Aluminum killed steel anti-al2o3 accretion nozzle inner lining material and preparation method thereof

Abstract

The application belongs to the technical field of continuous casting functional refractory material, and discloses an Al2O3 accretion prevention nozzle lining material for aluminum killed steel and a preparation method thereof. The solid phase raw material ratio of the Al2O3 accretion prevention nozzle lining material for aluminum killed steel is 100wt% in total solid phase mass, specifically: 75-88% of fused magnesite, h 6-14% of BN, 3-8% of CaB 6 2-5% of anhydrous MgCl2 powder, and additionally added is MgCl2 saturated aqueous solution, with an additional amount of 2-4% of the total mass of the solid phase, for controlling the plasticity of the mixture. The application constructs a complete accretion prevention system from four dimensions of precursor thermodynamics, interface wetting thermodynamics, oxidation competition thermodynamics and multi-component eutectic corrosion thermodynamics, and the four mechanisms work together to inhibit the growth of Al2O3 accretion from the root.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting functional refractory materials technology. It discloses an aluminum-killed steel anti-Al2O3 nodule lining material and its preparation method. It is a magnesium-based composite lining system without silicon, aluminum, or free elemental carbon. It is suitable for long-term anti-clogging production of high-end continuous casting refractory materials and belongs to the original preparation technology of continuous casting lining anti-Al2O3 nodule. Background Technology

[0002] The existing problem of nodule formation in the sprue lining of aluminum-killed steel continuous casting: Aluminum-killed steel is produced by deep deoxidation of metallic aluminum, which instantaneously generates a large number of nano / micron-sized Al2O3 non-metallic inclusions in the molten steel. During continuous casting, the suspended Al2O3 inclusions continuously scour the inner wall of the sprue with the steel flow. Under the coupling effect of high temperature, interfacial tension, charge, and solid phase agglomeration, they gradually deposit, agglomerate, and adhere to the solid phase, forming an Al2O3 nodule layer. Nodule formation continuously reduces the cross-sectional area of ​​the nozzle, causing steel flow deviation, unplanned flow blockage, and interruption of molten steel pouring, significantly reducing continuous casting efficiency. Simultaneously, large nodule fragments detach and become trapped in the molten steel, significantly increasing the content of large inclusions in the billet and worsening surface defects and mechanical properties of the steel. This is a core bottleneck restricting stable, long-cycle production of high-end aluminum-killed steel. From a high-temperature thermodynamic perspective, traditional nozzle linings generally contain three types of harmful components that induce nodule formation. The Gibbs free energy of the reactions involving these components is ΔG≪0, which can spontaneously proceed in a positive direction, continuously providing a sintering substrate for Al2O3 deposition. 1) SiO2-containing system: SiO2 and Al2O3 spontaneously react in the range of 1400-1600 ℃ to generate mullite, calcium aluminum feldspar and other phases. The system eutecticly melts to form a low melting point liquid phase. The liquid phase acts as a binding medium to capture solid Al2O3 particles, causing them to sinter and grow rapidly. 2) Free elemental carbon / graphite system: Carbon reduces FeO and MnO in steel slag, causing Al2O3 to precipitate out of the molten steel for the second time; at the same time, carbon and Al2O3 undergo a carbothermic reduction reaction to generate gaseous aluminum Al(g), and the gaseous aluminum is oxidized again to generate new Al2O3, which further aggravates nodulation. 3) Aluminosilicate matrix: The matrix has a high degree of lattice matching with Al2O3 crystals, a small interfacial wetting angle, and low interfacial free energy; Al2O3 inclusions are very easy to spread and grow epitaxially on the matrix surface, forming a continuous and dense nodular layer.

