Porous olivine tundish dry material and preparation method thereof

Abstract

The invention discloses a porous olivine tundish dry material and a preparation method thereof, and belongs to the technical field of tundish dry material processing, the porous olivine tundish dry material specifically comprises the following raw materials by mass: 80-100 parts of a composite sand material, 2-3 parts of silicon powder, 10-15 parts of a composite binder, 15-20 parts of modified aerogel and 4-7 parts of a sintering promoter, heat-resistant whiskers are prepared through a molten salt method, and the porous olivine tundish dry material is prepared through a hot melt method. The preparation method comprises the following steps: preparing a composite binder from a dry tundish material, carrying out centrifugal spinning to obtain modified zirconium oxide fibers with a hollow structure, and further preparing modified aerogel from the modified zirconium oxide fibers, aluminum chloride hexahydrate, hydroxyethyl cellulose and epoxy chloropropane, so that the high temperature resistance and mechanical properties of the cured dry tundish material are improved; and the mechanical property is also improved.

Description

Technical Field

[0001] The invention relates to the technical field of tundish dry material processing, and in particular to a porous olivine tundish dry material and a preparation method thereof. Background Art

[0002] As a key refractory material for metallurgical continuous casting, the tundish dry material has been continuously upgraded in recent years with a focus on environmental protection and high performance. The traditional tundish dry material has been gradually replaced by olivine-based, spinel-based and other systems. Olivine, as a natural silicate mineral, is mainly composed of magnesium silicate. It has a high melting point and good thermal stability, and can effectively withstand high temperatures and drastic temperature changes during the smelting process.

[0003] At present, olivine dry tundish material has been widely used in high-temperature environments such as tundishes and furnace linings in steel smelting, and has gradually developed towards porosity and lightweight in the research and development of refractory materials to improve its thermal stability, thermal insulation performance and energy-saving effect. Although olivine dry tundish material has achieved remarkable application results in steel smelting, it still faces some problems in actual use.

[0004] In the prior art, although olivine-based dry tundish materials have a high melting point and good thermal stability, due to the relatively dense molecular structure of olivine and the lack of sufficient porosity, it is difficult to effectively isolate heat at high temperatures and cannot provide ideal thermal insulation.

[0005] When olivine tundish dry material is subjected to high temperature during the smelting process, its relatively large volume density intensifies heat conduction, making it impossible to maintain temperature stability under sufficiently high temperature differences. In addition, the dense crystal structure lacks sufficient microcracks or pores to effectively absorb external stress, which makes it difficult to maintain sufficient toughness at high temperatures and prone to brittle fracture. Secondly, as a silicate mineral, olivine has a certain stability in its crystal structure, but its relatively large thermal expansion coefficient makes it prone to thermal cracking when it experiences rapid changes in high temperature, thereby reducing its resistance to thermal shock and resulting in a decrease in its mechanical strength and durability. Summary of the Invention

[0006] The object of the present invention is to provide a porous olivine tundish dry material and a preparation method thereof, so as to solve the technical problem in the prior art that the high temperature resistance and thermal insulation performance of the tundish dry material after solidification need to be further improved.

[0007] The object of the present invention can be achieved by the following technical solution: a porous olivine tundish dry material, comprising the following raw materials, calculated by mass: 60-80 parts of forsterite fine powder, 25-35 parts of composite sand, 2-3 parts of silicon powder, 10-15 parts of composite binder, 15-20 parts of modified aerogel and 4-7 parts of sintering promoter;

[0008] The composite sand material is composed of sintered magnesia and fused magnesia in a mass ratio of 20:15, and the sintering promoting agent is one or more of borax, iron oxide, sodium tripolyphosphate and sodium silicate nonahydrate.

[0009] Furthermore, the composite adhesive is prepared by the following steps:

[0010] A1. Sodium sulfate, aluminum fluoride, aluminum sulfate and kaolin are placed in a crucible, heated, and post-treated to obtain heat-resistant whiskers;

[0011] The preparation reaction principle of heat-resistant whiskers is:

[0012] At high temperature, sodium sulfate forms a liquid phase environment, promoting the dehydroxylation of kaolin to generate active alumina and silica at high temperature. Aluminum sulfate decomposes under heat to generate alumina, replenishing the aluminum source. Aluminum fluoride acts as a mineralizer to reduce the energy barrier for crystal nucleation and promote the directional growth of whiskers. In the range of 800-1000℃, alumina and silica react to generate mullite through solid-phase reaction. The shear force of the molten salt induces the crystals to grow preferentially along specific crystal planes, eventually forming needle-shaped heat-resistant whiskers. In the post-treatment process, deionized water can wash away the residual sodium sulfate molten salt and unreacted aluminum fluoride to obtain heat-resistant whiskers.

[0013] A2. Phosphoric acid and deionized water are placed in a reaction kettle, heated to 20-25°C, aluminum hydroxide is added, and the mixture is kept warm for 20-24 hours. Chromium trioxide is added and the mixture is kept warm for 2-4 hours to obtain a composite binder precursor solution.

