Method for improving automatic tapping rate of high-temperature ladle by using rare earth modified channel sand

Abstract

This invention discloses a method for improving the automatic casting rate of high-temperature steel ladles using rare earth modified guide sand, belonging to the field of steel continuous casting technology. This invention uses silicon-aluminum-magnesium-calcium based sand particles as the core, employing a layered high-temperature spraying process to sequentially coat an inner layer of light rare earth La2O3 / CeO2 and an outer layer of heavy rare earth Y2O3. Relying on a gradient sintering mechanism, the outer Y2O3 layer generates a high-melting-point phase at low temperatures to prevent molten steel penetration and leakage, while the inner light rare earth layer slowly releases sintering strength at high temperatures to avoid dense, hard shells clogging the nozzle. A complete set of processes, including sand pretreatment, slurry preparation, segmented curing, standardized filling, and temperature-controlled argon purging, is included. This method is suitable for high-temperature steel ladles of carbon steel and low-alloy steel at 1500~1650℃, and can stably increase the automatic casting rate to over 98%, significantly reducing manual burn-in and secondary oxidation of molten steel. It solves the problem of mutually exclusive anti-leakage and anti-clogging performance of traditional guide sand, and has wider temperature adaptability and greater versatility compared to existing layered nozzle filling technologies.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting production technology in iron and steel metallurgy, specifically involving a complete process method that uses light and heavy rare earth layered gradient coating modified diversion sand to improve the automatic casting rate of high-temperature steel ladles through a gradient sintering mechanism. Background Technology

[0002] The automatic ladle casting rate is a core indicator that determines the continuous production, billet cleanliness, and production and maintenance costs of a continuous casting production line. The guide sand, filling the interior of the ladle nozzle seat bricks, must simultaneously satisfy two contradictory properties under the action of high-temperature molten steel: firstly, it must form a sintered layer of sufficient strength to prevent molten steel from penetrating and leaking; secondly, it must not form a dense, non-porous, hard, rapidly hardened crust to prevent clogging of the nozzle channel and casting failure.

[0003] Traditional diversion sand has three major defects under existing high-temperature ladle working conditions (1500~1650℃): Rapid crust blockage: The surface of molten steel undergoes intense sintering upon contact with the sand layer, forming a dense rapid crust. This rapid crust is hard and non-porous, directly blocking the molten steel flow channel, leading to flow failure. It requires manual oxygen lance burning, increasing labor intensity and causing secondary oxidation of the molten steel, which deteriorates the quality of the billet. Insufficient sintering and steel leakage: In order to alleviate the problem of blockage, the sintering activity of the sand is reduced. Insufficient sintering capacity leads to a loose structure of the sand layer at high temperature. Molten steel seeps through the gaps between the particles, causing steel leakage safety accidents and resulting in significant economic losses. Narrow sintering window: The sintering performance of conventional sintering sand is highly sensitive to temperature and settling time. Small temperature fluctuations can cause blockage or leakage of steel, resulting in poor production stability and an average automatic start-up rate that has been below 85% for a long time.

[0004] Existing sand diversion improvement technologies fall into three categories, all of which have significant technical shortcomings: Single rare earth powder integral doping: directly physical mixing of rare earth oxides with diversion sand, without layered structure, unable to achieve temperature zone gradient reaction, still unable to balance the requirements of leak prevention and blockage prevention. Single oxide single-layer coating: Only one modified coating, the sintering behavior in the high and low temperature range cannot be differentiated and controlled, and the coating fails quickly or clumps up at high temperature; Layered filling process for sprue filler: It does not change the properties of the sprue sand particles themselves, but only achieves physical isolation by filling two layers of different sand materials. It belongs to the back-end process optimization and does not broaden the sintering window from the material itself. When the temperature of molten steel and the waiting time for pouring fluctuate greatly, sintering defects still exist. The applicable steel grades are limited to high manganese steel, and the versatility is poor.

