Thermal shock resistant quoin material and method of making

Abstract

The application belongs to the technical field of refractory materials for blast furnace ironmaking, and particularly relates to a thermal shock cracking resistant taphole clay material and a preparation method thereof. The taphole clay material comprises aggregates, matrix powder and a binder system; the binder system is composed of polysilazane, isocyanate curing agent and B4C micropowder. By introducing polysilazane as the main binder, the application realizes high ceramic yield and low volume shrinkage by using the characteristics of polysilazane being converted into Si-B-C-N ceramic at high temperature. Meanwhile, B4C micropowder is oxidized to generate B2O3 at high temperature, which fills pores, promotes sintering and protects carbon phase, so as to realize volume shrinkage compensation and high temperature strength improvement. The taphole clay material has low shrinkage rate, high cold compressive strength, high high-temperature bending strength and excellent thermal shock cracking resistance, and solves the technical problems of poor volume stability and insufficient high-temperature strength of traditional taphole clay caused by binder carbonization shrinkage.

Description

Technical Field

[0001] This application belongs to the technical field of refractory materials for blast furnace ironmaking, and in particular relates to a heat shock resistant taphole clay material and its preparation method. Background Technology

[0002] Taphole clay is a key refractory material used to seal the taphole during the ironmaking process in large blast furnaces. Its working environment is extremely harsh, requiring it to withstand drastic temperature fluctuations (from room temperature to over 1400-1500℃) caused by intermittent tapping, chemical erosion and mechanical scouring from high-temperature molten iron and slag, as well as mechanical stress during tapping. Therefore, taphole clay materials must possess excellent thermal shock resistance, high-temperature strength, erosion resistance, and volumetric stability. Among these, thermal shock cracking resistance is one of the core performance indicators for measuring the service life of taphole clay and ensuring the safe operation of the blast furnace.

[0003] Traditional clay often uses phenolic resin or coal tar as binders. However, these organic binders have the following technical problems during the carbonization process at high temperatures to form a carbon bonded network: (1) Carbonization shrinkage of binders: Traditional phenolic resin undergoes thermal decomposition under high temperature (>400℃) oxygen-free conditions, and the macromolecular chains break, releasing small molecule gases such as H2, CH4, and CO. Carbon atoms are lost in gaseous form, and at the same time, the arrangement between molecular chains changes from disorder to order, resulting in mass loss and volume shrinkage occurring simultaneously. This drastic chemical change generates huge shrinkage stress in the clay matrix. If it cannot be effectively released or compensated, it will destroy the newly formed ceramic bonded network, reduce high-temperature strength, and even cause microcracks. (2) Insufficient thermal shock resistance: The thermal expansion coefficients of the various phases in the clay differ greatly. When the temperature changes drastically, significant thermal stress is generated at the grain boundaries and phase interfaces. When the stress exceeds the material strength limit, microcracks are generated and propagated, leading to material cracking. (3) Environmental issues: Traditional coal tar binders contain polycyclic aromatic hydrocarbons, which will volatilize toxic "yellow smoke" during production and service, seriously polluting the environment and endangering the health of operators.

[0004] To address the aforementioned problems, existing technologies have proposed various solutions. For example, adding high thermal conductivity, low expansion phases such as silicon carbide can improve thermal shock resistance; introducing expansive raw materials such as kyanite can compensate for volume shrinkage; using modified phenolic resins to increase residual carbon content; and adding metal powders for in-situ reaction to generate reinforcing phases. However, these methods are mostly based on a "physical compensation" approach, meaning that the expansion of one component offsets the shrinkage of another, while lacking fundamental chemical control and improvement over the "source" of shrinkage—the carbonization and shrinkage behavior of the binder itself at high temperatures.

