High refractoriness low expansion silicon carbide roller and its preparation method

Abstract

The application provides a high-fire-resistance low-expansion silicon carbide roller and a preparation method thereof. The preparation method comprises the following steps: grading first-particle-size silicon carbide powder, second-particle-size silicon carbide powder and third-particle-size silicon carbide powder, and mixing the graded silicon carbide powder with solid additives and liquid additives to obtain sintering material; mixing the sintering material with liquid additives to obtain plasticized molding material; and sequentially performing extrusion, drying and sintering on the plasticized molding material to obtain the high-fire-resistance low-expansion silicon carbide roller; and the sintering is an integrated sintering process of first degassing and then sintering. The silicon carbide roller prepared by the preparation method has a use temperature of greater than or equal to 1500 DEG C and a load softening temperature of greater than or equal to 1700 DEG C, meets the demand of the industrial field for high-temperature materials, and simultaneously has a low expansion coefficient, excellent thermal shock resistance and a long service life.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of silicon carbide roller preparation, and relates to a high-refractory low-expansion silicon carbide roller and a preparation method thereof. BACKGROUND

[0002] As a kind of high-temperature resistant material widely used in high-temperature process fields such as ceramics and glass, silicon carbide roller has the advantages of good wear resistance, corrosion resistance, high thermal conductivity and low thermal expansion coefficient. However, the silicon carbide rollers currently used on the market are mainly of reaction sintered silicon carbide material, which has some problems and deficiencies.

[0003] Firstly, the content of metallic silicon in the reaction sintered silicon carbide roller is relatively high, generally more than 10%. Since the melting point of metallic silicon is lower than that of silicon carbide, the service temperature of the roller is relatively low, generally not more than 1350℃. In the high-temperature process, the roller may fail due to excessive temperature, thereby affecting the normal production.

[0004] Secondly, the thermal expansion coefficient of reaction sintered silicon carbide is relatively high, generally more than 4×10 -6 / ℃. This means that during the high-temperature process, the roller may expand greatly, thereby affecting the normal operation of the equipment and the quality of the product. At the same time, the high thermal expansion coefficient makes the roller have poor thermal shock resistance, and it is easy to produce thermal stress due to temperature fluctuations, resulting in the breakage of the roller.

[0005] In view of these problems in the prior art, it is urgent to develop a preparation method of high-refractory low-expansion silicon carbide roller to meet the demand for high-temperature resistance and thermal shock resistance in the industrial field. SUMMARY

[0006] To solve the above technical problems, the present application provides a high-refractory low-expansion silicon carbide roller and a preparation method thereof. The silicon carbide roller prepared by the preparation method has a service temperature of ≥1500℃ and a load softening temperature of ≥1700℃, which meets the demand for high-temperature materials in the industrial field, and at the same time has a low expansion coefficient, excellent thermal shock resistance and a long service life.

[0007] To achieve the above technical effects, the present application adopts the following technical solutions:

[0008] One of the objects of the present application is to provide a preparation method of high-refractory low-expansion silicon carbide roller, which comprises:

[0009] grading the first particle size of silicon carbide powder, the second particle size of silicon carbide powder and the third particle size of silicon carbide powder, and mixing them with solid additives and liquid additives to obtain sintering material;

[0010] Mix the sintering material with a liquid additive to obtain a plasticized clay;

[0011] The plasticized clay is sequentially subjected to extrusion, drying and sintering to obtain the high-refractory low-expansion silicon carbide roller.

[0012] The sintering is an integrated sintering process of first degassing and then sintering.

[0013] As a preferred technical solution of the present application, the first particle size is greater than the second particle size, which is greater than the third particle size.

[0014] Preferably, the first particle size is 5 μm, the second particle size is 2 μm, and the third particle size is 0.5 μm.

[0015] Preferably, the mass fraction of the silicon carbide micro-powder of the first particle size in the grading is 5-25%, the mass fraction of the silicon carbide micro-powder of the second particle size is 25-65%, and the mass fraction of the silicon carbide micro-powder of the third particle size is 15-45%. The mass fraction of the silicon carbide micro-powder of the first particle size can be 5%, 10%, 15%, 20% or 25%, the mass fraction of the silicon carbide micro-powder of the second particle size can be 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or 65%, and the mass fraction of the silicon carbide micro-powder of the third particle size can be 15%, 20%, 25%, 30%, 35% or 40%, but is not limited to the listed values, and other values not listed in the above ranges are also applicable.

[0016] As a preferred technical solution of the present application, in the integrated sintering process of first degassing and then sintering, the process parameters for degassing are to raise the temperature from room temperature to 400-500°C at a rate of 0.5-2°C / min, while inert gas is introduced. The final temperature for degassing can be 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C or 500°C, and the rate of temperature rise can be 0.5°C / min, 0.6°C / min, 0.8°C / min, 1°C / min, 1.2°C / min, 1.5°C / min, 1.8°C / min, 2°C / min or the like, but is not limited to the listed values, and other values not listed in the above ranges are also applicable.

