Low-seepage electrically fused zirconia-corundum and method for producing the same

Abstract

This invention discloses a low-permeability fused zirconia alumina and its preparation method, comprising 37% zirconium, 9% silicon, 0.9% sodium, and 1% yttrium. The low-permeability fused zirconia alumina of this application effectively reduces the exudation of the glass phase during use by controlling the total amount of the glass phase, thus minimizing contamination of customer products. The addition of an appropriate amount of yttrium oxide in this solution effectively controls product cracking, thereby improving the product yield.

Description

Technical Field

[0001] This invention relates to the field of high-temperature resistant materials, and in particular to a low-permeability fused zirconia alumina and its preparation method. Background Technology

[0002] Refractory bricks are designed for extreme environments, capable of withstanding temperatures of 1580℃-1770℃, and are widely used in metallurgy, glass manufacturing, cement kilns, and other applications. Their core characteristics include high temperature resistance, excellent thermal insulation, strong thermal shock resistance, and high chemical stability.

[0003] The main types include: Silicate-alumina refractory bricks: based on the Al2O3-SiO2 system, including silica bricks (containing over 93% SiO2, used in coke ovens and glass kilns) and clay bricks (Al2O3 content 30%-48%, refractoriness 1580℃-1750℃). High-alumina bricks: Al2O3 content 55%-85%, refractoriness exceeding 1770℃, apparent porosity 16%-22%, suitable for insulation layers in electric furnaces, heating furnaces, and other equipment. Lightweight insulating bricks: low thermal conductivity, high strength, bulk density 0.6-1.8 g / cm³, operating temperature 800℃-1600℃, can reduce the overall energy consumption of industrial furnaces and kilns by 15%-20%.

[0004] However, existing zirconium corundum products suffer from severe glass phase leaching, causing serious contamination to customers' products. Summary of the Invention

[0005] The problem to be solved by this invention is to propose an innovative solution to address the shortcomings of the prior art, particularly a solution that can effectively control the total amount of glass phase in the product and effectively reduce the exudation problem of glass phase during use.

[0006] To solve the above problems, the present invention adopts the following solution: a low-permeability fused zirconium alumina, characterized in that it has a zirconium content of 37%, a silicon content of 9%, a sodium content of 0.9%, and a yttrium content of 1%, and its preparation method includes the following steps: Raw material preparation: Zirconium oxide ZrO2 and silicon dioxide SiO2 are obtained by high-temperature electrofusion decomposition of zircon sand ZrSiO4, and pure sodium carbonate Na2CO3 and yttrium oxide Y2O3 are prepared.

[0007] Preparation of auxiliary materials: Prepare pure calcium oxide (CaO) and boron oxide (B2O3).

[0008] Pretreatment: Weigh ZrO2, SiO2, Na2CO3, Y2O3, CaO, and B2O3 in proportion and wet mix them in a ball mill for 4 hours to ensure uniform particle dispersion; dry the mixture at 110℃ to remove moisture and prevent gas from escaping during the electrofusion process, which could lead to porosity.

[0009] Electric melting: An electric arc furnace is used, with a melting temperature ≥2200℃. Argon gas (Ar) is introduced in the early stage of melting to prevent oxidation. In the later stage, the atmosphere is adjusted to a reducing atmosphere of CO / CO2 mixture to reduce the contamination of the glass phase by high-valence metal ions. After melting, the temperature is held for 2 hours to promote composition homogenization and reduce the risk of glass phase segregation.

[0010] Casting: The inclined casting method is used to inject the molten material into the graphite mold to avoid internal stress cracks caused by rapid cooling.

[0011] Cooling: Initial rapid cooling: After casting, cool to 1200℃ at a rate of 50℃ / h to reduce the precipitation of glass phase. Later slow cooling: When the temperature reaches below 1200℃, slow cooling is carried out at 20℃ / h to suppress the ZrO2 phase transformation through the stabilizing effect of yttrium oxide and avoid volume expansion cracks.

[0012] Annealing treatment: The annealing temperature is controlled at 600℃ and held for 4 hours to eliminate residual stress and improve the integrity of the billet. The annealing atmosphere is protected with nitrogen (N2) to prevent surface oxidation, and finally low-permeability fused zirconia corundum is obtained.

[0013] Furthermore, the low-permeability fused zirconia alumina is characterized in that the amount of boron oxide (B2O3) added in the preparation method accounts for 0.3% of the total mass, which controls the total amount of glass phase at 12%–15%, thus avoiding excessive glass phase leading to permeation.

[0014] Furthermore, the low-permeability fused zirconia alumina is characterized in that the preparation method further includes acid washing of the low-permeability fused zirconia alumina to remove the glass phase enriched on the surface and reduce permeation in the initial stage of use.

