A sintering method and a sintering device for wear-resistant alumina ceramic balls

Abstract

The application relates to a wear-resistant alumina ceramic ball sintering method, which comprises four stages of a forming stage, a glue removing stage, a shaping stage and a sintering stage. In the sintering stage, the shaped green body is kept in a rolling state in a sintering furnace. The application also discloses a sintering device for the wear-resistant alumina ceramic ball, which comprises a mesh belt type tunnel sintering furnace. The mesh belt type tunnel sintering furnace has a fine chain mesh belt, and the outer side of the chain mesh belt is in sliding contact with a chain rod conveying belt. The transmission speed of the chain rod conveying belt is slower than that of the chain mesh belt. The chain rod conveying belt is provided with mesh holes, and the mesh holes are used for containing spherical ceramic raw materials. When the spherical ceramic raw materials are located in the mesh holes, the lower end of the spherical ceramic raw materials is in contact with the chain mesh belt, and the side surface is in contact with the mesh holes. In the sintering process, the alumina ceramic ball is kept in a rolling state, the side surface is uniformly directed to a heating element, the surface temperature uniformity is maintained, and the sintering device is suitable for the production of large-diameter alumina ceramic balls.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of alumina ceramics, and particularly relates to a sintering method and a sintering device for wear-resistant alumina ceramic balls. BACKGROUND

[0002] Alumina ceramics are ceramic materials mainly composed of alumina, which are widely used in chemical industry, electronics, aerospace, etc. due to their high-temperature resistance, wear resistance, and good electrical insulation, etc. The spherical alumina ceramics are mainly used as fillers of reaction towers, grinding balls of grinding equipment, and rolling bodies of some bearings.

[0003] The alumina ceramic balls usually include the steps of clay refining, drying, calcining, ball milling, granulating, forming, sintering, and grinding in production. In the sintering step, the green bodies of the alumina ceramic balls in the form of spheres are usually stacked in a crucible for sintering in a muffle furnace or a tunnel furnace (net belt type or push plate type). The conventional method is to stack the green bodies of the alumina ceramic balls in the form of spheres in the crucible. In the sintering process, the inner layer of the alumina ceramic balls and the outer layer of the alumina ceramic balls are prone to uneven heating. The inner layer product is under-fired, while the outer layer product is prone to over-fired, resulting in a high rate of defective products. In addition, the heating methods of the muffle furnace and the tunnel furnace are usually gas heating or silicon molybdenum rod heating. In the heating process, not only is there heat convection and heat conduction, but also a high energy is transferred by radiation. The green bodies of the alumina ceramic balls remain relatively stationary with the net belt or the push plate. Affected by the heating element, the temperature of the side facing the heating element is relatively high, and the temperature of the side away from the heating element is relatively low. The temperature difference can reach 15-25℃, which is a temperature difference sufficient to affect the product quality, especially for large-diameter (20-200mm) alumina ceramic balls. Therefore, a sintering method is needed to keep the surface temperature of the alumina ceramic balls uniform during the sintering process. SUMMARY

[0004] To solve the above technical problems, the application provides a sintering method and a sintering device for wear-resistant alumina ceramic balls. In the sintering process, the alumina ceramic balls are kept in a rolling state, so that the side faces the heating element uniformly, maintaining the uniformity of the surface temperature, and being suitable for the production of large-diameter alumina ceramic balls.

[0005] To achieve the above-mentioned purposes, the technical solution of the application is as follows:

[0006] A sintering method for wear-resistant alumina ceramic balls, which includes a forming stage, a glue removal stage, a shaping stage, and a sintering stage, a total of four stages. The specific processes of the four stages are as follows:

[0007] The forming stage is to form the alumina powder into a spherical shape to obtain a spherical blank, and the forming stage is not limited to forming means, and one or a combination of several of a semi-automatic mechanical forming machine, a cold isostatic pressing machine or other devices capable of pressure forming into a ball can be used as long as the forming specification is met and the pressure is sufficient;

[0008] The glue discharging stage is to heat and discharge the spherical blank in a glue discharging furnace to obtain a ceramic blank;

[0009] The shaping stage is to perform primary grinding processing on the ceramic blank, retain a certain processing allowance, and make the ceramic blank close to a standard sphere to obtain a shaped blank;

[0010] The sintering stage is to sinter the shaped blank in a sintering furnace to form a dense alumina ceramic ball;

[0011] In the sintering stage, the shaped blank is kept in a rolling state in the sintering furnace, and the shaped blank after shaping can be well rolled, so that each part is uniformly heated.