[0014] A3. Evenly mix the composite binder precursor liquid, calcium hydroxide and heat-resistant whiskers to obtain a composite binder.

[0015] The preparation reaction principle of the composite binder is:

[0016] During the reaction, phosphoric acid dissociates in deionized water to form hydrogen ions and hydrogen phosphate ions, which neutralize with aluminum hydroxide to form aluminum dihydrogen phosphate. After the addition of chromium trioxide, the chromium ions on its surface form a complex coordination structure with the aluminum ions in the aluminum dihydrogen phosphate. Calcium hydroxide provides an alkaline environment to promote gel formation, and heat-resistant whiskers are embedded in the gel as a rigid skeleton to obtain a composite adhesive.

[0017] Furthermore, in step A1, the amount of sodium sulfate, aluminum fluoride, aluminum sulfate and kaolin is 10-15g:1-2g:8-12g:4-6g, and the post-processing step includes: after the reaction is completed, waiting for the product to cool to room temperature, washing it with deionized water 2-3 times, transferring it to an oven at a temperature of 100-110°C, and drying it to constant weight to obtain heat-resistant whiskers; in step A2, the amount ratio of phosphoric acid, deionized water, aluminum hydroxide and chromium trioxide is 10-15mL:7-10mL:3-5g:2-4g; in step A3, the amount ratio of the composite binder precursor solution, calcium hydroxide and heat-resistant whiskers is 10-12g:0.5-1g:0.5-1g.

[0018] Furthermore, the modified aerogel is prepared by the following steps:

[0019] B1. Place aluminum chloride hexahydrate, deionized water, and ethanol in a reaction kettle, stir for 10-15 minutes, add modified zirconia fiber and hydroxyethyl cellulose, and stir for 2-4 hours to obtain a mixed slurry;

[0020] B2. Place the mixed slurry and epichlorohydrin in a reactor, stir for 5-10 minutes, let stand for 4-6 hours, replace the solvent, and obtain a modified aerogel precursor;

[0021] B3. Place the modified aerogel precursor in a reactor and perform supercritical drying to obtain the modified aerogel.

[0022] The preparation reaction principle of aerogel is:

[0023] During the reaction, aluminum chloride hexahydrate dissociates into aluminum ions and chloride ions in deionized water to form an aluminum hydroxide sol network. The modified zirconia fiber is embedded in the network through hydrogen bonding between its surface hydroxyl groups and the aluminum hydroxide sol. Hydroxyethyl cellulose acts as a dispersant and is adsorbed on the modified zirconia fiber and sol particles through its long-chain molecules, making the substance evenly dispersed through steric hindrance. The epoxy group of epichlorohydrin undergoes a ring-opening reaction with the hydroxyl group on the surface of aluminum hydroxide in the mixed slurry to form Al-OC chemical bonds, generating a three-dimensional interpenetrating network structure. After the solvent is replaced by ethanol, it is further supercritically dried with carbon dioxide to obtain a modified aerogel.

[0024] Furthermore, in step B1, the usage ratio of aluminum chloride hexahydrate, deionized water, ethanol, modified zirconia fiber and hydroxyethyl cellulose is 5-8g:80-100mL:50-60mL:0.5-1g:0.1-0.4g; in step B2, the usage ratio of the mixed slurry and is 10-12g:2-4mL.

[0025] Furthermore, the supercritical drying step includes: placing the modified aerogel precursor in a reactor, introducing carbon dioxide gas at an air inlet rate of 0.3 MPa / min, and after the reactor is pressurized to 8 MPa, heating it to 30-40°C, continuing to pressurize it to 13 MPa, keeping the temperature for 25-35 minutes, discharging carbon dioxide gas and ethanol gas while maintaining the pressure, and releasing the pressure to obtain the modified aerogel.

[0026] Furthermore, the modified zirconia fiber is prepared by the following method:

[0027] C1. Place zirconium oxychloride octahydrate, yttrium nitrate hexahydrate, deionized water, and ethanol in a reaction kettle, stir for 10-15 minutes, add polyvinyl pyrrolidone solution, and stir for 4-6 hours to obtain a spinning solution;

[0028] C2. The spinning solution is centrifugally spun and post-treated to obtain modified zirconia fibers.

[0029] Preparation reaction principle of modified zirconia fiber:

[0030] During the reaction process, the spinning solution is centrifuged to form a gel layer to maintain the fiber morphology. The ionic radius of yttrium ions is significantly different from that of zirconium ions. Through high-temperature calcination, yttrium ions replace part of the zirconium ions and enter the zirconia lattice to form a yttrium-stabilized zirconia solid solution. This doping causes lattice distortion, inhibits the transformation of zirconia from high-temperature tetragonal phase to low-temperature monoclinic phase, and maintains the metastable tetragonal phase structure. Under high temperature conditions, the octahydrate zirconium oxychloride on the surface of the fiber preferentially decomposes into zirconium dioxide crystal nuclei, forming a concentration gradient from the center to the surface, driving the outward diffusion of inorganic salts. The octahydrate zirconium oxychloride diffuses faster than zirconium dioxide, triggering the Kirkendall effect, causing vacancies to aggregate to form a hollow structure. At the same time, the decomposition of polyvinyl pyrrolidone produces gas, which drives the internal material to migrate to the surface. The zirconium dioxide crystal nuclei form a dense shell through directional attachment, and a modified zirconia fiber with a hollow structure is obtained.

