Low-carbon magnesium-carbon refractory materials for smelting silicon-manganese deoxidized steel and their preparation methods

Abstract

This invention discloses a low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel and its preparation method; the method includes the following steps: S1, preparing CMA fine powder; wherein, CMA is a limited solid solution of magnesium oxide in calcium hexaaluminate, containing Ca2Mg2Al 28 O 46 With CaMg2Al 16 O 27 Two core components: CMA fine powder is prepared from 6.93 wt% calcium oxide powder, 89.65 wt% alumina powder, and 3.42 wt% magnesium oxide powder; S2, magnesium oxide fine powder, CMA fine powder, Al powder, and B4C powder are mixed to obtain the first mixture; magnesium oxide aggregate is mixed with phenolic resin, and then natural flake graphite is added and mixed again to obtain the second mixture; S3, the first mixture and the second mixture are mixed to obtain the target mixture; S4, the target mixture is pressed into a crucible blank and cured to obtain a low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel. The low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel exhibits improved thermal shock resistance, enhanced oxidation resistance, and improved slag resistance, showing good application prospects in the smelting process of silicon-manganese deoxidized steel.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically relating to low-carbon magnesium-carbon refractory materials for smelting silicon-manganese deoxidized steel and their preparation methods. Background Technology

[0002] Magnesia-carbon (MgO-C) refractories are core lining materials for steelmaking equipment such as converters, electric furnaces, and ladles. During service, the working face needs to be in contact with high-temperature molten steel for extended periods, endure severe thermal shocks, and face the severe challenge of highly corrosive steel slag. The structural stability of the lining directly affects the safety of the smelting process and the operating efficiency of the equipment.

[0003] With the continuous expansion of high-quality clean steel and low-carbon steel production, the reduction of carbon content (<5wt%) in magnesia-carbon materials has become an inevitable trend to avoid carbonization and contamination of molten steel by refractory materials. However, the sharp drop in carbon content significantly weakens the material's resistance to slag penetration and its ability to buffer thermal stress. Especially in the smelting of ferrosilicon deoxidized steel, low-basicity, highly corrosive deoxidized slag easily penetrates the low-carbon system, reacting with the matrix periclase to form a low-melting-point silicate phase, causing the matrix structure to rapidly collapse and peel off, severely shortening the lining life, and even triggering furnace burnout accidents.

[0004] Therefore, how to break through the limitations of traditional matrix modification materials under the premise of low carbonization and solve the technical bottleneck of poor slag erosion resistance and thermal shock stability of low carbon magnesia-carbon refractories when facing silicon-manganese deoxidizing slag is a pain point that the steel smelting industry urgently needs to solve. Summary of the Invention

[0005] In view of this, some embodiments disclose a method for preparing low-carbon magnesium-carbon refractory materials for smelting silicon-manganese deoxidized steel, including the following steps:

[0006] S1. Preparation of CMA fine powder; wherein, CMA is a limited solid solution of magnesium oxide in calcium hexaaluminate, containing Ca2Mg2Al 28 O 46 With CaMg2Al 16 O 27 Two core components; the preparation methods for CMA fine powder include:

[0007] CMA raw material powders were mixed to obtain CMA mixed powder; by mass percentage, the CMA raw material powder contained 6.93 wt% calcium oxide powder, 89.65 wt% alumina powder, and 3.42 wt% magnesium oxide powder.

[0008] Add 4% (by weight of CMA mixed powder) of binder and mix thoroughly.

[0009] The uniformly mixed CMA powder was pressed into a CMA green body under a pressure of 150 MPa.

[0010] CMA green blanks were fired at 1690℃ in air and held for 8 hours. After cooling, CMA bulk material was obtained. The CMA bulk material was then crushed and passed through a 200-mesh sieve to obtain CMA fine powder.

[0011] S2. Weigh the refractory raw materials and phenolic resin; the magnesia-carbon refractory raw materials include magnesium oxide aggregate, magnesium oxide fine powder, CMA fine powder, flake graphite, Al powder and B4C powder;

[0012] The first mixture is obtained by mixing fine magnesium oxide powder, fine CMA powder, Al powder and B4C powder.

