Oilstone for bearing superfinishing and preparation method of oilstone

Abstract

The invention provides an oilstone for superfinishing of a bearing and a preparation method of the oilstone. The preparation method comprises the following steps: stirring and mixing of raw materials, cold press molding, heat treatment sintering, low-temperature wax filling and dimensional precision machining. The raw materials comprise white corundum, a ceramic bond, a pore forming agent and a temporary binder. The oilstone for superfinishing of the bearing is used for superfinishing of the bearing, a machined bearing workpiece can obtain high surface quality precision and long service life, meanwhile, the service life of the oilstone can be prolonged, cost is reduced, and efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of finishing grinding tools, discloses an oil stone for bearing super finishing and a preparation method thereof, and in particular relates to a grinding tool for bearing super finishing. Background Art

[0002] In the existing bearing processing, the precision requirements are very high, and the bearing market as a whole still has a large demand. The development of an ultra-precision oilstone is of great significance to the development of the bearing industry market.

[0003] CN113442069A uses specific amounts of pure copper, tin and silver, combined with a certain amount of abrasives and wetting agents, to prepare a fine honing oilstone for use in honing processing; it uses specific amounts of pure copper, tin and silver, combined with a certain amount of abrasives and wetting agents, to prepare a fine honing oilstone for use in the honing and fine grinding of engine cylinder blocks, ensuring high surface integrity and reticulation uniformity of the cylinder block during fine grinding.

[0004] CN107793157A first mixes cubic silicon carbide micropowder and white corundum uniformly to obtain an abrasive, then adds boron glass powder, potassium feldspar powder, talc powder and a pore-forming agent to the abrasive, mixes to obtain a mixture, then sieves the mixture to obtain a sieved material, then adds an organic binder to the sieved material, mixes to obtain a wet material, then rolls the wet material, and then passes it through 40-mesh and 60-mesh sieves in sequence to obtain a sieve undersize, which is then placed in a mold for compression molding to obtain an oilstone wet blank, and finally dries and sinters the oilstone wet blank and then undergoes a sulfurization treatment to obtain a cubic silicon carbide superfine oilstone. The cubic silicon carbide micropowder, white corundum, boron glass powder, potassium feldspar powder and talc powder selected are all with a particle size of no more than 28μm, which is conducive to the formation of high-density super-fine oilstone, meeting the requirements of super-finishing. Moreover, the wire drawing process is not broken, the wire drawing effect is good, and the super-fine oilstone does not stick to iron. The decibel value of the bearing after fine processing is below 18dB after assembly.

[0005] CN115557799A adds a fixing agent to deionized water and stirs to dissolve, adds CBN abrasive and β-silicon carbide to the solution in sequence and stirs, then adds low-temperature high-borosilicate glass powder and stirs, then adds PMMA microspheres and stirs to prepare raw materials, then adds reactants and defoaming agents in sequence and stirs to the raw materials, pours the prepared solution into a mold, lets it stand at room temperature, and solidifies to obtain a molded block, places the molded block in a vacuum drying oven to dry, then sinters and infiltrates paraffin, and cuts to obtain a finished low-noise bearing raceway super-fine oilstone.

[0006] Most existing oilstones are designed to reduce the noise of bearings during rotation. However, for precision bearing machining, good machining results and long service life are areas where oilstones need improvement. In particular, bearing products used in high-precision and advanced fields in recent years require uniform surface textures and no visible patterns after machining. Existing oilstones cannot meet this requirement. Summary of the Invention

[0007] The present invention aims to provide a method for preparing an oilstone for superfinishing bearings. The method comprises preparing an oilstone sintered body using white corundum, a ceramic binder, a pore-forming agent, and a temporary adhesive as raw materials. The method then utilizes a low-temperature filling process to rapidly cool and solidify the liquid paraffin filled in the oilstone sintered body, thereby obtaining the oilstone for superfinishing bearings. This method overcomes the prior art's bias of using a vacuum impregnation machine to infiltrate the semi-finished superfinished oilstone under pressure generated by evacuation, thereby avoiding the technical problems of expensive equipment, complex operation, and unstable infiltration results associated with vacuum-assisted operation. In particular, the oilstone prepared by the present invention, when used in bearing processing, not only achieves excellent processing quality and extends the oilstone's service life, but also unexpectedly achieves a uniform surface texture after processing, with no visible markings.