[0005] Therefore, developing a clay material that can chemically regulate the carbonization shrinkage behavior of the binder and possesses excellent thermal shock resistance, high-temperature strength, and environmental protection properties is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the aforementioned problems, the purpose of this application is to overcome the shortcomings of existing gunning clay materials, where high-temperature strength and volume stability are difficult to achieve simultaneously due to binder carbonization shrinkage. This application provides a thermal shock resistant gunning clay material and its preparation method. This gunning clay material, by employing a polyborosilazane in-situ ceramicized modified binder system, fundamentally reduces mass loss and volume shrinkage during the carbonization process, achieving a balance between high residual carbon content, low shrinkage rate, and high strength.

[0007] To achieve the above objectives, this application adopts the following technical solution: Firstly, this application provides a heat-shock-resistant drilling mud material.

[0008] A thermal shock resistant drilling mud material, comprising aggregate, matrix powder and binder system.

[0009] The binder system consists of the following components: 100 parts by weight of polyborosilazane; 10-15 parts by weight of isocyanate curing agent; 3-5 parts by weight of B4C micro powder.

[0010] The polyborosilicate is a boron-modified polysilazane, which can be converted into Si-BCN ceramic at high temperatures.

[0011] Preferably, the isocyanate curing agent is one or a mixture of several of diphenylmethane diisocyanate (MDI), isoflurone diisocyanate (IPDI), and polymethylene polyphenyl polyisocyanate (PAPI).

[0012] Preferably, the B4C micro powder has a particle size D50 of 1-3 μm and a purity of ≥98%.

[0013] Preferably, the aggregate comprises the following components in parts by weight: Brown fused alumina (3-5mm) 15-25 parts; Brown fused alumina (1-3mm) 10-20 parts; Brown fused alumina (0-1mm) 5-15 parts; 8-12 parts of silicon carbide (0-1mm); Silicon carbide (200 mesh) 6-10 parts; 6-10 parts of coke (0-1mm).

[0014] Preferably, the matrix powder comprises the following components in parts by weight: 4-8 parts of α-Al₂O₃ micro powder; 2-6 parts of SiO2 micro powder; 3-7 parts clay; 2-6 parts of kyanite.

[0015] Preferably, the total amount of the binder system is 8-12% of the total mass of the aggregate and matrix powder.

[0016] Secondly, this application provides a method for preparing the above-mentioned thermal shock resistant cracking gunning material, comprising the following steps: Step 1: Preparation of binder premix Mix polyborosilazane, isocyanate curing agent, and B4C micro powder, and stir at 500-800 rpm for 10-20 minutes to uniformly disperse the B4C micro powder, thus obtaining a binder premix. If the viscosity is too high and affects mixing, add 10-20 parts by weight of xylene / ethyl acetate mixed solvent (volume ratio 1:1) to adjust the viscosity.

[0017] Step 2: Premixing raw materials Add coarse brown fused alumina particles (3-5mm, 1-3mm) and coke to a mixer and dry mix for 1-3 minutes.

[0018] Step 3: Add binder once Add 1 / 3 of the total amount of the binder premix obtained in step 1, and stir for 2-4 minutes to wet the surface of the coarse particles with the binder.

[0019] Step 4: Add fine powder Add the remaining aggregates (0-1mm brown fused alumina, silicon carbide) and all matrix powders (α-Al2O3 micro powder; SiO2 micro powder, clay, kyanite) in sequence, and stir for 4-6 minutes to ensure that the powder fully coats the particles.

[0020] Step 5: Add binder for the second time Add the remaining 2 / 3 of the binder premix and continue stirring for 8-12 minutes to ensure a uniform mixture.

[0021] Step 6: Vacuum kneading Transfer the mixture into a vacuum kneader and knead for 15-25 minutes at 40-60℃ and a vacuum of -0.08 to -0.1 MPa to remove air bubbles. The preferred temperatures are 50℃, a vacuum of -0.08 MPa, and a time of 20 minutes.

[0022] Step 7: Trapping the material Remove the clay, wrap it with plastic film, and let it sit at 20-30℃ for 20-28 hours to allow the binder to fully cure.

[0023] Step 8: Molding After the clay has been trapped, it is filled into a 40mm×40mm×160mm mold and molded on a hydraulic molding machine under a pressure of 40-60kN for 20-40 seconds.

