Method and device for preparing copper-based diamond superhard grinding wheel by spark plasma sintering

Abstract

This invention relates to the field of superhard abrasive technology, specifically to a method and apparatus for preparing copper-based diamond superhard grinding wheels by spark plasma sintering. The method includes the following steps: sintering a mixture containing diamond abrasive and a metal binder using spark plasma sintering to obtain an integrally formed abrasive ring; the metal binder mainly consists of bronze powder and titanium powder; and bonding the abrasive ring with a steel core to obtain the copper-based diamond superhard grinding wheel. This invention eliminates the need for binders, drying, sieving steps, and cold pressing. It directly forms the abrasive ring integrally after spark plasma sintering, resulting in a short process flow and high production efficiency. Furthermore, the spark plasma sintering method allows for rapid heating and short holding time, and the resulting abrasive ring has low porosity, reducing diamond detachment during part processing and significantly decreasing wear weight loss.

Description

Technical Field

[0001] This invention relates to the field of superhard abrasive technology, and more specifically, to a method and apparatus for preparing copper-based diamond superhard grinding wheels by spark plasma sintering. Background Technology

[0002] With the development of modern machining towards higher precision, higher speed, harder machining, dry machining (without coolant), and lower costs, the performance requirements for grinding wheels have become increasingly stringent. Traditional silicon carbide and corundum abrasive molds can no longer fully meet the current demands for high-speed, high-efficiency, and high-precision grinding. Therefore, developing various superhard grinding materials with excellent wear resistance and stable machining capabilities over extended periods is an inevitable trend. Currently, commonly used superhard grinding materials include diamond and cubic boron nitride. Diamond is the hardest material and has extremely high wear resistance, making it suitable for high-speed and ultra-precision grinding. Diamond grinding wheels are ideal for grinding harder, brittle materials with short shavings, such as non-ferrous metals, carbides, glass, ceramics, quartz products, and semiconductor and chip materials. The grinding efficiency, machining accuracy, and wear resistance of diamond superhard grinding wheels are key issues in high-speed precision grinding.

[0003] In superhard abrasives, the binder used to bond the abrasive grains is a key factor affecting the performance of the superhard abrasive. Traditional superhard abrasives (grinding wheels) are mostly manufactured using processes such as resin, ceramic, and metal binder sintering and electroplating. A problem with this is that the single-crystal grains are merely mechanically embedded in the binder and electroplating layer, resulting in weak interaction between the grains and the binder / plating layer. Specifically, while resin binders are relatively easy to process and dress, they have poor heat resistance, low bonding strength, and significant abrasive detachment, severely impacting efficiency. Ceramic binders are relatively easy to dress and can be used at high temperatures; however, they are brittle, have poor impact toughness and fatigue resistance, and are prone to cracking, making them unsuitable for high-speed machining. Although metal binder sintering offers strong heat resistance, a chemical metallurgical bond usually cannot form between the binder and the abrasive grains; therefore, the abrasive grains are merely mechanically embedded in the binder, resulting in limited holding force. In metal electroplating, abrasive grains are merely mechanically embedded, making the grinding wheel prone to overall failure due to abrasive grain shedding and plating peeling off in sheets. This is especially noticeable when grinding materials that are difficult to machine efficiently. In addition, with thick plating, low abrasive grain exposure height, and small chip space, the grinding wheel is easily blocked by chip adhesion during grinding, leading to failure.

[0004] Traditional methods for manufacturing diamond grinding wheels typically involve cold pressing to create a green wheel blank, followed by vacuum high-temperature sintering to create the abrasive ring, and finally bonding the steel core to the abrasive ring to produce the diamond grinding wheel. (See [link to documentation]). Figure 1As shown, the specific operation is as follows: The composition and proportions of the raw materials are determined, and then the raw materials are weighed and mixed. The uniformly mixed powder is then poured into a beaker, a binder is added, and the mixture is stirred. The mixture is then placed in a drying oven to dry. After drying, the powder is sieved, and a certain amount of the mixture is placed into a custom mold. It is then cold-pressed using a press, and after holding the pressure, it is demolded to obtain a green blank. The green blank is placed in a vacuum high-temperature furnace for sintering, and then cooled with the furnace to obtain an abrasive ring. Finally, the abrasive ring is combined with a steel core for assembly and finishing to obtain a diamond grinding wheel. Although this method improves the method of embedding diamond with binder and increases the bonding strength between diamond and metal matrix, the above method has the following disadvantages: (1) The processing flow is complicated, the process is long, and the production efficiency is low; (2) During the cold pressing stage, the green blank will adhere to the mold surface when demolding, causing shape defects of the green blank; (3) During the preparation process, binder needs to be added, sieved and dried, and the quality loss of binder during drying is not easy to control; (4) The heating rate of vacuum high temperature sintering is slow, the holding time is long, and the porosity of the abrasive ring prepared after sintering is high, which makes it easy for diamond to fall off when processing parts, resulting in significant abrasive loss.

[0005] Furthermore, patent application number CN201710819270.9 discloses a method for creating a composite material in which a high-entropy alloy holds abrasive particles. The method involves heating and melting various raw materials, then using gas atomization to obtain high-entropy alloy powder. The obtained powder is then mechanically ball-milled to activate the alloy powder particles. The activated high-entropy alloy powder is then mixed with abrasive particles to obtain a uniform powder. Finally, the powder is poured into a mold and subjected to spark plasma sintering to obtain the composite material. However, the composite material obtained by this patent is commonly used for cutting stone, refractory materials, and glass, belonging to the field of high-entropy alloys, but not to the field of superhard abrasives, and is not suitable for processing steel parts or semiconductor silicon wafers. This patent combines high-entropy alloys and abrasives through an embedded holding method. If this type of combination is used for processing parts or removing rust, the abrasive is prone to detaching from the metal matrix, causing damage to the abrasive. This type of combination exhibits poor wear resistance. In addition, the patent has the following disadvantages: (1) The high-entropy alloy powder particles obtained by the gas atomization method are large, which leads to uneven contact with abrasive particles during sintering and easy porosity; (2) The high-entropy alloy powder particles need to be activated by mechanical ball milling, which makes the process complicated; (3) The composite cylindrical blank obtained after the discharge plasma sintering needs to be further processed to obtain the abrasive ring for the grinding wheel; (4) The high-entropy alloy and abrasive are bonded by inlay bonding, and Mo reacts with the abrasive but is not strong.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The primary objective of this invention is to provide a method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering. This method eliminates the need for binders, drying and sieving steps, and cold pressing. The invention directly pours the mixture into a mold for spark plasma sintering, resulting in a one-piece abrasive ring. This process is simple, short, and highly efficient. Furthermore, the spark plasma sintering method allows for rapid heating and short holding times, and the resulting abrasive ring has low porosity, reducing diamond shedding during machining and significantly decreasing wear weight loss. This method solves the problems of traditional diamond grinding wheel preparation methods, which involve first cold pressing to prepare a green wheel blank and then vacuum high-temperature sintering to prepare the abrasive ring. These problems include long processes, low production efficiency, defects in the green wheel blank, and high porosity in the prepared abrasive ring.