[0008] To achieve the above object, the present invention adopts the following technical solutions: A method for preparing an oil stone for superfinishing bearings comprises the following steps: raw materials are sequentially mixed, cold pressed, heat treated and sintered, and low-temperature wax filled to obtain the oil stone for superfinishing bearings.

[0009] In the present invention, the raw materials include white corundum, a ceramic binder, a pore-forming agent, and a temporary adhesive.

[0010] Preferably, the vitrified bond is a low-temperature vitrified bond of a boroaluminosilicate glass system. The raw materials for preparing the vitrified bond include silicon dioxide, boron oxide, sodium oxide, potassium oxide, calcium oxide, magnesium oxide, and aluminum oxide. Preferably, by weight, boron oxide is 15-25%, sodium oxide, potassium oxide, calcium oxide, magnesium oxide, and aluminum oxide are each 2-7%, with the balance being silicon dioxide.

[0011] Preferably, the weight percentage of the raw materials (white corundum, ceramic binder, pore former, temporary binder) is 100%, wherein the white corundum accounts for 50-70wt%, the ceramic binder accounts for 10-30wt%, the pore former accounts for 15-20wt%, and the temporary binder is the balance.

[0012] Further preferably, the weight percentage of the raw materials (white corundum, ceramic binder, pore former, temporary binder) is 100%, wherein white corundum accounts for 55-65wt%, ceramic binder accounts for 15-25wt%, pore former accounts for 17-19wt%, and temporary binder is the balance.

[0013] In the present invention, the amount of pore-forming agent used is higher than that of existing oilstones or grinding wheels. After mixing, cold pressing, heat treatment and sintering, and low-temperature wax filling at atmospheric pressure, the resulting oilstone for bearing superfinishing exhibits excellent technical performance. As an example, a further preferred embodiment comprises 100% by weight of the raw materials (white corundum, vitrified binder, pore-forming agent, and temporary binder), with the white corundum comprising 55-60% by weight, the vitrified binder comprising 19-21% by weight, the pore-forming agent comprising 17-18% by weight, and the temporary binder comprising the remainder.

[0014] In the present invention, the maximum heat treatment temperature is 650-800°C, and the holding time is 0.5-2 hours. Preferably, the maximum heat treatment temperature is 700°C, and the holding time is 1 hour. The sintering is combined with the subsequent low-temperature paraffin soaking to prepare the oilstone while maintaining good processing quality and improving the processing life.

[0015] In the present invention, the oilstone sintered body is processed by low-temperature filling process, which includes the following steps: immersing the oilstone sintered body obtained by heat treatment and sintering in paraffin liquid, taking it out after heat preservation, and cooling it at room temperature to obtain the oilstone for bearing superfinishing.

[0016] The details are as follows: select microcrystalline paraffin with a melting point of 120-150℃, heat it until it is completely melted, immerse the prepared oilstone sintered body completely in the melted paraffin liquid, and keep it warm for 1-3 hours. Then take the oilstone out of the paraffin liquid and cool it in the air (natural cooling in room temperature air) to allow the liquid paraffin filled in the oilstone sintered body to cool and solidify, thereby obtaining an oilstone for bearing superfinishing.

[0017] The low-temperature filling process of the present invention is carried out under normal pressure, which overcomes the technical bias of the existing technology that all uses vacuum impregnation equipment to infiltrate the super-fine oil stone semi-finished product under the pressure formed after vacuuming, and avoids the technical problems of expensive equipment, complicated operation and unstable penetration effect caused by vacuum operation.

[0018] Furthermore, the present invention manufactures an oil stone for bearing superfinishing to perform machining with dimensional accuracy and to perform angle cutting and other processing according to the requirements of the drawings, which is a conventional technology.

[0019] In the present invention, the particle size of the white corundum is 1000#-2000#, preferably 1200#-1500#.

[0020] In the present invention, the temporary adhesive is a phenolic resin liquid.

[0021] In the present invention, the pore-forming agent is resin microspheres. Compared with carbon powder, biomass or inorganic pore-forming agents, the resin microspheres can achieve the high filling designed by the present invention without affecting the molding of the oilstone. After high-temperature sintering, suitable channels are formed in the oilstone. The subsequent infiltration of paraffin wax combined with white corundum and ceramic binder can improve the processing effect of the oilstone. The surface quality of the processed product is good, and the service life of the oilstone is improved. In particular, the surface texture of the workpiece after processing is uniform, and no pattern is observed.

