A visual simulation test method for high-temperature service performance of a nozzle for ultra-thin strip continuous casting

Abstract

The present application belongs to the technical field of performance detection of refractory materials for steel continuous casting, and discloses a visual simulation test device and method for high-temperature service performance of a nozzle for ultra-thin strip continuous casting. The device comprises a medium-frequency induction melting furnace, a molten steel transfer ladle, a simulation tundish, a nozzle fixing tool, a high-temperature visual online monitoring unit, a molten steel collection and safety protection unit, and an electric control and data acquisition system. The method melts high-temperature molten steel by the medium-frequency furnace, and the molten steel flows through the nozzle to be detected after being transferred and passing through the simulation tundish. The high-temperature infrared thermal imager and the high-speed camera with a protection device are used to monitor the thermal shock cracking of the nozzle caused by thermal impact and the fracture of the nozzle caused by molten steel impact in the process of the molten steel flowing into the nozzle under the simulated service working condition, so as to evaluate the high-temperature service performance of the nozzle. The present application highly reduces the service working condition of the nozzle for ultra-thin strip continuous casting, and realizes the full-process visualization, low cost and low-risk test detection of the high-temperature service performance of the nozzle.

Description

Technical Field

[0001] This invention belongs to the field of performance testing technology for refractory materials used in continuous casting of steel, and specifically relates to a visualization simulation test method for the high-temperature service performance of ultra-thin strip continuous casting nozzles. Background Technology

[0002] The tundish nozzle is a key functional refractory material component in the continuous casting process that guides high-temperature molten steel from the tundish to the crystallizer or controls the flow state of the molten steel. During its service, it must withstand the coupled effects of instantaneous thermal shock, high-speed scouring, and static pressure of molten steel at 1500-1700℃. The sudden temperature change at the moment of casting can easily cause thermal shock cracking of the nozzle, resulting in uncontrolled molten steel flow and interruption of continuous casting. Insufficient thermal shock resistance of the nozzle can also lead to spalling and peeling, directly affecting the quality of the cast billet and production safety.

[0003] There are currently three main methods for testing the thermal shock resistance of refractory materials: (1) Laboratory small electric furnace test method: Air or water is used as the cooling medium to conduct rapid cooling and heating cycle test. There is no actual molten steel in contact. Its thermal shock rate, temperature gradient and stress state are significantly different from the actual steel pouring conditions, and cannot truly reflect the anti-thermal shock behavior of the nozzle at the moment of pouring.

[0004] (2) Laboratory water simulation method: Using room temperature or heated water (or other transparent fluids) instead of molten steel, the flow behavior of molten steel is simulated under laboratory conditions. The fluid flow pattern can be observed and there is a certain cost advantage. However, this method still uses water as a medium, which is fundamentally different from real high-temperature molten steel in terms of thermophysical properties (thermal conductivity, heat capacity, viscosity), wettability of refractory materials and thermochemical effects. It cannot simulate the severe thermal shock and temperature gradient at the moment of casting above 1500℃, and it cannot evaluate the thermal shock cracking behavior of the nozzle in real high-temperature environment.

[0005] (3) Online test method for industrial continuous casting machine: The sprue to be tested is directly installed on the industrial continuous casting machine for online testing. The working conditions are real, but the test cost is extremely high, the cycle is long, the safety risk is high, and the cracking and failure process of the sprue cannot be directly observed. It can only be disassembled and analyzed after the machine is stopped. It is difficult to obtain real-time thermal shock response data at the moment of casting, and it is even more impossible to realize dynamic visualization recording of crack initiation and propagation process under high temperature environment.

