Neutral ramming material for intermediate frequency furnace

Abstract

The invention discloses a neutral ramming material for an intermediate frequency furnace, and belongs to the technical field of steel smelting. Comprising the following raw materials in parts by weight: 35-40 parts of microporous sintered corundum particles with the particle size of 3-5mm, 35-40 parts of microporous sintered corundum particles with the particle size of 1-3mm, 20-25 parts of magnesium aluminate spinel particles with the particle size of 1-3mm, 9-11 parts of activated aluminum oxide micro powder, 5-7 parts of modified cordierite fine powder, 1-2 parts of pretreated boron nitride, 0.5-1.5 parts of nano aluminum oxide and 0.2 part of nano aluminum oxide. 0.4 part by weight of zinc borosilicate glass powder, 0.6-0.8 part by weight of high-temperature organic silicon resin and 0.05-0.1 part by weight of anti-burst fiber. The prepared neutral ramming material for the intermediate frequency furnace has good compression strength, thermal shock resistance and slag resistance.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, and specifically to a neutral ramming mix for medium-frequency furnaces. Background Technology

[0002] Medium-frequency induction furnaces (IF furnaces for short) achieve efficient metal heating based on the principle of electromagnetic induction. With advantages such as rapid heating rate, uniform temperature distribution, high energy conversion efficiency, and low pollutant emissions, they have become core equipment for metal smelting in casting, machining, and other fields. In cast steel applications, smelting temperatures often need to exceed 1600°C, which places stringent requirements on the furnace lining material. It must possess high refractoriness, excellent high-temperature volume stability, good mechanical strength, and strong resistance to slag erosion. The service life of the furnace lining material directly affects the production efficiency of the medium-frequency furnace.

[0003] Currently, dry ramming mixes are commonly used lining materials for medium-frequency furnaces. They consist of particles of varying sizes and compositions, and through vigorous ramming, can form a lining structure with a certain density. No water or liquid binder needs to be added during use; they simply sinter into a solid whole at a suitable heating temperature. Based on their composition, they are mainly divided into three categories: acidic, neutral, and alkaline. Neutral dry ramming mixes are primarily composed of neutral oxides such as corundum and mullite, exhibiting wear resistance, high-temperature resistance, and strong chemical stability, making them suitable for high-temperature cast steel applications and large furnace lining construction. However, existing neutral dry ramming mixes suffer from problems such as a high coefficient of expansion, insufficient surface sintering strength, and excessively thick sintered layers, resulting in poor slag resistance and thermal shock stability. Especially during intermittent operation of the medium-frequency furnace, the lining is prone to cracking, shortening its service life and ultimately affecting the production efficiency of the cast steel medium-frequency furnace.

[0004] Patent CN103693983A discloses a neutral furnace lining for a medium-frequency induction furnace used in the smelting of sintered NdFeB permanent magnet materials. This material is primarily composed of high-alumina bauxite clinker, with the addition of magnesia powder and additives. The mixture is then stirred and kiln-dried to obtain the lining. The neutral furnace lining obtained by this invention exhibits high refractoriness, excellent chemical stability, and volume stability. Furthermore, it is simple and quick to construct, requires short drying time, has a long service life, and low overall cost. However, the slag resistance and thermal shock stability of the lining material prepared by this invention still have room for improvement.

[0005] In summary, existing technologies in the field of neutral ramming mixes still have shortcomings, especially in terms of slag resistance and thermal shock stability, which still need further optimization and improvement. Summary of the Invention

[0006] To address the problems of existing technologies, this invention provides a neutral ramming mix for medium-frequency furnaces. Specifically, the technical solution of this invention includes the following: A neutral ramming mix for medium-frequency furnaces comprises the following raw materials in parts by weight: 35-40 parts by weight of microporous sintered corundum particles with a particle size of 3-5 mm, 35-40 parts by weight of microporous sintered corundum particles with a particle size of 1-3 mm, 20-25 parts by weight of magnesium aluminum spinel particles with a particle size of 1-3 mm, 9-11 parts by weight of activated alumina micro powder, 5-7 parts by weight of modified cordierite fine powder, 1-2 parts by weight of pretreated boron nitride, 0.5-1.5 parts by weight of nano alumina, 0.2-0.4 parts by weight of zinc borosilicate glass powder, 0.6-0.8 parts by weight of high-temperature silicone resin, and 0.05-0.1 parts by weight of explosion-proof fiber.

