Manufacturing method of high-uniformity grinding wheel easy to sharpen and grind single crystal diamond cutter

Abstract

The invention discloses a manufacturing method of a grinding wheel for a high-uniformity and easy-to-sharpen grinding single crystal diamond cutter, and belongs to the field of superhard materials and products in machining, the manufacturing method mainly comprises the steps of wet mixing, tape casting, laser cutting, lamination, matrix surface treatment, integrated sintering, size processing, sharpening and the like, and finally the grinding wheel with the total thickness of an abrasive layer being 7-15 mm is formed. The grinding wheel layer is formed by intersecting and laminating a piece a and a piece b, the height of diamonds at the junction of the piece a and the piece b tends to be consistent, the diamond exposure height and smoothness are better compared with direct feeding sintering, meanwhile, the piece a can be designed to be of a porous structure through proper binder selection, and therefore the dressing efficiency is further improved, and the dressing effect is better. And higher processing quality and efficiency of the diamond cutter are indirectly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of superhard materials and products in machining, and particularly relates to a manufacturing method of a high-uniform and easy-sharpening grinding wheel for monocrystalline diamond cutters. BACKGROUND

[0002] In recent years, the development of traditional metal processing technology has been mature, and under the background of increasing requirements for processing stability and precision in the fields of microelectronics industry, biomedical equipment, electronic communication, precision instruments, aerospace, etc., super-precision machining technology has developed rapidly. With the application and promotion of super-precision cutting machining technology, the machining precision of super-precision cutting gradually approaches nanometer scale and its ultimate precision. In super-precision cutting machining, in order to obtain nanometer and sub-nanometer feature machining precision of the machined parts, in addition to super-precision lathes, high-resolution detection instruments and super-stable machining environment, high-precision diamond cutters are also required.

[0003] At present, monocrystalline diamond cutters require nanometer surface roughness and edge radius, and generally require no chipping at 500 magnification. The manufacturing process of monocrystalline diamond cutters generally includes material selection, sawing, roughing, clamping, rough grinding, fine grinding and inspection. The rough grinding and fine grinding are mainly completed by metal-based diamond grinding wheels. The performance and stability of the diamond cutter grinding wheel directly affect the precision of the monocrystalline cutter product. Therefore, the precision and shape retention of the grinding wheel are extremely high. Since the processing object is diamond, the processing efficiency also needs to be considered, and a good sharpening process is required.

[0004] In the prior art, CN103203453B proposes a grinding wheel for sharpening monocrystalline diamond cutters. The grinding wheel is mainly made by powder metallurgy of Mo, W and Cr powders. The grinding is mainly through chemical reaction grinding, and the diamond is removed by catalytic graphitization of diamond. The processing is only through chemical grinding, and the grinding efficiency is much lower than that of mechanical-chemical grinding. Moreover, Mo, W and Cr are high-melting-point powders, and the combination strength of the three is poor, which can easily cause uneven wear of the grinding wheel during grinding.

[0005] In the prior art, CN111618749B proposes a resin-based diamond grinding wheel for grinding hard alloy cutters. The resin-based grinding wheel has high self-sharpening property and slightly low combination strength. Although the grinding efficiency is high, the grinding precision is insufficient, so it cannot meet the requirements of grinding stability and high machining precision of monocrystalline diamond cutters.

[0006] To meet the use requirements, the metal-based diamond grinding wheel for grinding monocrystal cutters has high abrasive layer thickness, high diamond concentration, low diamond granularity, high density, high grinding efficiency and other characteristics. Due to high diamond concentration and mismatch with the powder granularity of the binder, the diamond is prone to floating and segregation during the manufacturing process of the grinding wheel, which indirectly causes problems such as difficult indirect processing and finishing and low finishing precision, and brings great difficulties to the manufacturing and application of the grinding wheel, indirectly affects the precision and quality of the diamond cutter, and hinders the development and iteration of the super-precision machining technology in China. SUMMARY

[0007] In view of the problems of diamond floating and segregation, difficult finishing, low density and other related problems in the manufacturing process of the metal-based diamond grinding wheel for grinding monocrystal cutters with high thickness, high concentration, ultra-fine granularity and high surface type precision, a manufacturing method of the metal-based high-uniformity and easy-sharpening diamond grinding wheel for grinding monocrystal cutters is provided. The diamond grinding wheel with uniform distribution of diamond micro-powder and high surface type precision after sharpening is obtained through special wet mixing process, alternating layering of the binder and the abrasive layer, combined with rapid sintering process and appropriate finishing process.