[0015] Furthermore, the low-permeability fused zirconia alumina is characterized in that the pickling is performed by immersing in a 5% HCl solution for 30 minutes.

[0016] The technical effects of this invention are as follows: The low-permeability fused zirconia alumina product of this application has a zirconium content of 37%, a silicon content of 9%, a sodium content of 0.9%, and a yttrium content of 1%. It can control the total amount of glass phase in the product, effectively reducing the permeation of the glass phase during use and minimizing contamination of customer products. The addition of an appropriate amount of yttrium oxide in this solution can effectively control product cracking, thereby improving the product yield.

[0017] By adding 0.3% B2O3, the total amount of glass phase can be controlled at 12%–15%, avoiding exudation caused by excessive glass phase. Furthermore, B2O3 reduces the viscosity of the glass phase, causing it to accumulate at grain boundaries during cooling and reducing its fluidity during use.

[0018] Precise component control: Through the decomposition of zircon sand and the addition of yttrium oxide, a precise ratio of 37% ZrO2 and 1% Y2O3 is achieved.

[0019] By controlling the viscosity of the glass phase with B2O3, the exudation of the glass phase is suppressed. Combined with surface acid washing, the exudation rate is ≤0.5%.

[0020] Yttrium oxide stabilizes the ZrO2 crystal phase, reduces phase transformation cracks, and achieves crack control and improved yield, with a yield of ≥95%.

[0021] Yttrium oxide (Y2O3) forms a solid solution with ZrO2, which strengthens the grain boundary bonding force and prevents the glass phase from escaping.

[0022] By pickling the finished product (soaking in 5% HCl solution for 30 minutes), the glassy phase enriched on the surface is removed, reducing exudation in the early stages of use.

[0023] Y₂O₃ forms a cubic phase (c-ZrO₂) with ZrO₂, suppressing the phase transformation from the tetragonal phase (t-ZrO₂) to the monoclinic phase (m-ZrO₂), avoiding volume expansion cracks, and achieving crystal phase stability. The microcracks induced by Y₂O₃ deflect at the grain boundaries, consuming fracture energy and improving the material's toughness. Detailed Implementation

[0024] The present invention will now be described in further detail.

[0025] Example: A low-permeability fused zirconium alumina, characterized by having a zirconium content of 37%, a silicon content of 9%, a sodium content of 0.9%, and a yttrium content of 1%. Its preparation method is as follows.

[0026] I. Material Design Selection of main raw materials Zirconium source: Zircon sand (ZrSiO4, zirconium content ≥65%) is selected and decomposed into zirconium oxide (ZrO2) and silicon dioxide (SiO2) through high-temperature electrofusion to ensure precise control of zirconium content at 37%.

[0027] Silicon source: SiO2 (9%) generated directly from the decomposition of zircon sand, avoiding the addition of additional silicon raw materials and reducing the introduction of impurities.

[0028] Sodium source: Added in the form of sodium carbonate (Na2CO3), with an actual amount of 1.0% (to compensate for sintering volatilization) to ensure a sodium content of 0.9%.

[0029] Yttrium source: Yttrium oxide (Y2O3, purity ≥99.9%) is introduced at an addition amount of 1% as a stabilizer and crack control agent.

[0030] auxiliary components Stabilizer: 0.5% calcium oxide (CaO), which works synergistically with yttrium oxide to stabilize the ZrO2 crystal phase and reduce microcracks caused by high-temperature phase transformation.

[0031] Glass phase control agent: 0.3% boron oxide (B2O3), which reduces the viscosity of the glass phase, causing it to accumulate at the grain boundaries during cooling and reducing exudation during use.

[0032] II. Production Process Raw material pretreatment Crushing and mixing: Weigh zircon sand, Na2CO3, Y2O3, CaO and B2O3 in proportion and wet mix them in a ball mill for 4 hours to ensure uniform particle dispersion.

[0033] Drying: The mixture is dried at 110℃ to remove moisture and prevent gas from escaping during the electrofusion process, which could cause porosity.

[0034] Smelting Melting temperature: An electric arc furnace is used with a melting temperature ≥2200℃ to ensure that zircon sand is completely decomposed into ZrO2 and SiO2 and forms a homogeneous melt.

[0035] Atmosphere control: Argon (Ar) is introduced in the early stage of melting to protect against oxidation; in the later stage, the atmosphere is adjusted to a reducing atmosphere (CO / CO2 mixture) to reduce the contamination of the glass phase by high-valence metal ions (such as Fe³⁺).

[0036] Holding time: Hold for 2 hours after melting to promote homogenization of composition and reduce the risk of glass phase segregation.