[0005] None of the aforementioned existing technologies have broken through the technical bottleneck of "mutual exclusion between sintering strength and anti-caking performance," and cannot simultaneously meet the requirements of wide temperature range and long waiting time for general high-temperature steel ladles. The industry urgently needs a new material modification solution to address this pain point. Summary of the Invention

[0006] To address the shortcomings of existing diversion sands, such as easy blockage and steel leakage at high temperatures, poor temperature adaptability, and the fact that existing layered filling patents only provide temporary solutions, this invention provides a method for improving the automatic start-up rate of high-temperature steel ladles using rare earth modified diversion sand. This method constructs a gradient sintering reaction mechanism, taking into account both resistance to molten steel penetration and prevention of dense and rapid crust formation, thereby stably increasing the automatic start-up rate of high-temperature steel ladles to over 98%, and is suitable for high-temperature steel ladles of various steel types, including carbon steel and low alloy steel.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for improving the automatic casting rate of high-temperature steel ladles using rare earth modified diversion sand includes the following steps: 1) Preparation of rare earth modified diversion sand: Using basic diversion sand particles as the core, a layered high-temperature spray coating process is adopted. First, a layer of light rare earth oxide inner coating is coated on the outer surface of the core, and then a layer of heavy rare earth oxide outer coating is coated on the outside of the light rare earth oxide inner coating. The light rare earth oxide is at least one of La2O3 or CeO2, and the heavy rare earth oxide is Y2O3. 2) Filling of diversion sand: The prepared rare earth modified diversion sand is filled into the interior of the ladle nozzle seat brick; the filling process adopts a slow filling and slow lifting injection method, and the surface of the sand layer is leveled after filling is completed. 3) Steel ladle heating and temperature control: The steel ladle is heated synchronously during the baking stage to prevent the coating from falling off due to temperature difference; when the molten steel is poured into the ladle, it avoids the area filled with guide sand to prevent the molten steel from directly washing away the sand layer and damaging the coating; after the molten steel is poured, the steel ladle is kept at a high temperature and constant temperature to control the fluctuation range of the molten steel temperature. 4) Continuous casting start-up: After the molten steel has been allowed to stand for a preset time, the tap slide is opened completely at once, and the ladle is automatically started to pour steel by relying on the double-layer rare earth gradient sintering effect.

[0008] Furthermore, the basic guiding sand particles are used as the core after pretreatment. The pretreatment method includes the following steps in sequence: selecting raw materials, coarse crushing, grinding, drying, natural cooling, and ultrasonic cleaning. The drying temperature is 150-250℃, the drying time is 10-120 minutes, and the moisture is removed to a mass fraction of ≤0.2%. During the drying process, the heating rate is controlled at 2-3℃ / min to avoid particle cracking.

[0009] Furthermore, the raw material composition of the basic diversion sand particles, by mass percentage, is: SiO2 65%~75%, Al2O3 15%~20%, MgO 3%~5%, CaO 1%~3%, with the balance being unavoidable impurities.

[0010] Furthermore, the basic drainage sand particles, after grinding, have a particle size of 0.3~1.2mm, accounting for ≥94%, and the content of fine powder with a particle size <0.3mm accounts for ≤4%.

[0011] Furthermore, the raw materials for the light rare earth oxide inner coating and the heavy rare earth oxide outer coating are light rare earth oxide coating slurry and heavy rare earth oxide coating slurry, respectively. The light rare earth oxide coating slurry is mainly composed of La2O3 or CeO2 powder with a particle size ≤200 mesh, and the heavy rare earth oxide coating slurry is mainly composed of Y2O3 powder with a particle size ≤200 mesh. The formulation systems of the two slurries are consistent, and by weight, they contain: 3-20 parts of main raw material, 3-10 parts of inorganic binder, 1-5 parts of dispersant, and 40-60 parts of deionized water. The slurry is placed in a high-speed stirrer and stirred at 800-1000 r / min for 30-60 min to obtain uniform mixing. The Y2O3 powder is made of 4N grade high-purity raw material, which is wet ultrafine grinding, spray granulation and agglomeration, and then calcined at a high temperature of 1400-1500℃ for shaping.

[0012] Furthermore, the specific operation of the layered high-temperature spray coating process in step 1) is as follows: The pretreated base sand is fed into the spraying rotary drum, with the rotation speed controlled at 30-50 r / min. The drum is preheated to 80-120℃, and the spraying pressure is 0.3-0.5 MPa. First, the light rare earth oxide inner coating is sprayed at a temperature of 800-900℃ for 10-15 min, forming an inner coating with a thickness of 5-10 μm. After cooling to 300-400℃, the heavy rare earth oxide outer coating is sprayed at a temperature of 850-950℃ for 5-8 min, forming an outer coating with a thickness of 2-5 μm. Atmospheric plasma spraying is used to ensure no missed coating or exposed substrate. The coating porosity is controlled at 3%-8%. After spraying, inorganic high-temperature sealing treatment is performed.