[0024] Step 9: Drying After molding, the sample is placed at room temperature for 20-28 hours to allow the solvent to evaporate; then it is transferred to a forced-air drying oven and dried at 100-120℃ for 10-14 hours.

[0025] Step 10: High-temperature heat treatment After drying, place the sample in an air atmosphere and treat it according to the following heating curves: room temperature - 600℃, heating rate 5℃ / min, hold at 600℃ for 30-40 minutes; 600℃ - 800℃, heating rate 2℃ / min, hold at 800℃ for 1-2 hours; switch to a reducing atmosphere, 800℃ - 1000℃, heating rate 2℃ / min, hold at 1000℃ for 1-1.5 hours; 1000℃ - 1350℃, heating rate 5℃ / min; hold at 1350℃ for 2-4 hours, and allow to cool naturally.

[0026] Preferably, the reducing atmosphere in step 10 is a nitrogen / argon protective atmosphere.

[0027] Preferably, the Massia value of the sample after drying in step 9 is controlled within the range of 0.8-1.2 MPa before high-temperature heat treatment.

[0028] This application introduces polyborosilazane as the main binder, utilizing its ability to transform into Si-BCN ceramic at high temperatures to generate a Si-BCN ceramic phase and a B4C-SiC composite ceramic reinforcing phase in situ, forming a robust ceramic bonding network. This achieves high ceramic yield and low volume shrinkage. Simultaneously, by oxidizing some B4C micropowder at high temperatures to generate a B2O3 liquid phase, it fills pores, promotes sintering, and protects the carbon phase, compensating for volume shrinkage and improving high-temperature strength. The prepared gunning putty material exhibits low shrinkage, high room-temperature compressive strength, high-temperature flexural strength, and excellent resistance to thermal shock cracking, solving the technical problems of poor volume stability and insufficient high-temperature strength in traditional gunning putty caused by binder carbonization and shrinkage.

[0029] Compared with the prior art, this application has the following beneficial effects: 1. The volume shrinkage rate of the heat-shock-resistant taphole material of this application is significantly reduced: the linear shrinkage rate of the taphole material after heat treatment at 1350℃ is only 0.3-0.5%, which is far lower than the 1.2-1.5% of traditional phenolic resin taphole materials.

[0030] 2. The high-temperature strength of the heat-shock-resistant taphole clay material of this application is significantly improved: the high-temperature flexural strength of the taphole clay material at 1400℃ reaches 15-18MPa, which is 50-80% higher than that of traditional taphole clay.

[0031] 3. The thermal shock resistant drilling mud material of this application has excellent thermal shock resistance: low shrinkage rate and uniform microstructure reduce thermal stress concentration and significantly improve thermal shock resistant cracking performance.

[0032] 4. The thermal shock resistant cracking putty material of this application can be cured at room temperature and is easy to construct: it adopts an isocyanate curing system, which can be cured at room temperature without heating equipment, thus reducing the construction threshold.

[0033] 5. The thermal shock resistant drilling mud material of this application is green and environmentally friendly: it abandons the traditional coal tar binder, reduces the emission of polycyclic aromatic hydrocarbons, and meets the requirements of green manufacturing. Attached Figure Description

[0034] Figure 1 This is a process flow diagram of the method for preparing the gunning clay material in this application.

[0035] Figure 2 SEM image of the clay material prepared in Example 1 after heat treatment at 1350℃. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments are only for explaining this application and are not intended to limit it. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0037] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0038] Example 1 This embodiment provides a thermal shock resistant drilling clay material, the composition of which is as follows: aggregate: Brown fused alumina (3-5mm) 20 parts by weight; Brown fused alumina (1-3mm) 15 parts by weight; Brown fused alumina (0-1mm) 10 parts by weight; 10 parts by weight of silicon carbide (0-1mm); 8 parts by weight of silicon carbide (200 mesh); 8 parts by weight of coke (0-1mm).

