A castable for blast furnace tapping trough and its preparation process

Abstract

The present invention provides a castable for a blast furnace tapping channel and a preparation process thereof, belonging to the technical field of refractory materials. The castable comprises the following steps: preparing liquid A and liquid B and calcining them at high temperature; ball milling, mixing in molybdenum disilicide, and calcining; dispersing BN micropowder and Si3N4 powder, semi-carbonizing them, and sintering them; introducing nitrogen and sintering them at high temperature; and mixing the components to prepare the castable. The present invention utilizes silicon powder and quartz powder as raw materials, and synthesizes rod-shaped and columnar oxygen-containing silicon nitride micropowders through high-temperature sintering in a nitrogen atmosphere. This enhances the mechanical properties of the castable and, during use, forms well-distributed cross-shaped whiskers, thereby improving the castable's oxidation resistance, high-temperature flexural strength, and slag erosion resistance, thereby increasing the castable's service life.

Description

Technical Field

[0001] The invention relates to the technical field of refractory materials, and in particular to a castable for a blast furnace tapping channel and a preparation process thereof. Background Art

[0002] Iron trough castable is a castable mixture specially used in the iron trough area of blast furnaces in the metallurgical industry. It is composed of a variety of high-quality refractory raw materials, such as corundum (including dense corundum, white corundum, brown corundum, sintered corundum, etc.), silicon carbide, spherical asphalt and special binders (such as aluminate cement, ultrafine powder, etc.). It is poured on site, vibrated and hardened to form a solid lining layer, which can effectively resist the strong erosion and scouring of high-temperature molten iron and slag, as well as chemical corrosion at high temperatures.

[0003] At present, with the continuous increase in blast furnace volume and the continuous increase in molten iron temperature, the molten iron flow rate increases, the flow rate becomes faster, and the number of iron tappings becomes frequent, which causes serious damage to the iron trough castables. The service environment of the blast furnace iron tapping trough is worse than before. Therefore, the performance of traditional iron trough castables is increasingly unable to meet the requirements of the current ironmaking process.

[0004] Based on this, it is necessary to propose a technical solution and corresponding preparation process for high-life blast furnace iron ditch castables that can improve the high-temperature flexural strength, oxidation resistance, scouring resistance, and slag corrosion resistance of the castables, so as to extend the service life of the iron ditch castables. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the object of the present invention is to provide a castable for a blast furnace tapping channel and a preparation process thereof.

[0006] A process for preparing a castable for a blast furnace tapping trough comprises the following steps:

[0007] S1: Prepare liquid A and liquid B and calcine at high temperature

[0008] Calcium nitrate and strontium nitrate are prepared into liquid A, diammonium phosphate and ammonium fluoride are prepared into liquid B, liquid A is then heated in a water bath and liquid B is added, the mixture is stirred and allowed to stand for aging, filtered, washed, dried and ground, and then calcined at high temperature to obtain strontium-containing micropowder;

[0009] S2: Ball milling, mixing with molybdenum disilicide and calcining

[0010] The magnesium slag, molybdenum disilicide and alumina are dried and ball-milled, and then PVA plasticizer is added and pressed into shape. After high-temperature calcination and crushing and grinding, molybdenum-containing micropowder is obtained;

[0011] S3: Disperse BN micropowder and Si3N4 powder and perform semi-carbonization and sintering

[0012] After BN micropowder and Si3N4 powder are evenly dispersed in a toluene solution, they are then added to the molten coal tar at a uniform speed and placed in an autoclave for reaction and semi-carbonization. After isostatic pressing, high-temperature sintering, and crushing and grinding, composite micropowder is obtained.

[0013] S4: Nitrogen is introduced and high temperature sintering is performed

[0014] The Si powder and quartz powder are dispersed at high speed, uniformly mixed, and then sintered at high temperature in a nitrogen atmosphere. After crushing and grinding, oxygen-containing silicon nitride micropowder is obtained;

[0015] S5: Mix the components to prepare the castable

[0016] Add brown corundum, white corundum, silicon carbide particles, silicon carbide fine powder, activated alumina micropowder, the above-mentioned strontium-containing micropowder, silicon oxide micropowder, spherical asphalt, the above-mentioned molybdenum-containing micropowder, the above-mentioned composite micropowder, the above-mentioned oxygen-containing silicon nitride micropowder, silicon oxide micropowder, pure calcium aluminate cement and water reducer into a mixer, stir for 10-20 minutes, and dry mix. Then, add water into the mixer at a material-liquid ratio of 1g: (30-40)mL, continue stirring for 5-10 minutes, pour into a mold, vibrate, cure and bake to obtain a castable.

[0017] Furthermore, step S1 specifically includes the following steps:

[0018] S1.1: Dissolve calcium nitrate, strontium nitrate, and deionized water in a material-liquid ratio of (1.3-1.5) g:1 g:(25-35) mL, stirring to obtain Solution A.

[0019] S1.2: Dissolve diammonium hydrogen phosphate, ammonium fluoride, and deionized water in a material-liquid ratio of 1 g:(2-3) g:(30-40) mL with stirring to obtain Solution B.

[0020] S1.3: Heat Solution A in a hot water bath at 60-70°C and adjust the pH to 9-10 by adding aqueous ammonia. Then, add Solution B to Solution A while continuing to add aqueous ammonia to maintain the pH at 9-10. Stir for 2-3 hours and allow to age for 20-24 hours to obtain an aged solution.

[0021] S1.4: Filter the aged liquid, wash it with deionized water and anhydrous ethanol 2-3 times, dry it in an oven, and grind it into a powder to obtain a dry powder with a median diameter of 1-2 μm;

[0022] S1.5: Place the above-mentioned dry powder in a muffle furnace, heat it to 1150-1250°C at a rate of 5-10°C / min, calcine it, and keep it at this temperature for 1-2 hours, and cool it to room temperature with the furnace to obtain strontium-containing micropowder.