[0012] When the surface temperature of the alumina ceramic ball is not uniform, the high-temperature side is prone to "overburning", that is, the heating temperature is higher than the melting point of the low-melting-point eutectic, which causes the re-melting of the low-melting-point eutectic and the grain boundary. When the product is severely overburned, the surface color is black or dark. In the microstructure, local widening of the grain boundary can be observed, re-melting balls are generated in the grain interior, and obvious triangular re-melting areas are present at the grain junction, which affects other properties of the product. The high-temperature side is "underburned", that is, the sintering temperature is too low and / or the sintering time is too short, which causes the product to not reach the required performance. Underburning will lead to poor porcelain formation and reduced density.

[0013] The present application is mainly developed and improved to solve the problem of uneven surface temperature of alumina ceramic balls during sintering. In the sintering process, the shaped blank is rolled, and in the rolling process, each part of the shaped blank can uniformly receive radiant energy, thereby achieving uniform temperature and avoiding the problem of excessively high temperature in some parts and excessively low temperature in some parts of the shaped blank. Whether using gas heating or silicon-molybdenum rod heating, the temperature can be uniform.

[0014] Further, in the glue discharging stage, the glue discharging furnace is heated at a speed of 15℃ / min, heated to 470℃-530℃, and then cooled with the furnace for 2-3 hours.

[0015] The present application does not limit the heating equipment in the glue discharging stage, and only names the equipment as glue discharging furnace according to the use, and the tunnel furnace, the muffle furnace or other heating equipment capable of reaching the established temperature with a suitable temperature rising speed and then performing the heat preservation can be used, because the temperature rising temperature is low, only the moisture and part of the plasticizing component are removed, and even if the stacking is heated and then the heat preservation is performed, the glue discharging state is not affected,

[0016] Further, in the shaping stage, the ceramic blank is subjected to the turning treatment, and the machining allowance is 20% to 25% of the diameter of the finished product of the wear-resistant alumina ceramic ball.

[0017] The wear-resistant alumina ceramic ball is mainly formed by sintering the alumina powder, and the spheroid formed by the powder contains a large amount of gas. The ceramic blank after forming often contains 20% to 50% porosity. In the sintering process, the gas is overflowed, the pores are removed, and the volume shrinkage is substantially equal to the volume of the removed pores. The pre-sintered raw material can reduce the shrinkage. If the sintering is performed to complete densification, a volume shrinkage of several tens of percent and a considerable linear shrinkage will be generated. In addition, the alumina will also generate a crystal type transformation at a higher temperature, for example, the crystal type of the alumina is transformed from γ-Al2O3 to α-Al2O3, and the density is increased, and the volume shrinkage is about 14.3%. The above-mentioned volume shrinkage will generally make the diameter smaller by several tens of percent to several twenties of percent, which is not conducive to the precision of the size. When the ball body has different shrinkages, the distortion or crack and other serious product quality problems will also be caused. In order to reduce such unevenness, the glue is discharged and then immediately shaped, which can remove the excess material on the outer surface of the ceramic blank in the early stage, avoid the increase of the processing difficulty due to the increase of the wear resistance after sintering, and also enable the ceramic blank to form a uniform spheroid. The uniform spheroid enables the alumina ceramic ball to have a better adaptability in the sintering process, avoids the state of different shrinkages due to the presence of part of the excess material on the surface, and enables the ball body to form a relatively uniform and stable rolling state in the rolling process, so that each part of the surface of the ball body uniformly receives the convection and radiation, and a uniform temperature is formed, which fundamentally reduces the situation of different shrinkages, thereby improving the product quality. The rolling state also has a homogenizing effect on the large-diameter ball body, avoids the deformation of the ball body due to the generation of liquid phase in the sintering process, enables the ball body to more stably maintain the spheroid, reduces the grinding time and energy consumption after sintering, and enables the grinding to more easily and quickly reach the required accuracy.