[0013] Magnesium oxide aggregate is mixed and stirred with phenolic resin, and then natural flake graphite is added and mixed again to obtain a second mixture;

[0014] S3. The first mixture and the second mixture are mixed to obtain the target mixture; wherein, in the target mixture, by mass percentage, the content of magnesium oxide aggregate is 70wt%, the content of magnesium oxide fine powder is 7~19wt%, the content of CMA fine powder is 4~16wt%, the content of natural flake graphite is 4wt%, the content of Al powder is 2.5wt%, and the content of B4C powder is 0.5wt%; the mass of phenolic resin is 5.3% of the total mass of raw materials;

[0015] S4. The target mixture is pressed into a crucible blank and cured to obtain a low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel.

[0016] Furthermore, in some embodiments of the preparation method of low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel, in step S1, the particle size of calcium oxide powder is ≤5µm, wherein the CaO content is ≥99%; the particle size of alumina powder is ≤5µm, wherein the Al2O3 content is ≥99%; and the particle size of magnesium oxide powder is ≤5µm, wherein the MgO content is ≥99%.

[0017] Some embodiments disclose a method for preparing low-carbon magnesium-carbon refractory materials for smelting silicon-manganese deoxidized steel. In step S1, Ca2Mg2Al in CMA... 28 O 46 The content is 86wt%, CaMg2Al 16 O 27 The content is 14wt%.

[0018] Some embodiments disclose a method for preparing low-carbon magnesium-carbon refractory materials for smelting silicon-manganese deoxidized steel. In step S2, the magnesium oxide aggregate is fused magnesia aggregate with a particle size of 0-5 mm and an MgO content ≥98%; the magnesium oxide fine powder is fused magnesia fine powder with a particle size of 180 mesh and an MgO content ≥98%; the CMA fine powder has a particle size of 200 mesh; the natural flake graphite has a particle size of 100 mesh and a C content ≥99%; the Al powder has a particle size of 180 mesh and an Al content ≥99%; and the B4C powder has a particle size of 325 mesh and a B4C content ≥99%.

[0019] In some embodiments, a method for preparing low-carbon magnesium-carbon refractory materials for smelting silicon-manganese deoxidized steel is disclosed. In step S2, magnesium oxide aggregate and phenolic resin are mixed and stirred for 10 minutes, and then natural flake graphite is added and mixed for another 10 minutes to obtain a second mixture.

[0020] In some embodiments, a method for preparing low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel is disclosed. In step S4, the target mixture is pressed under a pressure of 150 MPa using an isostatic press to obtain a crucible blank. The crucible blank is then cured at 240°C for 24 hours to obtain the low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel.

[0021] On the other hand, the low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel disclosed in some embodiments is obtained by the preparation method of the low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel disclosed in the embodiments of the present invention.

[0022] The low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel and its preparation method disclosed in the embodiments of the present invention have at least the following beneficial technical effects:

[0023] 1. Improved thermal shock resistance: The in-situ reaction of CMA generates magnesium aluminum spinel accompanied by volume expansion, and the new phase exhibits a mismatch in thermal expansion coefficients with the MgO matrix, inducing a uniformly distributed microcrack network within the material. These microcracks effectively reduce the elastic modulus of the material and promote the deflection and bifurcation of the main crack during thermal shock (microcrack toughening); simultaneously, an appropriate amount of glassy phase at high temperatures can passivate the crack tips through viscous flow, buffering thermal stress.

[0024] 2. Enhanced antioxidant properties: The glass phase associated with CMA decomposition softens and flows at high temperatures, forming a dense liquid phase layer on the surface of carbon particles and in the matrix pores through capillary action, achieving dynamic self-healing of microcracks and open pores; the expansion and densification effect generated by in-situ spinel completely blocks the inward diffusion channels of external oxygen.

