs to be strictly controlled between 20% and 30%. Too high or too low a content will lead to excessive wear on one side. Since the bolt shank rotates during use, its maximum wear thickness is lower than that at the inner hole. Therefore, the thickness of the wear-resistant layer at the bolt shank is controlled to be slightly lower than the thickness of the inner hole reinforcing layer 4 of the bushing 1 to ensure that the wear progress of the bushing 1 and the bolt are synchronized.

[0063] After spray welding, a remelting process is performed to form a metallurgically bonded reinforced surface layer, which, together with the wear-resistant layer on the inner wall of bushing 1, forms a wear pair with matching performance.

[0064] Therefore, this embodiment transforms the problem of reinforcing the inner hole, which was originally difficult to process directly, into a problem of externally controllable processing of the bushing 1 by enlarging the inner hole of the connecting hardware and inserting the reinforced bushing 1, effectively improving the feasibility of the process and the stability of the reinforcement layer quality. The bushing 1 has a simple structure, which facilitates standardized clamping, powder loading, pressing and sintering.

[0065] Compared to directly modifying the inner hole of complex-shaped connecting fittings, this embodiment can use powder metallurgy to construct a metal matrix composite reinforcement layer 4 on the bushing 1. The process is more stable, suitable for mass production, which helps to improve product consistency and reduce processing difficulty and manufacturing costs.

[0066] Since the inner hole of the connecting fitting and the bolt form a typical friction pair during operation, improving the wear resistance of only one side can easily lead to rapid wear and failure of the other side. In this embodiment, the bushing 1 is reinforced with powder metallurgy for its inner surface, and the bolt is reinforced with thermal spraying for its outer surface. Both processes can use metal-based composite powder systems with similar compositional bases, which facilitates the matching design of hardness, wear resistance, and self-lubricating properties on both sides of the friction pair, thereby avoiding the wear imbalance problem caused by excessive reinforcement on one side.

[0067] In this embodiment, the metal matrix composite reinforcing layer 4 is composed of Ni60, TiC, and carbon black. Ni60 can form a continuous metal matrix, providing good formability, bonding strength, and corrosion resistance. TiC can improve the hardness and abrasive wear resistance of the reinforcing layer 4. Carbon black powder is added as an additive, which can play a solid lubricating role during friction, reduce the coefficient of friction, and slow down adhesive wear and abrasive wear. Therefore, the bushing 1 can have better service stability under heavy load, fretting, and corrosive environments.

[0068] In summary, this embodiment achieves controllable enhancement of the critical wear zone 2 of the inner hole without directly changing the overall structure and installation method of the connecting hardware. This reduces the wear rate of the inner hole of the connecting hardware, suppresses the expansion of the hole-groove gap and local failure, and improves the overall matching and durability of the friction pair between the connecting hardware and the bolt. This enhances the service reliability of the connecting hardware of overhead transmission lines under conditions of strong winds, sandstorms, heavy corrosion and long-term vibration.

[0069] Example 2: This embodiment provides a hole-shaft connection hardware structure, manufactured using the hole-shaft connection hardware processing technology described in Embodiment 1. The inner hole of the connection hardware is fixed with... Figure 2 Bushing 1 is shown.

[0070] The wear area 2 of bushing 1 is provided with a reinforcing layer 4; the outer surface of the bolt that matches the connecting hardware is provided with a wear-resistant layer. By the bolt and the reinforced bushing 1, the wear resistance, corrosion resistance and service life of the overall hardware structure are improved.

[0071] Specifically, bushing 1 is a cylindrical integrated structure. Its outer diameter matches the inner hole of the connecting hardware after the hole is enlarged. Its axial length is greater than the thickness of the connecting hardware body. After assembly, the two end faces of bushing 1 in the axial direction are higher than the edge of the hardware hole and form an annular protruding limiting structure at the hole position. This can effectively limit the axial movement of the bolt after assembly and improve the overall locking stability of the hole-shaft connection.

