Methods and Systems for Predicting Nitrogen Content in Liquid Steel During VD Refining

Abstract

This application provides a method and system for predicting the nitrogen content of molten steel in the VD refining process. The method includes: acquiring process parameters of the VD vacuum degassing process, constructing a nitrogen content prediction model to output a target nitrogen content prediction value based on the process parameters. In the prediction model, a first calculation module calculates the activity coefficient of nitrogen in the molten steel, a second calculation module calculates the dissolution equilibrium constant, a third calculation module calculates the mass percentage of nitrogen in the molten steel when dissolution equilibrium is reached, a fourth calculation module calculates the ratio of the interfacial reaction area to the molten pool volume, a correction module obtains the corrected mass transfer coefficient, and a fifth calculation module calculates the target nitrogen content prediction value. The constructed prediction model uses thermodynamic principles for calculation, which can predict the nitrogen content in molten steel during the vacuum degassing process, solving the problem of not being able to obtain the nitrogen content during degassing. Furthermore, calculating the nitrogen content prediction value using the corrected mass transfer coefficient improves the accuracy of the calculation results.

Description

Technical Field

[0001] This application relates to the field of nitrogen content calculation technology in molten steel, and in particular to a method and system for predicting nitrogen content in molten steel during VD refining. Background Technology

[0002] Vacuum degassing (VD) is a vacuum degassing process that effectively removes harmful gases such as hydrogen and oxygen from molten steel. It also offers comprehensive functions including desulfurization, fine-tuning of alloy composition, homogenization of molten steel composition, and temperature control. It is used in the manufacture of steel grades with extremely high performance requirements, such as pipeline steel, heavy rail steel, and tire cord steel. However, due to increasingly stringent quality requirements, especially in the production of specific steel grades with strict upper and lower limits for nitrogen content control, VD refining technology still faces several challenges.

[0003] Due to the complex environment inside the VD furnace, involving high temperature, high pressure, and various physicochemical reactions, and limitations in detection methods, it is impossible to sample and test the nitrogen content in the molten steel during vacuum degassing, making real-time monitoring difficult. Therefore, the vacuum level and degassing time are mainly controlled by manual experience. Because this process relies on human judgment, the accuracy of the degassing process is low. Furthermore, for steel grades with upper and lower limits for nitrogen content control, the nitrogen content can only be sampled and measured after the degassing process is completed. If the nitrogen content is not up to standard at this point, it is necessary to re-vacuum or add nitrogen, resulting in cumbersome, time-consuming, and labor-intensive operations, thereby reducing the overall efficiency of VD refining and lowering economic benefits. Summary of the Invention

[0004] This application provides a method and system for predicting the nitrogen content in liquid steel during the VD refining process, in order to solve the problem that the nitrogen content cannot be obtained during the vacuum degassing process.

[0005] The first aspect of this application provides a method for predicting the nitrogen content in liquid steel during the VD refining process, including:

[0006] The process parameters for the VD vacuum degassing process are obtained, including the steel temperature, interaction coefficient, mass percentage of elements in the steel, partial pressure of nitrogen in nitrogen bubbles, vacuum chamber pressure, type of bottom-blown gas, and bottom-blown gas flow rate per unit time; the interaction coefficient is the interaction coefficient between elements in the steel and nitrogen.

[0007] A nitrogen content prediction model is constructed to output a predicted value of the target nitrogen content in molten steel based on the process parameters; the prediction model includes:

[0008] The first calculation module is used to calculate the activity coefficient of nitrogen in the molten steel based on the interaction coefficient and the mass percentage of the elements in the molten steel.

[0009] The second calculation module is used to calculate the dissolution equilibrium constant of nitrogen in the molten steel based on the temperature of the molten steel.

[0010] The third calculation module is used to calculate the first nitrogen content based on the partial pressure of nitrogen in the nitrogen bubble, the activity coefficient and the dissolution equilibrium constant. The first nitrogen content is the mass percentage of nitrogen element in molten steel when dissolution equilibrium is reached.

[0011] The fourth calculation module is used to calculate a first ratio based on the vacuum chamber pressure and the bottom-blown gas flow rate per unit time, wherein the first ratio is the ratio of the interface reaction area to the molten pool volume.

[0012] The correction module is used to correct the model parameters of the prediction model based on the initial mass transfer coefficient to obtain the corrected mass transfer coefficient.