[0031] Furthermore, in step C1, the amount ratio of the zirconium oxychloride octahydrate, yttrium nitrate hexahydrate, deionized water and ethanol is 10-12mL:0.5-1g:10-15mL:10-15mL, and the polyvinyl pyrrolidone solution is composed of polyvinyl pyrrolidone and deionized water in a ratio of 1-2g:10-15mL; in step C2, the post-treatment step includes: after spinning is completed, transferring the fiber bundle to an oven at a temperature of 55-65°C and drying for 12h, and calcining to obtain modified zirconium oxide fiber.

[0032] The present invention also provides a method for preparing a porous olivine tundish dry material, comprising the following steps:

[0033] S1. Add composite sand, silicon powder, modified aerogel and sintering agent into a grinder, grind them and pass them through a 400-600 mesh sieve to obtain a mixture;

[0034] S2. After adding the mixed material into the homogenizer, add the composite binder into the homogenizer, and homogenize and mix for 8-10 minutes to obtain the tundish dry material.

[0035] The present invention has the following beneficial effects:

[0036] 1. The present invention prepares heat-resistant whiskers by a molten salt method, uses phosphoric acid, aluminum hydroxide and chromium trioxide as raw materials, adopts a constant temperature water bath method to prepare a composite binder precursor solution, adds calcium hydroxide as a curing agent to the precursor solution, adds heat-resistant whiskers as a reinforcing agent to prepare a composite binder, prepares a modified zirconia fiber with a hollow structure by centrifugal spinning, further prepares a modified aerogel using the modified zirconia fiber, aluminum chloride hexahydrate, hydroxyethyl cellulose and epichlorohydrin as raw materials, and mixes composite sand material, silicon powder, composite binder, modified aerogel and sintering promoting agent to obtain a tundish dry material; The invention prepares heat-resistant whiskers through a molten salt method. The Al-O and Si-O bonds in the molecular structure of the heat-resistant whiskers have very high bond energy, making the heat-resistant whiskers not easily decomposed or undergoing phase change at high temperatures. The heat-resistant whiskers are prepared together with phosphoric acid, aluminum hydroxide and chromium trioxide to prepare a composite binder, so that the tundish dry material can maintain good thermal shock resistance under high-temperature working conditions, effectively resist the erosion and thermal shock of molten steel, and improve the high-temperature stability of the tundish dry material. The heat-resistant whiskers have a high aspect ratio and excellent mechanical properties, and can form a three-dimensional network structure in the composite binder, thereby improving the mechanical properties of the tundish dry material.

[0037] 2. The present invention also prepares modified zirconia fibers with a hollow structure by centrifugal spinning and calcining, and further adds the fibers to the preparation of alumina-modified aerogel to obtain modified aerogel. Zirconia itself has a high melting point and excellent high-temperature resistance. The modified zirconia fibers prepared by centrifugal spinning not only retain the high-temperature stability of zirconia, but also reduce heat conduction and density by designing a hollow structure, thereby improving the thermal insulation performance of the intermediate dry material and reducing its volume density. The modified aerogel is prepared with modified zirconia fibers as reinforcement, aluminum chloride hexahydrate as aluminum source, hydroxyethyl cellulose as dispersant, and epichlorohydrin as cross-linking agent. The aerogel itself has extremely low thermal conductivity and a porous structure. These tiny pores can significantly reduce the density of the material and improve its thermal insulation performance. The modified aerogel The gel further combines the high-temperature stability of zirconia fibers, allowing the entire tundish dry material to maintain structural stability at high temperatures. At the same time, the zirconia fibers in the modified aerogel serve as reinforcements, forming a good interface bond with the aerogel matrix, thereby improving the mechanical properties of the aerogel. The low density and high porosity of the aerogel also help to reduce the weight of the tundish dry material and improve its thermal shock resistance. The surface of the zirconia fibers in the modified aerogel contains hydroxyl groups, which chemically bond with the aluminum phosphate matrix in the composite binder to form a strong interface bond. This chemical bond not only enhances the bonding force between the aerogel and the binder, but also helps to effectively transfer stress between the two. The high strength and toughness of the modified zirconia fibers can withstand and disperse these stresses, thereby improving the overall mechanical properties of the tundish dry material. DETAILED DESCRIPTION

[0038] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] The hydroxyethyl cellulose used in the present invention was purchased from Guangdong Mingtong Biotechnology Co., Ltd., with a CAS number of 9004-62-0 and a product specification of 1 kg.