[0018] Further, in the sintering stage, the rolling speed of the shaped blank is 2 revolutions per minute to 10 revolutions per minute.

[0019] The rolling speed of the profiled blank in the sintering process needs to achieve uniform rolling, so that each part of the outer surface can be towards the heating element, and it cannot roll too fast, otherwise it will lead to the length of the alumina ceramic ball in the sintering furnace and the heating time to be shortened, and the problem of "under-burning" is easy to appear. According to the length and heating state of the existing sintering furnace, 2-10 revolutions per minute is a suitable rolling speed.

[0020] Even if the rolling speed of the profiled blank has been limited, there are still only a few sintering furnaces in the prior art that can achieve the sintering method of the present application, and the specific reason is that the length of the sintering furnace is too short to meet the sintering needs, and in reality, manufacturers usually cannot match a sintering furnace for a new production process, so it is necessary to improve the existing sintering furnace to quickly realize the production equipment matched with the production process at a lower cost.

[0021] The application discloses a sintering device for wear-resistant alumina ceramic balls, which comprises a mesh belt type tunnel sintering furnace, wherein the mesh belt type tunnel sintering furnace is provided with a fine and dense chain mesh belt, the chain mesh belt is tensioned by a first support roller set, the chain mesh belt is driven by a first driving roller, the chain mesh belt is in sliding contact with a chain rod conveying belt outside, the chain rod conveying belt is tensioned by a second support roller set, the chain rod conveying belt is driven by a second driving roller, the transmission speed of the chain rod conveying belt is slower than that of the chain mesh belt, the chain rod conveying belt is provided with mesh holes, and the mesh holes are used for containing spherical ceramic raw materials; when the spherical ceramic raw materials are located in the mesh holes, the lower end of the spherical ceramic raw materials is in contact with the chain mesh belt, and the side surface of the spherical ceramic raw materials is in contact with the mesh holes, and the spherical ceramic raw materials are shape correction blanks, and of course, the spherical ceramic raw materials can also be other spherical ceramic intermediate semi-finished products which need to be sintered, that is, the sintering device for wear-resistant alumina ceramic balls is not limited to the sintering method for the wear-resistant alumina ceramic balls, and is applicable to all relevant heating operations of the spherical materials with large diameters (20mm-200mm) by adjusting temperature and materials, such as degumming, drying and sintering of ceramic materials, heating of metal grinding balls and metal bearing rolling bodies in heat treatment and the like. The sintering device for wear-resistant alumina ceramic balls is mainly used for solving the problem that the existing tunnel type sintering furnace is usually too short and is not suitable for the production method, and the specific improvement method is that a chain rod conveying belt is additionally arranged outside the chain mesh belt of the existing sintering furnace, wherein the mesh holes of the chain rod conveying belt are used for limiting the moving speed of the spherical ceramic raw materials in the sintering furnace, the chain mesh belt is used for making the spherical ceramic raw materials generate a rolling effect, and the moving speed difference between the chain mesh belt and the chain rod conveying belt controls the rolling speed of the spherical ceramic raw materials, so that the spherical ceramic raw materials can have a suitable rolling speed in the short sintering furnace, and the spherical ceramic raw materials can also have a suitable temperature rising speed and a suitable holding time, and the heating length of the sintering furnace and the rolling speed of the spherical ceramic raw materials can no longer become the limiting conditions of the sintering process, and the application can make most of the existing sintering furnaces realize the rolling sintering of the spherical ceramic raw materials.

[0022] Further, the chain rod conveying belt is composed of chains and chain rods, each chain rod is rotationally connected with a shaft sleeve, and the space between each two adjacent shaft sleeves is a mesh hole.

