Brazed silicon carbide grinding wheel and preparation method thereof

Abstract

The invention relates to the technical field of superhard abrasives, in particular to a brazed silicon carbide grinding wheel and a preparation method thereof. The preparation method of the brazed silicon carbide grinding wheel comprises the steps that a silicon carbide grinding material, a metal binding agent and an auxiliary binding agent are mixed, and a mixture is obtained; wherein the metal binding agent is mainly composed of copper powder and titanium powder; the mixture is subjected to cold press molding, and an abrasive ring green body is obtained; the abrasive ring green body is brazed, and the abrasive ring is obtained; and the brazed silicon carbide grinding wheel is obtained after the abrasive ring and the aluminum core are bonded. According to the preparation method of the brazed silicon carbide grinding wheel, the brazed silicon carbide grinding material and the metal bonding agent form chemical metallurgical bonding, the bonding strength of the brazed silicon carbide grinding wheel is remarkably improved, and the holding effect of the metal matrix on silicon carbide is good; and the brazing time is short.

Description

Technical Field

[0001] The invention relates to the technical field of superhard abrasives, and in particular to a brazed silicon carbide grinding wheel and a preparation method thereof. Background Art

[0002] Silicon carbide has high hardness, high wear resistance, high temperature resistance and good corrosion resistance, and is inexpensive. It has become a high-quality abrasive for processing hard and brittle materials in industry, gradually replacing high-cost diamond abrasives and CBN (cubic boron nitride) abrasives. In actual application, since diamond grinding wheels cannot process ferrous metals and CBN grinding wheels are difficult to dress, the application advantages of silicon carbide grinding wheels are more obvious. However, the toughness of silicon carbide particles is poor, and brittle fracture is prone to occur during the processing process, while consolidation matching with the metal matrix can maximize the grinding performance. However, in traditional sintered and electroplated silicon carbide grinding tools, the silicon carbide particles and the metal are only mechanically bonded, and the bonding strength is low, which can no longer fully meet the current high-speed, high-efficiency, and high-precision grinding requirements.

[0003] At present, the binders used in traditional silicon carbide grinding wheels are mainly glass binders and ceramic binders. For example, the Chinese invention patent with the announcement number CN117655936A discloses a grinding wheel, a binder, a silicon carbide ceramic grinding wheel and a preparation method thereof. The key points of its technical solution are: the binder is mainly composed of white clay powder, low-melting point boron glass powder, quartz powder and feldspar powder. Among them, the low-melting point boron glass powder can significantly reduce the refractoriness of the binder, so that the binder can achieve low-temperature sintering, and the binder has good melting fluidity at low temperatures, better wraps the silicon carbide abrasive, and finally makes the silicon carbide ceramic grinding wheel obtained by low-temperature sintering have higher strength; the main function of quartz powder is to increase the activity of the binder at a lower sintering temperature, so that the binder can participate in the reaction at a lower temperature, and also effectively improve the hardness of silicon carbide ceramics, while improving the grinding efficiency of abrasive particles and the grinding efficiency of silicon carbide ceramic grinding wheels, thereby extending the service life of silicon carbide ceramic grinding wheels.

[0004] Although the silicon carbide ceramic grinding wheel produced by the above patent has a high hardness, the binder in this method and the silicon carbide ceramic only form a mechanical connection. In a high-speed and high-impact environment, this mechanical bridging effect is very easy to fail, thereby limiting the service life of the grinding wheel. At the same time, the sintering time of the above patent is 10-14 hours. If silicon carbide is exposed to a hot environment for a long time, the mechanical properties will be greatly reduced.

[0005] The application of metal binders in diamond tools has achieved great success. However, they have not been effectively applied in silicon carbide grinding wheels. The main reason is that the reaction mechanism between metal binders and silicon carbide abrasives is unclear, and it is difficult to match the strength and toughness of the two.

[0006] Brazing has obvious advantages in the connection of silicon carbide ceramics and metals. During the brazing process, the metallurgical bonding of abrasives and metal binders can effectively improve the bonding strength and toughness of the grinding tool, reduce holes and cracks on the processed surface, and thus improve the surface grinding quality. The brazing time is short, which can reduce the processing time of silicon carbide grinding wheels. It has great potential in replacing traditional silicon carbide grinding tools.

[0007] However, there is currently little basic research on the application of brazing methods in silicon carbide abrasive tools. The shape retention and porosity of the matrix during brazing are issues worth considering. Specifically, on the one hand, the volume expansion of the matrix before and after brazing cannot be too large. If the volume of the matrix expands excessively during the sintering process, the metal binder will have a poor grip on the silicon carbide particles, and the expansion may cause the size of the green embryo to change, thereby affecting the final size and processing accuracy of the grinding wheel; in addition, uneven expansion of the green embryo may cause cracks on the surface of the grinding wheel or internal stress concentration. On the other hand, the abrasive tool should also have sufficient pores. If the chip space is small, it is easy to fail due to chip adhesion and clogging during grinding.