[0003] The existing anti-nodulation nozzle technology has the following systemic defects: Currently compatible with low carbon oxide liners, calcium zirconate liners, and silicon carbide / boron nitride liners. hThe anti-nodulation gate design of BN-based liners has significant shortcomings. Most liner types in the industry use a carbon bonding system to ensure billet strength and density, a common defect. Under high-temperature continuous casting conditions, the internal carbon components and residual carbon components of the liner continuously undergo carbothermic reduction reactions, which not only damage the structural stability of the base material but also induce the sintering and enrichment of Al2O3 and silicate inclusions in the molten steel, continuously providing the thermodynamic conditions required for nodulation. This results in a short service life for existing protection solutions and a high recurrence rate of nodulation problems. In addition to these common shortcomings, different liner materials also have their own independent defects: h -BN modified carbon-based nozzle surface h -BN oxidizes at high temperatures to generate gaseous B2O3, which volatilizes and is lost, causing the protective layer to fail after only a few casting cycles; pure... h -BN spray coating has poor thermal expansion compatibility with the nozzle substrate, making it prone to peeling under thermal cycling. It also has weak oxidation resistance and is only suitable for short-cycle production. Calcium zirconate linings can only dissolve a small amount of Al2O3 impurities, lack an interfacial barrier phase, have limited impurity removal capabilities, and are insufficient for long-term anti-caking effects. Silicon nitride linings are chemically inert, but cannot inhibit impurity adhesion and solid-phase sintering. Long-term casting can easily lead to stubborn nodules, making it difficult to meet the needs of multi-furnace long-cycle continuous casting production.

[0004] Existing technologies have not constructed a three-in-one thermodynamic synergistic system of "nodulation-free precursors + anti-oxidation non-wetting isolation + in-situ low-melting-point phase dissolution," and have three key deficiencies: First, they fail to completely eliminate components that easily induce sintering, such as silicon, aluminum, and free elemental carbon, and cannot block the nodulation reaction from the thermodynamic source; second, they do not introduce an anti-oxidation functional phase that can protect BN for a long time, making it difficult to alleviate the high-temperature oxidation loss of BN and resulting in insufficient long-term protection; third, they lack a controllable calcium source, making it impossible to continuously generate a low-melting-point liquid phase to wash away and dissolve the attached Al2O3 particles. Relying solely on a single physical barrier or a single chemical dissolution mechanism is not suitable for the industrial production conditions of high-speed casting and long-cast secondary aluminum killed steel.

[0005] Therefore, the industry urgently needs a compound that completely avoids silicon, aluminum, and free elemental carbon. h -BN-Calcium hexaboride (CaB6) bifunctional phase, resin-free carbonization bonding, and a sprue lining material that effectively inhibits Al2O3 nodulation by relying on multilayer thermodynamic synergy. Summary of the Invention

[0006] The purpose of this invention is to provide an aluminum-killed steel anti-Al2O3 nodulation liner material and its preparation method. This liner is completely free of nodulation precursors such as SiO2, Al2O3, and free elemental carbon, and uses fused magnesia as the matrix. h-BN serves as the interface barrier phase, CaB6 as the antioxidant and in-situ low-melting phase functional phase, and anhydrous MgCl2 is chemically bonded and formed at low temperature. Relying on the synergistic effects of multiple high-temperature thermodynamic competitive reactions, interface wetting thermodynamics, and multi-element oxide eutectic thermodynamics, it inhibits nodulation reactions from the source, blocks inclusion adhesion, and dissolves and attaches Al2O3 particles in situ, while also meeting the multiple needs of long-term casting stability and anti-clogging, and adapting to the production of various types of aluminum killed steel.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A type of aluminum-killed steel anti-Al2O3 nodule liner material, wherein the solid phase raw material ratio of the aluminum-killed steel anti-Al2O3 nodule liner material is, by mass fraction, 100wt% of total solid phase; specifically: 75-88% fused magnesia. h -BN 6~14%, CaB6 3~8%, anhydrous MgCl2 powder 2~5%, and an additional saturated aqueous solution of MgCl2, the amount of which is 2%~4% of the total mass of the solid phase, is used to control the plasticity of the mixture.

[0008] The gradation of fused magnesia is 0.5~0.1mm:0.1~0.074mm:200 mesh = 4:3:2; MgO ≥ 97.5wt%.

[0009] h -BN purity ≥99.0wt%, particle size <45μm, free oxygen content ≤0.3wt%.

[0010] The purity of CaB6 is ≥98.0wt%, the particle size of the ultrafine powder is <38μm, and the metallic calcium impurity is <0.1wt%.

[0011] The moisture content of anhydrous MgCl2 powder is ≤0.5wt%.

