Device and method for processing silicon nitride ceramic balls

Abstract

The present invention relates to the field of precision machining technology, specifically to the precision machining of silicon nitride ceramic balls, and more specifically to a device and method for machining silicon nitride ceramic balls. The present invention provides a grooved disk for machining silicon nitride ceramic balls, the grooved disk being provided with variable curvature grooves. The variable curvature grooves include staggered concentric circular curves, eccentric circular curves, and straight lines, and the angles at the intersections of the concentric circular curves, eccentric circular curves, and straight lines vary. Using the grooved disk to machine ceramic balls, the variable curvature grooves on the disk can achieve a sudden change in the rotation angle of the ceramic ball, thereby improving the efficiency of the machining trajectory enveloping the entire spherical surface.

Description

Technical Field

[0001] The present invention relates to the technical field of precision machining, in particular to the precision machining of silicon nitride ceramic balls, and in particular to a device and method for machining silicon nitride ceramic balls. Background Art

[0002] As industrial technology continues to advance, the demand for machining precision is also increasing, requiring higher-speed, more stable machining equipment. Among bearing rolling elements, silicon nitride ceramic balls offer advantages such as high hardness, high strength, high wear resistance, and stable chemical properties. Compared to other bearing steels, this chemical stability allows them to operate in more extreme environments. Furthermore, their exceptional strength, wear resistance, and durability can increase bearing service life by approximately two to five times. These superior properties make silicon nitride ceramic balls an indispensable material in high-end mechanical parts, electronic devices, chemical equipment, and other fields.

[0003] Due to the brittleness, chemical stability and difficulty in processing of silicon nitride materials, grinding has become the main means of ceramic processing. At present, traditional grinding mainly adopts concentric V-groove processing, using free abrasive as a single grinding tool for grinding and polishing. This grinding method changes the direction of the rotation axis by the phenomenon of the sphere constantly slipping and rotating in the V-groove, so that three coaxial ring-shaped processing tracks are formed on the surface of the sphere. However, the change in the direction of the rotation axis depends only on the eccentricity of the eccentric circle, so the angle of the rotation axis changes very little, resulting in the processing track not being able to completely envelop the entire sphere. The probability of each cutting point on the sphere is not equal, the processing efficiency is low, and it is difficult to obtain a sphere with high precision and high consistency.

[0004] To this end, the inventors have invented a track-changing grinding method and track-changing device for a concentric V-groove ball grinding machine, with application number CN201710594175.3. The track-changing device changes the rotation angle of the bearing steel ball on the concentric V-groove with the assistance of the track-changing device. Specifically, it refers to the process in which the sphere to be processed moves in the V-groove circular track of the concentric circle V-groove ball grinder, and after changing the track through the track changing block of the track changing device, it rolls from one V-groove circular track to the adjacent inner circle V-groove circular track; when the sphere to be processed enters the V-groove circular track of the outermost circle and passes through the track changing block of the track changing device, it progresses circle by circle to the V-groove circular track of the innermost circle; when the sphere to be processed in the V-groove circular track of the innermost circle passes through the track changing block of the track changing device, it directly enters the V-groove circular track of the outermost circle; when the sphere enters the V-groove circular track of the innermost circle twice adjacently, it is a grinding cycle, and after the sphere to be processed has gone through one grinding cycle, the variable curvature grinding is completed.

[0005] While this approach can mitigate the increased probability of cracks forming on the surface and subsurface areas of bearing steel balls due to prolonged grinding caused by inefficient machining processes, it still requires the influence of external tools and the reliance on multiple, sequentially arranged concentric V-shaped tracks, complicating the grinding process and limiting its practical application. Furthermore, bearing steel balls require low machining precision and inherently possess high hardness and strength, whereas ceramic balls, in addition to their high hardness, are also somewhat brittle, making them more susceptible to breakage during machining. Therefore, the machining methods suitable for bearing steel balls have certain limitations when applied to ceramic balls. Summary of the Invention

[0006] The present invention aims to overcome the defects in the prior art of ceramic balls requiring high processing precision, the complex existing ball processing process, and the need for external tools to achieve high-precision and high-efficiency processing. A device and method for processing silicon nitride ceramic balls are provided to overcome the above defects.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a grooved disk for processing silicon nitride ceramic balls. The grooved disk is provided with variable curvature grooves. The variable curvature grooves include staggered concentric circular curves, eccentric circular curves and straight lines. The angle change values ​​at the intersections of the concentric circular curves, eccentric circular curves and straight lines are different.