[0013] The fifth calculation module is used to calculate the second nitrogen content in the molten steel based on the first nitrogen content, the corrected mass transfer coefficient, the type of bottom-blown gas, and the first ratio, and output the second nitrogen content as the predicted value of the target nitrogen content.

[0014] Optionally, the dissolution equilibrium constant of nitrogen in molten steel can be calculated using the following formula:

[0015]

[0016] Among them, K N Here, T is the dissolution equilibrium constant, and T is the temperature of the molten steel.

[0017] Optionally, the first nitrogen content can be calculated using the following formula:

[0018]

[0019] Among them, [%N] eq The first nitrogen content, K N It is the dissolution equilibrium constant. P is the partial pressure of nitrogen gas in a nitrogen bubble. θ For standard atmospheres, f N This is the activity coefficient.

[0020] Optionally, the first ratio can be calculated using the following formula:

[0021]

[0022] Where B is the first ratio, Q is the bottom blowing gas flow rate per unit time, P1 is the vacuum chamber pressure, and Δt is the time change.

[0023] Optionally, the step of correcting the model parameters of the prediction model based on the initial mass transfer coefficient to obtain the corrected mass transfer coefficient includes:

[0024] Obtain the initial mass transfer coefficient, which is a continuous value within a preset range;

[0025] The initial mass transfer coefficient is divided according to a preset step size to obtain several mass transfer coefficients;

[0026] Acquire historical data, which are the measured values ​​of nitrogen content in molten steel after the degassing process;

[0027] The first nitrogen content prediction value is calculated based on the mass transfer coefficient. The first nitrogen content prediction value is the nitrogen content prediction value in the molten steel after the degassing process.

[0028] The mean absolute error is calculated based on the historical data and the first predicted nitrogen content value.

[0029] Iterate through the mass transfer coefficients to obtain the mass transfer coefficient corresponding to the minimum mean absolute error, and output the mass transfer coefficient as the corrected mass transfer coefficient.

[0030] Optionally, the mean absolute error can be calculated using the following formula:

[0031]

[0032] Where MAE is the mean absolute error. The first predicted nitrogen content, y i This represents the measured nitrogen content in the molten steel after the degassing process.

[0033] Optionally, the bottom-blown gas includes nitrogen and argon, and the calculation of the second nitrogen content in the molten steel based on the first nitrogen content, the corrected mass transfer coefficient, the type of bottom-blown gas, and the first ratio includes:

[0034] When the bottom-blown gas is nitrogen, the second nitrogen content is calculated using the following formula:

[0035] [%N]2=[%N]1-η×A×B×([%N]1-[%N] eq )×Δt1;

[0036] When the bottom-blown gas is argon, the second nitrogen content is calculated using the following formula:

[0037] [%N]2=[%N]1-A×B×([%N]1-[%N] eq )×Δt1;

[0038] Wherein, [%N]2 is the second nitrogen content, [%N]1 is the predicted nitrogen content in the molten steel at the initial time of the preset duration, η is the dimensionless number, A is the corrected mass transfer coefficient, B is the first ratio, and Δt1 is the preset duration.

[0039] Optionally, when the initial time of the preset duration is the start time of degassing, the predicted value of the nitrogen content in the molten steel is the measured value of the nitrogen content in the molten steel.

[0040] Optionally, the method further includes:

[0041] If the degassing process is not completed, the dissolution equilibrium constant is calculated by the second calculation module based on the temperature of the molten steel.

[0042] The third calculation module calculates the first nitrogen content based on the partial pressure of nitrogen in the nitrogen bubble, the activity coefficient, and the solubility equilibrium constant.

[0043] The fourth calculation module calculates the first ratio based on the vacuum chamber pressure and the bottom-blowing gas flow rate per unit time.

[0044] The fifth calculation module calculates the second nitrogen content based on the first nitrogen content, the corrected mass transfer coefficient, the bottom-blown gas type, and the first ratio.

[0045] Until the degassing process is completed, the second nitrogen content is output as the predicted value of the target nitrogen content.

[0046] A second aspect of this application provides a system for predicting the nitrogen content in liquid steel during the VD refining process, applied to the method described in the first aspect, the system comprising:

[0047] Acquisition module: used to acquire process parameters of the VD vacuum degassing process, including molten steel temperature, interaction coefficient, mass percentage of elements in molten steel, partial pressure of nitrogen in nitrogen bubbles, vacuum chamber pressure, type of bottom-blown gas, and bottom-blown gas flow rate per unit time; the interaction coefficient is the interaction coefficient between elements in molten steel and nitrogen.

