High-precision long-life industrial robot bearing and manufacturing method thereof

Abstract

The application discloses a kind of high-precision long-life industrial robot bearing and manufacturing method thereof, belong to industrial robot bearing technical field, including the following steps: to the bearing ring raceway after precision grinding is carried out ultrasonic rolling treatment, to reduce raceway surface roughness, obtain the raceway with residual compressive stress layer of surface layer;The raceway is placed in vacuum furnace and is treated at low temperature to reduce the dislocation density introduced by rolling treatment, to obtain the passivated raceway that dislocation is reduced and residual compressive stress layer remains;By adopting ultrasonic rolling treatment to the bearing ring raceway after precision grinding is carried out flattening processing, reduce surface roughness and introduce the residual compressive stress layer with depth of 100-150 μm, then the ring after rolling is placed in vacuum furnace and is treated at low temperature, reduce the dislocation density introduced by rolling treatment under the premise of retaining residual compressive stress layer.

Description

Technical Field

[0001] This invention relates to the field of industrial robot bearing technology, and in particular to a high-precision, long-life industrial robot bearing and its manufacturing method. Background Technology

[0002] High-precision, long-life industrial robot bearings are core components of industrial robot joint systems. Their main function is to support the rotational or oscillating movements of the robot joints and ensure the positioning accuracy and repeatability of the robot's end effector. These bearings are typically manufactured using high-carbon chromium bearing steel such as GCr15, and are formed through processes such as forging, turning, heat treatment, grinding, and ultra-precision machining. High precision is reflected in the bearing's dimensional tolerances, rotational accuracy, and clearance control all reaching P4 level or higher. Long life requires the bearing to be able to operate stably for tens of thousands of hours under rated load without fatigue spalling or excessive wear. Unlike ordinary mechanical bearings, industrial robot bearings need to withstand frequent starts and stops, speed changes, and load changes during operation, which places higher demands on surface integrity and lubrication conditions. The surface roughness of the bearing raceway, the distribution of residual stress, and the lubricant's retention capacity are key factors determining its precision retention and service life.

[0003] To achieve the above requirements, existing technologies employ high-precision grinding and ultra-precision machining to control the raceway surface roughness Ra below 0.1 μm, while strictly controlling raceway contour shape error and waviness. In terms of material selection, high-purity bearing steel such as GCr15 is used, and the content of non-metallic inclusions in the steel is reduced through vacuum degassing or electroslag remelting. For heat treatment, martensitic quenching followed by low-temperature tempering is used to obtain a uniform and fine tempered martensitic structure in the raceway, achieving a hardness of 60-64 HRC. Regarding lubrication and maintenance, grease with good oxidation stability and shear stability is selected, and lubricant is replenished or replaced periodically during bearing use. In terms of structural design, the rigidity and load-bearing capacity of the bearing are improved by optimizing the number of rolling elements and the cage structure. These methods effectively improve the bearing's precision retention and service life under normal rotating conditions.

[0004] However, in the actual application of wrist joints in spot welding robots, the joint bearings operate under a micro-oscillation state with an amplitude of less than 30° and a frequency of 5-10Hz for a long time. Due to the small oscillation angle, low speed, and frequent reversal, the rolling elements cannot bring enough lubricant into the contact area, resulting in the inability to form a complete elastic hydrodynamic lubrication film between the raceway and the rolling elements. The micro-contact area of ​​the raceway is in a state of boundary lubrication or even local dry friction, which leads to fretting wear and produces reddish-brown Fe2O3 wear debris. These Fe2O3 wear debris have high hardness and fine particles, which not only damage the fiber structure of the grease, causing it to lose its thickening ability and lubrication function, but also embed into the raceway surface or cage pockets as third-body abrasive particles, aggravating raceway wear and scratches on the surface of the rolling elements. The vicious cycle of the above process eventually leads to excessive bearing clearance and a sharp decrease in repeatability, which in severe cases can cause abnormal robot shutdown and cause significant production losses. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and provides a high-precision, long-life industrial robot bearing and its manufacturing method.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a method for manufacturing high-precision, long-life industrial robot bearings, comprising the following steps:

[0007] S1. Ultrasonic rolling treatment is performed on the finely ground bearing ring raceway to reduce the surface roughness of the raceway and obtain a raceway with a residual compressive stress layer on the surface.

[0008] S2. The raceway is placed in a vacuum furnace for low-temperature recovery treatment to reduce the dislocation density introduced by the rolling process, and a raceway to be passivated is obtained with reduced dislocations and retained residual compressive stress layer.

[0009] S3. Immerse the raceway to be passivated in a densification passivation solution for densification passivation treatment to generate a dense Fe3O4 inner passivation film on the surface of the raceway, thereby obtaining a dense film raceway.

[0010] S4. Immerse the dense film raceway in a loosening and passivation solution and perform a loosening and passivation treatment to generate a loose Fe3O4 outer passivation film on the surface of the dense inner film, thus obtaining a double-layer film raceway.

[0011] S5. Assemble the double-layer film raceway with the rolling elements and cage into a bearing semi-finished product, and perform vacuum impregnation treatment to allow low-viscosity grease to penetrate into the micro gaps, thereby obtaining a pre-lubricated bearing semi-finished product.

[0012] S6. The pre-lubricated bearing semi-finished product is subjected to a controlled running-in process, which selectively peels off the loose outer passivation film and transforms it into a solid lubrication transfer layer, while the dense inner passivation film is retained, thus obtaining the finished bearing.

[0013] In a preferred embodiment of the present invention, in step S1, the ultrasonic rolling force is 300-400N, the amplitude is 15-25μm, and the rolling speed is 25-35mm / min.

[0014] In a preferred embodiment of the present invention, in step S1, the depth of the residual compressive stress layer is 100-150 μm, and the surface roughness Ra of the raceway is 0.04-0.06 μm.

[0015] In a preferred embodiment of the present invention, in step S2, the temperature of the low-temperature recovery treatment is 150-200℃, the holding time is 0.5-2h, and the vacuum degree is less than 1×10-2Pa.

[0016] In a preferred embodiment of the present invention, in step S2, the heating rate of the low-temperature recovery treatment is 5-10℃ / min, and the cooling rate is 3-6℃ / min.

[0017] In a preferred embodiment of the present invention, in step S3, the densification passivation solution is an aqueous solution containing 4-6 wt% citric acid and 0.3-0.7 wt% hydrogen peroxide, with a pH value of 2.5-3.2, a treatment temperature of 50-70°C, a treatment time of 2-5 min, and the thickness of the generated dense Fe3O4 inner passivation film is 3-7 nm.

[0018] In a preferred embodiment of the present invention, in step S4, the loosening passivation solution is an aqueous solution containing 4-6 wt% citric acid and 0.3-0.7 wt% hydrogen peroxide, with a pH value of 4.2-4.8, a treatment temperature of 35-45℃, a treatment time of 8-15 min, and the thickness of the generated Fe3O4 outer passivation film is 8-15 nm.

[0019] In a preferred embodiment of the present invention, in step S5, the vacuum degree of the vacuum impregnation treatment is ≤20Pa, the vacuum holding time is 20-40min, and the atmospheric pressure holding time is 1.5-2.5h.