[0072] Both the inner and outer surfaces of bushing 1 are sandblasted, and the surface roughness is stably controlled between Ra6.3μm and 12.5μm. This not only ensures the tight interference fit between bushing 1 and the inner hole of the fitting, but also provides a good surface foundation for the sintering and bonding of the inner wall reinforcing layer 4, avoiding problems such as coating peeling and bonding failure.

[0073] like Figure 2 As shown, the internal cavity of bushing 1 is divided into two functional areas: the wear zone 2 and the non-wear zone 3. Specifically: The inner wall of the non-wear zone 3 is a standard arc-shaped structure. Its inner diameter is consistent with the original inner diameter of the connecting hardware before the hole is enlarged. This area does not participate in the main frictional movement of the bolt, but only plays the role of auxiliary positioning and coaxiality correction. The structure is dimensionally stable and there is no deviation in the thickness of the reinforcing layer, which can ensure the initial coaxiality of the bolt assembly and reduce the local wear problem caused by assembly eccentricity.

[0074] Wear zone 2 is the core friction working area. In the initial forming state, the inner wall is an elliptical arc structure. The major semi-axis of the elliptical arc is 10%~12.5% ​​longer than the minor semi-axis, which corresponds to the design thickness of the inner wall reinforcement layer 4. This ensures that the reinforcement layer has sufficient wear resistance and corrosion resistance to meet the requirements of long-term wear conditions, while avoiding problems such as insufficient wear resistance and rapid wear due to the reinforcement layer 4 being too thin, or insufficient thickness of the bushing 1 substrate wall, insufficient structural strength, easy deformation, and coating cracking and structural defects during sintering.

[0075] like Figure 2 As shown, the inner wall of the wear zone of bushing 1 is integrally formed with a reinforcing layer 4, which is a dense composite coating formed by powder metallurgy sintering. The reinforcing layer 4 is formed by sintering composite powders in a specific ratio. Its core raw materials include 60%~70% Ni60 powder, 30%~40% TiC powder, and 5%~10% carbon black powder, with 2.5%~4% paraffin wax added as a molding aid.

[0076] Among them, Ni60 alloy powder forms a continuous metal matrix, ensuring that the reinforcing layer has excellent toughness, corrosion resistance and structural continuity; TiC hard powder is distributed in a dispersed state inside the matrix to form a hard and wear-resistant support skeleton, improving the surface hardness and wear resistance; carbon black powder is uniformly dispersed, continuously playing a lubricating and friction-reducing role, reducing the friction coefficient of hole-shaft fit.

[0077] Meanwhile, the reinforcing layer 4 is formed through segmented dewaxing and high-temperature metallurgical sintering. The paraffin additives are completely removed through a two-stage dewaxing process at 250℃~300℃ and 400℃~450℃, avoiding defects such as pores, bubbles, and cracks. Then, it is sintered at a high temperature of 1050℃~1070℃ to allow the composite powder to fully diffuse and metallurgically bond, ensuring the density and interfacial bonding strength of the reinforcing layer 4 and avoiding problems such as coating peeling and looseness.

[0078] During the cold pressing and sintering process of the mold, the elliptical arc structure of the wear zone 2 is pressed and corrected into a standard circular arc shape by the mold, and connected with the non-wear zone to form a regular circular assembly inner hole. While ensuring the assembly accuracy of the inner hole, the reinforcing layer 4 is uniformly covered to cover the core friction working surface, achieving uniform wear-resistant protection in the whole area.

[0079] Example 3: The hole-shaft connection hardware processing technology of this embodiment takes the ZBD mounting plate as an example and includes the following process: (1) Enlarge the mounting plate hole.

[0080] The holes in the ZBD mounting plate made of 35CrMo material were enlarged to increase the inner diameter by 6mm.

[0081] (2) Prepare the mixed powder.

[0082] Select Ni60 powder with a particle size of 60 μm, TiC powder with a particle size of 20 μm, and carbon black powder with a particle size of 15 μm, and mix the Ni60 powder, TiC powder, and carbon black powder in a mass percentage of 60:35:5.

