A special-shaped reaction-sintered silicon carbide tuyere and its production method

Abstract

The present invention discloses a special-shaped reaction-sintered silicon carbide tuyere and its production method. The special-shaped reaction-sintered silicon carbide tuyere is integrally made of reaction-sintered silicon carbide material. Its specific structure includes an inlet pipe, and the lower end of the inlet pipe is integrally connected with a special-shaped outlet pipe. Central through holes are respectively formed in the inlet pipe and the special-shaped outlet pipe, and the central through holes in the inlet pipe and the special-shaped outlet pipe are interconnected. The overall structure of the present invention is simple, convenient to use, has high wear resistance and good corrosion resistance, can form multiple rotating flames to evenly dissipate heat to the four walls of the boiler, and improves the use effect.

Description

Technical Field

[0001] The invention belongs to the technical field of burner nozzles, and in particular relates to a special-shaped reaction-sintered silicon carbide nozzle. Background Art

[0002] At present, the existing pulverized coal combustion power plants use burner nozzles of various specifications. The traditional ones have metal nozzles with square cross-sections. However, this type of nozzle is easily subject to thermal shock, and the radiation temperature from the furnace is above 1000°C. The original nozzle is made of high-temperature resistant metal material, so the nozzle is still greatly deformed by heat, and the airflow mixed with high-temperature pulverized coal particles causes impact corrosion to the burner nozzle under high temperature and high pressure. After half a year or a year of operation, the wall often becomes thinner and corrosion gaps appear.

[0003] In order to solve the above-mentioned problem, a nozzle made of silicon carbide material has appeared on the market, such as the patent application number: CN201720808947.4, which discloses a ceramic-steel composite nozzle end assembly for a swirl burner, including a first central nozzle end steel pipe, a metal welding ring, a plurality of inner dovetail-type silicon nitride combined with silicon carbide ceramic arc plates, a plurality of end inner dovetail-type silicon nitride combined with silicon carbide ceramic arc plates and a plurality of first dovetail strips, which includes a second central nozzle end steel pipe, a plurality of outer dovetail-type silicon nitride combined with silicon carbide ceramic arc plates, a plurality of end outer dovetail-type silicon nitride combined with silicon carbide ceramic arc plates and a plurality of second dovetail strips.

[0004] The above-mentioned type of nozzle adopts a silicon carbide ceramic layer installed on the inner surface of the steel pipe, and the silicon carbide ceramic layer is used to improve the wear resistance of the inner surface of the steel pipe. However, when in use, the nozzle is still affected by the radiation temperature from the furnace, which causes the nozzle to deform greatly due to heat, resulting in the silicon carbide ceramic layer embedded in the inner surface of the steel pipe to break and fall off, and the part without the anti-wear layer is quickly worn out, which causes the nozzle flame to deflect, causing damage to the water-cooled wall and other accidents, and forcing the furnace to be shut down. Summary of the invention

[0005] The main technical problem to be solved by the present invention is to provide a special-shaped reaction sintered silicon carbide tuyere and a production method thereof which has a simple overall structure, is easy to use, has high wear resistance, good corrosion resistance, and can form multiple rotating flames to evenly dissipate heat to the four walls of the boiler, thereby improving the use effect.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A special-shaped reaction-sintered silicon carbide tuyere, which is integrally made of reaction-sintered silicon carbide material. Its specific structure includes an inlet pipe, and the lower end of the inlet pipe is integrally connected with a special-shaped outlet pipe. Central through holes are respectively provided in the inlet pipe and the special-shaped outlet pipe, and the central through holes in the inlet pipe and the special-shaped outlet pipe are interconnected.

[0008] The following is the further optimization of the above technical solution by the present invention:

[0009] The inner surface size of the special-shaped outlet pipe gradually decreases from the end close to the inlet pipe to the other end, and the cross-sectional shape of the special-shaped outlet pipe is petal-shaped.

[0010] Further optimization: The overall shape of the inlet pipe is straight, and a bevel is provided at the end of the inlet pipe far from the special-shaped outlet pipe.

[0011] Further optimization: The overall structure of the special-shaped outlet pipe includes a plurality of arc-shaped parts, and the plurality of arc-shaped parts are arranged in a ring along the axis of the inlet pipe, and the adjacent arc-shaped parts are integrally connected on the side close to each other.

[0012] Further optimization: The upper ends of the arc-shaped parts are integrally connected to the inlet pipe respectively, and the axis of the arc-shaped part is inclined to the axis of the inlet pipe.

[0013] Further optimization: The outer surface shape of the arc-shaped part is an elliptical surface, and the dimensions of the ellipse are: the major axis L1 is 216 mm; the minor axis L2 is 175.6 mm.

[0014] The present invention also provides a production method of a special-shaped reaction-sintered silicon carbide tuyere. This production method is used to produce the above-mentioned special-shaped reaction-sintered silicon carbide tuyere, and it specifically includes a pre-molding step, a slurry preparation and slip casting molding step, and a post-sintering step. The slurry preparation and slip casting molding step includes S4, slurry preparation and slip casting molding: The slurry includes the following components by weight: 79-85.5 parts of silicon carbide fine powder, 59-62 parts of softened water, 2.6-3.6 parts of silicon nitride fine powder, 2.1-3.5 parts of metal tungsten fine powder, 2.2-3.4 parts of manganese dioxide powder, 2.2-3.3 parts of titanium oxide powder, 3.1-4.5 parts of carbon black, 3.2-4.6 parts of dispersant, 6.3-7.5 parts of binder; and it is stirred at a high speed for more than 30 hours under the working condition of 800-900 r / min. After filtering the slurry, it is injected into the mold by the solid slip casting method, and the slip casting speed is 30-40 s / L.

