Microwave sintering method and microwave sintering equipment for ceramic roller

Abstract

The present invention relates to the technical field of the preparation of ceramic rollers. Disclosed are a microwave sintering method and microwave sintering equipment for a ceramic roller. The microwave sintering method of the present invention comprises the following steps: conducting microwave sintering by using a microwave sintering kiln, wherein the microwave sintering kiln comprises a sintering cavity and an outer cavity surrounding the sintering cavity, the outer cavity is provided with a focusing reflector, and a heating zone, a sintering zone and a cooling zone are sequentially formed in the sintering cavity from top to bottom; starting a microwave source, and adjusting the working frequency and power of the microwave source to make the temperature of the sintering zone be 1200-1600ºC; placing an auxiliary heating base in the sintering cavity; and enabling the ceramic roller to enter and pass through the sintering cavity at the speed V1 to undergo microwave sintering while maintaining a rotary motion, so as to obtain a microwave sintered ceramic roller. The microwave sintering method and microwave sintering equipment for a ceramic roller of the present invention can achieve effective microwave sintering of an aluminum oxide ceramic roller, the temperature for the microwave sintering of the ceramic roller reaches 1200ºC or higher, and the ceramic roller can be heated more evenly by means of dynamic continuous sintering.

Description

A microwave sintering method and microwave sintering equipment for ceramic rollers Technical Field

[0001] This invention relates to the field of ceramic roller preparation technology, and in particular to a microwave sintering method and microwave sintering equipment for ceramic rollers. Background Technology

[0002] Ceramic rollers are a special type of refractory kiln furniture that supports and conveys ceramic bricks and other products in roller kilns and drying kilns. They are the core component of roller kilns and have a significant impact on energy saving, product firing cycle, and automated operation. They are widely used in fields such as building ceramics, daily-use ceramics, electronic ceramics, magnetic materials, and glass heat treatment.

[0003] Currently, ceramic roller sintering mainly adopts pit kiln hoisting sintering, which has the following main problems: (1) Pit kiln hoisting sintering relies on the heating element to transfer heat to the ceramic rollers through convection, conduction or radiation to reach the sintering temperature. The heat is transferred from the outside to the inside, and there is a temperature gradient inside the ceramic rollers. (2) Pit kiln hoisting sintering uses fuel combustion, which results in a large thermal inertia. If the control experience is insufficient, the firing temperature and holding time will have an overshoot phenomenon at the inflection point. The actual firing temperature and holding time deviate from the sintering curve specified by the process, and the formation of ceramic roller phase is affected. (3) Affected by the high temperature airflow, there is also a temperature gradient on the horizontal and vertical surfaces inside the kiln. During the sintering process, there are temperature differences between different positions of the ceramic rollers and different parts of the ceramic rollers inside the kiln, which can easily lead to uneven heating of the ceramic rollers. Based on the above problems, the ceramic rollers after hoisting and sintering in the well kiln have defects such as inconsistent shrinkage and uneven grain structure. This will affect the strength and thermal shock resistance of the ceramic rollers, and also challenge the uniformity of the ceramic roller size and performance, as well as the yield of ceramic rollers.

[0004] Microwave sintering is a novel method for ceramic sintering. It involves the direct interaction of microwaves with material particles (molecules, ions), utilizing the dielectric loss of the material to allow the sample to directly absorb microwave energy, thus heating and sintering the ceramic. It features rapid heating, high energy efficiency, environmental friendliness, no thermal inertia, high heating efficiency, and precise control of the heating process. Microwave heating enables uniform heating from the inside out, improving product uniformity and yield, and enhancing the microstructure and properties of the sintered product. It has become a new research hotspot in the field of ceramic roller sintering.

[0005] Although microwave sintering has many advantages over traditional well kiln hoisting sintering, it also has problems when sintering ceramic rollers: (1) Ceramic production enterprises mainly use alumina ceramic rollers in roller kilns. Alumina ceramic rollers have too low dielectric loss at room temperature and weak microwave coupling ability, so they cannot be effectively microwave sintered. (2) The weak electric field strength in the microwave multimode resonant cavity and the low dielectric loss of the ceramic rollers make it difficult to reach a microwave sintering temperature of more than 1,200 degrees Celsius. (3) The dielectric loss of the material changes with temperature. When the dielectric loss of the heated ceramic roller changes, the electric field distribution in the microwave resonant cavity changes drastically. The position and size of the uniform field area are unstable. Due to the long size of the ceramic rollers, non-uniform heating is likely to occur during the sintering process, resulting in local overheating and scorching problems, which affect the sintering effect of the ceramic rollers. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a microwave sintering method for ceramic rollers, which can effectively microwave sinter alumina ceramic rollers. During microwave sintering, the temperature of the ceramic rollers reaches above 1200°C, and dynamic continuous sintering is adopted, which can make the heating of the ceramic rollers more uniform. This solves the problems of traditional microwave sintering methods, which are difficult to effectively microwave sinter alumina ceramic rollers and the microwave sintering temperature is difficult to reach above 1200°C. At the same time, it also solves the problem of uneven heating of ceramic rollers during microwave sintering.

[0007] Another objective of this invention is to provide a microwave sintering apparatus. This microwave sintering apparatus can form a heating zone, a sintering zone, and a cooling zone within the sintering chamber that meet the sintering parameters for alumina ceramic rollers, and can achieve dynamic continuous sintering. This solves the problem that existing microwave sintering devices are difficult to use for microwave sintering of alumina ceramic rollers, and also solves the problem of uneven heating that occurs when using existing microwave sintering devices to microwave sinter ceramic rollers.

[0008] To address the aforementioned technical problems, this invention provides a microwave sintering method for ceramic rollers, comprising the following steps:

[0009] (1) Microwave sintering is carried out in a microwave sintering kiln. The microwave sintering kiln includes a sintering cavity and an outer cavity surrounding the sintering cavity. The outer cavity is equipped with a focusing reflector. The focusing reflector can adjust the electric field intensity in the sintering cavity so that a heating zone, a sintering zone and a cooling zone are formed in sequence in the sintering cavity. The microwave source is turned on and the working frequency and power of the microwave source are adjusted so that the temperature of the sintering zone is 1200-1600℃.

[0010] (2) The built-in auxiliary heating base is placed in the sintering cavity; the auxiliary heating base can absorb microwaves at room temperature;

[0011] (3) While keeping the ceramic roller in rotation, it enters and passes through the sintering cavity at a speed of V1 to perform microwave sintering, thereby obtaining a microwave sintered ceramic roller.

