A method for improving temperature control capability of a continuous casting tundish

Abstract

This invention relates to a method for improving the temperature control capability of the tundish in continuous casting, belonging to the technical field of continuous casting methods in iron and steel metallurgy. The technical solution of this invention is as follows: A ladle thermal state prediction model is established, calculating the ladle heat saturation coefficient using ladle baking parameters and turnover time; a tundish thermal state prediction model is established, calculating the tundish thermal damping coefficient using the tundish baking curve and heat storage factor; a multi-dimensional thermally coupled temperature prediction formula is constructed, comprehensively considering the molten steel outlet temperature, ladle heat saturation, tundish thermal damping, and process temperature drop rate to accurately predict the real-time temperature of the molten steel in the tundish. The beneficial effects of this invention are: by quantitatively coupling the baking efficiency and turnover cycle of the ladle and tundish, it solves the problem that traditional empirical formulas cannot accurately reflect the influence of equipment on molten steel temperature, significantly improving the temperature control accuracy in the continuous casting process of rail steel, and effectively avoiding billet quality problems caused by temperature fluctuations.

Description

Technical Field

[0001] This invention relates to a method for improving the temperature control capability of the tundish in continuous casting, belonging to the technical field of continuous casting methods in iron and steel metallurgy. Background Technology

[0002] In the production of rail steel, the temperature stability of the molten steel in the continuous casting tundish directly determines the internal quality (such as segregation and shrinkage cavities) and surface quality of the cast billet. Excessive temperature fluctuations in the tundish can lead to unstable casting speeds, potentially causing accidents such as leaks or billet cracks. Currently, the industry's commonly used empirical control method typically estimates the tundish temperature by subtracting a fixed empirical temperature drop value (e.g., 0.5~1.0℃ / min) from the tapping temperature. However, this method ignores the following key variables:

[0003] 1. Dynamic nature of ladle thermal state: Ladle turnover time varies, with ladles with shorter turnover times being "hot" and those with longer turnover times being "cold", resulting in significant differences in their heat absorption capacity; moreover, existing technologies lack quantitative evaluation of ladle baking effects (especially offline baking).

[0004] 2. The complexity of thermal inertia in the tundish: After the tundish is baked, the heat storage state of its lining directly affects the temperature drop during the initial casting. The traditional "tundish baking temperature" is only the surface temperature and cannot reflect the heat storage capacity (thermal damping effect) of the deeper parts of the lining.

[0005] 3. Lack of coupling effect: Existing technologies often calculate the temperature drop of the ladle and the temperature drop of the tundish separately, without considering the complex heat exchange process when hot molten steel enters the "cold tundish" or "cold molten steel" enters the "hot tundish".

[0006] Therefore, developing a novel predictive model that covers ladle baking, tundish baking, turnaround time, and process temperature drop is of great significance for improving the quality of continuous casting of rail steel.

[0007] Application number CN201910900487.1 provides a "smelting method for stably controlling the tundish temperature of U75V heavy rail steel". The core process control idea is to achieve a good heat preservation effect by controlling the viscosity of the ladle refining slag without increasing production costs, so that the superheat of the molten steel in the tundish is controlled within the range of 20-30℃. The porosity and shrinkage defects in the center of the billet are significantly improved, which meets the current requirements for heavy rail steel. However, it does not address how the tundish, ladle baking and process turnover affect the tundish temperature. Application number CN202310939130.0 provides a method for achieving low-temperature isothermal casting of heavy rail steel. The core control concept is as follows: maintaining the main process parameters of the original casting machine unchanged, designing and applying electromagnetic induction heating to the tundish; adopting a symmetrical "eight"-shaped dual-flow steel channel design; employing a zoned design to divide the internal structure of the tundish into a ladle impact zone and a casting flow zone; and using numerical simulation to optimize the molten steel flow field in the tundish to achieve a method for low-temperature isothermal casting of heavy rail steel, resulting in a significant improvement in the internal quality level of the cast billet. However, this invention patent does not address the precise prediction and control of the tundish temperature through smelting process parameters. Summary of the Invention

[0008] The purpose of this invention is to provide a method for improving the temperature control capability of the tundish in continuous casting. By converting the "baking effect" into specific coefficients for calculation, the problem of temperature drop misjudgment caused by "baking temperature reaching but lining not being fully heated" is solved. Innovatively, the ladle turnover, baking, and tundish thermal state are coupled into a single formula, revealing for the first time the nonlinear heat transfer relationship among "turnover time - baking efficiency - tundish damping". Precise temperature control makes the continuous casting speed of rail steel more stable, effectively improves the equiaxed crystal ratio of the billet, reduces the incidence of center segregation and porosity defects, and effectively solves the above-mentioned problems existing in the background technology.