[0023] Furthermore, step S2 specifically includes the following steps:

[0024] S2.1: Place magnesium slag, molybdenum disilicide, and aluminum oxide in a drying oven and dry them at 80-90°C for 12-15 hours to obtain dry magnesium slag, dry molybdenum disilicide, and dry aluminum oxide;

[0025] S2.2: Add the above-mentioned dried molybdenum disilicide, dried magnesium slag and dried alumina in a mass ratio of 1:(1-2):(8-10) into a planetary ball mill and mill at a speed of 300-400 r / min for 40-50 min to obtain a mixed powder;

[0026] S2.3: PVA plasticizer is added to the mixed powder, and the mixture is ball-milled for 20-30 minutes. The mixture is then placed in a molding machine and pressed into a columnar body at a pressure of 35-45 MPa to obtain a precursor body.

[0027] S2.4: Place the above-mentioned precursor body in a calcining furnace and calcine it at a temperature of 1200-1400°C for 2-3 hours. After cooling to room temperature in the furnace, crush and grind it to obtain molybdenum-containing micropowder with a median diameter of 1-2 μm.

[0028] Furthermore, step S3 specifically includes the following steps:

[0029] S3.1: Add BN powder and Si3N4 powder to a toluene solution at a material-liquid ratio of 1 g:(1-3) g:(20-30) mL. Ultrasonic dispersion is performed for 20-30 min. Stir at 400-500 rpm for 20-30 min to obtain a dispersion.

[0030] S3.2: Place the coal tar pitch in a melting furnace and fully melt it. Then, add the above dispersion into the melting furnace at a constant rate of 5-10 mL / min and disperse it evenly to obtain a mixed melt.

[0031] S3.3: The mixed melt is placed in an autoclave and reacted for 3-4 hours to achieve semi-carbonization. The mixed melt is then placed in a grinder and ground into a fine powder to obtain carbonized fine powder.

[0032] S3.4: The carbonized fine powder is isostatically pressed and placed in a sintering furnace. The temperature is raised to 1000-1050°C at a heating rate of 4-6°C / h, and kept warm for 40-50 minutes. The temperature is then raised to 1800-1900°C at a heating rate of 150-180°C / h, and kept warm for 40-50 minutes. After crushing and grinding, a composite micropowder with a median diameter of 1-2 μm is obtained.

[0033] Furthermore, step S4 specifically includes the following steps:

[0034] S4.1: Place Si powder and quartz powder in a high-speed disperser at a mass ratio of 1:2-3, disperse at high speed for 1-2 hours to mix thoroughly, and then place them into a sagger in a loose stacking manner;

[0035] S4.2: Place the sagger in a sealed high-temperature shuttle kiln, evacuate the kiln, introduce nitrogen, and sinter at 1300-1400°C for 1-2 hours. Cool naturally to room temperature to obtain an oxynitride silicon material.

[0036] S4.3: Place the above-mentioned oxygen-containing silicon nitride material in a crushing and grinding machine, crush and grind it to obtain oxygen-containing silicon nitride fine powder with a median diameter of 1-2 μm.

[0037] Furthermore, the volume ratio of liquid A to liquid B is 1:(20-25).

[0038] Furthermore, the mass percentage of the PVA plasticizer in the mixed powder is 3-5%.

[0039] Furthermore, the particle size of the spherical asphalt is less than 0.2 mm, the median diameter of the activated alumina powder is less than 3 μm, and the median diameter of the silica powder is less than 0.8 μm.

[0040] Furthermore, the water reducer is one or more of sodium tripolyphosphate, sodium hexametaphosphate, and FDN.

[0041] A castable for a blast furnace tapping channel comprises, by mass percentage, 5-10% silicon carbide particles, 5-10% silicon carbide fine powder, 2-3% activated alumina micropowder, 2-3% oxygen-containing silicon nitride micropowder, 2-3% strontium-containing micropowder, 1-2% silicon oxide micropowder, 1-2% spherical asphalt, 1-2% molybdenum-containing micropowder, 1-2% composite micropowder, 1-2% pure calcium aluminate cement, 0.6-1% water reducer, and the remainder being brown corundum and white corundum.

[0042] Compared with the prior art, the present invention has at least the following beneficial effects:

[0043] 1. The present invention uses calcium nitrate, strontium nitrate, ammonium fluoride and diammonium hydrogen phosphate as raw materials, and prepares strontium-containing micropowder through the steps of heating reaction, static aging, grinding into powder and high-temperature roasting. The strontium-containing micropowder is added to the castable, which not only improves the high-temperature flexural strength of the castable, but also synergizes with the activated alumina micropowder to promote the densification of the matrix structure, thereby achieving the effect of improving the castable's resistance to slag erosion, thereby increasing the service life of the castable.

[0044] 2. The present invention first mixes magnesium slag, molybdenum disilicide and alumina by ball milling, then adds PVA plasticizer, mixes thoroughly, presses into shape and calcines at high temperature, and then crushes and grinds into powder. The obtained molybdenum-containing micropowder is added to the castable. Due to the difference in thermal expansion coefficient in its structure, the crack propagation path will deviate from the original direction, thereby dispersing the concentrated stress of the castable and enhancing the toughness of the result, thereby increasing the critical thermal shock temperature of the castable and improving its thermal shock resistance.

[0045] 3. The present invention disperses BN micropowder and Si3N4 powder in a toluene solution, adds the mixture to molten coal tar, uniformly mixes the mixture, and semi-carbonizes and sinters it in an autoclave to obtain a composite micropowder. Since a composite solid solution is formed during the high-temperature sintering process, cracks in the matrix are effectively sealed, thereby effectively improving the antioxidant properties of the castable and further increasing its service life.