[0040] The sintered magnesia used in the present invention is purchased from Pengxia Furnace Lining Material Processing Plant in Lingshou County, with a density of 3.60 g / cm 3 , particle size is 5μm;

[0041] The fused magnesia used in the present invention is purchased from Haicheng Taiding Huaxin Mineral Products Processing Co., Ltd., with a model of TDNH-97 and a particle size of 200 mesh;

[0042] The forsterite fine powder used in the present invention was purchased from Xinmi Zhengyang Casting Material Factory, with a particle size of 300 mesh and a magnesium content of 46.3;

[0043] The silicon powder used in the present invention is purchased from Shandong Hanxinzun New Materials Co., Ltd., with a brand name of SF98 and a particle size of 200 mesh.

[0044] Example 1

[0045] This embodiment provides a method for preparing a composite binder for a porous olivine tundish dry material, comprising the following steps:

[0046] Step (1) Preparation of heat-resistant whiskers

[0047] Weigh: 100 g of sodium sulfate, 10 g of aluminum fluoride, 80 g of aluminum sulfate and 40 g of kaolin, place them in a crucible, gradually heat them to 700°C, 800°C, 900°C, 1000°C, 1100°C and 1200°C at a heating rate of 5°C, and keep them reacting at each temperature for 1.5 h. After the reaction is completed, wait for the product to cool to room temperature, wash it twice with deionized water, transfer it to an oven at a temperature of 100°C, and dry it to constant weight to obtain heat-resistant whiskers.

[0048] Step (2): preparing a composite adhesive

[0049] Weigh: 100 mL of phosphoric acid and 70 mL of deionized water are placed in a reactor, heated to 20°C, 30 g of aluminum hydroxide is added, and the reaction is kept warm for 20 hours. 20 g of chromium trioxide is added, and the reaction is kept warm for 2 hours to obtain a composite binder precursor solution;

[0050] Weigh 100 g of a composite binder precursor solution, 5 g of calcium hydroxide, and 5 g of heat-resistant whiskers, and mix them evenly to obtain a composite binder.

[0051] Example 2

[0052] This embodiment provides a method for preparing a composite binder for a porous olivine tundish dry material, comprising the following steps:

[0053] Step (1) Preparation of heat-resistant whiskers

[0054] Weigh: 125 g of sodium sulfate, 15 g of aluminum fluoride, 100 g of aluminum sulfate and 50 g of kaolin, place them in a crucible, gradually heat them to 700°C, 800°C, 900°C, 1000°C, 1100°C and 1200°C at a heating rate of 5°C, and react at each temperature for 2 hours. After the reaction is completed, wait for the product to cool to room temperature, wash it twice with deionized water, transfer it to an oven at a temperature of 105°C, and dry it to constant weight to obtain heat-resistant whiskers.

[0055] Step (2): preparing a composite adhesive

[0056] Weigh: 125 mL of phosphoric acid and 85 mL of deionized water are placed in a reactor, heated to 22°C, 40 g of aluminum hydroxide is added, and the reaction is kept warm for 22 hours. 30 g of chromium trioxide is added, and the reaction is kept warm for 3 hours to obtain a composite binder precursor solution;

[0057] Weigh: 110 g of composite binder precursor solution, 7 g of calcium hydroxide and 7 g of heat-resistant whiskers and mix them evenly to obtain a composite binder.

[0058] Example 3

[0059] This embodiment provides a method for preparing a composite binder for a porous olivine tundish dry material, comprising the following steps:

[0060] Step (1) Preparation of heat-resistant whiskers

[0061] Weigh: 150 g of sodium sulfate, 20 g of aluminum fluoride, 120 g of aluminum sulfate and 60 g of kaolin, place them in a crucible, gradually heat them to 700°C, 800°C, 900°C, 1000°C, 1100°C and 1200°C at a heating rate of 5°C, and react at each temperature for 2.5 hours. After the reaction is completed, wait for the product to cool to room temperature, wash it three times with deionized water, transfer it to an oven at a temperature of 110°C, and dry it to constant weight to obtain heat-resistant whiskers.

[0062] Step (2): preparing a composite adhesive

[0063] Weigh: 150 mL of phosphoric acid and 100 mL of deionized water are placed in a reactor, heated to 25°C, 50 g of aluminum hydroxide is added, and the reaction is kept warm for 24 hours. 40 g of chromium trioxide is added and the reaction is kept warm for 4 hours to obtain a composite binder precursor solution;

[0064] Weigh 120 g of a composite binder precursor solution, 10 g of calcium hydroxide, and 10 g of heat-resistant whiskers, and mix them evenly to obtain a composite binder.

[0065] Example 4

[0066] This embodiment provides a method for preparing modified zirconia fiber for preparing modified aerogel for porous olivine tundish dry material, comprising the following steps:

[0067] Step ①, prepare spinning solution,

[0068] Weigh: 10 g of polyvinyl pyrrolidone and 100 mL of deionized water, mix well to obtain a polyvinyl pyrrolidone solution, set aside;

[0069] Weigh 100 mL of zirconium oxychloride octahydrate, 5 g of yttrium nitrate hexahydrate, 100 mL of deionized water, and 100 mL of ethanol, place them in a reaction kettle, stir for 10 minutes, add polyvinyl pyrrolidone solution, and stir for 4 hours to obtain a spinning solution.