[0009] The grooved disc with a track-changing effect, which can achieve a change in the sphere's rotation angle, is primarily achieved through a variable-curvature groove composed of multiple curved segments. Its characteristic is that the intersections of the curves exhibit angle changes. The practical effect of this arrangement is that when the grooved disc is mounted on the lower disc of the grinder, grinding is started, and grinding fluid is poured between the abrasive disc and the grooved disc, the movement of the silicon nitride ceramic ball within the concentric arcs, eccentric arc segments, and straight segments is consistent with traditional grinding methods, and the direction of its rotation axis can only undergo continuous, slight changes. However, at the intersections of the segments, there is an angle change, causing the ceramic ball's forward direction to suddenly change, thereby driving a large angle change in the ceramic ball's rotation axis. This allows the three cut-off points on the ceramic ball's surface to quickly envelop the entire sphere surface, significantly improving the ball's machining accuracy and efficiency.

[0010] Among them, the design of the variable curvature groove is based on the following considerations: the concentric curve with an eccentricity of 0 cannot achieve trajectory envelope, but the processing is stable and the vibration of the ball is small. The eccentricity of the straight line segment is infinite, and if the eccentricity is too large, it is easy to cause the balls to gather, making the processing unstable and causing the balls to jump. Therefore, the proportion of straight line segments can be controlled at a low level. The eccentric arc segments with appropriate eccentricity are introduced and staggered with the concentric curves and straight lines to achieve a balance to achieve trajectory envelope and balance the problem of unstable processing caused by the excessive eccentricity of the straight line segments. Ultimately, the requirements of the trajectory envelope are met, but the balls will not gather or jump during the processing, and the grinding process can be carried out smoothly and continuously.

[0011] Furthermore, the entire process does not involve the use of a track change device, relying entirely on the curve setting of the variable curvature groove itself and the angle change setting at the intersection. This eliminates the track change process, resulting in increased processing efficiency, lower equipment requirements, and higher processing precision, making it more suitable for the processing of ceramic balls. Of course, it can also be used for the processing of bearing steel balls with processing precision requirements lower than or similar to that of ceramic balls, thus having a wide range of applications.

[0012] Preferably, the eccentric circular curve includes three sections of eccentric circular curves with an eccentricity of 300° and a corresponding angle of 16°, and one section of eccentric circular curve with an eccentricity of 5° and a corresponding angle of 66°.

[0013] It can be seen that the larger the eccentricity, the more likely it is to achieve full trajectory envelope. Therefore, concentric circles with an eccentricity of 0 cannot achieve trajectory envelope, and the eccentricity of the straight line segment is infinite. The larger the eccentricity, the more serious the sphere aggregation and the worse the processing stability. An eccentric circle curve with eccentricity is introduced to balance the two. And in order to prevent serious sphere aggregation, the proportion of straight line segments and groove segments with large eccentricity needs to be small. Therefore, the curve with a larger eccentricity in the four eccentric circle curves accounts for a small proportion, and is divided into 3 sections staggered between concentric circles and straight lines. The variable curvature groove as a whole is mainly composed of concentric circles and groove segments with small eccentricity, which can not only meet the needs of quickly achieving full trajectory envelope, but also achieve processing stability.

[0014] Preferably, the angle change value a at the intersection of the concentric circle curve, the eccentric circle curve and the straight line is within 10°. <a<15°。

[0015] In order to reduce the collision damage between the ceramic ball and the track and speed up the grinding rate, the angle mutation range at the junction of the curvature change area of ​​the groove curve in the present invention is less than 15° and greater than 10°.

[0016] The curvature mutation groove consists of different groove segments. At the contact of the two groove segments, there must be an angular change. When the mutation angle is too large, during the grinding process, the ceramic ball will collide at the groove corner. For example, when the angle is 90°, the ball will vertically collide with the groove wall, generating micro-damages such as cracks. When the mutation angle is small, the change in the self-rotation angle of the ball is small, and the surface full envelope cannot be achieved quickly. Experiments have proved that controlling the angular change range within 10° < a < 15° will result in better processing effects.

[0017] The present invention also provides a processing method for the above groove disk. A variable curvature groove is opened on the groove disk. The variable curvature groove includes concentric circle curves, eccentric circle curves, and straight lines arranged alternately, and at the same time, the angular change values at the intersections of the concentric circle curves, eccentric circle curves, and straight lines are different from each other, obtaining a groove disk provided with a variable curvature groove.