[0083] Add 3% paraffin by mass to the mixed powder, mix the powder using a powder mixer at a speed of 1000 rpm for 2 minutes.

[0084] (3) Manufacturing bushing 1.

[0085] The major axis of the wear zone 2 of bushing 1 is 2mm longer than the inner diameter of the mounting plate before reaming, and the minor axis is the same as the inner diameter of the mounting plate before reaming. The axial length of bushing 1 is 3mm greater than the thickness of the mounting plate, and the surface of bushing 1 is sandblasted.

[0086] (4) Mixed powder filling and sintering.

[0087] The mixed powder is filled into the bushing 1, and the powder is pressed into the wear area 2 of the bushing 1 under cold pressing conditions, so that the shape of the wear area 2 of the bushing 1 changes from an elliptical arc to a circular arc, and the inner diameter of the circular arc is 1 mm smaller than the minor axis of the original elliptical arc.

[0088] Furthermore, the powder filling and pressing of bushing 1 is completed using a special pressing mold, such as... Figures 3-5 As shown, the pressing mold mainly consists of two parts: the mold body 5 and the mold shaft 6. The mold body 5 has a support groove that matches the shape of the bushing 1. During operation, the bushing 1 is placed in the support groove with its axis horizontal.

[0089] After placement, the two ends of the mold body 5 can form a shielding structure corresponding to the bushing wear area 2, which can not only form a closed powder receiving cavity to hold the mixed powder to be processed, but also effectively prevent the mixed powder from overflowing during the pressing process, thus ensuring the stability of the pressing operation.

[0090] The specific powder pressing process is as follows: The first step is tooling positioning. Place the bushing 1 stably in the support groove of the mold body 5, ensuring that the wear area 2 of the bushing 1 is directly opposite the support groove, so that the wear area 2 and the inner wall of the support groove together form a sealed powder-containing space.

[0091] The second step is quantitative powder filling. Mixed powder is filled into the area inside bushing 1 corresponding to wear zone 2. The powder filling amount is based on completely covering wear zone 2, and the powder height is slightly higher than the final target profile.

[0092] The third step is rolling compaction. After the powder filling is completed, the mold shaft 6 is smoothly inserted into the inner hole of the bushing 1, so that the outer surface of the mold shaft 6 is in full contact with the mixed powder, and the mixed powder is compacted by the rolling motion of the mold shaft 6.

[0093] Through continuous rolling pressing, the mixed powder can be gradually and evenly filled into the wear area 2. At the same time, under the limiting action of the support groove of the mold body 5, it is fully compacted and formed, effectively improving process defects such as local powder accumulation, positional displacement, and uneven compaction.

[0094] The process of repeatedly filling powder, rolling and pressing, and inspecting and repairing continues until the powder layer completely and fully fills the wear area 2, and the surface quality of the powder layer meets the standards, specifically: the surface is continuous and dense, without obvious cracks, obvious holes, or powder falling off. This indicates that the pressing operation is complete.

[0095] Next, the pressed bushing 1 is placed on a support fixture and fed into a vacuum sintering furnace. The furnace chamber is evacuated to a vacuum level of -1 bar to provide an oxygen-free or weakly oxidizing environment for dewaxing and sintering. Dewaxing and metallurgical sintering are then carried out in the vacuum sintering furnace.

[0096] The first stage of dewaxing was sintered at 300℃ for 1 hour; the second stage was sintered at 400℃ for 1 hour. The heating rate was controlled at 3℃ / min during the process of raising the temperature from room temperature to both stages. After dewaxing and sintering, metallurgical sintering was performed. Without opening the furnace, the temperature was raised to 1050℃ at a rate of 10℃ / min. After holding at 1050℃ for 30 minutes, the furnace was cooled to 150℃ before removal.

[0097] (5) Inlaid bushing 1.

