Alumina-silicon carbide carbon unfired brick for iron ladle and its production method

Abstract

The application discloses a production method of aluminum silicon carbide carbon unfired brick for molten iron tank, and is prepared according to the following steps: firstly, aluminum-containing aggregates, modified silicon carbide whiskers, modified graphite powder and phenolic resin are weighed according to proportions and added into a stirring tank to be uniformly mixed; secondly, the stirring tank is vacuumized and aged for 2-3 hours; then, the mixed material is added into a mold to be pressed and formed; finally, the green brick is sintered in a kiln at 180-220 DEG C for 18-20 hours, and is cooled to obtain the aluminum silicon carbide carbon unfired brick. The aluminum silicon carbide carbon unfired brick prepared by the method has the excellent performances of low apparent porosity, high compressive strength and bending strength and strong erosion resistance.

Description

Technical Field

[0001] This invention relates to the field of refractory brick technology, and in particular to an aluminum silicon carbide carbon non-fired brick for molten iron ladles and its production method. Background Technology

[0002] The molten iron ladle is an important piece of equipment for conveying molten iron in integrated iron and steel enterprises. Its working inner layer is made of refractory material and is in direct contact with the molten iron. The quality of the refractory material seriously affects the safety and service life of the molten iron ladle. Alumina silicon carbide carbon bricks are widely used as furnace lining materials in various molten iron containers in ironmaking systems due to their excellent erosion resistance and thermal shock resistance. The carbon element in the bricks refers to graphite. Graphite has excellent thermal conductivity and refractory properties, low thermal expansion coefficient, and a large wetting angle with slag, which can prevent slag from penetrating into the product, thereby reducing erosion. However, graphite is very easy to oxidize. Once graphite is oxidized, the erosion resistance of the refractory material is reduced. Various antioxidants are usually added to improve the service life of alumina silicon carbide carbon bricks.

[0003] Application No. 202011157931.4 discloses an aluminum silicon carbide carbon brick and its preparation method, which achieves the coating of silicon carbide and graphite by using alumina powder of different particle sizes, thus achieving excellent functions such as high temperature resistance and long service life.

[0004] Application No. 202111030106.2 discloses an anti-oxidation silicon carbide alumina brick and its preparation method. By adding barite, silicon powder and boron carbide, the material density is improved, the porosity is reduced, and the fire resistance and oxidation resistance are enhanced. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing aluminum silicon carbide carbon bricks, such as low thermal shock stability, easy detachment, low oxidation resistance, and short lifespan, and to provide an aluminum silicon carbide carbon non-fired brick for molten iron ladles and its production method.

[0006] The objective of this invention is achieved through the following technical solution: a method for producing aluminum silicon carbide carbon non-fired bricks for molten iron ladles, characterized by preparation according to the following steps.

[0007] S1. Weigh the aluminum-containing aggregate, modified silicon carbide whiskers, modified graphite powder, and phenolic resin according to the specified proportions and add them to a mixing tank to mix evenly.

[0008] S2. Vacuum the mixing tank and age for 2-3 hours;

[0009] S3. Add the mixture to the mold and press it into shape;

[0010] S4. Place the brick blanks in a kiln at 180-220℃ for 18-20 hours, and then cool them to obtain the final product.

[0011] Preferably, in step S1, by mass parts, the aluminum-containing aggregate comprises 70-80 parts, the modified silicon carbide whiskers comprises 10-12 parts, the modified graphite powder comprises 15-20 parts, and the phenolic resin comprises 5-8 parts.

[0012] Preferably, the aluminum-containing aggregate in step S1 is Guyana bauxite clinker, wherein the aluminum-containing aggregate is Guyana bauxite clinker with an Al2O3 mass content ≥89%, a total Al2O3+SiO2 mass content ≥94%, and a total K2O+Na2O mass content ≤0.1%.

[0013] Preferably, it also includes 5-8 parts of andalusite, wherein the andalusite has a particle size of 1-3 mm.

[0014] Preferably, the modified silicon carbide whiskers are prepared according to the following method:

[0015] S1. Dissolve sodium azide in water to prepare a salt solution;

[0016] S2. Immerse silicon carbide whiskers in a sodium azide solution and dry them under vacuum;

[0017] S3. Add the dried silicon carbide whiskers to the silicon tetrachloride solvent and heat at a constant temperature for 4-5 hours;

[0018] S4. Filter the solvent and vacuum dry to obtain silicon nitride modified silicon carbide whiskers.