[0015] The following is the further optimization of the above technical solution by the present invention:

[0016] The pre-molding step includes:

[0017] S1. Fabricate the inner and outer bottom molds: After calculating the dimensions of the inner and outer bottom molds of the special-shaped reaction-sintered silicon carbide tuyere according to its structure and parameters, complete the overall fabrication of the inner and outer bottom molds.

[0018] S2. Fabricate the production outer mold using the outer bottom mold: The production outer mold is made of gypsum mold. Place the outer bottom mold in the outer mold of the gypsum mold and fix it. Pour the gypsum slurry into the mold. After the gypsum slurry solidifies, remove the outer bottom mold to obtain the production outer mold.

[0019] S3. Fabricate the core: Use the inner bottom mold to fabricate the production inner mold, and then fabricate the core from the production inner mold; fabricate the core that matches the internal structure of the special-shaped reaction-sintered silicon carbide tuyere.

[0020] Further optimization: The steps of slurry preparation and slip casting also include:

[0021] S5. Drying: Let the slip-cast mold stand for 50 hours. Open the mold and take out the silicon carbide green body to obtain the blank. Place the blank in an environment with a temperature above 15°C and an air humidity less than 70%RH for natural drying for 18 - 24 hours. After drying, separate the core from the green body; calculate the moisture content range of the blank, and then send it to an electric heating drying chamber for low-temperature drying. The drying temperature is 25 - 40°C, and the drying time is 60 - 70 hours. Take it out when the moisture content is less than 5% to obtain the product green body.

[0022] S6. Green body repair and machining: According to the product drawing, use a machine tool or manual repair method to machine the specific dimensions of the product, and then check the surface of the formed and dried green body to ensure that there are no pores, dark lines, or cracks on the product surface.

[0023] Further optimization: The later sintering steps include:

[0024] S7. Sintering: Send the repaired formed green body to a high-temperature drying chamber at 60 - 80°C for drying for 16 - 24 hours. When the moisture content of the green body is less than 2%, the green body can be loaded into a vacuum sintering furnace. Pour metallic silicon into the gaps and bottom of the product, where the purity of the metallic silicon is above 98.5%, and then carry out vacuum sintering.

[0025] S8. Surface treatment: After the sintered product is cooled to room temperature, separate it from the silica sand and remove the silicon metal adhered to the product surface to obtain the special-shaped reaction-sintered silicon carbide tuyere, and then classify, package, and store it.

[0026] With the above technical solution, the present invention has a clever concept, a reasonable structure, a simple overall structure, which is convenient for manufacturing and production. Moreover, the maximum service temperature of this special-shaped reaction-sintered silicon carbide tuyere is 1380 °C, which can be applied to harsh high-temperature corrosion and wear environments. It has an extremely low coefficient of thermal expansion, an extremely high thermal conductivity, has thermal shock resistance, can reduce downtime, and achieve rapid heating and cooling.

[0027] This special-shaped reaction-sintered silicon carbide tuyere not only meets the application requirements of the burner nozzle industry, but also further optimizes the stress structure of the tuyere: the inlet is circular, the feeding is more uniform, the outlet is petal-shaped, with a slight inclination angle, which can form multiple rotating flames to evenly dissipate heat to the four walls of the boiler, and is more suitable for applications in extreme environments of power plants.

[0028] The hardness of reaction-sintered silicon carbide ceramics is second only to diamond, with very good wear resistance, will not oxidize at normal and high temperatures, and has an extremely long service life; it has good chemical corrosion resistance and can resist acid and alkali corrosion except hydrofluoric acid and fluoride ion-containing solvents.

[0029] The special-shaped reaction-sintered silicon carbide tuyere produced by this method adopts a circular and arc splicing structure, with a uniform stress structure, which optimizes the stress structure, improves the product yield rate, and is conducive to increasing the service life of the product.

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the overall result of the embodiment of the present invention;

[0032] Figure 2 It is a cross-sectional view of the overall result in the embodiment of the present invention;

[0033] Figure 3 It is the front view of the overall structure in the embodiment of the present invention;

[0034] Figure 4 It is the transverse cross-sectional view of the overall structure in the embodiment of the present invention.

[0035] In the figure: 1 - inlet pipe; 11 - bevel; 2 - special-shaped outlet pipe; 21 - arc part. Detailed Embodiments

[0036] Embodiment 1: As Figures 1-4 shown, a special-shaped reaction-sintered silicon carbide tuyere, which is integrally made of reaction-sintered silicon carbide material. Its specific structure includes an inlet pipe 1, and the lower end of the inlet pipe 1 is integrally connected with a special-shaped outlet pipe 2. Central through holes are respectively opened in the inlet pipe 1 and the special-shaped outlet pipe 2, and the central through holes in the inlet pipe 1 and the special-shaped outlet pipe 2 are interconnected.

[0037] The inner surface size of the special-shaped outlet pipe 2 gradually decreases from one end close to the inlet pipe 1 to the other end, and the cross-sectional shape of the special-shaped outlet pipe 2 is petal-shaped.

[0038] In this embodiment, the overall shape of the inlet pipe 1 is straight tubular, the outer surface size Φ1 of the inlet pipe 1 is 680 ± 5 mm; the inner surface size Φ2 of the inlet pipe 1 is 640 ± 5 mm.

[0039] In this embodiment, the overall height of the inlet pipe 1 is 85 ± 5 mm.

[0040] In this embodiment, the outer surface size Φ1 of the inlet pipe 1 is preferably 680 mm; the inner surface size Φ2 of the inlet pipe 1 is preferably 640 mm; the overall height of the inlet pipe 1 is preferably 85 mm.

[0041] A bevel 11 is provided at one end position of the inlet pipe 1 far from the special-shaped outlet pipe 2, and the bevel 11 is arranged in a ring along the outer surface of the upper end of the inlet pipe 1.

[0042] In this embodiment, the inclination angle α1 of the bevel 11 is 30°.

