Low-glass-phase fused zirconia corundum brick with special structure and preparation method of low-glass-phase fused zirconia corundum brick

Abstract

The invention discloses a low-glass-phase fused zirconia corundum brick with a special structure and a preparation method thereof. The fused zirconia corundum brick comprises the following chemical components in percentage by mass: greater than or equal to 32.5% of ZrO2, less than or equal to 15% of SiO2, less than or equal to 1.4% of K2O + Na2O + CaO + MgO, and the balance of Al2O3 and inevitable impurities. In addition, the content of a glass phase of the fused zirconia corundum brick is smaller than or equal to 20%, and the glass phase is divided into discontinuous blocky areas by a corundum phase in a microstructure. By optimizing the raw material ratio and the casting process, a unique microstructure is formed in the fused zirconia corundum brick, the glass phase of the fused zirconia corundum brick is uniformly divided into discontinuous areas by a dendritic corundum phase, coarse baddeleyite grains are accompanied around the discontinuous areas, the viscosity of the glass phase is remarkably improved by the structure, the flow connectivity of the fused zirconia corundum brick is effectively limited, and the fused zirconia corundum brick has good heat resistance. The product has excellent characteristics of high glass phase exudation temperature and low exudation amount, the product is particularly suitable for flame space parts of the glass melting furnace, pollution to molten glass can be avoided due to the low glass phase exudation characteristic of the product, the quality of the glass product can be improved, and the service life of the furnace can be prolonged.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically a low-glass phase electrofused zirconia-corundum brick with a special structure and its preparation method. Background Technology

[0002] With the rapid development of the glass industry, the continuous optimization of melting furnace structures, the emergence of new melting processes, and the constant upgrading of product quality, more stringent performance requirements have been placed on castable refractories. In particular, the vastly different operating environments of different parts of the melting furnace (such as the pool walls, bottom, and flow channels in contact with molten glass, as well as the flame space) necessitate castable refractories possessing specific properties adapted to these environments. However, traditional technical solutions often use a single type of castable refractories with the same properties in different parts, which is not the optimal choice.

[0003] In existing technologies, research on fused cast zirconia corundum (AZS) products generally focuses on reducing the glass phase content, studying the impact of oxidation degree on glass phase properties, and improving the macroscopic distribution of the glass phase in the product. These studies aim to enhance the overall resistance to molten glass erosion to meet the application requirements of areas in contact with molten glass. However, for areas such as the flame space of melting furnaces, the core requirement is that the refractory material possesses a high initial glass phase precipitation temperature and a low glass phase exudation rate to prevent premature exudation and contamination of the molten glass. Existing general-purpose AZS products have shortcomings in this regard; the composition, microstructure, and crucial influence of the glass phase on exudation behavior have not been fully studied and effectively controlled, resulting in unsatisfactory application performance under specific working conditions, thus hindering further improvement in glass product quality and extension of furnace life. Therefore, developing a low-glass-phase AZS material with a special glass phase structure that can specifically meet the requirements of flame space applications is particularly urgent. Summary of the Invention

[0004] The technical solution adopted in this invention is as follows:

[0005] A low-glass phase fused zirconia-corundum brick with a special structure, wherein the chemical composition of the fused zirconia-corundum brick, by mass percentage, includes: ZrO2 ≥ 32.5%, SiO2 ≤ 15%, K2O + Na2O + CaO + MgO ≤ 1.4%, with the balance being Al2O3 and unavoidable impurities; and wherein the glass phase content of the fused zirconia-corundum brick is ≤ 20%, and the glass phase is separated into discontinuous blocky regions by the corundum phase in the microstructure.

[0006] Furthermore, the corundum phase is dendritic in distribution, and coarse zircon grains are associated with the corundum phase.

[0007] Furthermore, the glass phase exudation temperature of the electrofused zirconia-corundum brick is ≥1420℃.

[0008] Furthermore, under the test condition of holding at 1500℃ for 16 hours, the glass phase exudation of the electrofused zirconia-corundum brick was ≤1.26 vol%.