[0070] Step ②: Preparation of modified zirconia fiber

[0071] The spinning solution was injected into the feed port of the electrospinning machine, and the spinning solution was ejected through the nozzle. At the same time, the electrostatic field was used to stretch it into filaments and form fiber bundles on an aluminum foil collector. The fiber bundles were transferred to an oven at a temperature of 55°C and dried for 12 hours. The temperature was then increased to 600°C at a heating rate of 1°C / min, kept warm for 1 hour, and then increased to 1200°C at a heating rate of 3°C / min, kept warm for 1 hour, cooled naturally, and chopped into 1mm pieces to obtain modified zirconia fibers.

[0072] Example 5

[0073] This embodiment provides a method for preparing modified zirconia fiber for preparing modified aerogel for porous olivine tundish dry material, comprising the following steps:

[0074] Step ①, prepare spinning solution,

[0075] Weigh: 15 g of polyvinyl pyrrolidone and 125 mL of deionized water and mix them evenly to obtain a polyvinyl pyrrolidone solution for later use;

[0076] Weigh 110 mL of zirconium oxychloride octahydrate, 7 g of yttrium nitrate hexahydrate, 125 mL of deionized water, and 125 mL of ethanol into a reaction kettle, stir for 13 minutes, add polyvinyl pyrrolidone solution, and stir for 5 hours to obtain a spinning solution.

[0077] Step ②: Preparation of modified zirconia fiber

[0078] The spinning solution was injected into the feed port of the electrospinning machine, and the spinning solution was ejected through the nozzle. At the same time, the electrostatic field was used to stretch it into filaments and form fiber bundles on an aluminum foil collector. The fiber bundles were transferred to an oven at 60°C and dried for 12 hours. The temperature was then increased to 600°C at a heating rate of 1°C / min and kept warm for 1 hour. The temperature was then increased to 1200°C at a heating rate of 3°C / min and kept warm for 1 hour. The fibers were naturally cooled and chopped into 3 mm pieces to obtain modified zirconia fibers.

[0079] Example 6

[0080] This embodiment provides a method for preparing modified zirconia fiber for preparing modified aerogel for porous olivine tundish dry material, comprising the following steps:

[0081] Step ①, prepare spinning solution,

[0082] Weigh: 20 g of polyvinyl pyrrolidone and 150 mL of deionized water and mix them evenly to obtain a polyvinyl pyrrolidone solution for later use;

[0083] Weigh 120 mL of zirconium oxychloride octahydrate, 10 g of yttrium nitrate hexahydrate, 150 mL of deionized water, and 150 mL of ethanol, place them in a reactor, stir for 15 minutes, add polyvinyl pyrrolidone solution, and stir for 6 hours to obtain a spinning solution.

[0084] Step ②: Preparation of modified zirconia fiber

[0085] The spinning solution was injected into the feed port of the electrospinning machine, and the spinning solution was ejected through the nozzle. At the same time, the electrostatic field was used to stretch it into filaments and form fiber bundles on an aluminum foil collector. The fiber bundles were transferred to an oven at 65°C and dried for 12 hours. The temperature was then increased to 600°C at a heating rate of 1°C / min and kept warm for 1 hour. The temperature was then increased to 1200°C at a heating rate of 3°C / min and kept warm for 1 hour. The fibers were naturally cooled and chopped into 5 mm pieces to obtain modified zirconia fibers.

[0086] Example 7

[0087] This embodiment provides a method for preparing a modified aerogel for a porous olivine tundish dry material, comprising the following steps:

[0088] Step I: Preparation of modified aerogel precursor

[0089] Weigh 50 g of aluminum chloride hexahydrate, 800 mL of deionized water, and 500 mL of ethanol into a reactor and stir for 10 min. Then, add 5 g of the modified zirconia fiber prepared in Example 6 and 1 g of hydroxyethyl cellulose and stir for 2 h to obtain a mixed slurry.

[0090] Weigh: 100 g of the mixed slurry and 20 mL of epichlorohydrin were placed in a reactor, stirred for 5 minutes, allowed to stand for 4 hours, and the solvent was replaced with ethanol every 12 hours for a total of 4 times to obtain a modified aerogel precursor.

[0091] Step II: Preparation of modified aerogel

[0092] The modified aerogel precursor was placed in a reactor, and carbon dioxide gas was introduced at an air inlet rate of 0.3 MPa / min. After the reactor was pressurized to 8 MPa, the temperature was raised to 30°C, and the pressure was further increased to 13 MPa. The reaction was kept warm for 25 minutes, and the carbon dioxide gas and ethanol gas were discharged while maintaining the pressure, and the pressure was released to obtain the modified aerogel.

[0093] Example 8

[0094] This embodiment provides a method for preparing a modified aerogel for a porous olivine tundish dry material, comprising the following steps:

[0095] Step I: Preparation of modified aerogel precursor

[0096] Weigh 60 g of aluminum chloride hexahydrate, 900 mL of deionized water, and 550 mL of ethanol into a reactor and stir for 13 min. Then, add 7 g of the modified zirconia fiber prepared in Example 6 and 2 g of hydroxyethyl cellulose and stir for 3 h to obtain a mixed slurry.

