A method for manufacturing a metal-bonded sintered grinding head and a grinding wheel

Abstract

This invention belongs to the field of abrasive technology, and discloses a method for manufacturing a metal-bonded sintered grinding head and a grinding wheel. The method comprises the following steps: pre-processing, hot-pressing and sintering of the outer grinding layer, shaping of the outer grinding layer, forming and filling of the inner grinding layer, sintering of the inner grinding layer, and overall shaping. In the preparation of the outer grinding layer, 70wt% Cu-Sn powder, 15wt% Co powder, 10wt% Fe powder, and 5wt% Ni powder are selected and mixed with 100# diamond at a mass ratio of 4:1 for 4 hours. The mixture is then hot-pressed and sintered into a ring blank using a graphite mold, and then connected to the substrate by vacuum brazing. The inner grinding layer is prepared by mixing Ag-Cu-Sn pre-alloyed powder with 400# diamond at a mass ratio of 6:1, adding 3% TiC powder of the total mass of the two mixtures, and cold-pressing into a cylindrical blank, which is then tightly bonded to the inner ring of the outer grinding layer to form a radial double-layer structure. Finally, the finished product is obtained through sintering. This method employs a dual-layer grinding design, with the outer layer adapting to efficient material removal during roughing and the inner layer ensuring surface quality during finishing. This allows for a single grinding head to perform a single-pass machining process that balances efficiency, lifespan, and precision, thereby reducing machining and tooling costs.

Description

Technical Field

[0001] This invention belongs to the field of abrasive technology, and particularly relates to a method for manufacturing a metal-bonded sintered grinding head and a grinding wheel. Background Technology

[0002] With the development of modern industry, such as aerospace, electronics, and optics, the demand for processing hard and brittle materials like cemented carbide, ceramics, glass, and gemstones is increasing. These materials are characterized by high hardness and brittleness, making them difficult to process efficiently and with high precision using traditional grinding wheels. Diamond grinding wheels, due to their extremely high hardness and wear resistance, have become the ideal choice for processing such materials. Among diamond grinding wheels, metal-bonded sintered grinding wheels are used in many processing applications due to their excellent performance. The common process for metal-bonded sintered diamond grinding wheels involves mixing powder metallurgy metal powder with diamond abrasive grains, pressing them into shape, and then sintering them at high temperatures. After sintering, mechanical interlocking forces and metallurgical bonding forces are generated between the metal powder and the diamond abrasive grains, firmly holding the diamond abrasive grains together. Under many processing conditions, customers require a long service life for the grinding wheel, high load processing efficiency, and high surface quality. These three requirements are inherently contradictory in terms of the performance of grinding wheels. Grinding wheels capable of high-load, rapid removal are inevitably used for roughing, resulting in lower surface finish. Conversely, grinding wheels producing higher surface finish are typically used for medium- and finish machining, where they are prone to severe wear or even burnout under high-load, rapid removal. Therefore, in practical applications, multiple grinding wheels of different models are often used in multiple machining operations to handle both the high-load roughing and the high-quality medium- and finish machining respectively. This separation of roughing and finishing processes necessitates at least two different grinding wheels and more than two grinding operations and wheel changes. This not only increases tool procurement costs but also extends working hours due to downtime for tool changes and parameter adjustments, while simultaneously increasing the complexity of grinding wheel inventory management and equipment debugging. Summary of the Invention

[0003] To address this issue, this invention proposes a method for manufacturing a metal-bonded sintered grinding head and a grinding wheel that combines two grinding wheels for roughing and finishing into one, achieving the coexistence of coarse and fine abrasive regions on the same grinding wheel. This solves the cost and efficiency problems caused by multiple grinding wheels in the prior art.

[0004] In a first aspect, the present invention proposes a method for manufacturing a metal-bonded sintered grinding head, comprising the following steps performed sequentially: a pre-process, hot pressing and sintering of the outer grinding layer, shaping of the outer grinding layer, forming and filling of the inner grinding layer, sintering of the inner grinding layer, and overall shaping; wherein... Pre-processing: Raw material cleaning, mixing, and granulation; The hot-pressing sintering of the outer grinding layer includes: selecting 70wt% Cu-Sn powder, with a Cu to Sn ratio of 10:1; 15wt% Co powder, 10wt% Fe powder, and 5wt% Ni powder, and stirring together with 100# diamond for 4 hours, controlling the metal powder particle size to -300#, and setting the mass ratio of metal powder to diamond abrasive grains to 4:1; after stirring, it is fed into a graphite mold for hot-pressing sintering, and the sintered blank is circular. After hot-pressing sintering, copper welding rods are used to weld the sintered blank onto the substrate through vacuum brazing; External grinding layer shaping: Using an electrical discharge machine to shape the inner hole of the external grinding layer; The inner grinding layer forming filler includes: Ag-Cu-Sn pre-alloyed powder with a three-element ratio of 3:6:1 and a powder particle size of -500#, mixed with 400# diamond abrasive grains at a mass ratio of 6:1, and TiC powder is added. After stirring, the mixture is cold-pressed to obtain a compact, which is cylindrical. The compact is tightly fitted to the inner ring of the outer grinding layer ring, resulting in a grinding wheel with two radially distributed grinding layers of different particle size concentrations. The sintering of the inner grinding layer includes: sintering the grinding wheel to obtain the final grinding wheel product.