[0008] The second objective of this invention is to provide a device with a simple structure and easy manufacturing process. The mixture can be directly integrally formed into an abrasive ring with low porosity after being sintered by spark plasma in the device, avoiding the possibility of demolding failure in cold pressing and saving processing time and improving production efficiency.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0010] This invention first provides a method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering, comprising the following steps: subjecting a mixture containing diamond abrasive and a metal binder to spark plasma sintering to obtain an integrally formed abrasive ring; the metal binder is mainly composed of bronze powder and titanium powder; after the abrasive ring is combined with a steel core, the copper-based diamond superhard grinding wheel is obtained.

[0011] Furthermore, the mass ratio of the diamond abrasive to the metal binder is 40-48:52-60.

[0012] Furthermore, the metal binder is composed of bronze powder and titanium powder in a mass ratio of 90-95:5-10.

[0013] Furthermore, the bronze powder is Cu60Sn40 bronze powder.

[0014] Furthermore, the preparation method of the mixture includes: uniformly mixing the diamond abrasive, the bronze powder, and the titanium powder; or, plasma atomizing the bronze powder to obtain ultrafine bronze powder, ball milling the titanium powder and the diamond abrasive to obtain titanium-coated diamond powder, and uniformly mixing the ultrafine bronze powder and the titanium-coated diamond powder.

[0015] Furthermore, the plasma gas used for plasma atomization includes argon.

[0016] Furthermore, the median particle size of the bronze powder is 40–80 μm.

[0017] Furthermore, the median particle size of the ultrafine bronze powder is 25–40 μm.

[0018] Furthermore, the ball milling time is 10–24 hours, the ball milling speed is 150–280 r / min, and the ball-to-material ratio is 5–18:1.

[0019] Furthermore, the pressure of the discharge plasma sintering is 25–30 MPa.

[0020] Furthermore, the reaction temperature of the discharge plasma sintering is 930–980 °C.

[0021] Furthermore, the heating rate of the discharge plasma sintering is 50–100 °C / min.

[0022] Furthermore, the holding time for the discharge plasma sintering is 1 to 10 minutes.

[0023] Furthermore, the atmosphere for the discharge plasma sintering is an argon atmosphere.

[0024] Furthermore, the DC pulse output current of the discharge plasma sintering is 4500–5500 A.

[0025] Furthermore, the pulse frequency of the discharge plasma sintering is 20–30 ms.

[0026] Furthermore, the density of the abrasive ring is 80% to 85%.

[0027] This invention further provides an apparatus suitable for the method of preparing copper-based diamond superhard grinding wheels by spark plasma sintering. The apparatus serves as a mold for spark plasma sintering of the mixture. The apparatus includes an inner graphite column, an outer graphite sleeve, an upper pressure head base, and a lower pressure head base. The upper pressure head base includes an integrally formed, non-removable upper pressure plate and an upper pressure ring, and the lower pressure head base includes an integrally formed, non-removable lower pressure plate and a lower pressure ring. The upper and lower pressure rings are annular in shape. The inner graphite column is cylindrical, and the outer graphite sleeve is annular. The outer graphite sleeve is fitted around the inner graphite column, and there is a receiving space between the outer graphite sleeve and the inner graphite column for accommodating the upper and lower pressure rings. The inner graphite column, the outer graphite sleeve, the upper pressure head base, and the lower pressure head base surround and form a reaction chamber, where the mixture is sintered by spark plasma within the reaction chamber to form an abrasive ring.

[0028] Furthermore, at least one layer of graphite paper is provided on the inner wall of the outer graphite sleeve, at least one layer of graphite paper is provided on the outer wall of the inner graphite column, at least one layer of graphite paper is provided on the outer surface of the lower pressure head base, and at least one layer of graphite paper is provided on the outer surface of the upper pressure head base.

[0029] Furthermore, the outer surface of the graphite paper is covered with at least one layer of porous graphite insulating layer.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) The method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering provided by this invention does not require the addition of binders during the abrasive preparation process, nor does it require drying, sieving, or cold pressing. The mixture is directly poured into a mold for spark plasma sintering, which is simple, has a short process, and high production efficiency. At the same time, the heating rate of spark plasma sintering is relatively fast, and the processing can be completed in a short time. Moreover, the porosity of the abrasive ring obtained after spark plasma sintering is low, which can withstand a large load during high-speed grinding. It is not easy for diamond to fall off when processing parts, and it also has excellent impact resistance and good shape retention.

[0032] (2) The method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering provided by the present invention obtains fine metal bronze powder particles by plasma atomization, which are half the particle size of powder obtained by atomization. During the sintering process, it is fully combined with diamond abrasive and has low porosity.

[0033] (3) The method for preparing copper-based diamond superhard grinding wheels by discharge plasma sintering provided by the present invention has a stronger metallurgical bond between diamond and metal matrix, and the abrasive is not easy to fall off during the processing.

