Silicon carbide sintered grate bar and method of making same

Abstract

This invention discloses a silicon carbide sintering machine grate and its preparation method, relating to the technical field of refractory materials for sintering machines in the steel industry. The invention utilizes silicon carbide, silicon nitride, silane, andalusite, zirconium mullite, aluminum titanate, zirconium boride, and Y₂O₃ as main materials, phenolic resin and polycarbosilane as binders, aluminum powder and silicon powder as active additives, calcium lignosulfonate as a dispersant, and azodicarbonamide as a pore-forming agent to prepare the silicon carbide sintering machine grate. This silicon carbide sintering machine grate exhibits good thermal shock stability, corrosion resistance, wear resistance, and service life, meeting the operating conditions of sintering machine trolleys. Specifically, compared to cast iron grates, the silicon carbide sintering machine grate prepared by this invention can withstand more than 15 thermal shock cycles at 1200℃ water cooling, reduces the corrosion rate by more than 80% under a mixed atmosphere of CO, CO₂, and water vapor, reduces the volumetric wear rate by more than 60%, and increases the average service life by more than 50%.

Description

Technical Field

[0001] This invention relates to the field of refractory materials for sintering machines in the steel industry, and in particular to a silicon carbide sintering machine grate and its preparation method. Background Technology

[0002] Sintering machines are crucial thermal equipment in steel smelting. The sintering machine grate, as a key load-bearing component of the sintering machine trolley, primarily supports the sintered ore, ensuring smooth airflow through the material layer during sintering. During operation, the grate is constantly exposed to a complex environment involving high temperatures, rapid heating and cooling, mechanical impact, sintered ore abrasion, and the combined effects of CO, CO2, water vapor, and alkali metal vapors. Its service condition directly impacts the ventilation efficiency, sintered ore quality, equipment operational stability, and production rate of the sintering machine.

[0003] Currently, sintering machine grates are generally made of cast iron or high-chromium cast iron. Cast iron grates are prone to oxidation at high temperatures, have poor thermal shock stability, and are insufficiently resistant to CO, CO2, and water vapor corrosion, resulting in a short service life. In actual production, the average service life of cast iron grates is about 6-8 months, and in severe cases, they break, deform, or corrode after only 4-5 months. Frequent replacements not only increase production costs but also affect the operating rate of the sintering machine. In recent years, silicon carbide refractories, due to their high temperature resistance, wear resistance, good thermal conductivity, and good oxidation resistance, have been increasingly used in the preparation of high-temperature bearing structures. Therefore, the question is how to prepare silicon carbide sintering machine grates with good thermal shock stability, wear resistance, and corrosion resistance without changing the structure of the sintering machine grate bars, so as to overcome the problems of easy oxidation, easy corrosion, insufficient thermal shock stability, severe wear, and frequent replacement of existing cast iron grate bars, and meet the requirements for long-term continuous and stable operation of the sintering machine. Summary of the Invention

[0004] To address the aforementioned limitations of existing technologies, the present invention aims to provide a silicon carbide sintering machine grate and its preparation method. This invention utilizes silicon carbide, silicon nitride, silane, andalusite, zirconium mullite, aluminum titanate, zirconium boride, and Y₂O₃ as main materials, phenolic resin and polycarbosilane as binders, aluminum powder and silicon powder as active additives, calcium lignosulfonate as a dispersant, and azodicarbonamide as a pore-forming agent to prepare the silicon carbide sintering machine grate. This silicon carbide sintering machine grate exhibits excellent thermal shock resistance, corrosion resistance, wear resistance, and service life, meeting the operating conditions of sintering machine trolleys. Specifically, compared to cast iron grates, the silicon carbide sintering machine grate prepared by this invention can withstand more than 15 thermal shock cycles at 1200℃ water cooling, exhibits a corrosion rate reduction of over 80% under a mixed atmosphere of CO, CO₂, and water vapor, a volumetric wear rate reduction of over 60%, and an average service life increase of over 50%.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a silicon carbide sintering machine grate, prepared from the following raw materials in weight percentages: Silicon carbide 15%-35%, silicon nitride 10%-25%, silane 5%-15%, andalusite 8%-18%, zircon-mullite 5%-12%, aluminum titanate 4%-10%, zirconium boride 3%-8%, Y2O3 2%-6%, phenolic resin 2%-5%, polycarbosilane 1%-4%, aluminum powder 1%-3%, silicon powder 1%-3%, calcium lignosulfonate 1%-2%, azodicarbonamide 0.5%-2%.