[0008] In view of this, the present invention is proposed. Summary of the invention

[0009] The first purpose of the present invention is to provide a method for preparing a brazed silicon carbide grinding wheel. After brazing, the silicon carbide abrasive and the metal binder form a chemical metallurgical bond, which significantly improves the bonding strength of the brazed silicon carbide grinding wheel, and the metal matrix has a good holding effect on the silicon carbide; and the brazing time is short. The problem of low bonding strength of the mechanical bonding between the abrasive and the binder in the prior art, which limits the service life of the grinding wheel, is solved.

[0010] The second purpose of the present invention is to provide a brazed silicon carbide grinding wheel, which has high bonding strength and a good holding effect of the metal matrix on silicon carbide, thereby improving the self-sharpening and grinding efficiency of the brazed silicon carbide grinding wheel. In addition, the brazed silicon carbide grinding wheel has a suitable porosity, good shape retention, and good mechanical properties, thereby broadening the application range of the brazed silicon carbide grinding wheel.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0012] The present invention first provides a method for preparing a brazed silicon carbide grinding wheel, comprising the following steps:

[0013] The silicon carbide abrasive, the metal binder and the auxiliary binder are mixed to obtain a mixture; wherein the metal binder is mainly composed of copper powder and titanium powder;

[0014] Cold pressing the mixed material to obtain a green abrasive ring;

[0015] Brazing the abrasive ring green body to obtain an abrasive ring;

[0016] After the abrasive ring is bonded to the aluminum core, the brazed silicon carbide grinding wheel is obtained.

[0017] Furthermore, the metal binder is composed of copper powder and titanium powder in a mass ratio of 4-6:3-5.

[0018] Furthermore, the auxiliary adhesive includes acrylic emulsion.

[0019] Furthermore, the mass ratio of the silicon carbide abrasive, the metal binder and the auxiliary binder is 35-50:40-60:5-20.

[0020] Furthermore, the method of mixing silicon carbide abrasive, metal binder and auxiliary binder comprises: firstly mixing and ball-milling the silicon carbide abrasive and the metal binder to obtain a premixed powder with a median particle size of 250 to 300 μm; then mixing the liquid auxiliary binder with the premixed powder, stirring evenly, and drying.

[0021] Furthermore, before the cold pressing forming, the mixed material is screened, the mesh size of the screen used for the screening is 20 to 350 meshes, and the number of screening times is ≥2 times.

[0022] Furthermore, the cold press forming pressure is 80 to 200 kN, and the holding time is 5 to 25 min.

[0023] Furthermore, the brazing is performed at a vacuum degree of 2×10 -3 ~7×10 -3 Pa in a vacuum environment.

[0024] Furthermore, the temperature is raised from room temperature to a brazing temperature of 1050-1150° C. at a heating rate of 5-10° C. / min, and the brazing holding time is 10-50 min.

[0025] Furthermore, the abrasive ring and the aluminum core are bonded together using a resin adhesive and a hardener.

[0026] The present invention further provides a brazed silicon carbide grinding wheel prepared according to the preparation method of the brazed silicon carbide grinding wheel. The brazed silicon carbide grinding wheel comprises an aluminum core and an abrasive ring arranged outside the aluminum core.

[0027] Furthermore, the composition of the abrasive ring is as follows by volume percentage: 30% to 45% silicon carbide abrasive, 35% to 60% metal binder, and 25% to 40% pores.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention provides a method for preparing a brazed silicon carbide grinding wheel. During the brazing process, the silicon carbide abrasive reacts with the titanium atoms in the metal binder to generate titanium carbide and various copper-silicon-titanium compounds, achieving a smooth transition between silicon carbide with covalent bonds as the main component and metal with metal bonds as the main component. The silicon carbide abrasive and the metal binder form a chemical metallurgical bond, which improves the metal matrix's holding effect on silicon carbide, forming a high-strength match, thereby improving the bonding strength of the brazed silicon carbide grinding wheel, extending the service life of the brazed silicon carbide grinding wheel, and improving the self-sharpening and grinding efficiency of the brazed silicon carbide grinding wheel. The problem of low bonding strength of the mechanical bonding between the abrasive and the binder in the prior art, which limits the service life of the grinding wheel, is solved.

[0030] (2) The preparation method of the brazed silicon carbide grinding wheel provided by the present invention has good matching between the metal binder and the silicon carbide abrasive, and the demolding success rate after cold pressing is as high as 99%. The abrasive ring green body has good shape retention before and after sintering, which reduces the processing time of the brazed silicon carbide grinding wheel.

[0031] (3) The preparation method of the brazed silicon carbide grinding wheel provided by the present invention adopts a suitable metal binder, so that the metal binder and the silicon carbide abrasive react in situ, and at the same time, the independent silicon carbide particles are connected into an integral network with controllable porosity. The present invention is a silicon carbide grinding wheel that can withstand a large load during high-speed grinding, and at the same time has excellent impact resistance and good shape retention. The expansion rate of the height and diameter of the matrix after brazing is low, which effectively shortens the dressing time of the silicon carbide grinding wheel.