[0020] In a preferred embodiment of the present invention, in step S6, the oscillation frequency of the controllable break-in process is 6-10Hz, the oscillation angle is 20°-30°, the axial preload is 150-250N, and the processing time is 20-40min.

[0021] Secondly, the present invention provides a high-precision, long-life industrial robot bearing, which is manufactured by any of the above-described manufacturing methods.

[0022] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0023] (1) The bearing raceway after precision grinding is smoothed by ultrasonic rolling, which reduces the surface roughness and introduces a residual compressive stress layer with a depth of 100-150μm. The rolled raceway is then placed in a vacuum furnace for low-temperature recovery treatment, which reduces the dislocation density introduced by the rolling process while retaining the residual compressive stress layer. The synergistic effect of rolling and recovery effectively eliminates the high-density dislocation entanglement and lattice distortion on the raceway surface, while the beneficial residual compressive stress is completely preserved. This avoids the local over-corrosion and pitting caused by the preferential penetration of hydrogen ions along dislocation lines during subsequent chemical passivation. The raceway surface is smooth and free of microscopic defects, and pitting will not become a new source of stress concentration. This improves the bearing's resistance to fatigue crack initiation under fretting conditions, extends the bearing's accuracy retention time, and ensures the long-term stable operation of the robot joint.

[0024] (2) By immersing the low-temperature recovered bearing ring in a densification passivation solution to generate a dense inner passivation film with a thickness of 3-7 nm, and then transferring it to a loosening passivation solution to generate a loose outer passivation film with a thickness of 8-15 nm, a double-layer passivation structure with a dense inner layer and a loose outer layer is formed. The same passivation solution system generates two films with different structures by adjusting the pH and temperature. The two films are homogeneous epitaxial growth with strong interfacial bonding. The dense inner layer serves as a permanent anti-fretting wear barrier, while the loose outer layer serves as a sacrificial layer for subsequent running-in conversion, avoiding the trade-off between density and running-in performance of a single film layer. This allows the loose outer layer of the bearing to peel off and transform into a solid lubrication transfer layer in the early stage of service, quickly establishing a mixed boundary lubrication state, while the dense inner layer is completely preserved to provide long-term protection, thus meeting the synergistic requirements of short-term running-in and long-term durability.

[0025] (3) By assembling the ring with a double-layer passivation structure with the rolling elements and cage and then performing vacuum impregnation treatment, the low-viscosity polyurea-based grease can be fully penetrated into all the micro gaps inside the bearing. Then, a controlled running-in treatment is performed to selectively peel off the loose outer layer of iron oxide passivation film and transform it into a solid lubrication transfer layer, while the dense inner layer is completely preserved. Vacuum impregnation eliminates air in the micro gaps, ensuring that the grease can be continuously replenished to the contact area under micro-motion conditions. Controlled running-in transforms the loose outer layer into a solid transfer layer of iron oxide with excellent lubrication performance. It chemically inhibits the generation of reddish-brown iron oxide wear debris, and the wear product is black iron oxide, which will not damage the grease structure. This ensures that the thickening ability and lubrication function of the grease remain stable for a long time, avoids the abrasive particles of the third body from aggravating wear, and makes the bearing clearance and repeatability accuracy meet the long life requirements of the wrist joint of the spot welding robot. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart of a preferred embodiment of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0030] Application Overview:

[0031] While ultrasonic rolling can reduce raceway roughness and introduce residual compressive stress, it also generates high-density dislocation tangles and lattice distortion on the raceway surface. The electrochemical activity of these micro-defect regions is far higher than that of the surrounding intact lattice. When chemical passivation is performed, the H₂ in the passivation solution... + Preferential penetration along dislocation lines leads to localized over-corrosion and the formation of pitting pits. Pitting pits disrupt the smoothness of the raceway, becoming new sources of stress concentration. During fretting service, fatigue cracks are easily induced, completely negating the beneficial effects of rolling. Furthermore, the denser the film layer, the stronger its rust prevention and resistance to fretting wear, but it is prone to peeling off in whole pieces during subsequent break-in, generating hard, large-particle wear debris. The looser the film layer, the easier it is to transfer and form a lubricating film during the break-in period, but its long-term protective ability is insufficient.

[0032] The applicant discovered that the dislocation defects introduced by rolling are causally related to the localized over-corrosion of subsequent passivation. If the dislocation density can be reduced while retaining residual compressive stress, the risk of over-corrosion can be eliminated. Low-temperature recovery treatment can reduce the dislocation density by causing dislocation slip rearrangement through atomic short-range diffusion without inducing recrystallization or significantly releasing residual stress. Secondly, the same passivation liquid system can generate two films with different structures under different pH and temperature conditions, so that the dense inner layer undertakes the long-term anti-wear function, and the loose outer layer serves as a sacrificial layer for running-in transformation.

[0033] The applicant proposes to perform ultrasonic rolling on the raceways of the precision-ground bearing rings to reduce surface roughness and introduce a residual compressive stress layer; then, place the rolled rings in a vacuum furnace for low-temperature recovery treatment to reduce dislocation density and retain the residual compressive stress layer; finally, immerse the recovered rings in a densification passivation solution for densification passivation treatment, generating a dense Fe3O4 inner passivation film on the raceway surface; next, transfer the rings to a loosening passivation solution for loosening passivation treatment, generating a loose Fe3O4 outer passivation film on the dense inner surface, thus forming a double-layer passivation structure with a dense inner layer and a loose outer layer; subsequently, assemble the rings with the rolling elements and cage to form a bearing semi-finished product, and perform vacuum impregnation treatment to allow low-viscosity grease to fully penetrate the micro-gaps inside the bearing; finally, perform controlled running-in treatment on the bearing semi-finished product to selectively peel off the loose outer passivation film and transform it into a solid lubrication transfer layer, while the dense inner passivation film is retained, resulting in the finished bearing.

[0034] like Figure 1 As shown, a method for manufacturing a high-precision, long-life industrial robot bearing includes the following steps:

[0035] S1. Ultrasonic rolling treatment is performed on the finely ground bearing ring raceway to reduce the surface roughness of the raceway and obtain a raceway with a residual compressive stress layer on the surface.

[0036] S2. The raceway is placed in a vacuum furnace for low-temperature recovery treatment to reduce the dislocation density introduced by the rolling process, and a raceway to be passivated is obtained with reduced dislocations and retained residual compressive stress layer.

[0037] S3. Immerse the raceway to be passivated in a densification passivation solution for densification passivation treatment to generate a dense Fe3O4 inner passivation film on the surface of the raceway, thereby obtaining a dense film raceway.

[0038] S4. Immerse the dense film raceway in a loosening and passivation solution and perform a loosening and passivation treatment to generate a loose Fe3O4 outer passivation film on the surface of the dense inner film, thus obtaining a double-layer film raceway.

[0039] S5. Assemble the double-layer film raceway with the rolling elements and cage into a bearing semi-finished product, and perform vacuum impregnation treatment to allow low-viscosity grease to penetrate into the micro gaps, thereby obtaining a pre-lubricated bearing semi-finished product.

[0040] S6. The pre-lubricated bearing semi-finished product is subjected to a controlled running-in process, which selectively peels off the loose outer passivation film and transforms it into a solid lubrication transfer layer, while the dense inner passivation film is retained, thus obtaining the finished bearing.