[0017] / min or 2°C / min, but is not limited to the listed values, and other values not listed in the above ranges are also applicable.

[0018] As a preferred technical scheme of the present application, in the integral sintering process of the first degumming and then sintering, the sintering process parameters are as follows: after the degumming is finished, the temperature is raised to 1400-1500℃ at a heating rate of 5-10℃ / min; then raised to 1800-2200℃ at a heating rate of 1-3℃ / min, and kept for 1-4h. Among them, the terminal temperature of the first time raising after the degumming is finished can be 1400℃, 1410℃, 1420℃, 1430℃, 1440℃, 1450℃, 1460℃, 1470℃, 1480℃, 1490℃ or 1500℃, etc., the heating rate can be 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min, etc., the terminal temperature of the second time raising can be 1800℃, 1850℃, ≥1700℃℃, 1950℃, 2000℃, 2050℃, 2100℃, 2150℃ or 2200℃, etc., the heating rate can be 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min or 3℃ / min, etc., and the holding time can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h, etc., but not limited to the listed values, and other values not listed in the above ranges are also applicable.

[0019] As a preferred technical scheme of the present application, after sintering, cooling is performed, and the cooling rate is 3-5℃ / min, and the terminal temperature is room temperature. Among them, the cooling rate can be 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min or 5℃ / min, etc., but not limited to the listed values, and other values not listed in the range are also applicable.

[0020] As a preferred technical scheme of the present application, the solid additive includes a sintering aid, silicon powder and carbon powder, boride and a binder.

[0021] Preferably, the mass fraction of the sintering aid in the sintering material is ≤8%, the mass fraction of the silicon powder and carbon powder is 2-6%, the mass fraction of the boride is 0.5-3%, and the mass fraction of the binder is ≤5%. Among them, the mass fraction of the sintering aid can be 1%, 2%, 3%, 4%, 5%, 6%, 7% or 8%, etc., the mass fraction of the silicon powder and carbon powder can be 2%, 3%, 4%, 5% or 6%, etc., the mass fraction of the boride can be 0.5%, 1%, 1.5%, 2%, 2.5% or 3%, etc., and the mass fraction of the binder can be 1%, 2%, 3%, 4% or 5%, etc., but not limited to the listed values, and other values not listed in the above ranges are also applicable.

[0022] As a preferred technical scheme of the present application, the liquid additive does not contain water.

[0023] Preferably, the liquid additive is a non-ionic surfactant.

[0024] Preferably, the mass fraction of the liquid additive in the sintering material is 5-8%, such as 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or 8%, etc., but not only limited to the listed values, other values not listed in the range are also applicable.

[0025] Preferably, the amount of liquid additive added in the plastic clay is 2-5% of the total amount of powder, such as 2%, 2.5%, 3%, 3.5%, 4%, or 4.5%, etc., but not only limited to the listed values, other values not listed in the range are also applicable.

[0026] As a preferred technical solution of the present application, the extrusion parameters are an extrusion pressure of 8-12 MPa, a vacuum degree of <-0.095 MPa, and an extrusion speed of 3-5 m / min. Among them, the extrusion pressure can be 8 MPa, 8.5 MPa, 9 MPa, 9.5 MPa, 10 MPa, 10.5 MPa, 11 MPa, 11.5 MPa, or 12 MPa, etc., and the extrusion speed can be 3 m / min, 3.5 m / min, 4 m / min, 4.5 m / min, or 5 m / min, etc., but not only limited to the listed values, other values not listed in the range of the above values are also applicable.

[0027] Preferably, after extrusion, the non-determined plastic roller bar wet blank is received by a gas suspension V-shaped track type tray.

[0028] As a preferred technical solution of the present application, the drying includes first drying, second drying, and third drying performed in sequence.

[0029] Preferably, the first drying is to raise the drying temperature from room temperature to 80-100℃, and the temperature rising rate is 10-20℃ / h. Among them, the final temperature of the temperature rising can be 80℃, 85℃, 90℃, 95℃, or 100℃, etc., and the temperature rising rate can be 10℃ / h, 11℃ / h, 12℃ / h, 13℃ / h, 14℃ / h, 15℃ / h, 16℃ / h, 17℃ / h, 18℃ / h, 19℃ / h, or 20℃ / h, etc., but not only limited to the listed values, other values not listed in the range of the above values are also applicable.

[0030] Preferably, the second drying is to raise the drying temperature to 120-150℃, and the temperature rising rate is 5-10℃ / h. In this case, the temperature rising end point temperature can be 120℃, 125℃, 130℃, 135℃, 140℃, 145℃ or 150℃, etc., and the temperature rising rate can be 5℃ / h, 6℃ / h, 7℃ / h, 8℃ / h, 9℃ / h or 10℃ / h, etc., but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0031] Preferably, the third drying is to keep the temperature at the second drying temperature rising end point temperature for 4-8h, such as 4h, 4.5h, 5.5h, 6h, 6.5h, 7h, 7.5h or 8h, etc., but is not limited to the listed values, and other values not listed in the range are also applicable.