[0008] To achieve the above object, the technical scheme adopted by the present application is as follows: A manufacturing method of a high-uniformity and easy-sharpening diamond grinding wheel for grinding monocrystal cutters, which mainly includes the steps of wet mixing, rolling, layering, substrate surface treatment, integrated sintering, size processing, sharpening and the like, and finally forms a grinding wheel with a total abrasive layer thickness of 7mm to 15mm. The specific steps are as follows: (1) Mixing: uniformly mix the metal-based binder and the binder to obtain a piece of raw material paste; uniformly mix the diamond micro-powder, the metal-based binder, the active element, the structure strengthening element and the binder to obtain another piece of raw material paste; (2) Rolling and casting + laser cutting: the mixed a piece of raw material paste and the b piece of raw material paste are made into a billet through rolling and casting equipment, and a piece and b piece are obtained by cutting with laser or punching; (3) Substrate surface treatment: groove processing is performed on the side of the substrate which contacts the layering, and then electroplating is performed on the contact surface, and the electroplated material is the main metal element in the metal-based binder in the grinding wheel; (4) Layering: cross-layering a piece and b piece into a graphite mold; wherein the uppermost layer and the lowermost layer are a piece; (5) Integrated sintering: placing the substrate and the related layering in the plasma activated sintering equipment for sintering; (6) Size processing: processing the substrate, the outer circle and the end face to achieve the related size precision; (7) Sharpening: sharpening on the basis that the precision of the mating surface is not damaged.

[0009] Further, in step (1), the binder of the a sheet is selected from one or more than two kinds of paraffin, polyethylene glycol, polyvinyl butyral, glycerol and acetone in any proportion, the metal-based binder used in the a sheet is selected from one or more than two kinds of iron, copper, cobalt, tungsten, tin and alloy powder in any proportion, and the mass ratio of the metal-based binder and the binder in the a sheet is (8-12):1. The main purpose of the binder of the a sheet is to make the particles uniformly dispersed and form a related skeleton, and the size difference of the metal powder used in the a sheet is as small as possible without adding diamond.

[0010] Further, in step (1), the binder of the b sheet is selected from one or more than two kinds of polyvinyl butyral and polyethylene glycol in any proportion, the metal-based binder used is selected from one or more than two kinds of copper, tin, iron, cobalt, tungsten and alloy powder in any proportion, the active element is selected from one or more than two kinds of yttrium, iron, cobalt, manganese and vanadium in any proportion, the structure strengthening element is selected from one or more than two kinds of silver, cobalt, lead and tin in any proportion, the particle size of the diamond micro powder is 8-20 microns, and the mass ratio of the diamond micro powder, the metal-based binder, the active element, the structure strengthening element and the binder is (10-20):(50-70):(15-25):(1-5):(3-5). The main function of the binder of the b sheet is to form a stable slurry (which also has the functions of solvent, binder, plasticizer and dispersant), which can be mixed with PVB and PEG to ensure that the binder system can be completely thermally decomposed above 520°C without affecting the strength and performance of the grinding wheel after sintering; the mixing method includes electromagnetic stirring, acoustic resonance heating stirring, ball milling and the like.

[0011] Further, in step (2), the paste is made into a sheet with controllable thickness by single-roll, double-roll or multi-roll methods to improve the density, and the thickness can be controlled by casting, wherein the thickness of the a sheet is controlled to be 0.05-0.1 mm, and the thickness of the b sheet is controlled to be 0.4-0.6 mm. After the paste to be made into a sheet is dried or naturally air-dried, laser or punching is used for green body cutting.

[0012] Further, in step (3), a matching graphite tool is designed, and the a and b sheets are placed by alternating stacking, wherein the uppermost layer and the lowermost layer are a sheets. The green body stacking thickness is determined according to the actual required thickness and the shrinkage of the selected binder. Generally, the total thickness of the green body stacking is 1.5-2 times the total thickness of the actual abrasive layer. The plating layer thickness is 100-500 µm.

[0013] Further, in step (4), the substrate used is a steel substrate, and the substrate is subjected to tempering treatment, the tempering temperature is 530-570 DEG C, the tempering time is 60-120 min, the heating rate is 9-11 DEG C / min, and the substrate is naturally cooled to room temperature after the tempering treatment. The grooving type of the contact surface includes a circular ring, a rectangle, a wave shape, etc., and the purpose is to increase the contact area of the substrate and the binder; then the contact surface is plated with a metal layer, and particularly, the metal layer plated on the surface of the substrate is consistent with the main metal elements in the metal bond in the grinding wheel, so that the metal layer has good wettability.