[0005] Overall shaping: After sintering, the inner grinding layer blank has fully filled the inner hole of the outer grinding layer and is sintered tightly with the hole wall as one piece. Electrical discharge machining (EDM) can be used for shaping.

[0006] The metal-bonded sintered grinding head manufacturing method described in this application integrates a coarse abrasive layer and a fine abrasive layer radially onto the same grinding wheel. It precisely utilizes the difference in linear velocity between the outer and inner rings during end-face grinding: the outer ring coarse abrasive layer, with its high rotational speed and strong cutting ability, preferentially contacts the workpiece, undertaking over 90% of the material removal. Its high-hardness bond system ensures wear resistance and abrasive grain holding force under heavy loads, significantly extending the overall lifespan of the grinding wheel. The inner ring fine abrasive layer follows up to refine the surface after coarse grinding. Utilizing the micro-cutting action of the fine abrasive grains and the bond properties adapted to fine grinding, surface roughness is controlled to an even lower level. Compared to the traditional dual-wheel, multi-stage processing method, this invention eliminates the need for downtime to replace the grinding wheel, reducing tool change and debugging time by over 40% and significantly improving processing efficiency. Simultaneously, it eliminates the procurement, storage, and management costs of a set of grinding wheels, reducing the overall tool cost by over 35%.

[0007] Preferably, the hot pressing and sintering of the outer grinding layer further includes: The sintering temperature is 800° to 1000°, the pressure is 30 MPa, the holding time is 300 s, and the vacuum degree is 10⁻² Pa. The sintered blank is a ring with an outer diameter of 16.5 mm, an inner diameter of 9.5 mm, and a length of 10 mm.

[0008] Preferably, the external grinding layer shaping further includes: The inner hole of the external grinding layer is modified using an electrical discharge machine with a cylindrical red copper electrode. First, it is machined vertically, and then it is bored for finishing. The inner hole diameter is modified to 10mm with a tolerance of ±0.05. The modification current is a three-stage current of 28A, 18A and 10A.

[0009] Preferably, the sintering of the inner grinding layer further includes: The TiC powder is 3% of the sum of the mass of the pre-alloyed powder and the diamond abrasive grains; The TiC powder has a particle size of 1200# and an irregular dendritic shape.

[0010] Preferably, the sintering of the inner grinding layer further includes: Cold pressing is performed at a pressure of 50 MPa. During cold pressing, 1-5% by weight of binder is added. The diameter of the pressed blank is 9.8 mm, and its height is 10% to 20% higher than the depth of the inner hole of the outer grinding layer. The gap between the pressed blank and the inner ring of the outer grinding layer does not exceed 0.2 mm.

[0011] Preferably, the sintering of the inner grinding layer further includes: The cold-pressed blank is sent into a vacuum brazing furnace. The process is set as follows: heating time 3 hours, holding temperature at 750° to 850° for 4 hours, vacuum degree not higher than 10-3 Pa, and then natural cooling and solidification to obtain an inner grinding layer and an outer grinding layer sintered into one. During sintering, the inner grinding layer is in a solid-liquid mixed phase sintering state, wherein the liquid phase ratio is greater than 50%.

[0012] Preferably, the overall modification further includes: Using an electrical discharge machine, the outer diameter of the integral milling wheel is dressed to 16mm, the end face is flattened, and a chip removal groove is cut.

[0013] Preferably, the overall modification further includes: The sintering temperature of the outer grinding layer is at least 100° higher than that of the inner grinding layer during hot pressing.

[0014] Preferably, the internal grinding layer forming filler further includes: When molding the filler, additives containing Ti and / or Cr are added to adjust the performance of the grinding wheel and stirred.

