Porous metal-ceramic composite binding agent diamond grinding wheel with prefabricated double-layer hollow particles and preparation of porous metal-ceramic composite binding agent diamond grinding wheel

Abstract

The invention relates to the technical field of grinding materials and grinding tools, in particular to a porous metal-ceramic composite binding agent diamond grinding wheel with prefabricated double-layer hollow particles and preparation of the porous metal-ceramic composite binding agent diamond grinding wheel. The double-layer hollow particle provided by the invention sequentially comprises a central cavity, a ceramic bond layer and a brazing filler metal alloy layer from inside to outside. The double-layer hollow particles are prefabricated and then used for preparing the porous metal-ceramic composite binding agent diamond grinding wheel working layer segment, adjustment of the porosity of the porous diamond grinding wheel and arrangement of a pore structure can be achieved, the porosity is improved, the chip containing space is increased, meanwhile, the strength of the grinding wheel is kept, and the service life of the grinding wheel is prolonged. And the high-quality processing requirements of different hard and brittle materials are met.

Description

Technical Field

[0001] The invention relates to the technical field of abrasive materials and grinding tools, and in particular to a double-layer hollow particle and a preparation method thereof, a porous metal-ceramic composite binder diamond grinding wheel working layer segment and a preparation method thereof, and a diamond grinding wheel. Background Art

[0002] The rapid development of science and technology has led to the emergence of a large number of new materials and their wide application in engineering, including a large number of hard and brittle materials that are difficult to process. When using grinding wheels to thin these difficult-to-process materials, surface cracks and surface damage are often formed on the surface of the workpiece due to the large grinding force and the hardness and brittleness of the material. The part that plays a grinding role in the thinning process of the grinding wheel is the working layer of the grinding wheel. The organizational structure of the working layer affects the grinding quality. For example, the pores in the working layer can play the role of chip storage, chip removal, and heat dissipation. When the porosity is too low, the grinding efficiency and quality of the grinding wheel are easily reduced, while when the porosity is too high, the strength of the grinding wheel is reduced.

[0003] The commonly used porous metal bond diamond grinding wheels at present are often made by mixing the bond, diamond abrasive and pore-forming agent, pressing the powder into shape and then sintering it. They have good interface bonding and toughness, but poor self-sharpening, insufficient chip space in the working layer, and the pore structure formed by the pore-forming agent (such as titanium hydride, nickel hydride, sodium chloride, etc.) used. There are also problems such as uneven pore shape, size, and distribution, which reduce the strength and grinding quality of the grinding wheel, and are prone to problems such as insufficient workpiece processing accuracy, frequent grinding wheel dressing, and poor grinding quality stability. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a double-layer hollow particle and a preparation method thereof, a porous metal-ceramic composite binder diamond grinding wheel working layer segment and a preparation method thereof, and a diamond grinding wheel. The present invention can increase the porosity of the grinding wheel while ensuring the strength of the grinding wheel, optimize the shape, size and distribution of the pore structure, and improve the self-sharpening property of the grinding wheel.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The invention provides a double-layer hollow particle, which comprises, from the inside to the outside, a central cavity, a ceramic binder layer and a solder alloy layer.

[0007] Preferably, the outer diameter of the double-layer hollow particles is 0.08-1.00 mm, the thickness of the ceramic binder layer is 0.01-0.2 mm, and the thickness of the solder alloy layer is 0.03-0.6 mm.

[0008] Preferably, the solder in the solder alloy layer includes Cu-Sn-Ti alloy solder and / or Ni-Cr alloy solder.

[0009] Preferably, the ceramic binder in the ceramic binder layer is a SiO2-Al2O3-B2O3-R2O based ceramic binder.

[0010] Preferably, the SiO2-Al2O3-B2O3-R2O based ceramic binder comprises: 30-65wt.% silicon dioxide, 5-10wt.% aluminum oxide, 10-30wt.% boric acid and 20-30wt.% sodium carbonate.

