Long-life refining ladle brick and method for producing the same

Abstract

The present application relates to the technical field of refractory materials for steelmaking, and particularly relates to a long-life refining ladle brick and a preparation method thereof. The long-life refining ladle brick provided by the present application is composed of a mixture and a binder; the mixture comprises the following raw materials in parts by weight: 55-84 parts of RH magnesium-aluminum spinel brick recycling material with a particle size of less than or equal to 8 mm, 5-9 parts of fused magnesite with a particle size of less than or equal to 1 mm, 10-15 parts of large-crystal fused magnesite fine powder, and 6-15 parts of nano carbon fibers; and the binder comprises the following raw materials in parts by weight: 1-3 parts of liquid phenolic resin, 1-6 parts of silica sol, and 1-2 parts of liquid water glass. The long-life refining ladle brick provided by the present application has the advantages of good volume stability, strong thermal shock resistance, excellent oxidation resistance and slag corrosion resistance, and long comprehensive service life.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refractory materials for steelmaking, and particularly relates to a long-service-life refining ladle brick and a preparation method thereof. BACKGROUND

[0002] The refining ladle is a key equipment in the modern steelmaking process, which is used for secondary refining of molten steel from the primary refining furnace (such as converter or electric arc furnace). Through a series of process operations such as deoxidation, desulfurization, composition fine-tuning and temperature control in the ladle, the molten steel can be effectively purified, and the purity and final quality of the steel can be significantly improved. Especially in the LF refining furnace, RH vacuum treatment and other strict refining conditions, the lining refractory material in the ladle needs to withstand extremely severe tests. The characteristics of its working environment are: long time (tens of minutes or even longer) under the action of high-temperature steel liquid of 1500-1750 ℃, and continuously subjected to the severe erosion and chemical corrosion of molten steel and high-alkalinity slag.

[0003] At present, the traditional refractory material used for the lining of the refining ladle is mainly magnesia-carbon brick or alumina-magnesia-carbon brick. However, this kind of material has several defects that are difficult to overcome in actual use:

[0004] (1) Insufficient comprehensive performance and short service life: In the erosion environment of high temperature above 1600 ℃ and strong alkaline slag, the matrix of traditional magnesia-carbon material is easy to react with the slag, resulting in loose material structure, and then structural spalling and penetration corrosion. This makes the damage speed of the ladle brick accelerate, and its service life is usually not more than 100 heats, frequent replacement not only increases the production cost, but also affects the continuity of steelmaking.

[0005] (2) Poor thermal shock stability and easy to crack and spall: In order to improve the slag resistance of the material, the existing technology usually chooses to add electric smelting magnesia as the main aggregate. However, electric smelting magnesia itself has the characteristics of coarse grain and high thermal expansion coefficient, which leads to poor thermal shock stability. In the cycle process of rapid heating and cooling of the ladle, cracks are easy to occur in the brick body due to thermal stress concentration, and even large-area thermal shock spalling occurs, which exists safety hidden trouble.

[0006] (3) Existence of harmful secondary reaction and volume expansion: In the alumina-magnesia-carbon brick system, corundum raw materials are usually added to form spinel (MgAl2O4) to improve the slag resistance. In the use process, magnesium oxide (MgO) in the electric smelting magnesia will react with aluminum oxide (Al2O3) in the corundum to generate spinel at high temperature. This reaction is accompanied by significant volume expansion, which will generate huge organizational stress in the brick body, further aggravating the formation and expansion of thermal shock cracks.

[0007] (4) Poor and uneven oxidation resistance: In order to prevent carbon in the brick from being oxidized at high temperature, the traditional ladle brick often uses metal aluminum powder or metal silicon powder as an antioxidant. However, these metal powders are difficult to achieve complete uniform dispersion during mixing, and are prone to agglomeration. This uneven distribution of the antioxidant can lead to poor oxidation resistance and slag resistance in local areas of the brick, forming weak points in performance, thereby accelerating the overall damage of the brick.

