A high speed super hard ceramic cBN channel grinding wheel for channel forming grinding

Abstract

The application discloses a high-speed superhard ceramic cBN channel grinding wheel for channel forming grinding, and adds cBN abrasive, auxiliary abrasive, inorganic composition, metal composition and carbon powder pore-forming agent into a solution such as acetone or alcohol, and obtains ceramic powder after rotary evaporation; then, the ceramic powder is filled into a metal mold, and is cold-pressed and flattened to obtain a ceramic blank; finally, the grinding wheel blank is sintered to obtain the superhard ceramic cBN grinding wheel. The grinding wheel has large-size pores, excellent chip capacity, and can effectively avoid grinding burn and grinding cracks caused by grinding. The inorganic material and the metal composition make the processing capacity excellent, the consistency of the processing size of the ring channel, the surface quality of the channel and the channel curvature retention far better than those of ordinary abrasive grinding wheels and existing cBN channel grinding wheels; and the method for preparing the superhard ceramic cBN channel grinding wheel is not reported in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of ceramic cBN grinding wheel preparation technology, specifically relating to a high-speed superhard ceramic cBN groove grinding wheel for groove forming grinding. Background Technology

[0002] With the development of my country's bearing industry, the level of bearing manufacturing technology in China is constantly improving, and some fields have reached the international advanced level. For example, high-end bearings in fields such as high-speed railways, wind power, and automobiles have achieved localization or partial localization. Correspondingly, the performance requirements for bearing rings are also becoming increasingly higher. The grinding process of bearing rings is developing towards high precision and high efficiency, and in order to meet diverse requirements, the shapes and styles of bearing ring grooves are also becoming more and more diverse. Due to the special machining method of the bushing ring groove, the machining accuracy is ensured by the shape of the outer circle R-angle of the grinding wheel. The shape of the outer circle R-angle of the grinding wheel is consistent with the shape of the groove. The contact line between the grinding wheel and the workpiece is an arc, and the contact area is larger than that of ordinary internal grinding. The grinding heat generated is also correspondingly larger, and the coolant cannot be effectively sprayed into the grinding zone. Currently, ceramic cBN grinding wheels on the market are very prone to workpiece burns during high-speed machining, and grinding cracks are also easily generated due to the grinding effect, resulting in a rapid decline in the grinding wheel's machining performance. On the other hand, conventional ordinary abrasive grinding wheels wear out very quickly, resulting in low machining efficiency, poor workpiece dimensional consistency, and inability to be used for a long time. The grinding wheels need to be dressed frequently. Summary of the Invention

[0003] The purpose of this invention is to provide a method and product for producing a high-speed superhard ceramic cBN (cBN) groove grinding wheel suitable for groove forming grinding. The resulting cBN grinding wheel blank exhibits excellent chip-holding capacity after sintering, and in particular, effectively avoids grinding burns and cracks caused by high-speed grinding. This grinding wheel can be widely used for high-speed grinding of bearing raceways.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A high-speed superhard ceramic cBN groove grinding wheel for groove forming grinding is disclosed. The raw materials for preparing the high-speed superhard ceramic cBN groove grinding wheel for groove forming grinding include cBN abrasive, auxiliary abrasive, inorganic composition, metal composition, and carbon powder. Preferably, the raw materials for preparing the high-speed superhard ceramic cBN groove grinding wheel for groove forming grinding are cBN abrasive, auxiliary abrasive, inorganic composition, metal composition, and carbon powder.

[0005] This invention discloses a method for preparing the above-mentioned high-speed superhard ceramic cBN groove grinding wheel that can be used for groove forming grinding, comprising the following steps: mixing cBN abrasive, auxiliary abrasive, inorganic composition, metal composition and carbon powder to obtain ceramic powder; then cold pressing the ceramic powder to obtain a ceramic blank; and finally sintering the grinding wheel blank to obtain a high-speed superhard ceramic cBN groove grinding wheel that can be used for groove forming grinding.