[0046] 4. The present invention uses silicon powder and quartz powder as raw materials and synthesizes rod-shaped and columnar oxygen-containing silicon nitride micropowder through high-temperature sintering in a nitrogen atmosphere. The mechanical properties of the castable can be enhanced, and well-cross-distributed whiskers can be formed during the use of the castable, thereby improving the castable's oxidation resistance, high-temperature flexural strength and slag erosion resistance, thereby increasing the service life of the castable. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable one skilled in the relevant art to make and use the present disclosure.

[0048] Figure 1 This is a flow chart of the preparation process of the castable for the blast furnace iron ditch used in the embodiment of the present invention. DETAILED DESCRIPTION

[0049] The following describes in detail a castable for a blast furnace tapping channel and a preparation process thereof provided by the present invention in conjunction with the accompanying drawings and specific embodiments. Example 1

[0050] A preparation process for a castable for a blast furnace tapping trough, such as Figure 1 As shown, the following steps are included:

[0051] S1: Prepare liquid A and liquid B and calcine at high temperature

[0052] Calcium nitrate, strontium nitrate and deionized water were stirred and dissolved in a material-liquid ratio of 1.3g:1g:25mL to obtain liquid A for standby use. Diammonium hydrogen phosphate, ammonium fluoride and deionized water were stirred and dissolved in a material-liquid ratio of 1g:2g:30mL to obtain liquid B for standby use. Liquid A was then heated in a hot water bath at 60°C and ammonia water was added to adjust the pH to 9. Liquid B was then added to liquid A while continuing to add ammonia water to maintain the pH at 9. After stirring for 2 hours, the mixture was allowed to stand. Aging for 20 hours to obtain an aging liquid, wherein the volume ratio of liquid A to liquid B is 1:20. Subsequently, the aging liquid is filtered, then washed twice with deionized water and anhydrous ethanol respectively, and then placed in an oven for drying. After grinding into powder, a dry powder with a median diameter of 1 μm is obtained. The dry powder is then placed in a muffle furnace, heated to 1150°C at a rate of 5°C / min, calcined, and kept warm for 1 hour. It is then cooled to room temperature with the furnace to obtain strontium-containing micropowder;

[0053] S2: Ball milling, mixing with molybdenum disilicide and calcining

[0054] The magnesium slag, molybdenum disilicide and alumina were placed in a drying oven, dried at 80 ° C for 12 hours to obtain dry magnesium slag, dry molybdenum disilicide and dry alumina, and then the dry molybdenum disilicide, dry magnesium slag and dry alumina were added to a planetary ball mill in a mass ratio of 1:1:8, and ball milled at a rate of 300r / min for 40 minutes to obtain a mixed powder. Subsequently, PVA plasticizer was added to the mixed powder, wherein the PVA plasticizer accounted for 3% by mass of the mixed powder. After continuing ball milling for 20 minutes, the mixture was placed in a molding machine and pressed into a columnar body under a pressure of 35MPa to obtain a precursor body. The precursor body was then placed in a calcining furnace and calcined at a temperature of 1200 ° C for 2 hours. After cooling to room temperature with the furnace, it was crushed and ground to obtain a molybdenum-containing micropowder with a median diameter of 1μm;

[0055] S3: Disperse BN micropowder and Si3N4 powder and perform semi-carbonization and sintering

[0056] BN powder and Si3N4 powder were added to the toluene solution at a material-liquid ratio of 1g:1g:20mL, ultrasonically dispersed for 20min, and then stirred at a rate of 400r / min for 20min to obtain a dispersion liquid for standby use. The coal tar was then placed in a melting furnace for full melting. The dispersion liquid was then added to the melting furnace at a uniform rate of 5mL / min. After uniform dispersion, a mixed melt was obtained. Subsequently, the mixed melt was placed in an autoclave and reacted for 3h for semi-carbonization. The mixture was then placed in a grinder and ground into fine powder to obtain carbonized fine powder. The carbonized fine powder was then isostatically pressed and placed in a sintering furnace. The temperature was increased to 1000℃ at a heating rate of 4℃ / h, kept warm for 40min, and then increased to 1800℃ at a heating rate of 150℃ / h, kept warm for 40min. After crushing and grinding, a composite powder with a median diameter of 1μm was obtained.

[0057] S4: Nitrogen is introduced and high temperature sintering is performed

[0058] Si powder and quartz powder are placed in a high-speed disperser in a mass ratio of 1:2, dispersed at high speed for 1 hour, and fully mixed, and then loaded into a sagger in a loose stacking manner, and then the sagger is placed in a closed high-temperature shuttle kiln, and the kiln is vacuumed, and then nitrogen is introduced, and sintered at a temperature of 1300°C for 1 hour, and naturally cooled to room temperature to obtain an oxygen-containing silicon nitride material, and then the oxygen-containing silicon nitride material is placed in a crushing and grinding machine for crushing and grinding to obtain oxygen-containing silicon nitride micropowder with a median diameter of 1 μm;

[0059] S5: Mix the components to prepare the castable

[0060] Brown corundum, white corundum, silicon carbide particles, silicon carbide powder, activated alumina powder, the above-mentioned strontium-containing powder, silicon oxide powder, spherical asphalt, the above-mentioned molybdenum-containing powder, the above-mentioned composite powder, the above-mentioned oxygen-containing silicon nitride powder, silicon oxide powder, pure calcium aluminate cement and water reducer are added to a mixer and stirred for 10 minutes for dry mixing. Water is then added to the mixer at a material-liquid ratio of 1g:30mL. After further stirring for 5 minutes, the mixture is poured into a mold, and after vibration, curing and baking, a castable is obtained. The materials, calculated by mass percentage, include: 5% silicon carbide particles, 5% silicon carbide fine powder, 2% activated alumina micropowder, 2% oxygen-containing silicon nitride micropowder, 2% strontium-containing micropowder, 1% silica micropowder, 1% spherical asphalt, 1% molybdenum-containing micropowder, 1% composite micropowder, 1% pure calcium aluminate cement, 0.6% water reducer, and the balance is brown corundum and white corundum. The particle size of the spherical asphalt is less than 0.2 mm, the median diameter of the activated alumina micropowder is less than 3 μm, and the median diameter of the silicon micropowder is less than 0.8 μm.