[0034] (4) The apparatus for spark plasma sintering provided by the present invention can integrally form an abrasive ring with low porosity and avoid the possibility of failure of cold pressing molding and demolding, thereby saving processing time and improving production efficiency. Attached Figure Description

[0035] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the traditional method for preparing diamond grinding wheels;

[0037] Figure 2 A schematic flowchart of the method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering provided by the present invention.

[0038] Figure 3 This is a schematic diagram of the structure of the abrasive ring provided by the present invention;

[0039] Figure 4 A schematic diagram of the structure of the copper-based diamond superhard grinding wheel provided by the present invention;

[0040] Figure 5 This is a schematic diagram of the structure of the device provided by the present invention. Detailed Implementation

[0041] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0042] Unless otherwise specified, in this invention, terms such as "first aspect," "second aspect," "third aspect," and "fourth aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, terms such as "first," "second," "third," and "fourth" serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0043] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0044] Unless otherwise specified, in this invention, "one or more" or "at least one" refers to any one, any two, or any two or more of the listed items. "Several" refers to any two or more.

[0045] In a first aspect, the present invention provides a method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering, comprising the following steps:

[0046] A mixture containing diamond abrasive and a metal binder is placed in a mold, and the mold is placed in a spark plasma sintering furnace for spark plasma sintering. After sintering, the mixture is cooled in the furnace to obtain an integrally formed abrasive ring.

[0047] The metal binder is mainly composed of bronze powder and titanium powder (metallic titanium powder).

[0048] After the abrasive ring is combined with the steel core, the copper-based diamond superhard grinding wheel is obtained.

[0049] The present invention provides a method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering. This method eliminates the need for binders, drying, sieving, and cold pressing during abrasive preparation. The mixture is directly poured into a mold for spark plasma sintering, resulting in a simple, short, and highly efficient process. Furthermore, spark plasma sintering offers rapid heating and requires only a short holding time to complete the process. The resulting abrasive ring has low porosity, allowing it to withstand high loads during high-speed grinding and reducing the risk of diamond detachment during part processing. It also exhibits excellent impact resistance and good shape retention.

[0050] Compared to the superhard grinding wheel abrasive ring prepared by vacuum high-temperature sintering, the superhard grinding wheel abrasive ring prepared by spark plasma sintering in this invention has the same reaction layer thickness, but the porosity and wear mass loss are significantly reduced.

[0051] Specifically, the microstructure of the copper-based diamond superhard grinding wheel abrasive ring prepared by spark plasma sintering was analyzed by SEM, EDS, and XRD. Its phase composition, elemental distribution, and interfacial reaction layer thickness were basically consistent with those of the copper-based diamond superhard grinding wheel abrasive ring prepared by vacuum high-temperature sintering. Performance tests were conducted on the copper-based diamond superhard grinding wheel abrasive ring prepared by this invention. The porosity of the abrasive ring prepared by spark plasma sintering was 15%–20%, and the tribological weight loss was 1–5 mg. In contrast, the porosity of the abrasive ring prepared by vacuum high-temperature sintering was approximately 35%–40%, and the tribological weight loss was 35–40 mg. Therefore, the method provided by this invention not only significantly improves the wear performance and density of the grinding wheel abrasive ring but also greatly shortens the processing time and improves production efficiency.

[0052] A flowchart illustrating the method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering provided by this invention is shown below. Figure 2 As shown.

[0053] See the schematic diagram of the abrasive ring obtained by this invention. Figure 3 As shown.

[0054] See the schematic diagram of the copper-based diamond superhard grinding wheel prepared by this invention. Figure 4As shown.

[0055] In some specific embodiments, the mass ratio of the diamond abrasive to the metal binder is 40-48:52-60, for example, 40:60, 41:59, 42:58, 43:57, 44:56, 45:55, 46:54, 47:53, 48:52, 49:51, 50:50, 51:49, or 52:48. The diamond abrasive, as the wear-resistant particle, cannot have too low a content. If it is too low, it will lead to reduced wear resistance of the grinding wheel and excessive weight loss due to wear. The diamond abrasive content also cannot be too high, as it will cause agglomeration in the metal matrix, leading to a large amount of diamond particles falling off during processing and reducing the wear resistance of the grinding wheel.

[0056] In some specific embodiments, the metal binder is composed of bronze powder and titanium powder in a mass ratio of 90-95:5-10. The mass ratio of bronze powder to titanium powder can be 90:10, 91:9, 92:8, 93:7, 94:6, or 95:5.

[0057] In some specific embodiments, the bronze powder is Cu60Sn40 bronze powder.

[0058] The bronze powder mentioned is Cu60Sn40, mainly composed of Cu-Sn intermetallic compounds, and does not react with pure titanium powder. Using the above-mentioned ratio as the metal binder, the titanium powder can completely react with the diamond particles, forming a high-strength metallurgical bond at the interface. No excess titanium powder will remain in the metal matrix, reducing its strength. The metal matrix at this point consists only of bronze powder, exhibiting a good balance of hardness and brittleness, resulting in high strength and good wear resistance.

[0059] In some specific embodiments, the preparation method of the mixture includes: mixing the diamond abrasive, the bronze powder and the titanium powder evenly.

[0060] Unlike vacuum high-temperature sintering, this invention eliminates the need for sieving and adding binders after the raw materials are mixed evenly. This invention reduces the steps of sieving, adding binders, and drying, saving time and improving efficiency.

[0061] Alternatively, the preparation method of the mixture includes: plasma atomizing the bronze powder to obtain ultrafine bronze powder; drying the titanium powder and the diamond abrasive to remove moisture, then mixing and ball milling to obtain titanium-coated diamond powder, i.e., titanium powder coated on the outer surface of the diamond abrasive; and then mixing the ultrafine bronze powder and the titanium-coated diamond powder evenly.

[0062] The abrasive rings and grinding wheels prepared by this method are suitable for the processing of steel parts and semiconductor silicon wafers and other superhard abrasives. They have specific requirements for the strength of the holding force between the metal substrate and the abrasive.

[0063] The present invention produces fine metallic bronze powder particles by plasma atomization, which are half the particle size of powder obtained by atomization. During the sintering process, the powder is fully combined with diamond abrasive and has low porosity.