[0006] Preferably, the silicon carbide sintering machine grate is made from the following raw materials by weight percentage: Silicon carbide 22%-24%, silicon nitride 16%-18%, silane 8%-9%, andalusite 10%-11%, zircon-mullite 7%-8%, aluminum titanate 6%-7%, zirconium boride 5%-6%, Y2O3 3%-4%, phenolic resin 2%-3%, polycarbosilane 2%-3%, aluminum powder 1%-2%, silicon powder 1%-2%, calcium lignosulfonate 1%-2%, azodicarbonamide 0.5%-1%.

[0007] Preferably, the particle size of silicon carbide is 3mm-5mm, the particle size of silicon nitride is 1mm-3mm, the particle size of silane is 1mm-3mm, the particle size of andalusite is 1mm-2mm, the particle size of zirconium mullite is ≤1mm, the particle size of aluminum titanate is <0.088mm, the particle size of zirconium boride is <30μm, the particle size of Y2O3 is <10μm, the particle size of aluminum powder and silicon powder is 150-250 mesh, the particle size of calcium lignosulfonate is 160-200μm, and the particle size of azodicarbonamide is 150-250 mesh.

[0008] A second aspect of the present invention provides a method for preparing the above-mentioned silicon carbide sintering machine grate, comprising the following steps: The raw materials are mixed according to their weight percentages and stirred for the first time to obtain a mixture. Water is added to the mixture and stirred for the second time to obtain a molding material. The molding material is pressed and shaped, cured and dried, and then sintered in an inert atmosphere and cooled to obtain a silicon carbide sintering machine grate.

[0009] Preferably, the first stirring time is 8-12 min and the second stirring time is 10-15 min.

[0010] Preferably, the pressure during the compression molding process is 110-130 MPa.

[0011] As a preferred option, the curing time is 24 hours.

[0012] Preferably, the drying temperature is 100-120℃ and the drying time is 20-25h.

[0013] Preferably, the inert atmosphere is nitrogen, the sintering temperature is 1400-1500℃, and the sintering time is 5-7h.

[0014] The beneficial effects of this invention are: This invention utilizes silicon carbide, silicon nitride, silane, andalusite, zirconium mullite, aluminum titanate, zirconium boride, and Y₂O₃ as main materials, phenolic resin and polycarbosilane as binders, aluminum powder and silicon powder as active additives, calcium lignosulfonate as a dispersant, and azodicarbonamide as a pore-forming agent to produce silicon carbide sintering machine grates. These silicon carbide sintering machine grates exhibit good thermal shock resistance, corrosion resistance, wear resistance, and service life, meeting the operating conditions of sintering machine trolleys.

[0015] Specifically, compared to cast iron grate bars, the silicon carbide sintering machine grate bars produced by this invention can withstand more than 15 water-cooled thermal shock cycles at 1200℃, reduce the corrosion rate by more than 80% under a mixed atmosphere of CO, CO2 and water vapor, reduce the volumetric wear rate by more than 60%, and increase the average service life by more than 50%, reaching more than 12 months.

[0016] Furthermore, compared with existing cast iron grate bars, the silicon carbide grate bars have a wide range of raw material sources and a lower overall cost than cast iron, resulting in significant economic benefits. Detailed Implementation

[0017] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0018] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0019] The experimental materials used in the embodiments of this invention are all conventional experimental materials in the art and can be purchased through commercial channels.

[0020] Examples 1-7: Silicon carbide sintering machine grates and their preparation methods 1. Raw material composition The raw material composition of the silicon carbide sintering machine grate bars in Examples 1-7 is shown in Table 1.

[0021] Table 1. Raw material list for silicon carbide sintering machine grate bars in Examples 1-7 (by weight percentage) 2. Preparation method: Mix the raw materials according to their weight percentages and stir for 10 minutes to obtain a mixture. Add water to the mixture, the amount of water being 7.5% of the mixture mass, and stir for 12 minutes to obtain a molding material. Press the molding material under 120 MPa to obtain a molded blank. After naturally curing the molded blank for 24 hours, dry it at 110℃ for 24 hours. Then, place it in a nitrogen atmosphere, heat it to 1450℃, and hold it for 6 hours for sintering. Cool it with the furnace to obtain a silicon carbide sintering machine grate.

[0022] Experimental Example 1: The physicochemical properties of the silicon carbide sintering machine grates prepared in Examples 1-7 were tested, and the results are shown in Table 2. Details are as follows: Bulk density (g / cm³) 3 The bulk density of the sample was tested according to GB / T 2997-2015.