[0006] In summary, existing technologies lack a detection method that can highly simulate service conditions in a laboratory setting while simultaneously providing online visualization of thermal shock damage at continuous casting nozzles and the impact process of molten steel in a high-temperature environment. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a visual simulation test method for the high-temperature service performance of nozzles in ultra-thin strip continuous casting. This method utilizes a complete steel molten metal transport and temperature control system encompassing the entire process from "medium-frequency furnace - sub-ladle - simulated tundish - nozzle under test" to highly replicate the thermal shock and long-term scouring conditions encountered during industrial continuous casting. Combined with a high-temperature infrared thermal imager and a high-speed camera, the method monitors online the thermal shock cracking and fracture of the nozzle caused by physical impact from the molten steel during its inflow into the nozzle under simulated service conditions, thereby evaluating the high-temperature service performance of the nozzle. This invention highly replicates the service conditions of nozzles in ultra-thin strip continuous casting, achieving full-process visualization, low-cost, and low-risk testing of nozzle high-temperature service performance, providing a reliable basis for the development, performance control, and structural optimization of nozzle materials for ultra-thin strip continuous casting.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A visualization simulation test method for the high-temperature service performance of ultra-thin strip continuous casting nozzles includes the following steps: Step 1, preheating of the sprue: Preheat the sprue to be tested to 800-1200℃ in a nitrogen atmosphere according to the on-site service conditions and keep it at that temperature for 30-120 minutes; install the sprue fixing fixture at the bottom of the simulated intermediate ladle; debug the high-temperature infrared thermal imager and high-speed camera to confirm that the monitoring is normal. The second step is steel melting and temperature control: the medium frequency furnace melts the steel block, raises the temperature to the target temperature (1500-1700℃, depending on the process requirements), holds the temperature for 10-15 minutes to ensure uniform temperature; the furnace body is tilted, and the molten steel is smoothly poured into the steel ladle through the guide channel. The third step is the transfer of molten steel: the molten steel is transferred to the molten steel receiving area of ​​the simulated tundish, and after passing through the stabilization zone, it flows smoothly to the outflow zone; The fourth step is to simulate the steel pouring-high temperature thermal shock stage: molten steel flows through the nozzle to be tested, triggering a severe thermal shock the instant the pouring begins; a high-speed camera records the crack initiation, propagation, and spalling in a high-temperature environment; an infrared thermal imager captures the instantaneous temperature rise, temperature gradient distribution, and maximum temperature difference on the outer wall in real time; the flow rate of molten steel is controlled by adjusting the number and size of the controllable outlets in the simulated tundish, making the pouring time adjustable within the range of 3-5 minutes, simulating the thermal shock and initial scouring conditions at the moment of pouring, and examining the influence of different molten steel flow rates on the nozzle's thermal shock resistance and scouring behavior; it should be noted that this time range covers the main action time of industrial pouring thermal shock, namely 1-3 minutes after pouring begins and the critical stage of thermal shock crack initiation and propagation, while also fully considering the heat dissipation and solidification limitations during the molten steel flow process, and all tests are completed once the molten steel has flowed out, without the need to extend the pouring time; Step 5, High-Temperature Strength and Erosion Resistance Assessment: Examine the deformation, inner diameter expansion, erosion depth, and structural integrity under high-temperature molten steel load and erosion during steel pouring; record abnormalities such as flow fluctuations, leakage, and blockages in real time. Step 6: Shutdown, Cooling, and Post-Processing Inspection: Stop the supply of molten steel and allow it to cool naturally to room temperature; disassemble the sprue for macroscopic crack inspection, cross-sectional microscopic analysis, inner diameter measurement, and mass loss rate calculation; combine online high-temperature temperature-video data to comprehensively evaluate the thermal shock cracking resistance (whether cracks have occurred, the number / length / depth of cracks, and cracking time), high-temperature strength (resistance to deformation, resistance to spalling, and structural stability), and resistance to erosion (inner diameter expansion rate, erosion thickness, etc.). Step 7, Data Fusion and Performance Grading: Fusion of thermal imaging, temperature measurement, video, and dimensional / mass data to establish a correlation model of thermal shock temperature gradient-crack propagation-strength decay; and provide qualified / unqualified or excellent / good / medium / poor grading according to enterprise / industry standards to guide formulation and structural optimization. The medium-frequency induction melting furnace is equipped with a tilting mechanism and a molten steel guide trough, with a capacity of 800-1500 kg. The medium-frequency furnace can melt molten steel at a temperature of 1450-1800℃.

[0009] The molten steel transfer vessel is a refractory-lined vessel equipped with a tilting mechanism, a molten steel diversion channel, and a hoisting mechanism, used to receive and transfer molten steel.

[0010] The simulated tundish consists of a steel structure and a refractory material cavity. The steel structure comprises an outer shell and supporting and fixing components. The outer shell facilitates the construction and protection of the refractory material wall. The supporting and fixing components work in conjunction with the nozzle fixing fixture to achieve synchronous stability and positioning of the simulated tundish and the nozzle. The refractory material cavity is constructed of hollow alumina spherical refractory material. A partition I is provided on the side of the refractory material cavity near the tundish inlet. The height of partition I is lower than the height of the refractory material cavity, and partition I is fixed to the bottom of the refractory material cavity. A molten steel receiving area is formed between partition I and the cavity plate on the side of the refractory material cavity near the tundish inlet. The molten steel receiving area is the inlet area for the molten steel poured into the tundish, used to receive the steel flow and buffer the impact of the molten steel. The refractory material cavity is also equipped with a baffle plate II; there is a gap between the baffle plate II and the bottom surface of the refractory material cavity for the flow of molten steel; a steady flow zone is formed between the baffle plate II and the baffle plate I to eliminate turbulence, uniformize temperature, and smoothly adjust the flow field; an outflow zone is formed between the baffle plate II and the cavity plate on the other side of the refractory material cavity; 7-10 zirconia refractory material outlets with a diameter of 8-15mm are arranged at the bottom of the outflow zone to smoothly guide the high-temperature molten steel downward into the test nozzle, and the number and diameter of the zirconia outlets can be adjusted according to the casting process; a test nozzle is set directly below the outflow zone; the test nozzle is supported directly below the outflow zone by a nozzle fixing fixture; a molten steel collection mechanism is set directly below the test nozzle.