[0006] Preferably, cBN abrasive, auxiliary abrasive, inorganic composition, metal composition and carbon powder are added to an organic solvent, such as acetone, alcohol or other solutions, and the mixture is rotary evaporated to obtain ceramic powder; then the ceramic powder is filled into a metal mold and cold-pressed to obtain a ceramic blank; finally, the grinding wheel blank is sintered to obtain an ultra-hard ceramic cBN grinding wheel.

[0007] A high-speed superhard ceramic cBN grooved grinding wheel blank suitable for groove forming grinding is disclosed. The raw materials for preparing the high-speed superhard ceramic cBN grooved grinding wheel blank suitable for groove forming grinding include cBN abrasive, auxiliary abrasive, inorganic composition, metal composition, and carbon powder. Preferably, the raw materials for preparing the high-speed superhard ceramic cBN grooved grinding wheel blank suitable for groove forming grinding are cBN abrasive, auxiliary abrasive, inorganic composition, metal composition, and carbon powder.

[0008] This invention discloses a method for preparing a high-speed superhard ceramic cBN grooved grinding wheel blank that can be used for groove forming grinding, comprising the following steps: mixing cBN abrasive, auxiliary abrasive, inorganic composition, metal composition and carbon powder to obtain ceramic powder; and then cold pressing the ceramic powder to obtain a high-speed superhard ceramic cBN grooved grinding wheel blank that can be used for groove forming grinding.

[0009] Preferably, cBN abrasive, auxiliary abrasive, inorganic composition, metal composition and carbon powder are added to an organic solvent, such as acetone, alcohol or other solutions, and the ceramic powder is obtained by rotary evaporation; then the ceramic powder is filled into a metal mold and cold-pressed flat to obtain a high-speed superhard ceramic cBN groove grinding wheel that can be used for groove forming grinding.

[0010] In this invention, the inorganic composition includes boron oxide, aluminum oxide, sodium oxide, and magnesium oxide, preferably composed of boron oxide, aluminum oxide, sodium oxide, and magnesium oxide. The weight percentages of each component in the inorganic composition are: aluminum oxide 57%–68%, boron oxide 15–30%, magnesium oxide 3–5%, and sodium oxide as the balance. The auxiliary abrasive can be aluminum oxide, silicon carbide, microcrystalline corundum, etc. The metallic composition is a copper-tin-zinc alloy, wherein the weight percentages of each component are: copper 68–75%, zinc 15–20%, and tin as the balance.

[0011] In the raw materials for preparing high-speed superhard ceramic cBN grooved grinding wheels for groove forming grinding, the weight percentage of cBN abrasive is 45-70 wt%, the weight percentage of auxiliary abrasive is 8-15 wt%, the weight percentage of carbon powder is 3-8 wt%, the weight percentage of metal composition is 3-8 wt%, and the balance is an inorganic composition. Preferably, in the raw materials for preparing high-speed superhard ceramic cBN grooved grinding wheels for groove forming grinding, the weight percentage of cBN abrasive is 50-60 wt%, the weight percentage of auxiliary abrasive is 10-15 wt%, the weight percentage of carbon powder is 6-8 wt%, the weight percentage of metal composition is 4-8 wt%, and the balance is an inorganic composition.

[0012] In this invention, the rotary evaporation time is 45 to 60 minutes; the cold pressing pressure is 35 to 70 tons.

[0013] In this invention, the green blank of the high-speed superhard ceramic cBN channel grinding wheel, which can be used for channel forming grinding, is dried for 6-12 hours before sintering at a temperature of 80-120°C. Sintering is then carried out in a nitrogen atmosphere. The sintering process involves raising the temperature from room temperature to 400-600°C over 2-3 hours, holding for 2.5-3.5 hours, then raising it to 700-800°C over 2-3 hours, holding for 1-3 hours, then raising it to 850-1000°C over 3 hours, holding for 2-3 hours, and finally cooling it in the furnace. Preferably, the sintering process involves raising the temperature from room temperature to 500°C over 3 hours, holding for 3 hours, then raising it from 500°C to 750°C over 3 hours under nitrogen atmosphere protection, holding for 2 hours, then raising it from 750°C to 850-960°C over 3 hours, holding for 2-3 hours, and finally cooling it in the furnace.