[0012] In one embodiment, the focusing reflector is located in the middle of the outer cavity in the vertical direction, so that the electric field intensity in the middle of the sintering cavity is greater than the electric field intensity in the upper and lower parts of the sintering cavity, so that the middle of the sintering cavity forms a sintering zone, the upper part of the sintering cavity forms a heating zone, and the lower part of the sintering cavity forms a cooling zone.

[0013] In one embodiment, the angle of the focusing reflector is adjustable from 0 to 90 degrees;

[0014] In step (1), the angle of the focusing reflector is adjusted according to the sintering parameters of the ceramic roller so that the length of the heating zone is 80-120mm, the length of the sintering zone is 70-90mm, and the length of the cooling zone is 80-120mm; the lengths of the heating zone, sintering zone, and cooling zone in the sintering cavity are measured using the silica gel method.

[0015] In one implementation, in step (3), the velocity V1 satisfies the following formula:

[0016] The heat preservation time of the ceramic roller is 2 to 10 minutes.

[0017] In one embodiment, in step (3), the rotational speed of the ceramic roller is 1-3 r / min, and the speed V1 entering and passing through the sintering chamber is 13-16 mm / min.

[0018] In one implementation, in step (2), it is also necessary to adjust the placement device of the auxiliary heating base so that the distance between the auxiliary heating base and the outer surface of the ceramic roller is 10-20 mm.

[0019] In one implementation, in step (1), the auxiliary heating base is made of silicon carbide and / or graphite.

[0020] In one implementation, in step (1), the microwave source operates at a frequency of 2.45 to 3.0 GHz and has a power of 0.5 to 5 kW.

[0021] In one embodiment, the ceramic roller is an alumina ceramic roller; the ceramic roller comprises 65-85% alumina by mass percentage.

[0022] On the other hand, the present invention also provides a microwave sintering apparatus for the microwave sintering method of the above-mentioned ceramic rollers, comprising a microwave sintering kiln, a microwave source, a focusing regulator, a driving device, and an auxiliary heating base;

[0023] The microwave sintering furnace includes a sintering cavity and an outer cavity surrounding the sintering cavity. The sintering cavity is used to sinter ceramic rollers. The auxiliary heating base is installed inside the sintering cavity. After absorbing microwaves, the auxiliary heating base is used to heat the ceramic rollers so that the temperature of the ceramic rollers reaches the critical temperature of microwave sintering.

[0024] A microwave feed port is provided on one side of the microwave sintering kiln. The microwave source is located outside the microwave sintering kiln and is positioned on the side where the microwave feed port is located. The focusing regulator is installed inside the outer cavity and away from the microwave feed port. The installation positions of the microwave source, the microwave feed port, and the focusing regulator are corresponding.

[0025] The driving device is installed above the sintering chamber, and the driving device is used to drive the ceramic roller to enter and pass through the sintering chamber while maintaining rotational motion.

[0026] Implementing this invention has the following beneficial effects:

[0027] 1. The microwave sintering method of this technical solution uses an auxiliary heating base with strong microwave coupling capability at room temperature placed in the sintering cavity to heat the ceramic roller. This indirectly heats the ceramic roller to reach the critical temperature for microwave sintering, overcoming the difficulty that the ceramic roller's dielectric loss is too low at room temperature, resulting in weak microwave coupling capability and preventing effective microwave sintering. A focusing reflector is placed on the side of the sintering cavity opposite to the microwave feed port, and its azimuth angle is adjusted. This creates a mixed field in the sintering cavity, composed of a standing wave field and a focusing field. The intensity of this mixed field in the sintering zone allows the ceramic roller to reach a temperature above 1200℃ during microwave sintering. Furthermore, the use of dynamic continuous sintering ensures more uniform heating of the ceramic roller, thereby improving its quality and mitigating the uneven heating phenomenon caused by the change in dielectric loss of the ceramic roller with temperature during microwave sintering.

[0028] 2. The roundness deviation of the ceramic roller obtained by the microwave sintering method provided by the present invention is less than 0.20%, the straightness deviation is less than 0.15%, and its thermal shock resistance test can be repeated 3 times. The high temperature bending strength of the ceramic roller at 1350℃ is greater than 45MPa, and the room temperature bending strength is greater than 60MPa. Attached Figure Description

[0029] Figure 1 is a schematic diagram of the structure of a microwave sintering device in one embodiment of the present invention;

[0030] Figure 2 is a schematic diagram of the microwave sintering kiln in the microwave sintering equipment shown in Figure 1.

[0031] Figure 3 is a schematic diagram of the drive device in the microwave sintering equipment shown in Figure 1;

[0032] Figure 4 is an exploded schematic diagram of the drive device shown in Figure 3;

[0033] Figure 5 is a geometric schematic diagram of the mixed field type;

[0034] In the diagram: 1. Microwave sintering kiln; 2. Microwave source; 3. Circulator; 5. Clamping mechanism; 6. Rotation mechanism; 7. Rotation drive mechanism; 8. Feeding mechanism; 9. Insulation material; 10. Temperature detection device; 20. Focusing regulator; 50. Ceramic roller; 80. Auxiliary heating base; 11. Sintering chamber; 101. Insulation chamber; 102. Microwave power supply port; 103. Inner cavity; 104. Fastener; 51. Clamping cylinder; 52. Connecting plate; 53. Coupling; 81. Feeding push rod; 82. Connecting part; 83. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0036] Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Raw materials whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0037] A microwave sintering method for ceramic rollers includes the following steps:

[0038] (1) Microwave sintering is carried out in a microwave sintering kiln. The microwave sintering kiln includes a sintering cavity and an outer cavity surrounding the sintering cavity from the inside to the outside. The outer cavity is equipped with a focusing reflector, which can adjust the electric field intensity in the sintering cavity so that the sintering cavity forms a heating zone, a sintering zone and a cooling zone from top to bottom. The microwave source is turned on and the working frequency and power of the microwave source are adjusted so that the temperature of the sintering zone is 1200-1600℃.

[0039] (2) The auxiliary heating base is placed inside the sintering cavity; the auxiliary heating base can absorb microwaves at room temperature;

[0040] (3) While keeping the ceramic roller (the ceramic roller here is an unsintered ceramic roller blank) rotating, it enters and passes through the sintering cavity at a speed of V1 to be microwave sintered, thus obtaining a microwave sintered ceramic roller.