[0097] Weigh: 110 g of the mixed slurry and 30 mL of epichlorohydrin are placed in a reactor, stirred for 7 minutes, allowed to stand for 5 hours, and the solvent is replaced with ethanol every 12 hours for a total of 4 times to obtain a modified aerogel precursor.

[0098] Step II: Preparation of modified aerogel

[0099] The modified aerogel precursor was placed in a reactor, and carbon dioxide gas was introduced at an air inlet rate of 0.3 MPa / min. After the reactor was pressurized to 8 MPa, the temperature was raised to 35°C, and the pressure was further increased to 13 MPa. The reaction was kept warm for 30 minutes, and the carbon dioxide gas and ethanol gas were discharged while maintaining the pressure, and the pressure was released to obtain the modified aerogel.

[0100] Example 9

[0101] This embodiment provides a method for preparing a modified aerogel for a porous olivine tundish dry material, comprising the following steps:

[0102] Step I: Preparation of modified aerogel precursor

[0103] Weigh 80 g of aluminum chloride hexahydrate, 1000 mL of deionized water, and 600 mL of ethanol into a reactor, stir for 15 min, add 10 g of the modified zirconia fiber prepared in Example 6 and 4 g of hydroxyethyl cellulose, and stir for 4 h to obtain a mixed slurry;

[0104] Weigh: 120 g of the mixed slurry and 40 mL of epichlorohydrin are placed in a reactor, stirred for 10 minutes, allowed to stand for 6 hours, and the solvent is replaced with ethanol every 12 hours for a total of 4 times to obtain a modified aerogel precursor.

[0105] Step II: Preparation of modified aerogel

[0106] The modified aerogel precursor was placed in a reactor, and carbon dioxide gas was introduced at an air inlet rate of 0.3 MPa / min. After the reactor was pressurized to 8 MPa, the temperature was raised to 40°C, and the pressure was further increased to 13 MPa. The reaction was kept warm for 35 minutes, and the carbon dioxide gas and ethanol gas were discharged while maintaining the pressure, and the pressure was released to obtain the modified aerogel.

[0107] Example 10

[0108] This embodiment provides a method for preparing a porous olivine tundish dry material, comprising the following steps:

[0109] Sintered magnesia and fused magnesia are mixed uniformly in a mass ratio of 20:15 to obtain a composite sand material for standby use;

[0110] Weigh out by mass: 60 parts of forsterite fine powder, 25 parts of composite sand, 2 parts of silica fume, 10 parts of composite binder, 15 parts of modified aerogel and 4 parts of sodium tripolyphosphate;

[0111] The composite sand material, silicon powder, modified aerogel and sintering promoting agent are added into a grinder, crushed and passed through a 400-mesh sieve to obtain a mixture;

[0112] After the mixed material is added into the homogenizer, the composite binder is added into the homogenizer, and the mixture is homogenized and mixed for 8 minutes to obtain the tundish dry material.

[0113] Example 11

[0114] This embodiment provides a method for preparing a porous olivine tundish dry material, comprising the following steps:

[0115] Sintered magnesia and fused magnesia are mixed uniformly in a mass ratio of 20:15 to obtain a composite sand material for standby use;

[0116] Weigh out by mass: 70 parts of forsterite fine powder, 30 parts of composite sand, 2.5 parts of silica fume, 13 parts of composite binder, 17 parts of modified aerogel and 6 parts of sodium tripolyphosphate;

[0117] The composite sand material, silicon powder, modified aerogel and sintering promoting agent are added into a grinder, crushed and passed through a 500-mesh sieve to obtain a mixture;

[0118] After the mixed material is added into the homogenizer, the composite binder is added into the homogenizer, and the mixture is homogenized and mixed for 9 minutes to obtain the tundish dry material.

[0119] Example 12

[0120] This embodiment provides a method for preparing a porous olivine tundish dry material, comprising the following steps:

[0121] Sintered magnesia and fused magnesia are mixed uniformly in a mass ratio of 20:15 to obtain a composite sand material for standby use;

[0122] Weigh the following by mass: 80 parts of forsterite fine powder, 35 parts of composite sand, 3 parts of silicon powder, 15 parts of the composite binder prepared in Example 3, 20 parts of the modified aerogel prepared in Example 9, and 7 parts of sodium tripolyphosphate;

[0123] The composite sand material, silicon powder, modified aerogel and sintering promoting agent are added into a grinder, crushed and passed through a 600-mesh sieve to obtain a mixture;

[0124] After the mixed material is added into the homogenizer, the composite binder is added into the homogenizer, and the mixture is homogenized and mixed for 10 minutes to obtain the tundish dry material.

[0125] Comparative Example 1

[0126] The difference between this comparative example and Example 12 is that, in the preparation process of the composite adhesive used, the use of heat-resistant whiskers is omitted in step (2).

[0127] Comparative Example 2

[0128] The difference between this comparative example and Example 12 is that in the preparation process of the modified aerogel used, the modified zirconia fiber is omitted in step I.