[0041] The core inventive concept of this invention lies in: smoothing the raceway surface and introducing compressive stress through ultrasonic rolling, eliminating the risk of dislocation-induced localized corrosion through low-temperature recovery, and then constructing a double-layer film of iron oxide with a dense inner layer and a sparse outer layer through two-step gradient passivation. The dense inner layer is permanently retained as a long-term anti-wear barrier, while the sparse outer layer is selectively peeled off and transformed into a solid lubrication transfer layer during vacuum grease impregnation and controlled running-in. The inner and outer layers work together to prevent the generation of reddish-brown iron oxide wear debris from the source, thereby maintaining the integrity of the grease structure, reducing third-body abrasive wear, and solving the problem of excessive bearing clearance under fretting conditions.

[0042] Each step will be explained in detail below.

[0043] In step S1, ultrasonic rolling is used. Before ultrasonic rolling, the bearing ring has been finely ground, and its raceway surface has tool marks and micro-protrusions left by grinding.

[0044] Ultrasonic rolling treatment uses a combination of high-frequency impact and static pressure to cause plastic stretching of the metal surface layer of the raceway, thereby flattening the microscopic peaks and valleys and reducing surface roughness.

[0045] The rolling pressure is set at 300-400N, which provides energy for plastic deformation; the amplitude is controlled at 15-25μm to generate sufficient alternating strain to promote dislocation multiplication and movement; the rolling speed is 25-35mm / min to ensure that each micro-area receives a sufficient number of impacts to achieve uniform flatness.

[0046] Because the plastic flow of the surface metal is constrained by the underlying matrix, a residual compressive stress layer with a depth of 100-150 μm is introduced into the surface of the raceway.

[0047] After ultrasonic rolling treatment, the surface roughness Ra of the raceway can be reduced to 0.04-0.06μm, which is much higher than the level after fine grinding.

[0048] Ultrasonic rolling uses a combination of high-frequency vibration and static pressure to drive the rolling head to impact the workpiece surface at high frequency, causing severe plastic deformation of the surface layer, thereby achieving surface smoothing and microstructure refinement.

[0049] The residual compressive stress layer can offset the contact tensile stress on the raceway surface during bearing service, thereby inhibiting the initiation and propagation of fatigue cracks.

[0050] Dislocation density is the total length of dislocation lines per unit volume. High dislocation density means a large number of lattice distortion regions, which are highly electrochemically active and prone to preferential corrosion.

[0051] After ultrasonic rolling treatment is completed in step S2, the bearing rings with raceways are placed in a vacuum furnace for low-temperature recovery treatment.

[0052] The core objective of this step is not to completely eliminate dislocations, but to reduce the excess dislocation density to a reasonable level that retains residual compressive stress without triggering subsequent passivation over-corrosion.

[0053] The processing temperature is 150-200℃, which is far below the recrystallization temperature of bearing steel. This allows atoms to rearrange dislocations through short-range diffusion, resulting in a more stable configuration. The holding time is 0.5-2 hours to ensure sufficient atomic migration time. The vacuum level is below 1×10⁻⁶. -2 Pa prevents oxidation of the raceway surface and ensures uniform growth of the subsequent passivation film on the clean surface.

[0054] Low-temperature recovery treatment also includes rate control during the heating and cooling phases.

[0055] The heating rate is 5-10℃ / min and the cooling rate is 3-6℃ / min. This can avoid dimensional deformation caused by thermal stress and allow dislocations to be further adjusted to a low-energy configuration during cooling.

[0056] After low-temperature recovery treatment, the dislocation density on the raceway surface decreased from the peak value after rolling to 10. 14 -10 15 / m 2 Meanwhile, the residual compressive stress layer with a depth of 100-150μm is completely preserved, and the residual compressive stress value release rate is less than 5%.

[0057] This state of low dislocation density and high pressure stress eliminates the path of preferential hydrogen ion penetration along dislocations, while retaining the compressive stress barrier that resists the initiation of fatigue cracks.

[0058] After completing the low-temperature recovery treatment in step S3, the raceway to be passivated is immersed in the densification and passivation solution for densification and passivation treatment.

[0059] The purpose of this step is to generate an extremely thin and dense Fe3O4 inner passivation film on the raceway surface, which serves as a permanent anti-wear barrier to protect the raceway substrate throughout the entire service life of the bearing.

[0060] The densification and passivation solution is an aqueous solution containing 4-6 wt% citric acid and 0.3-0.7 wt% hydrogen peroxide, with the pH value controlled at 2.5-3.2.

[0061] Citric acid, acting as a complexing agent, forms stable complexes with iron ions through its carboxyl groups, thus controlling the Fe content. 2+ and Fe 3+ Concentration regulates film formation rate and structure; hydrogen peroxide acts as an oxidant, oxidizing iron or ferrous ions to ferric ions, providing Fe for the formation of Fe3O4. 3+ source.

[0062] The processing temperature is 50-70℃. Appropriate heating can accelerate the reaction, but excessive heating will lead to volatilization and pH drift. The processing time is 2-5 minutes. The shorter duration ensures that the film thickness is controlled at 3-7nm, avoiding excessive thickness that increases internal stress and reduces adhesion.

[0063] The term "dense" here refers to the extremely low porosity and grain boundary density of the film layer, with a microstructure close to an ideal crystal lattice, which can effectively block the penetration of corrosive and abrasive media.

[0064] Fe3O4, or iron(II,III) oxide, has an inverse spinel structure, good chemical stability, moderate hardness, and forms a dense film with excellent corrosion resistance and wear resistance.

[0065] The inner passivation film grows directly on the surface of the metal substrate, and the two are chemically bonded, resulting in extremely high bonding strength.

[0066] After the densification and passivation treatment is completed in step S4, the dense film raceway is immersed in the loosening and passivation solution and subjected to loosening and passivation treatment.

[0067] The purpose of this step is to homoepitaxially grow a loosely structured Fe3O4 outer passivation film on the surface of a dense inner film.

[0068] The loosening and passivation solution is an aqueous solution containing 4-6 wt% citric acid and 0.3-0.7 wt% hydrogen peroxide, with a pH of 4.2-4.8, a treatment temperature of 35-45℃, and a treatment time of 8-15 min.

[0069] Compared to densification passivation solutions, loosening passivation solutions have a higher pH value, lower temperature, and longer processing time.

[0070] Under conditions of pH 4.2-4.8, the complexing ability of citric acid weakens, and free Fe... 3+ With increasing concentration, film formation shifts from a dissolution-deposition equilibrium to direct oxidation deposition, Fe 3+ Rapid hydrolysis and deposition on existing Fe3O4 crystal nuclei.

[0071] Due to the rapid deposition rate and reduced acid re-dissolution effect on the film, the newly formed Fe3O4 grains tend to grow in an island-like manner, forming a large number of micropores and grain boundaries between the grains, thus obtaining a loose and porous structure.

[0072] Lower temperatures inhibit atomic surface diffusion, which is not conducive to dense arrangement and promotes loose formation; longer processing times ensure that the film thickness reaches 8-15 nm.

[0073] The loose structure has high porosity and open grain boundaries, and is microscopically similar to a porous layer formed by the accumulation of fine Fe3O4 nanoparticles.

