Carbon-based ceramic side sealing plate for thin strip continuous casting and preparation method thereof

Abstract

The application provides a carbon-based ceramic side sealing plate for thin strip continuous casting and a preparation method thereof. ® N1055 and T85 are weighed and stirred uniformly to obtain a mixture, deionized water is added and stirred to form a slurry; then the slurry is subjected to spray drying, mixed with liquid phenolic resin, and granulated to obtain a granulation powder; the granulation powder is placed in a mold, and near-net-size forming is performed by using a hydraulic machine to obtain a green body; the green body is solidified; the solidified green body is placed in a sagger, and is fully buried with silicon powder; the sagger is placed in a vacuum electric furnace for staged sintering, and a carbon-based side sealing plate is obtained. The side sealing plate prepared by the method has the characteristics of low preparation cost and long service life, solves the problem of insufficient anti-friction and wear performance of the side sealing plate, and meets the service requirements of the side sealing plate for thin strip continuous casting in terms of resistance to molten steel corrosion, resistance to molten steel thermal shock, and resistance to friction and wear.

Description

Technical Field

[0001] This invention relates to the field of high-temperature structural ceramics technology, specifically to a carbon-based ceramic side sealing plate for thin strip continuous casting and its preparation method. Background Technology

[0002] Thin strip continuous casting and rolling is a simpler, more efficient, and energy-saving technology with significant emission reduction benefits. It is a typical green manufacturing technology for steel and has received widespread international attention and high regard. A number of industrial technology developers and practitioners have emerged, including Nucor, Nippon Steel, ThyssenKrupp, POSCO, Baosteel, Northeastern University, and Shagang Group, achieving breakthroughs in key industrial technologies and realizing the initial application of thin strip continuous casting and rolling technology in the steel industry. Side sealing technology in thin strip continuous casting is one of the key technologies restricting the application and development of twin-roll thin strip continuous casting and rolling. The side sealing plate is the core of the side sealing technology. Its main function is to cooperate with the casting roll to form a molten pool, preventing molten steel leakage. Because it is pressed against the casting roll, it suffers mechanical stress; it is corroded by contact with molten steel; it is worn by contact with the casting roll and the nascent strip; and it is subjected to thermal shock upon initial contact with molten steel. Therefore, it is required to have good thermal shock resistance, resistance to molten steel corrosion, and high-temperature wear resistance. The side sealing plate and working surface area, such as... Figure 1-2 As shown.

[0003] Side sealing plate materials have evolved through fused silica, carbonaceous, zirconium, and boron nitride-based ceramics. Currently, BN-ZrO2-SiC hot-pressed ceramic side sealing plates have become the main material for industrial applications, capable of meeting certain requirements for thermal shock resistance, corrosion resistance, and friction and wear resistance. However, the following three problems still exist:

[0004] (1) The cost of BN raw materials is high. The lamellar structure of h-BN grains makes it easy to form a card-like structure during sintering, which makes it difficult to sinter and densify the material. Therefore, hot pressing sintering is required, which results in a high sintering cost.

[0005] (2) The side sealing plate has an irregular shape and cannot be formed to near net size through hot pressing sintering process. Therefore, it needs to be processed later. The yield of hot pressing material is about 50%, while the cutting material is difficult to play a role in other fields, resulting in great waste.

[0006] (3) After the boron nitride-based ceramic side sealing plate binder BN is oxidized, it volatilizes directly in the gas phase or becomes a low melting point phase. Its resistance to molten steel erosion and wear resistance (primary billet shell) decreases significantly. In particular, its resistance to friction and wear of primary strip determines the service life of the side sealing plate, and thus determines the number of furnaces for thin strip continuous casting.