[0011] The present invention provides a method for preparing the double-layer hollow particles described in the above scheme, comprising the following steps:

[0012] Ceramic binder powder and a first binder are coated on the surface of polystyrene spherical particles, and an inner coating layer is formed after drying; solder alloy powder and a second binder are coated on the outer surface of the inner coating layer, and an outer coating layer is formed after drying to obtain a double-layer hollow particle blank;

[0013] The double-layer hollow particle blank is subjected to a first sintering to remove the binder and the polystyrene spherical particles, a heating and a second sintering in sequence to obtain the double-layer hollow particle.

[0014] The present invention provides a method for preparing a porous metal-ceramic composite bond diamond grinding wheel working layer segment, comprising the following steps:

[0015] The diamond abrasive grains and the double-layer hollow particles are mixed, and the obtained mixture is pressed into a shape to obtain a diamond grinding wheel segment blank;

[0016] Sintering the diamond grinding wheel segment blank to obtain the porous metal-ceramic composite binder diamond grinding wheel working layer segment;

[0017] The double-layer hollow particles are the double-layer hollow particles described in the above scheme or the double-layer hollow particles prepared by the preparation method described in the above scheme.

[0018] Preferably, the content of diamond abrasive particles in the mixture is 30-55wt.%, and the content of double-layer hollow particles is 45-70wt.%.

[0019] The present invention provides a porous metal-ceramic composite binder diamond grinding wheel working layer segment prepared by the preparation method described in the above scheme.

[0020] The invention provides a porous metal-ceramic composite bond diamond grinding wheel, comprising a substrate and a working layer bonded to the substrate, wherein the working layer is composed of the porous metal-ceramic composite bond diamond grinding wheel working layer segments described in the above scheme.

[0021] The invention provides a double-layer hollow particle, which comprises, from the inside to the outside, a central cavity, a ceramic binder layer and a solder alloy layer.

[0022] The present invention prefabricates double-layer hollow particles and then uses them for the preparation of porous metal-ceramic composite binder diamond grinding wheel working layer segments, which can adjust the porosity of the porous diamond grinding wheel and arrange the pore structure, while improving the porosity and increasing the chip space, maintaining the strength of the grinding wheel, and meeting the high-quality processing requirements of different hard and brittle materials. Specifically, the porosity can be controlled by adjusting the amount of double-layer hollow particles; the arrangement of the pore structure can be achieved by pre-arranging the double-layer hollow particles, for example, using a binder to pre-arrange the hollow particles according to a close-packed hexagonal or simple cubic structure; in addition, since the pore structure of the double-layer hollow particles is uniform, the pore size in the grinding wheel working layer can be kept uniform, avoiding stress concentration and pore cell wall rupture caused by uneven pore structure, thereby maintaining the strength of the grinding wheel.

[0023] In addition, the double-layer hollow particles introduce ceramic binder so that it is evenly distributed in the porous metal-ceramic composite binder diamond grinding wheel, which enhances the self-sharpening property of the grinding wheel. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of double-layer hollow particles;

[0025] Figure 2 It is a schematic diagram of the structure of a porous metal-ceramic composite bond diamond grinding wheel;

[0026] Figure 3 Schematic diagram of the preparation process of double-layer hollow particles in the embodiment. DETAILED DESCRIPTION

[0027] like Figure 1 As shown, the present invention provides a double-layer hollow particle, which comprises, from the inside to the outside, a central cavity, a ceramic binder layer and a solder alloy layer.

[0028] In the present invention, the outer diameter of the double-layer hollow particles is preferably 0.08-1.00 mm. In a specific embodiment, the outer diameter of the double-layer hollow particles can be 0.08 mm, 0.15 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1.00 mm.

[0029] In the present invention, the thickness of the ceramic binder layer is preferably 0.01-0.2 mm. In a specific embodiment, the thickness of the ceramic binder layer may be 0.01 mm, 0.05 mm, 0.1 mm, 0.15 mm, or 0.2 mm.