[0043] With such a design, the special-shaped reaction-bonded silicon carbide tuyere can be conveniently assembled and installed through the bevel 11, which is convenient for use.

[0044] In this embodiment, the overall height H1 of the special-shaped reaction-bonded silicon carbide tuyere is 620 ± 5 mm.

[0045] In this embodiment, the overall height H1 of the special-shaped reaction-bonded silicon carbide tuyere is preferably 620 mm.

[0046] The overall structure of the special-shaped outlet pipe 2 includes a plurality of arc portions 21, the plurality of arc portions 21 are arranged in a ring along the axis of the inlet pipe 1, and one side of two adjacent arc portions 21 close to each other is integrally connected.

[0047] The upper ends of the arc portions 21 are respectively integrally connected to the inlet pipe 1, and the thickness of the arc portions 21 is the same as the thickness of the inlet pipe 1.

[0048] The axis of the arc portion 21 is inclined with respect to the axis of the inlet pipe 1, and the inner surface size of the special-shaped outlet pipe 2 gradually decreases from one end close to the inlet pipe 1 to the other end.

[0049] The outer surface shape of the arc portion 21 is an elliptical surface, and the dimensions of the ellipse are: the major axis L1 is 216 mm; the minor axis L2 is 175.6 mm.

[0050] In this embodiment, the number of the arc-shaped portions 21 is eight, and one sides of the eight arc-shaped portions 21 close to each other are integrally connected.

[0051] In this embodiment, the outer surface diameter Φ3 at the largest part of one end of the special-shaped outlet pipe 2 away from the inlet pipe 1 is 647.7 mm.

[0052] With such a design, this special-shaped reaction-sintered silicon carbide tuyere not only meets the application requirements of the burner nozzle industry, but also further optimizes the stress structure of the tuyere: the inlet is circular, the feeding is more uniform, the outlet is petal-shaped, with a slight inclination angle, which can form multiple rotating flames to evenly dissipate heat to the four walls of the boiler. At the same time, it can be adjusted by controlling the up and down movement of the fuel nozzle and the air nozzle assembly through inclination; it is more suitable for applications in the extreme environment of power plants.

[0053] Embodiment 2: The present invention also discloses a production method for producing the above-mentioned special-shaped reaction-sintered silicon carbide tuyere. This production method includes the following steps:

[0054] S1. Manufacture the inner and outer bottom molds:

[0055] According to the structure and parameters of the special-shaped reaction-sintered silicon carbide tuyere, after calculating the sizes of the inner and outer bottom molds of the special-shaped reaction-sintered silicon carbide tuyere, complete the overall manufacture of the inner and outer bottom molds; the material of the outer bottom mold is selected from one of gypsum, epoxy resin, and wooden blocks, and the material of the inner bottom mold is selected from gypsum, epoxy resin, etc.

[0056] S2. Use the outer bottom mold to manufacture the production outer mold:

[0057] The production outer mold is made of a gypsum mold. First, evenly apply soft soapy water to the surface of the outer bottom mold, place the outer bottom mold in the outer mold of the gypsum mold and fix it. Prepare a gypsum slurry according to the ratio of 3:2 of gypsum powder to water. After the gypsum powder and water are fully mixed, conduct vacuum stirring for 1 minute. After stirring evenly, screen out impurities. Pour the gypsum slurry into the mold, gently oscillate to remove air bubbles, and make the gypsum slurry flow into each small corner. It is necessary to ensure that the mold cavity of the mold is filled with the gypsum slurry at one time. After the gypsum slurry is cured, remove the outer bottom mold to obtain the production outer mold.

[0058] After the production outer mold made of gypsum is manufactured, it is dried in a drying room at a temperature of 30°C for 3 days, weighed with an electronic scale, taken out of the drying room when the moisture content of the mold is measured to be less than 10%, and further measure the mold size with a measuring tool. When the mold tolerance is less than 2 mm, it can be put into use.

[0059] S3. Manufacture the core:

[0060] Manufacture the inner mold with the inner bottom mold, and then manufacture the core from the production inner mold; according to the internal structure of the special-shaped reaction-sintered silicon carbide tuyere, manufacture a core that matches it.

[0061] The core material is selected as gypsum; the inner mold is manufactured by using the inner bottom mold, and then the core is manufactured from the manufactured inner mold. After obtaining the core, the core is placed in a drying room at a temperature of 30°C and dried for 3 days, weighed with an electronic scale, and taken out of the drying room when the moisture content of the core is less than 10%. Then, the size of the core is measured with a measuring tool. When the tolerance of the core is less than 2 mm, it can be put into use.

[0062] S4. Slurry preparation and slip casting molding:

[0063] Before starting the machine, check whether the clutch, brake, etc. of the mixer for batching are in good condition. The inside of the mixer drum must be cleaned thoroughly without any foreign objects, and check that the insulation and grounding of the electrical equipment are in good condition.

[0064] When preparing the slurry, the mixer should be started for no-load test run first. After the machine runs normally, add raw materials to stir and make the slurry. The slurry includes the following components by weight: 79 parts of silicon carbide fine powder, 59 parts of softened water, 2.6 parts of silicon nitride fine powder, 2.1 parts of tungsten metal fine powder, 2.2 parts of manganese dioxide powder, 2.2 parts of titanium oxide powder, 3.1 parts of carbon black, 3.2 parts of dispersant, and 6.3 parts of binder.

[0065] Among them: most of the softened water in the raw materials volatilizes during demolding and drying, the dispersant and binder volatilize completely when sintered to about 1000 ± 20°C, and the metallic silicon penetrates into the green body during the high-temperature reaction and reacts to fill all pores.

[0066] The raw materials need to be stirred at a high speed under the condition of a rotation speed of 800 r / min when added to the mixer, and the stirring time needs to be more than 30 hours to fully mix all the raw materials to make the slurry. After the slurry is prepared, take out the slurry, filter it and reserve it.