[0032] (4) The preparation method of the brazed silicon carbide grinding wheel provided by the present invention, on the one hand, fixes the silicon carbide abrasive and the metal binder together by cold pressing; on the other hand, during the brazing process, the auxiliary binder volatilizes, and the titanium powder forms a binder bridge with the silicon carbide in situ, connecting the silicon carbide abrasive and the metal binder together. These two factors control the volume expansion of the matrix before and after brazing, thereby achieving the effect of maintaining the shape.

[0033] (5) The preparation method of the brazed silicon carbide grinding wheel provided by the present invention is conducive to the formation of pores in the brazed silicon carbide grinding wheel by adding an auxiliary binder. The porosity of the brazed silicon carbide grinding wheel is in the range of 20% to 55%, which can effectively increase the chip space, reduce the temperature of the grinding wheel during service, and reduce the thermal damage to the abrasive. The problem that the grinding tool has small pores, i.e., small chip space, which leads to failure due to adhesion and blockage of chips during grinding is solved.

[0034] (6) The preparation method of the brazed silicon carbide grinding wheel provided by the present invention does not add tin during the preparation process. Compared with the traditional tin-containing copper-based matrix, the mechanical properties of the tin-free brazed silicon carbide grinding wheel prepared by the present application are better and the holding effect of the silicon carbide abrasive is better.

[0035] (7) The method for preparing the brazed silicon carbide grinding wheel provided by the present invention has a short brazing time and can ensure good mechanical properties of the silicon carbide abrasive, thus solving the problem of the prior art that the mechanical properties of silicon carbide are greatly reduced due to the long sintering time. DETAILED DESCRIPTION

[0036] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If specific conditions are not indicated in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0037] If there is no special explanation, in the present invention, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "the first", "the second", "the third", "the fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0038] If there is no special explanation, the "include" and "comprising" mentioned in the present invention represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0039] If there is no special explanation, in the present invention, "one or more" or "at least one" refers to any one, any two or more of the listed items. Among them, "several" refers to any two or more of the listed items.

[0040] In a first aspect, the present invention provides a method for preparing a brazed silicon carbide grinding wheel, comprising the following steps:

[0041] Silicon carbide abrasive, metal binder and auxiliary binder are mixed to obtain a mixture. The metal binder is mainly composed of copper powder (metal copper) and titanium powder (metal titanium). Silicon carbide and metal matrix (formed by the reaction of copper and titanium) are solidified and matched to maximize the grinding performance.

[0042] The mixed material is cold pressed to obtain an abrasive ring green body.

[0043] The abrasive ring green body is brazed to obtain an abrasive ring. The purpose of brazing is to make the titanium powder and silicon carbide in the abrasive ring green body chemically react (not for welding, no need to add brazing agent and other materials). During the brazing process, the metallurgical bonding of silicon carbide abrasive and metal binder can effectively improve the bonding strength and toughness of the abrasive ring, reduce holes and cracks on the processed surface, and thus improve the surface grinding quality. In addition, the brazing time is short, the mechanical properties of silicon carbide abrasive are good, and the processing time of brazing silicon carbide grinding wheel can be reduced.

[0044] After the abrasive ring is bonded to the aluminum core, the brazed silicon carbide grinding wheel is obtained.

[0045] The present invention provides a method for preparing a brazed silicon carbide grinding wheel. After brazing, the silicon carbide abrasive and the metal binder form a chemical metallurgical bond, so the obtained brazed silicon carbide grinding wheel has a higher bonding strength, and the metal matrix has a good holding effect on silicon carbide. The improvement in bonding strength changes the defect of easy shedding of traditional silicon carbide abrasives. The silicon carbide particles change from overall shedding to small-area crushing, which effectively improves the self-sharpening of the brazed silicon carbide grinding wheel and greatly improves the grinding efficiency of the brazed silicon carbide grinding wheel. The problem of low bonding strength of the mechanical bonding between the abrasive and the binder in the prior art, which limits the service life of the grinding wheel, is solved.

[0046] Specifically, the metal binder and the silicon carbide abrasive have good matching properties, the demoulding success rate after cold pressing is as high as 99%, the abrasive ring green body has good shape retention before and after sintering, and the processing time of the brazed silicon carbide grinding wheel is reduced.

[0047] During the brazing process, the titanium atoms in the silicon carbide abrasive and the metal binder react to generate titanium carbide and various copper-silicon-titanium compounds, achieving a smooth transition between silicon carbide with covalent bonds as the main component and metal with metallic bonds as the main component, which is beneficial to improving the metal matrix's holding effect on silicon carbide and forming a high-strength match. The binder bridge is effectively broken during grinding, the grinding wheel has good self-sharpening properties, and has extremely good grinding performance. It can be used to process ceramics and titanium alloys, expanding the application range of brazed silicon carbide grinding wheels.

[0048] Suitable metal binder allows the metal binder and silicon carbide abrasive to react in situ while connecting independent silicon carbide particles into an integral network with controllable porosity. It is a silicon carbide grinding wheel that can withstand heavy loads during high-speed grinding and has excellent impact resistance and good shape retention. The expansion rate of the height and diameter of the matrix after brazing is low, which effectively shortens the dressing time of the silicon carbide grinding wheel.