[0014] Further, in step (5), the equipment used for integrated sintering includes but is not limited to a vacuum plasma rapid activation sintering equipment, different equipment matches different sintering process parameters, the sintering temperature is 550-700 DEG C, the holding time is 15-40 min, the heating rate is 0.5-1.5 DEG C per second, and the vacuum degree in the sintering chamber is less than 10 Pa during sintering.

[0015] Further, in step (6), after sintering, the sample is subjected to sand blasting, turning, electric spark processing, grinding, blade opening and other processes, and the processing technology is adjusted according to the actual situation. Further, in step (7), first, the diamond micro powder is used for blade opening, the blade opening time is 0.5-1.5 h, then the green silicon carbide powder is used for blade opening, the blade opening time is 1-2 h, the particle size of the diamond micro powder used for blade opening is 1-3 particle size numbers larger than the particle size of the diamond micro powder in the b piece, and the particle size of the silicon carbide micro powder is the same as or close to the particle size of the diamond micro powder.

[0016] The application provides a new high-uniform easy-sharpening grinding monocrystal diamond cutter grinding wheel manufacturing method, high-precision rolling and casting technology is used, the casting gap is 0.2-2 mm, and the casting rate is 200-600 mm / min. Different binders and proportions are used for a piece and b piece with different functions, integrated sintering is carried out through cross lamination by a plasma sintering equipment, the grinding wheel blank is obtained, and the grinding wheel is prepared through suitable post-processing technology and sharpening technology. Compared with the current product, the beneficial effects of the product are as follows: 1. The combination of layered preparation and rolling and casting forming process can avoid the problems of diamond floating, easy layering between different raw materials and fine particle size diamond powder segregation in high-thickness diamond grinding wheels. 2. According to the common sharpening and sharpening experience, the thickness of the designed binder layer can effectively avoid the difficult sharpening problem caused by too high diamond micro powder concentration; meanwhile, the a piece and the b piece are laminated to form the grinding wheel, the diamond height at the junction of the a piece and the b piece tends to be consistent, the diamond blade height and flatness are better than those of direct feeding sintering, and through suitable binder selection, the a piece can be designed as a porous structure, so as to further improve the sharpening efficiency and indirectly improve the machining quality and efficiency of the diamond cutter.

[0017] 3. The grinding wheel is made by plating relevant metal elements on the slotted base body, and the last layer is a binder, which is combined with the two schemes, so as to effectively improve the bonding strength of the base body and the abrasive layer, and effectively improve the running stability and grinding precision of the grinding wheel. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The flow chart of the grinding wheel of the present application is shown in the figure; Figure 2 The microstructure of the abrasive layer of the grinding wheel prepared in the example is shown in the figure; Figure 3 The abrasive layer morphology of the grinding wheel prepared in the example is shown in the figure. DETAILED DESCRIPTION

[0019] Example 1: A method for manufacturing a 7.5mm abrasive layer grinding wheel for a copper-based high-uniformity easy-to-trim single crystal diamond cutter, wherein the grinding wheel part is composed of a base body and a double-layer abrasive layer from bottom to top, the base body is made of 40Cr, the metal powder used for the a piece adhesive layer is 8515 copper-tin alloy powder with a particle size of W5, the adhesive used for the a piece is PVB+PEG (referred to as double-P adhesive, the mass fraction ratio of PVB:PEG is 3:2), and potassium sulfate is added at the same time. The main function of potassium sulfate is to adjust the pore, so that the adhesive layer can be removed as much as possible while maintaining the strength. The mass ratio of each component in the a piece is 8515: (PVB+PEG):K2SO4=17:2:1; the b piece abrasive layer is composed of diamond micro powder, 8515 copper-tin alloy powder, Co powder (active element), Ag (strengthening element) and adhesive (PVB+PEG; PVB:PEG=3:2). The adhesive used for the b piece is double-P adhesive, the particle size of the diamond micro powder used is 13-18µm, and the mass ratio of the b piece mixture is 8515 copper-tin alloy powder: Dia (diamond micro powder): Co: (PVB+PEG): Ag = 60:15:20:4:1. The specific preparation steps are as follows: 1) Mixing Mix the double-P adhesive, mix the potassium sulfate and 8515 copper-tin alloy with an alumina mortar first, then mix them together, and the mixing process is constant temperature stirring process, the temperature is 60℃, and the stirring time is 15 min, to obtain the a piece mixed paste; the b piece also needs to be mixed with a mortar first, then the abrasive and the adhesive are fully mixed by constant temperature stirring, the mixing temperature is 60℃, and the stirring time is 30 min; 2) Roller pressing and casting First, use the roller to improve the density of the blank, the roller speed is 180 r / min, the roller frequency is 3 times, use high-precision casting machine for casting, the casting speed is 400 mm / min, the a piece scraper height is 0.15 mm, the b piece scraper height is 1 mm, the a piece thickness after forming is 0.1-0.2 mm, the b piece thickness after forming is 0.8-1.2 mm; after forming, place it in the oven for drying, the oven temperature is 50-70℃, the drying time is 1-2h; Use a laser cutting machine to cut the rolled material belt, a material belt cutting process: laser power 15%-25%, scanning speed 500 mm / s, filling interval: 0.01 mm; b material belt cutting process: laser power 35%-45%, scanning speed 500 mm / s, filling interval: 0.01 mm; cut a and b material belts into rings, the outer circle diameter of the ring is 87 mm, and the inner circle diameter of the ring is 29.5 mm; place the cut sample in a dehumidifying cabinet.