[0015] Secondly, the present invention also provides a grinding wheel, including a substrate and a welding position for an outer grinding layer, wherein the grinding wheel further includes: The outer grinding layer is in the form of a ring. The outer grinding layer is made of 70wt% Cu-Sn powder, with a Cu to Sn ratio of 10:1; 15wt% Co powder, 10wt% Fe powder, and 5wt% Ni powder, together with 100# diamond. The outer grinding layer is made by using copper welding rods to weld the sintered billet onto the substrate through vacuum brazing. The inner grinding layer is cylindrical and is made of Ag-Cu-Sn pre-alloyed powder with a ratio of 3:6:1 and a particle size of -500#. It is mixed with 400# diamond abrasive grains at a mass ratio of 6:1 and TiC powder is added. The inner grinding layer is tightly bonded to the inner ring of the outer grinding layer to obtain a grinding wheel with two grinding layers of different particle size concentrations distributed radially.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for manufacturing a metal-bonded sintered grinding head and a grinding wheel, combining two grinding wheels for roughing and finishing into one. On the same grinding wheel, coarse and fine abrasive grain regions coexist, and for face grinding wheels, the coarse and fine abrasive grains are radially distributed. The coarse abrasive grain layer is located in the outer ring layer, possessing a high linear velocity, and first contacts and grinds the workpiece, undertaking the majority of material processing and removal tasks. The fine abrasive grain layer is located in the inner layer, contacting the workpiece after grinding in the outer ring layer, undertaking the finishing of the machined surface. This achieves the following: the coarse abrasive grain layer first performs roughing, the fine abrasive grain layer follows, and the machined surface after coarse abrasive grinding is then finished with fine abrasive grains, thus achieving a longer grinding wheel life, faster processing efficiency, and higher processing quality. Attached Figure Description

[0017] Figure 1 This is a process diagram of a metal-bonded sintered grinding head manufacturing method described in this embodiment.

[0018] Figure 2 This is a schematic diagram of the grinding wheel structure described in this embodiment.

[0019] Figure 3 This is a finished image of the grinding wheel in this embodiment.

[0020] Figure 4 This is a schematic diagram of the grinding wheel material in this embodiment.

[0021] Wherein, 1-substrate; 2-welding position of outer grinding layer; 3-inner grinding layer; 4-outer grinding layer; 5-shank; 6-sintered grinding layer. Detailed Implementation

[0022] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0023] Example 1, as Figure 1 As shown, this invention proposes a method for manufacturing a metal-bonded sintered grinding head, comprising the following steps performed sequentially: a pre-process, hot pressing and sintering of the outer grinding layer, shaping of the outer grinding layer, forming and filling of the inner grinding layer, sintering of the inner grinding layer, and overall shaping; wherein, The pre-processing includes: The cleaning process involves surface cleaning of various metal powders and diamond abrasive grains to remove impurities such as oil, dust, and oxide scale that adhere to the raw materials during production and storage. Anhydrous ethanol or acetone is commonly used as the cleaning medium. After cleaning, the materials are vacuum dried to ensure surface cleanliness.

[0024] The mixing process, which refers to the initial premixing of raw materials after they enter the factory (not the subsequent fine mixing with diamond abrasive grains), involves homogenizing and mixing single metal powders of the same batch and specification to ensure the particle size distribution and composition uniformity of the single component powders.

[0025] In the granulation process, conventional methods such as spray granulation are used to produce particles with uniform particle size for some metal powders with finer particle size or poorer flowability. This improves the flowability and bulk density of the powder, making it easier to weigh and fill molds in the future.

[0026] The hot pressing and sintering of the outer grinding layer includes: Industrial-grade metal powders were selected, with the following specific proportions and parameters: 70wt% copper (Cu) and tin (Sn) powder, with a Cu:Sn ratio of 10:1, where Sn forms a liquid phase to promote densification, and Cu provides basic strength; 15wt% cobalt (Co) powder to enhance the interfacial binder and improve the high-temperature stability of the matrix; 10wt% iron (Fe) powder, which, by adding Fe, forms a solid solution with the C atoms of diamond, improving wettability and reducing the coefficient of thermal expansion; and 5wt% nickel (Ni) powder, which, together with 100# diamond, was stirred for 4 hours, with the metal powder particle size controlled at -300#, and the mass ratio of metal powder to diamond abrasive grains set at 4:1. After stirring, the mixture was fed into a graphite mold for hot pressing and sintering. The sintered blank was annular, and after hot pressing and sintering, copper welding rods were used to weld the sintered blank onto the substrate via vacuum brazing.

[0027] In this embodiment, according to the above-mentioned material ratio requirements for the outer grinding layer, 700g of Cu-Sn alloy powder, 150g of Co powder, 100g of Fe powder, and 50g of Ni powder were weighed as the base material, for a total mass of 1000g. Based on a 4:1 mass ratio of metal powder to diamond abrasive grains, 250g of 100# diamond abrasive grains were weighed. The weighed metal binder powder and diamond abrasive grains were added together to an agate grinding jar, and 50mL of anhydrous ethanol was added as a dispersion medium to prevent powder agglomeration. The grinding jar was placed in a planetary ball mill, and the speed was set to 200r / min. The mixture was continuously stirred and mixed for 4 hours to ensure uniform distribution of the diamond abrasive grains in the metal powder. After mixing, the slurry was placed in a vacuum drying oven and dried at 60℃ for 2 hours to remove the anhydrous ethanol, resulting in a uniform mixed powder.