[0032] Preferably, the drying is carried out under an inert gas atmosphere.

[0033] The second object of the present application is to provide a high fire resistance low expansion silicon carbide roller prepared by the preparation method of the high fire resistance low expansion silicon carbide roller provided in the first object.

[0034] Compared with the prior art, the present application has at least the following beneficial effects:

[0035] (1) The present application provides a preparation method of a high fire resistance low expansion silicon carbide roller, and the silicon carbide roller prepared by the preparation method has a use temperature of ≥1500℃ and a load softening temperature of ≥1700℃, which meets the demand of the industrial field for high temperature materials.

[0036] (2) The present application provides a preparation method of a high fire resistance low expansion silicon carbide roller, and the silicon carbide roller prepared by the preparation method has a thermal expansion coefficient of ≥4.0*10 -6 / ℃, which is higher than that of reaction sintered silicon carbide, and the silicon carbide roller produced by the present application has smaller expansion during high temperature process, thereby improving the stability of the equipment and the product quality.

[0037] (3) The present application provides a preparation method of a high fire resistance low expansion silicon carbide roller, and the silicon carbide roller prepared by the preparation method has a cold bending strength of ≥450MPa and a high temperature bending strength of ≥350MPa at 1500℃; the lower thermal expansion coefficient makes the silicon carbide roller of the present application have better thermal shock resistance, which can effectively resist the thermal stress generated by temperature fluctuation and reduce the risk of roller rupture at high temperature; therefore, the service life of the roller can be prolonged and the maintenance cost can be reduced.

[0038]

[0039] ​(4) The application provides a preparation method of high-fire-resistance low-expansion silicon carbide roller, which effectively prevents deformation of the wet blank after roller extrusion molding under the support of a gas suspension V-shaped track type tray; a stepwise drying process also contributes to uniform drying of the inside and outside of the wet blank, avoiding cracking and deformation problems in the drying process.

[0040] (5) The application provides a preparation method of high-fire-resistance low-expansion silicon carbide roller, wherein the liquid additive used in the preparation method does not contain mixed water, which helps to reduce wastewater discharge in the production process and meets environmental protection requirements. DETAILED DESCRIPTION

[0041] The technical solutions of the application are further described below through specific embodiments.

[0042] The application provides a preparation method of high-fire-resistance low-expansion silicon carbide roller, which comprises the following steps:

[0043] The first particle size silicon carbide powder, the second particle size silicon carbide powder and the third particle size silicon carbide powder are graded and mixed with solid additives and liquid additives to obtain sintering material;

[0044] The sintering material is mixed with liquid additives to obtain plasticized clay;

[0045] The plasticized clay is sequentially subjected to extrusion, drying and sintering to obtain the high-fire-resistance low-expansion silicon carbide roller;

[0046] The sintering is an integrated sintering process of glue removal first and then sintering.

[0047] In the application, by selecting silicon carbide powders with different particle sizes and reasonable proportions and precisely controlling the sintering process, the silicon carbide roller prepared by the application has higher fire resistance. Compared with the conventional reaction sintered silicon carbide roller, the use temperature of which is generally lower than 1350℃, the silicon carbide roller of the application can be used at a higher temperature. Through detection, the roller use temperature is ≥1500℃, the load softening temperature is ≥1700℃, which meets the demand of the industrial field for high-temperature materials.

[0048] In one specific embodiment of the application, the first particle size silicon carbide powder is β-silicon carbide or β-silicon carbide powder with a content of >50%.

[0049] In one specific embodiment of the application, the first particle size silicon carbide powder has a D90-D10 of <3 μm; the second particle size silicon carbide powder has a D90-D10 of <1.5 μm; and the third particle size silicon carbide powder has a D90-D10 of <0.5 μm.

[0050] In one specific embodiment of the present application, the silicon powder and the carbon powder are high-purity silicon powder and carbon powder, and the high purity specifically refers to a purity of ≥ 99.5%. The mass ratio of the silicon powder and the carbon powder can be 7: (3-5), such as 7:3, 7:3.5, 7:4, 7:4.5 or 7:5, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0051] In one specific embodiment of the present application, the sintering aid can be any one or a combination of at least two of aluminum nitride, silicon nitride or aluminum oxide; the boride can be boric acid; and the binder can be any one or a combination of at least two of PVA, CMC, HPMC or HEC.

[0052] In the present application, by precisely regulating the raw material composition and the preparation method, a silicon carbide roller with a relatively low coefficient of thermal expansion is prepared. Compared with the coefficient of thermal expansion of reaction sintered silicon carbide, which is above 4.0*10 -6 / ℃, the silicon carbide roller has a smaller expansion during high-temperature process, thereby improving the stability of the equipment and the product quality.