[0018] It mainly opens a variable curvature groove on the groove disk. The variable curvature groove is a closed-loop curve obtained by alternately arranging concentric circle curves, eccentric circle curves, and straight lines. Taking the rotation center of the abrasive disk as the center of the circle to establish a polar coordinate system, the curvature of the straight line segment and the curve segment is a fixed value, but at the intersection of each line segment, the curvature value suddenly changes, that is, the angular mutation at the intersection of the variable curvature region of the groove curve.

[0019] The present invention also provides a grinding processing device for silicon nitride ceramic balls, including an abrasive disk installed on the upper disk and a groove disk installed on the lower disk.

[0020] The above groove disk can be applied to any ceramic ball grinding processing device to achieve an equivalent fine processing effect.

[0021] Preferably, the preparation method of the abrasive disk is as follows: Mix abrasive, ceramic binder, pore-forming agent, and phenolic resin powder evenly, and after hot pressing, trim it into a fixed abrasive block, and install it into the reserved groove of the abrasive disk; the grooves are arranged alternately on the abrasive disk, so that the finally obtained abrasive disk is a non-continuous abrasive disk.

[0022] Mix 55% by mass of abrasive, 20% of ceramic binder, 15% of pore-forming agent, and 10% of phenolic resin powder evenly, hot press the mixture to obtain a green abrasive block, cut and trim the green block, obtain a fixed abrasive block with an angle of 40° (any other angle is acceptable as long as a non-continuous abrasive disk can be obtained), install it into the groove of the abrasive disk, and finally trim the flatness of the abrasive disk.

[0023] It's worth noting that the fixed abrasive blocks are staggered on the abrasive disc, resulting in a discontinuous disc. The different surface materials of the discontinuous areas of the disc result in varying surface roughness. Combined with the variable curvature grooves, this allows the ceramic ball's rotational axis to undergo a sudden change in angle during the grinding process, allowing the grinding trajectory to more quickly encompass the entire sphere.

[0024] In this grinding device, the combined effects of the variable-curvature grooves and the discontinuous fixed abrasive disc allow the ceramic ball's rotational axis to undergo a sudden change in angle during grinding, allowing the grinding trajectory to more quickly encompass the entire spherical surface. The ball also rapidly removes surface material through various surface interactions, including those between the fixed abrasive block and the sphere surface, and between the grinding fluid and the sphere surface, improving both machining efficiency and precision.

[0025] Preferably, the abrasive is selected from one or more of diamond, cerium oxide, zirconium oxide, iron oxide, and silicon carbide.

[0026] Preferably, the fixed abrasive block and the abrasive disc are mounted using a metal adhesive.

[0027] Use metal adhesive to bond the fixed abrasive block to the groove of the abrasive disc, ensuring there is no noticeable gap between the two. The advantages of using metal adhesive for installation include a large bonding area, ease of installation, flexible installation methods, and minimal gaps. Furthermore, metal adhesives are inherently strong, corrosion-resistant, and heat-resistant, significantly extending the life of the abrasive disc.

[0028] Preferably, after the fixed abrasive block is installed in the reserved groove of the abrasive disc, the abrasive disc is trimmed to a flatness of less than 0.1 mm.

[0029] After installation, trim the entire abrasive disc to ensure that the overall flatness is within 0.1mm. Perform small-scale trimming first to initially adjust the disc's flatness. Use a grinding wheel or other grinding tool to grind the area requiring trimming, gradually approaching the desired flatness. Then, inspect the disc using a flatbed gauge to ensure that the overall flatness meets the required 0.1mm. If not, continue trimming and inspecting until the required flatness is achieved.

[0030] The present invention provides a method for processing silicon nitride ceramic balls, comprising the following steps:

[0031] S1, groove disc processing;

[0032] S2, assembling the grinding device;

[0033] S3. Grinding process: The silicon nitride ceramic ball is placed on the groove curve of the grooved disc so that it is located between the grooved disc and the abrasive disc. Pressure is applied to the abrasive disc to transmit the pressure to the ceramic ball. The grinding process device is started to make the grooved disc start to rotate. Grinding fluid is injected between the grooved disc and the abrasive disc. The fixed abrasive block on the abrasive disc scratches the surface of the silicon nitride ceramic ball to complete the finishing.