[0028] Preferably, various reinforcing phases and functional additives, such as WC, TiC, Ni, and Ag, can be added to achieve other performance requirements, and are not limited to these. Among them, tungsten carbide (WC) can generally improve the hardness and wear resistance of the material; titanium carbide (TiC) can enhance the interfacial bonding strength between the binder and the abrasive grains; and elements such as nickel (Ni) and silver (Ag) may also play a role in improving wettability and increasing density.

[0029] Based on the material ratio of the external grinding layer, the pre-processed metal powder and diamond abrasive grains are uniformly filled into the graphite mold cavity. A pneumatic vibrator is used with an amplitude of 0.5 mm and a frequency of 50 Hz for 2 minutes to ensure uniform loose density of the powder, thus achieving the desired result. To avoid localized voids.

[0030] After covering the graphite pressure head, the mold is slowly pushed into the vacuum hot pressing sintering furnace cavity. The furnace door is closed and the vacuum system is started. Vacuuming is performed in stages: first, a mechanical pump is used to evacuate to 1 Pa, then a diffusion pump is started to evacuate to... After stabilizing for 3 minutes and confirming no rebound in vacuum level, the vacuum state was maintained throughout the sintering process. This vacuum level effectively isolates oxygen and prevents the diamond abrasive grains from contacting oxygen at temperatures above 800℃. Reaction generation The carbonization phenomenon.

[0031] Set the sintering process parameters for the outer grinding layer: heat to 600℃ at a rate of 10℃ / min, hold for 10min to remove residual moisture and impurities in the powder, and avoid generating bubbles at high temperature, which would lead to defects in the blank; continue to heat to 850℃ at a rate of 8℃ / min, while applying a hot pressing pressure of 25MPa; hold at 850℃ and 25MPa for 30min to fully densify the metal powder and form a metallurgical bond with the diamond abrasive grains.

[0032] After sintering, heating is stopped, and pressure is maintained until the furnace temperature drops below 200°C. The pressure is then released, and the furnace continues to cool to room temperature. The furnace door is then opened, and the sintered billet is removed. The sintered billet is annular, with dimensions matching the graphite mold cavity, specifically an outer diameter of 300 mm, an inner diameter of 120 mm, and a thickness of 15 mm.

[0033] In this embodiment, the external grinding layer modification also includes: using an electrical discharge machine to modify the inner hole of the external grinding layer, using a cylindrical red copper electrode, first vertical machining, and then boring for precision machining; wherein, the inner hole diameter is modified to 10mm with a tolerance of ±0.05; the modification current is a three-stage current of 28A, 18A, and 10A.

[0034] The DK7740 EDM machine has a maximum processing current of 50A, a positioning accuracy of ±0.005mm, and is equipped with an automatic Z-axis feed system and pulse power supply, supporting multi-segment current parameter settings. It uses cylindrical red copper electrodes with a purity ≥99.9%, a diameter of 9.8mm (with a 0.2mm finishing allowance), a length of 100mm, and a concentricity of ≤0.003mm at both ends. The surface is polished (Ra≤0.8μm).

[0035] Preferably, in the vertical machining stage: the machine tool is started, and the electrode is fed vertically downward along the Z-axis, performing electrical discharge machining with a high current of 28A. In this stage, the strong erosion capability of the high current is utilized to quickly machine the inner hole diameter from 10.5mm to 10.1mm, removing most of the reserved allowance; the slag discharge is observed in real time during the machining process, and a 10-second pause is made every 3mm to ensure that the electro-erosion products are fully discharged and to avoid slag accumulation that could lead to a short circuit.

[0036] Roughing and finishing stages of boring: After vertical machining to the preset depth, keep the electrode position unchanged, switch to 18A medium current, start the table rotation function (speed 50r / min), and slowly feed the electrode radially (feed amount 0.05mm / revolution). In this stage, the ovality and taper of the inner hole are corrected by the stable etching characteristics of the medium current, and the diameter is controlled to 10.02mm, and the tolerance is reduced to ±0.03mm.

[0037] During the boring finishing stage: While keeping the worktable rotating, switch to a low current of 10A, and reduce the electrode radial feed to 0.02mm / revolution. The low current corresponds to short pulse widths and long pulse intervals, resulting in finer etching marks. This can optimize the surface roughness of the inner hole from Ra3.2μm to Ra1.6μm, while precisely finishing the diameter to 10mm, with the final tolerance controlled within ±0.05mm.