[0053] In one specific embodiment of the present application, the liquid additive can be any one or a combination of at least two of a soap nonionic surfactant, a stearic acid nonionic surfactant or a polyether polyol nonionic surfactant.

[0054] In the present application, the liquid additive does not contain blending water, which helps to reduce the wastewater discharge in the production process and meets the environmental protection requirements.

[0055] In one specific embodiment of the present application, the extrusion can be performed by using a high-pressure vacuum horizontal continuous extruder to perform mold extrusion molding on the roller.

[0056] In one specific embodiment of the present application, the drying can be performed in an electric heating oven according to a stepwise drying curve.

[0057] In the present application, inert gas is introduced in the first drying stage to enable the surface moisture in the roller to be fully evaporated, and the oxygen concentration in the atmosphere is maintained low; in the second drying stage, in addition to removing moisture, volatile substances such as part of the sintering aid in the roller can also be volatilized; and in the third drying stage, the forming density of the roller is improved, and at the same time, the roller is prevented from being oxidized or damaged in the case of maintaining an inert atmosphere.

[0058] In the present application, the use of high-pressure vacuum extrusion molding and stepwise drying process helps to improve the dimensional stability and surface quality of the silicon carbide roller. After the roller is formed, the wet blank is effectively prevented from deforming under the support of the gas-suspended V-shaped track type tray. The stepwise drying process also helps to uniformly dry the inside and outside of the wet blank, and avoids cracking and deformation problems in the drying process.

[0059] The embodiment of the present application provides a high-fire-resistance low-expansion silicon carbide roller, the high-fire-resistance low-expansion silicon carbide roller has a thermal expansion coefficient of less than or equal to 4*10 -6 / ℃, a use temperature of greater than or equal to 1500℃, a load softening temperature of greater than or equal to 1700℃, a porosity of less than 1%, a bending strength at room temperature of greater than or equal to 450MPa, and a high-temperature bending strength at 1500℃ of greater than or equal to 350MPa.

[0060] In one embodiment of the present application, room temperature is defined in the art, which can be 0-35℃, such as 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃ or 35℃, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0061] In one embodiment of the present application, the inert gas atmosphere can be any one of nitrogen, helium or argon.

[0062] In order to facilitate the understanding of the present application, the present application lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present application, and should not be regarded as a specific limitation on the present application.

[0063] Example 1:

[0064] The embodiment provides a preparation method of a high-fire-resistance low-expansion silicon carbide roller, and the preparation method comprises the following steps:

[0065] Step S1: 5μm, 2μm and 0.5μm silicon carbide micropowder is used for batching, and the ratio is as follows: the weight ratio of 5μm silicon carbide micropowder is 10%, the weight ratio of 2μm silicon carbide micropowder is 50%, and the weight ratio of 0.5μm silicon carbide micropowder is 40%;

[0066] Step S2: the following ingredients are added to the prepared silicon carbide micropowder: the total content of aluminum nitride is 5%, the ratio of high-purity silicon micropowder and carbon powder is 7:4, the content is 5%, the content of boric acid is 1%, the total content of PVA is 3%, and the total content of polyether polyol is 5%;

[0067] Step S3: the mixed powder raw material in step S2 is added with 5% of the total powder mass of liquid additives (without mixing water) to uniformly mix and mold by a high-pressure vacuum horizontal continuous extruder (extrusion pressure is 10Mpa, vacuum degree is-0.095MPa, and extrusion speed is 4m / min).

[0068] Step S4: The unshaped plastic roller wet blank is received by the air suspension V-shaped track tray, and drying and shaping are performed according to a stepwise drying curve: the ambient temperature is gradually increased from room temperature to 80 DEG C at a rate of 15 DEG C / h, and nitrogen is introduced; then the ambient temperature is increased to 120 DEG C at a rate of 7 DEG C / h, and high-temperature drying is performed at 120 DEG C for 4 hours;

[0069] Step S5: The roller after drying treatment is placed into a high-temperature pressureless sintering furnace, and a glue removal and sintering integrated firing process is performed; during the firing process, the temperature is increased from room temperature to 500 DEG C at a rate of 1 DEG C / min by vacuumizing and heating, and argon is introduced; after glue removal, the temperature is increased from 500 DEG C to 1500 DEG C at a rate of 7 DEG C / min; then the temperature is increased from 1500 DEG C to 2000 DEG C at a rate of 2 DEG C / min, and the temperature is maintained for 2 hours after reaching the target temperature; after constant temperature, the temperature is gradually decreased to room temperature at a slow cooling rate of 4 DEG C / min, and the high-refractory low-expansion silicon carbide roller is obtained.