[0007] Furthermore, the preparation method of the modified cordierite fine powder includes the following steps: Alumina sol is obtained by reacting aluminum isopropoxide, deionized water, and nitric acid solution. A coating solution was obtained by ultrasonic treatment of alumina sol and ammonium polyacrylate. Cordierite powder is pre-fired to obtain pre-treated cordierite; Pretreated cordierite and coating solution are mixed and reacted to obtain a mixed slurry; The mixed slurry was spray-dried to obtain alumina-coated cordierite; The modified cordierite fine powder was obtained by activating alumina-coated cordierite.

[0008] Furthermore, the nitric acid solution is a 25 wt% nitric acid solution.

[0009] Furthermore, the weight ratio of aluminum isopropoxide, deionized water, and nitric acid solution is 4~5:35~45:1.

[0010] Furthermore, the reaction conditions for the aluminum isopropoxide, deionized water, and nitric acid solution include a reaction temperature of 80-90°C and a reaction time of 10-12 hours.

[0011] Furthermore, the weight ratio of the alumina sol to ammonium polyacrylate is 5~7:0.1~0.3.

[0012] Furthermore, the conditions for the ultrasonic treatment include an ultrasonic power of 400-600W and an ultrasonic time of 30-50min.

[0013] Furthermore, the pre-firing conditions include a processing temperature of 1400~1500℃ and a processing time of 2~3h.

[0014] Furthermore, the weight ratio of the pretreated cordierite to alumina sol is 80~100:5~7.

[0015] Furthermore, the conditions for the reaction of the pretreated cordierite and the coating solution include a reaction temperature of 35-40°C and a reaction time of 60-80 min.

[0016] Furthermore, the conditions for spray drying include an inlet air temperature of 300°C and an atomization pressure of 0.8 MPa.

[0017] Furthermore, the activation conditions include an activation temperature of 800~900℃ and an activation time of 60min.

[0018] Furthermore, the preparation method of the neutral ramming mix for the medium-frequency furnace includes the following steps: Microporous sintered corundum particles with a particle size of 3-5 mm, microporous sintered corundum particles with a particle size of 1-3 mm, and magnesium aluminum spinel particles with a particle size of 1-3 mm are mixed for 10-15 minutes to obtain the first mixture. The first mixture, activated alumina micro powder, and modified cordierite fine powder are mixed for 15-20 minutes to obtain the second mixture; The second mixture, pretreated boron nitride, nano-alumina and zinc borosilicate glass powder are mixed for 5-10 minutes to obtain the third mixture; The third mixture, high-temperature silicone resin and explosion-proof fiber are mixed for 3-8 minutes to obtain the fourth mixture; The neutral ramming mix for the medium-frequency furnace is prepared by gradient heating of the fourth mixing agent.

[0019] Furthermore, the gradient heating treatment conditions include heating to 300℃ at a heating rate of 25℃ / h and holding for 3h, then heating to 800℃ at a heating rate of 50℃ / h and holding for 4h, then heating to 1400℃ at a heating rate of 80℃ / h and holding for 5h, and then heating to 1600℃ at a heating rate of 100℃ / h and holding for 3h.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, aluminum isopropoxide is first hydrolyzed and catalytically reacted to obtain alumina sol, which is then mixed with a dispersant to form a coating liquid. Cordierite powder is pretreated at 1400-1500℃ to eliminate defects and refine particles, and then mixed with the coating liquid. The mixture is then spray-dried to form a core-shell structure. This process helps stabilize the cordierite crystal structure, and the alumina coating layer helps enhance the interfacial compatibility with the matrix, thereby increasing the compressive strength. The modified cordierite not only adjusts the coefficient of thermal expansion to buffer stress, but also works synergistically with hexagonal boron nitride to inhibit crack propagation and enhance thermal shock stability. The alumina coating layer of the modified cordierite, together with magnesium aluminum spinel, blocks the slag penetration path, significantly improving the slag penetration resistance. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise stated, all raw materials and reagents used in this invention are commercially available or can be prepared by known methods.