[0041] It is worth noting that the microwave sintering method of this technical solution can be used for microwave sintering of ceramic rollers. An auxiliary heating base with strong microwave coupling capability at room temperature is placed in the sintering cavity to assist in heating the ceramic rollers, allowing indirect heating to reach the critical temperature for microwave sintering. This overcomes the difficulty of effectively sintering ceramic rollers due to insufficient dielectric loss and weak microwave coupling capability at room temperature. Furthermore, this technical solution installs a focusing reflector inside the microwave sintering kiln, specifically in the microwave multimode resonant cavity, which can change the intensity of the mixed field in the sintering cavity. This creates a mixed field formed by the superposition of a standing wave field and a focusing field, resulting in heating, sintering, and cooling zones within the sintering cavity that meet the sintering parameters of the ceramic rollers (as shown in Figure 5). The intensity of the mixed field in the sintering zone within the sintering cavity allows the temperature of the ceramic rollers to reach above 1200℃ during microwave sintering, thus enabling the sintering of ceramic rollers with high sintering temperature requirements. Furthermore, this technical solution employs dynamic continuous sintering, which improves the uneven heating of ceramic rollers caused by temperature variations in dielectric loss during microwave sintering. Microwave-sintered ceramic rollers produced using this technical solution exhibit a roundness deviation of less than 0.20% and a straightness deviation of less than 0.15%. Their thermal shock resistance test can be repeated three times. The high-temperature bending strength of the ceramic rollers at 1350℃ is greater than 45 MPa, and their room-temperature bending strength is greater than 60 MPa.

[0042] It should be noted that the microwave sintering method of this technical solution is applicable to the preparation of ceramic rollers of most materials, such as alumina ceramic rollers, SiC ceramic rollers, etc. Preferably, the ceramic rollers of this technical solution are alumina ceramic rollers.

[0043] To further explain, the focusing reflector is located in the middle of the outer cavity in the vertical direction, so that the electric field intensity in the middle of the sintering cavity is greater than the electric field intensity in the upper and lower parts of the sintering cavity, so that the middle of the sintering cavity forms a sintering zone, the upper part of the sintering cavity forms a heating zone, and the lower part of the sintering cavity forms a cooling zone.

[0044] To further explain, the angle of the focusing reflector can be adjusted from 0 to 90 degrees.

[0045] In step (1), the angle of the focusing reflector is adjusted according to the sintering parameters of the ceramic roller so that the length of the heating zone is 80-120mm, the length of the sintering zone is 70-90mm, and the length of the cooling zone is 80-120mm; the lengths of the heating zone, sintering zone, and cooling zone in the sintering cavity are measured using the silica gel method.

[0046] Specifically, this technical solution incorporates an adjustable-angle focusing reflector within the outer cavity of the microwave sintering kiln. Through the focusing reflector, the field pattern within the sintering cavity is superimposed from a standing wave field and a microwave focusing field, forming a hybrid field. The focusing field within this hybrid field is not a perturbation field but rather a field with an intensity comparable to the standing wave component. By adjusting the angle of the focusing reflector, this technical solution can alter the electric field strength and distribution of the microwave multimode resonant cavity. This results in a stronger electric field in the region corresponding to the focusing reflector and a weaker electric field on the upper and lower sides of the reflector. Regions with stronger electric field strength exhibit higher ceramic roller temperatures, while regions with weaker electric field strength exhibit relatively lower temperatures. Therefore, during microwave sintering of the ceramic roller, regions with stronger electric field strength can be considered as sintering zones (i.e., firing zones), and regions with weaker electric field strength can be considered as heating zones (i.e., heating zones) or cooling zones (i.e., cooling zones). Thus, heating zones, sintering zones, and cooling zones that satisfy the sintering parameters of the ceramic roller are formed within the sintering zone.

[0047] Preferably, in step (1), thermometers (preferably infrared radiation thermometers) are installed in the heating zone, sintering zone, and cooling zone respectively. During microwave sintering, the temperature of the ceramic rollers in these zones can be monitored in real time. The thermometers are connected to an external control system, and they feed back their real-time temperature readings to the control system. The control system then controls the operating frequency and power of the microwave source. By adjusting the operating frequency and power of the microwave source, the temperature of the ceramic rollers in the heating, sintering, and cooling zones can be ensured to remain within a specified range.

[0048] Specifically, the ceramic roller in this technical solution is an alumina ceramic roller, which has a high sintering temperature of 1200-1600℃.

[0049] Further explanation: In step (1), the distribution of the heating zone, sintering zone and cooling zone in the sintering cavity is detected by the silica gel method, and the lengths of the heating zone, sintering zone and cooling zone are obtained by measurement;

[0050] In step (3), the velocity V1 satisfies the following formula:

[0051] The holding time of the ceramic roller is 2 to 10 minutes, and the holding time refers to the sintering time of the ceramic roller in the sintering zone.

[0052] This technical solution allows adjustment of the focusing reflector to alter the intensity of the mixing field within the sintering cavity. The intensity of the mixing field can be characterized by detecting the electromagnetic field distribution within the sintering cavity. Preferably, the silica gel method can be used to detect the electromagnetic field distribution within the sintering cavity. When the azimuth angle of the focusing reflector changes, the position and size of the uniform field area will change accordingly. By observing the color change of the silica gel (granules or powder) uniformly spread on the cardboard, the distribution of the heating zone, sintering zone, and cooling zone can be determined.

[0053] Furthermore, color-changing silica gel can be used to qualitatively test the electromagnetic field distribution within the sintering cavity. Color-changing silica gel is a commonly used desiccant, made by impregnating porous SiO2 particles with CoCl2 solution. Its color-changing reaction formula is: CoCl2 (blue) + 6H2O = CoCl2·6H2O (light red). It can be seen that the silica gel turns light red after absorbing water and turns blue after losing water upon heating. The method for detecting the electromagnetic field distribution within the sintering cavity using silica gel is as follows: Silica gel (granules or powder) impregnated with CoCl2 solution is evenly spread on a cardboard, then placed inside the sintering cavity. Microwave power is output at appropriate times and in appropriate amounts. The microwave electromagnetic field polarizes the SiO2-water interface of the silica gel, generating high heat. The water inside the silica gel is rapidly removed, and the silica gel changes color due to dehydration. The areas with high field strength density show obvious color changes (i.e., the sintering zone), while the areas with low density do not change color or change very lightly (i.e., the heating zone or cooling zone). This allows for a relatively intuitive measurement of the electromagnetic field distribution within the sintering cavity, that is, the distribution of the heating zone, sintering zone, and cooling zone. Further measurements can then be taken to determine the lengths of the heating zone, sintering zone, and cooling zone.