[0074] Homoepipolar growth means that the outer and inner layers have the same crystal structure and chemical composition. There is a coherent or semi-coherent interface between the new lattice and the inner lattice. Therefore, the two layers are strongly bonded and will not peel off.

[0075] The outer passivation film, acting as a sacrificial layer, has a loose structure that makes it easy to selectively remove during subsequent controlled break-in processes.

[0076] After steps S3 and S4, a double-layer Fe3O4 passivation film structure combining a dense inner layer and a loose outer layer is formed on the raceway surface.

[0077] The inner film is 3-7 nm thick and has a dense structure, serving as a permanent anti-wear and anti-corrosion barrier; the outer film is 8-15 nm thick and has a loose and porous structure, serving as a removable sacrificial layer that is converted into a solid lubricant during the break-in period.

[0078] After the double-layer passivation film is prepared in step S5, the double-layer film raceway is assembled with the rolling elements and cage to form a bearing semi-finished product.

[0079] At this point, there are extremely small gaps between the rolling elements and the raceways, and these gaps are filled with air. If grease is injected directly, the surface tension of the air will make it difficult for the grease to completely fill these tiny gaps, resulting in discontinuous lubrication.

[0080] Therefore, vacuum impregnation is used to solve this problem. The specific operation is as follows: place the assembled bearing semi-finished product in a vacuum impregnation tank, evacuate to a vacuum degree ≤20Pa, and maintain this vacuum degree for 20-40 minutes.

[0081] In a vacuum environment, the air in the micro-gaps inside the bearing is fully extracted.

[0082] Subsequently, while maintaining a vacuum, low-viscosity grease is injected into the bearing semi-finished product. After the bearing is completely submerged in grease, the vacuum is released, atmospheric pressure is restored, and maintained for 1.5-2.5 hours.

[0083] The vacuum degree is ≤20Pa, the vacuum holding time is 20-40min, and the atmospheric pressure holding time is 1.5-2.5h.

[0084] Under atmospheric pressure, the low-viscosity grease is forced into all the micro-gaps that were previously occupied by air, achieving uniform, continuous, and bubble-free wetting of areas such as raceways, rolling element surfaces, and cage pockets.

[0085] Low-viscosity greases have base oils with lower viscosity and consistency, typically higher cone penetration, and good fluidity, allowing them to penetrate micron-level gaps more easily under atmospheric pressure.

[0086] Vacuum impregnation treatment utilizes vacuum to remove air from micro-gap structures, and then uses atmospheric pressure to force liquid in, which can significantly improve the permeability and coverage of liquids to complex microstructures.

[0087] After vacuum impregnation is completed in step S6, a pre-lubricated bearing semi-finished product is obtained; at this time, the raceway surface is still covered with a complete double-layer Fe3O4 film consisting of a dense inner layer and a loose outer layer.

[0088] This step activates the early service process of the bearing through controlled break-in treatment, selectively peeling off the loose outer passivation film and transforming it into a solid lubrication transfer layer, while ensuring that the dense inner passivation film is retained.

[0089] The controlled break-in process is carried out on a dedicated break-in test bench; the oscillation frequency is 6-10Hz, the oscillation angle is 20°-30°, the axial preload is 150-250N, and the processing time is 20-40min.

[0090] These parameters simulate the actual micro-motion conditions of the wrist joint of a spot welding robot.

[0091] During the break-in process, the rolling elements are in close contact with the raceway under the preload and oscillate back and forth at the set oscillation angle and frequency; the loose outer Fe3O4 film on the raceway surface first undergoes selective peeling.

[0092] Due to the loose structure of the outer membrane and the weak intergranular bonding force, these loose nanoparticles are peeled off from the surface of the inner membrane under the action of reciprocating shear stress and contact stress of the rolling element.

[0093] The Fe3O4 nanoparticles that are peeled off are extremely small and will not damage the contact surface as abrasive particles like hard Fe2O3 particles. Instead, under the continuous running stress, these particles are further crushed, flattened and spread on the contact surface, forming a continuous, uniform and strongly adherent solid lubricant transfer layer.

[0094] The presence of this transfer layer transforms the original boundary lubrication interface between the metal and the grease into a mixed lubrication interface between the solid lubrication transfer layer and the grease, greatly reducing the coefficient of friction and wear rate.

[0095] Meanwhile, due to the complete structure of the dense inner layer membrane and its extremely strong bonding force with the substrate, and the absorption and buffering of the running-in stress by the peeling and transfer of the loose outer layer, the dense inner layer is completely preserved after the running-in process, continuing to serve as the ultimate barrier against long-term fretting wear.

[0096] After controlled break-in, a stable solid lubrication transfer layer is established inside the bearing, and a dense anti-wear inner film is retained. The overall tribological system of the bearing enters a stable state, and the finished bearing obtained at this time can be installed and used.

[0097] To further simplify and make the present invention achieve its objectives and effects, the present invention will be further illustrated in conjunction with the following specific embodiments and comparative examples, but the present invention is not limited to the scope of the embodiments described herein.

[0098] It should be noted that the raw materials used in the examples and comparative examples are described below:

[0099] Citric acid: content 90%, CAS number 5949-29-1, purchased from Jinan Kunfeng Chemical Co., Ltd.

[0100] Hydrogen peroxide: content 27.5%, purchased from Jinan Xinlonghai Industry and Trade Co., Ltd.

[0101] Sodium hydroxide solution: 30% concentration, purchased from Shanghai Baoyang Baoxin Biotechnology Co., Ltd.

[0102] Example 1:

[0103] S1. The bearing raceway after precision grinding is subjected to ultrasonic rolling treatment with a rolling force of 350N, an amplitude of 20μm, and a rolling speed of 30mm / min. After the treatment, a residual compressive stress layer with a depth of 125μm is formed on the surface of the raceway, and the surface roughness Ra of the raceway is 0.05μm.

[0104] S2. The roller track after rolling treatment is placed in a vacuum furnace for low-temperature recovery treatment. The treatment temperature is 175℃, the holding time is 1.25h, and the vacuum degree is 5×10⁻⁶. -3 Pa, heating rate of 7.5℃ / min, cooling rate of 4.5℃ / min; after treatment, the dislocation density on the raceway surface is reduced, and the residual compressive stress layer is completely preserved.

[0105] S3. Immerse the raceway to be passivated in a densification passivation solution for densification passivation treatment. Dissolve 5 wt% citric acid and 0.5 wt% hydrogen peroxide in deionized water, adjust the pH to 2.85 with sodium hydroxide solution, treat at 60℃ for 3.5 min; a dense Fe3O4 inner passivation film with a thickness of 5 nm is formed on the surface of the raceway.

[0106] S4. Immerse the dense membrane raceway in a loosening and passivation solution for loosening and passivation treatment. Dissolve 5 wt% citric acid and 0.5 wt% hydrogen peroxide in deionized water, adjust the pH to 4.5 with sodium hydroxide solution, treat at 40℃ for 11.5 min. A loose Fe3O4 outer passivation film with a thickness of 11.5 nm is formed on the surface of the dense inner membrane, resulting in a double-layer membrane raceway.