[0023] Microporous sintered corundum particles with a particle size of 3~5mm were purchased from Jiangsu Jingxin New Materials Co., Ltd. Microporous sintered corundum particles with a particle size of 1~3mm were purchased from Jiangsu Jingxin New Materials Co., Ltd. The magnesium aluminum spinel particles with a particle size of 1~3mm were purchased from Jiangsu Jingxin New Material Co., Ltd., and the model is JMA-78. The activated alumina micro powder was purchased from Jiangsu Jingxin New Material Co., Ltd., and the model number is HA110. Zinc borosilicate glass was purchased from Suzhou Qiuyi New Materials Co., Ltd. The high-temperature silicone resin was purchased from Changzhou Jianuo Silicone Co., Ltd., model number FJN-9802. The explosion-proof fiber was purchased from Gongyi Meile Refractory Materials Co., Ltd.

[0024] Preparation Example 1: The preparation method of modified cordierite fine powder includes the following steps: Four parts by weight of aluminum isopropoxide were dispersed in 35 parts by weight of deionized water and stirred at 80°C for 30 min. One part by weight of 25 wt% nitric acid solution was added and the mixture was stirred and reacted for 10 h. After the reaction was completed, the mixture was dried under vacuum at 90°C for 24 h to obtain alumina sol. Five parts by weight of alumina sol and 0.1 parts by weight of ammonium polyacrylate were dispersed in 50 parts by weight of deionized water and ultrasonically dispersed at 400W for 30 minutes to obtain a coating solution. 100 parts by weight of cordierite powder were spread evenly in a corundum crucible, heated to 1400℃ at a heating rate of 5℃ / min and held for 2 hours, then cooled to 190℃ and removed. After ball milling, the powder was passed through a 300-mesh sieve to obtain pretreated cordierite. 80 parts by weight of pretreated cordierite were added to the above coating liquid and stirred at 35°C for 60 minutes at a speed of 500 r / min to obtain a mixed slurry. The mixed slurry was pumped into a spray dryer and spray dried at an inlet air temperature of 300°C and an atomization pressure of 0.8 MPa to obtain alumina-coated cordierite. Cordierite coated with alumina was spread in a corundum crucible and heated to 800℃ at a heating rate of 10℃ / min. After holding at this temperature for 60 min, the mixture was passed through a 200-mesh sieve to obtain modified cordierite fine powder.

[0025] Preparation Example 2: The preparation method of modified cordierite fine powder includes the following steps: 4.2 parts by weight of aluminum isopropoxide were dispersed in 37 parts by weight of deionized water and stirred at 82°C for 35 min. 1 part by weight of 25 wt% nitric acid solution was added and the reaction was continued to be stirred for 10.5 h. After the reaction was completed, the mixture was dried under vacuum at 90°C for 24 h to obtain alumina sol. 5.5 parts by weight of alumina sol and 0.15 parts by weight of ammonium polyacrylate were dispersed in 50 parts by weight of deionized water and ultrasonically dispersed at 450W for 35 minutes to obtain a coating solution. 100 parts by weight of cordierite powder were spread evenly in a corundum crucible, heated to 1420℃ at a heating rate of 5℃ / min and held for 2.2h, then cooled to 195℃ and removed. After ball milling, the powder was passed through a 300-mesh sieve to obtain pretreated cordierite. 85 parts by weight of pretreated cordierite were added to the above coating liquid and stirred at 36°C for 65 minutes at a speed of 550 r / min to obtain a mixed slurry. The mixed slurry was pumped into a spray dryer and spray dried at an inlet air temperature of 300°C and an atomization pressure of 0.8 MPa to obtain alumina-coated cordierite. Cordierite coated with alumina was spread in a corundum crucible and heated to 820°C at a heating rate of 10°C / min. After holding at this temperature for 60 min, the mixture was passed through a 200-mesh sieve to obtain modified cordierite fine powder.