[0049] Furthermore, the present invention fixes the silicon carbide abrasive and the metal binder together by cold pressing on the one hand, and on the other hand, during the brazing process, the auxiliary binder volatilizes, and the titanium powder forms a binder bridge with the silicon carbide in situ, connecting the silicon carbide abrasive and the metal binder together. These two factors control the volume expansion of the matrix before and after brazing, thereby achieving the effect of maintaining the shape.

[0050] Furthermore, the invention adds an auxiliary binder, which is beneficial to the formation of pores in the brazed silicon carbide grinding wheel. The porosity of the brazed silicon carbide grinding wheel ranges from 20% to 55%, which can effectively increase the chip space, reduce the temperature of the grinding wheel during service, and reduce thermal damage to the abrasive.

[0051] In addition, the prior art often adds tin powder with a low melting point, usually because the higher brazing temperature easily causes thermal damage to diamond and CBN abrasives. In order to reduce the required heating temperature, tin is often added to the binder. However, silicon carbide abrasives have good thermal stability, and there is no need to consider the performance loss caused by too high a brazing temperature. In addition, the tin element has a negative impact on silicon carbide grinding wheels. The addition of tin elements easily causes thermal cracks to initiate inside the alloy, which reduces the mechanical properties of the metal matrix. The presence of some copper-tin compounds also greatly reduces the strength of the matrix and cannot inhibit the expansion of cracks. Therefore, compared with tin-containing copper-based matrix, the mechanical properties of the tin-free brazed silicon carbide grinding wheel prepared in this application are better, and the holding effect on silicon carbide abrasives is better.

[0052] In some specific implementations, after brazing, the expansion rate of the height and diameter of the abrasive ring is less than 5%, thereby reducing the subsequent dressing time.

[0053] In some specific embodiments, the metal binder is composed of copper powder and titanium powder in a mass ratio of 4-6:3-5, wherein the mass ratio of the two is, for example, 4:3, 4:4, 4:5, 5:3, 5:4, 6:3, 6:4 or 6:5.

[0054] In some specific implementations, the composition of the metal binder is calculated by mass percentage as follows: 40% to 60% copper powder, 30% to 50% titanium powder, wherein the sum of the mass percentages of Cu powder and Ti powder is 100%.

[0055] Among them, copper powder has two main functions: on the one hand, it lowers the melting point, thereby promoting the reaction between titanium powder and silicon carbide to form a binder bridge to ensure high-strength bonding; on the other hand, copper reacts with titanium to form a matrix material that holds silicon carbide. The matrix material is mainly composed of copper solid solution and copper-titanium compounds, and has high strength, which can ensure that silicon carbide will not fall off preferentially during the grinding process.

[0056] In addition, by using the copper powder and titanium powder in the above mass ratio, a copper-titanium compound CuTi2 can be formed, which has excellent strength and toughness, can inhibit the expansion and initiation of cracks, and can also prevent the base material from breaking before the silicon carbide falls off.

[0057] In some specific implementations, the auxiliary binder includes acrylic emulsion. The use of the auxiliary binder is conducive to the formation of pores in the brazed silicon carbide grinding wheel.

[0058] Compared with other auxiliary binders, acrylic emulsion has excellent bonding performance and good processability, which is conducive to the molding of green embryos. In addition, during the sintering process, the auxiliary binder will volatilize into the furnace, while acrylic emulsion is environmentally friendly and pollution-free. Therefore, acrylic emulsion has an excellent application effect in the preparation process of grinding wheels.

[0059] In some specific embodiments, the mass ratio of the silicon carbide abrasive, the metal binder and the auxiliary binder is 35-50 (e.g., 38, 40, 43, 45 or 47): 40-60 (e.g., 43, 45, 50, 55 or 58): 5-20 (e.g., 6, 8, 10, 13, 15 or 18). This ratio is beneficial to improving the bonding strength and toughness of the abrasive ring, increasing the service life of the brazed silicon carbide grinding wheel, improving the surface grinding quality and grinding efficiency, and controlling the expansion rate, shape retention and porosity.

[0060] In some specific embodiments, the method of mixing silicon carbide abrasive, metal binder and auxiliary binder comprises: firstly mixing and ball-milling the silicon carbide abrasive and the metal binder to obtain a premixed powder with a median particle size of 250 to 300 μm (e.g., 260 μm, 270 μm, 280 μm or 290 μm); this particle size range can maintain stability for a longer time because their cutting action is relatively mild, so the life of the silicon carbide grinding wheel is longer. Then the liquid auxiliary binder is mixed with the premixed powder, stirred evenly, and dried. Preferably, the ball milling is carried out in ethanol (alcohol); the ball milling time is 60 to 120 min; the ball milling frequency is 10 to 30 Hz. Preferably, the stirring time is 0.5 to 3 h.

[0061] In some specific implementations, the humidity of the mixed material obtained after the liquid auxiliary binder and the premixed powder are mixed and stirred uniformly is 5% to 15%, wherein the humidity refers to the mass fraction of water in the mixed material.