[0009] The technical solution of this invention is: a method for improving the temperature control capability of a continuous casting tundish, comprising the following steps:

[0010] S1: Collect the final temperature of ladle baking, ladle baking time, and ladle turnover time, substitute them into the ladle thermal state prediction model, and calculate the ladle heat saturation coefficient. ;

[0011] S2: Collect the final baking temperature of the tundish, the baking time of the tundish, and the material parameters of the working layer of the tundish, substitute them into the tundish thermal state prediction model, and calculate the thermal damping coefficient of the tundish. ;

[0012] S3: Temperature of molten steel when it reaches the ladle turret. Measured temperature drop rate and continuous casting time ;

[0013] S4: Substitute the above parameters into the multidimensional thermal coupling temperature prediction formula to calculate the predicted molten steel temperature in the tundish. The multidimensional thermal coupling temperature prediction formula is as follows: In the formula: The initial temperature at which the steel ladle begins casting, in °C; It is the basic physical temperature drop constant, in °C; is the ladle heat saturation coefficient, dimensionless; is the thermal damping coefficient of the tundish, which is dimensionless; The rate of temperature drop per unit time, expressed in °C / min; For the duration of casting; This is a correction value for process temperature drop fluctuations; These are the weighting coefficients;

[0014] S5: Based on predicted temperature With target temperature To compensate for deviations, the pulling speed or argon blowing intensity can be dynamically adjusted to achieve precise control of the intermediate package temperature.

[0015] In step S1, the ladle heat saturation coefficient The calculation formula is: In the formula: This refers to the ladle baking time. This is a function of the instantaneous temperature during the ladle baking process; Ambient temperature; For ladle turnaround time; The effective heat capacity of the ladle lining; This is a correction factor for the ladle material.

[0016] In step S2, the thermal damping coefficient of the intermediate liner The calculation formula is:

[0017] The thermal conductivity of the working layer of the intermediate package; This refers to the heated area of ​​the working layer of the intermediate package; This is the final baking temperature for the medium-sized bread. Standard reference temperature; The working layer thickness; For steel flow rate; This is the cumulative coefficient of secondary heat in a continuous casting furnace; This represents the current number of consecutive casting cycles.

[0018] In step S3, the process temperature drop parameters include the temperature drop during steel transport in the ladle, the argon protection effect parameters of the long nozzle of the ladle, and the liquid level fluctuation parameters in the tundish.

[0019] The beneficial effects of this invention are as follows: by converting the "baking effect" into specific coefficients for calculation, the problem of misjudgment of temperature drop caused by "baking temperature reached but the lining not being heated through" is solved; innovatively, the ladle turnover, baking and tundish thermal state are coupled into a single formula, revealing for the first time the nonlinear heat transfer relationship among "turnover time-baking efficiency-tundish damping"; precise temperature control makes the continuous casting speed of rail steel more stable, effectively improves the equiaxed crystal ratio of the billet, and reduces the incidence of center segregation and porosity defects. Detailed Implementation

[0020] To make the purpose, technical solutions, and advantages of the embodiments of the invention clearer, the technical solutions in the embodiments of the invention are described clearly and completely below. Obviously, the embodiments described are only a small part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without creative effort are within the protection scope of the invention.

