Preparation method of porous aggregate toughened high thermal shock resistance chrome corundum-spinel type air brick

Abstract

A method for preparing a porous aggregate-reinforced, highly thermally shock resistant chromium corundum-spinel permeable brick involves: Alumina micropowder is poured into a pelletizing machine; during the rotation of the pelletizing machine, zinc chloride solution is uniformly sprayed into the alumina micropowder; pelletizing is stopped after the powder gradually agglomerates and forms granules; the granulated pellets are dried and calcined to obtain alumina spherical aggregate; the aggregate particles are then graded into spherical particles of different sizes; ethanol and phenolic resin are mixed in a mass ratio to prepare a coating solution; alumina spherical particles of different sizes are completely immersed in the resin coating solution for 20 minutes, and dried to obtain resin-coated spherical particles; finally, resin-coated alumina spherical particles, tabular corundum particles, white corundum powder, spinel powder, alumina micropowder, chromium oxide micropowder, and pure calcium aluminate cement are used as raw materials, with the addition of a high-efficiency water-reducing agent, and the mixture is dry-mixed evenly, then water is added to form a mud mixture; the mud is then molded, demolded, dried, and fired to prepare the permeable brick of this invention.

Description

Technical Field

[0001] This invention belongs to the field of inorganic non-metallic materials technology, specifically relating to a method for preparing a porous aggregate-toughened, highly thermally shock resistant chromium corundum-spinel permeable brick. Background Technology

[0002] Ladle permeable bricks are key functional components in the ladle refining process of molten steel. Their function is to stir the molten steel with argon gas, homogenize the temperature and composition of the steel, accelerate metallurgical reactions, and promote the flotation of inclusions in the molten steel, thus purifying the steel. In recent years, the high scrap steel ratio has led to a significant increase in the smelting temperature and refining time of ladles, making ladle smelting conditions increasingly demanding. Currently used chromium corundum-spinel permeable bricks are prone to transverse breakage or spalling due to thermal stress generated by sudden temperature changes and the passage of large amounts of cold air, resulting in loss of permeability and shortened brick life. To address these issues, Chinese invention patent (publication number: CN107032770A) proposes a dispersion-type skeleton-reinforced corundum-spinel permeable brick and its preparation method. The technical solution involves mixing monoclinic zirconia fine powder, yttrium oxide powder, activated alumina powder, calcium aluminate cement, calcium lignosulfonate, polycarboxylate, carboxymethyl cellulose, and water to prepare a zirconia slurry. Dense sintered corundum particles, alumina fine powder, magnesium oxide fine powder, calcium aluminate cement, polycarboxylate, and water are then mixed to prepare a corundum castable. Polyurethane sponge is impregnated in the zirconia slurry and extruded or centrifuged, then dried to obtain a zirconia mesh porous ceramic green body. This green body is then fixed to the bottom of a permeable brick mold, and corundum castable is added to form a skeleton-reinforced corundum-spinel permeable brick green body. After high-temperature firing, a dispersion-type skeleton-reinforced corundum-spinel permeable brick is obtained. Chinese invention patent (publication number: CN111574708A) proposes a method for preparing a highly thermally shock resistant corundum-zirconium mullite permeable brick. The method uses phenolic resin-coated corundum particles, corundum particles and fine powder, zirconium mullite particles and fine powder, alumina micro powder, silica micro powder, and hydrated alumina powder as raw materials, adds a high-efficiency water-reducing agent, dry mixes evenly, adds water to mix into mud, pours it into a mold to form a permeable brick body, and then treats it at high temperature to prepare a highly thermally shock resistant corundum-zirconium mullite permeable brick. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of the prior art by providing a method for preparing a porous aggregate-toughened, highly thermally shock resistant chromium corundum-spinel permeable brick.

[0004] This invention replaces 60-70% of the corundum aggregate in the permeable brick mix with resin-coated alumina spherical particles. Utilizing the dense outer shell and porous inner layer of the spherical porous aggregate, it mitigates the formation of large cracks caused by particle fracture due to thermal stress. Furthermore, the burnable coating layer on the surface of the spherical particles creates micro-spaces of a certain size around the particles within the material, further reducing thermal stress damage to the permeable brick and inhibiting the propagation of thermal shock cracks. This significantly improves the thermal shock resistance of the permeable brick, solving the bottleneck problem of poor thermal shock stability limiting the lifespan of steel ladle permeable bricks. It significantly reduces abnormal damage and short lifespan of permeable bricks caused by thermal shock, thus extending the service life of the permeable bricks and also improving the service life of the refractory materials used in steel ladles.