[0062] In some specific embodiments, the drying method includes but is not limited to drying, for example, placing the mixed material in a drying oven at 50-65°C, keeping the temperature for 0.5-1h, and drying until the mass loss is 5%-15%. The acrylic emulsion evaporates during the drying process, and controlling the mass loss can ensure the strength of the green body, facilitate transfer to the furnace, and ensure that it will not crack in the early stage of sintering.

[0063] In some specific embodiments, the cold pressing process further includes a step of sieving the mixture to control the particle size of the mixture, the mesh size of the sieve used for sieving is 20 to 350 meshes (e.g., 50 meshes, 100 meshes, 150 meshes, 200 meshes, 250 meshes or 300 meshes), and the number of sieving is ≥ 2 times (e.g., 3 times, 4 times, 5 times or more). Sieving can avoid the phenomenon of agglomeration of materials after the auxiliary binder is added, and prevent the occurrence of uneven filler during the cold pressing process.

[0064] In some specific embodiments, the pressure of the cold press molding is 80 to 200 kN, including but not limited to any one of 80 kN, 100 kN, 120 kN, 130 kN, 150 kN, 180 kN, and 200 kN, or a range between any two of them; the holding time of the cold press molding is 5 to 25 min, including but not limited to any one of 10 min, 15 min, and 20 min, or a range between any two of them.

[0065] Cold pressing can obtain porous abrasive rings with higher porosity.

[0066] The cold pressing pressure used in this application is relatively small, and many pores will remain in the green abrasive ring. Although the copper-titanium powder will melt and react with silicon carbide during the brazing process, there will be a slight expansion at the joint, but it is not obvious.

[0067] It can be understood that after the mixed material is sieved, it is put into a mold for cold pressing and after the cold pressing is completed, it is demoulded to obtain the abrasive ring green body.

[0068] In some specific embodiments, the brazing is performed at a vacuum degree of 2×10 -3 ~7×10 -3 Pa in a high vacuum environment; the vacuum degree is, for example, 3×10 -3 Pa, 4×10 -3 Pa, 5×10 -3 Pa or 6×10 -3 Pa.

[0069] In some specific embodiments, the temperature is increased from room temperature to a brazing temperature of 1050-1150°C (e.g., 1070°C, 1080°C, 1100°C, 1120°C, or 1140°C) at a heating rate of 5-10°C / min (e.g., 6°C / min, 7°C / min, 8°C / min, or 9°C / min), and the brazing holding time is 10-50 min (e.g., 20 min, 30 min, or 40 min).

[0070] The preparation method of the brazed silicon carbide grinding wheel provided by the present invention has a short brazing time, and the total brazing process time is 4 to 8 hours, which can ensure that the mechanical properties of the silicon carbide abrasive are good, shorten the production time, improve the production efficiency, and reduce the energy consumption and production cost. The problem that the mechanical properties of silicon carbide are greatly reduced due to the long sintering time (10 to 14 hours) in the prior art is solved.

[0071] In some specific implementations, after brazing is completed, the abrasive ring blank is cooled to ≤40° C. and taken out of the furnace to obtain the abrasive ring blank.

[0072] In some specific embodiments, the abrasive ring and the aluminum core are bonded using a resin adhesive and a hardener, wherein the bonding is mechanical bonding. The burrs are then removed by grinding and trimming to obtain a brazed silicon carbide grinding wheel. Preferably, the resin adhesive includes a phenolic resin, and the hardener includes a peroxide hardener, such as dibenzoyl peroxide.

[0073] In a second aspect, the present invention provides a brazed silicon carbide grinding wheel obtained by the method for preparing the brazed silicon carbide grinding wheel, wherein the brazed silicon carbide grinding wheel comprises an aluminum core and an abrasive ring disposed outside the aluminum core, wherein the abrasive ring surrounds the aluminum core.

[0074] The brazed silicon carbide grinding wheel prepared by the present invention has high bonding strength, and the metal matrix has good holding effect on silicon carbide, thereby improving the self-sharpening and grinding efficiency of the brazed silicon carbide grinding wheel. In addition, the brazed silicon carbide grinding wheel has suitable porosity, good shape retention and good mechanical properties, thereby broadening the application range of the brazed silicon carbide grinding wheel.

[0075] In some specific embodiments, the composition of the abrasive ring is as follows by volume percentage: 30% to 45% (e.g., 33%, 35%, 38%, 40% or 42%) of silicon carbide abrasive, 35% to 60% (e.g., 40%, 45%, 48%, 50%, 52%, 55% or 58%) of metal binder, and 25% to 40% (e.g., 28%, 30%, 35% or 37%) of pores. The sum of the volume percentages of silicon carbide abrasive, metal binder and pores is 100%.

[0076] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0077] The “parts” in the following embodiments and comparative examples of the present invention are all parts by mass.