[0034] Grooved disc machining primarily involves creating variable-curvature grooves on the disc. Variable-curvature grooves are closed-loop curves formed by interlacing concentric, eccentric, and straight lines. Using a polar coordinate system centered at the abrasive disc's center of rotation, the curvature of straight and curved segments remains constant. However, at the intersection of each segment, the curvature suddenly changes. This means that the angle of the groove curve at the intersection of the variable-curvature region changes abruptly.

[0035] After the abrasive disc is mounted on the upper plate of the grinder and the grooved disc on the lower plate, the grinder is started and grinding fluid is poured between the abrasive disc and the grooved disc, the movement of the silicon nitride ceramic ball within the concentric arc, eccentric arc and straight line segments is consistent with the traditional grinding method, and the direction of its rotation axis can only undergo continuous slight changes; at the intersection of each line segment, there is an angle change, which causes the forward direction of the ceramic ball to suddenly change, thereby driving the ceramic ball's rotation axis to undergo a large angle change, so that the three resection points on the ceramic ball surface can quickly envelop the entire sphere surface, greatly improving the ball processing efficiency.

[0036] In addition to the effect of the variable curvature groove on the change of the sphere's rotation axis, the discontinuous characteristics of the abrasive disc itself in the grinding device and the combined effect of the variable curvature groove further improve the processing efficiency and processing accuracy.

[0037] Preferably, in step S3, the grinding liquid is prepared by using deionized water as a base liquid, adding 2 wt% chemical abrasive powder and 1 wt% diamond powder to mix.

[0038] To ensure the grinding fluid has a certain roughness to facilitate friction processing of the ball, an appropriate amount of chemical abrasive powder and diamond powder are added to the deionized water. The mesh size of the chemical abrasive powder and diamond powder is 8000 mesh. The fine particle size of the powder in the grinding fluid is controlled to enhance the fluidity of the grinding fluid. In contrast to the abrasive in the fixed abrasive block with a larger particle size, the combination of hard and soft abrasives of different particle sizes achieves multiple surface effects, resulting in better removal of material from the ball surface.

[0039] Diamond, as an extremely hard material, possesses excellent grinding properties. Adding diamond powder to the grinding fluid can enhance the grinding effect, helping the abrasive disc to dress and grind more effectively. Furthermore, the addition of diamond powder improves the surface quality of the abrasive disc and acts as a lubricant during the grinding process, extending the disc's lifespan and performance.

[0040] Preferably, the chemical abrasive powder is one or more of cerium oxide, zirconium oxide, and iron oxide.

[0041] When selecting chemical abrasive powder for the grinding fluid, soft abrasives such as cerium oxide, iron oxide, and zirconium oxide can be used. These soft abrasives react with the surface of the silicon nitride ceramic ball during processing to form an extremely thin soft layer. The following is the solid-phase reaction equation for the reaction between these chemical abrasives and silicon nitride ceramic materials:

[0042] Si3N4+CeO2→SiO2+CeO 1.72 +CeO 1.83 +Ce2O3+N2(g)

[0043] Si3N4+Fe2O3→SiO2+FeO+FeSiO3 / FeO.SiO2+Fe2N+N2(g)

[0044] Si3N4+ZrO2→SiO2+ZrSiO4 / ZrO 2· SiO2+ZrN+N2(g)

[0045] In a water-based environment, water also participates in the chemical reaction of silicon nitride ceramic materials, enhancing its chemical mechanical polishing effect.

[0046] The reaction equation is as follows:

[0047] Si3N4+6H2O→3SiO2+4NH3

[0048] Si3N4+6H2O→3SiO2+6H2(g)+2N2(g)(T>200℃)

[0049] The final product of these chemical reactions is primarily silicon oxide (SiO2), which has a Mohs hardness of approximately 7, significantly lower than that of silicon nitride ceramics. Therefore, during the grinding process, a soft silicon oxide layer gradually forms on the surface of the silicon nitride ceramic ball. The abrasive grains on the fixed abrasive block can more easily remove surface material without damaging the ball, reducing the appearance of pits and cracks.

[0050] Therefore, in addition to the combined effect of the variable curvature grooves and the discontinuous abrasive disc, the addition of the grinding fluid makes the surface of the sphere more diverse, which can quickly remove the surface material of the sphere and further improve the processing efficiency and processing accuracy.