[0039] Matrix powder: 6 parts by weight of α-Al2O3 micro powder (D50=3μm); 4 parts by weight of SiO2 micro powder (D50=0.8μm); 5 parts by weight of clay (≤320 mesh); Kyanite (30-80 mesh) 4 parts by weight.

[0040] Binder system (added externally, accounting for 10% of the total mass of aggregate and matrix powder): 100 parts by weight of polyborosilazane (viscosity approximately 2000 cps); 12 parts by weight of MDI curing agent; 4 parts by weight of B4C micro powder (D50=2μm, purity 99%); 15 parts by weight of xylene / ethyl acetate mixed solvent (1:1) (for viscosity adjustment).

[0041] The preparation method is as follows ( Figure 1 (as shown) Step 1: Preparation of binder premix Add polyborosilazane, MDI curing agent, B4C micro powder and mixed solvent to a container, and stir at 600 rpm for 15 minutes to uniformly disperse the B4C micro powder, resulting in a brownish-brown viscous liquid.

[0042] Step 2: Premixing raw materials Add coarse brown fused alumina particles (3-5mm, 1-3mm) and coke to a high-powered mixer and dry mix for 2 minutes.

[0043] Step 3: Add binder once Add 1 / 3 of the total volume of the binder premix obtained in step 1 and stir for 3 minutes.

[0044] Step 4: Add fine powder Add the remaining aggregates (0-1mm brown fused alumina, silicon carbide) and all matrix powders (α-Al2O3 micro powder, SiO2 micro powder, clay, kyanite) in sequence, and stir for 5 minutes.

[0045] Step 5: Add binder for the second time Add the remaining 2 / 3 of the binder premix and continue stirring for 10 minutes.

[0046] Step 6: Vacuum kneading Transfer the mixture into a vacuum kneader and knead for 20 minutes at 50°C and a vacuum of -0.08 MPa.

[0047] Step 7: Trapping the material Remove the clay, wrap it in plastic film, and let it sit at 25°C for 24 hours.

[0048] Step 8: Molding The Massia value of the taphole clay after being trapped was measured to be 1.0 MPa. The taphole clay was filled into a 40 mm × 40 mm × 160 mm mold and molded on a hydraulic molding machine with a pressure of 50 kN for 30 seconds. After demolding, a long strip-shaped sample was obtained.

[0049] Step 9: Drying The molded sample was left at room temperature for 24 hours, and then transferred to a forced-air drying oven and dried at 110°C for 12 hours.

[0050] Step 10: High-temperature heat treatment The dried sample was placed in a corundum crucible and then placed in a high-temperature air atmosphere furnace. The following heating curve was applied: room temperature - 600℃, heating rate 5℃ / min, holding at 600℃ for 35 minutes; 600℃ - 800℃, heating rate 2℃ / min, holding at 800℃ for 1.5 hours; then the atmosphere was switched to nitrogen, 800℃ - 1000℃, heating rate 2℃ / min, holding at 1000℃ for 75 minutes; 1000℃ - 1350℃, heating rate 5℃ / min; holding at 1350℃ for 3 hours, followed by natural cooling.

[0051] Example 2 This embodiment is basically the same as Embodiment 1, except that: the amount of B4C micro powder in the binder system is 3 parts by weight, and the amount of MDI curing agent is 10 parts by weight.

[0052] Example 3 This embodiment is basically the same as Embodiment 1, except that: the amount of B4C micro powder in the binder system is 5 parts by weight, and the amount of MDI curing agent is 15 parts by weight.

[0053] Comparative Example 1 This comparative example provides a conventional phenolic resin-bonded clay material, whose aggregate and matrix powder compositions are the same as in Example 1, and whose binder system is: 100 parts by weight of thermosetting phenolic resin; 8 parts by weight of hexamethylenetetramine curing agent; The preparation method is basically the same as that in Example 1.