[0030] In the present invention, the ceramic binder in the ceramic binder layer is preferably a SiO2-Al2O3-B2O3-R2O ceramic binder; the SiO2-Al2O3-B2O3-R2O ceramic binder preferably includes: 30-65wt.% silicon dioxide, 5-10wt.% aluminum oxide, 10-30wt.% boric acid and 20-30wt.% sodium carbonate. In a specific embodiment, the content of silicon dioxide in the SiO2-Al2O3-B2O3-R2O ceramic binder may be 30wt.%, 35wt.%, 40wt.%, 45wt.%, 50wt.%, 55wt.%, 60wt.% or 65wt.%, the content of aluminum oxide may be 5wt.%, 6wt.%, 7wt.%, 8wt.%, 9wt.% or 10wt.%, the content of boric acid may be 10wt.%, 15wt.%, 20wt.%, 25wt.% or 30wt.%, and the content of sodium carbonate may be 20wt.%, 22wt.%, 24wt.%, 26wt.%, 28wt.% or 30wt.%. In the present invention, the function of the ceramic binder layer is to enhance the self-sharpening property of the working layer.

[0031] In the present invention, the thickness of the solder alloy layer is preferably 0.03-0.6 mm. In a specific embodiment, the thickness of the solder alloy layer may be 0.03 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm or 0.6 mm.

[0032] In the present invention, the brazing filler metal in the brazing filler metal alloy layer preferably includes Cu-Sn-Ti alloy brazing filler metal and / or Ni-Cr alloy brazing filler metal. The present invention has no special requirements on the specific composition of the Cu-Sn-Ti alloy brazing filler metal and the Ni-Cr alloy brazing filler metal, and the composition well known in the art can be adopted. In the embodiment of the present invention, the Cu-Sn-Ti alloy brazing filler metal can specifically be Cu-20wt.%Sn-10wt.%Ti alloy brazing filler metal or Cu-30wt.%Sn-10wt.%Ti. In the present invention, the function of the brazing filler metal alloy layer is to infiltrate the diamond abrasive grains and form a good bond with the abrasive grains, so that the diamond grinding wheel segments can better hold the diamond abrasive grains, and at the same time form a good bond with the ceramic binder to form a metal-ceramic composite binder, thereby enhancing the self-sharpening property of the grinding wheel.

[0033] The present invention provides a method for preparing the double-layer hollow particles described in the above scheme, comprising the following steps:

[0034] Ceramic binder powder and a first binder are coated on the surface of polystyrene spherical particles, and an inner coating layer is formed after drying; solder alloy powder and a second binder are coated on the outer surface of the inner coating layer, and an outer coating layer is formed after drying to obtain a double-layer hollow particle blank;

[0035] The double-layer hollow particle blank is subjected to a first sintering to remove the binder and the polystyrene spherical particles, a heating and a second sintering in sequence to obtain the double-layer hollow particle.

[0036] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known in the art.

[0037] The invention coats ceramic binder powder and a first binder on the surface of polystyrene spherical particles, and forms an inner coating layer after drying.

[0038] In the present invention, the outer diameter of the polystyrene spherical particles is preferably 0.05-0.20 mm. In a specific embodiment, the particle diameter of the polystyrene spherical particles can be 0.05 mm, 0.10 mm, 0.15 mm or 0.20 mm.

[0039] The present invention has no special requirements for the preparation process of the ceramic binder powder, and a preparation method well known in the art can be used. In the present invention, the preparation of the ceramic binder powder preferably includes: weighing the ceramic binder raw materials according to the ratio, mixing them evenly in a ball mill after grinding, pressing them into blocks using a hydraulic press, putting them into a crucible and melting them in a high-temperature melting furnace, quenching the ceramic binder after melting to form glass material, drying, putting them into a ball mill for 2 hours, crushing them and sieving them to obtain the ceramic binder powder.

[0040] In the present invention, when the ceramic binder is a SiO2-Al2O3-B2O3-R2O ceramic binder, the ceramic binder raw materials include: 30-65wt.% silicon dioxide, 5-10wt.% aluminum oxide, 10-30wt.% boric acid and 20-30wt.% sodium carbonate.