[0014] This invention discloses the application of the above-mentioned high-speed superhard ceramic cBN groove grinding wheel, which can be used for groove forming grinding, in the machining of bearing ring grooves.

[0015] Compared with the prior art, the present invention has the following advantages: In practical applications, the grinding wheel of this invention can effectively avoid grinding burns and grinding cracks caused by grinding; it can effectively avoid grinding wheel layer cracking and detachment caused by matrix expansion; the added inorganic and metal compositions make its processing capabilities excellent, with excellent uniformity of ring groove processing dimensions, groove surface quality and groove curvature retention. Attached Figure Description

[0016] Figure 1 This is a photograph of the appearance of the ultra-hard ceramic cBN grooved grinding wheel according to Embodiment 1 of the present invention.

[0017] Figure 2 This is a micrograph of the ultra-hard ceramic cBN channel grinding wheel of Embodiment 1 of the present invention.

[0018] Figure 3 A photograph of the surface of a workpiece machined using the superhard ceramic cBN channel grinding wheel of the present invention.

[0019] Figure 4 Photographs of the surface of a workpiece machined using an existing superhard ceramic cBN grooved grinding wheel. Detailed Implementation

[0020] This invention involves adding cBN abrasive, auxiliary abrasive, pore-forming agent, metal composition, and inorganic composition to an inorganic solvent, followed by rotary evaporation to obtain ceramic powder. The ceramic powder is then filled into a metal mold, cold-pressed and flattened, and demolded after pressure holding to obtain a ceramic blank. The blank is dried and sintered to obtain an ultra-hard ceramic cBN grooved grinding wheel. Through formulation selection, this invention achieves ultra-hard ceramic cBN grooved grinding blanks with large pore sizes and high uniform shrinkage at the upper and lower ends of the grinding wheel after sintering. The cBN grinding wheels prepared from these blanks have pore sizes of 0.2-1.0 mm and excellent chip-holding capacity. In particular, the grinding wheels of this invention effectively avoid grinding burns and cracks caused by grinding. Their processing capabilities are excellent, with the uniformity of groove dimensions, groove surface quality, and groove curvature retention far superior to existing grinding wheels.

[0021] Specifically, the preparation method of the high-speed superhard ceramic cBN grooved grinding wheel of the present invention, which can be used for grooved forming grinding, is as follows: (1) Preparation of raw material solution: Weigh out cBN abrasive, auxiliary abrasive, inorganic composition, metal composition, and carbon powder. The weight percentage of cBN abrasive is 45-70 wt%, the weight percentage of auxiliary abrasive is 8-15 wt%, the weight percentage of carbon powder is 3-8 wt%, the weight percentage of metal composition is 3-8 wt%, and the balance is inorganic composition. Then dissolve it in solvents such as acetone or alcohol to obtain a ceramic powder solution. (2) Preparation of powder: The ceramic powder solution was placed in a rotary evaporation flask, and the rotary evaporation temperature was 45–65℃; the vacuum degree of rotary evaporation was -0.090–0.15 MPa, and the rotary evaporation time was 45–60 min; thus, the powder was obtained. (3) Compression molding: The powder is filled into a metal mold and cold-pressed for 3-5 minutes to obtain a ceramic grinding wheel blank. (4) Drying: The prepared ceramic grinding wheel blank was placed in an oven for drying at a temperature of 80–120°C for 6–12 hours. (5) Sintering: The dried ceramic grinding wheel blank was sintered in an atmosphere furnace (the sintering atmosphere was nitrogen). The temperature was raised to 850-960℃ using a segmented heating regime, held for 2-3 hours, and then cooled to room temperature with the furnace to obtain a superhard ceramic binder cBN grinding wheel.

[0022] (6) Bonding and grinding: After sintering, the ceramic grinding wheel is bonded to the substrate using commercially available AB glue as the adhesive. The bonded grinding wheel is then placed on a profile grinding machine to grind the outer radius (R) of the grinding wheel as needed. This step is a standard procedure in existing grinding wheel production.