[0007] As the commercialization of thin strip continuous casting technology further increases, the service life of the side sealing plate has become a bottleneck restricting the improvement of efficiency in thin strip continuous casting, which in turn affects the continuous reduction of the cost of thin strip process. Therefore, the demand for high-performance and low-cost side sealing plates is becoming increasingly urgent. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a carbon-based ceramic side sealing plate for thin strip continuous casting and its preparation method. It features low manufacturing cost and long service life, solves the problem of insufficient resistance to friction and wear of the initial billet shell in side sealing plates, and simultaneously meets the service requirements of thin strip continuous casting for side sealing plates to resist molten steel erosion, resist molten steel thermal shock, and resist friction and wear.

[0009] To achieve the above objectives, the specific solution adopted by the present invention is as follows:

[0010] On one hand, the present invention provides a method for preparing a carbon-based ceramic side sealing plate for thin strip continuous casting, which mainly includes the following steps:

[0011] S1. Weigh out, by mass fraction, 12-20% flake graphite, 10-15% ultrafine graphite, 10-20% zirconium oxide, 3-5% boron anhydride, 35-45% spinel, 5-10% boron carbide, and 0.1-0.3% [unclear - possibly a specific ingredient or component]. N1055 and 0.1-0.3% T85 are placed in a mixer and stirred evenly to obtain a mixture. 25-35% of deionized water is added to the mixture, and stirring is continued until the flake graphite and ultrafine graphite are fully dispersed to obtain a slurry. The dispersed slurry is then spray-dried to obtain a powder with a particle size of no more than 0.5 mm. The powder, 8-12% of liquid phenolic resin by weight of the powder, and 8% of hexamethylenetetramine by weight of the liquid phenolic resin are then placed in the feed pot of a high-speed mixing and granulating machine for mixing and granulation. After sieving, granulated powder with a particle size of no more than 3 mm is obtained.

[0012] S2. Place the granulated powder in a mold and use a hydraulic press to form it to near-net-shape under heating conditions to obtain a green body;

[0013] S3. The preform is cured at 300℃;

[0014] S4. Place the blank in a sagger and fully bury it with metallic silicon powder for silicon diffusion heat treatment. Place the sagger in a vacuum furnace for segmented sintering with a vacuum degree of <100Pa. After silicon diffusion densification is completed, clean the surface to obtain the carbon-based side sealing plate.

[0015] Furthermore, the particle size of the flake graphite is 0.1-0.5 mm;

[0016] The particle size of ultrafine graphite is less than 0.01 mm;

[0017] Zirconia particles are less than 5 μm in size;

[0018] Spinel has a grain size of less than 5 μm;

[0019] The particle size of boron carbide is 1000 mesh;

[0020] The boron anhydride crystals have a purity of 99.5% and a particle size of 325 mesh.

[0021] Furthermore, in step S1, the temperature of the mixing pot is maintained at 60-80°C during mixing.

[0022] Furthermore, in step S2, the mold is provided with venting holes;

[0023] The mold is equipped with a heating unit to ensure that the temperature of the blank is maintained at 60-80℃ during the forming process.

[0024] Furthermore, in step S2, the molding pressure is not less than 120 MPa.

[0025] Furthermore, in step S4, the specific parameters for segmented sintering are as follows:

[0026] First, raise the temperature from room temperature to the first target temperature, and then keep it at the first target temperature for 2-3 hours;

[0027] Then, raise the temperature from the first target temperature to the second target temperature and maintain it at the second target temperature for 2-5 hours.

[0028] Finally, the temperature is raised from the second target temperature to the third target temperature and held at the third target temperature for 1-5 hours.

[0029] The first target temperature is 900-950℃;

[0030] The second target temperature is 1100-1300℃;

[0031] The third target temperature is greater than 1400℃.

[0032] On the other hand, the present invention provides a carbon-based ceramic side sealing plate for thin strip continuous casting, which is prepared by the above-described method.

[0033] The role of each raw material will be analyzed in detail below.

[0034] Flake graphite: improves thermal shock resistance and toughness; solid lubricant;

[0035] Ultrafine graphite: improves thermal shock resistance and toughness; solid lubricant.