[0025] 3. Improved slag resistance: The highly active micro-fine spinel generated in situ can rapidly absorb and dissolve Fe in the molten slag. 2+ and Mn 2+The ions cause the viscosity of the molten slag that penetrates into the brick body to rise sharply and even solidify locally. At the same time, the excellent oxidation resistance allows the carbon network in the matrix to be well preserved, maintaining the material's "non-wetting" property to steel slag. This effectively inhibits the penetration and erosion of molten slag from two aspects. Attached Figure Description

[0026] Figure 1 SEM image of the surface of CMA fine powder in Example 1.

[0027] Figure 2 Example 1: XRD composition diagram of CMA fine powder.

[0028] Figure 3 Images of refractory materials after slag resistance in the examples and comparative examples. Detailed Implementation

[0029] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in these embodiments of the invention, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in these embodiments is merely for describing particular implementations and is not intended to limit the scope of the disclosure of these embodiments.

[0030] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this invention pertain; other experimental methods and technical means not specifically noted in the embodiments of this invention refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0031] The terms “basic” and “approximately” as used herein are used to describe small fluctuations. For example, they can mean less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Numerical data presented or expressed in range format herein are used for convenience and brevity only, and should therefore be interpreted flexibly to include not only the explicitly listed values ​​that define the range, but also all independent values ​​or subranges contained within that range. For example, a numerical range of “1–5%” should be interpreted to include not only the explicitly listed values ​​from 1% to 5%, but also the independent values ​​and subranges within the indicated range. Thus, this numerical range includes independent values ​​such as 2%, 3.5%, and 4%, and subranges such as 1%–3%, 2%–4%, and 3%–5%, etc. This principle also applies to ranges that list only one value. Furthermore, this interpretation applies regardless of the width of the range or the characteristics described.

[0032] In this document, including in the claims, conjunctions such as "comprising," "including," "with," "having," "containing," "involving," and "accommodating" are understood to be open-ended, meaning "including but not limited to." Only the conjunctions "consisting of" and "composed of" are closed conjunctions.

[0033] To better illustrate the content of this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that the invention can be practiced even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail, in order to highlight the main points of the invention.

[0034] Without conflict, the technical features disclosed in the embodiments of the present invention can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of the present invention.

[0035] In some embodiments, the preparation method of low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel includes the following steps:

[0036] S1. Preparation of CMA fine powder; wherein, CMA is a limited solid solution of magnesium oxide in calcium hexaaluminate, containing Ca2Mg2Al 28 O 46 With CaMg2Al 16 O 27 Two core components; the preparation methods for CMA fine powder include:

[0037] CMA raw material powders were mixed to obtain CMA mixed powder. By mass percentage, the CMA raw material powder contained 6.93 wt% calcium oxide powder, 89.65 wt% alumina powder, and 3.42 wt% magnesium oxide powder. A binder of 4% of the total mass of the CMA mixed powder was added and mixed evenly. The evenly mixed CMA mixed powder was pressed into CMA green blanks under a pressure of 150 MPa. The CMA green blanks were fired at 1690℃ in air and held for 8 hours. After cooling, CMA block material was obtained. The CMA block material was crushed and passed through a 200-mesh sieve to obtain CMA fine powder.

[0038] In some embodiments, the particle size of calcium oxide powder is ≤5µm, wherein the CaO content is ≥99%; the particle size of alumina powder is ≤5µm, wherein the Al2O3 content is ≥99%; and the particle size of magnesium oxide powder is ≤5µm, wherein the MgO content is ≥99%.

[0039] In some embodiments, the CMA fine powder contains 89.65 wt% Al₂O₃, 3.42 wt% MgO, and 6.93 wt% CaO; the CMA fine powder also contains 86 wt% Ca₂Mg₂Al.28 O 46 (abbreviated as C2M2A1) 14 ) with 14wt% CaMg2Al 16 O 27 (Abbreviated as CM2A8) Two phases. Generally, CMA fine powder is a powder sintered at high temperature with a special morphology and specific phase composition, exhibiting excellent thermal shock resistance and good oxidation resistance. If the corresponding Al2O3, MgO, and CaO powders are directly added to the refractory raw materials according to the CMA composition, the performance of the refractory material is not as good as that of the refractory raw materials with CMA fine powder added.