[0011] The nozzle fixing fixture consists of a support assembly and a fixing assembly, and is made entirely of steel. The support assembly includes a top support flange, four vertical support bolts, and a locking nut. The top of the flange cooperates with the simulated tundish support structure to support the simulated tundish. It is tightened upwards by the bolts and locking nuts, and the distance between the nozzle to be tested and the bottom of the tundish can be adjusted between 50-350mm to adapt to different molten steel impact simulation conditions. The fixing assembly is located in the middle of the support assembly and is used to support and fix the nozzle to be tested. It also reserves a thermal expansion gap, and its shape and size can be replaced according to the shape and size of the nozzle and the support method requirements.

[0012] The high-temperature visualization online monitoring unit includes two types of monitoring equipment: a high-temperature infrared thermal imager and a high-speed camera. The high-temperature infrared thermal imager is equipped with a heat-insulating protective sleeve, with its lens facing the nozzle for observation. It can collect data on the outer wall temperature of the nozzle under test, the instantaneous thermal shock temperature rise rate, and the cross-sectional temperature gradient distribution in real time. The high-speed camera is equipped with a water-cooled heat-insulating protective cover and a high-temperature resistant quartz observation window. Its lens is aimed at the tooling visualization observation position, and the equipment has a shooting frame rate of no less than 100 frames per second. It can continuously capture dynamic images of nozzle crack initiation, extension, chipping, and deformation during the entire process of molten steel thermal shock impact. Both the infrared thermal imager and the high-speed camera are electrically connected to the electronic control and data acquisition system through signal lines to achieve synchronous storage, time-series alignment, and playback analysis of temperature data and high-definition video.

[0013] The molten steel collection and safety protection unit includes a molten steel collection mechanism, a protective baffle, and an emergency cooling system.

[0014] The electrical control and data acquisition system is used to synchronously collect and store temperature, thermal images, video, and flow parameters.

[0015] The nozzle to be tested is an ultra-thin strip continuous casting nozzle, which can be compatible with conventional immersion nozzles and long nozzles after tooling replacement; the nozzle material is a carbon-containing functional refractory material.

[0016] The method requires the use of a sprue baking oven, which is equipped with a programmable temperature control module to precisely adjust the heating rate, and the baking atmosphere is nitrogen to prevent oxidation at high temperatures.

[0017] The present invention proposes a visualization simulation test method for the high-temperature service performance of ultra-thin strip continuous casting nozzles. The beneficial effects of adopting the above technical solution are as follows: (1) High-fidelity simulation of service conditions: “Induction furnace-subcontracting-simulated intermediate ladle-test nozzle” fully reproduces the entire process of industrial continuous casting steel tapping-transfer-stabilization-pouring; using real high-temperature molten steel as the medium, combined with thermal shock damage cracking and physical impact fracture of molten steel, it is highly consistent with the industrial site, and the test results can be directly used for industrial prediction.

[0018] (2) Full visualization of high temperature environment: Using a high temperature infrared thermal imager and a high-speed camera with protection device, the online real-time recording of crack initiation, propagation and temperature field evolution of continuous casting nozzle at the moment of opening the pouring is realized for the first time in a high temperature environment above 1500℃. It intuitively reveals the coupling mechanism of thermal shock cracking and physical impact fracture of molten steel, and overcomes the problem that existing technologies cannot directly observe nozzle behavior in the real high temperature steel pouring process.

[0019] (3) Flexible and controllable test conditions, and simultaneous detection of multiple performance parameters: thermal shock cracking is simulated by changing the temperature of the molten steel; physical impact fracture is simulated by adjusting the distance between the tundish taphole and the nozzle, as well as the size and number of taphole openings; the casting time can be adjusted within a range of 3-5 minutes by controlling the amount and flow rate of molten steel. This design monitors the thermal shock cracking and physical impact fracture of the nozzle during the molten steel flow into the nozzle online, thereby evaluating the service performance of the nozzle.