[0061] Performance testing:

[0062] 1. According to GB / T3002-2017, the high temperature flexural strength of the castable was tested at 1400℃ for 0.5h. The results are shown in Table 1 below.

[0063] 2. The slurry obtained after stirring and mixing the components in step S5 was vibrated and cast into a crucible with an outer dimension of 70 mm × 70 mm × 70 mm and an inner hole dimension of φ30 / 20 mm × 40 mm. The crucible was cured at room temperature for 24 hours, then demolded, cured outside the mold for 24 hours, dried at 110° C., and then heat treated at 1450° C. for 3 hours. 30 g of blast furnace slag was then added to the heat-treated crucible, heated to 1500° C., held at this temperature for 3 hours, and cooled. 10 g of blast furnace slag was then added, and the crucible was heated to 1500° C. and held at this temperature for 3 hours. After cooling, the crucible was cut along the axis of the crucible hole, and the slag corrosion depth was measured. The results are shown in Table 1 below.

[0064] 3. The prepared castable was kept at 1100°C for 15 minutes, then air-cooled for 5 minutes, and then reheated and air-cooled for 3 cycles. The flexural strength of the castable after thermal shock was measured. The thermal shock resistance of the castable was calculated according to the formula: Strength retention rate = (flexural strength after thermal shock / flexural strength before thermal shock) × 100%. The results are shown in Table 1 below.

[0065] 4. The prepared castable was oxidized in a high-temperature furnace in an air atmosphere at 1450°C for 3 hours, and then a cross section was taken to measure the oxidized area and total area. The oxidation resistance of the castable was calculated according to the formula: oxidation index = (oxidized area / total area) × 100%. The results are shown in Table 1 below. Example 2

[0066] A preparation process for a castable for a blast furnace tapping trough, such as Figure 1 As shown, the following steps are included:

[0067] S1: Prepare liquid A and liquid B and calcine at high temperature

[0068] Calcium nitrate, strontium nitrate and deionized water were stirred and dissolved in a material-liquid ratio of 1.4g:1g:30mL to obtain liquid A for standby use. Diammonium hydrogen phosphate, ammonium fluoride and deionized water were stirred and dissolved in a material-liquid ratio of 1g:2.5g:35mL to obtain liquid B for standby use. Liquid A was then heated in a hot water bath at 65°C and ammonia water was added to adjust the pH to 9.5. Liquid B was then added to liquid A while continuing to add ammonia water to maintain the pH at 9.5. After stirring for 2.5h, the mixture was allowed to stand for 2 hours. Aged for 22 hours to obtain an aging liquid, wherein the volume ratio of liquid A to liquid B is 1:22.5. Subsequently, the aging liquid is filtered, then washed twice with deionized water and anhydrous ethanol respectively, and then placed in an oven for drying. After grinding into powder, a dry powder with a median diameter of 1.5 μm is obtained. The dry powder is then placed in a muffle furnace, heated to 1200° C. at a rate of 7.5° C. / min, calcined, and kept warm for 1.5 hours. It is then cooled to room temperature with the furnace to obtain strontium-containing micropowder;

[0069] S2: Ball milling, mixing with molybdenum disilicide and calcining

[0070] The magnesium slag, molybdenum disilicide and alumina were placed in a drying oven, dried at a temperature of 85 ° C for 13.5 hours to obtain dry magnesium slag, dry molybdenum disilicide and dry alumina, and then the dry molybdenum disilicide, dry magnesium slag and dry alumina were added to a planetary ball mill in a mass ratio of 1:1.5:9, and ball milled at a rate of 350r / min for 45 minutes to obtain a mixed powder. Subsequently, PVA plasticizer was added to the mixed powder, wherein the PVA plasticizer accounted for 4% by mass of the mixed powder. After continuing ball milling for 25 minutes, the mixture was placed in a molding machine and pressed into a columnar body under a pressure of 40MPa to obtain a precursor body. The precursor body was then placed in a calcining furnace and calcined at a temperature of 1300 ° C for 2.5 hours. After cooling to room temperature with the furnace, it was crushed and ground to obtain a molybdenum-containing micropowder with a median diameter of 1.5μm;

[0071] S3: Disperse BN micropowder and Si3N4 powder and perform semi-carbonization and sintering

[0072] BN powder and Si3N4 powder were added to the toluene solution at a material-liquid ratio of 1g:2g:25mL, ultrasonically dispersed for 25min, and then stirred at a rate of 450r / min for 25min to obtain a dispersion for standby use. The coal tar was then placed in a melting furnace for full melting. The dispersion was then added to the melting furnace at a uniform rate of 7.5mL / min to obtain a mixed melt after uniform dispersion. Subsequently, the mixed melt was placed in an autoclave and reacted for 3.5h for semi-carbonization. The mixture was then placed in a grinder and ground into fine powder to obtain carbonized fine powder. The carbonized fine powder was then isostatically pressed and placed in a sintering furnace. The temperature was increased to 1025°C at a heating rate of 5°C / h, kept warm for 45min, and then increased to 1850°C at a heating rate of 165°C / h, kept warm for 45min, and crushed and ground to obtain a composite micropowder with a median diameter of 1.5μm.

[0073] S4: Nitrogen is introduced and high temperature sintering is performed

[0074] Si powder and quartz powder were placed in a high-speed disperser at a mass ratio of 1:2.5, dispersed at high speed for 1.5 hours, and fully mixed. The powder was then loosely packed into a sagger, and the sagger was placed in a closed high-temperature shuttle kiln. The kiln was vacuumed, and then nitrogen was introduced. The mixture was sintered at a temperature of 1350°C for 1.5 hours and naturally cooled to room temperature to obtain an oxygen-containing silicon nitride material. Subsequently, the oxygen-containing silicon nitride material was placed in a crushing and grinding machine for crushing and grinding to obtain oxygen-containing silicon nitride micropowder with a median diameter of 1.5 μm.