[0005] The objective of this invention can be achieved through the following technical measures: The method of the present invention uses resin-coated alumina spherical particles, tabular corundum particles, white corundum powder, spinel powder, alumina micro powder, chromium oxide micro powder, and pure calcium aluminate cement as raw materials, adds a high-efficiency water-reducing agent, dry mixes evenly, adds water to mix into mud, pours it into a mold to form a permeable brick body, cures at room temperature, demolds, dries, and then fires at high temperature to prepare a porous aggregate-toughened chromium corundum-spinel permeable brick.

[0006] The specific preparation method includes the following steps: a. Preparation of alumina spherical particles: Alumina micro powder is poured into a pelletizing machine. During the rotation of the pelletizing machine, a 30% zinc chloride solution is sprayed evenly into the alumina micro powder. The amount of zinc chloride solution added is 8-10% of the mass of the alumina micro powder. After the powder gradually agglomerates and forms a pellet, pelletizing is stopped. The pellets are dried at 110°C and then calcined at 1400-1500°C to obtain alumina spherical aggregate. The particles are graded into spherical particles with particle sizes of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm using a sieve. The spherical particles have a core-shell structure, with a dense outer layer and a porous inner layer, and the particles are spherical. b. Preparation of resin-coated alumina spherical particles: A resin coating solution was prepared by mixing ethanol and phenolic resin at a mass ratio of 30:70. Spherical particles with diameters of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm were completely immersed in the resin coating solution for 10 minutes. The alumina spherical particles were then filtered out using a filter screen, and the solution was recycled. The filtered spherical particles were placed in a tray and dried in an oven at 110°C for 12 hours to obtain resin-coated alumina spherical particles with diameters of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm, respectively. c. By weight, add 25 parts of 6-3mm plate-shaped corundum particles, 20-30 parts of 3-1mm resin-coated alumina spherical particles, 5-10 parts of 1-0.5mm resin-coated alumina spherical particles, 10 parts of 0.5-0-0.08mm resin-coated alumina spherical particles, 5-15 parts of white corundum fine powder, 6-10 parts of activated alumina micro powder, and 3-6 parts of chromium oxide micro powder. -5 parts of pure calcium aluminate cement, 5-10 parts of sintered spinel powder, and 0.15-0.30 parts of polyethylene glycol-based high-efficiency water-reducing agent (total of the above raw materials) are mixed evenly. Then, 4-5% of the total mass of the above raw materials is added and stirred evenly. The mixture is then vibrated and cast into a permeable brick blank. The molded blank is cured in an environment of 20-50℃ for 12-24 hours, then demolded and dried at 200-300℃ to obtain the permeable brick blank. d. Place the permeable brick blank prepared in step c in a high-temperature furnace and fire it at 1550-1650℃ for 3-12 hours to obtain a porous aggregate toughened high thermal shock resistant chromium corundum-spinel permeable brick.

[0007] In step d of this invention, the permeable brick blank prepared in step c is placed in a high-temperature furnace and heated to 1000°C at a rate of 60-200°C / hour, and held for 1-3 hours; then heated to 1300°C at a rate of 30-120°C / hour, and held for 2-6 hours; then heated to 1550-1650°C at a rate of 30-60°C / hour, and held for 3-12 hours; after cooling to room temperature, a porous aggregate-toughened, highly thermally shock resistant chromium corundum-spinel permeable brick is obtained.

[0008] The resin-coated alumina spherical aggregate of the present invention is spherical in shape and has a core-shell structure. It is characterized by a dense outer layer and a porous inner layer. The mass percentage of alumina in its constituent raw materials is 98% and the mass percentage of ZnO is 2%.

[0009] The alumina spherical particles are made from alumina micro powder with a purity greater than 99% and a particle size of less than 10 micrometers.

[0010] The fused white corundum powder has a particle size of less than 0.074 mm; the chromium oxide micro powder has a chromium oxide content of greater than 98% and a particle size of less than 10 micrometers; the alumina micro powder has an alumina content of ≥99% and a particle size of less than 5 micrometers; the sintered spinel powder has an alumina content of greater than 72%, an MgO content of less than 27%, and a particle size of less than 45 micrometers; the pure calcium aluminate cement has an alumina content of ≥70% and a particle size of less than 50 micrometers. The phenolic resin liquid is a thermosetting phenolic resin liquid with a solid content of 72-78% and a free phenol content of less than 28%; the ethanol has a purity of greater than 95%.