[0019] Preferably, the modified graphite powder is prepared according to the following steps:

[0020] S1. Prepare a uniform mixture of flake graphite, metallic aluminum powder, and aluminum dihydrogen phosphate;

[0021] S2. Place the mixture in a kiln and heat it by introducing nitrogen gas;

[0022] S3. Gradually raise the temperature of the kiln to 800 degrees Celsius and maintain the temperature for 2-3 hours;

[0023] S4. Continue heating to 1200℃ and maintain the temperature for 3-4 hours;

[0024] S5. After natural cooling, the modified graphite powder is obtained.

[0025] The present invention also provides an aluminum silicon carbide carbon non-fired brick for molten iron ladles prepared according to the above method.

[0026] The present invention has the following advantages:

[0027] 1. By modifying the surface of silicon carbide whiskers with silicon nitride, silicon nitride is grafted onto the smooth, long-fiber silicon carbide surface, increasing the surface roughness and improving its connection strength with other components. At the same time, silicon nitride is more easily oxidized than silicon carbide, which can play an antioxidant protection role for silicon carbide whiskers.

[0028] 2. Coating the graphite surface with aluminum nitride and aluminum phosphate, compared with the traditional method of directly adding silicon powder, aluminum powder, and magnesium powder antioxidants for protection, can achieve a tight film coverage of the carbon element surface, isolate oxygen, and provide better anti-oxidation performance.

[0029] 3. After high-temperature sintering and carbonization, phenolic resin forms cavities, increasing apparent porosity. By reasonably adding a certain proportion of andalusite, the voids can be filled, improving the density of refractory bricks and enhancing their resistance to slag erosion and oxidation.

[0030] 4. This invention combines high-alumina aggregate, modified silicon carbide, modified graphite powder and phenolic resin, and further reduces dissolved air in the mixture through vacuum degassing. This avoids the initial reaction of oxygen with multiple components such as graphite and silicon carbide during high-pressure pressing, resulting in aluminum silicon carbide carbon bricks with excellent properties such as low apparent porosity, high compressive strength, high flexural strength and strong erosion resistance. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with specific embodiments.

[0032] To prepare modified silicon carbide whiskers, firstly, 100g of commercially available sodium azide was dissolved in 500ml of purified water to obtain a sodium azide salt solution. Silicon nitride whisker powder was then added to the sodium azide salt solution and stirred until the silicon nitride whiskers were completely wetted. The mixture was filtered and vacuum dried at room temperature for 5 hours. The dried silicon carbide whiskers were then placed in a reaction vessel, and 600ml of silicon tetrachloride and 3ml of Grignard reagent were added. Nitrogen gas was introduced and the temperature was raised to 160 degrees Celsius. The mixture was then kept at a constant temperature for 20 hours. After naturally cooling to room temperature, the mixture was filtered and washed successively with anhydrous ethanol and purified water. Finally, the mixture was dried in a 40-degree oven to obtain silicon carbide whiskers with a silicon nitride-modified surface.

[0033] To prepare modified graphite powder, firstly, 100-mesh flake graphite, 400-mesh aluminum powder, and 100-mesh aluminum dihydrogen phosphate powder are mixed using a V-shaped mixer. Then, the mixture is placed in a muffle furnace, nitrogen is introduced for 5 minutes, and the temperature is raised to 800 degrees Celsius and kept constant for 3 hours. After that, the temperature is raised to 1200 degrees Celsius and kept constant for 4 hours. Then, the heating is turned off and the mixture is allowed to cool naturally to room temperature. After that, the nitrogen is turned off, and the graphite powder with aluminum nitride and aluminum phosphate mixed coating is obtained.

[0034] Example 1: An aluminum silicon carbide carbon non-fired brick for molten iron ladles, prepared according to the following steps.

[0035] S1. Purchase commercially available Guyana bauxite clinker. The Guyana bauxite clinker has an Al2O3 content ≥89%, a total Al2O3+SiO2 content ≥94%, and a total K2O+Na2O content ≤0.1%. Compared with other aluminum-containing aggregates, it has a high aluminum content, low sodium content, and few impurities. Weigh out 70 parts of Guyana bauxite clinker, 10 parts of silicon carbide whiskers modified with silicon nitride, 20 parts of commercially available graphite powder, and 8 parts of thermosetting phenolic resin and add them to a mixing tank for 1 hour.