[0075] S5: Mix the components to prepare the castable

[0076] Brown corundum, white corundum, silicon carbide particles, silicon carbide powder, activated alumina powder, the above-mentioned strontium-containing powder, silicon oxide powder, spherical asphalt, the above-mentioned molybdenum-containing powder, the above-mentioned composite powder, the above-mentioned oxygen-containing silicon nitride powder, silicon oxide powder, pure calcium aluminate cement and water reducer are added to a mixer, stirred for 15 minutes, and dry mixed. Water is then added to the mixer at a material-liquid ratio of 1g:35mL. After further stirring for 7.5 minutes, the mixture is poured into a mold, and after vibration, curing and baking, a castable is obtained. The castable, by mass percentage, , including: 7.5% silicon carbide particles, 7.5% silicon carbide fine powder, 2.5% activated alumina micropowder, 2.5% oxygen-containing silicon nitride micropowder, 2.5% strontium-containing micropowder, 1.5% silica micropowder, 1.5% spherical asphalt, 1.5% molybdenum-containing micropowder, 1.5% composite micropowder, 1.5% pure calcium aluminate cement, 0.8% water reducer, the remainder is brown corundum and white corundum, the spherical asphalt particle size is less than 0.2mm, the median diameter size of activated alumina micropowder is less than 3μm, and the median diameter size of silicon micropowder is less than 0.8μm.

[0077] Performance testing:

[0078] 1. According to GB / T3002-2017, the high temperature flexural strength of the castable was tested at 1400℃ for 0.5h. The results are shown in Table 1 below.

[0079] 2. The slurry obtained after stirring and mixing the components in step S5 was vibrated and cast into a crucible with an outer dimension of 70 mm × 70 mm × 70 mm and an inner hole dimension of φ30 / 20 mm × 40 mm. The crucible was cured at room temperature for 24 hours, then demolded, cured outside the mold for 24 hours, dried at 110° C., and then heat treated at 1450° C. for 3 hours. 30 g of blast furnace slag was then added to the heat-treated crucible, heated to 1500° C., held at this temperature for 3 hours, and cooled. 10 g of blast furnace slag was then added, and the crucible was heated to 1500° C. and held at this temperature for 3 hours. After cooling, the crucible was cut along the axis of the crucible hole, and the slag corrosion depth was measured. The results are shown in Table 1 below.

[0080] 3. The prepared castable was kept at 1100°C for 15 minutes, then air-cooled for 5 minutes, and then reheated and air-cooled for 3 cycles. The flexural strength of the castable after thermal shock was measured. The thermal shock resistance of the castable was calculated according to the formula: Strength retention rate = (flexural strength after thermal shock / flexural strength before thermal shock) × 100%. The results are shown in Table 1 below.

[0081] 4. The prepared castable was oxidized in a high-temperature furnace in an air atmosphere at 1450°C for 3 hours, and then a cross section was taken to measure the oxidized area and total area. The oxidation resistance of the castable was calculated according to the formula: oxidation index = (oxidized area / total area) × 100%. The results are shown in Table 1 below. Example 3

[0082] A preparation process for a castable for a blast furnace tapping trough, such as Figure 1 As shown, the following steps are included:

[0083] S1: Prepare liquid A and liquid B and calcine at high temperature

[0084] Calcium nitrate, strontium nitrate and deionized water were stirred and dissolved in a material-liquid ratio of 1.5g:1g:35mL to obtain liquid A for standby use. Diammonium hydrogen phosphate, ammonium fluoride and deionized water were stirred and dissolved in a material-liquid ratio of 1g:3g:40mL to obtain liquid B for standby use. Liquid A was then heated in a hot water bath at 70°C and ammonia water was added to adjust the pH to 10. Liquid B was then added to liquid A while continuing to add ammonia water to maintain the pH at 10. After stirring for 3 hours, the mixture was allowed to stand for 2 hours. Aged for 24 hours to obtain an aging liquid, wherein the volume ratio of liquid A to liquid B is 1:25. Subsequently, the aging liquid is filtered, and then washed with deionized water and anhydrous ethanol three times respectively, and then placed in an oven for drying. After grinding into powder, a dry powder with a median diameter of 2 μm is obtained. The dry powder is then placed in a muffle furnace, heated to 1250° C. at a rate of 10° C. / min, calcined, and kept warm for 2 hours. It is then cooled to room temperature with the furnace to obtain strontium-containing micropowder;

[0085] S2: Ball milling, mixing with molybdenum disilicide and calcining

[0086] The magnesium slag, molybdenum disilicide and alumina are placed in a drying oven respectively, and dried at a temperature of 90°C for 15 hours to obtain dry magnesium slag, dry molybdenum disilicide and dry alumina, and then the dry molybdenum disilicide, dry magnesium slag and dry alumina are added to a planetary ball mill in a mass ratio of 1:2:10, and ball milled at a rate of 400r / min for 50min to obtain a mixed powder, and then PVA plasticizer is added to the mixed powder, wherein the PVA plasticizer accounts for 5% by mass of the mixed powder, and after continuing ball milling for 30min, it is placed in a molding machine and pressed into a columnar body under a pressure of 45MPa to obtain a precursor body, and then the precursor body is placed in a calcining furnace and calcined at a temperature of 1400°C for 3h. After cooling to room temperature with the furnace, it is crushed and ground to obtain a molybdenum-containing micropowder with a median diameter of 2μm;

[0087] S3: Disperse BN micropowder and Si3N4 powder and perform semi-carbonization and sintering

[0088] BN powder and Si3N4 powder were added to the toluene solution at a material-liquid ratio of 1g:3g:30mL, ultrasonically dispersed for 30min, and then stirred at a rate of 500r / min for 30min to obtain a dispersion for standby use. The coal tar was then placed in a melting furnace for full melting. The dispersion was then added to the melting furnace at a uniform rate of 10mL / min. After uniform dispersion, a mixed melt was obtained. Subsequently, the mixed melt was placed in an autoclave and reacted for 4h for semi-carbonization. The mixture was then placed in a grinder and ground into fine powder to obtain carbonized fine powder. The carbonized fine powder was then isostatically pressed and placed in a sintering furnace. The temperature was increased to 1050°C at a heating rate of 6°C / h, kept warm for 50min, and then increased to 1900°C at a heating rate of 180°C / h, kept warm for 50min, and crushed and ground to obtain a composite powder with a median diameter of 2μm.