[0011] The aforementioned polyethylene glycol-based high-efficiency water-reducing agent is FS60.

[0012] The beneficial effects of this invention are as follows: 1. The porous aggregate-toughened chromium corundum-spinel permeable brick prepared by the present invention has the characteristics of high high temperature strength, excellent thermal shock resistance, and long service life.

[0013] 2. The physicochemical properties of the porous aggregate-toughened chromium corundum-spinel permeable brick prepared using this invention are: bulk density not less than 3.0 g / cm³. 3 The apparent porosity is not greater than 20.0%, the flexural strength at room temperature is not less than 28.0 MPa, the flexural strength at 1400℃ is not less than 20.0 MPa, and the number of water cooling cycles at 1100℃ is greater than 15. Detailed Implementation

[0014] The present invention will be further described below with reference to embodiments: The white corundum powder described in this invention has a particle size of less than 0.074 mm; the chromium oxide micro powder has a chromium oxide content greater than 98% and a particle size of less than 10 micrometers; the alumina micro powder has an alumina content of ≥99% and a particle size of less than 5 micrometers; the sintered spinel powder has an alumina content of ≥72%, an MgO content of less than 27%, and a particle size of less than 45 micrometers; the pure calcium aluminate cement has an alumina content of ≥70% and a particle size of less than 50 micrometers. The phenolic resin liquid is a thermosetting phenolic resin liquid with a solid content of 72-78% and a free phenol content of less than 28%; the ethanol has a purity greater than 95%. Further details are omitted below.

[0015] Example 1: 1000 parts of alumina micro powder were poured into a pelletizing machine. While the machine was rotating, 80 parts of a 30% zinc chloride solution were sprayed evenly onto the alumina micro powder. Once the alumina powder gradually agglomerated and formed pellets, pelletizing was stopped. The pellets were removed and placed in a drying oven at 110°C for drying. Then, they were placed in a corundum saggar and fired at 1400°C for 2 hours to obtain alumina spherical aggregate. The alumina spherical aggregate has a dense surface layer of zinc-aluminum spinel and an inner porous alumina layer, forming a composite structure. The alumina spherical particles were graded using a sieve into spherical particles with diameters of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm. A coating solution with a 50% phenolic resin content was prepared using anhydrous ethanol and phenolic resin solution at a mass ratio of 50:50. The 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm particles were then coated with the phenolic resin solution. Spherical particles of 3-1 mm were completely immersed in the resin solution. The particles were filtered out using a filter screen. The filtered particles were placed in a tray and dried in an oven at 110℃ for 10 hours to obtain coated alumina spherical particles of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm, respectively. According to the mass fractions, 25 parts of 6-3mm tabular corundum particles, 25 parts of 3-1mm resin-coated alumina spherical particles, 10 parts of 1-0.5mm resin-coated alumina spherical particles, 10 parts of 0.5-0-0.09mm resin-coated alumina spherical particles, 10 parts of white corundum powder, 8 parts of sintered spinel powder, 6 parts of alumina micro powder, 3 parts of chromium oxide micro powder, 3 parts of pure calcium aluminate cement, and 2 parts of FS600 (added) are placed in a mixer and dry-mixed evenly. Then, 4.2% of the total raw material weight of water is added and mixed evenly to form a mud. The mud is placed in a mold, vibrated and cast into shape. After curing for 24 hours, it is demolded and then dried at 260℃ to obtain the green body. The above materials were placed in a high-temperature furnace for firing. The temperature was increased to 1000℃ at a rate of 180℃ / hour and held for 1 hour; the temperature was increased to 1300℃ at a rate of 60℃ / hour and held for 2 hours; the temperature was increased to 16000℃ at a rate of 30℃ / hour and held for 6 hours; after cooling to room temperature, chromium corundum-spinel permeable bricks were obtained.

[0016] The physicochemical properties of the porous aggregate-reinforced chromium corundum-spinel permeable brick are as follows: bulk density 3.10 g / cm³. 3 The apparent porosity is 18.0%, the flexural strength at room temperature is 31.0 MPa, the flexural strength at 1400℃ is 25.0 MPa, and the number of water cooling cycles at 1100℃ is greater than 15.