[0040] S2. Weigh the refractory raw materials and phenolic resin; the magnesia-carbon refractory raw materials include magnesium oxide aggregate, magnesium oxide fine powder, CMA fine powder, flake graphite, Al powder and B4C powder;

[0041] The first mixture is obtained by mixing fine magnesium oxide powder, fine CMA powder, Al powder and B4C powder.

[0042] Magnesium oxide aggregate is mixed and stirred with phenolic resin, and then natural flake graphite is added and mixed again to obtain a second mixture;

[0043] In some embodiments, the magnesium oxide aggregate is fused magnesia aggregate with a particle size of 0-5 mm, wherein the MgO content is ≥98%; the magnesium oxide fine powder is fused magnesia fine powder with a particle size of 180 mesh, wherein the MgO content is ≥98%; the CMA fine powder has a particle size of 200 mesh; the natural flake graphite has a particle size of 100 mesh, wherein the C content is ≥99%; the Al powder has a particle size of 180 mesh, wherein the Al content is ≥99%; and the B4C powder has a particle size of 325 mesh, wherein the B4C content is ≥99%.

[0044] In some embodiments, magnesium oxide aggregate and phenolic resin are mixed and stirred for 10 minutes, and then natural flake graphite is added and mixed for another 10 minutes to obtain a second mixture.

[0045] S3. The first mixture and the second mixture are mixed to obtain the target mixture; wherein, in the target mixture, by mass percentage, the content of magnesium oxide aggregate is 70wt%, the content of magnesium oxide fine powder is 7~19wt%, the content of CMA fine powder is 4~16wt%, the content of natural flake graphite is 4wt%, the content of Al powder is 2.5wt%, and the content of B4C powder is 0.5wt%; the mass of phenolic resin is 5.3% of the total mass of refractory raw materials;

[0046] S4. The target mixture is pressed into a crucible blank and cured to obtain a low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel. In some embodiments, the target mixture is pressed at 150 MPa using an isostatic press to obtain a crucible blank; the crucible blank is cured at 240°C for 24 hours to obtain the low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel.

[0047] The low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel disclosed in some embodiments is obtained by the preparation method of the low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel disclosed in the embodiments of the present invention.

[0048] The technical details are further illustrated below with reference to the embodiments.

[0049] Example 1

[0050] In Example 1, the preparation method of low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel includes the following steps:

[0051] 1. Preparation of CMA fine powder; including:

[0052] CMA mixed powder is prepared by mixing 6.93 wt% calcium oxide powder, 89.65 wt% alumina powder, and 3.42 wt% magnesium oxide powder by weight percentage; wherein the particle size of calcium oxide powder is ≤5 µm and the CaO content is ≥99%; the particle size of alumina powder is ≤5 µm and the Al2O3 content is ≥99%; and the particle size of magnesium oxide powder is ≤5 µm and the MgO content is ≥99%.

[0053] Add 4 wt% of binder to the total mass of the CMA mixed powder and mix thoroughly;

[0054] The uniformly mixed CMA powder was pressed into a CMA green body under a pressure of 150 MPa.

[0055] CMA green bodies were fired at 1690℃ in air and held for 8 hours, then cooled to obtain CMA bulk material. The CMA bulk material was then crushed and passed through a 200-mesh sieve to obtain CMA fine powder. The SEM morphology of the CMA fine powder is shown in [Figure number missing]. Figure 1 XRD composition can be found in Figure 2 ; Figure 2 In this context, A14 represents Ca2Mg2Al 28 O 46 Phase, A8 represents CaMg2Al 16 O 27 phase of matter;

[0056] 2. Weigh the refractory raw materials and phenolic resin; the raw materials for magnesium-carbon refractory materials include magnesium oxide aggregate, magnesium oxide fine powder, CMA fine powder, flake graphite, Al powder and B4C powder;

[0057] The first mixture is obtained by mixing fine magnesium oxide powder, fine CMA powder, Al powder and B4C powder.