[0009] Furthermore, the fused zirconia-corundum brick has a room temperature compressive strength ≥200MPa and a load softening temperature ≥1700℃.

[0010] A preparation process for a low-glass phase electrofused zirconia-alumina brick with a special structure, applied to any one of the above-mentioned low-glass phase electrofused zirconia-alumina bricks with a special structure, includes the following steps:

[0011] Step 1: Batching and Mixing: Zircon sand and Al2O3 powder are used as the main raw materials, and Na2CO3, accounting for 2% to 5% of the total mass of the main raw materials, is added to the main raw materials and mixed evenly to form a batch; wherein, the zircon sand contains ZrO2+HfO2>65%, SiO2<34%, Fe2O3<0.03%, and loss on ignition<0.5%; the Al2O3 powder contains Al2O3 content>98.5%, SiO2<0.03%, Fe2O3<0.03%, and loss on ignition<0.5%; the Na2CO3 contains Na2CO3 content>98.5%, oxides<0.8%, and other impurities<0.5%;

[0012] Step 2, Electrofusion Treatment: The batch material is fed into an electric furnace for electrofusion treatment, which includes a feeding period, a melting period, and a clarification and oxygen blowing period performed sequentially.

[0013] Step 3: Casting: The molten liquid obtained after the electrofusion treatment is cast under electric current.

[0014] Step 4: Insulation and Cooling: Place the cast product in an insulated box for insulation and cooling;

[0015] Step 5, Inspection and Processing: Perform non-destructive testing on the cooled brick blanks, and process the qualified brick blanks.

[0016] Furthermore, in step two:

[0017] The process parameters for the feeding period are: one-time centralized feeding, deep arc immersion for 8 minutes after feeding, voltage at the lowest level, current of 5800A to 6000A, and reactor power of 500kW.

[0018] The process parameters for the melting period are: voltage of 310V to 320V, current of 4500A to 5100A, and reactor power of 0kW.

[0019] The process for the clarification and oxygen blowing period is as follows: After the melting period, a first clarification is performed for 5 minutes, with a voltage of 280V and a current of 3000A during the clarification period; then, a first oxygen blowing is performed for 2 to 3 minutes, with a primary side pressure of 0.8MPa to 1.0MPa and a secondary side pressure of 0.4MPa to 0.6MPa, and an oxygen lance insertion depth of 300mm; followed by a second clarification for 5 minutes; then, a second oxygen blowing is performed for 2 to 3 minutes, with a primary side pressure of 0.8MPa to 1.0MPa and a secondary side pressure of 0.4MPa to 0.6MPa, and an oxygen lance insertion depth of 250mm; during the first and second oxygen blowing, the voltage is 280V and the current is 3000A to 3500A.

[0020] Furthermore, in step three, the process parameters for the electric casting are: voltage of 280V to 300V, current of 2800A to 3500A, casting temperature of 1850-1890℃, and casting speed of 18kg / min to 25kg / min.

[0021] Furthermore, the insulation layer inside the insulation box meets the following conditions: the thickness of the insulation layer from the bottom of the product to the bottom of the insulation box is 220mm to 250mm, and the thickness of the insulation layer between the product and the sides of the insulation box is not less than 250mm; when multiple products are placed in the same insulation box, the thickness of the insulation layer between two adjacent products is not less than 150mm; after the insulation material is put into the insulation box, the insulation box is placed on a vibration compactor for compaction, and the compaction time is not less than 10s.

[0022] Furthermore, in step five, non-destructive testing technology is used to inspect the brick blanks, and qualified brick blanks are selected based on the inspection results.

[0023] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0024] (1) By optimizing the raw material ratio and casting process, the present invention forms a special microstructure in fused zirconia corundum bricks. The glass phase is uniformly divided into multiple discontinuous blocky regions by the dendritic corundum phase. This unique structure fundamentally changes the existence form of the glass phase.