[0021] A method for improving the temperature control capability of a continuous casting tundish includes the following steps:

[0022] S1: Collect the final temperature of ladle baking, ladle baking time, and ladle turnover time, substitute them into the ladle thermal state prediction model, and calculate the ladle heat saturation coefficient. ;

[0023] S2: Collect the final baking temperature of the tundish, the baking time of the tundish, and the material parameters of the working layer of the tundish, substitute them into the tundish thermal state prediction model, and calculate the thermal damping coefficient of the tundish. ;

[0024] S3: Temperature of molten steel when it reaches the ladle turret. Measured temperature drop rate and continuous casting time ;

[0025] S4: Substitute the above parameters into the multidimensional thermal coupling temperature prediction formula to calculate the predicted molten steel temperature in the tundish. The multidimensional thermal coupling temperature prediction formula is as follows: In the formula: The initial temperature at which the steel ladle begins casting, in °C; It is the basic physical temperature drop constant, in °C; is the ladle heat saturation coefficient, dimensionless; is the thermal damping coefficient of the tundish, which is dimensionless; The rate of temperature drop per unit time, expressed in °C / min; For the duration of casting; This is a correction value for process temperature drop fluctuations; These are the weighting coefficients;

[0026] S5: Based on predicted temperature With target temperature To compensate for deviations, the pulling speed or argon blowing intensity can be dynamically adjusted to achieve precise control of the intermediate package temperature.

[0027] In step S1, the ladle heat saturation coefficient The calculation formula is: In the formula: This refers to the ladle baking time. This is a function of the instantaneous temperature during the ladle baking process; Ambient temperature; For ladle turnaround time; The effective heat capacity of the ladle lining; This is a correction factor for the ladle material.

[0028] In step S2, the thermal damping coefficient of the intermediate liner The calculation formula is:

[0029] The thermal conductivity of the working layer of the intermediate package; This refers to the heated area of ​​the working layer of the intermediate package; This is the final baking temperature for the medium-sized bread. Standard reference temperature; The working layer thickness; For steel flow rate; This is the cumulative coefficient of secondary heat in a continuous casting furnace; This represents the current number of consecutive casting cycles.

[0030] In step S3, the process temperature drop parameters include the temperature drop during steel transport in the ladle, the argon protection effect parameters of the long nozzle of the ladle, and the liquid level fluctuation parameters in the tundish.

[0031] In practical applications, this invention proposes a "multidimensional thermal coupling temperature prediction formula." The core innovation of this formula lies in the introduction of two previously undefined parameters: the ladle heat saturation coefficient (…). ) and the thermal damping coefficient of the tundish ( ).

[0032] 1. Thermal saturation coefficient of steel ladle Definition and calculation logic:

[0033] This reflects the net heat content of the ladle after undergoing baking heat accumulation and turnover heat dissipation. Traditional methods only consider turnover time; this invention calculates the ratio of the integral of the baking process to the turnover time, quantifying the trade-off between "heat gain during baking" and "heat loss during turnover." Formula: The higher the value, the "hotter" the ladle is, and the less heat loss from the molten steel.

[0034] 2. Thermal damping coefficient of the tundish Definition and calculation logic: This reflects the tundish lining's ability to resist temperature changes and dissipate heat to the outside. It integrates baking temperature, working layer thickness, thermal conductivity, and the heat accumulation effect of consecutive casting cycles. Formula: The higher the coefficient, the better the insulation performance of the tundish, and the smaller the temperature drop of the molten steel inside the tundish.

[0035] 3. Final formula for predicting the intermediate temperature: This formula creatively applies a logarithmic function to correct the influence of heat saturation and uses the reciprocal relationship to characterize the ability of the thermal damping coefficient to suppress temperature drop, thereby achieving precise control of the tundish temperature.

[0036] Example 1: Casting of U75V rail steel under standard working conditions

[0037] • Operating conditions: The ladle turnover is normal, the tundish is in the second continuous casting furnace, producing U75V standard speed rails.

[0038] • Parameter acquisition:

[0039] Steel ladle turnover time The ladle was baked well, and the ladle heat saturation coefficient was calculated. .

[0040] One tundish has been cast, and the lining has sufficient heat storage. The thermal damping coefficient of the tundish has been calculated. .

[0041] Temperature of molten steel reaching the rotary table Base temperature drop rate of temperature drop Casting time .

[0042] • Prediction and Control:

[0043] Substituting into the formula, the predicted temperature is calculated. .

[0044] target temperature ,deviation The system automatically fine-tunes the pulling speed, and the actual ladle temperature remains stable at... .

[0045] oResult: Verified the baseline accuracy of the formula under standard operating conditions.

[0046] Example 2: Long-cycle turnover (cold packaging) working condition

[0047] • Working conditions: Due to fluctuations in the steelmaking rhythm, the turnaround time of a certain steel ladle is too long and the ladle lining temperature is low, resulting in the production of U71Mn steel rails.