[0020] (4) Wide range of applications: It is mainly used for ultra-thin strip continuous casting nozzles. After tooling replacement, it can be compatible with conventional submerged nozzles and long nozzles.

[0021] (5) Quantitative evaluation system: Establish a correlation model of thermal shock temperature rise rate-crack propagation-strength decay to realize qualitative observation and quantitative evaluation, which is convenient for standardization.

[0022] (6) Simplified structure, low cost, low risk and repeatability: No industrial continuous casting machine is required, the device structure is simplified, the operation is convenient, and it can be carried out in the laboratory; the steel volume is controllable, the protection is complete, and it is safe and reliable; different formulas / structures of nozzles can be tested in batches, the optimal solution can be quickly screened, the R&D cycle can be greatly shortened, and the overall test cost can be reduced. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the core structure of the device described in the test method of the present invention.

[0024] Figure 2 This is a schematic diagram of a high-temperature visual online monitoring unit.

[0025] In the diagram: 1-Simulated tundish; 2-Steel structure shell; 3-Refractory material cavity; 4-Baffle I; 5-Baffle II; 6-Steel molten receiving area; 7-Flow stabilization zone; 8-Outflow zone; 9-Steel outlet; 10-Support and fixing assembly; 11-Sprue fixing fixture; 12-Top support flange; 13-Support bolt; 14-Locking nut; 15-Fixing assembly; 16-Sprue to be tested; 17-Steel molten collection mechanism; 18-High-temperature visual online detection unit; 19-High-temperature infrared thermal imager; 20-High-speed camera. Detailed Implementation

[0026] The present invention will be described in conjunction with the given embodiments: like Figure 1 As shown. A visualization simulation test method for the high-temperature service performance of ultra-thin strip continuous casting nozzles includes the following steps: Step 1, preheating of the sprue: Preheat the sprue to be tested to 800-1200℃ in a nitrogen atmosphere according to the on-site service conditions and keep it at that temperature for 30-120 minutes; install the sprue fixing fixture 11 at the bottom of the simulated intermediate ladle 1; debug the high-temperature infrared thermal imager 19 and the high-speed camera 20 to confirm that the monitoring is normal. The second step is steel melting and temperature control: the medium frequency furnace melts the steel block, raises the temperature to the target temperature (1500-1700℃, depending on the process requirements), holds the temperature for 10-15 minutes to ensure uniform temperature; the furnace body is tilted, and the molten steel is smoothly poured into the steel ladle through the guide channel. The third step is the transfer of molten steel: the molten steel is transferred to the molten steel receiving area 6 of the simulated tundish, and after passing through the stabilization zone 7, it flows smoothly to the outflow zone 8; The fourth step is to simulate the steel pouring-high temperature thermal shock stage: the molten steel flows through the nozzle to be tested, and a severe thermal shock is triggered the moment the pouring begins; the high-speed camera 20 records the crack initiation, propagation, and spalling in a high-temperature environment; the high-temperature infrared thermal imager 19 captures the instantaneous temperature rise, temperature field gradient distribution, and maximum temperature difference of the outer wall in real time; the flow rate of the molten steel is controlled by adjusting the number and size of the controllable outlets of the simulated tundish, so that the pouring time is adjustable within the range of 3-5 minutes, simulating the thermal shock and initial scouring conditions at the moment of pouring, and the influence of different molten steel flow rates on the thermal shock resistance and scouring behavior of the nozzle can be examined; it should be noted that this time range covers the main action time of industrial pouring thermal shock, namely 1-3 minutes after pouring and the critical stage of thermal shock crack initiation and propagation, and also fully considers the heat dissipation and solidification limitations during the flow of molten steel, and all tests are completed once the molten steel has flowed out, without the need to extend the pouring time; Step 5, High-Temperature Strength and Erosion Resistance Assessment: Examine the deformation, inner diameter expansion, erosion depth, and structural integrity under high-temperature molten steel load and erosion during steel pouring; record abnormalities such as flow fluctuations, leakage, and blockages in real time. Step 6: Shutdown, Cooling, and Post-Processing Inspection: Stop the supply of molten steel and allow it to cool naturally to room temperature; disassemble the sprue for macroscopic crack inspection, cross-sectional microscopic analysis, inner diameter measurement, and mass loss rate calculation; combine online high-temperature temperature-video data to comprehensively evaluate the thermal shock cracking resistance (whether cracks have occurred, the number / length / depth of cracks, and cracking time), high-temperature strength (resistance to deformation, resistance to spalling, and structural stability), and resistance to erosion (inner diameter expansion rate, erosion thickness, etc.). Step 7, Data Fusion and Performance Grading: Fusion of thermal imaging, temperature measurement, video, and dimensional / mass data to establish a correlation model of thermal shock temperature gradient-crack propagation-strength decay; and provide qualified / unqualified or excellent / good / medium / poor grading according to enterprise / industry standards to guide formulation and structural optimization. The medium-frequency induction melting furnace is equipped with a tilting mechanism and a molten steel guide trough, with a capacity of 800-1500 kg. The medium-frequency furnace can melt molten steel at a temperature of 1450-1800℃.