[0129] Comparative Example 3

[0130] The difference between this comparative example and Example 12 is that the modified aerogel is not used.

[0131] Performance testing:

[0132] The tundish dry materials prepared in Examples 10-12 and Comparative Examples 1-3 were further prepared into solidified samples with reference to the standard GB / T 4513.5-2017 "Monoshaped Refractory Materials Part 5: Preparation and Pretreatment of Samples". The bulk density, permanent linear change upon heating, room temperature flexural strength and high temperature flexural strength of the solidified samples prepared in Examples 10-12 and Comparative Examples 1-3 were tested with reference to the standard GB / T 4513.6-2017 "Monoshaped Refractory Materials Part 6: Determination of Physical Properties". The thermal shock resistance and thermal conductivity of the solidified samples prepared in Examples 10-12 and Comparative Examples 1-3 were tested with reference to the standard GB / T 4513.8-2017 "Monoshaped Refractory Materials Part 8: Determination of Special Properties". The specific data are shown in Table 1.

[0133] Table 1 - Performance test data of each sample

[0134]

[0135] Data Analysis:

[0136] Comparing and analyzing the data in Table 1 above, the bulk density of the solidified sample of the tundish dry material prepared by the present invention is 0.6 g·cm -3 , heating permanent linear change is -0.2%, high temperature flexural strength is 10.5MPa, room temperature flexural strength is 6.8MPa, thermal conductivity is 0.15W·(m·K) -1 And the residual flexural strength percentage is 76.3%;

[0137] By comparing the data of Example 12 and Comparative Example 1, it can be found that the permanent linear change after heating, the residual flexural strength, the high-temperature flexural strength and the room-temperature flexural strength of Comparative Example 1 are significantly reduced, indicating that the present invention prepares heat-resistant whiskers by a molten salt method, and the Al-O and Si-O bonds in the molecular structure of the heat-resistant whiskers have very high bond energy, making the heat-resistant whiskers less likely to decompose or undergo phase change at high temperatures. The heat-resistant whiskers are prepared together with phosphoric acid, aluminum hydroxide and chromium trioxide to form a composite binder, so that the tundish dry material can maintain good thermal shock resistance under high-temperature working conditions, effectively resist erosion and thermal shock of molten steel, and improve the high-temperature stability of the tundish dry material. In addition, the heat-resistant whiskers have a high aspect ratio and excellent mechanical properties, and can form a three-dimensional network structure in the composite binder, thereby improving the mechanical properties of the tundish dry material.

[0138] By comparing the data of Example 12 and Comparative Example 2, it can be found that the bulk density and thermal conductivity of Comparative Example 2 are significantly increased, and the permanent linear change upon heating, residual flexural strength, high-temperature flexural strength, and room-temperature flexural strength are significantly decreased. This indicates that the present invention prepares modified zirconia fibers with a hollow structure by centrifugal spinning and calcination, and further adds the fibers to the preparation of alumina-modified aerogel to obtain modified aerogel. Zirconia itself has a high melting point and excellent high-temperature resistance. The modified zirconia fibers prepared by centrifugal spinning not only retain the high-temperature stability of zirconia, but also reduce heat conduction by designing a hollow structure, thereby improving the thermal insulation performance of the tundish dry material. The surface of the zirconia fibers in the modified aerogel contains hydroxyl groups, which chemically bond with the aluminum phosphate matrix in the composite binder to form a strong interfacial bond. This chemical bonding not only enhances the bonding force between the aerogel and the binder, but also contributes to the effective transfer of stress between the two. The high strength and toughness of the modified zirconia fibers can withstand and disperse these stresses, thereby improving the overall mechanical properties of the tundish dry material.

[0139] By comparing the data of Example 12 and Comparative Example 3, it can be found that the volume density and thermal conductivity of Comparative Example 3 are significantly increased, and the permanent linear change after heating, the residual flexural strength, the high-temperature flexural strength and the room-temperature flexural strength are significantly reduced, indicating that the present invention prepares a modified zirconia fiber with a hollow structure by centrifugal spinning and calcination, and further adds it to the preparation of alumina-modified aerogel to obtain a modified aerogel. Zirconia itself has a high melting point and excellent high-temperature resistance. The modified zirconia fiber prepared by centrifugal spinning not only retains the high-temperature stability of zirconia, but also reduces heat conduction by designing a hollow structure, thereby improving the thermal insulation performance of the intermediate dry material. The modified aerogel is prepared with modified zirconia fiber as a reinforcement, aluminum chloride hexahydrate as an aluminum source, hydroxyethyl cellulose as a dispersant, and epichlorohydrin as a cross-linking agent, and the aerogel The modified aerogel has extremely low thermal conductivity. The high-temperature stability of zirconia fiber is further combined with the modified aerogel, so that the entire tundish dry material can still maintain structural stability at high temperatures. At the same time, the zirconia fiber in the modified aerogel acts as a reinforcement and forms a good interface bond with the aerogel matrix, thereby improving the mechanical properties of the aerogel. The low density and high porosity of the aerogel also help to reduce the weight of the tundish dry material and improve its thermal shock resistance. The surface of the zirconia fiber in the modified aerogel contains hydroxyl groups. These groups chemically bond with the aluminum phosphate matrix in the composite binder to form a strong interface bond. This chemical bond not only enhances the bonding force between the aerogel and the binder, but also helps to effectively transfer stress between the two. The high strength and toughness of the modified zirconia fiber can withstand and disperse these stresses, thereby improving the overall mechanical properties of the tundish dry material.