[0036] S2. Evacuate the mixing tank to 0.5-0.6 MPa and remove volatile gases for 2-3 hours;

[0037] S3. Discharge the mixture into the mold and press it into a brick blank under a pressure of 80MPa;

[0038] S4. Demold and sinter in a kiln at 180-220℃ for 18-20 hours, then cool to obtain the final product.

[0039] Example 2: An aluminum silicon carbide carbon non-fired brick for molten iron ladles, prepared according to the following steps.

[0040] S1. Weigh out 70 parts of Guyana bauxite clinker, 10 parts of commercially available silicon carbide whiskers, 20 parts of modified graphite powder prepared by the method of this patent, and 8 parts of thermosetting phenolic resin, and add them to a mixing tank for 1 hour.

[0041] S2. Evacuate the mixing tank to 0.5-0.6 MPa and remove volatile gases for 2-3 hours;

[0042] S3. Discharge the mixture into the mold and press it into a brick blank under a pressure of 80MPa;

[0043] S4. Demold and sinter in a kiln at 180-220℃ for 18-20 hours, then cool to obtain the final product.

[0044] Example 3: An aluminum silicon carbide carbon non-fired brick for molten iron ladles, prepared according to the following steps.

[0045] S1. Weigh out 70 parts of Guyana bauxite clinker, 10 parts of modified silicon carbide whiskers prepared by the method of this patent, 20 parts of modified graphite powder prepared by the method of this patent, and 8 parts of thermosetting phenolic resin, and add them together into a mixing tank for 1 hour.

[0046] S2. Evacuate the mixing tank to 0.5-0.6 MPa and remove volatile gases for 2-3 hours;

[0047] S3. Discharge the mixture into the mold and press it into a brick blank under a pressure of 80MPa;

[0048] S4. Demold and sinter in a kiln at 180-220℃ for 18-20 hours, then cool to obtain the final product.

[0049] Example 4: An aluminum silicon carbide carbon non-fired brick for molten iron ladles, prepared according to the steps of Example 3, except that in step S1, the mass ratio of the components is 80 parts of Guyana bauxite clinker, 12 parts of modified silicon carbide whiskers prepared by the method of this patent, 15 parts of modified graphite powder prepared by the method of this patent, and 5 parts of thermosetting phenolic resin. The subsequent steps are the same as in Example 3.

[0050] The physical and chemical properties and related parameters of the aluminosilicate carbon bricks produced in Examples 1-4 are compared in the table below.

[0051]

[0052]

[0053] A comparison of the data results from Examples 1-4 shows that as the graphite content in the aluminum silicon carbide carbon brick decreases, the apparent porosity gradually decreases and the bulk density gradually increases. A comparison of the decarburized layer thickness results between Examples 1 and 3 shows that the modified graphite powder prepared in this patent has superior antioxidant properties compared to ordinary graphite. A comparison of the flexural strength between Examples 2 and 3 shows that modified silicon carbide can improve the flexural strength of aluminum silicon carbide carbon bricks compared to ordinary silicon carbide.

[0054] Example 5: Based on Example 3, 5-8 parts of andalusite with a particle size of 1-3 mm were added to the raw material components, and other conditions remained unchanged to prepare silicon carbide aluminum carbon bricks.

[0055] Example 6: Based on Example 3, 20-22 parts of andalusite with a particle size of 1-3 mm were added to the raw material components, and other conditions remained unchanged to prepare silicon carbide aluminum carbon bricks.

[0056] The physical and chemical properties and related parameters of the aluminosilicate carbon bricks produced in Examples 5-6 are compared in the table below.

[0057]

[0058] According to the data results of Examples 3, 5, and 6, the micro-expansion caused by the addition of andalusite can fill the pores and improve the oxidation resistance and slag erosion resistance. However, excessive addition of andalusite will lead to increased expansion and the generation of microcracks, which will reduce the flexural strength, oxidation resistance, and erosion resistance. In actual production, the amount of andalusite added needs to be controlled.

[0059] Example 7: Based on Example 5, 70 parts of Guyana bauxite clinker, 10 parts of commercially available silicon carbide whiskers, 5 parts of commercially available silicon nitride powder, 20 parts of modified graphite powder prepared by the method of this patent, 5-8 parts of andalusite, and 5 parts of thermosetting phenolic resin were weighed and mixed for 1 hour. The subsequent steps were the same as those in Example 1.