[0070] Example 2:

[0071] The embodiment provides a preparation method of a high-refractory low-expansion silicon carbide roller, and the preparation method comprises the following steps:

[0072] Step S1: Three kinds of silicon carbide micropowder with particle sizes of 5 μm, 2 μm and 0.5 μm are used for batching, and the ratio is as follows: the weight ratio of 5 μm silicon carbide micropowder is 20%, the weight ratio of 2 μm silicon carbide micropowder is 60%, and the weight ratio of 0.5 μm silicon carbide micropowder is 20%;

[0073] Step S2: The following ingredients are added to the prepared silicon carbide micropowder: the total content of aluminum nitride is 5%, the ratio of high-purity silicon micropowder and carbon powder is 7:4, the content is 6%, the content of boric acid is 1%, the total content of PVA is 3%, and the total content of polyether polyol is 5%;

[0074] Step S3: The mixed powder raw material in step S2 is added with 5% of the total powder mass of liquid additives (without mixing water) for uniform mixing, and is subjected to mold extrusion forming by a high-pressure vacuum horizontal continuous extruder (extrusion pressure is 10 MPa, vacuum degree is-0.095 MPa, and extrusion speed is 4 m / min);

[0075] Step S4: The unshaped plastic roller wet blank is received by the air suspension V-shaped track tray, and drying and shaping are performed according to a stepwise drying curve: the ambient temperature is gradually increased from room temperature to 80 DEG C at a rate of 15 DEG C / h, and nitrogen is introduced; then the ambient temperature is increased to 120 DEG C at a rate of 7 DEG C / h, and high-temperature drying is performed at 120 DEG C for 4 hours;

[0076] Step S5: After the drying treatment, the roller bar is placed in a high-temperature pressureless sintering furnace, and a glue removal and sintering integrated sintering process is adopted. During the sintering process, the temperature is first raised from room temperature to 500°C at a rate of 1°C / min while vacuumizing and argon is introduced; after glue removal is completed, the temperature is raised from 500°C to 1500°C at a rate of 7°C / min; then the temperature is raised from 1500°C to 2000°C at a rate of 2°C / min, and the target temperature is maintained for 2 hours; after constant temperature, the temperature is gradually lowered to room temperature at a rate of 4°C / min by slow cooling, and the high-fire resistance and low-expansion silicon carbide roller bar is obtained.

[0077] Example 3:

[0078] The embodiment provides a preparation method of a high-fire resistance and low-expansion silicon carbide roller bar, and the preparation method comprises the following steps:

[0079] Step S1: Three kinds of silicon carbide micropowder with particle sizes of 5 μm, 2 μm and 0.5 μm are used for batching, and the ratio is as follows: the weight ratio of 5 μm silicon carbide micropowder is 10%, the weight ratio of 2 μm silicon carbide micropowder is 50%, and the weight ratio of β-silicon carbide powder is 40%;

[0080] Step S2: The following ingredients are added to the prepared silicon carbide micropowder: the total content of aluminum nitride is 5%, the ratio of high-purity silicon micropowder and carbon powder is 7:4, the content is 7%, the content of boric acid is 1%, the total content of PVA is 3%, and the total content of liquid additive (polyether polyol) is 5%;

[0081] Step S3: The mixed powder raw material in step S2 is added with 5% of the total powder mass of liquid additive (without mixing water) for uniform mixing, and is subjected to mold extrusion forming by a high-pressure vacuum horizontal continuous extruder (extrusion pressure is 10 MPa, vacuum degree is -0.095 MPa, and extrusion speed is 4 m / min);

[0082] Step S4: The plastic roller bar wet blank is received by a gas suspension V-shaped track type tray, and is dried and shaped according to a stepwise drying curve: the ambient temperature is gradually raised from room temperature to 80°C at a rate of 15°C / h and nitrogen is introduced; then the ambient temperature is raised to 120°C at a rate of 7°C / h, and high-temperature drying is maintained at 120°C for 4 hours;

[0083] Step S5: After the drying treatment, the roller is placed in a high-temperature pressureless sintering furnace, and a glue-removing and sintering integrated sintering process is adopted; during the sintering process, the temperature is first raised from room temperature to 500°C at a rate of 1°C / min while vacuumizing and argon is introduced; after glue removal is completed, the temperature is raised from 500°C to 1500°C at a rate of 7°C / min; then the temperature is raised from 1500°C to 2000°C at a rate of 2°C / min, and the target temperature is maintained for 2 hours; after the constant temperature ends, the temperature is gradually reduced to room temperature at a slow cooling rate of 4°C / min, and the high-fire-resistance low-expansion silicon carbide roller is obtained.