[0022] In the present invention, the manufactured oilstone for bearing superfinishing is used as a grinding tool in the superfinishing process of bearings.

[0023] The invention discloses an oil stone prepared by the method for preparing the oil stone for bearing superfinishing.

[0024] The invention discloses the application of the oilstone in processing bearings.

[0025] The invention discloses the application of the oilstone in superfinishing bearings.

[0026] The invention discloses a bearing superfinishing method, which comprises the following steps: using the oilstone to process the bearing to complete the bearing superfinishing.

[0027] In the present invention, super finishing means that the surface roughness of the bearing workpiece after processing is less than 0.15Ra, and the surface of the bearing after processing is smooth and has no pattern.

[0028] Existing oilstones for bearing machining are mostly designed to reduce bearing noise during rotation. However, for precision bearing machining, good machining results and a long service life are areas where oilstones need improvement. In the present invention, the raw materials are conventionally mixed and then cold-pressed to produce an oilstone blank for bearing superfinishing. Furthermore, the resulting oilstone blank is dried, heat-treated, and sintered to produce a sintered oilstone body for bearing superfinishing. The sintered oilstone body is then subjected to a low-temperature filling process, which rapidly cools and solidifies the liquid paraffin filled in the sintered oilstone body, resulting in an oilstone for bearing superfinishing. The present low-temperature filling process is performed at atmospheric pressure, overcoming the prior art's bias of using a vacuum impregnation machine to infiltrate the semi-finished superfinished oilstone under pressure after evacuation. This avoids the technical issues associated with vacuum impregnation, such as expensive equipment, complex operation, and unstable infiltration results. Furthermore, the oilstone produced by the present invention not only achieves high machining quality and extends its service life when used in bearing machining, but also addresses the problem of existing oilstone-processed bearings achieving low roughness but also causing surface markings on the workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the surface condition of the bearing inner raceway after being processed with three oilstones.

[0030] Figure 2 This is a micrograph of the workpiece before ultra-precision, magnified 100 times.

[0031] Figure 3 This is a micrograph of a workpiece after superfinishing with the oilstone of the present invention, magnified 100 times.

[0032] Figure 4 This is a micrograph of the workpiece after superfinishing with an existing oilstone, magnified 100 times. DETAILED DESCRIPTION

[0033] In the present invention, the raw materials are stirred uniformly in a conventional manner and then cold-pressed to obtain an oilstone blank for bearing superfinishing. Furthermore, the obtained oilstone blank is dried, heat-treated and sintered to obtain an oilstone sintered body for bearing superfinishing. Then, the obtained oilstone sintered body is subjected to a low-temperature filling process, so that the liquid paraffin filled in the oilstone sintered body is quickly cooled and solidified to obtain an oilstone for bearing superfinishing.

[0034] In the present invention, a sintered oilstone body is prepared and subjected to a low-temperature filling process, specifically as follows: microcrystalline paraffin with a melting point of 120-150°C is selected and heated until it is completely melted, the prepared sintered oilstone body is completely immersed in the melted paraffin liquid and kept warm for 2 hours, and then the oilstone is taken out of the paraffin liquid and naturally cooled in the air, so that the liquid paraffin filled in the oilstone sintered body is quickly cooled and solidified, thereby obtaining an oilstone for bearing superfinishing.

[0035] Furthermore, the present invention manufactures an oil stone for bearing superfinishing to perform machining with dimensional accuracy and to perform angle cutting and other processing according to the requirements of the drawings, which is a conventional technology.

[0036] In the present invention, the manufactured oilstone for bearing superfinishing is used as a grinding tool in the superfinishing process of bearings.

[0037] In the bearing industry's ultra-finishing process, precision requirements are primarily reflected in process stability, machining efficiency, and the quality of the finished workpiece surface, often expressed in terms of roughness. Furthermore, as client applications expand, the demand for a uniform, unobservable surface pattern is growing. The following examples illustrate the oilstones used for bearing ultra-finishing. The raw materials used are all existing products that meet conventional oilstone requirements. The specific preparation and performance testing (including workpieces and machining methods) are conventional techniques. As a general rule, low-temperature wax filling is followed by conventional dimensional precision machining as needed to produce the oilstones suitable for bearing ultra-finishing.

[0038] Unless otherwise specified, all operations are carried out in normal pressure and air. The processing and testing methods for different oilstones are the same and are parallel experiments. The bearings are conventional forged products. The surface finish is the maximum data tested within the processing life. The surface texture and pattern after processing are observed.