[0038] After processing is completed, turn off the discharge power, raise the electrode, drain the processing fluid, remove the sintered billet from the worktable, and repeatedly rinse the inner hole and surface with anhydrous ethanol to remove residual processing fluid and electro-erosion residue.

[0039] The modified inner hole was inspected using an inside micrometer with an accuracy of 0.001 mm: the diameter in the X and Y axes was measured at three positions: the hole opening, the middle of the hole, and the bottom of the hole. The measured diameter values ​​were all within the range of 9.95 mm to 10.05 mm, and the tolerance met the requirements. The coaxiality between the inner hole axis and the outer circle axis was checked using a dial indicator, and the error was ≤0.02 mm, which met the requirements for subsequent assembly.

[0040] Internal grinding layer forming filler: Specifically, the inner grinding layer forming filler includes: selecting Ag-Cu-Sn pre-alloyed powder, with the three elements in a ratio of 3:6:1 and a powder particle size of -500#, mixing it with 400# diamond abrasive grains at a mass ratio of 6:1, adding TiC powder, stirring, and then cold pressing to obtain a blank. The blank with a certain strength after cold pressing is placed into the inner hole of the outer grinding layer to complete the filler.

[0041] Preferably, when formulating the inner grinding layer material, additives such as active elements like Ti and Cr can be added to adjust the performance of the grinding wheel. For example: adding Ti powder: purity ≥99.9%, particle size -800# (particle size ≤15μm), irregular morphology, the amount added is 1.0wt% of the total mass of the pre-alloy powder and diamond; adding Cr powder: purity ≥99.5%, particle size -800# (particle size ≤15μm), plate-like structure, the amount added is 0.5wt% of the total mass of the pre-alloy powder and diamond.

[0042] According to the above requirements, the internal grinding layer material is prepared as follows: 600g of Ag-Cu-Sn pre-alloy powder, 100g of 400# diamond abrasive, 21g of TiC powder (3%), 7g of Ti powder (1.0%), and 3.5g of Cr powder (0.5%) are weighed in proportion. Calculate the amount of PVA adhesive used: (600+100+21+7+3.5)×3%≈21.94g, which corresponds to 219.4g of a 10% concentration aqueous solution.

[0043] The first stage involves pre-dispersion of active elements: Ti powder, Cr powder and 50% Ag-Cu-Sn pre-alloy powder are added to an inert atmosphere mixing device, and Ar gas is introduced to replace the air at a flow rate of 2L / min for 10min. The mixture is then pre-mixed at 350r / min for 1h. The pre-alloy powder particles are used as a carrier to achieve the initial dispersion of Ti and Cr, thus avoiding direct contact and oxidation of active elements with air.

[0044] The second stage involves overall mixing: the remaining Ag-Cu-Sn pre-alloy powder, TiC powder and diamond abrasive grains are added to the device, Ar gas is continuously introduced, and the mixture is mixed at 300 r / min for 2 hours. During this period, PVA binder aqueous solution is slowly added dropwise to form uniform and moist granular powder.

[0045] Finally, transfer the mixed powder to a vacuum drying oven and dry it at 50℃ and -0.09MPa for 5 hours. If necessary, the drying time can be extended by 1 hour to ensure that the moisture is fully removed. After passing through an 80-mesh sieve, it is ready for use.

[0046] Preferably, the inner grinding layer forming filler further includes a blank obtained by cold pressing, the blank being cylindrical, the blank being tightly fitted with the inner ring of the outer grinding layer ring, to obtain a grinding wheel with two grinding layers of different particle size concentrations distributed radially.

[0047] Preferably, the internal grinding layer is cold-pressed using a powder cold pressing machine with a maximum pressure of 100MPa and a pressure control accuracy of ±0.5MPa.

[0048] Preferably, the mixed powder is filled into the cavity of a cylindrical mold, the surface is leveled with a scraper, and pre-pressed at 5MPa for 30s to remove air. Cold pressing is performed at a pressure of 50MPa, so the pressure is increased to 50MPa at a rate of 10MPa / min and held at 50MPa for 300s to ensure powder densification. During cold pressing, 1-5% by weight of binder is added to prevent breakage upon demolding. After demolding, both ends of the compact are trimmed to obtain a compact diameter of 9.8mm ± 0.02mm and a height of 9mm ± 0.03mm. It should be noted that the height of the compact should be higher than the depth of the inner hole of the outer grinding layer, with the height difference being 10% to 20% of the total height.