[0048] • Parameter acquisition:

[0049] Steel ladle turnover time (far exceeding normal values), leading to Down to (Cold package).

[0050] The status of the package is normal. .

[0051] initial temperature .

[0052] • Prediction and Control:

[0053] The formula accurately identifies The lower temperature results in an additional heat absorption effect. Predictions indicate a significantly larger temperature drop. Lower than traditional experience value .

[0054] The system provides early warnings, and operators can remedy the situation by intensifying online baking before the ladle arrives.

[0055] Results: The formula successfully avoided low-temperature alarms and billet quality problems caused by heat absorption in the "cold ladle", proving that the formula is extremely sensitive to the thermal state of the ladle.

[0056] Example 3: First Furnace Casting Condition

[0057] • Working conditions: The tundish has just finished baking and is in use. It is a typical "cold tundish" heat absorption stage, producing high-strength steel rails.

[0058] • Parameter acquisition:

[0059] The intermediate loaf was new; although it was baked properly, the lining lacked sufficient heat retention, resulting in a low thermal damping coefficient. Only .

[0060] The ladle is in normal condition. .

[0061] • Prediction and Control:

[0062] In the formula The value of the indicator has increased significantly, and a sharp temperature drop is predicted. Calculations show that the molten steel temperature will rapidly fall below the target lower limit within the first 10 minutes.

[0063] Control strategy: System commands increase initial pouring temperature And it adopts the "black slag insulation" operation.

[0064] Results: The water successfully passed through the temperature drop peak and trough period at the beginning of the pouring process, and no water inlet blockage occurred.

[0065] Example 4: Extremely High Heat Saturation Condition

[0066] • Operating conditions: Production organization is optimized, ladle turnover is rapid, and the ladle lining is in a red-hot state.

[0067] • Parameter acquisition:

[0068] The ladle turnover time is only And after online intense drying, Gundam .

[0069] The status of the package is stable. .

[0070] • Prediction and Control:

[0071] The formula predicts a very small temperature drop, and there is even a possibility that the temperature of the molten steel may rise. The displayed temperature will be higher than the target value.

[0072] The system recommends lowering the tapping temperature. .

[0073] Effect: Effectively avoids problems such as excessively fast drawing speed and loose center caused by overheating of molten steel, achieving energy saving and consumption reduction.

[0074] Example 5: Low-temperature environment conditions in winter

[0075] • Operating conditions: Production in northern winter, ambient temperature As low as The heat dissipation conditions deteriorated.

[0076] • Parameter acquisition:

[0077] ambient temperature The reduction in heat dissipation from the ladle and tundish accelerates, and the model automatically corrects itself. and The calculation parameters, It decreases due to rapid heat dissipation in the environment. Reduced due to external cold shock.

[0078] o Process temperature drop fluctuation correction value The model assigns a positive compensation value.

[0079] • Prediction and Control:

[0080] The formula automatically adds a correction for temperature drop caused by environmental cooling shock.

[0081] Effect: Under extreme climatic conditions, the temperature prediction error is still controlled within [a certain range]. Within this range, the low-temperature toughness index of the rail steel is kept stable.

[0082] Example 6: Abnormally Long Casting Time Condition

[0083] • Background: Due to a downstream rolling line malfunction, the continuous casting machine was forced to reduce its speed during billet pulling, extending the casting time per furnace to [time missing]. .

[0084] • Parameter acquisition:

[0085] o Casting time Extended, rate of temperature drop It increases due to the decrease in pulling speed.

[0086] The o model focuses on the impact of the time integral term.

[0087] • Prediction and Control:

[0088] Formula o predicts that as time goes on, if the molten steel stays in the ladle for too long, the cumulative effect of temperature drop will be significant.

[0089] The system dynamically adjusts the secondary cooling water volume and instructs the intermediate drum to add insulation.

[0090] Effect: Under long-term low-speed operation, the temperature of the tundish remained relatively stable, avoiding coarse microstructure caused by large temperature fluctuations.

[0091] Example 7: Offline Baking Remedial Operation

[0092] • Context: A steel ladle that has been idle for a long time (turnover time) It was put into use after being remedied by an offline gas-fired baking device.

[0093] • Parameter acquisition:

[0094] Although the turnaround time is long, the offline baking parameters... big, high.