[0036] Zirconia: Resistant to molten steel corrosion, improves material toughness;

[0037] Boric anhydride: promotes sintering and forms ZrB2;

[0038] Spinel: Resistant to molten steel corrosion;

[0039] Boron carbide: an antioxidant;

[0040] Urotropine: a resin curing agent;

[0041] N1055: Graphite dispersant;

[0042] T85: Zirconia micro powder dispersant;

[0043] Liquid phenolic resin: a binder that forms bound carbon after heat treatment.

[0044] Beneficial effects:

[0045] The carbon-based ceramic side sealing plate proposed in this invention effectively improves the oxidation resistance of the carbon-based side sealing plate by combining B4C in the raw material with in-situ formed ZrB2. After surface oxidation (during baking and transfer), a B2O3 protective film is formed on the surface of the side sealing plate, inhibiting further oxidation. During service, the non-working surface is in a N2 atmosphere. After oxidation of the molten steel contact surface, a ZrO2 and spinel high-refractory decarburization layer is formed. In particular, the spinel can react well with FeO and MnO in the molten steel to form a stable composite spinel, thereby preventing further reaction with other components of the side sealing plate. Therefore, the resistance to molten steel erosion is improved compared to the past. In the strip wear zone, due to the in-situ formed SiC structure network, SiC and Si oxidize to form a dense SiO2 film. Compared with the molten B2O3 liquid film formed by BN-based side sealing plates, the friction and wear resistance is greatly improved, thereby increasing the service life of the existing side sealing plate from the current 7 heats to more than 9 heats. At the same time, the cost of the main raw material graphite is lower than that of BN raw material. Furthermore, the use of pressureless sintering and near-net-shape forming process eliminates the need for processing scraps, significantly reducing the preparation cost. Compared with existing technologies, it is significantly innovative and practical, and has value for widespread application. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the side sealing plate.

[0047] Figure 2 This is a schematic diagram of the working surface area of ​​the side sealing plate.

[0048] Figure 2 The meanings of the letters in the text are as follows: A represents the molten steel erosion zone, B represents the casting roll wear zone, and C represents the strip wear zone. Detailed Implementation

[0049] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0050] This invention provides a method for preparing a carbon-based ceramic side sealing plate for thin strip continuous casting, which mainly includes the following steps:

[0051] S1. By mass fraction, weigh 12-20% flake graphite with a particle size of 0.1-0.5 mm, 10-15% ultrafine graphite with a particle size <0.01 mm, 10-20% zirconium oxide with a particle size <5 μm (using monoclinic zirconium oxide), 3-5% boron anhydride (crystal purity 99.5%, 325 mesh), 35-45% spinel with a particle size <5 μm, 5-10% boron carbide passing through a 1000-mesh sieve, and 0.1-0.3% of... N1055 (dispersant for graphite) and 0.1-0.3% T85 (dispersant for zirconia) are placed in a mixer and stirred evenly to obtain a mixture. 25-35% of deionized water is added to the mixture, and stirring is continued until the flake graphite and ultrafine graphite in the powder are fully dispersed to obtain a slurry. The dispersed slurry is then spray-dried to obtain a powder with a particle size of no more than 0.5 mm. The powder, 8-12% of liquid phenolic resin by weight of the powder, and 8% of hexamethylenetetramine by weight of the liquid phenolic resin are placed in the feed pot of a high-speed mixing and granulating machine for mixing and granulation. The temperature of the feed pot is kept at 60-80℃ during mixing. The mixture is then sieved to obtain granulated powder with a particle size of no more than 3 mm.

[0052] S2. Place the granulated powder in a mold. The mold is equipped with venting holes and a heating function to ensure that the temperature of the molding blank is 60-80℃. Use a hydraulic press to perform near-net-shape molding with a molding pressure ≥120MPa to obtain the blank.

[0053] S3. The preform is cured at 300℃. Curing causes the resin to form a network of three-dimensional polymers, resulting in higher strength. After curing at 300℃, the porosity of the preform is less than 1%.