[0025] (2) In this invention, the glass phase is divided and surrounded by the corundum phase, and the coarse zircon grains that accompany the corundum phase further hinder the flow of the glass phase, resulting in a significant increase in the viscosity of the overall glass phase. Its fluidity and permeability are effectively restricted, thereby achieving control over the exudation behavior of the glass phase.

[0026] (3) Based on the above-mentioned special microstructure, the electrofused zirconia corundum brick of the present invention exhibits excellent performance. Its glass phase exudation temperature is increased to above 1420 degrees Celsius. At the same time, under the test condition of heat preservation at 1500 degrees Celsius for 16 hours, the glass phase exudation amount is significantly reduced to about 1.26 volume percentage, and its performance is significantly better than the domestic AZS-33 product.

[0027] (4) The product of this invention is particularly suitable for the flame space and other parts of glass melting furnace. Its low glass phase exudation characteristics can effectively prevent refractory materials from contaminating the glass melt, improve the quality of glass products, and extend the service life of the furnace.

[0028] (5) The optimization of the glass phase composition and structure of the present invention is the fundamental reason why the product of the present invention obtains excellent performance such as low exudation and high exudation temperature. This special structure can be realized and stably controlled through specific process conditions. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the electronic image of the sample of the present invention;

[0030] Figure 2 This is a three-dimensional view of the macroscopic electronic image of the glass phase of the present invention;

[0031] Figure 3 This is a schematic diagram of the structure of the glass phase in the sample brick of the present invention;

[0032] Figure 4 This is a schematic diagram of the conventional AZS glass phase structure of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] Example 1, please refer to Figures 1-4 Preparation of low glassy phase fused zirconia-corundum bricks

[0035] 1. Ingredients and Mixing

[0036] The raw materials required for preparation are as follows:

[0037] Zircon sand: Its chemical composition meets the following requirements: ZrO2+HfO2>65%, SiO2<34%, Fe2O3<0.03%, and loss on ignition<0.5%.

[0038] Alumina powder: Its chemical composition meets the following requirements: Al2O3 > 98.5%, SiO2 < 0.03%, Fe2O3 < 0.03%, and loss on ignition < 0.5%.

[0039] Soda ash: Its chemical composition meets the following requirements: Na2CO3 > 98.5%, oxides < 0.8%, and others < 0.5%.

[0040] Using zircon sand and alumina powder as the main raw materials, 3% soda ash (by mass of the main raw materials) is added and mixed evenly to form a batch. The addition of soda ash makes the batch easier to melt, preventing the high-melting-point zirconium oxide, which is prone to phase transformation during solidification, from forming coarse zircon crystals that could cause cracking in the bricks.

[0041] 2. Electrofusion treatment

[0042] The batch material is fed into an electric furnace for electro-melting treatment. The specific process parameters are as follows:

[0043] Feeding period: Feeding is done in one go. After feeding, the arc is buried for 8 minutes, the voltage is at the lowest level, the current is 5900A, and the reactor is 500kW.

[0044] Melting period: voltage 315V, current 4800A, reactor 0kW.

[0045] Clarification and oxygen blowing period: Clarification is carried out immediately after the melting period, with a voltage of 280V, a current of 3000A, and a clarification time of 5min.

[0046] Then, the first oxygen purging was performed: the time was 2.5 minutes, the primary side pressure was 0.9 MPa, the secondary side pressure was 0.5 MPa, and the oxygen lance was inserted to a depth of 300 mm. The electrical parameters during oxygen purging were: voltage 280V, current 3250A.

[0047] Then clarify for another 5 minutes.

[0048] The second oxygen purging was then performed for 2.5 minutes, with a primary side pressure of 0.9 MPa and a secondary side pressure of 0.5 MPa. The oxygen lance was inserted to a depth of 250 mm. The electrical parameters during oxygen purging were: voltage 280V and current 3250A.

[0049] After secondary oxygen blowing, it can be cast. The improved production process effectively improves the composition and structure of the glass phase, thereby improving the exudation amount and exudation temperature performance indicators of the glass phase.