[0012] A method for preparing an aluminum-killed steel anti-Al2O3 nodulation sprue liner material is as follows: (1) Segmented gradient mixing: First stage coarse mixing: All graded fused magnesia is put into a high-speed high-intensity mixer and dry-mixed for 5-10 minutes to achieve uniform dispersion of aggregates; The second stage involves the composite mixing of functional phases: CaB6 and anhydrous MgCl2 powders are added in steps and mixed for 5–10 min. Then, h-BN is slowly added and dry-mixed for another 10 min. Gradual addition avoids the breakage of BN flakes due to high shear force and prevents local agglomeration of ultrafine CaB6, ensuring that the two functional phases are uniformly dispersed within the magnesia matrix. Finally, a saturated aqueous solution of MgCl2 is slowly atomized and sprayed into the uniformly mixed powder. The mixture is then wet-mixed at low speed for 5–10 min to obtain a plastic mixture. The uniformity of the mixture is observed in real time to control the moisture content and prevent dry-wet stratification. (2) Molding: The plastic mixture is filled into the sprue mold. The liner can be pre-formed independently or integrally formed with the sprue matrix material. First, low-frequency vibration is used to remove air bubbles inside the blank to ensure that the liner blank is dense and uniform. Then, cold isostatic pressing is used for molding, and the molding pressure is controlled at 30-120 MPa. (3) Curing and firing: Anhydrous MgCl2 is slightly melted at low temperature to form a continuous magnesium salt crystal bridging network on the surface of fused magnesia particles, thus completing the solidification of the green body at room temperature; after solidification, the green body is placed in a carbon-buried atmosphere or an inert non-oxidizing atmosphere for firing at a firing temperature of 800-1200℃ and the target temperature is held for 2-4 hours; the carbon-buried medium is a mixture of coke powder and Al2O3 powder to prevent the magnesia matrix from oxidizing at high temperature. (4) Post-processing: After firing, allow the material to cool naturally to room temperature. You can choose to apply a layer of anti-BN oxidation protective coating to the inner wall, or you can leave the coating unapplied.

[0013] This invention constructs a complete anti-nodulation system from four dimensions: precursor elimination thermodynamics, interfacial wetting thermodynamics, oxidation competition thermodynamics, and multi-element eutectic corrosion thermodynamics. These four mechanisms work synergistically to inhibit Al2O3 nodule growth at its source. (1) Completely eliminate nodule precursors and cut off the thermodynamic driving force of sintering reaction. Traditional silicon- and carbon-containing linings exhibit two types of spontaneously exothermic reactions (ΔG<0) at casting temperatures of 1500–1600℃, continuously generating composite liquid or solid sintered phases that can bind Al2O3. In this system, the matrix uses only high-purity fused MgO, without adding SiO2, Al2O3, graphite, carbon black, or other components throughout the process. The system contains no silicon or free elemental carbon, and the aforementioned sintering-promoting reactions lack reactants, making it thermodynamically impossible to proceed in the forward direction. This completely cuts off the liquid-phase bonding carrier required for the sintering and agglomeration of Al2O3 particles, eliminating the basic conditions for nodule formation from the lining's own composition level (this mechanism only isolates harmful components within the lining; external SiO2 and Al2O3 from molten steel and slag are removed through in-situ low-melting-point dissolution mechanisms).

[0014] (2) Thermodynamic barrier mechanism of non-wetting at h-BN interface Boron nitride (BN) possesses a graphite-like layered crystal structure with only weak van der Waals forces between the layers, resulting in extremely low surface energy. Thermodynamic calculations show that within the casting temperature range of 1550–1600℃ for aluminum-killed steel, the wetting angle at the solid-liquid interface between molten steel, solid Al2O3 inclusions, and BN is >125°, with an interfacial adsorption process ΔG >0, meaning that wetting, spreading, and adhesion processes cannot occur spontaneously. When Al2O3 particles contact the lining surface, they cannot achieve stable adhesion by reducing interfacial free energy. Simultaneously, in a neutral / weakly oxidizing atmosphere at 1600℃, BN does not undergo a solid-solid chemical reaction with MgO or Al2O3, and does not generate a composite sintered phase. It can form a continuous inert isolation film on the lining surface, physically isolating Al2O3 inclusions from direct contact with the magnesium matrix and blocking the epitaxial sintering growth path of Al2O3. Under actual working conditions, the wetting angle fluctuates between 125° and 140° depending on the steel grade and oxygen partial pressure, maintaining its difficult-to-wet characteristics.