[0013] Furthermore, the layered coating of the guiding sand is dried and cured in stages: the first stage is dried at 200-250℃ and kept at that temperature for 30-40 minutes to remove free water; the second stage is dried at 400-500℃ and kept at that temperature for 20-30 minutes to cure the adhesive; after curing, the temperature is slowly reduced to room temperature at 1-2℃ / min to prevent the coating from cracking due to thermal stress.

[0014] Furthermore, the cured and cooled guiding sand is screened twice by a vibrating screen to remove agglomerated particles; after screening, samples are taken to test the coating thickness, coating uniformity, moisture, particle size and composition. After passing the inspection, the products are sealed and dried for storage, while unqualified products are returned for re-coating and curing.

[0015] Furthermore, in step 2), the filling thickness of the rare earth modified diversion sand is 12-15cm, and the surface of the leveled sand layer is flush with the bowl of the water outlet seat brick, with no foreign impurities mixed into the sand layer.

[0016] Furthermore, in step 3), the ladle baking heating rate is 5-8℃ / min; the molten steel constant temperature range is 1500-1650℃, and the temperature fluctuation during the waiting stage for pouring does not exceed ±20℃; argon gas is introduced into the sand layer surface every 5 minutes, with an argon gas purging flow rate of 5-10NL / min; in step 4), the molten steel standing time is 10-15 minutes.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: Completely resolves the performance incompatibilities: The outer layer of heavy rare earth oxides (Y2O3) preferentially reacts with the components in molten steel and the guiding sand at 1350–1450℃ to generate high-melting-point Y-silicate phase, forming a preliminary sintered shell that effectively blocks the rapid penetration of molten steel and prevents steel leakage; the inner layer of light rare earth oxides (La2O3 or CeO2) gradually reacts with SiO2 and Al2O3 in the basic guiding sand above 1500℃ to generate products with low liquid phase content, which slowly softens the preliminary sintered shell and avoids the formation of a dense and compacted rapid sintered shell, thereby constructing a stable gradient sintering window without sacrificing any performance, and the industrial-scale 100-furnace casting rate is stable at over 98%; Reduce production losses and labor costs: Eliminate the need for frequent oxygen lance burning, reduce secondary oxidation of molten steel, improve billet purity, shorten continuous casting downtime, and increase production line operating rate; Strong process stability: Heating rate, argon purging, settling time, and filling thickness are all quantitatively controlled, and fluctuations in human operation have minimal impact on the casting rate, making on-site implementation simple; This invention reconstructs the micro-coating structure of sand particles to form a gradient sintering reaction system, significantly widening the sintering window, adapting to high-temperature working conditions for both carbon steel and low-alloy steel, and has a wider range of applications. Detailed Implementation

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below through examples.

[0019] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0020] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0021] Example 1

[0022] Applicable working conditions: 150t high-temperature carbon steel ladle, target molten steel temperature range of 1550~1600℃, automatic start-up rate verified for 100 consecutive heats.

[0023] 1. Pretreatment of foundation drainage sand 1.1) Raw material preparation: Weigh out 70% SiO2, 18% Al2O3, 4% MgO, and 2% CaO by mass percentage, with the remainder being trace amounts of unavoidable impurities; 1.2) Crushing and Grinding: The raw material is fed into a jaw crusher for coarse crushing, and then transferred to a ball mill for fine grinding. After discharge, it is classified and screened by a multi-layer vibrating screen to control the proportion of 0.3-1.2mm particles to be 95% and the proportion of fine powder with a particle size <0.3mm to be 3%. 1.3) Drying treatment: The screened sand particles are sent to a drying oven, the drying temperature is 200℃, the heating rate is 2.5℃ / min, the drying temperature is 2.5℃, the holding time is 60min, and the moisture content after cooling is 0.15% by mass. 1.4) Ultrasonic cleaning: After drying and cooling to room temperature, use ultrasonic cleaning equipment to remove dust and oxidized impurities from the surface of the sand particles. After cleaning, let it air dry for later use.

[0024] 2. Preparation of Rare Earth Coating Slurry 2.1) Light rare earth La2O3 coating slurry Raw material weight parts: 10 parts of 200 mesh La2O3 powder, 6 parts of silica sol, 3 parts of calcium lignosulfonate, and 50 parts of deionized water; put all materials into a high-speed mixing kettle, stir at 900 r / min, and stir continuously for 45 min to obtain a uniform and non-agglomerated light rare earth La2O3 coating slurry.