[0008] Therefore, in view of the problems of existing refining ladle bricks, such as difficult to balance slag resistance and thermal shock stability, short service life, easy to crack due to volume expansion, and uneven oxidation resistance, there is an urgent need to develop a new type of refining ladle brick with excellent thermal shock stability, strong slag resistance, stable structure and long service life. SUMMARY

[0009] The present application provides a long-life refining ladle brick and a preparation method thereof, to solve the problems of poor thermal shock stability, volume expansion induced thermal shock cracking, and easy peeling during use caused by the use of single magnesium oxide component in the existing traditional ladle brick, as well as uneven dispersion of the antioxidant and poor oxidation resistance.

[0010] According to the first aspect of the present application, the present application provides a long-life refining ladle brick composed of a mixture and a binder; the mixture includes the following raw materials in parts by weight: RH magnesia-alumina spinel brick recycling material with a particle size of ≤8mm 55-84 parts, fused magnesia with a particle size of ≤1mm 5-9 parts, large crystalline fused magnesia fine powder 10-15 parts, and nano carbon fiber 6-15 parts; the binder includes the following raw materials in parts by weight: liquid phenolic resin 1-3 parts, silica sol 1-6 parts, and liquid water glass 1-2 parts.

[0011] The long-life refining ladle brick provided by the present application uses specific raw materials and proportions, so that the components synergize with each other to prepare a long-life ladle brick with excellent comprehensive performance, thereby fundamentally solving the core problems of poor volume stability, uneven oxidation resistance, and insufficient bonding strength in the prior art.

[0012] The present application uses RH magnesia-alumina spinel brick recycling material as the main aggregate, which is different from the traditional use of fused magnesia and corundum to generate spinel in situ at high temperature. Instead, the present application directly uses pre-synthesized spinel recycling material as aggregate, which can fundamentally avoid excessive volume expansion caused by secondary reaction during the use of the brick, thereby significantly improving the thermal shock stability and structural integrity of the brick, and reducing the risk of cracking and peeling caused by organizational stress.

[0013] The present application introduces nanometer carbon fiber, which has extremely high specific surface area and excellent dispersibility compared with traditional metal powder (such as aluminum powder, silicon powder) or flake graphite as antioxidant and carbon source. This makes it form a uniform and dense three-dimensional carbon network in the brick matrix, thereby greatly improving the overall oxidation resistance and slag penetration resistance of the material, avoiding the local performance weakness caused by uneven dispersion of traditional antioxidants. At the same time, the toughening effect of the fiber also further improves the shock resistance and strength of the material.

[0014] The present application uses a composite binder, which uses liquid phenolic resin, silica sol and liquid water glass three binders with different properties. Liquid phenolic resin can adsorb and uniformly disperse nanometer carbon fiber, provide good forming performance and green strength at low temperature, and carbonize to form carbon bond during subsequent heat treatment, forming more and complete graphite structure with carbon fiber, enhancing the high temperature resistance of the material; silica sol and water glass as inorganic binders, form a solid ceramic bond through chemical reaction at medium and high temperature. This organic-inorganic composite bonding method ensures that the brick has stable and reliable bonding strength in the entire working temperature range from low temperature to ultra-high temperature, making up for the defects of single binder in performance decline at a certain temperature range.

[0015] According to the long-life refining ladle brick of the present application, the amount of the binder is 5-10% of the mass of the mixture.

[0016] The present application optimizes the amount of binder, which can maximize the control of porosity after forming and heat treatment on the premise of ensuring sufficient bonding strength, so as to obtain the final product with high density and good mechanical strength. If the amount of binder is too small, the inter-particle bonding force will be insufficient, the green strength will be low, and the structure will be loose; if the amount of binder is too large, too many pores will be produced due to the volatilization and carbonization of the binder during heat treatment, resulting in increased porosity and decreased bulk density of the material, thereby reducing its slag penetration resistance.