[0058] Magnesium oxide aggregate and phenolic resin were mixed and stirred for 10 minutes, then natural flake graphite was added and mixed for another 10 minutes to obtain the second mixture.

[0059] 3. The first mixture and the second mixture are mixed to obtain the target mixture; wherein, in the target mixture, by mass percentage, the content of 180-mesh magnesium oxide fine powder is 19wt%, the content of CMA fine powder is 4%, the content of 3-5mm magnesium oxide aggregate is 28%, the content of 1-3mm magnesium oxide aggregate is 24wt%, the content of 0-1mm magnesium oxide aggregate is 18wt%, the content of 100-mesh natural flake graphite is 4wt%, the content of 180-mesh Al powder is 2.5wt%, and the content of 325-mesh B4C powder is 0.5wt%; the mass of phenolic resin is 5.3wt% of the total mass of refractory raw materials;

[0060] 4. Press the target mixture under 150MPa pressure using an isostatic press to obtain a crucible blank; cure the crucible blank at 240℃ for 24h to obtain a low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel.

[0061] Example 2

[0062] In Example 2, the preparation method of the low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel is the same as in Example 1; wherein, in step 3, the content of magnesium oxide fine powder is 15 wt%, and the content of CMA fine powder is 8 wt%.

[0063] In step 4, the solidified crucible blank is embedded in flake graphite and heat-treated at 1400℃ for 3 hours, then naturally cooled to obtain low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel.

[0064] Example 3

[0065] In Example 3, the preparation method of low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel is the same as in Example 1; wherein, in step 3, the content of magnesium oxide fine powder is 11 wt%, and the content of CMA fine powder is 12 wt%.

[0066] In step 4, the solidified blank is embedded in flake graphite and heat-treated at 1400℃ for 3 hours, then naturally cooled to obtain a low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel.

[0067] Example 4

[0068] In Example 4, the preparation method of low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel is the same as in Example 1; wherein, in step 3, the content of magnesium oxide fine powder is 7wt% and the content of CMA fine powder is 16wt%.

[0069] In step 4, the solidified blank is embedded in flake graphite and heat-treated at 1400℃ for 3 hours, then naturally cooled to obtain a low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel.

[0070] Comparative Example 1

[0071] In Comparative Example 1, the preparation method of low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel includes the following steps:

[0072] 1. The first mixture is obtained by mixing fine magnesium oxide powder, Al powder and B4C powder; magnesium oxide aggregate is mixed with phenolic resin and stirred for 10 minutes, then natural flake graphite is added and mixed for another 10 minutes to obtain the second mixture.

[0073] 2. Weigh the refractory raw materials and phenolic resin; the raw materials for magnesium-carbon refractory materials include magnesium oxide aggregate, magnesium oxide fine powder, flake graphite, Al powder and B4C powder;

[0074] The first mixture and the second mixture are mixed to obtain the target mixture; wherein, in the target mixture, by mass percentage, the content of 180-mesh magnesia fine powder is 23wt%, the content of 3-5mm magnesia aggregate is 28%, the content of 1-3mm magnesia aggregate is 24wt%, the content of 0-1mm magnesia aggregate is 18wt%, the content of 100-mesh natural flake graphite is 4wt%, the content of 180-mesh Al powder is 2.5wt%, and the content of 325-mesh B4C powder is 0.5wt%; the mass of phenolic resin is 5.3wt% of the total mass of the refractory raw materials;

[0075] 3. Press the target mixture under 150MPa pressure using an isostatic press to obtain a crucible blank; cure the crucible blank at 240℃ for 24h to obtain a low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel.