[0064] In some specific embodiments, the porosity of the abrasive rings obtained by the present invention is 15% to 20%.

[0065] Furthermore, this invention mixes diamond abrasive with titanium powder and ball mills it to obtain titanium-coated diamond, which can refine the diamond particles and allow the diamond and titanium powder to fully contact each other, so that the diamond and titanium powder are densely and uniformly sintered with the metal matrix during the sintering process, and titanium carbide is formed on the surface of the diamond after sintering.

[0066] Furthermore, the superhard grinding wheel produced by this invention has a reaction layer thickness of 1.7 μm. The diamond and the metal matrix are bonded together by forming a compound, which is much stronger than the inlay hold, and the abrasive is not easy to fall off during the processing.

[0067] In some specific embodiments, the mixing is carried out in a mixer, such as the TD-6 three-dimensional vortex mixer, where the mixing speed can be 18 to 40 r / min, the operation mode is unidirectional, and the mixing time can be 8 to 14 hours, but is not limited thereto.

[0068] In some specific embodiments, the plasma gas used for plasma atomization includes argon or helium. Argon is preferred due to its lower cost.

[0069] In some specific embodiments, the median particle size of the bronze powder is 40-80 μm; including but not limited to point values ​​or ranges between any one of 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, and 80 μm.

[0070] In some specific embodiments, the median particle size of the ultrafine bronze powder is 25–40 μm, including but not limited to a single value or a range between any two of 25 μm, 28 μm, 30 μm, 33 μm, 35 μm, 37 μm, and 40 μm. Specifically, the bronze powder is injected into an inert gas plasma, where it is completely evaporated and converted into vapor under high temperature. Rapid cooling is then achieved using gas quenching technology to obtain the ultrafine bronze powder. This invention employs a plasma atomization method for powder preparation, resulting in a smaller median particle size. Using ultrafine bronze powder allows for more uniform mixing with titanium powder, resulting in a more uniform metal matrix composition and better wear resistance in the abrasive.

[0071] In some specific embodiments, the median particle size of the titanium powder is 40 to 80 μm, including but not limited to point values ​​or ranges between any one of 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, and 80 μm.

[0072] In some specific embodiments, the ball milling time is 10–24 hours, for example, 12 hours, 15 hours, 18 hours, or 20 hours; the ball milling speed is 150–280 r / min, for example, 180 r / min, 200 r / min, or 240 r / min; and the ball-to-material ratio is 5–18:1, for example, 6:1, 8:1, 10:1, 12:1, or 15:1. Preferably, the diamond abrasive and titanium powder are dried to remove moisture before being fed into a planetary ball mill for ball milling. The ball milling equipment can be any equipment commonly used in the art, such as a planetary ball mill, but is not limited thereto.

[0073] In some specific embodiments, the discharge plasma sintering pressure is 25–30 MPa; including but not limited to any one of 25 MPa, 26 MPa, 27 MPa, 28 MPa, 29 MPa, and 30 MPa, or a range between any two. Under this pressure condition, a good balance can be achieved between the wear resistance, chip containment, and heat dissipation of the diamond grinding wheel. If the pressure is too high, the grinding wheel becomes too dense, resulting in low porosity, which hinders the removal of workpiece debris and heat during processing, potentially burning the workpiece surface and affecting quality. If the pressure is too low, the grinding wheel porosity is too high, reducing its wear resistance. Therefore, the aforementioned pressure range can balance the excellent wear resistance of the grinding wheel with good chip containment and heat dissipation.

[0074] In some specific embodiments, the reaction temperature of the spark plasma sintering is 930–980°C; including but not limited to any one of 940°C, 950°C, 960°C, and 970°C, or a range between any two. Within this temperature range, a good interfacial bonding strength can be formed between the diamond particles and the metal matrix in the grinding wheel. Excessively high temperatures can cause thermal damage to the diamond particles, such as graphitization, reducing their strength and consequently their wear resistance. Conversely, excessively low temperatures result in an incomplete interfacial reaction, lower interfacial bonding strength, and reduced wear resistance.

[0075] In some specific embodiments, the heating rate of the discharge plasma sintering is 50 to 100 °C / min; including but not limited to any one of 60 °C / min, 70 °C / min, 80 °C / min, 90 °C / min or any range between two of them.

[0076] In some specific embodiments, the holding time of the discharge plasma sintering is 1 to 10 minutes; including but not limited to any one of 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, and 9 minutes, or any range between two of them.

[0077] In some specific embodiments, the atmosphere for the discharge plasma sintering is an argon atmosphere or a helium atmosphere. An argon atmosphere is preferred due to its lower cost.

[0078] In some specific embodiments, the pressure of argon gas is below 0.5 MPa during the discharge plasma sintering process.

[0079] In some specific embodiments, the DC pulse output current of the discharge plasma sintering is 4500–5500 A; including but not limited to any one of 4500 A, 4600 A, 4800 A, 5000 A, 5200 A, and 5500 A, or a range between any two. The magnitude of the output current is directly related to the output heat. If the output current is too small, the heat will be low, failing to achieve the effect of rapidly heating the sample interior. This will not only slow down the interfacial reaction and reduce the interfacial bonding strength, but also cause the fluidity of the melted metal matrix to deteriorate, increase porosity, and ultimately reduce the wear resistance of the grinding wheel. If the output current is too large, the internal temperature of the sample will rise too quickly, which may cause adverse effects such as graphitization of diamond particles and over-melting of the metal matrix, also reducing the wear resistance of the grinding wheel.

[0080] In some specific embodiments, the pulse frequency of the discharge plasma sintering is 20-30 ms, including but not limited to any one of 20 ms, 22 ms, 23 ms, 25 ms, 28 ms, and 30 ms, or a range between any two. The pulse frequency is also related to the output heat. If the pulse frequency is too low, the heat input is slow, failing to achieve the effect of rapidly heating the sample interior. This results in slower interfacial reactions and poorer fluidity of the melted metal matrix, leading to lower interfacial bonding strength and increased porosity, ultimately reducing the wear resistance of the grinding wheel. If the pulse frequency is too high, the sample interior heats up too quickly, potentially causing graphitization of diamond particles and over-melting of the metal matrix, also reducing the wear resistance of the grinding wheel.