[0054] In this technical solution, the speed V1 is equal to the length of the sintering zone divided by the holding time of the ceramic roller. This ensures that the holding time of the ceramic roller in the sintering zone meets its sintering specifications, thereby obtaining a ceramic roller of good quality. In one embodiment of this technical solution, the sintering parameters for this type of ceramic roller are as follows: the ceramic roller is uniformly heated from room temperature to a sintering temperature of 1400℃ within approximately 6 minutes, held at the sintering temperature for 5 minutes, and then cooled within 6 minutes. The field strength distribution length in the sintering chamber was measured using the silica gel method. The test showed that the length of the sintering zone is approximately 80 mm, and the lengths of both the heating and cooling zones are approximately 95 mm. To ensure a 5-minute holding time, the speed V1 is 80 mm / 5 min, or 16 mm / min, at which the ceramic roller enters and passes through the holding device.

[0055] Further explanation: In step (3), the rotational speed V2 of the ceramic roller is 1 to 3 r / min, and the speed V1 entering and passing through the sintering chamber is 13 to 16 mm / min.

[0056] It is worth noting that due to the relatively long length of the ceramic rollers, non-uniform heating is easily observed during the sintering process, leading to localized overheating and scorching, which affects the sintering effect. This technical solution employs a dynamic continuous sintering method for microwave sintering. The ceramic rollers enter at a speed V1 and pass through the heat preservation device for sintering, rotating at a speed of 1–3 r / min. This ensures uniform heating of the ceramic rollers, further improving their quality, reducing roundness and straightness deviations, and addressing the uneven heating issues that arise during microwave sintering due to variations in dielectric loss with temperature.

[0057] Further explanation: the focusing reflector has an arc-shaped structure, and the reflecting surface of the focusing reflector is a concave surface of the arc-shaped structure. The reflecting surface of the focusing reflector faces the microwave power supply port of the microwave sintering kiln; thus, a mixed field consisting of a standing wave field and a focusing field is formed in the sintering cavity, and the intensity of the mixed field in the sintering zone of the sintering cavity is sufficient to make the temperature of the ceramic roller reach above 1200℃ during microwave sintering of the ceramic roller.

[0058] The focusing reflector can be adjusted from 0 to 90 degrees. In this technical solution, the angle of the focusing reflector can be adjusted from 0 to 90 degrees. By adjusting the orientation angle of the focusing reflector in the microwave sintering furnace, the intensity and distribution of the mixing field in the sintering cavity can be changed, thereby adjusting the distribution and length of the heating zone, sintering zone, and cooling zone.

[0059] Specifically, the focusing reflector used in this technical solution is available for purchase on the market.

[0060] Further explanation: In step (2), it is also necessary to adjust the placement device of the auxiliary heating base so that the distance between the auxiliary heating base and the outer surface of the ceramic roller is 10-20mm.

[0061] It is worth noting that the ceramic roller in this technical solution is an alumina ceramic roller. Since alumina ceramic rollers absorb almost no microwaves at room temperature, their loss tangent only becomes significant after reaching the critical temperature for microwave sintering, allowing them to absorb microwaves for sintering. This technical solution employs a hybrid heating method. Before reaching the critical temperature, an auxiliary heating base with higher dielectric loss absorbs microwaves and releases heat to indirectly heat the ceramic roller. Once the ceramic roller reaches the critical temperature, it absorbs microwaves, thus achieving microwave sintering. This technical solution controls the distance between the auxiliary heating base and the outer surface of the ceramic roller to be 10–20 mm, allowing the heat released by the auxiliary heating base to better heat the ceramic roller, enabling it to reach the critical temperature for microwave sintering more quickly.

[0062] To further explain, the auxiliary heating base is made of silicon carbide and / or graphite.

[0063] Specifically, the auxiliary heating base material of this technical solution is one or a combination of silicon carbide and graphite. Silicon carbide and graphite have high dielectric loss and strong microwave coupling ability at room temperature. Therefore, they can absorb microwaves and release heat at room temperature, indirectly heating the ceramic roller and making the ceramic roller reach the critical temperature (200-450℃), thereby enabling the ceramic roller to absorb microwaves and achieve the purpose of microwave sintering.

[0064] To further clarify, the microwave source operates at a frequency of 2.45–3.0 GHz and has a power of 0.5–5 kW.

[0065] This technical solution ensures the formation of heating, sintering, and cooling zones within the sintering cavity that meet the sintering parameters of alumina ceramic rollers by controlling the microwave source's operating frequency to 2.45–3.0 GHz and power to 0.5–5 kW, and by using a focusing reflector to further enhance the electric field strength in the sintering cavity.

[0066] Further explanation: the ceramic roller is an alumina ceramic roller;

[0067] The ceramic roller comprises 65-85% alumina by mass percentage.

[0068] The ceramic rollers in this technical solution are alumina ceramic rollers. Alumina ceramic rollers are ceramic rollers with alumina (AL2O3) as the main component, and are mainly used in roller kilns and electric furnaces for producing wall tiles, floor tiles, and daily-use ceramics. Alumina ceramic rollers have excellent bending strength at high temperatures and exhibit reliable thermal stability and excellent thermal shock resistance for products fired below 1000℃.

[0069] In one embodiment of this technical solution, the raw materials for the alumina ceramic roller, calculated by mass percentage, include 40 wt% corundum sand, 26 wt% kaolin, 24 wt% alumina, 8 wt% zirconium silicate, and 2 wt% sodium carboxymethyl cellulose. The alumina ceramic roller prepared using this formula has a mass percentage of 69.9% alumina (Al₂O₃).

[0070] A microwave sintering apparatus, as shown in Figures 1 to 4, is applied to the microwave sintering method of the above-mentioned ceramic rollers, including a microwave sintering kiln 1, a microwave source 2, a focusing regulator 50, a driving device, and an auxiliary heating base 11.

[0071] The microwave sintering furnace 1 includes a sintering cavity 101 and an outer cavity 104 from the inside to the outside. The sintering cavity 101 is used to sinter ceramic rollers. The auxiliary heating base 11 is installed inside the sintering cavity 101. After absorbing microwaves, the auxiliary heating base 11 is used to heat the ceramic rollers 80 so that the temperature of the ceramic rollers 80 reaches the critical temperature of microwave sintering.

[0072] A microwave feed port 103 is provided on one side of the microwave sintering kiln 1. The microwave source 2 is located outside the microwave sintering kiln 1 and is located on the side where the microwave feed port 103 is located. The focusing regulator 50 is installed in the outer cavity 104 and away from the microwave feed port 103. The installation positions of the microwave source 2, the microwave feed port 103 and the focusing regulator 50 are corresponding.