[0060] Example 8: An aluminum silicon carbide carbon non-fired brick for molten iron ladles, prepared according to the following steps.

[0061] To prepare modified graphite powder, firstly, 100-mesh flake graphite, 400-mesh aluminum powder, and 100-mesh aluminum dihydrogen phosphate powder are mixed using a V-shaped mixer. Then, the mixture is placed in a muffle furnace, heated to 1200 degrees Celsius, and reacted at a constant temperature for 2 hours. After the heating is turned off and the mixture is allowed to cool naturally to room temperature, the graphite powder with alumina and aluminum phosphate mixed coating is obtained.

[0062] S1. Weigh out 70 parts of Guyana bauxite clinker, 10 parts of modified silicon carbide whiskers prepared by the method of this patent, 20 parts of modified graphite powder coated with alumina and phosphorus oxide, 5-8 parts of andalusite, and 5 parts of thermosetting phenolic resin, and add them together into a mixing tank for 1 hour.

[0063] S4. Evacuate the mixing tank to 0.5-0.6 MPa and remove volatile gases for 2-3 hours;

[0064] S5. Discharge the mixture into the mold and press it into a brick blank under a pressure of 80MPa;

[0065] S6. Demold and sinter in a kiln at 180-220℃ for 18-20 hours, then cool to obtain the final product.

[0066] Example 9: Based on Example 8, 5 parts of 200-mesh aluminum nitride powder were added in step S1, and the subsequent processing steps were the same as those in Example 8.

[0067] The physical and chemical properties and related parameters of the aluminum silicon carbide carbon bricks produced in Examples 7-9 are compared in the table below.

[0068]

[0069]

[0070] Based on the comparison of the flexural strength results of Examples 5 and 7, the silicon carbide whiskers with attached silicon nitride can further improve the flexural strength of aluminum silicon carbide carbon bricks compared to direct mixing. Based on the comparison of the decarburized layer thickness and filter residue erosion depth results of Examples 5, 8, and 9, it can be seen that the addition of aluminum nitride can improve the oxidation resistance and slag resistance, but the improvement effect is less than that of graphite powder modified with aluminum nitride.

[0071] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing aluminum silicon carbide carbon non-fired bricks for molten iron ladles, characterized in that, Prepare according to the following steps. S1. Weigh out 70-80 parts of aluminum-containing aggregate, 10-12 parts of modified silicon carbide whiskers, 15-20 parts of modified graphite powder, and 5-8 parts of phenolic resin by weight and add them to a mixing tank and mix evenly. S2. Vacuum the mixing tank and age for 2-3 hours; S3. Add the mixture to the mold and press it into shape; S4. Sinter the brick blanks in a kiln at 180-220℃ for 18-20 hours, then cool to obtain the final product; The modified silicon carbide whiskers are prepared by dissolving sodium azide in water to make a salt solution, immersing silicon carbide whiskers in the sodium azide salt solution and drying them under vacuum, adding the dried silicon carbide whiskers to a silicon tetrachloride solution and heating and reacting at a constant temperature for 4-5 hours, filtering the solution and drying it under vacuum to obtain silicon nitride modified silicon carbide whiskers. The modified graphite powder is prepared according to the following steps: flake graphite is mixed with aluminum powder and aluminum dihydrogen phosphate to form a uniform mixture. The mixture is placed in a kiln and heated by introducing nitrogen gas. The kiln temperature is gradually increased to 800 degrees Celsius and kept constant for 2-3 hours. The temperature is then increased to 1200 degrees Celsius and kept constant for 3-4 hours. The mixture is then cooled naturally and removed to obtain the modified graphite powder.

2. The method for producing aluminum silicon carbide carbon non-fired bricks for molten iron ladles according to claim 1, characterized in that, The aluminum-containing aggregate mentioned in step S1 is Guyana bauxite clinker.

3. The method for producing aluminum silicon carbide carbon non-fired bricks for molten iron ladles according to claim 1, characterized in that, In step S1, 5-8 parts of andalusite are also included.

4. Aluminum silicon carbide carbon non-fired bricks for molten iron ladles prepared by any one of the methods described in claims 1-3.

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