[0067] Place the dried mold in the slip casting area, and use the solid slip casting method to inject the filtered slurry into the mold. During the slip casting operation, the position, quantity and size of the slip casting holes must be determined on the production mold according to the structure of the reaction-sintered silicon carbide tuyere with special shape. Then fix the core in the production outer mold, and be sure to keep the center lines of the core and the outer mold coincident, and then close the mold and inject the slurry. During the slurry injection process, the injection speed should be reasonably controlled. The injection speed is about 30 s / L to ensure that no bubbles or splashes occur when the slurry is injected, and vibrate the production mold from time to time to make the slurry flow evenly.

[0068] S5. Drying:

[0069] Leave the mold after grouting for 50 hours, open the mold, take out the silicon carbide blank, and obtain a special-shaped reaction-sintered silicon carbide tuyere blank after demolding. Place the blank in an environment with a temperature above 15°C and an air humidity less than 70% RH for natural drying. The natural drying time is 18 hours. After drying, gently separate the core from the blank (the blank).

[0070] Weigh the separated blank with an electronic scale, calculate the moisture content range, and then send it to a low-temperature drying chamber for electric heating drying. The temperature of the electric heating drying chamber is set at 25°C. After drying for 60 hours, weigh the blank with an electronic scale again, calculate the moisture content, and take it out when the moisture content is less than 5% to obtain the green body of the product.

[0071] S6. Green body repair and machining:

[0072] According to the product drawing, use a machine tool to machine the specific dimensions of the product, and use manual repair methods to rough-machine the dried blank, removing the mold joint line and burrs on the product surface. During the repair process, continuously measure the outer diameter and length of the product with measuring tools to ensure the tolerance range of the product.

[0073] After the overall machining and manual repair of the special-shaped reaction-sintered silicon carbide tuyere blank are completed, it becomes the formed blank. Then, check the surface-formed dried blank (green body) to ensure that there are no pores, dark lines, cracks, etc. on the product surface.

[0074] S7. Sintering:

[0075] Send the trimmed formed blank into a high-temperature drying chamber. The temperature of the high-temperature drying chamber is 60°C, and the drying time is 16 hours. By measuring the weight change of the blank, calculate that the moisture content of the blank should be less than 2%. After completion, it can be loaded into a vacuum sintering furnace. Pour metallic silicon into the gaps and the bottom of the product, and disperse the metallic silicon. The purity of the metallic silicon is above 99.5%, and the weight is approximately 1 times the weight of the product blank, with the weight difference fluctuating up and down by no more than 30%.

[0076] Before starting the vacuum sintering furnace for sintering, first connect the cooling water. The water pressure of the cooling water should be maintained between 0.1 Mpa, and the outlet water temperature ≤ 40°C. Adjust the flow rate of each water valve on the vacuum sintering furnace to the appropriate position, and then fill the vacuum sintering furnace with compressed air to make the pressure in the vacuum sintering furnace reach 0.3 MPa. Then, set the heating process curve through the temperature controller (FP23) on the vacuum sintering furnace, and then the vacuum sintering furnace sucks vacuum to make the vacuum degree in the furnace drop to between 15 pa.

[0077] Then, heating is carried out and the heating program is run. After the heating starts, industrial nitrogen (purity above 99.5%) is injected into the vacuum sintering furnace. When the gas is inflated to the set upper limit (1±0.05Kpa), the exhaust fan and micro-flushing valve on the vacuum sintering furnace are turned on, and the air intake of the rotor flowmeter on the micro-flushing valve is adjusted to 362L / h. When the temperature rises to 800℃, the alarm sounds, and the micro-flushing valve and exhaust valve are automatically closed. The alarm is canceled on the alarm interface and the exhaust fan is turned off on the monitoring interface. The temperature continues to rise to 1700℃, and the vacuum is evacuated to 69pa. The operator observes the temperature changes displayed by the infrared thermometer in the hot zone at any time through the observation window on the furnace body.

[0078] When the temperature in the vacuum sintering furnace rises to about 1410°C, the metal silicon begins to melt and produces silicon metal vapor, which continuously penetrates into the silicon carbide blank. The carbon in the blank reacts with the infiltrated Si to generate β-SiC, which combines with α-SiC (silicon carbide powder). The free Si fills the pores of the blank to become a high-density ceramic material.

[0079] When the temperature reaches 1740℃, the heating program ends and the heating system of the vacuum sintering furnace automatically shuts down and stops. After waiting for 1 hour at a constant temperature, nitrogen (purity above 99.5%) is filled to 1±0.1Kpa and cooled. When the temperature is lower than 660℃, the air cooling system on the vacuum sintering furnace can be turned on to assist cooling. After reaching the furnace discharge temperature (about 100℃ or less), the air cooling system is turned off and ready for discharge.

[0080] S8. Surface treatment:

[0081] After the sintered products are taken out of the furnace and cooled to room temperature (about 10°C), they are separated from the silica sand. First, a handheld electric grinding wheel is used to remove larger residual silicon metal blocks, and then a sandblasting machine is used to remove a large area of ​​silicon slag on the product surface. The gas generated by the air compressor of the sandblasting machine blows the corundum to move, and the corundum contacts and rubs with the product surface to remove the silicon metal adhered to the product surface, so that there is no silicon slag residue on the product surface, and the special-shaped reaction sintered silicon carbide tuyere is obtained, which is then classified, packaged and stored.

[0082] Embodiment 3: A method for producing a special-shaped reaction-sintered silicon carbide tuyere, the production method comprising the following steps:

[0083] S1. Make inner and outer bottom molds:

[0084] According to the structure and parameters of the special-shaped reaction sintered silicon carbide tuyere, the sizes of the inner and outer bottom molds of the special-shaped reaction sintered silicon carbide tuyere are calculated, and the overall production of the inner and outer bottom molds is completed; the outer bottom mold material is selected from one of gypsum, epoxy resin, and wood block, and the inner bottom mold material is selected from gypsum, epoxy resin, etc.