[0078] Example 1

[0079] The preparation method of the brazed silicon carbide grinding wheel provided in this embodiment comprises the following steps:

[0080] (1) 35 parts of silicon carbide abrasive and 50 parts of metal binder were mixed and ball-milled in alcohol for 60 minutes to obtain a premixed powder with a median particle size of 250 μm. The metal binder was composed of copper powder and titanium powder in a mass ratio of 6:4. Then, 15 parts of acrylic emulsion (auxiliary binder) were uniformly mixed with the premixed powder by stirring, wherein the stirring time was 0.5 h, to obtain a mixture. That is, the mass ratio of silicon carbide abrasive, metal binder and auxiliary binder was 35:50:15. The mixture was then placed in a drying oven at 60°C for drying, and the mass loss of the mixture after drying was 6%. The dried mixture was then sieved 3 times, wherein the mesh size of the sieve used for sieving was 60 mesh.

[0081] (2) The sieved mixture obtained in step (1) is placed into a mold for cold pressing, wherein the cold pressing pressure is 80 kN and the holding time is 25 min. After demolding, the abrasive ring green body is obtained.

[0082] (3) The abrasive ring green body obtained in step (2) is placed in a vacuum of 7×10 -3 Pa's high vacuum environment, wherein the temperature was raised from room temperature to a brazing temperature of 1080°C at a heating rate of 10°C / min, the brazing holding time was 20 min, and after the brazing was completed, the temperature was cooled to ≤40°C and taken out of the furnace to obtain an abrasive ring.

[0083] (4) Using a resin adhesive (phenolic resin) and a hardener (benzoyl peroxide), the abrasive ring obtained in step (3) is bonded to the aluminum core, and the burrs are removed by grinding and trimming to obtain a brazed silicon carbide grinding wheel. The composition of the abrasive ring in the brazed silicon carbide grinding wheel is as follows by volume percentage: 32% silicon carbide abrasive, 40% metal binder, and 28% pores.

[0084] Example 2

[0085] The preparation method of the brazed silicon carbide grinding wheel provided in this embodiment comprises the following steps:

[0086] (1) 45 parts of silicon carbide abrasive and 45 parts of metal binder were mixed and ball-milled in alcohol for 120 minutes to obtain a premixed powder with a median particle size of 300 μm. The metal binder was composed of copper powder and titanium powder in a mass ratio of 5:5. Then, 10 parts of acrylic emulsion (auxiliary binder) were uniformly mixed with the premixed powder by stirring for 3 hours to obtain a mixture. That is, the mass ratio of silicon carbide abrasive, metal binder and auxiliary binder was 45:45:10. The mixture was then placed in a drying oven at 60°C for drying, and the mass loss of the mixture after drying was 10%. The dried mixture was then sieved 4 times, and the mesh size of the sieve used for sieving was 50 mesh.

[0087] (2) The sieved mixture obtained in step (1) is placed into a mold for cold pressing, wherein the cold pressing pressure is 200 kN and the holding time is 5 min. After demolding, an abrasive ring green body is obtained.

[0088] (3) The abrasive ring green body obtained in step (2) is placed in a vacuum of 2×10 -3 Pa's high vacuum environment, wherein the temperature was raised from room temperature to a brazing temperature of 1050°C at a heating rate of 5°C / min, the brazing holding time was 30min, and after the brazing was completed, the temperature was cooled to ≤40°C and the abrasive ring was obtained.

[0089] (4) Using a resin adhesive (phenolic resin) and a hardener (benzoyl peroxide), the abrasive ring obtained in step (3) is bonded to the aluminum core, and the burrs are removed by grinding and trimming to obtain a brazed silicon carbide grinding wheel. The composition of the abrasive ring in the brazed silicon carbide grinding wheel is as follows by volume percentage: 35% silicon carbide abrasive, 40% metal binder, and 25% pores.

[0090] Example 3

[0091] The preparation method of the brazed silicon carbide grinding wheel provided in this embodiment comprises the following steps:

[0092] (1) 40 parts of silicon carbide abrasive and 40 parts of metal binder were mixed and ball-milled in alcohol for 90 minutes to obtain a premixed powder with a median particle size of 250 μm. The metal binder was composed of copper powder and titanium powder in a mass ratio of 6:4. Then, 20 parts of acrylic emulsion (auxiliary binder) were uniformly mixed with the premixed powder by stirring for 3 hours to obtain a mixture. That is, the mass ratio of silicon carbide abrasive, metal binder and auxiliary binder was 40:40:20. The mixture was then placed in a drying oven at 50°C for drying, and the mass loss of the mixture after drying was 5%. The dried mixture was then sieved twice, and the mesh size of the sieve used for sieving was 200 mesh.

[0093] (2) The sieved mixture obtained in step (1) is placed into a mold for cold pressing, wherein the cold pressing pressure is 120 kN and the holding time is 15 min. After demolding, the abrasive ring green body is obtained.

[0094] (3) The abrasive ring green body obtained in step (2) is placed in a vacuum of 7×10 -3 Pa's high vacuum environment, wherein the temperature was raised from room temperature to a brazing temperature of 1150°C at a heating rate of 10°C / min, the brazing holding time was 10 min, and after the brazing was completed, the temperature was cooled to ≤40°C and taken out of the furnace to obtain an abrasive ring.