[0026] Preparation Example 3: The preparation method of modified cordierite fine powder includes the following steps: 4.5 parts by weight of aluminum isopropoxide were dispersed in 40 parts by weight of deionized water and stirred at 85°C for 40 min. 1 part by weight of 25 wt% nitric acid solution was added and the reaction was continued to be stirred for 11 h. After the reaction was completed, the mixture was dried under vacuum at 90°C for 24 h to obtain alumina sol. Six parts by weight of alumina sol and 0.2 parts by weight of ammonium polyacrylate were dispersed in 50 parts by weight of deionized water and ultrasonically dispersed at 500W for 40 minutes to obtain a coating solution. 100 parts by weight of cordierite powder were spread evenly in a corundum crucible, heated to 1450℃ at a heating rate of 5℃ / min and held for 2.5h, then cooled to 200℃ and removed. After ball milling, the powder was passed through a 300-mesh sieve to obtain pretreated cordierite. 90 parts by weight of pretreated cordierite were added to the above coating liquid and stirred at 37°C for 70 minutes at a speed of 600 r / min to obtain a mixed slurry. The mixed slurry was pumped into a spray dryer and spray dried at an inlet air temperature of 300°C and an atomization pressure of 0.8 MPa to obtain alumina-coated cordierite. Cordierite coated with alumina was spread in a corundum crucible and heated to 850°C at a heating rate of 10°C / min. After holding at this temperature for 60 min, the mixture was passed through a 200-mesh sieve to obtain modified cordierite fine powder.

[0027] Preparation Example 4: The preparation method of modified cordierite fine powder includes the following steps: 4.7 parts by weight of aluminum isopropoxide were dispersed in 42 parts by weight of deionized water and stirred at 88°C for 45 min. 1 part by weight of 25 wt% nitric acid solution was added and the reaction was continued to be stirred for 11.5 h. After the reaction was completed, the mixture was dried under vacuum at 90°C for 24 h to obtain alumina sol. 6.5 parts by weight of alumina sol and 0.25 parts by weight of ammonium polyacrylate were dispersed in 50 parts by weight of deionized water and ultrasonically dispersed at 550W for 45 minutes to obtain a coating solution. 100 parts by weight of cordierite powder were spread evenly in a corundum crucible, heated to 1480℃ at a heating rate of 5℃ / min and held for 2.7h, then cooled to 205℃ and removed. After ball milling, the powder was passed through a 300-mesh sieve to obtain pretreated cordierite. 95 parts by weight of pretreated cordierite were added to the above coating liquid and stirred at 38°C for 75 minutes at a speed of 700 r / min to obtain a mixed slurry. The mixed slurry was pumped into a spray dryer and spray dried at an inlet air temperature of 300°C and an atomization pressure of 0.8 MPa to obtain alumina-coated cordierite. Cordierite coated with alumina was spread in a corundum crucible and heated to 870°C at a heating rate of 10°C / min. After holding at this temperature for 60 min, the mixture was passed through a 200-mesh sieve to obtain modified cordierite fine powder.

[0028] Preparation Example 5: The preparation method of modified cordierite fine powder includes the following steps: Five parts by weight of aluminum isopropoxide were dispersed in 45 parts by weight of deionized water and stirred at 90°C for 50 min. One part by weight of 25 wt% nitric acid solution was added and the mixture was stirred and reacted for 12 h. After the reaction was completed, the mixture was dried under vacuum at 90°C for 24 h to obtain alumina sol. 7 parts by weight of alumina sol and 0.3 parts by weight of ammonium polyacrylate were dispersed in 50 parts by weight of deionized water and ultrasonically dispersed at 600W for 50 minutes to obtain a coating solution. 100 parts by weight of cordierite powder were spread evenly in a corundum crucible, heated to 1500℃ at a heating rate of 5℃ / min and held for 3 hours, then cooled to 210℃ and removed. After ball milling, the powder was passed through a 300-mesh sieve to obtain pretreated cordierite. 100 parts by weight of pretreated cordierite were added to the above coating liquid and stirred at 800 r / min at 40°C for 80 min to obtain a mixed slurry. The mixed slurry was pumped into a spray dryer and spray dried at an inlet air temperature of 300°C and an atomization pressure of 0.8 MPa to obtain alumina-coated cordierite. Cordierite coated with alumina was spread in a corundum crucible and heated to 900℃ at a heating rate of 10℃ / min. After holding at that temperature for 60 min, the mixture was passed through a 200-mesh sieve to obtain modified cordierite fine powder.