[0081] In some specific embodiments, the density of the abrasive ring is 80% to 85%, including but not limited to point values ​​of any one of 81%, 82%, 83%, 84%, and 85%, or a range between any two.

[0082] The abrasive ring prepared by this invention consists of diamond, a metal matrix, and an interface reaction layer, wherein the interface reaction layer is titanium carbide. It is understood that the bronze powder is Cu60Sn40, therefore the metal matrix is ​​mainly composed of copper-tin intermetallic compounds Cu3Sn and Cu6Sn5, which are both hard and brittle.

[0083] In some specific embodiments, the abrasive ring and the steel core are bonded together with a special bonding agent, wherein the bonding agent can be any reagent commonly used in the art, and the present invention is not limited thereto. Afterwards, the burrs are removed and the material is trimmed to obtain the copper-based diamond superhard grinding wheel.

[0084] The dimensions of the copper-based diamond superhard grinding wheel obtained by this invention can be set as needed. For example, the inner diameter of the copper-based diamond superhard grinding wheel is 85mm, the outer diameter is 95mm, and the width is 10mm, but it is not limited to these.

[0085] In some specific implementations, the dry friction load of the copper-based diamond superhard grinding wheel is 50N, the friction time is 60min, and the mass loss is 1-5mg.

[0086] Secondly, the present invention provides an apparatus suitable for the method of preparing copper-based diamond superhard grinding wheels by spark plasma sintering. The apparatus serves as a mold for spark plasma sintering of the mixture. (See also...) Figure 3 As shown, the device includes an inner graphite column, an outer graphite sleeve, an upper pressure head base, and a lower pressure head base.

[0087] The inner graphite column, outer graphite sleeve, upper pressure head base, and lower pressure head base are all made of graphite, preferably high-strength graphite, with a compressive strength of 600-800 MPa. The upper pressure head base includes an integrally formed, non-removable upper pressure plate and upper pressure ring; these are referred to as upper pressure plate and upper pressure ring respectively for ease of describing the shape, size, and positional relationship of the upper pressure head base. The upper pressure ring is annular, and the upper pressure plate is disc-shaped. The lower pressure head base includes an integrally formed, non-removable lower pressure plate and lower pressure ring; these are referred to as lower pressure plate and lower pressure ring respectively for ease of describing the shape, size, and positional relationship of the lower pressure head base. The lower pressure ring is annular, and the lower pressure plate is disc-shaped. The inner and outer diameters of the upper and lower pressure rings are the same.

[0088] It is understandable that the heights of the upper and lower pressure rings can be the same or different.

[0089] The inner graphite column is a solid cylinder, and the outer graphite sleeve is a hollow ring. The outer graphite sleeve is fitted over the inner graphite column, and there is a receiving space between the outer graphite sleeve and the inner graphite column. This receiving space is used to accommodate the upper pressure ring and the lower pressure ring, and forms a reaction chamber for adding the mixture and performing spark plasma sintering.

[0090] The inner graphite column, the outer graphite sleeve, the upper pressure head base, and the lower pressure head base surround to form a reaction chamber. In use, the inner graphite column, the outer graphite sleeve, and the lower pressure head base are assembled and a mixture is added into the enclosed gap, i.e., the reaction chamber. The shape of the reaction chamber is circular, and the size of the reaction chamber is adapted to the size of the abrasive ring. Then, the upper pressure head base is placed and pressed tightly. The mixture is sintered by spark plasma in the reaction chamber to form the abrasive ring.

[0091] Understandably, the dimensions of the reaction chamber can be adjusted by the dimensions of the inner graphite column, the outer graphite sleeve, the upper pressure head base, and the lower pressure head base.

[0092] The device provided by this invention is the mold used for spark plasma sintering in the above-mentioned method for preparing copper-based diamond superhard grinding wheels. It has a simple structure and is easy to manufacture. After the mixture is sintered by spark plasma in this device, it can be directly integrally formed to obtain an abrasive ring with low porosity, avoiding the possibility of demolding failure in cold pressing, and saving processing time and improving production efficiency.

[0093] Understandably, the apparatus containing the mixture is placed in a spark plasma sintering furnace. The upper and lower pressure head bases are connected to the hydraulic system of the furnace, respectively. The hydraulic system applies pressure to the upper and lower pressure head bases, thus pressurizing the mixture. During spark plasma sintering, a pulsed current is introduced, and the upper and lower pressure head bases are connected to the pulsed current generator of the furnace. Under the action of the pulsed current, discharge occurs between the material particles, exciting plasma and achieving rapid sintering of the mixture.

[0094] A schematic diagram of the abrasive ring produced using the device or mold provided by this invention is shown below. Figure 3 As shown, the abrasive ring is circular in shape.

[0095] In some specific embodiments, at least one layer of graphite paper is disposed on the inner wall of the outer graphite sleeve, at least one layer of graphite paper is disposed on the outer wall of the inner graphite column, at least one layer of graphite paper is disposed on the outer surface of the lower pressure head base, and at least one layer of graphite paper is disposed on the outer surface of the upper pressure head base. The graphite paper disposed at each location is at least one layer, for example, two, three, or more layers.

[0096] Graphite paper isolates the mixture inside the device from the upper and lower pressure head bases, the inner graphite column, and the outer graphite sleeve, preventing current from passing through the mixture and creating a temperature gradient across the outer graphite sleeve. In other words, the graphite paper primarily functions as insulation, preventing current from passing through the material and avoiding short circuits. Furthermore, the high thermal conductivity of graphite paper allows for uniform Joule heating between powder particles, enabling rapid heating and accelerating the sintering process.