[0095] (4) Using a resin adhesive (phenolic resin) and a hardener (benzoyl peroxide), the abrasive ring obtained in step (3) is bonded to the aluminum core, and the burrs are removed by grinding and trimming to obtain a brazed silicon carbide grinding wheel. The composition of the abrasive ring in the brazed silicon carbide grinding wheel is as follows by volume percentage: 35% silicon carbide abrasive, 37% metal binder, and 28% pores.

[0096] Example 4

[0097] The preparation method of the brazed silicon carbide grinding wheel provided in this embodiment comprises the following steps:

[0098] (1) 40 parts of silicon carbide abrasive and 55 parts of metal binder were mixed and ball-milled in alcohol for 90 minutes to obtain a premixed powder with a median particle size of 250 μm. The metal binder was composed of copper powder and titanium powder in a mass ratio of 5:5. Then, 5 parts of acrylic emulsion (auxiliary binder) were uniformly mixed with the premixed powder by stirring for 3 hours to obtain a mixture. That is, the mass ratio of silicon carbide abrasive, metal binder and auxiliary binder was 40:55:5. The mixture was then placed in a drying oven at 50°C for drying, and the mass loss of the mixture after drying was 5%. The dried mixture was then sieved 5 times, and the mesh size of the sieve used for sieving was 300 mesh.

[0099] (2) The sieved mixture obtained in step (1) is placed into a mold for cold pressing, wherein the cold pressing pressure is 80 kN and the holding time is 15 min. After demolding, the abrasive ring green body is obtained.

[0100] (3) The abrasive ring green body obtained in step (2) is placed in a vacuum of 2×10 -3 Pa's high vacuum environment, wherein the temperature was raised from room temperature to a brazing temperature of 1050°C at a heating rate of 5°C / min, the brazing holding time was 10min, and after the brazing was completed, the temperature was cooled to ≤40°C and taken out of the furnace to obtain an abrasive ring.

[0101] (4) Using a resin adhesive (phenolic resin) and a hardener (benzoyl peroxide), the abrasive ring obtained in step (3) is bonded to the aluminum core, and the burrs are removed by grinding and trimming to obtain a brazed silicon carbide grinding wheel. The composition of the abrasive ring in the brazed silicon carbide grinding wheel is as follows by volume percentage: 38% silicon carbide abrasive, 35% metal binder, and 27% pores.

[0102] Comparative Example 1

[0103] The preparation method of the brazed silicon carbide grinding wheel provided in this comparative example is basically the same as that in Example 1, except that the metal binder is replaced with pure titanium powder (the amount of the metal binder added remains unchanged).

[0104] The composition of the abrasive ring in the brazed silicon carbide grinding wheel obtained in this comparative example is as follows by volume: 36% silicon carbide abrasive, 53% metal binder, and 11% pores.

[0105] Comparative Example 2

[0106] The preparation method of the brazed silicon carbide grinding wheel provided in this comparative example is basically the same as that in Example 1, except that the metal binder is replaced with pure copper powder (the amount of the metal binder added remains unchanged).

[0107] The composition of the abrasive ring in the brazed silicon carbide grinding wheel obtained in this comparative example is as follows by volume: 50% silicon carbide abrasive, 36% metal binder, and 14% pores.

[0108] Comparative Example 3

[0109] The preparation method of the brazed silicon carbide grinding wheel provided in this comparative example is basically the same as that in Example 1, except that the metal binder is composed of copper powder and titanium powder in a mass ratio of 2:8.

[0110] The composition of the abrasive ring in the brazed silicon carbide grinding wheel obtained in this comparative example is as follows by volume: 35% silicon carbide abrasive, 45% metal binder, and 20% pores.

[0111] Comparative Example 4

[0112] The preparation method of the brazed silicon carbide grinding wheel provided in this comparative example is basically the same as that of Example 1, except that no acrylic emulsion is added.

[0113] The composition of the abrasive ring in the brazed silicon carbide grinding wheel obtained in this comparative example is as follows by volume: 40% silicon carbide abrasive, 52% metal binder, and 8% pores.

[0114] Comparative Example 5

[0115] The preparation method of the brazed silicon carbide grinding wheel provided in this comparative example is basically the same as that in Example 1, except that the cold pressing pressure is replaced with 20 kN.

[0116] The composition of the abrasive ring in the brazed silicon carbide grinding wheel obtained in this comparative example is as follows by volume percentage: 30% silicon carbide abrasive, 32% metal binder, and 38% pores.

[0117] Experimental example

[0118] The grinding performance of the brazed silicon carbide grinding wheels prepared in each embodiment and each comparative example was tested, and the results are shown in Table 1.

[0119] Table 1 Grinding performance test results

[0120] Group Forming rate (%) Grinding performance Example 1 99 Good grinding performance, can be self-sharpened in time Example 2 99 Good grinding performance, can be self-sharpened in time Example 3 99 Good grinding performance, can be self-sharpened in time Example 4 99 Good grinding performance, can be self-sharpened in time Comparative Example 1 75 The grinding wheel is worn over a large area and needs to be repaired before being used again Comparative Example 2 71 The grinding wheel is worn over a large area and needs to be repaired before being used again Comparative Example 3 80 Silicon carbide grinding wheels have poor self-sharpening properties Comparative Example 4 42 The abrasive ring of the silicon carbide grinding wheel is broken Comparative Example 5 36 The abrasive ring of the silicon carbide grinding wheel is broken

[0121] It can be seen from Table 1 that, compared with the comparative examples, the brazed silicon carbide grinding wheels prepared in the embodiments have good grinding performance.