[0023] The grinding wheel processing and workpiece processing involved in this invention are both performed on conventional equipment. The performance characterization methods for grinding wheels, such as the testing methods for pore size, are conventional methods in the field. The processing performance characterization methods for grinding wheels, such as feed rate, processing cycle time, roughness, curvature, and dressing interval, are also conventional methods in the field. The raw materials involved in this invention are all commercially available products that meet the requirements for grinding wheel applications. The metal composition is a copper-tin-zinc alloy powder, wherein the weight percentages of each component are: copper 75%, zinc 18%, and tin 7%. The inorganic composition is obtained by melting, cooling, crushing, and ball milling. After the materials in the formula are mixed evenly, they are sequentially subjected to melting, quenching, drying, ball milling, and sieving steps. The melting temperature is 1200℃, and the melting time is 100 min; the quenching temperature is 30℃, and the time is 45 min; the drying temperature is 200℃, and the time is 6 h; the ball milling method is high-energy ball milling, and the time is 1.5 h; the sieving screen mesh is 320 mesh. Example 1

[0024] Weigh 72g of cBN abrasive, 12g of auxiliary abrasive microcrystalline corundum, 9.6g of carbon powder, 7.2g of metal composition, and 19.2g of inorganic composition. Add an alcohol solution, then place the mixture in a rotary evaporator and evaporate at 60℃ and -0.12MPa for 50 minutes to obtain ceramic powder. Fill the ceramic powder into a conventional metal mold, cold press it flat, and after holding it under 50 tons of pressure, demold to obtain a ceramic blank. Dry the grinding wheel blank in a 120℃ drying oven for 12 hours. After drying, place the removed grinding wheel blank in a high-temperature atmosphere furnace for segmented heating and sintering. Finally, cool it with the furnace to obtain an ultra-hard ceramic cBN grooved grinding wheel for machining. The bearing raceway; the grinding wheel has an outer diameter of 90mm, an inner diameter of 70mm, a height of 18mm, and an outer radius of 9.17°; the matrix is ​​a titanium alloy matrix with an outer diameter of 70mm, an inner diameter of 20mm, and a height of 18mm; the inorganic composition consists of 65% alumina, 25% boron oxide, 3% magnesium oxide, and the balance sodium oxide, obtained by melting, cooling, crushing, and ball milling; the sintering is carried out under a nitrogen atmosphere, and the sintering process is as follows: sintering temperature is increased from room temperature to 500°C in 3 hours, then held for 3 hours, then nitrogen is introduced, and the temperature is increased from 500°C to 750°C in 3 hours, then held for 2 hours, then increased from 750°C to 930°C in 3 hours, then held for 2 hours, and finally cooled in the furnace.

[0025] Compared with existing ordinary grinding wheels and ceramic CBN grinding wheels (of which ceramic CBN is the grinding wheel with the best processing effect at existing customers), the grinding of bearing ring grooves using existing equipment is shown in Table 1. This table compares some processing performance parameters of the superhard ceramic CBN groove grinding wheel of the present invention with existing ordinary grinding wheels and ceramic CBN grinding wheels.

[0026] Table 1 Grinding wheel properties and machining performance This invention grinding wheel 0.50mm 100um / s 28s 135-150 -1-5u Ra 0.18-0.29 Existing ordinary grinding wheels none 70um / s 40s 3-5 Untested Ra0.25-Ra0.38 Existing cBN grinding wheels 0.13mm 70um / s 40s 70-90 -1-8u Ra0.23-Ra0.33 In the application of grinding wheels, after the grinding wheel is mounted on the machine, it is generally dressed online, that is, the dimensions of the grinding wheel are readjusted before subsequent processing. During the processing, the abrasive grains inside the grinding wheel will continuously break and fall off, thus affecting the processing efficiency and quality of the workpiece. Therefore, the grinding wheel needs to be dressed again before processing can begin. After the grinding wheel is dressed, it starts processing the workpiece until it can no longer be processed normally (usually due to processing problems such as dimensional deviations or roughness), at which point the grinding wheel needs to be dressed again before processing can begin. Ordinary grinding wheels generally have very short intervals, while the grinding wheel interval of this invention is about 50 times that of ordinary grinding wheels, which can maintain dimensional stability for a long time.