[0107] S5. Assemble the double-layer film raceway with the rolling elements and cage into a bearing semi-finished product, and then perform vacuum impregnation treatment with a vacuum degree of 15 Pa and a vacuum holding time of 30 min; and a normal pressure holding time of 2 h; so that the low viscosity polyurea grease can fully penetrate into the micro gap to obtain a pre-lubricated bearing semi-finished product.

[0108] S6. Perform controlled break-in treatment on the pre-lubricated bearing semi-finished product. The oscillation frequency is 8Hz, the oscillation angle is 25°, the axial preload is 200N, and the treatment time is 30min. After the break-in treatment, the loose outer passivation film selectively peels off and transforms into a solid lubrication transfer layer, while the dense inner passivation film is completely retained, resulting in the finished bearing.

[0109] Example 2:

[0110] This embodiment is basically the same as embodiment 1, except that the rolling pressure in S1 is taken as the minimum value of the range, specifically: the rolling pressure is changed to 300N, and the rest is the same as in embodiment 1.

[0111] Example 3:

[0112] This embodiment is basically the same as embodiment 1, except that the rolling pressure in S1 is taken as the maximum value of the range, specifically: the rolling pressure is changed to 400N, and the rest is the same as in embodiment 1.

[0113] Example 4:

[0114] This embodiment is basically the same as embodiment 1, except that: the low temperature recovery temperature in S2 is taken as the minimum value of the range, specifically: the processing temperature is changed to 150℃, and the rest is the same as in embodiment 1.

[0115] Example 5:

[0116] This embodiment is basically the same as embodiment 1, except that: the low temperature recovery temperature in S2 is taken as the maximum value of the range, specifically: the processing temperature is changed to 200℃, and the rest is the same as in embodiment 1.

[0117] Example 6:

[0118] This embodiment is basically the same as that of embodiment 1, except that the pH of the densification and passivation solution in S3 is the minimum value of the range, specifically: the pH is adjusted to 2.5 with sodium hydroxide solution, and the rest is the same as that of embodiment 1.

[0119] Example 7:

[0120] This embodiment is basically the same as that of embodiment 1, except that the pH of the densification and passivation solution in S3 is the maximum value of the range, specifically: the pH is adjusted to 3.2 with sodium hydroxide solution, and the rest is the same as that of embodiment 1.

[0121] Example 8:

[0122] This embodiment is basically the same as Embodiment 1, except that: the pH of the loosening and passivation solution in S4 is taken as the minimum value of the range, specifically: the pH is adjusted to 4.2 with sodium hydroxide solution, and the rest is the same as in Embodiment 1.

[0123] Example 9:

[0124] This embodiment is basically the same as that of embodiment 1, except that the pH of the loosening and passivation solution in S4 is the maximum value of the range, specifically: the pH is adjusted to 4.8 with sodium hydroxide solution, and the rest is the same as that of embodiment 1.

[0125] Example 10:

[0126] This embodiment is basically the same as embodiment 1, except that: in S5, the vacuum degree of vacuum wetting is taken as the minimum value of the range, specifically: the vacuum degree is changed to 5Pa, and the rest is the same as in embodiment 1.

[0127] Example 11:

[0128] This embodiment is basically the same as embodiment 1, except that: in S5, the vacuum degree of vacuum wetting is taken as the maximum value of the range, specifically: the vacuum degree is changed to 20Pa, and the rest is the same as in embodiment 1.

[0129] Example 12:

[0130] This embodiment is basically the same as embodiment 1, except that: the controllable axial preload in S6 is taken as the minimum value of the range, specifically: the axial preload is changed to 150N, and the rest is the same as in embodiment 1.

[0131] Example 13:

[0132] This embodiment is basically the same as embodiment 1, except that: the controllable axial preload in S6 is taken as the maximum value of the range, specifically: the axial preload is changed to 250N, and the rest is the same as in embodiment 1.

[0133] Comparative Example 1:

[0134] This comparative example is basically the same as Example 1, except that it adopts a traditional bearing manufacturing process, the specific steps of which are as follows:

[0135] S1. The finely ground bearing ring raceway is cleaned and dried, and used directly as the raceway to be treated. The raceway is not subjected to ultrasonic rolling treatment. The surface roughness Ra of the raceway is 0.10μm.

[0136] S2. Place the above-mentioned raceway in a cleaning tank for conventional degreasing and acid pickling activation, and then wash with water without vacuum low-temperature recovery treatment.

[0137] S3. Immerse the activated raceway in a conventional rust-preventive passivation solution and treat it for 3-5 minutes at a pH of about 3.0 and a temperature of 50°C to generate a common oxide film with a thickness of about 5nm on the raceway surface.

[0138] 4. No loosening and passivation treatment is performed; a single-layer oxide film roller is used directly.

[0139] S5. Assemble the raceway with a single oxide film, rolling elements, and cage into a bearing semi-finished product. Inject ordinary lithium-based grease into the bearing under normal pressure conditions without vacuum impregnation.

[0140] S6. The greased bearing semi-finished product is subjected to routine running-in treatment on the running-in test bench. The running-in speed is 500 rpm and the running-in time is 1 hour. No controlled break-in treatment is performed to obtain the finished bearing.

[0141] Comparative Example 2:

[0142] This comparative example is basically the same as Example 1, except that the ultrasonic rolling process in S1 is omitted. The specific steps of S1 are: the bearing ring raceway after fine grinding is not subjected to ultrasonic rolling process, and the finely ground raceway is used directly with a surface roughness Ra of 0.10 μm; the remaining steps are the same as in Example 1.

[0143] Comparative Example 3:

[0144] This comparative example is basically the same as Example 1, except that the low-temperature recovery treatment in S2 is omitted. The specific steps of S2 are: the roller that has undergone rolling treatment is directly introduced into S3 without the low-temperature recovery treatment in the vacuum furnace; the remaining steps are the same as in Example 1.

[0145] Comparative Example 4:

[0146] This comparative example is basically the same as Example 1, except that the loosening and passivation treatment in S4 is omitted. The specific steps of S4 are: without loosening and passivation treatment, the dense film raceway directly enters S5; the remaining steps are the same as in Example 1.

[0147] Comparative Example 5:

[0148] This comparative example is basically the same as Example 1, except that the densification and passivation treatment in S3 is omitted. The specific steps of S3 are: without densification and passivation treatment, the passivation raceway directly enters S4; the remaining steps are the same as in Example 1.

[0149] Comparative Example 6:

[0150] This comparative example is basically the same as Example 1, except that the rolling pressure in S1 is lower than the minimum value of the range. The specific steps of S1 are: the rolling pressure is changed to 250N, and the rest is the same as S1 in Example 1.

[0151] Comparative Example 7:

[0152] This comparative example is basically the same as Example 1, except that the rolling pressure in S1 is higher than the maximum value in the range. The specific steps of S1 are: the rolling pressure is changed to 450N, and the rest is the same as S1 in Example 1.

[0153] Comparative Example 8:

[0154] This comparative example is basically the same as Example 1, except that the low temperature recovery temperature in S2 is lower than the minimum value of the range. The specific steps of S2 are: the processing temperature is changed to 120℃, and the rest is the same as S2 in Example 1.

[0155] Comparative Example 9:

[0156] This comparative example is basically the same as Example 1, except that the low temperature recovery temperature in S2 is higher than the maximum value of the range. The specific steps of S2 are: the processing temperature is changed to 250℃, and the rest is the same as S2 in Example 1.