[0097] In some specific embodiments, the outer surface of the graphite paper is covered with at least one porous graphite insulating layer. This graphite insulating layer can be at least one layer, for example, two, three, or more layers. The graphite insulating layer primarily serves as electrical insulation, preventing current from conducting along unintended paths during plasma discharge, avoiding short circuits, and thus ensuring the normal operation of the equipment and the stability of the sintering process. The graphite insulating layer also has certain thermal insulation properties, reducing heat loss from the sintering area to the surrounding environment, thus providing heat preservation. The pores primarily allow air between powder particles to be effectively discharged during sintering. During sintering, the sample and the graphite insulating layer release gases, such as adsorbed air, moisture, and gases produced by the decomposition of the material itself. These pores provide channels for gas discharge, preventing gas accumulation in the sintering cavity and the formation of high pressure, which could affect the quality of the sintered body and prevent defects such as pores and cracks.

[0098] The dimensions of the inner graphite column, outer graphite sleeve, upper pressure head base, and lower pressure head base in this invention can be set according to the required size of the abrasive ring. For example, the diameter of the inner graphite column is 80 mm, the inner diameter of the outer graphite sleeve is 100 mm, and the width of the upper and lower pressure rings is 20 mm (i.e., the width of the reaction chamber is 20 mm, and the width of the resulting abrasive ring is 20 mm), but it is not limited to these.

[0099] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0100] Example 1

[0101] The apparatus (i.e., mold) for spark plasma sintering provided in this embodiment is described in [reference needed]. Figure 5As shown, it includes an inner graphite column, an outer graphite sleeve, an upper pressure head base, and a lower pressure head base. The upper pressure head base includes an integrally formed, non-removable upper pressure plate and an upper pressure ring, and the lower pressure head base includes an integrally formed, non-removable lower pressure plate and a lower pressure ring. The upper and lower pressure rings are annular in shape, with the same inner and outer diameters. The upper and lower pressure plates are disc-shaped. Both the inner graphite column and the outer graphite sleeve are made of graphite material with a compressive strength of 600 MPa. The inner graphite column is a solid cylinder, and the outer graphite sleeve is a hollow annular shape. The outer graphite sleeve is fitted over the inner graphite column, and there is a space between the outer graphite sleeve and the inner graphite column to accommodate the upper and lower pressure rings. The inner graphite column, outer graphite sleeve, upper pressure head base, and lower pressure head base together form a reaction chamber. A layer of graphite paper is provided on the inner wall of the outer graphite sleeve, a layer of graphite paper is provided on the outer wall of the inner graphite column, a layer of graphite paper is provided on the outer surface of the lower pressure head base, and a layer of graphite paper is provided on the outer surface of the upper pressure head base; and each graphite paper is covered with a porous graphite insulating layer on its outer surface.

[0102] Example 2

[0103] Using the apparatus (i.e., mold) of Example 1, the method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering provided in this example includes the following steps:

[0104] (1) Diamond abrasive, bronze powder (Cu60Sn40, purity ≥99.9%) and pure titanium powder (purity ≥99.9%) were poured into a TD-6 three-dimensional vortex mixer and mixed for 12 hours to obtain a mixture. The mass ratio of diamond abrasive to metal binder was 45:55, the mass ratio of bronze powder to pure titanium powder was 93:7, and the median particle size of both bronze powder and pure titanium powder was 40 μm.

[0105] (2) The mixture is poured into the reaction chamber formed by the lower pressure head base, the inner graphite column, and the outer graphite sleeve, and the upper pressure head base is then placed on top. The mold is then placed in a discharge plasma sintering furnace for discharge plasma sintering. The upper and lower pressure head bases are connected to the hydraulic system of the discharge plasma sintering furnace. Pressure is applied to the mixture through the hydraulic system at a pressure of 28 MPa. The sintering reaction temperature is 950°C, the heating rate is 80°C / min, and the temperature is maintained at a constant temperature. The heating time was 10 minutes, and the sintering atmosphere was argon. The pressure of the argon gas was always set below 0.5 MPa during the sintering process. At the same time, a pulsed current was applied. The upper and lower pressure head bases were connected to the pulsed current generator of the discharge plasma sintering furnace. The DC pulse output current was 5000A and the pulse frequency was 25ms. Under the action of the pulsed current, discharge was generated between the material particles, which excited the plasma and achieved rapid sintering of the mixture. After the heat preservation was completed, it was naturally cooled to obtain the copper-based diamond superhard grinding wheel abrasive ring.

[0106] Testing revealed that the density of the copper-based diamond superhard abrasive wheel ring prepared in this embodiment was 84.6% (high density indicates low porosity). The copper-based diamond superhard abrasive wheel ring is composed of diamond, a metal matrix, and an interface reaction layer, with the interface reaction layer being titanium carbide.

[0107] (3) The abrasive ring and steel core prepared above are bonded together with a special bonding agent for grinding wheels (epoxy resin), and the burrs are removed and the shape is trimmed to obtain a copper-based diamond superhard grinding wheel.

[0108] Example 3

[0109] Using the apparatus (i.e., mold) of Example 1, the method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering provided in this example is basically the same as that in Example 2, except that step (1) is different. Step (1) of this example is as follows: using plasma atomization, bronze powder with a median particle size of 40 μm is injected into argon plasma, and under high temperature, it is completely evaporated and converted into steam. Then, gas quenching cooling technology is used to achieve rapid cooling, thereby obtaining ultrafine copper-based metal powder with a median particle size of 25 μm. After drying and removing moisture from diamond abrasive and pure titanium powder, they are poured into a planetary ball mill for ball milling. The ball milling time is 12 h, the ball milling speed is 200 r / min, and the ball-to-material ratio is 10:1. Titanium-coated diamond powder is obtained after ball milling. Then, the above ultrafine copper-based metal powder and the above titanium-coated diamond powder are added to a TD-6 three-dimensional vortex mixer and mixed for 12 h to obtain a mixture.