[0041] In the present invention, the melting temperature is preferably 1200-1500°C. In a specific embodiment, the melting temperature may be 1200°C, 1300°C, 1400°C or 1500°C.

[0042] In the present invention, the ceramic binder powder is preferably able to pass through a 200-mesh sieve.

[0043] In the present invention, the first binder is preferably a polyvinyl alcohol aqueous solution with a mass concentration of 2 to 6%.

[0044] In the present invention, the mass ratio of the polystyrene spherical particles to the first binder is preferably 1:2-3, and in a specific embodiment, it can be 1:2, 1:2.5 or 1:3; the mass ratio of the polystyrene spherical particles to the ceramic binder powder is preferably 1:20-30, and in a specific embodiment, it can be 1:20, 1:22, 1:24, 1:26, 1:28 or 1:30.

[0045] In the present invention, the coating is preferably carried out in an automatic coating machine. In the present invention, the polystyrene spherical particles are preferably placed in the automatic coating machine, the coating machine speed is adjusted to 25 to 50 r / min, the first binder and the ceramic binder powder are added into the coating machine using a nozzle device, the ceramic binder powder is evenly coated on the surface of the polystyrene spherical particles, and the coating is taken out after 2 to 5 minutes to form a wet inner coating layer.

[0046] The present invention has no special requirements on the drying conditions.

[0047] After the inner coating layer is formed, the present invention coats the outer surface of the inner coating layer with solder alloy powder and a second binder, and forms an outer coating layer after drying to obtain a double-layer hollow particle blank.

[0048] In the present invention, the second binder is preferably a polyvinyl alcohol aqueous solution with a mass concentration of 2 to 6%.

[0049] In the present invention, the mass ratio of the second binder to the solder alloy powder is preferably 1:20-40; in a specific embodiment, it can be 1:20, 1:25, 1:30, 1:35 or 1:40.

[0050] The present invention preferably puts the particles coated with the inner coating layer into the automatic coating machine again, adds a second binder and solder alloy powder, and evenly coats the solder alloy powder outside the inner coating layer. After coating for 2 to 5 minutes, the particles are taken out to form a wet outer coating layer.

[0051] After obtaining the double-layer hollow particle blank, the present invention sequentially performs a first sintering to remove the binder and the polystyrene spherical particles, heats up, and performs a second sintering on the double-layer hollow particle blank to obtain the double-layer hollow particle.

[0052] In the present invention, the temperature of the first sintering is preferably 300-350°C, and the holding time is preferably 10-20 minutes; in a specific embodiment, the temperature of the first sintering can be 300°C, 320°C, 340°C or 350°C, and the holding time of the first sintering can be 10 minutes, 15 minutes or 20 minutes. In the present invention, the rate of heating to the temperature of the first sintering is preferably 1-3°C / min. The present invention volatilizes and removes the binder and polystyrene spherical particles through the first sintering to form a central cavity, a ceramic binder layer and a solder alloy layer.

[0053] In the present invention, the rate of heating from the first sintering temperature to the second sintering temperature is preferably 10-20°C / min; in specific embodiments, it can be 10°C / min, 13°C / min, 15°C / min, 17°C / min or 20°C / min.

[0054] In the present invention, the temperature of the second sintering is preferably 0.9 to 1.1 times the melting point of the solder alloy powder, and the holding time is preferably 30 to 120 minutes; in a specific embodiment, the temperature of the second sintering can be 0.9 times, 1 times or 1.1 times the melting point of the solder alloy powder, and the holding time of the second sintering can be 30 minutes, 60 minutes, 90 minutes or 120 minutes. The present invention forms a connection between the particles of the ball wall through the second sintering to form a complete ball wall. In the present invention, the first sintering and the second sintering are preferably performed under vacuum conditions.