[0073] The driving device is installed above the sintering chamber 101, and the driving device is used to drive the ceramic roller 80 to enter and pass through the sintering chamber 101 while maintaining rotational motion.

[0074] Preferably, the microwave source 2, the microwave feed port 103, and the focusing regulator 50 are installed on the same horizontal line. The connecting line between the microwave feed port 103 and the focusing regulator 50 is perpendicular to the vertical centerline of the sintering cavity 101, so that the focusing regulator 50 can better adjust the electric field strength inside the sintering cavity 101, thereby adjusting the distribution of the heating zone, sintering zone, and cooling zone.

[0075] Specifically, the interior of the microwave sintering kiln 1 in this technical solution is a microwave multimode resonant cavity.

[0076] The microwave sintering equipment of this technical solution uses an auxiliary heating base 11 with strong microwave coupling capability at room temperature, placed in the sintering cavity 101 to assist in heating the alumina ceramic roller. This indirectly heats the alumina ceramic roller to reach its critical temperature for microwave sintering, overcoming the difficulty that the alumina ceramic roller cannot be effectively microwave sintered due to its low dielectric loss and weak microwave coupling capability at room temperature. Furthermore, this technical solution places a focusing reflector 50 in the center of a portion of the outer cavity 104 away from the microwave feed port 103, forming a mixed field in the sintering cavity 101 composed of a standing wave field and a focusing field. This creates a heating zone, a sintering zone, and a cooling zone within the sintering cavity 101 that satisfy the sintering parameters of the alumina ceramic roller (as shown in Figure 5). The intensity of the mixed field in the sintering zone within the sintering cavity 101 is sufficient to allow the alumina ceramic roller to reach a temperature above 1200℃ during microwave sintering. In addition, the microwave sintering equipment of this technical solution is also equipped with a driving device. The driving device can drive the ceramic roller 80 to enter and pass through the sintering chamber 101 while maintaining rotational motion, thereby realizing dynamic continuous sintering. This improves the phenomenon of uneven heating of ceramic rollers caused by the change of ceramic roller dielectric loss with temperature when using traditional microwave sintering equipment.

[0077] Specifically, in this technical solution, a microwave power supply port 103 is provided in the middle of the vertical direction of the side wall of the microwave sintering kiln 1. The focusing regulator 50 is installed in the outer cavity 104 of the microwave sintering kiln 1 and is far away from the microwave power supply port 103. That is, the microwave power supply port 103 and the focusing regulator 50 are located on both sides of the sintering cavity 101, and their positions correspond to each other. By installing a focusing regulator 50 inside the microwave sintering furnace 1, i.e., inside the outer cavity 104, the sintering cavity field is made into a mixed field formed by the superposition of a standing wave field and a microwave focusing field. The focusing field in this mixed field is not a perturbation field but a field with an intensity comparable to that of the standing wave component. This increases the electric field intensity inside the microwave sintering furnace 1 and makes the electric field intensity inside the microwave sintering furnace 1 decrease from the middle to the upper and lower ends respectively. The area with stronger electric field intensity corresponds to a higher temperature, and the area with weaker electric field intensity corresponds to a lower temperature. Thus, a heating zone, a sintering zone, and a cooling zone are formed from top to bottom inside the sintering cavity 101. The electric field intensity in the sintering zone can enable the sintering temperature of the ceramic roller 80 to reach above 1200℃.

[0078] It should be noted that in this technical solution, an auxiliary heating base 11 is placed inside the sintering cavity 101. The auxiliary heating base 11 is made of a material that can absorb microwaves at room temperature. After absorbing microwaves, the auxiliary heating base 11 is used to assist in heating the ceramic roller 80, so that the ceramic roller 80 is indirectly heated to reach its critical temperature for microwave sintering. This overcomes the difficulty that alumina ceramic rollers cannot be effectively microwave sintered because the dielectric loss is too small at room temperature and the microwave coupling ability is weak.

[0079] Specifically, the auxiliary heating base 11 in this technical solution is made of a material with strong microwave coupling capability at room temperature, enabling the auxiliary heating base 11 to absorb microwaves and dissipate heat at room temperature, thereby heating the ceramic roller 80 and raising the temperature of the ceramic roller 80 to the critical temperature for microwave sintering. An exemplary auxiliary heating base 11 is made of silicon carbide and / or graphite, but is not limited to these.

[0080] Specifically, the top and bottom of the sintering chamber 101 are respectively provided with an inlet and an outlet for the alumina ceramic roller 80 to enter and exit.

[0081] Further explanation: the microwave sintering kiln 1 is also provided with a heat preservation cavity 102, which is located between the sintering cavity 101 and the outer cavity, and the heat preservation cavity 102 is filled with heat preservation material 10.

[0082] Preferably, the microwave sintering furnace 1 has a cylindrical multi-mode cavity structure. The center of the microwave sintering furnace 1 is the sintering cavity 101, and the outside of the sintering cavity 101 consists of a heat preservation cavity 102 and an outer cavity 104. The heat preservation cavity 102 can be non-uniformly filled with heat preservation material 10, which can reduce heat loss during the sintering process, ensure the temperature stability within the microwave multi-mode resonant cavity, and facilitate microwave sintering.

[0083] Preferably, the thermal insulation material 10 is a porous alumina fiber and / or a polycrystalline mullite fiber material.

[0084] Preferably, the microwave sintering equipment further includes a temperature detection device 20, which is inserted horizontally into the wall of the microwave sintering kiln 1, and one end of the temperature detection device 20 extends into the interior of the microwave sintering kiln 1. The temperature detection device 20 is used to monitor the temperature inside the microwave sintering kiln 1.

[0085] Preferably, the temperature detection device 20 is an infrared radiation thermometer, which is an instrument that uses the infrared radiation of an object to measure temperature. It can complete the temperature measurement in a short time and does not need to be in direct contact with the ceramic roller. It can measure the temperature of the ceramic roller from a certain distance without causing interference or damage to the ceramic roller.

[0086] Preferably, there are three temperature detection devices 20, which are respectively located in the upper, middle and lower parts of the microwave sintering kiln 1, and are used to monitor the temperature of the heating zone, the sintering zone and the cooling zone inside the microwave sintering kiln 1.