[0098] The bushing 1 is pressed into the hole of the mounting plate, and the outer diameter of the bushing 1 and the diameter of the mounting plate hole are interference-fitted or slightly interference-fitted. After the bushing 1 is assembled, its two axial end faces are 1.5mm higher than the edge of the mounting plate hole, forming an annular protrusion structure at the hole.

[0099] Before welding, the mounting plate and the assembled wear-resistant bushing 1 were preheated to 200℃. Welding was performed using gas-shielded arc welding with 1.2mm diameter low-alloy steel welding wire and argon as the shielding gas at a flow rate of 15L / min. The welding current was controlled between 90A and 100A, the welding voltage between 18V and 20V, and the welding speed between 5mm / s and 6mm / s. During welding, continuous circumferential welding or symmetrical segmented welding was used to ensure uniform heat distribution in the circumferential direction and avoid localized overheating. After welding, the plates were cooled in air.

[0100] (6) Bolt reinforcement.

[0101] Bolts with a strength grade of 6.8 were selected as the hole-shaft connectors, and the bolt shanks were sandblasted to remove the hot-dip galvanized layer.

[0102] Ni60 powder with a particle size of 60 μm and WC powder with a particle size of 40 μm were used as thermal spray welding powders. A wear-resistant layer with a thickness of 1 mm was deposited on the bolt shank through a thermal spray welding process. After spray welding, a remelting treatment was performed to form a metallurgically bonded reinforced surface layer, which together with the wear-resistant layer on the inner wall of bushing 1 forms a wear-matching pair with matching performance.

[0103] (7) Abrasion resistance test.

[0104] Two ZBD mounting plates and one bolt from the same batch of products were subjected to wear resistance testing according to DL / T 1693-2017 Transmission Line Fittings Wear Test Method. The wear condition is as follows. Figure 6 As shown. Figure 8 The image shows the wear condition of ZBD mounting plate holes and unreinforced bolts made of ordinary Q355 steel after a wear test. Figure 9 The wear condition of the ZBD mounting plate holes and unreinforced bolts made of 35CrMo steel after the wear test.

[0105] contrast Figure 6 , Figure 8 and Figure 9 It can be seen that the processing technology in this embodiment can reduce the wear rate of the inner hole of the connecting hardware, suppress the expansion of the hole-groove gap and local failure, and at the same time improve the overall matching and durability of the friction pair between the connecting hardware and the bolt.

[0106] Example 4: The hole-shaft connection hardware processing technology of this embodiment takes the ZBD mounting plate as an example and includes the following process: (1) Enlarge the mounting plate hole.

[0107] The holes in the ZBD mounting plate made of 35CrMo material were enlarged to increase the inner diameter by 6mm.

[0108] (2) Prepare the mixed powder.

[0109] Select Ni60 powder with a particle size of 60 μm, TiC powder with a particle size of 20 μm, and carbon black powder with a particle size of 15 μm, and mix the Ni60 powder, TiC powder, and carbon black powder in a mass percentage of 60:30:10.

[0110] Add 3% paraffin by mass to the mixed powder, mix the powder using a powder mixer at a speed of 1000 rpm for 2 minutes.

[0111] (3) Manufacturing bushing 1.

[0112] The major axis of the wear zone 2 of bushing 1 is 2mm longer than the inner diameter of the mounting plate before reaming, and the minor axis is the same as the inner diameter of the mounting plate before reaming. The axial length of bushing 1 is 3mm greater than the thickness of the mounting plate, and the surface of bushing 1 is sandblasted.

[0113] (4) Mixed powder filling and sintering.

[0114] The mixed powder is filled into the bushing 1, and the powder is pressed into the wear area 2 of the bushing 1 under cold pressing conditions, so that the shape of the wear area 2 of the bushing 1 changes from an elliptical arc to a circular arc, and the inner diameter of the circular arc is 1 mm smaller than the minor axis of the original elliptical arc.

[0115] Furthermore, the powder filling and pressing operation of bushing 1 is completed using a dedicated pressing mold, such as... Figures 3-5 As shown, the pressing mold includes a mold body 5 and a mold shaft 6. The mold body 5 has a support groove that matches the shape of the bushing 1.