[0051] Therefore, the present invention has the following beneficial effects:

[0052] (1) The present invention provides a grooved disk that helps achieve a sudden change in the rotation angle of a sphere. The principle and mechanism are simple, and can help improve the processing accuracy and efficiency of ceramic balls, thereby reducing production costs.

[0053] (2) The processing method designed by the present invention realizes a sudden change in the sphere's rotation angle by using a grooved disk with grooves of variable curvature, thereby improving the efficiency of the processing trajectory enveloping the entire sphere;

[0054] (3) The processing method provided by the present invention can accelerate the removal of surface material and improve processing efficiency and precision through the combined action of fixed abrasive and free abrasive;

[0055] (4) The processing method provided by the present invention adopts chemical mechanical polishing, which can effectively reduce the surface damage of silicon nitride ceramic balls. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 Schematic diagram of the structure of the grooved disk;

[0057] Figure 2 Schematic diagram of the variable curvature groove;

[0058] Figure 3 Schematic diagram of the structure of the fixed abrasive block;

[0059] Figure 4 Schematic diagram of the structure of the abrasive disc;

[0060] Figure 5 Schematic diagram of the grinding working principle of grooved disc and abrasive disc.

[0061] The codes in the figure are: ceramic bond 1; abrasive 2; phenolic resin 3; fixed abrasive block 4; abrasive disc 5; grinding liquid inlet 6; silicon nitride ceramic ball 7; variable curvature groove 8; groove disc 9; angle variation range a. DETAILED DESCRIPTION

[0062] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below generally represent only a portion of the present invention, rather than all of the embodiments. Therefore, all other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0063] [Example]

[0064] Example 1

[0065] S1. Grooved disc processing: a variable curvature groove 8 is formed on the grooved disc 9, wherein the variable curvature groove 8 comprises two concentric circular curves, four eccentric circular curves and one straight line arranged in an alternating manner, and the angle change value at the intersection of the concentric circular curves, the eccentric circular curves and the straight line is 13°, and the following is obtained: Figure 1 The grooved plate 9 shown is provided with a groove of variable curvature 8. The four eccentric circular curves include three eccentric circular curves with an eccentricity of 30° at a corresponding angle of 16°, and one eccentric circular curve with an eccentricity of 5° at a corresponding angle of 66°.

[0066] S2. Preparation of abrasive disc: 55% silicon carbide abrasive 2, 20% ceramic binder 1, 15% pore former and 10% phenolic resin powder 3 were mixed and stirred evenly, and the mixture was hot pressed to obtain a fixed abrasive block 4 blank. The blank was cut and trimmed to obtain a fixed abrasive block 4 with an angle of 40° (such as Figure 3 After that, install it into the groove of the abrasive disc 5, and finally trim the abrasive disc 5 to make its flatness less than 0.1mm. Figure 4 , the fixed abrasive block 4 is bonded to the groove of the abrasive disc 5 using a metal adhesive.

[0067] S3. Prepare grinding liquid: Deionized water is selected as the base liquid, and 2% by mass of 8000 mesh cerium oxide powder and 1% by mass of 8000 mesh diamond powder are added to the base liquid to obtain the grinding liquid.

[0068] S4, assembling the grinding machine: installing the abrasive disc 5 on the upper plate of the grinding machine, and installing the grooved disc 9 on the lower plate of the grinding machine;

[0069] S5, grinding: using a silicon nitride ceramic ball 7 with a diameter of 1 mm, refer to Figure 5 , place the unprocessed silicon nitride ceramic ball 7 into the variable curvature groove 8, apply a certain pressure to the abrasive disc 5 on the ceramic ball 7, and ensure that the pressure fluctuation range is controlled below 0.05N / ball. The grooved disc 9 rotates at a certain speed. At the same time, the grinding liquid drips into the space between the abrasive disc 5 and the grooved disc 9 at a certain speed from the grinding liquid inlet 6 on the abrasive disc 5. When the silicon nitride ceramic ball 7 is rolling, the free cerium oxide abrasive reacts with silicon nitride in a solid phase reaction, so that a soft layer is produced on the surface of the silicon nitride ceramic sphere. After the soft layer is formed, the free abrasive and the grinding wheel block slide on the surface of the ceramic ball, continuously removing the soft layer.