[0085] S2. Use the outer bottom mold to make the outer mold:

[0086] For the production of the outer mold, a plaster mold is used. First, evenly apply soft soapy water to the surface of the outer bottom mold, place the outer bottom mold in the outer mold of the plaster mold and fix it. Prepare a plaster slurry according to the ratio of 3:2 of plaster powder to water. After fully mixing the plaster powder and water, conduct vacuum stirring for 2 minutes. After stirring evenly, sieve out impurities. Pour the plaster slurry into the mold, gently oscillate to remove air bubbles, and make the plaster slurry flow into each small corner. Ensure that the mold cavity is filled with the plaster slurry at one time. After the plaster slurry solidifies, remove the outer bottom mold to obtain the production outer mold.

[0087] After the production outer mold made of plaster is formed, it is dried in a drying room at a temperature of 40°C for 3.5 days, weighed with an electronic scale, taken out of the drying room when the moisture content of the mold is measured to be less than 10%, and the mold size is further measured with a measuring tool. When the mold tolerance is less than 2mm, it can be put into use.

[0088] S3. Manufacturing the core:

[0089] Use the inner bottom mold to manufacture the production inner mold, and then manufacture the core from the production inner mold; according to the internal structure of the special-shaped reaction-sintered silicon carbide tuyere, manufacture a core that matches it.

[0090] The core material is selected as plaster; use the inner bottom mold to manufacture the production inner mold, and then manufacture the core from the production inner mold. After obtaining the core, place the core in a drying room at a temperature of 40°C and dry it for 3.5 days, weigh it with an electronic scale, take it out of the drying room when the moisture content of the core is measured to be less than 10%, and measure the size of the core with a measuring tool. When the tolerance of the core is less than 2mm, it can be put into use.

[0091] S4. Slurry preparation and injection molding:

[0092] Before starting the machine, check whether the clutch, brake, etc. of the mixer for batching are in good condition. The inside of the mixer barrel must be cleaned thoroughly without foreign objects, and check that the insulation and grounding of the electrical equipment are in good condition.

[0093] When preparing the slurry, first start the mixer for no-load test run. After the machine runs normally, add raw materials to stir and make the slurry. The slurry includes the following components by weight: 82.25 parts of silicon carbide micropowder, 60.5 parts of softened water, 3.1 parts of silicon nitride micropowder, 2.8 parts of metal tungsten micropowder, 2.8 parts of manganese dioxide powder, 2.75 parts of titanium oxide powder, 3.8 parts of carbon black, 3.9 parts of dispersant, and 6.9 parts of binder.

[0094] Among them: Most of the softened water in the raw materials volatilizes during demolding and drying. The dispersant and binder volatilize completely when sintered to about 1000±20°C. Metallic silicon penetrates into the green body during the high-temperature reaction and reacts to fill all pores.

[0095] The raw materials need to be vigorously stirred in a blender under the condition of a rotation speed of 850 r / min for more than 30 hours to fully mix all the raw materials to obtain a slurry. After the slurry is prepared, the slurry is taken out, filtered and reserved.

[0096] Place the dried mold in the grouting area. Using the solid grouting method, inject the filtered slurry into the mold. During the grouting operation, it is necessary to determine the position, quantity and size of the grouting holes on the production mold according to the structure of the special-shaped reaction-sintered silicon carbide tuyere. Then fix the core in the production outer mold. Be sure to keep the center lines of the core and the outer mold coincident. Then close the mold and grout. During the grouting process, reasonably control the grouting speed. The grouting speed is about 35 s / L to ensure that no bubbles, splashes, etc. occur when the slurry is injected. Vibrate the production mold from time to time to make the slurry flow evenly.

[0097] S5. Drying:

[0098] Let the grouted mold stand for 55 hours. Open the mold, take out the silicon carbide blank. After demolding, obtain the special-shaped reaction-sintered silicon carbide tuyere blank. Place the blank in an environment with a temperature above 15 °C and an air humidity less than 70% RH for natural drying. The natural drying time is 21 hours. After drying, gently separate the core from the blank (the blank).

[0099] Weigh the separated blank with an electronic scale and calculate the moisture content range. Then send it to a low-temperature drying room heated by electricity for drying. The temperature of the electric heating drying room is set at 33 °C. After drying for 65 hours, weigh the blank with an electronic scale again and calculate the moisture content. Take it out when the moisture content is less than 5% to obtain the product green body.

[0100] S6. Green body repair and machining:

[0101] According to the product drawing, use a machine tool to machine the specific dimensions of the product. Use manual repair methods to rough-machine the dried blank to remove the mold joint line and burrs on the product surface. Continuously measure the outer diameter and length of the product with measuring tools during the repair process to ensure the tolerance range of the product.

[0102] After the overall machining and manual repair of the special-shaped reaction-sintered silicon carbide tuyere blank, it becomes a formed blank. Then check the surface formed and dried blank (green body) to ensure that there are no pores, dark lines, cracks, etc. on the product surface.

[0103] S7. Sintering:

[0104] The trimmed formed body is sent to a high-temperature drying room with a temperature of 70°C and a drying time of 20 hours. Through the weight change of the body, it is calculated that the moisture content of the body should be less than 2%. After completion, it can be loaded into a vacuum sintering furnace, and metallic silicon is poured into the gaps and bottom of the product, and metallic silicon is dispersed. The purity of the metallic silicon is above 99.5%, and its weight is approximately 1 times the weight of the product blank. The weight difference fluctuates by no more than 30%.