[0025] 2.2) Heavy rare earth Y2O3 coating slurry 4N high-purity Y2O3 powder was selected, and after wet ultrafine grinding, spray granulation and agglomeration, it was calcined and shaped at 1450℃, with a powder particle size ≤200 mesh; the raw material weight parts were: 8 parts of calcined Y2O3 powder, 6 parts of silica sol, 3 parts of calcium lignosulfonate, and 50 parts of deionized water; the heavy rare earth Y2O3 coating slurry was prepared by high-speed stirring at 900r / min for 45min for later use.

[0026] 3. Layered high-temperature plasma spraying coating process 3.1) Equipment preheating: The pretreated base guiding sand is fed into the rotary spraying cylinder at a speed of 40 r / min. The cylinder is preheated to 100℃ to reduce the thermal stress of spraying. The spraying system pressure is kept constant at 0.4 MPa. 3.2) Spraying of light rare earth oxide inner layer coating: Spraying temperature 850℃, continuous spraying for 12min, a uniform 8μm thick La2O3 inner layer coating is formed on the surface of the sand particles, the coating coverage is 2.0% of the base sand mass; after spraying, the cylinder is naturally cooled to 350℃; 3.3) Heavy rare earth oxide outer coating spraying: Keep the cylinder rotation speed and spraying pressure constant, adjust the spraying temperature to 900℃, and spray for 6 minutes to form a 3μm thick Y2O3 outer coating, with a coating amount of 0.5% of the base sand mass; 3.4) Sealing treatment: Atmospheric plasma spraying ensures that there are no missing sand particles or exposed substrate, and the porosity of the coating is controlled at 5%. After spraying, high temperature sealing treatment with silica sol is used to seal the internal pores of the coating and prevent high temperature molten steel from seeping in and damaging the double-layer gradient structure.

[0027] 4. Segmented drying and curing process 4.1) Low-temperature dehydration section: The coated sand is sent into the curing furnace and kept at 220℃ for 35 minutes to completely remove the free water inside the slurry; 4.2) High-temperature curing section: Heat to 450℃ and hold for 25 minutes to fully cure the silica sol inorganic binder and improve the bonding strength between the two rare earth coatings and the sand core; 4.3) Temperature control and cooling: After curing, slowly cool down to room temperature at 1.5℃ / min to avoid cracking and peeling of the coating due to thermal stress.

[0028] 5. Screening and finished product inspection 5.1) Secondary screening: The cooled modified sand is fed into a vibrating screen to remove agglomerated and adhering particles, ensuring uniform sand particle size. 5.2) Sampling and testing: Random samples were taken to test coating thickness, coating uniformity, moisture content, particle size, and rare earth coating amount; all test results met the standards. 5.3) Sealed storage: Qualified products should be sealed in packaging and stored in a dry and ventilated warehouse to prevent moisture absorption and clumping.

[0029] 6. Ladle filling operation 6.1) Packing operation: A special packing cylinder is used. The cylinder body is inserted into the bottom of the water inlet seat brick and modified diversion sand is slowly poured in. At the same time, the cylinder body is slowly lifted upwards. The sand layer compaction and separation of coarse and fine particles are avoided throughout the process. The total filling thickness is 13cm. 6.2) Sand surface treatment: After filling, level the surface of the sand layer so that the top surface of the sand layer is flush with the bowl of the water outlet seat brick. Clean the surface scum and refractory fragments to ensure that no foreign impurities are mixed into the sand layer.

[0030] 7. Ladle heating, temperature control, and argon purging management 7.1) Steel ladle baking and heating: Control the overall heating rate of the steel ladle to 6℃ / min, and guide the sand to heat up synchronously and uniformly with the steel ladle to prevent local temperature difference peeling of the coating; 7.2) Steel inlet protection: The steel guide channel is offset from the nozzle area to prevent high-temperature molten steel from directly scouring the sand layer; 7.3) Temperature control: After the molten steel is poured, the temperature is kept stable at 1550~1580℃, and the temperature fluctuation during the entire pouring process is ≤±20℃; 7.4) Timed argon purging: Argon gas is purged on the surface of the sand layer every 5 minutes at a flow rate of 8 NL / min to remove surface slag and prevent surface pore blockage.