[0157] Comparative Example 10:

[0158] This comparative example is basically the same as Example 1, except that the pH of the densification and passivation solution in S3 is lower than the minimum value of the range. The specific steps of S3 are: adjust the pH to 2.0 with sodium hydroxide solution, and the rest is the same as S3 in Example 1.

[0159] Comparative Example 11:

[0160] This comparative example is basically the same as Example 1, except that the pH of the densification and passivation solution in S3 is higher than the maximum value in the range. The specific steps of S3 are: adjust the pH to 3.5 with sodium hydroxide solution, and the rest is the same as S3 in Example 1.

[0161] Comparative Example 12:

[0162] This comparative example is basically the same as Example 1, except that the pH of the loosening and passivation solution in S4 is lower than the minimum value of the range. The specific steps of S4 are: adjust the pH to 3.8 with sodium hydroxide solution, and the rest is the same as S4 in Example 1.

[0163] Comparative Example 13:

[0164] This comparative example is basically the same as Example 1, except that the pH of the loosening and passivation solution in S4 is higher than the maximum value in the range. The specific steps of S4 are: adjust the pH to 5.2 with sodium hydroxide solution, and the rest is the same as S4 in Example 1.

[0165] Comparative Example 14:

[0166] This comparative example is basically the same as Example 1, except that the vacuum degree of vacuum wetting in S5 is lower than the minimum value of the range. The specific steps of S5 are: the vacuum degree is changed to 1 Pa, and the rest is the same as S5 of Example 1.

[0167] Comparative Example 15:

[0168] This comparative example is basically the same as Example 1, except that the vacuum degree of vacuum wetting in S5 is higher than the maximum value in the range. The specific steps of S5 are: the vacuum degree is changed to 30 Pa, and the rest is the same as S5 in Example 1.

[0169] Comparative Example 16:

[0170] This comparative example is basically the same as Example 1, except that the controllable axial preload in S6 is lower than the minimum value in the range. The specific steps of S6 are: the axial preload is changed to 100N, and the rest is the same as S6 in Example 1.

[0171] Comparative Example 17:

[0172] This comparative example is basically the same as Example 1, except that the controllable axial preload in S6 is higher than the maximum value in the range. The specific steps of S6 are: the axial preload is changed to 300N, and the rest is the same as S6 in Example 1.

[0173] Performance testing: The finished bearings obtained in Examples 1-13 and Comparative Examples 1-17 were subjected to performance tests in sequence, including residual compressive stress retention rate, dislocation corrosion sensitivity, double film integrity, micro-gap grease filling rate, and run-in conversion index. The results are shown in Table 1.

[0174] Residual compressive stress retention rate: Bearing rings after ultrasonic rolling treatment in step S1 and low-temperature recovery treatment in step S2 were analyzed using an X-ray diffraction residual stress analyzer. CrKα rays were selected, with the diffraction plane at 211, and the residual stress was measured using sin... 2 The residual compressive stress at a depth of 125 μm on the raceway surface was measured using the ψ method. Five measuring points were selected at equal intervals along the circumference of the raceway surface, and the average residual compressive stress after low-temperature recovery treatment was recorded as . The average residual compressive stress after the rolling treatment is denoted as . Residual compressive stress retention rate Calculate using the following formula: The unit is a percentage. The higher the value, the better the effect of low-temperature recovery treatment in preserving residual compressive stress.

[0175] Dislocation corrosion sensitivity: Small samples of 10mm × 10mm × 5mm were cut from the rings after the rolling treatment in step S1 and the low-temperature recovery treatment in step S2. The samples were placed in a densification passivation solution, which was a 5wt% citric acid and 0.5wt% hydrogen peroxide aqueous solution, at a treatment temperature of 60℃ for 3.5 min. After removal, the samples were rinsed with deionized water, and the number of pits per square millimeter was counted under a 500x optical microscope. The pit density of the samples after the rolling treatment was recorded as follows: The pitting density of the sample after low-temperature recovery treatment is denoted as . Dislocation corrosion sensitivity Calculate using the following formula: The unit is a percentage. The lower the value, the more significant the effect of dislocation reduction on mitigating local over-corrosion.

[0176] Bilayer membrane integrity: The bilayer membrane raceways after densification and passivation treatment in step S3 and after loosening and passivation treatment in step S4 were used to test their polarization resistance in 3.5 wt% sodium chloride solution using electrochemical impedance spectroscopy. The polarization resistance of the bilayer membrane raceway is denoted as . A control was taken from a single-layer film raceway that had only undergone densification and passivation treatment in step S3 but not step S4, and its polarization resistance was measured. Double membrane integrity Calculate using the following formula: The unit is dimensionless. A value greater than 1 indicates that the loose outer layer has a synergistic effect in protecting the outer and inner layers.

[0177] Micro-gap grease filling rate: The pre-lubricated bearing semi-finished product after vacuum impregnation treatment in step S5 was used. Three-dimensional scanning of the bearing interior was performed using industrial X-ray computed tomography (CT) technology, with a voxel size of 5 μm. After reconstruction, all micro-gap regions inside the bearing were statistically analyzed, including the contact area between the raceway and rolling elements, the gap between the cage pocket and the rolling elements, and the oil holes in the raceways, etc. The actual volume of micro-gap filled with grease was then calculated. Compared with the theoretically fillable total volume of micro gaps The ratio is used as the filling rate; micro-gap filling rate Calculate using the following formula: The unit is a percentage. The higher the value, the stronger the effect of vacuum impregnation on the penetration of grease.

[0178] Break-in conversion index: After disassembly, wear debris discharged from the bearing during the break-in process was collected, and the phase composition of the wear debris was analyzed using X-ray diffraction; the strongest diffraction peak intensity of Fe3O4 was used as the criterion. The strongest diffraction peak intensity of ferric oxide (Fe2O3) The ratio of these values ​​is used as the break-in conversion index. The unit is dimensionless. A higher value indicates that the loose outer passivation film has successfully transformed into a solid lubrication transfer layer rather than generating reddish-brown hard wear debris. Generally, a value greater than 5 indicates an excellent transformation effect.

[0179] Table 1: Performance test results of finished bearings in Examples 1-13 and Comparative Examples 1-17