[0087] Preferably, the driving device includes a clamping mechanism 5, a rotating mechanism 6, a rotating driving mechanism 7, a feeding mechanism 8, and a feeding driving mechanism 9;

[0088] The feeding drive mechanism 9 and the feeding mechanism 8 are connected by a transmission. The feeding drive mechanism 9 is used to drive the feeding mechanism 8 to reciprocate along the vertical direction of the sintering chamber 101. The feeding mechanism 8 is connected to the rotary drive mechanism 7. The rotary drive mechanism 7 and the rotary mechanism 6 are connected by a transmission. The rotary drive mechanism 7 is used to drive the rotary mechanism 6 to rotate in the horizontal plane. The rotary mechanism 6 and the clamping mechanism 5 are fixedly connected. The clamping mechanism 5 is used to clamp the ceramic roller 80.

[0089] The coupling of the rotary drive mechanism 7 and the feeding drive mechanism 9 in this technology enables the ceramic roller 80 to perform both rotary and linear motion relative to the sintering chamber 101.

[0090] The feeding drive mechanism 9 in this technical solution is a power source that enables the feeding mechanism 8 to reciprocate along the vertical direction of the sintering chamber 101. For example, the feeding drive mechanism 9 can be a drive cylinder, and the extension end of the drive cylinder is connected to the feeding mechanism 8. The drive cylinder enables the feeding mechanism 8 to reciprocate along the vertical direction of the sintering chamber 101.

[0091] The rotary drive mechanism 7 in this technical solution is a power source that enables the rotary mechanism 6 to rotate in a horizontal plane. Preferably, the rotary drive mechanism 7 is a motor, the fixed end of which is fixedly connected to the feeding mechanism 8 via a mounting base, and the rotating end of which is connected to the rotary mechanism 6 via a coupling 81.

[0092] Preferably, the clamping mechanism 5 includes a connecting plate 53, a clamping cylinder 52, and a fastener 51. One side of the connecting plate 53 is fixedly connected to the clamping cylinder 52, and the other side of the connecting plate 53 is connected to the rotating mechanism 6 by bolts. The inner cavity size of the clamping cylinder 52 corresponds to the size of the ceramic roller 80. The clamping cylinder 52 is used to clamp the ceramic roller 80. The fastener 51 is threadedly connected to the clamping cylinder 52 and is used to fix the position of the ceramic roller 80.

[0093] The feeding mechanism 8 includes a feeding push rod 82 and a connecting part 83. One end of the feeding push rod 82 is connected to the telescopic end of the feeding drive mechanism 9, and the other end of the feeding push rod 82 is connected to the connecting part 83. The connecting part 83 is connected to the fixed end of the rotary drive mechanism 7, and the rotating end of the rotary drive mechanism 7 is connected to the rotary mechanism 6.

[0094] Preferably, the microwave sintering equipment further includes a circulator 3, which is installed between the microwave source 2 and the microwave feed port 103. This technical solution provides a circulator 3 between the microwave source 2 and the microwave feed port 103. The circulator 3 can protect the microwave source 2 by ensuring that the reflected power of the system is absorbed by the water load connected to the circulator 3 and does not return to the microwave source 2, thereby protecting the microwave source 2 from damage by high-power reflected waves.

[0095] Preferably, the microwave source 2, the circulator 3, and the microwave feed port 103 are located on the same horizontal line, which can play a better role in protecting the microwave source 2.

[0096] Specifically, the circulator 3 used in this technical solution can be purchased from the market.

[0097] Preferably, the microwave source 2, the temperature detection device 20, the rotary drive mechanism 7, and the feeding drive mechanism 9 are all connected to an external control system. The temperature detection device 20 will feed back the real-time temperature it monitors to the control system, and the control system can fine-tune the operating frequency and power of the microwave source 2.

[0098] The technical solution of the present invention will be further described below through embodiments and comparative examples.

[0099] Example 1

[0100] In this embodiment, the alumina ceramic roller has an outer diameter of 40 mm and a length of 2.5 m. The sintering parameters are as follows: the temperature needs to be uniformly raised from room temperature to sintering temperature of 1400℃ within about 6 minutes (i.e., the heating rate is about 233℃ / min), and then cooled after holding at that temperature for 5 minutes.

[0101] The microwave sintering method for ceramic rollers in this embodiment includes the following steps:

[0102] (1) Microwave sintering was performed using a microwave multimode resonant cavity in a microwave sintering kiln. The microwave multimode resonant cavity consists of a sintering cavity and an outer cavity from the inside out. The outer cavity is equipped with a focusing reflector, which can adjust the electric field strength in the sintering cavity so that the sintering cavity forms a heating zone, a sintering zone, and a cooling zone from top to bottom. The microwave source was turned on, and the operating frequency of the microwave source was adjusted to 2.45 GHz and the power to 1.0 kW, so that the temperature of the sintering zone was 1400℃. According to the sintering parameters of the alumina ceramic roller in this embodiment, the angle of the focusing reflector in the microwave multimode resonant cavity was adjusted so that the heating zone, sintering zone, and cooling zone that meet the sintering parameters of the ceramic roller were formed in the sintering cavity. The electric field distribution in the sintering cavity was measured using the silica gel method. After testing, the length of the sintering zone was about 80 mm, and the lengths of the heating zone and the cooling zone were both about 95 mm.

[0103] (2) Place the silicon carbide auxiliary heating base in the sintering chamber, and adjust the placement device of the silicon carbide auxiliary heating base according to the size of the alumina ceramic roller, so that the distance between the silicon carbide auxiliary heating base and the outer wall of the ceramic roller is 10mm.

[0104] (3) Turn on the electric power source. In order to ensure a 5-minute heat preservation time, the alumina ceramic roller rod enters and passes through the sintering chamber at a speed of 16 mm / min while maintaining a rotation speed of 1 r / min, and then microwave sintering is performed to obtain the microwave sintered ceramic roller rod.

[0105] Example 2

[0106] In this embodiment, the alumina ceramic roller has an outer diameter of 40 mm and a length of 3.0 m. The sintering parameters are as follows: the temperature needs to be uniformly raised from room temperature to sintering temperature of 1400℃ within 7 minutes, held at that temperature for 5 minutes, and then cooled down.