[0140] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A porous olivine tundish dry material, characterized in that: The invention comprises the following raw materials in parts by mass: 60-80 parts of forsterite fine powder, 25-35 parts of composite sand, 2-3 parts of silicon powder, 10-15 parts of composite binder, 15-20 parts of modified aerogel and 4-7 parts of sintering promoter; The composite sand material is composed of sintered magnesia and fused magnesia in a mass ratio of 20:15, and the sintering promoting agent is one or more of borax, iron oxide, sodium tripolyphosphate and sodium silicate nonahydrate.

2. The porous olivine tundish dry material according to claim 1, characterized in that: The composite adhesive is prepared by the following steps: A1. Sodium sulfate, aluminum fluoride, aluminum sulfate and kaolin are placed in a crucible, heated, and post-treated to obtain heat-resistant whiskers; A2. Phosphoric acid and deionized water are placed in a reaction kettle, heated to 20-25°C, aluminum hydroxide is added, and the mixture is kept warm for 20-24 hours. Chromium trioxide is added and the mixture is kept warm for 2-4 hours to obtain a composite binder precursor solution. A3. Evenly mix the composite binder precursor liquid, calcium hydroxide and heat-resistant whiskers to obtain a composite binder.

3. The porous olivine tundish dry material according to claim 2, characterized in that: In step A1, the amount of sodium sulfate, aluminum fluoride, aluminum sulfate and kaolin is 10-15g:1-2g:8-12g:4-6g; in step A2, the amount ratio of phosphoric acid, deionized water, aluminum hydroxide and chromium trioxide is 10-15mL:7-10mL:3-5g:2-4g; in step A3, the amount ratio of the composite binder precursor solution, calcium hydroxide and heat-resistant whisker is 10-12g:0.5-1g:0.5-1g.

4. The porous olivine tundish dry material according to claim 1, characterized in that: The modified aerogel is prepared by the following steps: B1. Place aluminum chloride hexahydrate, deionized water, and ethanol in a reaction kettle, stir for 10-15 minutes, add modified zirconia fiber and hydroxyethyl cellulose, and stir for 2-4 hours to obtain a mixed slurry; B2. Place the mixed slurry and epichlorohydrin in a reactor, stir for 5-10 minutes, let stand for 4-6 hours, replace the solvent, and obtain a modified aerogel precursor; B3. Place the modified aerogel precursor in a reactor and perform supercritical drying to obtain the modified aerogel.

5. The porous olivine tundish dry material according to claim 4, characterized in that: In step B1, the amount ratio of the aluminum chloride hexahydrate, deionized water, ethanol, modified zirconia fiber and hydroxyethyl cellulose is 5-8g:80-100mL:50-60mL:0.5-1g:0.1-0.4g; in step B2, the amount ratio of the mixed slurry is 10-12g:2-4mL.

6. The porous olivine tundish dry material according to claim 4, characterized in that: The supercritical drying step includes: placing the modified aerogel precursor in a reactor, introducing carbon dioxide gas at an air inlet rate of 0.3 MPa / min, raising the temperature to 30-40°C after the reactor is pressurized to 8 MPa, further pressurizing to 13 MPa, maintaining the temperature for reaction for 25-35 minutes, exhausting the gas while maintaining the pressure, and releasing the pressure to obtain the modified aerogel.

7. The porous olivine tundish dry material according to claim 1, characterized in that: The modified zirconia fiber is prepared by the following method: C1. Place zirconium oxychloride octahydrate, yttrium nitrate hexahydrate, deionized water, and ethanol in a reaction kettle, stir for 10-15 minutes, add polyvinyl pyrrolidone solution, and stir for 4-6 hours to obtain a spinning solution; C2. The spinning solution is centrifugally spun and post-treated to obtain modified zirconia fibers.

8. The porous olivine tundish dry material according to claim 7, characterized in that: In step C1, the usage ratio of the zirconium oxychloride octahydrate, yttrium nitrate hexahydrate, deionized water and ethanol is 10-12 mL:0.5-1 g:10-15 mL:10-15 mL.

9. The porous olivine dry tundish material according to any one of claims 1 to 8, characterized in that: The method for preparing the porous olivine tundish dry material comprises the following steps: S1. Add composite sand, silicon powder, modified aerogel and sintering agent into a grinder, grind them and pass them through a 400-600 mesh sieve to obtain a mixture; S2. After adding the mixed material into the homogenizer, add the composite binder into the homogenizer, and homogenize and mix for 8-10 minutes to obtain the tundish dry material.

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