[0048] First calculation module: used to calculate the activity coefficient of nitrogen in molten steel based on the interaction coefficient and the mass percentage of elements in the molten steel;

[0049] The second calculation module is used to calculate the dissolution equilibrium constant of nitrogen in the molten steel based on the temperature of the molten steel.

[0050] The third calculation module is used to calculate the first nitrogen content based on the partial pressure of nitrogen in the nitrogen bubble, the activity coefficient, and the dissolution equilibrium constant. The first nitrogen content is the mass percentage of nitrogen element in molten steel when dissolution equilibrium is reached.

[0051] The fourth calculation module is used to calculate a first ratio based on the vacuum chamber pressure and the bottom-blown gas flow rate per unit time. The first ratio is the ratio of the interfacial reaction area to the molten pool volume.

[0052] Correction module: used to correct the model parameters of the prediction model based on the initial mass transfer coefficient, so as to obtain the corrected mass transfer coefficient;

[0053] The fifth calculation module is used to calculate the second nitrogen content in the molten steel based on the first nitrogen content, the corrected mass transfer coefficient, the type of bottom-blown gas, and the first ratio, and output the second nitrogen content as the predicted value of the target nitrogen content.

[0054] This application provides a method and system for predicting the nitrogen content of molten steel in the VD refining process. The method includes: acquiring process parameters of the VD vacuum degassing process, constructing a nitrogen content prediction model to output a target nitrogen content prediction value based on the process parameters. The prediction model includes a first calculation module for calculating the activity coefficient of nitrogen in the molten steel, a second calculation module for calculating the dissolution equilibrium constant, a third calculation module for calculating the mass percentage of nitrogen in the molten steel when dissolution equilibrium is reached, a fourth calculation module for calculating the ratio of the interfacial reaction area to the molten pool volume, a correction module for obtaining the corrected mass transfer coefficient, and a fifth calculation module for calculating the target nitrogen content prediction value. By using thermodynamic principles for calculation through the constructed prediction model, the nitrogen content in molten steel during the vacuum degassing process can be predicted, solving the problem of not being able to obtain the nitrogen content during vacuum degassing. Furthermore, calculating the nitrogen content prediction value using the corrected mass transfer coefficient improves the accuracy of the calculation results. Attached Figure Description

[0055] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 A schematic diagram of the process for predicting the nitrogen content in liquid steel during the VD refining process provided in this application embodiment;

[0057] Figure 2 This is a schematic flowchart of a method for obtaining a modified mass transfer coefficient provided in an embodiment of this application;

[0058] Figure 3 This is a schematic diagram of the predictive model workflow provided in the embodiments of this application;

[0059] Figure 4 A schematic diagram of the structure of the VD refining process steel liquid nitrogen content prediction system provided in this application embodiment. Detailed Implementation

[0060] The embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described below do not represent all embodiments consistent with this application. They are merely examples of systems and methods consistent with some aspects of this application as detailed in the claims.

[0061] Due to the complex environment inside the VD furnace, involving high temperature, high pressure, and various physicochemical reactions, it is impossible to sample and detect the nitrogen content in the molten steel during vacuum degassing, making real-time monitoring difficult. Therefore, the vacuum level and degassing time are mainly controlled by manual experience. Because this process relies on human judgment, the accuracy of the degassing process is low. Furthermore, for steel grades with upper and lower limits for nitrogen content control, the nitrogen content can only be sampled and measured after the degassing process is completed. If the nitrogen content is not up to standard at this point, it is necessary to re-vacuum or add nitrogen, resulting in cumbersome, time-consuming, and labor-intensive operations, thereby reducing the overall efficiency of VD refining and lowering economic benefits.

[0062] To address the issue of nitrogen content being unavailable during vacuum degassing, some embodiments of this application first provide a method for predicting nitrogen content in molten steel during VD refining, see [link to relevant documentation]. Figure 1 The methods include:

[0063] S100: Obtain the process parameters for the VD vacuum degassing process.