[0029] Example 1: A method for preparing a neutral ramming mix for an intermediate frequency furnace includes the following steps: Hexagonal boron nitride was pretreated by heat treatment at 800℃ for 60 min in a nitrogen-protected environment. 35 parts by weight of microporous sintered corundum particles with a particle size of 3 mm, 35 parts by weight of microporous sintered corundum particles with a particle size of 1 mm, and 20 parts by weight of JMA-78 magnesium aluminum spinel particles with a particle size of 1 mm were placed in a mixer and mixed at a speed of 30 r / min for 10 min to obtain the first mixture. The first mixture contains 9 parts by weight of HA110 activated alumina micro powder and 5 parts by weight of modified cordierite fine powder prepared in Example 1. The mixture is stirred at 40 r / min for 15 min to obtain the second mixture. The second mixture contains 1 part by weight of pretreated boron nitride, 0.5 parts by weight of nano alumina, and 0.2 parts by weight of zinc borosilicate glass powder. The mixture is stirred at 20 r / min for 5 min to obtain the third mixture. Add 0.6 parts by weight of FJN-9802 high-temperature silicone resin and 0.05 parts by weight of explosion-proof fiber to the third mixture and mix at 30 r / min for 3 min to obtain the fourth mixture; After the fourth mixture is tamped into shape, it is heated to 300℃ at a heating rate of 25℃ / h and held for 2 hours, then heated to 800℃ at a heating rate of 50℃ / h and held for 3 hours, then heated to 1400℃ at a heating rate of 80℃ / h and held for 4 hours, and finally heated to 1600℃ at a heating rate of 100℃ / h and held for 2 hours to obtain neutral tamping material for medium frequency furnace.

[0030] Example 2: A method for preparing a neutral ramming mix for an intermediate frequency furnace includes the following steps: Hexagonal boron nitride was pretreated by heat treatment at 800℃ for 60 min in a nitrogen-protected environment. 36 parts by weight of microporous sintered corundum particles with a particle size of 3.5 mm, 36 parts by weight of microporous sintered corundum particles with a particle size of 1.5 mm, and 21 parts by weight of JMA-78 magnesium aluminum spinel particles with a particle size of 1.5 mm were placed in a mixer and mixed at a speed of 30 r / min for 11 min to obtain the first mixture. The first mixture contains 9.5 parts by weight of HA110 activated alumina micro powder and 5.5 parts by weight of modified cordierite fine powder prepared in Example 2. The mixture is stirred at 40 r / min for 16 min to obtain the second mixture. The second mixture contains 1.2 parts by weight of pretreated boron nitride, 0.7 parts by weight of nano-alumina, and 0.25 parts by weight of zinc borosilicate glass powder. The mixture is stirred at 20 r / min for 6 min to obtain the third mixture. Add 0.65 parts by weight of FJN-9802 high-temperature silicone resin and 0.06 parts by weight of explosion-proof fiber to the third mixture and mix at 30 r / min for 4 min to obtain the fourth mixture; After the fourth mixture is tamped into shape, it is heated to 300℃ at a heating rate of 25℃ / h and held for 2 hours, then heated to 800℃ at a heating rate of 50℃ / h and held for 3 hours, then heated to 1400℃ at a heating rate of 80℃ / h and held for 4 hours, and finally heated to 1600℃ at a heating rate of 100℃ / h and held for 2 hours to obtain neutral tamping material for medium frequency furnace.