[0031] 8. Continuous casting start-up operation After the molten steel has been standing in the ladle for 12 minutes, the sprue slide is opened completely at once, and automatic pouring is achieved by relying on the double-layer rare earth gradient sintering effect.

[0032] Implementation results: After 100 consecutive heats of tracking and statistics, the automatic ladle opening rate was 98.5%, with no steel leakage accidents, no oxygen-required burning and blockage during pouring, and no billet defects caused by secondary oxidation of molten steel.

[0033] Example 2 Applicable working conditions: 200t high temperature low alloy steel ladle, target molten steel temperature range of 1580~1650℃, automatic start-up rate verified for 100 consecutive heats.

[0034] 1. Pretreatment of foundation drainage sand 1.1) Raw material preparation: Weigh out SiO2 68%, Al2O3 19%, MgO 3.5%, CaO 2.5% by mass percentage, with the remainder being trace amounts of unavoidable impurities; 1.2) Crushing and Grinding: The raw material is fed into a jaw crusher for coarse crushing, and then transferred to a ball mill for fine grinding. After discharge, it is classified and screened by a multi-layer vibrating screen to control the proportion of 0.3-1.2mm particles to be 94% and the proportion of fine powder with a particle size <0.3mm to be 3.5%. 1.3) Drying treatment: The screened sand particles were sent to a drying oven, the drying temperature was 230℃, the heating rate was 3℃ / min, the drying temperature was 3℃, the holding time was 90min, and the moisture content after cooling was 0.18%. 1.4) Ultrasonic cleaning: After drying and cooling to room temperature, use ultrasonic cleaning equipment to remove dust and oxidized impurities from the surface of the sand particles. After cleaning, let it air dry for later use.

[0035] 2. Preparation of Rare Earth Coating Slurry 2.1) Light rare earth CeO2 coating slurry Raw material weight parts: 15 parts of 200 mesh CeO2 powder, 8 parts of aluminum sol, 4 parts of sodium carboxymethyl cellulose, and 55 parts of deionized water; put all materials into a high-speed mixing kettle, stir at 950 r / min, and stir continuously for 50 min to obtain a uniform and non-agglomerated light rare earth CeO2 coating slurry.

[0036] 2.2) Heavy rare earth Y2O3 coating slurry 4N high-purity Y2O3 powder was selected, and after wet ultrafine grinding, spray granulation and agglomeration, it was calcined and shaped at 1480℃, with a powder particle size ≤200 mesh; the raw material weight parts were: 7 parts of calcined Y2O3 powder, 8 parts of aluminum sol, 4 parts of sodium carboxymethyl cellulose, and 55 parts of deionized water; the heavy rare earth slurry was prepared by high-speed stirring at 950r / min for 50min.

[0037] 3. Layered high-temperature plasma spraying coating process 3.1) Equipment preheating: The pretreated base guiding sand is fed into the rotary spraying cylinder at a speed of 45 r / min. The cylinder is preheated to 110℃ to reduce spraying thermal stress. The spraying system pressure is kept constant at 0.45 MPa. 3.2) Spraying of light rare earth oxide inner layer coating: Spraying temperature 880℃, continuous spraying for 14min, a 10μm thick CeO2 inner layer coating is uniformly formed on the surface of the sand particles, and the coating coverage is 2.8% of the base sand mass; after spraying, the cylinder is naturally cooled to 380℃. 3.3) Heavy rare earth oxide outer coating spraying: Keep the cylinder rotation speed and spraying pressure constant, adjust the spraying temperature to 920℃, and spray for 7 minutes to form a 4μm thick Y2O3 outer coating, with a coating amount of 0.7% of the base sand mass; 3.4) Sealing treatment: Atmospheric plasma spraying ensures that there are no missing sand particles or exposed substrate, and the porosity of the coating is controlled at 6%. After spraying, high temperature sealing treatment with silica sol is used to seal the internal pores of the coating and prevent high temperature molten steel from seeping in and damaging the double-layer gradient structure.

[0038] 4. Segmented drying and curing process 4.1) Low-temperature dehydration section: The coated sand is sent into the curing furnace and kept at 240℃ for 38 minutes to completely remove the free water inside the slurry; 4.2) High-temperature curing section: Heat to 480℃ and hold for 28 minutes to fully cure the silica sol inorganic binder and improve the bonding strength between the two rare earth coatings and the sand core; 4.3) Temperature control and cooling: After curing, slowly cool down to room temperature at 1.2℃ / min to avoid cracking and peeling of the coating due to thermal stress.