[0089] S4: Nitrogen is introduced and high temperature sintering is performed

[0090] Si powder and quartz powder are placed in a high-speed disperser in a mass ratio of 1:3, dispersed at high speed for 2 hours, and fully mixed, and then loaded into a sagger in a loose stacking manner, and then the sagger is placed in a closed high-temperature shuttle kiln, and the kiln is vacuumed, and then nitrogen is introduced, and sintered at a temperature of 1400°C for 2 hours, and naturally cooled to room temperature to obtain an oxygen-containing silicon nitride material, and then the oxygen-containing silicon nitride material is placed in a crushing and grinding machine for crushing and grinding to obtain oxygen-containing silicon nitride micropowder with a median diameter of 2 μm;

[0091] S5: Mix the components to prepare the castable

[0092] Brown corundum, white corundum, silicon carbide particles, silicon carbide powder, activated alumina powder, the above-mentioned strontium-containing powder, silicon oxide powder, spherical asphalt, the above-mentioned molybdenum-containing powder, the above-mentioned composite powder, the above-mentioned oxygen-containing silicon nitride powder, silicon oxide powder, pure calcium aluminate cement and water reducer are added into a mixer and stirred for 20 minutes for dry mixing. Water is then added into the mixer at a material-liquid ratio of 1g:40mL. After further stirring for 10 minutes, the mixture is poured into a mold and vibrated, cured and baked to obtain a castable. The injection material, calculated by mass percentage, includes: 10% silicon carbide particles, 10% silicon carbide fine powder, 3% activated alumina micropowder, 3% oxygen-containing silicon nitride micropowder, 3% strontium-containing micropowder, 2% silica micropowder, 2% spherical asphalt, 2% molybdenum-containing micropowder, 2% composite micropowder, 2% pure calcium aluminate cement, 1% water reducer, and the remainder is brown corundum and white corundum. The particle size of the spherical asphalt is less than 0.2 mm, the median diameter of the activated alumina micropowder is less than 3 μm, and the median diameter of the silicon micropowder is less than 0.8 μm.

[0093] Performance testing:

[0094] 1. According to GB / T3002-2017, the high temperature flexural strength of the castable was tested at 1400℃ for 0.5h. The results are shown in Table 1 below.

[0095] 2. The slurry obtained after stirring and mixing the components in step S5 was vibrated and cast into a crucible with an outer dimension of 70 mm × 70 mm × 70 mm and an inner hole dimension of φ30 / 20 mm × 40 mm. The crucible was cured at room temperature for 24 hours, then demolded, cured outside the mold for 24 hours, dried at 110° C., and then heat treated at 1450° C. for 3 hours. 30 g of blast furnace slag was then added to the heat-treated crucible, heated to 1500° C., held at this temperature for 3 hours, and cooled. 10 g of blast furnace slag was then added, and the crucible was heated to 1500° C. and held at this temperature for 3 hours. After cooling, the crucible was cut along the axis of the crucible hole, and the slag corrosion depth was measured. The results are shown in Table 1 below.

[0096] 3. The prepared castable was kept at 1100°C for 15 minutes, then air-cooled for 5 minutes, and then reheated and air-cooled for 3 cycles. The flexural strength of the castable after thermal shock was measured. The thermal shock resistance of the castable was calculated according to the formula: Strength retention rate = (flexural strength after thermal shock / flexural strength before thermal shock) × 100%. The results are shown in Table 1 below.

[0097] 4. The prepared castable was oxidized in a high-temperature furnace in an air atmosphere at 1450°C for 3 hours, and then a cross section was taken to measure the oxidized area and total area. The oxidation resistance of the castable was calculated according to the formula: oxidation index = (oxidized area / total area) × 100%. The results are shown in Table 1 below.

[0098] Table 1: Summary of performance test results of Examples 1-3

[0099] Performance indicators High temperature flexural strength (MPa) Slag corrosion depth (mm) Thermal shock resistance (strength retention, %) Oxidation index (%) Example 1 4.95 0.58 98.3 26.6 Example 2 4.97 0.55 98.5 26.3 Example 3 4.98 0.57 98.6 25.8 Comparative Example 1

[0100] The difference between this comparative example 1 and Example 1 is that step S1 is removed, and the strontium-containing powder in step S5 is replaced with an equal amount of activated alumina powder. Then, referring to the performance test method in Example 1, the performance test of the prepared castable is carried out, and the results are shown in Table 2 below. Comparative Example 2

[0101] The difference between Comparative Example 2 and Example 1 is that the activated alumina powder in step S5 is replaced with an equal amount of strontium-containing powder, and then the performance test method in Example 1 is referred to to perform a performance test on the prepared castable. The results are shown in Table 2 below.