[0049] Further, clean the inner hole of the outer grinding layer and the outer surface of the inner grinding layer blank to remove oil and impurities. Slowly push the blank in along the axis of the inner hole of the outer grinding layer, and use a feeler gauge to check the assembly clearance: the maximum clearance in the circumferential direction is 0.18mm, the minimum clearance is 0.15mm, and both are ≤0.2mm to ensure a tight fit. Use a dial indicator to calibrate the coaxiality, controlling the error within 0.03mm to avoid eccentricity after sintering. Sintering of internal grinding layer: After cold pressing, the inner grinding layer is sintered. Specifically, the entire grinding wheel, including the substrate, the outer grinding layer (which has been shaped and welded), the loosely assembled inner grinding layer blank (located within the inner hole of the outer grinding layer), is fed into a vacuum sintering furnace. The vacuum value is ensured to be no higher than 10⁻³ Pa. A suitable sintering temperature is selected based on the material composition of the inner grinding layer.

[0050] Preferably, the assembled double-layer structure is placed into a vacuum brazing furnace, the furnace door is closed, the vacuum system is started, and a vacuum is drawn until... The entire process is kept in a high vacuum state.

[0051] Preferably, in the vacuum brazing furnace, the temperature rise is controlled in three stages: The first stage involves slow heating: the temperature is increased from room temperature to 750°C at a rate of 5°C / min, taking 3 hours, to avoid the difference in thermal stress between the inner and outer layers caused by a sudden temperature rise.

[0052] The second stage involves heat treatment and sintering: holding at 750-850℃ for 4 hours, preferably 800℃. At this temperature, the low-melting-point phase in the Ag-Cu-Sn pre-alloyed powder melts, forming a liquid phase ratio of ≥55%. This liquid phase fills the pores and assembly gaps of the compact and simultaneously diffuses and fuses with the outer grinding layer metal matrix. During sintering, the inner grinding layer is in a solid-liquid mixed-phase sintering state, with a liquid phase ratio greater than 50%.

[0053] Preferably, the solid phase in the solid-liquid mixture consists mainly of Ag-Cu solid solution particles with a melting point of about 900-1085℃ and a sintering temperature above 800℃. During sintering, they remain solid and are interconnected to form a rigid skeleton. This is the core source of the hardness and wear resistance of the inner grinding layer, avoiding the material becoming too soft due to solidification of the entire liquid phase, which would prevent it from being unable to perform the grinding function.

[0054] The liquid phase consists mainly of Sn-based phase or Ag-Cu-Sn ternary eutectic phase, with a melting point of 221-415℃, which is much lower than the sintering temperature. It melts completely at 800℃ and has a volume ratio of >50%, exhibiting high fluidity. Its core function is to fill the medium, act as a diffusion carrier, and bind the bond, solving the problems of numerous pores and weak interfacial bonding that cannot be overcome by solid-phase sintering.

[0055] During the sintering process, the liquid phase permeates and fills the space under the action of capillary force. At the same time, some solid particles Ag-Cu will dissolve in the liquid phase in small amounts and then precipitate uniformly after 4 hours of heat preservation. This ensures the fluidity of the liquid phase and avoids excessive dissolution of the solid skeleton, which could lead to structural collapse. In the end, a stable microstructure is formed in which solid particles are embedded in the continuous liquid phase binder.

[0056] It should be noted that liquid phase sintering is the key technology in this scheme. The liquid phase can penetrate and solidify along the gap, achieving a seamless connection between the inner and outer structures. This allows the inner grinding layer to be tightly bonded to the inner hole surface of the outer grinding layer. When the inner grinding layer is subjected to impact, the tougher binder phase can absorb energy, preventing the solid particles from fracturing directly, thus increasing the fracture toughness (KIC) of the inner grinding layer to a higher level. It effectively prevents chipping and breakage caused by impact during grinding.

[0057] The third stage is natural cooling: After the heat preservation is completed, the heating system is turned off and the furnace is cooled to room temperature at a cooling rate of ≤10℃ / min. The liquid phase crystallizes and solidifies during slow cooling, realizing the metallurgical bonding of the inner and outer layers, and obtaining an inner grinding layer and an outer grinding layer sintered into one.

[0058] Preferably, the TiC powder is 3% of the sum of the mass of the pre-alloyed powder and the diamond abrasive grains; Preferably, the TiC powder has a particle size of 1200# and an irregular dendritic shape.

[0059] Overall shaping: Preferably, based on the integrated inner and outer grinding layers obtained in the previous step, an overall shaping process is performed, specifically including: using an electrical discharge machine to dress the outer diameter of the integral milling wheel to 16mm, flattening the end face, and sharpening it with an oilstone. After completion, a grinding wheel with two grinding layers of different grit concentrations distributed radially is obtained.

[0060] It should be noted that the sintering temperature of the outer grinding layer during hot pressing is at least 100° higher than that of the inner grinding layer during sintering.