[0015] (3) Thermodynamic competition of CaB6 oxidation at high temperature, providing long-term protection h -BN BN is highly susceptible to oxidation in high-temperature, oxygen-containing environments, with the oxidation product B2O3 volatilizing in gaseous form, leading to rapid failure of the BN protective layer. In this system, CaB6 oxidation has a higher thermodynamic priority than BN. Under the same oxygen partial pressure, CaB6 oxidation has a lower Gibbs free energy, preferentially capturing dissolved oxygen in the molten steel and atmospheric oxygen seeping into the nozzle gaps. As a sacrificial antioxidant phase, CaB6 continuously consumes local oxygen, significantly reducing the oxygen partial pressure on the lining surface, inhibiting BN oxidation loss, and ensuring the continuous and stable interfacial barrier function of BN within the lining during long casting cycles. This addresses the short-casting-cycle failure defect of traditional BN-modified products. Operating conditions are differentiated: during the firing stage, in a carbon-buried, oxygen-free environment, CaB6 remains stable and is not consumed; during the continuous casting high-temperature pouring stage, oxygen is continuously supplied, and CaB6 is gradually consumed; the formula limits the minimum CaB6 addition to 3wt%, ensuring that residual CaB6 remains for continuous oxidation resistance even after 12 or more heats.

[0016] (4) The oxidation products form a ternary eutectic phase in situ, and the Al2O3 particles are thermodynamically and spontaneously dissolved. CaB6 oxidation generates CaO in situ. When CaO, the matrix MgO, and the Al2O3 adhering to the lining surface come into contact, a spontaneous composite oxide formation reaction occurs (ΔG<0). The lowest eutectic point of this CaO-MgO-Al2O3 ternary system is only 1180–1280 ℃, far lower than the casting temperature of aluminum-killed steel (1550–1600 ℃). From a thermodynamic stability perspective, the Gibbs free energy of the liquid multi-component eutectic phase is much lower than that of the solid Al2O3 crystal. Once a small amount of Al2O3 particles adhere to the lining surface, they will instantly melt with the in-situ generated CaO and MgO to form a highly fluid liquid phase, which is continuously washed away by the steel flow, preventing aggregation, accumulation, and sintering to form hard nodules. This achieves a dynamic self-cleaning effect where Al2O3 inclusions adhere and are immediately melted and washed away. Component boundary control: The maximum amount of CaB6 added is 8wt%. Excessive amounts will continuously generate a large amount of CaO, exacerbating high-temperature erosion and shortening the overall service life of the lining.

[0017] This invention provides an aluminum-killed steel anti-Al2O3 nodulation liner material and its preparation method. Using the above technical solution, the following beneficial effects are achieved: (1) Multiple thermodynamic synergistic inhibition of nodule formation, with the effect at the source: The inner lining is free of silicon, aluminum, free elemental carbon and other nodule-forming endogenous precursors, blocking the sintering reaction from the thermodynamic source; the superimposed BN non-wetting interface barrier, CaB6 long-term antioxidant protection, and in-situ ternary low melting phase dissolution triple mechanism work together to stabilize nodule formation over long casting cycles, making it suitable for industrial production of high-speed aluminum-killed steel, ultra-low carbon steel and automotive sheet steel.

[0018] (2) Significantly improved continuous casting times and reduced production failures: CaB6 preferential oxidation protection h -BN avoids the problem of rapid failure of BN at high temperatures; compared with traditional BN modified carbon-based nozzles, the number of continuous casting furnaces is increased by more than 80wt%, significantly reducing unplanned downtime such as flow blockage and interruption of casting; the number of large Al2O3 inclusions in the billet is reduced by more than 60wt%, and the cleanliness of molten steel is significantly improved.

[0019] (3) Raw material costs are controllable and industrial adaptability is strong: There is a sufficient market supply of fused magnesia as the main material, and the proportion of boron nitride and CaB6 added is low. The overall cost of the formula is lower than that of commercial BN coating nozzles. The segmented gradient mixing and low-temperature curing process can be directly mass-produced based on existing refractory material forming and drying equipment without the need for new large-scale high-temperature kilns, and the equipment investment threshold is low.