[0050] 3. Casting

[0051] The molten liquid obtained after electrofusion is then electrically cast. The casting process parameters are: voltage 290V, current 3200A, casting temperature 1870℃, and casting speed strictly controlled at 22Kg / min. This is to control the solidification-crystallization-annealing process of the cast product, so that the product forms the optimal microstructure, minimizes residual stress, and improves the stability of the product's internal quality.

[0052] 4. Heat preservation and cooling

[0053] After casting, the product is placed in an insulated box for cooling. The thickness, compactness, and material properties of the insulation layer within the box are carefully designed to control cooling and ensure even heat dissipation, reducing defects such as sand adhesion, bulging, foaming, and cracking, thus improving the product's appearance quality. Specific conditions are: the insulation layer thickness from the bottom of the product to the bottom of the box is 235mm, and the insulation layer thickness between the product and the sides of the box is 260mm. After the insulation material is added, the box is placed on a vibratory compactor for 12 seconds.

[0054] 5. Inspection and Processing

[0055] Non-destructive testing (NDT) techniques are used to detect flaws, eliminating substandard brick blanks and rationally utilizing qualified brick blanks with varying quality to improve the final service life of the materials. Qualified brick blanks are then processed to obtain finished low-glass phase fused zirconia-corundum bricks.

[0056] Example 2: Performance Characterization of Low Glass Phase Electrofused Zirconia Corundum Bricks

[0057] 1. Product technical performance indicators and parameters

[0058] The performance of the low-glass phase fused zirconia-corundum brick prepared in Example 1 was tested, and its main technical performance indicators and parameters are shown in the table below:

[0059] project index <![CDATA[Al2O3]]> margin <![CDATA[ZrO2]]> ≥32.5 <![CDATA[SiO2]]> ≤15 K₂O + Na₂O + CaO + MgO ≤1.4 room temperature pressure resistance (MPa) ≥200 Softening temperature under load (0.2 MPa, ℃) ≥1700 Glass phase content (%) ≤20

[0060] 2. Special glass phase structure

[0061] The test samples were derived from the "low-glass phase electrofused zirconia-corundum bricks" prepared in Example 1. Sampling was conducted according to the chemical composition testing standards of the building materials industry standard JC493-2015 "Fused Cast Zirconia-Corundum Refractory Products for Glass Melting Furnaces." The samples were prepared into 10mm × 10mm × 5mm blocks, ground, polished, and carbon-sprayed. Testing was performed using an electron scanning microscope with a backscattering probe. Typical microstructure images of the samples are shown below. Figure 1 , Figure 2 As shown.

[0062] Depend on Figure 1 It can be seen that the typical structural composition of fused cast zirconium corundum products consists of zircon (white and granular in the figure), corundum phase (grayish-black in the figure, appearing as strips, plates, and dendrites), aluminum-zirconium eutectic phase (small grayish-white dots appearing as feathers in the figure), and glassy phase (large and irregular gray areas in the figure).

[0063] Depend on Figure 2It can be seen that in the macroscopic structure of the glass phase (large and irregular gray area in the figure), the corundum phase (dendritic with a small amount of aluminum-zirconium eutectic phase) of the fused cast zirconium corundum product is clearly divided into different blocks by the corundum phase (dendritic with a small amount of aluminum-zirconium eutectic phase).

[0064] 3. The Influence of Special Microstructure on the Effusion Properties of the Glass Phase

[0065] Depend on Figures 1-2 As can be seen from the microstructure images related to the product, the "low-glass phase electrofused zirconia-alumina brick" prepared in Example 1 still mainly consists of ZrO2, Al2O3, and SiO2, belonging to the fused cast zirconia-alumina series. However, its glass phase microstructure is significantly different from that of existing fused cast AZS series products (e.g., Figure 3 (As shown). Existing products focus on achieving the highest resistance to molten glass erosion, aiming to form more aluminum-zirconium eutectoids and minimize the glass phase. These products are suitable for use in areas that come into contact with molten glass, such as the walls, bottom, and flow channels of melting furnaces. However, the low-glass-phase-exudation cast zirconia-corundum product prepared in this embodiment is best suited for use in the flame space of the melting furnace. The focus is on performance aspects such as glass phase exudation temperature and amount to avoid contaminating the molten glass. Therefore, the glass phase microstructure differs from existing products, with some aluminum-zirconium eutectoids forming and more corundum phase entering the glass phase, resulting in a unique glass phase composition and structure, such as... Figure 3 The typical structure of the glass phase in the sample brick is shown.