[0055] The present invention provides a method for preparing a porous metal-ceramic composite bond diamond grinding wheel working layer segment, comprising the following steps: mixing diamond abrasive grains and the above-mentioned double-layer hollow particles, pressing the obtained mixture into a shape to obtain a diamond grinding wheel segment blank;

[0056] The diamond grinding wheel segment blank is sintered to obtain the porous metal-ceramic composite binder diamond grinding wheel working layer segment.

[0057] In the present invention, the particle size of the diamond abrasive grains is preferably 75 to 150 μm; in a specific embodiment, the particle size of the diamond abrasive grains may be 75 μm, 100 μm, 120 μm, 130 μm or 150 μm.

[0058] In the present invention, the mixing is preferably performed in a mixer.

[0059] In the present invention, the content of diamond abrasive in the mixture is preferably 30-55wt.%, and the content of double-layer hollow particles is preferably 45-70wt.%; in a specific embodiment, the content of diamond abrasive in the mixture can be 30wt.%, 35wt.%, 40wt.%, 45wt.%, 50wt.% or 55wt.%, and the balance is double-layer hollow particles. The present invention can regulate the porosity of the working layer by controlling the content of double-layer hollow particles, and the more the amount used, the higher the porosity. The present invention controls the content of double-layer hollow particles within the above range, and can ensure the strength of the grinding wheel while increasing the porosity of the grinding wheel.

[0060] In the present invention, the press molding is preferably cold press molding, and the pressure of the cold press molding is preferably 10-30 MP. In a specific embodiment, the pressure of the cold press molding can be 10 MP, 20 MP or 30 MP. The present invention is preferably press molding on a hydraulic press.

[0061] In the present invention, the sintering temperature is preferably 0.9 to 1.1 times the melting point of the solder alloy powder, and the holding time is preferably 10 to 60 minutes. In a specific embodiment, the sintering temperature can be 0.9 times, 1 times or 1.1 times the melting point of the solder alloy powder, and the holding time of the sintering can be 10 minutes, 20 minutes, 30 minutes, 40 minutes or 60 minutes. In the present invention, the sintering is preferably carried out under vacuum conditions. The present invention promotes the formation of a firm bond between the diamond abrasive and the double-layer hollow particles through sintering.

[0062] The present invention provides a porous metal-ceramic composite bond diamond grinding wheel working layer segment prepared by the preparation method described in the above scheme. The porous metal-ceramic composite bond diamond grinding wheel working layer segment has high porosity and high strength. Specifically, the porosity of the porous metal-ceramic composite bond diamond grinding wheel working layer segment is preferably 40-60%, and the strength is preferably 50-70MPa.

[0063] The invention provides a porous metal-ceramic composite bond diamond grinding wheel, comprising a substrate and a working layer bonded to the substrate, wherein the working layer is composed of the porous metal-ceramic composite bond diamond grinding wheel working layer segments described in the above scheme.

[0064] The present invention has no special requirements on the preparation method of the porous metal-ceramic composite binder diamond grinding wheel, and the segment block and the matrix can be directly bonded by curing with an organic binder.

[0065] Figure 2 is a schematic diagram of the structure of a porous metal-ceramic composite bond diamond grinding wheel. Figure 2 As shown, the double-layer hollow particles and diamond abrasive particles are evenly distributed in the working layer, wherein the cavities of the double-layer hollow particles provide chip holding space during grinding.

[0066] The porous metal-ceramic composite binder diamond grinding wheel provided by the present invention can adjust the porosity of the porous diamond grinding wheel and arrange the pore structure by using prefabricated double-layer particles. While improving the porosity and increasing the chip holding space, the strength of the grinding wheel is maintained, thereby meeting the high-quality processing requirements of different hard and brittle materials.

[0067] In addition, the double-layer hollow particles introduce ceramic binder so that it is evenly distributed in the porous metal-ceramic composite binder diamond grinding wheel, which enhances the self-sharpening property of the grinding wheel.