[0017] According to the long-life refining ladle brick of the present application, the liquid phenolic resin has residual C≥48% and solid content≥80%; the viscosity of the liquid phenolic resin at 25℃ is 10000-15000CP.

[0018] In the present application, the liquid phenolic resin has residual C≥48%, which can ensure that more carbon is retained in the brick after high-temperature carbonization, which can form a stronger and more complete carbon bonding network, which is beneficial to resist slag erosion and prevent molten steel penetration. The high solid content (≥80%) means that there is less volatile solvent in the resin, which can reduce the pores caused by solvent volatilization during mixing and curing, thereby improving the bulk density and overall density of the brick.

[0019] The long-life refining ladle brick according to the present application, the silica sol is 40 silica sol, the SiO2 content is 39%-41%, the viscosity is ≤10 mPa·s (preferably 5-8 mPa·s), and 9.0≤pH≤10.5.

[0020] In the present application, the silica sol is limited to a low-viscosity (≤10 mPa·s) silica sol, which can ensure that the silica sol has good fluidity during mixing and can uniformly coat the surfaces of aggregate and powder particles, achieving uniform dispersion at the micron level and avoiding local agglomeration. The specific SiO2 content (39%-41%) and pH value range (9.0≤pH≤10.5) ensure the stability of the silica sol itself and the reactivity as a binder, allowing it to undergo the expected chemical reactions with components such as water glass in subsequent processes, and stably form a high-strength silicate network bonding phase, providing protection for the medium-high temperature strength of the brick body.

[0021] The long-life refining ladle brick according to the present application, the modulus of the liquid water glass is 2.4-3.0. Water glass with this modulus (molar ratio of silicon dioxide to sodium oxide) range can provide moderate setting speed and good medium-high temperature bonding performance in an environment coexisting with other binders, helping to quickly establish preliminary inorganic bonding strength during curing and heating, and ultimately forming a stable ceramic bond.

[0022] The long-life refining ladle brick according to the present application, the carbon content of the nanometer carbon fiber is ≥99.9%; the diameter of the nanometer carbon fiber is 50-300 nm. Nanometer carbon fiber with such purity can ensure that the performance of nanometer carbon fiber as an antioxidant and toughening phase is fully utilized, while avoiding the damage caused by the introduction of harmful impurities to the high-temperature performance of the brick body.

[0023] The long-life refining ladle brick according to the present application, 55-84 parts of the RH magnesium-aluminum spinel brick recycling material with a particle size of ≤8 mm include: 8-15 parts of RH magnesium-aluminum spinel brick recycling material with a particle size of 5-8 mm, 12-18 parts of RH magnesium-aluminum spinel brick recycling material with a particle size of 3-5 mm, 25-32 parts of RH magnesium-aluminum spinel brick recycling material with a particle size of 1-3 mm, and 10-19 parts of RH magnesium-aluminum spinel brick recycling material with a particle size of ≤1 mm.

[0024] The present application divides the total particle size range (≤8 mm) into four different particle size intervals (5-8 mm, 3-5 mm, 1-3 mm, ≤1 mm) and gives the respective proportions, forming a "coarse, medium, fine, and micro" four-level particle grading. This allows different sized particles to fill voids to the maximum extent, resulting in extremely high packing density and extremely low original porosity.

[0025] The mass percentage of MgO in the RH magnesia-alumina spinel brick recycling material with particle size ≤8mm is ≥65% (preferably 65-75%), the mass percentage of Al2O3 is ≥15% (preferably 15-25%), and the bulk density is ≥3.0g / cm 3 (preferably 3.0-3.2g / cm 3 )。

[0026] The present application defines the minimum content of MgO and Al2O3 and the minimum value of the bulk density of the RH magnesia-alumina spinel brick recycling material, which can ensure that the recycling material itself has excellent refractory performance and dense structure as the "skeleton" of the brick, laying a solid foundation for the high performance of the whole brick.