[0076] Comparative Example 2

[0077] In Comparative Example 2, the preparation method of low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel includes the following steps:

[0078] 1. Preparation of the compound fine powder: Calcium oxide powder (6.93 wt%), alumina powder (89.65 wt%), and magnesium oxide powder (3.42 wt%) were physically mixed and compounded to obtain the compound fine powder. The calcium oxide powder had a particle size ≤5 µm and a CaO content ≥99%; the alumina powder had a particle size ≤5 µm and an Al2O3 content ≥99%; and the magnesium oxide powder had a particle size ≤5 µm and an MgO content ≥99%.

[0079] 2. Weigh the refractory raw materials and phenolic resin; the raw materials for magnesium-carbon refractory materials include magnesium oxide aggregate, magnesium oxide fine powder, compound fine powder, flake graphite, Al powder and B4C powder;

[0080] Magnesium oxide fine powder, compound fine powder, Al powder and B4C powder are mixed to obtain the first mixture; magnesium oxide aggregate is mixed with phenolic resin and stirred for 10 minutes, then natural flake graphite is added and mixed for another 10 minutes to obtain the second mixture.

[0081] 3. The first mixture and the second mixture are mixed to obtain the target mixture; wherein, in the target mixture, by mass percentage, the content of 180-mesh magnesium oxide fine powder is 15wt%, the content of compound fine powder is 8wt%, the content of 3-5mm magnesium oxide aggregate is 28%, the content of 1-3mm magnesium oxide aggregate is 24wt%, the content of 0-1mm magnesium oxide aggregate is 18wt%, the content of 100-mesh natural flake graphite is 4wt%, the content of 180-mesh Al powder is 2.5wt%, and the content of 325-mesh B4C powder is 0.5wt%; the mass of phenolic resin is 5.3wt% of the total mass of raw materials;

[0082] 4. Press the target mixture under 150MPa pressure using an isostatic press to obtain a crucible blank; cure the crucible blank at 240℃ for 24h to obtain a low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel.

[0083] Example 5

[0084] The performance of the refractory materials in Examples 1-4 and Comparative Examples 1-2 was tested.

[0085] The method for assessing the thermal shock resistance of refractory materials includes the following specific steps:

[0086] The uniformly mixed raw materials were pressed into strips of 1400×25×25mm using a mold under 150MPa and cured at 240℃ for 24h. The cured blanks were then embedded in flake graphite and heat-treated at 1400℃ for 3h, followed by natural cooling to obtain samples. The pre-heat shock flexural strength at room temperature was tested using a universal testing machine according to national standards GB / T 3001-2017 "Test Method for Flexural Strength of Refractory Materials at Room Temperature" and GB / T 30873-2014 "Test Method for Thermal Shock Resistance of Refractory Materials". The samples were then held at 1100℃ in air for 20min, followed by air cooling for 5min. This process was repeated three times. After cooling, the post-heat shock flexural strength at room temperature was measured using a universal testing machine. The residual strength retention rate was calculated as: Post-heat shock flexural strength at room temperature / Pre-heat shock flexural strength at room temperature.

[0087] The test method for the oxidation resistance of refractory materials includes the following specific steps:

[0088] According to the national standard GB / T 13244-1991 "Test Method for Oxidation Resistance of Carbon-Containing Refractory Materials", the uniformly mixed raw materials were pressed into cylindrical samples of 50×50mm using a mold under 150MPa and cured at 240℃ for 24h. The cured blanks were then embedded in flake graphite and heat-treated at 1400℃ for 3h, followed by natural cooling to obtain the samples. Subsequently, according to the national standard GB / T 13244-1991 "Test Method for Oxidation Resistance of Carbon-Containing Refractory Materials", the samples were oxidized at 1400℃ in air for 3h. After oxidation, the oxidized samples were removed and transversely cut along the centerline. The thickness of the decarburized layer at four points on the two cross-sections was measured using vernier calipers, and the average value was taken.