[0054] S4. Place the blank in a sagger and fully bury it with metallic silicon powder for silicon diffusion heat treatment. Place the sagger in a vacuum furnace for segmented sintering with a vacuum degree of <100Pa. After silicon diffusion densification is completed, clean the surface to obtain the carbon-based side sealing plate.

[0055] It should be noted that in step S4, the specific parameters for segmented sintering are as follows: first, the temperature is raised from room temperature to the first target temperature and held at the first target temperature for 2-3 hours; then, the temperature is raised from the first target temperature to the second target temperature and held at the second target temperature for 2-5 hours; then, the temperature is raised from the second target temperature to the third target temperature and held at the third target temperature for 1-5 hours; wherein, the first target temperature is 900-950℃, the second target temperature is 1100-1300℃, and the third target temperature is greater than 1400℃. When the billet is at room temperature to 900℃, the resin mainly decomposes to form bound carbon. At this time, certain channels are formed inside the material due to the decomposition of the resin. In the 1100-1300℃ stage, a carbothermic reduction reaction occurs: ZrO2 + B2O3 + C → ZrB2 + CO. The above channels facilitate the discharge of CO, thereby promoting the formation of ZrB2. In the stage above 1400℃, the silicon powder on the periphery of the side sealing plate begins to melt and penetrate into the side sealing plate along the internal pores. Based on the thickness of the billet of about 3-5cm, the internal pores are eventually filled with Si, which increases the density of the material. At the same time, some of the molten silicon metal further reacts with some carbon in the following way: Si + C → SiC. The in-situ formed SiC can significantly enhance the toughness and friction and wear resistance of the side sealing plate. After the Si densification is completed, the surface is cleaned and a near-net-shape carbon-based side sealing plate is finally obtained.

[0056] The technical solution of the present invention will be described in detail below with reference to specific embodiments. It should be noted that all raw materials used are commercially available products.

[0057] Example 1

[0058] A method for preparing a carbon-based ceramic side sealing plate for thin strip continuous casting is as follows:

[0059] S1. Weigh out, by mass fraction, 14.4% flake graphite, 10% ultrafine graphite, 20% zirconium oxide, 5% boron anhydride, 45% spinel, 5% boron carbide, and 0.3%... N1055 and 0.3% T85 are added to a mixer and thoroughly mixed to obtain a mixture. Then, 30% of the mass of deionized water is added to the mixture, and stirring is continued to ensure that the flake graphite and ultrafine graphite are fully dispersed to obtain a slurry. The dispersed slurry is then dried in a spray dryer to obtain a powder with a particle size of ≤0.5mm. The powder, 8% of the mass of liquid phenolic resin, and 8% of the mass of liquid phenolic resin are then mixed and granulated in a high-speed mixing and granulating machine. During granulation, the temperature of the mixing pot is kept at 70℃. After sieving, granulated powder with a particle size of no more than 3mm is obtained.

[0060] S2. Place the granulated powder in the mold and use a hydraulic press to form it to near net size. The mold needs to be equipped with vent holes and heating function. The forming blank temperature is 60℃ and the forming pressure is 120MPa. Finally, a side sealing plate blank with near net size is obtained.

[0061] S3. The preform is cured at 300℃;

[0062] S4. Place the billet in a silicon carbide sagger and fully bury it with silicon metal powder. Then, fire it in a vacuum furnace with a vacuum degree of <100Pa. Set three heat preservation points: 900℃×3h, 1300℃×3h, and 1400℃×5h. After cooling in the furnace, clean the surface to obtain a near-net-shape carbon-based side sealing plate.