[0020] (4) Excellent thermal shock resistance and long service life of the lining: The high-purity magnesia matrix combined with the dispersed scaly BN phase can buffer the thermal stress of hot and cold cycles, and the thermal shock resistance of the lining is significantly improved; it is not easy to crack or peel off under repeated hot and cold cycles of continuous casting, and its service life is better than that of traditional aluminum-carbon and magnesium-carbon nozzles. Detailed Implementation

[0021] The present invention will be described in conjunction with specific embodiments: Example 1: Ingredient formulation: The solid phase raw material ratio (total solid phase 100wt%) is shown in Table 1. Added binding agent: saturated aqueous solution of MgCl2, added at a rate of 2.5wt% of the total solid phase mass. Table 1 shows the solid raw material ratio for Example 1: .

[0022] Preparation process: All graded fused magnesia was dry-mixed in a high-speed mixer for 8 min; CaB6 and anhydrous MgCl2 powders were added sequentially and mixed for 8 min, then slowly added to the mixture. h - Continue dry mixing with BN for 10 min; atomize and spray in a saturated aqueous solution of MgCl2 and wet mix at low speed for 7 min until the mixture is plastically uniform and without stratification; fill the mixture into the sprue mold and form it as a single piece with the sprue substrate (suitable for low-pressure molding blanks); after low-frequency vibration to exhaust air, cold isostatic pressing is performed at a molding pressure of 30 MPa; the firing temperature is 800 ℃, and the temperature is held for 3 h under a carbon-buried atmosphere protection; after cooling, the inner wall is not coated with an anti-oxidation coating.

[0023] Performance and application results: The lining is free of SiO2, Al2O3 and free elemental carbon. The wetting angle between the molten steel and the lining is 128° at 1580 ℃. After 22 cycles of water cooling thermal shock at 1200 ℃, the sample showed no cracking or peeling. When used for aluminum-killed automotive steel casting, it can continuously cast 12 heats in a single casting. Only a trace amount of Al2O3 adheres to the inner wall of the nozzle, and no hard nodules are formed.

[0024] Example 2: Ingredient formulation: The solid phase raw material ratio (total solid phase 100wt%) is shown in Table 2. Added binding agent: saturated aqueous solution of MgCl2, added at a rate of 3wt% of the total solid phase mass. Table 2 shows the solid raw material ratio for Example 2:

[0025] Preparation process: First, dry mix fused magnesia in the equipment for 7 minutes, then add CaB6 and anhydrous MgCl2 and mix for 7 minutes. Slowly add... h -BN was dry-mixed for 10 min, then MgCl2 solution was atomized and wet-mixed at low speed for 8 min to complete the segmented gradient mixing; the mixture was filled into the sprue mold and integrally formed with the sprue matrix (suitable for low-pressure forming blanks), and then cold isostatically pressed after low-frequency vibration to exhaust the air, with a forming pressure of 45 MPa; the firing temperature was 1200 ℃, and the temperature was held for 3 h under a carbon-buried atmosphere protection; after cooling, an anti-oxidation coating was applied to the inner wall.

[0026] Performance and application results: The wetting angle between molten steel and the lining at 1580 ℃ is 133°, and no cracks were observed after 28 cycles of water-cooled thermal shock at 1200 ℃; calcium boride can effectively prevent cracking. h -BN forms an effective protective layer. When applied to industrial tests of high-speed ultra-low carbon aluminum-killed steel, it can stably cast 11 heats in a single casting. The cross-sectional area of ​​the sprue does not shrink significantly, and there are no problems with flow blockage or interruption of casting. The number of continuous casting heats is increased by 85 wt% compared to the traditional low-carbon oxide lining sprue.

[0027] Example 3:

[0028] Ingredient formulation: The solid phase raw material ratio (total solid phase 100wt%) is shown in Table 3. Added binding agent: saturated aqueous solution of MgCl2, added at a rate of 4wt% of the total solid phase mass. Table 3 shows the solid raw material ratio for Example 3:

[0029] Preparation process: During the segmented gradient mixing, the fused magnesia is first dry-mixed for 10 min, then calcium hexaboride and anhydrous MgCl2 are added and mixed for 10 min. After that, the mixture is slowly added at a low speed. h - Continue dry mixing with BN for 10 min to prevent BN flakes from breaking. Then, atomize and add water for wet mixing for 10 min and adjust until the plasticity index is qualified. The mixture is vented by low-frequency vibration and cold isostatic pressing at a pressure of 120 MPa. The firing temperature is 950 ℃, and the temperature is held for 3 h under a carbon atmosphere protection. After cooling, an anti-oxidation coating is applied to the inner wall.