[0031] Example 3: A method for preparing a neutral ramming mix for an intermediate frequency furnace includes the following steps: Hexagonal boron nitride was pretreated by heat treatment at 800℃ for 60 min in a nitrogen-protected environment. 37 parts by weight of microporous sintered corundum particles with a particle size of 4 mm, 37 parts by weight of microporous sintered corundum particles with a particle size of 2 mm, and 22 parts by weight of JMA-78 magnesium aluminum spinel particles with a particle size of 2 mm were placed in a mixer and mixed at a speed of 30 r / min for 12 min to obtain the first mixture. The first mixture contains 10 parts by weight of HA110 activated alumina micro powder and 6 parts by weight of modified cordierite fine powder prepared in Example 3. The mixture is stirred at 40 r / min for 17 min to obtain the second mixture. The second mixture contains 1.5 parts by weight of pretreated boron nitride, 1.0 parts by weight of nano-alumina, and 0.3 parts by weight of zinc borosilicate glass powder. The mixture is stirred at 20 r / min for 7 min to obtain the third mixture. The third mixture contains 0.7 parts by weight of FJN-9802 high-temperature silicone resin and 0.07 parts by weight of explosion-proof fiber. The mixture is stirred at 30 r / min for 5 min to obtain the fourth mixture. After the fourth mixture is tamped into shape, it is heated to 300℃ at a heating rate of 25℃ / h and held for 2 hours, then heated to 800℃ at a heating rate of 50℃ / h and held for 3 hours, then heated to 1400℃ at a heating rate of 80℃ / h and held for 4 hours, and finally heated to 1600℃ at a heating rate of 100℃ / h and held for 2 hours to obtain neutral tamping material for medium frequency furnace.

[0032] Example 4: A method for preparing a neutral ramming mix for an intermediate frequency furnace includes the following steps: Hexagonal boron nitride was pretreated by heat treatment at 800℃ for 60 min in a nitrogen-protected environment. 38 parts by weight of microporous sintered corundum particles with a particle size of 4.5 mm, 38 parts by weight of microporous sintered corundum particles with a particle size of 2.5 mm, and 23 parts by weight of JMA-78 magnesium aluminum spinel particles with a particle size of 2.5 mm were placed in a mixer and mixed at a speed of 30 r / min for 13 min to obtain the first mixture. The first mixture contains 10.5 parts by weight of HA110 activated alumina micro powder and 6.5 parts by weight of modified cordierite fine powder prepared in Example 4. The mixture is stirred at 40 r / min for 18 min to obtain the second mixture. The second mixture contains 1.7 parts by weight of pretreated boron nitride, 1.2 parts by weight of nano-alumina, and 0.35 parts by weight of zinc borosilicate glass powder. The mixture is stirred at 20 r / min for 7 min to obtain the third mixture. The third mixture contains 0.75 parts by weight of FJN-9802 high-temperature silicone resin and 0.08 parts by weight of explosion-proof fiber. The mixture is then mixed at 30 r / min for 6 min to obtain the fourth mixture. After the fourth mixture is tamped into shape, it is heated to 300℃ at a heating rate of 25℃ / h and held for 2 hours, then heated to 800℃ at a heating rate of 50℃ / h and held for 3 hours, then heated to 1400℃ at a heating rate of 80℃ / h and held for 4 hours, and finally heated to 1600℃ at a heating rate of 100℃ / h and held for 2 hours to obtain neutral tamping material for medium frequency furnace.