[0023] Apparent porosity (%): The apparent porosity of the sample was tested according to GB / T 2997-2015.

[0024] Room temperature compressive strength (MPa): The compressive strength of the specimen is tested according to GB / T 5072-2008.

[0025] High-temperature flexural strength (MPa): The high-temperature flexural strength of the specimens was tested according to GB / T 3002-2017.

[0026] Thermal shock stability (times): The thermal shock stability of the sample was tested according to YB / T 376-1995.

[0027] Antioxidant properties (weight gain rate at 1200℃ for 100h): The antioxidant properties of the samples were tested according to GB / T 32331-2015.

[0028] Table 2. Property parameters of silicon carbide sintering machine grates obtained in Examples 1-7 As shown in Table 2, the bulk density of the silicon carbide sintering machine grate bar prepared by this invention is 2.85-2.89 g / cm³. 3 The apparent porosity is 2.5%-3.0%, the room temperature compressive strength is 182-190 MPa, the high temperature flexural strength (1400℃) is 35-39 MPa, the thermal shock stability is 15-19 cycles, and the oxidation resistance (1200℃, 100h weight gain rate) is 0.40-0.50%. Therefore, the silicon carbide sintering machine grate prepared by this invention exhibits significantly improved thermal shock resistance, high temperature oxidation resistance, resistance to sinter impact and wear, and service life, meeting the operating conditions of the sintering machine trolley.

[0029] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A silicon carbide sintered grate bar, characterized by, The silicon carbide sintering machine grate bars are prepared from the following raw materials by weight percentage: Silicon carbide 15%-35%, silicon nitride 10%-25%, silane 5%-15%, andalusite 8%-18%, zircon-mullite 5%-12%, aluminum titanate 4%-10%, zirconium boride 3%-8%, Y2O3 2%-6%, phenolic resin 2%-5%, polycarbosilane 1%-4%, aluminum powder 1%-3%, silicon powder 1%-3%, calcium lignosulfonate 1%-2%, azodicarbonamide 0.5%-2%.

2. A sintered silicon carbide grate bar as claimed in claim 1, characterized in that The silicon carbide sintering machine grate bars are made from the following raw materials by weight percentage: Silicon carbide 22%-24%, silicon nitride 16%-18%, silane 8%-9%, andalusite 10%-11%, zircon-mullite 7%-8%, aluminum titanate 6%-7%, zirconium boride 5%-6%, Y₂O₃ 3%-4%, phenolic resin 2%-3%, polycarbosilane 2%-3%, aluminum powder 1%-2%, silicon powder 1%-2%, calcium lignosulfonate 1%-2%, azodicarbonamide 0.5%-1%.

3. A sintered silicon carbide grate bar as claimed in claim 1 or 2, c h a r a c t e r i z e d in that The particle size of silicon carbide is 3mm-5mm, silicon nitride is 1mm-3mm, silane is 1mm-3mm, andalusite is 1mm-2mm, zircon mullite is ≤1mm, aluminum titanate is <0.088mm, zirconium boride is <30μm, Y2O3 is <10μm, aluminum powder and silicon powder are both 150-250 mesh, calcium lignosulfonate is 160-200μm, and azodicarbonamide is 150-250 mesh.

4. The method of producing a silicon carbide sintered grate bar as claimed in any one of claims 1 to 3, characterized in that, Includes the following steps: The raw materials are mixed according to their weight percentages and stirred for the first time to obtain a mixture. Water is added to the mixture and stirred for the second time to obtain a molding material. The molding material is pressed and shaped, cured and dried, and then sintered in an inert atmosphere and cooled to obtain a silicon carbide sintering machine grate.

5. The method of producing a silicon carbide sintered grate bar as set forth in claim 4, wherein The first stirring time is 8-12 minutes, and the second stirring time is 10-15 minutes.

6. The method of producing a silicon carbide sintered grate bar as set forth in claim 4, wherein During the pressing process, the pressure is 110-130MPa and the curing time is 24h.

7. The method of producing a silicon carbide sintered grate bar as set forth in claim 4, wherein The drying temperature is 100-120℃ and the drying time is 20-25h.

8. The method of producing a silicon carbide sintered grate bar as set forth in claim 4, wherein The inert atmosphere is nitrogen, the sintering temperature is 1400-1500℃, and the sintering time is 5-7h.

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