[0039] The resin balls are solid PS microspheres; the cold pressing pressure is 5-10MPa, and the pressure is maintained for 3-5s.

[0040] Preparation Example 6 kg of silicon dioxide, 2 kg of boron oxide, 0.5 kg of sodium oxide, 0.4 kg of potassium oxide, 0.5 kg of calcium oxide, 0.3 kg of magnesium oxide, and 0.3 kg of aluminum oxide were smelted at 1500°C for 1 hour, then water quenched and ball-milled to obtain a ceramic binder for the following experiments.

[0041] Example 1 The raw materials (total 100wt%) and the proportions are as follows: 59wt% of 1200# white corundum; 20wt% of ceramic binder; 18wt% of resin balls with a particle size of 10-20μm as pore-forming agent; and the remainder as temporary adhesive, which is phenolic resin liquid.

[0042] The ingredients are mixed according to the above proportions, and then cold pressed at 10 MPa for 5 seconds to form. The obtained cold-pressed green body is then heat treated: the room temperature is heated to 350°C at a heating rate of 5°C / min, kept warm for 2 hours, heated to 550°C at a heating rate of 10°C / min, kept warm for 1 hour, and heated to 700°C at a heating rate of 10°C / min and kept warm for 1 hour to obtain a ceramic sintered body; under normal pressure, the ceramic sintered body is completely immersed in a microcrystalline wax liquid melted at 150°C, allowed to stand for 1 hour, and then quickly (within 1 second) taken out and placed in the air for natural cooling, and then mechanically processed to obtain an ultra-fine processing oilstone.

[0043] Using the existing production processing methods, the ultra-finished oilstone prepared above can obtain a surface finish of 0.08Ra for processing the inner raceway of the bearing ring, without any blackening or sticking debris. The service life can reach 3,000 pieces, and the surface texture of all workpieces is uniform, with no observed patterns.

[0044] Figure 2 This is a micrograph of the workpiece before ultra-precision. Figure 3 This is a micrograph of the workpiece after superfinishing. The texture is good, the stripes are clear, and no patterns are observed.

[0045] Example 2 Referring to Example 1, 1500# white corundum was selected, and other conditions were the same as in Example 1. Using existing production processing methods, the superfinished oilstone prepared above can achieve a surface finish of 0.05Ra for processing bearings, with a service life of up to 2500 pieces. All workpiece surfaces have uniform textures, with no visible patterns.

[0046] Comparative Example 1 Referring to Example 1, a ceramic sintered body was completely immersed in microcrystalline wax melted at 80°C using microcrystalline wax with a melting point of 80°C, with all other parameters remaining the same, to prepare a processing oilstone. Using existing production methods, this superfinishing oilstone exhibited unstable processing power during machining of the inner raceway of a bearing ring, inconsistent workpiece surface finish, and uneven texture (observable patterning). The roughness fluctuated between 0.1 and 0.13 Ra, resulting in a lifespan of 1,700 pieces. This suggests that microcrystalline waxes with different melting points affect the overall microstructure of the oilstone after immersion, leading to significant differences in workpiece performance.

[0047] Comparative Example 2 Referring to Example 1, 7 wt% of the white corundum was replaced with 7 wt% of 1200# silicon carbide (heat treated in nitrogen) to prepare an ultra-finishing oilstone. The existing production processing method was used to process the bearing to obtain a surface finish of 0.12 Ra.

[0048] In particular, the silicon carbide system will experience blistering, black core and other phenomena during high-temperature heat treatment. In order to solve this problem, atmosphere protection is required. The process is relatively complex and has high process requirements. The cost of the prepared ultra-fine processing oilstone is high.

[0049] Comparative Example 3 Referring to Example 1, the amount of white corundum was adjusted to 65wt%, the amount of resin balls was adjusted to 12%, and the rest remained unchanged. The surface finish of the inner raceway of the bearing ring processed by the oilstone was low, with a roughness of 0.17Ra.

[0050] Comparative Example 4 Referring to Example 1, the amount of white corundum was adjusted to 54wt%, the amount of resin balls was adjusted to 23%, and the rest remained unchanged. The inner raceway surface of the bearing ring processed by the oilstone obtained showed light and dark patterns.