[0110] Example 4

[0111] Using the apparatus (i.e., mold) of Example 1, the method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering provided in this example includes the following steps:

[0112] (1) Bronze powder (Cu60Sn40, purity ≥99.9%) with a median particle size of 80 μm was injected into argon plasma using plasma atomization. Under high temperature, it was completely evaporated and converted into vapor. Subsequently, rapid cooling was achieved using gas quenching technology, resulting in ultrafine copper-based metal powder with a median particle size of 35 μm. Diamond abrasive and pure titanium powder were dried to remove moisture and then ball-milled in a planetary ball mill. The ball milling time was 10 h, the ball milling speed was 280 r / min, and the ball-to-powder ratio was 15:1. Titanium-coated diamond powder was obtained after ball milling. The ultrafine copper-based metal powder and the titanium-coated diamond powder were then added to a TD-6 three-dimensional vortex mixer and mixed for 12 h to obtain a mixture. The mass ratio of diamond abrasive to metal binder was 48:52, the mass ratio of bronze powder to pure titanium powder was 95:5, and the median particle size of both bronze powder and pure titanium powder was 60 μm.

[0113] (2) The mixture is poured into the reaction chamber formed by the lower pressure head base, the inner graphite column, and the outer graphite sleeve, and the upper pressure head base is then placed on top. The mold is then placed in a spark plasma sintering furnace for spark plasma sintering. The upper and lower pressure head bases are connected to the hydraulic system of the spark plasma sintering furnace. The hydraulic system applies pressure to the upper and lower pressure head bases to pressurize the mixture. The pressure is 25 MPa, the sintering reaction temperature is 930 °C, and the heating rate is 50 °C / min. The holding time is 5 minutes, the sintering atmosphere is argon, and the pressure of argon is always set below 0.5 MPa during the sintering process. At the same time, a pulsed current is applied, and the upper and lower pressure head bases are connected to the pulsed current generator of the discharge plasma sintering furnace. The DC pulse output current is 4500A and the pulse frequency is 20ms. Under the action of the pulsed current, discharge is generated between the material particles, which excites the plasma and achieves rapid sintering of the mixture. After the holding time is completed, it is naturally cooled to obtain a copper-based diamond superhard grinding wheel abrasive ring.

[0114] The density of the copper-based diamond superhard abrasive wheel ring prepared in this embodiment is 82.6%. The composition of the copper-based diamond superhard abrasive wheel ring is diamond, metal matrix and interface reaction layer, and the interface reaction layer is titanium carbide.

[0115] (3) The abrasive ring and steel core prepared above are bonded together with a special bonding agent for grinding wheels (epoxy resin), and the burrs are removed and the shape is trimmed to obtain a copper-based diamond superhard grinding wheel.

[0116] Example 5

[0117] Using the apparatus (i.e. mold) of Example 1, the method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering provided in this example is basically the same as that in Example 4, except that in step (1), the mass ratio of diamond abrasive to metal binder is 40:60.

[0118] The density of the copper-based diamond superhard grinding wheel abrasive ring prepared in this embodiment is 83.6%.

[0119] Example 6

[0120] Using the apparatus (i.e. mold) of Example 1, the method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering provided in this example is basically the same as that in Example 4, except that in step (1), the mass ratio of bronze powder to pure titanium powder is 90:10.

[0121] The density of the copper-based diamond superhard grinding wheel abrasive ring prepared in this embodiment is 82.0%.

[0122] Example 7

[0123] Using the apparatus (i.e. mold) of Example 1, the method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering provided in this example is basically the same as that in Example 4, except that: in step (2), the parameters of spark plasma sintering are as follows: pressure is 30 MPa, sintering reaction temperature is 980 °C, heating rate is 50 °C / min, holding time is 1 min, DC pulse output current is 5500 A, and pulse frequency is 30 ms.

[0124] The density of the copper-based diamond superhard grinding wheel abrasive ring prepared in this embodiment is 82.2%.

[0125] Comparative Example 1

[0126] This comparative example uses a traditional method for preparing diamond grinding wheels, specifically including the following steps:

[0127] (1) Diamond abrasive, bronze powder (Cu60Sn40, purity ≥99.9%) and pure titanium powder (purity ≥99.9%) were poured into a TD-6 three-dimensional vortex mixer and mixed for 12 hours to obtain a mixture. The mass ratio of diamond abrasive to metal binder was 45:55, the mass ratio of bronze powder to pure titanium powder was 93:7, and the median particle size of both bronze powder and pure titanium powder was 40 μm.

[0128] (2) Pour the mixture into a beaker and add the binder (acrylic acid solution, which is 5% of the mass of the mixture) and stir evenly. Then place the mixed material in a drying oven to dry. After drying, sieve the powder (300 mesh) and weigh a certain amount of the mixture powder into a mold. Use a press to cold press and form (40t, 2min). After holding the pressure, demold to obtain the green body.

[0129] (3) The green blank is placed in a vacuum high-temperature furnace for sintering (950℃, 30min), and then cooled with the furnace to obtain the abrasive ring.

[0130] (4) The abrasive ring and the steel core are bonded together with a special bonding agent for grinding wheels (the same type as in Example 2), and the burrs are removed and the shape is trimmed to obtain a diamond grinding wheel.

[0131] The density of the abrasive rings prepared in this comparative example is 64.0%.

[0132] Comparative Example 2

[0133] Using the apparatus (i.e. mold) of Example 1, the method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering provided in this comparative example is basically the same as that of Example 4, except that pure titanium powder is not added, that is, only bronze powder is used as the metal binder, and the amount of metal binder remains unchanged.

[0134] The density of the abrasive rings prepared in this comparative example is 78.4%.

[0135] Comparative Example 3

[0136] Using the apparatus (i.e. mold) of Example 1, the method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering provided in this comparative example is basically the same as that of Example 4, except that the mass ratio of diamond abrasive to metal binder is 70:30, and the mass ratio of bronze powder to pure titanium powder is 80:20.

[0137] The density of the abrasive rings prepared in this comparative example is 45.0%.

[0138] Comparative Example 4

[0139] Using the apparatus (i.e. mold) of Example 1, the method for preparing copper-based diamond superhard grinding wheels by discharge plasma sintering provided in this comparative example is basically the same as that of Example 4, except that: in step (2), the parameters of discharge plasma sintering are as follows: pressure is 10 MPa, sintering reaction temperature is 900 °C, heating rate is 100 °C / min, holding time is 1 min, DC pulse output current is 3500 A, and pulse frequency is 10 ms.

[0140] The density of the abrasive rings prepared in this comparative example is 75.0%.