[0122] Among them, since no copper powder is added in Comparative Example 1, the metal binder has a very poor holding effect on the silicon carbide abrasive grains.

[0123] In Comparative Example 2, since titanium powder is not added, the metal binder has a very poor holding effect on the silicon carbide abrasive grains.

[0124] In Comparative Example 3, due to the unsuitable copper-titanium ratio in the metal binder, cracks appeared on the surface of the abrasive ring.

[0125] In Comparative Example 4, since no auxiliary binder was added, large cracks appeared on the surface of the abrasive ring.

[0126] In Comparative Example 5, the cold pressing pressure is too low, which makes it difficult to form the green embryo.

[0127] In addition, the brazed silicon carbide grinding wheel obtained in each embodiment of the present invention can be used stably for a long time at a rotation speed of 200 rpm and a pressure of 150N when grinding silicon nitride ceramics, and the friction coefficient is maintained at about 0.1. In the same time, its wear ratio is higher than that of imported silicon carbide grinding wheels, and its grinding efficiency and service life are better than those of imported grinding wheels. Since the brazed silicon carbide grinding wheel prepared by the present invention has high strength and excellent porosity, the friction coefficient is maintained at a low value during the grinding process. When the porosity of the abrasive ring is 25% to 40%, the brazed silicon carbide grinding wheel of the present invention is used to grind high-strength titanium alloy materials under alkaline coolant. After grinding, the surface morphology is good, and the surface roughness can reach 0.8 microns, which broadens the processing range of the silicon carbide grinding wheel.

[0128] In summary, the brazed silicon carbide grinding wheel prepared by the present invention has high bonding strength, the metal matrix has a good holding effect on silicon carbide, the self-sharpening and grinding efficiency of the brazed silicon carbide grinding wheel are improved, and the brazed silicon carbide grinding wheel has a suitable porosity, good shape retention, and good mechanical properties, which is conducive to wide promotion and use.

[0129] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing a brazed silicon carbide grinding wheel, characterized in that: The steps include: The silicon carbide abrasive, the metal binder and the auxiliary binder are mixed to obtain a mixture; wherein the metal binder is mainly composed of copper powder and titanium powder; Cold pressing the mixed material to obtain a green abrasive ring; Brazing the abrasive ring green body to obtain an abrasive ring; After the abrasive ring is bonded to the aluminum core, the brazed silicon carbide grinding wheel is obtained.

2. The method for preparing a brazed silicon carbide grinding wheel according to claim 1, characterized in that: The metal binder is composed of copper powder and titanium powder in a mass ratio of 4-6:3-5; And / or, the auxiliary binder includes acrylic emulsion.

3. The method for preparing a brazed silicon carbide grinding wheel according to claim 1, characterized in that: The mass ratio of the silicon carbide abrasive, the metal binder and the auxiliary binder is 35-50:40-60:5-20.

4. The method for preparing a brazed silicon carbide grinding wheel according to claim 1, characterized in that: The method for mixing silicon carbide abrasive, metal binder and auxiliary binder comprises: firstly mixing and ball-milling the silicon carbide abrasive and the metal binder to obtain a premixed powder with a median particle size of 250 to 300 μm; then mixing and stirring the liquid auxiliary binder with the premixed powder evenly, and drying.

5. The method for preparing a brazed silicon carbide grinding wheel according to claim 1, characterized in that: The method further comprises the step of screening the mixed material before the cold pressing, wherein the mesh number of the sieve used for the screening is 20 to 350 meshes, and the number of screening times is ≥2 times.

6. The method for preparing a brazed silicon carbide grinding wheel according to claim 1, characterized in that: The cold press forming pressure is 80-200 kN, and the holding time is 5-25 min.

7. The method for preparing a brazed silicon carbide grinding wheel according to claim 1, characterized in that: The brazing is carried out at a vacuum degree of 2×10 -3 ~7×10 -3 Pa in a vacuum environment; And / or, the temperature is raised from room temperature to a brazing temperature of 1050-1150° C. at a heating rate of 5-10° C. / min, and the brazing holding time is 10-50 min.

8. The method for preparing a brazed silicon carbide grinding wheel according to claim 1, characterized in that: The abrasive ring is bonded to the aluminum core using a resin adhesive and a hardener.

9. The brazed silicon carbide grinding wheel obtained by the method for preparing a brazed silicon carbide grinding wheel according to any one of claims 1 to 8, characterized in that: The brazed silicon carbide grinding wheel comprises an aluminum core and an abrasive ring arranged outside the aluminum core.

10. The brazed silicon carbide grinding wheel according to claim 9, characterized in that: The composition of the abrasive ring is as follows by volume percentage: 30% to 45% of silicon carbide abrasive, 35% to 60% of metal binder, and 25% to 40% of pores.