[0039] 5. Screening and finished product inspection 5.1) Secondary screening: The cooled modified sand is fed into a vibrating screen to remove agglomerated and adhering particles, ensuring uniform sand particle size. 5.2) Sampling and testing: Random samples were taken to test coating thickness, coating uniformity, moisture content, particle size, and rare earth coating amount; all test results met the standards. 5.3) Sealed storage: Qualified products should be sealed in packaging and stored in a dry and ventilated warehouse to prevent moisture absorption and clumping.

[0040] 6. Ladle filling operation 6.1) Packing operation: A special packing cylinder is used. The cylinder body is inserted into the bottom of the water inlet seat brick and modified diversion sand is slowly poured in. At the same time, the cylinder body is slowly lifted upwards. The sand layer compaction and separation of coarse and fine particles are avoided throughout the process. The total filling thickness is 14cm. 6.2) Sand surface treatment: After filling, level the surface of the sand layer so that the top surface of the sand layer is flush with the bowl of the water outlet seat brick. Clean the surface scum and refractory fragments to ensure that no foreign impurities are mixed into the sand layer.

[0041] 7. Ladle heating, temperature control, and argon purging management 7.1) Steel ladle baking and heating: Control the overall heating rate of the steel ladle to 7℃ / min, and guide the sand to heat up synchronously and uniformly with the steel ladle to prevent local temperature difference peeling of the coating; 7.2) Steel inlet protection: The steel guide channel is offset from the nozzle area to prevent high-temperature molten steel from directly scouring the sand layer; 7.3) Temperature control: After the molten steel is poured, the temperature is kept stable at 1580~1620℃, and the temperature fluctuation during the entire casting process is ≤±20℃; 7.4) Timed argon purging: Argon gas is purged on the surface of the sand layer every 5 minutes at a flow rate of 6-9 NL / min to remove surface slag and prevent surface pore blockage.

[0042] 8. Continuous casting start-up operation After the molten steel has been standing in the ladle for 14 minutes, the sprue slide is opened completely at once, and automatic pouring is achieved by relying on the double-layer rare earth gradient sintering effect.

[0043] Results: After 100 consecutive heats of tracking and statistics, the automatic ladle opening rate was 99.2%, with no steel leakage accidents, no oxygen-required burning or blockage during pouring, and no billet defects caused by secondary oxidation of molten steel.

[0044] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for improving the automatic casting rate of high-temperature steel ladles using rare earth modified diversion sand, characterized in that, Includes the following steps: 1) Preparation of rare earth modified diversion sand: Using basic diversion sand particles as the core, a layered high-temperature spray coating process is adopted. First, a layer of light rare earth oxide inner coating is coated on the outer surface of the core, and then a layer of heavy rare earth oxide outer coating is coated on the outside of the light rare earth oxide inner coating. The light rare earth oxide is at least one of La2O3 or CeO2, and the heavy rare earth oxide is Y2O3. 2) Filling of diversion sand: The prepared rare earth modified diversion sand is filled into the interior of the ladle nozzle seat brick; the filling process adopts a slow filling and slow lifting injection method, and the surface of the sand layer is leveled after filling is completed. 3) Steel ladle heating and temperature control: The steel ladle is heated synchronously during the baking stage to prevent the coating from falling off due to temperature difference; when the molten steel is poured into the ladle, it avoids the area filled with guide sand to prevent the molten steel from directly washing away the sand layer and damaging the coating; after the molten steel is poured, the steel ladle is kept at a high temperature and constant temperature to control the fluctuation range of the molten steel temperature. 4) Continuous casting start-up: After the molten steel has been allowed to stand for a preset time, the tap slide is opened completely at once, and the ladle is automatically started to pour steel by relying on the double-layer rare earth gradient sintering effect.

2. The method for improving the automatic casting rate of high-temperature steel ladles using rare earth modified diversion sand according to claim 1, characterized in that, The basic guiding sand particles are used as the core after pretreatment. The pretreatment method includes the following steps in sequence: selecting raw materials, coarse crushing, grinding, drying, natural cooling, and ultrasonic cleaning. The drying temperature is 150-250℃, the drying time is 10-120 minutes, and the moisture is removed to a mass fraction of ≤0.2%. During the drying process, the heating rate is controlled at 2-3℃ / min to avoid particle cracking.