[0030] Performance and Application Effects: The flake-like BN phase can be continuously distributed on the surface of the lining, with a wetting angle of up to 138° at 1580 ℃, making it difficult for Al2O3 inclusions to adhere; the lining showed no peeling after 31 thermal shock cycles, demonstrating high content. h -BN provides a strong interfacial barrier effect; this lining is suitable for the production of ultra-high speed thin-plate killed aluminum steel, and can be used for 12 heats in a single casting. Only a thin liquid phase film, easily washed away by the steel flow, forms locally on the inner wall, preventing the formation of hard Al2O3 nodules; although h - The amount of BN added increases the cost, but it is still lower than that of commercially available BN-lined nozzles.

Claims

1. A type of aluminum-killed steel anti-Al2O3 nodulation liner material for sprue nozzles, characterized in that: The solid raw material ratio of the aluminum-killed steel anti-Al2O3 nodule lining material for the nozzle is as follows: total solid mass is 100wt%; specifically: 75-88% fused magnesia. h -BN 6~14%, CaB6 3~8%, anhydrous MgCl2 powder 2~5%, and an additional saturated aqueous solution of MgCl2, the amount of which is 2%~4% of the total mass of the solid phase, is used to control the plasticity of the mixture.

2. The aluminum-killed steel anti-Al2O3 nodulation liner material as described in claim 1, characterized in that: The gradation of fused magnesia is 0.5~0.1mm:0.1~0.074mm:200 mesh = 4:3:2; MgO ≥ 97.5wt%.

3. The aluminum-killed steel anti-Al2O3 nodulation liner material as described in claim 1, characterized in that: h -BN purity ≥99.0wt%, particle size <45μm, free oxygen content ≤0.3wt%.

4. The aluminum-killed steel anti-Al2O3 nodulation liner material as described in claim 1, characterized in that: The purity of CaB6 is ≥98.0wt%, the particle size of the ultrafine powder is <38μm, and the metallic calcium impurity is <0.1wt%.

5. The aluminum-killed steel anti-Al2O3 nodulation sprue lining material as described in claim 1, characterized in that: The moisture content of anhydrous MgCl2 powder is ≤0.5wt%.

6. A method for preparing the aluminum-killed steel anti-Al2O3 nodulation sprue liner material according to any one of claims 1-5, characterized in that: The specific steps of the preparation method are as follows: (1) Segmented gradient mixing: First stage coarse mixing: All graded fused magnesia is put into a high-speed high-intensity mixer and dry-mixed for 5-10 minutes to achieve uniform dispersion of aggregates; The second stage of functional phase composite mixing: CaB6 and anhydrous MgCl2 powder are added stepwise and mixed for 5-10 min. Then, h-BN is slowly added and dry mixing continues for 10 min. Gradual feeding can avoid the BN flakes from being broken by high shear force and prevent the local agglomeration of ultrafine CaB6, ensuring that the two functional phases are uniformly dispersed in the magnesia matrix. Finally, saturated aqueous solution of MgCl2 is slowly atomized and sprayed into the uniformly mixed powder. The mixture is wet-mixed at low speed for 5-10 min throughout the process to obtain a plastic mixture. The uniformity of the mixture is observed in real time to control the uniformity of the material moisture and prevent dry-wet stratification. (2) Molding: The plastic mixture is filled into the sprue mold. The liner can be pre-formed independently or integrally formed with the sprue matrix material. First, low-frequency vibration is used to remove air bubbles inside the blank to ensure that the liner blank is dense and uniform. Then, cold isostatic pressing is used for molding, and the molding pressure is controlled at 30-120 MPa. (3) Curing and firing: Anhydrous MgCl2 is slightly melted at low temperature, forming a continuous magnesium salt crystal bridging network on the surface of fused magnesia particles, thus completing the curing of the green body at room temperature; after curing, the green body is placed in a carbon-buried atmosphere or an inert non-oxidizing atmosphere for firing at a temperature of 800-1200℃, and the target temperature is maintained for 2-4 hours. (4) Post-processing: After firing, allow to cool naturally to room temperature.

7. The preparation method of an aluminum-killed steel anti-Al2O3 nodulation sprue liner material as described in claim 6, characterized in that: In step (3), the carbon embedding medium is a mixture of coke powder and Al2O3 powder.

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