[0089] The test method for the slag erosion resistance of refractory materials includes the following specific steps:

[0090] The uniformly mixed raw materials were pressed into strips of 140×25×25mm using a mold under 150MPa. The strips were then cured at 240℃ for 24 hours. The cured green body was embedded in flake graphite and heat-treated at 1400℃ for 3 hours, followed by natural cooling to obtain the sample. Subsequently, the slag was pre-melted for 4 hours and held at that temperature for 30 minutes. The refractory sample was then slowly fed into a silicon-molybdenum furnace and preheated above the molten slag for 10 minutes before being slowly fed into a graphite crucible. The sample was rotated at 20 r / min to resist the slag and held at that temperature for 100 minutes. At the end of the slag-resistant treatment, the sample was slowly lifted from the crucible and suspended above it for 10 minutes (to allow the molten slag to drip into the crucible). Once the molten slag had completely fallen into the crucible, the power was turned off. The sample was removed when the equipment temperature dropped to room temperature. Finally, the circumference of the sample at a distance of 8 cm from the top was measured, and the erosion percentage was calculated.

[0091] Physical images of the refractory materials used in Examples 1-4 and Comparative Examples 1-2 are shown below. Figure 3 Table 1 lists the composition and content of different refractory materials in the comparative examples and embodiments. Table 2 lists the performance test results of different refractory materials in the comparative examples and embodiments.

[0092] Table 1. List of refractory material compositions for comparative examples and embodiments.

[0093]

[0094] Table 2 Performance test results of comparative and example examples

[0095]

[0096] The data in Table 1 shows that in Comparative Example 2, the CaO+MgO+Al2O3 compound fine powder is a physically mixed fine powder according to the CMA phase composition ratio. Among them, Al2O3 (≤5µm, Al2O3≥99%) accounts for 7.172% of the total mass of refractory raw materials, CaO (≤5µm, CaO≥99%) accounts for 0.5544%, and MgO (≤5µm, MgO≥99%) accounts for 0.2736%, totaling 8wt%. The compound fine powder is only a physical mixture of the components and has not undergone high-temperature sintering at 1690℃ to form a solid solution structure.

[0097] As shown in Table 2, after adding CMA fine powder to the refractory materials of Examples 1-4, compared with the comparative example, the residual strength retention rate was significantly improved by 6-37%, the oxidation resistance was improved by about 2-41%, and the slag resistance was improved by 10-23%. This indicates that the refractory materials prepared by the present invention have good thermal shock resistance, slag resistance, and excellent oxidation resistance.

[0098] The low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel and its preparation method disclosed in the embodiments of the present invention have at least the following beneficial technical effects:

[0099] 1. Improved thermal shock resistance: The in-situ reaction of CMA generates magnesium aluminum spinel accompanied by volume expansion, and the new phase exhibits a mismatch in thermal expansion coefficients with the MgO matrix, inducing a uniformly distributed microcrack network within the material. These microcracks effectively reduce the elastic modulus of the material and promote the deflection and bifurcation of the main crack during thermal shock (microcrack toughening); simultaneously, an appropriate amount of glassy phase at high temperatures can passivate the crack tips through viscous flow, buffering thermal stress.

[0100] 2. Enhanced antioxidant properties: The glass phase associated with CMA decomposition softens and flows at high temperatures, forming a dense liquid phase layer on the surface of carbon particles and in the matrix pores through capillary action, achieving dynamic self-healing of microcracks and open pores; the expansion and densification effect generated by in-situ spinel completely blocks the inward diffusion channels of external oxygen.

[0101] 3. Improved slag resistance: The highly active micro-fine spinel generated in situ can rapidly absorb and dissolve Fe in the molten slag. 2+ and Mn 2+ The ions cause the viscosity of the molten slag that penetrates into the brick body to rise sharply and even solidify locally. At the same time, the excellent oxidation resistance allows the carbon network in the matrix to be well preserved, maintaining the material's "non-wetting" property to steel slag. This effectively inhibits the penetration and erosion of molten slag from two aspects.

[0102] The technical solutions and technical details disclosed in the embodiments of this invention are merely illustrative of the inventive concept of this invention and do not constitute a limitation on the technical solutions of the embodiments of this invention. Any conventional changes, substitutions, or combinations made to the technical details disclosed in the embodiments of this invention have the same inventive concept as this invention and are within the protection scope of the claims of this invention.