[0064] After the refining furnace enters the blowing station, degassing begins. Before degassing begins, the process parameters for the vacuum degassing process are obtained, including the molten steel temperature, interaction coefficient, mass percentage of elements in the molten steel, partial pressure of nitrogen in nitrogen bubbles, vacuum chamber pressure, type of bottom-blown gas, and bottom-blown gas flow rate per unit time. The interaction coefficient is the interaction coefficient between elements in the molten steel and nitrogen, a parameter that can be obtained through querying. The molten steel temperature, mass percentage of elements in the molten steel, and partial pressure of nitrogen in nitrogen bubbles can be obtained through actual measurement. The vacuum chamber pressure, type of bottom-blown gas, and bottom-blown gas flow rate per unit time are process parameters set before degassing.

[0065] S200: Construct a nitrogen content prediction model to output the predicted value of the target nitrogen content in molten steel based on the input process parameters.

[0066] The prediction model includes a first calculation module, a second calculation module, a third calculation module, a fourth calculation module, a correction module, and a fifth calculation module. Among them,

[0067] The first calculation module is used to calculate the activity coefficient of nitrogen in molten steel based on the interaction coefficient and the mass percentage of elements in the molten steel. In some embodiments, the activity coefficient of nitrogen in molten steel can be calculated using the following formula:

[0068] lgf N =∑e j N w j ;

[0069] Among them, f N e is the activity coefficient. j N is the interaction coefficient between the element in the molten steel and the nitrogen element; w j This represents the mass percentage of the elements in the molten steel. In the embodiments of this application, the elements in the molten steel mainly include nitrogen, carbon, silicon, manganese, phosphorus, and sulfur. After obtaining the interaction coefficients of nitrogen, carbon, silicon, manganese, phosphorus, and sulfur with nitrogen, the activity coefficient of nitrogen in the molten steel is calculated.

[0070] The second calculation module is used to calculate the dissolution equilibrium constant of nitrogen in molten steel based on the temperature of the molten steel. In some embodiments, the dissolution equilibrium constant of nitrogen in molten steel can be calculated using the following formula:

[0071]

[0072] Among them, K N Here, T is the dissolution equilibrium constant, and T is the temperature of the molten steel.

[0073] The third calculation module is used to calculate the first nitrogen content based on the partial pressure, activity coefficient, and dissolution equilibrium constant of nitrogen in the nitrogen bubbles. The first nitrogen content is the mass percentage of nitrogen in the molten steel when it reaches dissolution equilibrium. When nitrogen in the molten steel reaches dissolution equilibrium, the vacuum degassing process reaches equilibrium, i.e., degassing equilibrium. Degassing equilibrium means that under the current parameter conditions, the nitrogen content in the molten steel reaches its minimum value, and without changing the environmental parameters, the nitrogen content cannot be further reduced; it is the theoretical equilibrium moment in thermodynamics. To achieve degassing, the degassing reaction must meet thermodynamic requirements, i.e., the limiting equilibrium value must be low enough. Otherwise, even extending the time will hardly meet the degassing requirements. Therefore, it is necessary to calculate the mass percentage of nitrogen in the molten steel when it reaches dissolution equilibrium, and predict the nitrogen content in the molten steel based on this mass percentage. In some embodiments, the first nitrogen content can be calculated using the following formula:

[0074]

[0075] Among them, [%N] eq The first nitrogen content, K N It is the dissolution equilibrium constant. P is the partial pressure of nitrogen gas in a nitrogen bubble. θ For standard atmospheres, f N This is the activity coefficient.

[0076] The fourth calculation module is used to calculate a first ratio based on the vacuum chamber pressure and the bottom-blown gas flow rate per unit time. The first ratio is the ratio of the interfacial reaction area to the molten pool volume. In some embodiments, the first ratio can be calculated using the following formula:

[0077]

[0078] Where B is the first ratio, Q is the bottom-blowing gas flow rate per unit time, P1 is the vacuum chamber pressure, and Δt is the time change. It should also be noted that the nitrogen bubbles generated during the degassing process escape from the molten steel. When the internal pressure of the bubble equals the external pressure, the degassing process reaches equilibrium. The external pressure of the bubble is the vacuum chamber pressure, and the internal pressure of the bubble is the nitrogen partial pressure. Therefore, the partial pressure P of nitrogen in the nitrogen bubble can be considered as... N2 It is equal to the vacuum chamber pressure P1.

[0079] The correction module is used to correct the model parameters of the prediction model based on the initial mass transfer coefficient, in order to obtain the corrected mass transfer coefficient. See also Figure 2 In some embodiments, correcting the model parameters of the prediction model based on the initial mass transfer coefficient to obtain the corrected mass transfer coefficient includes the following steps:

[0080] S251: Obtain the initial mass transfer coefficient.