[0061] On the same grinding wheel, coarse and fine abrasive grain regions coexist, and for face grinding wheels, the coarse and fine abrasive grains are distributed radially. The coarse abrasive grain layer is located in the outer ring layer, possessing a higher linear velocity, and first contacts and grinds the workpiece, undertaking the majority of material processing and removal tasks. The fine abrasive grain layer is located in the inner layer, and after being ground by the outer ring layer, it contacts the workpiece, undertaking the finishing of the machined surface, with a lighter grinding removal task. Thus, the coarse abrasive grain layer first achieves rough machining, followed by the fine abrasive grain layer, and the machined surface after being ground by the coarse abrasive grains is then finished with a fine abrasive grain, thereby achieving the goals of longer grinding wheel life, faster processing efficiency, and higher processing quality.

[0062] Furthermore, by designing the sintering process for the two grinding layers to have a significant temperature difference, it is relatively convenient to sinter the two grinding layers sequentially. That is, the layer requiring a higher temperature can be sintered first, and then the layer requiring a lower temperature can be sintered in the furnace a second time, without adversely affecting the original grinding layer sintered at a higher temperature. This two-stage sintering process is simple and convenient, only requiring certain performance from the vacuum sintering equipment, and can be extended to a multi-stage sintering process.

[0063] To further illustrate the technical effects of the metal-bonded sintered grinding head manufacturing method described in this invention, the following tests were conducted: Test method: Alumina ceramic thinned by 99% was machined using the end face of a grinding wheel. Machining parameters: spindle speed 18000 rpm, Z-axis depth of cut 0.15 mm, feed rate F1200, stepover 8 mm, Z-path layer milling. Total machining depth: 200*200*20 mm.

[0064] The test grinding wheels were of the same size and the structure was divided into 3 groups to examine machining wear, appearance of the machined surface, and roughness of the machined surface; Group 1 (control group): D16-100#, a single particle size of 100#; Group 2 (control group): D16-400#, a single particle size of 400#; Group 3 (Experimental Group): D16-100# / 400#, which is the outer layer 100# and the inner layer 400#.

[0065] The test results are as follows:

[0066] Test data analysis: 1. Group 3 is comparable to Group 1 in terms of wear amount, but the appearance and roughness of the machined surface are significantly better than Group 1; 2. The wear of Group 2 is severe and the machined surface is seriously damaged. It is determined that under these processing parameters, the single grit size of 400# cannot be sustained, and the grinding wheel has been damaged and failed.

[0067] In summary, the combined milling wheel with an outer 100# and an inner 400# layer can achieve the same processing efficiency as a single 100# wheel, while maintaining good wheel performance and not failing. In terms of wheel wear, it is also very close to that of a single 100# wheel. In terms of surface finish, it is significantly superior to a single 100# wheel.

[0068] Secondly, such as Figure 2-3 As shown, the present invention also proposes a grinding wheel, including a base material and an outer grinding layer welding position. The base material is made of 45# steel, and the structure is as follows. Figure 3 As shown, a welding boss is reserved at the end.

[0069] The grinding wheel also includes: The outer grinding layer is in the form of a ring. The outer grinding layer is made of 70wt% Cu-Sn powder, with a Cu to Sn ratio of 10:1; 15wt% Co powder, 10wt% Fe powder, and 5wt% Ni powder, together with 100# diamond. The outer grinding layer is made by using copper welding rods to weld the sintered billet onto the substrate through vacuum brazing. The inner grinding layer is cylindrical and is made of Ag-Cu-Sn pre-alloyed powder with a ratio of 3:6:1 and a particle size of -500#. It is mixed with 400# diamond abrasive grains at a mass ratio of 6:1 and TiC powder is added. The inner grinding layer is tightly bonded to the inner ring of the outer grinding layer to obtain a grinding wheel with two grinding layers of different particle size concentrations distributed radially.

[0070] The radial double-layer structure design integrates the roughing outer ring and the finishing inner ring into the same grinding wheel, enabling continuous machining of efficient material removal and precision shaping without changing tools.

[0071] like Figure 4 As shown, the coarse abrasive layer first achieves rough machining, and the fine abrasive layer follows up with the fine abrasive layer. The machined surface after being ground by the coarse abrasive is then finished with a fine abrasive, thereby achieving the goal of longer grinding wheel life, faster processing efficiency, and higher processing quality.