[0027] Machining roughness refers to the range of roughness fluctuations among different workpieces within the same batch of workpieces processed, specifically within the same machining and dressing interval. Generally, within the same dressing interval, the roughness gradually increases as abrasive grains from the grinding wheel are shed.

[0028] Figure 1 , Figure 2 The images show the appearance and micrographs of the superhard ceramic cBN channel grinding wheel of Example 1. Both the appearance and the microstructure show that the grinding wheel prepared by this invention has regular and uniformly distributed large-sized pores.

[0029] Figure 3 , Figure 4 The images show the effects of the superhard ceramic cBN grooved grinding wheel of the present invention and the existing ceramic cBN grinding wheel after processing the same workpiece on the same equipment. It can be seen that the surface grinding texture of the workpiece processed by the grinding wheel of the present invention is very fine and regular, which is significantly better than the existing ceramic CBN grinding wheel.

[0030] Comparative Example 1 Based on Example 1, walnut shell powder was used to replace carbon powder, while everything else remained the same. The resulting grinding wheel had a reduced dressing interval of 95-110.

[0031] Based on Example 1, ammonium carbonate was used to replace carbon powder, while everything else remained the same. The resulting grinding wheel feed speed was slower, at 85 μm / s.

[0032] Comparative Example 2 Based on Example 1, a mixture of copper powder, zinc powder, and tin powder was used to replace the copper-tin-zinc alloy powder, while everything else remained the same. The resulting grinding wheel had a reduced dressing interval of 105-115.

[0033] Based on Example 1, a mixture of CuSn45 alloy powder was used to replace the copper-tin-zinc alloy powder, while everything else remained the same. The resulting grinding wheel feed speed was slower, at 90 μm / s.

[0034] Comparative Example 3 Based on Example 1, the inorganic composition was modified; in this inorganic composition, the weight percentages of each component are: silicon oxide 55%, boron oxide 17%, aluminum oxide 16%, calcium oxide 6%, and sodium oxide as the balance. The inorganic mixture was also obtained by high-temperature melting, cooling, crushing, and ball milling. With other components remaining the same, the resulting grinding wheel had a reduced dressing interval of 100-110. Example 2

[0035] Weigh 45g of cBN abrasive, 13.5g of auxiliary abrasive white corundum, 5.4g of carbon powder, 7.2g of metal composition, and 18.9g of inorganic composition; dissolve them in an alcohol solution and place them in a rotary evaporator. Evaporate at 65℃ and -0.09MPa for 45 minutes to obtain ceramic powder. Then fill the ceramic powder into a metal mold, cold press and flatten it, and demold it after holding the pressure to obtain a ceramic blank. Place the grinding wheel blank in a drying oven at 100℃ for 10 hours to dry. After drying, place the removed grinding wheel blank in a high-temperature atmosphere furnace for segmented heating and sintering. Finally, cool it with the furnace to obtain an ultra-hard ceramic cBN grooved grinding wheel. The grinding wheel is used for machining bearing raceway grooves. Its outer diameter is 60mm, inner diameter is 40mm, height is 11mm, and outer radius (R) is 6.3. The substrate is a titanium alloy substrate with an outer diameter of 40mm, an inner diameter of 16mm, and a height of 11mm. The inorganic composition consists of 68% alumina, 28% boron oxide, 5% magnesium oxide, and the balance sodium oxide. The sintering process is carried out under a nitrogen atmosphere. The sintering process involves raising the temperature from room temperature to 500℃ over 3 hours, holding for 3 hours, then introducing nitrogen and raising the temperature from 500℃ to 750℃ over 3 hours, holding for 2 hours, then raising the temperature from 750℃ to 900℃ over 3 hours, holding for 3 hours, and finally cooling in the furnace. Example 3