[0081] The initial mass transfer coefficient is a continuous value within a preset range. If the initial mass transfer coefficient is set to A0, then A0∈[0.005, 0.1].

[0082] S252: Divide the initial mass transfer coefficient according to a preset step size to obtain several mass transfer coefficients.

[0083] In some embodiments, the preset step size can be 0.005. After dividing the initial mass transfer coefficient according to the preset step size, several mass transfer coefficients A can be obtained. i For example, 0.005, 0.01, 0.015, 0.02…0.1.

[0084] S253: Obtain historical data, which is the measured value of nitrogen content in molten steel after the degassing process.

[0085] S254: Calculate the first predicted value of nitrogen content based on the mass transfer coefficient.

[0086] The first nitrogen content prediction value is the predicted nitrogen content in the molten steel after the degassing process. When the bottom-blown gas is nitrogen, the first nitrogen content prediction value is calculated using the following formula:

[0087]

[0088] When the bottom-blown gas is argon, the predicted value of the first nitrogen content is calculated using the following formula:

[0089]

[0090] in, The first predicted nitrogen content, y i ′ represents the measured nitrogen content at the start of degassing, [%N] eq The first nitrogen content is η, which is a dimensionless number ranging from 0.3 to 0.8. i is the mass transfer coefficient, B is the first ratio, and t is the degassing time.

[0091] S255: Calculate the average absolute error based on historical data and the first predicted nitrogen content.

[0092] In some embodiments, the mean absolute error can be calculated using the following formula:

[0093]

[0094] Where MAE is the mean absolute error. The first predicted nitrogen content, y i This represents the measured nitrogen content in the molten steel after the degassing process. Each historical data point corresponds to a first predicted nitrogen content value. The mean absolute error can be calculated by combining the acquired historical data with the first predicted nitrogen content value calculated based on one of the mass transfer coefficients.

[0095] S256: Iterate through the mass transfer coefficients to obtain the mass transfer coefficient corresponding to the minimum mean absolute error, and output this mass transfer coefficient as the corrected mass transfer coefficient.

[0096] By correcting the model parameters, the accuracy of the model can be improved, and the accuracy of the calculation results can be increased.

[0097] The fifth calculation module is used to calculate the second nitrogen content in the molten steel based on the first nitrogen content, the corrected mass transfer coefficient, the type of bottom-blown gas, and the first ratio, and outputs the second nitrogen content as the predicted value of the target nitrogen content.

[0098] For steel grades with low nitrogen content, if the initial nitrogen content in the molten steel is high, argon can be chosen as the bottom-blowing gas to remove other gaseous components (hydrogen, oxygen, etc.) without increasing the nitrogen content. For steel grades with upper and lower limits for nitrogen content, nitrogen can be chosen as the bottom-blowing gas to remove other gaseous components (hydrogen, oxygen, etc.) while retaining nitrogen as much as possible. Therefore, the bottom-blowing gas includes nitrogen and argon. The second nitrogen content in the molten steel is calculated using the fifth calculation module based on the first nitrogen content, the corrected mass transfer coefficient, the type of bottom-blowing gas, and the first ratio.

[0099] In some embodiments, when the bottom-blown gas is nitrogen, the second nitrogen content is calculated using the following formula:

[0100] [%N]2=[%N]1-η×A×B×([%N]1-[%N] eq )×Δt1;

[0101] When the bottom-blown gas is argon, the second nitrogen content is calculated using the following formula:

[0102] [%N]2=[%N]1-A×B×([%N]1-[%N] eq )×Δt1;

[0103] Where [%N]2 represents the second nitrogen content, [%N]1 represents the predicted nitrogen content in the molten steel at the initial time of the preset duration, A represents the corrected mass transfer coefficient, B represents the first ratio, and Δt1 represents the preset duration. The second nitrogen content is the predicted nitrogen content in the molten steel during the degassing process, i.e., the predicted target nitrogen content. It can be understood that when the initial time of the preset duration is the start time of degassing, the predicted nitrogen content in the molten steel is the measured value of the nitrogen content in the molten steel. In some embodiments, the preset duration can be 1 second or an integer greater than 1 second.