[0116] During operation, the bushing 1 is placed in the support groove with the axis horizontal. The two ends of the mold body 5 can form a shielding structure corresponding to the bushing wear area 2. This not only forms a closed powder receiving cavity to hold the mixed powder to be processed, but also effectively prevents the mixed powder from overflowing during the pressing process, thus stabilizing the overall pressing operation process.

[0117] Specifically, when the bushing powder pressing operation is carried out, the bushing 1 is first placed stably in the support groove of the mold body 5, ensuring that the wear area 2 of the bushing 1 is facing the support groove. The wear area 2 and the inner wall of the support groove cooperate to form a closed powder containing space.

[0118] After the tooling is positioned, the mixed powder is filled into the bushing 1 at the position corresponding to the wear area 2. The powder filling is based on the standard of completely covering the wear area 2, while the powder height is controlled to be slightly higher than the final target forming contour, so as to reserve process allowance for subsequent compaction forming.

[0119] After the powder filling is completed, the mold shaft 6 is smoothly inserted into the inner hole of the bushing 1 to ensure that the outer surface of the mold shaft 6 is fully in contact with the mixed powder. The mixed powder is compacted by the continuous rolling motion of the mold shaft 6.

[0120] Under the combined effect of the rolling pressing of the mold shaft and the limiting function of the mold body support groove, the mixed powder can gradually and evenly fill the wear area 2 and fully compact it into shape, effectively avoiding process problems such as local powder accumulation, positional displacement, and uneven compaction.

[0121] During the operation, the powder filling, rolling pressing, and inspection and finishing processes are continuously repeated until the powder layer fully and completely fills the wear area 2, and the surface quality of the powder layer meets the process standards. When the powder layer is in a continuous and dense state, without obvious cracks or holes, and there are no problems such as powder shedding, the bushing powder pressing operation can be judged to be completed.

[0122] Next, the pressed bushing 1 is placed on a support fixture and fed into a vacuum sintering furnace. The furnace chamber is evacuated to a vacuum level of -1 bar to provide an oxygen-free or weakly oxidizing environment for dewaxing and sintering. Dewaxing and metallurgical sintering are then carried out in the vacuum sintering furnace.

[0123] The first stage of dewaxing was sintered at 300℃ for 1 hour; the second stage was sintered at 400℃ for 1 hour. The heating rate was controlled at 3℃ / min during the process of raising the temperature from room temperature to both stages. After dewaxing and sintering, metallurgical sintering was performed. The furnace was not opened; the temperature was continued to rise until 1050℃ at a rate of 10℃ / min. After holding at 1070℃ for 20 minutes, the furnace was cooled to 150℃ before removal.

[0124] (5) Inlaid bushing 1.

[0125] The bushing 1 is pressed into the hole of the mounting plate, and the outer diameter of the bushing 1 and the diameter of the mounting plate hole are interference-fitted or slightly interference-fitted. After the bushing 1 is assembled, its two axial end faces are 1.5mm higher than the edge of the mounting plate hole, forming an annular protrusion structure at the hole.

[0126] Before welding, the mounting plate and the assembled wear-resistant bushing 1 are preheated to 200℃. In this embodiment, gas-shielded arc welding is used, with 1.2mm diameter low-alloy steel welding wire and argon as the shielding gas, with a flow rate controlled at 15L / min. The welding current is controlled within the range of 90A~100A, the welding voltage within the range of 18V~20V, and the welding speed within the range of 5 mm / s~6 mm / s.

[0127] During the welding process, continuous circumferential welding or symmetrical segmented welding is used to ensure that the welding heat is evenly distributed in the circumferential direction and to avoid local overheating. After welding, the equipment is placed in air to cool.

[0128] (6) Bolt reinforcement.