[0037] Pouring and Cooling Casting method: The inclined casting method is used to inject the melt into the graphite mold to avoid internal stress cracks caused by rapid cooling.

[0038] Cooling methods include rapid cooling and slow cooling stages.

[0039] Rapid cooling stage: After casting, the temperature is cooled to 1200℃ at a rate of 50℃ / h to reduce the precipitation of glass phase.

[0040] Slow cooling stage: Below 1200℃, slow cooling is carried out at 20℃ / h. The stabilizing effect of yttrium oxide inhibits the ZrO2 phase transformation and avoids volume expansion cracks.

[0041] Annealing treatment Annealing temperature: 600℃ for 4 hours to eliminate residual stress and improve the integrity of the green body.

[0042] Annealing atmosphere: Nitrogen (N2) protection to prevent surface oxidation.

[0043] Stress monitoring: Residual stress is analyzed by X-ray diffraction (XRD) to adjust the annealing process and reduce cracking of the billet.

[0044] Defect detection: Ultrasonic testing (UT) is used to detect internal pores and cracks, and defective products are rejected to ensure a yield rate of ≥95%.

[0045] III. Quality Inspection Testing items method Test results Zirconium content X-ray fluorescence spectroscopy (XRF) 37% ±0.5% Total amount of glass phase Microscopic observation + image analysis 12%–15% Leakage rate High-temperature immersion test (1600℃×4h) ≤0.5% (quality loss rate) Flexural strength Three-point bending test (ASTM C674) ≥120 MPa Thermal shock stability 1100℃ → Water cooling circulation No cracks after ≥30 cycles The low-permeability fused zirconia alumina of this application can be used in key parts of glass melting furnaces as lining bricks in flow channels and refining sections, withstanding temperatures above 1600℃ and erosion from molten sodium-calcium silicate glass, with a permeation rate of ≤0.5%. It can also be used in the production of electronic glass substrates for LCD and photovoltaic glass production, preventing glass phase permeation from contaminating the product.

Claims

1. A low-leaching electrofused zirconia-corundum, characterized in that, The zirconium content is 37%, silicon content is 9%, sodium content is 0.9%, and yttrium content is 1%. Its preparation method includes the following steps: Raw material preparation: Zircon sand ZrSiO4 is decomposed by high-temperature electrofusion to obtain zircon ZrO2 and silicon dioxide SiO2, and pure sodium carbonate Na2CO3 and yttrium oxide Y2O3 are prepared. Preparation of auxiliary materials: Prepare pure calcium oxide (CaO) and boron oxide (B2O3); Pretreatment: Weigh ZrO2, SiO2, Na2CO3, Y2O3, CaO, and B2O3 in proportion and wet mix them in a ball mill for 4 hours to ensure uniform particle dispersion; the mixture is then dried at 110℃ to remove moisture and prevent gas from escaping during the electrofusion process, which could lead to porosity. Electric melting: An electric arc furnace is used, with a melting temperature ≥2200℃. Argon gas (Ar) is introduced in the early stage of melting to prevent oxidation. In the later stage, the atmosphere is adjusted to a reducing atmosphere of CO / CO2 mixture to reduce the contamination of the glass phase by high-valence metal ions. After melting, the temperature is held for 2 hours to promote composition homogenization and reduce the risk of glass phase segregation. Casting: The inclined casting method is used to inject the molten material into the graphite mold to avoid internal stress cracks caused by rapid cooling; Cooling: Initial rapid cooling: After casting, cool to 1200℃ at a rate of 50℃ / h to reduce glass phase precipitation. Later slow cooling: When the temperature reaches below 1200℃, slow cooling at 20℃ / h is used to suppress ZrO2 phase transformation through the stabilizing effect of yttrium oxide and avoid volume expansion cracks. Annealing treatment: The annealing temperature is controlled at 600℃ and held for 4 hours to eliminate residual stress and improve the integrity of the billet. The annealing atmosphere is protected with nitrogen (N2) to prevent surface oxidation, and finally low-permeability fused zirconia corundum is obtained.

2. The low-seeping electrofused zirconia-corundum according to claim 1, characterized in that In the preparation method, the amount of boron oxide (B2O3) added accounts for 0.3% of the total mass, which controls the total amount of glass phase at 12%–15% to avoid excessive glass phase causing exudation.

3. The low-seeded electrofused zirconia-corundum according to claim 1, characterized in that The preparation method also includes acid washing of low-permeability fused zirconia alumina to remove the glassy phase enriched on the surface and reduce permeation in the early stages of use.

4. The low-sealing electrically fused zirconia-corundum according to claim 3, characterized in that The pickling process involves immersing the sample in a 5% HCl solution for 30 minutes.