[0023] The chain rod conveying belt is used for limiting the moving speed of the spherical ceramic raw materials at a slow conveying speed, so that the space between the shaft sleeves of the adjacent two chain rods is used as the mesh hole, the moving of the shape correction blanks can be better limited, the shape correction blanks can be uniformly arranged at the shaft sleeves in the moving process, the shaft sleeves can be in contact with the spherical ceramic raw materials to rotate, excessive friction can be avoided to affect the sphericity and the raw material residue, and the raw materials can not be stacked, so that the shape correction blanks can not form an inner layer and an outer layer, and the state that the temperature of the inner layer is low and the temperature of the outer layer is high is avoided.

[0024] Further, the shaft sleeve has an annular groove, and the annular groove has two circular cone sides, one of which has a larger taper than the other, that is, the included angle between the two circular cone sides is at an angle to the driving direction of the chain link conveying belt.

[0025] The rolling shaft sleeve has an annular groove, and the annular groove can separate the spherical ceramic raw materials, each annular groove corresponds to a spherical ceramic raw material, so that each spherical ceramic raw material can roll at a reasonable position, and the rolling of the profiled blank can make the surface uniformly receive radiation or heat convection, but if the ball only rolls along the conveying direction of the chain mesh belt, the heating will not reach the most uniform state, therefore, the annular groove is composed of two circular cone sides with different tapers, the two circular cone sides with different tapers can make the ball have a "rotation" state at an angle to the driving direction of the conveying belt, and the angle is preferably 20°-40°, the "rotation" state is not a real rotation of the spherical ceramic raw material, but refers to the state that the spherical ceramic raw material rolls at an angle to the driving direction of the conveying belt and forms friction with the chain link conveying belt and the chain mesh belt, and such a rolling state can make any point on the surface of the spherical ceramic raw material have a chance to face the heating body, so that the spherical ceramic raw material can receive heat convection and heat radiation, and the temperature of the surface of the spherical ceramic raw material is uniform.

[0026] Further, the diameter of the shaft sleeve is smaller than the height of the chain, and when the chain link conveying belt contacts the chain mesh belt, there is a gap between the lower end of the shaft sleeve and the chain mesh belt.

[0027] The shaft sleeve only contacts and rotates with the spherical ceramic raw material, and does not contact the chain mesh belt.

[0028] Further, the second driving roller is provided with a multi-stage speed change sprocket set, and the second driving roller is linked with the first driving roller through the multi-stage speed change sprocket set.

[0029] The multi-stage speed change sprocket set can adjust the transmission ratio, so as to adjust the rolling speed of the spherical ceramic raw material.

[0030] Further, there is a gap between the end of the chain link conveying belt close to the outlet end of the mesh belt type tunnel sintering furnace and the end of the chain mesh belt, which is used for discharging.

[0031] The present application can use the equipment to realize the feeding (adding the spherical ceramic raw material into the mesh hole) and discharging (the sintered alumina ceramic ball is separated from the mesh hole), and does not need manual processing, such as a feeder and a chute.

[0032] The profiled blank of the present application is in a rolling state during the sintering process, can make the alumina ceramic ball uniformly heated, keep the spherical shape without losing roundness, so as to ensure the yield, and ensure the wear resistance and firmness of the alumina ceramic ball.

[0033] The present application performs the shaping before sintering, which can make the shaping speed uniform and stable when rolling, ensure the surface to be heated uniformly, ensure the stability of product shrinkage, eliminate product defects, reduce the grinding time and energy consumption after sintering, and make the grinding easier and faster to reach the required precision.

[0034] The sintering device for the wear-resistant alumina ceramic ball of the present application is matched with the production process at a low cost, solves the problem that the existing tunnel type sintering furnace is usually too short and is not suitable for the production of the present application, and eliminates the disadvantage of uneven heating of the ball blank by the heating mode.