[0141] Experimental Example

[0142] The performance of the grinding wheels prepared in each embodiment and each comparative example was tested, and the results are shown in Table 1.

[0143] Table 1. Test Results of Superhard Grinding Wheel Performance

[0144] Example 2 1.70μm 5.0mg 15.4％ <![CDATA[4.31J / cm 2 ]]> Example 3 1.75μm 3.0mg 15.2％ <![CDATA[4.36J / cm 2 ]]> Example 4 1.38μm 15.8mg 17.4％ <![CDATA[3.74J / cm 2 ]]> Example 5 1.38μm 14.2mg 16.4％ <![CDATA[3.88J / cm 2 ]]> Example 6 1.38μm 19.6mg 18.0％ <![CDATA[3.58J / cm 2 ]]> Example 7 0.86μm 24.6mg 17.8％ <![CDATA[3.72J / cm 2 ]]> Comparative Example 1 1.70μm 31.4mg 36.0％ <![CDATA[3.24J / cm 2 ]]> Comparative Example 2 0μm 76.4mg 21.6％ <![CDATA[3.41J / cm 2 ]]> Comparative Example 3 1.38μm 58.7mg 55.0％ <![CDATA[2.7J / cm 2 ]]> Comparative Example 4 0.67μm 28.4mg 25.0％ <![CDATA[3.2J / cm 2 ]]>

[0145] As can be seen from Table 1, the diamond / Cu-based superhard grinding wheels prepared by plasma discharge sintering in each embodiment have lower porosity, lower wear weight loss, and higher impact toughness.

[0146] In Comparative Example 1, the traditional vacuum high-temperature sintering method involves cold pressing followed by sintering. This method produces grinding wheels with high porosity, resulting in significant weight loss during wear. Example 2, using spark plasma sintering, involves simultaneous heating and sintering within the reaction chamber, resulting in lower porosity, less weight loss during wear, and better impact toughness. Furthermore, the interface reaction layer thickness is consistent in both methods.

[0147] In Comparative Example 2, no Ti powder was added. Since diamond and bronze powder do not react, this method causes diamond to be embedded in the metal matrix, resulting in significant wear loss. However, due to the use of spark plasma sintering and the relatively dense bronze powder, the porosity is small and the impact toughness is poor.

[0148] In Comparative Example 3, due to the excessively high proportion of diamond abrasive, agglomeration easily occurs during the sintering process, resulting in higher porosity, greater wear loss, and poorer impact toughness.

[0149] Comparative Example 4: The discharge plasma sintering process parameters were not suitable, resulting in too short a reaction time of the mixture in the reaction chamber. This led to a thin interfacial reaction layer, high porosity, significant wear loss, and poor impact toughness.

[0150] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering, characterized in that, Includes the following steps: The mixture containing diamond abrasive and metal binder is subjected to spark plasma sintering to obtain an integrally formed abrasive ring. After the abrasive ring is combined with the steel core, the copper-based diamond superhard grinding wheel is obtained. The mass ratio of the diamond abrasive to the metal binder is 40~48:52~60; The metal binder is composed of bronze powder and titanium powder in a mass ratio of 90~95:5~10; the bronze powder is Cu60Sn40 bronze powder. The preparation method of the mixture includes: uniformly mixing the diamond abrasive, the bronze powder, and the titanium powder, wherein the median particle size of the bronze powder is 40~80μm; or, subjecting the bronze powder to plasma atomization to obtain ultrafine bronze powder, ball milling the titanium powder and the diamond abrasive to obtain titanium-coated diamond powder, and uniformly mixing the ultrafine bronze powder and the titanium-coated diamond powder, wherein the median particle size of the ultrafine bronze powder is 25~40μm; The pressure of the discharge plasma sintering is 25~30 MPa; the reaction temperature of the discharge plasma sintering is 930~980℃; the DC pulse output current of the discharge plasma sintering is 4500~5500A; and the pulse frequency of the discharge plasma sintering is 20~30 ms.

2. The method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering according to claim 1, characterized in that, The plasma gas used for plasma atomization includes argon.

3. The method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering according to claim 1, characterized in that, The ball milling time is 10~24h, the ball milling speed is 150~280r / min, and the ball-to-material ratio is 5~18:

1.

4. The method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The heating rate of the discharge plasma sintering is 50~100℃ / min; (2) The holding time for the discharge plasma sintering is 1~10 min; (3) The atmosphere of the discharge plasma sintering is an argon atmosphere.

5. The method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering according to any one of claims 1 to 4, characterized in that, The density of the abrasive ring is 80%~85%.

6. An apparatus, characterized in that, The apparatus is applicable to the method for preparing copper-based diamond superhard grinding wheels by spark plasma sintering as described in any one of claims 1 to 5, wherein the apparatus serves as a mold for spark plasma sintering of the mixture, and the apparatus includes an inner graphite column, an outer graphite sleeve, an upper pressure head base, and a lower pressure head base. The upper pressure head base includes an integrally formed, non-removable upper pressure plate and an upper pressure ring, and the lower pressure head base includes an integrally formed, non-removable lower pressure plate and a lower pressure ring. The upper pressure ring and the lower pressure ring are annular in shape. The inner graphite column is cylindrical in shape, and the outer graphite sleeve is annular in shape. The outer graphite sleeve is fitted around the inner graphite column, and there is a receiving space between the outer graphite sleeve and the inner graphite column for accommodating the upper pressure ring and the lower pressure ring. The inner graphite column, the outer graphite sleeve, the upper pressure head base, and the lower pressure head base surround and form a reaction chamber. The mixture is sintered by spark plasma in the reaction chamber to form an abrasive ring.

7. The apparatus according to claim 6, characterized in that, At least one layer of graphite paper is provided on the inner wall of the outer graphite sleeve, at least one layer of graphite paper is provided on the outer wall of the inner graphite column, at least one layer of graphite paper is provided on the outer surface of the lower pressure head base, and at least one layer of graphite paper is provided on the outer surface of the upper pressure head base.

8. The apparatus according to claim 7, characterized in that, The outer surface of the graphite paper is covered with at least one layer of porous graphite insulating layer.

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