[0070] The overall concept behind the ceramic ball machining method designed in this invention is that the surface roughness varies depending on the material of the non-continuous fixed abrasive disc. When the ball contacts the fixed abrasive disc, the two contact points between the ball and the groove slip. Under the pressure of compression, the silicon nitride ceramic ball reacts with the chemical abrasive, forming a soft layer on its surface. The free diamond abrasive then plows and removes this soft layer by rolling. The contact motion between the ball and the fixed abrasive block is rolling. Because the abrasive particle size on the fixed abrasive block is larger than the free particle size (the powder particle size in the grinding fluid is controlled at 8000 mesh, which is a finer particle), the free abrasive can no longer act on the surface of the silicon nitride ceramic ball. The removal method at this contact point is mechanical removal of the fixed abrasive, which is a two-body removal. When the ball contacts the cast iron area (non-fixed abrasive block area), only the free abrasive removes the surface of the silicon nitride ceramic ball at the three contact points, which is a three-body removal. The contact point between the ball and the abrasive disc slips, and the diamond abrasive mainly removes the soft layer in the form of scratching. The contact point between the ball and the groove is rolling, and the diamond abrasive mainly removes the soft layer in the form of rolling.

[0071] When considering the groove trajectory of the groove disk with sudden curvature changes, the movement mode of the silicon nitride ceramic ball in the concentric arc segment, eccentric arc segment and straight line segment is consistent with the traditional grinding method, and the direction of its rotation axis can only change continuously and slightly; at the intersection of each line segment, the forward direction of the ceramic ball suddenly changes, thereby driving the ceramic ball's rotation axis to change at a large angle, so that the three resection points on the ceramic ball surface can quickly envelope the entire sphere surface.

[0072] Under the combined action of the variable curvature grooves and the fixed abrasive disc in the discontinuous area, the ceramic ball's rotation axis direction can undergo a certain angle mutation during the grinding process, so that the grinding trajectory can more quickly envelope the entire spherical surface. In addition, the spherical surface has a variety of surface removal methods, which can quickly remove surface materials and improve processing efficiency and processing accuracy.

[0073] The specific processing conditions are shown in Table 1:

[0074] Table 1 Processing parameters

[0075]

[0076] Example 2

[0077] S1. Grooved disc processing: a variable curvature groove 8 is formed on the grooved disc 9, wherein the variable curvature groove 8 comprises two concentric circular curves, four eccentric circular curves and one straight line arranged in an alternating manner, and the angle change value at the intersection of the concentric circular curves, the eccentric circular curves and the straight line is 13°, and the following is obtained: Figure 1The grooved plate 9 shown is provided with a groove of variable curvature 8. The four eccentric circular curves include three eccentric circular curves with an eccentricity of 30° at a corresponding angle of 16°, and one eccentric circular curve with an eccentricity of 5° at a corresponding angle of 66°.

[0078] S2. Preparation of abrasive disc: 55% diamond abrasive 2, 20% ceramic binder 1, 15% pore former and 10% phenolic resin powder 3 were mixed and stirred evenly, and the mixture was hot pressed to obtain a fixed abrasive block 4 blank. The blank was cut and trimmed to obtain a fixed abrasive block 4 with an angle of 40° (such as Figure 2 After that, install it into the groove of the abrasive disc 5, and finally trim the abrasive disc 5 to make its flatness less than 0.1mm. Figure 3 , the fixed abrasive block 4 is bonded to the groove of the abrasive disc 5 using a metal adhesive.

[0079] S3. Prepare grinding liquid: Deionized water is selected as the base liquid, and 2% by mass of 8000 mesh zirconium oxide powder and 1% by mass of 8000 mesh diamond powder are added to the base liquid to obtain the grinding liquid.

[0080] S4, assembling the grinding machine: installing the abrasive disc 5 on the upper plate of the grinding machine, and installing the grooved disc 9 on the lower plate of the grinding machine;

[0081] S5, grinding: using a silicon nitride ceramic ball 7 with a diameter of 1 mm, refer to Figure 4 , place the unprocessed silicon nitride ceramic ball 7 into the variable curvature groove 8, apply a certain pressure to the abrasive disc 5 on the ceramic ball 7, and ensure that the pressure fluctuation range is controlled below 0.05N / ball. The grooved disc 9 rotates at a certain speed. At the same time, the grinding liquid drips into the space between the abrasive disc 5 and the grooved disc 9 at a certain speed from the grinding liquid inlet 6 on the abrasive disc 5. When the silicon nitride ceramic ball 7 is rolling, the free cerium oxide abrasive reacts with silicon nitride in a solid phase reaction, so that a soft layer is produced on the surface of the silicon nitride ceramic sphere. After the soft layer is formed, the free abrasive and the grinding wheel block slide on the surface of the ceramic ball, continuously removing the soft layer.