[0027] According to the long-life refining ladle brick of the present application, in the electric smelting magnesia, the mass percentage of MgO is ≥96.5% (preferably 96.5-98.5%), and the bulk density is ≥3.25g / cm 3 (preferably 3.25-3.45g / cm 3 )。

[0028] According to the long-life refining ladle brick of the present application, in the large-crystal electric smelting magnesia, the mass percentage of MgO is ≥97.8% (preferably 97.8-99.0%), the mass percentage of CaO is ≤1.5% (preferably 0.6-1.2%), the mass percentage of SiO2 is ≤1.2% (preferably 0.3-0.6%), the mass percentage of Fe2O3 is ≤0.7% (preferably 0.35-0.65%), and the bulk density is ≥3.46g / cm 3 (preferably 3.49-3.51g / cm 3 )。

[0029] According to the second aspect of the present application, the present application also provides a preparation method of the above-mentioned long-life refining ladle brick, which comprises the steps of mixing, shaping and natural curing; wherein the mixing is dry mixing of the mixture and then adding the binder for mixing at 10-35℃.

[0030] The present application adopts the step of first uniformly dry mixing all solid materials and then adding liquid binder for mixing, which can effectively avoid the agglomeration of nanomaterials and fine powder, and ensure the uniform distribution of all components in the brick blank from macroscopic to microscopic scale.

[0031] According to the preparation method of the long-life refining ladle brick of the present application, the mixing time is 15-20min, and the temperature after mixing is ensured to be not higher than 40℃. In this way, it can ensure that all particles are fully and uniformly wetted and coated by the binder, while avoiding the premature polymerization reaction of the resin binder due to frictional heat or too long time, ensuring the good plasticity of the mud and the subsequent shaping quality.

[0032] According to the preparation method of the long-life refining ladle brick, the forming is to press the mixed mud under 800-1200 tons, in the pressure range, the air between the mud particles can be effectively removed, so that the bricks are tightly combined, thereby obtaining the bricks with low porosity and high bulk density.

[0033] Preferably, the pressing process emphasizes four-corner feeding, four-corner pressing, and high-pressure forming, and the pressing is light at first and heavy later.

[0034] According to the preparation method of the long-life refining ladle brick, the natural curing is to naturally cure the formed bricks for 36-60 hours. In the natural curing time range, the preliminary curing of the resin and the chemical reaction of the water glass and the silica sol are provided with the necessary time, so that the bricks obtain sufficient “green strength” without heating, so as to facilitate subsequent handling, stacking and heat treatment, and prevent damage during processing.

[0035] The beneficial effects of the present application are as follows:

[0036] The long-life refining ladle brick provided by the present application takes RH magnesium-aluminum spinel brick recycling material and fused magnesia as main raw materials, generates high-purity forsterite by introducing silicon dioxide phase, improves the slag resistance, solves the problems of poor thermal shock stability of single magnesium oxide component and thermal shock spalling during use. The introduction of nanoscale carbon fibers effectively solves the problem of uneven dispersion of flaky graphite in traditional ladle bricks. The ladle brick adopts a combination of thermal and air hardening binders, and the prepared magnesite-carbon brick does not need to be baked. The ladle brick forms a silicon dioxide anti-oxidation coating on the surface by adding silica sol, and does not need to add an anti-oxidation agent separately, and good anti-oxidation effect can be obtained. The ladle brick of the present application greatly improves the service life of the refining ladle after being used on the refining ladle. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0038] The raw materials used in the following embodiments are as follows:

[0039] The RH magnesium-aluminum spinel brick recycling material with a particle size of 5-8 mm: the mass percentage of MgO is 75%, the mass percentage of Al2O3 is 20%, and the bulk density is 3.2 g / cm 3 ;