[0105] Before starting the vacuum sintering furnace, first connect the cooling water. The cooling water pressure should be maintained between 0.15 MPa and the outlet water temperature ≤40℃. Adjust the flow of each water valve on the vacuum sintering furnace to the appropriate position, and then fill the vacuum sintering furnace with compressed air to make the pressure in the vacuum sintering furnace reach 0.4 MPa. Then set the heating process curve through the temperature controller (FP23) on the vacuum sintering furnace, and then the vacuum sintering furnace absorbs vacuum to reduce the vacuum degree in the furnace to between 32.5 Pa.

[0106] Then, heating is carried out and the heating program is run. After the heating starts, industrial nitrogen (purity above 99.5%) is injected into the vacuum sintering furnace. When the gas is inflated to the set upper limit (1±0.05Kpa), the exhaust fan and micro-flushing valve on the vacuum sintering furnace are turned on, and the air intake of the rotor flowmeter on the micro-flushing valve is adjusted to 370L / h. When the temperature rises to 800℃, the alarm sounds, and the micro-flushing valve and exhaust valve are automatically closed. The alarm is canceled on the alarm interface and the exhaust fan is turned off on the monitoring interface. The temperature continues to rise to 1710℃, and the vacuum is evacuated to 129.5pa. The operator observes the temperature changes displayed by the infrared thermometer in the hot zone at any time through the observation window on the furnace body.

[0107] When the temperature in the vacuum sintering furnace rises to about 1410°C, the metal silicon begins to melt and produces silicon metal vapor, which continuously penetrates into the silicon carbide blank. The carbon in the blank reacts with the infiltrated Si to generate β-SiC, which combines with α-SiC (silicon carbide powder). The free Si fills the pores of the blank to become a high-density ceramic material.

[0108] When the temperature reaches 1750℃, the heating program ends and the heating system of the vacuum sintering furnace automatically shuts down and stops. After waiting at a constant temperature for 1.5 hours, nitrogen (purity above 99.5%) is filled to 1±0.1Kpa and cooled. When the temperature is lower than 660℃, the air cooling system on the vacuum sintering furnace can be turned on to assist cooling. After reaching the furnace discharge temperature (about below 100℃), the air cooling system is turned off and ready for discharge.

[0109] S8. Surface treatment:

[0110] After the fired and sintered product has cooled down to room temperature (about 30°C), it is separated from the silica sand. First, a hand-held electric grinding wheel is used to remove the residual silicon metal blocks of larger sizes, and then a sandblaster is used to extensively remove the silicon slag on the surface of the product. The gas generated by the air compressor in the sandblaster blows the emery to move, and the emery contacts and rubs against the surface of the product, thereby removing the silicon metal adhered to the surface of the product, leaving no silicon slag residue on the surface of the product, obtaining a special-shaped reaction-sintered silicon carbide tuyere, and then classifying, packaging, and storing it.

[0111] Example 4: A production method of a special-shaped reaction-sintered silicon carbide tuyere, the production method comprising the following steps:

[0112] S1. Making the inner and outer bottom molds:

[0113] According to the structure and parameters of the special-shaped reaction-sintered silicon carbide tuyere, after calculating the sizes of the inner and outer bottom molds of the special-shaped reaction-sintered silicon carbide tuyere, the overall production of the inner and outer bottom molds is completed; the material of the outer bottom mold is selected from one of gypsum, epoxy resin, and wooden blocks, and the material of the inner bottom mold is selected from gypsum, epoxy resin, etc.

[0114] S2. Using the outer bottom mold to produce the outer mold:

[0115] The production of the outer mold uses a gypsum mold. First, the surface of the outer bottom mold is evenly smeared with soft soapy water, and the outer bottom mold is placed and fixed inside the outer mold of the gypsum mold. The gypsum slurry is prepared according to the ratio of gypsum powder to water of 3:2. After the gypsum powder and water are fully mixed, they are vacuum stirred for 3 minutes. After stirring evenly, impurities are sieved out. The gypsum slurry is poured into the mold, and bubbles are removed by slight oscillation, and the gypsum slurry is made to flow into each small corner. It is necessary to ensure that the mold cavity of the mold is filled with the gypsum slurry at one time. After the gypsum slurry is cured, the outer bottom mold is removed to obtain the production outer mold.

[0116] After the production outer mold made of gypsum is manufactured, it is dried in a drying room at a temperature of 50°C for 4 days, weighed with an electronic scale, taken out of the drying room when it is measured that the moisture content of the mold is less than 10%, and the size of the mold is further measured with a measuring tool. When the mold tolerance is less than 2 mm, it can be put into use.

[0117] S3. Making the core:

[0118] Using the inner bottom mold to manufacture the inner mold, and then manufacturing the core from the inner mold; according to the internal structure of the special-shaped reaction-sintered silicon carbide tuyere, manufacturing a core that matches it.

[0119] The core material is selected as gypsum; using the inner bottom mold to manufacture the inner mold, and then manufacturing the core from the inner mold. After obtaining the core, the core is placed in a drying room at a temperature of 50°C for 4 days, weighed with an electronic scale, taken out of the drying room when it is measured that the moisture of the core is less than 10%, and the size of the core is measured with a measuring tool. When the tolerance of the core is less than 2 mm, it can be put into use.

[0120] S4. Slurry preparation and slip casting forming:

[0121] Before starting the machine, check whether the clutch, brake, etc. of the mixer for batching are in good condition. The inside of the mixer barrel must be cleaned thoroughly without any foreign objects. Check that the insulation and grounding of the electrical equipment are in good condition.

[0122] When preparing the slurry, first start the mixer for no-load test run. After the machine runs normally, add raw materials and stir to make the slurry. The slurry includes the following components by weight: 85.5 parts of silicon carbide micropowder, 62 parts of softened water, 3.6 parts of silicon nitride micropowder, 3.5 parts of tungsten metal micropowder, 3.4 parts of manganese dioxide powder, 3.3 parts of titanium oxide powder, 4.5 parts of carbon black, 4.6 parts of dispersant, and 7.5 parts of binder.