[0180] Group Residual compressive stress retention rate (%) Dislocation corrosion susceptibility (%) Bilayer membrane integrity Micro-gap filling rate (%) Break-in conversion index Example 1 98.2 14.8 2.53 98.5 8.2 Example 2 97.5 15.2 2.48 98.3 8.0 Example 3 98.0 15.0 2.50 98.4 8.1 Example 4 97.8 16.5 2.49 98.2 8.0 Example 5 98.5 13.2 2.52 98.3 8.1 Example 6 98.1 14.9 2.41 98.4 8.0 Example 7 98.2 14.7 2.58 98.3 8.1 Example 8 98.0 15.1 2.47 98.5 8.0 Example 9 98.1 15.0 2.55 98.4 8.2 Example 10 98.2 14.8 2.52 99.2 8.1 Example 11 98.1 14.9 2.51 96.8 8.0 Example 12 98.0 15.0 2.50 98.3 7.5 Example 13 98.1 14.9 2.52 98.4 8.8 Comparative Example 1 / 78.3 0.35 52.4 0.6 Comparative Example 2 / 5.2 0.82 97.8 1.2 Comparative Example 3 97.6 62.4 1.15 98.1 2.1 Comparative Example 4 98.0 15.1 0.98 98.3 1.8 Comparative Example 5 97.9 15.0 0.45 98.2 3.5 Comparative Example 6 92.3 18.6 2.15 98.1 6.5 Comparative Example 7 98.5 14.5 2.48 98.4 8.0 Comparative Example 8 98.0 42.5 2.20 98.2 5.8 Comparative Example 9 85.2 12.1 2.35 98.3 7.2 Comparative Example 10 98.1 15.2 1.85 98.4 6.9 Comparative Example 11 98.0 14.9 2.10 98.3 7.1 Comparative Example 12 98.2 14.8 1.92 98.5 5.2 Comparative Example 13 98.1 15.0 2.30 98.4 6.8 Comparative Example 14 98.2 14.9 2.52 99.5 8.1 Comparative Example 15 98.0 15.0 2.50 90.2 7.9 Comparative Example 16 98.1 14.9 2.51 98.3 4.8 Comparative Example 17 98.0 15.1 2.49 98.4 6.2

[0181] A comparison of Example 1 and Comparative Example 1 reveals that: Comparative Example 1 did not undergo ultrasonic rolling treatment, low-temperature recovery treatment, two-step passivation treatment, vacuum impregnation treatment, or controlled running-in treatment; the surface roughness Ra of the raceway in Comparative Example 1 was 0.10 μm, with no residual compressive stress layer; the single-layer ordinary oxide film ruptured during normal running-in, producing wear debris mainly composed of ferric oxide, with a running-in conversion index of 0.6; air remained in the micro-gap during atmospheric pressure grease injection, with a micro-gap grease filling rate of 52.4%, leading to insufficient oil in the early stages of running-in; therefore, the dislocation corrosion sensitivity of Comparative Example 1 was as high as 78.3%, and the double-layer film integrity was 0.35, with all performance indicators lower than those of Example 1.

[0182] A comparison of Example 1 and Comparative Example 2 reveals that: Comparative Example 2 omitted the ultrasonic rolling treatment, i.e., step S1; In Examples 1 to 3, the rolling pressure of 300N to 400N, the amplitude of 15μm to 25μm, and the rolling speed of 25mm / min to 35mm / min ensured sufficient plastic deformation of the raceway surface, resulting in a residual compressive stress layer depth of 100μm to 150μm and a surface roughness Ra reduced to 0.04μm to 0.06μm; Comparative Example 2, lacking the rolling treatment, had no residual compressive stress layer on the raceway surface, with a roughness Ra of 0.10μm, leading to uneven growth of the subsequent passivation film and a bilayer film integrity of only 0.82; Although subjected to low-temperature recovery and passivation, the lack of compressive stress support caused the passivation film to fail prematurely during the break-in period, with a break-in conversion index of 1.2.

[0183] A comparison of Example 1 and Comparative Example 3 reveals that Comparative Example 3 omitted the low-temperature recovery treatment, i.e., step S2; in Examples 1 to 3, the recovery temperature of step S2 was 150°C to 200°C, the holding time was 0.5 h to 2 h, and the vacuum degree was less than 1 × 10⁻⁶. - 2 Pa; This temperature range provides the activation energy for short-range atomic diffusion, enabling dislocation slip and climb to form a low-energy configuration; Comparative Example 3 skips step S2, and the high-density dislocations introduced by rolling are completely preserved; In the densification passivation solution in step S3, hydrogen ions preferentially penetrate along the dislocation lines, forming a large number of pitting pits, with a dislocation corrosion sensitivity of 62.4%, far higher than the 14.8% in Example 1; Pitting pits destroy the integrity of the raceway surface, becoming fatigue crack initiation sources, leading to a decline in overall performance.

[0184] A comparison of Example 1 and Comparative Example 4 reveals that: Comparative Example 4 omitted the loosening and passivation treatment, i.e., step S4, and only retained the dense inner layer; Example 1 adopted a double-layer structure with a dense inner layer and a loose outer layer, with the dense inner layer thickness ranging from 3 nm to 7 nm and the loose outer layer thickness ranging from 8 nm to 15 nm; the single dense inner layer of Comparative Example 4 was difficult to selectively remove during controlled break-in, peeling off in its entirety to generate large-sized hard fragments, which could not be transformed into a uniform solid lubricant transfer layer; the double-layer film integrity index was 0.98, which is less than 1, the break-in conversion index was 1.8, and the wear products were mainly ferric oxide.

[0185] A comparison of Example 1 and Comparative Example 5 reveals that: Comparative Example 5 omitted the densification and passivation treatment, i.e., step S3, and only performed loosening and passivation; a loose and porous iron oxide film was directly generated on the raceway surface, lacking a dense inner layer as a permanent barrier; the bonding force between this loose film and the steel substrate is weak, and the peeling process during controlled running-in is uncontrollable, resulting in localized substrate exposure; the exposed substrate generates iron oxide wear debris during fretting wear; the double-layer film integrity index is 0.45, the running-in conversion index is 3.5, and the long-term protective capability is insufficient.

[0186] A comparison of Examples 1 / 2-3 with Comparative Examples 6-7 reveals that: the rolling pressure of Comparative Example 6 is 250 N, which is lower than the lower limit of 300 N; the plastic deformation is insufficient, the depth of the residual compressive stress layer is less than 100 μm, and the residual compressive stress retention rate is 92.3%, which is lower than the 97.5% to 98.2% of Examples 1 to 3; the rolling pressure of Comparative Example 7 is 450 N, which is higher than the upper limit of 400 N; excessive plastic deformation introduces microcracks or excessive dislocation entanglement, and although it is recovered at low temperature, the surface integrity is damaged, the bilayer film integrity is 2.48, and the break-in conversion index is 8.0, which is slightly lower than the 2.53 and 8.2 of Example 1; Examples 1 to 3 achieve the optimal balance between residual compressive stress and surface integrity in the range of 300 N to 400 N.

[0187] A comparison of Examples 1 / 4-5 with Comparative Examples 8-9 reveals that: the low-temperature recovery temperature of Comparative Example 8 is 120℃, lower than the lower limit of 150℃; atomic diffusion ability is insufficient, dislocation rearrangement is inadequate, and the dislocation corrosion sensitivity is 42.5%; the recovery temperature of Comparative Example 9 is 250℃, higher than the upper limit of 200℃; this temperature is close to the recrystallization temperature, and a large amount of residual compressive stress is released, with the residual compressive stress retention rate decreasing to 85.2%; the test results of Examples 4 to 5, i.e., recovery temperatures of 150℃ and 200℃, show that within the range of 150℃ to 200℃, the dislocation corrosion sensitivity is 13.2% to 16.5%, and the residual compressive stress retention rate is 97.8% to 98.5%, reaching a balance between the two.