[0063] Example 2

[0064] A method for preparing a carbon-based ceramic side sealing plate for thin strip continuous casting is as follows:

[0065] S1. Weigh out, by mass fraction, 20% flake graphite, 15% ultrafine graphite, 10% zirconium oxide, 3% boron anhydride, 41.6% spinel, 10% boron carbide, and 0.2%... N1055 and 0.2% T85 are added to a mixer and thoroughly mixed to obtain a mixture. Then, 25% of the mass of deionized water is added to the mixture, and stirring is continued to ensure that the flake graphite and ultrafine graphite are fully dispersed to obtain a slurry. The dispersed slurry is then dried in a spray dryer to obtain a powder with a particle size of ≤0.5mm. The powder, 12% of the mass of liquid phenolic resin, and 8% of the mass of liquid phenolic resin are then mixed and granulated in a high-speed mixing and granulating machine. During granulation, the temperature of the mixing pot is kept at 80℃. The mixture is then sieved to obtain granulated powder with a particle size of no more than 3mm.

[0066] S2. Place the granulated powder in the mold and use a hydraulic press to form it to near net size. The mold needs to be equipped with vent holes and heating function. The forming blank temperature is 80℃ and the forming pressure is 150MPa. Finally, a side sealing plate blank with near net size is obtained.

[0067] S3. The preform is cured at 300℃;

[0068] S4. Place the billet in a silicon carbide crucible and fully bury it with silicon metal powder. Then, fire it in a vacuum furnace with a vacuum degree of <100Pa. Set three heat preservation points: 950℃×3h, 1100℃×5h, and 1500℃×2h. After cooling in the furnace, clean the surface to obtain a near-net-shape carbon-based side sealing plate.

[0069] Example 3

[0070] A method for preparing a carbon-based ceramic side sealing plate for thin strip continuous casting is as follows:

[0071] S1. Weigh out, by mass fraction, 19% flake graphite, 14% ultrafine graphite, 18.8% zirconium oxide, 4% boron anhydride, 35% spinel, 9% boron carbide, and 0.1%... N1055 and 0.1% T85 are added to a mixer and thoroughly mixed to obtain a mixture. Then, 35% of the mass of deionized water is added to the mixture, and stirring is continued to ensure that the flake graphite and ultrafine graphite are fully dispersed to obtain a slurry. The dispersed slurry is then dried in a spray dryer to obtain a powder with a particle size of ≤0.5mm. The powder, 10% of the mass of liquid phenolic resin, and 8% of the mass of liquid phenolic resin are then mixed and granulated in a high-speed mixing and granulating machine. During granulation, the temperature of the mixing pot is kept at 80℃. After sieving, granulated powder with a particle size of no more than 3mm is obtained.

[0072] S2. Place the granulated powder in the mold and use a hydraulic press to form it to near net size. The mold needs to be equipped with vent holes and have a heating function. The forming blank temperature is 60℃ and the forming pressure is 130MPa. Finally, a side sealing plate blank with near net size is obtained.

[0073] S3. The preform is cured at 300℃;

[0074] S4. Place the billet in a silicon carbide sagger and fully bury it with silicon metal powder. Then, fire it in a vacuum furnace with a vacuum degree of <100Pa. Set three heat preservation points: 950℃×3h, 1250℃×4h, and 1600℃×1h. After cooling in the furnace, clean the surface to obtain a near-net-shape carbon-based side sealing plate.

[0075] Comparative Example 1

[0076] Comparative Example 1 is a commercially available BN-based side sealing plate manufactured by Saint-Gobain, France.

[0077] Experimental Analysis

[0078] The bulk density, apparent porosity, flexural strength, coefficient of thermal expansion, resistance to molten steel erosion, resistance to molten steel thermal shock, and resistance to friction and wear of the side sealing plates prepared in Examples 1-3 and Comparative Example 1 were tested, and the results are shown in Table 1.