3. The method for improving the automatic casting rate of high-temperature steel ladles using rare earth modified diversion sand according to claim 2, characterized in that, The raw material composition of the basic guiding sand particles, by mass percentage, is: SiO2 65%~75%, Al2O3 15%~20%, MgO 3%~5%, CaO 1%~3%, with the balance being unavoidable impurities.

4. The method for improving the automatic casting rate of high-temperature steel ladles using rare earth modified diversion sand according to claim 2, characterized in that, The basic drainage sand particles, after grinding, have a particle size of 0.3~1.2mm, accounting for ≥94%, and the content of fine powder with a particle size <0.3mm accounts for ≤4%.

5. The method for improving the automatic casting rate of high-temperature steel ladles using rare earth modified diversion sand according to any one of claims 1-4, characterized in that, The raw materials for the light rare earth oxide inner coating and the heavy rare earth oxide outer coating are light rare earth oxide coating slurry and heavy rare earth oxide coating slurry, respectively. The light rare earth oxide coating slurry is mainly composed of La2O3 or CeO2 powder with a particle size ≤200 mesh, and the heavy rare earth oxide coating slurry is mainly composed of Y2O3 powder with a particle size ≤200 mesh. The formulation systems of the two slurries are consistent, and by weight, they contain: 3-20 parts of main raw material, 3-10 parts of inorganic binder, 1-5 parts of dispersant, and 40-60 parts of deionized water. The slurry is placed in a high-speed stirrer and stirred at 800-1000 r / min for 30-60 min to obtain uniform mixing. The Y2O3 powder is made of 4N grade high-purity raw material, which is wet ultrafine grinding, spray granulation and agglomeration, and then calcined at a high temperature of 1400-1500℃ for shaping.

6. The method for improving the automatic casting rate of high-temperature steel ladles using rare earth modified diversion sand according to claim 5, characterized in that, Step 1) The specific operation of the layered high-temperature spray coating process is as follows: The pretreated base sand is fed into the spraying rotary drum, with the rotation speed controlled at 30-50 r / min. The drum is preheated to 80-120℃, and the spraying pressure is 0.3-0.5 MPa. First, the light rare earth oxide inner coating is sprayed at a temperature of 800-900℃ for 10-15 min, forming an inner coating with a thickness of 5-10 μm. After cooling to 300-400℃, the heavy rare earth oxide outer coating is sprayed at a temperature of 850-950℃ for 5-8 min, forming an outer coating with a thickness of 2-5 μm. Atmospheric plasma spraying is used to ensure no missed coating or exposed substrate. The coating porosity is controlled at 3%-8%. After spraying, inorganic high-temperature sealing treatment is performed.

7. The method for improving the automatic casting rate of high-temperature steel ladles using rare earth modified diversion sand according to claim 6, characterized in that, The layered coating of the diverting sand is dried and cured in stages: the first stage is dried at 200-250℃ and kept at that temperature for 30-40 minutes to remove free water; the second stage is dried at 400-500℃ and kept at that temperature for 20-30 minutes to cure the adhesive; after curing, the temperature is slowly reduced to room temperature at 1-2℃ / min to prevent the coating from cracking due to thermal stress.

8. The method for improving the automatic casting rate of high-temperature steel ladles using rare earth modified diversion sand according to claim 7, characterized in that, After solidification and cooling, the guiding sand is screened twice by a vibrating screen to remove agglomerated particles. After screening, samples are taken to test the coating thickness, coating uniformity, moisture content, particle size and composition. After passing the inspection, the products are sealed and dried for storage. Unqualified products are returned for re-coating and curing.

9. The method for improving the automatic casting rate of high-temperature steel ladles using rare earth modified diversion sand according to claim 1, characterized in that, In step 2), the filling thickness of the rare earth modified diversion sand is 12-15cm. The surface of the leveled sand layer is flush with the bowl of the water outlet seat brick, and no foreign impurities are mixed into the sand layer.

10. The method for improving the automatic casting rate of high-temperature steel ladles using rare earth modified diversion sand according to claim 1, characterized in that, Step 3) The heating rate of the ladle baking is 5-8℃ / min; the constant temperature range of the molten steel is 1500-1650℃, and the temperature fluctuation during the waiting stage for pouring does not exceed ±20℃; argon gas is introduced into the surface of the sand layer every 5 minutes, with an argon gas purging flow rate of 5-10NL / min. Step 4) The molten steel standing time is 10-15 minutes.