[0035] The special annular groove on the shaft sleeve can make the ball blank roll at an angle to the driving direction of the conveying belt, so that any point on the surface of the spherical ceramic raw material can have a chance to face the heating body when rolling, and can receive heat convection and heat radiation, further improving the temperature uniformity of the surface of the spherical ceramic raw material. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a structural schematic view of the sintering device for the wear-resistant alumina ceramic ball of the present application;

[0037] Figure 2 is a cross-sectional view of the sintering device for the wear-resistant alumina ceramic ball of the present application;

[0038] Figure 3 is a position relationship diagram (axonometric view) of the chain mesh belt and the chain link conveying belt of the present application;

[0039] Figure 4 is a position relationship diagram (cross-sectional left view) of the chain mesh belt and the chain link conveying belt of the present application;

[0040] Figure 5 is a state diagram of the spherical ceramic raw material in the chain link conveying belt mesh hole.

[0041] In the drawings, 1 is a chain mesh belt, 2 is a first driving roller, 3 is a chain link conveying belt, 4 is a second driving roller, 5 is a multi-stage speed change sprocket set, 6 is a supporting roller one, 7 is a supporting wheel, 8 is a supporting roller two, 9 is a tension roller, 10 is a connecting rod, 11 is a sprocket, 12 is a chain, 13 is a chain link, 14 is a shaft sleeve, and 15 is an annular groove. DETAILED DESCRIPTION

[0042] The present application will be further described below in combination with the drawings and specific embodiments:

[0043] For example, Figure 1 and Figure 2As shown, a sintering device for wear-resistant alumina ceramic balls comprises a mesh belt type tunnel sintering furnace, the mesh belt type tunnel sintering furnace has a fine chain mesh belt 1, the chain mesh belt 1 is tensioned by a first support roller group, the chain mesh belt 1 is driven by a first driving roller 2, the outer side of the chain mesh belt 1 is in sliding contact with a chain rod conveying belt 3, the chain rod conveying belt 3 is tensioned by a second support roller group, the chain rod conveying belt 3 is driven by a second driving roller 4, the transmission speed of the chain rod conveying belt 3 is slower than the transmission speed of the chain mesh belt 1, a multi-stage speed change sprocket group 5 is arranged on the second driving roller 4, the second driving roller 4 is linked with the first driving roller 2 through the multi-stage speed change sprocket group 5, the multi-stage speed change sprocket group 5 can adjust the transmission ratio, realize the speed difference adjustment of the chain mesh belt 1 and the chain rod conveying belt 3, and the speed difference between the chain mesh belt 1 and the chain rod conveying belt 3 can be adjusted between 125 mm / min and 6000 mm / min.

[0044] The present application also has various alternatives, for example: the chain rod conveying belt 3 and the chain mesh belt 1 are connected to the same group of driving rollers, a planetary gear transmission mechanism is adopted to connect the first driving roller 2 and the chain rod conveying belt 3, the chain rod conveying belt 3 is in sliding contact with the chain mesh belt 1, or the chain rod conveying belt 3 is located above the chain mesh belt 1, the lower part of the chain rod conveying belt 3 is in sliding contact with the upper part of the chain mesh belt 1, etc., various alternatives only need to achieve the speed difference between the chain rod conveying belt 3 and the chain mesh belt 1, in various alternatives, the technical scheme in the embodiment has the smallest modification to the prior art, has the smallest influence on the heating effect of the sintering furnace, and has the lowest cost.

[0045] As shown in the drawings, Figure 3 and Figure 4As shown, the relationship between the chain link conveying belt 3 and the chain mesh belt 1 is as follows: the two ends of the support roller one 6 of the input end (the end close to the sintering furnace inlet) of the chain mesh belt 1 are rotatably connected with two support wheels 7, the outer diameter of the two support wheels 7 is slightly larger than the outer diameter of the connected support roller one 6, after the support wheel 7 contacts the chain link conveying belt 3, there is a gap between the chain link conveying belt 3 and the outer side of the chain mesh belt 1, but the gap is less than 5mm, the output end (the end close to the sintering furnace outlet) of the chain mesh belt 1 is provided with a support roller two 8 and a tension roller 9 higher than the chain mesh belt 1, the support roller two 8, the tension roller 9 and the support wheel 7 form a second support roller group, the support roller two 8 and the tension roller 9 cooperate with the support wheel 7 to tension the chain link conveying belt 3, a second driving roller 4 engaged with the chain link conveying belt 3 is arranged above the chain mesh belt 1 outside the sintering furnace outlet, the second driving roller 4 includes a connecting rod 10 and two sprockets 11, one sprocket 11 is coaxially connected to each end of the connecting rod 10, the distance between the chain mesh belt 1 and the connecting rod 10 is greater than 200mm, so that the spherical ceramic raw materials can pass below the connecting rod 10, one sprocket 11 is connected with a multi-stage speed change sprocket set 5, and the multi-stage speed change sprocket set 5 is connected with the first driving roller 2 to realize transmission, this arrangement not only facilitates the placement of spherical ceramic raw materials at the input end of the chain mesh belt 1, but also enables the sintered products to automatically fall off at the output end of the chain mesh belt 1, without the need for manual picking.