[0027] The molten steel transfer vessel is a refractory-lined vessel equipped with a tilting mechanism, a molten steel diversion channel, and a hoisting mechanism, used to receive and transfer molten steel.

[0028] like Figure 1 As shown, the simulated tundish consists of a steel structure and a refractory material cavity 3. The steel structure comprises an outer shell and supporting and fixing components. The outer shell 2 is for facilitating the construction and protection of the refractory material wall. The supporting and fixing components cooperate with the nozzle fixing fixture to achieve synchronous stability and positioning of the simulated tundish and the nozzle as a whole. The refractory material cavity 3 is constructed of alumina hollow spherical refractory material. A partition I4 is provided on the side of the refractory material cavity 3 near the tundish inlet. The height of the partition I4 is lower than the height of the refractory material cavity, and the partition I4 is fixed to the bottom of the refractory material cavity. A molten steel receiving area 6 is formed between the partition I4 and the cavity plate on the side of the refractory material cavity near the tundish inlet. The molten steel receiving area 6 is the inlet area for the molten steel poured into the tundish, used to receive the steel flow and buffer the molten steel. Impact; a baffle plate II5 is also provided inside the refractory material cavity; there is a gap between the baffle plate II5 and the bottom surface of the refractory material cavity for the flow of molten steel; a flow stabilization zone 7 is formed between the baffle plate II5 and the baffle plate I4 to eliminate turbulence, uniform temperature, and smoothly adjust the flow field; an outflow zone 8 is formed between the baffle plate II5 and the cavity plate on the other side of the refractory material cavity; 7-10 zirconia refractory steel outlets 9 with a diameter of 8-15mm are arranged at the bottom of the outflow zone to smoothly guide the high-temperature molten steel downward into the test nozzle, and the number and diameter of the zirconia steel outlets can be adjusted according to the casting process; a test nozzle is set directly below the outflow zone; the test nozzle is supported directly below the outflow zone by a nozzle fixing fixture; a molten steel collection mechanism is set directly below the test nozzle.

[0029] The nozzle fixing fixture consists of a support assembly and a fixing assembly, and is made entirely of steel. The support assembly includes a top support flange, four vertical support bolts, and a locking nut. The top of the flange cooperates with the simulated tundish support structure to support the simulated tundish. It is tightened upwards by the bolts and locking nuts, and the distance between the nozzle to be tested and the bottom of the tundish can be adjusted between 50-350mm to adapt to different molten steel impact simulation conditions. The fixing assembly is located in the middle of the support assembly and is used to support and fix the nozzle to be tested. It also reserves a thermal expansion gap, and its shape and size can be replaced according to the shape and size of the nozzle and the support method requirements.

[0030] Combination Figure 2 The high-temperature visualization online monitoring unit includes two types of monitoring equipment: a high-temperature infrared thermal imager and a high-speed camera. The high-temperature infrared thermal imager is equipped with a heat-insulating protective sleeve, with its lens facing the nozzle for observation. It can collect data on the outer wall temperature of the nozzle under test, the instantaneous thermal shock temperature rise rate, and the cross-sectional temperature gradient distribution in real time. The high-speed camera is equipped with a water-cooled heat-insulating protective cover and a high-temperature resistant quartz observation window. Its lens is aimed at the tooling visualization observation position, and the equipment has a shooting frame rate of no less than 100 frames / second. It can continuously capture dynamic images of nozzle crack initiation, extension, chipping, and deformation during the entire process of molten steel thermal shock impact. Both the infrared thermal imager and the high-speed camera are electrically connected to the electronic control and data acquisition system through signal lines to realize synchronous storage, time-series alignment, and playback analysis of temperature data and high-definition video.

[0031] Example 1: Visual simulation test of high-temperature service performance of aluminum carbon nozzles for ultra-thin strip continuous casting (1) Test steel liquid: 1500 kg of steel liquid was smelted at a temperature of 1550℃.