[0104] See Figure 3 In some implementations, the method further includes: if the degassing process is not completed, the second calculation module continues to calculate the dissolution equilibrium constant based on the temperature of the molten steel; the third calculation module calculates the first nitrogen content based on the partial pressure of nitrogen in the nitrogen bubbles, the activity coefficient, and the dissolution equilibrium constant; the fourth calculation module calculates the first ratio based on the vacuum chamber pressure and the bottom-blown gas flow rate per unit time; the fifth calculation module calculates the second nitrogen content based on the first nitrogen content, the corrected mass transfer coefficient, the type of bottom-blown gas, and the first ratio; until the degassing process is completed, the second nitrogen content is output as the predicted value of the target nitrogen content, at which point the prediction model stops.

[0105] It should be noted that, due to the different supply pressures of nitrogen and argon, the order of bottom-blowing gases during the degassing process is nitrogen first, followed by argon. For molten steel with different initial nitrogen contents, the predicted nitrogen content values ​​calculated for vacuum degassing using different bottom-blowing gases are shown in Tables 1 and 2, respectively.

[0106] Table 1 shows the predicted nitrogen content of molten steel during the degassing process when the initial nitrogen content is high.

[0107]

[0108]

[0109] In Table 1, the initial nitrogen content of the molten steel was measured to be 337 ppm. This value is the initial value [%N]1 for predicting the molten steel content at the next preset time (i.e., the 1st second). As can be seen from Table 1, the bottom-blown gas changed at the 1465th second, and the vacuum degassing process ended at the 1781st second. At this time, the nitrogen content in the molten steel predicted by the 1781st second was 135.4 ppm. The degassing process ended at this time, and the actual measured nitrogen content in the molten steel after the degassing process was 131 ppm. It can be seen that the difference between the measured value and the predicted value of nitrogen content after the degassing process is about 4.4 ppm.

[0110] Table 2 shows the predicted nitrogen content of molten steel during the degassing process when the initial nitrogen content is low.

[0111]

[0112] In Table 2, the initial measured nitrogen content of the molten steel is 281 ppm. This value is the initial value [%N]1 for predicting the nitrogen content of the molten steel at the next preset time (i.e., the 1st second). Table 2 shows that the bottom-blown gas changes at 2333 seconds, and the vacuum degassing process ends at 2662 seconds. At this point, the predicted nitrogen content in the molten steel is 103.2 ppm, indicating the end of the degassing process. The actual measured nitrogen content in the molten steel after the degassing process is 101 ppm. Therefore, the difference between the measured and predicted nitrogen content after the degassing process is 2.2 ppm. The results in Tables 1 and 2 show that the error between the calculated predicted nitrogen content and the measured nitrogen content is small, and the calculated predicted nitrogen content can be used as the actual nitrogen content in the molten steel during the degassing process.

[0113] The method provided in this application uses a constructed prediction model based on thermodynamic principles to predict the nitrogen content in molten steel during vacuum degassing, solving the problem of not being able to obtain nitrogen content during vacuum degassing. Furthermore, by calculating the predicted nitrogen content using a corrected mass transfer coefficient, the accuracy of the calculation results is improved. Since the predicted nitrogen content during the degassing process calculated using this method has a small error, it can provide theoretical guidance for actual production and better monitor changes in the nitrogen content of molten steel during vacuum processes. For low-nitrogen steel, it can improve the degassing pass rate and avoid re-extraction; for high-nitrogen steel, it helps avoid excessively low nitrogen content in the molten steel, thus improving the intelligence level of the refining process.

[0114] Based on the above prediction method, some embodiments of this application also provide a steel liquid nitrogen content prediction system for the VD refining process, applied to the method provided in the above real-time example, see [link to relevant documentation]. Figure 4 The system includes:

[0115] Acquisition Module: Used to acquire process parameters of the VD vacuum degassing process; process parameters include molten steel temperature, interaction coefficient, mass percentage of elements in molten steel, partial pressure of nitrogen in nitrogen bubbles, vacuum chamber pressure, type of bottom-blown gas and flow rate of bottom-blown gas per unit time, wherein the interaction coefficient is the interaction coefficient between elements in molten steel and nitrogen.

[0116] First calculation module: used to calculate the activity coefficient of nitrogen in molten steel based on the interaction coefficient and the mass percentage of elements in molten steel;

[0117] The second calculation module is used to calculate the dissolution equilibrium constant of nitrogen in molten steel based on the temperature of the molten steel.