[0046] The chain link conveying belt 3 is composed of a chain 12 and a chain link 13, an axle sleeve 14 is rotatably connected to each chain link 13, and the space between each adjacent two axle sleeves 14 forms a mesh, which is used to hold the spherical ceramic raw materials, when the spherical ceramic raw materials are located in the mesh, the lower end of the spherical ceramic raw materials contacts the chain mesh belt 1, and the side surface contacts the axle sleeve 14, the chain link conveying belt 3 has 3-5 specifications to adapt to ceramic balls of various specifications in the range of 20-200mm.

[0047] The axle sleeve 14 has an annular groove 15, the annular groove 15 has two circular cone side surfaces, one of which has a larger taper than the other, that is, the included angle between the two circular cone side surfaces is at an angle to the transmission direction of the chain link conveying belt 3.

[0048] Specifically as Figure 5As shown in the figure, the figure is a state diagram of the spherical ceramic raw material in the chain link conveyor belt 3 mesh, wherein direction i represents the driving direction of the chain link conveyor belt 3 and the chain mesh belt 1, and is also the moving direction of the spherical ceramic raw material. The driving speed of the chain link conveyor belt 3 is slower than that of the chain mesh belt 1. When the speed of the spherical ceramic raw material moving with the chain link conveyor belt 3 is ignored, it can be considered that the spherical ceramic raw material rotates around the axis j. Such a state of motion can make every point on the surface of the spherical ceramic raw material have a chance to face upwards (or in all directions). That is, the surface of the spherical ceramic raw material has a chance to face the heating element, and as the spherical ceramic raw material rolls, the surface of the spherical ceramic raw material has an equal chance (time) to face the heating element, and the surface of the spherical ceramic raw material is uniformly heated.

[0049] The diameter of the shaft sleeve 14 is smaller than the height of the chain 12. When the chain link conveyor belt 3 contacts the chain mesh belt 1, there is a gap between the lower end of the shaft sleeve 14 and the chain mesh belt 1 to reduce the resistance of the spherical ceramic raw material when rolling. There is a gap between the end of the chain link conveyor belt 3 and the chain mesh belt 1 near the outlet end of the mesh belt type tunnel sintering furnace for discharging.

[0050] A sintering method of wear-resistant alumina ceramic balls, including a forming stage, a glue removal stage, a shaping stage and a sintering stage, a total of four stages, the specific process of the four stages is as follows:

[0051] The forming stage is to form the powder into a spherical shape to obtain a spherical blank. The forming stage does not limit the forming means, and semi-automatic mechanical forming machines or cold isostatic presses can be used as long as the forming specifications are met and the pressure is sufficient;

[0052] The glue removal stage is to heat and remove glue for the spherical blank placed in the glue removal furnace to obtain a ceramic blank. In the glue removal stage, the glue removal furnace is heated at a speed of 15℃ / min, heated to 470℃-530℃, and then cooled with the furnace for 2-3 hours;

[0053] The shaping stage is to perform primary grinding processing on the ceramic blank to retain a certain processing allowance while making the ceramic blank close to a standard sphere to obtain a shaped blank. In the shaping stage, the ceramic blank is processed by turning to retain a processing allowance of 20%-25% of the diameter of the finished wear-resistant alumina ceramic ball. The volume of the ceramic blank will shrink during the sintering process, and the diameter will change by about 15%-20%. The 20%-25% not only retains the allowance for the shrinkage of the ceramic blank during the sintering process, but also reserves a grinding allowance.