[0051] See also Figure 1 The oilstones on the left, middle and right are the actual photos of the oilstones of Comparative Example 3, Example 1 and Comparative Example 4 after processing 1000 bearings. It can be seen that the application effect of the product of the present invention is the best, it is also sharp, and there is no sticky debris clogging phenomenon. The dimensional accuracy and texture of the workpieces processed by continuing to use are good.

[0052] Comparative Example 5 Referring to Example 1, 7wt% of the white corundum was replaced with 7wt% of 1200# boron nitride abrasive, and the oilstone was prepared using the existing production processing method. There was a light and dark pattern phenomenon on the surface of the inner raceway of the processed bearing ring, and the roughness was 0.16Ra.

[0053] Control Example The best oilstone (imported) with the same specifications as in Example 1 was used to process the inner raceway of the same bearing ring. The surface roughness of the workpiece reached 0.11Ra and the service life was 2000 pieces. However, some bearing surfaces showed patterns after processing. Figure 4 This is a micrograph of the workpiece after superfinishing. The texture is poor, the stripes are not clear, and patterns are observed.

[0054] Bearings are essential components for the operation of various machines. To ensure optimal performance and quality, bearings are processed using ultra-finishing technology. Precision machining refers to various machining processes that achieve higher precision and surface finish than comparable finishing methods. This technology plays an important role in reducing or eliminating circular deviations left over from grinding, repairing groove shape errors, refining surface roughness, improving surface physical and mechanical properties, reducing bearing vibration and noise, and ultimately enhancing bearing performance. The oilstones currently used in China are primarily corundum oilstone, diamond oilstone, and cubic boron nitride oilstone. Different oilstones offer varying application benefits. Corundum oilstone offers the highest cost-effectiveness in production, but the lifespan of existing products needs to be improved. For different workpieces, targeted oilstones need to be selected for processing to achieve processing accuracy. The applicant previously disclosed a high-speed super-hard ceramic cBN groove grinding wheel for groove forming grinding, and its processing roughness data was relatively large; the present invention only uses corundum as abrasive, maintaining the low-cost advantage, and through the formulation of ceramic binder, pore-forming agent and highly filled microspheres, combined with cold pressing, hot sintering, and normal pressure wax impregnation, a corundum oilstone with good bearing processing quality and service life is obtained, especially meeting the requirements of high-precision fields for bearing surfaces without patterns. It not only solves the problem that the existing technology requires vacuum operation, but also significantly improves the competitiveness of the use of corundum oilstone.

Claims

1. A method for preparing an oilstone for superfinishing a bearing, characterized in that: The method comprises the following steps: raw materials are sequentially mixed, cold pressed, heat treated and sintered, and low temperature wax filled to obtain oilstone for bearing super finishing; the raw materials include white corundum, ceramic binder, pore former, and temporary adhesive.

2. The method for preparing an oilstone for bearing superfinishing according to claim 1, characterized in that: The weight percentage of the raw materials is 100%, wherein the white corundum accounts for 50-70wt%, the ceramic binder accounts for 10-30wt%, the pore-forming agent accounts for 15-20wt%, and the temporary binder is the balance.

3. The method for preparing an oilstone for bearing superfinishing according to claim 1, characterized in that: The ceramic bond is a boroaluminosilicate glass ceramic bond.

4. The method for preparing an oilstone for bearing superfinishing according to claim 1, characterized in that: The maximum temperature of the heat treatment is 650-800°C and the time is 0.5-2 hours.

5. The method for preparing an oilstone for bearing superfinishing according to claim 1, characterized in that: The low-temperature wax filling method comprises the following steps: immersing the oilstone sintered body obtained by heat treatment and sintering in paraffin liquid, taking it out after heat preservation, and cooling it at room temperature to obtain the oilstone for bearing superfinishing.

6. The method for preparing an oilstone for superfinishing bearings according to claim 1, characterized in that: The wax is microcrystalline wax with a melting point of 120-150°C; the particle size of white corundum is 1000#-2000#; the temporary adhesive is phenolic resin liquid; and the pore-forming agent is resin microspheres.

7. An oilstone prepared by the method for preparing an oilstone for bearing superfinishing according to any one of claims 1 to 6.

8. Use of the oilstone according to claim 7 in machining bearings.

9. Use of the oilstone according to claim 7 in superfinishing bearings.

10. A method for superfinishing a bearing product, comprising the following steps: processing the bearing product using the oilstone according to claim 7 to complete the superfinishing of the bearing product.

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