[0095] Integral term in formula o Significantly increased, resulting in the final rebounded to .

[0096] • Prediction and Control:

[0097] Traditional experience would consider this a "cold package" and refuse to use it or increase the temperature significantly, but the formula of this invention accurately calculates that its thermal state has been restored to a usable level.

[0098] Effect: It achieves efficient utilization of idle steel ladles and reduces energy waste caused by misjudgment (unnecessary secondary heating).

[0099] Example 8: End-stage continuous casting condition

[0100] • Operating conditions: The tundish is continuously casting for the 8th heat. The tundish lining is completely thermally saturated and in a state of extremely high thermal damping.

[0101] • Parameter acquisition:

[0102] o Continuous casting furnace The thermal damping coefficient of the tundish was calculated. Gundam (Excellent thermal insulation performance).

[0103] o Steel ladle status .

[0104] • Prediction and Control:

[0105] In the formula The value is extremely small, and the predicted temperature drop is very slow.

[0106] The system indicates that the tapping temperature can be further reduced. .

[0107] Effect: By fully utilizing the thermal inertia in the later stage of the tundish, low-temperature rapid injection was achieved throughout the entire process, which significantly reduced the erosion rate of refractory materials and improved the cleanliness of the rail steel.

[0108] The above eight embodiments cover various complex working conditions in rail continuous casting production, including cold / hot ladles, cold / hot tundishes, seasonal variations, rhythm fluctuations, and special remedial measures. Application results show that the prediction formula provided by this invention can accurately quantify the nonlinear effects of ladle baking, turnaround time, and tundish thermal state on molten steel temperature, achieving a temperature prediction accuracy of over 95%, significantly improving the quality stability of rail products.

[0109] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for improving the temperature control capability of a continuous casting tundish, characterized in that... Includes the following steps: S1: Collect the final temperature of ladle baking, ladle baking time, and ladle turnover time, substitute them into the ladle thermal state prediction model, and calculate the ladle heat saturation coefficient. ; S2: Collect the final baking temperature of the tundish, the baking time of the tundish, and the material parameters of the working layer of the tundish, substitute them into the tundish thermal state prediction model, and calculate the thermal damping coefficient of the tundish. ; S3: Temperature of molten steel when it reaches the ladle turret. Measured temperature drop rate and continuous casting time ; S4: Substitute the above parameters into the multidimensional thermal coupling temperature prediction formula to calculate the predicted molten steel temperature in the tundish. The multidimensional thermal coupling temperature prediction formula is as follows: In the formula: The initial temperature at which the steel ladle begins casting, in °C; It is the basic physical temperature drop constant, in °C; is the ladle heat saturation coefficient, dimensionless; is the thermal damping coefficient of the tundish, which is dimensionless; The rate of temperature drop per unit time, expressed in °C / min; For the duration of casting; This is a correction value for process temperature drop fluctuations; These are the weighting coefficients; S5: Based on predicted temperature With target temperature To compensate for deviations, the pulling speed or argon blowing intensity can be dynamically adjusted to achieve precise control of the intermediate package temperature.

2. The method for improving the temperature control capability of a continuous casting tundish according to claim 1, characterized in that: In step S1, the ladle heat saturation coefficient The calculation formula is: In the formula: This refers to the ladle baking time. This is a function of the instantaneous temperature during the ladle baking process; Ambient temperature; For ladle turnaround time; The effective heat capacity of the ladle lining; This is a correction factor for the ladle material.

3. The method for improving the temperature control capability of a continuous casting tundish according to claim 1, characterized in that: In step S2, the thermal damping coefficient of the intermediate liner The calculation formula is: ； The thermal conductivity of the working layer of the intermediate package; This refers to the heated area of ​​the working layer of the intermediate package; This is the final baking temperature for the medium-sized bread. Standard reference temperature; The working layer thickness; For steel flow rate; This is the cumulative coefficient of secondary heat in a continuous casting furnace; This represents the current number of consecutive casting cycles.

4. The method for improving the temperature control capability of a continuous casting tundish according to claim 1, characterized in that: In step S3, the process temperature drop parameters include the temperature drop during steel transport in the ladle, the argon protection effect parameters of the long nozzle of the ladle, and the liquid level fluctuation parameters in the tundish.

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