[0107] The microwave sintering method for ceramic rollers in this embodiment includes the following steps:

[0108] (1) Microwave sintering is performed using a microwave multimode resonant cavity in a microwave sintering kiln. The microwave multimode resonant cavity consists of a sintering cavity and an outer cavity from the inside out. The outer cavity is equipped with a focusing reflector, which can adjust the electric field strength in the sintering cavity so that the sintering cavity forms a heating zone, a sintering zone and a cooling zone from top to bottom. The microwave source is turned on and the working frequency of the microwave source is adjusted to 2.85 GHz and the power is 2.0 kW, so that the temperature of the sintering zone is 1400℃. According to the sintering parameters of the alumina ceramic roller in this embodiment, the angle of the focusing reflector is adjusted so that the heating zone, sintering zone and cooling zone that meet the sintering parameters of the ceramic roller are formed in the sintering cavity. The field strength distribution in the sintering cavity is measured by the silica gel method. After testing, the length of the sintering zone is 75 mm, and the lengths of the heating zone and the cooling zone are both 100 mm.

[0109] (2) Place the silicon carbide auxiliary heating base in the sintering chamber, and adjust the placement device of the silicon carbide auxiliary heating base according to the size of the alumina ceramic roller, so that the distance between the silicon carbide auxiliary heating base and the outer surface of the ceramic roller is 20mm.

[0110] (3) Turn on the pneumatic source. In order to ensure a 5-minute heat preservation time, the alumina ceramic roller rod is rotated at a speed of 1.5 r / min and enters and passes through the sintering chamber at a speed of 15 mm / min for microwave sintering, thus obtaining the microwave sintered ceramic roller rod.

[0111] Example 3

[0112] In this embodiment, the alumina ceramic roller has an outer diameter of 45 mm and a length of 3.5 m. The sintering parameters are as follows: the temperature needs to be uniformly raised from room temperature to sintering temperature of 1400℃ within 7 minutes, held at that temperature for 5 minutes, and then cooled down.

[0113] The microwave sintering method for ceramic rollers in this embodiment includes the following steps:

[0114] (1) Microwave sintering was performed using a microwave multimode resonant cavity in a microwave sintering kiln. The microwave multimode resonant cavity consists of a sintering cavity and an outer cavity from the inside out. The outer cavity is equipped with a focusing reflector, which can adjust the electric field strength in the sintering cavity so that the sintering cavity forms a heating zone, a sintering zone, and a cooling zone from top to bottom. The microwave source was turned on, and the operating frequency of the microwave source was adjusted to 3.0 GHz and the power to 4.0 kW, so that the sintering temperature was 1400℃. According to the sintering parameters of the alumina ceramic roller in this embodiment, the orientation angle of the focusing reflector in the microwave multimode resonant cavity was adjusted so that the heating zone, sintering zone, and cooling zone that meet the sintering parameters of the ceramic roller were formed in the sintering cavity. The field strength distribution in the sintering cavity was measured using the silica gel method. After testing, the length of the sintering zone was about 80 mm, and the lengths of the heating zone and the cooling zone were both about 95 mm.

[0115] (2) Place the graphite auxiliary heating base in the sintering cavity, and adjust the placement device of the graphite auxiliary heating base according to the size of the alumina ceramic roller, so that the distance between the graphite auxiliary heating base and the outer wall of the ceramic roller is 15mm. Then place the heat preservation device in the microwave multimode resonant cavity.

[0116] (3) Turn on the pneumatic source. In order to ensure a 5-minute heat preservation time, the alumina ceramic roller rod enters and passes through the sintering chamber at a speed of 15 mm / min while maintaining a rotation speed of 3.0 r / min, so as to obtain the microwave sintered ceramic roller rod.

[0117] Example 4

[0118] In this embodiment, the alumina ceramic roller has an outer diameter of 45 mm and a length of 3.5 m. The sintering parameters are as follows: the temperature needs to be uniformly raised from room temperature to sintering temperature of 1400℃ in about 7 minutes, held at that temperature for 6 minutes, and then cooled.

[0119] The microwave sintering method for ceramic rollers in this embodiment includes the following steps:

[0120] (1) Microwave sintering was performed using a microwave multimode resonant cavity in a microwave sintering kiln. The microwave multimode resonant cavity consists of a sintering cavity and an outer cavity from the inside out. The outer cavity is equipped with a focusing reflector, which can adjust the electric field strength within the sintering cavity, so that the sintering cavity forms a heating zone, a sintering zone, and a cooling zone from top to bottom. The microwave source was turned on, and the operating frequency of the microwave source was adjusted to 3.0 GHz and the power to 4.0 kW, so that the temperature of the sintering zone was 1400℃. According to the sintering parameters of the alumina ceramic roller in this embodiment, the azimuth angle of the focusing reflector in the microwave multimode resonant cavity was adjusted, and the field strength distribution width in the sintering cavity was measured using the silica gel method. After testing, the width of the sintering zone was approximately 80 mm, and the widths of the heating zone and the cooling zone were both approximately 95 mm.

[0121] (2) Place the silicon carbide auxiliary heating base in the sintering chamber, and adjust the placement device of the silicon carbide auxiliary heating base according to the size of the alumina ceramic roller, so that the distance between the silicon carbide auxiliary heating base and the outer wall of the ceramic roller is 20mm.

[0122] (3) Turn on the pneumatic source. In order to ensure a 6-minute heat preservation time, the alumina ceramic roller is rotated at a speed of 2.5 r / min and enters and passes through the sintering chamber at a speed of 13.3 mm / min for microwave sintering, thus obtaining the microwave sintered ceramic roller.

[0123] Example 5

[0124] In this embodiment, the alumina ceramic roller has an outer diameter of 50 mm and a length of 2.5 m. The sintering parameters are as follows: the temperature needs to be uniformly raised from room temperature to sintering temperature of 1400℃ in about 7 minutes, held at that temperature for 6 minutes, and then cooled down.

[0125] The microwave sintering method for ceramic rollers in this embodiment includes the following steps:

[0126] (1) Microwave sintering was performed using a microwave multimode resonant cavity. The microwave multimode resonant cavity consists of a sintering cavity and an outer cavity from the inside out. The outer cavity is equipped with a focusing reflector, which can adjust the electric field strength in the sintering cavity so that the sintering cavity forms a heating zone, a sintering zone, and a cooling zone from top to bottom. The microwave source was turned on, and the operating frequency of the microwave source was adjusted to 2.7 GHz and the power to 3.0 kW. According to the sintering parameters of the alumina ceramic roller in this embodiment, the orientation angle of the focusing reflector in the microwave multimode resonant cavity was adjusted so that the heating zone, sintering zone, and cooling zone that meet the sintering parameters of the ceramic roller are formed in the sintering cavity. The temperature of the sintering zone was set to 1400℃. The field strength distribution in the sintering cavity was measured using the silica gel method. After testing, the length of the sintering zone was about 80 mm, and the lengths of the heating zone and the cooling zone were both about 95 mm.