[0054] Comparative Example 2 This comparative example provides a phenolic resin and B4C bonded clay material, whose aggregate and matrix powder composition is the same as in Example 1, and the binder system is as follows: 100 parts by weight of thermosetting phenolic resin; 8 parts by weight of hexamethylenetetramine curing agent; 4 parts by weight of B4C micro powder.

[0055] The preparation method is basically the same as that in Example 1.

[0056] Performance testing The performance of the gunning clay samples prepared in Examples 1-3 and Comparative Examples 1-2 was tested using the following methods: 1. Bulk density and apparent porosity: The Archimedes method was used to determine the density of the sample after heat treatment at 1350℃, according to GB / T2997 standard.

[0057] 2. Linear shrinkage rate: Measure the length of the sample before and after heat treatment, and calculate according to the formula (L0-L) / L0×100%, where L0 is the length of the sample before heat treatment and L is the length of the sample after heat treatment.

[0058] 3. Compressive strength at room temperature: The test specimen after heat treatment at 1350℃ was determined according to GB / T5072 standard.

[0059] 4. Flexural strength at room temperature: The strength of the sample after heat treatment at 1350℃ was determined according to GB / T3001 standard.

[0060] 5. High-temperature flexural strength: determined according to GB / T3002 standard at 1400℃ in a carbonized atmosphere.

[0061] 6. Thermogravimetric analysis: Take samples of each component that have not been heat-treated after molding, heat them to 1400℃ at 10℃ / min under nitrogen atmosphere, record the TG curve, and then calculate the residual weight rate at 800℃ and 1350℃.

[0062] 7. Thermal Shock Resistance: Performed according to YB / T 376 standard. The specimen (40mm×40mm×160mm) after heat treatment at 1350℃ is held at 1100℃ for 30 minutes, then rapidly cooled in flowing cold water for 3 minutes, constituting one cycle. The number of cycles required for the specimen to exhibit significant cracking (through crack length greater than 1 / 2 of the cross-sectional dimension) or a strength reduction rate exceeding 30% is used as the evaluation index for thermal shock crack resistance. Simultaneously, the retention rate of flexural strength at room temperature after 3 thermal shock cycles (post-thermal shock strength / original strength × 100%) is recorded.

[0063] The test results are shown in Table 1.

[0064] Table 1. Performance test results of the examples and comparative examples. As shown in Table 1, the linear shrinkage rates (0.3-0.5%) of Examples 1-3 were significantly lower than those of Comparative Example 1 (1.4%) and Comparative Example 2 (1.0%), indicating that the polyborosilicate binder system effectively suppressed carbonization shrinkage. Example 3 exhibited the lowest shrinkage rate at 0.3%. The residual weight of Examples 1-3 at 1350℃ reached 81.0-83.5%, significantly higher than the 45.2% of Comparative Example 1 and 52.6% of Comparative Example 2. The high-temperature flexural strength of Examples 1-3 at 1400℃ reached 15.5-18.2 MPa, an increase of 80-110% compared to Comparative Example 1 (8.6 MPa) and 35-58% compared to Comparative Example 2 (11.5 MPa). The higher bulk density and lower apparent porosity of Examples 1-3 indicate a denser material, which is beneficial for improving resistance to slag and iron corrosion.

[0065] 7. Scanning electron microscopy observation of the stemming clay sample prepared in Example 1: A cross-section of the sample after heat treatment at 1350℃ was taken to observe the microstructure, such as... Figure 2 As shown.

[0066] from Figure 2 It can be seen that the aggregate and matrix in the gunning mix are tightly bonded, with a clear interface and no cracks. Nanoscale ceramic particles are distributed within the matrix, with fine and uniformly distributed pores and no large through-cracks. It exhibits glass liquid phase filling characteristics: a glass liquid phase exists in the pores and interparticle spaces, binding the particles together.

[0067] Although this application 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 this application should be included within the protection scope of this application.

Claims

1. A thermal shock resistant drilling mud material, characterized in that, Including aggregate, matrix powder and binder system; The binder system consists of the following components: 100 parts by weight of polyborosilazane; 10-15 parts by weight of isocyanate curing agent; and 3-5 parts by weight of B4C micro powder.