[0040] RH magnesia-alumina spinel brick recycled material with particle size of 3-5 mm: mass percentage of MgO is 75%, mass percentage of Al2O3 is 20%, bulk density is 3.2 g / cm 3 ;

[0041] RH magnesia-alumina spinel brick recycled material with particle size of 1-3 mm: mass percentage of MgO is 75%, mass percentage of Al2O3 is 20%, bulk density is 3.2 g / cm 3 ;

[0042] RH magnesia-alumina spinel brick recycled material with particle size of ≤1 mm: mass percentage of MgO is 75%, mass percentage of Al2O3 is 20%, bulk density is 3.2 g / cm 3 ;

[0043] Liquid phenolic resin: C is 52%, solid content is 80%, viscosity at 25℃ is 15000 CP;

[0044] Silica sol: 40 silica sol, SiO2 content is 40%, viscosity is 7 mPa·s, pH is 9.5;

[0045] Liquid water glass: modulus is 2.8;

[0046] Nanometer carbon fiber: mass percentage of carbon content is ≥99.9%, diameter is 150-200 nm;

[0047] Fused magnesia: mass percentage of MgO is 98.0%, bulk density is 3.45 g / cm 3 ;

[0048] Large crystal fused magnesia: mass percentage of MgO is 98.3%, mass percentage of CaO is 0.8%, mass percentage of SiO2 is 0.4%, mass percentage of Fe2O3 is 0.45%, bulk density is 3.5 g / cm 3 .

[0049] The bulk density test method is: the detection standard is GB / T 2997-2015.

[0050] The porosity test method is: the detection standard is GB / T 2997-2015.

[0051] The compressive strength test method is: the detection standard is GB / T 5072-2023.

[0052] The fired line change test method is: the detection standard is GB / T 5988-2022.

[0053] The hot modulus of rupture test method is: the detection standard is GB / T 3002-2017.

[0054] The method for testing antioxidant properties is as follows: after the sample is kept at 1400℃ for 3 hours, it is cut open and the area of ​​the oxide layer in the test section is measured.

[0055] The slag resistance test method is the rotary slag erosion method in the standard GB / T 8931-2007 Test Methods for Slag Resistance of Refractory Materials.

[0056] Example 1

[0057] This embodiment provides a long-life refining ladle brick, the raw material composition of which is shown in Table 1 below, and its preparation method is as follows:

[0058] (1) Ingredients: Weigh the raw materials of each component according to the proportions in Table 1 and set aside.

[0059] (2) Mixing: Add the granules, nano carbon fibers, fine powder and additives to the mixer and dry mix for 3 minutes. Then add liquid phenolic resin, 40 silica sol and liquid water glass. Mix at 10~35℃ for 15 minutes and then discharge the material, ensuring that the discharge temperature is not higher than 40℃.

[0060] (3) Molding: The mixed mud is pressed on a 1000-ton brick press. The pressing process emphasizes the four corners of the material being scraped, the four corners of the material being pressed, and high pressure molding, starting with light pressure and then increasing the pressure.

[0061] (4) Maintenance: Natural maintenance for 48 hours.

[0062] Example 2

[0063] This embodiment provides a long-life refining ladle brick, the raw material composition of which is shown in Table 1 below, and its preparation method is the same as in Embodiment 1.

[0064] Example 3

[0065] This embodiment provides a long-life refining ladle brick, the raw material composition of which is shown in Table 1 below, and its preparation method is the same as in Embodiment 1.

[0066] Comparative Example 1

[0067] This comparative example provides a refined ladle brick, the raw material composition of which is shown in Table 1 below, and its preparation method is the same as that in Example 1.

[0068] Comparative Example 2

[0069] This comparative example provides a refined ladle brick, the raw material composition of which is shown in Table 1 below, and its preparation method is the same as that in Example 1.