[0084] Example 4:

[0085] The embodiment provides a preparation method of a high-fire-resistance low-expansion silicon carbide roller, and the preparation method comprises the following steps:

[0086] Step S1: Three kinds of silicon carbide micropowder with particle sizes of 5 μm, 2 μm and 0.5 μm are used for batching, and the ratio is as follows: the weight ratio of 5 μm silicon carbide micropowder is 10%, the weight ratio of 2 μm silicon carbide micropowder is 50%, and the weight ratio of 0.5 μm silicon carbide micropowder is 40%; the particle size distribution range of 5 μm silicon carbide micropowder is D90-D10<2 μm; the particle size distribution range of 2 μm silicon carbide micropowder is D90-D10<1 μm; and the particle size distribution range of 0.5 μm silicon carbide micropowder is D90-D10<0.3 μm;

[0087] Step S2: The following ingredients are added to the prepared silicon carbide micropowder: the total content of aluminum nitride is 5%, the ratio of high-purity silicon micropowder and carbon powder is 7:4, the content is 8%, the content of boric acid is 1%, the total content of adhesive (PVA) is 3%, and the total content of polyether polyol is 5%;

[0088] Step S3: The mixed powder raw material in step S2 is added with 5% of the total powder mass of liquid additives (without mixing water) for uniform mixing, and is subjected to mold extrusion forming by a high-pressure vacuum horizontal continuous extruder (extrusion pressure is 10 MPa, vacuum degree is-0.095 MPa, and extrusion speed is 4 m / min).

[0089] Step S4: The plastic roller wet blank is received by a gas suspension V-shaped track type tray, and drying is performed according to a stepwise drying curve: the ambient temperature is gradually raised from room temperature to 80°C at a rate of 15°C / h while nitrogen is introduced; then the ambient temperature is raised to 120°C at a rate of 7°C / h, and high-temperature drying is maintained at 120°C for 4 hours;

[0090] Step S5: After the drying treatment, the roller is placed in a high-temperature pressureless sintering furnace, and a glue-removing and sintering integrated sintering process is adopted; during the sintering process, the temperature is first raised from room temperature to 500°C at a rate of 1°C / min while vacuumizing and argon is introduced; after glue removal is completed, the temperature is raised from 500°C to 1500°C at a rate of 7°C / min; then the temperature is raised from 1500°C to 2000°C at a rate of 2°C / min, and the target temperature is maintained for 2 hours; after the constant temperature ends, the temperature is gradually lowered to room temperature at a slow cooling rate of 4°C / min, and the high-fire resistance and low-expansion silicon carbide roller is obtained.

[0091] Example 5:

[0092] The embodiment provides a preparation method of a high-fire resistance and low-expansion silicon carbide roller, and the preparation method comprises the following steps:

[0093] Step S1: Three kinds of silicon carbide micropowder with particle sizes of 5 μm, 2 μm and 0.5 μm are used for batching, and the proportions are as follows: the weight ratio of 5 μm silicon carbide micropowder is 10%, the weight ratio of 2 μm silicon carbide micropowder is 50%, and the weight ratio of 0.5 μm silicon carbide micropowder is 40%.

[0094] Step S2: The following ingredients are added to the prepared silicon carbide micropowder: the total content of the sintering aid (a mixture of aluminum nitride and aluminum oxide) is 8%, the ratio of high-purity silicon micropowder and carbon powder is 7:4, the content is 8%, the content of boric acid is 1%, the total content of PVA is 3%, and the total content of polyether polyol is 5%.

[0095] Step S3: The mixed powder raw material in step S2 is added with 5% of the total powder mass of liquid additives (without mixing water) for uniform mixing, and is subjected to mold extrusion forming by a high-pressure vacuum horizontal continuous extruder (extrusion pressure is 10 MPa, vacuum degree is -0.095 MPa, and extrusion speed is 4 m / min).

[0096] Step S4: The plastic roller wet blank is received by a gas suspension V-shaped track type tray, and is dried and shaped according to a stepwise drying curve: the ambient temperature is gradually raised from room temperature to 80°C at a rate of 15°C / h while nitrogen is introduced; then the ambient temperature is raised to 120°C at a rate of 7°C / h, and high-temperature drying is maintained at 120°C for 4 hours.

[0097] Step S5: After the drying treatment, the roller bar is placed in a high-temperature pressureless sintering furnace, and a glue removal and sintering integrated sintering process is adopted; during the sintering process, the temperature is first raised from room temperature to 500°C at a rate of 1°C / min while vacuumizing and argon is introduced; after glue removal is completed, the temperature is raised from 500°C to 1500°C at a rate of 7°C / min; then the temperature is raised from 1500°C to 2000°C at a rate of 2°C / min, and the target temperature is maintained for 2 hours; after the constant temperature ends, the temperature is gradually lowered to room temperature at a slow cooling rate of 4°C / min, and the high-fire resistance and low-expansion silicon carbide roller bar is obtained.

[0098] Example 6

[0099] The embodiment provides a preparation method of a high-fire resistance and low-expansion silicon carbide roller bar, and the preparation method comprises the following steps:

[0100] Step S1: Three kinds of silicon carbide micropowder with particle sizes of 5 μm, 2 μm and 0.5 μm are used for batching, and the proportions are as follows: the weight ratio of 5 μm silicon carbide micropowder is 5%, the weight ratio of 2 μm silicon carbide micropowder is 65%, and the weight ratio of 0.5 μm silicon carbide micropowder is 30%.