[0032] (2) Test gate: The aluminum-carbon gate has excellent thermal shock resistance (thermal expansion coefficient of 4.5×10 from room temperature to 1400℃). -6 / ℃), high high temperature strength (12-13MPa).

[0033] (3) Test gate baking conditions: The gate was preheated to 1200℃ and held at 10℃ / min using an atmosphere baking oven.

[0034] (4) Simulated steel pouring conditions and process: 9 8mm zirconia steel outlets, the distance between the test outlet and the bottom of the tundish is 50mm, and the steel pouring time is 5min.

[0035] (5) Test results: The infrared thermal imager clearly showed that the temperature of the outer wall at the bottom of the sprue rose sharply at the moment of pouring. The high-speed camera recorded the whole process. There was no cracking of the sprue during the 5-minute pouring process.

[0036] (6) Observation after the nozzle is cooled: The nozzle structure is intact, without cracks, and the inner wall is covered with a small amount of molten steel.

[0037] Conclusion: The aluminum carbon nozzle for ultra-thin strip continuous casting exhibits excellent thermal shock resistance and good resistance to physical impact from molten steel. This method effectively simulates the high-temperature service performance of ultra-thin strip nozzles.

[0038] Example 2: Visual simulation test of high-temperature service performance of aluminum carbon nozzles for ultra-thin strip continuous casting (1) Test steel liquid: 1500 kg of steel liquid was smelted at a temperature of 1650℃.

[0039] (2) Test gate: The aluminum-carbon gate has excellent thermal shock resistance (thermal expansion coefficient 4.5×10). -6 / ℃), high high temperature strength (12-13MPa).

[0040] (3) Test gate baking conditions: The gate was preheated to 1100℃ and held at the temperature for 60min using an atmosphere baking oven with a heating rate controlled at 10℃ / min.

[0041] (4) Simulated steel pouring conditions and process: 9 15mm zirconia steel outlets, the distance between the test outlet and the bottom of the tundish is 350mm, and the steel pouring time is 3min.

[0042] (5) Test results: The infrared thermal imager clearly showed that the temperature of the outer wall at the bottom of the sprue rose sharply at the moment of pouring. The high-speed camera recorded the whole process. There was no cracking of the sprue during the 3-minute pouring process.

[0043] (6) Observation after the nozzle is cooled: The nozzle structure is intact, without cracks, and the inner wall is covered with a small amount of molten steel.

[0044] Conclusion: The aluminum carbon nozzle for ultra-thin strip continuous casting exhibits excellent thermal shock resistance and good resistance to physical impact from molten steel. This method effectively simulates the high-temperature service performance of ultra-thin strip nozzles.

[0045] Example 3: Visual simulation test of high-temperature service performance of aluminum carbon nozzles for ultra-thin strip continuous casting (1) Test steel liquid: 1500 kg of steel liquid was smelted at a temperature of 1550℃.

[0046] (2) Test gate: The aluminum-carbon gate has excellent thermal shock resistance (thermal expansion coefficient of 4.5×10 from room temperature to 1400℃). -6 / ℃), high high temperature strength (6-7MPa).

[0047] (3) Test gate baking conditions: The gate was preheated to 1100℃ and held at the temperature for 60min using an atmosphere baking oven with a heating rate controlled at 10℃ / min.

[0048] (4) Simulated steel pouring conditions and process: 9 8mm zirconia steel outlets, the distances between the test outlet and the bottom of the tundish are 50mm and 350mm respectively, and the steel pouring time is 5min.

[0049] (5) Test results: The infrared thermal imager clearly showed that the temperature of the outer wall at the bottom of the sprue rose sharply at the moment of pouring. The high-speed camera recorded the whole process. The sprue broke in the middle during the 30s of pouring.

[0050] (6) Observation after the nozzle is cooled: the nozzle is broken in the middle and a small amount of molten steel is stuck to the inner wall.

[0051] Conclusion: Aluminum carbon nozzles for ultra-thin strip continuous casting exhibit excellent thermal shock resistance but poor resistance to physical impact from molten steel. This method effectively simulates the thermal shock resistance and physical impact resistance of ultra-thin strip nozzles.

[0052] Example 4: Visual simulation test of high-temperature service performance of zirconium-carbon nozzle for ultra-thin strip continuous casting (1) Test steel liquid: 1500 kg of steel liquid was smelted at a temperature of 1650℃.

[0053] (2) Test nozzle: Zirconium-carbon nozzle has poor thermal shock resistance (coefficient of thermal expansion 8.5×10). -6 / ℃), high high temperature strength (12-13MPa).