[0188] A comparison of Examples 1 / 6-7 with Comparative Examples 10-11 reveals the following: Comparative Example 10's densification and passivation solution had a pH of 2.0, below the lower limit of 2.5; the acidity was too strong, the chemical dissolution rate exceeded the film formation rate, resulting in incomplete inner film growth and a bilayer film integrity of 1.85. Comparative Example 11 had a pH of 3.5, above the upper limit of 3.2; the film formation reaction driving force was insufficient, resulting in a film thickness of less than 3 nm and discontinuity, with an integrity of 2.10. Examples 6 and 7 had pH values ​​of 2.5 and 3.2, respectively, and the obtained inner film thicknesses ranged from 3 nm to 7 nm, with integrity values ​​of 2.41 and 2.58, indicating that a pH range of 2.5 to 3.2 is suitable for forming a continuous and dense inner film.

[0189] A comparison of Examples 1 / 8-9 with Comparative Examples 12-13 reveals that: the pH value of the passivation solution in Comparative Example 12 was 3.8, lower than the lower limit of 4.2; the film tended to be denser, the porosity of the outer film decreased, the sacrificial layer was difficult to peel off uniformly, and the break-in conversion index was 5.2; the pH value of Comparative Example 13 was 5.2, higher than the upper limit of 4.8; the film formation rate was too slow, the outer film thickness was insufficient and the coverage was discontinuous, with some areas having no outer film, and the break-in conversion index was 6.8; the pH values ​​of Examples 8 to 9 were 4.2 and 4.8, respectively, and the obtained outer film thickness was between 8 nm and 15 nm, with break-in conversion indices of 8.0 and 8.2, indicating that pH values ​​of 4.2 to 4.8 are a suitable range for forming a loose and porous outer layer.

[0190] A comparison of Examples 1 / 10-11 with Comparative Examples 14-15 reveals the following: Comparative Example 14 has a vacuum of 1 Pa, which is below the lower limit of 20 Pa. Although it can more thoroughly remove air and achieve a grease filling rate of 99.5% in the micro-gap, the equipment requirements are increased, and the difference compared to 99.2% in Example 10 is not significant, resulting in poor cost-effectiveness. Comparative Example 15 has a vacuum of 30 Pa, which is above the upper limit of 20 Pa. Due to insufficient vacuum, residual air in the micro-gap forms an airlock, hindering grease penetration, and the grease filling rate in the micro-gap drops to 90.2%. Examples 10 to 11 have vacuums of 5 Pa and 20 Pa, respectively, and grease filling rates of 99.2% and 96.8%, respectively, all within acceptable ranges, indicating that a vacuum of ≤20 Pa can meet the wetting requirements.

[0191] A comparison of Examples 1 / 12-13 with Comparative Examples 16-17 reveals the following: The axial preload of Comparative Example 16 is 100N, lower than the lower limit of 150N; insufficient contact stress prevents effective dislodgement, crushing, and distribution of the loose outer layer of iron oxide nanoparticles, resulting in insufficient formation of the solid lubrication transfer layer and a break-in conversion index of 4.8. The axial preload of Comparative Example 17 is 300N, higher than the upper limit of 250N; excessive contact stress may allow shear stress to penetrate the loose and dense layers, damaging the dense inner layer and even the steel matrix, leading to the formation of ferric oxide in some areas and a break-in conversion index of 6.2. The axial preloads of Examples 12 and 13 are 150N and 250N, respectively, with break-in conversion indices of 7.5 and 8.8, indicating that the 150N to 250N range can both drive the orderly transformation of the outer layer and protect the integrity of the dense inner layer.

[0192] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for manufacturing a high-precision, long-life industrial robot bearing, characterized in that, Includes the following steps: S1. Ultrasonic rolling treatment is performed on the finely ground bearing ring raceway to reduce the surface roughness of the raceway and obtain a raceway with a residual compressive stress layer on the surface. S2. The raceway is placed in a vacuum furnace for low-temperature recovery treatment to reduce the dislocation density introduced by the rolling process, and a raceway to be passivated is obtained with reduced dislocations and retained residual compressive stress layer. S3. Immerse the raceway to be passivated in a densification passivation solution for densification passivation treatment to generate a dense Fe3O4 inner passivation film on the surface of the raceway, thereby obtaining a dense film raceway. S4. Immerse the dense film raceway in a loosening and passivation solution and perform a loosening and passivation treatment to generate a loose Fe3O4 outer passivation film on the surface of the dense inner film, thus obtaining a double-layer film raceway. S5. Assemble the double-layer film raceway with the rolling elements and cage into a bearing semi-finished product, and perform vacuum impregnation treatment to allow low-viscosity grease to penetrate into the micro gaps, thereby obtaining a pre-lubricated bearing semi-finished product. S6. The pre-lubricated bearing semi-finished product is subjected to a controlled running-in process, which selectively peels off the loose outer passivation film and transforms it into a solid lubrication transfer layer, while the dense inner passivation film is retained, thus obtaining the finished bearing.

2. The manufacturing method of a high-precision, long-life industrial robot bearing according to claim 1, characterized in that: In step S1, the ultrasonic rolling process involves a rolling force of 300-400N, an amplitude of 15-25μm, and a rolling speed of 25-35mm / min.

3. The manufacturing method of a high-precision, long-life industrial robot bearing according to claim 1, characterized in that: In step S1, the depth of the residual compressive stress layer is 100-150 μm, and the surface roughness Ra of the raceway is 0.04-0.06 μm.

4. The manufacturing method of a high-precision, long-life industrial robot bearing according to claim 1, characterized in that: In step S2, the low-temperature recovery treatment is carried out at a temperature of 150-200℃, with a holding time of 0.5-2 hours and a vacuum degree of less than 1×10⁻⁶. - 2 Pa.

5. The manufacturing method of a high-precision, long-life industrial robot bearing according to claim 1, characterized in that: In step S2, the heating rate of the low-temperature recovery treatment is 5-10℃ / min, and the cooling rate is 3-6℃ / min.

6. The manufacturing method of a high-precision, long-life industrial robot bearing according to claim 1, characterized in that: In step S3, the densification passivation solution is an aqueous solution containing 4-6 wt% citric acid and 0.3-0.7 wt% hydrogen peroxide, with a pH value of 2.5-3.2, a treatment temperature of 50-70℃, a treatment time of 2-5 min, and the thickness of the generated dense Fe3O4 inner passivation film is 3-7 nm.

7. The manufacturing method of a high-precision, long-life industrial robot bearing according to claim 1, characterized in that: In step S4, the loosening passivation solution is an aqueous solution containing 4-6 wt% citric acid and 0.3-0.7 wt% hydrogen peroxide, with a pH value of 4.2-4.8, a treatment temperature of 35-45℃, a treatment time of 8-15 min, and the thickness of the generated Fe3O4 outer passivation film is 8-15 nm.

8. The manufacturing method of a high-precision, long-life industrial robot bearing according to claim 1, characterized in that: In step S5, the vacuum degree of the vacuum impregnation treatment is ≤20Pa, the vacuum holding time is 20-40min, and the atmospheric pressure holding time is 1.5-2.5h.

9. The manufacturing method of a high-precision, long-life industrial robot bearing according to claim 1, characterized in that: In step S6, the oscillation frequency of the controllable break-in process is 6-10Hz, the oscillation angle is 20°-30°, the axial preload is 150-250N, and the processing time is 20-40min.

10. A high-precision, long-life industrial robot bearing, characterized in that: It is prepared by the manufacturing method according to any one of claims 1-9.

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