[0017] Example 2: 1000 parts of alumina micro powder were poured into a pelletizing machine. During the rotation of the pelletizing machine, 90 parts of a 30% zinc chloride solution were sprayed evenly into the alumina micro powder. After the alumina powder gradually agglomerated and formed pellets, the pelletizing process was stopped. The pellets were removed and placed in a drying oven and dried at 110°C. Then, they were placed in a corundum saggar and fired at 1450°C for 2 hours to obtain alumina spherical aggregate. The alumina spherical aggregate has a dense surface layer of zinc-aluminum spinel and an inner porous alumina layer. The alumina spherical particles were graded into spherical particles with particle sizes of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm using a sieve. A coating solution containing 50% phenolic resin was prepared by mixing anhydrous ethanol and phenolic resin solution at a mass ratio of 50:50. Spherical particles with sizes of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm were completely immersed in the resin solution. The particles were filtered out using a filter screen, and the filtered particles were placed in a tray and dried in an oven at 110°C for 10 hours to obtain coated alumina spherical particles with sizes of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm. According to the mass fractions, 25 parts of 6-3mm tabular corundum particles, 30 parts of 3-1mm resin-coated alumina spherical particles, 5 parts of 1-0.5mm resin-coated alumina spherical particles, 10 parts of 0.5-0-0.09mm resin-coated alumina spherical particles, 14 parts of white corundum powder, 5 parts of sintered spinel powder, 6 parts of alumina micro powder, 3 parts of chromium oxide micro powder, 2 parts of pure calcium aluminate cement, and 15 parts of FS600 (added) are placed in a mixer and dry-mixed evenly. 4.0% of the total raw material weight of water is added and mixed evenly to form a mud. The mud is placed in a mold, vibrated and cast into shape. After curing for 24 hours, it is demolded and then dried at 260℃ to obtain the green body. The above materials were placed in a high-temperature furnace for firing. The temperature was increased to 1000℃ at a rate of 150℃ / hour and held for 2 hours; the temperature was increased to 1300℃ at a rate of 50℃ / hour and held for 2 hours; the temperature was increased to 1650℃ at a rate of 40℃ / hour and held for 5 hours; after cooling to room temperature, porous aggregate toughened chromium corundum-spinel permeable bricks were obtained.

[0018] The physicochemical properties of chrome corundum-spinel permeable bricks are as follows: bulk density is 3.15 g / cm³. 3 The apparent porosity is 18.0%, the flexural strength at room temperature is 34.0 MPa, the flexural strength at 1400℃ is 26.0 MPa, and the number of water cooling cycles at 1100℃ is greater than 15.

[0019] Example 3: 1000 parts of alumina micro powder were poured into a pelletizing machine. During the rotation of the pelletizing machine, 95 parts of a 30% zinc chloride solution were sprayed evenly into the alumina micro powder. After the alumina powder gradually agglomerated and formed pellets, the pelletizing process was stopped. The pellets were removed and placed in a drying oven and dried at 110°C. Then, they were placed in a corundum saggar and fired at 1500°C for 2 hours to obtain alumina spherical aggregate. The alumina spherical aggregate has a dense surface layer of zinc-aluminum spinel and an inner porous alumina layer. The alumina spherical particles were graded into spherical particles with particle sizes of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm using a sieve. A coating solution containing 50% phenolic resin was prepared by mixing anhydrous ethanol and phenolic resin solution at a mass ratio of 50:50. Spherical particles with sizes of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm were completely immersed in the resin solution. The particles were filtered out using a filter screen, and the filtered particles were placed in a tray and dried in an oven at 110°C for 10 hours to obtain coated alumina spherical particles with sizes of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm. According to the mass fractions, 25 parts of 6-3mm tabular corundum particles, 27 parts of 3-1mm resin-coated alumina spherical particles, 10 parts of 1-0.5mm resin-coated alumina spherical particles, 10 parts of 0.5-0-0.09mm resin-coated alumina spherical particles, 6 parts of white corundum powder, 6 parts of sintered spinel powder, 8 parts of alumina micro powder, 4 parts of chromium oxide micro powder, 4 parts of pure calcium aluminate cement, and 3 parts of FS600 (added) are placed in a mixer and dry-mixed evenly. Then, 4.5% of the total raw material weight of water is added and mixed evenly to form a mud. The mud is placed in a mold, vibrated and cast into shape. After curing for 24 hours, it is demolded and then dried at 260℃ to obtain the green body. The above materials were placed in a high-temperature furnace for firing, with the temperature increased to 1000℃ at a rate of 150℃ / hour and held for 2 hours; the temperature was increased to 1300℃ at a rate of 60℃ / hour and held for 2 hours; the temperature was increased to 1620℃ at a rate of 50℃ / hour and held for 6 hours; after cooling to room temperature, porous aggregate toughened chromium corundum-spinel permeable bricks were obtained.