[0101] Step S2: The following ingredients are added to the prepared silicon carbide micropowder: the total content of the sintering aid (a mixture of aluminum nitride and aluminum oxide) is 5%, the ratio of high-purity silicon micropowder and carbon powder is 7:3, the content is 6%, the content of boric acid is 0.5%, the total content of PVA is 2%, and the total content of polyether polyol is 5%.

[0102] Step S3: The mixed powder raw material in step S2 is added with 2% of the total powder mass of liquid additives (without mixing water) for uniform mixing, and mold extrusion forming is performed by a high-pressure vacuum horizontal continuous extruder (extrusion pressure is 8 MPa, vacuum degree is -0.095 MPa, and extrusion speed is 3 m / min).

[0103] Step S4: The plastic roller bar wet blank is received by a gas suspension V-shaped track type tray, and drying and setting are performed according to a stepwise drying curve: the ambient temperature is gradually raised from room temperature to 80°C at a rate of 10°C / h and nitrogen is introduced; then the ambient temperature is raised to 120°C at a rate of 5°C / h, and high-temperature drying is maintained at 120°C for 8 hours.

[0104] Step S5: After the drying treatment, the roller is placed in a high-temperature pressureless sintering furnace, and a glue removal and sintering integrated sintering process is adopted; during the sintering process, the temperature is first raised from room temperature to 400℃ at a rate of 0.5℃ / min while vacuumizing and argon is introduced; after glue removal is completed, the temperature is raised from 400℃ to 1400℃ at a rate of 5℃ / min; then the temperature is raised from 1400℃ to 1800℃ at a rate of 1℃ / min, and the temperature is maintained for 3h after reaching the target temperature; after constant temperature, the temperature is gradually reduced to room temperature at a slow cooling rate of 3℃ / min, and the high-fire-resistance low-expansion silicon carbide roller is obtained.

[0105] Example 7

[0106] The embodiment provides a preparation method of a high-fire-resistance low-expansion silicon carbide roller, and the preparation method comprises the following steps:

[0107] Step S1: Three kinds of silicon carbide micropowder with particle sizes of 5μm, 2μm and 0.5μm are used for batching, and the ratio is as follows: the weight ratio of 5μm silicon carbide micropowder is 25%, the weight ratio of 2μm silicon carbide micropowder is 30%, and the weight ratio of 0.5μm silicon carbide micropowder is 45%.

[0108] Step S2: The following ingredients are added to the prepared silicon carbide micropowder: the total content of the sintering aid (a mixture of aluminum nitride and aluminum oxide) is 8%, the ratio of high-purity silicon micropowder and carbon powder is 7:5, the content is 7%, the content of boric acid is 3%, the total content of PVA is 5%, and the total content of polyether polyol is 5%.

[0109] Step S3: The mixed powder raw material in step S2 is added with 5% of the total powder mass of liquid additives (without mixing water) for uniform mixing, and mold extrusion forming is performed by a high-pressure vacuum horizontal continuous extruder (extrusion pressure is 12MPa, vacuum degree is-0.095MPa, and extrusion speed is 5m / min).

[0110] Step S4: The plastic roller wet blank is received by a gas suspension V-shaped track type tray, and drying and setting are performed according to a stepwise drying curve: the ambient temperature is gradually raised from room temperature to 100℃ at a rate of 20℃ / h and nitrogen is introduced; then the ambient temperature is raised to 150℃ at a rate of 10℃ / h, and high-temperature drying is maintained at 150℃ for 4h.

[0111] Step S5: After the drying treatment, the roller is placed in a high-temperature pressureless sintering furnace, and a glue-removing and sintering integrated sintering process is adopted; during the sintering process, the temperature is first raised from room temperature to 500℃ at a rate of 2℃ / min while vacuumizing and argon is introduced; after the glue-removing is completed, the temperature is raised from 500℃ to 1500℃ at a rate of 10℃ / min; then the temperature is raised from 1500℃ to 2200℃ at a rate of 3℃ / min, and the temperature is kept for 1h after reaching the target temperature; after the constant temperature ends, the temperature is gradually reduced to room temperature at a slow cooling rate of 5℃ / min, and the high-fire resistance and low-expansion silicon carbide roller is obtained.

[0112] Comparative Example 1

[0113] The comparative example is the same as Example 1 except that 5μm silicon carbide powder is replaced by equal mass of 2μm silicon carbide powder.

[0114] Comparative Example 2

[0115] The comparative example is the same as Example 1 except that 2μm silicon carbide powder is replaced by equal mass of 0.5μm silicon carbide powder.

[0116] Comparative Example 3

[0117] The comparative example is the same as Example 1 except that 0.5μm silicon carbide powder is replaced by equal mass of 5μm silicon carbide powder.