[0118] The third calculation module is used to calculate the first nitrogen content based on the partial pressure, activity coefficient and dissolution equilibrium constant of nitrogen in nitrogen bubbles. The first nitrogen content is the mass percentage of nitrogen element in molten steel when dissolution equilibrium is reached.

[0119] The fourth calculation module is used to calculate the first ratio based on the vacuum chamber pressure and the bottom-blown gas flow rate per unit time. The first ratio is the ratio of the interfacial reaction area to the molten pool volume.

[0120] Correction module: Used to correct the model parameters of the prediction model based on the initial mass transfer coefficient, so as to obtain the corrected mass transfer coefficient;

[0121] The fifth calculation module is used to calculate the second nitrogen content in the molten steel based on the first nitrogen content, the corrected mass transfer coefficient, the type of bottom-blown gas, and the first ratio, and outputs the second nitrogen content as the predicted value of the target nitrogen content.

[0122] As can be seen from the above technical solutions, this application provides a method and system for predicting the nitrogen content of molten steel in a VD refining process. The method includes: acquiring process parameters of the VD vacuum degassing process, constructing a nitrogen content prediction model, and outputting a predicted value of the target nitrogen content in the molten steel based on the process parameters. The prediction model includes a first calculation module for calculating the activity coefficient of nitrogen in the molten steel, a second calculation module for calculating the dissolution equilibrium constant, a third calculation module for calculating the mass percentage of nitrogen in the molten steel when dissolution equilibrium is reached, a fourth calculation module for calculating a first ratio, a correction module for obtaining a corrected mass transfer coefficient, and a fifth calculation module for calculating the predicted value of the target nitrogen content. This method uses a constructed prediction model based on thermodynamic principles to predict the nitrogen content in molten steel during the vacuum degassing process, solving the problem of not being able to obtain the nitrogen content during vacuum degassing. Furthermore, calculating the predicted nitrogen content using the corrected mass transfer coefficient improves the accuracy of the calculation results.

[0123] Similar parts between the embodiments provided in this application can be referred to mutually. The specific implementation methods provided above are only a few examples under the overall concept of this application and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any other implementation methods extended from the solution of this application without creative effort shall fall within the scope of protection of this application.

Claims

1. A method for predicting the nitrogen content in liquid steel during VD refining, characterized in that, include: The process parameters for the VD vacuum degassing process are obtained, including the steel temperature, interaction coefficient, mass percentage of elements in the steel, partial pressure of nitrogen in nitrogen bubbles, vacuum chamber pressure, type of bottom-blown gas, and bottom-blown gas flow rate per unit time; the interaction coefficient is the interaction coefficient between elements in the steel and nitrogen. A nitrogen content prediction model is constructed to output the predicted value of the target nitrogen content in molten steel based on the process parameters; The prediction model includes: The first calculation module is used to calculate the activity coefficient of nitrogen in the molten steel based on the interaction coefficient and the mass percentage of the elements in the molten steel. The second calculation module is used to calculate the dissolution equilibrium constant of nitrogen in the molten steel based on the temperature of the molten steel. The dissolution equilibrium constant of nitrogen in molten steel can be calculated using the following formula: in, It is the dissolution equilibrium constant. The temperature of the molten steel; The third calculation module is used to calculate the first nitrogen content based on the partial pressure of nitrogen in the nitrogen bubble, the activity coefficient and the dissolution equilibrium constant. The first nitrogen content is the mass percentage of nitrogen element in molten steel when dissolution equilibrium is reached. The first nitrogen content is calculated using the following formula: in, The first nitrogen content, It is the dissolution equilibrium constant. This represents the partial pressure of nitrogen gas in a nitrogen bubble. Standard atmospheric pressure Activity coefficient; The fourth calculation module is used to calculate a first ratio based on the vacuum chamber pressure and the bottom-blown gas flow rate per unit time, wherein the first ratio is the ratio of the interface reaction area to the molten pool volume. The first ratio is calculated using the following formula: in, The first ratio, The bottom blowing gas flow rate per unit time. For vacuum chamber pressure, It is a quantity that changes over time; The correction module is used to correct the model parameters of the prediction model based on the initial mass transfer coefficient to obtain the corrected mass transfer coefficient. The fifth calculation module is used to calculate the second nitrogen content in the molten steel based on the first nitrogen content, the corrected mass transfer coefficient, the type of bottom-blown gas, and the first ratio, and output the second nitrogen content as the predicted value of the target nitrogen content. The bottom-blown gas includes nitrogen and argon, and the calculation of the second nitrogen content in the molten steel based on the first nitrogen content, the corrected mass transfer coefficient, the type of bottom-blown gas, and the first ratio includes: When the bottom-blown gas is nitrogen, the second nitrogen content is calculated using the following formula: When the bottom-blown gas is argon, the second nitrogen content is calculated using the following formula: in, The second nitrogen content, This is the predicted value of nitrogen content in molten steel at the initial time of the preset duration. It is a dimensionless number. To correct the mass transfer coefficient, The first ratio, This is the preset duration.