[0054] The sintering stage is to sinter the shaped blank in a sintering furnace to form a dense alumina ceramic ball.

[0055] In the sintering stage, the shaped green body is kept in a rolling state in the sintering furnace, and the rolling speed of the shaped green body is 2-10 rounds per minute.

[0056] The effects of the present application are shown by different embodiments as follows:

[0057] Materials: micron-sized γ-A12O3 powder with a particle size range of 1-3 μm and a chemical purity of 99.9% without obvious agglomeration, produced by Henan Changxing Industry Co., Ltd.; nanometer-sized γ-A12O3 powder with a particle size range of 20-50 nm and a chemical purity of 99.9% without obvious agglomeration, produced by Henan Changxing Industry Co., Ltd. Equipment: dry pressing forming machine, cold isostatic pressing machine, muffle furnace and self-modified tunnel furnace.

[0058] Example One

[0059] The nanometer-sized γ-A12O3 powder is granulated and added to the metal cavity of the dry pressing forming machine, and is pressed to form a ball blank. The ball blank is then cold isostatic pressed to increase the density and strength of the ball blank. The diameter of the ball blank after cold isostatic pressing is 25-26 mm. The ball blank is then placed in a square crucible and put into a muffle furnace to remove the binder. The heating rate is 15°C / min, and the temperature is raised to 470°C and maintained for 2 hours. The ball blank is then cooled in the furnace, and the hardness of the ball blank is increased to obtain a ceramic green body. The ceramic green body is then ground to a diameter of 24-25 mm with a diameter deviation of less than 0.5 mm to obtain a shaped green body.

[0060] The shaped green body is placed in the mesh above the chain mesh belt 1. As the chain mesh belt 1 moves, the shaped green body contacts the shaft sleeve 14 and forms a rolling state. The shaped green body is then put into a sintering furnace and heated to 1370°C at a rate of 10°C / min. The rolling speed of the shaped green body during sintering is 10 rounds per minute.

[0061] A total of 1000 ball blanks are produced. 16 are discarded due to adhesion during the binder removal stage, and 14 are damaged during the shaping stage. The remaining ball blanks are sintered. After sintering, 22 of the sintered pieces are discarded due to insufficient processing allowance caused by a large shrinkage rate during sintering. The remaining sintered pieces without distortion are sent to the next process, and a total of 948 sintered products are produced.

[0062] Example Two

[0063] The micron-sized γ-Al2O3 powder is granulated, added into a metal cavity of a dry pressing machine, and pressed to form a green body. The green body is then cold isostatic pressed to increase the density and strength of the green body. The green body is then placed in a square crucible with a spacing between each two adjacent ceramic balls, and heated in a muffle furnace to remove the binder. The heating rate is 15°C / min, and the temperature is raised to 530°C and maintained for 3 hours. The green body is then cooled in the furnace, and the hardness of the green body is increased to obtain a ceramic green body.

[0064] The ceramic green body is then ground to a diameter of 240-245mm with a deviation of less than 1mm to obtain a modified green body.

[0065] The modified green body is placed in the mesh above the chain mesh belt 1. As the chain mesh belt 1 moves, the modified green body contacts the shaft sleeve 14 and rolls with the shaft sleeve 14. The modified green body is then placed in a sintering furnace and heated at a rate of 10°C / min to 1450°C and maintained for 3 hours. During sintering, the rolling speed of the modified green body is 2 revolutions / min.

[0066] A total of 500 green bodies are produced. During the binder removal stage, 4 green bodies are damaged, and the remaining green bodies are sintered. After sintering, 8 green bodies are discarded due to insufficient machining allowance caused by a large shrinkage rate during sintering. The remaining sintered products without distortion are 488, which are sent to the next process.