[0070] Table 1. Raw material composition of the examples and comparative schemes

[0071]

[0072] The refining ladle bricks prepared in examples 1-3 and comparative examples 1 and 2 are subjected to performance testing, and the testing indexes include bulk density, apparent porosity, pressure resistance, linear change after firing (1600℃×3h), hot modulus of rupture (1400℃×0.5h), oxidation resistance (1400℃×3h), and slag resistance, and the specific performance indexes are shown in Table 2.

[0073] Table 2 Performance testing results of examples and comparative example samples

[0074]

[0075] As shown in Table 2, compared with the experimental effects of comparative examples 1-2, the oxidation resistance and slag resistance of the long-life refining ladle brick of the application are obviously improved.

[0076] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A long-life refining ladle brick, characterized in that, It is composed of a mixture and a binder; the mixture comprises the following raw materials in parts by weight: 55-84 parts of recycled RH magnesium-aluminum spinel brick with a particle size ≤8mm, 5-9 parts of fused magnesia with a particle size ≤1mm, 10-15 parts of fine powder of large-crystal fused magnesia, and 6-15 parts of nano-carbon fiber; the binder comprises the following raw materials in parts by weight: 1-3 parts of liquid phenolic resin, 1-6 parts of silica sol, and 1-2 parts of liquid water glass; the amount of binder is 5-10% of the mass of the mixture; The 55-84 parts of the RH magnesium-aluminum spinel brick recycled material with a particle size ≤8mm include: 8-15 parts of RH magnesium-aluminum spinel brick recycled material with a particle size of 5-8mm, 12-18 parts of RH magnesium-aluminum spinel brick recycled material with a particle size of 3-5mm, 25-32 parts of RH magnesium-aluminum spinel brick recycled material with a particle size of 1-3mm, and 10-19 parts of RH magnesium-aluminum spinel brick recycled material with a particle size ≤1mm.

2. The long-life refining ladle brick according to claim 1, characterized in that, The liquid phenolic resin has a residual carbon content of ≥48% and a solid content of ≥80%; the viscosity of the liquid phenolic resin at 25°C is 10000-15000 CP.

3. The long-life refining ladle brick according to claim 1, characterized in that, The silica sol is 40 silica sol with a SiO2 content of 39%-41%, a viscosity of ≤10 mPa∙s, and a pH value of 9.0≤10.

5.

4. The long-life refining ladle brick according to claim 1, characterized in that, The modulus of the liquid water glass is 2.4-3.

0.

5. The long-life refining ladle brick according to claim 1, characterized in that, The carbon nanofibers have a carbon content of ≥99.9% by mass; the diameter of the carbon nanofibers is 50-300 nm.

6. The long-life refining ladle brick according to claim 1, characterized in that, The recycled RH magnesium-aluminate spinel brick material with a particle size ≤8mm has the following composition: MgO mass percentage ≥65%, Al2O3 mass percentage ≥15%, and bulk density ≥3.0g / cm³. 3 .

7. The long-life refining ladle brick according to claim 1, characterized in that, The fused magnesia contains ≥96.5% MgO by mass and ≥3.25 g / cm³ in its bulk density. 3 ; And / or, in the large-crystal fused magnesia, the mass percentage of MgO is ≥97.8%, the mass percentage of CaO is ≤1.5%, the mass percentage of SiO2 is ≤1.2%, the mass percentage of Fe2O3 is ≤0.7%, and the bulk density is ≥3.46 g / cm³. 3 .

8. The method for preparing long-life refining ladle bricks according to any one of claims 1-7, characterized in that, It includes the steps of mixing, molding and natural curing; wherein the mixing is to dry mix the mixture and then add a binder and mix and grind at 10~35℃.

9. The method for preparing long-life refining ladle bricks according to claim 8, characterized in that, The mixing and grinding time is 15-20 minutes, and the discharge temperature after mixing and grinding is guaranteed to be no higher than 40℃. And / or, the molding is achieved by pressing the mixed and rolled mud material under 800-1200 tons; And / or, the natural curing refers to naturally curing the formed bricks for 36-60 hours.

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