[0068] The double-layer hollow particles and their preparation method, the porous metal-ceramic composite binder diamond grinding wheel working layer segment and their preparation method, and the diamond grinding wheel provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0069] Example 1

[0070] Step 1. Weigh the raw materials according to 45wt.% of silicon dioxide, 6wt.% of aluminum oxide, 23wt.% of boric acid, and 26wt.% of sodium carbonate, grind them in a mortar and add them to a ball mill to mix evenly, use a hydraulic press to press them into blocks, put them into a crucible, heat them to 1400°C in a high-temperature melting furnace to melt, and after insulation, quench the molten ceramic binder with water to form a glass material, dry it at 80°C in a drying oven, put it into a ball mill and ball-mill for 2h, crush it and pass it through a 200-mesh sieve to obtain a ceramic binder powder.

[0071] Step 2: Figure 3 As shown, 1g of polystyrene spherical particles with an outer diameter of 0.1mm is placed in an automatic coating machine, the speed of the coating machine is adjusted to 40r / min, and 2g of a 3% polyvinyl alcohol aqueous solution and 20g of a ceramic binder powder are added to the coating machine in sequence using a nozzle device. Under the action of the binder, the ceramic binder powder is evenly coated on the surface of the spherical particles. After coating for 3 minutes, the particles are taken out and placed in a dryer for drying. After drying, the obtained blank is placed in the coating machine again, and 2g of a 3% polyvinyl alcohol aqueous solution and 40g of a solder alloy with a composition of Cu-20wt.% Sn-10wt.% Ti are added to the coating machine in sequence. Powder (melting point is 840℃), so that the solder alloy is evenly coated on the outside of the ceramic binder layer, taken out after coating for 3 minutes, and put into a dryer for drying to obtain a double-layer particle blank; the blank is placed in a vacuum sintering furnace, heated to 300℃ at a heating rate of 2℃ / min and then kept warm for 10min to volatilize the polystyrene spherical particles, then quickly heated to 920℃ at a rate of 10℃ / min and kept warm for 30min to form hollow particles, and then taken out after cooling with the furnace to obtain double-layer hollow particles, with an outer diameter of 0.16mm, a ceramic binder layer thickness of 0.02mm, and a solder alloy layer thickness of 0.06mm.

[0072] Step 3: Weigh diamond abrasive grains with a particle size of 75 μm and double-layer hollow particles with an outer diameter of 0.16 mm according to 35 wt.% of diamond abrasive grains and 65 wt.% of double-layer hollow particles, and mix them evenly in a mixer; pour the mixed materials into a mold, put it on a hydraulic press and apply a pressure of 18 MPa to cold-press the diamond grinding wheel segment blank.

[0073] Step 4: Place the segment blank into a vacuum sintering furnace and sinter the segment blank at 900° C. for 10 minutes to promote a strong bond between the diamond abrasive grains and the double-layer hollow particles, thereby obtaining a porous metal-ceramic composite binder diamond grinding wheel working layer segment.

[0074] Step 5: Bond the working layer segment to the aluminum substrate by curing with an organic binder to obtain a porous metal-ceramic composite binder diamond grinding wheel containing prefabricated double-layer hollow particles in which the working layer and the substrate are tightly bonded.

[0075] Example 2

[0076] Step 1. Weigh the raw materials according to 40wt.% of silicon dioxide, 6wt.% of aluminum oxide, 30wt.% of boric acid, and 24wt.% of sodium carbonate, grind them in a mortar and add them to a ball mill to mix evenly, use a hydraulic press to press them into blocks, put them into a crucible, heat them to 1450°C in a high-temperature melting furnace to melt, and after insulation, quench the molten ceramic binder with water to form a glass material, dry it at 80°C in a drying oven, put it into a ball mill and ball-mill for 2h, crush it and pass it through a 200-mesh sieve to obtain a ceramic binder powder.