[0102] Table 2: Comparison of performance test results of Example 1, Comparative Example 1 and Comparative Example 2

[0103] Performance indicators High temperature flexural strength (MPa) Slag corrosion depth (mm) Example 1 4.95 0.58 Comparative Example 1 2.89 0.93 Comparative Example 2 4.68 0.85

[0104] By comparing the performance test results of Example 1 with those of Comparative Examples 1 and 2, it can be seen that strontium-containing micropowder is prepared by using calcium nitrate, strontium nitrate, ammonium fluoride and diammonium hydrogen phosphate as raw materials, and undergoing the steps of heating reaction, static aging, grinding into powder and high-temperature roasting. Adding the strontium-containing micropowder to the castable can not only improve the high-temperature flexural strength of the castable, but also synergize the activated alumina micropowder to promote the densification of the matrix structure, thereby achieving the effect of improving the castable's resistance to slag erosion, thereby increasing the service life of the castable. Comparative Example 3

[0105] The difference between this comparative example 3 and Example 1 is that step S2 is removed, and the molybdenum-containing fine powder in step S5 is removed. Then, the performance test method in Example 1 is referred to to perform a performance test on the prepared castable. The results are shown in Table 3 below.

[0106] Table 3: Comparison of performance test results of Example 1 and Comparative Example 3

[0107] Performance indicators High temperature flexural strength (MPa) Thermal shock resistance (strength retention, %) Example 1 4.95 98.3 Comparative Example 3 3.48 77.4

[0108] From the performance test results of Example 1 and Comparative Example 3, it can be seen that by first ball-milling magnesium slag, molybdenum disilicide and alumina, adding PVA plasticizer, fully mixing, pressing and molding, and calcining at high temperature, and then crushing and grinding into powder, the obtained molybdenum-containing micropowder is added to the castable. Due to the difference in thermal expansion coefficient in its structure, the crack propagation path will deviate from the original direction, thereby dispersing the concentrated stress of the castable and enhancing the resulting toughness, thereby increasing the critical thermal shock temperature of the castable and improving its thermal shock resistance. Comparative Example 4

[0109] The difference between this comparative example 4 and Example 1 is that step S3 is removed, and the composite micropowder in step S5 is removed. Then, referring to the performance test method in Example 1, the performance test of the prepared castable is carried out, and the results are shown in Table 4 below.

[0110] Table 4: Comparison of performance test results of Example 1 and Comparative Example 4

[0111] Performance indicators High temperature flexural strength (MPa) Slag corrosion depth (mm) Thermal shock resistance (strength retention, %) Oxidation index (%) Example 1 4.95 0.58 98.3 26.6 Comparative Example 4 3.72 0.83 82.4 37.2

[0112] By comparing the performance test results of Example 1 and Comparative Example 4, it can be seen that by dispersing BN micropowder and Si3N4 powder in a toluene solution, adding them to molten coal tar, uniformly mixing and semi-carbonizing and sintering in an autoclave to obtain a composite micropowder, since a composite solid solution is formed during the high-temperature sintering process, the cracks in the matrix are effectively sealed, thereby effectively improving the antioxidant properties of the castable and further improving its service life. Comparative Example 5

[0113] The difference between this comparative example 5 and Example 1 is that step S4 is removed, and the oxygen-containing silicon nitride powder in step S5 is removed. Then, the performance test method in Example 1 is referred to, and the performance test of the prepared castable is carried out. The results are shown in Table 5 below.

[0114] Table 5: Comparison of performance test results of Example 1 and Comparative Example 5

[0115] Performance indicators High temperature flexural strength (MPa) Slag corrosion depth (mm) Oxidation index (%) Example 1 4.95 0.58 26.6 Comparative Example 5 3.62 0.89 34.9

[0116] By comparing the performance test results of Example 1 with those of Comparative Example 5, it can be seen that the rod-shaped and columnar oxygen-containing silicon nitride micropowder synthesized by using silicon powder and quartz powder as raw materials and sintering at high temperature in a nitrogen atmosphere can enhance the mechanical properties of the castable, and can form well-cross-distributed whiskers during the use of the castable, thereby improving the oxidation resistance, high-temperature flexural strength and slag erosion resistance of the castable, thereby improving the service life of the castable.

[0117] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A process for preparing a castable for a blast furnace tapping channel, characterized in that: The steps include: S1: Prepare liquid A and liquid B and calcine at high temperature Calcium nitrate and strontium nitrate are prepared into liquid A, diammonium phosphate and ammonium fluoride are prepared into liquid B, liquid A is then heated in a water bath and liquid B is added, the mixture is stirred and allowed to stand for aging, filtered, washed, dried and ground, and then calcined at high temperature to obtain strontium-containing micropowder; S2: Ball milling, mixing with molybdenum disilicide and calcining The magnesium slag, molybdenum disilicide and alumina are dried and ball-milled, and then PVA plasticizer is added and pressed into shape. After high-temperature calcination and crushing and grinding, molybdenum-containing micropowder is obtained; S3: Disperse BN micropowder and Si3N4 powder and perform semi-carbonization and sintering After BN micropowder and Si3N4 powder are evenly dispersed in a toluene solution, they are then added to the molten coal tar at a uniform speed and placed in an autoclave for reaction and semi-carbonization. After isostatic pressing, high-temperature sintering, and crushing and grinding, composite micropowder is obtained. S4: Nitrogen is introduced and high temperature sintering is performed The Si powder and quartz powder are dispersed at high speed, uniformly mixed, and then sintered at high temperature in a nitrogen atmosphere. After crushing and grinding, oxygen-containing silicon nitride micropowder is obtained; S5: Mix the components to prepare the castable Add brown corundum, white corundum, silicon carbide particles, silicon carbide fine powder, activated alumina micropowder, the above-mentioned strontium-containing micropowder, silicon oxide micropowder, spherical asphalt, the above-mentioned molybdenum-containing micropowder, the above-mentioned composite micropowder, the above-mentioned oxygen-containing silicon nitride micropowder, silicon oxide micropowder, pure calcium aluminate cement and water reducer into a mixer, stir for 10-20 minutes, and dry mix. Then, add water into the mixer at a material-liquid ratio of 1g: (30-40)mL, continue stirring for 5-10 minutes, pour into a mold, vibrate, cure and bake to obtain a castable.