[0079] Table 1. Test results of the side sealing plates prepared in Examples 1-3 and Comparative Example 1

[0080]

[0081]

[0082] As shown in Table 1, the performance of the side sealing plate prepared in this application is basically the same as that of the BN-based side sealing plate, which indicates that the side sealing plate prepared in this application meets the service requirements of thin strip continuous casting for the side sealing plate to resist molten steel erosion, resist molten steel thermal shock, and resist friction and wear.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention in any way. All equivalent transformations or modifications made in accordance with the essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for producing a carbon-based ceramic side seal plate for thin strip continuous casting, characterized by, The method mainly comprises the following steps: S1, 12-20% of flaky graphite, 10-15% of ultra-fine graphite, 10-20% of zirconium oxide, 3-5% of boron anhydride, 35-45% of spinel, 5-10% of boron carbide, 0.1-0.3% of GLYDOL ® N1055 and 0.1-0.3% of T85 are weighed in mass fraction and stirred in a blender to obtain a mixture, 25-35% of deionized water by mass of the mixture is added and stirring is continued until the flaky graphite and the ultra-fine graphite are fully dispersed to obtain a slurry; then the dispersed slurry is spray-dried to obtain a powder with a particle size not greater than 0.5 mm; then the powder, 8-12% of liquid phenolic resin by mass of the powder, and 8% of urotropine by mass of the liquid phenolic resin are placed in a material pot of a high-speed mixing and granulating machine for mixing and granulation, and sieving is performed to obtain a granulated powder with a particle size not greater than 3 mm; S2, placing the granulated powder in a mold, and using a hydraulic machine to perform near-net size forming under heating to obtain a green body; S3, performing solidification treatment on the green body at 300℃; S4, placing the green body in a sagger, and fully burying it with silicon powder to perform siliconizing heat treatment, and placing the sagger in a vacuum electric furnace to perform step-by-step sintering, with a vacuum degree less than 100 Pa, and after completing siliconizing densification, cleaning the surface to obtain a carbon-based side sealing plate.

2. The method of claim 1, wherein the carbon-based ceramic side sealing plate for thin strip casting is prepared by the steps of: The particle size of the flaky graphite is 0.1-0.5 mm; ​ The particle size of the ultra-fine graphite is less than 0.01 mm; The particle size of the zirconia is less than 5 μm; The particle size of the spinel is less than 5 μm; The particle size of the boron carbide is 1000 mesh; The crystal purity of the boron anhydride is 99.5%, and the particle size is 325 mesh.

3. The method of claim 1, wherein the carbon-based ceramic side sealing plate for thin strip casting is prepared by the steps of: preparing a carbon-based ceramic side sealing plate by mixing and sintering a carbon-based ceramic powder and a binder; and coating the carbon-based ceramic side sealing plate with a carbon-based coating material. In step S1, the temperature of the mixing kettle is kept at 60-80℃ during mixing.

4. The method of claim 1, wherein the carbon-based ceramic side sealing plate for thin strip casting is prepared by the steps of: preparing a carbon-based ceramic side sealing plate by mixing and sintering a carbon-based ceramic powder and a binder; and coating the carbon-based ceramic side sealing plate with a carbon-based coating material. In step S2, an exhaust hole is arranged on the mold; A heating unit is arranged on the mold to ensure that the temperature during forming of the green body is kept at 60-80℃.

5. The method of claim 1, wherein the carbon-based ceramic side sealing plate for thin strip casting is prepared by the steps of: preparing a mixture of a carbon-based material and a ceramic material; and sintering the mixture to form the carbon-based ceramic side sealing plate. In step S2, the forming pressure is not less than 120 MPa.

6. The method of claim 1, wherein the carbon-based ceramic side sealing plate for thin strip casting is prepared by the steps of: preparing a mixture of a carbon-based material and a ceramic material; and sintering the mixture to form the carbon-based ceramic side sealing plate. In step S4, the specific parameters of step-by-step sintering are as follows: First, increasing the temperature from room temperature to a first target temperature, and keeping the temperature at the first target temperature for 2-3 h; Then, increasing the temperature from the first target temperature to a second target temperature, and keeping the temperature at the second target temperature for 2-5 h; Finally, increasing the temperature from the second target temperature to a third target temperature, and keeping the temperature at the third target temperature for 1-5 h; The first target temperature is 900-950℃; The second target temperature is 1100-1300℃; The third target temperature is greater than 1400℃.

7. A carbon-based ceramic side sealing plate for thin strip continuous casting, which is prepared by the method of any one of claims 1-6.

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