[0020] 3) Surface treatment of the base The base material is 40Cr steel, a ring-shaped groove is opened by a turning tool, the groove depth is 1 mm, the groove width is 1.5 mm, and the groove spacing is 1.5 mm. After cleaning the base by removing oil and dust, copper plating is performed, the plating solution is CuSO4.5H2O: 150-200 g / L, H2SO4: 30-50 g / L, pH value is 1-3; temperature is 20-30℃; the final plating thickness is 0.2 mm; 4) Lamination, cross-laminate a and b pieces, and the top and bottom layers need to be a pieces; 5) Integrated sintering, design appropriate graphite mold, graphite material is Hongxing-8, matching precision is 0.02 mm, sintering equipment is plasma activated sintering equipment, sintering process: sintering temperature: 550-650℃, holding time: 20-40 min, sintering pressure: 50-60 MPa, vacuum degree: <10 Pa, heating rate is 1.5℃ / s, natural cooling; 6) Dimension processing: use multi-axis numerical control lathe to process the base matching surface and the base outer circle, select CBN superhard tool, cutting speed is 150-200 m / min, feed amount is 0.1-0.3 mm, the base precision after cutting is about 0.02 mm, use electric spark trimming machine for outer circle processing, discharge current is 0.1-0.3 A, pulse width is 20-50 µs, size tolerance reaches ±0.02 mm; use flat grinding equipment for abrasive layer surface removal and precision control, single wheel feed amount is 0.01 mm, select ceramic-based diamond wheel with particle size of 80 / 100, the final surface roughness is ≤Ra1.6 µm; 7) Dressing: Dressing the finished grinding wheel, using a single-sided grinder for dressing, abrasive first uses diamond powder, particle size of 30-35 pm, the speed of the lower plate of the grinder is 30-50 r / min, the air pressure is 0.8 MPa, and the dressing is performed. Observe every 30 min, dress for 1.5 h, then use green silicon carbide abrasive, particle size of 18-20 pm, speed of the lower plate of the grinder is 15-20 r / min, air pressure is 0.8 MPa, and the dressing is performed. Observe every 15 min until there is obvious diamond exposure, and the dressing time is between 1-2 h; 8) The dressing surface and gradient direction are observed using a field emission scanning electron microscope, as shown in FIGS. 1-3, Figure 2 、 Figure 3 , Figure 2 It can be seen that the a and b layers are distributed alternately, and the diamond is uniformly distributed in the abrasive layer without gradient settlement. Figure 3 FIG. 4 shows the abrasive layer morphology after dressing, Figure 3 It can be seen that the abrasive is obviously exposed, and the flatness is about 0.02 pm measured using a white light interferometer.

[0021] After the above processing technology, the abrasive copper-based diamond grinding wheel (outer diameter 86.5 mm x thickness 12.5 mm x inner diameter 30.16 mm x abrasive layer thickness 7.5 mm) for single crystal cutter has been completed, the flatness of the abrasive layer is ≤0.02 pm, the diamond dressing is obvious, and the tensile strength between the substrate and the abrasive layer interface reaches 70 MPa. The single crystal cutter is processed on the Coborn PG3B grinding machine, the speed is 4200 r / min, and the feed speed is 5 pm / min. The edge observation of the single crystal diamond cutter processed using the grinding wheel shows that the rake edge has no chipping under 500 times of optical microscope. Single wheel dressing can be used for 150 h, and the normal life of each grinding wheel is about 1 year.