[0020] The physicochemical properties of chrome corundum-spinel permeable bricks are as follows: bulk density is 3.13 g / cm³. 3 The apparent porosity is 18.7%, the flexural strength at room temperature is 35.0 MPa, the flexural strength at 1400℃ is 28.0 MPa, and the number of water cooling cycles at 1100℃ is greater than 15.

Claims

1. A method for preparing a porous aggregate-reinforced, highly thermally shock resistant chromium corundum-spinel permeable brick, characterized in that: The method steps are as follows: a. Preparation of alumina spherical particles: Alumina micro powder is poured into a pelletizing machine. During the rotation of the pelletizing machine, a 30% zinc chloride solution is sprayed evenly into the alumina micro powder using a spray method. The amount of zinc chloride solution added is 8-10% of the mass of the alumina micro powder. After the powder gradually agglomerates and forms a pellet, pelletizing is stopped. The pellets are dried at 110°C and then calcined at 1400-1500°C to obtain alumina spherical aggregate. The particles are graded into spherical particles with particle sizes of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm using a sieve. The spherical particles have a core-shell structure, characterized by a dense outer layer and a porous inner layer, and are spherical in shape. The alumina micro powder contains ≥99% alumina and has a particle size of less than 5 micrometers. b. Preparation of resin-coated alumina spherical particles: A resin coating solution was prepared using ethanol and phenolic resin solution at a mass ratio of 30:

70. Spherical particles with diameters of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm were completely immersed in the resin coating solution for 10 minutes. The alumina spherical particles were then filtered out using a filter screen, and the solution was recycled. The filtered spherical particles were placed in a tray and dried in an oven at 110°C for 12 hours to obtain resin-coated alumina spherical particles with diameters of 3-1 mm, 1-0.5 mm, and 0.5-0.09 mm, respectively. The purity of the ethanol was greater than 95%. The phenolic resin solution was a thermosetting phenolic resin solution with a solid content of 72-78% and a free phenol content of less than 28%. c. By weight, mix 25 parts of 6-3mm plate-shaped corundum particles, 20-30 parts of 3-1mm resin-coated alumina spherical particles, 5-10 parts of 1-0.5mm resin-coated alumina spherical particles, 10 parts of 0.5-0.09mm resin-coated alumina spherical particles, 5-15 parts of fine corundum powder, 6-10 parts of activated alumina micro powder, 3-6 parts of chromium oxide micro powder, 2-5 parts of pure calcium aluminate cement, 5-10 parts of sintered spinel powder, and 0.15-0.3 parts of polyethylene glycol-based high-efficiency water-reducing agent. Then add 4 parts of the total weight of the above raw materials. After mixing with 5% water until uniform, the mixture is vibrated and poured into molds to form a breathable brick blank. The molded blank is then cured at 20-50℃ for 12-24 hours before demolding and drying at 200-300℃ to obtain the breathable brick blank. The corundum fine powder is taken from fused white corundum with a particle size less than 0.088mm; the pure calcium aluminate cement has an alumina content ≥70% and a particle size less than 50 micrometers; the chromium oxide micro powder has a chromium oxide content greater than 98% and a particle size less than 10 micrometers; the polyethylene glycol-based high-efficiency water-reducing agent is FS60; the sintered spinel powder has an alumina content greater than 72%, an MgO content less than 27%, and a particle size less than 45 micrometers. d. Place the permeable brick blank prepared in step c in a high-temperature furnace, heat it to 1000℃ at a rate of 60-200℃ / hour, and hold it for 1-3 hours; heat it to 1300℃ at a rate of 30-120℃ / hour and hold it for 2-6 hours; heat it to 1550-1650℃ at a rate of 30-60℃ / hour and hold it for 3-12 hours; after cooling to room temperature, a porous aggregate-toughened high thermal shock resistant chromium corundum-spinel permeable brick is obtained.