[0036] Weigh 42g of cBN abrasive, 10.5g of silicon carbide auxiliary abrasive, 5.6g of carbon powder, 2.8g of metal composition, and 9.1g of inorganic composition; dissolve them in an alcohol solution and place them in a rotary evaporator. Evaporate the mixture at 65℃ and -0.12MPa for 55 minutes to obtain ceramic powder. Then fill the ceramic powder into a metal mold, cold press and flatten it, and remove it from the mold after holding the pressure to obtain a ceramic blank. Place the grinding wheel blank in a drying oven at 100℃ for 8 hours to dry. After drying, place the removed grinding wheel blank in a high-temperature atmosphere furnace for segmented heating and sintering. Finally, cool it with the furnace to obtain an ultra-hard ceramic cBN grooved grinding wheel. The grinding wheel is used for machining bearing raceway grooves. Its outer diameter is 25.5 mm, inner diameter is 10 mm, height is 5.5 mm, and outer radius (R) is 3.1. The substrate is Invar, with an outer diameter of 10 mm and a height of 27.5 mm. The inorganic composition consists of 60% alumina, 28% boron oxide, 4% magnesium oxide, and the balance sodium oxide. The sintering process is carried out under a nitrogen atmosphere. The sintering process involves raising the temperature from room temperature to 500°C over 3 hours, holding for 3 hours, then introducing nitrogen and raising the temperature from 500°C to 750°C over 3 hours, holding for 2 hours, then raising the temperature from 750°C to 960°C over 3 hours, holding for 3 hours, and finally cooling with the furnace.

[0037] This invention innovatively incorporates a large amount of multi-component pore-forming agent during grinding wheel preparation, resulting in grinding wheels with large-sized pores, excellent chip-holding capacity, and good thermal conductivity. Furthermore, the innovative use of titanium alloy or Invar steel for the grinding wheel matrix effectively avoids grinding burns and cracks caused by grinding heat. The added metal composition enhances its machining performance, with the uniformity of the groove dimensions, groove surface quality, and groove curvature retention far superior to ordinary abrasive grinding wheels and existing cBN grooved grinding wheels. No similar methods for preparing ultra-hard ceramic cBN grooved grinding wheels have been reported in this invention.

Claims

1. A high-speed superhard ceramic cBN groove grinding wheel that can be used for groove forming grinding, characterized in that, The raw materials for preparing the high-speed superhard ceramic cBN groove grinding wheel that can be used for groove forming grinding include cBN abrasive, auxiliary abrasive, inorganic composition, metal composition, and carbon powder; the inorganic composition includes boron oxide, aluminum oxide, sodium oxide, and magnesium oxide; the auxiliary abrasive includes one or more of aluminum oxide, silicon carbide, and microcrystalline corundum; the metal composition is a copper-tin-zinc alloy; in the inorganic composition, the weight percentages of each component are: aluminum oxide 57%–68%, boron oxide 15–30%, magnesium oxide 3–5%, and sodium oxide as the balance; the weight percentages of cBN abrasive are 45–70 wt%, the weight percentages of auxiliary abrasive are 8–15 wt%, the weight percentages of carbon powder are 3–8 wt%, the weight percentages of metal composition are 3–8 wt%, and the balance is inorganic composition.

2. The method for preparing the high-speed superhard ceramic cBN grooved grinding wheel for groove forming grinding as described in claim 1, characterized in that, The process includes the following steps: mixing cBN abrasive, auxiliary abrasive, inorganic composition, metal composition and carbon powder to obtain ceramic powder; then cold pressing the ceramic powder to obtain a ceramic blank; finally sintering the ceramic blank to obtain a high-speed superhard ceramic cBN groove grinding wheel that can be used for groove forming grinding.

3. The method for preparing a high-speed superhard ceramic cBN grooved grinding wheel for groove forming grinding according to claim 2, characterized in that, CCBN abrasive, auxiliary abrasive, inorganic composition, metal composition and carbon powder are added to an organic solvent and then rotary evaporated to obtain ceramic powder.

4. The application of the high-speed superhard ceramic cBN groove grinding wheel of claim 1, which can be used for groove forming grinding, in the machining of bearing ring grooves.

5. A method for machining bearing ring grooves, characterized in that, The bearing raceway is machined using the high-speed superhard ceramic cBN groove grinding wheel as described in claim 1, which can be used for groove forming grinding.

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