Claims

1. A method for producing a high-uniform and easy-sharpening grinding wheel for single-crystal diamond tools, characterized in that: The specific steps are as follows: (1) Mixing: Mix the metal-based binder and the adhesive evenly to obtain the raw material paste of sheet A; mix the diamond powder, metal-based binder, active element, tissue strengthening element and adhesive evenly to obtain the raw material paste of sheet B; (2) Casting: The mixed raw material paste of sheet a and sheet b is made into a blank by roller pressing and casting equipment, and sheet a and sheet b are obtained after cutting; (3) Surface treatment of substrate: groove the substrate in contact with the laminate, and then electroplate the contact surface. The electroplating material is the metal element with the highest proportion in the metal-based binder in sheet a; (4) Lamination: Cross-laminate sheet a and sheet b and place them in a graphite mold; the top and bottom layers are sheet a; (5) Integrated sintering: Place the substrate and related laminates together in a plasma activated sintering device for sintering; (6) Dimension processing: Processing the base, outer circle and end face to achieve relevant dimensional accuracy; (7) Sharpening: Sharpening is performed without destroying the precision of the mating surface.

2. The method for manufacturing a high-uniform and easy-sharpening single-crystal diamond tool grinding wheel according to claim 1, characterized in that: In step (1), the binder of sheet a is selected from one or a mixture of two or more of paraffin wax, polyethylene glycol, polyvinyl butyral, glycerol and acetone in any proportion, and the metal-based binder used in sheet a is selected from one or a mixture of two or more of iron, copper, cobalt, tungsten, tin and alloy powders thereof in any proportion, and the mass ratio of the metal-based binder to the binder in sheet a is (8-12):

1.

3. The method for manufacturing a high-uniform and easy-sharpening single-crystal diamond tool grinding wheel according to claim 1, characterized in that: In step (1), the binder in sheet b is selected from one or a mixture of any proportion of polyvinyl butyral and polyethylene glycol, the metal-based binder used is selected from one or a mixture of any proportion of copper, tin, iron, cobalt, tungsten and alloy powders thereof, the active element is selected from one or a mixture of any proportion of yttrium, iron, cobalt, manganese and vanadium, the tissue strengthening element is selected from one or a mixture of any proportion of silver, cobalt, lead and tin, the particle size of the diamond powder is 8 to 20 microns, and the mass ratio of the diamond powder, the metal-based binder, the active element, the tissue strengthening element and the binder is (10 to 20): (50 to 70): (15 to 25): (1 to 5): (3 to 5).

4. The method for manufacturing a high-uniform and easy-sharpening single-crystal diamond tool grinding wheel according to claim 1, characterized in that: In step (2), the thickness of sheet a is controlled at 0.05-0.1 mm, and the thickness of sheet b is controlled at 0.4-0.6 mm. After the sheet paste is dried or air-dried, the green sheet is cut by laser or punching.

5. The method for manufacturing a high-uniform and easy-sharpening single-crystal diamond tool grinding wheel according to claim 1, characterized in that: In step (3), the total thickness of the green sheets is 1.5 to 2 times the thickness of the grinding wheel abrasive layer, and the thickness of the grinding wheel abrasive layer is 7 mm to 15 mm.

6. The method for manufacturing a high-uniform and easy-sharpening single-crystal diamond tool grinding wheel according to claim 1, characterized in that: In step (3), the substrate used is a steel substrate and is tempered, and the groove is an annular groove, a rectangular groove or a wavy groove.

7. The method for manufacturing a high-uniform and easy-sharpening single-crystal diamond tool grinding wheel according to claim 1, characterized in that: In step (5), the sintering temperature is 550-700°C, the holding time is 15-40 min, the heating rate is 0.5-1.5°C per second, and the vacuum degree in the sintering chamber is within 10 Pa during sintering.

8. The method for manufacturing a high-uniform and easy-sharpening single-crystal diamond tool grinding wheel according to claim 1, characterized in that: In step (7), diamond micropowder is first used for sharpening, and the sharpening time is 0.5~1.5h, and then green silicon carbide powder is used for sharpening, and the sharpening time is 1~2h. The particle size of the diamond micropowder used for sharpening is 1~3 particle sizes larger than the particle size of the diamond micropowder in the b plate, and the particle size of the silicon carbide micropowder is the same as or close to the particle size of the diamond micropowder.

9. The method for manufacturing a high-uniform and easy-sharpening grinding wheel for single-crystal diamond tools according to claim 6, characterized in that: The tempering temperature of the tempering treatment is 530-570° C., the tempering time is 60-120 min, the heating rate is 9-11° C. / min, and the temperature naturally drops to room temperature after the tempering treatment is completed.

10. The method for manufacturing a high-uniform and easy-sharpening single-crystal diamond tool grinding wheel according to claim 2, characterized in that: The a sheet also contains a pore-forming agent, which is selected from at least one of potassium sulfate, sodium sulfate, sodium chloride, calcium carbonate and graphite. The amount of the pore-forming agent added is 1% to 10% of the total mass of the a sheet raw materials.

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