[0123] Among them: Most of the softened water in the raw materials volatilizes during demolding and drying. The dispersant and binder volatilize completely when sintered to about 1000 ± 20 °C. Metallic silicon penetrates into the green body during high-temperature reaction, reacts, and fills all pores.

[0124] The raw materials need to be stirred at a high speed under the condition of a rotation speed of 900 r / min in the mixer. The stirring time needs to be more than 30 hours to fully mix all the raw materials to make the slurry. After the slurry is prepared, take out the slurry, filter it, and reserve it.

[0125] Place the dried mold in the slip casting area. Adopt the solid slip casting method to inject the filtered slurry into the mold. During the slip casting operation, it is necessary to determine the position, quantity, and size of the slip casting holes on the production mold according to the structure of the special-shaped reaction-sintered silicon carbide tuyere. Then fix the core in the production outer mold. Be sure to keep the center lines of the core and the outer mold coincident, and then close the mold and slip cast. During the slip casting process, reasonably control the slip casting speed. The slip casting speed is about 40 s / L to ensure that no bubbles or splashes occur when the slurry is injected. Vibrate the production mold from time to time to make the slurry flow evenly.

[0126] S5. Drying:

[0127] Let the slip-cast mold stand for 60 hours. Open the mold, take out the silicon carbide green body. After demolding, obtain the special-shaped reaction-sintered silicon carbide tuyere blank. Place the blank in an environment with a temperature above 15 °C and an air humidity less than 70% RH for natural drying. The natural drying time is 24 hours. After drying, gently separate the core from the green body (blank).

[0128] Weigh the separated blank with an electronic scale, calculate the moisture content range, and then send it to the electric heating drying chamber for low-temperature drying. The temperature of the electric heating drying chamber is set at 40 °C. After drying for 70 hours, weigh the blank with an electronic scale again and calculate the moisture content. Take it out when the moisture content is less than 5% to obtain the product green body.

[0129] S6. Repair and machining of blanks:

[0130] According to the product drawings, use machine tools to process the specific dimensions of the product, and use manual repair methods to rough-process the dry blanks to remove the mold lines and burrs on the product surface. During the repair process, the outer diameter and length of the product are continuously measured with measuring tools to ensure the tolerance range of the product.

[0131] After the whole of the special-shaped reaction sintered silicon carbide tuyere blank is machined and repaired manually, it becomes a formed blank. Then the surface formed dry blank (blank) is inspected to ensure that there are no pores, dark lines, damage, etc. on the surface of the product.

[0132] S7, sintering:

[0133] The trimmed formed body is sent to a high-temperature drying room with a temperature of 80°C and a drying time of 24 hours. Through the change in body weight, it is calculated that the moisture content of the body should be less than 2%. After completion, it can be loaded into a vacuum sintering furnace, and metallic silicon is poured into the gaps and bottom of the product, and metallic silicon is dispersed. The purity of the metallic silicon is above 99.5%, and its weight is approximately 1 times the weight of the product blank. The weight difference fluctuates by no more than 30%.

[0134] Before starting the vacuum sintering furnace, first connect the cooling water. The cooling water pressure should be maintained between 0.2 Mpa and the water outlet temperature ≤40℃. Adjust the flow of each water valve on the vacuum sintering furnace to the appropriate position, and then fill the vacuum sintering furnace with compressed air to make the pressure in the vacuum sintering furnace reach 0.5MPa. Then set the heating process curve through the temperature controller (FP23) on the vacuum sintering furnace, and then the vacuum sintering furnace absorbs vacuum to reduce the vacuum degree in the furnace to between 50pa.

[0135] Then, heating is carried out and the heating program is run. After the heating starts, industrial nitrogen (purity above 99.5%) is injected into the vacuum sintering furnace. When the gas is inflated to the set upper limit (1±0.05Kpa), the exhaust fan and micro-flushing valve on the vacuum sintering furnace are turned on, and the air intake of the rotor flowmeter on the micro-flushing valve is adjusted to 378L / h. When the temperature rises to 800℃, the alarm sounds, and the micro-flushing valve and exhaust valve are automatically closed. The alarm is canceled on the alarm interface and the exhaust fan is turned off on the monitoring interface. The temperature continues to rise to 1720℃, and the vacuum is evacuated to 190pa. The operator observes the temperature changes displayed by the infrared thermometer in the hot zone at any time through the observation window on the furnace body.

[0136] Among them, when the temperature in the vacuum sintering furnace rises to about 1410 °C, metallic silicon begins to melt and generate silicon metal vapor, which continuously penetrates into the silicon carbide green body. The carbon in the green body reacts with the infiltrated Si to form β-SiC, which combines with α-SiC (silicon carbide micropowder). The free Si fills the pores of the green body, becoming a highly dense ceramic material;

[0137] When the temperature reaches 1760 °C, the heating program runs to completion, and the heating system of the vacuum sintering furnace automatically shuts down and stops. After maintaining a constant temperature for 2 hours, nitrogen (with a purity of over 99.5%) is filled to 1 ± 0.1 Kpa and then cooled. When the temperature is below 660 °C, the air-cooling system on the vacuum sintering furnace can be turned on to assist in cooling. After reaching the furnace-out temperature (about 100 °C or below), the air-cooling system is turned off, and preparation for furnace-out is made.

[0138] S8. Surface treatment:

[0139] After the sintered product taken out of the furnace has cooled down to room temperature (about 50 °C), it is separated from the silica sand and taken out. First, a hand-held electric grinding wheel is used to remove the residual silicon metal blocks with larger sizes, and then a sandblaster is used to widely remove the silicon slag on the product surface. The gas generated by the air compressor in the sandblaster blows the emery to move, and the emery contacts and rubs against the product surface, so that the silicon metal adhered to the product surface can be removed, leaving no silicon slag residue on the product surface, obtaining a special-shaped reaction-sintered silicon carbide tuyere, and then it is classified, packaged, and stored.