[0118] Comparative Example 4

[0119] The comparative example is the same as Example 1 except that glue-removing is performed in other equipment and sintering is performed in a high-temperature pressureless sintering furnace.

[0120] Comparative Example 5

[0121] The comparative example is the same as Example 1 except that the drying is performed by directly raising the temperature from room temperature to 120℃ at a rate of 7℃ / h.

[0122] In Examples 1-7 and Comparative Examples 1-5, the content in Step S2 refers to mass content, and room temperature refers to 25℃.

[0123] The thermal expansion coefficient, load softening temperature, porosity, bending strength and 1500℃ high-temperature bending strength of the silicon carbide roller prepared in Examples 1-7 and Comparative Examples 1-5 are tested, and the results are shown in Table 1.

[0124] The test method of the thermal expansion coefficient is to measure the linear displacement of the sample in the length direction at room temperature-800℃ to calculate the expansion coefficient.

[0125] The test method of the load softening temperature is the thermal expansion rate test method;

[0126] The test method of the porosity is the boiling + Archimedes method;

[0127] The test method of the flexural strength and the flexural strength at 1500 DEG C is to measure the 3*4*40mm test sample on the universal strength testing machine.

[0128] Table 1

[0129]

[0130] The applicant declares that the detailed process equipment and process flow of the present application are illustrated by the above examples, but the present application is not limited to the above detailed process equipment and process flow, that is, it does not mean that the present application must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific modes, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a high-refractory and low-expansion silicon carbide roller, characterized in that: The preparation method comprises: The silicon carbide micropowder of the first particle size, the silicon carbide micropowder of the second particle size, and the silicon carbide micropowder of the third particle size are graded and mixed with a solid additive and a liquid additive to obtain a sintering material; The solid additives include sintering aids, silicon powder and carbon powder, boride and binder; The first particle size is 5 μm, the second particle size is 2 μm, and the third particle size is 0.5 μm; The mass fraction of the silicon carbide fine powder of the first particle size in the gradation is 5-25%, the mass fraction of the silicon carbide fine powder of the second particle size is 25-65%, and the mass fraction of the silicon carbide fine powder of the third particle size is 15-45%; Mixing the sintered material with a liquid additive to obtain a molding clay material; The shaping clay is sequentially extruded, dried and sintered to obtain the high-refractory low-expansion silicon carbide roller; the drying comprises a first drying, a second drying and a third drying performed sequentially; The first drying step is to increase the drying temperature from room temperature to 80-100°C at a heating rate of 10-20°C / h; The second drying step is to increase the drying temperature to 120-150°C at a heating rate of 5-10°C / h; The third drying is to keep the temperature at the end point of the second drying temperature rise for 4 to 8 hours; the drying is carried out under an inert gas atmosphere; The sintering is an integrated sintering process of first debinding and then sintering.

2. The preparation method according to claim 1, characterized in that In the integrated sintering process of debinding first and then sintering, the process parameters of the debinding process are to increase the temperature from room temperature to 400-500°C at a heating rate of 0.5-2°C / min while introducing inert gas.

3. The preparation method according to claim 1, characterized in that In the integrated firing process of debinding first and then sintering, the sintering process parameters are as follows: after debinding, the temperature is raised to 1400-1500°C, and the heating rate is 5-10°C / min; Then raise the temperature to 1800~2200℃ at a heating rate of 1~3℃ / min and keep warm for 1~4h.

4. The preparation method according to claim 1, characterized in that After the sintering, the cooling is performed at a cooling rate of 3-5°C / min, and the cooling end point is room temperature.

5. The preparation method according to claim 1, characterized in that The mass fraction of the sintering aid in the sintering material is ≤8%, the mass fraction of the silicon powder and the carbon powder is 2-6%, the mass fraction of the boride is 0.5-3%, and the mass fraction of the binder is ≤5%.

6. The preparation method according to claim 1, characterized in that The liquid additive does not contain water.

7. The preparation method according to claim 1, characterized in that The liquid additive is a nonionic surfactant.

8. The preparation method according to claim 1, characterized in that The mass fraction of the liquid additive in the sintering material is 5-8%.

9. The preparation method according to claim 1, characterized in that The amount of liquid additive added to the molding clay is 2-5% of the total amount of powder.

10. The preparation method according to claim 1, characterized in that The extrusion parameters are: extrusion pressure of 8-12 MPa, vacuum degree <-0.095 MPa, and extrusion speed of 3-5 m / min.

11. The preparation method according to claim 1, characterized in that After the extrusion, an air-suspended V-shaped track type tray is used to receive the unshaped plastic roller rod wet blank.

12. A high refractoriness and low expansion silicon carbide roller, characterized in that: The high-refractory, low-expansion silicon carbide roller is prepared by the preparation method according to any one of claims 1 to 11.

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