[0033] Example 5: A method for preparing a neutral ramming mix for an intermediate frequency furnace includes the following steps: Hexagonal boron nitride was pretreated by heat treatment at 800℃ for 60 min in a nitrogen-protected environment. 40 parts by weight of microporous sintered corundum particles with a particle size of 5 mm, 40 parts by weight of microporous sintered corundum particles with a particle size of 3 mm and 25 parts by weight of JMA-78 magnesium aluminum spinel particles with a particle size of 3 mm were placed in a mixer and mixed at a speed of 30 r / min for 15 min to obtain the first mixture. The first mixture contains 11 parts by weight of HA110 activated alumina micro powder and 7 parts by weight of modified cordierite fine powder prepared in Example 5. The mixture is stirred at 40 r / min for 20 min to obtain the second mixture. The second mixture contains 2 parts by weight of pretreated boron nitride, 1.5 parts by weight of nano-alumina, and 0.4 parts by weight of zinc borosilicate glass powder. The mixture is stirred at 20 r / min for 10 min to obtain the third mixture. Add 0.8 parts by weight of FJN-9802 high-temperature silicone resin and 0.1 parts by weight of explosion-proof fiber to the third mixture and mix at 30 r / min for 8 min to obtain the fourth mixture; After the fourth mixture is tamped into shape, it is heated to 300℃ at a heating rate of 25℃ / h and held for 3 hours, then heated to 800℃ at a heating rate of 50℃ / h and held for 4 hours, then heated to 1400℃ at a heating rate of 80℃ / h and held for 5 hours, and finally heated to 1600℃ at a heating rate of 100℃ / h and held for 3 hours to obtain neutral tamping material for medium frequency furnace.

[0034] Comparative Example 1: A method for preparing a neutral ramming mix for an intermediate frequency furnace includes the following steps: Remove the modified cordierite powder obtained in Preparation Example 5 from Example 5, and keep all other operations consistent with Example 5.

[0035] Comparative Example 2: A method for preparing a neutral ramming mix for an intermediate frequency furnace includes the following steps: The modified cordierite fine powder prepared in Example 5 was replaced with cordierite powder, and other operations were kept the same as in Example 5.

[0036] Comparative Example 3: A method for preparing a neutral ramming mix for an intermediate frequency furnace includes the following steps: Remove hexagonal boron nitride from Example 5, and keep all other operations the same as in Example 5.

[0037] Comparative Example 4: A method for preparing a neutral ramming mix for an intermediate frequency furnace includes the following steps: Remove the nano-alumina and zinc borosilicate glass powder from Example 5, and keep all other operations the same as in Example 5.

[0038] Test Example: Performance Testing The neutral ramming mixes prepared in Examples 1-5 and Comparative Examples 1-4 were tested to determine their compressive strength, linear shrinkage rate, slag resistance, and thermal shock stability. The test results are shown in Table 1.

[0039] Table 1. Performance Testing

[0040] According to the data in Table 1, it can be observed that the neutral ramming mixes prepared in Examples 1 to 5 have good compressive strength, linear change rate, slag erosion resistance and thermal shock stability, while the neutral ramming mixes prepared in Comparative Examples 1 to 4 all show varying degrees of performance decline.

[0041] The reason for the performance degradation in Comparative Example 1 may be that the modified cordierite is coated with alumina, which reacts with the matrix in a high-temperature environment to form magnesium aluminum spinel, enhancing the bonding force with the matrix. Removal of this coating leads to a decrease in structural density. The lack of the thermal expansion coefficient regulating effect of cordierite results in a significant decrease in thermal shock stability.

[0042] The reason for the performance degradation in Comparative Example 2 may be that the cordierite without alumina coating has poor compatibility with the matrix and weak interfacial bonding, which affects its strength and slag resistance; ordinary cordierite has insufficient thermal stability and is prone to cracking at high temperatures, resulting in a decrease in thermal shock resistance.

[0043] The reason for the performance degradation in Comparative Example 3 may be that hexagonal boron nitride, as a high-temperature lubricant, can buffer thermal stress and inhibit crack propagation. Its absence leads to a significant deterioration in thermal shock performance. The lamellar structure of hexagonal boron nitride may also improve the toughness of ramming mix, but its removal results in a simultaneous decrease in compressive strength.

[0044] The reason for the performance degradation in Comparative Example 4 may be that nano-alumina can fill micropores and enhance sintering density. Its absence increases porosity and intensifies slag penetration. Zinc borosilicate glass powder may form a liquid phase under high temperature, promoting interparticle bonding. Its removal leads to a loose structure and a decrease in strength and erosion resistance.