[0054] (3) Test gate baking conditions: The gate was preheated to 1200℃ and held at 10℃ / min using an atmosphere baking oven.

[0055] (4) Simulated steel pouring conditions and process: 9 8mm zirconia steel outlets, the distance between the test outlet and the bottom of the tundish is 50mm, and the steel pouring time is 5min.

[0056] (5) Test results: The infrared thermal imager clearly showed that the temperature of the outer wall at the bottom of the nozzle rose sharply at the moment of pouring. The high-speed camera recorded the whole process. During the 1 minute of pouring, cracks were found in many places on the outer wall of the nozzle, and the cracks gradually expanded.

[0057] (6) Observation after the nozzle is cooled: multiple parts of the nozzle cracked, and there was condensed steel in the cracked parts, and a small amount of molten steel adhered to the inner wall.

[0058] Conclusion: Zirconium-carbon nozzles used for ultra-thin strip continuous casting have poor thermal shock resistance but good resistance to physical impact from molten steel. This method can effectively simulate thermal shock cracking of ultra-thin strip nozzles.

Claims

1. A visual simulation test method for the high-temperature service performance of ultra-thin strip continuous casting nozzles, characterized in that: Includes the following steps: Step 1, preheating of the sprue: Preheat the sprue to be tested to 800-1200℃ in a nitrogen atmosphere according to the on-site service conditions and keep it at that temperature for 30-120 minutes; install the sprue fixing fixture at the bottom of the simulated intermediate ladle; debug the high-temperature infrared thermal imager and high-speed camera to confirm that the monitoring is normal. The second step, steel melting and temperature control: the medium frequency furnace melts the steel block, heats it to the target temperature, and holds it at that temperature for 10-15 minutes to ensure uniform temperature; the furnace body is tilted, and the molten steel is smoothly poured into the steel ladle through the guide channel; The third step is the transfer of molten steel: the molten steel is transferred to the molten steel receiving area of ​​the simulated tundish, and after passing through the stabilization zone, it flows smoothly to the outflow zone; The fourth step is to simulate the steel pouring-high temperature thermal shock stage: the molten steel flows through the nozzle to be tested, and a violent thermal shock is triggered the moment the pouring begins; a high-speed camera records the crack initiation, propagation, and spalling in a high-temperature environment; an infrared thermal imager captures the instantaneous temperature rise, temperature field gradient distribution, and maximum temperature difference of the outer wall in real time; the flow rate of molten steel is controlled by adjusting the number and size of the controllable outlets of the simulated tundish, so that the pouring time is adjustable within the range of 3-5 minutes, simulating the thermal shock and initial scouring conditions at the moment of pouring, and the influence of different molten steel flow rates on the thermal shock resistance and scouring behavior of the nozzle can be examined; Step 5, High-Temperature Strength and Erosion Resistance Assessment: Examine the deformation, inner diameter expansion, erosion depth, and structural integrity under high-temperature molten steel load and erosion during steel pouring; record flow fluctuations, leakage, and blockage anomalies in real time; Step 6: Shutdown, Cooling and Post-processing Inspection: Stop the supply of molten steel and allow it to cool naturally to room temperature; disassemble the sprue and perform macroscopic crack inspection, cross-sectional microscopic analysis, inner diameter measurement, and mass loss rate calculation; combine online high-temperature temperature-video data to comprehensively evaluate the thermal shock cracking resistance, high-temperature strength and erosion resistance. Step 7, Data Fusion and Performance Grading: Fusion of thermal imaging, temperature measurement, video, and dimensional / mass data to establish a correlation model of thermal shock temperature gradient-crack propagation-strength decay; and provide qualified / unqualified or excellent / good / medium / poor grading according to enterprise / industry standards to guide formulation and structural optimization.

2. The method for visual simulation test of high-temperature service performance of ultra-thin strip continuous casting nozzle as described in claim 1, characterized in that, The medium-frequency induction melting furnace is equipped with a tilting mechanism and a molten steel guide trough, with a capacity of 800-1500 kg. The medium-frequency furnace can melt molten steel at a temperature of 1450-1800℃.

3. The high-temperature service performance visualization simulation test method for ultra-thin strip continuous casting nozzles as described in claim 1, characterized in that: The molten steel transfer vessel is a refractory-lined vessel equipped with a tilting mechanism, a molten steel diversion channel, and a hoisting mechanism, used to receive and transfer molten steel.