[0082] The processing conditions used are shown in Table 1.

[0083] Example 3

[0084] S1. Grooved disc processing: a variable curvature groove 8 is formed on the grooved disc 9, wherein the variable curvature groove 8 comprises two concentric circular curves, four eccentric circular curves and one straight line arranged in an alternating manner, and the angle change value at the intersection of the concentric circular curves, the eccentric circular curves and the straight line is 13°, and the following is obtained: Figure 1The grooved plate 9 shown is provided with a groove of variable curvature 8. The four eccentric circular curves include three eccentric circular curves with an eccentricity of 30° at a corresponding angle of 16°, and one eccentric circular curve with an eccentricity of 5° at a corresponding angle of 66°.

[0085] S2. Preparation of abrasive disc: 55% silicon carbide abrasive 2, 20% ceramic binder 1, 15% pore former and 10% phenolic resin powder 3 were mixed and stirred evenly, and the mixture was hot pressed to obtain a fixed abrasive block 4 blank. The blank was cut and trimmed to obtain a fixed abrasive block 4 with an angle of 40° (such as Figure 2 After that, install it into the groove of the abrasive disc 5, and finally trim the abrasive disc 5 to make its flatness less than 0.1mm. Figure 3 , the fixed abrasive block 4 is bonded to the groove of the abrasive disc 5 using a metal adhesive.

[0086] S3. Prepare grinding liquid: Deionized water is selected as the base liquid, and 2% by mass of 8000 mesh zirconium oxide powder and 1% by mass of 8000 mesh diamond powder are added to the base liquid to obtain the grinding liquid.

[0087] S4, assembling the grinding machine: installing the abrasive disc 5 on the upper plate of the grinding machine, and installing the grooved disc 9 on the lower plate of the grinding machine;

[0088] S5, grinding: using a silicon nitride ceramic ball 7 with a diameter of 1 mm, refer to Figure 4 , place the unprocessed silicon nitride ceramic ball 7 into the variable curvature groove 8, apply a certain pressure to the abrasive disc 5 on the ceramic ball 7, and ensure that the pressure fluctuation range is controlled below 0.05N / ball. The grooved disc 9 rotates at a certain speed. At the same time, the grinding liquid drips into the space between the abrasive disc 5 and the grooved disc 9 at a certain speed from the grinding liquid inlet 6 on the abrasive disc 5. When the silicon nitride ceramic ball 7 is rolling, the free cerium oxide abrasive reacts with silicon nitride in a solid phase reaction, so that a soft layer is produced on the surface of the silicon nitride ceramic sphere. After the soft layer is formed, the free abrasive and the grinding wheel block slide on the surface of the ceramic ball, continuously removing the soft layer.

[0089] The processing conditions used are shown in Table 1.

[0090] Example 4

[0091] This embodiment is the same as the solution of embodiment 1, except that the angle change value at the intersection of the concentric circle curve, the eccentric circle curve, and the straight line is 11°.

[0092] Example 5

[0093] This embodiment is the same as the solution of embodiment 1, except that the angle change value at the intersection of the concentric circle curve, the eccentric circle curve, and the straight line is 14°.

[0094] Example 6

[0095] This embodiment is the same as the solution of embodiment 1, except that the angle change values ​​at the intersections of the concentric circle curve, the eccentric circle curve, and the straight line are 12°, 13°, and 14°.

[0096] Comparative Example 1

[0097] This comparative example is the same as the solution of Example 1, except that concentric circular grooves are provided on the grooved disk.

[0098]

Performance test

[0099] The silicon nitride ceramic balls used in the above experiments are hard and brittle materials. The diamonds used in conventional grinding processes can cause cracks on the ceramic surface and subsurface areas, and can even create pits on the ceramic ball surface. In the above examples, the free abrasives used were cerium oxide (hardness 5.5-6.5) and zirconium oxide (hardness 8), and the fixed abrasive discs were silicon carbide (hardness 9-9.5) and diamond (hardness 10). These abrasives, when in contact with the silicon nitride ceramic balls (hardness 9-9.5), effectively prevent machining defects on the ceramic ball surfaces.