[0066] Depend on Figure 3 and Figure 4 The glass phase is clearly divided into different regions by the corundum phase strips, with a small amount of fine-grained zircon also present around the corundum phase. This structure greatly increases the viscosity of the glass phase and restricts its flow permeability, thereby increasing the glass phase exudation temperature and reducing the amount of glass phase exuded.

[0067] 4. Glass phase exudation test

[0068] The brick sample prepared in Example 1 was cut into 30mm*30mm*15mm blocks or a 30mm thick, 15mm round sample was drilled. Simultaneously, a sample holder was fabricated. Figure 4 As shown, the sample is cut from a sintered alumina tube approximately 40 mm long. The bottom of the alumina spacer should be ground flat to ensure sample stability. Before placing the sample in the high-temperature furnace, the mass and apparent quality of the saturated sample and the support should be measured.

[0069] The test temperature was set at 1500℃ and held for 16 hours, then allowed to cool naturally to room temperature. The samples were then removed, and the amount of glass phase exudation was calculated. The final measurement result was the average of the results from three samples, as shown in Table 1. The exudation performance was significantly better than that of similar domestic brick products, as shown in Table 2.

[0070] Table 1. Glass phase exudation test results (1500℃×16hrs) / vol%.

[0071]

[0072] Table 2 Comparison of the permeation performance of similar brick products in China (typical values)

[0073]

[0074] Technical effects:

[0075] In the glass phase macrostructure of fused cast zirconia corundum products, the corundum phase (dendritic with a small amount of aluminum-zirconia eutectic phase) is clearly and uniformly separated into different blocks.

[0076] In the product, the glassy phase is divided into different regions by elongated corundum phase segments, while a small amount of coarse-grained zircon is also present around the corundum phase. This structure greatly increases the viscosity of the glassy phase and restricts its flow permeability, thereby increasing the glassy phase exudation temperature and reducing the amount of glassy phase exuded.

[0077] The glass phase exudation temperature of the fused cast zirconia corundum sample can reach above 1420℃, and the glass phase exudation amount is reduced to about 1.25%, which is significantly better than the exudation performance of similar domestic brick products.

[0078] The optimization of the glass phase composition and structure is the main reason for the improvement in the exudation amount and exudation temperature performance of the glass phase.

[0079] The product can be widely used in the flame space of melting furnaces, and its low glass phase exudation can avoid contamination of the molten glass.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-glass phase fused zirconia-corundum brick with a special structure, characterized in that, The chemical composition of the fused zirconia-corundum brick, by mass percentage, includes: ZrO2 ≥ 32.5%, SiO2 ≤ 15%, K2O + Na2O + CaO + MgO ≤ 1.4%, with the balance being Al2O3 and unavoidable impurities; and the glass phase content of the fused zirconia-corundum brick is ≤ 20%, wherein the glass phase is separated into discontinuous blocky regions by the corundum phase in the microstructure.

2. The low-glass phase fused zirconia-corundum brick with a special structure as described in claim 1, characterized in that: The corundum phase is dendritic, and coarse zircon grains are associated with the corundum phase.

3. The low-glass phase fused zirconia-corundum brick with a special structure as described in claim 1, characterized in that: The glass phase exudation temperature of the electrofused zirconia-corundum brick is ≥1420℃.

4. The low-glass phase fused zirconia-corundum brick with a special structure as described in claim 1, characterized in that: Under the test conditions of holding at 1500℃ for 16 hours, the glass phase exudation of the electrofused zirconia-corundum brick was ≤1.26 vol%.