[0045] In summary, modified cordierite and hexagonal boron nitride can jointly optimize the thermal shock stability of neutral ramming mixes. Modified cordierite can adjust the coefficient of expansion, while hexagonal boron nitride can release stress. Nano-alumina and zinc borosilicate glass powder can synergistically improve density, effectively enhancing compressive strength and slag resistance.

[0046] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A neutral ramming mix for a medium-frequency furnace, characterized in that, Including the following parts by weight of raw materials: 35-40 parts by weight of microporous sintered corundum particles with a particle size of 3-5 mm, 35-40 parts by weight of microporous sintered corundum particles with a particle size of 1-3 mm, 20-25 parts by weight of magnesium aluminum spinel particles with a particle size of 1-3 mm, 9-11 parts by weight of activated alumina micro powder, 5-7 parts by weight of modified cordierite fine powder, 1-2 parts by weight of pretreated boron nitride, 0.5-1.5 parts by weight of nano alumina, 0.2-0.4 parts by weight of zinc borosilicate glass powder, 0.6-0.8 parts by weight of high-temperature silicone resin, and 0.05-0.1 parts by weight of explosion-proof fiber.

2. The neutral ramming mix for a medium-frequency furnace as described in claim 1, characterized in that, The preparation method of the modified cordierite fine powder includes the following steps: Alumina sol is obtained by reacting aluminum isopropoxide, deionized water, and nitric acid solution. A coating solution was obtained by ultrasonic treatment of alumina sol and ammonium polyacrylate. Cordierite powder is pre-fired to obtain pre-treated cordierite; Pretreated cordierite and coating solution are mixed and reacted to obtain a mixed slurry; The mixed slurry was spray-dried to obtain alumina-coated cordierite; The modified cordierite fine powder was obtained by activating alumina-coated cordierite.

3. The neutral ramming mix for a medium-frequency furnace as described in claim 2, characterized in that, The nitric acid solution is a 25 wt% nitric acid solution.

4. The neutral ramming mix for a medium-frequency furnace as described in claim 2, characterized in that, The weight ratio of aluminum isopropoxide, deionized water, and nitric acid solution is 4~5:35~45:

1.

5. The neutral ramming mix for a medium-frequency furnace as described in claim 2, characterized in that, The weight ratio of the alumina sol to ammonium polyacrylate is 5~7:0.1~0.

3.

6. The neutral ramming mix for a medium-frequency furnace as described in claim 2, characterized in that, The pre-firing conditions include a processing temperature of 1400~1500℃ and a processing time of 2~3h.

7. The neutral ramming mix for a medium-frequency furnace as described in claim 2, characterized in that, The weight ratio of the pretreated cordierite to alumina sol is 80~100:5~7.

8. The neutral ramming mix for a medium-frequency furnace as described in claim 2, characterized in that, The conditions for the reaction of the pretreated cordierite and the coating solution include a reaction temperature of 35-40℃ and a reaction time of 60-80 min.

9. The neutral ramming mix for a medium-frequency furnace as described in claim 2, characterized in that, The activation conditions include an activation temperature of 800~900℃ and an activation time of 60min.

10. A neutral ramming mix for a medium-frequency furnace as described in any one of claims 1 to 9, characterized in that, The preparation method of the neutral ramming mix for the medium-frequency furnace includes the following steps: Microporous sintered corundum particles with a particle size of 3-5 mm, microporous sintered corundum particles with a particle size of 1-3 mm, and magnesium aluminum spinel particles with a particle size of 1-3 mm are mixed for 10-15 minutes to obtain the first mixture. The first mixture, activated alumina micro powder, and modified cordierite fine powder are mixed for 15-20 minutes to obtain the second mixture; The second mixture, pretreated boron nitride, nano-alumina and zinc borosilicate glass powder are mixed for 5-10 minutes to obtain the third mixture; The third mixture, high-temperature silicone resin and explosion-proof fiber are mixed for 3-8 minutes to obtain the fourth mixture; The neutral ramming mix for the medium-frequency furnace is prepared by gradient heating of the fourth mixing agent.

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