4. The high-temperature service performance visualization simulation test method for ultra-thin strip continuous casting nozzles as described in claim 1, characterized in that: The simulated tundish consists of a steel structure and a refractory material cavity. The steel structure comprises an outer shell and supporting and fixing components. The outer shell facilitates the construction and protection of the refractory material wall. The supporting and fixing components work in conjunction with the nozzle fixing fixture to achieve synchronous stability and positioning of the simulated tundish and the nozzle. The refractory material cavity is constructed of hollow alumina spherical refractory material. A partition I is provided on the side of the refractory material cavity near the tundish inlet. The height of partition I is lower than the height of the refractory material cavity, and partition I is fixed to the bottom of the refractory material cavity. A molten steel receiving area is formed between partition I and the cavity plate on the side of the refractory material cavity near the tundish inlet. The molten steel receiving area is the inlet area for the molten steel poured into the tundish, used to receive the steel flow and buffer the impact of the molten steel. The refractory material cavity is also equipped with a baffle plate II; there is a gap between the baffle plate II and the bottom surface of the refractory material cavity for the flow of molten steel; a steady flow zone is formed between the baffle plate II and the baffle plate I to eliminate turbulence, uniformize temperature, and smoothly adjust the flow field; an outflow zone is formed between the baffle plate II and the cavity plate on the other side of the refractory material cavity; 7-10 zirconia refractory material outlets with a diameter of 8-15mm are arranged at the bottom of the outflow zone to smoothly guide the high-temperature molten steel downward into the test nozzle, and the number and diameter of the zirconia outlets can be adjusted according to the casting process; a test nozzle is set directly below the outflow zone; the test nozzle is supported directly below the outflow zone by a nozzle fixing fixture; a molten steel collection mechanism is set directly below the test nozzle.

5. The high-temperature service performance visualization simulation test method for ultra-thin strip continuous casting nozzles as described in claim 1, characterized in that: The nozzle fixing fixture consists of a support assembly and a fixing assembly, and is made entirely of steel. The support assembly includes a top support flange, four vertical support bolts, and a locking nut. The top of the flange cooperates with the simulated tundish support structure to support the simulated tundish. It is tightened upwards by the bolts and locking nuts, and the distance between the nozzle to be tested and the bottom of the tundish can be adjusted between 50-350mm to adapt to different molten steel impact simulation conditions. The fixing assembly is located in the middle of the support assembly and is used to support and fix the nozzle to be tested. It also reserves a thermal expansion gap, and its shape and size can be replaced according to the shape and size of the nozzle and the support method requirements.

6. The high-temperature service performance visualization simulation test method for ultra-thin strip continuous casting nozzles as described in claim 1, characterized in that, The high-temperature visualization online monitoring unit includes two types of monitoring equipment: a high-temperature infrared thermal imager and a high-speed camera. The high-temperature infrared thermal imager is equipped with a heat-insulating protective sleeve, with its lens facing the nozzle for observation. It can collect data on the outer wall temperature of the nozzle under test, the instantaneous thermal shock temperature rise rate, and the cross-sectional temperature gradient distribution in real time. The high-speed camera is equipped with a water-cooled heat-insulating protective cover and a high-temperature resistant quartz observation window. Its lens is aimed at the tooling visualization observation position, and the equipment has a shooting frame rate of no less than 100 frames per second. It can continuously capture dynamic images of nozzle crack initiation, extension, chipping, and deformation during the entire process of molten steel thermal shock impact. Both the infrared thermal imager and the high-speed camera are electrically connected to the electronic control and data acquisition system through signal lines to achieve synchronous storage, time-series alignment, and playback analysis of temperature data and high-definition video.

7. The high-temperature service performance visualization simulation test method for ultra-thin strip continuous casting nozzles as described in claim 1, characterized in that, The molten steel collection and safety protection unit includes a molten steel collection mechanism, a protective baffle, and an emergency cooling system.

8. The high-temperature service performance visualization simulation test method for ultra-thin strip continuous casting nozzles as described in claim 1, characterized in that, The electrical control and data acquisition system is used to synchronously collect and store temperature, thermal images, video, and flow parameters.

9. The method for visual simulation test of high-temperature service performance of ultra-thin strip continuous casting nozzle as described in claim 1, characterized in that, The nozzle to be tested is an ultra-thin strip continuous casting nozzle, which can be compatible with conventional immersion nozzles and long nozzles after tooling replacement; the nozzle material is a carbon-containing functional refractory material.

10. The high-temperature service performance visualization simulation test method for ultra-thin strip continuous casting nozzles as described in claim 1, characterized in that, The method requires the use of a sprue baking oven, which is equipped with a programmable temperature control module to precisely adjust the heating rate, and the baking atmosphere is nitrogen to prevent oxidation at high temperatures.

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