2. The method for predicting the nitrogen content in liquid steel during the VD refining process according to claim 1, characterized in that, The step of correcting the model parameters of the prediction model based on the initial mass transfer coefficient to obtain the corrected mass transfer coefficient includes: Obtain the initial mass transfer coefficient, which is a continuous value within a preset range; The initial mass transfer coefficient is divided according to a preset step size to obtain several mass transfer coefficients; Acquire historical data, which are the measured values ​​of nitrogen content in molten steel after the degassing process; The first nitrogen content prediction value is calculated based on the mass transfer coefficient. The first nitrogen content prediction value is the nitrogen content prediction value in the molten steel after the degassing process. The mean absolute error is calculated based on the historical data and the first predicted nitrogen content value. Iterate through the mass transfer coefficients to obtain the mass transfer coefficient corresponding to the minimum mean absolute error, and output the mass transfer coefficient as the corrected mass transfer coefficient.

3. The method for predicting the nitrogen content in liquid steel during the VD refining process according to claim 2, characterized in that, The mean absolute error is calculated using the following formula: in, The mean absolute error, This is the first predicted value for nitrogen content. This represents the measured nitrogen content in the molten steel after the degassing process.

4. The method for predicting the nitrogen content in liquid steel during the VD refining process according to claim 1, characterized in that, When the initial time of the preset duration is the start time of degassing, the predicted value of the nitrogen content in the molten steel is the measured value of the nitrogen content in the molten steel.

5. The method for predicting the nitrogen content in liquid steel during the VD refining process according to claim 1, characterized in that, The method further includes: If the degassing process is not completed, the dissolution equilibrium constant is calculated by the second calculation module based on the temperature of the molten steel. The third calculation module calculates the first nitrogen content based on the partial pressure of nitrogen in the nitrogen bubble, the activity coefficient, and the solubility equilibrium constant. The fourth calculation module calculates the first ratio based on the vacuum chamber pressure and the bottom-blowing gas flow rate per unit time. The fifth calculation module calculates the second nitrogen content based on the first nitrogen content, the corrected mass transfer coefficient, the bottom-blown gas type, and the first ratio. Until the degassing process is completed, the second nitrogen content is output as the predicted value of the target nitrogen content.

6. A system for predicting the nitrogen content in liquid steel during VD refining, characterized in that, The system, applied to the method of any one of claims 1-5, comprises: Acquisition module: used to acquire process parameters of the VD vacuum degassing process, including molten steel temperature, interaction coefficient, mass percentage of elements in molten steel, partial pressure of nitrogen in nitrogen bubbles, vacuum chamber pressure, type of bottom-blown gas, and bottom-blown gas flow rate per unit time; the interaction coefficient is the interaction coefficient between elements in molten steel and nitrogen. First calculation module: used to calculate the activity coefficient of nitrogen in molten steel based on the interaction coefficient and the mass percentage of elements in the molten steel; The second calculation module is used to calculate the dissolution equilibrium constant of nitrogen in the molten steel based on the temperature of the molten steel. The third calculation module is used to calculate the first nitrogen content based on the partial pressure of nitrogen in the nitrogen bubble, the activity coefficient, and the dissolution equilibrium constant. The first nitrogen content is the mass percentage of nitrogen element in molten steel when dissolution equilibrium is reached. The fourth calculation module is used to calculate a first ratio based on the vacuum chamber pressure and the bottom-blown gas flow rate per unit time. The first ratio is the ratio of the interfacial reaction area to the molten pool volume. Correction module: used to correct the model parameters of the prediction model based on the initial mass transfer coefficient, so as to obtain the corrected mass transfer coefficient; The fifth calculation module is used to calculate the second nitrogen content in the molten steel based on the first nitrogen content, the corrected mass transfer coefficient, the type of bottom-blown gas, and the first ratio, and output the second nitrogen content as the predicted value of the target nitrogen content.

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