2. The process for preparing a castable for a blast furnace tapping channel according to claim 1, wherein: S1 includes the following steps: S1.1: Dissolve calcium nitrate, strontium nitrate, and deionized water in a material-liquid ratio of (1.3-1.5) g:1 g:(25-35) mL, stirring to obtain Solution A. S1.2: Dissolve diammonium hydrogen phosphate, ammonium fluoride, and deionized water in a material-liquid ratio of 1 g:(2-3) g:(30-40) mL with stirring to obtain Solution B. S1.3: Heat Solution A in a hot water bath at 60-70°C and adjust the pH to 9-10 by adding aqueous ammonia. Then, add Solution B to Solution A while continuing to add aqueous ammonia to maintain the pH at 9-10. Stir for 2-3 hours and allow to age for 20-24 hours to obtain an aged solution. S1.4: Filter the aged liquid, wash it with deionized water and anhydrous ethanol 2-3 times, dry it in an oven, and grind it into a powder to obtain a dry powder with a median diameter of 1-2 μm; S1.5: Place the above-mentioned dry powder in a muffle furnace, heat it to 1150-1250°C at a rate of 5-10°C / min, calcine it, and keep it at this temperature for 1-2 hours, and cool it to room temperature with the furnace to obtain strontium-containing micropowder.

3. The process for preparing a castable for a blast furnace tapping channel according to claim 1, wherein: S2 includes the following steps: S2.1: Place magnesium slag, molybdenum disilicide, and aluminum oxide in a drying oven and dry them at 80-90°C for 12-15 hours to obtain dry magnesium slag, dry molybdenum disilicide, and dry aluminum oxide; S2.2: Add the above-mentioned dried molybdenum disilicide, dried magnesium slag and dried alumina in a mass ratio of 1:(1-2):(8-10) into a planetary ball mill and mill at a speed of 300-400 r / min for 40-50 min to obtain a mixed powder; S2.3: PVA plasticizer is added to the mixed powder, and the mixture is ball-milled for 20-30 minutes. The mixture is then placed in a molding machine and pressed into a columnar body at a pressure of 35-45 MPa to obtain a precursor body. S2.4: Place the above-mentioned precursor body in a calcining furnace and calcine it at a temperature of 1200-1400°C for 2-3 hours. After cooling to room temperature in the furnace, crush and grind it to obtain molybdenum-containing micropowder with a median diameter of 1-2 μm.

4. The process for preparing a castable for a blast furnace tapping channel according to claim 1, wherein: S3 includes the following steps: S3.1: Add BN powder and Si3N4 powder to a toluene solution at a material-liquid ratio of 1 g:(1-3) g:(20-30) mL. Ultrasonic dispersion is performed for 20-30 min. Stir at 400-500 rpm for 20-30 min to obtain a dispersion. S3.2: Place the coal tar pitch in a melting furnace and fully melt it. Then, add the above dispersion into the melting furnace at a constant rate of 5-10 mL / min and disperse it evenly to obtain a mixed melt. S3.3: The mixed melt is placed in an autoclave and reacted for 3-4 hours to achieve semi-carbonization. The mixed melt is then placed in a grinder and ground into a fine powder to obtain carbonized fine powder. S3.4: The carbonized fine powder is isostatically pressed and placed in a sintering furnace. The temperature is raised to 1000-1050°C at a heating rate of 4-6°C / h, and kept warm for 40-50 minutes. The temperature is then raised to 1800-1900°C at a heating rate of 150-180°C / h, and kept warm for 40-50 minutes. After crushing and grinding, a composite micropowder with a median diameter of 1-2 μm is obtained.

5. The process for preparing a castable for a blast furnace tapping channel according to claim 1, wherein: S4 includes the following steps: S4.1: Place Si powder and quartz powder in a high-speed disperser at a mass ratio of 1:2-3, disperse at high speed for 1-2 hours to mix thoroughly, and then place them into a sagger in a loose stacking manner; S4.2: Place the sagger in a sealed high-temperature shuttle kiln, evacuate the kiln, introduce nitrogen, and sinter at 1300-1400°C for 1-2 hours. Cool naturally to room temperature to obtain an oxynitride silicon material. S4.3: Place the above-mentioned oxygen-containing silicon nitride material in a crushing and grinding machine, crush and grind it to obtain oxygen-containing silicon nitride fine powder with a median diameter of 1-2 μm.

6. The process for preparing a castable for a blast furnace tapping channel according to claim 2, wherein: The volume ratio of liquid A to liquid B is 1:(20-25).

7. The process for preparing a castable for a blast furnace tapping channel according to claim 3, characterized in that: The mass percentage of PVA plasticizer in the mixed powder is 3-5%.

8. The process for preparing a castable for a blast furnace tapping channel according to claim 1, wherein: The particle size of spherical asphalt is less than 0.2 mm, the median diameter of activated alumina powder is less than 3 μm, and the median diameter of silica powder is less than 0.8 μm.

9. The process for preparing a castable for a blast furnace tapping channel according to claim 1, wherein: The water reducer is one or more of sodium tripolyphosphate, sodium hexametaphosphate and FDN.

10. A castable for a blast furnace tapping channel prepared by the preparation process according to any one of claims 1 to 9, characterized in that: Calculated by mass percentage, it includes: 5-10% silicon carbide particles, 5-10% silicon carbide fine powder, 2-3% activated alumina micropowder, 2-3% oxygen-containing silicon nitride micropowder, 2-3% strontium-containing micropowder, 1-2% silicon oxide micropowder, 1-2% spherical asphalt, 1-2% molybdenum-containing micropowder, 1-2% composite micropowder, 1-2% pure calcium aluminate cement, 0.6-1% water reducer, and the balance is brown corundum and white corundum.

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