[0077] Step 2: Put 1g of polystyrene spherical particles with an outer diameter of 0.2mm into an automatic coating machine, adjust the coating machine speed to 50r / min, use a nozzle device to add 2g of a 4% polyvinyl alcohol aqueous solution and 25g of a ceramic binder powder into the coating machine in sequence, and under the action of the binder, the ceramic binder powder is evenly coated on the surface of the spherical particles, and taken out after coating for 3 minutes, and placed in a dryer for drying; after drying, the obtained blank is put into the coating machine again, and 2g of a 3% polyvinyl alcohol aqueous solution and 50g of a solder alloy with a composition of Cu-30wt.%Sn-10wt.%Ti are added into the coating machine in sequence. Powder (melting point is 780℃), so that the solder alloy is evenly coated on the outside of the ceramic binder layer, taken out after coating for 3 minutes, and put into a dryer for drying to obtain a double-layer particle blank; the blank is placed in a vacuum sintering furnace, heated to 300℃ at a heating rate of 2℃ / min and then kept warm for 20min to volatilize the polystyrene spherical particles, then quickly heated to 850℃ at a rate of 10℃ / min and kept warm for 120min to form hollow particles, and taken out after cooling with the furnace to obtain double-layer hollow particles, with an outer diameter of 0.38mm, a ceramic binder layer thickness of 0.05mm, and a solder alloy layer thickness of 0.15mm.

[0078] Step 3: Weigh diamond abrasive grains with a particle size of 100 μm and double-layer hollow particles with an outer diameter of 0.38 mm according to 50 wt.% of diamond abrasive grains and 50 wt.% of double-layer hollow particles, and mix them evenly in a mixer; pour the mixed materials into a mold, put it on a hydraulic press to apply a pressure of 20 MPa, and cold-press to form a diamond grinding wheel segment blank.

[0079] Step 4: Place the segment blank into a vacuum sintering furnace and sinter the segment blank at 830° C. for 20 minutes to promote a strong bond between the diamond abrasive grains and the double-layer hollow particles, thereby obtaining a porous metal-ceramic composite binder diamond grinding wheel working layer segment.

[0080] Step 5: Bond the working layer segment to the aluminum substrate by curing with an organic binder to obtain a porous metal-ceramic composite binder diamond grinding wheel containing prefabricated double-layer hollow particles in which the working layer and the substrate are tightly bonded.

[0081] Example 3

[0082] Step 1. Weigh the raw materials according to 55wt.% of silicon dioxide, 7wt.% of aluminum oxide, 10wt.% of boric acid, and 28wt.% of sodium carbonate, grind them in a mortar and add them to a ball mill to mix evenly, use a hydraulic press to press them into blocks, put them into a crucible, heat them to 1400°C in a high-temperature melting furnace to melt, and after insulation, quench the molten ceramic binder with water to form a glass material, dry it at 80°C in a drying oven, put it into a ball mill and mill it for 2h, and then pulverize it and pass it through a 200-mesh sieve to obtain a ceramic binder powder.

[0083] Step 2: Put 1g of polystyrene spherical particles with an outer diameter of 0.2mm into the automatic coating machine, adjust the coating machine speed to 50r / min, use a nozzle device to add 2g of 4% polyvinyl alcohol aqueous solution and 20g of ceramic binder powder into the coating machine in sequence, and under the action of the binder, the ceramic binder powder is evenly coated on the surface of the spherical particles. After coating for 5 minutes, take it out and put it into the dryer for drying; after drying, put the obtained blank into the coating machine again, and add 2g of 3% polyvinyl alcohol aqueous solution, 40g Ni-Cr solder alloy powder (melting point 1050℃) into the coating machine in sequence. ), so that the solder alloy is evenly coated on the outside of the ceramic binder layer, taken out after coating for 3 minutes, and placed in a dryer for drying to obtain a double-layer particle blank; the blank is placed in a vacuum sintering furnace, heated to 320°C at a heating rate of 2°C / min, and then kept warm for 20 minutes to volatilize the polystyrene spherical particles, and then quickly heated to 1150°C at a rate of 15°C / min and kept warm for 90 minutes to form hollow particles, which are taken out after cooling with the furnace to obtain double-layer hollow particles, with an outer diameter of 0.38mm, a ceramic binder layer thickness of 0.05mm, and a solder alloy layer thickness of 0.15mm.