Claims

1. A method for preparing low-carbon magnesium-carbon refractory materials for smelting silicon-manganese deoxidized steel, characterized in that, Including the following steps: S1. Preparation of CMA fine powder; wherein, CMA is a limited solid solution of magnesium oxide in calcium hexaaluminate, containing Ca2Mg2Al 28 O 46 With CaMg2Al 16 O 27 Two core components; the preparation methods for CMA fine powder include: CMA raw material powders were mixed to obtain CMA mixed powder; by mass percentage, the CMA raw material powder contained 6.93 wt% calcium oxide powder, 89.65 wt% alumina powder, and 3.42 wt% magnesium oxide powder. Add 4% (by weight of CMA mixed powder) of binder and mix thoroughly. The uniformly mixed CMA powder was pressed into a CMA green body under a pressure of 150 MPa. CMA green blanks were fired at 1690℃ in air and held for 8 hours. After cooling, CMA bulk material was obtained. The CMA bulk material was then crushed and passed through a 200-mesh sieve to obtain CMA fine powder. S2. Weigh the refractory material raw materials and phenolic resin; the magnesia-carbon refractory material raw materials include magnesia aggregate, magnesia fine powder, CMA fine powder, flake graphite, Al powder and B4C powder; The first mixture is obtained by mixing fine magnesium oxide powder, fine CMA powder, Al powder and B4C powder. Magnesium oxide aggregate is mixed and stirred with phenolic resin, and then natural flake graphite is added and mixed again to obtain a second mixture; S3. The first mixture and the second mixture are mixed to obtain the target mixture; wherein, in the target mixture, by mass percentage, the content of magnesium oxide aggregate is 70wt%, the content of magnesium oxide fine powder is 7~19wt%, the content of CMA fine powder is 4~16wt%, the content of natural flake graphite is 4wt%, the content of Al powder is 2.5wt%, and the content of B4C powder is 0.5wt%; the mass of phenolic resin is 5.3% of the total mass of raw materials; S4. The target mixture is pressed into a crucible blank and cured to obtain a low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel.

2. The method for preparing low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel according to claim 1, characterized in that, In step S1, the particle size of calcium oxide powder is ≤5µm, and the CaO content is ≥99%; the particle size of aluminum oxide powder is ≤5µm, and the Al2O3 content is ≥99%; the particle size of magnesium oxide powder is ≤5µm, and the MgO content is ≥99%.

3. The method for preparing low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel according to claim 1, characterized in that, In step S1, Ca2Mg2Al in CMA 28 O 46 The content is 86wt%, CaMg2Al 16 O 27 The content is 14wt%.

4. The method for preparing low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel according to claim 1, characterized in that, In step S2, the magnesium oxide aggregate is fused magnesia aggregate with a particle size of 0~5mm and an MgO content ≥98%; the magnesium oxide fine powder is fused magnesia fine powder with a particle size of 180 mesh and an MgO content ≥98%; the CMA fine powder has a particle size of 200 mesh; the natural flake graphite has a particle size of 100 mesh and a C content ≥99%; the Al powder has a particle size of 180 mesh and an Al content ≥99%; and the B4C powder has a particle size of 325 mesh and a B4C content ≥99%.

5. The method for preparing low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel according to claim 1, characterized in that, In step S2, magnesium oxide aggregate and phenolic resin are mixed and stirred for 10 minutes, and then natural flake graphite is added and mixed for another 10 minutes to obtain the second mixture.

6. The method for preparing low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel according to claim 1, characterized in that, In step S4, the target mixture is pressed under a pressure of 150 MPa using an isostatic press to obtain a crucible blank; the crucible blank is cured at 240℃ for 24 h to obtain a low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel.

7. A low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel, characterized in that, It is obtained by the preparation method of low-carbon magnesium-carbon refractory material for smelting silicon-manganese deoxidized steel according to any one of claims 1 to 6.

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