[0072] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A method for manufacturing a metal-bonded sintered grinding head, characterized in that, include: The steps are performed sequentially: pre-processing, hot pressing and sintering of the outer grinding layer, shaping of the outer grinding layer, forming and filling of the inner grinding layer, sintering of the inner grinding layer, and overall shaping; among which, The hot-pressing sintering of the outer grinding layer includes: selecting 70wt% Cu-Sn powder with a Cu-Sn ratio of 10:1; 15wt% Co powder, 10wt% Fe powder, and 5wt% Ni powder, which are stirred together with 100# diamond for 4 hours. The particle size of the metal powder is controlled at -300#, and the mass ratio of metal powder to diamond abrasive is set to 4:

1. After stirring, the mixture is fed into a graphite mold for hot-pressing sintering. The sintered blank is circular. After hot-pressing sintering, copper welding rods are used to weld the sintered blank onto the substrate through vacuum brazing. The inner grinding layer forming filler includes: Ag-Cu-Sn pre-alloyed powder with a ratio of 3:6:1 and a powder particle size of -500#, mixed with 400# diamond abrasive grains at a mass ratio of 6:1, and TiC powder is added. After stirring, the mixture is cold-pressed to obtain a compact. The compact is cylindrical and is tightly fitted with the inner ring of the outer grinding layer sintered compact to obtain a grinding wheel with two grinding layers of different particle size concentrations distributed radially. The sintering of the inner grinding layer includes: sintering the grinding wheel to obtain the final grinding wheel product.

2. The method for manufacturing a metal-bonded sintered grinding head according to claim 1, characterized in that, The hot-pressing sintering of the outer grinding layer also includes: Sintering temperature: 800°C to 1000°C; pressure: 30 MPa; holding time: 300 s; vacuum degree:

10. -2 Pa; The sintered blank is a ring with an outer diameter of 16.5 mm, an inner diameter of 9.5 mm, and a length of 10 mm.

3. The method for manufacturing a metal-bonded sintered grinding head according to claim 2, characterized in that, The external grinding layer shaping also includes: The inner hole of the external grinding layer is modified using an electrical discharge machine with a cylindrical red copper electrode. First, it is machined vertically, and then it is bored for finishing. The inner hole diameter is modified to 10mm with a tolerance of ±0.

05. The modification current is a three-stage current of 28A, 18A and 10A.

4. The method for manufacturing a metal-bonded sintered grinding head according to claim 3, characterized in that, The internal grinding layer forming filler also includes: The TiC powder is 3% of the sum of the mass of the pre-alloyed powder and the diamond abrasive grains; The TiC powder has a particle size of 1200# and an irregular dendritic shape.

5. The method for manufacturing a metal-bonded sintered grinding head according to claim 4, characterized in that, The internal grinding layer forming filler also includes: Cold pressing is performed at a pressure of 50 MPa. During cold pressing, 1-5% by weight of binder is added, and the compact diameter is 9.8 mm, with the height exceeding the depth of the inner hole of the outer grinding layer by 10% to 20%. The gap between the pressed blank and the inner ring of the outer grinding layer does not exceed 0.2mm.

6. The method for manufacturing a metal-bonded sintered grinding head according to claim 5, characterized in that, The sintering of the inner grinding layer also includes: The cold-pressed compact is fed into a vacuum brazing furnace. The process is set as follows: heating time 3 hours, holding temperature at 750°C to 850°C for 4 hours, and vacuum degree not exceeding 10. -3 Pa, then naturally cooled and solidified to obtain an inner grinding layer and an outer grinding layer sintered into one piece; During sintering, the inner grinding layer is in a solid-liquid mixed phase sintering state, wherein the liquid phase ratio is greater than 50%.

7. The method for manufacturing a metal-bonded sintered grinding head according to claim 6, characterized in that, The overall modification also includes: Using an electrical discharge machine, the outer diameter of the integral milling wheel is dressed to 16mm, the end face is flattened, and a chip removal groove is cut.

8. The method for manufacturing a metal-bonded sintered grinding head according to claim 7, characterized in that, Also includes: The sintering temperature of the outer grinding layer is at least 100°C higher than that of the inner grinding layer.

9. The method for manufacturing a metal-bonded sintered grinding head according to claim 1, characterized in that, The internal grinding layer forming filler also includes: When molding the filler, additives containing Ti and / or Cr are added to adjust the performance of the grinding wheel and stirred.

10. A grinding wheel, comprising a base material and an outer grinding layer welded together, characterized in that, The grinding wheel also includes: The outer grinding layer is in the form of a ring. The outer grinding layer is made of 70wt% Cu-Sn powder, with a Cu to Sn ratio of 10:1; 15wt% Co powder, 10wt% Fe powder, and 5wt% Ni powder, together with 100# diamond. The outer grinding layer is made by using copper welding rods to weld the sintered billet onto the substrate through vacuum brazing. The inner grinding layer is cylindrical and is made of Ag-Cu-Sn pre-alloyed powder with a ratio of 3:6:1 and a particle size of -500#. It is mixed with 400# diamond abrasive grains at a mass ratio of 6:1 and TiC powder is added. The inner grinding layer is tightly bonded to the inner ring of the outer grinding layer to obtain a grinding wheel with two grinding layers of different particle size concentrations distributed radially.

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