2. The thermal shock resistant drilling mud material according to claim 1, characterized in that, The isocyanate curing agent is one or a mixture of several of diphenylmethane diisocyanate, isoflurane diisocyanate, and polymethylene polyphenyl polyisocyanate.

3. The thermal shock resistant drilling mud material according to claim 1, characterized in that, The particle size D50 of the B4C micro powder is 1-3 μm.

4. The thermal shock resistant drilling mud material according to claim 1, characterized in that, The aggregate comprises the following components in parts by weight: 15-25 parts of brown fused alumina with a particle size of 3-5 mm; 10-20 parts of brown fused alumina with a particle size of 1-3 mm; 5-15 parts of brown fused alumina with a particle size of 0-1 mm; 8-12 parts of silicon carbide with a particle size of 0-1 mm; 6-10 parts of silicon carbide with a particle size of 200 mesh; and 6-10 parts of coke with a particle size of 0-1 mm.

5. The thermal shock resistant drilling mud material according to claim 1, characterized in that, The matrix powder comprises the following components in parts by weight: 4-8 parts α-Al2O3 micro powder; 2-6 parts SiO2 micro powder; 3-7 parts clay; and 2-6 parts kyanite.

6. The thermal shock resistant drilling mud material according to claim 1, characterized in that, The total amount of the binder system is 8-12% of the total mass of the aggregate and matrix powder.

7. A method for preparing a thermal shock resistant drilling mud material as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Preparation of binder premix Polyborosilazane, isocyanate curing agent and B4C micro powder are mixed and stirred to uniformly disperse the B4C micro powder to obtain binder premix liquid; Step 2: Premixing raw materials Brown fused alumina with a particle size of 3-5mm, brown fused alumina with a particle size of 1-3mm, and coke are added to a mixer and dry-mixed. Step 3: Add binder once Add 1 / 3 of the total volume of the binder premix obtained in step 1 and stir until homogeneous; Step 4: Add fine powder Add the remaining aggregate and all the matrix powder in sequence, and mix well; Step 5: Add binder for the second time Add the remaining 2 / 3 of the binder premix and continue stirring until homogeneous; Step 6: Vacuum kneading The mixture is transferred to a vacuum kneader and kneaded at 40-60℃ and a vacuum of -0.08 to -0.1 MPa. Step 7: Trapping the material Remove the clay, wrap it in plastic film, and let it rest at 20-30℃ for 20-28 hours; Step 8: Molding Fill the mold with the trapped clay and press it under 40-60kN pressure for 20-40 seconds to form the product. Step 9: Drying After molding, the sample is left at room temperature for 20-28 hours, and then dried at 100-120℃ for 10-14 hours. Step 10: High-temperature heat treatment After drying, place the sample in an air atmosphere and treat it according to the following heating curves: room temperature - 600℃, heating rate 5℃ / min, hold at 600℃ for 30-40 minutes; 600℃ - 800℃, heating rate 2℃ / min, hold at 800℃ for 1-2 hours; switch to a reducing atmosphere, 800℃ - 1000℃, heating rate 2℃ / min, hold at 1000℃ for 1-1.5 hours; 1000℃ - 1350℃, heating rate 5℃ / min; hold at 1350℃ for 2-4 hours, and allow to cool naturally.

8. The method for preparing a thermal shock resistant drilling mud material according to claim 7, characterized in that, The vacuum kneading process in step 6 involves a temperature of 40-60°C, a vacuum degree of -0.08 to -0.1 MPa, and a time of 15-25 minutes.

9. The method for preparing a thermal shock resistant drilling mud material according to claim 7, characterized in that, The reducing atmosphere described in step 10 is a nitrogen / argon protective atmosphere.

10. The method for preparing a thermal shock resistant drilling mud material according to claim 7, characterized in that, Before high-temperature heat treatment, the Massia value of the dried sample in step 9 is controlled within the range of 0.8-1.2 MPa.

Images