[0067] As can be seen from the above examples, the sintering method and device of the present application are particularly suitable for sintering large-diameter high-wear-resistant alumina ceramic. Although the present application may also cause damage due to modification and size unqualified due to sintering shrinkage during production, the present application can greatly reduce the waste rate by achieving uniform heating of the ball.

[0068] The preferred embodiments of the present application are described in detail above with reference to the accompanying drawings, but the present application is not limited to the above examples. The technical solutions of the present application can be modified in various ways without departing from the spirit of the present application, i.e., the scope of the disclosure.

Claims

1. A sintering method of wear-resistant alumina ceramic balls, comprising a forming stage, a de-binding stage, a trimming stage and a sintering stage, a total of four stages, characterized in that, The specific processes of the four stages are as follows: The forming stage is to form the powder into a spherical shape to obtain a spherical blank; The glue discharging stage is to heat and discharge the spherical blank in a glue discharging furnace to obtain a ceramic blank; The shaping stage is to perform primary grinding processing on the ceramic blank, retain a certain processing allowance, and make the ceramic blank close to a standard sphere to obtain a shaped blank; The sintering stage is to sinter the shaped blank in a sintering furnace to make the shaped blank form a dense alumina ceramic sphere; In the sintering stage, the shaped blank is kept in a rolling state in the sintering furnace, In the sintering stage, the rolling speed of the shaped blank is 2-10 r / min.

2. The sintering method of the wear resistant alumina ceramic ball according to claim 1, characterized in that, In the glue discharging stage, the glue discharging furnace is heated at a speed of 15 ℃ / min, heated to 470-530 ℃, and kept for 2-3 hours, and then cooled with the furnace.

3. The method of sintering wear resistant alumina ceramic balls according to claim 1, wherein, In the shaping stage, the ceramic blank is subjected to a turning treatment, and the processing allowance is retained to be 20-25% of the diameter of the finished product of the wear-resistant alumina ceramic sphere.

4. A sintering device for sintering wear-resistant aluminum oxide ceramic balls for carrying out a sintering method according to any one of claims 1 to 3, comprising a mesh belt tunnel sintering furnace, said mesh belt tunnel sintering furnace having a fine mesh chain belt (1), said chain belt (1) being tensioned by a first support roller set, the chain belt (1) being driven by a first drive roller (2), characterized in that The chain link belt (1) is in sliding contact with a chain link conveying belt (3) on the outer side, the chain link conveying belt (3) is tensioned by a second supporting roller group, the chain link conveying belt (3) is driven by a second driving roller (4), the transmission speed of the chain link conveying belt (3) is slower than that of the chain link belt (1), the chain link conveying belt (3) has mesh holes, the mesh holes are used for containing spherical ceramic raw materials, when the spherical ceramic raw materials are located in the mesh holes, the lower end of the spherical ceramic raw materials contacts the chain link belt (1), and the side surface contacts the mesh hole, the chain link conveying belt (3) is composed of a chain (12) and a chain link (13), each chain link (13) is rotationally connected with a shaft sleeve (14), and the space between each adjacent two shaft sleeves (14) is a mesh hole, The shaft sleeve (14) has an annular groove (15), and the annular groove (15) has two circular cone side surfaces, one of which has a larger taper than the other.

5. The sintering apparatus of the wear resistant alumina ceramic ball according to claim 4, characterized in that, The diameter of the shaft sleeve (14) is smaller than the height of the chain (12), and when the chain link conveying belt (3) contacts the chain link belt (1), there is a gap between the lower end of the shaft sleeve (14) and the chain link belt (1).

6. The sintering apparatus of the wear resistant alumina ceramic ball according to claim 4, characterized in that, The second driving roller (4) is provided with a multi-stage speed change sprocket set (5), and the second driving roller (4) is linked with the first driving roller (2) through the multi-stage speed change sprocket set (5).

7. The sintering device for wear-resistant alumina ceramic balls according to claim 4, characterized in that: The chain link conveying belt (3) near the outlet end of the mesh belt type tunnel sintering furnace has a gap with the end of the chain link belt (1) for discharging materials.

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