5. The low-glass phase fused zirconia-corundum brick with a special structure as described in claim 1, characterized in that: The fused zirconia-corundum brick has a room temperature compressive strength ≥200MPa and a load softening temperature ≥1700℃.

6. A preparation process for a low-glass phase fused zirconia-corundum brick with a special structure, characterized in that, The method of applying the low-glass phase electrofused zirconia-corundum brick with a special structure as described in any one of claims 1-5 includes the following steps: Step 1: Batching and Mixing: Zircon sand and Al2O3 powder are used as the main raw materials, and Na2CO3, accounting for 2% to 5% of the total mass of the main raw materials, is added to the main raw materials and mixed evenly to form a batch; wherein, the zircon sand contains ZrO2+HfO2>65%, SiO2<34%, Fe2O3<0.03%, and loss on ignition<0.5%; the Al2O3 powder contains Al2O3 content>98.5%, SiO2<0.03%, Fe2O3<0.03%, and loss on ignition<0.5%; the Na2CO3 contains Na2CO3 content>98.5%, oxides<0.8%, and other impurities<0.5%; Step 2, Electrofusion Treatment: The batch material is fed into an electric furnace for electrofusion treatment, which includes a feeding period, a melting period, and a clarification and oxygen blowing period performed sequentially. Step 3: Casting: The molten liquid obtained after the electrofusion treatment is cast under electric current. Step 4: Insulation and Cooling: Place the cast product in an insulated box for insulation and cooling; Step 5, Inspection and Processing: Perform non-destructive testing on the cooled brick blanks, and process the qualified brick blanks.

7. The preparation process of a low-glass phase electrofused zirconia-corundum brick with a special structure as described in claim 6, characterized in that: In step two: The process parameters for the feeding period are: one-time centralized feeding, deep arc immersion for 8 minutes after feeding, voltage at the lowest level, current of 5800A to 6000A, and reactor power of 500kW. The process parameters for the melting period are: voltage of 310V to 320V, current of 4500A to 5100A, and reactor power of 0kW. The process for the clarification and oxygen blowing period is as follows: After the melting period, a first clarification is performed for 5 minutes, with a voltage of 280V and a current of 3000A during the clarification period; then, a first oxygen blowing is performed for 2 to 3 minutes, with a primary side pressure of 0.8MPa to 1.0MPa and a secondary side pressure of 0.4MPa to 0.6MPa, and an oxygen lance insertion depth of 300mm; followed by a second clarification for 5 minutes; then, a second oxygen blowing is performed for 2 to 3 minutes, with a primary side pressure of 0.8MPa to 1.0MPa and a secondary side pressure of 0.4MPa to 0.6MPa, and an oxygen lance insertion depth of 250mm; during the first and second oxygen blowing, the voltage is 280V and the current is 3000A to 3500A.

8. The preparation process of a low-glass phase electrofused zirconia-corundum brick with a special structure as described in claim 6, characterized in that: In step three, the process parameters for the electric casting are: voltage of 280V to 300V, current of 2800A to 3500A, casting temperature of 1850-1890℃, and casting speed of 18kg / min to 25kg / min.

9. The preparation process of a low-glass phase electrofused zirconia-corundum brick with a special structure as described in claim 6, characterized in that: The insulation layer inside the insulation box meets the following conditions: the thickness of the insulation layer from the bottom of the product to the bottom of the insulation box is 220mm to 250mm, and the thickness of the insulation layer between the product and the sides of the insulation box is not less than 250mm; when multiple products are placed in the same insulation box, the thickness of the insulation layer between two adjacent products is not less than 150mm; after the insulation material is put into the insulation box, the insulation box is placed on a vibration compactor for compaction, and the compaction time is not less than 10s.

10. The preparation process of a low-glass phase electrofused zirconia-corundum brick with a special structure as described in claim 6, characterized in that: In step five, non-destructive testing technology is used to inspect the brick blanks for flaws, and qualified brick blanks are selected based on the inspection results.

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