[0084] Step 3: Weigh diamond abrasive grains with a particle size of 150 μm and double-layer hollow particles with an outer diameter of 0.38 mm according to 40 wt.% of diamond abrasive grains and 60 wt.% of double-layer hollow particles, and mix them evenly in a mixer; pour the mixed materials into a mold, put it on a hydraulic press to apply a pressure of 20 MPa, and cold-press the diamond grinding wheel segment blank.

[0085] Step 4: Place the segment blank into a vacuum sintering furnace and sinter the segment blank at 1050° C. for 10 minutes to promote a strong bond between the diamond abrasive grains and the double-layer hollow particles, thereby obtaining a porous metal-ceramic composite binder diamond grinding wheel working layer segment.

[0086] Step 5: Bond the working layer segment to the aluminum substrate by curing with an organic binder to obtain a porous metal-ceramic composite binder diamond grinding wheel containing prefabricated double-layer hollow particles in which the working layer and the substrate are tightly bonded.

[0087] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A double-layer hollow particle, which comprises, from the inside to the outside, a central cavity, a ceramic binder layer and a solder alloy layer.

2. The double-layer hollow particles according to claim 1, characterized in that: The outer diameter of the double-layer hollow particles is 0.08-1.00 mm, the thickness of the ceramic binder layer is 0.01-0.2 mm, and the thickness of the solder alloy layer is 0.03-0.6 mm.

3. The double-layer hollow particles according to claim 1 or 2, characterized in that: The solder in the solder alloy layer includes Cu-Sn-Ti alloy solder and / or Ni-Cr alloy solder.

4. The double-layer hollow particles according to claim 1 or 2, characterized in that: The ceramic binder in the ceramic binder layer is a SiO2-Al2O3-B2O3-R2O ceramic binder.

5. The double-layer hollow particles according to claim 4, characterized in that: The SiO2-Al2O3-B2O3-R2O ceramic binder comprises: 30-65 wt.% of silicon dioxide, 5-10 wt.% of aluminum oxide, 10-30 wt.% of boric acid and 20-30 wt.% of sodium carbonate.

6. The method for preparing the double-layer hollow particles according to any one of claims 1 to 5, comprising the following steps: Ceramic binder powder and a first binder are coated on the surface of polystyrene spherical particles, and an inner coating layer is formed after drying; The solder alloy powder and the second binder are coated on the outside of the inner coating layer, and then dried to form an outer coating layer to obtain a double-layer hollow particle blank; The double-layer hollow particle blank is subjected to a first sintering to remove the binder and the polystyrene spherical particles, a heating and a second sintering in sequence to obtain the double-layer hollow particle.

7. A method for preparing a porous metal-ceramic composite bond diamond grinding wheel working layer segment, characterized in that: The following steps are involved: The diamond abrasive grains and the double-layer hollow particles are mixed, and the obtained mixture is pressed into a shape to obtain a diamond grinding wheel segment blank; Sintering the diamond grinding wheel segment blank to obtain the porous metal-ceramic composite binder diamond grinding wheel working layer segment; The double-layer hollow particles are the double-layer hollow particles according to any one of claims 1 to 5 or the double-layer hollow particles prepared by the preparation method according to claim 6.

8. The preparation method according to claim 7, characterized in that: The content of diamond abrasive grains in the mixture is 30-55wt.%, and the content of double-layer hollow particles is 45-70wt.%.

9. The porous metal-ceramic composite bond diamond grinding wheel working layer segment prepared by the preparation method according to claim 7 or 8.

10. A porous metal-ceramic composite bond diamond grinding wheel, characterized in that: It comprises a substrate and a working layer bonded to the substrate, wherein the working layer is composed of the porous metal-ceramic composite bond diamond grinding wheel working layer segments as claimed in claim 8.

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