[0129] Bolts with a strength grade of 6.8 were selected as the hole-shaft connectors, and the bolt shanks were sandblasted to remove the hot-dip galvanized layer. Ni60 powder with a particle size of 70μm and WC powder with a particle size of 20μm were used as thermal spraying powders, and a wear-resistant layer with a thickness of 1mm was deposited on the bolt shanks through a thermal spraying process.

[0130] After spray welding, a remelting process is performed to form a metallurgically bonded reinforced surface layer, which, together with the wear-resistant layer on the inner wall of bushing 1, forms a wear pair with matching performance.

[0131] (7) Abrasion resistance test.

[0132] Two ZBD mounting plates and one bolt from the same batch of products were subjected to wear resistance testing according to DL / T 1693-2017 Transmission Line Fittings Wear Test Method. The wear condition is as follows. Figure 7 As shown.

[0133] contrast Figure 7 , Figure 8 and Figure 9 It can be seen that the processing technology in this embodiment can reduce the wear rate of the inner hole of the connecting hardware, suppress the expansion of the hole-groove gap and local failure, and at the same time improve the overall matching and durability of the friction pair between the connecting hardware and the bolt.

[0134] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A machining process for a hole-shaft connection fitting, characterized in that, include: Enlarge the inner hole of the connecting hardware to a preset size range; A bushing is installed inside the enlarged inner bore, wherein the inner wall of the bushing has a reinforcing layer; A wear-resistant layer is formed on the outer surface of the matching bolts using a thermal spraying process, so that the outer surface of the bolts and the inner wall of the bushing form a matching wear pair.

2. The machining process for a hole-shaft connection fitting according to claim 1, characterized in that, The inner hole of the bushing is divided into a wear zone and a non-wear zone. The inner wall of the wear zone is elliptical and the inner wall of the non-wear zone is circular. The reinforcing layer is located in the wear area.

3. The machining process for a hole-shaft connection fitting according to claim 2, characterized in that, The short axis of the wear zone is consistent with the inner diameter of the inner hole of the connecting hardware before enlargement, and its long half-axis is larger than the set value of the short half-axis.

4. The machining process for a hole-shaft connection fitting according to claim 2 or 3, characterized in that, The method for setting the reinforcing layer in the wear zone includes: The mixed powder is filled into the wear area of ​​the bushing, and the mixed powder is pressed under cold pressing conditions so that the wear area has an arc-shaped outer contour after pressing. The pressed bushing is sent into a vacuum sintering furnace for dewaxing and metallurgical sintering to form a reinforcing layer in the wear zone.

5. The machining process for a hole-shaft connection fitting according to claim 4, characterized in that, The dewaxing process is divided into two stages. In the first stage, the sintering temperature is 250~300℃ and the sintering time is 1~1.5 hours. In the second stage, the sintering temperature is 400~450℃ and the sintering time is 1~1.5 hours. The metallurgical sintering temperature is 1050~1070℃, and the holding time is 20~30 minutes.

6. The machining process for a hole-shaft connection fitting according to claim 4, characterized in that, The method for preparing the mixed powder includes: Mix Ni60 powder, TiC powder, and carbon black powder according to the set mass percentage; add the set mass fraction of paraffin to the mixed powder and mix evenly.

7. The machining process for a hole-shaft connection fitting according to claim 1, characterized in that, The method of installing the bushing into the inner bore includes: Press the bushing into the inner hole; The bushing and connecting hardware are preheated, and then the bushing and connecting hardware are welded together.

8. The machining process for a hole-shaft connection fitting according to claim 1, characterized in that, The process of forming the wear-resistant layer includes: Using Ni60 and WC reinforcing phase powder as thermal spraying powder, a wear-resistant layer of a set thickness is deposited on the bolt shank through thermal spraying process.

9. A machining process for a hole-shaft connection fitting according to claim 1 or 8, characterized in that, Bolts that have undergone thermal spraying are remelted to form a metallurgically bonded, reinforced surface layer.

10. A hole-shaft connection hardware structure, characterized in that, It is manufactured using the hole-shaft connection hardware processing technology as described in any one of claims 1-9.

Images