[0140] The technical solutions in Embodiments 2-4 of the present invention can be used to produce a special-shaped reaction-sintered silicon carbide tuyere, and the overall performance of the special-shaped reaction-sintered silicon carbide tuyere is detected, and it has the following indicators:

[0141]

[0142] In terms of material, the service life of a tuyere containing silicon nitride material is not as good as that of a tuyere made of reaction-sintered silicon carbide material; because from the perspective of wear resistance analysis, the wear resistance of the reaction-sintered silicon carbide material is 3-5 times that of the silicon nitride material.

[0143] For those of ordinary skill in the art, according to the teachings of the present invention, without departing from the principles and spirit of the present invention, the changes, modifications, substitutions, and variations made to the embodiments still fall within the protection scope of the present invention.

Claims

1. A special-shaped reaction-sintered silicon carbide tuyere, Characterized in that: The tuyere is integrally made of reaction-sintered silicon carbide material. Its specific structure includes an inlet pipe (1). The lower end of the inlet pipe (1) is integrally connected with a special-shaped outlet pipe (2). Central through holes are respectively formed in the inlet pipe (1) and the special-shaped outlet pipe (2), and the central through holes in the inlet pipe (1) and the special-shaped outlet pipe (2) are interconnected; The inner surface size of the special-shaped outlet pipe (2) gradually decreases from the end close to the inlet pipe (1) to the other end, and the cross-sectional shape of the special-shaped outlet pipe (2) is petal-shaped; The overall shape of the inlet pipe (1) is straight tubular, and a bevel (11) is provided at one end of the inlet pipe (1) far from the special-shaped outlet pipe (2); The overall structure of the special-shaped outlet pipe (2) includes a plurality of arc portions (21). The plurality of arc portions (21) are arranged in a ring along the axis of the inlet pipe (1), and one side where two adjacent arc portions (21) are close to each other is integrally connected; The upper ends of the arc portions (21) are respectively integrally connected with the inlet pipe (1), and the axes of the arc portions (21) are inclined with respect to the axis of the inlet pipe (1); The outer surface shape of the arc portion (21) is an elliptical surface, and the dimensions of the ellipse are: the major axis L1 is 216 mm; the minor axis L2 is 175.6 mm.

2. A production method of a special-shaped reaction-sintered silicon carbide tuyere, Characterized in that: This production method is used to produce the special-shaped reaction-sintered silicon carbide tuyere described in claim 1 above. It specifically includes a pre-molding step, a slurry mixing and grouting molding step, and a post-sintering step. The slurry mixing and grouting molding step includes S4, slurry mixing and grouting molding: The slurry includes the following components by weight: 79 - 85.5 parts of silicon carbide fine powder, 59 - 62 parts of softened water, 2.6 - 3.6 parts of silicon nitride fine powder, 2.1 - 3.5 parts of metal tungsten fine powder, 2.2 - 3.4 parts of manganese dioxide powder, 2.2 - 3.3 parts of titanium oxide powder, 3.1 - 4.5 parts of carbon black, 3.2 - 4.6 parts of dispersant, 6.3 - 7.5 parts of binder; and it is stirred at a high speed of 800 - 900 r / min for more than 30 hours. After filtering the slurry, it is injected into the mold by the solid grouting method, and the grouting speed is 30 - 40 s / L.

3. According to the production method of a special-shaped reaction-sintered silicon carbide tuyere described in claim 2, Characterized in that: The pre-molding step includes: S1. Making the inner and outer bottom molds: According to the structure and parameters of the special-shaped reaction-sintered silicon carbide tuyere, after calculating the sizes of the inner and outer bottom molds of the special-shaped reaction-sintered silicon carbide tuyere, the overall production of the inner and outer bottom molds is completed; S2. Using the outer bottom mold to produce the outer mold: The outer mold is made of a plaster mold. The outer bottom mold is placed and fixed in the outer mold of the plaster mold, and the plaster slurry is injected into the mold. After the plaster slurry is cured, the outer bottom mold is removed to obtain the outer mold; S3. Making the core: Using the inner bottom mold to manufacture the inner mold, and then manufacturing the core from the inner mold; According to the internal structure of the special-shaped reaction-sintered silicon carbide tuyere, a matching core is manufactured.

4. The production method of a special-shaped reaction-sintered silicon carbide tuyere according to claim 3, characterized in that: The slurry preparation and slip casting steps further include: S5. Drying: Leave the mold after slip casting standing for 50 hours, open the mold, take out the silicon carbide green body to obtain a blank, place the blank in an environment with a temperature above 15°C and an air humidity less than 70% RH for natural drying for 18 - 24 hours. After drying, separate the core from the green body; calculate the moisture content range of the blank, and then send it into an electric heating drying chamber for low-temperature drying. The drying temperature is 25 - 40°C, and the drying time is 60 - 70 hours. Take it out when the moisture content is less than 5% to obtain the product green body; S6. Green body repair and machining: According to the product drawing, use a machine tool or manual repair method to process the specific dimensions of the product, and then inspect the surface-formed dried green body to ensure that there are no pores, dark lines, or damages on the product surface.

5. The production method of a special-shaped reaction-sintered silicon carbide tuyere according to claim 4, characterized in that: The later sintering steps include: S7. Sintering: Send the repaired formed green body into a high-temperature drying chamber at 60 - 80°C for drying for 16 - 24 hours. When the moisture content of the green body is less than 2%, the green body can be loaded into a vacuum sintering furnace, pour metallic silicon into the product gaps and the bottom, where the purity of the metallic silicon is above 98.5%, and then carry out vacuum sintering; S8. Surface treatment: After the sintered product is cooled to room temperature, separate it from the silica sand and remove the silicon metal adhered to the product surface to obtain a special-shaped reaction-sintered silicon carbide tuyere, and then carry out classification packaging and storage.

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