[0127] (2) Place the silicon carbide auxiliary heating base in the sintering chamber, and adjust the placement device of the silicon carbide auxiliary heating base according to the size of the alumina ceramic roller, so that the distance between the silicon carbide auxiliary heating base and the outer wall of the ceramic roller is 10mm.

[0128] (3) Turn on the pneumatic source. In order to ensure a 6-minute heat preservation time, the alumina ceramic roller rod is rotated at a speed of 1.5 r / min and enters and passes through the sintering chamber at a speed of 13.3 mm / min for microwave sintering, thus obtaining the microwave sintered ceramic roller rod.

[0129] Comparative Example 1

[0130] An alumina ceramic roller with an outer diameter of 40 mm and a length of 2.5 m is placed in the sintering chamber. A microwave source is turned on, with a working frequency of 2.45 GHz and a power of 1.0 kW. The temperature is increased from room temperature to sintering temperature of 1200 °C at a heating rate of 200 °C per minute. After holding at this temperature for 6 minutes, the temperature is lowered and cooled to obtain the microwave-sintered ceramic roller.

[0131] Specifically, the microwave sintered ceramic rollers prepared in Examples 1 to 5 and Comparative Example 1 were tested for their resistance to rapid cooling and heating, room temperature bending strength (MPa), high temperature bending strength (MPa), roundness deviation (%), and straightness deviation (%). The test results are shown in Table 1.

[0132] Resistance to rapid heating and cooling, flexural strength at room temperature (25℃) (MPa), flexural strength at high temperature (1300℃) (MPa), roundness deviation (%), and straightness deviation (%) were all tested according to the People's Republic of China Building Materials Industry Standard JC / T413-2005.

[0133] Table 1 Performance Test Results

[0134] The experimental data above show that the microwave-sintered ceramic rollers prepared by the microwave sintering methods of Examples 1 to 5 have better performance than ceramic rollers prepared by conventional microwave sintering. Specifically, the roundness deviation of the microwave-sintered ceramic rollers prepared in Examples 1 to 5 is 0.08%–0.15%, all less than 0.20%; the straightness deviation is 0.08%–0.12%, all less than 0.15%; the room temperature bending strength is 61 MPa–67 MPa, all greater than 60 MPa; the high temperature bending strength is 48 MPa–55 MPa, all greater than 45 MPa; and the thermal shock resistance test of the microwave-sintered ceramic rollers prepared in Examples 1 to 5 can be repeated three times.

[0135] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method of microwave sintering of a ceramic roller bar, characterized in that, Includes the following steps: (1) Microwave sintering is carried out in a microwave sintering kiln. The microwave sintering kiln includes a sintering cavity and an outer cavity surrounding the sintering cavity. The outer cavity is equipped with a focusing reflector. The focusing reflector can adjust the electric field intensity in the sintering cavity so that a heating zone, a sintering zone and a cooling zone are formed in sequence in the sintering cavity. The microwave source is turned on and the working frequency and power of the microwave source are adjusted so that the temperature of the sintering zone is 1200-1600℃. (2) The auxiliary heating base is placed in the sintering cavity, and the auxiliary heating base can absorb microwaves at room temperature; (3) While keeping the ceramic roller in rotation, it enters and passes through the sintering cavity at a speed of V1 to perform microwave sintering, thereby obtaining a microwave sintered ceramic roller.

2. The microwave sintering method of a ceramic roller bar according to claim 1, characterized by, The focusing reflector is located in the middle of the outer cavity in the vertical direction, so that the electric field strength in the middle of the sintering cavity is greater than the electric field strength in the upper and lower parts of the sintering cavity, so that the middle of the sintering cavity forms a sintering zone, the upper part of the sintering cavity forms a heating zone, and the lower part of the sintering cavity forms a cooling zone.

3. The microwave sintering method of a ceramic roller bar according to claim 2, characterized by, The angle of the focusing reflector can be adjusted from 0 to 90 degrees. In step (1), the angle of the focusing reflector is adjusted according to the sintering parameters of the ceramic roller so that the length of the heating zone is 80-120mm, the length of the sintering zone is 70-90mm, and the length of the cooling zone is 80-120mm; the lengths of the heating zone, sintering zone, and cooling zone in the sintering cavity are measured using the silica gel method.

4. The microwave sintering method for ceramic rollers according to claim 3, characterized in that, In step (3), the speed V1 satisfies the following equation: The heat preservation time of the ceramic roller is 2 to 10 minutes.

5. The microwave sintering method of a ceramic roller bar according to claim 4, characterized by, In step (3), the rotational speed V2 of the ceramic roller is 1 to 3 r / min, and the speed V1 entering and passing through the sintering chamber is 13 to 16 mm / min.

6. The microwave sintering method of a ceramic roller bar according to claim 1, wherein In step (2), it is also necessary to adjust the placement device of the auxiliary heating base so that the distance between the auxiliary heating base and the outer surface of the ceramic roller is 10-20mm.

7. The microwave sintering method of a ceramic roller bar according to claim 1, wherein In step (2), the auxiliary heating base is made of silicon carbide and / or graphite.

8. The method of microwave sintering of a ceramic roller according to claim 1, characterized in that, In step (1), the microwave source operates at a frequency of 2.45 to 3.0 GHz and has a power of 0.5 to 5 kW.

9. The method of microwave sintering of a ceramic roller according to claim 1, characterized in that, The ceramic roller is an alumina ceramic roller. The alumina ceramic roller comprises 65-85% alumina by weight percentage.

10. A microwave sintering apparatus, characterized by, The microwave sintering method applied to the ceramic rollers according to any one of claims 1-9 includes a microwave sintering kiln, a microwave source, a focusing regulator, a driving device, and an auxiliary heating base; The microwave sintering furnace includes a sintering cavity and an outer cavity surrounding the sintering cavity. The sintering cavity is used to sinter ceramic rollers. The auxiliary heating base is installed inside the sintering cavity. After absorbing microwaves, the auxiliary heating base is used to heat the ceramic rollers so that the temperature of the ceramic rollers reaches the critical temperature of microwave sintering. One side of the microwave sintering furnace is provided with a microwave feeding port, the microwave source is located outside the microwave sintering furnace, and the microwave source is arranged on the side where the microwave feeding port is located; the focusing regulator is installed in the outer cavity and away from the microwave feeding port, and the installation positions of the microwave source, the microwave feeding port and the focusing regulator correspond to each other; The driving device is used for driving the ceramic roller to enter and pass through the sintering cavity while keeping rotating motion.

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