[0100] The machining method of the present invention effectively and rapidly removes surface material, achieving a material removal rate 3-4 times higher than that of conventional grinding methods, reaching 15-20 μm / h. The surface of the processed ceramic ball is free of large-area pits, with a roundness of approximately 0.10 μm and a surface roughness of approximately 18 nm. This method not only increases the grinding rate but also effectively addresses the problems associated with conventional grinding methods, improving the surface quality of the ground silicon nitride ceramic.

[0101] Moreover, the use of different abrasives has almost no effect on the grinding effect. When the angle change between the curves is between 10 and 15°, a good processing effect can be achieved. The change of the angle within the range has little effect on the processing.

[0102] From the data of comparative example 1 in Table 2, it can be seen that the processing effect of this solution is significantly improved compared with the processing effect of ordinary concentric grooves.

[0103] Table 2 Comparison of data of each scheme

[0104] Surface roughness (nm) Material removal rate (μm / h) Roundness (μm) Example 1 18.0 15～20 0.10 Example 2 17.9 16～20 0.11 Example 3 18.2 15～19 0.13 Example 4 18.1 15～20 0.10 Example 5 17.8 15～20 0.09 Example 6 18.0 15～20 0.11 Comparative Example 1 70 No obvious removal 1.10

Claims

1. A grooved disc for processing silicon nitride ceramic balls, characterized in that: The grooved plate is provided with variable curvature grooves, which include staggered concentric circular curves, eccentric circular curves and straight lines, and the angle change values ​​at the intersections of the concentric circular curves, eccentric circular curves and straight lines are different; The eccentric circular curve includes three sections of eccentric circular curves with an eccentricity of 300° and an angle of 16°, and one section of eccentric circular curve with an eccentricity of 5° and an angle of 66°; The variable curvature groove includes two segments of concentric circular curves, four segments of eccentric circular curves and one segment of straight line which are arranged alternately.

2. A grooved disk for machining silicon nitride ceramic balls according to claim 1, characterized in that: The range of the angle change value a at the intersection of the concentric circle curve, the eccentric circle curve and the straight line is 10° <a<15°。 3. A method for processing a grooved disk according to any one of claims 1 to 2, characterized in that: Variable curvature grooves are opened on the groove disk, wherein the variable curvature grooves include staggered concentric circle curves, eccentric circle curves and straight lines, while ensuring that the angle change values ​​at the intersections of the concentric circle curves, eccentric circle curves and straight lines are different, thereby obtaining a groove disk with variable curvature grooves.

4. A silicon nitride ceramic ball grinding device, characterized in that: The invention comprises an abrasive disc mounted on an upper disc, and a grooved disc as claimed in any one of claims 1 to 2 mounted on a lower disc.

5. A silicon nitride ceramic ball grinding device according to claim 4, characterized in that: The abrasive disc is prepared by mixing and stirring abrasive, a ceramic binder, a pore-forming agent and phenolic resin powder evenly, hot-pressing and trimming the mixture into a fixed abrasive block, and installing the fixed abrasive block into a reserved groove of the abrasive disc; the grooves are staggered on the abrasive disc, so that the final abrasive disc is a discontinuous abrasive disc.

6. The silicon nitride ceramic ball grinding device according to claim 5, characterized in that: After the fixed abrasive block is installed in the reserved groove of the abrasive disc, the abrasive disc is trimmed until its flatness is less than 0.1 mm.

7. A method for processing silicon nitride ceramic balls, characterized in that: The following steps are involved: S1. Processing the grooved disc according to the method of claim 3; S2. Assembling the grinding device according to any one of claims 4 to 6; S3. Grinding process: The silicon nitride ceramic ball is placed on the variable curvature groove of the grooved disk so that it is located between the grooved disk and the abrasive disk. Pressure is applied to the abrasive disk to transmit the pressure to the ceramic ball. The grinding process device is started to make the grooved disk start to rotate. Grinding fluid is injected between the grooved disk and the abrasive disk. The fixed abrasive block on the abrasive disk scratches the surface of the silicon nitride ceramic ball to complete the finishing.

8. A method for processing silicon nitride ceramic balls according to claim 7, characterized in that: In step S3, the grinding liquid is prepared by using deionized water as a base liquid, adding 2 wt% of chemical abrasive powder and 1 wt% of diamond powder to mix.

9. A method for processing silicon nitride ceramic balls according to claim 8, characterized in that: The chemical abrasive powder is one or more of cerium oxide, zirconium oxide and iron oxide.

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